Document:

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                                                                 EXHIBIT 10.7(a)

                              ASSIGNMENT OF LEASES
                                 (Space Lease)

THE STATE OF TEXAS  )
                    )              KNOW ALL MEN BY THESE PRESENTS:
COUNTY OF HARRIS    )

     THIS ASSIGNMENT, made the 23rd day of November, 1998, by TMX REALTY
CORPORATION, a Delaware corporation, hereinafter referred to as the "Assignor",
to RIVERWAY BANK, with its banking house located in Houston, Harris County,
Texas, hereinafter referred to as "Assignee";

                                  W I T N E S S E T H:

     That the Assignor, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, hereby grants, transfers and
assigns to the Assignee all of Assignor's interest in and to any and all
sublease and/or sub-sublease agreements or any other agreements wherein
Assignor is Lessor (collectively called the "Leases") now or hereafter made and
entered into covering (1) any or all of the space located in the improvements
now or hereafter constructed on the property (the "Property") described in
Exhibit "A", (2) any or all of the property described in Exhibit "A", and (3)
any of Assignor's rights with respect to the Property or improvements located
thereon.

     Assignee acknowledges the existence of (1) that certain Ground Sublease
(herein so called) covering the Property as evidenced by the Amended and
Restated Ground Sublease Agreement dated November 23rd, 1998 by and between
Assignor as subtenant and Amelang Partners, Inc., as sublandlord and (2) this
certain Enhanced-Use Lease (the "Ground Lease") by and between Amelang
Partners, Inc., as Ground Lessee and the United States Department of Veteran
Affairs is Ground Lessor. The term Lease as used herein shall mean any and all
leases affecting the Property including, without limitation, any existing
leases and any subleases or sub-subleases hereinafter entered into by Assignor
and any tenants for office space or otherwise. The term Lease, for the purposes
hereof shall exclude the Ground lease.

     TOGETHER with all rents, income and profits arising from the Leases and
renewals thereof and together with all rents, income and profits for the use
and occupation of the premises described in the Leases.

                                       I.

     The Assignor covenants with the Assignee to observe and perform all of the
obligations imposed upon the lessor under the Leases and not to do or permit to
be done anything to impair the security thereof; not to collect any of the rent,
income and profits arising or accruing under the Leases or from the Property in
advance of the time when the same shall become due (except for the last month's
rent); not to execute any assignment, collateral assignment or security
agreement covering any of lessor's interest in the Leases or the Property; not
to alter, modify or change the terms of the Leases or give any consent or
exercise any option required or permitted by such terms without the prior
written consent of Assignee, or cancel or terminate any of the Leases or accept
a surrender thereof or convey or transfer or suffer or permit a conveyance or
transfer of the Property or of any interest therein so as to effect directly or
indirectly, proximately or remotely, a merger of the estates and rights of, or a
termination or diminution of the obligations of, lessee thereunder; nor to
consent to any assignment of or subletting under the Leases, whether or not in
accordance with their terms, without the prior written consent of the Assignee;
to assign and transfer to the Assignee any and all subsequent leases upon all or
any part of the Property or improvements located thereon and to execute and
deliver at the request of the Assignee all such further equal assurances and
assignments with respect to the Property, the improvements located or to be
located thereon, or any part thereof, as the Assignee shall from time to time
require.
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                                      II.

          Assignor shall have the right to collect at the time of, but not
prior to, the date provided for the payment thereof, all rents, income and
profits arising under the Leases or from the Property and to retain, use and
enjoy the same, so long as there shall exist no default (after notice and
opportunity to cure as provided in the Construction Loan Agreement) by the
Assignor in:

          (a) The payment of the principal sum, interest and indebtedness
          evidenced by that certain promissory note (the "Note") and any
          amendments, extensions, consolidations, increases or renewals thereof,
          whether represented by modification agreement, renewal note, letter
          agreement or otherwise, in the original principal amount of
          $6,000,000.00, executed by Assignor, payable to Assignee, dated of
          even date herewith and secured by, among other collateral, a
          Leasehold Deed of Trust (the "Deed of Trust") covering the Property.

          (b) The payment of all other sums with interest thereon becoming due
          and payable by Assignor to Assignee.

          (c) The performance and discharge of each and every obligation,
          covenant and agreement of the Assignor contained (i) herein, (ii) in
          the Leases, (iii) in the Note, (iv) in the Deed of Trust, (v) the
          Construction Loan Agreement or (vi) in any documents executed by
          Assignor in connection with the Note.

                                      III.

         Upon or at any time after default in the performance of any obligation,
covenant or agreement herein or in the Note, Deed of Trust or Leases on the part
of the Assignor to be performed (after notice and opportunity to cure as
provided in the Construction Loan Agreement), the Assignee without in any way
waiving such default may, at its option without further notice and without
regard to the adequacy of the security for the payment of the Note, either in
person or by agent, with or without bringing any action or proceeding or by a
receiver appointed by a court, take possession of the Property and improvements
thereon located and have, hold, manage, lease and operate the same on such terms
and for such period of time as the Assignee may deem proper and either with or
without taking possession of the Property in its own name, demand, sue for or
otherwise collect and receive all rents, income and profits of the Property,
including those past due and unpaid with full power to make from time to time
all alterations, renovations, repairs or replacements thereto or thereof as may
seem proper to the Assignee and to apply such rents, income and profits to the
payment of: (a) all expenses of managing the Property, together with the
improvements located thereon, including without being limited thereto, the
salaries, fees and wages of a managing agent and such other employees as the
Assignee may deem necessary or desirable and all expenses of operating and
maintaining the Property and improvements, including without being limited
thereto, all taxes, charges, claims, assessments, water rents, sewer rents, and
any other liens and premiums for all insurance which the Assignee may deem
necessary or desirable, and the cost of all alterations, renovations, repairs or
replacements, and all expenses incident to taking and retaining possession of
the Property and improvements; and (b) the principal, interest due and payable
pursuant to the Note, together with all costs and attorneys' fees provided for
therein, in such order of priority as to any of the items mentioned herein as
the Assignee in its sole discretion may determine. The exercise by the Assignee
of the option granted it in this Section III and the collection of the rents,
income and profits and the application thereof as herein provided shall not be
considered a waiver of any default by the Assignor under the Note, Deed of
Trust, Leases or this Assignment. Assignor agrees that the possession by
Assignee subsequent to default shall be conclusively deemed to be a "lawful
possession" of the Property and the improvements thereon located.

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                                      IV.

     The Assignee shall not be liable for any loss sustained by the Assignor
resulting from the Assignee's failure to let the Property or improvements after
default or from any other act or omission of the Assignee in managing the
Property or improvements after default unless such loss is caused by the
willful misconduct and bad faith of the Assignee. Nor shall the Assignee be
obligated to perform or discharge nor does the Assignee hereby undertake to
perform or discharge any obligation, duty or liability under the Leases or
under or by reason of this Assignment and the Assignor shall and does hereby
agree to indemnify the Assignee for, and to hold the Assignee harmless from,
any and all liability, loss or damage which may or might be incurred under the
Leases or under or by reason of this Assignment and from any and all claims and
demands whatsoever which may be asserted against the Assignee by reason of any
alleged obligations or undertakings on its part to perform or discharge any of
the terms, covenants or agreements contained in the Leases. Should the Assignee
incur any such liability under the Leases or under or by reason of this
Assignment or in defense of any such claims or demands, the amount thereof,
including costs, expenses and reasonable attorneys' fees, shall be secured
hereby and the Assignor shall reimburse the Assignee therefor immediately upon
demand and upon the failure of the Assignor so to do, the Assignee may, at its
option, declare the Note immediately due and payable, if the same have not
theretofore been accelerated. And it is further understood that this Assignment
shall not operate to place responsibility for the control, care, management or
repair of the Property or improvements upon the Assignee nor shall Assignee be
responsible or liable for any waste committed on the Property or improvements
by the tenants or any other parties, or for any dangerous or defective
condition of the Property or improvements, or for any negligence in the
management, upkeep, repair or control of the Property or improvements resulting
in loss or injury or death to any tenant, licensee, employee or stranger.
Assignor acknowledges that Assignee retains the rights set forth in this
Section only for the protection of its collateral, and this Section is in no
manner to be construed as interference with or control of Assignor's business
or tenants.

                                       V.

     Upon payment in full of the Note and performance in full of the provisions
of the Deed of Trust, this Assignment shall become and be void and of no
effect. The Assignor hereby authorizes and directs the lessees named in the
Leases or any other or future lessees or occupant of the Property, or any part
thereof, upon receipt from the Assignee of written notice to the effect that a
default exists under the Note, Deed of Trust or this Assignment, to pay over to
the Assignee all rents, income and profits arising or accruing under the Leases
and to continue to do so until otherwise notified by the Assignee.

                                      VI.

     The Assignee may take or release any security for the payment of the Note,
may release any party primarily or secondarily liable thereon and may apply any
security held by it to the satisfaction of such principal, interest or
indebtedness without prejudice to any of its rights under this Assignment.

                                      VII.

     Nothing contained in this Assignment and no act done or omitted by the
Assignee pursuant to the powers and rights granted it hereunder shall be deemed
to be a waiver by the Assignee of its rights and remedies under the Note or
Deed of Trust, and this Assignment is accepted without prejudice to any of the
rights and remedies possessed by the Assignee under the terms of the Note and
Deed of Trust, and it is agreed that this is an absolute assignment and not a
security agreement, pledge or collateral assignment. The right of the Assignee
to collect the principal and interest and to enforce any security therefor held
by it may be exercised by the Assignee either prior to, simultaneously with, or
subsequent to any action taken by it hereunder.

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                                     VIII.

     When this Assignment is executed by more than one person, it shall be
construed as though Assignor were written Assignors and words in their number
were changed to correspond; and pronouns of masculine gender, wherever used
herein, shall include persons of the female sex and corporations and
associations of every kind and character; and the words "heirs, executors and
administrators", when this instrument is executed by a corporation, shall be
construed to mean "successors and assigns". If Assignee is more than one person,
it shall be construed as though Assignee were written Assignees and words in
their number were changed to correspond; and pronouns of the masculine gender,
where used herein as to Assignee, shall be construed to include persons of the
female sex, corporations and associations of every kind and character and, as to
a corporation, the words "heirs" shall be construed as "successors".

                                      IX.

     This Assignment, together with the covenants and warranties herein
contained, shall inure to the benefit of the Assignee and any subsequent holder
of the Note and Deed of Trust and shall be binding upon the Assignor, his heirs,
executors, administrators, successors and assigns, and any subsequent owner of
the Property, or any part thereof.

                                       X.

     ASSIGNOR HEREBY EXPRESSLY RECOGNIZES THAT CONTAINED IN SECTION IV. OF THIS
ASSIGNMENT OF LEASES ARE PROVISIONS WHICH REQUIRE ASSIGNOR TO INDEMNIFY ASSIGNEE
UNDER CERTAIN CIRCUMSTANCES AND ASSIGNOR HEREBY ACKNOWLEDGES THAT BY EXECUTING
THIS ASSIGNMENT OF LEASES, ASSIGNOR ACCEPTS THESE PROVISIONS AND THE OBLIGATIONS
TO INDEMNIFY ASSIGNEE UNDER SUCH CIRCUMSTANCES.

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     EXECUTED on this the 23rd day of November, 1998.

                                              TMX REALTY CORPORATION, a Delaware
                                              corporation

                                              By: /s/ JAMES W. ALBRECHT, JR.
                                                  ---------------------------
                                              Name:   JAMES W. ALBRECHT, JR.
                                                    -------------------------
                                              Title:  CHIEF FINANCIAL OFFICER
                                                    -------------------------

THE STATE OF TEXAS )
                   )
COUNTY OF HARRIS   )

     This instrument was acknowledged before me on this 23 day of November,
1998, by James W. Albrecht, Jr., CEO of TMX REALTY CORPORATION, a Delaware
corporation, for and on behalf of said corporation.

                                                      /s/ LAWANA HARDIN
                                                      ----------------------
[SEAL]                                   [SEAL]       Notary Public in and
                                                      for the STATE OF TEXAS

Printed Name of Notary:                               My Commission Expires:

----------------------------                          ----------------------

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                                  EXHIBIT "A"

Being a tract or parcel containing 2.619 acres (114,086 square feet) of land
situated in the DWC Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 2.619 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

COMMENCING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3,147,967.40,
Y=698,487.10, thence:

     South 14 degrees 53'21" West, with said west ROW line, a distance of 206.00
     feet to a set 5/8-inch iron rod with plastic cap;

     North 75 degrees 06'39" West, a distance of 329.30 feet to a 5/8-inch iron
     rod with plastic cap set marking the POINT OF BEGINNING and northeast
     corner of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, a distance of 330.70 feet to a 5/8-inch
iron rod with plastic cap set marking the southeast corner of the herein
described tract;

THENCE, NORTH 75 degrees 06'39" West, a distance of 432.78 feet to a 5/8-inch
iron rod with plastic cap set marking the southwest corner of the herein
described tract;

THENCE, North 41 degrees 44'27" East, a distance of 334.23 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 03 degrees 35'59", an arc length of 47.75 feet, and a chord
which bears North 39 degrees 56'28" East, 47.74 feet to an "X" in concrete set
marking the most northwesterly corner of the herein described tract;

THENCE, SOUTHEASTERLY, with a non-tangent curve to the left having a radius of
87.50 feet, an arc length of 93.13 feet, a central angle of 60 degrees 59'01",
and a chord which bears South 58 degrees 25'28" East, 88.80 feet to a 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH 88 degrees 54'58" East, a distance of 27.76 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, EASTERLY, with a curve to the right having a radius of 281.50 feet, an
arc length of 67.83 feet, a central angle of 13 degrees 48'19", and a chord
which bears South 82 degrees 00'48" East, 67.66 feet to a 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH 75 degrees 06'39" East, a distance of 82.41 feet to the POINT OF
BEGINNING and containing 2.619 acres (114,086 square feet) of land (this
description is based on a Land Title Survey and plat prepared by Terra
Surveying Company, Inc. Project Number 0163-9801-S).

                                                                         [STAMP]
                                    [STAMP]
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ANY PROVISION HEREIN WHICH RESTRICTS THE SALE, RENTAL OR USE OF THE DESCRIBED
REAL PROPERTY BECAUSE OF COLOR OR RACE IS INVALID AND UNENFORCEABLE UNDER
FEDERAL LAW

THE STATE OF TEXAS   )
COUNTY OF HARRIS     )

     I hereby certify that this instrument was FILED in File Number Sequence on
the date and at the time stamped hereon by me, and was duly RECORDED, in the
Official Public Records of Real Property of Harris County, Texas on

                                   DEC 3 1998

[SEAL]
                                 /s/ BEVERLY B. KAUFMAN
                                 COUNTY CLERK
                                 HARRIS COUNTY TEXAS

<PAGE>   8
                 CONSENT TO ASSIGNMENT OF CONSTRUCTION CONTRACT

     The undersigned Contractor hereby acknowledges receipt of a copy of the
Assignment of Construction Contract set out in Section 4.18 of that certain
Construction Loan Agreement of even date herewith by and between TMX Realty
Corporation, a Delaware corporation and RIVERWAY BANK and consents to be bound
by the provisions thereof.

                                          J.T. Vaughn Construction Company, Inc.

                                          By: /s/ J. THOMAS VAUGHN
                                             -----------------------------------
                                          Name: J. Thomas Vaughn
                                               ---------------------------------
                                          Title: Exec. V.P.
                                                --------------------------------
<PAGE>   9
                          CONSTRUCTION LOAN AGREEMENT

         THIS LOAN AGREEMENT dated November 23, 1998, is made by and between
RIVERWAY BANK ("Lender"), whose address is Five Riverway, Houston, Texas 77056
and TMX REALTY CORPORATION, a Delaware corporation ("Borrower"), whose address
is 301 Congress Avenue, Suite 1850, Austin, Texas 78701, in respect of a loan in
the principal sum of SIX MILLION AND NO/100 DOLLARS ($6,000,000).

                            ARTICLE 1 - DEFINITIONS

         For purposes of this Loan Agreement, the following terms shall have the
respective meanings assigned to them.

1.1      Advance.

         The term "Advance" shall mean a disbursement by Lender of any of the
proceeds of the Loan and/or the Borrower's Deposit.

1.2      Affidavit of Borrower.

         The term "Affidavit of Borrower" shall mean a sworn affidavit of
Borrower (and such other parties as Lender may require) to the effect that all
statements, invoices, bills, and other expenses incident to the acquisition of
the Property and the construction of the Improvements incurred to a specified
date, whether or not specified in the Approved Budget, have been paid in full,
except for (a) amounts retained pursuant to the Construction Contract, and (b)
items to be paid from the proceeds of an Advance then being requested or in
another manner satisfactory to Lender.

1.3      Application for Advance.

         The term "Application for Advance" shall mean a written application (on
a form approved by Lender) by Borrower (and such other parties as Lender may
require) to Lender specifying by name, current address, and amount all parties
to whom Borrower is obligated for labor, materials, or services supplied for the
construction of the improvements and all other expenses incident to the Loan,
the Property, and the construction of the Improvements, whether or not specified
in the Approved Budget requesting an Advance for the payment of such items,
containing, if requested by Lender, an Affidavit of Borrower, accompanied by
such schedules, affidavits, releases, waivers, statements, invoices, bills, and
other documents as Lender may reasonably request.

1.4      Approved Budget

         The term "Approved Budget" shall mean a budget or cost itemization
prepared by Borrower specifying the cost by item of (a) all labor, materials,
and services necessary for the construction of the Improvements in accordance
with the Plans and all Governmental Requirements, and (b) all other expenses
anticipated by Borrower incident to the Loan, the Property, and the construction
of Improvements. The Approved Budget is attached hereto as Exhibit "C" and
incorporated herein by reference.

1.5      Appraisal.

         The term "Appraisal" shall mean a Fair Value appraisal from a MAI
appraiser approved by Lender and reflecting a completed value of not less than
$7,860,000. The term Fair Value shall mean the cash price that might reasonably
be anticipated in a current sale under all conditions requisite to a fair sale.
A fair sale means that buyer and seller are each acting prudently, knowledgeably
and under no necessity to buy or sell - i.e., other than in a forced or
liquidation sale. The appraiser should estimate the cash price that might
received upon exposure to the open market

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for a reasonable time, considering the property type and local market
conditions. When a current sale is unlikely - i.e., when it is unlikely that the
sale can be completed within 12 months - the appraiser must discount all cash
flows generated by the Property to obtain the estimate of Fair Value. These cash
flows include, but are not limited to, those arising from ownership,
development, operation, and sale of the Property. The discount applied shall
reflect the appraiser's judgement of what a prudent, knowledgeable purchaser
under no necessity to buy would be willing to pay to purchase property in a
current sale.

1.6      Architect.

         The term "Architect" shall mean Browne Penland McGregor Architects,
Inc.

1.7      Architectural Contract.

         The term "Architectural Contract" shall mean a written agreement
between Borrower and Architect for architectural services pertaining to
construction of the Improvements.

1.8      Assignment of Landlord's Interest in Leases.

         The term "Assignment of Landlord's Interest in Leases" shall mean a
document so entitled, effectuating an assignment by Borrower to Lender of the
landlord's (in this case sub-sublandlord) interest in the leases (in this case
sub-sublessor), lease proceeds, and/or rents from the Property.

1.9      Borrower.

         The term "Borrower" shall mean TMX REALTY CORPORATION, a Delaware
corporation.

1.10     Borrower's Deposit.

         The term "Borrower's Deposit" shall mean such cash sums as Lender may
deem necessary, from time to time until the Loan is paid in full, in addition to
the Loan, for the payment of the costs of labor, materials, and services
required for the construction of the Improvements, other costs and expenses
specified in the Approved Budget, and other costs and expenses required to be
paid in connection with the construction of the Improvements in accordance with
the Plans, any Governmental Requirements and the requirements of any lessee, if
applicable.

1.11     Code.

         The term "Code" shall mean the Uniform Commercial Code as in force in
the state in which the Property is located and, if different, the state of the
Borrower's residence.

1.12     Completion Date.

         The term "Completion Date" shall mean one year from the date of this
Construction Loan Agreement.

1.13     Construction Contract.

         The term "Construction Contract" shall mean all construction contracts
executed by Borrower for the construction of the Improvements, including,
without limitation, contracts between Borrower and Contractor.

1.14     Contractor.

         The term "Contractor" shall mean J.T. Vaughn Construction Company, Inc.

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<PAGE>   11

1.15     Debtor Relief Laws.

         The term "Debtor Relief Laws" shall mean any applicable liquidation,
conservatorship, bankruptcy, moratorium, rearrangement, insolvency,
reorganization, or similar laws affecting the rights or remedies of creditors
generally, as in effect from time to time.

1.16     Event of Default.

         The term "Event of Default" shall mean the occurrence of any one of the
following (subject to the requirement of notice by Lender and opportunity to
cure as provided below):

         (a)   Any indebtedness evidenced, governed or secured by any of the
               Loan Instruments is not paid when due, whether by acceleration or
               otherwise.

         (b)   Any covenant in this Agreement or any of the other Loan
               Instruments is not fully and timely performed, or the occurrence
               of any default or event of default thereunder.

         (c)   Any statement, representation or warranty in the Loan
               Instruments, any Financial Statements or any other writing
               delivered to Lender in connection with the Loan is false,
               misleading or erroneous in any material respect.

         (d)   The cessation of the construction of the Improvements for more
               than fifteen (15) days without the written consent of Lender,
               unless such cessation is due to weather, shortages or
               unavailability of labor or materials, nonperformance by the
               Contractor or Architect, or other causes beyond Borrower's
               control.

         (e)   Failure of the construction of the Improvements or any materials
               for which an Advance has been requested to comply with the Plans,
               any Governmental Requirements or the requirements of any lessee,
               if applicable.

         (f)   Failure of Borrower to satisfy any condition specified herein as
               precedent to the obligation of Lender to make an Advance after an
               Application for Advance has been submitted by Borrower to Lender.

         (g)   A reasonable determination by Lender that construction of the
               Improvements will not be completed on or before the Completion
               Date, or within ninety days thereafter, unless such cessation is
               due to weather, shortages or unavailability of labor or
               materials, non-performance by the Contractor or Architect
               (caused through no fault of Borrower) or other causes beyond
               Borrower's control.

         (h)   Any person obligated to pay any part of the indebtedness
               evidenced, governed or secured by the Loan Instruments

               (1)  makes a general assignment for the benefit of creditors; or

               (2)  commences any case, proceeding or other action seeking
                    reorganization, arrangement, adjustment, liquidation,
                    dissolution or composition of it or its debts under any
                    Debtor Relief Laws; or

               (3)  in any involuntary case, proceeding or other action
                    commenced against it which seeks to have an order for relief
                    entered against it, as debtor, or seeks reorganization,
                    arrangement, adjustment, liquidation, dissolution or
                    composition

                                        3
<PAGE>   12

                    of it or its debts under any law relating to bankruptcy,
                    insolvency, reorganization or relief of debtors, (i) fails
                    to obtain a dismissal of such case, proceeding or other
                    action within sixty (60) days of its commencement, or (ii)
                    converts the case from one chapter of the Federal Bankruptcy
                    Code to another chapter, or (iii) is the subject of an order
                    for relief; or

               (4)  conceals, removes, or permits to be concealed or removed,
                    any part of its property, with intent to hinder, delay or
                    defraud its creditors or any of them, or makes or suffers a
                    transfer of any of its property which is fraudulent under
                    any bankruptcy, fraudulent conveyance or similar law; or
                    makes any transfer of its property to or for the benefit of
                    a creditor at a time when other creditors similarly situated
                    have not been paid; or suffers or permits, while insolvent,
                    any creditor to obtain a lien upon any of its property
                    through legal proceedings which is not vacated within sixty
                    (60) days from the date thereof; or

               (5)  has a trustee, receiver, custodian or other similar official
                    appointed for or take possession of all or any part of the
                    Property or any other of its property or has any court take
                    jurisdiction of any other of its property which continues
                    for a period of sixty (60) days (except where a shorter
                    period is specified in the immediately following
                    subparagraph (6)); or

               (6)  fails to have discharged within a period of thirty (30) days
                    any attachment, sequestration, or similar writ levied upon
                    any property of such person; or

               (7)  fails to pay immediately any final, nonappealable money
                    judgment against such person.

         (i)   Title to all or any part of the Property (other than obsolete or
               worn personal property replaced by adequate substitutes of equal
               or greater value than the replaced items when new) shall become
               vested in any party other than the granting party named in the
               Mortgage, whether by operation of law or otherwise. Lender may,
               in its sole discretion, waive this Event of Default, but it shall
               have no obligation to do so, and any waiver may be conditioned
               upon such one or more of the following as Lender may require; the
               grantee's integrity, reputation, character, creditworthiness and
               management ability being satisfactory to Lender in its sole
               judgment, the grantee executing, prior to such sale or transfer,
               a written assumption agreement containing such terms as Lender
               may require, a principal paydown on the Note, an increase in the
               rate of interest payable under the Note, a transfer fee, and any
               other modification of the Loan Instruments which Lender may
               require.

         (j)   Without the prior written consent of Lender, the owner of the
               Property grants any easement or dedication, files any plat,
               condominium declaration, or restriction, or otherwise encumbers
               the Property, unless such action is expressly permitted by the
               Loan Instruments or does not affect the Property.

         (k)   Without the prior written consent of Lender, Borrower enters into
               any lease of part or all of the Property.

         (1)   Borrower abandons any of the Property.

         (m)   Lender reasonably determines that the condition of the Property
               has materially deteriorated in value.

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<PAGE>   13

         (n)   The holder of any lien, security interest or assignment on the
               Property institutes foreclosure or other proceedings or takes
               other action for the enforcement of its remedies thereunder.

         (o)   The liquidation, termination, dissolution, death, or legal
               incapacity of Borrower.

         (p)   If Borrower is a partnership or joint venture, a default by any
               general partner or joint venturer under Borrower's partnership
               agreement or joint venture agreement.

         (q)   If Borrower is a corporation, the sale, pledge, encumbrance or
               assignment of any shares of its stock without the prior written
               consent of Lender. If Borrower or the owner of the Property (if
               other than Borrower) is a partnership or joint venture, the sale,
               pledge, encumbrance or assignment of any of its partnership or
               joint venture interests or the withdrawal from or admission into
               it of any general partner or joint venturer without the prior
               written consent of Lender.

         (r)   There is an event of default pursuant to the Ground Lease or the
               Ground Sublease after notice and expiration of opportunity to
               cure as provided therein and under circumstances in which the
               Government is not obligated to honor the Ground Sublease or to
               enter into a Replacement Lease with Borrower or Introgen
               Therapeutics, Inc.

Any other provision of this Construction Loan Agreement or any of the Loan
Instruments (which term is defined in Section 1.35 below) notwithstanding,
Borrower shall not be deemed to be in default in connection with the Loan or any
of the Loan Instruments nor shall any Event of Default be deemed to have
occurred or to exist, until Lender has first delivered to Borrower notice of
default ("Notice of Default") and an opportunity to cure, as follows: (i) with
respect to any failure by Borrower to timely pay any monthly payment or the
balloon payment described in the Note, Lender shall provide to Borrower Notice
of Default and a period of ten (10) days following delivery of such notice
within to cure such default, and (ii) with respect to any other event or
occurrence which would otherwise constitute an Event of Default, Lender shall
deliver to Borrower notice of such default and Borrower shall have a period of
thirty (30) days within which to cure such default, provided that if such
default is of a nature that it cannot reasonably be cured within such thirty day
period, then Borrower shall have a further reasonable period of time to cure
such default so long as Borrower is working diligently to effect such cure.
However, Lender shall have no obligation to send more than three Notices of
Default pursuant to (i) above within any calendar year.

1.17     Financial Statements.

         The term "Financial Statements" shall mean such balance sheets, profit
and loss statements, reconciliations of capital and surplus, changes in
financial condition, schedules of sources and uses of funds, operating
statements with respect to the Property, pro forma schedules of sources and uses
of funds for ensuing twelve-month periods, and other financial information of
Borrower as shall be required by Lender, from time to time, which statements
shall be certified as true and correct by the party submitting such statements
or, if required by Lender, shall be certified by an independent certified public
accountant.

1.18     Financing Statements.

         The term "Financing Statements" shall mean the Form UCC-1 financing
statements perfecting the security interests securing the Loan, to be filed with
the appropriate offices for the perfection of a security interest in any of the
Property.

                                        5
<PAGE>   14

1.19     Governmental Authority.

         The term "Governmental Authority" shall mean the United States, the
state, the county, the city, or any other political subdivision in which the
Property is located, and any other political subdivision, agency, or
instrumentality exercising jurisdiction over Borrower or the Property.

1.20     Governmental Requirements.

         The term "Governmental Requirements" shall mean all laws, ordinances,
rules, and regulations of any Governmental Authority applicable to Borrower or
the Property.

1.21     Ground Lease.

         The term "Ground Lease" shall mean that certain Enhanced-Use Agreement
dated August 25, 1993, by and between the Secretary of Veterans Affairs, an
officer of the United States on behalf of the United States Department of
Veterans Affairs, as Ground Lessor, and Amelang Partners, Inc., as Ground
Lessee, as amended.

1.22     Ground Lessee.

         The term "Ground Lessee" shall mean Amelang Partners, Inc., a Texas
corporation.

1.23     Ground Lessor.

         The term "Ground Lessor" shall mean the Secretary of Veterans Affairs,
an officer of the United States on behalf of the United States Department of
Veterans Affairs.

1.24     Ground Sublease.

         The term "Ground Sublease" or "Ground Sublease Agreement" shall mean
that certain Amended and Restated Ground Sublease Agreement dated the 23 day of
November, 1998, by and between Amelang Partners, Inc., as Ground Sublessor and
Introgen Therapeutics, Inc., as Ground Sublessee, as the same was assigned by
Ground Sublessee by Assignment dated November 23, 1998 to Borrower.

1.25     Ground Sublessee.

         The term "Ground Sublessee" shall mean Introgen Therapeutics, Inc. or
Borrower, as assignee of the Ground Sublease, as the case may be.

1.26     Ground Sublessor.

         The term "Ground Sublessor" shall mean Amelang Partners, Inc.

1.27     Hazardous Materials.

         The term "Hazardous Materials" shall mean (a) any "hazardous waste" as
defined by the Resource Conservation and Recovery Act of 1976 (42 U.S.C. Section
6901 et seq.), as amended from time to time, and regulations promulgated
thereunder; (b) any "hazardous substance" as defined by the Comprehensive
Environmental Response, Compensation and Liability Act of 1980 (42 U.S.C.
Section 9601 et seq.), as amended from time to time, and regulations promulgated
thereunder; (c) asbestos; (d) polychlorinated biphenyls; (e) underground storage
tanks, whether empty, filled or partially filled with any substances (f) any
substance the presence of which on the Property is prohibited by any
Governmental Requirements; and (g) any other substance which by any
Governmental Requirements requires special handling or notification of any
federal, state or local governmental entity in its collection, storage,
treatment or disposal.

                                        6
<PAGE>   15

1.28     Hazardous Materials Contamination.

         The term "Hazardous Materials Contamination" shall mean the
contamination (whether presently existing or hereafter occurring) of the
Improvements, facilities, soil, groundwater, air or other elements on or of the
Property by Hazardous Materials, or the contamination of the buildings,
facilities, soil, groundwater, air or other elements on or of any other property
as a result of Hazardous Materials at any time (whether before or after the date
of this Loan Agreement) emanating from the Property. In no event will Borrower's
use and storage of Hazardous Materials in connection with its research and
business activities constitute "Hazardous Materials Contamination", provided
that such storage and use is in compliance with all applicable laws and
governmental regulations governing the use and storage of such materials.

1.29     Improvements.

         The term "Improvements" shall mean two buildings with exterior
elevations and appearances substantially in accordance with Exhibits "C" and "D"
of the Ground Sublease Agreement.

1.30     Inspecting Architects/Engineers.

         The term "Inspecting Architects/Engineers" shall mean such employees,
representatives and agents of Lender or third parties, who may, from time to
time, conduct inspections of the Property or offer other services related
thereto.

1.31     Insurance Policies.

         The term "Insurance Policies" shall mean:

         (a)   All-risk builder's risk insurance during the construction of the
               Improvements, in an amount equal to 100% of the replacement cost
               of the Improvements, providing all risk coverage on the
               Improvements and materials stored on the Property and elsewhere,
               and including the perils of collapse, damage resulting from error
               in design or faulty workmanship or materials, water damage and,
               if requested by Lender, flood, earthquake, business interruption
               and other risks;

         (b)   All-risk insurance after the completion of the construction of
               the Improvements, as determined by Lender, in the amount of at
               least 100% of the replacement cost of such Improvements or in
               such additional amounts as Lender may require, providing all-risk
               coverage on the Improvements, and, if requested by Lender, to
               include the perils of flood, earthquake, business interruption
               and other risks;

         (c)   Comprehensive General Liability Insurance for owners and
               contractors, including blanket contractual liability, products
               and completed operations, personal injury (including employees),
               independent contractors, explosion, collapse and underground
               hazards for not less than $5,000,000 arising out of any one
               occurrence or in any increased amount required by Lender;

         (d)   Comprehensive Automobile Liability Insurance for contractors for
               not less than $500,000 for bodily injury and $100,000 for
               property damage arising out of any one occurrence or in any
               increased amount required by Lender;

         (e)   Worker's Compensation Insurance for contractors for statutory
               limits; and

         (f)   Such other insurance as Lender may reasonably require.

                                        7
<PAGE>   16

         All insurance Policies shall be issued on forms and by companies
reasonably satisfactory to Lender and shall be delivered to Lender. All-risk
Insurance Policies shall have loss made payable to Lender as mortgagee together
with the standard mortgagee rider set forth on Exhibit "D" attached hereto.
Comprehensive General Liability, Comprehensive Automobile Liability and Worker's
Compensation coverages shall have a provision giving Lender thirty (30) days
prior notice of cancellation or material change of the coverage. However, should
any provision of the Ground Lease or the Ground Sublease require insurance in
addition to or in excess of what is required pursuant to this section, Borrower
shall maintain such additional insurance as may be required by the Ground Lease
or the Ground Sublease.

1.32     Lender.

         The term "Lender" shall mean Riverway Bank.

1.33     Loan.

         The term "Loan" shall mean the Loan by Lender to Borrower, in an amount
set forth in the first paragraph of this Loan Agreement, not to exceed, in the
aggregate, the payment of the costs of labor, materials, and services supplied
for the construction of the Improvements and all other expenses incident to the
acquisition and the construction of the Property, all as specified in the
Approved Budget.

1.34     Loan Finance Charge.

         The term "Loan Finance Charge" shall mean the sum of money set forth on
Exhibit "B" attached hereto and incorporated herein by reference, to be paid to
Lender on the date hereof.

1.35     Loan Instruments.

         The term "Loan Instruments" shall mean this Loan Agreement the
Mortgage, the Note, the Assignment of Landlord's Interest in Leases, the
Financing Statements and such other instruments evidencing, securing, or
pertaining to the Loan as shall, from time to time, be executed and delivered by
Borrower or any other party to Lender pursuant to this Loan Agreement,
including, without limitation, each Affidavit of Borrower, each Application for
Advance, and the Approved Budget.

1.36     Mortgage

         The term "Mortgage" shall mean the Mortgage, Deed of Trust, Trust Deed,
or Deed to Secure Debt securing the payment of the Note and the payment and
performance of all obligations specified in the Mortgage and this Loan
Agreement, and evidencing a valid and enforceable lien and direct assignment of
Borrower's subleasehold estate in the Property.

1.37     Note.

         The term "Note" shall mean the Note from Borrower to Lender dated of
even date herewith in the amount of and evidencing the Loan.

1.38     Plans.

         The term "Plans" shall mean the final working drawings and
specifications for the construction of the Improvements.

                                        8
<PAGE>   17

1.39     Property.

         The term "Property" shall mean Borrower's subleasehold interest in the
real property described in Exhibit "A" attached hereto and incorporated herein
by reference, together with the Improvements and all other property constituting
the "Mortgaged Property," as described in the Mortgage.

1.40     Survey.

         The term "Survey" shall mean a current certified survey of the
Property satisfying the requirements set forth on Exhibit "D" attached hereto
and/or a recorded plat or map of the Property, as required by Lender, which such
plat or map shall be approved and accepted by all Governmental Authorities
having jurisdiction of the Property.

1.41     Subordination, Attornment and Non-Disturbance Agreement.

         The term "Subordination, Attornment and Non-Disturbance Agreement"
shall mean that certain agreement by and between Aid Association for Lutherans,
a Wisconsin corporation ("Lutherans"), Ground Sublessee and Ground Sublessor,
in form and substance acceptable to Lender.

1.42     Title Company.

         The term "Title Company" shall mean Partners Title Company.

1.43     Title Insurance.

         The term "Title Insurance" shall mean a title insurance policy, in the
amount of the Loan, insuring that the Mortgage constitutes a valid lien covering
the Property having the priority required by Lender and subject only to those
exceptions and encumbrances which Lender may approve, issued by the Title
Company.

                        ARTICLE 2 - ADVANCES OF THE LOAN

2.1      Commitment of Lender.

         Subject to the conditions hereof, and provided that an Event of Default
has not occurred (after notice and expiration of Borrower's opportunity to
cure), Lender will make Advances to Borrower in accordance with this Loan
Agreement.

2.2      Interest on the Loan.

         Interest on the Loan, at the rate or rates specified in the Note, shall
be computed on the unpaid principal balance which exists from time to time and
shall be computed with respect to each Advance only from the date of such
Advance (as to the portion of each Advance not constituting a portion of
Borrower's Deposit).

2.3      Advances.

         Advances for the payment of costs of labor, materials, and services
supplied for the construction of the Improvements and the other items shown in
the Approved Budget shall be made by Lender, not more frequently than monthly,
upon compliance by Borrower with this Loan Agreement, after actual commencement
of construction of the Improvements, for work actually done during the preceding
period. From time to time, Borrower shall submit an Application for Advance to
Lender requesting an Advance for the payment of costs of labor, materials, and
services supplied for the construction of the Improvements or for the payment of
other costs and expenses incident to the Loan, the acquisition of the Property,
or the construction of the Improvements, and specified in the Approved Budget.
Lender may require an inspection of and favorable report on the Improvements by
the Inspecting Architects/Engineers prior

                                       9
<PAGE>   18

to making any Advance. Each Advance for Payment of costs of construction of the
Improvements and the other items shown in the Approved Budget shall be limited
to the amounts shown in the Approved Budget and not exceed the aggregate of (a)
the costs of labor, materials, and services incorporated into the Improvements
in a manner reasonably acceptable to Lender, plus (b) if approved by Lender, the
purchase price of all uninstalled materials to be utilized in the construction
of the Improvements, title to which has passed to Borrower, stored on the
Property or elsewhere with the written consent of, and in a manner acceptable
to, Lender, less (c) twenty percent (20%) of the sum of the aforesaid items (a)
and (b), less (d) retainage, if any, and less (e) all prior Advances for payment
of costs of labor, materials, and services for the construction of the
Improvements. Prior to each Advance, Borrower must contribute 20% of the amount
of such request with the results being that 80% of all items in the Approved
Budget are advanced by Lender and 20% contributed simultaneously by Borrower.
Each Application for Advance shall be submitted by Borrower to Lender a
reasonable time (but not less than 5 days) prior to the date on which an Advance
is desired by Borrower. The final Advance, including all retainage, will not be
made until the Lender has received the following: (1) a completion certificate
from the Inspecting Architects/Engineers, if any, (2) evidence that all
Governmental Requirements have been satisfied, including, but not limited to,
delivery to Lender of Certificates of Occupancy permitting the Improvements to
be legally occupied, (3) evidence that no mechanic's or materialmen's liens or
other encumbrances have been filed and remain in effect against the Property,
and (4) final lien releases or waivers by Architect, Contractor, and all
subcontractors, materialmen, and other parties who have supplied labor,
materials, or services for the construction of the Improvements, or who
otherwise might be entitled to claim a contractual, statutory, or constitutional
lien against the Property, and (5) if available under local rules, the Title
Insurance shall be endorsed and extended to acknowledge completion of
construction of the Improvements without any encroachment and in compliance with
all applicable matters of public record and Governmental Requirements, with no
additional exception objectionable to Lender. In addition, the Final Advance
hereunder shall, at Lender's option, be withheld until thirty (30) days after
(i) the "completion" (as that term is defined in Section 53.106 of the Texas
Property Code) of the Improvements and (ii) an affidavit of completion has been
filed with the county clerk of the county in which the Property is located in
compliance with Section 53.106 of the Texas Property Code.

2.4      Conditions to the First Advance.

         As a condition precedent to the first Advance hereunder, Borrower must
(i) satisfy the conditions required hereby, (ii) execute and deliver to, procure
for and deposit with, and pay to Lender and, if appropriate, record in the
proper records with all filing and recording fees paid the documents,
certificates, and other items that are described in Exhibit "B" attached hereto
and incorporated herein by reference, together with such other documents,
instruments, and certificates as Lender may reasonably require, and (iii)
deliver to Lender an irrevocable unconditional straight letter of credit in the
face amount of $1,734,582 in favor of Lender, issued by a bank acceptable to
Lender in its sole discretion, with an expiration date of not earlier than 390
days from date hereof. Such credit and any replacements thereof is herein called
the "Letter of Credit". If not therefore drawn, the Letter of Credit shall be
returned to Borrower at the time the Note is fully advanced provided there is
then no Event of Default. Lender may draw on the Letter of Credit at any time an
Event of Default exists. The Letter of Credit may be replaced by Borrower from
time to time with a new irrevocable unconditional straight letter of credit in
favor of Lender issued by a bank acceptable to Lender in its sole discretion in
the face amount of $1,734,582, less equity contributions made by Borrower as
contemplated by Section 2.3. As a condition precedent to the first Advance for
labor, materials, or construction services (whether or not it is the first
Advance), Borrower and each original contractor shall have jointly executed and
recorded with the county clerk Of the county in which the Property is situated
an affidavit of commencement of work, in form and substance approved by Lender,
which contains the information required by Section 53.124(c) of the Texas
Property Code, provided further that the date of commencement of work specified
in such affidavit shall be subsequent to the date of recordation of the
Mortgage. Such affidavit shall be executed and recorded after the date the work
actually commenced, but not later than the 10th day thereafter.

                                       10
<PAGE>   19
2.5      Conditions to Subsequent Advances.

         As a condition precedent to each Advance other than the first Advance,
in addition to all other requirements herein, Borrower must satisfy the
following requirements and, if required by Lender, deliver to Lender evidence of
such satisfaction:

         (a)   All conditions precedent to the first Advance shall have been
               satisfied;

         (b)   There shall then exist no Event of Default (after giving notice
               by Lender and expiration of Borrower's opportunity to cure);

         (c)   A foundation survey, if required by Lender, shall have been
               furnished to Lender within ten (10) days after laying of the
               foundation of the Improvements, showing no encroachment of the
               Improvements on any boundary line, easement, building setback
               line, or other restricted area;

         (d)   The representations and warranties made in this Loan Agreement
               shall be true and correct on and as of the date of each Advance
               with the same effect as if made on that date;

         (e)   Borrower will procure and deliver to Lender, if required by
               Lender, releases or waivers of mechanic's liens and receipted
               bills showing payment of all parties who have furnished materials
               or services or performed labor of any kind in connection with the
               construction of any of the Improvements; and

         (f)   The Title Insurance shall be endorsed and extended, if available
               under the local rules, to cover each Advance with no additional
               title exceptions objectionable to Lender.

2.6      Reallocation of Approved Budget.

         Lender reserves the right to make Advances which are allocated to any
of the designated items in the Approved Budget for such other purposes or in
such different proportions as Lender may, in its sole discretion, deem necessary
or advisable. Borrower may not reallocate items of cost or change the Approved
Budget without the prior written consent of Lender.

2.7      No Waiver.

         No Advance shall constitute a waiver of any condition precedent to the
obligation of Lender to make any further Advance or preclude Lender from
thereafter declaring the failure of Borrower to satisfy such condition precedent
to be an Event of Default.

2.8      Conditions Precedent for the Benefit of Lender.

         All conditions precedent to the obligation of Lender to make any
Advance are imposed hereby solely for the benefit of Lender, and no other party
may require satisfaction of any such condition precedent or be entitled to
assume that Lender will refuse to make any Advance in the absence of strict
compliance with such conditions precedent. All requirements of this Loan
Agreement may be waived by Lender, in whole or in part, at any time.

2.9      Subordination.

         Lender shall not be obligated to make, nor shall Borrower be entitled
to, any Advance until such time as Lender shall have received, to the extent
requested by Lender, subordination agreements from Architect, Contractor, and
all

                                       11

<PAGE>   20

other persons furnishing labor, materials, or services for the design or
construction of the Improvements, subordinating to the lien of the Mortgage any
lien, claim, or charge they may have against Borrower or the Property.

             ARTICLE 3 - REPRESENTATIONS AND WARRANTIES OF BORROWER

3.1      Financial Statements.

         The Financial Statements are true, correct, and complete as of the
dates specified therein and fully and accurately present the financial condition
of Borrower as of the dates specified. No material adverse change has occurred
in the financial condition of Borrower since the dates of the Financial
Statements.

3.2      Suits, Actions, Etc.

         There are no material actions, suits, or proceedings pending or, to the
knowledge of Borrower, threatened, in any court or before or by any Governmental
Authority against or affecting Borrower or the Property, or involving the
validity, enforceability, or priority of any of the other Loan Instruments, at
law or in equity. The consummation of the transactions contemplated hereby, and
the performance of any of the terms and conditions hereof and of the other Loan
Instruments, will not result in a breach of, or constitute a default in, any
mortgage, deed of trust, lease, promissory note, loan agreement, credit
agreement, partnership agreement, or other agreement to which Borrower is a
party or by which Borrower may be bound or affected. Borrower is not in default
of any order of any court or any requirement of any Governmental Authority.

3.3      Valid and Binding Obligation.

         All of the Loan Instruments, and all other documents referred to herein
to which Borrower is a party, upon execution and delivery will constitute valid
and binding obligations of Borrower, enforceable in accordance with their terms
except as limited by Debtor Relief Laws.

3.4      Title to the Property.

         Borrower holds full leasehold title to the Property, subject only to
title exceptions set forth in the Title Insurance.

3.5      Commencement of Construction.

         Prior to the recordation of the Mortgage, no work of any kind
(including the destruction or removal of any existing improvements, site work,
clearing, grading, grubbing, draining, or fencing of the Property) shall have
commenced or shall have been performed on the Property, no equipment or material
shall have been delivered to or upon the Property for any purpose whatsoever.
Further, no affidavit of commencement showing a commencement date prior to the
recordation of the Mortgage shall be filed in the records of the County in which
the Property is located.

3.6      Disclosure.

         To the best of Borrower's knowledge, there is no fact that Borrower has
not disclosed to Lender in writing that could materially adversely affect the
property, business or financial condition of Borrower or the Property.

3.7      Compliance with Environmental Requirements; No Hazardous Materials.

         (a)   To the best of Borrower's knowledge, except as otherwise provided
               herein, no Hazardous Materials are located on the Property or
               have been released into the environment, or

                                       12
<PAGE>   21

               deposited, discharged, placed or disposed of at, on, under or
               near the Property. To the best of Borrower's knowledge, except as
               otherwise provided herein, no portion of the Property is being
               used or, to the knowledge of Borrower, has been used at any
               previous time for the disposal, storage, treatment, processing or
               other handling of Hazardous Materials nor is the Property
               affected by any Hazardous Materials Contamination.

         (b)   To the best of Borrower's knowledge, no polychlorinated biphenyls
               are located on or in the Property, in the form of electrical
               transformers, fluorescent light fixtures with ballasts, cooling
               oils, or any other device or form.

         (c)   To the best of Borrower's knowledge, no investigation,
               administrative order, consent order and agreement, litigation or
               settlement with respect to Hazardous Materials or Hazardous
               Materials Contamination is proposed, threatened, anticipated or
               in existence with respect to the Property. To the best of
               Borrower's knowledge, the Property and its existing and prior
               uses comply and at all times have complied with any applicable
               Governmental Requirements relating to environmental matters or
               Hazardous Materials. To the best of Borrower's knowledge, there
               is no condition on the Property which is in violation of any
               applicable Governmental Requirements relating to Hazardous
               Materials, and Borrower has received no communication from or on
               behalf of any Governmental Authority that any such condition
               exists. The Property is not currently on and, to Borrower's
               knowledge after diligent investigation and inquiry, has never
               been on any federal or state "Superfund" or "Superlien" list.

         (d)   All representations and warranties contained in this Section
               shall survive the consummation of the transactions contemplated
               in this Loan Agreement.

         Any other provision of this Loan Agreement or the Loan Instruments
notwithstanding, Borrower's lawful use and storage of Hazardous Materials in
connection with its research and business activities at the Property shall not
constitute a default under any of the Loan Instruments.

3.8      System Compliance.

         The storm and sanitary sewer system, water system, all mechanical
systems of the Property and other parts of the Improvements do (or when
constructed will) comply with all applicable environmental, pollution control
and ecological laws, ordinances, rules and regulations, and all Governmental
Authorities having jurisdiction of the Property have or will have issued all
necessary permits, licenses or other authorizations for the construction,
occupancy, operation, and use of the Improvements (specifically including the
named systems).

3.9      Submittals.

         The Loan Instruments and all Financial Statements, Plans, budgets,
schedules, opinions, certificates, confirmations, Contractor's statements,
applications, rent rolls, affidavits, agreements, Construction Contract,
Architectural Contract and other materials submitted to the Lender in connection
with or in furtherance of the Loan Instruments by or on behalf of the Borrower
fully and fairly state the matters with which they purport to deal, and do not
misstate any material fact.

3.10     Utility Availability.

         Subject only to payment of fees to be paid from the Approved Budget,
all utility and municipal services required for the construction, occupancy and
operation of the Improvements, including, but not limited to, water supply,
storm and sanitary sewer systems, gas, electric and telephone facilities, are or
will be available for use and tap-on at the boundaries of the Property and will
be available in sufficient amounts for the normal and intended use of the

                                       13
<PAGE>   22

Improvements, and written permission has been or will be obtained from
the applicable utility companies or municipalities to connect the Improvements
into each of said services.

3.11     Inducement to Lender.

         The representations and warranties contained in the Loan Instruments
are made by Borrower as an inducement to Lender to make the Loan and Borrower
understands that Lender is relying on such representations and warranties and
that such representations and warranties shall survive any (a) bankruptcy
proceedings involving Borrower or the Property, or (b) foreclosure of the
Mortgage or (c) conveyance of title to the Property in lieu of foreclosure of
the Mortgage. Acceptance of each Advance constitutes reaffirmation, as of the
date of such acceptance, of the representations and warranties of Borrower in
the Loan Instruments, on which Lender shall rely in making such Advance.

3.12     Year 2000.

         Borrower represents and warrants to Lender the following:

         a.    all software, hardware and critical systems used by Borrower and
               its subsidiaries, if any, in the conduct of Borrower's and such
               subsidiaries' business ("Borrower's Computer Items") will record,
               store, process and present calendar dates falling on or after
               January 1, 2000, and all information pertaining to such dates
               correctly;

         b.    Borrower's Computer Items will have all appropriate capability
               and compatibility for handling century-aware or year 2000
               compliant data; and

         c.    the data related user interface functions, data fields and data
               related program instructions and functions of Borrower's Computer
               Items will include the indication of the century.

                ARTICLE 4 - COVENANTS AND AGREEMENTS OF BORROWER

         Borrower hereby covenants and agrees as follows:

4.1      Compliance With Governmental Requirements.

         Borrower shall timely comply with all Governmental Requirements and
deliver to Lender evidence thereof. Borrower assumes full responsibility for the
compliance of the Plans and the Property with all Governmental Requirements and
with sound building and engineering practices, and, notwithstanding any
approvals by Lender, Lender shall have no obligation or responsibility
whatsoever for the Plans or any other matter incident to the Property or the
construction of the Improvements. Immediately upon Borrower's receipt of any
notice from a Governmental Authority of noncompliance with any Governmental
Requirements, Borrower shall provide Lender with written notice thereof.

4.2      Construction Contract.

         Borrower shall become party to no contract, including the Construction
Contract, for the performance of any work on the Property or for the supplying
of any labor, materials, or services for the construction of the Improvements
except upon such terms and with such parties as shall be approved in writing by
Lender. The Construction Contract shall provide that all liens of the Contractor
are subordinate to the Mortgage and that the Contractor waives any right to
remove removable improvements and shall require all subcontracts and purchase
orders to contain a provision subordinating the subcontractors' and
materialmen's liens to the Mortgage and waiving any right to remove removable
improvements. The Construction Contract shall also provide that no change order
of a material amount shall be effective

                                       14
<PAGE>   23

without the prior written approval of Lender. No approval by Lender of any
Construction Contract or change order shall make Lender responsible for the
adequacy, form, or content of such Construction Contract or change order.

4.3      Construction of the Improvements.

         Borrower shall commence construction of the Improvements within thirty
(30) days from the date hereof, and the construction of the Improvements shall
be prosecuted with diligence and continuity, in a good and workmanlike manner,
and in accordance with sound building and engineering practices, all applicable
Governmental Requirements, the Plans and the requirements of any lessee, if
applicable. Borrower shall not permit cessation of work for a period in excess
of 15 days without the prior written consent of Lender and shall complete
construction of the Improvements on or before the Completion Date (unless such
cessation or failure to timely complete the Improvements is due to weather,
shortages or unavailability of labor or materials, non-performance by the
Contractor, or Architect, or other causes beyond Borrower's control), free and
clear of all liens (except those as to which Borrower has furnished a bond or
other security acceptable to Lender and otherwise complied with the requirements
of Section 4.22).

4.4      Correction of Defects.

         Borrower shall correct or cause to be corrected (a) any material defect
in the Improvements, (b) any material departure in the construction of the
Improvements from the Plans, Governmental Requirements, or the requirements of
any lessee, if applicable, or (c) any encroachment by any part of the
Improvements, or any structure located on the Property, on any easement,
property line, or restricted area, or any encroachment by any such structure on
any building line.

4.5      Storage of Materials.

         Borrower shall cause all materials supplied for, or intended to be
utilized in, the construction of the Improvements, but not affixed to or
incorporated into the Improvements or the Property, to be stored on the Property
or at such other location as may be approved by Lender in writing, with adequate
safeguards, as required by Lender, to prevent loss, theft, damage, or
commingling with other materials or projects.

4.6      Inspection of the Property.

         Borrower shall permit Lender, any Governmental Authority, and their
agents and representatives, to enter upon the Property and any location where
materials intended to be utilized in the construction of the Improvements are
stored, for the purpose of inspection of the Property and such materials at all
reasonable times.

4.7      Notices by Governmental Authority, Casualty, Condemnation.

         Borrower shall timely comply with and promptly furnish to Lender true
and complete copies of any notice or claim by any Governmental Authority
pertaining to the Property. Borrower shall promptly notify Lender of any fire or
other casualty or any notice of taking or eminent domain action or proceeding
affecting the Property, or the threat of any such action or proceeding of which
Borrower becomes aware.

4.8      Special Account.

         Borrower shall maintain a special account with Lender, into which all
Advances (but no other funds), and excluding direct disbursements made by Lender
pursuant to Section 4.11 hereof, shall be deposited by Borrower, and against
which checks shall be drawn only for the payment of (a) costs of labor,
materials, and services supplied for the construction of the Improvements
specified in the Approved Budget, and (b) other costs and expenses incident to
the Loan, the Property, and the construction of the Improvements specified in
the Approved Budget. Such account will be a custodial account segregated from
all other funds of Lender. Lender will hold such funds as a fiduciary for the
benefit of Borrower. Borrower shall have the right to direct investments of such
funds.

                                       15
<PAGE>   24

4.9      Application of Advances.

         Borrower shall disburse all Advances for payment of costs and expenses
specified in the Approved Budget, and for no other purpose.

4.10     Borrower's Deposit.

         If Lender reasonably determines at any time that the sum of the
unadvanced portion of the Loan, and the amount of the Borrower's equity
contribution specified in Section 2.4 (or letter of credit), will be
insufficient for payment in full of (a) costs of labor, materials, and services
required for the construction of the Improvements, (b) other costs and expenses
specified in the Approved Budget, and (c) other costs and expenses required to
be paid in connection with the construction of the Improvements in accordance
with the Plans, any Governmental Requirements or the requirements of any lessee,
if applicable, then Borrower shall, on request of Lender, make the Borrower's
Deposit with Lender. Lender shall hold the Borrower's Deposit in a custodial
account segregated from all other funds of Lender. Lender shall hold such funds
as a fiduciary for the benefit of Borrower. Borrower shall have the right to
direct investments of such account. Lender may advance all or a portion of the
Borrower's Deposit prior to any portion of the Loan proceeds. Borrower shall
promptly notify Lender in writing if and when the cost of the construction of
the Improvements exceeds, or appears likely to exceed, the amount of the
unadvanced portion of the Loan and the unadvanced portion of the Borrower's
Deposit. The above notwithstanding, no Borrower's deposit will be required
before Lender has made the first Advanced Funds under the Loan.

4.11     Direct Disbursement and Application by Lender.

         Lender shall have the right, but not the obligation, to disburse and
directly apply the proceeds of any Advance to the satisfaction of any of
Borrower's obligations hereunder or under any of the other Loan Instruments,
including, without limitation, payments to the Ground Sublessee to cure default
or potential default under the Ground Sublease. Any Advance by Lender for such
purpose, except Borrower's Deposit, shall be part of the Loan and shall be
secured by the Loan Instruments. Borrower hereby authorizes Lender to hold, use,
disburse, and apply the Loan and the Borrower's Deposit for payment of costs of
construction of the Improvements, expenses incident to the Loan and the
Property, and the payment or performance of any obligation of Borrower hereunder
or under any of the other Loan Instruments. Borrower hereby assigns and pledges
the proceeds of the Loan and the Borrower's Deposit to Lender for such purposes.
Lender may advance and incur such expenses as Lender deems necessary for the
completion of construction of the Improvements and to preserve the Property and
any other security for the Loan, and such expenses, even though in excess of the
amount of the Loan, shall be secured by the Loan Instruments and payable to
Lender. Lender may disburse any portion of any Advance at any time, and from
time to time, to persons other than Borrower for the purposes specified in this
Section 4.11 irrespective of the provisions of Section 2.3 hereof, and the
amount of Advances to which Borrower shall thereafter be entitled shall be
correspondingly reduced.

4.12     Costs and Expenses.

         Borrower shall pay when due all costs and expenses required by this
Loan Agreement, including, without limitation, (a) all taxes and assessments
applicable to the Property, (b) all fees for filing or recording the Loan
Instruments, (c) all fees and commissions lawfully due to brokers, salesmen, and
agents in connection with the Loan or the Property, (d) all fees and expenses of
counsel to Lender, (e) all title insurance and title examination charges,
including premiums for the Title Insurance, (f) all survey costs and expenses,
including the cost of the Survey, (g) all premiums for the Insurance Policies,
and (h) all other costs and expenses payable to third parties incurred by Lender
in connection with the consummation of the transactions contemplated by this
Loan Agreement. Lender has not engaged and is not obligated to pay any brokerage
commissions or finder's fee in connection with the Loan.

                                       16
<PAGE>   25

4.13     Additional Documents.

         Borrower shall execute and deliver to Lender, from time to time as
requested by Lender, such other documents as shall reasonably be necessary to
provide the rights and remedies to Lender granted or provided for by the Loan
Instruments.

4.14     Inspection of Books and Records.

         Borrower shall permit Lender, at all reasonable times, to examine and
copy the books and records of Borrower pertaining to the Loan and the Property,
and all contracts, statements, invoices, bills, and claims for labor, materials,
and services supplied for the construction of the Improvements.

4.15     No Liability of Lender.

         Lender shall have no liability, obligation, or responsibility
whatsoever with respect to the construction of the Improvements except to
advance the Loan and the Borrower's Deposit pursuant to this Loan Agreement.
Lender shall not be obligated to inspect the Property or the construction of the
Improvements, nor be liable or responsible for any defect in the Property or the
Improvements by reason of inspecting same, nor be liable for the performance or
default of Borrower, Architect, the Inspecting Architects/Engineers, Contractor,
or any other party, or for any failure to construct, complete, protect, or
insure the Improvements, or for the payment of costs of labor, materials, or
services supplied for the construction of the Improvements, or for the
performance of any obligation of Borrower whatsoever. Nothing, including without
limitation any Advance or acceptance of any document or instrument, shall be
construed as a representation or warranty, express or implied, to any party by
Lender.

4.16     No Conditional Sale Contracts, Etc.

         No materials, equipment, or fixtures shall be supplied, purchased, or
installed for the construction or operation of the Improvements or the Mortgaged
Property (as defined in the Mortgage) pursuant to security agreements,
conditional sale contracts, lease agreements, or other arrangements or
understandings whereby a security interest or title is retained by any party or
the right is reserved or accrues to any party to remove or repossess any of the
Improvements or the Mortgaged Property (as defined in the Mortgage).

4.17     Defense of Actions.

         Lender may (but shall not be obligated to) commence, appear in, or
defend any action or proceeding purporting to affect the Loan, the Property, or
the respective rights and obligations of Lender and Borrower pursuant to this
loan Agreement. Lender may (but shall not be obligated to) pay all necessary
expenses, including attorneys' fees and expenses incurred in connection with
such proceedings or actions, which Borrower agrees to repay to Lender on demand.

4.18     Assignment of Construction Contract.

         As additional security for the payment of the Loan, Borrower hereby
transfers and assigns to Lender all of Borrower's rights and interest, but not
its obligations, in, under, and to the Construction Contract, upon the following
terms and conditions:

         (a)   Borrower represents and warrants that the copy of any
               Construction Contract it has furnished to Lender is a true and
               complete copy thereof and that Borrower's interest therein is not
               subject to any claim, set off, or encumbrance.

         (b)   Neither this assignment nor any action by Lender shall constitute
               an assumption by Lender of any obligation under the Construction
               Contract, and Borrower shall continue to be liable

                                       17
<PAGE>   26
               for all obligations of Borrower thereunder, Borrower hereby
               agreeing to perform all of its obligations under the Construction
               Contract. Borrower indemnifies and holds Lender harmless against
               and from any loss, cost, liability, or expense (including, but
               not limited to, attorneys' fees and expenses) resulting from any
               failure of Borrower to so perform.

         (c)   Lender shall have the right at any time, after giving notice of
               default and expiration of Borrower's right to cure the default
               (but shall have no obligation), to take in its name or in the
               name of Borrower such action as Lender may at any time determine
               to be necessary or advisable to cure any default under the
               Construction Contract or to protect the rights of Borrower or
               Lender thereunder. Lender shall incur no liability if any action
               so taken by it or in its behalf shall prove to be inadequate or
               invalid, and Borrower agrees to hold Lender free and harmless
               against and from any loss, cost, liability or expense (including,
               but not limited to, attorneys' fees and expenses) incurred in
               connection with any such action.

         (d)   Borrower hereby irrevocably constitutes and appoints Lender as
               Borrower's attorney-in-fact, in Borrower's name or in Lender's
               name, to enforce all rights of Borrower under the Construction
               Contract.

         (e)   Prior to an Event of Default, Borrower shall have the right to
               exercise its rights as Owner under the Construction Contract,
               provided that Borrower shall not cancel or amend the Construction
               Contract or do or suffer to be done any act which would impair
               the security constituted by this assignment without the prior
               written consent of Lender.

         (f)   This assignment shall inure to the benefit of Lender, its
               successors and assigns, including any purchaser upon foreclosure
               of the Mortgage, any receiver in possession of the Property, and
               any corporation formed by or on behalf of Lender which assumes
               Lender's rights and obligations under this Loan Agreement.

4.19     Assignment of Plans.

         As additional security for the payment of the Loan, Borrower hereby
transfers and assigns to Lender all of Borrower's right, title, and interest in
and to the Architectural Contract and Plans and hereby represents and warrants
to and agrees with Lender as follows:

         (a)   The schedule of the Plans delivered to Lender is a complete and
               accurate description of the Plans.

         (b)   The Plans are complete and adequate for the construction of the
               Improvements and there have been no modifications thereof except
               as described in such schedule. The Plans shall not be modified
               without the prior written consent of Lender.

         (c)   Lender may use the Plans for any purpose relating to the
               Improvements, including but not limited to inspections of
               construction and the completion of the Improvements.

         (d)   Lender's acceptance of this assignment shall not constitute
               approval of the Plans by Lender. Lender has no liability or
               obligation whatsoever in connection with the Plans and no
               responsibility for the adequacy thereof or for the construction
               of the Improvements contemplated by the Plans. Lender has no duty
               to inspect the Improvements, and, if Lender should inspect the
               Improvements, Lender shall have no liability or obligation to
               Borrower arising out of such inspection. No such inspection nor
               any failure by Lender to make objections after any such
               inspection shall constitute a representation by Lender that the

                                       18
<PAGE>   27

               Improvements are in accordance with the Plans or constitute a
               waiver of Lender's right thereafter to insist that the
               Improvements be constructed in accordance with the Plans.

         (e)   This assignment shall inure to the benefit of Lender, its
               successors and assigns, including any purchaser upon foreclosure
               of the Mortgage, any receiver in possession of the Property, and
               any corporation formed by or on behalf of Lender which assumes
               Lender's rights and obligations under this Loan Agreement.

4.20     Prohibition on Assignment of Borrower's Interest.

         Borrower shall not assign or encumber any interest of Borrower
hereunder without the prior written consent of Lender.

4.21     Payment of Claims.

         Borrower shall promptly pay or cause to be paid when due all costs and
expenses incurred in connection with the Property and the construction of the
Improvements, and Borrower shall keep the Property free and clear of any lien,
charge, or claim other than the encumbrances of the Mortgage and other liens
approved in writing by Lender. Notwithstanding anything to the contrary
contained in this Loan Agreement, Borrower (a) may contest the validity or
amount of any claim of any contractor, consultant, architect, or other person
providing labor, materials, or services with respect to the Property, (b) may
contest any tax or special assessments levied by any Governmental Authority, and
(c) may contest the enforcement of or compliance with any Governmental
Requirements, and such contest on the part of Borrower shall not be a default
hereunder and shall not release Lender from its obligations to make Advances
hereunder; provided, however, that during the pendency of any such contest
Borrower shall furnish to Lender and Title Company an indemnity bond with
corporate surety satisfactory to Lender and Title Company or other security
reasonably acceptable to them in an amount equal to the amount being contested
plus a reasonable additional sum to cover possible costs, interest, and
penalties, and provided further that Borrower shall pay any amount adjudged by a
court of competent jurisdiction to be due, with all costs, interest, and
penalties thereon, before such judgment becomes a lien on the Property.

4.22     Restrictions and Annexation.

         Borrower shall not impose any restrictive covenants, easements or other
encumbrances upon the Property, execute or file any subdivision plat affecting
the Property, or consent to the annexation of the Property to any city without
the prior written consent of Lender.

4.23     Advertising by Lender.

         Borrower agrees that, during the term of the Loan, Lender may erect and
maintain on the Property one or more reasonable and typical advertising signs
indicating that the construction financing for the Property has been provided by
Lender; provided that such signs are not objectionable to the Ground Lessor or
the Ground Sublessor.

4.24     Current Financial Statements.

         Borrower shall, (1) on or before the forty-fifth (45th) day after the
end of each calendar quarter after completion of the Improvements, deliver to
Lender current financial statements itemizing the income and expenses of the
Property for the immediately preceding quarter, (2) on or before the ninetieth
(90th) day after the end of each fiscal year, deliver or cause to be delivered
to Lender then current Financial Statements of Borrower, and (3) from time to
time, as Lender may reasonably request, deliver to Lender additional Financial
Statements of Borrower.

                                       19
<PAGE>   28

4.25     Tax Receipts.

         Subject to the provisions of Section 4.22 hereof, Borrower shall
furnish Lender with receipts or tax statements marked "Paid" to evidence the
payment of all taxes levied on the Property on or before 30 days prior to the
date such taxes become delinquent.

4.26     Loan Participations.

         Borrower acknowledges and agrees that Lender may, from time to time,
sell or offer for sale participation interests in the Loan and the Loan
Instruments to one or more participants. Borrower authorizes Lender to
disseminate any information it has pertaining to the Loan, including, without
limitation, complete and current credit information of Borrower or any of its
principals to any participant or prospective participant in the Loan.

4.27     Notice of Litigation, Claims, and Financial Change.

         Borrower shall promptly inform Lender of (a) any litigation against
Borrower or affecting the Property, which, if determined adversely, might have a
material adverse effect upon the financial condition of Borrower or upon the
Property, or might cause an Event of Default, (b) any claim or controversy which
might become the subject of such litigation, and (c) any material adverse change
in the financial condition of Borrower. For purposes hereof, a material adverse
change shall be deemed to have occurred when (1) there has been a decline of
fifteen percent (15%) or more in the tangible net worth of Borrower as shown
on the Financial Statements delivered to Lender in connection with the Loan or
(2) actual sources and uses of funds for any twelve-month period adversely vary
by fifteen percent (15%) or more with the pro forma sources and uses of funds
statement submitted for such period.

4.28     No Occupancy Contrary to Builder's Risk Policy.

         The Improvements shall not be occupied until Borrower has obtained and
furnished to Lender a "permission to occupy" endorsement to the builder's risk
insurance policy, which endorsement is satisfactory to Lender, or Borrower has
obtained replacement coverage in the form of an all-risk insurance policy upon
the completed Improvements, which policy will not be impaired by the occupancy
of the Improvements and is satisfactory to Lender.

4.29     Hold Harmless.

         Borrower shall defend, at its own cost and expense, and hold Lender
harmless from, any proceeding or claim in any way relating to the Property or
the Loan Instruments. All costs and expenses incurred by Lender in protecting
its interests hereunder, including all court costs and attorneys' fees and
expenses, shall be borne by Borrower. The provisions of this Section shall
survive the payment in full of the Loan and all other indebtedness secured by
the Mortgage and the release of the Mortgage as to events occurring and causes
of action arising before such payment and release.

4.30     Hazardous Materials; Indemnification.

         (a)   Borrower agrees to (i) give notice to Lender immediately upon
               Borrower's acquiring knowledge of any Hazardous Materials
               Contamination with a full description thereof; (ii) promptly, at
               Borrower's sole cost and expense, comply with any Governmental
               Requirements requiring the use, storage, removal, treatment or
               disposal of such Hazardous Materials or Hazardous Materials
               Contamination and provide Lender with satisfactory evidence of
               such compliance; and (iii) provide the Lender, within thirty (30)
               days after demand by Lender, with a bond, letter of credit or
               similar financial assurance evidencing to Lender's satisfaction
               that the necessary funds are available to pay the cost of
               removing, treating and disposing of any Hazardous Materials
               Contamination and discharging any assessments which may be
               established on the Property as a result thereof.

                                       20
<PAGE>   29

         (b)   Borrower shall not cause or suffer any liens to be recorded
               against the Property as a consequence of, or in any way related
               to, the presence, remediation or disposal of Hazardous Material
               in or about the Property, including any state, federal or local
               so-called "Superfund" lien relating to such matters.

         (c)   Borrower shall at all times retain any and all liabilities
               arising from the presence, handling, treatment, storage,
               transportation, removal or disposal of Hazardous Materials on the
               Property. Regardless of whether any Event of Default shall have
               occurred and be continuing or any remedies in respect of the
               Property are exercised by Lender, Borrower shall defend,
               indemnify and hold harmless Lender from and against any and all
               liabilities (including strict liability), suits, actions, claims,
               demands, penalties, damages (including, without limitation, lost
               profits, consequential damages, interest, penalties, fines and
               monetary sanctions), losses, costs or expenses (including,
               without limitation, attorneys' fees and expenses, and remedial
               costs) (the foregoing are hereinafter collectively referred to as
               "Liabilities") which may now or in the future (whether before or
               after the culmination of the transactions contemplated by this
               Loan Agreement) incurred or suffered by Lender by reason of,
               resulting from, in connection with, or arising in any manner
               whatsoever out of the breach of any warranty or covenant or the
               inaccuracy of any representation of Borrower contained or
               referred to in this Section or Section 3.7 of this Loan Agreement
               or which may be asserted as a direct or indirect result of the
               presence on or under, or escape, seepage, leakage, spillage,
               discharge, emission, or release from the Property of any
               Hazardous Materials or any Hazardous Materials Contamination or
               arise out of or result from the environmental condition of the
               Property or the applicability of any Governmental Requirements
               relating to Hazardous Materials, whether or not occasioned wholly
               or in part by any condition, accident or event caused by any act
               or omission of Lender.

               Such Liabilities shall include, without limitation; (i) injury or
               death to any person; (ii) damage to or loss of the use of any
               property; (iii) the cost of any demolition and rebuilding of the
               Improvements, repair or remediation and the preparation of any
               activity required by any Governmental Authority; (iv) any lawsuit
               brought or threatened, good faith settlement reached, or
               governmental order relating to the presence, disposal, release or
               threatened release of any Hazardous Material on, from or under
               the Property; and (v) the imposition of any lien on the Property
               arising from the activity of Borrower or Borrower's predecessors
               in interest on the Property or from the existence of Hazardous
               Materials or Hazardous Materials Contamination upon the Property.

               The covenants and agreements contained in this Section shall
               survive the consummation of the transactions contemplated by this
               Loan Agreement.

         Notwithstanding anything contained in this Loan Agreement, the Note,
the Mortgage or in any of the Loan Instruments, the Borrower shall not be
released of corporate liability and shall have corporate liability for any and
all of Lender's costs, expenses, damages or liabilities (including, without
limitation, all reasonable attorneys' fees, whether incurred by Lender prior to
or following foreclosure of the Mortgage and whether Lender shall be in the
status of a lienholder or an owner of the Property following foreclosure)
directly or indirectly arising out of or attributable to the use, generation,
manufacture, storage, release, threatened release, discharge, disposal, or
presence on, under, to, from or about the Property of any Hazardous Materials.

4.31     Disclaimer of Loan Extension.

         Borrower acknowledges and agrees that Lender has not made any
commitments, either express or implied, to extend the term of the Loan past its
stated maturity date.

                                       21
<PAGE>   30
4.32     Evidence of Year 2000 Compliance.

         Within thirty (30) days of any request therefor by Lender, Borrower
will deliver to Lender a statement from a person reasonably acceptable to Lender
to the effect that Borrower's Computer Items comply with the representations
contained in Section 3.12 hereof.

                   ARTICLE 5 - RIGHTS AND REMEDIES OF LENDER

5.1      Rights of Lender.

         Upon the occurrence of an Event of Default, after Lender has given the
requisite notice and opportunity to cure as provided herein and if Borrower has
failed to cure the default, Lender shall have the right, in addition to any
other right or remedy of Lender, but not the obligation, in its own name or in
the name of Borrower, to enter into possession of the Property; to perform all
work necessary to complete the construction of the Improvements substantially in
accordance with the Plans, Governmental Requirements and the requirements of any
lessee, if applicable; and to employ watchmen and other safeguards to protect
the Property. Borrower hereby appoints Lender as the attorney-in-fact of
Borrower, with full power of substitution, and in the name of Borrower, if
Lender elects to do so, upon the occurrence of an Event of Default, to (a) use
such sums as necessary, including any proceeds of the Loan and the Borrower's
Deposit, make such changes or corrections in the Plans, and employ such
architects, engineers, and contractors as may be required for the purpose of
completing the construction of the Improvements substantially in accordance with
the Plans and Governmental Requirements, (b) execute all applications and
certificate in the name of Borrower which may be required for completion of
construction of the Improvements, (c) endorse the name of Borrower on any checks
or drafts representing proceeds of the Insurance Policies, or other checks or
instruments payable to Borrower with respect to the Property, (d) do every act
with respect to the construction of the Improvements which Borrower may do, and
(e) prosecute or defend any action or proceeding incident to the Property. The
power of attorney granted hereby is a power coupled with an interest and
irrevocable. Lender shall have no obligation to undertake any of the foregoing
actions, and, if Lender should do so, it shall have no liability to Borrower for
the sufficiency or adequacy of any such actions taken by Lender.

5.2      Acceleration.

         Upon the occurrence of an Event of Default, after Lender has given the
requisite notice and opportunity to cure as provided herein and if Borrower has
failed to cure the default, Lender may, at its option, declare the Loan
immediately due and payable (unless further notice is required by applicable
law).

5.3      Cessation of Advances.

         Upon the occurrence of an Event of Default, after Lender has given the
requisite notice and opportunity to cure as provided herein and if Borrower has
failed to cure the default, the obligation of Lender to disburse the Loan and
the Borrower's Deposit and all other obligations of Lender hereunder shall, at
Lender's option, immediately terminate.

5.4      Funds of Lender.

         Any funds of Lender used for any purpose referred to in this Article 5
shall constitute Advances secured by the Loan Instruments and shall bear
interest at the rate specified in the Note to be applicable after default
thereunder.

5.5      No Waiver or Exhaustion.

         No waiver by Lender of any of its rights or remedies hereunder,
in the other Loan Instruments, or otherwise, shall be considered a waiver of any
other or subsequent right or remedy of Lender; no delay or omission in the
exercise or enforcement by Lender of any rights or remedies shall ever be
construed as a waiver of any right or remedy of

                                       22
<PAGE>   31

Lender; and no exercise or enforcement of any such rights or remedies shall
ever be held to exhaust any right or remedy of Lender.

                    ARTICLE 6 - GENERAL TERMS AND CONDITIONS

6.1      Notices.

         All notices, demands, requests, approvals and other communications
required or permitted hereunder shall be in writing and shall be deemed to have
been given when presented personally or deposited in a regularly maintained mail
receptacle of the United States Postal Service, postage prepaid, registered, or
certified, return receipt requested, addressed to Borrower or Lender, as the
case may be, at the respective addresses set forth on the first page of this
Loan Agreement, or such other address as Borrower or Lender may from time to
time designate by written notice to the other as herein required.

6.2      Entire Agreement and Modifications.

         The Loan Instruments constitute the entire understanding and agreement
between the undersigned with respect to the transactions arising in connection
with the Loan and supersede all prior written or oral understandings and
agreements between the undersigned in connection therewith. No provision of this
Loan Agreement or the other Security Instruments may be modified, waived, or
terminated except by instrument in writing executed by the party against whom a
modification, waiver, or termination is sought to be enforced.

6.3      Severability.

         In case any of the provisions of this Loan Agreement shall for any
reason be held to be invalid, illegal, or unenforceable, such invalidity,
illegality, or unenforceability shall not affect any other provision hereof, and
this Loan Agreement shall be construed as if such invalid, illegal, or
unenforceable provision had never been contained herein.

6.4      Election of Remedies.

         Lender shall have all of the rights and remedies granted in the
Security Instruments and available at law or in equity, and these same rights
and remedies shall be cumulative and may be pursued separately, successively, or
concurrently against Borrower or any property covered under the Security
Instruments, at the sole discretion of Lender. The exercise or failure to
exercise any of the same shall not constitute a waiver or release thereof or of
any other right or remedy, and the same shall be nonexclusive.

6.5      Form and Substance.

         All documents, certificates, insurance policies, evidence, and other
items required under this Loan Agreement to be executed and/or delivered to
Lender shall be in form and substance satisfactory to Lender.

6.6      Limitation on Interest.

         All agreements between Borrower and Lender, whether now existing or
hereafter arising and whether written or oral, are hereby limited so that in no
contingency, whether by reason of acceleration of the maturity of any
indebtedness governed hereby or otherwise, shall the interest contracted for,
charged or received by Lender exceed the maximum amount permissible under
applicable law. If, from any circumstance whatsoever, interest would otherwise
be payable to Lender in excess of the maximum lawful amount, the interest
payable to Lender shall be reduced to the maximum amount permitted under
applicable law; and, if from any circumstance the Lender shall ever receive
anything of value deemed interest by applicable law in excess of the maximum
lawful amount, an amount equal to any excessive interest shall be applied to the
reduction of the principal of the Loan and not to the payment of interest, or
if such

                                       23
<PAGE>   32

excessive interest exceeds the unpaid balance of principal of the Loan such
excess shall be refunded to Borrower. All interest paid or agreed to be paid to
Lender shall, to the extent permitted by applicable law, be amortized, prorated,
allocated, and spread throughout the full period until payment in full of the
principal of the Loan (including the period of any renewal or extension thereof)
so that interest thereon for such full period shall not exceed the maximum
amount permitted by applicable law. This paragraph shall control all agreements
between the Borrower and Lender.

6.7      No Third Party Beneficiary.

         This Loan Agreement is for the sole benefit of Lender and Borrower and
is not the benefit of any third party.

6.9      Borrower In Control.

         In no event shall Lender's rights and interests under the Loan
Instruments be construed to give Lender the right to, or be deemed to indicate
that Lender is in control of the business, management or properties of Borrower
or has power over the daily management functions and operating decisions made by
Borrower.

6.9      Number and Gender.

         Whenever used herein, the singular number shall include the plural and
the plural the singular, and the use of any gender shall be applicable to all
genders. The duties, covenants, obligations, and warranties of Borrower in this
Loan Agreement shall be joint and several obligations of Borrower and of each
Borrower if more than one.

6.10     Captions.

         The captions, headings, and arrangements used in this Loan Agreement
are for convenience only and do not in any way affect, limit, amplify, or modify
the terms and provisions hereof.

6.11     Applicable Law.

         This Loan Agreement and the Loan Instruments shall be governed by and
construed in accordance with the laws of the State of Texas and the laws of the
United States applicable to transactions within such State.

6.12     Statutory Notice.

         IN ACCORDANCE WITH SECTION 26.02 OF THE TEXAS BUSINESS AND COMMERCE
CODE, LENDER HEREBY NOTIFIES BORROWER THAT:

         (a)   A LOAN AGREEMENT IN WHICH THE AMOUNT INVOLVED IN THE LOAN
               AGREEMENT EXCEEDS $50,000 IN VALUE IS NOT ENFORCEABLE UNLESS THE
               AGREEMENT IS IN WRITING AND SIGNED BY THE PARTY TO BE BOUND OR BY
               THAT PARTY'S AUTHORIZED REPRESENTATIVE.

         (b)   THE RIGHTS AND OBLIGATIONS OF THE PARTIES TO AN AGREEMENT SUBJECT
               TO SUBSECTION (a) OF THIS SECTION SHALL BE DETERMINED SOLELY FROM
               THE WRITTEN LOAN AGREEMENT, AND ANY PRIOR ORAL AGREEMENTS BETWEEN
               THE PARTIES ARE SUPERSEDED BY AND MERGED INTO THE LOAN AGREEMENT.

         (c)   THE LOAN INSTRUMENTS REPRESENT THE FINAL AGREEMENT BETWEEN THE
               PARTIES AND MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR,
               CONTEMPORANEOUS, OR SUBSEQUENT ORAL AGREEMENTS OF THE PARTIES.

                                       24
<PAGE>   33

           THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE PARTIES.

         EXECUTED AND DELIVERED on the date first recited.

                                        "LENDER"

                                        RIVERWAY BANK

                                        By:    /s/ GLEN R. BELL
                                            -------------------------------
                                        Name:      Glen R. Bell
                                             ------------------------------
                                        Title:     Vice-President
                                              -----------------------------

                                        "BORROWER"

                                        TMX REALTY CORPORATION,
                                        a Delaware corporation

                                        By:   /s/ JAMES W. ALBRECHT, JR.
                                            -------------------------------
                                        Name:     James W. Albrecht, Jr.
                                             ------------------------------
                                        Title:    Chief Financial Officer
                                              -----------------------------

                                       25
<PAGE>   34
                                   EXHIBIT A

Being a tract or parcel containing 2.619 acres (114,086 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 2.619 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

COMMENCING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3,147,967.40,
Y=698,487.10, thence:

     South 14 degrees 53'21" West, with said west ROW line, a distance of 206.00
     feet to a set 5/8-inch iron rod with plastic cap;

     North 75 degrees 06'39" West, a distance of 329.30 feet to a 5/8-inch iron
     rod with plastic cap set marking the POINT OF BEGINNING and northeast
     corner of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, a distance of 330.70 feet to a 5/8-inch
iron rod with plastic cap set marking the southeast corner of the herein
described tract;

THENCE, NORTH 75 degrees 06'39" West, a distance of 432.78 feet to a 5/8-inch
iron rod with plastic cap set marking the southwest corner of the herein
described tract;

THENCE, NORTH 41 degrees 44'27" East, a distance of 334.23 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 03 degrees 35'59", an arc length of 47.75 feet, and a chord
which bears North 39 degrees 56'28" East, 47.74 feet to an "X" in concrete set
marking the most northwesterly corner of the herein described tract;

THENCE, SOUTHEASTERLY, with a non-tangent curve to the left having a radius of
87.50 feet, an arc length of 93.13 feet, a central angle of 60 degrees 59'01",
and a chord which bears South 58 degrees 25'28" East, 88.80 feet to a 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH 88 degrees 54'58" East, a distance of 27.76 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, EASTERLY, with a curve to the right having a radius of 281.50 feet, an
arc length of 67.83 feet, a central angle of 13 degrees 48'19", and a chord
which bears South 82 degrees 00'48" East, 67.66 feet to a 5/8-inch iron rod with
plastic cap set marking a point of tangency;

THENCE, SOUTH 75 degrees 06'39" East, a distance of 82.41 feet to the POINT OF
BEGINNING and containing 2.619 acres (114,086 square feet) of land (this
description is based on a Land Title Survey and plat prepared by Terra Surveying
Company, Inc. Project Number 0163-9801-S).
<PAGE>   35

                                   EXHIBIT "B"

                    ATTACHED TO AND INCORPORATED BY REFERENCE
                   IN LOAN AGREEMENT DATED NOVEMBER 23, 1998,
                        BETWEEN RIVERWAY BANK, AS LENDER
                     AND TMX REALTY CORPORATION, AS BORROWER

    1.  The Loan Finance Charge in the amount of $120,000 in cash;

    2.  The Note;

    3.  The Mortgage;

    4.  The Assignment of Landlord's Interest in Leases;

    5.  Subordination of all leases affecting the Property;

    6.  The Title Insurance;

    7.  The Construction Contract;

    8.  The consent of Contractor to the assignment of the Construction
        Contracts;

    9.  Subordination of mechanics' and materialmen's liens from all
        subcontractors and suppliers;

    10. The Architectural Contract, if in writing;

    11. The Plans;

    12. Consent of Architect to the assignment of the Plans and Architectural
        Contract;

    13. The Survey;

    14. Financing Statements (Form UCC-1) with respect to the security interest
        granted in the Loan Instruments, together with evidence of the priority
        of the respective security interests perfected hereby;

    15. Executed ground sublease between Borrower and Amelang Partners in form
        and content acceptable to Lender, with a minimum term of 28 years;

    16. Financial Statements;

    17. Evidence of approval of the Plans by any lessee of the Property, if
        applicable, and any necessary Governmental Authority;

    18. Building permit and all other permits required by the Governmental
        Requirements with respect to the then current phase of construction and
        development of the Property;

    19. Evidence of Borrower's compliance with or satisfaction of all conditions
        applicable to any leases affecting the Property;

<PAGE>   36

    20. Evidence that all applicable zoning ordinances or restrictive covenants
        affecting the Property permit the use for which the Property is intended
        and have been or will be complied with;

    21. Evidence of the Property's compliance with the requirements of all
        applicable "environmental protection" laws, rules, and regulations,
        whether federal, state, or municipal including an environmental audit
        satisfactory to Lender;

    22. Evidence that all of the streets providing access to the Property either
        have been dedicated to public use or established by private easement,
        duly recorded in the records of the County in which the Property is
        located, and have been fully installed and accepted by Governmental
        Authority (if applicable), that all costs and expenses of the
        installation and acceptance thereof have been paid in full, and that
        there are no restrictions on the use and enjoyment of such streets that
        adversely affect, limit, or impair Borrower's ability to develop and
        construct the Property or operate the Property for the purposes and in
        the manner represented to Lender;

    23. Evidence of the availability of all utilities to the Property, including
        specifically, but without limitation, gas, electricity, sewer, and water
        services;

    24. Evidence that all necessary action on the part of Borrower has been
        taken with respect to the execution and delivery of this Loan Agreement
        and the consummation of the transactions contemplated hereby, so that
        this Loan Agreement and all Security Instruments to be executed and
        delivered by or on behalf of Borrower will be valid and binding upon
        Borrower or the person or entity executing and delivering such document.
        Such evidence shall include, at the option of the Lender, a legal
        opinion of Borrower's legal counsel confirming such authority, validity,
        and binding effect, confirming that neither the Loan nor any of the
        financing arrangements contemplated by this Loan Agreement violates the
        usury laws of the State of, or any other applicable jurisdiction, and
        covering such other matters as Lender may require;

    25. A flood insurance policy, or binder therefor, in an amount equal to the
        outstanding principal amount of the Loan or the maximum amount available
        under the Flood Disaster Protection Act of 1973 and regulations issued
        pursuant thereto (the "Act"), whichever is less, in form complying with
        the "insurance purchase requirement" of the Act, or evidence that no
        portion of the Property lies within a designated flood plain or flood
        hazard area;

    26. The Insurance Policies or Certificates of such Insurance Policies;

    27. Breakdown of all costs and expenses required to complete development and
        construction of the Property, in detail and in amount reasonably
        acceptable to Lender;

    28. Application for Advance;

    29. Certified Articles of Incorporation and Bylaws of Borrower, and all
        amendments thereto;

    30. Certificate of existence and certificate of good standing of Borrower
        from the appropriate officer of the State of Texas;

    31. Certified resolutions of the board of directors of Borrower authorizing
        such corporation to execute the Loan Instruments and perform its
        obligations thereunder;

    32. Tax or assessment certificates or other similar evidences of payment
        from all appropriate bodies or entities which have taxing or assessing
        authority over any of the Property, stating that all taxes and
        assessments are current;

    33. Either a statement by a qualified third party unrelated to Borrower or
        an Environmental Site Assessment by an engineer acceptable to Lender
        providing that there is no evidence that any Hazardous Materials have
        been

<PAGE>   37
        or are being generated, treated, stored or disposed of on any of the
        Property and none exists on, under or at the Property; and

    34. Soils Report.

    35. Estoppel letters from Ground Lessor, Ground Sublessor, Lutheran and any
        other parties as Lender may require.

    36. The Subordination, Non-Disturbance and Attornment Agreement.

    37. Executed copy, with all amendments to the Ground Lease.

    38. Such amendments as Lender may reasonably require with respect to the
        Ground Lease.

    39. The Letter of Credit.

<PAGE>   38
                                  EXHIBIT "C"

                                      1998_1030 RAB-PLF Construction Cost Report
                                                                        11/11/98

    INTROGEN THERAPEUTICS, INC.
    RAB/PLF CONSTRUCTION PROJECT
    CONSTRUCTION COST REPORT
    MASTER BUDGET
    10/30/98
<TABLE>
<CAPTION>

                                   HARD COSTS
    ----------------------------------------------------------------------------

    <S>                             <C>                                <C>
    Construction                    Vaughn Construction                6,987,073
    Telephone/Security                                                   150,000
    Graphics/Signage                                                      13,000
                                                                       ---------
    TOTAL HARD COSTS                                                   7,150,073
                                                                       ---------

                                   SOFT COSTS
    ----------------------------------------------------------------------------

    Architect                       Browne Penland McGregor              613,750
    Project management              ccrd partners                        120,600
    Planning & Schematic Design     BioMetics                            106,107
    Construction Materials Testing  Kenneth Tand & Assoc.                 15,000
    Tap fees                                                              18,100
    Testing/balancing                                                      9,000
    Roof consultant                 Advanced Technology                    6,000
    Surveys                         G P Surveyors                          8,000
    Geotechnical                    Kenneth Tand & Assoc.                  6,680
    Acoustical consultant                                                  3,000
    Environmental                   Environ. Resource Csltnts              4,100
    Property taxes                                                         2,500
    Validation consultant                                                  9,000
    Comm/tech consultant                                                   1,000
    Insurance (builder risk)                                              30,000
    Legal                                                                100,000
    Title/closing/appraisal                                               50,000
                                                                       ---------
    TOTAL SOFT COSTS                                                   1,102,837
                                                                       ---------
                       CONTINGENCY AND TOTAL PROJECT COST
    ----------------------------------------------------------------------------

    Contingency                                      5%                  420,000
                                                                       ---------
    TOTAL PROJECT COST                                                 8,672,910
                                                                       ---------
</TABLE>

    THIS INFORMATION IS CONFIDENTIAL AND FOR INTERNAL USE SOLELY BY INTROGEN
  THERAPEUTICS, INC. AND/OR PARTIES COVERED BY AN INTROGEN THERAPEUTICS, INC.
                 CONFIDENTIALITY AND NON-DISCLOSURE AGREEMENT.

<PAGE>   39

                                   EXHIBIT "D"

                    ATTACHED TO AND INCORPORATED BY REFERENCE
                   IN LOAN AGREEMENT DATED NOVEMBER 21, 1998,
                        BETWEEN RIVERWAY BANK, AS LENDER
                     AND TMX REALTY CORPORATION, AS BORROWER

1.  The Survey Requirements:

    (a) Field Note Description. The Survey should contain a certified metes and
        bounds description and should comply with the following requirements:

        (i)    The beginning point should be established by a monument located
               at the beginning point, or by reference to a nearby monument;

        (ii)   The sides of the Property should be described by giving the
               distances and bearings of each;

        (iii)  The distances, bearings, and angles should be taken from a recent
               instrument survey, or recently recertified instrument survey, by
               a licensed Professional Engineer or Registered Surveyor;

        (iv)   Curved sides should be described by data including; length of
               arc, central angle, radius of circle for the arc and chord
               distance, and bearing;

        (v)    The legal description should be a single perimeter description of
               the entire Property;

        (vi)   The description should include a reference to all streets,
               alleys, and other rights-of-way that abut the Property surveyed,
               and the width of all rights-of-way mentioned should be given the
               first time these rights-of-way are referred to; and

        (vii)  If the Property surveyed has been recorded on a map or plat as
               part of an abstract or subdivision, reference to such recording
               data should be made.

    (b) Lot and Block Description. If the Property is included within a properly
        established, recorded subdivision or addition, then a lot and block
        description will be an acceptable substitute for a metes and bounds
        description, provided that the lot and block description must completely
        and properly identify the name or designation of the recorded
        subdivision or addition and give the recording information therefor.

    (c) Map or Plat. The Survey should also contain a certified map or plat
        showing the following:

        (i)    the plot to be covered by the Mortgage;

        (ii)   the relation of the point of beginning of said plot to the
               monument from which it is fixed;

        (iii)  monuments for corners and points of curves;

<PAGE>   40

        (iv)   all easements, showing recording information therefor by volume
               and page;

        (v)    the established building line, if any;

        (vi)   all easements appurtenant to said plot;

        (vii)  the boundary line of the street or streets abutting the plot and
               the width of said streets; and

        (viii) encroachments and the extent thereof in terms of distance upon
               said plot or any easement appurtenant thereto.

        The Survey should also contain all structures and improvements on said
        plot with horizontal lengths of all sides and the relation thereof by
        distances to (a) all boundary lines of the plot, (b) easements, (c)
        established building lines, and (d) street lines.

    (d) Certification. The certification for the Property description and the
        map or plat should be addressed to Lender (and to the interested title
        company, if required by the title company), signed by the surveyor,
        bearing current date, registration number, and seal, and should be in
        the following form or its substantial equivalent:

                The undersigned hereby certifies to Lender that (i) this survey
                was made on the ground as per the field notes shown hereon and
                correctly shows the boundary lines and dimensions and area of
                the land indicated hereon and each individual parcel thereof
                indicated hereon; (ii) all monuments shown hereon actually
                exist, and the location, size and type of Such monuments are
                correctly shown; (iii) this survey correctly shows the location
                of all buildings, structures, other improvements and visible
                items on the subject Property; (iv) this survey correctly shows
                the location and dimensions of all alleys, streets, roads,
                rights-of-way, easements, and other matters of record of which
                the undersigned has been advised affecting the subject Property
                according to the legal description in such easements and other
                matters (with instrument, book, and page number indicated); (v)
                except as shown, there are no visible easements, rights-of-way,
                party walls, drainage ditches, streams, or conflicts, visible
                encroachments onto adjoining premises, streets, or alleys by any
                of said buildings, structures, or other improvements, or visible
                encroachments onto the subject Property by buildings,
                structures, or other improvements on adjoining premises; (vi)
                the distance from the nearest intersecting street and road is as
                shown hereon; and (vii) the subject property has direct access
                to dedicated public roads accepted for maintenance by the entity
                to which such roads were dedicated.

    (e) The Survey shall also contain a flood plain designation evidencing the
        Property is located in Zone "X".

2.  Standard Mortgage Clause For All-Risk Insurance Policy:

    The mortgage clause to be contained in the All-Risk Insurance Policy
    covering the Improvements should be in the following form:

        This policy, as to the interest of mortgagee only therein, shall not be
        invalidated by any act or neglect of mortgagor or owner of the within
        described property, nor by any foreclosure or other proceedings or
        notice of sale relating to the property, nor by any change in the title
        or ownership of the property, nor by the occupation of the premises for
        purposes more hazardous than are permitted by this policy, provided that
        the mortgagee shall notify this Company of any change of ownership or
        increase of hazard which shall come to the knowledge of said mortgagee,
        and, unless permitted by this policy,

<PAGE>   41

        it shall be noted hereon; and provided, further, that upon failure of
        the insured to render proof of loss, such mortgagee upon notice shall
        render proof of loss in the form herein specified within ninety-one (91)
        days thereafter and shall be subject to the provisions hereof relating
        to appraisal and time of payment and of bringing suit.

        Failure upon the part of mortgagee to comply with any of the foregoing
        obligations shall render the insurance under this policy null and void
        as to the interest of mortgagee.

        This policy may be canceled as to the interest of any mortgagee named
        hereon by giving such mortgagee thirty (30) days' written notice.

        If this Company shall claim that no liability existed as to mortgagor or
        owner, it shall, to the extent of payment of loss to mortgagee, be
        subrogated to all mortgagee's rights of recovery, but without impairing
        mortgagee's right to sue or it may pay off the mortgage debt and require
        an assignment thereof and of the mortgage without recourse.

        The word "mortgagee" shall be construed to mean "mortgagee or trustee."

<PAGE>   42
[SEAL]            [DEPARTMENT OF VETERANS AFFAIRS LETTERHEAD]

                                                      In Reply Refer To: 580/138

November 24, 1998

Amelang Partners, Inc.
952 Echo Lane, Suite 100
Houston, Texas 77024

SUBJ: Enhanced-Use Lease between the United States Department of Veterans
Affairs (the "Government") and Amelang Partners, Inc. ("API")

Dear Sirs:

Reference is hereby made to those certain Utility Letters (herein so called)
issued by the City of Houston dated October 23, 1998, which evidence that
certain water, storm sewer and wastewater capacities (collectively the
"Utilities") are available to the 2.619 acres of land fronting on Ringness
Road in the Houston VA Medical Center, which property is subject to the Amended
and Restated Ground Sublease Agreement between API and Introgen Therapeutics,
Inc. (the "Amended Sublease Premises"). The Utility Letters have been issued to
the Government. The Government hereby agrees that API, as ground lease tenant
pursuant to the Enhanced-Use Lease, may make such Utilities available to the
owner and tenants, including any future owners and tenants, of the buildings to
be constructed upon the Amended Sublease Premises, and the Government further
agrees that it will take no action to utilize, divert, sell, or in any way
decrease the availability or the capacity of Utilities to the Amended Sublease
Premises.

Further, the Government has reviewed the plans for rerouting of the storm sewer
line which lies partially under the Amended Sublease Premises, as illustrated
on the drawing attached as Exhibit "A" to this letter and the Government hereby
approves the routing of said storm sewer line as illustrated in said drawing.

Sincerely yours,

/s/ W. HOWARD GIBSON

W. Howard Gibson

<PAGE>   43
                                ESCROW AGREEMENT

     This Escrow Agreement ("Escrow Agreement") is by and among Riverway Bank,
Five Riverway, Houston, Texas 77056 ("Bank"), TMX Realty Corporation, a Delaware
corporation ("TMX") and Introgen Therapeutics, Inc. a Delaware corporation
("Introgen"), the foregoing parties being hereinafter collectively referred to
as the "Parties", who agree as follows:

                                    RECITALS

     Reference is hereby made to that certain Amended and Restated Ground
Sublease Agreement (the "Ground Sublease") dated effective September 24, 1998,
by and between Introgen, as ground sublessee and Amelang Partners, Inc., as
ground sublessor. The interest of Introgen in and to the Ground Lease was
assigned to TMX, pursuant to Assignment of Lease dated November 23, 1998.
Pursuant to the Assignment of Lease, Introgen remains liable for all obligations
and liabilities of the ground sublessee pursuant to the Ground Sublease. For the
purposes of this Agreement, Introgen and TMX are hereby sometimes collectively
referred to herein as "Ground Sublessee". Reference is also made to that certain
Loan (herein so called) dated on or about even date herewith from the Bank to
TMX, as evidenced, in part, by that certain promissory note dated on or about
even date herewith from TMX as maker to the Bank as payee. As a condition
precedent to the Bank making the Loan, and as further security therefore, Ground
Lessee has agreed to deposit, in advance with the Bank, the annual rent to be
paid by Introgen to Ground Lessor pursuant to the Ground Lease.

                                    AGREEMENT

     1.  APPOINTMENT AND ACCEPTANCE, COMPENSATION.

     1.1 Appointment and Acceptance. Ground Sublessee hereby appoints the Bank
as escrow agent under this Escrow Agreement and the Bank accepts the
appointment.

     1.2 Compensation. The Bank shall not be compensated for its services under
this Agreement, except as otherwise provided herein.

     1.3 Deposit. Contemporaneously with the execution hereof, Ground Lessee
shall deposit with the Bank the amount of $136,191, the same being the maximum
amount of annual rent due through and including the year 2000.

     1.4 Payment of Escrowed Funds. Bank is hereby authorized and directed, on
or before the date such amounts are due, to pay rent accruing pursuant to the
Ground Sublease for the year 1999, if any and the year 2000 from the funds
deposited pursuant to Section 1.3 hereof. On or before January 1, 2000, Ground
Sublessee shall deliver to Bank all sums due and payable pursuant to the Ground
Sublease for the first calendar quarter of the year 2000. Ground Sublessee
agrees to deposit,

<PAGE>   44
on or before the first day of each succeeding calendar quarter thereafter during
the term that the Loan is outstanding, an amount sufficient to cover all
payments due pursuant to the Ground Sublessee for the next calendar quarter
year. The net effect of Section 1.3 and 1.4 being that there is always held in
escrow sufficient funds to pay at least one year's rent due under the Ground
Sublease.

     1.5 Payment by Bank. All sums delivered to Bank pursuant to this Agreement
shall be held by Bank and paid as rent, and other obligations as the same are
payable pursuant to the Ground Sublease provided sufficient funds have been
deposited hereunder.

     1.6 Other Payments by Bank. The foregoing to contrary notwithstanding,
should a Event of Default occur, (as such term is defined in the loan agreement
executed in connection with the Loan), the Bank may use any funds deposited
pursuant to this Agreement to prepay rent pursuant to the Ground Sublease, or,
at the Bank's option, to cure any Event(s) of Default, pursuant to the Loan.

     1.7 Fiduciary Account, Investment of Funds. The funds placed in escrow will
be held in a separate segregated account in accordance with this Agreement and
shall be invested from time to time by the Bank as set forth in written
instructions of TMX which must be acceptable to Bank. If no such instructions
are given, the funds shall be invested in certificates of deposit of the Bank
with maturities of thirty (30) days.

     2.  SUCCESSOR ESCROW AGENTS.

     2.1 The Bank or any successor escrow agent may, at any time, resign by
giving notice in writing to TMX and shall be discharged from its duties under
this Escrow Agreement on the first to occur of (a) the appoint of a successor
escrow agent, as provided in this Paragraph 3, or (b) the expiration of thirty
(30) calendar days after the notice is given. In the event of any resignation, a
successor escrow agent shall be appointed by the Bank. If the Bank fails or
refuses to appoint a successor escrow agent, the successor escrow agent shall be
appointed by TMX. Any successor escrow agent shall deliver to the TMX, a written
instrument accepting appointment under this Escrow Agreement and hereupon it
shall succeed to all the rights and duties of the Bank hereunder and shall be
entitled to receive any funds held by the Bank in its capacity as predecessor
escrow agent.

     3.  RIGHTS, PRIVILEGES, IMMUNITIES AND LIABILITIES OF THE BANK.

         The following shall govern the rights, privileges, immunities and
liabilities of the Bank in its capacity as escrow agent.

     3.1 Indemnity. In the event the Bank becomes involved in litigation in
connection with this Escrow Agreement or any transaction related in any way
hereto, TMX agrees to indemnify and save the Bank harmless from all loss, cost,
damage, expense and reasonable attorney's fees suffered

                                       2

<PAGE>   45

or incurred by the Bank as a result thereof, except for any loss, cost, damage
or expense resulting from the gross negligence, willful misconduct, or bad faith
breach of this agreement by the Bank.

     3.2 Good Faith Actions. The Bank shall not be liable for anything which it
may do or refrain from doing in connection herewith, provided that it acts in
good faith.

     3.3 Legal Counsel. The Bank may advise with legal counsel in the event of
any dispute or question as to the construction of any of the provisions of this
Escrow Agreement or its duties hereunder and TMX shall pay any and all
reasonable legal fees so incurred.

     3.4 Event of Dispute. In the event of any disagreement involving the
Parties resulting in adverse claims or demands being made in connection with the
matters covered by this Escrow Agreement or in the event that the Bank, in good
faith, shall be in doubt as to what action it should take hereunder, the Bank
may, at its option, refuse to comply with any claims or demands on it or refuse
to take any other action hereunder, so long as such disagreement continues or
such doubt exists and, in such event, the Bank shall not be or become liable in
any way or to any person for its failure or refusal to act and the Bank shall be
entitled to continue so to refrain from acting until (a) the rights of all
interested parties shall have been fully and finally adjudicated by a court of
competent jurisdiction, or (b) all differences shall have been adjusted and all
doubt resolved by agreement among all of the interest parties and the Bank shall
have been notified thereof in writing signed by all parties. The rights of the
Bank under this subparagraph are cumulative of all other rights which it may
have by law or otherwise and shall in no manner impair the Bank's ability to
apply the Escrow Funds to payment on the Loan in the Event of Default
thereunder.

     3.5 Discharge. When the Loan has been paid in full and the Bank has
delivered all of the proceeds pursuant to the terms of this Escrow Agreement,
the Bank and Introgen shall be discharged from any further obligation hereunder.

     3.6 Statements of Accounts. Bank will deliver to Introgen monthly
statements of account, on or before the fifteenth (15) day of each month,
reflecting all activity in the account and interest earned thereon.

     4.  MISCELLANEOUS.

     4.1 Notices. Any and all notices permitted or required to be given under
the terms of this Escrow Agreement shall be in writing and may be served by
mail, postage prepaid and addressed to the person or entity to be notified at
the appropriate address specified on the signature page hereof or by delivering
the same to such person or entity or by overnight delivery and addressed to the
person or entity to be notified at said address. Actual notice, however
received, shall be valid. Addresses may be changed by notice given in the manner
provided in this subparagraph.

                                       3
<PAGE>   46

     4.2 Effect of Escrow Agreement. This Escrow Agreement shall be binding on,
inure to the benefit of and be enforceable by and against the Parties, their
successors and assigns.

     4.3 Choice of Law. This Escrow Agreement is performable in whole or in part
in the State of Texas and shall be interpreted and construed in accordance with
and shall be governed by the laws of the State of Texas.

     4.4 Counterparts. This Escrow Agreement may be executed in multiple
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

     4.5 Effective Date of Escrow Agreement. This Escrow Agreement shall be
deemed effective for all purposes as of the date hereof.

     This Escrow Agreement is executed and delivered by the Parties and the Bank
on the date specified below.

                                     TMX REALTY CORPORATION

                                     By:    /s/ JAMES W. ALBRECHT, JR.
                                            ----------------------------------
                                     Name:  James W. Albrecht, Jr.
                                            ----------------------------------
                                     Title: Chief Financial Officer
                                            ----------------------------------

                                     Address:  301 Congress Avenue, Suite 1850,
                                               Austin, Texas 78701

                                     Date: November 23, 1998

                                     INTROGEN THERAPEUTICS, INC.

                                     By:    /s/ JAMES W. ALBRECHT, JR.
                                            ----------------------------------
                                     Name:  James W. Albrecht, Jr.
                                            ----------------------------------
                                     Title: Chief Financial Officer
                                            ----------------------------------

                                     Address:  301 Congress Avenue, Suite 1850,
                                               Austin, Texas 78701

                                     Date: November 23, 1998

                                       4

<PAGE>   47

                                     RIVERWAY BANK

                                     By:     /s/ GLEN R. BELL
                                             ---------------------------------
                                     Name:   Glen R. Bell
                                             ---------------------------------
                                     Title:  Vice President
                                             ---------------------------------
                                     Address: Five Riverway
                                              Houston, Texas 77056

                                     Date: November 23, 1998

                                       5

<PAGE>   48
                                                                       EXHIBIT C
                                                                        11-23-98

                                  [SITE PLAN]

<PAGE>   49
                                   EXHIBIT D
                                    11-23-98

                          INTROGEN THERAPEUTICS, INC.
                          NEW PRODUCT LAUNCH FACILITY
                                  HOUSTON, TX

                                 PROJECT MANUAL
                             BPM Project No. 98027
                                October 15, 1998

                                  VOLUME TWO

                                   Including:
                           Mechanical and Electrical

                                   ARCHITECT:
                    BROWNE PENLAND MCGREGOR ARCHITECTS, INC.
                520 Post Oak Blvd. Suite 880, Houston, TX 77027
                            Contact: Ken Shanks, AIA
                          Phone: 713-850-1733 ext. 18
                               Fax: 713-850-0833

                             STRUCTURAL ENGINEERS:
                            ASA CONSULTING ENGINEERS
                1155 Dairy Ashford, Suite 111, Houston, TX 77079
                            Contact: Saad Ahmed, PE

                        MECHANICAL/ELECTRICAL ENGINEERS:
                                      HMG
                3508 Far West Blvd. Suite 350, Austin, TX 78731
                            Contact: Brian Moore, PE

                                CIVIL ENGINEERS:
                                 PATE ENGINEERS
             13405 Northwest Freeway, Suite 300, Houston, TX 77040
                             Contact: Jeff Ross, PE

                              LANDSCAPE ARCHITECT:
                          THE OFFICE OF JAMES BURNETT
                   1973 West Gray, Suite 5, Houston, TX 77019
                          Contact: Chip Trageser, ASLA

                            CLEAN ROOM CONSULTANTS:
                         MSS CLEAN ROOM TECHNOLOGY LTD.
                  Fredrick House, Fulton Road, York Y01 4EG UK
                             Contact: Paul Stubley

<PAGE>   50
                                                                    EXHIBIT D(1)
                                                                      11-23-98

                                  [SITE PLAN]

<PAGE>   51

                                       THIS SPACE FOR USE OF FILING OFFICER
ACKNOWLEDGMENT COPY
                                                    98-241163
                                                 12/4/98  10:14 AM
                                             TEXAS SECRETARY OF STATE

                                                      FILED

<PAGE>   52
             UNIFORM COMMERCIAL CODE -- FINANCING STATEMENT -- UCC1

     This instrument is prepared as, and is intended to be, a Financing
Statement, complying with the formal requisites therefor, as set forth in the
Texas Business and Commerce Code, Article 9 (also known as the Texas Uniform
Commercial Code -- Secured Transactions), and, in particular, Section 9.402
thereof.

                              FINANCING STATEMENT

     1.     Debtor -- Name and Mailing Address:

            TMX Realty Corporation
            301 Congress Avenue, Suite 1850
            Austin, Texas 78701

     2.     The name and address of the secured party ("Secured Party") is:

            RIVERWAY BANK
            Five Riverway
            Houston, Texas 77056

     3.    This Financing Statement covers the following types (or items) of
           property (the "Collateral"):

           Construction Contracts: Any and all contracts, subcontracts, and
           agreements, written or oral, between Debtor and any other party, and
           between parties other than Debtor, in any way relating to the
           construction of the Improvements (as hereinafter defined) on the Land
           (as hereinafter defined) or the supplying of material (specially
           fabricated or otherwise), labor, supplies, or other services
           therefor.

           Contracts: All of the right, title and interest of Debtor in, to, and
           under any and all (i) Contracts (herein so called) for the purchase
           or sale of all or any portion of that certain real property described
           in Exhibit "A" attached hereto and made a part hereof for all
           purposes (the "Land"), together with all Improvements (herein so
           called) thereon and appurtenances thereto (the Improvements, together
           with the Land are collectively called the "Mortgaged Property"),
           whether such Contracts are now or at any time hereafter existing,
           including all amendments and supplements to and renewals and
           extensions of the Contracts at any time made, and together with all
           payments, earnings, income, and profits arising from the sale of all
           or any portion of the Mortgaged Property or from the Contracts and
           all other sums due or to become due under and pursuant thereto and
           together with any and all earnest money, security, letters of credit
           or other deposits under any of the Contracts; (ii) contracts,
           licenses,

                                       1

<PAGE>   53
permits and living unit equivalents of water, wastewater, and other utility
services whether executed, granted, or issued by a private person or entity or
a governmental or quasi-governmental agency, which are directly or indirectly
related to, or connected with, the development of the Mortgaged Property,
whether such contracts, licenses, and permits are now or at any time hereafter
existing, including without limitation, any and all living unit equivalents of
water, wastewater, and other utility services, certificates, licenses, zoning
variances, permits, and no-action letters from each governmental authority
required: (a) to evidence full compliance by Debtor and all improvements
constructed or to be constructed on the Mortgaged Property with all legal
requirements applicable to the Mortgaged Property, and (b) to complete
construction of any improvements on the Mortgaged Property; (iii) any and all
right, title, and interest Debtor may have in any financing arrangements
relating to the financing of the purchase of all or any portion of the
Mortgaged Property by future purchasers; (iv) all plans, specifications, and
drawings prepared for the Mortgaged Property, including all amendments and
supplements to and renewals and extensions of such contracts any time made, and
together with all rebates, refunds or deposits, and all other sums due or to
become due under and pursuant thereto and together with all powers, privileges,
options, and other benefits of Debtor under such contracts; and (v) all other
contracts which in any way relate to the use, enjoyment, occupancy, operation,
maintenance, or ownership of the Mortgaged Property (save and except any and
all leases, subleases, or other agreements pursuant to which Debtor is granted
a possessory interest in the Land), including but not limited to engineer's
contracts, architect's contracts, maintenance agreements and service contracts.

Fixtures: All materials, supplies, equipment, systems, apparatus, and other
items now owned or hereafter acquired by Debtor and now or hereafter attached
to, installed in, or used in connection with (temporarily or permanently) the
Mortgaged Property, which are now owned or hereafter acquired by Debtor and are
now or hereafter attached to the Mortgaged Property and needed in the operation
thereof, and including, but not limited to, any and all motors, engines,
boilers, furnaces, pipes, sprinkler systems, fire extinguishing apparatus and
equipment, water tanks, heating, ventilating, refrigeration, plumbing,
lighting, transportation (of people or things, including, but not limited to,
stairways, elevators, escalators, and conveyors), incinerating, air
conditioning and air cooling equipment and systems, gas and electric machinery,
and water, gas, electrical, storm and sanitary sewer facilities, and all other
utilities whether or not situated in easements, together with all accessions,
appurtenances, replacements, betterments, and substitutions for any of the
foregoing and the proceeds thereof.

Leases: Any and all leases, subleases, sub-subleases licenses, concessions, or
other agreements (written or oral, now or hereafter in effect) which grant to
third parties a possessory interest in and to, or the right to use, all or any
part of the Mortgaged Property, together with all security and other deposits
made in connection therewith.

                                       2
<PAGE>   54
     Personalty: All of the right, title and interest of Debtor in and to the
     Plans, all building and construction materials and equipment, insurance
     proceeds, accounts, contract and subcontract rights pertaining to the
     buildings, all refundable, returnable, or reimbursable fees, deposits or
     other funds or evidences of credit or indebtedness deposited by or on
     behalf of Debtor in connection with the Mortgaged Property with any
     governmental agencies, boards, corporations, providers of utility services,
     public or private, including specifically, but without limitation, all
     refundable, returnable, or reimbursable tap fees, utility deposits,
     commitment fees and development costs, any awards, remunerations,
     reimbursements, settlements, or compensation heretofore made or hereafter
     to be made by any Governmental Authority pertaining to the Land,
     Improvements, Fixtures, Construction Contracts, including but not limited
     to those for any vacation of, or change of grade in, any streets affecting
     the Land or the Improvements and those for municipal utility district or
     other utility costs incurred or deposits made in connection with the Land;
     which are now owned or hereinafter acquired by Debtor, which are now or
     hereafter situated in, on, or about the Land or the Improvements, or used
     in or necessary to the complete and proper planning, development,
     construction, financing, use, occupancy, or operation thereof, or acquired
     (whether delivered to the Land or stored elsewhere) for use in or on the
     Land or the Improvements, together with all accessions, replacements, and
     substitutions thereto or therefor and the proceeds thereof.

     Rents: All of the rents, revenues, income, proceeds, profits, security
     and other types of deposits, and other benefit paid or payable by parties
     to the Leases other than Debtor for using, leasing, licensing, possessing,
     operating from, residing in, selling, or otherwise enjoying the Mortgaged
     Property.

     Excluded Property: Any other provision hereof notwithstanding, there is
     hereby excepted from the definition of the "Mortgaged Property" and the
     "Collateral" and from all liens and security interests held by Secured
     Party all property of Debtor described on Exhibit "B" attached hereto,
     which Exhibit "B" is incorporated herein for all purposes.

4.   Proceeds of the Collateral are also covered.

5.   Number of additional sheets presented: Two (2)

     DATED as of the 23 day of November, 1998.

                                        "DEBTOR"

                                        TMX REALTY CORPORATION,
                                        a Delaware corporation

                                        By: /s/  JAMES W. ALBRECHT, JR.
                                        -------------------------------
                                        Name:  James W. Albrecht, Jr.
                                        Title: Chief Financial Officer

                                       3
<PAGE>   55
                                  EXHIBIT "A"

Being a tract or parcel containing 2.619 acres (114,086 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 2.619 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 9.9998632):

COMMENCING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3,147,967.40,
Y=698,487.10, thence:

     South 14 degrees 53'21" West, with said west ROW line, a distance of
     206.00 feet to a set 5/8-inch iron rod with plastic cap;

     North 75 degrees 06'39" West, a distance of 329.30 feet to a 5/8-inch
     iron rod with plastic cap set marking the POINT OF BEGINNING and
     northeast corner of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, a distance of 330.70 feet to a 5/8-inch
iron rod with plastic cap set marking the southeast corner of the herein
described tract;

THENCE, NORTH 75 degrees 06'39" West, a distance of 432.78 feet to a 5/8-inch
iron rod with plastic cap set marking the southwest corner of the herein
described tract;

THENCE, NORTH 41 degrees 44'27" East, a distance of 334.23 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 03 degrees 35'59", an arc length of 47.75 feet, and a chord
which bears North 39 degrees 56'28" East, 47.74 feet to an "X" in concrete set
marking the most northwesterly corner of the herein described tract;

THENCE, SOUTHEASTERLY, with a non-tangent curve to the left having a radius of
87.50 feet, an arc length of 93.13 feet, a central angle of 60 degrees 59'01",
and a chord which bears South 58 degrees 25'28" East, 88.80 feet to a 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH 88 degrees 54'58" East, a distance of 27.76 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, EASTERLY, with a curve to the right having a radius of 281.50 feet, an
arc length of 67.83 feet, a central angle of 13 degrees 48'19", and a chord
which bears South 82 degrees 00'48" East, 67.66 feet to a 5/8-inch iron rod
with plastic cap set marking a point of tangency;

THENCE, SOUTH 75 degrees 06'39" East, a distance of 82.41 feet to the POINT OF
BEGINNING and containing 2.619 acres (114,086 square feet) of land (this
description is based on a Land Title Survey and plat prepared by Terra
Surveying Company, Inc. Project Number 0163-9801-S).

<PAGE>   56
                                  EXHIBIT "B"

     There is hereby excepted from the definition of the "Mortgaged Property"
and the "Collateral", and from all liens and security interests held by Secured
Party, all property of Debtor which is not a part of the plumbing, electrical,
heating, cooling, ventilation, standard lighting, ceiling tile, sprinkler
equipment and related equipment together with other fixtures and equipment
necessary for the use and operation of the buildings for general purposes and
all property (save and except the foregoing) which is not permanently attached
or affixed to the building and is not an integral part of the building and
needed for the same to be functional as an office building. Without limiting the
foregoing sentence, the property described below is excepted from said
definitions of "Mortgaged Property" and "Collateral" and shall not be in any way
secured or encumbered by any lien or security interest held by Secured Party.

                               Excluded Property

Furniture
Computers and related equipment, computer network equipment and software
Laboratory equipment
Production Equipment
Modular clean room units
Telephone equipment
Office equipment
Artwork
Decorative items
Plants
Inventory, including raw materials, work in progress and finished goods
Office supplies
Lab notebooks
Electronic media
Backup power generator
Cold storage equipment
Waste treatment equipment

Whether now owned or hereafter acquired

                                       5
<PAGE>   57

                     ENVIRONMENTAL MONITORING REPORT LOG IN
                                     ROOM 3

<TABLE>
<CAPTION>
DATE           OPERATION                               L/N OR C/N
<S>            <C>                                     <C>
11 Feb 98      DHGF(10) Prep                           N/A
19 Feb 98      Expand to 1 CF 10                       B0419901
23 Feb 98      Thaw                                    C/N 05498001
26 Feb 98      Expansion                               C/N 05498001
02 Mar 98      Expansion                               C/N 05498001
06 Mar 98      Split to 10 - trays                     C/N 05498001
13 Mar 98      10 - tray harvest                       C/N 05498001
13 Mar 98      Seeding 6 CF 10's                       C/N 05498001
17 Mar 98      Harvest 10 - trays                      C/N 05498001
20 Mar 98      Thaw of 08198001                        C/N 08198001
23 Mar 98      Harvest 4 - T 150                       C/N 08198001
25 Mar 98      Splitting T - 150's                     C/N 08198001
26 Mar 98      Splitting tray T - 10=50's to CF 10     C/N 08198001
27 Mar 98      Media Prep                              C/N 08198001
30 Mar 98      Split CF 10 to 4 -CR 10's               C/N 08198001
01 Apr 98      CellCube Assembly                       C/N 08198001
03 Apr 98      Split to 10 - trays                     C/N 08198001
07 Apr 98      Harvest CR 10's to Seed Side I          C/N 08198001
07 Apr 98      Harvest CF 10 to Seed Side 2            C/N 08198001
13 Apr 98      Cell Thaw                               B1039801
16 Apr 98      Expand to 8 T 150                       B1039801
19 Apr 98      Split to 1 CF10                         B1039801
24 Apr 98      Media Prep/Split to 4 10 - trays        B1039801
24 Apr 98      Cube Assembly                           B1039801
28 Apr 98      Harvest to Seed Cube Side I             B1039801
28 Apr 98      Thaw 11898001/Harvest 1039801           C/N 11898001 &
                 to Seed Cube *                          B1039801
01 May 98      Split to 8 T 150                        C/N 11898001
04 May 98      Split to 1, CF 10                       B11898001
08 May 98      Split to 4 10 - trays                   B1189801
08 May 98      Cube Setup                              B1189801
11 May 98      Thaw                                    C/N 13198001
13 May 98      Harvest For Cube Side I                 B1189801
13 May 98      Harvest 2 CF 10's for Side II           B1189801
14 May 98      Split to 8 T - 150's                    B1319801
18 May 98      Split to 1 CF 10                        C/N 13198001
</TABLE>

<PAGE>   58
                                         THIS STATEMENT IS PRESENTED TO A FILING
                                         OFFICER FOR FILING PURSUANT TO THE
                                         UNIFORM COMMERCIAL CODE.
<TABLE>

                                                                              11. [ ] CHECK TO REQUEST SAME DEBTOR
                                                                                  SEARCH CERTIFICATE (INSTRUCTION B.11)

<S>                                               <C>          <C>           <C>          <C>              <C>
1.  DEBTOR (IF PERSONAL) LAST NAME                FIRST NAME                  MI          1A. PREFIX       1B. SUFFIX
    AMELANG PARTNERS INCORPORATED

1C. MAILING ADDRESS                                            1D. CITY, STATE            1E ZIP CODE
    952 Echo Lane, Suite 100                                       Houston, Texas            77024

2.  ADDITIONAL DEBTOR (IF PERSONAL) LAST NAME     FIRST NAME                  MI          2A. PREFIX       2B. SUFFIX

2C. MAILING ADDRESS                                            2D. CITY, STATE            2E. ZIP CODE

3.  SECURED PARTY (IF PERSONAL) LAST NAME         FIRST NAME                   MI
    Aid Association for Lutherans

3A. MAILING ADDRESS                                            3B. CITY, STATE             3C. ZIP CODE
    4321 North Ballard Road                                        Appleton, Wisconsin         54919

4.  ADDITIONAL SECURED PARTY (IF ANY)

4A. MAILING ADDRESS                                            4B. CITY, STATE             4C. ZIP CODE

5   ORIGINAL FINANCING STATEMENT NUMBER    5A. ORIGINAL DATE FILED      6. CHECK            THIS FINANCING STATEMENT CHANGE IS
    S-319698                                   2/12/97                     IF               TO BE FILED IN THE REAL ESTATE RECORDS.
                                                                           APPLICABLE [X]   NO. OF ADDITIONAL SHEETS PRESENTED   1.
                                                                                                                                ---

7. A. [ ]  AMENDMENT - THE FINANCING STATEMENT IS AMENDED AS SET FORTH IN ITEM 8 BELOW. (INSTRUCTION B.7(A))
   B. [ ]  TOTAL ASSIGNMENT - ALL OF SECURED PARTY'S RIGHTS UNDER THE FINANCING STATEMENT HAVE BEEN ASSIGNED TO THE ASSIGNEE
           WHOSE NAME AND ADDRESS ARE SET FORTH IN ITEM 8 BELOW. (INSTRUCTION B.7(B))
   C. [ ]  PARTIAL ASSIGNMENT - SOME OF SECURED PARTY'S RIGHTS HAVE BEEN ASSIGNED TO THE ASSIGNEE SHOWN IN ITEM 8 BELOW.
           (INSTRUCTION B.7(C))
   D. [ ]  CONTINUATION - THE ORIGINAL STATEMENT IS STILL EFFECTIVE. (INSTRUCTION B.7(D))
   E. [ ]  TOTAL RELEASE - THE SECURED PARTY RELEASES ALL OF THEIR INTEREST IN THE COLLATERAL. (INSTRUCTION B.7(E))
   F. [X]  PARTIAL RELEASE - THE SECURED PARTY RELEASES THE FOLLOWING COLLATERAL DESCRIBED IN ITEM 8 BELOW. (INSTRUCTION B.7(F))
   G. [ ]  TERMINATION - THE SECURED PARTY(IES) OF RECORD NO LONGER CLAIMS A SECURITY INTEREST AND THE FINANCING STATEMENT IS
           TERMINATED. (INSTRUCTION B.7(G))

8.  The 5.119 acre tract being more particularly described on Exhibit "A" attached hereto.

9.  SIGNATURE(S)                                                THIS SPACE FOR USE OF FILING OFFICER
    OF                                                         (DATE, TIME, NUMBER, FILING OFFICER)
    DEBTOR(S)

    SIGNATURE(S)
    OF
    SECURED PARTY(IES)      /s/ [illegible]

10. Return copy to:

NAME                Barry E. Putterman
ADDRESS             9 Greenway Plaza, Suite 2300
CITY                Houston, Texas  77046
STATE
ZIP

STANDARD FORM - FORM UCC-3 (REV. 9/1/92) [C] 1992 OFFICE OF THE SECRETARY OF STATE OF TEXAS

                       (1) FILING OFFICER COPY - NUMERICAL

</TABLE>
<PAGE>   59
                                  EXHIBIT "A"

Being a tract or parcel containing 5.119 acres (222,986 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118,831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 5.119 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

COMMENCING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3,147,967.40,
Y=698,487.10, thence:

     South 14 degrees 53'21" West, with said west ROW line, a distance of
     206.00 feet to a 5/8-inch iron rod with plastic cap set marking the POINT
     OF BEGINNING and northeast corner of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, continuing with said west ROW line, a
distance of 330.70 feet to a 5/8-inch iron rod with plastic cap set marking the
southeast corner of the herein described tract;

THENCE, NORTH 75 degrees 06'39" West, a distance of 762.08 feet to a 5/8-inch
iron rod with plastic cap set marking the southwest corner of the herein
described tract;

THENCE, NORTH 41 degrees 44'27" East, a distance of 334.23 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 03 degrees 35'59" an arc length of 47.75 feet, and a chord
which bears North 39 degrees 56'28" East, 47.74 feet to an "X" in concrete set
marking the most northwesterly corner of the herein described tract;

THENCE, SOUTHEASTERLY, with a non-tangent curve to the left having a radius of
87.50 feet, an arc length of 93.13 feet, a central angle of 60 degrees 59'01"
and a chord which bears South 58 degrees 25'28" East, 88.80 feet to a
5/8-inch iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH 88 degrees 54'58" East, a distance of 27.76 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, EASTERLY, with a curve to the right having a radius of 281.50 feet, an
arc length of 67.83 feet, a central angle of 13 degrees 48'19" and a chord
which bears South 82 degrees 00'48" East, 67.66 feet to a 5/8-inch iron rod
with plastic cap set marking a point of tangency;

THENCE, SOUTH 75 degrees 06'39" East, a distance of 411.72 feet to the POINT OF
BEGINNING and containing 5.119 acres (222,986 square feet) of land (this
description is based on an ALTA/ACSM Land Title Survey and plat prepared by
Terra Surveying Company, Inc. Project Number 0043-9603-S).
<PAGE>   60

                          GROUND SUB-SUBLEASE AGREEMENT

1.   PARTIES. This Ground Sub-Sublease Agreement (this "Lease") is entered into
effective the 23rd day of November, 1998, and is by and between TMX REALTY
CORPORATION, A DELAWARE CORPORATION (the "Lessor"), and INTROGEN THERAPEUTICS,
INC., A DELAWARE CORPORATION (the "Lessee").

2.   PREMISES.

     2.1 Lessor leases to Lessee, and Lessee leases from Lessor, to have and to
hold same for the term, at the rental and upon all of the conditions set forth
herein, real property generally described as approximately 2,619 acres near the
corner of Almeda Road and Holcombe Boulevard, in Houston, Harris County, Texas,
as more particularly described on Exhibit "A" attached hereto and incorporated
by reference, including all improvements to be constructed thereon and all
easements, rights-of-way and appurtenances thereto (the "Premises"). This Lease
is made and Lessee accepts leasehold title to the Premises subject to the
matters affecting title which are described on Exhibit "B" to the Ground
Sublease (the "Permitted Title Exceptions") and the following conditions and
limitations: the "Premises" is a portion of a larger tract of real property
which is subject to the terms and provisions of an Enhanced-Use Lease dated
August 25, 1993, as amended, (the "Enhanced-Use Lease") between Amelang
Partners, Inc. and the United States Department of Veterans Affairs (the
"Department"), and is also subject to the Amended and Restated Ground Sublease
Agreement between Amelang Partners, Inc., and Introgen Therapeutics, Inc., dated
September 24, 1998, (the "Ground Sublease"), which Ground Sublease was assigned
to Lessor by an Assignment and Assumption Agreement between Introgen
Therapeutics, Inc. and Lessor dated November 23, 1998, and the parties hereto
agree that nothing herein shall constitute a modification of, waiver of or
amendment to such terms, conditions, rights and responsibilities of the parties
to the Enhanced-Use Lease or the Ground Sublease. The Permitted Title Exceptions
expressly include an easement granted by Lessor to Aid Association for Lutherans
described in Section 7.3 hereof.

     2.2 Lessor will construct two buildings on the Premises (collectively
referred to as the "Buildings"), as required by the Ground Sublease.

     2.3 As between Lessor and Lessee, Lessor is solely responsible for the
diligent construction of any and all leasehold improvements to be made to the
Premises, including the Buildings. All exterior elevations, architectural
structures, colors and appearances of the Buildings will be completed
substantially in accordance with those shown in the plans and specifications
attached as Exhibits "C" and "D" to the Ground Sublease. Lessor will be solely
responsible for securing the consent of any and all governmental,
quasi-governmental, regulatory and other authorities, and such other permits,
consents and permissions as are required to complete the Buildings and any other
improvements to be constructed by Lessor on the Premises.

<PAGE>   61
3. TERM

         3.1 Term. The term of this Lease (the "Term") will commence on the date
first written above (the "Commencement Date") and end September 30, 2026.

4. RENT

         4.1 Lessee agrees to pay the Lessor monthly rental payments equal in
amount to the sum of (a) the amount due and owing by Lessor to Amelang Partners,
Inc. as monthly rent under the Ground Sublease, plus (b) the amount of each
monthly payment, including principal and interest, which becomes due and owing
each month by Lessor to Riverway Bank pursuant to that certain Promissory Note
in the original amount of $6,000,000 executed by Lessor herein and payable to
the order of Riverway Bank, which Promissory Note is secured by a Leasehold Deed
of Trust upon Lessor's interest in the Premises, plus (c) five (5%) percent of
the amounts stipulated in subparagraphs 4.1(a) and 4.1(b). The amount of rent
owing by Lessee to Lessor calculated in accordance with the foregoing sentence
for each month during the term of this Lease shall be due and owing on the first
day of said month.

         4.2 Lease Year. The term "Lease Year" means, for the first Lease Year,
the period that commences on the Commencement Date and terminates on the last
day of the twelfth (12th) full calendar month after the Commencement Date. Each
subsequent Lease Year means a period of twelve (12) full calendar months
commencing on the anniversary of the day following the end of the first Lease
Year. The last Lease Year of the Term may be less than twelve (12) full calendar
months, depending upon the date of termination of the Lease.

         4.3 Late Charges. If Lessee fails to either pay any installment of
Annual Basic Rent when due or make any other payment for which Lessee is
obligated under this Lease when due, Lessor will incur costs and expenses not
contemplated by this Lease, the exact amount of which are difficult and
impractical to ascertain, including without limitation, processing and
accounting charges and financing costs and late changes that may be imposed by
the terms of any incumbrance on or note secured by the Premises. Therefor, in
the event of any such late payment, Lessee will pay to Lessor a late charge
equal to five percent (5%) of the amount due or One Hundred Dollars ($100.00),
whichever is greater, to compensate Lessor for the extra costs incurred as a
result of such late payment. All such delinquent rent and other sums will bear
interest from due date until paid at fifteen percent (15%) per annum or the
maximum lawful rate, whichever is less.

5. INTENTIONALLY OMITTED

6. CONSTRUCTION

         6.1 Lessor will construct the improvements described in the plans and
specifications described in Exhibits "C" and "D" to the Ground Sublease. Lessor
will pay for the cost of construction of the Buildings and other improvements,
including expenses of construction, building permits, plans and specifications,
plat plans, removing existing improvements from the Premises,

<PAGE>   62

bringing utilities to the Premises, soil preparation, pavement, removal of
underground obstructions, soil fill, compacting soil, and other work required to
complete the construction.

         6.2 Lessor must obtain Lessee's approval of any change orders under the
contract to be entered into by Lessee to construct the improvements described in
the plans and specifications referred to in Exhibits "C" and "D" attached
hereto, but only to the extent that such change orders will materially alter the
exterior elevations, architectural design, colors, or other external appearance
of the Buildings. Such approval will not be unreasonably withheld. Lessor will
provide in its construction contract that the general contractor will construct
the improvements in a good and workmanlike manner and in accordance with such
plans and specifications.

7. USE AND RESTRICTIONS THEREON.

         7.1 Use. Lessee will use the Premises only for purposes and uses
permitted under the VA Lease Agreement and the Ground Sublease. Lessee will not
use or occupy the Premises in violation of law or of the certificate of
occupancy issued for the Premises, and will, upon written notice of Lessor,
discontinue any use of the Premises which is declared by any governmental
authority having jurisdiction to be a violation of law or said certificate of
occupancy. Lessee will not use or allow the Premises to be used for any immoral
or unlawful purpose, nor will Lessee cause, maintain or permit any loud noise,
vibration or other nuisance in, on or about the Premises or otherwise disturb
the peaceful possession of adjoining or nearby property. Lessee will not keep
any incinerators, storage tanks or like equipment in the open or exposed to
public view or view from adjacent buildings.

         7.2 Use Restrictions. In addition, except with the prior written
consent of Lessor (which consent may be withheld in Lessor's sole and absolute
discretion, and shall always be withheld until Lessor has obtained the prior
written consent of Lessor's third party lender), Lessee shall not use the
Premises in a manner inconsistent with the following restrictions, which shall
be covenants running with the Premises and be binding upon Lessee and its
successors and assigns during the term of this Sublease or any renewal or
extension hereof: (a) the exterior design of and development shall be compatible
with the exterior architectural design of the adjacent VA Medical Center and the
improvements situated on the Initial Development (as defined in Section 7.3
hereof); (b) the Buildings shall be situated on the Premises at least
twenty-five (25) feet away from F.M. 521 (Almeda Road) and at least ten (10)
feet away from the common boundary line with the Initial Development; (c)
adequate on-site parking shall be established, including, without limitation,
meeting the minimum requirements of the City of Houston Parking Ordinance as
they apply generally to all properties; (d) the Premises shall contain adequate
surface drainage so that no excessive drainage flows onto the surface of any
other portion of the property covered by the Enhanced Use Lease, and (e) no curb
cuts for vehicular traffic shall be located on any portion of the Premises
within twenty (20) feet of the northern boundary of the Premises. Within twelve
(12) days of a request from time to time by Lessor, Lessee shall deliver or
cause to be delivered to Lessor evidence reasonably satisfactory to Lessor that
Lessee is bound by and is then in compliance with the foregoing restrictions.

                                       3
<PAGE>   63

         7.3 Utility Easement. Lessee hereby acknowledges and agrees that
Amelang Partners, Inc. has granted to Aid Association for Lutherans ("AAL"),
and any successor to the interest of AAL, a non-exclusive easement on and Under
the Premises to provide water to the Initial Development (as hereinafter
defined) and to treat wastewater from the Initial Development through the lines
presently existing under the Premises, together with reasonable rights of
access to repair such lines. Amelang Partners, Inc., at its sole cost and
expense may, and hereby reserves the right, at Lessee's sole cost and expense,
to relocate such lines to other locations on the Premises. The "Initial
Development" is the 3,135 acre tract described in Deed of Trust and Security
Agreement executed by Lessor to Barry E. Putterman, Trustee, filed under
Clerk's File No. S319696, and recorded under Film Code Reference No.
###-##-#### in the Official Public Records of Real Property of Harris County,
Texas, as amended to date.

8. QUIET ENJOYMENT. Lessee, upon payment the Annual Basic Rent and performing
its other covenants and agreements herein set forth, will peaceably and quietly
have, hold and enjoy the Premises for the Term without hindrance or molestation,
subject to the Permitted Title Exceptions. Lessor shall perform its obligations
under the Enhanced Use Lease and the Ground Sublease and shall not agree to any
termination thereof during the term of this Lease. In the event Lessor should
default in timely payment of the rentals due under the Ground Sublease, Lessee
may, at its option and in addition to any other remedies available to Lessee,
make such payments on behalf of Lessor and receive credit for amounts so paid
against rent due or to become due hereunder.

9. CONDITION OF PREMISES.

         9.1 Acceptance. By taking possession of the Premises, Lessee will be
deemed to have accepted the Premises as being in good and acceptable order,
condition, and repair, and in accordance with the requirements of this Lease.
LESSOR MAKES NO REPRESENTATION OR WARRANTY AS TO THE CONDITION OF THE PREMISES
OR AS TO THE USE OR OCCUPANCY WHICH MAY BE MADE THEREOF, EITHER EXPRESS OR
IMPLIED. LESSEE WAIVES ANY AND ALL IMPLIED WARRANTIES OTHER THAN THE WARRANTY OF
QUIET ENJOYMENT SET FORTH IN SECTION 8, INCLUDING, WITHOUT LIMITATION, ANY
IMPLIED WARRANTY OF MERCHANTABILITY, HABITABILITY OR SUITABILITY FOR ANY
INTENDED COMMERCIAL PURPOSES. LESSOR MAKES NO REPRESENTATIONS OR WARRANTIES AND
SHALL NOT IN ANY WAY BE LIABLE FOR ANY REPRESENTATIONS OR WARRANTIES, INCLUDING,
WITHOUT LIMITATION, (A) THE DIMENSIONS, SIZE OR ACREAGE OF THE PREMISES; (B) THE
CONDITION OF THE PREMISES OR ANY BUILDINGS, STRUCTURES OR IMPROVEMENTS THEREON
OR THE SUITABILITY OF THE PREMISES FOR HABITATION OR FOR LESSEE'S INTENDED USE
OR FOR ANY USE WHATSOEVER; (C) ANY APPLICABLE ENVIRONMENTAL, BUILDING, ZONING OR
FIRE LAWS OR REGULATIONS OR WITH RESPECT TO COMPLIANCE THEREWITH OR WITH RESPECT
TO THE EXISTENCE OF OR COMPLIANCE WITH ANY REQUIRED PERMITS, IF ANY, OR ANY
GOVERNMENTAL AGENCY OR OTHER

                                       4
<PAGE>   64

THIRD PARTY; AND/OR (D) THE ABSENCE OF ANY HAZARDOUS OR TOXIC MATERIALS OR
SUBSTANCES. LESSEE ACKNOWLEDGES TO LESSOR THAT LESSEE HAS HAD THE OPPORTUNITY TO
FULLY INSPECT THE PREMISES, AND LESSEE ASSUMES THE RESPONSIBILITY AND RISKS OF
ALL DEFECTS AND CONDITIONS, INCLUDING SUCH DEFECTS AND CONDITIONS, IF ANY, THAT
CANNOT BE OBSERVED BY CASUAL INSPECTION.

         9.2 Regulation. Except as otherwise provided in this Lease, Lessee
accepts the Premises in their condition existing as of the Commencement Date,
subject to all applicable zoning, municipal, county and state laws, ordinances
and regulations governing and regulating the use of the Premises, and Permitted
Title Exceptions.

         9.3 Lease Termination. On the last day of the Term or on the sooner
termination of this Lease, Lessee will surrender the Premises to Lessor in good
condition and repair, normal wear and tear excepted.

         9.4 Ownership of Buildings, Improvements and Fixtures. Any buildings,
improvements, additions, alterations and fixtures (except furniture and trade
fixtures) constructed, placed or maintained on any part of the Premises during
the Term are considered part of the real property of the Premises and must
remain on the Premises and become Lessor's property when this Lease terminates.
Lessee shall have the right to, from time to time, remodel, renovate and
reconfigure, the Buildings provided that: (1) Lessee shall comply with all
applicable laws and regulations pertaining to such activities including, without
limitation, building and zoning ordinances, and (2) Lessee shall not materially
alter the external appearance of the Buildings without Lessor's written consent,
which consent will not be unreasonably withheld.

         9.5 Right to Remove Personal Property. Lessee may, at any time while it
occupies the Premises, remove any furniture, machinery, equipment or other trade
fixtures owned or placed by Lessee, its subtenants or licensee, in, under or on
the Premises, or acquired by the Lessee, whether before or during the Term.
Before this Lease terminates, Lessee must repair any damage to any buildings or
improvements on the Premises resulting from use that causes damage beyond normal
wear and tear, or from the removal of any such items. Any such items not removed
at or before the date this Lease terminates will become Lessor's property on
that date, except for those items which Lessor requires Lessee to remove, which
shall remain the property of Lessee.

10. NOTICES. Any notice, demand or communication required or permitted to be
given hereunder must be in writing and may be given by personal delivery or by
mail, and if given by mail, will be deemed given when deposited in the United
States mail, registered or certified mail, postage prepaid, addressed to Lessee
at the Premises, or to Lessor at 301 Congress Avenue, Suite 2025, Austin, Texas
78701. Either party may specify a different or additional address for notice
purposes by written notice to the other, except that Lessor may in any event use
the Premises as Lessee's sole address for notice purposes.

                                       5
<PAGE>   65

11. HOLDING OVER. If Lessee holds over after the expiration or earlier
termination of the Term without the express written consent of Lessor, Lessee
will become a lessee at sufferance only, at a rental rate equal to one hundred
fifty percent (150%) of the Annual Basic Rent in effect upon the date of such
expiration (prorated on a daily basis) and otherwise subject to the terms,
covenants and conditions herein specified, so far as applicable. Acceptance by
Lessor of rent after such expiration or earlier termination will not result in a
renewal of this Lease.

12. MAINTENANCE, REPAIRS AND ALTERATIONS.

         12.1 Lessee's Obligations. Lessee will, at Lessee's sole cost and
expense, keep in good order, condition and repair the Premises and every part
thereof, structural and nonstructural (whether or not such portion of the
Premises requiring repair or the means of repairing the same are reasonably or
readily accessible to Lessee, and whether or not the need for such repairs
occurs as a result of Lessee's use, any prior use, the elements, the age or
quality of construction of such portion of the Premises) including, without
limiting the generality of the foregoing, all plumbing, heating, ventilation,
air conditioning (Lessee will procure and maintain, at Lessee's expense, a
heating, ventilation and air conditioning system maintenance contract acceptable
to Lessor), electrical, lighting facilities and equipment within the Premises,
fixtures, walls (interior and exterior), foundations, ceiling, roofs (interior
and exterior), floors, windows, doors, plate glass and skylights located within
the Premises, and all landscaping (Lessee will procure and maintain, at Lessee's
expense, a landscaping maintenance contract acceptable to Lessor), driveways,
parking lots, fences and signs located on the Premises and sidewalks and
parkways adjacent to the Premises. Lessor acknowledges that Lessor will charge
no fees or expenses to Lessee for Lessor's overhead, services, or any other
item, except to the extent that may be necessary to cure Lessee's defaults under
express provisions of this Lease.

         12.2 Lessor's Rights. If Lessee fails to perform Lessee's obligations
under this Article 12 or under any other article of this Lease, Lessor may, at
its option (but is not required to), in addition to any other remedies available
to Lessor, enter upon the Premises after ten (10) days prior written notice to
Lessee (except in the case of an emergency, in which case no notice is
required), perform such obligations on Lessee's behalf and put the same in good
order, condition and repair, and the cost thereof together with interest at the
rate described in paragraph 4.5 will become due and payable as additional rental
to Lessor.

         12.3 Lessor's Obligations. Lessor has no obligation to either repair
and maintain the Premises or the fixtures or improvements thereon or any
equipment or other personal property therein, whether structural or
nonstructural (all of which obligations are Lessee's), or to pay any other cost
or expense whatsoever directly or indirectly relating to the construction,
maintenance, repairs, renovation, reconstruction, management, leasing, operation
or use of the Premises. Lessee waives the benefit of any statute now or
hereinafter in effect which would otherwise afford Lessee the right to make
repairs at Lessor's expense or to terminate this Lease because of Lessor's
failure to keep the Premises in good order, condition and repair.

                                       6
<PAGE>   66

13. LIENS. Lessee will not permit any mechanic's, materialmen's or other lien to
be filed against the interest of the United States Department of Veterans
Affairs or Amelang Partners, Inc., or of Lessor in the Premises. Lessor has the
right at all reasonable times to post and keep posted on the Premises any
notices which it deems necessary for protection from such liens. If any such
liens are filed, Lessor may, without waiving its rights and remedies based on
such breach of this Lease by Lessee and without releasing Lessee from any of its
obligations, cause such liens to be released by any means it deems proper,
including payment in satisfaction of the claim giving rise to such lien. Lessee
will pay to Lessor at once, upon notice by Lessor, any sum paid by Lessor to
remove such liens, together with interest at the rate per annum described in
paragraph 4.5 above. Lessor acknowledges that Lessee will create liens and
security interests in Lessee's leasehold estate, and Lessor expressly consents
to such liens and security interests.

14. BANKRUPTCY. If Lessee files a petition in bankruptcy under any provision of
the Bankruptcy Code, or if Lessee is adjudicated a bankrupt in involuntary
bankruptcy proceedings and such adjudication has not been vacated within ninety
(90) days from the date of filing, or if a receiver or trustee is appointed of
Lessee's property and the order appointing such receiver or trustee is not set
aside or vacated within ninety (90) days after the entry thereof, or if Lessee
makes a general assignment for the benefit of creditors, or if Lessee's interest
in this Lease or a substantial portion of Lessee's assets located at the
Premises are seized or attached and such seizure or attachment is not discharged
within ninety (90) days, or if this Lease, by operation of law or otherwise,
passes to any person or persons other than Lessee, then in any such event Lessor
may terminate this Lease, if Lessor so elects, with or without notice of such
election and with or without entry or action by Lessor. In addition to any and
all rights and remedies allowed by law or equity, Lessor is, upon such
termination, entitled to recover damages in the amount provided in paragraph
20.2.

15. INDEMNIFICATION. Lessee will indemnify, defend and hold Lessor and its
officers, directors, agents and employees and the Department and its officers,
employees and agents, harmless from all claims, demands, costs and expenses
(including reasonable attorneys' fees) directly or indirectly arising from or in
connection with the Premises, including the construction contemplated thereon.
Lessee's use of the Premises or the conduct or its business or from any
activity, work or thing done, permitted or suffered by Lessee in or about the
Premises. Lessor will indemnify, hold harmless and defend Lessee and its
officers, directors, agents, representatives and employees harmless from all
claims, demands, costs and expenses (including reasonable attorney's fees)
directly or indirectly arising from or in connection with the grossly negligent,
willful or intentional acts or omissions of Lessor.

16. INSURANCE.

         16.1 Liability Insurance. Lessee will, at Lessee's expense, obtain and
keep in force during the Term of this Lease, and any other period of occupancy
hereof, insurance with companies acceptable to Lessor and in the minimum amounts
of coverage, all as set forth in the insurance

                                       7
<PAGE>   67

schedule below. Lessee will cause its insurer to name Lessor, Amelang Partners,
Inc., and the Department as additional insureds on said insurance policies. Said
insurance schedule is as follows:

                  (a) Worker's Compensation (including occupational disease)
and Employer's Liability Insurance coverages which supply to all employees in
accordance with the benefits afforded by the statutory Worker's Compensation
Acts applicable to the State, Territory or District of hire, supervision or
place of accident. Employer's liability limits must be at least $500,000.00,
each accident; $500,000.00, disease, each employee; $500,000.00, disease, policy
limit;

                  (b) Comprehensive General Liability Insurance will cover: the
Premises, operations, products and completed operations, independent
contractors, blanket contractual liability, and a cross liability provision, and
contain an endorsement that "the insurance provided the Lessor will be primary
and noncontributing with any other insurance available to the Lessor". The
limits of said insurance will not, however, be less than One Million Dollars
($1,000,000.00) per occurrence and Two Million Dollars ($2,000,000.00)
aggregate;

                  (c) Excess/Umbrella Liability Insurance will be required with
a Two Million Dollar ($2,000,000.00) per occurrence limit; and

                  (d) A policy or policies of insurance covering loss or damage
to the Premises in the amount of the full replacement value thereof, as the same
may exist from time to time, but in no event less than the total amount required
by lenders having liens on the Premises, against all perils included within the
classification of fire, extended coverage, vandalism, malicious mischief, flood,
earthquake and special extended perils ("All Risk" as such term is used in the
insurance industry).

                  (e) Lessee shall require Lessee's Contractor to obtain
insurance coverage of such types and amounts that are standard for construction
projects of this type and reasonably acceptable to Lessor, and all such policies
shall name Lessor and the United States Department of Veterans' Affairs as
additional insureds. Prior to commencement of construction, Lessee shall deliver
to Lessor appropriate certificates evidencing such insurance coverage.

         16.2 Insurers. All insurance policies will be in a form reasonably
satisfactory to Lessor and issued by insurance companies holding a "General
Policyholders Rating" of at least A+XII, or such other rating as may be required
by a lender having a lien on the Premises as set forth in the most current issue
of "Best's Insurance Guide".

         16.3 Exemption of Lessor from Liability. None of the Lessor nor Amelang
Partners, Inc. nor the Department will be liable for injury to Lessee's business
or any loss of income therefrom or for damage to the goods, wares, merchandise
or other property of Lessee, Lessee's employees, invitees, customers or any
other person in or about the Premises, nor will such parties be liable for
injury to the person of Lessee, Lessee's employees, agents or contractors,
whether such damage or injury is caused by or results from any event, natural or
otherwise, including, without limiting the generality of the foregoing, fire,
steam, electricity, gas, water or rain, or from the breakage, leakage,

                                       8
<PAGE>   68

obstruction or other defects of pipes, sprinklers, wires, appliances, plumbing,
air conditioning or lighting fixtures.

         16.4 Insurance Policies. All insurance policies obtained by Lessee
will:

                  (a) Provide for waiver of subrogation releasing Lessor and
Amelang Partners, Inc. from any claims for damage to any persons or property in
or about the Premises or any other insured risk and contain all endorsements for
Lessor's or Lessee's insurance company which may be necessary or required to
effect this waiver of subrogation (except that this Section 16.4(a) will not
apply to workers' compensation insurance policies);

                  (b) Provide that such policy may not be canceled, reduced in
coverage or amount, or amended in any manner for any reason whatsoever except
after at least thirty (30) days prior written notice to Lessor and Lessor's
lender, if any;

                  (c) Within ten (10) days after execution of this Lease, and
thereafter, upon demand at any time during the Term, Lessee will deliver to
Lessor copies of policies or certificates of insurance evidencing existence of
the amounts and forms of coverage and proof of payment satisfactory to Lessor;
and

                  (d) Lessee will, at least ten (10) days prior to the
expiration of the policies required hereunder, furnish Lessor with renewal
policies or certificates or "binders" thereof. Failure to do so may result in
Lessor ordering such insurance and charging the cost to Lessee as additional
rent, or may, in Lessor's sole discretion, constitute a default under this
Lease. If Lessor does obtain any insurance that is the responsibility of Lessee
under this Lease, Lessor will deliver to Lessee a written statement setting
forth the cost of such insurance and showing in reasonable detail the manner in
which it has been computed.

17. DAMAGE OR DESTRUCTION.

         17.1 Definitions.

                  (a) "PREMISES PARTIAL DAMAGE" means damage or destruction to
the Premises to the extent that the cost of repair is less than twenty-five
percent (25%) of the then replacement cost of the Premises;

                  (b) "PREMISES BUILDING PARTIAL DAMAGE" means damage or
destruction to the building, if any, constructed on the Premises to the extent
that the cost of repair is less than twenty-five percent (25%) of the then
replacement cost of such building as a whole;

                  (c) "PREMISES TOTAL DESTRUCTION" means damage or destruction
to the Premises to the extent that the cost of repair is twenty-five percent
(25%) or more of the then replacement cost of the Premises;

                                       9
<PAGE>   69

                  (d) "PREMISES BUILDING TOTAL DESTRUCTION" means damage or
destruction to the building, if any, constructed on the Premises to the extent
that the cost of repair is twenty-five percent (25%) or more of the then
replacement cost of such building as a whole; and

                  (e) "INSURED LOSS" means damage or destruction which was
caused by an event required to be covered by any of the insurance described in
Article 16 and for which the insurance proceeds of such policies are sufficient
to pay the full cost to repair, excluding any deductible amounts.

         17.2 Partial Damage. Subject to the provisions of paragraphs 17.3 and
17.4, if there is damage which is an Insured Loss and which is classified as
either Premises Partial Damage or Premises Building Partial Damage, then Lessee
will, utilizing only insurance proceeds, repair such damage, as soon as
reasonably possible, and this Lease will continue in full force and effect
without any abatement of rent.

         17.3 Total Destruction. If there is damage, whether or not an Insured
Loss (including destruction required by any authorized public authority), which
is classified as either Premises Total Destruction or Premises Building Total
Destruction, Lessee shall have the option to either: (a) terminate this Lease as
of the date of such total destruction, in which event all insurance proceeds
will be payable solely to Lessee, and Lessor waives any and all claims to such
insurance proceeds, or (b) repair the Premises as soon as reasonably possible,
in which event this Lease will continue in full force and effect.

         17.4 Damage Near End of Term. If at any time during the last twelve
(12) months of the Term (including any renewals or extensions) of this Lease
there is damage, whether or not an Insured Loss, which is classified as either
Premises Partial Damage or Premises Building Partial Damage, either party may,
at its option, cancel and terminate this Lease as of the date of occurrence of
such damage by giving written notice to the other party of its election to do so
within thirty (30) days after the date of occurrence of such damage in which
event all insurance proceeds will be payable solely to Lessee, and Lessor waives
any and all claims to such insurance proceeds.

         17.5 Demolition and Removal. If pursuant to Section 17.3 or 17.4 either
party elects to terminate the Lease, then Lessee shall demolish and remove the
damaged Buildings and improvements and restore the Premises as nearly as
reasonably possible to their original condition.

18. REAL PROPERTY TAXES

         18.1 Payment of Taxes. Lessee will pay the real property tax, as
defined in paragraph 18.2, applicable to the Premises and all personal property
taxes during the Term. All payments will be made at least ten (10) days prior to
the due date. Lessee will, within five (5) days after payment, furnish Lessor
with satisfactory evidence that such real property taxes have been paid. If any
real property taxes paid by Lessee covers any period of time prior to or after
the expiration of the Term,

                                       10

<PAGE>   70
Lessee's share of such real property taxes will be equitably prorated to cover
only the period of time within the tax year during which this Lease was in
effect, and Lessor will reimburse Lessee to the extent required. If Lessee fails
to pay any such real property taxes, Lessor has the right to pay the same, in
which case, Lessee will repay such amounts to Lessor on the due date of Lessee's
next rent installment, together with interest at the rate described in paragraph
4.4.

         18.2 Definition of "Real Property Tax". The term "real property tax"
means all ad valorem taxes and assessments upon the real property constituting
the Premises, including city, county, and state and all other ad valorem taxes,
existing now or in the future.

19. UTILITIES AND MAINTENANCE. Lessee will pay for all water, gas, heat, light,
power, telephone, waste removal, sewer and other utilities and services supplied
to the Premises including the cost of bringing utilities to the Premises and any
tap or connection fees, together with any taxes thereon. Lessee will also pay
for all maintenance and repair of the entire premises, both interior and
exterior.

20. DEFAULTS AND REMEDIES.

         20.1 The occurrence of any one or more of the following events
constitutes a default by Lessee:

                  (a) the abandonment of the Premises by Lessee. Abandonment is
defined to mean failure of Lessee to keep the Premises (including grounds and
landscaping) clean for ten (10) consecutive business days or longer, or for
fifteen (15) or more days in any month, after notice and opportunity to cure as
provided in Section 20.1(c) below;

                  (b) the failure by Lessee to make any payment of rent or
additional rent, or any other payment required to be made by Lessee hereunder,
as and when due if such failure continues for a period of ten (10) days after
Lessor gives notice of such failure; and

                  (c) the failure by Lessee to observe or perform any of the
express or implied covenants or provisions of this Lease to be observed or
performed by Lessee other than specified in Paragraph 20.1(b) above, and such
failure continues for thirty (30) days after written notice thereof from Lessor
to Lessee. Any such notice will be in lieu of and not in addition to any notice
required under applicable state statutes regarding unlawful detainer actions. If
the nature of Lessee's default is such that more than thirty (30) days are
reasonably required for its cure, then Lessee will not be deemed to be in
default if Lessee commences such cure within said thirty (30) day period and
thereafter diligently prosecutes such cure to completion, which completion must
occur within a reasonable period of time, considering the nature of the
particular default in question.

         20.2 Upon the occurrence of any event of default, Lessor has the option
to pursue any one or more of the following remedies without any notice or
demand:

                                       11
<PAGE>   71

                  (a) Without declaring the Lease terminated, Lessor may
terminate Lessee's right to possession of the Premises and enter upon and take
possession of the Premises by picking and changing locks if necessary, and lock
out, expel or remove Lessee and any other person who may be occupying all or any
part of the Premises without being liable for any claim for damages, and relet
the Premises on behalf of Lessee and receive the rent directly by reason of the
reletting. Lessee agrees to pay Lessor on demand any deficiency that may arise
by reason of any reletting of the Premises; further Lessee agrees to reimburse
Lessor for any expenditures made by it in order to relet the Premises,
including, but not limited to, brokerage fees, remodeling and repair costs; or

                  (b) Without declaring the Lease terminated, Lessor may
terminate Lessee's right to possession of the Premises and enter upon the
Premises by picking and changing locks if necessary without being liable for any
claim for damages, and do whatever Lessee is obligated to do under the terms of
this Lease. Lessee agrees to reimburse Lessor on demand for any expenses which
Lessor may incur in effecting compliance with Lessee's obligations under this
Lease. LESSEE AGREES THAT LESSOR WILL NOT BE LIABLE FOR ANY DAMAGES RESULTING TO
LESSEE FROM EFFECTING COMPLIANCE WITH LESSEE'S OBLIGATIONS UNDER THIS LEASE
CAUSED BY THE NEGLIGENCE OF LESSOR, OR OTHERWISE; or

                  (c) Lessor may terminate this Lease, in which event Lessee
will immediately surrender the Premises to Lessor, and if Lessee fails to
surrender the Premises, Lessor may, without prejudice to any other remedy which
it may have for possession or arrearages in rent, enter upon and take possession
of the Premises by picking or changing locks if necessary, and lock out, expel
or remove Lessee and any other person who may be occupying all or any part of
the Premises without being liable for any claim for damages. Lessee agrees to
pay on demand the amount of all loss and damages which Lessor may suffer by
reason of the termination of this Lease under this section, including, without
limitation, loss and damage due to failure of Lessee to maintain and repair the
Premises as required hereunder and/or due to the inability to relet the Premises
on satisfactory terms or otherwise. This Lease may be terminated by Lessor only
by mailing or delivering written notice of such termination to Lessee, and no
other act or omission of Lessor will be construed as a termination of this
Lease.

                  (d) If Lessor exercises its remedy to lock out Lessee in
accordance with any provision of this Lease, Lessee agrees that no notice is
required to be posted by Lessor on any door to the Premises (or elsewhere)
disclosing the reason for such action or any other information, and that Lessor
is not obligated to provide a key to the changed lock to Lessee unless Lessee
has:

                           (i) brought current all payments due to Lessor under
                  this Lease (unless Lessor has permanently repossessed the
                  Premises or terminated this Lease, in which event payment of
                  all past due amounts will not obligate Lessor to provide a
                  key);

                                       12
<PAGE>   72

                           (ii) fully cured and remedied to Lessor's
                  satisfaction all other defaults of Lessee under this Lease
                  (unless Lessee has abandoned or vacated the Premises, in which
                  event Lessor will not be obligated to provide the new key to
                  Lessee under any circumstances); and

                           (iii) provided Lessor with an additional security
                  deposit and assurances satisfactory to Lessor that Lessee
                  intends to and is able to meet and comply with its future
                  obligations under this Lease, both monetary and nonmonetary.

THE PROVISIONS OF THIS PARAGRAPH 20.2(d) ARE INTENDED TO OVERRIDE AND SUPERSEDE
ANY CONFLICTING PROVISIONS OF THE TEXAS PROPERTY CODE OR ANY SIMILAR LAW IN ANY
OTHER STATE, AND ANY AMENDMENTS OR SUCCESSOR STATUTES THERETO, AND OF ANY OTHER
LAW, TO THE MAXIMUM EXTENT PERMITTED BY THE LAW.

21. CONDEMNATION. If more than either thirty percent (30%) of the floor area of
either Building located on the Premises or fifty percent (50%) of the land
area of the Premises which is not occupied by any building is taken by power of
eminent domain (herein called "condemnation"), Lessee may, at Lessee's option,
to be exercised in writing only within thirty (30) days after Lessor has given
Lessee written notice of such taking (or in absence of such notice, within
thirty (30) days after the condemning authority has taken possession), terminate
this Lease as of the date the condemning authority takes such possession. If
Lessee does not terminate this Lease in accordance with the foregoing, this
Lease and the obligation to pay rent will remain in full force and effect,
except that rent will be reduced to the same proportion that the floor area of
the Buildings on the Premises bears to the original floor area of the Buildings
on the Premises. No reduction of rent will occur if the only area taken is that
which does not have a building located thereon. Any award for the taking of all
or any part of the Premises under the power of eminent domain or any payment
made under threat of the exercise of such power will be first allocated to
Lessee up to the replacement cost of the Buildings and other improvements on the
Premises, and then equitably allocated to Lessor and Lessee in proportion to the
value of their respective leasehold interests, whether such award is made as
compensation for diminution in value of the leasehold or for the taking of the
fee, or as severance damages, or for the bonus value or market value of this
Lease, or for the value of any option to extend the term of this Lease or to
purchase the Premises; provided, however, that Lessee is entitled to any award
for loss of or damage to Lessee's trade fixtures and removable personal
property, provided such award is separately made. If this Lease is not
terminated by reason of such condemnation, Lessee, to the extent of severance
damages received by Lessee in connection with such condemnation, will repair any
damage to the Premises caused by such condemnation, except to the extent that
Lessor has been reimbursed therefor by the condemning authority. Lessee will pay
any amount in excess of such severance damages required to complete such repair.

                                       13
<PAGE>   73

22. ESTOPPEL CERTIFICATE. Within ten (10) days following any written request
which Lessor or Lessee may make to the other from time to time, the requested
party will execute and deliver to the requesting party a statement certifying
(i) the date of commencement of this Lease; (ii) the fact that this Lease is
unmodified and in full force and effect (or, if there have been modifications
hereto, that this Lease is in full force and effect, and stating the date and
nature of such modifications); (iii) the date to which the rental and other sums
payable under this Lease have been paid; (iv) that there are no current defaults
under this Lease by either Lessor or Lessee, except as specified in the
statement; and (v) such other matters reasonably requested. Lessor and Lessee
intend that any statement delivered pursuant to this Paragraph 22 may be relied
upon by any underwriter, mortgagee, beneficiary, purchaser or prospective
purchaser of the Premises or any interest herein or any other party with whom
the requesting party may contemplate conducting a business transaction.

23. GOVERNING LAW. This Lease will be governed by and construed pursuant to the
laws of the state in which the Premises are located.

24. SUCCESSORS AND ASSIGNS. All of the covenants, conditions and provisions of
this Lease are binding upon and will inure to the benefit of the parties hereto
and their respective heirs, personal representatives, successors and assigns.

25. ATTORNEYS' FEES. If a party defaults in the performance of any of the terms,
covenants, agreements or conditions contained in this Lease, the other party
places in the hands of an attorney the enforcement of all or any part of the
defaulting party's obligations under this Lease, including the recovery of
possession of the Premises, the defaulting party shall pay the non-defaulting
party's costs of collection, including reasonable attorneys' fees, whether suit
is actually filed or not.

26. PERFORMANCE BY LESSEE. All covenants and agreements to be performed by
Lessee under any of the terms of this Lease will be performed by Lessee at
Lessee's sole cost and expense, and without any abatement of rent.

27. MORTGAGE PROTECTION. In the event of any default on the part of Lessee,
Lessor will give notice by registered or certified mail to any beneficiary of a
deed of trust or mortgage covering Lessee's interest in the Premises whose
address has been furnished to Lessor, and offer such beneficiary or mortgagee a
reasonable opportunity to cure the default, including time to obtain possession
of the Premises by power of sale or a judicial foreclosure, if such should prove
necessary to effect a cure, but in no event shall beneficiary or mortgagee be
given more than ninety (90) days to effect such cure.

28. WAIVER. The waiver by Lessor of any breach of any term, covenant or
condition herein contained will not be deemed to be a waiver of any subsequent
breach of the same or any other term, covenant or condition herein contained,
nor will any custom or practice established between the parties in the
administration of the terms hereof be deemed a waiver of or in any way affect
the right of Lessor to insist upon the performance by Lessee in strict
accordance with the terms of this Lease.

                                       14
<PAGE>   74

The subsequent acceptance of rent by Lessor will not be deemed to be a waiver of
any preceding breach by Lessee of any term, covenant or condition of this Lease,
other than the failure of Lessee to pay the particular rent so accepted,
regardless of Lessor's knowledge of such preceding breach at the time of
acceptance of such rent.

29. TERMS AND HEADINGS. The words "Lessor" and "Lessee" as used herein include
the plural as well as the singular. Words used in any gender include other
genders.

30. TIME. Time is of the essence with respect to the performance of every
provision of this Lease.

31. PRIOR AGREEMENT; AMENDMENTS. This Lease contains all of the agreements of
the parties with respect to any matter covered or mentioned in this Lease, and
no prior agreement or understanding pertaining to any such matter will be
effective for any purpose. No provisions of this Lease may be amended or added
to except by an agreement in writing signed by the parties hereto or their
respective successors in interest.

32. SEPARABILITY. Any provision of this Lease which proves to be invalid, void
or illegal in no way affects, impairs or invalidates any other provision hereof,
and such other provision will remain in full force and effect.

33. AUTHORITY. Each person executing this Lease on behalf of a party represents
and warrants that he has been duly authorized by appropriate action of such
party. Lessee agrees to provide to Lessor such information or documents as
Lessor may reasonably request in connection with the foregoing.

34. LESSOR'S ACCESS . Lessor and Lessor's agents have the right upon reasonable
advance notice (except in case of an emergency, when no notice shall be
required) to enter the Premises at reasonable times for the purpose of
inspecting the same.

35. SIGNS. All signs will comply with rules and regulations established by
Lessor, as they may be modified from time to time. Lessee will not place any
signs or other display materials in or about the Premises, if such sign is
visible from the exterior of the Premises, without Lessor's prior written
consent, which will not be unreasonably withheld. Any signs or display materials
violating this provision may be removed and destroyed by Lessor without
compensation to Lessee.

36. PARTY'S LIABILITY. If a party recovers a money judgment against the other
party for acts or failures to act which in any way relate to this Lease, such
judgment will be satisfied only out of the right, title and interest of such
party in the Premises as the same may then be encumbered, and neither party nor
any person or entity comprising a party will be liable for any deficiency.
Neither Lessor nor Lessee shall have the right to levy execution against any
property of the other nor any person or entity comprising the other party other
than to levy against the other party's interest in the Premises.

                                       15
<PAGE>   75

37. SUBORDINATION AND ATTORNMENT. This Lease will be subordinate to the
Enhanced-Use Lease, now on the real property of which the Premises are a part.
Notwithstanding such subordination, Lessee's right to quiet possession of the
Premises will not be disturbed if Lessee is not in default and so long as Lessee
pays the rent and observes and performs all of the provisions of this Lease,
unless this Lease is otherwise terminated pursuant to its terms. In the event of
any sale or assignment of the Premises, Lessee will attorn to the purchaser and
recognize such purchaser as Lessor hereunder.

38. MODIFICATION FOR LENDER. If in connection with obtaining construction,
interim or permanent financing for the Buildings or other improvements on the
Premises, the lender requests reasonable modifications to this Lease as a
condition to such financing, Lessor will not unreasonably withhold, delay or
defer its consent thereto, provided such modifications do not materially
increase the obligations of Lessor or materially adversely affect the leasehold
interest created or Lessor's rights hereunder.

39. ASSIGNMENT AND SUBLETTING. Lessee will not either voluntarily or by
operation of law assign, sell, encumber, pledge or otherwise transfer all or any
part of Lessee's leasehold estate hereunder or permit the Premises to be
occupied by anyone other than Lessee, or sublet the Premises or any portion
thereof without Lessor's prior written consent in each instance, which consent
may not be unreasonably withheld, except that Lessor's consent shall not be
required if: the assignee or sublessee in any such instance shall undertake in
writing to (1) assume this Lease and all of Lessee's duties, liabilities and
obligations hereunder, including, without limitation, the obligation to maintain
the Premises, including exterior grounds and landscaping, in a clean and
attractive manner, (2) refrain from altering the exterior elevation, appearance
or color of the Buildings without Lessor's written consent, (3) operate the
Buildings only for a use or uses consistent and compatible with, and which will
not detract from, the then existing uses of the buildings located on the
surrounding real property which is also subject to the VA Lease Agreement, as
determined by Lessee in its reasonable discretion. In the event that any
proposed sublessee or assignee demonstrates the financial ability, as determined
by Lessor in its reasonable discretion, to operate the Premises and to perform
Lessee's obligations in accordance with the terms and provisions of this Lease
(including payment of rent hereunder), and if such proposed sublessee or
assignee undertakes in writing to perform all such obligations remaining to be
performed after the effective date of the proposed sublease or assignment, then
Lessee shall upon the effective date of such assignment be released from all of
its obligations remaining to be performed under this Lease to be performed
after the effective date of the proposed sublease or assignment, in which event
Lessee shall have no further liability or obligation under this Lease except for
those obligations to be performed up to and through the effective date of such
sublease or assignment; otherwise no subletting or assignment, even with the
consent of Lessor, will relieve Lessee of its obligation to pay the rent and
perform all the other obligations to be performed by Lessee hereunder. In no
event will payment of rent be delayed or abated in connection with any proposal
to sublet or assign this Lease. Consent by Lessor to one or more assignments of
this Lease or to one or more sublettings of the Premises will not operate to
exhaust Lessor's rights under this Article. Lessee agrees to reimburse Lessor
for Lessor's reasonable costs and attorneys' fees incurred

                                       16
<PAGE>   76

in conjunction with the processing and documentation of any such assignment,
subletting, transfer, change of ownership or hypothecation of this Lease. The
acceptance of rent by Lessor from any other person will not be deemed to be a
waiver by Lessor of any provision of this Lease or to be a consent to any
assignment or subletting where consent is necessary. Any other provision hereof
notwithstanding neither sale or transfer of Lessee's corporate stock, nor
purchase by a mortgagee or purchaser at a foreclosure sale shall require
Lessor's consent.

40. HOLD HARMLESS. THE DEPARTMENT AND LESSOR WILL NOT BE LIABLE TO LESSEE'S
EMPLOYEES, AGENTS, INVITEES, LICENSEES OR VISITORS OR TO ANY OTHER PERSON FOR
THE DEATH OF ANY PERSON, AN INJURY TO PERSON OR DAMAGE TO PROPERTY ON OR ABOUT
THE PREMISES LESSEE HEREBY WAIVING AND RELEASING LESSOR FROM ANY AND ALL CLAIMS
FOR DAMAGE, INJURY OR DEATH. LESSEE AGREES TO INDEMNIFY AND HOLD HARMLESS
LESSOR AND THE DEPARTMENT OF AND FROM ANY LOSS, ATTORNEYS' FEES, EXPENSES OR
CLAIMS ARISING OUT OF ANY DEATH, DAMAGE OR INJURY OCCURRING IN OR ON THE
PREMISES.

41. LIMITATION OF WARRANTIES. LESSOR AND LESSEE EXPRESSLY AGREE THAT THERE ARE
AND WILL BE NO IMPLIED WARRANTIES OF MERCHANTABILITY, HABITABILITY, FITNESS FOR
A PARTICULAR PURPOSE OR OF ANY OTHER KIND ARISING OUT OF THIS LEASE (EXCEPT FOR
THE WARRANTY OF QUIET ENJOYMENT SET FORTH IN SECTION 8), AND THERE ARE NO
WARRANTIES WHICH EXTEND BEYOND THOSE EXPRESSLY SET FORTH IN THIS LEASE.

42. LESSOR'S LIEN. Lessor hereby expressly and unconditionally waives any and
all liens which Lessor may have, whether contractual, statutory, constitutional,
or at common law, against any goods, wares, equipment, furniture, inventory,
accounts, fixtures, contract rights, and other property of Lessee now or
hereafter situated on the Premises. Lessor will, upon request by Lessee,
certify its waiver of all such liens to Lessee's lenders, vendors and others
with whom Lessee proposes to conduct business.

43. HAZARDOUS WASTE.

         43.1 The term "Substances" as used in this Lease means pollutants,
contaminants, toxic or hazardous wastes, or any other substances, the use,
storage, handling, disposal, transportation or removal of which is regulated,
restricted, prohibited or penalized by any "Environmental Law". "Environmental
Law" means any federal, state or local law, ordinance or other statute of a
governmental or quasi-governmental authority relating to pollution or protection
of the environment and shall specifically include, but not be limited to, any
"hazardous substance" as that term is defined under the Comprehensive
Environmental Response, Compensation and Liability Act of 1980 and any
amendments or successors in function thereto. Lessee agrees that (i) no activity
will be conducted on the Premises that will use or produce any Substance, except
for such activities that are part of the

                                       17
<PAGE>   77

ordinary course of Lessee's business activities (the "Permitted Activities")
provided said Permitted Activities are conducted in accordance with all
Environmental Laws; Lessee is responsible for obtaining any required permits
and paying any fees and providing any testing required by any governmental
agency; (ii) the Premises will not be used in any manner for the storage of any
Substances, except for the storage of such materials that are used or produced
in the ordinary course of Lessee's business (the "Permitted Materials") provided
such Permitted Materials are properly stored in a manner and location meeting
all Environmental Laws; Lessee is responsible for obtaining any required permits
and paying any fees and providing any testing required by any governmental
agency; (iii) no portion of the Premises will be used as a landfill or a dump;
(iv) Lessee will not install any underground tanks of any type; (v) Lessee will
not allow any surface or subsurface conditions to exist or come into existence
that constitute, or with the passage of time may constitute a public or private
nuisance; and (vi) Lessee will not permit any Substances to be brought onto the
Premises, except for the Permitted Materials or upon any written permission from
Lessor, and if so brought or found located thereon, the same will be immediately
removed, with proper disposal, and all required cleanup procedures will be
diligently undertaken pursuant to all Environmental Laws.

         43.2 Lessor or Lessor's representative has the right, but not the
obligation to enter the Premises for the purpose of inspecting the storage, use
and disposal of Permitted Materials to ensure compliance with all Environmental
Laws. Should it be determined, in Lessor's reasonable opinion, that said
Permitted Materials are being improperly stored, used or disposed of, then
Lessee will immediately take such corrective action as required by Lessor.
Should Lessee fail to take such corrective action within twenty-four (24) hours,
Lessor will have the right to perform such work, and Lessee will promptly
reimburse Lessor for any and all costs associated with said work and compensate
Lessor for any other damages which Lessor may sustain which result, in whole or
in part, from the failure of Lessee to take such corrective action. If at any
time during or after the Term of this Lease the Premises are found to be
contaminated or subject to said conditions, Lessee will diligently institute
proper and thorough cleanup procedures at Lessee's sole cost, and Lessee agrees
to indemnify and hold Lessor harmless from all claims, demands, actions,
liabilities, costs, expenses, damages, finds, reimbursement, restitution,
response costs, clean up costs and obligations (including investigative
responses and attorneys' fees) of any nature arising from or as a result of the
use of the Premises by Lessee. The foregoing indemnification and the
responsibilities of Lessee will survive the termination or expiration of this
Lease.

         43.3 On a date not more than thirty (30) days nor less than five
(5) days prior to the termination of the Term of this Lease, Lessee will, at its
sole cost and expense, cause to be prepared and delivered to Lessor a Phase I
Environmental Risk Analysis and Asbestos Survey of the Premises, prepared by a
firm reasonably acceptable to the Lessor, which analysis will describe and
evaluate the environmental condition of the Premises as of a date not more than
sixty (60) days prior to the termination of the Term of this Lease.

44. BROKERS. Lessee and Lessor each warrants that it has had no dealings with
any real estate broker or agent in connection with the negotiation of this
Lease. Lessee and Lessor each knows of no other real estate broker or agent who
is or might be entitled to a commission in connection with this Lease. If Lessee
or Lessor has dealt with any other person, firm or real estate broker with
respect

                                       18
<PAGE>   78

to leasing the Premises, such party will be solely responsible for the payment
of any fee due said person or firm, and will hold the other party free and
harmless from any liability in respect thereto, including attorneys' fees and
costs.

45. TITLE, GROUND LEASE. Lessor's interest in the Premises is a leasehold estate
and interest existing or created under the Enhanced Use Lease. This Lease is
subject to all terms and provisions of the Enhanced Use Lease. Lessor warrants
that: (a) the Enhanced Use Lease remains in full force and effect and is valid
and binding upon the Lessor and Lessee thereunder, (b) Lessor is not in default
under the Enhanced Use Lease, and no circumstances exist which, with the mere
passage of time, will constitute a default on the Enhanced Use Lease, and (c)
there are no liens, encumbrances, easements, restrictions, reservations or other
matters affecting title except as listed on Exhibit "B" attached hereto.

46. LESSEE'S RIGHT TO TERMINATE. Lessee may at any time upon sixty (60) days
written notice to Lessor terminate this Lease provided that upon termination
Lessee will pay to Lessor in cash the entire net present value of all unpaid
monthly installments of rent contracted to be paid through the Term of this
Lease (not including any extensions which Lessee has not yet exercised),
discounted at an interest rate equal to the "Prime Rate" as set forth in the
"Money Rates" section of the Wall Street Journal on the nearest date preceding
the date of Lessee's notice to terminate, plus three percentage points. For
example, if the Prime Rate as published in the "Money Rate" section of the Wall
Street Journal on the date immediately preceding the date of Lessee's notice to
terminate is seven (7%) percent, then the discount rate for purposes of
determining net present value will be ten (10%) percent per annum.

47. SURVIVAL. Sections 9.3, 9.4, 9.5, 11, 15, 16.3, 17.5, 18.1, 25, 40, 41,
and 43 (HAZARDOUS WASTE) shall survive expiration or other termination of the
Lease.

48. INTENTIONALLY OMITTED.

49. THIRD PARTY BENEFICIARY. Lessee acknowledges and agrees that Sections 2.1,
16.3, 40 and 45 are expressly for the benefit of Lessor and the Department, and
may be enforced by Lessor and the Department.

         SIGNED AND AGREED TO this the 23rd day of November, 1998, but effective
for all purposes as of the date reflected in Article 1 above.

                                   LESSOR
                                   TMX REALTY CORPORATION

                                   By:   /s/ JAMES W. ALBRECHT, JR.
                                      ------------------------------------------
                                             James W. Albrecht, Jr.
                                        Its Chief Financial Officer
                                           -------------------------------------

                                       19

<PAGE>   79
SIGNED AND AGREED TO this the 23rd day of November, 1998.

                                        LESSEE:
                                        INTROGEN THERAPEUTICS, INC.

                                        By:  /s/ JAMES W. ALBRECHT, JR.
                                             -----------------------------------
                                                  Its Chief Financial Officer
                                                      --------------------------

Exhibit A--Subleased Premises (2.619 Acres)
Exhibit B--Omitted
Exhibit C--Plans
Exhibit D--Specifications

THE STATE OF TEXAS       )
                         )
COUNTY OF HARRIS         )

     BEFORE ME, the undersigned authority, on this day personally appeared James
W. Albrecht, Jr., the Chief Financial Officer of TMX REALTY CORPORATION, a
Texas corporation, known to me to be the person whose name is subscribed to the
foregoing instrument, and acknowledged to me that he executed the same for the
purposes and consideration therein expressed, in the capacity therein stated and
as the act and deed of said corporation.

     GIVEN under my hand and seal of office on this the 23rd day of November,
1998.

[SEAL]                                       /s/ TIA M. STOVALL-ARTISST
                                             -----------------------------------
                                             Notary Public, State of Texas

THE STATE OF TEXAS       )
                         )
COUNTY OF HARRIS         )

     BEFORE ME, the undersigned authority, on this day personally appeared James
W. Albrecht, Jr., the Chief Financial Officer of INTROGEN THERAPEUTICS, INC., a
Delaware corporation, known to me to be the person whose name is subscribed to
the foregoing instrument, and acknowledged to me that he executed the same for
the purposes and consideration therein expressed, in the capacity therein stated
and as the act and deed of said corporation.

     GIVEN under my hand and seal of office on this the 23rd day of November,
1998.

[SEAL]                                       /s/ TIA M. STOVALL-ARTISST
                                             -----------------------------------
                                             Notary Public, State of Texas

                                       20
<PAGE>   80

                            LEASEHOLD DEED OF TRUST

THE STATE OF TEXAS       )
                         )    KNOW ALL MEN BY THESE PRESENTS:
COUNTY OF HARRIS         )

     THAT THE UNDERSIGNED, TMX REALTY CORPORATION, a Delaware corporation
(hereinafter called "Grantors", whether one or more), whose mailing address is
301 Congress Avenue, Suite 1850, Austin, Texas 78701, for and in consideration
of the debt hereinafter described, have granted, bargained, sold and conveyed,
and by these presents do grant, bargain, sell and convey, in trust, unto JOHN
E. PHILLIPS of Harris County, Texas, as Trustee, and unto his successors in the
trust hereby created and unto his or their assigns and the heirs of such
assigns (all of whom are hereinafter called "Trustee"), forever, all Grantor's
subleasehold estate in that certain tract of land (the "Real Property")
described in Exhibit "A" attached hereto and made a part hereof for all
purposes. To have and to hold unto Trustee and his substitutes, successors and
assigns said subleasehold estate in the property described in Exhibit "A"
which subleasehold estate was created pursuant to and by virtue of that certain
Amended and Restated Ground Sublease Agreement (the "Ground Sublease") dated
effective September 24, 1998, executed by INTROGEN THERAPEUTICS, INC., a
Delaware corporation, as Ground Sublessee (herein so called) and AMELANG
PARTNERS, INC., as Ground Sublessor (herein so called), together with any and
all buildings and improvements of every kind and character now or hereafter
situated or placed thereon (including, but not limited to, any and all
plumbing, electrical, heating, cooling and other fixtures, equipment and
appliances necessary for the use and operation of the buildings), and all
replacements of and additions thereto, and all of Grantors' rights with respect
to utility capacity, utilities and utility taps, wastewater capacity, proceeds
arising from any claim pursuant to any policy of title insurance covering the
leasehold in the Real Property and all and singular the rights, privileges,
hereditaments, appurtenances, rents, revenues, profits and income thereunto now
or hereafter incident or belonging thereto but excluding all of the Property
described on Exhibit "B" (collectively referred to herein as the "Mortgaged
Property"), forever and Grantors do hereby bind themselves, their heirs,
successors, assigns and legal representatives to warrant and forever defend,
all and singular the Mortgaged Property unto the Trustee, his substitutes or
successors and assigns forever, against the claim or claims of all persons to
claim the same or any part thereof. It is hereby agreed that to the extent
permitted by law all of the Mortgaged Property is to be deemed and held to be a
part of and affixed to the realty. By assignment and assumption of lease dated
November 23, 1998, Ground Sublessee assigned all of its rights, title and
interest as Ground Sublessee in and to the Ground Sublease to Grantor. Such
assignment and assumption was consented to by Amelang Partners, Inc. ("Ground
Sublessor") and Ground Lessor (as hereinafter defined) by instrument dated
November 23, 1998. The Ground Sublessor is the lessee pursuant to that certain
Enhanced-Use Lease dated August 25, 1993, as amended, (the "Enhanced-Use
Lease") wherein the United States Department of Veteran Affairs is the Ground
Lessor (herein so called).

     This conveyance is made in trust, however, to secure and enforce the
payment of a promissory note (hereinafter referred to as "Note", whether one or
more) of even date herewith, executed by Grantors, payable to the order of
RIVERWAY BANK (hereinafter called "Beneficiary"), whose mailing address is Five
Riverway, Houston, Texas 77056, in the principal amount of $6,000,000, bearing
interest and being payable as provided therein.

     This Deed of Trust shall secure, in addition to the Note, all funds
hereafter advanced by Beneficiary to or for the benefit of Grantors, as
contemplated by any covenant or provision herein contained or for any other
purpose, and all other indebtedness, of whatever kind or character, owing or
which may hereafter become owing by Grantors to Beneficiary, whether such
indebtedness is evidenced by note, open account, overdraft, endorsement, surety
agreement, guaranty or otherwise, it being contemplated that Grantors may
hereafter become indebted to Beneficiary in further sum or sums. All
indebtedness secured hereby shall be payable in Harris County, Texas, until
Beneficiary gives written notice to Grantors designating another place of
payment; and unless otherwise provided in the instrument evidencing said
indebtedness, shall bear interest at the maximum non-usurious rate allowed by
applicable law. If the Note or any other indebtedness secured hereby shall be
collected by legal proceedings or through a probate or bankruptcy court or

<PAGE>   81
shall be placed in the hands of an attorney for collection after maturity,
whether matured by the expiration of time or by the option given to the
Beneficiary to mature same, Grantors agree that all attorney's or collection
fees as provided for in the Note shall be paid by Grantors and shall be a part
of the indebtedness secured hereby. This Deed of Trust shall also secure all
renewals, rearrangements and extensions of any of the indebtedness secured
hereby.

     Better to secure payment of said indebtedness, Grantors do hereby jointly
and severally covenant and agree with the Beneficiary and with the Trustee as
follows:

     (1)  Grantors will pay all of the indebtedness secured hereby, together
with the interest and other appurtenant charges thereon, when the same shall
become due in accordance with the terms of the Note or other instruments
evidencing said indebtedness or evidencing any renewal or extension of the same
or any part thereof.

     (2)  Grantors have, in their own right, good and marketable leasehold title
to the Mortgaged Property, which is free from encumbrance superior to the liens
and security interests hereby created unless otherwise herein provided and have
full right and authority to make this conveyance. Grantors shall at all times
comply with and perform all obligations under any applicable laws, statutes,
regulations, covenants, restrictions or ordinances relating to the Mortgaged
Property.

     (3)  Grantors will keep all buildings and other property covered by this
Deed of Trust insured against fire, lightning, tornado, hail, explosion and
against such other risks as Beneficiary may require, all in amounts approved by
Beneficiary. In addition to the above required insurance, Grantors will keep all
buildings and other property covered by this Deed of Trust and all personal
property covered hereby or covered by any other instrument securing payment of
the Note insured for the term of the Note with flood insurance in an amount at
least equal to the outstanding principal of the Note or to the maximum limit of
coverage made available with respect to the particular type of property under
the National Flood Insurance Act of 1968, whichever is less. Such flood
insurance is required hereunder only when such property is located or to be
located in an area that has been identified by the Secretary of Housing and
Development as an area having special flood hazards and in which flood insurance
has been made available under the National Flood Insurance Act of 1968. Such
insurance is to be written in form and in companies acceptable to the
Beneficiary with mortgagee clauses of standard form in favor of Beneficiary and
will deliver the policies of insurance to the Beneficiary promptly as issued;
and, in case the Grantors fail so to do, Beneficiary, at its option, may procure
such insurance at Grantors' expense. All renewal and substitute policies of
insurance shall be delivered at the office of Beneficiary, premiums paid, at
least ten (10) days before termination of policies theretofore delivered to
Beneficiary. All policies shall provide, by way of riders, endorsements or
otherwise, that the insurance provided thereby shall not be terminated, reduced
or otherwise limited, regardless of any breach of the representations and
agreements set forth therein and that the interest of the Beneficiary will not
be invalidated by any act or omission of the Grantors and that no such policy
shall be canceled, endorsed or amended to any extent unless the issuer thereof
shall have first given Beneficiary at least fifteen (15) days prior written
notice. In case Grantors fail to furnish such policies, Beneficiary, at its
option, may procure such insurance at Grantors' expense. In case of loss,
Beneficiary, at its option, shall be entitled to receive and retain the proceeds
of the insurance policies, applying the same toward payment of said indebtedness
as Beneficiary shall see fit or, at Beneficiary's option, Beneficiary may pay
the same over wholly or in part to Grantors for the repair of said building or
buildings or for the erection of a new building or buildings in their place or
for any other purpose satisfactory to Beneficiary, but Beneficiary shall not be
obligated to see to the proper application of any amount paid over to Grantors.
If Beneficiary elects to allow payment of all or part of such proceeds to
Grantors, such payments shall be disbursed on such terms and subject to such
conditions as Beneficiary may specify. Should Beneficiary elect to allow
Grantors to repair such damage, Grantors agree that, regardless of whether any
insurance proceeds payable to them are sufficient to pay the costs of repair and
restoration of the Mortgaged Property, Grantors shall promptly commence and
carry out the repair, replacement, restoration and rebuilding of any and all of
the Mortgaged Property damaged or destroyed by fire or other casualty so as to
return same, to the extent practicable, to its condition immediately prior to
such damage to or destruction thereof. Grantors shall not permit or carry on any
activities within or relating to the Mortgaged Property that is prohibited by
the terms of any insurance policy covering any part of the Mortgaged Property or
which permits cancellation of or increase in the premium payable for any
insurance policy covering any part of the Mortgaged Property. In the event of a
foreclosure of this Deed of Trust, the purchaser of the Mortgaged Property shall
succeed to all the rights of Grantors, including any right to unearned premiums,
in and to all policies of insurance assigned and

                                      -2-

<PAGE>   82
delivered to Beneficiary pursuant to the provisions of this Deed of Trust.
Regardless of the types or amounts of insurance required and approved by
Beneficiary, Grantors shall assign and deliver to Beneficiary all policies of
insurance that insure against any loss or damage to the Mortgaged Property as
collateral and further security for the payment of the Note and any other
indebtedness secured hereby. Grantors shall also obtain and maintain in force
and effect such liability and other insurance policies and protection as
Beneficiary may from time to time specify.

     (4) Grantors will pay all taxes and assessments against the Mortgaged
Property including, without limitation, all taxes in lieu of ad valorem taxes as
the same become due and payable. In the event of the passage after date of this
Deed of Trust of any law by the State of Texas deducting from the Mortgaged
Property for the purposes of taxation any lien thereon or changing in any way
the laws now in force for the taxation of mortgages, deeds of trust or
indebtedness secured thereby for the State or local purposes or the manner of
the operation of any such taxes so as to affect the interest of Beneficiary,
then, and in such event, Grantors shall bear and pay the full amount of such
taxes. If Grantors fail to pay any such taxes and assessments including, without
limitation, taxes in lieu of ad valorem taxes and taxes against this Deed of
Trust or said indebtedness secured hereby, Beneficiary may pay the same,
together with all costs and penalties thereon, at Grantors' expense; provided,
however, that if, for any reason, payment by Grantors of any such new or
additional taxes would be unlawful or if the payment thereof would constitute
usury or render said indebtedness wholly or partially usurious under any of the
terms or provisions of the Note or this Deed of Trust or otherwise, Beneficiary
may, at its option, declare the indebtedness secured hereby, with all accrued
interest thereon, to be immediately due and payable or Beneficiary may, at its
option, pay the amount or portion of such taxes as renders the indebtedness
secured hereby unlawful or usurious, in which event Grantors shall concurrently
therewith pay the remaining lawful and non-usurious portion or balance of said
taxes.

     (5) All judgments, decrees, awards or payment for injury or damage to the
Mortgaged Property and all awards pursuant to proceeding for condemnation
thereof, including interest thereon, are hereby assigned in their entirety to
the Beneficiary, who may apply the same first to reimbursement of all costs and
expenses incurred by Beneficiary in connection with such condemnation proceeding
and the balance to the indebtedness secured hereby in such manner as it may
elect; and Beneficiary is hereby authorized, in the name of Grantors, to execute
and deliver valid acquittances for and to appeal from any such award, judgment
or decree. Grantors shall promptly notify Beneficiary of the institution or
threatened institution of any proceeding for the condemnation of any of the
Mortgaged Property. Beneficiary shall have the right to participate in any such
condemnation proceeding.

     (6) If, while this trust is in force, the title of the Trustee to the
Mortgaged Property or any part thereof shall be endangered or shall be attached
directly or indirectly, Grantors hereby authorize the Beneficiary, at Grantors'
expense, to take all necessary and proper steps for the defense of said title,
including the employment of counsel, the prosecution or defense of litigation
and the compromise or discharge of claims made against said title.

     (7) If, in pursuance of any covenant herein contained, the Beneficiary
shall pay out any money chargeable to Grantors or subject to reimbursement by
Grantors under the terms of said covenant or agreement, Grantors will repay to
the same to Beneficiary immediately at the place where the Note or other
indebtedness hereby secured is payable, together with interest thereon at the
maximum non-usurious rate allowed by applicable law from and after the date of
Beneficiary's making such payment. The sum of each such payment shall be added
to the Note and thereafter shall form a part of the same; and it shall be
secured by this Deed of Trust and by subrogation to all the rights of the
person, corporation or body politic receiving such payment.

     (8) Grantors will keep every part of the Mortgaged Property in first-class
condition and presenting a first-class appearance, making promptly all repairs,
renewals and replacements necessary to such end and doing promptly all else
necessary to such end; but Grantors will discharge all claims for labor
performed and material furnished therefor; and will not suffer any lien of
mechanics or materialmen therefor to attach to any part of the Mortgaged
Property; and Grantors will guard every part of the Mortgaged Property from
removal, destruction and damage, and will not do or suffer to be done any act
whereby the value of any part of the Mortgaged Property may be lessened. No
building or other property now or hereafter covered by the lien of this Deed of
Trust shall be removed, demolished or materially altered or enlarged, nor shall
any new building be constructed, without the prior written consent of
Beneficiary. Grantors shall not initiate, join in or consent to any change in
any private restrictive covenants, zoning ordinances

                                      -3-
<PAGE>   83
or other public or private restrictions limiting or defining the uses that may
be made of the Mortgaged Property or any part thereof without the prior written
consent of Beneficiary. Beneficiary and its agents or representatives shall have
access to the Mortgaged Property upon reasonable advance notice at all
reasonable times in order to inspect same and verify Grantors' compliance with
their duties and obligations under this Deed of Trust. Grantors shall not,
without prior written approval of Beneficiary, grant, convey or otherwise
create or permit to be created, any type of mortgage, lien, security interest
or other encumbrance on any of the Mortgaged Property, regardless whether same
shall be inferior and subordinate to the liens and security interests of
Beneficiary in and to the Mortgaged Property.

     (9)  Grants shall not sell, transfer, assign or mortgage all or any
portion of the Mortgaged Property (including any utilities, utility capacity,
utility taps or any rights or interests thereto), nor shall Grantors grant any
easement or right-of-way, except for utility easements granted in connection
with the development of the Mortgaged Property, or file of record any
restrictive covenants or restrictions whatsoever with respect to the Mortgaged
Property, not shall Grantors rent or lease any or all of the Mortgaged Property
for a period in excess of one (1) year without the express written consent of
the Beneficiary. The sale of any partnership interests (limited or general)
shall constitute a sale of the Mortgaged Property for the purposes hereof, with
the exception of the addition of limited partners not to exceed a ten percent
(10%) interest in Borrower.

     (10) In the event the ownership of the Mortgaged Property or any part
thereof becomes vested in a person other than Grantors, Beneficiary may,
subject to the requirements for notice and opportunity to cure defaults set
forth in the Loan Agreement, deal with such successor or successors in interest
with reference to this Deed of Trust and to said indebtedness in the same
manner as with Grantors, without in any way vitiating or discharging Grantors'
liability hereunder or upon said indebtedness. No sale of the Mortgaged
Property and no forbearance on the part of Beneficiary and no extension of the
time for the payment of said indebtedness given by Beneficiary shall operate to
release, discharge, modify, change or affect, either in whole or in part, any
original liability of Grantors or the liability of the guarantors or sureties
of Grantors or of any other party liable for payment of said indebtedness or any
part thereof.

     (11) In the event Grantors shall default in the prompt payment when due of
the indebtedness secured hereby or any part thereof, or fail to keep and
perform any of the covenants or agreements herein contained; or in the event
any of the representations or warranties made to Beneficiary or set forth
herein prove to be false; or in the event Grantors or any person liable for the
indebtedness secured hereby or any part thereof file a voluntary petition in
bankruptcy, make an assignment for the benefit of any creditor or are
adjudicated a bankrupt or insolvent or if the Mortgaged Property is placed under
control or in the custody of any court or if the Grantors abandon any of the
Mortgaged Property; then, subject to the requirements for notice and
opportunity to cure defaults set forth in the Loan Agreement, the Beneficiary,
at its option, may declare the entire indebtedness secured hereby immediately
due and payable, whereupon it shall be so due and payable.

     (12) All of the covenants and agreements of Grantors set forth herein
shall survive the execution and delivery of this Deed of Trust and shall
continue in force until the indebtedness secured hereby is paid in full.
Accordingly, if Grantors shall perform faithfully each and all of the covenants
and agreements herein contained, then, and then only, this conveyance shall
become null and void and shall be released in due form at Grantors' expense;
otherwise, it shall remain in full force and effect. No release of this
conveyance or the lien thereof shall be valid unless executed by the
Beneficiary.

     (13) If Grantors shall fail to perform faithfully any covenant or
agreement herein contained, Grantors hereby authorize and empower the Trustee
and each and all of his successors in this trust, at the request of the
Beneficiary, at any time when Grantors shall be in default in the performance of
any such covenant or agreement, to sell the Mortgaged Property at public vendue
to the highest bidder for cash at the door of the County Courthouse of the
county in Texas in which the Mortgaged Property or any part thereof is
situated, as herein described, between the hours of 10:00 a.m. and 4:00 p.m. of
the first Tuesday of any month, after advertising the time, place and terms of
said sale and the Mortgaged Property to be sold, by positing (or by having some
person or persons acting for him post) for at least twenty-one (21) days
preceding the date of the sale, written or printed notice of the proposed sale
at the Courthouse door of said county in which the sale is to be made and, if
the Mortgaged Property is in more than one county, one such notice of sale
shall be posted at the Courthouse door of each county in which part of the
Mortgaged Property is situated and

                                      -4-
<PAGE>   84
the Mortgaged Property may be sold at the Courthouse door of any one of such
counties and the notice so posted shall designate in which county the Mortgaged
Property shall be sold; in addition to such posting of notice, the holder of the
indebtedness hereby secured shall, at least twenty-one (21) days preceding the
date of sale: (a) serve written or printed notice of the proposed sale by
certified mail on Grantors and on each other debtor, if any, obligated to pay
the indebtedness hereby secured according to records of such holder, and (b)
file a copy of the notice of proposed sale with the County Clerk or County
Clerks of the county or counties where such notice was posted. Service of such
notice shall be completed upon deposit of the notice, enclosed in a postpaid
wrapper, properly addressed to Grantors and such other debtors at their most
recent address or addresses as shown by the records of the holder of the
indebtedness hereby secured, in a post office or official depository under the
care and custody of the United States Postal Service. The affidavit of any
person having knowledge of the facts to the effect that such service was
completed shall be prima facie evidence of the fact of service. The provisions
hereof with respect to posting and giving notices of sale are intended to
comply with the provisions of Section 51.002 of the Property Code of the State
of Texas, and, in the event the requirement for any notice under such Section
51.002 shall be eliminated or the prescribed manner of giving same modified by
future amendment to or adoption of any statute superseding such Section 51.002,
the requirement for such particular notice shall be deemed stricken from or
modified in this instrument in conformity with such amendment or superseding
statute, effective as of the effective date of same. The manner herein
prescribed for serving or giving any notice, other than that to be posted or
caused to be posted by the Trustee, shall not be deemed exclusive, but such
notice or notices may be given in any other manner which may be permitted by
applicable law. Grantors agree that no notice of any sale other than as set out
in this paragraph need be given by Trustee, Beneficiary or any other person.
Grantors hereby designate as their address for the purposes of such notice the
address set out in the first paragraph hereof and agree that such address shall
be changed only by deposing notice of such change, enclosed in a postpaid
wrapper, in a post office or official depository under the care and custody of
the United States Postal Service, certified mail, postage prepaid, return
receipt requested, addressed to Beneficiary at the address for Beneficiary set
out herein (or to such other address as Beneficiary may have designated by
notice given as above provided to Grantors and such other debtors), any such
notice of change of address of Grantors or other debtors shall be effective
upon receipt by Beneficiary. Any change of address of Beneficiary shall be
effective three (3) business days after deposit thereof in the above described
manner in a post office or official depository under the care and custody of
the United Sates Postal Service. Grantors do hereby authorize and empower
Trustee and each and all of his successors in this trust to sell the Mortgaged
Property or any interest or estate in the Mortgaged Property, together or in
lots or parcels, as such Trustee shall deem expedient and to execute and
deliver to the purchaser or purchasers of the Mortgaged Property good and
sufficient deed or deeds of conveyance thereof and bills of sale with covenants
of general warranty binding on Grantors and Grantors' respective heirs, legal
representatives, successors and assigns. Trustee making such sale shall receive
the proceeds thereof and shall apply the same as follows: (a) he shall pay the
reasonable expense of executing this trust, (b) after paying such expenses, he
shall pay, so far as may be possible, the indebtedness hereby secured,
discharging first that portion of said indebtedness arising under the covenants
or agreements herein contained and then to sums remaining unpaid pursuant to
the Note; (c) then, he shall pay, so far as may be possible, the indebtedness
secured by any liens equal or superior to the lien created hereby; (d) then he
shall pay, so far as may be possible, to indebtedness owed to the Permanent
Lender; and (e) he shall pay the residue, if any, to Grantors, their respective
heirs, legal representatives, successors or assigns. Payment of the purchase
price to the Trustee shall satisfy the obligation of the purchaser at such sale
therefor and he shall not be bound to look after the application thereof.

     (14) If the herein-named Trustee shall die or become disqualified from
acting in the execution of this trust or shall fail or refuse to execute the
same when requested by Beneficiary so to do or if, for any reason, Beneficiary
shall prefer to appoint a substitute trustee to act instead of the herein-named
Trustee, Beneficiary shall have full power to appoint, by written instrument, a
substitute trustee and, if necessary, several substitute trustees in
succession, who shall succeed to all the estate, rights, powers and duties of
Trustee named herein and no notice of such appointment need be given to
Grantors or to any other person or filed for record in any public office. Such
appointment may be executed by any authorized agent of the Beneficiary; and
such appointment executed in its behalf by any officer of such entity shall be
conclusively presumed to be executed with authority and shall be valid and
sufficient without proof of any action by the board of directors or any
superior officer of such entity. Grantors severally hereby ratify and confirm
any and all acts that Trustee, or his successor or successors in this trust
shall do lawfully by virtue hereof. Grantors hereby agree, on behalf of
Grantors and of Grantors' heirs, legal representatives, successors and
assigns, that the recitals contained in any deed or deeds or other instrument
executed in due form by any Trustee or substitute trustee acting

                                      -5-
<PAGE>   85
           under the provisions of this Deed of Trust shall be prima facie
           evidence of the facts recited and that it shall not be necessary to
           prove in any court, otherwise than by such recitals, the existence of
           the facts essential to authorize the execution and delivery of such
           deed or deeds or other instrument and the passing of title thereby
           and all prerequisites and requirements of any sale or sales shall be
           conclusively presumed to have been performed and all persons
           subsequently dealing with the Mortgaged Property purported to be
           conveyed by such deed or deeds or other instrument including,
           without limitation, the purchaser or purchasers thereof, shall be
           fully protected in relying upon the truthfulness of such recitals.

                (15) The purchaser at any trustee's or foreclosure sale
           hereunder, may disaffirm any easement granted or rental or lease
           contract made in violation of any provision of this Deed of Trust
           and may take immediate possession of the Mortgaged Property free
           from and despite the terms of such grant of easement and rental or
           lease contract.

                (16) The Beneficiary may bid and become the purchaser of the
           Mortgaged Property at any trustee's or foreclosure sale hereunder.

                (17) Subsequent to default hereunder or default pursuant to the
           Note or any other instrument securing payment thereof, Grantors
           hereby authorize the Beneficiary, if and whenever it shall desire, to
           demand and receive, in Grantors' right, all sums that may become due
           under any and each oil, gas, mineral or other lease, rental contract
           and easement contract pertaining to any portion of the Mortgaged
           Property and, when received, to apply the same on the indebtedness
           secured hereby. No demand for and no receipt or application of any
           such sum shall be deemed to minimize, subordinate or affect in any
           way the liens and rights hereunder of the Beneficiary or any rights
           of a purchaser of the Mortgaged Property as trustee's or foreclosure
           sale hereunder as against the person from whom such sum was demanded
           or received or his executors, administrators or assigns or anyone
           claiming under such lease, rental or easement contract.

                (18) Any part of the Mortgaged Property may be released by the
           Beneficiary without affecting the lien hereof against the remainder.
           The lien and rights hereby granted shall not affect or be affected
           by any other security taken for the same indebtedness or any part
           thereof. The taking of additional security or the extension, renewal
           or rearrangement of the same indebtedness or any part thereof, shall
           at no time release or impair the lien and rights granted hereby or
           affect the liability of any endorser or surety or improve the right
           of any junior lienholder; and this Deed of Trust, as well as any
           instrument given to secure any renewal or extension of the
           indebtedness secured hereby or any part thereof, shall be and remain
           a first and prior lien on all of the Mortgaged Property not
           expressly released until the said indebtedness is completely paid.

                (19) The invalidity or unenforceability in particular
           circumstances of any provision of this Deed of Trust shall not extend
           beyond such provision or such circumstances and no other provision of
           this Deed of Trust shall be affected thereby. It is the intention of
           the parties hereto to comply with applicable usury laws; accordingly,
           it is agreed that, notwithstanding any provisions to the contrary in
           the Note, or any instrument evidencing any indebtedness secured
           hereby, in this Deed of Trust or in any of the documents or
           instruments securing payment of said indebtedness or otherwise
           relating thereto, in no event shall the Note or such documents
           require the payment or permit the collection of interest in excess of
           the maximum amount permitted by such laws. If any such excess of
           interest is contracted for, charged or received under the Note or any
           instrument evidencing said indebtedness under this Deed of Trust or
           under the terms of any of the other documents securing payment of
           said indebtedness or otherwise relating thereto or in the event the
           maturity of any of said indebtedness is accelerated in whole or in
           part or in the event that all or part of the principal or interest of
           said indebtedness shall be prepaid so that, under any of such
           circumstances, the amount of interest contracted for, charged or
           received under the Note or any instruments evidencing said
           indebtedness under this Deed of Trust or under any of the instruments
           securing payment of said indebtedness or otherwise relating thereto
           on the amount of principal actually outstanding from time to time
           under the Note and other instruments evidencing said indebtedness
           shall exceed the maximum amount of interest permitted by applicable
           usury laws, then, in any such event, (a) the provisions of this
           paragraph shall govern and control, (b) neither Grantors nor any
           other person or entity now or hereafter liable for the payment of the
           Note or any instrument evidencing said indebtedness shall be
           obligated to pay the amount of such interest to the extent that it is
           in excess of the maximum amount of interest permitted by applicable
           usury laws, (c) any such excess that may have been collected shall be
           either applied as a credit against the then unpaid principal

                                      -6-
<PAGE>   86
pal amount of the Note or refunded to Grantors, at the holder's option, and (d)
the effective rate of interest shall be automatically reduced to the maximum
non-usurious rate allowed under applicable usury laws as now or hereafter
construed by the courts having jurisdiction thereof. It is further agreed that,
without limitation of the foregoing, all calculations of the rate of interest
contracted for, charged or received under the Note or any instrument evidencing
said indebtedness under this Deed of Trust or under such other documents that
are made for the purpose of determining whether such rate exceeds the maximum
non-usurious applicable rate, shall be made, to the extent permitted, by
amortizing, prorating, allocating and spreading in equal parts during the
period of the full stated term of the loans evidenced by the Note or the
instruments evidencing said indebtedness, all interest at any time contracted
for, charged or received from Grantors or otherwise by the holder or holders
hereof in connection with such loans.

     (20) None of the Grantors, their heirs, executors, administrators or
assigns, ever shall have or assert any right under any statute or rule of law
pertaining to the marshaling of assets, the exemption of homestead, the
administration of estates of decedents or other matter whatever to defeat,
reduce or affect the right of the Beneficiary under the terms of this Deed of
Trust to a sale of the Mortgaged Property for the collection of said
indebtedness (without any prior or different resort for collection) or the
right of Beneficiary under the terms of this Deed of Trust to the payment of
such indebtedness out of the proceeds of sale of the Mortgaged Property in
preference to every other person and claimant whatever (only reasonable
expenses as aforesaid being first deducted).

     (21) It is agreed that if default be made in the payment of any
installment of the Note, after notice and opportunity to cure as provided in
the Loan Agreement, the holder of the indebtedness or any part thereof on which
the payment is delinquent shall have the option to proceed with foreclosure in
satisfaction of such item, either through the courts or by directing the
Trustee or his successors in trust to proceed as if under a full foreclosure,
conducting the sale as herein provided and without declaring the whole debt due
and provided that, if sale is made because of default of an installment or a
part of an installment, such sale may be made subject to the unmatured part of
the Note and debt secured by this Deed of Trust; and it is agreed that such
sale, if so made, shall not in any manner affect the unmatured part of the debt
secured by this Deed of Trust but, as to such unmatured part of this Deed of
Trust, shall remain in full force and effect just as though no sale had been
made under the provisions of this paragraph. And it is further agreed that
several sales may be made hereunder without exhausting the right of sale for
any unmatured part of the debt secured hereby, it being the purpose to provide
for a foreclosure and sale of the security for any matured portion of the debt
secured hereby without exhausting the power to foreclose and to sell the
security for any other part of the debt secured hereby, whether matured at the
time or subsequently maturing. It is agreed that an assignee holding any
installment or installments or part of any installment of the Note secured
hereby shall have the same powers as are hereby conferred on the holder of the
indebtedness to proceed with foreclosure on a matured installment or
installments and also to request the Trustee or successors in trust to sell the
Mortgaged Property; but if an assignee forecloses or causes a sale to be made
to satisfy any installment, part of an installment or installments, then such
foreclosure or sale shall be made subject to the unmatured part of the Note and
the debt secured hereby owned by the holder of the indebtedness at the time or
assigned subsequent to the assignment of the item to satisfy which the sale is
being made.

     (22) It is expressly agreed that (a) no waiver of any default on the part
of Grantors or breach of any of the provisions of this Deed of Trust shall be
considered a waiver of any other or subsequent default or breach and no delay
or omission in exercising or enforcing the rights and powers herein granted
shall be construed as a waiver of such rights and powers and, likewise, no
exercise or enforcement of any right or powers hereunder shall be held to
exhaust such rights and powers and every such right and power may be exercised
from time to time; (b) any failure by Beneficiary to insist upon the strict
performance by Grantors of any of the terms and provisions hereof shall not be
deemed to be a waiver of any of the terms and provisions hereof and
Beneficiary, notwithstanding any such failure, shall have the right thereafter
to insist upon the strict performance by Grantors of any and all of the terms
and provisions of this Deed of Trust; (c) neither Grantors nor any other person
now or hereafter obligated for the payment of the whole or any part of said
indebtedness shall be relieved of such obligation by reason of the failure of
Beneficiary or Trustee to comply with any request of Grantors or of any other
person so obligated to take action to foreclose this Deed of Trust or otherwise
enforce any of the provisions of this Deed of Trust or of any obligations
secured by this Deed of Trust or by reason of the release, regardless of
consideration, of the whole or any part of the security held for said
indebtedness or by reason of the subordination in whole or in part by
Beneficiary of the lien, security interest or rights evidenced hereby or by
reason of any agreement or stipulation which any subsequent owner or owners
of the Mortgaged Property extending

                                      -7-
<PAGE>   87
the time of payment or modifying the terms of said indebtedness or this Deed of
Trust without first having obtained the consent of Grantors or such other
person and, in the latter event, Grantors and all such other persons shall
continue liable to make such payments according to the terms of any such
agreement of extension or modification unless expressly released and discharged
in writing by Beneficiary; (d) regardless of consideration and without the
necessity for any notice to or consent by the holder of any subordinate lien
or security interest on the Mortgage Property, Beneficiary may release the
obligation of anyone at any time liable for any of said indebtedness or any
part of the security held for said indebtedness and may extend the time of
payment or otherwise modify the terms of said indebtedness and/or this Deed of
Trust without, as to the security or the remainder thereof, in anywise impairing
or affecting the lien or security interest of this Deed of Trust or the
priority of such lien or security interest as security for the payment of said
indebtedness as it may be so extended or modified over any subordinate lien or
security interest; (e) the holder of any subordinate lien or security interest
shall have no right to terminate any lease affecting the Mortgaged Property,
whether or not such lease be subordinate to this Deed of Trust; and (f)
Beneficiary may resort, for the payment of said indebtedness, to any security
therefor held by Beneficiary in such order and manner as Beneficiary may elect.

     (23) In the event that there be a trustee's sale hereunder and if, at the
time of such sale, Grantors, their heirs, executors, administrators or assigns,
be occupying the premises so sold, each and all shall immediately become the
tenant of the purchaser at such sale, which tenancy shall be a tenancy from
day to day, terminable at the will of either tenant or landlord, at a
reasonable rental per day, based upon the value of the Mortgaged Property, such
rental to be due daily to the purchaser. An action of forcible detainer shall
lie if the tenant holds over after a demand in writing for possession of the
Mortgaged Property; and this Deed of Trust and the trustee's deed shall
constitute a lease and agreement under which the tenant's possession, each and
all, arose and continued.

     (24) In the event any portion of said indebtedness contemplated by the
loan documents is not, for any reason whatsoever, secured by this Deed of Trust
on the Mortgaged Property, the full amount of all payments made on said
indebtedness shall first be applied to such unsecured portion of said
indebtedness until the same has been fully paid.

     (25) It is agreed that the lien hereby created shall take precedence over
and be a prior lien to any other lien of any character, whether vendor's
materialmen's or mechanics' lien hereafter created on the Mortgaged Property
and, in the event the proceeds of the Note are used to pay off and satisfy any
liens heretofore existing on the Mortgaged Property, then Beneficiary is and
shall be subrogated to all of the rights, liens and remedies of the holders of
the indebtedness so paid.

     (26) The covenants herein contained shall bind and the benefits and
advantages shall inure to the respective heirs, executors, administrators,
successors and assigns of the parties hereto and to any substitute trustee.
Whenever used, the singular number shall include the plural, the plural the
singular, and the use of any gender shall be applicable to all genders. The term
"Beneficiary" shall also include any lawful owner, holder or pledgee of any
indebtedness secured hereby.

     (27) Without limiting any of the provisions of this Deed of Trust, the
Grantors, as Debtors and referred to in this Paragraph as "Debtors", expressly:

          (a) Grant unto the holder of all indebtedness described herein, as
     Secured Party and referred to in this Paragraph as "Secured Party", a
     security interest in all of the Mortgaged Property hereinabove described
     (including both now and hereafter existing) to the full extent that same
     may be subject to Chapter 9 of the Texas Business and Commerce Code as now
     adopted and existing and as it may hereinafter be amended or succeeded
     (hereinafter called "Uniform Commercial Code").

          (b) Agree that, in addition to any other remedies granted in this
     instrument to the Secured Party or Trustee, the Secured Party may, in the
     event of any default, proceed under the Uniform Commercial Code as to all
     or any part of the personal property (tangible or intangible) and fixtures
     included in the Mortgaged Property (such portion of the properties being
     herein referred to as "Collateral") and shall have and may exercise, with
     respect to the Collateral, all the rights,

                                      -8-
<PAGE>   88
remedies, and powers of a Secured Party under the Uniform Commercial Code
including, without limitation, the right and power to sell at public or private
sale or sales or otherwise dispose of, lease or utilize the Collateral and any
part or parts thereof in any manner authorized or permitted under said Uniform
Commercial Code after default by a debtor and to apply the proceeds thereof
toward payment of any costs and expenses and attorney's fees and legal expenses
thereby incurred by Secured Party and toward payment of the Debtors' obligations
including the Note and all other indebtedness described in this instrument in
such order or manner as Secured Party may elect. Among the rights of Secured
Party in the event of default and, without limitation, Secured Party shall have
the right to take possession of the Collateral and to enter upon any premises
where same may be situated for such purpose without being deemed guilty of
trespass and without liability for damages thereby occasioned and to take any
action deemed necessary or appropriate or desirable by Secured Party, at its
option and in its discretion, to repair, refurbish or otherwise prepare the
Collateral for sale, lease or other use or disposition as herein authorized. To
the extent permitted by law, Debtors expressly waive any notice of sale or other
disposition of the Collateral and any other rights or remedies of a debtor or
formalities prescribed by law relative to sale or disposition of the Collateral
or exercise of any other right or remedy of Secured Party existing after default
hereunder; and to the extent any such notice is required and cannot be waived,
Debtors agree that if such notice is mailed, postage prepaid, to the Debtors at
the address shown herein at least ten (10) days before the time of the sale or
disposition, such notice shall be deemed reasonable and shall fully satisfy any
requirement for giving of said notice.

     (c) Grant to the Secured Party, after default hereunder, the right, at its
option, to transfer at any time to itself or to its nominee the Collateral or
any part thereof and to receive the monies, income, proceeds or benefits
attributable or accruing thereto and to hold the same as security for the
Debtors' obligations or to apply it on the principal and interest or other
amounts owing on any of the Debtors' obligations, whether or not then due, in
such order or manner as the Secured Party may elect. All rights or marshaling
of assets of Debtors, including any such right with respect to the Collateral,
are hereby waived.

     (d) Covenant, stipulate and agree that all recitals in any instrument of
assignment or any other instrument executed by Secured Party incident to sale,
transfer, assignment, lease or other disposition or utilization of the
Collateral or any part thereof hereunder shall be full proof of the matters
stated therein and no other proof shall be requisite to establish full legal
propriety of the sale or other action taken by Secured Party or of any fact,
condition or thing incident thereto and all pre-requisites of such sale or
other action or of any fact, condition or thing incident thereto shall be
presumed conclusively to have been performed or to have occurred.

     (e) Covenant and agree that Secured Party may require Debtors, after
default hereunder, to assemble the Collateral and make it available to Secured
Party at a place to be designated by Secured Party that is reasonably
convenient to both parties. All expenses of retaking, holding, preparing for
sale, lease or other use or disposition, selling, leasing or otherwise using or
disposing of the Collateral and the like which are incurred or paid by Secured
Party as authorized or permitted hereunder, including also all attorney's fees,
legal expenses and costs, shall be added to the Debtors' obligations and the
Debtors shall be liable therefor.

     (f) Covenant and agree that the Secured Party may, at its election, at any
time after delivery of this instrument, sign one or more copies of this
instrument in order that such copies may be used as a Financing Statement under
the Uniform Commercial Code. Such signature by the Secured Party may be placed
between the last sentence of the instrument and the Debtors' acknowledgment or
may follow the Debtors' acknowledgment. The Secured Party's signature need not
be acknowledged and is not necessary to the effectiveness of this instrument as
a deed of trust, mortgage, assignment, pledge or security agreement.

                                      -9-
<PAGE>   89
     Except for the security interest granted hereby in the Collateral, Debtors
are the owners and holders of the Collateral free of any adverse claim,
security interest or encumbrance and Debtors will defend the Collateral against
all claims and demands of any person at any time claiming the same or any
interest therein. Debtors have not heretofore signed any financing statement
covering the Collateral and no such financing statement signed by Debtors is
now on file in any public office except those statements true and correct
copies of which have been delivered to the Secured Party. So long as any amount
remains unpaid on any indebtednesses described in this Deed of Trust, Debtors
will not execute and there will not be filed in any public office such
financing statement or statements affecting the Collateral other than financing
statements in favor of Secured Party hereunder unless the prior written
specific consent and approval of Secured Party shall have first been obtained.
Debtors authorize Secured Party to file, in jurisdictions where this
authorization will be given effect, a financing statement signed only by
Secured Party covering the Collateral and, at the request of Secured Party,
Debtors will join Secured Party in executing one or more financing statements
pursuant to the Uniform Commercial Code, in form satisfactory to Secured Party,
and will pay the cost of filing the same or filing or recording this instrument
as a financing statement in all public offices at any time and from time to
time whenever filing or recording of any financing statement or of this
instrument is deemed by Secured Party to be necessary or desirable.

     (28) Portions of the Mortgaged Property are goods which are or are to
become fixtures relating to the property described in Exhibit "A" and the
Grantors herein expressly covenant and agree that the filing of this Deed of
Trust in the real estate records of the county where the Mortgaged Properties
are located shall also operate from time of filing therein as a financing
statement filed as a fixture filing in accordance with Section 9.402(f) of the
Uniform Commercial Code - secured Transaction of the State of Texas.

     (29) Grantors will pay all fees or costs for appraisals that the
Beneficiary may reasonably require from time to time, but in no event more than
one (1) appraisal annually. In addition, Grantors will pay all recording fees,
taxes, abstract fees, attorneys' fees and all other costs and expenses of every
character from time to time incurred in connection with the making, closing and
servicing of the loan evidenced by the Note, or any renewal, modification,
rearrangement or extension thereof and will pay all reasonable fees and charges
made by the Trustee for services performed hereunder and will reimburse
Beneficiary and the Trustee for all expenses incurred by them, respectively,
and will indemnify and hold harmless Beneficiary and the Trustee from and
against all claims, demands, liabilities and causes of action asserted against
either of them on account of any act performed or omitted to be performed
hereunder or on account of any transaction arising out of or in any way
connected with the Mortgaged Property or this Deed of Trust, save and
except for their willful misconduct. In the event that Beneficiary should pay
for expenses incurred in way of attorneys' fees in connection with title
examination and legal matters and/or appraisal fees or costs connected with the
making, closing or servicing the Note or any renewal, modification,
rearrangement or extension thereof, or pay any recording or filing fee or fees
incident to recording instruments, title insurance premiums and title insurance
endorsement fees, Grantors shall reimburse the Beneficiary for all such sums
upon demand. Any such sums shall become part of the indebtedness secured by
this Deed of Trust and shall bear interest from the date incurred by
Beneficiary at the rate provided in the Note.

     (30) This is a "construction mortgage" within the meaning of Sections
9.105(a)(10) and 9.313(a)(3) of the Uniform Commercial Code - Secured
Transactions of the State of Texas. This Deed of Trust secures an obligation
for the construction of an improvement on land including the acquisition cost,
if any, of the land.

     (31) This Deed of Trust and Security Agreement is executed and delivered
pursuant to and is entitled to the benefits of that Loan Agreement of even date
herewith between Grantors and Beneficiary.

     (32) Grantors represent and warrant to Beneficiary that to the best of
Grantors' knowledge:

          (a)  Neither Grantors nor the Mortgaged Property is in violation or
subject to any existing, pending or threatened investigation by any entity,
governmental body, or individual under any Environmental Law (as hereinafter
defined);

                                      -10-
<PAGE>   90

                    (b)  Grantors have not received any notice from any entity,
          government body, or individual claiming any violation of or requiring
          compliance with any Environmental Law and the Grantors have not
          received any request for information, notice of claim, demand or other
          notification that the Grantors may be responsible for a threatened or
          actual release of any Hazardous Substance (as hereinafter defined) or
          for any damage or threat to the environment, public health and safety,
          or to natural resources;

                    (c)  Grantors' intended use of the Mortgaged Property will
          not result in the unlawful discharge, dispersal, storage, treatment,
          use, manufacture, installation, generation, production, disposal or
          release of any Hazardous Substance on, under, about, to, from or
          within the Mortgaged Property.

     Grantors represent and warrant to Beneficiary that Grantors have no actual
knowledge and have no reason to know that:

                    (a) Any of the land, improvements or any part of the
     Mortgaged Property is or has been in violation of or subject to any
     existing, pending, or threatened investigation, inquiry, order or
     directive order by any governmental authority under any Environmental Law;

                    (b) Any Hazardous Substance is being or has been
     discharged, dispersed, disposed of or released on, under, to, from, about
     or within the Mortgaged Property; and

                    (c) Any underground storage tanks located on or about the
     Mortgaged Property or which have been located on or about the Mortgaged
     Property have been subsequently removed or filled.

     Grantors further represent and warrant that:

                    (a) Grantors will not use, generate, manufacture, treat,
     install, produce, store, release, discharge, or dispose of, on, under, to,
     from or about the Mortgaged Property or transport to or from the Mortgaged
     Property any Hazardous Substance or allow any other person or entity to do
     so except under conditions permitted by applicable laws;

                    (b) Grantors will not locate, or permit to be located, any
     underground storage tanks on the Mortgaged Property; and

                    (c) Grantors shall keep and maintain the Mortgaged Property
     in strict compliance with, and shall not cause or permit the Mortgaged
     Property to be in violation of, any Environmental Law.

     Grantors shall give prompt written notice to Beneficiary of:

                    (i)   any proceeding or inquiry by any governmental
                          authority with respect to (a) the presence of any
                          Hazardous Substance on the Mortgaged Property or the
                          migration thereof from or to other property or (b)
                          any other breach or violation of any Environmental
                          Law;

                    (ii)  all claims made or threatened by any third party
                          against Grantors or the Mortgaged Property relating
                          to any loss or injury resulting from any Hazardous
                          Substance or the breach of any Environmental Law; and

                    (iii) Grantors' discovery of any occurrence or condition on
                          the Mortgaged Property that could cause the Mortgaged
                          Property or any part thereof to be subject to any
                          restrictions on the ownership, occupancy,
                          transferability or use of the Mortgaged

                                      -11-
<PAGE>   91
          Property under any Environmental Law, or to be otherwise subject to
          any restrictions on the ownership, occupancy, transferability or use
          of the Mortgaged Property under any Environmental Law.

     Beneficiary shall have the right to join and participate in, as a party if
it so elects, any legal proceedings or actions initiated with respect to the
Mortgaged Property in connection with any Environmental Law and have its
attorneys' fees in connection therewith paid by Grantors.

     Grantors shall protect, indemnify and hold harmless Beneficiary, its
directors, officers, employees, agents, attorneys, successors and assigns from
and against any and all loss, damage, cost, expense, penalty, fine, action,
cause of action or liability (including attorneys' fees and costs) directly or
indirectly arising out of or attributable to the use, generation, manufacture,
production, treatment, installation, storage, release, threatened release,
discharge, disposal, or presence of a Hazardous Substance on, under or from the
Mortgaged Property including without limitation (i) all foreseeable
consequential damage; and (ii) the costs of any required or necessary repair,
cleanup or detoxification of the Mortgaged Property and the preparation and
implementation of any closure, remedial or other required plan. This indemnity
shall survive the release of the lien of this Deed of Trust, or the
extinguishment of the lien by foreclosure or action, deed or conveyance in lieu
thereof, and this covenant of indemnity shall survive such release or
extinguishment; however, this indemnity shall exclude any acts by the
Beneficiary.

     In the event that any investigation, site monitoring, containment, cleanup,
removal, restoration or other remedial work of any kind or nature (the "Remedial
Work") is reasonably necessary or desirable under any applicable local, state or
federal law or regulation, any judicial order, or by any governmental or
nongovernmental entity or person because of, or in connection with, the current
or future presence, suspected presence, release or suspected release of a
Hazardous Substance in or into the air, soil, groundwater, surface water or soil
vapor at, on, about, under or within the Mortgaged Property (or any portion
thereof), Grantors shall within thirty (30) days after written demand for
performance thereof by Beneficiary (or such shorter period of time as may be
required under any applicable law, regulation, order or agreement), commence and
thereafter diligently prosecute to completion, all such Remedial Work. All
Remedial Work shall be performed by contractors approved in advance by
Beneficiary, and under the supervision of a consulting engineer approved by
Beneficiary. All costs and expenses of such Remedial Work shall be paid by
Grantors including, without limitation, Beneficiary's reasonable attorneys' fees
and costs incurred in connection with monitoring or review of such Remedial
Work. In the event Grantors shall fail to timely commence, or cause to be
commenced, or fail to diligently prosecute to completion, such Remedial Work,
Beneficiary may, but shall not be required to, cause such Remedial Work to be
performed and all costs and expenses thereof, or incurred in connection
therewith, including without limitation, attorney fees, shall become part of the
indebtedness secured hereby.

     Notwithstanding anything contained in the Note, this Deed of Trust or in
any of the loan documents, the Grantors shall not be released of corporate
liability and shall have corporate liability for any and all of Beneficiary's
costs, expenses, damages or liabilities (including, without limitation, all
reasonable attorneys' fees, whether incurred by Beneficiary prior to or
following foreclosure of the Deed of Trust and whether Beneficiary shall be in
the status of a lienholder or an owner of the Mortgaged Property following
foreclosure) directly or indirectly arising out of or attributable to the use,
generation, manufacture, storage, release, threatened release, discharge,
disposal, or presence on under, to or from the Mortgaged property of any
Hazardous Substance.

     For the purposes of this Deed of Trust, the following terms shall have the
following meanings:

     (1)  "Environmental Laws" means any federal, state or local law, statute,
          ordinance, or regulation pertaining to health, industrial hygiene, or
          the environmental conditions on, under or about the Mortgaged
          Property, including without limitation the Comprehensive Environmental
          Response, Compensation, and Liability Act of 1980 ("CERCLA") as
          amended 42 U.S.C. Sections 9601 et seq., and the Resource Conservation
          and Recovery Act of 1976 ("RCRA"), 42 U.S.D. Sections 6901 et seq.

     (2) "Hazardous Substance" includes, without limitation:

                                      -12-
<PAGE>   92
          (i)   Those substances included within the definitions of "hazardous
                substances", "hazardous materials", "toxic substances", or
                "solid waste" in CERCLA, RCRA, and the Hazardous Materials
                Transportation Act, 49 U.S.C. Section 801 et seq., and in the
                regulations promulgated pursuant to said laws;

          (ii)  Those substances listed in the United States Department of
                Transportation Table (49 CFR 172.101 and any amendments thereto)
                or by the Environmental Protection Agency (or any successor
                agency) as hazardous substances (40 DFR Part 302 and any
                amendments thereto);

          (iii) Such other substances, materials and wastes which are or become
                regulated under applicable local, state or federal law, or the
                United States government, or which are classified as hazardous
                or toxic under federal, state or local laws or regulations; and

          (iv)  Any material, waste or substance which is (A) asbestos; (B)
                polychlorinated biphenyls; (C) designated as a "hazardous
                substance" pursuant to Section 311 of the Clean Water Act, 33
                U.S.C. Sections 1251 et. seq. (33 U.S.C. Section 1321) or listed
                pursuant to Section 307 of the Clean Water Act (33 U.S.C.
                Section 1373); (D) explosives; (E) radioactive materials; or (F)
                gasoline, diesel fuel, kerosene or other petroleum products not
                contained in an underground storage tank upon the Mortgaged
                Property.

     (33) Grantor represents and warrants to Beneficiary that as of the date
hereof:

          (a) The Ground Sublease is a valid and subsisting lease of the
property therein described and purported to be demised and is in full force and
effect in accordance with its terms and has not been amended or modified in any
respect.

          (b) No default has occurred and is continuing under the Ground
Sublease and no event has occurred or is occurring which, with the passage of
time or service of notice or both would constitute an event of default under the
Ground Sublease.

          (c) The Ground Sublease is subject to no liens or encumbrances other
than the as set forth in the Mortgagee's Title Insurance issued in connection
with this Deed of Trust.

          (d) Grantor is the owner of the subleasehold estate created by the
Ground Sublease and has the right and authority under the Ground Sublease to
execute this Deed of Trust and to encumber the subleasehold estate as provided
herein.

     (34) Grantor will promptly perform and observe all the terms, covenants
and conditions required to be performed and observed by Grantor, as Sublessee
under the Ground Sublease, within the periods provided in the Ground Sublease,
and will do all things necessary to preserve and keep unimpaired its rights
under the Ground Sublease. Grantor will furnish Beneficiary, upon demand, proof
of payment of all items which are required to be paid by Grantor under the
Ground Sublease, with the exception of rent payments which shall be escrowed
with Beneficiary pursuant to separate agreement covering both Ground Lease rent
and Ground Sublease rent, such agreement to be executed by Grantor, Ground
Sublessor and Beneficiary. Upon request of Beneficiary, within five (5) days
after the date of each such payment, Grantor shall deliver to Beneficiary the
original or photostatic copy of the official receipt evidencing such payment or
other proof of payment of any such item required to be paid by Grantor under the
Ground Sublease. Grantor shall not waive any of its rights under the Ground
Sublease (or Ground Lease, if applicable), or refrain from exercising any right
or remedy accorded to it under the Ground Sublease (or Ground Lease, if
applicable) on account of any default thereunder, or release any party from any
liability or condone or excuse any improper actions of any party thereunder
without first obtaining the written consent of Beneficiary.

                                     -13-

<PAGE>   93
     (35) In the event that (i) all the terms, provisions and conditions of the
Ground Sublease or any instrument executed in connection with the Ground
Sublease are not complied with so as to result in a default thereunder and/or
(ii) any statement, representation or warranty made by Grantor hereunder shall
be false, misleading or erroneous in any respect, such failure shall constitute
an event of default under this Deed of Trust, and shall entitle Beneficiary,
after notice and opportunity to cure as provided in the Loan Agreement, at its
option, to exercise any and all rights and remedies given Beneficiary in the
event of a default hereunder, and Grantor agrees to hold harmless and indemnify
Beneficiary therefrom to the full extent permitted by law.

     (36) For the purpose of preventing or curing any default by Grantor under
the Ground Lease or the Ground Sublease Beneficiary, may (but shall be under no
obligation to) do any act or execute any document in the name of Grantor or as
its attorney-in-fact, as well as in the name of Beneficiary. Grantor hereby
irrevocably appoints Beneficiary its true and lawful attorney-in-fact in its
name or otherwise to do any and all acts and to execute any and all documents
which in the opinion of Beneficiary may be necessary or desirable to prevent
or cure any default under the Ground Sublease, the Ground Lease or to preserve
any rights of Grantor in, to or under the Ground Sublease or the Ground Lease,
including the right to effectuate a renewal of the Ground Sublease or to
preserve any rights of Grantor whatsoever in respect of any part of the
Mortgaged Property.

     (37) The curing by Beneficiary of any default by Beneficiary under the
Ground Lease or Ground Sublease shall not remove or waive, as between Grantor
and Beneficiary, the default which occurred hereunder by virtue of the default
by Grantor under the Ground Lease or Ground Sublease, and all sums expended by
Beneficiary in order to cure any such default and costs and expenses incurred
by Beneficiary in connection with the curing of such default shall be paid by
Grantor to Beneficiary upon demand with interest thereon at the default rate of
interest set forth in the Note (but in no event at a rate in excess of the
maximum lawful rate which may be permitted by applicable law) from the date of
advancement until paid, and any such indebtedness shall be deemed to be secured
by this Deed of Trust.

     (38) Grantor will not surrender or abandon the subleasehold estate created
by the Ground Sublease, nor terminate or cancel the Ground Sublease, and Grantor
will not without the express written consent of Beneficiary modify, change,
supplement, alter or amend the Ground Sublease either orally or in writing, and
as further security for the repayment of the indebtedness secured hereby and for
the performance of the covenants herein and in the Ground Sublease contained,
Grantor hereby assigns to Beneficiary (Beneficiary not assuming any obligations
by virtue of such assignment) all of its rights, privileges and prerogatives as
Ground Sublessee under the Ground Sublease or the Ground Lease, if applicable,
to terminate, cancel, modify, change, supplement, alter or amend the Ground
Sublease or the Ground Lease, if applicable, and any such termination,
cancellation, modification, change, supplement, alteration or amendment of the
Ground Sublease or the Ground Lease, if applicable, without the prior written
consent thereby by Beneficiary shall be void and of no force and effect.

     (39) Grantor shall notify Beneficiary promptly of (i) the occurrence of any
default by the lessor under the Ground Lease or Ground Sublease or the
occurrence of any event which, with the passage or time or service of notice, or
both, would constitute a default by the lessor under the Ground Lease or Ground
Sublease, and (ii) the receipt by Grantor of any notice (written or oral) from
the lessor under the Ground Lease or Ground Sublessor and of any notice (written
or oral) noting or claiming the occurrence of any event of default under the
Ground Lease or Ground Sublease or the occurrence of any event which, with the
passage of time or service of notice or both, would constitute a default under
the Ground Lease or Ground Sublease.

     (40) Promptly upon demand by Beneficiary, Grantor shall obtain from the
Ground Lessor under the Ground Lease and Ground Sublessor under the Ground
Sublease and furnish to Beneficiary an estoppel certificate in form and
substance reasonably satisfactory to Beneficiary.

     (41) Promptly upon request by Beneficiary, Grantor shall give its
unqualified consent in writing to any and all modifications of the Ground
Sublease which the Ground Sublessor agrees to make at the request of
Beneficiary for the purpose of maintaining or preserving Beneficiary's security
in the Ground Sublease.

                                      -14-
<PAGE>   94
                (42)  No release or forbearance of any obligations of Grantor
           under the Ground Sublease pursuant to the Ground Sublease or
           otherwise, shall release Grantor from any of its obligations under
           this Deed of Trust, including its obligations with respect to
           payment of rent as provided for in the Ground Sublease and the
           performance of all of the terms, provisions, covenants, conditions
           and agreements contained in the Ground Sublease, to be kept,
           performed and complied with by the lessee therein.

                (43)  All sub-subleases entered into by Grantor must provide
           that (i) the sub-sublease is subordinate to the lien of this Deed of
           Trust and any extensions, replacements or modifications hereof, and
           (ii) if Beneficiary enters into a new lease with the Ground Lessor
           under the Ground Lease or Ground Sublease under the Ground Sublease
           under the circumstances therein stated the sublessee or
           sub-sublessee, as the case may be, must agree to attorn to
           Beneficiary.

                (44)  So long as the indebtedness shall remain unpaid, unless
           Beneficiary shall otherwise consent in writing, the fee title to and
           the leasehold estate in the Mortgaged Property shall not merge but
           shall always be kept separate and distinct, notwithstanding the
           ownership of both such estates by the Ground Lessor or the Ground
           Sublessor under the Ground Lease or the Sublessor or Grantor
           pursuant to the Ground Sublease, or by a third party. Nothing herein
           contained shall be construed as authorizing the sale by Grantor of
           any leasehold estate without the written consent of Beneficiary.

                (45)  The lien of this Deed of Trust shall attach to all of
           Grantor's rights arising under Subsection 365(h) of the United
           States Bankruptcy Code (the "Bankruptcy Code"). Grantor shall not,
           without first obtaining Beneficiary's prior written consent, elect
           to treat the Ground Sublease as terminated under Subsection
           365(h)(1) of the Bankruptcy Code. Any such election made without
           first obtaining Beneficiary's prior written consent shall be null and
           void. Grantor hereby unconditionally assigns to Beneficiary all of
           Grantor's claims and rights to payment of damages arising in any
           rejection by the landlord of the Ground Sublease or Ground Lease
           under the Bankruptcy Code. Beneficiary shall have the right to
           pursue in its own name or in the name of Grantor in respect of any
           such claim relating to the rejection of the Ground Lease or Ground
           Sublease, as the case may be. This assignment constitutes a present,
           irrevocable and unconditional assignment of the foregoing claims,
           and shall continue in effect until the Note and other obligations of
           this Deed of Trust have been satisfied and discharged in full. Any
           amounts received by Beneficiary as damages arising out of the
           rejection of the Ground Lease or Ground Sublease, as the case may
           be, shall be applied to the Note in reverse order of maturity. If
           there shall be filed by or against Grantor a case under the
           Bankruptcy Code, and Grantor, as Ground Sublessee under the Ground
           Sublease (or as a lessee pursuant to the Ground Lease if such event
           occurs), shall determine to reject the Ground Sublease or Ground
           Sublease pursuant to Section 365(a) of the Bankruptcy Code, Grantor
           shall give Beneficiary prior written notice of the date on which
           Grantor shall apply to the appropriate Bankruptcy Court for
           authority to reject the Ground Lease or Ground Sublease, as the case
           may be. Such date of application by Grantor shall not be less than
           ten (10) days from the date of receipt as provided herein by
           Beneficiary. Beneficiary shall have the right, but not the
           obligation, to serve upon Grantor within such ten (10) day period a
           written notice stating: (i) that Beneficiary demands that Grantor
           assume and assign the Ground Lease or Ground Sublease, as the case
           may be, to Beneficiary pursuant to Section 365 of the Bankruptcy
           Code; and (ii) that Beneficiary covenants to cure or provide
           adequate assurance of prompt cure of all defaults and provide
           adequate assurance of future performance under the Ground Lease or
           Ground Sublease, as the case may be. If Beneficiary serves Grantor
           the written notice described in the preceding sentence, Grantor
           shall not seek to reject the Ground Lease or Ground Sublease, as the
           case may be, and shall comply with the demand provided for in clause
           (i) of the preceding sentence within thirty (30) days after such
           written notice shall have been given subject to the performance by
           Beneficiary of the covenant provided for in clause (ii) of the
           preceding sentence. Effective upon the entry of any order for relief
           with respect to Grantor under the Bankruptcy Code, Grantor hereby
           assigns and transfers to Beneficiary a non-exclusive right to apply
           to the bankruptcy court under Subsection 365(d)(1) of the Bankruptcy
           Code for an order extending the period during which the Ground Lease
           or Ground Sublease, as the case may be, may be rejected or assumed.

                (46)  Pursuant to the Enhanced-Use Lease, as amended, if Ground
           Lessor terminates the Enhanced-Use Lease, Grantors have certain
           rights and the Ground Lessor has certain obligations, to enter into
           a Replacement Lease (herein so called) with the Ground Lessor
           wherein Grantors would be ground lessee, covering the Property
           described on Exhibit "A" attached hereto. In the event that Ground
           Lessor terminates the Enhanced-Use Lease, Grantors agree to enter
           into the Replacement Lease in accordance with the provisions of the
           Enhanced Use-Lease. In the event

                                      -15-
<PAGE>   95

Grantors enter into a Replacement Lease and in the event that the liens
evidenced by this Deed of Trust have not theretofore been released by
Beneficiary, Grantors covenant and agree to enter into a new leasehold deed of
trust (the "Replacement Deed of Trust") covering Grantor's interest as ground
lessee in and to the Replacement Lease. The Replacement Deed of Trust shall be
in substantially the same form and substance as this Deed of Trust; however, the
Replacement Deed of Trust shall grant to Beneficiary a first lien interest in
Grantors' leasehold estate in and to the Mortgaged Property and the same shall
secure the indebtedness secured hereby, as the same may be modified, amended,
renewed or increased from time to time.

     (47) The term "Loan Agreement" as used herein shall mean that certain
Construction Loan Agreement of even date herewith by and between Grantors as
Borrower and Beneficiary as Lender.

     (48) GRANTORS HEREBY EXPRESSLY RECOGNIZE THAT CONTAINED IN SECTIONS 29 AND
32 OF THIS DEED OF TRUST ARE PROVISIONS WHICH REQUIRE GRANTORS TO INDEMNIFY
BENEFICIARY UNDER CERTAIN CIRCUMSTANCES AND GRANTORS HEREBY ACKNOWLEDGE THAT BY
EXECUTING THIS DEED OF TRUST, GRANTORS ACCEPT THESE PROVISIONS AND THE
OBLIGATIONS TO INDEMNIFY BENEFICIARY UNDER SUCH CIRCUMSTANCES.

     EXECUTED this 23rd day of November, 1998.

                                        TMX REALTY CORPORATION,
                                        a Delaware corporation

                                        By: /s/ JAMES W. ALBRECHT, JR.
                                           ---------------------------------
                                        Name: James W. Albrecht, Jr.
                                             -------------------------------
                                        Title: Chief Financial Officer
                                              ------------------------------

THE STATE OF TEXAS  )
                    )
COUNTY OF HARRIS    )

     This instrument was acknowledged before me on this 23rd day of November,
1998, by James W. Albrecht, Jr., CEO of TMX REALTY CORPORATION, a Delaware
corporation, for and on behalf of said corporation.

[SEAL]                                  /s/ LAWANA HARDIN
                                        ------------------------------------
                           [SEAL]       Notary Public in and
                                        for the STATE OF TEXAS

Printed Name of Notary:                 My Commission Expires:

-------------------------------         ------------------------------------

                                      -16-
<PAGE>   96

                                EXHIBIT "A"

Being a tract or parcel containing 2,619 acres (114,085 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 2,619 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

COMMENCING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3,147,967.40,
Y=698,487.10, thence:

          South 14 degrees 53'21" West, with said west ROW line, a distance of
          206.00 feet to a set 5/8-inch iron rod with plastic cap;

          North 75 degrees 06'39" West, a distance of 329.30 feet to a 5/8-inch
          iron rod with plastic cap set marking the POINT OF BEGINNING and
          northeast corner of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, a distance of 330.70 feet to a 5/8-inch
iron rod with plastic cap set marking the southeast corner of the herein
described tract;

THENCE, NORTH 75 degrees 06'39" West, a distance of 432.78 feet to a 5/8-inch
iron rod with plastic cap set marking the southwest corner of the herein
described tract;

THENCE, NORTH 41 degrees 44'27" East, a distance of 334.23 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 03 degrees 35'59", an arc length of 47.75 feet, and a chord
which bears North 39 degrees 56'28" East, 47.74 feet to a "X" in concrete set
marking the most northwesterly corner of the herein described tract;

THENCE, SOUTHEASTERLY, with a non-tangent curve to the left having a radius of
87.50 feet, an arc length of 93.13 feet, a central angle of 60 degrees 59'01",
and a chord which bears South 58 degrees 25'28" East, 88.80 feet to 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH 88 degrees 54'58" East, a distance of 27.76 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, EASTERLY, with a curve to the right having a radius of 281.50 feet, an
arc length of 67.83 feet, a central angle of 13 degrees 48'19", and a chord
which bears South 82 degrees 00'48" East, 67.66 feet to a 5/8-inch iron rod with
plastic cap set marking a point of tangency;

THENCE, SOUTH 75 degrees 06'39" East, a distance of 82.41 feet to the POINT OF
BEGINNING and containing 2,619 acres (114,086 square feet) of land (this
description is based on a Land Title Survey and plat prepared by Terra
Surveying Company, Inc. Project Number 0163-9801-S).

<PAGE>   97
                                  EXHIBIT "B"

         There is hereby excepted from the definition of the "Mortgaged
Property", and from all liens and security interests covered by this Leasehold
Deed of Trust or any of the Loan Instruments, all property of Grantors which is
not a part of the plumbing, electrical, heating, cooling, ventilation, standard
lighting, ceiling tile, sprinkler equipment and related equipment together with
other fixtures and equipment necessary for the use and operation of the
buildings for general purposes and all property (save and except the foregoing)
which is not permanently attached or affixed to the building and is not an
integral part of the building and needed for the same to be functional as an
office building. Without limiting the foregoing sentence, the property described
below is excepted from said definition of "Mortgaged Property" and shall not be
in any way secured or encumbered by this Leasehold Deed of Trust or any of the
Loan Instruments (as such term is defined in the Loan Agreement).

                               Excluded Property

Furniture
Computers and related equipment, computer network equipment and software
Laboratory equipment
Production Equipment
Modular clean room units
Telephone equipment
Office equipment
Artwork
Decorative items
Plants
Inventory, including raw materials, work in progress and finished goods
Office supplies
Lab notebooks
Electronic media
Backup power generator
Cold storage equipment
Waste treatment equipment

Whether now owned or hereafter acquired

                                    [STAMP]

                                      -18-

<PAGE>   98
                             MEMORANDUM OF SUBLEASE
                                 AND ASSIGNMENT

     This Memorandum of Sublease and Assignment is executed by and between
Amelang Partners, Inc., a Texas corporation ("Amelang"), and Introgen
Therapeutics, Inc., a Delaware corporation, and TMX Realty Corporation, a
Delaware corporation.

     WHEREAS, a certain Enhanced-Use Lease Agreement was executed by and
between the United States Department of Veterans Affairs and Amelang Partners,
Inc., as set forth in the instrument dated August 25, 1993, and filed for record
under Harris County Clerk's File No. R182160 and supplemented by instrument
filed for record under Harris County Clerk's File No. S319699;

     WHEREAS, a portion of the real property described in said Enhanced-Use
Lease was subleased pursuant to a Ground Sublease Agreement ("Sublease") by and
between Amelang Partners, Inc., as sublessor, and Introgen Therapeutics, Inc.,
as sublessee, which Ground Sublease Agreement was signed November 23, 1998, with
an effective date of September 24, 1998, which Sublease covers 2.619 acres of
said real property (the "Subleased Property"), which Subleased Property is
described on Exhibit "A" attached hereto and incorporated herein for all
purposes; and

     WHEREAS, by a written Assignment and Assumption of Sublease Agreement
dated November 23, 1998, the said Introgen Therapeutics, Inc., assigned and
transferred all of its interest in the said Sublease and the Subleased Property
to TMX Realty Corporation.

     THEREFORE, all persons interested in said 2.619 acres described upon
Exhibit "A" attached hereto or the transactions described above may contact the
parties hereto as follows:

                         Amelang Partners, Inc.
                         952 Echo Lane, Suite 100
                         Houston, Texas 77024

                         Introgen Therapeutics, Inc.
                         301 Congress Avenue, Suite 1850
                         Austin, Texas 78701

                         TMX Realty Corporation
                         301 Congress Avenue, Suite 1850
                         Austin, Texas 78701

                                       1
<PAGE>   99
Signed by each of the undersigned this 24th day of November, 1998.

                                        AMELANG PARTNERS, INC.

                                        By:  /s/ WELLINGTON STEVENS III
                                             -----------------------------------
                                        Its: President
                                             -----------------------------------

                                        INTROGEN THERAPEUTICS, INC.

                                        By:  /s/ JAMES W. ALBRECHT, JR.
                                             -----------------------------------
                                        Its: Chief Financial Officer
                                             -----------------------------------

                                        TMX REALTY CORPORATION

                                        By:  /s/ JAMES W. ALBRECHT, JR.
                                             -----------------------------------
                                        Its: Chief Financial Officer
                                             -----------------------------------

[SEAL]

                          (Corporate Acknowledgement)

THE STATE OF TEXAS       )
                         )                                               [SEAL]
COUNTY OF HARRIS         )

     This instrument was acknowledged before me on the 24th day of November,
1998, by Wellington Stevens III, President of Amelang Partners, Inc., a Texas
corporation, on behalf of said corporation.

                                        /s/ FELICIA E. BOWMAN
                                        ----------------------------------------
                                        Notary Public, State of Texas

                          (Corporate Acknowledgement)

THE STATE OF TEXAS       )
                         )
COUNTY OF TRAVIS         )

     This instrument was acknowledged before me on the 24th day of November,
1998, by James W. Albrecht, Jr., Chief Financial Officer of Introgen
Therapeutics, Inc., a Delaware corporation, on behalf of said corporation.

                                        /s/ LYNNE MADDOX
                                        ----------------------------------------
                                        Notary Public, State of Texas

[SEAL]

                                       2
<PAGE>   100
                          (Corporate Acknowledgement)

STATE OF TEXAS    )
                  )
COUNTY OF TRAVIS  )

     This instrument was acknowledged before me on the 24 day of November, 1998
by James W. Albrecht, Jr., Chief Financial Officer of TMX Realty Corporation, a
Delaware corporation, on behalf of said corporation.

                                                   /s/ LYNNE MADDOX
                                                   -----------------------------
     [SEAL]           LYNNE MADDOX                Notary Public, State of Texas
               Notary Public, State of Texas
            My Commission Expires June 17, 2002

                                       3
<PAGE>   101
                               [TERRA LETTERHEAD]

     METES & BOUNDS DESCRIPTION
     2.619 ACRES (114,086 SQUARE FEET)
     D W C HARRIS SURVEY, ABSTRACT NUMBER 325
     HARRIS COUNTY, TEXAS

     Being a tract or parcel containing 2.619 acres (114,086 square feet) of
     land situated in the D W C Harris Survey, Abstract Number 325, Harris
     County, Texas, and being part of and out of that certain called 118.831
     acres, described in deed to the United States of America, as recorded in
     Volume 1297, Page 87, Deed Records of Harris County, Texas, said 2.619
     acre tract being more particularly described as follows (all bearings and
     coordinates are based on the Texas State Plane Coordinate System; South
     Central Zone; all distances and coordinates are surface and may be
     converted to grid by multiplying by a combined scale factor of 0.9998632):

     COMMENCING at a 5/8-inch iron rod with plastic cap set marking the
     intersection of the south right-of-way (ROW) line of Holcombe Boulevard
     with the west ROW line of Almeda Road, and having surface coordinates of
     X=3,147,967.40, Y=698,487.10, thence:

          South 14 degrees 53'21" West, with said west ROW line, a distance of
          206.00 feet to a set 5/8-inch iron rod with plastic cap;

          North 75 degrees 06'39" West, a distance of 329.30 feet to a
          5/8-inch iron rod with plastic cap set marking the POINT OF BEGINNING
          and northeast corner of the herein described tract;

     THENCE, SOUTH 14 degrees 53'21" West, a distance of 330.70 feet to a
     5/8-inch iron rod with plastic cap set marking the southeast corner of the
     herein described tract;

     THENCE, NORTH 75 degrees 06'39" West, a distance of 432.78 feet to a
     5/8-inch iron rod with plastic cap set marking the southwest corner of the
     herein described tract;

     THENCE, NORTH 41 degrees 44'27" East, a distance of 334.23 feet to a
     5/8-inch iron rod with plastic cap set marking the beginning of a tangent
     curve;

     THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00
     feet, a central angle of 03 degrees 35'59", an arc length of 47.75 feet,
     and a chord which bears North 39 degrees 56'28" East, 47.74 feet to an "X"
     in concrete set marking the most northwesterly corner of the herein
     described tract;

     THENCE, SOUTHEASTERLY, with a non-tangent curve to the left having a radius
     of 87.50 feet, an arc length of 93.13 feet, a central angle of 60 degrees
     59'01", and a chord which bears South 58 degrees 25'28" East, 88.80 feet to
     a 5/8-inch iron rod with plastic cap set marking a point of tangency;

     THENCE, SOUTH 88 degrees 54'58" East, a distance of 27.76 feet to a
     5/8-inch iron rod with plastic cap set marking the beginning of a tangent
     curve;

     THENCE, EASTERLY, with a curve to the right having a radius of 281.50 feet,
     an arc length of 67.83 feet, a central angle of 13 degrees 48'19", and a
     chord which bears South 82 degrees 00'48" East, 67.66 feet to a 5/8-inch
     iron rod with plastic cap set marking a point of tangency;
<PAGE>   102
METES & BOUNDS DESCRIPTION
2.619 ACRES (114,086 SQUARE FEET)
D W C HARRIS SURVEY, ABSTRACT NUMBER 325
HARRIS COUNTY, TEXAS

Page 2 of 2

THENCE, SOUTH 75 degrees 06'39" East, a distance of 82.41 feet to the POINT OF
BEGINNING and containing 2.619 acres (114,086 square feet) of land (this
description is based on a Land Title Survey and plat prepared by Terra Surveying
Company, Inc. Project Number 0163-9801-S).

Compiled by: Scott D Mandeville              [STAMP]
Compiled: October 22, 1998
TSC Project No: 0163-9801-S
SDM: 2-619ac.mb

ANY PROVISION HEREIN WHICH RESTRICTS THE SALE, RENTAL, OR USE OF THE DESCRIBED
REAL PROPERTY BECAUSE OF COLOR OR RACE IS INVALID AND UNENFORCEABLE UNDER
FEDERAL LAW
THE STATE OF TEXAS}
COUNTY OF HARRIS  }

     I hereby certify that this instrument was FILED in File Number Sequence on
the date and at the time stamped hereon by me; and was duly RECORDED, in the
Official Public Records of Real Property of Harris County, Texas on

                                   DEC 3 1998

[STAMP] COUNTY COURT OF HARRIS               /s/ BEVERLY B. KAUFMAN
        COUNTY, TEXAS *                      COUNTY CLERK
                                             HARRIS COUNTY TEXAS
<PAGE>   103
                                                                       EXHIBIT A
                                                                        11-23-98

                   [TERRA SURVEYING COMPANY INC. LETTERHEAD]

METES & BOUNDS DESCRIPTION
2.619 ACRES (114,086 SQUARE FEET)
D W C HARRIS SURVEY, ABSTRACT NUMBER 325
HARRIS COUNTY, TEXAS

Being a tract or parcel containing 2.619 acres (114,086 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 2.619 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

COMMENCING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3,147,967.40,
Y=698,487.10, thence:

     South 14 degrees 53'21" West, with said west ROW line, a distance of 206.00
     feet to a set 5/8-inch iron rod with plastic cap;

     North 75 degrees 06'39" West, a distance of 329.30 feet to a 5/8-inch iron
     rod with plastic cap set marking the POINT OF BEGINNING and northeast
     corner of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, a distance of 330.70 feet to a 5/8-inch
iron rod with plastic cap set marking the southeast corner of the herein
described tract;

THENCE, NORTH 75 degrees 06'39" West, a distance of 432.78 feet to a 5/8-inch
iron rod with plastic cap set marking the southwest corner of the herein
described tract;

THENCE, NORTH 41 degrees 44'27" East, a distance of 334.23 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 03 degrees 35'59", an arc length of 47.75 feet, and a chord
which bears North 39 degrees 56'28" East, 47.74 feet to an "X" in concrete set
marking the most northwesterly corner of the herein described tract;

THENCE, SOUTHEASTERLY, with a non-tangent curve to the left having a radius of
87.50 feet, an arc length of 93.13 feet, a central angle of 60 degrees 59'01",
and a chord which bears South 58 degrees 25'28" East, 88.80 feet to a 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH 88 degrees 54'58" East, a distance of 27.76 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, EASTERLY, with a curve to the right having a radius of 281.50 feet, an
arc length of 67.83 feet, a central angle of 13 degrees 48'19", and a chord
which bears South 82 degrees 00'48" East, 67.66 feet to a 5/8-inch iron rod with
plastic cap set marking a point of tangency;

<PAGE>   104
METES & BOUNDS DESCRIPTION
2.619 ACRES (114,086 SQUARE FEET)
D W C HARRIS SURVEY, ABSTRACT NUMBER 325
HARRIS COUNTY, TEXAS

Page 2 of 2

THENCE, SOUTH 75 degrees 06'39" East, a distance of 82.41 feet to the POINT OF
BEGINNING and containing 2.619 acres (114,086 square feet) of land (this
description is based on a Land Title Survey and plat prepared by Terra Surveying
Company, Inc, Project Number 0163-9801-S).

Compiled by: Scott D Mandeville              [STAMP]
Compiled: October 22, 1998
TSC Project No: 0163-9801-S
SDM: 2-619ac.mb

<PAGE>   105
                        NOTE, DEED OF TRUST AND GUARANTY
                              MODIFICATION AGREEMENT

     This Note, Deed of Trust and Guaranty Modification Agreement ("Agreement")
is made as of the 24th day of September, 1998, by and among AMELANG PARTNERS
INCORPORATED, a Texas corporation ("Borrower"); AID ASSOCIATION FOR LUTHERANS,
a Wisconsin corporation ("Lender"); and KARL J. AMELANG ("Guarantor").

                                    RECITALS

     A. Borrower is indebted to Lender for a previous loan evidenced by a
Promissory Note (the "Note") dated February 6, 1997, in the original principal
sum of $2,500,000.00, executed by Borrower, payable to Lender.

     B. The Note is secured by (i) a Deed of Trust and Security Agreement ("Deed
of Trust") executed by Borrower to Barry E. Putterman, Trustee, filed under
Clerk's File No. S319696, and recorded under Film Code Reference No. 511-82-2756
in the Official Public Records of Real Property of Harris County, Texas, (ii) an
Assignment of Rents and Leases ("Assignment of Rents") executed by Borrower to
Lender, filed under Clerk's File No. S319697, and recorded under Film Code
Reference No. ###-##-#### in the Official Public Records of Real Property of
Harris County, Texas, and (iii) other and sundry documents and agreements. All
documents and agreements given as security for the Note are referred to
collectively as the "Loan Documents."

     C. In connection with Borrower's execution of the Loan Documents,
Guarantor executed and delivered to Lender a Limited Guaranty (the "Guaranty")
and an Environmental Indemnity Agreement (the "Indemnity").

     D. Section 5.19 of the Deed of Trust entitles Borrower, upon satisfaction
of certain terms and conditions, to a partial release of the property defined
therein as the "Additional Collateral" and being more particularly described on
Exhibit "A" attached hereto.

     E. As a condition of Borrower being entitled to a partial release of the
Additional Collateral, Borrower, Guarantor and Lender are executing this
Agreement.

     NOW, THEREFORE, in consideration of the foregoing Recitals, and for other
good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, Borrower, Lender and Guarantor hereby agree as follows:

     1. Ratification of Recitals. Borrower, Lender and Guarantor hereby ratify
and confirm the above Recitals.

     2. Partial Release. Lender hereby RELEASES and DISCHARGES the Additional
Collateral from the liens, claims, security interests and encumbrances of the
Loan Documents. Without limiting the generality of the preceding sentence, the
definition of the term "Land" contained
<PAGE>   106

     5. Restrictions on Released Property. The following provision is hereby
added as new Section 5.21 of the Deed of Trust:

     "5.21 Restrictions on Released Property. Except with the prior written
     consent of Beneficiary, neither Grantor nor any of its successors or
     assigns shall use the Additional Collateral in a manner inconsistent with
     the following restrictions, which shall be covenants running with the
     Additional Collateral and be binding upon Grantor and its successors and
     assigns during the term of the Ground Lease: (a) the exterior design of and
     development shall be compatible with the exterior architectural design of
     the adjacent VA Medical Center and the improvements situated on the Initial
     Development; (b) all buildings shall be situated on the Additional
     Collateral at least twenty-five (25) feet away from F.M. 521 (Almeda Road)
     and at least ten (10) feet away from the common boundary line with the
     Initial Development; (c) adequate on-site parking shall be established,
     including, without limitation, meeting the minimum requirements of the City
     of Houston parking ordinance as they apply generally to all properties; (d)
     the development shall contain adequate surface drainage so that no
     excessive drainage flows onto the surface of the Initial Development, and
     (e) no curb cuts for vehicular traffic shall be located on any portion of
     the Additional Collateral within twenty (20) feet of the Initial
     Development. Grantor hereby grants to Beneficiary and any successor to the
     interest of Beneficiary in the Initial Development a non-exclusive easement
     on and under the Additional Collateral to provide water to the Initial
     Development and to treat wastewater from the Initial Development through
     the lines presently existing under the Additional Collateral, together with
     reasonable rights of access to repair such lines. Grantor, at its sole cost
     and expense, may relocate such lines to other locations on the Additional
     Collateral so long as utility service to the Initial Development is not
     interrupted and the point of connection remains the same. Within fifteen
     (15) days of a request from time to time by Beneficiary, Grantor shall
     deliver or cause to be delivered to Beneficiary evidence reasonably
     satisfactory to Beneficiary that Grantor's successors, assigns and/or
     subtenants have been bound by such restrictions and easements. The
     provisions of this Section 5.21 shall survive the release of this Deed of
     Trust or a foreclosure hereunder for the remainder of the term of the
     Ground Lease as it applies to the Initial Development, including a
     "Replacement Lease" (as such term is defined in the Ground Lease), and
     shall benefit Beneficiary and it successors and assigns."

     6. Separate Tax Parcel. Section 1.4 of the Deed of Trust, subparagraph
entitled "Property Taxes", is hereby modified by deleting the last two
sentences and substituting the following:

     "By no later than May 1, 1999, and all times thereafter, Grantor shall
     cause the Initial Development to be assessed separately for ad valorem tax
     purposes from any other property. Grantor shall by no later than May 1,
     1999, deliver proof of compliance with the preceding sentence to
     Beneficiary."

                                     Page 3
<PAGE>   107
       7.   Modification to Insurance Provisions. The fire, tornado, windstorm
and extended coverage insurance obligations set forth on Pages 12, 13, and 14 of
the Deed of Trust (including, without limitation, the insurance covering lost
rentals and other revenues) shall apply solely to the Initial Development. By
way of example, Grantor shall keep all improvements situated on the Initial
Development insured against loss as may be reasonably required by Beneficiary,
for the full replacement value, and the insurance covering rentals and other
revenues derived from the Premises shall mean and refer to the rentals and other
revenues derived from the Initial Development, with all of such insurance
policies to provide specifically that they cover the Initial Development in a
form reasonably acceptable to Beneficiary. Any liability policy may cover, at
Beneficiary's option, other property covered by the Ground Lease, in addition to
the Initial Development, or solely the Initial Development.

       8.  Ratification and Confirmation. Borrower hereby ratifies and confirms
the liens of the Deed of Trust and acknowledges and agrees that the Note and
Loan Documents remain in full force and effect in accordance with their original
terms, except as modified by this Agreement.

       9.  Ratification of Guaranty and Indemnity. Guarantor hereby ratifies and
confirms the Guaranty and the Indemnity, notwithstanding this Agreement.

       10. Representations and Warranties. Borrower and Guarantor represent and
warrant to and for the benefit of Lender that as of the date hereof:

       (a) Borrower is a duly formed Texas corporation and has all requisite
           power and authority to enter into this Agreement and perform its
           obligations hereunder;

       (b) Borrower is still the holder of the interest of the Tenant under the
           Ground Lease and has not prior to the date hereof transferred,
           assigned or encumbered any of its interests in the Ground Lease to
           any party other than Lender; and

       (c) Neither Borrower nor Guarantor has any defense to any of their
           respective obligations under the Loan Documents as amended hereby,
           including, without limitation, the Guaranty or the Indemnity.

       11. Additional Obligations. This Agreement is conditioned on the
following matters occurring to the satisfaction of Beneficiary by no later than
ten (10) days after the date hereof: (a) Grantor paying to Beneficiary a
one-time transaction fee in the amount of $12,500.00; (b) Grantor paying all
reasonable legal expenses incurred by Beneficiary in connection with the
preparation and negotiation of this Agreement and the transactions described
herein, (c) Grantor providing Beneficiary with a P-9(b)(3) endorsement to the
Mortgagee Policy of Title Insurance insuring the Deed of Trust, confirming that
said policy remains in full force and effect notwithstanding this Agreement; and
(d) Grantor delivering or causing to be delivered to Beneficiary an amendment to
the Ground Lease in a form satisfactory to Beneficiary.

                                    Page 4

<PAGE>   108
     12. Further Assurances. Borrower and Guarantor shall each execute,
acknowledge, and delivery all such instruments, and take all such actions as may
be reasonably necessary to further assure to Lender the full benefits of the
Loan Documents, including the collateral therefor, and to preserve and protect
the Loan Documents and all the rights, powers and remedies of Lender provided
for therein.

     13. Future Transfers. Borrower and Guarantor acknowledge that Lender's
consent to the partial release of the Additional Collateral does not constitute
a consent by Lender to any future transfer, conveyance, encumbrance or
assignment of any right, title or interest prohibited or restricted under the
Loan Documents.

     14. Binding Effect. This Agreement shall be binding upon and inure to the
benefit of the heirs, successors and assigns of the respective parties hereto
(without implying consent to any transfers or assignments prohibited or
restricted by the Loan Documents).

                                    AMELANG PARTNERS
                                    INCORPORATED

                                    By:    /s/ KARL J. AMELANG
                                           -------------------------------------
                                    Name:  Karl J. Amelang
                                           -------------------------------------
                                    Title: CEO
                                           -------------------------------------

                                           /s/ KARL J. AMELANG
                                    --------------------------------------------
                                           KARL J. AMELANG

                                    AID ASSOCIATION FOR LUTHERANS

                                    By:    /s/ DAVID CRIST
                                           -------------------------------------
                                    Name:  David Crist
                                           -------------------------------------
                                    Title: Assistant Secretary
                                           -------------------------------------

                                    By:    /s/ WAYNE C. STRECK
                                           -------------------------------------
                                    Name:  Wayne C. Streck
                                           -------------------------------------
                                    Title: Vice-President Mortgage & Real Estate
                                           -------------------------------------

                                     Page 5
<PAGE>   109
STATE OF TEXAS           )
                         )
COUNTY OF HARRIS         )

     This instrument was acknowledged before me on November 23rd, 1998, by Karl
J. Amelang, CEO of AMELANG PARTNERS INCORPORATED, a Texas corporation, on behalf
of said corporation.

          [SEAL]                            /s/ DEBORAH D. DUNN
                                            ------------------------------------
                                            Notary Public, State of Texas

STATE OF TEXAS           )
                         )
COUNTY OF HARRIS         )

     This instrument was acknowledged before me on November 23rd, 1998, by Karl
J. Amelang.

          [SEAL]                            /s/ DEBORAH D. DUNN
                                            ------------------------------------
                                            Notary Public, State of Texas

STATE OF WISCONSIN       )
                         )
COUNTY OF OUTGAMIE       )

     This instrument was acknowledged before me on November 30th, 1998, by
Wayne C. Streck and David Crist, the V-P (Mortg. & Real Estate), and Assistant
Secretary respectively, of AID ASSOCIATION FOR LUTHERANS, a Wisconsin
corporation, on behalf of said corporation.

                                            /s/ KATHLEEN M. VAN BOSTEL
                                            ------------------------------------
                                            Notary Public, State of Wisconsin

                                            Kathleen M. Van Bostel

Attachments: Exhibit "A" and Exhibit "D"

My commission expires 8-11-2002

                                     Page 6
<PAGE>   110

                                 EXHIBIT "A"

Being a tract or parcel containing 5.119 acres (222,986 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 5.119 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

COMMENCING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3,147,967.40,
Y=698,487.10, thence:

     South 14 degrees 53'21" West, with said west ROW line, a distance of
     206.00 feet to a 5/8-inch iron rod with plastic cap set marking the
     POINT OF BEGINNING and northeast corner of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, continuing with said west ROW line, a
distance of 330.70 feet to a 5/8-inch iron rod with plastic cap set marking the
southeast corner of the herein described tract;

THENCE, NORTH 75 degrees 06'39" West, a distance of 762.08 feet to a 5/8-inch
iron rod with plastic cap set marking the southwest corner of the herein
described tract;

THENCE, NORTH 41 degrees 44'27" East, a distance of 334.23 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 03 degrees 35'59", an arc length of 47.75 feet, and a chord
which bears North 39 degrees 56'28" East, 47.74 feet to an "X" in concrete set
marking the most northwesterly corner of the herein described tract;

THENCE, SOUTHEASTERLY, with a non-tangent curve to the left having a radius of
87.50 feet, an arc length of 93.13 feet, a central angle of 60 degrees 59'01",
and a chord which bears South 58 degrees 25'28" East, 88.80 feet to a 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH, 88 degrees 54'58" East, a distance of 27.76 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, EASTERLY, with a curve to the right having a radius of 281.50 feet, an
arc length of 67.83 feet, a central angle of 13 degrees 48'19", and a chord
which bears South 82 degrees 00'48" East, 67.66 feet to a 5/8-inch iron rod with
plastic cap set marking a point of tangency;

THENCE, SOUTH 75 degrees 06'39" East, a distance of 411.72 feet to the POINT OF
BEGINNING and containing 5.119 acres (222,986 square feet) of land (this
description is based on an AVTA/ACSM Land Title Survey and plat prepared by
Terra Surveying Company, Inc, Project Number 0043-9603-S).

<PAGE>   111
                                  EXHIBIT "D"

Being a tract or parcel containing 3.135 acres (136,574 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 3.135 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

BEGINNING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the southerly right-of-way (ROW) line of Holcombe Boulevard with the
westerly ROW line of Almeda Road, and having surface coordinates of
X=3,147,967.40, Y=698,487.10, said iron rod also marking the most easterly
corner of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, with said westerly ROW line, a distance
of 206.00 feet to a 5/8-inch iron rod with plastic cap set marking the most
southerly corner of the herein described tract;

THENCE, NORTH 75 degrees 06'39" West, at 380.00 feet pass a set 5/8-inch iron
rod with plastic cap, continuing in all, a distance of 411.72 feet to a
5/8-inch iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, WESTERLY, with a curve to the left having a radius of 281.50 feet, an
are length of 67.83 feet, a central angle of 13 degrees 48'19", and a chord
which bears North 82 degrees 00'48" West, 67.66 feet to a 5/8-inch iron rod
with plastic cap set marking a point of tangency;

THENCE, NORTH 88 degrees 54'58" West, a distance of 27.76 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHWESTERLY, with a curve to the right having a radius of 87.50 feet,
an arc length of 93.13 feet, a central angle of 60 degrees 59'01", and a chord
which bears North 58 degrees 25'28" West, 88.80 feet to an "X" in the top of a
concrete inlet set marking the southwest corner of the herein described tract,
and being in a non-tangent curve concave northwest;

THENCE, NORTHEASTERLY, with said non-tangent curve to the left, having a radius
of 760.00 feet, a central angle of 07 degrees 08'15", an arc length of 94.68
feet, and a chord which bears North 34 degrees 34'21" East, 94.61 feet to a
5/8-inch iron rod with plastic cap set marking a point of tangency;

THENCE, NORTH 31 degrees 00'14" East, a distance of 65.48 feet to a 5/8-inch
iron rod with plastic cap set for corner;

THENCE, NORTH 18 degrees 49'21" East, a distance of 51.16 feet to a lead plug
with tack set in a concrete footing marking the most westerly north corner of
the herein described tract;

                                  Page 1 of 2
<PAGE>   112
THENCE, SOUTH 71 degrees 10'39" East, a distance of 43.42 feet to a 5/8-inch
iron rod with plastic cap set for corner;

THENCE, NORTH 18 degrees 49'21" East, a distance of 23.88 feet to a 5/8-inch
iron rod with plastic cap set for corner;

THENCE, SOUTH 71 degrees 10'39" East, a distance of 15.90 feet to a lead plug
with tack set in a concrete footing for corner;

THENCE, NORTH 18 degrees 49'21" East, a distance of 20.16 feet to a lead plug
with tack set in a concrete footing for corner;

THENCE, SOUTH 71 degrees 10'39" East, a distance of 20.02 feet to a 5/8-inch
iron rod with plastic cap set for corner;

THENCE, NORTH 18 degrees 49'21" East, a distance of 20.56 feet to the southerly
ROW line of the aforesaid Holcombe Boulevard, also being the most northerly
west corner of the herein described tract;

THENCE, SOUTH 71 degrees 10'39" East, with said southerly ROW line, a distance
of 7.66 feet to the beginning of a tangent curve;

THENCE, SOUTHEASTERLY, with said southerly ROW line and a curve to the right
having a radius of 2,864.93 feet, at an arc length of 66.33 feet pass a set
5/8-inch iron rod with plastic cap, continuing in all, an arc length of 451.48
feet, a central angle of 09 degrees 01'45", and a chord which bears South 66
degrees 39'46" East, 451.01 feet to the POINT OF BEGINNING and containing 3.135
acres (136,574 square feet) of land (this description is based on an ALTA/ACSM
Land Title Survey and plat prepared by Terra Surveying Company, Inc. Project
Number 0043-9601-S).

                                  Page 2 of 2
<PAGE>   113
ISSUED BY                                      OWNER'S POLICY OF TITLE INSURANCE
COMMONWEALTH LAND TITLE INSURANCE COMPANY
--------------------------------------------------------------------------------
[LOGO]COMMONWEALTH                                             POLICY NUMBER
                                                                 175-163778

     SUBJECT TO THE EXCLUSIONS FROM COVERAGE, THE EXCEPTIONS FROM COVERAGE
CONTAINED IN SCHEDULE B AND THE CONDITIONS AND STIPULATIONS, Commonwealth Land
Title Insurance Company, a Pennsylvania corporation, herein called the Company,
insures, as of Date of Policy shown in Schedule A, against loss or damage, not
exceeding the Amount of Insurance stated in Schedule A, sustained or incurred by
the insured by reason of:

1. Title to the estate or interest described in Schedule A being vested other
   than as stated therein;
2. Any defect in or lien or encumbrance on the title;
3. Any statutory or constitutional mechanic's, contractor's, or materialman's
   lien for labor or material having its inception on or before Date of Policy;
4. Lack of a right of access to and from the land;
5. Lack of good and indefeasible title.

     The Company also will pay the costs, attorneys' fees and expenses incurred
in defense of the title, as insured, but only to the extent provided in the
Conditions and Stipulations.

IN WITNESS WHEREOF, COMMONWEALTH LAND TITLE INSURANCE COMPANY has caused its
corporate name and seal to be hereunto affixed by its duly authorized officers,
the Policy to become valid when countersigned by an authorized officer or agent
of the Company.

                                       COMMONWEALTH LAND TITLE INSURANCE COMPANY

Attest:                     [STAMP]                  By:

 /s/ [illegible]                                         /s/ [illegible]
               Secretary                    Chairman and Chief Executive Officer

                            EXCLUSIONS FROM COVERAGE

     The following matters are expressly excluded from the coverage of this
policy and the Company will not pay loss or damage, costs, attorneys' fees or
expenses which arise by reason of:

1. (a) Any law, ordinance or governmental regulation (including but not limited
   to building and zoning laws, ordinances, or regulations) restricting,
   regulating, prohibiting or relating to (i) the occupancy, use, or enjoyment
   of the land; (ii) the character, dimensions or location of any improvement
   now or hereafter erected on the land; (iii) a separation in ownership or a
   change in the dimensions or area of the land or any parcel of which the land
   is or was a part; or (iv) environmental protection, or the effect of any
   violation of these laws, ordinances or governmental regulations, except to
   the extent that a notice of the enforcement thereof or a notice of a defect,
   lien or encumbrance resulting from a violation or alleged violation affecting
   the land has been recorded in the public records at Date of Policy.

   (b) Any governmental police power not excluded by (a) above, except to the
   extent that a notice of the exercise thereof or a notice of a defect, lien or
   encumbrance resulting from a violation or alleged violation affecting the
   land has been recorded in the public records at Date of Policy.

2. Rights of eminent domain unless notice of the exercise thereof has been
   recorded in the public records at Date of Policy, but not excluding from
   coverage any taking that has occurred prior to Date of Policy which would be
   binding on the rights of a purchaser for value without knowledge.

3. Defects, liens, encumbrances, adverse claims or other matters:

   (a) created, suffered, assumed or agreed to by the insured claimant;

   (b) not known to the Company, not recorded in the public records at Date of
   Policy, but known to the insured claimant and not disclosed in writing to the
   Company by the insured claimant prior to the date the insured claimant became
   an insured under this policy;

   (c) resulting in no loss or damage to the insured claimant;

   (d) attaching or created subsequent to Date of Policy;

   (e) resulting in loss or damage that would not have been sustained if the
   insured claimant had paid value for the estate or interest insured by this
   policy.

4. The refusal of any person to purchase, lease or lend money on the estate or
   interest covered hereby in the land described in Schedule A because of
   unmarketability of the title.

5. Any claim which arises out of the transaction vesting in the person named in
   paragraph 3 of Schedule A the estate or interest insured by this policy, by
   reason of the operation of federal bankruptcy, state insolvency, or other
   state or federal creditors' rights laws that is based on either (i) the
   transaction creating the estate or interest insured by this Policy being
   deemed a fraudulent conveyance or fraudulent transfer or a voidable
   distribution or voidable dividend, (ii) the subordination or
   recharacterization of the estate or interest insured by this Policy as a
   result of the application of the doctrine of equitable subordination or (iii)
   the transaction creating the estate or interest insured by this Policy being
   deemed a preferential transfer except where the preferential transfer results
   from the failure of the Company or its issuing agent to timely file for
   record the instrument of transfer to the insured after delivery or the
   failure of such recordation to impart notice to a purchaser for value or a
   judgment or lien creditor.

Texas Owner Policy T-1 (Rev. 1-1-93)
<PAGE>   114
[COMMONWEALTH LOGO]

COMMONWEALTH LAND TITLE INSURANCE COMPANY

GF Number: 98011250
Policy Number: 175-163778
Premium: N/A
Date of Endorsement: December 3, 1998

                       LEASEHOLD OWNER POLICY ENDORSEMENT

                                   ISSUED BY
                   COMMONWEALTH LAND TITLE INSURANCE COMPANY

The conditions and stipulations of said policy are hereby amended in the
following particulars:
Section 1 of the Conditions and Stipulations of said policy is hereby amended
by adding subsection (h) thereto to read as follows:

     (h)  "leasehold estate": the right of possession for the term or terms
          described in Schedule A hereof subject to any provisions contained in
          the Lease which limits such right of possession.

The following new subsections (d) and (e) are inserted into Section 7 of said
Conditions and Stipulations:
     (d)  Valuation of Estate or Interest Insured
     If, in computing loss or damages incurred by the Insured, it
     becomes necessary to determine the value of the estate or interest insured
     by this policy, such value shall consist of the then present worth of the
     excess, if any, of the fair market rental value of such estate or interest,
     undiminished by any matters for which such claim is made, for that part of
     the term stated in Schedule A herein then remaining plus any renewal or
     extended term for which a valid option to renew or extend is contained in
     the Lease, over the value of the rent and other consideration required to
     be paid under the Lease for the same period.

     (e)  Miscellaneous Items of Loss
     In the event the Insured is evicted from possession of all or a part of the
     land by reason of any matters insured against by this policy the following,
     if applicable, shall be included in computing loss or damage incurred by
     the Insured, but not to the extent that the same are included in the
     valuation of the estate or interest insured by this policy.

     (i)  The reasonable cost of removing and relocating any personal property
          which the Insured has the right to remove and relocate, situated on
          the land at the time of eviction, the cost of transportation of such
          personal property for the initial twenty-five miles incurred in
          connection with such relocation, and the reasonable cost of repairing
          such personal property damaged by reason of said removal and
          relocation. The costs referred to above shall not exceed in the
          aggregate the value of the personal property prior to its removal and
          relocation. "Personal property", above referred to, shall mean
          chattels and property which because of its character and manner of
          affixation to the land, can be severed therefrom without causing
          appreciable damage to the property severed or to the land to which
          such property is affixed.

     (ii) Rent or damages for use and occupancy of the land prior to such
          eviction which the Insured as owner of the leasehold estate may be
          obligated to pay to any person having paramount title to that of the
          lessor in the Lease.

    (iii) The amount of rent which, by the terms of the Lease, the Insured must
          continue to pay to the lessor after eviction for the land, or part
          thereof, from which the Insured has been evicted.

     (iv) The fair market value, at the time of such eviction, of the estate or
          interest of the insured in any sublease of all or part of the land
          existing at the date of such eviction.

     (v)  Damages which the Insured may be obligated to pay to any sublease on
          account of the breach of any sublease of all or part of the land
          caused by such eviction.

The total liability of the Company under said policy and any endorsements
therein shall not exceed, in the aggregate, the face amount of said policy and
costs which the Company is obligated under the Conditions and Stipulations
thereof to pay.

This endorsement, when countersigned below by an Authorized Countersignature,
is made a part of said policy and is subject to the Schedules, Exclusions from
Coverage, and Conditions and Stipulations therein, except as modified by the
provisions hereof.

/s/ GLORIA DORECK
---------------------------
Authorized Countersignature
<PAGE>   115
                        OWNER POLICY OF TITLE INSURANCE

                                   SCHEDULE A

                                               Issued with Policy No. 535-370986
G.F. No. 98011250

Policy No. 175-163778

Amount of Insurance: $10,152,910.00

Premium: $56,515.45

Date of Policy: DECEMBER 3, 1998, 3:11 PM

1.   Name of Insured: TMX REALTY, INC., A DELAWARE CORPORATION

2.   The estate or interest in the land that is covered by this policy is:

     LEASEHOLD ESTATE CREATED IN THAT LEASE AGREEMENT EXECUTED BY AND BETWEEN
     THE UNITED STATES DEPARTMENT OF VETERANS AFFAIRS AND AMELANG PARTNERS,
     INC., AS SET FORTH IN INSTRUMENT DATED AUGUST 25, 1993, AND FILED FOR
     RECORD UNDER HARRIS COUNTY CLERK'S FILE NO. R182160 AND SUPPLEMENTED BY
     INSTRUMENT FILED FOR RECORD UNDER HARRIS COUNTY CLERK'S FILE NO. S319699.
     SUBLEASE CREATED BY MEMORANDUM OF SUBLEASE AND ASSIGNMENT BY AND BETWEEN
     AMELANG PARTNERS, INC., A TEXAS CORPORATION AND INTROGEN THERAPEUTICS,
     INC., A DELAWARE CORPORATION AND TMX REALTY CORPORATION, A DELAWARE
     CORPORATION DATED NOVEMBER 24, 1998, FILED FOR RECORD UNDER HARRIS COUNTY
     CLERK'S FILE NO. T418082.

3.   Title to the estate or interest in the land is insured as vested in:

     TMX REALTY CORPORATION, A DELAWARE CORPORATION

4.   The land referred to in this policy is described as follows:

     A TRACT OF LAND CONTAINING 2.619 ACRES, MORE OR LESS, SITUATED IN THE
     D.W.C. HARRIS SURVEY, ABSTRACT NO. 325, HARRIS COUNTY, TEXAS, AND BEING
     MORE PARTICULARLY DESCRIBED BY METES AND BOUNDS ON EXHIBIT "A" ATTACHED
     HERETO AND MADE A PART HEREOF.

     NOTE: THE COMPANY DOES NOT REPRESENT THAT THE ABOVE ACREAGE OR SQUARE
     FOOTAGE CALCULATIONS ARE CORRECT.
<PAGE>   116
TERRA                        4900 Woodway, Suite 1000 -- Houston, Texas 755056
SURVEYING                                 (713) 993-0327 -- Fax (713) 993-9231
COMPANY, INC.

                                  EXHIBIT "A"

METES & BOUNDS DESCRIPTION
2.619 ACRES (114,086 SQUARE FEET)
D W C HARRIS SURVEY, ABSTRACT NUMBER 325
HARRIS COUNTY, TEXAS

Being a tract or parcel containing 2.619 acres (114,086 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 2.619 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

COMMENCING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3,147,967.40,
Y=698,487.10, thence:

     South 14 degrees 53'21" West, with said west ROW line, a distance of 206.00
     feet to a set 5/8-inch iron rod with plastic cap;

     North 75 degrees 06'39" West, a distance of 329.30 feet to a 5/8-inch iron
     rod with plastic cap set making the POINT OF BEGINNING and northeast corner
     of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, a distance of 330.70 feet to a 5/8-inch
iron rod with plastic cap set marking the southeast corner of the herein
described tract;

THENCE, NORTH 75 degrees 06'39" West, a distance of 432.78 feet to a 5/8-inch
iron rod with plastic cap set marking the southwest corner of the herein
described tract;

THENCE, NORTH 41 degrees 44'27" East, a distance of 334.23 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 03 degrees 35'59", an arc length of 47.75 feet, and a chord
which bears North 39 degrees 56'28" East, 47.74 feet to an "X" in concrete set
marking the most northwesterly corner of the herein described tract;

THENCE, SOUTHEASTERLY, with a non-tangent curve to the left having a radius of
87.50 feet, an arc length of 93.13 feet, a central angle of 60 degrees 59' 01",
and a chord which bears South 58 degrees 25'28" East, 88.80 feet to a 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH 88 degrees 54'58" East, a distance of 27.76 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, EASTERLY, with a curve to the right having a radius of 281.50 feet, an
arc length of 67.83 feet, a central angle of 13 degrees 48'19", and a chord
which bears South 82 degrees 00'48" East, 67.66 feet to a 5/8-inch iron rod
with plastic cap set marking a point of tangency;

<PAGE>   117
METES & BOUNDS DESCRIPTION
2.619 ACRES (114,086 SQUARE FEET)
D W C HARRIS SURVEY, ABSTRACT NUMBER 325
HARRIS COUNTY, TEXAS

Page 2 of 2

THENCE, SOUTH 75 degrees 06'39" East, a distance of 82.41 feet to the POINT OF
BEGINNING and containing 2.619 acres (114,086 square feet) of land (this
description is based on a Land Title Survey and plat prepared by Terra Surveying
Company, Inc. Project Number 0163-9801-S).

Compiled by: Scott D. Mandeville                               [STAMP]
Compiled: October 22, 1998
TSC Project No: 0163-9801-S
SDM: 2-619ac.mb

<PAGE>   118
                        OWNER POLICY OF TITLE INSURANCE

                                   SCHEDULE B

G.F. No. 98011250

Policy No. 175-163778

                            EXCEPTIONS FROM COVERAGE

This policy does not insure against loss or damage (and the Company will not
pay costs, attorneys' fees or expenses) that arise by reason of the terms and
conditions of the leases or easements insured, if any, shown in Schedule A and
the following matters:

1.   The following restrictive covenants of record itemized below (the Company
     must either insert specific recording data or delete this exception):

     AS SET FORTH IN INSTRUMENT FILED FOR RECORD UNDER HARRIS COUNTY CLERK'S
     FILE NUMBER T415740, HARRIS COUNTY, TEXAS, BUT OMITTING ANY COVENANT OR
     RESTRICTION BASED ON RACE, COLOR, RELIGION, SEX, HANDICAP, FAMILIAL STATUS,
     OR NATIONAL ORIGIN.

2.   Shortages in area.

3.   Homestead or community property or survivorship rights, if any, of any
     spouse of any insured.

4.   Any titles or rights asserted by anyone, including, but not limited to,
     persons, the public, corporations, governments or other entities,

     a.   to tidelands, or land comprising the shores or beds of navigable or
          perennial rivers and streams, lakes, bays, gulfs or oceans, or

     b.   to lands beyond the line of the harbor or bulkhead lines as
          established or changed by any government, or

     c.   to filled-in lands, or artificial islands, or

     d.   to statutory water rights, including riparian rights, or

     e.   to the area extending from the line of mean low tide to the line of
          vegetation, or the right of access to that area or easement along and
          across that area.

5.   Standby fees, taxes and assessments by any taxing authority for the year
     1999 and subsequent years, and subsequent taxes and assessments by any
     taxing authority for prior years due to change in land usage and ownership.

6.   The following matters and all terms of the documents creating or offering
     evidence of the matters (We must insert matters or delete this exception.):

     a.   LEASEHOLD DEED OF TRUST DATED NOVEMBER 23, 1998, FILED FOR RECORD
          UNDER HARRIS COUNTY CLERK'S FILE NO. T418083, EXECUTED BY TMX REALTY
          CORPORATION, A DELAWARE CORPORATION TO JOHN E. PHILLIPS, TRUSTEE, AND
          ALL TERMS, CONDITIONS AND STIPULATIONS CONTAINED THEREIN, INCLUDING
          ANY ADDITIONAL INDEBTEDNESS SECURED THEREBY, SECURING THE PAYMENT OF
          ONE PROMISSORY NOTE OF EVEN DATE THEREWITH IN THE PRINCIPAL AMOUNT OF

                             See Continuation Page
<PAGE>   119
Continuation of Schedule B                                     G.F. No. 98011250

          $6,000,000.00, payable to Riverway Bank. Said Lien being additionally
          secured by Assignment of Leases (Space Lease) filed for record on
          December 3, 1998, under Harris County Clerk's File No. T418084.

     b.   Terms, conditions and stipulations of Lease dated August 25, 1993, as
          evidenced by Memorandum filed for record under Harris County Clerk's
          File No. R182160, as supplemented by Notice of Lease filed for record
          under Harris County Clerk's File No. S319699, between The United
          States Department of Veterans Affairs and Amelang Partners, Inc.
          Sublease created by Memorandum of Sublease and Assignment created by
          and between Amelang Partners, Inc., a Texas corporation and Introgen
          Therapeutics, Inc., a Delaware corporation and TMX Realty
          Corporation, a Delaware corporation dated November 24, 1998, filed
          for record under Harris County Clerk's File No. T418082.

     c.   Subordination, Attornment and Non-Disturbance Agreement by and among
          Amelang Partners Incorporated, a Texas corporation, Introgen
          Therapeutics, Inc., a Delaware corporation and Aid Association for
          Lutherans, a Wisconsin corporation recorded under Harris County
          Clerk's File No. T415741.

     d.   Storm sewer lines in various locations of subject property as shown
          on survey dated October 2, 1998, prepared by Ernest Roth, R.P.L.S.
          No. 2044.

     e.   Electric and telephone lines entering subject property as shown
          on survey dated October 2, 1998, prepared by Ernest Roth, R.P.L.S.
          No. 2044.

     f.   Any and all liens arising by reason of unpaid bills or claims for
          work performed or materials furnished in connection with improvements
          placed, or to be placed, upon the subject land. However, the Company
          does insure the insured against loss, if any, sustained by the
          Insured under this Policy if such liens have been filed with the
          County Clerk of Harris County, Texas, prior to the date hereof.

          Liability hereunder at the date hereof is limited to $6,000,000.00.
          Liability shall increase as contemplated improvements are made, so
          that any loss payable hereunder shall be limited to said sum plus the
          amount actually expended by the Insured in improvements, subsequent
          to the date of this policy, will be deemed made as of the date of the
          policy. In no event shall the liability of the Company hereunder
          exceed the face amount of this Policy. Nothing contained in this
          paragraph shall be construed as limiting any exception or any printed
          provision of this policy.

                                              Countersigned
                                              Partners Title Company

                                              By
                                                  ------------------------------
                                                  Authorized Countersignature
Page 2
<PAGE>   120
                                                               G.F. No. 98011250

                   COMMONWEALTH LAND TITLE INSURANCE COMPANY

Owner Policy Number: 175-163778

Issued with Policy Number: 535-370986

<TABLE>
<CAPTION>
-------------------------------------------------------------------------------------------------------

   Premium Amount     Rate Rules     Property        County         Liability at
                                       Type           Code          Reissue Rate
<S>                 <C>            <C>            <C>            <C>              <C>     <C>       <C>

1                   2              3              4              5                6       7         8
   $ 35,382.45                        C              201
-------------------------------------------------------------------------------------------------------
</TABLE>

<PAGE>   121
                          CONDITIONS AND STIPULATIONS
                                  (Continued)

7. DETERMINATION, EXTENT OF LIABILITY AND COINSURANCE.

This policy is a contract of indemnity against actual monetary loss or damage
sustained or incurred by the insured claimant who has suffered loss or damage
by reason of matters insured against by this policy and only to the extent
herein described.

         (a) The liability of the Company under this policy shall not exceed
the least of:

                 (i)  the Amount of Insurance stated in Schedule A;

                 (ii) The difference between the value of the insured estate or
interest as insured and the value of the insured estate or interest subject to
the detect, lien or encumbrance insured against by this policy at the date the
insured claimant is required to furnish to Company a proof of loss or damage in
accordance with Section 5 of these Conditions and Stipulations.

         (b) In the event the Amount of Insurance stated in Schedule A at the
Date of Policy is less than 80 percent of the value of the insured estate or
interest or the full consideration paid for the land, whichever is less, or if
subsequent to the Date of Policy an improvement is erected on the land which
increases the value of the insured estate or interest by at least 20 percent
over the Amount of Insurance stated in Schedule A, then this Policy is subject
to the following:

                 (i) where no subsequent improvement has been made, as to any
partial loss, the Company shall only pay the loss pro rata in the proportion
that the amount of insurance at Date of Policy bears to the total value of the
insured estate or interest at Date of Policy; or

                 (ii) where a subsequent improvement has been made, as to any
partial loss, the Company shall only pay the loss pro rata in the proportion
that 120 percent of the Amount of Insurance stated in Schedule A bears to the
sum of the Amount of Insurance stated in Schedule A and the amount expended for
the improvement.

                 The provisions of this paragraph shall not apply to costs,
attorneys' fees and expenses for which the Company is liable under this policy,
and shall only apply to that portion of any loss which exceeds, in the
aggregate, 10 percent of the Amount of Insurance stated in Schedule A.

         (c) The Company will pay only those costs, attorneys' fees and
expenses incurred in accordance with Section 4 of these Conditions and
Stipulations.

8. APPORTIONMENT.

If the land described in Schedule A consists of two or more parcels that are not
used as a single site, and a loss is established affecting one or more of the
parcels but not all, the loss shall be computed and settled on a pro rata basis
as if the amount of insurance under this policy was divided pro rata as to the
value on Date of Policy of each separate parcel to the whole, exclusive of any
improvements made subsequent to Date of Policy, unless a liability or value has
otherwise been agreed upon as to each parcel by the Company and the insured at
the time of the issuance of this policy and shown by an express statement or by
an endorsement attached to this policy.

9. LIMITATION OF LIABILITY.

         (a) If the Company establishes the title, or removes the alleged
defect, lien or encumbrance, or cures the lack of a right of access to or from
the land, all as insured, or takes action in accordance with Section 3 or
Section 6, in a reasonably diligent manner by any method, including litigation
and the completion of any appeals therefrom, it shall have fully performed its
obligations with respect to that matter and shall not be liable for any loss or
damage caused thereby.

         (b) In the event of any litigation, including litigation by the
Company or with the Company's consent, the Company shall have no liability for
loss or damage until there has been a final determination by a court of
competent jurisdiction, and disposition of all appeals therefrom, adverse to
the title as insured.

         (c) The Company shall not be liable for loss or damage to any insured
for liability voluntarily assumed by the insured in settling any claim or suit
without the prior written consent of the Company.

10. REDUCTION OF INSURANCE: REDUCTION OR TERMINATION OF LIABILITY.

All payments under this policy, except payments made for costs, attorneys' fees
and expenses, shall reduce the amount of the insurance pro tanto.

11. LIABILITY NONCUMULATIVE.

         It is expressly understood that the amount of insurance under this
policy shall be reduced by any amount the Company may pay under any policy
insuring a mortgage to which exception is taken in Schedule B or to which the
insured has agreed, assumed, or taken subject, or which is hereafter executed
by an insured and which is a charge or lien on the estate or interest described
or referred to in Schedule A, and the amount so paid shall be deemed a payment
under this policy to the insured owner.

12. PAYMENT OF LOSS.

         (a) No payment shall be made without producing this policy for
endorsement of the payment unless the policy has been lost or destroyed, in
which case proof of loss or destruction shall be furnished to the satisfaction
of the Company.

         (b) When liability and the extent of loss or damage has been
definitely fixed in accordance with these Conditions and Stipulations, the loss
or damage shall be payable within 30 days thereafter.

13. SUBROGATION UPON PAYMENT OR SETTLEMENT.

         (a) The Company's Right of Subrogation.

         Whenever the Company shall have settled and paid a claim under this
policy, all right of subrogation shall vest in the Company unaffected by any
act of the insured claimant.

         The Company shall be subrogated to and be entitled to all rights and
remedies that the insured claimant would have had against any person or
property in respect to the claim had this policy not been issued. If requested
by the Company, the insured claimant shall transfer to the Company all rights
and remedies against any person or property necessary in order to perfect this
right of subrogation. The insured claimant shall permit the Company to sue,
compromise or settle in the name of the insured claimant and to use the name of
the insured claimant in any transaction or litigation involving these rights or
remedies.

         If a payment on account of a claim does not fully cover the loss of
the insured claimant, the Company shall be subrogated to these rights and
remedies in the proportion which the Company's payment bears to the whole
amount of the loss.

         If loss should result from any act of the insured claimant, as stated
above, that act shall not void this policy, but the Company, in that event,
shall be required to pay only that part of any losses insured against by this
policy that shall exceed the amount, if any, lost to the Company by reason of
the impairment by the insured claimant of the Company's right of subrogation.

         (b) The Company's Rights Against Non-insured Obligors.

         The Company's right of subrogation against non-insured obligors shall
exist and shall include, without limitation, the rights of the insured to
indemnities, guaranties, other policies of insurance or bonds, notwithstanding
any terms or conditions contained in those instruments that provide for
subrogation rights by reason of this policy.

14. ARBITRATION.

         "Unless prohibited by applicable law or unless this arbitration
section is deleted by specific provision in Schedule B of this policy, either
the Company of the Insured may demand arbitration pursuant to the Title
Insurance Arbitration Rules or the American Arbitration Association. Arbitrable
matters include, but are not limited to, any controversy or claim between the
Company and the Insured arising out of or relating to this Policy, and service
of the Company in connection with its issuance or the breach of a policy
provision or other obligation. All arbitrable matters when the Amount of
Insurance is $1,000,000 or less SHALL BE arbitrated at the request of either
the Company or the Insured, unless the insured is an individual person (as
distinguished from a corporation, trust, partnership, association or other
legal entity). All arbitrable matters when the Amount of Insurance is in excess
of $1,000,000 shall be arbitrated only when agreed to by both the Company and
the Insured. Arbitration pursuant to this Policy and under the Rules in effect
on the date the demand for arbitration is made or, at the option of the
Insured, the Rules in effect at the Date of Policy shall be binding upon the
parties. The award may include attorneys' fees only if the laws of the state in
which the land is located permit a court to award attorneys' fees to a
prevailing party. Judgment upon the award rendered by the Arbitrator(s) may be
entered in any court having jurisdiction thereof.

         The Law of the situs of the land shall apply to any arbitration under
the Title Insurance Arbitration Rules.

         A Copy of the Rules may be obtained from the Company upon request."

15. LIABILITY LIMITED TO THIS POLICY: POLICY ENTIRE CONTRACT.

         (a) This policy together with all endorsements, if any, attached hereto
by the Company is the entire policy and contract between the insured and the
Company. In interpreting any provision of this policy, this policy shall be
construed as a whole.

         (b) Any claim of loss or damage, whether or not based on negligence,
and which arises out of the status of the title to the estate or interest
covered hereby or by any action asserting such claim, shall be restricted to
this policy.

         (c) No amendment of or endorsement to this policy can be made except
by a writing endorsed hereon or attached hereto signed by either the President,
a Vice President, the Secretary, an Assistant Secretary, or validating officer
or authorized signatory of the Company.

16. SEVERABILITY.

In the event any provision of the policy is held invalid or unenforceable
under applicable law, the policy shall be deemed not to include that provision,
and all other provisions shall remain in full force and effect.

17. NOTICES, WHERE SENT.

All notices required to be given the Company and any statement in writing
required to be furnished the Company shall include the number of this policy and
shall be addressed to COMMONWEALTH LAND TITLE INSURANCE COMPANY, 1700 MARKET
STREET, PHILADELPHIA, PENNSYLVANIA 19103-3990.

COMPLAINT NOTICE.

         SHOULD ANY DISPUTE ARISE ABOUT YOUR PREMIUM OR ABOUT A CLAIM THAT YOU
HAVE FILED, CONTACT THE AGENT OR WRITE TO THE COMPANY THAT ISSUED THE POLICY.
IF THE PROBLEM IS NOT RESOLVED, YOU ALSO MAY WRITE THE TEXAS DEPARTMENT OF
INSURANCE, P.O. BOX 149091, AUSTIN, TX 78714-9091, FAX NO. (512) 475-1771.
THIS NOTICE OF COMPLAINT PROCEDURE IS FOR INFORMATION ONLY AND DOES NOT BECOME
A PART OR CONDITION OF THIS POLICY.

                              FOR INFORMATION, OR
                           TO MAKE A COMPLAINT, CALL:
                                 1-800-925-0965

                              PARA INFORMATION, O
                          PARA HACER UNA QUEJA, HABLE
                                 1-800-925-0965

Texas Owner Policy T-1 (Rev. 10-1-97)
<PAGE>   122
                                PROMISSORY NOTE

$6,000,000.00                   Houston, Texas                 November 23,1998

FOR VALUE RECEIVED, TMX REALTY CORPORATION, a Delaware corporation ("Maker"),
promises to pay to the order of RIVERWAY BANK ("Payee"), at its banking house
in the City of Houston, Harris County, Texas, in lawful money of the United
States of America, the sum of SIX MILLION AND NO/100 DOLLARS ($6,000,000.00),
together with interest on the unpaid principal balance hereof from time to time
outstanding until maturity at the following rates:

1.   Commencing as of the date hereof and continuing until the first anniversary
     date hereof, this note shall accrue interest at the rate of 8.50% per
     annum.

2.   Commencing as of the first anniversary date hereof and continuing until the
     sixth anniversary date hereof, this note shall accrue interest at the rate
     of 7.50% per annum.

3.   Commencing as of the sixth anniversary date hereof and continuing
     throughout the remaining term hereof, this note shall accrue interest at a
     rate equal to the lesser of (i) the rate of the 5 Year Treasury Bond Note
     as published in the Wall Street Journal, fixed as of the close of business
     on the sixth anniversary date hereof, plus 2.0% per annum, or (ii) 8.50%
     per annum.

The rate from time to time in effect is herein referred to as the "Stated
Rate"; provided, however, in no event shall interest on this note ever be
charged or paid at a rate greater than the maximum non-usurious rate permitted
by applicable federal or Texas law from time to time in effect, whichever
shall permit the higher lawful rate (the "Highest Lawful Rate").

     If at any time or times the Stated Rate would exceed the Highest Lawful
Rate but for the limitation set forth above, the rate of interest to accrue on
the unpaid principal balance of this note during all such times shall be
limited to the Highest Lawful Rate, but any subsequent reduction in the Stated
Rate shall not become effective to reduce the interest rate payable below the
Highest Lawful Rate until the total amount of interest accrued on the unpaid
balance of this note equals the total amount of interest which would have
accrued if the Stated Rate had at all times been in effect.

     If, at maturity or final payment of this note, the total amount of
interest paid or accrued under the foregoing provisions is less than the total
amount of interest which would have accrued if the Stated Rate had at all times
been in effect, then Maker agrees to pay to Payee, to the extent allowed by
law, an amount equal to the difference between (a) the lesser of (i) the amount
of interest which would have accrued on this note if the Highest Lawful Rate
had at all times been in effect, or (ii) the amount of interest which would
have accrued if the Stated Rate had at all times been in effect, and (b) the
amount of interest accrued in accordance with the other provisions of this note.

     Interest shall be computed on the basis of the actual number of days
elapsed in a year composed of 360 days; however, if such computation would cause
the Stated Rate to exceed the Highest Lawful Rate, interest shall be computed on
the basis of a year composed of 365 or 366 days, as the case may be. At all such
times, if any, as Texas law shall establish the Highest Lawful Rate, the Highest
Lawful Rate shall be the "indicated rate ceiling" (as defined in V.T.C.A.,
Finance Code, Chapter 303, as amended) from time to time in effect; provided
that Payee may also rely on alternative maximum rates of interest from time to
time in effect under other applicable laws, if they are higher.

     This note is payable as follows:

     Accrued interest shall be due and payable monthly, on the first day of
each and every calendar month, commencing January 1, 1999, and continuing
regularly and monthly thereafter through and including the first
<PAGE>   123
anniversary date hereof. Thereafter, principal and interest shall be due and
payable in equal monthly installments (the "Monthly Payments"), due and payable
on the 1st day of each and every calendar month, commencing January 1, 2000, and
continuing regularly and monthly thereafter until Maturity (as hereinafter
defined). The amount of the Monthly Payments shall be based on an equal
amortization of the principal amount hereof over a three hundred (300) month
period at the Stated Rate in effect from time to time. The amount of the Monthly
Payments shall be recalculated according to the above referenced amortization
schedule at any time that there is a rate adjustment on this note. The entire
balance of this note, principal together with unpaid accrued interest, shall be
due and payable in full eleven (11) years from the date hereof (the "Maturity").
In all cases, interest shall be calculated on the unpaid principal to the date
of each installment paid and the payment made credited first to the discharge of
the interest accrued and the balance to the reduction of the principal.

        This note may be prepaid in whole or in part at any time without
penalty; provided, however, that all payments received by Payee from Maker upon
this note shall first be applied to the payment of accrued but unpaid interest,
with the balance thereof to be applied to the reduction of the outstanding
principal of this note. All prepayments in excess of accrued interest shall be
applied to the outstanding principal balance of this note in the inverse order
of maturity.

        Whenever any payment to be made under this note shall be stated to be
due on a Saturday, Sunday or legal holiday for commercial banks under the laws
of the State of Texas, then such payment shall be made on the next succeeding
business day.

        In addition to all principal and accrued interest on this note, Maker
agrees to pay (a) all reasonable costs and expenses incurred by all owners and
holders of this note in collecting this note through probate, reorganization,
bankruptcy or any other proceeding, (b) the reasonable attorneys' fees when and
if this note is placed in the hands of an attorney for collection after
default, and (c) the reasonable attorneys' fees, costs and expenses incurred by
Payee in connection with the preparation and filing of the agreements and
documents contemplated herein.

         Except for the notice of defaults and opportunity to cure them as
provided in the Construction Loan Agreement of even date herewith and unless
otherwise provided by law, Maker and any and all co-makers, endorsers,
guarantors and sureties severally waive notice (including, but not limited to,
notice of protest, notice of dishonor and notice of intent to accelerate and
notice of acceleration), demand, presentment for payment, protest and the filing
of suit for the purpose of fixing liability and consent that the time of payment
hereof may be extended and re-extended from time to time without notice to them
or any of them, and each agrees that his, her or its liability on or with
respect to this note shall not be affected by any release of or change in any
security at any time existing or by any failure to perfect or to maintain
perfection of any lien on or security interest in any such security.

        Maker warrants and represents to Payee, and to all other owners and
holders of any indebtedness evidenced hereby, that the loan evidenced by this
Note is and shall be solely for business, commercial or agricultural purposes
and not primarily for personal, family or household use. Maker acknowledges that
the loan evidenced by this Note is specifically exempted under Section 226.3(a)
of Regulation Z issued by the Board of Governors of the Federal Reserve System
and under the Truth-in-Lending Act and that no disclosures are required to be
given under such regulations and federal laws in connection with this Note.

        It is agreed that time is of the essence of this agreement, and that in
the event of default in the payment of any installment of principal or interest
when due the holder hereof may declare the unpaid principal balance plus all
accrued but unpaid interest due thereon immediately due and payable without
notice (except as provided in the Loan Agreement), and failure to exercise said
option shall not constitute a waiver on the part of the holder of the right to
exercise the same at any other time.

        In the event of (i) the failure of Maker to make any payment herein
provided when due (either of principal and/or interest), or (ii) in the event
the entirety of the unpaid principal balance plus accrued unpaid interest
thereon is declared due, interest on such past-due indebtedness (either
principal and/or interest) shall accrue at the Highest Lawful Rate.

                                       2
<PAGE>   124
     All agreements between the Maker and the Payee, whether now existing or
hereafter arising and whether written or oral, are hereby expressly limited so
that in no event, whether by reason of acceleration of maturity hereof or
otherwise, shall the amount paid or agreed to be paid to the Payee for the use,
forbearance, or detention of the money to be loaned hereunder or otherwise
exceed the Highest Lawful Rate. If fulfillment of any provision hereof or of any
mortgage, loan agreement, or other document evidencing or securing the
indebtedness evidenced hereby, at the time performance of such provision shall
be due, shall involve transcending the limit of validity prescribed by law,
then, ipso facto, the obligation to be fulfilled shall be reduced to the limit
of such validity; and if the Payee shall ever receive anything of value deemed
interest under applicable law which would exceed interest at the Highest Lawful
Rate, an amount equal to any excessive interest shall be applied to the
reduction of the principal amount owing hereunder and not to the payment of
interest, or if such excessive interest exceeds the unpaid balance of principal
hereof, such excess shall be refunded to the Maker. All sums paid or agreed to
be paid to the Payee for the use, forbearance, or detention of the indebtedness
of the Maker to the Payee shall, to the extent permitted by applicable law, be
amortized, prorated, allocated, and spread throughout the full term of such
indebtedness until payment in full so that the rate of interest on account of
such indebtedness is uniform throughout the term thereof. The provisions of this
paragraph shall control all agreements between the Maker and the Payee.

     Payment of this note is secured by a Leasehold Deed of Trust of even date
herewith from Maker to John E. Phillips, Trustee for the benefit of Payee
covering certain property located in Harris County, Texas, as more particularly
described therein (the "Property").

     Contemporaneously with the execution of this note, Maker has delivered to
Payee an Assignment of Leases of even date herewith executed by Maker in favor
of Payee covering the Property and Maker and Payee acknowledge that the
Assignment of Leases is an absolute assignment and not security for the payment
of this note.

     Maker shall pay to Payee on or before the closing hereof a commitment fee
in the amount of $120,000 and it is agreed that said fee shall be paid in
consideration for the Payee's taking appropriate action to insure that all of
the funds that it is required to advance pursuant hereto are available to the
Maker when it requests the same, subject to the terms and conditions hereof.

     This note is the promissory note referred to in, is subject to and is
entitled to the benefits of, the Construction Loan Agreement (the "Loan
Agreement") of even date herewith between Maker and Payee, as that Loan
Agreement may be amended, modified or supplemented from time to time. The Loan
Agreement contains, among other things, provisions for notice of default and
opportunity to cure same and the acceleration of the maturity hereof upon the
occurrence of certain stated events.

     The principal of this note represents funds which Payee will advance to
Maker from time to time, upon the request of Maker, in a series of increments
which will aggregate, in total, the principal sum of this note; each such
increment so advanced shall constitute a part of the principal hereof and shall
bear interest from the respective date of the advance thereof.

     This note has been executed and delivered in and shall be construed in
accordance with and governed by the laws of the State of Texas and of the United
States of America, except that Tex. Rev. Civ. Stat. Ann. Art. 5069, Ch. 15, as
amended (which regulates certain revolving credit loan accounts and revolving
tri-party accounts), shall not apply hereto.

     For purposes of any suit relating to this note, Maker hereof submits itself
to the jurisdiction of any court sitting in the State of Texas and further
agrees that venue in any suit arising out of this note or any venue shall be
fixed in Harris County, Texas. Final judgment in any suit shall be conclusive
and may be enforced in any jurisdiction within or without the United States of
America, by suit on the judgment, a certified or exemplified copy of which
shall be conclusive evidence of such liability.

                                       3
<PAGE>   125
                                  TMX REALTY CORPORATION, a Delaware corporation

                                  By: /s/ JAMES W. ALBRECHT, JR.
                                     ------------------------------------------
                                  Name:  JAMES W. ALBRECHT, JR.
                                       ----------------------------------------
                                  Title: CHIEF FINANCIAL OFFICER
                                        ---------------------------------------

                                       4

<PAGE>   126
                             PURCHASER'S STATEMENT

Date: December 2, 1998                                         GF No.: 98011250

Sale From: Amelang Partners, Inc.   To: TMX Realty, Inc., a Delaware corporation
           925 Echo Lane, Suite 100     301 Congress Avenue, Suite 1850
           Houston, TX 77024            Austin, TX 78701

Property: 2.619 Acres, D. W. C. Harris Survey, Abstract No. 325

<TABLE>

<S>                                                              <C>            <C>            <C>
Purchase Price.................................................................................$      1.00

Plus: Charges
Loan Charges to Riverway Bank...................................................$107,500.00
     Commitment Fee (Prepaid $12,500.00) balance outstanding.....$107,500.00
Fees to Partners Title Company..................................................$ 35,688.64
     Leasehold Owner Policy $10,152,910.00.......................$ 28,010.87
     Mortgage Policy $6,000,000.00...............................$    125.00
     Area & Boundary Deletion....................................$  7,371.58
     1/2 Escrow Fee..............................................$    100.00
     1/2 Tax Certificates........................................$     81.19
Fees to Partners Title Company..................................................$    200.00
     1/2 Messenger/Delivery Fees.................................$     50.00
     Recording Fees..............................................$    150.00
Adjustment - Security Deposit...................................................$ 20,000.00
Adjustment - Legal Fees.........................................................$ 10,000.00
Legal Fees to Porter & Hedges LLP...............................................$ 22,834.71
Brokerage Fees to States & Little Mortgage Company..............................$ 60,000.00

          Total Charges........................................................................$256,223.35
               Gross Amount Due By Purchaser...................................................$256,224.35

Less: Credits

          Total Credits........................................................................$      0.00
               Balance Due By Purchaser........................................................$256,224.35
                                                                                               ===========
</TABLE>

Purchaser Understands the Closing or Escrow Agent has assembled this
information representing the transaction from the best information available
from other sources and cannot guarantee the accuracy thereof. Any real estate
agent or lender involved may be furnished a copy of this statement.

Purchaser understands that tax and insurance prorations and reserves were based
on figures for the preceding year or supplied by others or estimates for
current year, and in the event of any change for current year, all necessary
adjustments must be made between Purchaser and Seller direct.

The undersigned hereby authorizes Partners Title Company to make expenditure
and disbursements as shown above and approves same for payment. The undersigned
also acknowledges receipt of Loan Funds, if applicable, in the amount shown
above and a receipt of a copy of this statement.

Partners Title Company             TMX Realty, Inc., a Delaware corporation

By /s/ GLORIA DORECK               By /s/ JAMES W. ALBRECHT
   -----------------                  ------------------------
   Gloria Doreck

12/02/98 (4:15 PM)       Compliments of PARTNERS TITLE COMPANY

                           THIS IS TO CERTIFY THAT THIS IS A TRUE AND CORRECT
                           [illegible]

                              [STAMP] PARTNERS TITLE COMPANY
                           BY /s/ [illegible]
                              -----------
<PAGE>   127
                               SELLER'S STATEMENT

<TABLE>

DATE: December 2, 1998                                          GF NO.: 98011250
<S>                                                   <C>                                  <C>
SALE FROM:  Amelang Partners, Inc.                    TO: TMX Realty, Inc., a Delaware corporation
            925 Echo Lake, Suite 100                      301 Congress Avenue, Suite 1850
            Houston, TX 77024                             Austin, TX 78701

PROPERTY: 2.619 Acres, D.W.C. Harris Survey, Abstract No. 325

Sales Price.................................................................................. $      1.00
REIMBURSEMENTS/CREDITS
Adjustment - Security Deposit.........................................  $ 20,000.00
Adjustment - Legal Fees...............................................  $ 10,000.00

                          TOTAL REIMBURSEMENTS/CREDITS....................................... $ 30,000.00
                                   GROSS AMOUNT DUE TO SELLER................................ $ 30,000.00

LESS: CHARGES AND DEDUCTIONS
Fees to Partners Title Company....................................................... $ 21,314.19
  Leasehold Owner Policy $10,152,910.00...............................  $ 21,133.00
  1/2 Escrow Fee......................................................  $    100.00
  1/2 Tax Certificates................................................  $     81.19
Fees to Partners Title Company....................................................... $     75.00
  1/2 Messenger/Delivery Fees.........................................  $     50.00
  Recording Fees......................................................  $     25.00

                          TOTAL CHARGES AND DEDUCTIONS....................................... $ 21,389.19
                                   NET AMOUNT DUE TO SELLER.................................. $  8,611.81
                                                                                              ===========
</TABLE>

Seller Understands the Closing or Escrow Agent has assembled this information
representing the transaction from the best information available from other
sources and cannot guarantee the accuracy thereof. Any real estate agent or
lender involved may be furnished a copy of this statement.

Seller understands that tax and insurance prorations and reserves were based on
figures for the preceding year or supplied by others or estimates for current
year, and in the event of any change for current year, all necessary adjustments
must be made between Purchaser and Seller direct.

The undersigned hereby authorizes Partners Title Company to make expenditure and
disbursements as shown above and approves same for payment. The undersigned also
acknowledges receipt of Loan Funds, if applicable, in the amount shown above
and a receipt of a copy of this Statement.

Partners Title Company                       Amelang Partners, Inc.

By /s/ GLORIA DORECK                         By /s/ ROCKY STEVENS
  ---------------------------                   --------------------------------
  Gloria Doreck                                 Rocky Stevens

                     Compliments of PARTNERS TITLE COMPANY

                                             THIS IS TO CERTIFY THAT THIS IS A
                                             TRUE AND CORRECT

                                             [illegible]

                                             BY /s/ [illegible]
                                                --------------------------------

<PAGE>   128
                  [STEWART TITLE HOUSTON DIVISION LETTERHEAD]

December 3, 1998

Ms. Gloria Doreck
Partners Title Company
Via fax 238-9166

Re: Amelang Partners

Dear Gloria:

Per our telephone conversation, we have recorded the following documents as
indicated:

1)  Note, Deed of Trust and Guaranty Modification Agreement having been filed
    with the Harris County Clerk's Office on December 3, 1998 under Clerk's File
    No. T-415740; and

2)  Subordination, Attornment and Non-Disturbance Agreement having been filed
    with the Harris County Clerk's Office on December 3, 1998 under Clerk's File
    No. T-415741, and

3)  UCC-3 having been filed with the Harris County Clerk's Office on December 3,
    1998 under Clerk's File No. T-415742.

Please do not hesitate to call me should you have any questions or if anything
further is needed at this time.

Thank you.

/s/ BETH FORREST
Beth Forrest
Commercial Escrow Officer

Bf
encls

<PAGE>   129
                           SUBORDINATION, ATTORNMENT
                         AND NON-DISTURBANCE AGREEMENT

     THIS AGREEMENT is made as of November 23, 1998, by and among AMELANG
PARTNERS INCORPORATED, a Texas corporation ("Borrower"), whose address is 952
Echo Lane, Suite 100, Houston, Texas 77024; and INTROGEN THERAPEUTICS, INC., a
Delaware corporation, ("Subtenant"), whose address is 301 Congress, Suite 1850,
Austin, Texas 78701 (Attn: James W. Albrecht, Chief Financial Officer); and AID
ASSOCIATION FOR LUTHERANS, a Wisconsin corporation (the "Beneficiary"), whose
address is 4321 North Ballard Road, Appleton, Wisconsin 54919.

     A. THE PROPERTY. The term "Property", as used herein, shall mean the real
property situated in the County of Harris, State of Texas, legally described in
EXHIBIT "A" attached hereto and by this reference made a part hereof, together
with all buildings, structures, improvements and fixtures now or hereafter
located thereon, and together with all easements and other rights appurtenant
thereto.

     B. THE LOAN; SECURITY DOCUMENTS; DEED OF TRUST. Borrower has previously
borrowed certain sums from Beneficiary as evidenced by a promissory note dated
February 6, 1997, in the amount of $2,500,000.00 (the "Note"). The Note is
secured, in part, by Borrower's leasehold estate under that certain
Enhanced-Use Lease No. 084B-029-92 dated August 25, 1993, between the United
States Department of Veterans Affairs, as landlord (the "Government"), and
Borrower, as tenant, and all subsequent amendments, addendum and supplements
thereto (collectively being referred to as the "Prime Lease"). The Prime Lease
covers certain land more particularly described therein, including the land
described in that certain Notice of Lease filed under Clerk's File No. S319699,
and recorded under Film Code Reference No. 511-82-2828 in the Official Public
Records of Real Property of Harris County, Texas. The land covered by the Prime
Lease includes the Property. Borrower has heretofore encumbered its interest
in the Prime Lease as security for payment of the Note and its obligations to
Beneficiary and, for such purpose, has entered into various instruments and
documents (collectively, as amended, the "Security Documents"), including,
without limitation, that certain Deed of Trust and Security Agreement of even
date with the Note (as amended, the "Deed of Trust") from Borrower to Barry E.
Putterman, Trustee, filed under Clerk's File No. S319696, and recorded under
Film Code Reference No. 511-82-2756 in the Official Public Records of Real
Property of Harris County, Texas, and an Assignment of Rents and Leases of even
date with the Note (as amended, the "Assignment"). The Deed of Trust and the
Assignment have been amended by that certain Note, Deed of Trust and Guaranty
Modification Agreement dated September 24, 1998.

     C. THE SUBLEASE. Pursuant to the terms and provisions of that certain
Amended and Restated Ground Sublease Agreement dated effective September 24,
1998, between Borrower and Subtenant (the "Sublease"), for a term of
twenty-eight (28) years plus certain options as therein set forth, a portion of
the Property (the "Subleased Premises") has been subleased to Subtenant, which
Sublease is subordinate to the terms and provisions of the Security Documents.

     D. PURPOSES. In connection with the above-mentioned transactions, Borrower
and Subtenant have agreed to offer certain assurances and representations to
the Beneficiary, and all parties agree to provide for (i) confirmation of the
subordination of the Sublease to the Security Documents; (ii) the
<PAGE>   130
continuation of the Sublease notwithstanding any foreclosure of the Deed of
Trust subject only to certain conditions set forth in this Agreement; (iii) the
acknowledgment that Beneficiary reserves the right to foreclose on Borrower's
interest in the Prime Lease as it affects land other than the Subleased
Premises and not to foreclose on its lien and security interest on Borrower's
interest in the Prime Lease as it affects the Subleased Premises; and (iv)
Subtenant's attornment to the Beneficiary or to such other parties as may
succeed to the interest of Borrower in the Prime Lease as the result of any
foreclosure, any conveyance of the Prime Lease in lieu of foreclosure, or
otherwise.

                                   AGREEMENT

     NOW, THEREFORE, in consideration of the mutual terms and provisions
hereinafter contained and other good and valuable consideration received by
each party from the other, the receipt and sufficiency of which are hereby
acknowledged, the parties agree as follows:

     1.   NOTICES OF DEFAULT TO BENEFICIARY. Notwithstanding anything to the
contrary in the Sublease, Subtenant shall deliver to Beneficiary by an
independent, nationally recognized courier service or mail to Beneficiary (by
certified mail, return receipt requested, adequate postage prepaid), at
Beneficiary's address set forth above, written notice of any default under the
Sublease by Borrower, and if within the time provided in the Sublease for
curing thereof by Borrower, if any, Beneficiary performs or causes to be
performed all such obligations with respect to which Borrower is in default
which can be cured by the payment of money, any right of Subtenant to terminate
the Sublease by reason of such default shall cease and be null and void;
provided, however, Beneficiary shall not be obligated to cure any such default
by Borrower under the Sublease. Any notice sent to Beneficiary shall be deemed
given upon the earlier to occur of actual receipt or seven (7) days after
deposit in the U.S. Mail as provided above.

     2.   SUBORDINATION OF SUBLEASE TO SECURITY DOCUMENTS. Subtenant hereby
confirms that its leasehold estate in the Subleased Premises and all of
Subtenant's right under the Sublease are subordinate to the Security Documents
(insofar as the Security Documents encumber Borrower's interest in the Prime
Lease) and to all extensions, renewals, modifications, consolidations and
replacements thereof, to the full extent of all obligations secured or to be
secured thereby including interest thereon and any future advances thereunder.

     3.   NON-DISTURBANCE OF SUBTENANT. Neither the Sublease nor Subtenant's
rights pursuant thereto (nor the rights, liens or security interests of any
mortgagee of Subtenant) shall be disturbed or affected by any foreclosure of
the lien created by the Deed of Trust or conveyance in lieu of foreclosure, or
by any other act or election by Beneficiary pursuant to the Security Documents.
Beneficiary's obligations under this Paragraph 3 shall be null and void if
Subtenant is at the time of any such foreclosure or conveyance in lieu thereof
then in default in the timely performance of the Subtenant's obligations under
the Sublease or this Agreement and does not cure such default within the time,
if any, allowed in the Sublease. Subtenant acknowledges and agrees that
Beneficiary shall have the right and option in the event of a default by
Borrower under the Security Documents not to perform all or any obligations of
Borrower under the Sublease or the Prime Lease with the possible effect that
Subtenant would have to make arrangements with the Government to preserve and
protect Subtenant's rights and interests under the Sublease.

     4.   BENEFICIARY AS LESSOR AFTER FORECLOSURE. In the event that
Beneficiary (or any other party) shall succeed to Borrower's interest in the
Sublease, whether through foreclosure of the liens created by the Deed of
Trust, conveyance in lieu of foreclosure, or otherwise, Beneficiary (or such
other party) shall thereupon, and without the necessity of attornment or other
act or agreement, be substituted as Subtenant's

                                      -2-
<PAGE>   131
landlord under the Sublease, and shall be entitled to the rights and benefits
and subject to the obligations thereof; provided that neither Beneficiary nor
any other party shall be:

               (a) liable for any act or omission of any prior landlord under
     the Sublease (including Borrower) and all liability of Beneficiary (or such
     other party) for damages for breach of any covenant, duty or obligation of
     landlord under the Sublease shall be satisfied only out of the interest of
     Beneficiary (or such other party) in the Subleased Premises; or

               (b) subject to any offsets or defenses which Subtenant might have
     against any prior landlord (including Borrower); however, if Borrower and
     Beneficiary have been given notice by Subtenant of Borrower's default under
     the Sublease prior to foreclosure or conveyance in lieu thereof, any such
     default has not been cured, Subtenant may offset the reasonable actual
     out-of-pocket costs paid by Subtenant to cure such default from the portion
     of any net "Annual Basic Rent" (defined in the Sublease) payments later
     becoming due under the Sublease, which portion would otherwise be retained
     by the landlord under the Sublease (i.e., the portion remaining after such
     landlord pays rent under the Prime Lease attributable thereto); or

               (c) bound by Subtenant's payment of any rent or additional rent
     that Subtenant may have paid to any prior landlord under the Sublease
     (including Borrower) for a period in excess of one month in advance; or

               (d) bound by any amendment, modification, extension, supplement,
     or assignment of the Sublease made without Beneficiary's prior written
     consent; or

               (e) bound by any agreement for abatement of rent or bound by any
     agreement for "free rent" unless the same is specifically provided in the
     Sublease or agreed to in writing by Beneficiary; or

               (f) liable to Subtenant or any other party for any conflict
     between the provisions of the Sublease and the provisions of the Prime
     Lease, including, but not limited to, any provisions relating to renewal
     options and options to expand, or any breach of the Sublease due to
     violations of any restrictions on the use of the Sublease Premises or other
     property contained in the Sublease, and in the event of such conflict or
     violations, Subtenant shall have no right to take remedial action against
     Beneficiary or against any other party succeeding to Borrower. Nothing in
     this subparagraph (f) shall preclude Subtenant from asserting any right
     under the Sublease that it may have against Borrower; or

               (g) liable with respect to any warranties or representations of
     any nature whatsoever, either express or implied, made to Subtenant by
     Borrower, any agent or employee of Borrower or any other party, whether
     pursuant to the Sublease or otherwise, including, without limitation, any
     warranties or representations respecting use, compliance with zoning,
     Borrower's title, Borrower's authority, habitability, environmental
     matters, fitness for purpose or possession; or

               (h) liable for any tenant improvements or construction
     requirements (including, without limitation, any allowances for tenant
     improvements or construction) of any prior landlord under the Sublease
     (including Borrower);

                                      -3-
<PAGE>   132
and Subtenant hereby agrees to attorn to and recognize such Beneficiary (or
such other party) as lessor under the Sublease.

     5.   SPECIAL REMEDIES OF BENEFICIARY. In the event of a default under the
Note or the Security Documents, Beneficiary shall have the right and option
to foreclose on Borrower's interest in the Prime Lease as it affects property
other than the Subleased Premises without foreclosing on Borrower's interest in
the Prime Lease as it affects the Subleased Premises (a "Partial Foreclosure").
Following such a Partial Foreclosure (which may include a foreclosure of other
property and property rights of Borrower), Beneficiary (or its successors and
assigns) may enter into a "Replacement Lease" (as such term is defined in the
Prime Lease) with the Government covering property other than the Subleased
Premises. Subtenant acknowledges and agrees that in the event of a Partial
Foreclosure neither Beneficiary nor its successors or assigns shall have any
obligation or liability whatsoever to Subtenant (or its successors and assigns)
under the Sublease, this Agreement or otherwise. Any Partial Foreclosure that
fails to include the Borrower's interest in the Prime Lease as it affects the
Subleased Premises shall not affect the Sublease which shall continue subject
to Beneficiary's interest therein pursuant to the Security Documents and
Subtenant's rights in the Sublease shall not be disturbed thereby.

     6.   SPECIAL RIGHTS OF SUBTENANT. Borrower and Beneficiary agree that in
the event of a dispute as to whether Beneficiary, Borrower, or the Government,
or their successors or assigns, is entitled to receive rent or any other
payment which may become due under the Sublease, Subtenant shall have the right
to pay one-half of the Annual Basic Rent directly to the Government, in which
event such payment shall be credited as being properly paid under the terms of
the Sublease at the time it is paid to the Government, provided it interpleads
the remaining portion of the Annual Basic Rent into the registry of any
District Court in Harris County, Texas, in which event such amount shall be
deemed properly paid under the terms of the Sublease at the time it is tendered
to the Clerk of the Court.

     7.   BINDING EFFECT. The provisions of this Agreement shall be covenants
running with the Subleased Premises, and shall be binding upon and shall inure
to the benefit of the parties hereto and their respective heirs,
representatives, successors and assigns, including, without limitation, any
mortgage whose loan replaces the loan evidenced by the Note. The term
"Beneficiary" shall include, without limitation, any party that acquires an
interest in the Prime Lease (as it relates to the Subleased Premises) pursuant
to the Security Documents, and any subsequent owner and holder of the Note. The
term "Subtenant" shall include, without limitation, TMX Realty Corporation, a
Delaware corporation, as assignee of Subtenant's rights in the Sublease
pursuant to Assignment and Assumption Agreement dated November 23, 1998, and
any mortgagee that succeeds to the rights of Subtenant pursuant to foreclosure
of Subtenant's interest in the Sublease. Notwithstanding this Agreement or any
other matter (including, without limitation, Beneficiary's succession to the
interest of Borrower under the Prime Lease or Beneficiary's abandonment of all
or any portion of its rights under the Security Documents), Subtenant's sole
recourse against Beneficiary (or its successors and assigns) shall be a
judgment against Beneficiary's interest, if any, in the Sublease and the
Subleased Premises; and Subtenant shall have no other rights or remedies
against Beneficiary (or its successors and assigns).

     8.   MISCELLANEOUS. Borrower, as landlord under the Sublease and grantor
or trustor under the Deed of Trust, acknowledges and agrees for itself and its
successors and assigns that this Agreement does not constitute a waiver by
Beneficiary of any of its rights under the Deed of Trust or any other Security
Documents, or in any way release Borrower from its obligations to comply with
the terms, provisions, conditions, covenants, agreements, or clauses of the
Deed of Trust or any other such Security Document or confer any rights or
benefits upon Borrower. Borrower and Subtenant agree that, in the event of any
conflict between the Sublease and this Agreement, the terms and provisions of
this Agreement shall govern and control. Nothing contained in this Agreement
shall be construed to derogate from or in any way impair or affect the lien or
provisions of the Deed

                                      -4-
<PAGE>   133

of Trust, except as specifically provided in Paragraph 4 above. This Agreement
is subject and subordinate to the Prime Lease.

     9. MULTIPLE COUNTERPARTS. This Agreement may be executed in multiple
counterparts where the signature and acknowledgment of one or more parties may
not be on the same page as the other parties. By signing below, each party
authorizes the attorney for Beneficiary or the Title Company recording this
Agreement to affix counterpart signature and acknowledgment pages of one or
more parties into one or more versions of this Agreement so that at least one
counterpart will contain the original signature and acknowledgment pages of
each party hereto (with the same effect as if all signatures and
acknowledgments were made to such counterpart).

BORROWER:                               SUBTENANT:

AMELANG PARTNERS INCORPORATED           INTROGEN THERAPEUTICS, INC.

By: /s/ WELLINGTON STEVENS III          By: /s/ JAMES W. ALBRECHT, JR.
   -------------------------------         -------------------------------
Name: Wellington Stevens III            Name: James W. Albrecht, Jr.
     -----------------------------           -----------------------------
Title: President                        Title: Chief Financial Officer
      ----------------------------            ----------------------------

BENEFICIARY:

AID ASSOCIATION FOR LUTHERANS

By: /s/ DAVID CRIST
   -------------------------------
Name: David Crist
     -----------------------------
Title: Assistant Secretary
      ----------------------------

By: /s/ WAYNE C. STRECK
   -------------------------------
Name: Wayne C. Streck
     -----------------------------
Title: Vice-President Mortgage &
       Real Estate
      ----------------------------

                                      -5-
<PAGE>   134
THE STATE OF TEXAS       )
                         )
COUNTY OF HARRIS         )

          This instrument was acknowledged before me on this 23rd day of
November, 1998, by Wellington Stevens III, the President of AMELANG PARTNERS
INCORPORATED, a Texas corporation, on behalf of said corporation.

TYPE, PRINT OR STAMP NAME
OF NOTARY AND COMMISSION
EXPIRATION DATE BELOW       /s/ LAWANA HARDIN
                           ----------------------------------------------------
                                Notary Public

                                                                          [SEAL]
THE STATE OF TEXAS       )
                         )
COUNTY OF HARRIS         )

          This instrument was acknowledged before me on this 23rd day of
November, 1998, by James W. Albrecht, Jr., the CEO of INTROGEN THERAPEUTICS,
INC., a Delaware corporation, on behalf of said corporation.

TYPE, PRINT OR STAMP NAME
OF NOTARY AND COMMISSION
EXPIRATION DATE BELOW       /s/ LAWANA HARDIN
                           ----------------------------------------------------
                                Notary Public

                                                                          [SEAL]

THE STATE OF WISCONSIN       )
                             )
COUNTY OF OUTGAMIE           )

          This instrument was acknowledged before me on this 30th day of
November, 1998, by Wayne C. Streck, and David Crist, the V.P. - Mort. & Real
Estate and Assistant Secretary, respectively, of AID ASSOCIATION FOR
LUTHERANS., a Wisconsin corporation, on behalf of said corporation.

TYPE, PRINT OR STAMP NAME
OF NOTARY AND COMMISSION
EXPIRATION DATE BELOW       /s/ KATHLEEN M. VAN BOSTEL
                           ----------------------------------------------------
                                Notary Public in and for the State of Wisconsin

                                Kathleen M. Van Bostel

My Comm. expires 8-11-2002.

                                      -6-
<PAGE>   135
                                  EXHIBIT "A"

Being a tract or parcel containing 2.619 acres (114,086 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 2.619 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

COMMENCING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3,147,967.40,
Y=698,487.10, thence:

     South 14 degrees 53'21" West, with said west ROW line, a distance of
     206.00 feet to a set 5/8-inch iron rod with plastic cap;

     North 75 degrees 06'39" West, a distance of 329.30 feet to a 5/8-inch iron
     rod with plastic cap set marking the POINT OF BEGINNING and northeast
     corner of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, a distance of 330.70 feet to a 5/8-inch
iron rod with plastic cap set marking the southeast corner of the herein
described tract;

THENCE, NORTH 75 degrees 06'39" West, a distance of 432.78 feet to a 5/8-inch
iron rod with plastic cap set marking the southwest corner of the herein
described tract;

THENCE, NORTH 41 degrees 44'27" East, a distance of 334.23 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 03 degrees 35'59", an arc length of 47.75 feet, and a chord
which bears North 39 degrees 56'28" East, 47.74 feet to an "X" in concrete set
marking the most northwesterly corner of the herein described tract;

THENCE, SOUTHEASTERLY, with a non-tangent curve to the left having a radius of
87.50 feet, an arc length of 93.13 feet, a central angle of 60 degrees 59'01",
and a chord which bears South 58 degrees 25'28" East, 88.80 feet to a 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH 88 degrees 54'58" East, a distance of 27.76 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, EASTERLY, with a curve to the right having a radius of 281.50 feet, an
arc length of 67.83 feet, a central angle of 13 degrees 48'19", and a chord
which bears South 82 degrees 00'48" East, 67.66 feet to a 5/8-inch iron rod with
plastic cap set marking a point of tangency;

THENCE, SOUTH 75 degrees 06'39" East, a distance of 82.41 feet to the POINT OF
BEGINNING and containing 2.619 acres (114,086 square feet) of land (this
description is based on a Land Title Survey and plat prepared by Terra
Surveying Company, Inc, Project Number 0163-9801-S).

<PAGE>   136
GENERAL SERVICES ADMINISTRATION          SUPPLEMENTAL AGREEMENT      DATE
PUBLIC BUILDING SERVICE                  NO. 4                      2/5/97
SUPPLEMENTAL LEASE AGREEMENT             ---------------------------------------
                                         TO: ENHANCED-USE LEASE NO. 084B-029-92,
                                             HOUSTON, TX
--------------------------------------------------------------------------------
ADDRESS OF PREMISES - 2002 Holcombe Blvd., Houston, Texas

--------------------------------------------------------------------------------
THIS AGREEMENT, made and entered into this date by and between  AMELANG PARTNERS
                                                                INCORPORATED

whose address is  c/o KARL AMELANG
                  952 ECHO LANE, SUITE 100
                  HOUSTON, TX 77024

hereinafter called the DEVELOPER, and the UNITED STATES OF AMERICA, hereinafter
called the Government.

WHEREAS, the parties hereto entered into that certain Enhanced-Use Lease dated
August 25, 1993, as amended by (i) Supplemental Lease Agreement (SLA) No. 1,
dated November 1, 1994; (ii) SLA No. 2, dated March 25, 1995; and (iii) SLA No.
3, dated May 20, 1996,

WHEREAS, the parties hereby desire to amend the Lease.

NOW THEREFORE, these parties for the considerations hereinafter mentioned
covenant and agree that the said Lease is amended, effective______________, as
follows:

  THE ENHANCED-USE LEASE IS AMENDED AS FOLLOWS:

  1. Amend Paragraph 27 (c) of the Enhanced-Use Lease by modifying the sentence
     which begins with the phrase "Notwithstanding that the Developer may
     continue under the Lease as to the Mortgaged Property, upon such default by
     the Developer, the Developer shall be obligated to pay to the
     Government...". Substitute therefore the following:

       "Notwithstanding that the Developer may continue under the Lease as to
       the Mortgaged Property, upon such default by the Developer, the Developer
       (but not the lender) shall be obligated to promptly pay to the
       Government...".

  2. The phrase, "but not the lender" is to be added to the next to the last
     sentence in Paragraph 27c of the Lease so that such sentence shall read,
     "...shall be a debt owning by the Developer (but not the lender) to the
     Government..."

IN WITNESS WHEREOF, the parties subscribed their names as of the above date.
--------------------------------------------------------------------------------
DEVELOPER

By /s/ KARL J. AMELANG                            President
   -------------------------                      --------------------------
       (Signature)                                     (Title)

IN THE PRESENCE OF

    /s/ [illegible]                               952 Echo Lane, #100
    ------------------------                      --------------------------
        (Signature)                                    (Address)
                                                  Houston, Texas 77024
--------------------------------------------------------------------------------
UNITED STATES OF AMERICA

By /s/ TANGELA D. COOPER                          CONTRACTING OFFICER
   -------------------------                      --------------------------
       (Signature)                                     (Official Title)
--------------------------------------------------------------------------------

                                                               Page 1 of 3 pages
<PAGE>   137
Supplemental Lease Agreement No. 4
Enhanced-Use Lease No. 084B-029-92, Houston, TX
Page No. 2

3.   Amend Paragraph 27 of the Enhanced-Use Lease by adding the following new
     subparagraph (d):

     "d. Agreement with respect to defaults under the Lease which involve the
Mortgaged Property and other premises. The Government agrees that if the
Mortgaged Property is properly mortgaged per the terms of Paragraph 24 of the
Lease, and if the Developer defaults under the Lease with respect to an
obligation it has which pertains to the Mortgaged Property and other premises
covered by the Lease, the Government must elect whether to treat such default,
notice and opportunity to cure within the remedies provided in either
Paragraph 27(b) or 27(c) of the Lease, irrespective of whether the default
relates solely to the Mortgaged Property. The Government's failing to elect at
the time of the giving of notice of the default shall be its election to
proceed under Paragraph 27(b)."

4.   Amend Paragraph 27 of the Enhanced-Use Lease by adding the following new
     subparagraphs (e) and (f).

     "e. The remedies contained in subparagraphs (b), (c), and (d) of this
Paragraph 27 are the sole and exclusive remedies of the Government against the
lender attributable to any defaults occurring, in whole or in part, prior to the
lender or its successors and assigns succeeding to the interest of the
Developer under the Lease as to the Mortgaged Property.

      f. If the Government exercises its remedies under Paragraph 27(b), (c),
or (d) above, and a lender or purchaser at foreclosure sale succeeds to the
interest or the developer as to the Mortgaged Property (but not other
Property), of if Developer should ever reject this lease, in whole or in part,
pursuant to applicable provisions of the United States Bankruptcy Code, then, in
either such event, the Government hereby agrees to enter into a replacement
lease directly with the person succeeding to the interest of Developer in the
Mortgaged Property for the term and upon the conditions hereinafter set forth:

          (i)    The term of such lease (Replacement Lease) shall commence upon
                 the date of the termination of the Lease with Developer and
                 shall expire on the date otherwise set forth as the date of
                 expiration under the Lease.

          (ii)   Except as to the lease term and except as otherwise provided in
                 this Paragraph 27(f), all terms and provisions of the Lease
                 shall apply to the Replacement Lease as if the Government has
                 exercised its rights under Paragraphs 27(b), (c), or (d), as
                 applicable.

          (iii)  Within thirty (30) days of the request by the lender or
                 purchaser at foreclosure sale, the Government shall enter into
                 a Replacement Lease in a form reasonably satisfactory to the
                 Government consistent with the provisions hereof and without
                 making reference to any premises other than the Mortgaged
                 Property, except for the obligation to pay Additional Rent as
                 provided in SLA No. 2

5.   The Mortgaged Property is more particularly described in Exhibit "A"
     attached hereto.

6.   The Government agrees that any material amendment or material modification
     to the Lease that adversely affects Lender's rights or interests under the
     lease, without Lender's prior written consent, shall not be binding upon
     Lender or its successors or assigns.

7.   If the Government ever exercises its purchase rights under Paragraph 28 of
     the Lease, (a) any payments shall be made directly to the first lien
     mortgagee of the Mortgaged Property, and (b) the "Loan Balance" shall be
     deemed to include principal, interest, reasonable costs, and applicable
     prepayment premiums.

                               Page 2 of 3 pages
<PAGE>   138
Supplemental Lease Agreement No. 4
Enhanced-Use Lease No. 084B-029-92, Houston, TX
Page No. 3

     8.  The Government acknowledges that Developer has constructed a one-story
         building ("Building) situated at 2256-2280 Holcombe Boulevard, and
         covered by this Lease, over the existing VA 54-inch storm sewer line
         traversing a portion of the Mortgaged Property. The Government hereby
         consents to such encroachment and agrees that the Lender, its
         successors and assigns, will not be responsible for any losses,
         damages, liabilities, or expenses attributable to such encroachment.
         The Government does hereby further grant to Developer, its successors
         and assigns, and all subtenants under this Lease, during the term of
         this Lease, the non-exclusive right to drain into all storm sewer
         lines, subject to compliance with all applicable laws including
         environmental laws, situated on the Mortgaged Property or any portion
         thereof. The Government also consents to any approved encroachment of
         parking or driveways constructed over any such storm sewer lines,
         provided that the Developer takes reasonable precautions not to damage
         same.

     9.  The Government hereby grants to the Developer, its successors and
         assigns under this Lease, and all subtenants and invitees of such
         parties, in each case during the term of this lease only, the
         non-exclusive right of ingress and egress over and across the portions
         of Ringness Avenue, being particularly described on Exhibit "B"
         attached hereto, provided, however, that any access by vehicles over
         3/4 tons shall not be permitted without the prior consent of the
         Government and further, that such access shall be subject to such
         other controls as the Government determines necessary.

     All other terms and conditions of the lease shall remain in force and
     effect.

                               Page 3 of 3 pages
<PAGE>   139
                                  EXHIBIT "A"

                              [TERRA LETTERHEAD]

                          METES & BOUNDS DESCRIPTION
                       8.254 ACRES (359,560 SQUARE FEET)
                   D W C HARRIS SURVEY, ABSTRACT NUMBER 325
                             HARRIS COUNTY, TEXAS

TRACT I:

Being a tract or parcel containing 8.254 acres (359,560 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 8.254 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

BEGINNING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3.147,967.40,
Y=698,487.10 said iron rod also marking the northeast corner of the herein
described tract;

THENCE, SOUTH 14 degrees 53'21" West, with said west ROW line, a distance of
536.70 feet to a 5/8-inch iron rod with plastic cap set marking the southeast
corner of the herein described tract;

THENCE, NORTH 75 degrees 06'39" West, a distance of 762.08 feet to a 5/8-inch
iron rod with plastic cap set marking the southwest corner of the herein
described tract;

THENCE, NORTH 41 degrees 44'27" East, a distance of 334.23 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 10 degrees 44'13", an arc length of 142.42 feet, and a chord
which bears North 36 degrees 22'20" East, 142.21 feet to a 5/8-inch iron rod
with plastic cap set marking a point of tangency;

THENCE, NORTH 31 degrees 00'14" East, a distance of 65.48 feet to a 5/8-inch
iron rod with plastic cap set for corner;

THENCE, NORTH 18 degrees 49'21" East, a distance of 51.16 feet to a lead plug
with tack set in a concrete footing marking the most westerly northwest corner
of the herein described tract;

THENCE, SOUTH 71 degrees 10'39" East, a distance of 43.42 feet to a 5/8 inch
iron rod with plastic cap set for corner;

THENCE, NORTH 18 degrees 49'21" East, a distance of 23.88 feet to a 5/8-inch
iron rod with plastic cap set for corner;

THENCE, SOUTH 71 degrees 10'39" East, a distance of 15.90 feet to a lead plug
with tack set in a concrete footing for corner;

THENCE, NORTH 18 degrees 49'21" East, a distance of 20.16 feet to a lead plug
with tack set in a concrete footing for corner;

THENCE, SOUTH 71 degrees 10'39" East, a distance of 20.02 feet to a 5/8-inch
iron rod with plastic cap set for corner;

THENCE, NORTH 18 degrees 49'21" East, a distance of 20.56 feet to a 5/8-inch
iron rod with plastic cap set marking the south ROW line of the aforesaid
Holcombe Boule-
<PAGE>   140
                           METES & BOUNDS DESCRIPTION
                       8.254 ACRES (359,560 SQUARE FEET)
                    D W C HARRIS SURVEY, ABSTRACT NUMBER 325
                              HARRIS COUNTY, TEXAS

                                  PAGE 2 OF 2

THENCE, SOUTHEASTERLY, with said south ROW line and a curve to the right having
a radius of 2,864.93 feet, a central angle of 09 degrees 01'45", an arc length
of 451.48 feet, and a chord which bears South 66 degrees 39'46" East, 451.01
feet to the POINT OF BEGINNING and containing 8.254 acres (359,560 square feet)
of land (this description is based on an ALTA/ACSM Land Title Survey and plat
prepared by Terra Surveying Company, Inc. Project Number 0043-9602-S).

Compiled by: Scott D. Mandeville
Compiled: December 17, 1996
TSC Project No: 0043-9602-S
SDM: 00439602.mb

                     [SEAL OF STATE OF TEXAS LAND SURVEYOR]
<PAGE>   141
                          METES & BOUNDS DESCRIPTION
                        RINGNESS AVENUE ACCESS EASEMENT
                        -------------------------------
                        0.588 ACRE (28,596 SQUARE FEET)
                   D W C HARRIS SURVEY, ABSTRACT NUMBER 325
                             HARRIS COUNTY, TEXAS

TRACT II:

Being a tract or parcel containing 0.588 acre (28,596 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 0.588 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying a combined scale factor of
0.9998632):

COMMENCING at 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3,147,967.40,
Y=698,487.10, thence:

    South 14 degrees 83'21" seconds West, with said West ROW line, a distance
    of 536.70 feet to a set 5/8-inch iron rod with plastic cap;

    North 75 degrees 06'39" seconds West, a distance of 782.08 feet to a
    5/8-inch iron rod with plastic cap set marking the POINT OF BEGINNING;

THENCE, NORTH 41 degrees 44'27" seconds East, a distance of 334.23 feet to a
5/8-inch iron rod with plastic cap set marking the beginning of a tangent
curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 10 degrees 44'14", an arc length of 142.43 feet, and a
chord which bears North 36 degrees 22' 20" East, 142.22 feet to a 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, NORTH 31 degrees 0'14" East, a distance of 65.48 feet to a set 5/8-inch
iron rod with plastic cap;

THENCE, NORTH 18 degrees 48'21" East, at 51.16 feet pass a lead plug with tact
set in a concrete footing, continuing in all, a distance of 105.78 feet to an
angle point;

THENCE, NORTH 63 degrees 49'21" seconds East, a distance of 14.14 feet
to a point in the south ROW line of the aforesaid Holcombe Boulevard;

THENCE, NORTH 71 degrees 10'39" seconds West, with said South Row line,
a distance of 102.97 feet to an angle point;

THENCE, SOUTHEASTERLY, with a non-tangent curve concave southwest, having a
radius of 35.00 feet, an arc length of 54.96 feet, a central angle of 89
degrees 57'12", and a chord which bears South 28 degrees 09'15" East, 49.48
feet to a point of tangency:

                                  EXHIBIT "B"

<PAGE>   142

                           METES & BOUNDS DESCRIPTION
                        RINGNESS AVENUE ACCESS EASEMENT
                        0.388 ACRE (25,598 SQUARE FEET)
                    D W C HARRIS SURVEY, ABSTRACT NUMBER 325
                              HARRIS COUNTY, TEXAS

                                  PAGE 2 OF 2

THENCE, SOUTH 18 degrees 49'21" West, a distance of 105.05 feet to the
beginning of a tangent curve;

THENCE, SOUTHWESTERLY, with a curve to the right having a radius of 500.00
feet, an arc length of 200.00 feet, a central angle of 22 degrees 55'08", and a
chord which bears South 30 degrees 18'34" West, 198.87 feet to a point
of tangency;

THENCE, SOUTH 41 degrees 44'27" West, a distance of 316.68 feet to an
angle point;

THENCE, SOUTH 75 degrees 06'39" East, a distance of 33.83 feet to the
POINT OF BEGINNING and containing 0.388 acre (25,598 square feet) of land.

<PAGE>   143
GENERAL SERVICES ADMINISTRATION                NO. 2               3/23/95
PUBLIC BUILDINGS SERVICE                       ---------------------------------
                                               TO LEASE NO.
SUPPLEMENTAL LEASE AGREEMENT                   Enhanced-Use Lease  (084B-029-92)
--------------------------------------------------------------------------------
OF PREMISES
               Holcombe Blvd.
               Houston, TX
--------------------------------------------------------------------------------
THIS AGREEMENT, made and entered into this date by and between
                                                          AMELANG PARTNERS, INC.

                    c/o Karl Amelang
whose address is    952 Echo Lane, Suite 100
                    Houston, TX

hereinafter called the Lessor, and the UNITED STATES OF AMERICA, hereinafter
called the Government:

  WHEREAS, the parties hereto desire to amend the above Lease to allow the
  Developer flexibility in obtaining financing, to assist the Developer in
  completing the obligations imposed upon him by the Lease, and to allow the
  Developer to grant as security for such financing a security interest in the
  Mortgaged Property which would be acceptable to a lender.

  NOW THEREFORE, these parties for the considerations hereinafter mentioned
  covenant and agree that the said Lease is amended as follows:

          Add the following to "Definitions", Paragraph 1 of the Enhanced-Use
          Lease:

          "Mortgaged Property" -- means the Developer's Interest(s) in the 8.18
          acres and identified as Parcel A in Exhibit A and subject to Paragraph
          24.

          Amend Paragraph 9(c)(6) of the Enhanced-Use Lease with the following:

          The Developer will commence construction of the Mandatory Development
          on or before April 3, 1995.

  All other terms and conditions of the lease shall remain in force and effect.

  IN WITNESS WHEREOF, the parties subscribed their names as of the above date.
--------------------------------------------------------------------------------
LESSOR    AMELANG PARTNERS, INC.

  BY /s/ KARL J. AMELANG                     PRESIDENT
     -------------------                     -------------------
        (Signature)                           (Title)

  IN PRESENCE OF

     /s/[illegible]                           952 ECHO LANE
     -------------------                     -------------------
        (Signature)                            (Address)
--------------------------------------------------------------------------------
UNITED STATES OF AMERICA                     HOUSTON, TX 77024

  BY /s/ LAWRENCE J. HILL                    CONTRACTING OFFICER
     --------------------                    -------------------
        (Signature)                            (Official Title)
--------------------------------------------------------------------------------

                                                         Page 1 of 3 pages
<PAGE>   144
Page 2
Supplemental Lease Agreement No. 2
Enhanced-Use Lease (084B-029-92)

     Amend Paragraph 13(a)(2) of the Enhanced-Use Lease with the following:

     The Developer will commence construction of the Mandatory Development on or
before April 3, 1995, and the building shell for the Mandatory Development shall
be completed on or before September 15, 1995.

     Amend Paragraph 18 of the Enhanced-Use Lease with the following:

     The Developer will obtain a firm commitment of funds in an amount
sufficient to construct the Mandatory Development on or before March 24, 1995.

     Delete subparagraphs 24(f), (g), (h), and (i).

     Amend Paragraph 26 of the Enhanced-Use Lease by substituting "twenty (20)
days" for "fifteen (15) days" wherever it appears in the Paragraph.

     Amend Paragraph 27 of the Enhanced-Use Lease by numbering the existing
paragraph as (a) and adding the following new subparagraphs (b) and (c):

(b)  Agreement with respect to defaults under the Lease which involve the
Mortgaged Property. The Government agrees that if the Mortgaged Property is
properly mortgaged per the terms of Paragraph 24, of the Lease, and if the
developer defaults with respect to any monetary obligations it has related to
the Mortgaged Property and such default is cured by either a lender or the
Developer prior to the expiration of twenty (20) days after the lender and the
Developer receive notice of such default from the Government, the Government
expressly recognizes the rights of such lender under the Lease and the lender's
right to proceed to act under the Lease as it pertains to the Mortgaged Property
and under its security documents, and agrees that any such default under the
Lease by Developer will be deemed to be cured as to such lender or any successor
or assign of the lender, and deemed cured as to the Developer. If such default
is not cured within the time period stated above by either the lender or the
Developer, the Government is entitled to pursue any rights or remedies which it
has against the Developer including termination of the Lease. In the event that
Developer shall default under a non-monetary obligation of the Lease related
solely to the Mortgaged Property, and if such default is not timely cured by
Developer and if a lender is not a party to such default, the Government may
proceed against the Developer, but the Government shall not terminate a lender's
interest in the Lease but shall recognize the lender's rights as assignee of
Developer's interest and such lender shall assume the obligations of the
Developer under the Lease as it relates solely to the Mortgaged Property;
provided, however, after such interest is in a lender and in the event that
Additional Rent (as defined in Paragraph 27(c) below) becomes due and payable,
the payments due to the Government for the Mortgaged Property shall include the
Additional Rent in the same manner and to the same extent as provided in
Paragraph 27(c).

                                                               Page 2 of 3 pages
<PAGE>   145

PAGE 3
SUPPLEMENTAL LEASE AGREEMENT NO. 2
ENHANCED-USE LEASE (084B-029-92)

(c) Agreement with respect to defaults under the Lease which do not involve the
Mortgaged Property. The government agrees that if the Mortgaged Property is
properly mortgaged per the terms of Paragraph 24 of the Lease, and if the
Developer defaults under the Lease with respect to an obligation it has which
does not pertain to the Mortgaged Property, the Government will give written
notice to such lender and the Developer of such defaults. If such default is
cured by either the Developer or a lender prior to the expiration of twenty (20)
days from the date the lender and Developer receive notice of such default, the
Government expressly recognizes the rights of such lender under the Lease and
the lender's right to proceed to act under the Lease as it pertains to the
Mortgaged Property and under its security documents, and agrees that any such
default under the Lease by Developer will be deemed to be cured as to such
lender or any successor or assign of the lender, and will be deemed cured as to
the Developer as to the Mortgaged Property. If such default is not cured within
the time period stated above by either the lender or the Developer, the
Government is entitled to pursue any rights and remedies which it has against
the Developer under the Lease, save and except any rights which the Government
may have to terminate the Developer's rights to lease and operate the Mortgaged
Property. If Developer's default does not relate in any respect to obligations
which the developer has related to the Mortgaged Property, the Government waives
its right to terminate the Developer's interest in the Mortgaged Property as
granted to it by the Lease, based solely on a default which does not pertain to
the Mortgaged Property. Notwithstanding that the Developer may continue under
the Lease as to the Mortgaged Property, upon such default by the Developer, the
Developer shall be obligated to promptly pay to the Government, upon demand,
that amount necessary (i) to reimburse the Government for the actual costs and
expenses for undertaking Developer's obligations as set forth in the Lease for
maintaining and repairing the VA Parking (as defined in the Lease) as it accrues
for the remainder of the original term of the Lease plus, (ii) during the four
years after the commencement of the Government's payment of the Management Fee,
to reimburse the Government for the actual costs and expenses of the Government
for undertaking Developer's obligations as set forth in the Lease and in
procuring a new management company for the VBA Building and the VA Parking (with
any decrease in the management fee cost being credited to the cost of the VA
Parking maintenance expense due from the developer)(The sum of (i) and (ii)
above is referred to hereinafter as "the Additional Rent"). Additional Rent is
due and payable at the same time but in addition to the payments due for the
Mandatory Development as set forth in the lease; provided, however, the maximum,
annual Additional Rent that can be added to the payments due for the Mandatory
Development shall not exceed SIX THOUSAND AND NO/100 DOLLARS ($6,000) per year.
Additional Rent shall be adjusted annually in arrears based on one-hundred (100)
percent of the increase or decrease in the Consumer Price Index for the
Houston-metropolitan area, such indexing to begin on the commencement date of
the Government's payment of the Management Fee. Any remainder of actual costs
and expenses due the Government as reimbursement for undertaking Developer's
obligations defined in (i) and (ii) above, shall be a debt owing by the
Developer to the Government but shall not be an obligation chargeable to the
Mortgaged Property or a default under the Lease as to the Mortgaged Property. In
the event that Developer has constructed or has obtained approval for Optional
Development on the remainder of the Mortgaged Property, the Additional Rent
shall be allocated between the Mandatory Development and the Optional
Development as provided in the Government's approval of the Optional Development
plans or if not expressly addressed, in an equitable manner.

                                                            Page 3 of 3 pages

<PAGE>   146
GENERAL SERVICES ADMINISTRATION          SUPPLEMENTAL AGREEMENT   DATE
PUBLIC BUILDING SERVICE                  No. 3                   5/20/96
SUPPLEMENTAL LEASE AGREEMENT             ---------------------------------------
                                         TO: Enhanced-Use Lease No.084B-029-32,
                                             Houston, TX
--------------------------------------------------------------------------------
ADDRESS OF PREMISES - 2002 Holcombe Blvd., Houston, Texas

--------------------------------------------------------------------------------
THIS AGREEMENT, made and entered into this date by and between AMELANG PARTNERS
INC.

whose address is    c/o Karl Amelang
                    952 Echo Lane, Suite 100
                    Houston, TX 77024

hereinafter called the Developer, and the UNITED STATES OF AMERICA, hereinafter
called the Government:

WHEREAS,

  Amelang Partners Inc. (API) requested Government's approval, as required by
  Section 10 of the Lease, of future development on the Property;

  API's proposed future development will include development of 14,175 square
  feet for a kidney dialysis clinic, of which 11,900 square feet will be new
  construction added to the existing Mandatory Development ("Holcombe Center"),
  and the remaining 2,275 square feet will be buildout of existing vacant space
  in the Mandatory Development;

  The Developer has entered into a sublease (the "Sublease"), a copy of which is
  attached and made a part of this Supplemental Lease Agreement as Exhibit "A",
  between the Developer and Geraged Eknoyan, M.D., et al, for a 14,175 square
  foot kidney dialysis clinic:

  The Government approves API's future development of a kidney dialysis clinic
  as being consistent with its mission:

  The Government further agrees to the amount of additional benefit to be paid
  by the Developer in consideration of said future development, the Parties
  hereto desire to amend the above Lease.

NOW THEREFORE, these parties for the considerations hereinafter mentioned
covenant and agree that the said Lease is amended, effective upon commencement
of sublease, as follows:

  The Developer and Government agree all terms and conditions of the Lease
  pertaining to the Mandatory Development, including payment of rent in
  accordance with Section 4(b)(3), will apply to use and occupancy of said 2,275
  square feet in the Mandatory Development for a kidney dialysis clinic under
  API's Sublease.

IN WITNESS WHEREOF, the parties subscribed their names as of the above date.
--------------------------------------------------------------------------------
DEVELOPER

By /s/ KARL J. AMELANG                       PRESIDENT
   ------------------------                  ----------------------------
       (Signature)                                (Title)

IN THE PRESENCE OF                           952 ECHO LANE #100
   /s/ [illegible]                           HOUSTON, TX 77024
   ------------------------                  ----------------------------
       (Signature)                                (Address)

--------------------------------------------------------------------------------
UNITED STATES OF AMERICA

By /s/ LAWRENCE J. HILL                      Contracting Officer
   ------------------------                  ----------------------------
        (Signature)                               (Official Title)
--------------------------------------------------------------------------------

                                                         Page 1 of 2 pages
<PAGE>   147
Supplemental Lease Agreement No. 3
Enhanced-Use Lease No. 084B-029-92, Houston, TX
Page No. 2

Amend Section 4 of the Lease by adding the following new subsection at the end:

     (b)(4)(i) Pay to the Government Twelve percent (12%) of Eighty-four percent
     (84%) (11,900 square feet of new construction divided by 14,175 square
     feet) of the rent described in Section II. FINANCIAL OBLIGATIONS, A. RENT,
     of the Sublease to be paid to the Government monthly as if and when such
     rent is received by the Developer. It is understood that this payment does
     not include any minimum or guaranteed rent to the Government.

          (ii) The amount of the financial benefits to be paid to the Government
     for this proposed development are subject to re-evaluation and mutual
     agreement between Developer and the Government at the end of the primary
     term of the sublease as defined in Section I. LEASED PREMISES COMMENCEMENT
     AND TERM D, COMMENCEMENT AND LEASE TERM. Within eighty (80) days prior to
     the end of the primary term of the sublease, Developer shall provide to the
     Government an appraisal of the property described by metes and bounds
     (Exhibit "B" attached hereto), along with its proposed financial benefits
     to be paid to the Government for such use and occupancy. If the Government
     does not believe that the proposed amount reflects a fair market rental
     rate to the Government for such use, the Government will notify Developer
     within thirty (30) days of receipt of the appraisal and estimated financial
     benefits, and the Government may within sixty (60) days obtain an appraisal
     using an appraiser of the Government's choosing. If the Government's
     appraisal and estimate differ from Developer's, the parties agree to meet
     in a attempt to resolve the differences. If within thirty (30) days the
     parties do not agree on the financial benefits, such disagreement shall be
     resolved pursuant to Section 23 of the Lease. After the end of the primary
     term of the sublease, Developer will place into escrow each month, as, if
     and when received by API from the sublessee, to be held until either a
     final resolution is obtained as to the amount of financial benefit to be
     paid by Developer to the Government or an agreement is reached among the
     parties with respect to such amount, the greater of the following amounts:

          (1). the financial benefits Developer proposes to pay the Government
     for use and occupancy of the development or

          (2). the amount the Government believes should be the financial
     benefits to be paid by Developer to the Government for such use and
     occupancy.

     This proposal is specific to this sublease proposal. In event of early
     termination or other sublease of such space, such shall be negotiated
     pursuant to Section 10.b. of the Lease.

The consideration represents a complete equitable adjustment for all costs,
direct and indirect, associated with the work and time agreed to herein,
including but not limited to all costs incurred for extending overhead,
supervision, disruption or suspension of work, labor inefficiencies, and this
changes impact on unchanged work.

All other terms and conditions of the Lease shall remain in force and effect.

<PAGE>   148
GENERAL SERVICES ADMINISTRATION     SUPPLEMENTAL AGREEMENT        DATE
PUBLIC BUILDING SERVICE             No. 5                         Sept. 24, 1998
SUPPLEMENTAL LEASE AGREEMENT        --------------------------------------------
                                    TO:  Enhanced-Use Lease No. 984B-029-92.
                                         Houston, Texas

-------------------------------------------------------------------------------
ADDRESS OF PREMISES - 2002 Holcombe Blvd., Houston, Texas
-------------------------------------------------------------------------------
THIS AGREEMENT, made and entered into this date by and between Amazing
Partners, Incorporated whose address is               c/o Karl Amelang
                                                      952 Echo Lane, Suite 100
                                                      Houston, Texas   77024

hereinafter called the Developer, and the UNITED STATES DEPARTMENT OF VETERANS
AFFAIRS, hereinafter called the Government

WHEREAS,

The parties hereto entered into that certain Enhanced-Use Lease dated August 25,
1993, as amended by (i) Supplemental Lease Agreement ("SLA") No. 1, dated
November 1, 1994, (ii) SLA No. 2, dated March 25, 1995, (iii) SLA No. 3, dated
May 20, 1998, and (iv) SLA No. 4, dated February 5, 1997 (the "Lease" or the
"Enhanced-Use Lease"); Amelang Partners, Incorporated (API) requested
Government's consent, as required by Section 10 and Section 21 of the
Enhanced-Use Lease, of future development on the Property:

The parties hereby desire to amend the Lease.

NOW THEREFORE, these parties for the considerations hereinafter mentioned
covenant and agree that the said Enhanced-Use Lease is amended, effective
September 24, 1998, as follows:

1.  In the event a lender (currently Aid Association for Lutherans) should ever
    succeed to the interest of Developer under the Lease solely as to the
    Mortgaged Property, such lender and any permitted assignee shall (a) pay
    rent under Paragraph 4(b)(3) of the Lease solely on account of Gross Retail
    Receipts from the Mandatory Development, (b) pay rent with respect to the
    Optional Development situated on the Mortgaged Property as provided in
    Paragraph 4(b)(4) of the Lease, (c) pay $21,000.00 per year of the Annual
    Minimum Consideration, and (d) pay $8,000.00 per year of the "Additional
    Rent" (described in SLA No. 2 and SLA No. 4), as such amount may be adjusted
    due to changes in the Consumer Price Index (as explained in Paragraph 27(c)
    of the Lease); provided, furthermore, such lender and any permitted assignee
    shall only be liable under the Lease to the extent the liability relates
    solely to the Mortgaged Property and not to any other property covered by
    the Lease.

2.  The Government acknowledges and agrees that a lender (currently Aid
    Association for Lutherans) holding a mortgage secured by Developer's
    interest in the Mortgaged Property and some or all of Developer's other
    interests in the Lease may foreclose solely as to Developer's interest under
    the Lease in the Mortgaged Property, and, in such event, shall only be
    responsible for obligations thereafter accruing under the Lease solely as
    they relate to the Mortgaged Property and not any other property covered by
    the Lease.

IN WITNESS WHEREOF, the parties subscribed their names as of the above date.
-------------------------------------------------------------------------------
DEVELOPER

BY: /s/ [illegible]                          President
   ----------------------------------    ------------------------------------
         (Signature)                                  (Title)

IN THE PRESENCE OF

    /s/ SUSAN V. HUGHES                      Administrative Assistant
   ----------------------------------    ------------------------------------
         (Signature)                                  (Title)

DEPARTMENT OF VETERANS AFFAIRS

BY: /s/ TANGELA D. COOPER                       Contracting Officer
   ----------------------------------    ------------------------------------
         (Signature)                                  (Title)
<PAGE>   149

Supplemental Lease Agreement No. 5
Enhanced-Use Lease No. 084B-029-93, Houston, TX
Page 2 of 3

3.  No termination or cancellation of the Lease as to the Mortgaged Property
    exercised by Developer shall be binding on a lender, unless such lender's
    written consent is first obtained.

4.  If the nature of a non-monetary default cannot reasonably be cured by a
    lender within the time period provided in the Lease, the lender shall have
    such additional period of time as is reasonable under the circumstances
    (recognizing, in part, that until foreclosure the lender does not have
    possession of the Mortgaged Property), so long as the lender is acting in
    good faith to cure the default.

5.  Whenever the Lease requires the lender to notify the Government of a
    default by the Developer or of the termination, sale or transfer, or notice
    of the intent to terminate the Loan, the lender may satisfy any such
    requirements by sending the Government such notice simultaneously with the
    sending of any such notice to the Developer.

AMEND PARAGRAPH 1 OF THE LEASE, "DEFINITIONS", "MORTGAGED PROPERTY" TO READ:

    "Mortgaged Property - means the Developer's interest(s) in the
    approximately 3.135 acre tract described on Exhibit "A" attached hereto and
    all other property interests in such tract of land."

AMEND PARAGRAPH 1 OF THE LEASE, "DEFINITIONS", "i. MANDATORY DEVELOPMENT"
TO READ:

    "Mandatory Development - means approximately 17,150 square feet of the
    improvements comprising the retail center commonly known as the Holcombe
    Center situated on the Mortgaged Property, and identified on Exhibit "B"
    attached hereto. The improvements comprising the Mortgaged Property also
    include approximately 11,900 square feet of "Optional Development,"
    identified on Exhibit "B".

AMEND PARAGRAPH 27(f) (REFER TO SLA NO. 4 DATED FEBRUARY 5, 1997) OF THE LEASE,
"REMEDIES FOR DEFAULT BY DEVELOPER", TO READ:

     "(f)  if the Government exercises its remedies under Paragraph 27(b), (c)
or (d) above or under any other provision of the Lease, and a lender or
purchaser at foreclosure sale succeeds to the interest of the Developer as to
the Mortgaged Property (but not other Property), or if Developer should ever
terminate or cancel the Lease as to the Mortgaged Property without a lender's
written consent, or if Developer should ever reject this Lease, in whole or in
part, pursuant to applicable provisions of the United States Bankruptcy Code,
or if a lender or purchaser at foreclosure sale succeeds to the interest of the
Developer due to a default under the lender's loan documents, then, in any of
such events, the Government hereby agrees to enter into a replacement lease
directly with the person succeeding to the interest of Developer in the
Mortgaged Property (irrespective of whether the Lease has already been
terminated, canceled or suspended) for the term and upon the conditions
hereinafter set forth:

           (i)   The term of such lease (the "Replacement Lease") shall
                 commence upon the date of the termination, cancellation or
                 suspension of the Lease with Developer or, if applicable, the
                 date of the foreclosure sale, and shall expire on the date
                 otherwise set forth as the date of expiration under the Lease.

           (ii)  Except as to the lease term and except as otherwise provided
                 in this Paragraph 27(f), all terms and provisions of the Lease
                 shall apply to the Replacement Lease as if the Government had
                 exercised its rights under Paragraphs 27(b), (c), or (d), as
                 applicable.
<PAGE>   150

SUPPLEMENTAL LEASE AGREEMENT NO. 5
ENHANCED-USE LEASE NO. 084B-029-93, HOUSTON, TX
PAGE 3 OF 3

         (iii) Within thirty (30) days of the request by the lender or purchaser
               at foreclosure sale, the Government shall enter into a
               Replacement Lease in a form reasonably satisfactory to the
               Government consistent with the provisions hereof and without
               making reference to any premises other than the Mortgaged
               Property: except for the obligation to pay Additional Rent as
               provided in SLA No. 2.

     The references in Paragraph 27 of the Lease and in SLA No. 4 and in this
SLA No. 5 to a lender mean and refer to the holder of a first lien on the
Mortgaged Property (currently Aid Association for Lutherans)."

AMEND PARAGRAPH 7 OF SLA NO. 4 DATED FEBRUARY 5, 1997, TO READ:

"7. If the Government ever exercises its purchase rights under Paragraph 38 of
   the Lease, (a) any payments shall be made directly to the holder of the first
   lien on the Mortgaged Property (currently Aid Association for Lutherans), and
   (b) any repurchase shall be for at least the loan balance owed at the time to
   the holder of the first lien on the Mortgaged Property."

ALL OTHER TERMS AND CONDITIONS OF THE ENHANCED-USE LEASE SHALL REMAIN IN FORCE
AND EFFECT.
<PAGE>   151
                                   EXHIBIT A

                              [TERRA LETTERHEAD]

                          METES & BOUNDS DESCRIPTION
                       3.135 ACRES (136,574 SQUARE FEET)
                   D W C HARRIS SURVEY, ABSTRACT NUMBER 325
                             HARRIS COUNTY, TEXAS

Being a tract or parcel containing 3.135 acres (136,574 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 3.135 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

BEGINNING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the southerly right-of-way (ROW) line of Holcombe Boulevard with the
westerly ROW line of Almeda Road, and having surface coordinates of
X = 3,147,967.40, Y = 698,487.10 , said iron rod also marking the most easterly
corner of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, with said westerly ROW line, a distance
of 206.00 feet to a 5/8-inch iron rod with plastic cap set marking the most
southerly corner of the herein described tract;

THENCE, NORTH 75 degrees 06'39" West, at 380.00 feet pass a set 5/8-inch iron
rod with plastic cap, continuing in all, a distance of 411.72 feet to a
5/8-inch iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, WESTERLY, with a curve to the left having a radius of 281.50 feet, an
arc length of 67.83 feet, a central angle of 13 degrees 48'19", and a chord
which bears North 82 degrees 00'48" West, 67.66 feet to a 5/8-inch iron rod
with plastic cap set marking a point of tangency;

THENCE, NORTH 88 degrees 54'58" West, a distance of 27.76 feet to a
5/8-inch iron rod with plastic cap set marking the beginning of a tangent
curve;

THENCE, NORTHWESTERLY, with a curve to the right having a radius of 87.50 feet,
an arc length of 93.13 feet, a central angle of 60 degrees 59'01", and a chord
which bears North 58 degrees 25'28" West, 88.80 feet to an "X" in the top of a
concrete inlet set marking the southwest corner of the herein described tract,
and being in a non-tangent curve concave northwest;

THENCE, NORTHEASTERLY, with said non-tangent curve to the left, having a radius
of 760.00 feet, a central angle of 07 degrees 08'15", an arc length of 94.68
feet, and a chord which bears North 34 degrees 34'21" East, 94.61 feet to a
5/8-inch iron rod with plastic cap set marking a point of tangency;

THENCE, NORTH 31 degrees 00'14" East, a distance of 65.48 feet to a 5/8-inch
iron rod with plastic cap set for corner;

THENCE, NORTH 18 degrees 49'21" East, a distance of 51.16 feet to a lead plug
with tack set in a concrete footing marking the most westerly north corner of
the herein described tract;

THENCE, SOUTH 71 degrees 10'39" East, a distance of 43.42 feet to a 5/8-inch
iron rod with plastic cap set for corner;
<PAGE>   152
with plastic cap set for corner;

THENCE, SOUTH 71 degrees 10'39" East, a distance of 15.90 feet
to a lead plug with tack set in a concrete footing for corner;

THENCE, NORTH 18 degrees 49'21" East, a distance of 20.16 feet
to a lead plug with tack set in a concrete footing for corner;

THENCE, SOUTH 71 degrees 10'39" East, a distance of 20.02 feet
to a 5/8-inch iron rod with plastic cap set for corner;
<PAGE>   153
                              [TERRA LETTERHEAD]

                         METES AND BOUNDS DESCRIPTION
                       3.135 ACRES (136,574 SQUARE FEET)
                   D W C HARRIS SURVEY, ABSTRACT NUMBER 325
                             HARRIS COUNTY, TEXAS

                                  PAGE 2 OF 2

THENCE, NORTH 18 degrees 49'21" East, a distance of 20.56 feet
to the southerly ROW line of the aforesaid Holcombe Boulevard, also being the
most northerly west corner of the herein described tract;

THENCE, SOUTH 71 degrees 10'39" East, with said southerly ROW
line, a distance of 7.66 feet to the beginning of a tangent curve;

THENCE, SOUTHEASTERLY, with said southerly ROW line and a curve to the right
having a radius of 2,864.93 feet, at an arc length of 66.33 feet pass a set
5/8-inch iron rod with plastic cap, continuing in all, an arc length of 451.48
feet, a central angle of 09 degrees 01'45", and a chord which
bears South 66 degrees 39'46" East, 451.01 feet to the POINT OF
BEGINNING and containing 3.135 acres (136,574 square feet) of land (this
description is based on an ALTA/ACSM Land Title Survey and plat prepared by
Terra Surveying Company, Inc, Project Number 0043-9601-S).

Compiled By: Scott D. Mandeville
Compilation Date: April 9, 1996
Revised: January 20, 1997
Project No: 0043-9601-S
SDM: 00439601.mb

                                        [SEAL OF STATE OF TEXAS LAND SURVEYOR]

<PAGE>   154
                                   EXHIBIT B

SLA #5

                                     [MAP]

D W C HARRIS SURVEY

          ABSTRACT NO 325

                             F.M. 521 (ALMEDA ROAD)
<PAGE>   155
GENERAL SERVICES ADMINISTRATION      SUPPLEMENTAL AGREEMENT      DATE
   PUBLIC BUILDINGS SERVICE          NO. 1                       NOV. 1, 1994
                                     TO LEASE NO.
 SUPPLEMENTAL LEASE AGREEMENT        Enhanced-Use (084B-029-94)

ADDRESS OF PREMISES      Holcombe Blvd.
                         Houston, TX

THIS AGREEMENT, made and entered into this date by and between AMELANG PARTNERS
INC.

whose address is    c/o Karl Amelang
                    952 Echo Lane, Suite 100
                    Houston, TX

hereinafter called the Lessor, and the UNITED STATES OF AMERICA, hereinafter
called the Government:

WHEREAS, the parties hereto desire to amend the above Lease.

NOW THEREFORE, these parties for the considerations hereinafter mentioned
covenant and agree that the said Lease is amended, effective ________________
as follows:

     Issued to adjust the commencement date in accordance with Paragraph
     9(c)(6), "Representations", of the Enhanced Use Lease Agreement, and to
     provide definitions for Gross Retail Receipts, Annual Minimum
     Consideration, and Annual Percentage Consideration. Paragraphs 1, 4,
     9(c)(6); 13(a)(2); 13(d)(2)(a); 13(d)(2)(b), 13(d)(2)(c), and 18 are
     amended as follows:

          Paragraph 1, "Definitions" add:

          q.   "GROSS RETAIL RECEIPTS" - means Developer's gross rental income,
     which shall include, but not be limited to: all minimum, base and/or
     percentage rentals; other monetary consideration paid to the Developer,
     excluding reimbursements of Developer's costs for operating the leased
     premises, proportionate share charges for common area maintenance, real
     estate and other taxes, insurance charges, and other costs incurred by the
     Developer with respect to the use and/or occupancy of the sub-lease.

          r.   "ANNUAL MINIMUM CONSIDERATION" - means $21,000 per year,
     throughout the term of the Enhanced-Use lease. This amount is without any
     deduction or setoff whatsoever. The annual minimum consideration shall be
     paid to the Government in equal monthly installments on the first day of
     each calendar month.

          s.   "ANNUAL PERCENTAGE CONSIDERATION" - means ten percent (10%) of
     the Developer's gross retail receipts. This amount is without any deduction
     or setoff whatsoever.

All other terms and conditions of the lease shall remain in force and effect.

IN WITNESS WHEREOF, the parties subscribed their names as of the above date.

LESSOR    Amelang Partners Inc.

BY  /s/ KARL J. AMELANG                               PRESIDENT
   --------------------------------         ------------------------------------
             (Signature)                               (Title)

IN PRESENCE OF
   /s/ [illegible]                         952 ECHO LANE, SUITE 100, HOUSTON, TX
   --------------------------------        ------------------------------------
             (Signature)                              (Address)

UNITED STATES OF AMERICA
BY /s/ LAWRENCE J. HILL                            Contracting Officer
   --------------------------------        ------------------------------------
             (Signature)                             (Official Title)
<PAGE>   156

Supplemental Lease Agreement No. 1
Enhanced-Use Lease No. 084B-029-92

     Paragraph "4. Lease" -add the following:

     "The Developer shall furnish the Government a statement of gross rental
income within thirty (30) days after the close of each calendar month, and an
annual statement, including a monthly breakdown of gross rental income, on or
before forty-five (45) days following the expiration of each calendar year. The
statement of monthly and annual statement of gross rental income shall be
certified by the Developer's Controller.

     Paragraph 6(a)(1): Upon the VA Parking Commencement date as defined in
paragraph 3(a) herein, the Government, as consideration shall pay to the
Developer, VA Parking rental payments at the rate of $100.00 per quarter, in
arrears.

     Paragraph 9(c)(6): The Developer will commence construction of the
Mandatory Development and will have awarded the construction contract for the
work on or before November 1, 1994.

     Paragraph 13(a)(2): The construction of the Mandatory Development shall
commence on or before November 1, 1994, and shall be completed and Certificates
of Occupancy issued by May 1, 1995.

     Paragraph 13(d)(2)(c): Within 30 calendar days of execution of this
Supplemental Lease Agreement, the Developer shall submit working drawings at
the 100% completion stage.

     Paragraph 13(f): The Developer shall submit to the Contracting Officer a
finalized construction schedule within 10 days after execution of this SLA. the
schedule shall provide the dates on which the various phases of construction
will be completed to coincide with the delivery date of May 1, 1995.

     Paragraph 16(c): Delete "Compass Bank, 24 Greenway Plaza, Houston, TX
77210". Substitute "Frost National Bank, P.O. Box 1315, Houston, TX 77251".

     Paragraph 18, "Commitment of Funds": Within forty-five (45) calendar days
from the execution of this SLA, the Developer shall provide the Contracting
Officer evidence of a firm commitment of funds in an amount sufficient to
perform the work. Failure to meet the requirements as set forth in this
paragraph within this time frame shall be a basis for determination of
non-responsibility or for termination of this Lease for default.

     Attachment B of the Enhanced-Use Lease is deleted in its entirety.

     The consideration set forth in this Supplemental Lease Agreement
represents a complete equitable adjustment for all costs, direct and indirect,
associated with the work and time agreed to herein including, but not limited
to, all costs incurred for extended overhead, supervision, disruption or
suspension of work, labor inefficiencies, and this change's impact on unchanged
work.
<PAGE>   157
GENERAL SERVICES ADMINISTRATION         SUPPLEMENTAL AGREEMENT   DATE
PUBLIC BUILDING SERVICE                 No. 6                    SEP 24 1998
SUPPLEMENTAL LEASE AGREEMENT
                                        TO: ENHANCED-USE LEASE NO. 084B-029-92.
                                            HOUSTON, TEXAS

ADDRESS OF PREMISES - 2002 Holcombe Blvd., Houston, Texas

THIS AGREEMENT, MADE AND ENTERED INTO THIS DATE BY AND BETWEEN AMELANG
PARTNERS, INC. WHOSE ADDRESS IS    C/O KARL AMELANG
                                   952 ECHO LANE, SUITE 100
                                   HOUSTON, TEXAS 77024

HEREINAFTER CALLED THE DEVELOPER, AND THE UNITED STATES DEPARTMENT OF VETERANS
AFFAIRS, HEREINAFTER CALLED THE GOVERNMENT

WHEREAS,

Amelang Partners Inc. (API) requested Government's consent, as required by
Section 10 and Section 21 of the Enhanced-Use Lease, of future development on
the Property;

API's proposed future development will include development of two buildings for
use as a laboratory/pharmaceutical manufacturing facility and office building
on 2.5 acres of land at the corner of Almeda Road and Holcombe Boulevard as
more particularly describe in Exhibit "A" which is attached hereto (the
"Subleased Premises"); such development will consist of new construction added
to the existing Mandatory Development and Non-Mandatory Development ("Holcombe
Center");

The Developer has entered into a sublease (the "Sublease"), with Introgen
Therapeutics, Inc., a copy of which is attached and made a part of this
Supplemental Lease Agreement as Exhibit "B".

The Government acknowledges that the Sublease and the proposed future
development are consistent with its mission, provided that the Sublease and
sub-lessee's rights therein are expressly subordinate to the rights
and interests of the Government in the Lease.

The Government further agrees to the amount of additional benefit to be paid by
the Developer in consideration of said future development, and the Parties
hereto desire to amend the above Lease.

NOW THEREFORE, THESE PARTIES FOR THE CONSIDERATIONS HEREINAFTER MENTIONED
COVENANT AND AGREE THAT THE SAID LEASE IS AMENDED, EFFECTIVE SEP 24 1998, AS
FOLLOWS:

THE DEVELOPER AND GOVERNMENT AGREE THAT AS BETWEEN THE GOVERNMENT AND THE
DEVELOPER, ALL TERMS AND CONDITIONS OF THE LEASE PERTAINING TO THE MANDATORY
DEVELOPMENT, INCLUDING ALL CONSTRUCTION REVIEW AND APPROVALS AND PAYMENT OF
RENT IN ACCORDANCE WITH SECTION 4(b), WILL APPLY TO USE AND OCCUPANCY OF SAID
DEVELOPMENT IN THE NON-MANDATORY DEVELOPMENT UNDER THE SUBLEASE.

IN WITNESS WHEREOF, THE PARTIES SUBSCRIBED THEIR NAMES AS OF THE ABOVE DATE.

DEVELOPER

By: /s/ [ILLEGIBLE]                         PRESIDENT
   ---------------------------     -----------------------------
          (Signature)                        (Title)

IN THE PRESENCE OF
 /s/ SUSAN V. HUGHES               ADMINISTRATIVE ASSISTANT
------------------------------     -----------------------------
          (Signature)                        (Title)

DEPARTMENT OF VETERANS AFFAIRS

By: /s/ TANGELA D. COOPER            Contracting Officer
   ---------------------------     -----------------------------
          (Signature)                        (Title)
<PAGE>   158
Supplemental Lease Agreement No. 6
Enhanced-Use Lease No. 084B-029-93, Houston, TX
Page 2 of 3

AMEND SECTION 4 OF THE LEASE BY ADDING THE FOLLOWING NEW SUBSECTION AT THE END:

     (b)(5) Except as expressly set forth herein, API agrees to pay the
     Government, without prior demand and without any deduction or offset, as
     annual rent for the Premises, as such term is defined in the Sublease, the
     sum of Sixty-Five Thousand Dollars ($65,000.00) (subject to adjustment as
     herein provided) in equal monthly installments. The rental will be adjusted
     on the third anniversary of the Commencement Date, as such term is defined
     in the Sublease, and triennially thereafter based on eighty percent (80%)
     of any increase and sixty percent (60%) of any decrease in the Consumer
     Price Index for the Houston metropolitan area from its most recently
     published level as of the Commencement Date. The rental as adjusted will be
     effective from each such adjustment date until the next adjustment date. In
     no instance however, shall the annual rent be less than Sixty-Five Thousand
     Dollars ($65,000.00), except as expressly set forth herein. "Consumer Price
     Index" means the most current "Consumer Price Index, All Urban Consumers,
     All-items, . . ." for the metropolitan area in which the Premises is
     located, as compiled by the U.S. Department of Labor, Bureau of Labor
     Statistics (the "Bureau"). If the Bureau ceases to publish the Consumer
     Price Index, then the successor or most comparable index, as designated by
     API under the Sublease, will be used. It is contemplated by the parties
     hereto that Sublessee will build the Buildings (as such term is defined in
     the Sublease), and that the first Building will be completed several months
     before the second Building is completed. API will not be obligated to pay
     rent until the earlier of (i) January 1, 2000, or (ii) the first of the
     Buildings is completed and a certificate of occupancy for it is issued by
     the City of Houston. Upon completion of the first Building. API will be
     obligated to pay one-half of the rent provided herein (this being $2,708.34
     per month) commencing on the date such Certificate of Occupancy is issued.
     Rent shall continue at such rate until the second Building is completed and
     a Certificate of Occupancy is issued for it, or January 1, 2000, whichever
     is sooner, whereupon the entire rent stipulated herein will become due and
     payable monthly. In any event the entire rent stipulated herein will become
     due and payable monthly commencing on January 1, 2000.

     (b)(5)(1) API further agrees the Government shall be entitled to receive
     fifty percent (50%), without prior demand and without any deduction or
     offset, of any additional rent or any other amounts received or payments
     recovered by API as result of its ground sub-lease, termination or
     sub-lessee's default of the ground sub-lease: or in accordance with the
     terms of any other agreement between API and its sub-lessee relative to the
     occupancy of the Subleased Premises; provided however the Government shall
     not be entitled to any amounts received by API pursuant to Sections 5,
     12.2, 13, 15, 16, 16.4, 18.1, 20.2(a)-(c), 25, and 43 of the sub-lease.

THE ENHANCED-USE LEASE IS FURTHER AMENDED BY THE FOLLOWING PROVISIONS WITH
RESPECT TO THE PREMISES IDENTIFIED IN EXHIBIT A:

     Subject to the provisions in the Enhanced-Use Lease regarding Developer's
     default and the rights of mortgagees provided in such Enhanced-Use Lease,
     in instances where the Enhanced-Use Lease is terminated by reason of
     Developer's default, Sublessee and its successors and assigns, including
     any mortgagee and any purchaser of Sublessee's leasehold interest at
     foreclosure or by deed in lieu of foreclosure shall have the right to
     assume all rights and obligations of the Developer in the Enhanced-Use
     Lease with respect to the Premises identified in the Sublease, provided,
     however, that in the event of such an assumption by Sublessee: (1) the
     rental amount to the Government shall be ONE HUNDRED THIRTY THOUSAND
     DOLLARS ($130,000), subject to escalation as provided herein (with no rent
     being payable to Developer in that event); (2) the term of this Lease will
     be identical to the term of the Sub-Lease including renewal options; (3)
     Paragraphs 6, 13, 14(b), 14(d), 18 and 19 of the Enhanced-Use Lease will
     not be applicable to Sublessee, its successors or assigns, including
     mortgagees; (4) use of the Subleased Premises will be as stated in the
     Sublease; (5) Government agrees that any mortgage or security interest
     upon sublessee's leasehold interest and sublessee's furniture, equipment,
     fixtures and improvements located upon the Subleased Premises on the date
     of assumption of the Enhanced-Use Lease by Sublessee, its successors or
     assigns, shall be and hereby is deemed approved by the Government pursuant
     to Paragraph 24(c) of the Enhanced-Use Lease; (6) Paragraph 24(h) and
     24(i) of the Enhanced-Use Lease will not be applicable to Sublessee, its
     successors, assigns or mortgagees; (7) upon any assumption by Sublessee,
     its successors or assigns, including any mortgagee or purchaser at
     foreclosure or by deed in lieu of foreclosure, its obligations under the
     Enhanced-Use Lease will be limited so that it is
<PAGE>   159

Supplemental Lease Agreement No. 6
Enhanced-Use Lease No. 084B-029-93, Houston, TX
Page 3 of 3

    obligated only to the extent such obligations apply specifically to the
    Subleased Premises and improvements thereon, and not to other real property
    covered by the Enhanced-Use Lease; (8) the obligations of Sublessee, its
    successors or assigns, to pay taxes shall be limited to taxes attributable
    to the Subleased Property; (9) Paragraph 38 of the Enhanced-Use Lease will
    not apply on or after the date of any such assumption by Sublessee, its
    successors or assigns or mortgagees; and in the event the Government shall
    exercise its special repurchase rights under Paragraph 38 of the
    Enhanced-Use Lease prior to any assumption by Sublessee, its successors or
    assigns or mortgagees, then the Government shall allow Sublessee, its
    successors or assigns or mortgagees the continued possession, use and
    enjoyment of the Subleased Premises for so long as Sublessee, its
    successors, assigns, or mortgagees attorn to the Government as its landlord
    and is not in default under the Sublease; and (10) the Government and
    Developer agree that no amendment or modification of the Enhanced-Use Lease
    entered into after the date hereof shall be binding upon Sublessee without
    Sublessee's written consent.

    The Government agrees that, upon request by Sublessee, from time to time,
    it will furnish estoppel certificates to such persons, as Sublessee may
    reasonably request certifying (1) the fact that the Enhanced Use Lease is
    unmodified and in full force and effect or, if there have been
    modifications thereto, that the Enhanced Use Lease is in full force and
    effect and stating the date and nature of such modifications; (2) the date
    to which the rental and other sums payable under the Enhanced Use Lease
    have been paid; (3) that there are no current defaults under the Enhanced
    Use Lease by either Lessor or Lessee, except as specified in the statement;
    and (4) such other matters reasonably agreed to by Government and Sublessee.

    The Government agrees that this Supplemental Lease Agreement is made not
    only for the benefit of the Government and Developer, but also for the
    benefit of Sublessee, its successors and assigns, expressly including any
    mortgagee or purchaser at foreclosure or by deed in lieu of foreclosure.

    All proposed development and construction is to be reviewed and approved by
    the Department in accordance with the Enhanced-Use Lease.

    This proposal is specific to this sublease proposal. In event of early
    termination of the sublease or other sublease of such space by the
    Developer, such shall be negotiated pursuant to Section 10.b. of the Lease.

ALL OTHER TERMS AND CONDITIONS OF THE ENHANCED-USE LEASE SHALL REMAIN IN FORCE
AND EFFECT.
<PAGE>   160

                                                                       EXHIBIT A

                         METES AND BOUNDS DESCRIPTION
                            OF 2.500 ACRES OF LAND
                      IN THE D.W.C. HARRIS SURVEY, A-325
                             HARRIS COUNTY, TEXAS

All that certain 2.500 acres of land, out of the 118.831 acre tract described in
the deed from Brittermann Holding Corporation of Texas to the United States of
America, recorded under Volume 1297, Page 87, in the Deed Records of Harris
County, Texas, and out of the 20.11 acre Extract of Lease recorded under File
No. R182150, in the Official Public Records of Real Property of Harris County,
Texas, in the D.W.C. Harris Survey, A-325, Harris County, Texas, and being more
particularly described by metes and bounds as follows: (All bearings based on
the Texas State Plane Coordinate System, South Central Zone)

Commencing at the intersection of the south right-of-way line of Holcombe
Boulevard (width varies) and the west right-of-way line of Almeda Road (F.M.
521) (width varies); THENCE S 14 degrees 53' 21" W - 206.00', along said west
right-of-way line, to a 5/8" iron rod set for the northeast corner and POINT OF
BEGINNING of the herein described tract;

THENCE S 14 degrees 53' 21" W - 330.70', continuing along said west
right-of-way line to a 5/8" iron rod found for the southeast corner of the
herein described tract;

THENCE N 75 degrees 06' 39" W - 329.30', to a 5/8" iron rod set for the
southwest corner of the herein described tract;

THENCE N 14 degrees 53' 21" E - 330.70', to a 5/8" iron rod set for the
northwest corner of the herein described tract;

THENCE S 75 degrees 06' 39" E - 329.30' to the POINT OF BEGINNING of the herein
described tract and containing 2.500 acres of land.

Compiled by:

G.P. SURVEYORS, a division of               [STATE OF TEXAS SEAL]
PATE ENGINEERS, INC.
Job No. 684-002-52

Original Issue Date:
August 5, 1998
                                          /s/   [illegible]
                                        --------------------------------
                                                Certificate Date:
                                                 August 5, 1998

THIS LEGAL DESCRIPTION IS ISSUED AS "PART TWO", IN CONJUNCTION WITH THE LAND
TITLE SURVEY BY G. P. SURVEYORS LAST CERTIFIED AUGUST 5, 1998. REFERENCE IS
HEREBY MADE TO THE SURVEY AS "PART ONE".
<PAGE>   161

       UNIFORM COMMERCIAL CODE - FINANCING STATEMENT - UCC 1

This instrument is prepared as, and is intended to be, a Financing Statement,
complying with the formal requisites therefor, as set forth in the Texas
Business and Commerce Code, Article 9 (also known as the Texas Uniform
Commercial Code - Secured Transactions), and, in particular, Section 9.402
thereof.

                       FINANCING STATEMENT

1.   Debtor - Name and Mailing Address:

     TMX REALTY CORPORATION
     301 Congress Avenue, Suite 1850
     Austin, Texas 78701

2.   The name and address of the secured party ("Secured Party") is:

     RIVERWAY BANK
     Five Riverway
     Houston, Texas 77056

3.   This Financing Statement covers the following types (or items) of property
     (the" Collateral"):

     Construction Contracts: Any and all contracts, subcontracts, and
     agreements, written or oral, between Debtor and any other party, and
     between parties other than Debtor, in any way relating to the construction
     of the Improvements (as hereinafter defined) on the Land (as hereinafter
     defined) or the supplying of material (specially fabricated or otherwise),
     labor, supplies, or other services therefor.

     Contracts: All of the right, title and interest of Debtor in, to, and under
     any and all (i) Contracts (herein so called) for the purchase or sale of
     all or any portion of that certain real property described in Exhibit "A"
     attached hereto and made a part hereof for all purposes (the "Land"),
     together with all Improvements (herein so called) thereon and appurtenances
     thereto (the Improvements, together with the Land are collectively called
     the "Mortgaged Property"), whether such Contracts are now or at any time
     hereafter existing, including all amendments and supplements to and
     renewals and extensions of the Contracts at any time made, and together
     with all payments, earnings, income, and profits arising from the sale of
     all or any portion of the Mortgaged Property or from the Contracts and all
     other sums due or to become due under and pursuant thereto and together
     with any and all earnest money, security, letters of credit or other
     deposits under any of the Contracts; *ii) contracts, licenses,

                                       1

THIS IS TO CERTIFY                  RETURN TO:
THAT THIS IS A TRUE AND CORRECT
[ILLEGIBLE]                         PARTNERS TITLE COMPANY
                                    712 Main St., Suite 2000E
BY /s/ [ILLEGIBLE]                  Houston, TX 77002-3218
<PAGE>   162
permits and living unit equivalents of water, wastewater, and other utility
services whether executed, granted, or issued by a private person or entity or
a governmental or quasi-governmental agency, which are directly or indirectly
related to, or connected with, the development of the Mortgaged Property,
whether such contracts, licenses, and permits are now or at any time hereafter
existing, including without limitation, any and all living unit equivalents of
water, wastewater, and other utility services, certificates, licenses, zoning
variances, permits, and no-action letters from each governmental authority
required: (a) to evidence full compliance by Debtor and all improvements
constructed or to be constructed on the Mortgaged Property with all legal
requirements applicable to the Mortgaged Property, and (b) to complete
construction of any improvements on the Mortgaged Property; (iii) any and all
right, title, and interest Debtor may have in any financing arrangements
relating to the financing of the purchase of all or any portion of the
Mortgaged Property by future purchasers; (iv) all plans, specifications, and
drawings prepared for the Mortgaged Property, including all amendments and
supplements to and renewals and extensions of such contracts any time made, and
together with all rebates, refunds or deposits, and all other sums due or to
become due under and pursuant thereto and together with all powers, privileges,
options, and other benefits of Debtor under such contracts; and (v) all other
contracts which in any way relate to the use, enjoyment, occupancy, operation,
maintenance, or ownership of the Mortgaged Property (save and except any and
all leases, subleases, or other agreements pursuant to which Debtor is granted
a possessory interest in the Land), including but not limited to engineer's
contracts, architect's contracts, maintenance agreements and service contracts.

Fixtures: All materials, supplies, equipment, systems, apparatus, and other
items now owned or hereafter acquired by Debtor and now or hereafter attached
to, installed in, or used in connection with (temporarily or permanently) the
Mortgaged Property, which are now owned or hereafter acquired by Debtor and are
now or hereafter attached to the Mortgaged Property and needed in the operations
thereof, and including, but not limited to, any and all motors, engines,
boilers, furnaces, pipes, sprinkler systems, fire extinguishing apparatus and
equipment, water tanks, heating, ventilating, refrigeration, plumbing,
lighting, transportation (of people or things, including, but not limited to,
stairways, elevators, escalators, and conveyors), incinerating, air
conditioning and air cooling equipment and systems, gas and electric machinery,
and water, gas, electrical, storm and sanitary sewer facilities, and all other
utilities whether or not situated in easements, together with all accessions,
appurtenances, replacements, betterments, and substitutions for any of the
foregoing and the proceeds thereof.

Leases: Any and all leases, subleases, sub-subleases licenses, concessions, or
other agreements (written or oral, now or hereafter in effect) which grant to
third parties a possessory interest in and to, or the right to use, all or any
part of the Mortgaged Property, together with all security and other deposits
made in connection therewith.

                                       2

<PAGE>   163
    Personalty: All of the right, title and interest of Debtor in and to the
    Plans, all building and construction materials and equipment, insurance
    proceeds, accounts, contract and subcontract rights pertaining to the
    buildings, all refundable, returnable, or reimbursable fees, deposits or
    other funds or evidences of credit or indebtedness deposited by or on
    behalf of Debtor in connection with the Mortgaged Property with any
    governmental agencies, boards, corporations, providers of utility services,
    public or private, including specifically, but without limitation, all
    refundable, returnable, or reimbursable tap fees, utility deposits,
    commitment fees and development costs, any awards, remunerations,
    reimbursements, settlements, or compensation heretofore made or hereafter
    to be made by any Governmental Authority pertaining to the Land,
    Improvements, Fixtures, Construction Contracts, including but not limited
    to those for any vacation of, or change of grade in, any streets affecting
    the Land or the Improvements and those for municipal utility district or
    other utility costs incurred or deposits made in connection with the Land;
    which are now owned or hereinafter acquired by Debtor, which are now or
    hereafter situated in, on, or about the Land or the Improvements, or used
    in or necessary to the complete and proper planning, development,
    construction, financing, use, occupancy, or operation thereof, or acquired
    (whether delivered to the Land or stored elsewhere) for use in or on the
    Land or the Improvements, together with all accessions, replacements, and
    substitutions thereto or therefor and the proceeds thereof.

    Rents: All of the rents, revenues, income, proceeds, profits, security and
    other types of deposits, and other benefit paid or payable by parties to
    the Leases other than Debtor for using, leasing, licensing, possessing,
    operating from, residing in, selling, or otherwise enjoying the Mortgaged
    Property.

    Excluded Property: Any other provision hereof notwithstanding, there is
    hereby excepted from the definition of the "Mortgaged Property" and the
    "Collateral" and from all liens and security interests held by Secured
    Party all property of Debtor described on Exhibit "B" attached hereto,
    which Exhibit "B" is incorporated herein for all purposes.

4.  Proceeds of the Collateral are also covered.

5.  Number of additional sheets presented: two (2).

    DATED as of the 23rd day of November, 1998.

                                               "DEBTOR"

                                               TMX REALTY CORPORATION,
                                               a Delaware corporation

                                               By:  /s/ JAMES W. ALBRECHT, JR.
                                                    --------------------------

                                               Name:    James W. Albrecht, Jr.
                                                    --------------------------

                                               Title: Chief Financial Officer
                                                     -------------------------

                                       3

<PAGE>   164
                                  EXHIBIT "A"

Being a tract or parcel containing 2.619 acres (114,086 square feet) of land
situated in the D W C Harris Survey, Abstract Number 325, Harris County, Texas,
and being part of and out of that certain called 118.831 acres, described in
deed to the United States of America, as recorded in Volume 1297, Page 87, Deed
Records of Harris County, Texas, said 2.619 acre tract being more particularly
described as follows (all bearings and coordinates are based on the Texas State
Plane Coordinate System; South Central Zone; all distances and coordinates are
surface and may be converted to grid by multiplying by a combined scale factor
of 0.9998632):

COMMENCING at a 5/8-inch iron rod with plastic cap set marking the intersection
of the south right-of-way (ROW) line of Holcombe Boulevard with the west ROW
line of Almeda Road, and having surface coordinates of X=3,147,967.40,
Y=698,487.10, thence:

     South 14 degrees 53'21" West, with said west ROW line, a distance of 206.00
     feet to a set 5/8-inch iron rod with plastic cap;

     North 75 degrees 06'39" West, a distance of 329.30 feet to a 5/8-inch iron
     rod with plastic cap set marking the POINT OF BEGINNING and northeast
     corner of the herein described tract;

THENCE, SOUTH 14 degrees 53'21" West, a distance of 330.70 feet to a 5/8-inch
iron rod with plastic cap set marking the southeast corner of the herein
described tract;

THENCE, NORTH 75 degrees 06'39" West, a distance of 432.78 feet to a 5/8-inch
iron rod with plastic cap set marking the southwest corner of the herein
described tract;

THENCE, NORTH 41 degrees 44'27" East, a distance of 334.23 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, NORTHEASTERLY, with a curve to the left having a radius of 760.00 feet,
a central angle of 03 degrees 35'59", an arc length of 47.75 feet, and a chord
which bears North 39 degrees 56'28" East, 47.74 feet to an "X" in concrete set
marking the most northwesterly corner of the herein described tract;

THENCE, SOUTHEASTERLY, with a non-tangent curve to the left having a radius of
87.50 feet, an arc length of 93.13 feet, a central angle of 60 degrees 59'01",
and a chord which bears South 58 degrees 25'28" East, 88.80 feet to a 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH 88 degrees 54'58" East, a distance of 27.76 feet to a 5/8-inch
iron rod with plastic cap set marking the beginning of a tangent curve;

THENCE, EASTERLY, with a curve to the right having a radius of 281.50 feet, an
arc length of 67.83 feet, a central angle of 13 degrees 48'19", and a chord
which bears South 82 degrees 00'48" East, 67.66 feet to a 5/8-inch
iron rod with plastic cap set marking a point of tangency;

THENCE, SOUTH 75 degrees 06'39" East, a distance of 82.41 feet to the POINT OF
BEGINNING and containing 2.619 acres (114,086 square feet) of land (this
description is based on a Land Title Survey an plat prepared by Terra Surveying
Company, Inc. Project Number 0163-9801-S).
<PAGE>   165
                                  EXHIBIT "B"

     There is hereby excepted from the definition of the "Mortgaged Property",
and the "Collateral", and from all liens and security interests held by Secured
Party, all property of Debtor which is not a part of the plumbing, electrical,
heating, cooling, ventilation, standard lighting, ceiling tile, sprinkler
equipment and related equipment together with other fixtures and equipment
necessary for the use and operation of the buildings for general purposes and
all property (save and except the foregoing) which is not permanently attached
or affixed to the building and is not an integral part of the building and
needed for the same to be functional as an office building. Without limiting the
foregoing sentence, the property described below is excepted from said
definitions of "Mortgaged Property" and "Collateral" and shall not be in any way
secured or encumbered by any lien or security interest held by Secured Party.

                               Excluded Property

Furniture
Computers and related equipment, computer network equipment and software
Laboratory equipment
Production Equipment
Modular clean room units
Telephone equipment
Office equipment
Artwork
Decorative items
Plants
Inventory, including raw materials, work in progress and finished goods
Office supplies
Lab notebooks
Electronic media
Backup power generator
Cold storage equipment
Waste treatment equipment

Whether now owned or hereafter acquired<PAGE>   1
                                                                 EXHIBIT 10.7(b)

                                 LEASE AGREEMENT

THE STATE OF TEXAS         )

COUNTY OF HARRIS           )

         THIS LEASE AGREEMENT ("Lease") made and entered into as of this 7th day
of June, 1996, by and between PLAZA DEL ORO BUSINESS CENTER (hereinafter called
"Landlord") and Introgen Therapeutics, Inc., a Delaware corporation and its
subsidiaries and affiliates (hereinafter called "Tenant").

                               W I T N E S S E T H

                                    ARTICLE I

         A. Leased Premises. Subject to and upon the terms and conditions set
forth herein, and each in consideration of the duties, covenants and agreements
of the other hereunder, Landlord hereby leases, demises and lets to Tenant and
Tenant hereby leases from Landlord those certain premises consisting of a space
containing an area of 2,405 square feet, more or less, (hereinafter called the
"Leased Premises") in the building known as Building A (hereinafter called the
"Building") located upon the lot, tract or parcel of land situated in Harris
County, Texas, more particularly described by metes and bounds on Exhibit "A"
attached hereto and made a part hereof for all purposes and presently designated
as PLAZA DEL ORO BUSINESS CENTER, an office-warehouse center (hereinafter called
the "Center") consisting of the building and four (4) other buildings
(hereinafter called the "Other Buildings"), all as shown on the site plan
attached hereto as Exhibit "B" and made a part hereof for all purposes. The
Leased Premises are outlined in red on the building plan attached hereto as
Exhibit "C" and made a part hereof for all purposes.

         B. Use in Common. Subject to and upon the terms and conditions set
forth herein, the use and occupancy by Tenant of the Leased Premises shall
include the use in common with other tenants in the Building and the Other
Buildings, and their employees, agents, contractors, guests and invitees, of the
common areas of the Center (hereinafter called the "Common Areas") including,
without limitation, the sidewalks, landscaped areas, service areas, automobile
driveways, service driveways, access roads and parking areas shown on Exhibit
"B", and the easements and rights of way appurtenant to the center.

                                   ARTICLE II

         A. Term. Subject to and upon the terms and conditions set forth herein,
this Lease shall continue in force for a term of One (1) year (hereinafter
called the "Term"), commencing on the 15th day of June, 1996, and expiring on
the 31st day of June, 1997. In the event that the Leased Premises should not be
ready for occupancy by the said commencement date for any reason, Landlord shall
not
<PAGE>   2
be liable or responsible for any claims, damages or liabilities in connection
therewith or by reason thereof and the commencement date of this Lease shall be
the date that the Leased Premises become ready for occupancy by Tenant in
accordance with Paragraph F(2) of Article III hereof or the date Tenant accepts
the Leased Premises, whichever shall first occur. In such event Landlord and
Tenant will, at the request of either, execute a memorandum specifying the
revised commencement date of the Term. In the event the commencement date or
revised commencement date shall be a date other than the first day of a calendar
month, the Term shall be for one (1) full year plus the number of days remaining
in the month in which the Term commences.

         B. Use. The Leased Premises are to be used and occupied by Tenant
solely for the purpose of office and laboratory use and no other purpose.

         C. Net Rentable Area. As used herein, the term "Net Rentable Area of
the Leased Premises" shall include all space within the demising walls of the
Leased Premises as measured from the mid-point of the demising walls; the term
"Net Rentable Area of the Building" shall mean all space within the exterior
walls of the Building, as measured from the mid-point of said walls; and the
term "Net Rentable Area or the Center" shall mean all space within the exterior
walls of the Building and Other Buildings, as measured from the mid-point of
said walls. Based upon said definitions and for the purposes hereof, the Net
Rentable Area of the Leased Premises shall be deemed to be Seven and Nine One
Hundredths percent (7.9%) of the Net Rentable Area of the Building and the Net
Rentable Area of the Leased Premises shall be deemed to be One and Fifty-Four
One Hundredths percent (1.54%) of the Net Rentable Area of the Center.

         D. Base Rental and Security Deposit.

                  (a) Tenant promises and agrees to pay to Landlord, annually
throughout the Term, subject to adjustments as hereinafter provided, base rental
(hereinafter called the "Base Rental") in the amount of Twenty-four Thousand and
no/100 Dollars ($24,000.00). Base rental shall be due and payable in twelve (12)
equal monthly installments of Two Thousand and no/100 Dollars ($2,000.00) each,
on the first day of each calendar month during each year of the Term, and Tenant
hereby agrees to so pay such rent to Landlord at Landlord's address as provided
herein, monthly in advance, without demand, deduction or set-off. If the Term
commences on other than the first day of a calendar month, Tenant shall pay on
such commencement date a pro rata payment which shall be in addition to the full
monthly installments payable during the Term. In accordance with the terms of
this paragraph D of Article II, payment has been made and receipt is hereby
acknowledged of an amount sufficient to cover Base Rental as due and payable for
the first full calendar month and prorated rent for any prior partial month of
the Term.

                  (b) In addition, Tenant agrees to deposit with Landlord on the
date hereof the sum of Two Thousand and no/100 Dollars ($2,000.00), which sum
shall be held by Landlord, without obligation for interest, as security for the
performance of Tenant's covenants and obligations under this Lease, it being
expressly understood and agreed that such deposit is not an advance rental
deposit or a measure of Landlord's damages in case of Tenant's default. Upon the
occurrence of any event of default by Tenant, Landlord may, from time to time,
without prejudice to any other remedy provided

                                       -2-
<PAGE>   3
herein or provided by law, use such funds to the extent necessary to make good
any arrears of rent or other payments due Landlord hereunder, and any other
damage, injury, expense or liability caused by such event of default; and Tenant
shall pay to Landlord on demand the amount so applied in order to restore the
security deposit to its original amount. Although the security deposit shall be
deemed the property of Landlord, any remaining balance of such deposit shall be
returned by Landlord to Tenant at such time after termination of this Lease that
all of Tenant's obligations under this Lease have been fulfilled.

         E. Base Rental Adjustment. Base Rental may be increased or decreased
throughout the Term as follows:

                  1. For all purposes hereof, "Base Year" shall mean the
calendar year 1995.

                  2. Base Rental includes a component consisting of the Basic
Cost (as hereinafter defined) and the Basic Cost for the Base Year is hereby
stipulated to be One and 30/100 Dollars ($1.30) per square foot of Net Rentable
Area contained in the Center.

                  3. Within sixty (60) days after the commencement of each
calendar year (except the Base Year) during the Term, Landlord shall provide
Tenant with a written estimate of the Basic Cost for such calendar year, and the
Base Rental for such calendar year shall be increased by the amount, if any, of
the excess of Tenant's proportionate share of the Basic Cost for the Base Year,
but in no event shall there be any Base Rental Adjustment during the primary
lease term.

                  4. Within one hundred eighty (180) days after the end of each
calendar year (except the Base Year) of the Term, Landlord shall furnish Tenant
with a statement showing the actual Basic Cost for the calendar year just ended.
An amount equal to the difference between Tenant's proportionate share of the
actual Basic Cost and Tenant's proportionate share of the estimated Basic Cost
for the calendar year just ended shall be paid by Landlord to Tenant or by
Tenant to Landlord, as appropriate, within fifteen (15) days of the delivery of
such statement, to the end that Landlord shall receive, and Tenant shall pay, as
a portion of Base Rental for each calendar year during the Term, Tenant's
proportionate share of any increases in the Basic Cost over the Basic Cost for
the Basic Year. The obligations of Landlord and Tenant regarding any adjustment
for increases in the Basic Cost for the year in which this lease expires or
otherwise terminates shall expressly survive the termination of this Lease.

                  5. Any adjustment of Base Rental shall operate retroactively
and be effective as of the first day of each calendar year.

                  6. As an alternative to the procedure described in
subparagraphs 3, 4, and 5 above, Landlord, at its sole option, may elect to
invoice Tenant annually, within one hundred eighty days (180) days after the end
of each calendar year (except the Base Year) during the Term, for the amount, if
any, of the excess of Tenant's proportionate share of the Basic Cost for the
calendar year just ended over the Basic Cost for the Base Year, and Tenant shall
pay said amount as additional rent within fifteen (15) days after receipt of
such invoice from Landlord.

                                       -3-
<PAGE>   4
                  7. For all purposes hereof, "Tenant's proportionate share"
shall be that proportion which the Net Rentable Area of the Leased Premises
bears to the Net rentable area of the Center.

                  8. Notwithstanding anything contained herein to the contrary,
in no event shall Base Rental be reduced below the amounts specified in Article
II, Paragraph D hereof.

         F. Past Due Rent and Charges. Landlord shall be entitled to collect a
late charge of $5.00 for each day from the date due until the date paid on all
installments of Base Rental or other charges payable by Tenant hereunder which
are not paid within five (5) days after the date due. In addition, all
installments of Base Rental or other charges payable by Tenant hereunder which
are not paid within thirty (30) days after the date due shall bear interest at
the rate of eighteen percent (18%) per annum from the date due until the date
paid. Any election of Landlord to accept the payment of past due installments of
Base Rental and/or other charges payable by Tenant hereunder without the payment
of the late charge and/or interest described herein shall not be deemed a waiver
of Landlord's right to collect said late charge and/or interest in the event of
any subsequent past due installment or installments of Base Rental and/or other
charges payable by Tenant hereunder.

         G. Basic Cost. As used herein, the term "Basic Cost" shall consist of
the following:

                  1. Cost of Landlord's fire and extended coverage and liability
insurance applicable to the Center and the buildings therein;

                  2. All general and special taxes, except taxes based on
income, impositions, assessments and governmental charges, or any substitutions
in lieu thereof, imposed upon the Center and buildings therein, whether federal,
state, county or municipal, and whether by taxing districts or authorities
presently existing or by others subsequently created; and

                  3. Common Area Maintenance Costs, as defined in Article III,
Paragraph C hereof.

         H. Audit. Tenant, at its expense, shall have the right, once each
calendar year, upon thirty (30) days prior written notice to Landlord, to audit
Landlord's books and records relating to this Lease for the Base Year and any
calendar year thereafter.

                                   ARTICLE III

Landlord covenants and agrees with Tenant:

         A. Utilities. To provide, at Landlord's cost, normal water, sanitary
sewer, electricity and gas connections to the Leased Premises from the nearest
water, sanitary sewer, electric and gas mains, laterals and/or trunk lines
serving the Center. Any interruptions or cessation of said services shall not
render Landlord liable in any respect for injury, damage or loss to persons or
property, except in the case of said interruption being caused by Landlords
negligent acts, shall not be

                                       -4-
<PAGE>   5
construed as an eviction of Tenant, shall not work an abatement of rent, and
shall not relieve Tenant from fulfillment of any covenant or agreement hereof.

         B. Maintenance and Repairs to Building. Subject to the provisions of
Article IV, provisions Paragraph C and Article V, Paragraph F hereof, to make,
at Landlord's expense, all repairs and replacements, structural or otherwise,
necessary to keep the roof, foundation and the structural soundness of the
exterior walls of the Building in good repair; provided, however, that the term
"exterior walls" as used herein shall not include any items for which Tenant is
responsible under Article IV, Paragraph C, and nothing contained in this Article
III, Paragraph B shall require Landlord to paint the interior of the Leased
Premises or the interior of the Building or to make any other repairs or
replacements to the Building at any time except when such other repairs and
replacements are required under this Article III, Paragraph B, or under the
provisions of Article V, Paragraph F hereof. Landlord's liability hereunder
shall be limited to the cost of such repairs. Any entry for the purpose of
making such repairs shall not affect Tenant's obligations under this Lease and
shall not constitute any ground for abatement of any rentals or other charges
payable by Tenant hereunder, and Tenant hereby expressly waives all claims for
inconveniences, disturbance, interruption and/or loss of Tenants business or
other damages due to said entry, unless caused by the gross negligence of
Landlord or its agents.

         C. Common Area Maintenance and Repairs. To keep swept in a neat, clean
condition the common areas, untidiness due to normal and usual use only
excepted, and in addition, to (i) repair the Common Areas, including, without
limitation, surface of the driveways, sidewalks, service areas, and parking
areas, (ii) keep the parking and service areas stripped, and (iii) maintain the
landscaped areas, including landscape replacement. Said maintenance and repairs
shall include, as more specifically set forth below, all repairs and
replacements and the supplies and materials therefor, which in Landlord's
reasonable judgment are necessary to preserve the utility of the Common Areas in
the condition same were in at the time of completion, reasonable wear and tear
only excepted.

                  As used herein, "Common Area Maintenance Costs" shall mean all
costs and expenses of every kind paid or incurred during the Term in connection
with the operation and upkeep of Common Areas, including, without limitation,
sidewalks, landscaped areas, service areas, automobile driveways, service
driveways, parking areas, signs, lighting, sweeping, cleaning, draining and
striping the parking and service areas, and where necessary, the cost of
replacing any of said common facilities, and the cost of policing and protecting
same. In addition to the foregoing, and without limiting the generality thereof,
the Common Area Maintenance Costs shall include: wages paid to employees or
contractors of Landlord hired for the purpose of maintaining the Common Areas,
premiums for common area workmen's compensation and common area employees'
liability insurance, common area unemployment taxes, common area Social Security
taxes, personal property taxes for Common Areas, common area licenses and
permits, common area supplies, electricity, lighting fixtures and bulbs, and
rentals paid for equipment rented or leased or used in the operation and
maintenance thereof and a fee to be paid Landlord, or Landlord's designee, for
the administrative expense of maintaining the Common Areas, provided that said
fee shall not exceed five percent (5%) of all other common Area Maintenance
Costs for any calendar year.

                                       -5-
<PAGE>   6
         D. Keys. To furnish Tenant, free of charge, with two (2) keys for each
door entering the Leased Premises. Additional keys will be furnished at a charge
by Landlord equal to its cost plus fifteen percent (15%) on an order signed by
Tenant or Tenant's authorized representative. All such keys shall remain the
property of Landlord. No additional locks shall be allowed on any door of the
Leased Premises without the written consent of Landlord, and in the event
Landlord gives its consent, Tenant shall furnish Landlord a key for each such
additional lock upon the installation thereof. Tenant shall not make, or permit
to be made, any duplicate keys except those furnished by Landlord. Upon
termination of this Lease, Tenant shall surrender to Landlord all keys to the
Leased Premises and give to Landlord the combination of all locks for safes,
safe cabinets and vault doors, if any, in the Leased Premises.

         E. Signs. That Tenant shall have the right to install sign letters,
numerals, emblems, trademarks, insignia or other designs upon certain areas and
spaces designated by Landlord on the Leased Premises in accordance with the sign
criteria set forth in Exhibit "D" attached hereto and made a part hereof for all
purposes.

         F. Construction. That the condition of the Leased Premises as of the
date of this Lease is such that the Shell of the Building (as hereinafter
defined) and certain Leasehold Improvements are completed. In this connection,
Landlord and Tenant have agreed and do hereby agree as follows:

                  1. The definitions set out below apply to the following terms
as those terms are used in this Lease, unless the context clearly requires a
different meaning:

                           (a) "Shell of Building" means the building,
consisting of beams, structural steel, exterior walls, roof, paint on exterior
walls and trim, interior finish and paint in certain areas of the Building that
are common to the Building as a whole, such as entries and corridors exterior to
the Leased Premises and certain utility service lines, including electrical and
sanitary sewer service to the Building, sidewalks, parking area and other common
areas and facilities, all as shown on the approved plans and specifications (as
hereinafter defined).

                           (b) "Leasehold Improvements" means all existing
improvements as shown on the architectural floor plan attached hereto as
"Exhibit "E" and made a part hereof for all purposes and any other improvements
required by Tenant and approved by Landlord.

                  2. Subject to the foregoing terms and agreements of this
Lease, Tenant agrees to complete any additional improvements in a good and
workmanlike manner and in accordance with the plans and specifications furnished
by Tenant and approved by Landlord. All improvements or changes in addition to
the existing Leasehold Improvements on Exhibit "E" shall be for Tenant's account
and Tenant shall pay the cost thereof. Tenant agrees that upon expiration of
this lease, at Landlord's request Tenant shall, at Tenant's expense, cause the
removal of any portion of any additional leasehold improvements made by Tenant,
and repair any affected part of the existing leasehold improvements.

                                       -6-
<PAGE>   7
                  3. The rights of Tenant in and to the Leasehold Improvements,
when completed, shall be limited to Tenant's leasehold estate therein, which is
a possessory right, subject to all of the terms and conditions of this Lease,
and the Leasehold Improvements shall constitute a part of the fee remainder,
subject to Tenant's right of possession and use during the Term, and
notwithstanding that Tenant may have contributed to the initial cost or to the
subsequent repair or replacement thereof. Under no circumstances shall Tenant's
rights in the Leasehold Improvements entitle Tenant to collaterally assign,
grant a security interest in or remove the Leasehold Improvements, or any part
thereof, at any time during the Term.

         G. Quiet Enjoyment. That so long as Tenant shall pay all Base Rental,
additional rent and other charges payable by Tenant hereunder, and shall observe
and abide by all reasonable regulations regarding use of the Center, the
Building, the Other Buildings and the Common Areas, and shall observe and
perform all of the covenants on Tenant's part to be observed and performed
hereunder, then, subject to the limitations upon the title to the Center set
forth on Exhibit "G" attached hereto and made a part hereof for all purposes,
Tenant shall peaceably and quietly hold and enjoy the Leased Premises for the
entire term without interruption by Landlord or any person or persons lawfully
or equitably claiming by, through or under Landlord. It is understood and agreed
that this covenant and any and all other covenants of Landlord contained in this
Lease shall be binding upon Landlord and its successors and assigns only with
respect to breaches occurring during its and their respective ownership of the
Landlord's interest hereunder. In addition, Tenant specifically agrees to look
solely to Landlord's interest in the Center for the recovery of any judgment
from Landlord, it being expressly agreed and understood that Landlord shall
never be personally liable for any such judgment.

         H. Parking. Tenant shall have the right to six (6) parking spaces
located in the Center as shown in Exhibit B hereto. Landlord may designate
additional parking at an easement adjacent to Building B and at the rear of
Tenants Leasehold. Landlord reserves the right from time to time to assign, or
reassign, the location of such parking spaces in any manner that Landlord in
Landlord's sole discretion, deems more beneficial to the operation of the
Center. Tenant agrees that it will employ reasonable efforts to prevent the use
by Tenant's employees and visitors of any parking spaces allocated to other
tenants. Landlord reserves the right to promulgate rules and regulations for the
use of all parking areas at any time during the term of this Lease.

                                   ARTICLE IV

Tenant covenants and agrees with Landlord:

         A. Payment. To pay all Base Rental, additional rental and other charges
provided to be paid to Landlord hereunder at the times and in the manner herein
provided.

         B. Utility Payments. To pay all charges for water, sanitary sewer,
electricity, gas and telephone service used in, on or about the Leased Premises
and all maintenance charges for said utilities as follows:

                                      -7-
<PAGE>   8
                  1. Tenant promises and agrees to pay directly to the utility
                     companies, within thirty (30) days after receipt statement
                     for services, all charges for electricity, gas and
                     telephone service used in, on or about the Leased Premises
                     and all maintenance charges therefor.

                  2. Tenant promises and agrees to pay Landlord, within ten (10)
                     days after receipt of Landlord's statement therefor,
                     Tenant's proportionate share of all charges for water and
                     sanitary sewer services furnished to the Building provided,
                     however, that landlord reserves the right, at its sole
                     option, to install a separate flow meter on and for the
                     Leased Premises, and in such event, Tenant promises and
                     agrees to pay to Landlord within ten (10) days after
                     receipt of Landlord's statement therefore all charges for
                     water and sanitary sewage services furnished to the Leased
                     Premises. For purposes of the forgoing, Tenant's
                     proportionate share of all water and sanitary sewer charges
                     furnished to the Building shall be that proportion which
                     the Net Rentable area of the Leased Premises bears to the
                     Net Rentable Area of the Building, less any portion thereof
                     separately metered.

         C. Repairs and replacements. To make, at its sole cost and expense, all
repairs and replacements to the Building (except repairs and replacements for
which Landlord is expressly obligated under Article III, Paragraph B) and the
Leased Premises, and the fixture, appurtenances and equipment therein, as and
when needed to preserve them in good working order and condition.
Notwithstanding Landlord's obligations under Article III Paragraph B any damage
or injury to the Leased premises and to its fixtures, appurtenances and
equipment caused by Tenant's negligence or the negligence of Tenant's employees,
agents contractors, guests or invitees, or moving property in or out of the
Building by installation or removal of furniture, fixtures or other property,
shall be repaired or replaced promptly by Tenant at its sole cost and expense,
which repairs and replacements shall be in quality and class equal to the
original work or installations.

         Without limiting the generality of the foregoing, Tenant shall, at its
sole cost and expense, repair and/or replace all damaged windows, glass and
plate glass, doors, any specific office or warehouse front, interior walls, any
finish conditioning equipment and systems in and for the Leased Premises, water,
sanitary sewer, electricity and gas lines to the point of connection to the
Leased Premises (provided that any damage to the mains, laterals or trunk lines
from the point of connection to the Leased Premises caused by the Tenant or its
employees, agents, contractors, guests or invitees, shall be Tenant's
responsibility), plumbing and electrical work and fixtures, and shall suffer and
permit no waste; provided however, that Tenant shall not be obligated to repair
any damage caused by fire, tornado, or other casualty covered by fire and
extended coverage provisions of Landlord's fire and extended coverage insurance
policy.

         If Tenant fails to perform Tenant's obligations under this Article IV,
Paragraph C, Landlord may, at Landlord's option, enter upon the Leased Premises
after ten (10) days prior written notice to Tenant, and cause all necessary
repairs and/or replacements to be made, and the cost thereof shall be due and
payable to Landlord within ten (10) days after receipt of Landlord's statement
therefor.

                                       -8-
<PAGE>   9
         D. Tenant's Property and Liens. That Tenant shall be responsible for
and shall pay, before same become delinquent, all federal, state, country, and
municipal taxes assessed against any leasehold interest and all personal
property of any kinds owned by or placed in, on or about the Leased premises by
Tenant during the Term, including, without limitation, any additional leasehold
improvements or alterations made by Tenant, and all furnishings, equipment,
trade fixtures, inventory, and merchandise of Tenant. Tenant shall neither
permit nor suffer an involuntary lien to be filed or affixed against the Leased
Premises, any part thereof or any fixture attached thereto, whether same be
movable or not, and shall not voluntarily grant any lien or security interest
therein. In the event any such voluntary or involuntary lien, including, without
limitation, any mechanic's lien and tax lien, shall be filed and/or affixed
against the Leased Premises, any part thereof of any fixture attached thereto,
including, without limitation, items of work and improvement comprising the
interior (notwithstanding that same may or might constitute a part of the fee
remainder), and Tenant has not caused same to be released and discharged of
record within twenty (20) days after notice and demand by Landlord for the
release and discharge thereof, Landlord may, at its option, pursue the rights
and remedies provided in Article V, Paragraph H hereof without the necessity of
any further notice or demand, or Landlord may cause same to be vacated or
released either by paying the amount claimed to be due or by procuring the
release of such lien by giving security or in such other manner provided by law.
If Landlord elects to effect the release and discharge of record of such lien,
Tenant shall repay to Landlord, immediately upon demand, all such sums disbursed
or deposited by Landlord pursuant to the foregoing provision of this paragraph.
Nothing contained herein, however, shall imply any consent or agreement on the
part of Landlord or anyone holding under Landlord to subject Landlord's interest
to liability under any mechanics or other lien law, regardless of whether the
performance of the furnishing of such work, labor, services or materials to
Tenant or anyone holding under Tenant shall have been consented to by Landlord.

         All furnishings, equipment, trade fixtures and any other property
necessary for the proper operation of Tenant's business shall be furnished and
installed by Tenant at its sole cost and expense unless specifically provided to
the contrary herein. All property stored or warehoused at the Leased Premises
shall be stored or warehoused at the risk of Tenant only, and Tenant shall hold
Landlord harmless from any claims arising out of damage to the same, including
subrogation claims by Tenant's insurer, if any, unless such damage shall be
caused by the gross negligence of Landlord.

         E. Surrender. Not to commit or allow any waste or damage to be
committed on any portion of the Leased Premises, the Building, the Other
Buildings, or the Center, and at the expiration or earlier termination of this
Lease, to surrender the Leased Premises to Landlord in as good condition as at
the date of possession by Tenant, ordinary wear and tear expected; and upon such
expiration or earlier termination of this Lease, Landlord shall have the right
to re-enter and resume possession of the Leased Premises.

         F. Assign and Sublet. Not to assign this Lease or sublet the Leased
Premises, or any portion thereof, without the prior written consent of Landlord,
and any attempted assignment or subletting without such consent, whether express
or by operation of law, shall be void. Landlord and Tenant specifically agree
that in the event of any approved assignment or subletting, the rights of any
such assignee or subtenant of Tenant herein to the use and occupancy of the
Leased Premises shall be

                                       -9-
<PAGE>   10
subject to all of the terms, conditions and provisions of this Lease, including,
without limitation, restrictions on use and the covenant to pay Base Rental,
additional rent and other charges payable by Tenant hereunder, and Landlord may
collect Base Rental, additional rent and other charges payable by Tenant
hereunder directly from such assignee or subtenant and apply the amount so
collected to the rents herein reserved. Any consent to or recognition of any
such assignment or subletting, or a release of Tenant, or any guarantor or
Tenant's performance hereunder, from further performance by Tenant of covenants
undertaken to be performed by Tenant herein, and Tenant will remain liable and
responsible for all rents and other obligations herein imposed upon Tenant. In
the event Landlord shall sell or convey the Leased Premises, the grantee shall
take such property subject to the terms hereof and shall be subrogated to all
for the rights and privileges of Landlord hereunder.

         G. Alterations. Not to make or allow to be made any alterations or
physical additions in or to the Leased Premises without first obtaining the
written consent of Landlord. Upon the termination of this Lease by lapse of time
or otherwise, all such alterations, physical additions or improvements, and/or
fixtures furnished and installed by Tenant which are permanently attached to the
Leased Premises, including all heating and air conditioning equipment, shall, at
Landlord's option, become a part of the fee remainder; or in the alternative,
Landlord may require Tenant to remove such property, as well as Tenant's
moveable personal property, promptly upon the termination of this Lease and
repair, at Tenant's sole expense, any damage to the Leased Premises caused
thereby and Tenant's obligation to so repair shall expressly survive the
terminate of this Lease.

         H. Lawful use. Not to occupy or use, or permit the occupancy or use of,
the Leased Premises or any portion thereof for any purpose other than that
stated in Paragraph B of Article II hereof and in no event for any business or
purpose which is unlawful, disreputable or deemed to be extra hazardous on
account of fire, or permit anything to be done which would in any way increase
the rate of fire insurance coverage on the Building and/or its contents.

         I. Rules. To comply with all reasonable laws, ordinances, orders, rules
and regulations (state, federal, municipal and other agencies or bodies having
any jurisdiction thereof) in effect now or in the future, relating to the use,
condition or occupancy of the Leased Premises. Tenant will comply with all rules
of the Building, the Other Buildings and the Center, which may be adopted by
Landlord from time to time for the safety, care and cleanliness of the Leased
Premises, the Building, the Other Buildings and the Center, and for preservation
for good order therein, all of which will be sent by Landlord to Tenant in
writing and shall be thereafter carried out and observed by Tenant.

         J. Entry. To permit Landlord or its agents or representatives the right
of entry into and upon any part of the Leased Premises at all reasonable hours
to inspect same, clean or make repairs, alterations or additions thereto, as
Landlord may deem necessary or desirable, and Tenant shall not be entitled to
any abatement or reduction of rent by reason of such entry. During the period
that is six (6) months prior to the expiration of the Term, Landlord and
Landlord's authorized agents and representatives shall have the right to enter
the Leased Premises at any time during reasonable business hours for the purpose
of showing the Leased Premises and shall have the right to erect on the Leased
Premises a suitable sign indicating the Leased Premises are available.

                                      -10-
<PAGE>   11
         K. Nuisance. To conduct its business and control its agents, employees,
contractors, invitees and guests in such manner as not to create any nuisance or
to interfere with, annoy or disturb any other tenant or Landlord in its
operation of the Building, the Other Buildings and the Center.

                                    ARTICLE V

         Landlord and Tenant mutually covenant and agree as follows:

         A. Subordination. This Lease is expressly subject, subordinate and
inferior to the matters referred to on Exhibit "G" hereto, as presently or
hereafter affecting the Building, the Other Buildings or Center, and any future
expansion thereof or additions thereto, and to any first mortgage, deed of
trust, security agreement or other lien or encumbrance whatever resulting from
any method of financing or refinancing, presently or henceforth placed upon the
Building or Center, and any future expansion thereof or additions thereto, and
to all advances of money or other value heretofore or hereafter made upon the
Building, the Other Buildings or Center, and to any future expansion thereof or
additions thereto; provided, however, the foregoing provisions of this Paragraph
A of Article V to the contrary notwithstanding, if Landlord or the holder of any
such mortgage, deed of trust, security agreement or other lien or encumbrance
shall elect to make this lease superior, then this lease shall be deemed
superior to any such mortgage, deed or trust, security agreement or other lien
or encumbrance. Without limiting the generality or effect of the foregoing
provisions of this Paragraph A of Article V, Tenant covenants and agrees,
promptly upon request of Landlord, to execute and deliver in the recordable form
provided by Landlord, an acknowledgment of Lease subordination or superiority,
as the case may be, according to the election made by Landlord, or the holder of
such mortgage, deed of trust, security agreement or other lien or encumbrance as
hereinabove provided. Subject to the foregoing provisions of this Paragraph A of
Article V, Landlord reserves the right, without notice to or consent of Tenant,
to assign, pledge or mortgage this Lease and/or any and all rents hereunder as
security for the payment of any mortgage loan, deed of trust loan or other
method of financing or refinancing.

         B. Non-Disturbance. In the event any such mortgage is foreclosed, or in
the event of exercise of the power of sale under any such deed of trust, the
purchaser at said foreclosure or trustee's sale shall be considered the landlord
hereunder and shall be deemed to assume and to agree to perform the duties of
Landlord hereunder, and so long as Tenant complies with all of the terms and
provisions of this Lease, and is not in default hereunder, this lease shall not
be affected by said foreclosure or trustee's sale, and said purchaser shall
recognize Tenant's rights to continue to rights hereunder, and Tenant will
attorn to said purchaser and will recognize said purchaser as the owner and
landlord under this Lease.

         C. Eminent Domain - Total Taking. In the event of a taking of the Lease
Premises or damage related to the exercise of the power of eminent domain by any
agency, authority, public utility, person, or corporation or entity empowered to
condemn property ("Taking") of the entire Leased Premises or so much thereof as
to prevent or substantially impair their use by Tenant during the Lease term (i)
the rights of Tenant under the Lease and the leasehold estate of Tenant in and
to the Premises shall cease and terminate as of the date upon which title to the
Premises, or a portion

                                      -11-
<PAGE>   12
thereof, passes to and vests in the condemner or the effective date of any order
for possession if issued prior to the date title vests in the condemner ("Date
of Taking"), (ii) Landlord shall refund to Tenant any prepaid rent, (iii) Tenant
shall pay to Landlord any rent to charges due Landlord under the Lease, each
prorated as of the Date of Taking, (iv) Tenant shall receive from the Award
those portions of the Award attributable to relocation of Tenant, improvements
to the Premises made and paid for by Tenant and trade fixtures, equipment, and
furniture of Tenant, and (v) the remainder of the Award shall be paid to and be
the property of the Landlord.

         D. Eminent Domain - Partial Taking. In the event a portion of the
leased premises shall be taken for any public or quasi-public use under any
governmental law, ordinance or regulation, or by right of eminent domain or by
purchase in lieu thereof, and this Lease is not terminated as provided in
Article V, Paragraph C above, Lessor may, at Lessor's sole risk and expense,
restore and reconstruct the building and other improvements and on the leased
premises to the extent necessary to make it reasonably tenantable. The rent
payable under this Lease during the unexpired portion of the term shall be
adjusted to such an extent as may be fair and reasonable under the
circumstances. Lessee shall have no claim to the condemnation award.

         E. Holding over. In the event of holding over by Tenant after
expiration or earlier termination of this Lease without the written consent of
Landlord, Tenant shall pay as liquidated damages double rent for the entire
holdover period. No holding over by Tenant after the Term shall operate to
extend the Term and, in the event of any unauthorized holding over, Tenant shall
indemnify Landlord against any and all claims for damages or loss resulting
therefrom, including, but not limited to, claims by any other tenant to whom
Landlord may have leased all or any part of the Leased Premises covered hereby
effective upon the expiration or earlier termination of this Lease. Any holding
over with the consent of the Landlord in writing shall thereafter constitute
this Lease a tenancy from month to month.

         F. Destruction. In the event of a fire or other casualty in the Leased
Premises or the Building, Tenant shall immediately give notice thereof to
Landlord. If the Leased Premises shall be partially destroyed by fire or other
casualty so as to render the Leased Premises untenantable, Base Rental shall
abate thereafter until such time as the Leased Premises are made tenantable by
Landlord; provided, however, that if the Leased Premises are so partially
destroyed but are only rendered partially untenantable, there shall only be a
partial abatement of Base Rental corresponding to the time and extent the Leased
Premises or any other part of the Building shall be so damaged that Landlord
shall decide not to rebuild, then Landlord shall have the right, at its sole
option, to terminate this Lease and upon notice thereof from Landlord and upon
payment of all Base Rental and additional rental owed up to the time of
destruction, this Lease shall cease and come to an end.

         G. Conveyance by Landlord. Landlord shall have the right to sell,
transfer, or assign, in whole or in part, all its rights and obligations
hereunder, and all or any part of its interest in the Building, the Other
Buildings and the Center. In the event of any such conveyance, the grantee shall
take the property subject to the terms of this Lease and shall be subrogated to
all of the rights of the Landlord hereunder and in such event, no further
liability or obligation shall thereafter accrue against Landlord hereunder.

                                      -12-
<PAGE>   13
         H. Default. In the event of any failure of Tenant to pay any rent
reserved herein or any other payment or charge due hereunder in the time and
manner provided herein, or in the event Tenant shall violate, neglect, fail to
observe, keep or perform any covenant, agreement or stipulation herein contained
on Tenant's part to be observed, kept or performed, which default shall continue
(1) for ten (10) days after notice of failure to pay rent or other payment or
charge, or (2) for thirty (30) days after notice of default on account of any
failure to perform or keep any other of the terms, conditions or covenants of
this Lease (which notice in either instance shall be given by Landlord to Tenant
in writing), or if Tenant, or any guarantor of Tenant's performance under this
Lease, shall become bankrupt or insolvent, or file any debtor proceedings or
take or have taken against them, or either of them in any court, pursuant to any
state or federal statute, a petition in bankruptcy or insolvency or
reorganization or for the appointment of a receiver or trustee of all or a
portion of Tenant's or any such guarantor's property, or if Tenant or any such
guarantor petitions for or enters into an arrangement, or if Tenant shall
abandon the Leased Premises or suffer this Lease to be taken under any writ of
execution, then, in addition to all other remedies and courses of action now and
hereafter provided by law, Landlord shall have the immediate right to re-enter
the Leased Premises and remove all personal and property therefrom, and such
property may be removed and stored in a public warehouse or elsewhere at the
cost of, and for the account of, Tenant, all without service of notice or resort
to legal process and without being deemed guilty of trespass, or becoming liable
for any loss or damage which may be occasioned thereby.

         I. Re-entry. Should Landlord elect to re-enter, as provided above, or
should Landlord take possession of the Leased premises pursuant to legal
proceedings or pursuant to any notice provided by law, Landlord may either
terminate this Lease or Landlord may from time to time thereafter make such
alterations or repairs as may be necessary in order to relet the Leased Premises
or any portion thereof, and Landlord may relet the Leased Premises or any
portion thereof for such term or terms (not to extend beyond the Term), and for
such rental or rentals and upon such other agreements and conditions as
Landlord, in its sole discretion, may deem advisable; and upon such reletting,
all rentals actually received by Landlord from such reletting shall be applied,
first, to the payment of any sum other than rent due hereunder; second to the
payment of any cost and expense of reletting, including brokerage, attorney's
fees and the cost of alterations and repairs; third, to the payment of any rent
due and unpaid hereunder; and finally, the residue, if any, shall be held by
Landlord and applied in payment of future rent, as the same may become due and
payable hereunder. If such rentals received from such reletting during any month
be less than that agreed to be paid hereunder by Tenant during that month,
Tenant shall pay any such deficiency to Landlord, such deficiency to be
calculated and paid months. No such re-entry shall be constructed as an election
by Landlord to terminate this Lease unless a written notice of such intention is
given to tenant.

         J. Termination. Notwithstanding any prior election to terminate,
Landlord may, at any time subsequent to such re-entry, elect to terminate this
Lease on account of such previous breach, and in the event of any such
termination, whether subsequent to re-entry or contemporaneous therewith, in
addition to any other remedy it may have, Landlord may recover from Tenant all
damages incurred by reason of such breach, including reasonable attorney's fees
and actual cost incurred in recovering possession of the Leased Premises, and
including a sum equal to the excess, if any, of the amount of Base Rental and
additional rent reserved in this Leased Premises for such

                                      -13-
<PAGE>   14
period, all of which amounts shall be immediately due and payable from Tenant to
Landlord. For the purpose of determining the rent which would be payable by
tenant hereunder subsequent to default, the annual rent for each year of the
unexpired portion of the Term shall be equivalent to the average Base Rental and
additional rent paid by Tenant from the commencement of the Term to the time of
default, or during the preceding three (3) calendar years, whichever period is
shorter.

         K. Attorney's Fees. In the event either Landlord or Tenant files suit
to enforce any covenant of this Lease, the party against whom final,
non-appealable judgement is rendered shall pay all costs and expenses of suit
incurred by the prevailing party, including such reasonable attorney's fees as
shall be fixed by the court.

         L. Cumulative. The rights and remedies hereinabove provided Landlord in
the event of any default by Tenant, or in the event of any act, omission, or set
of circumstances constituting default hereunder, as hereinabove provided, shall
be cumulative and not exclusive, one of the other, and further provided, each of
said rights and remedies shall be cumulative of and without prejudice to the
rights, remedies and causes of action provided Landlord by law, present or
future.

         M. Waiver. One or more waivers of any breach or violation of any
agreement, covenant or conditions herein contained shall not be deemed to be a
waiver of any subsequent violation or breach of the same or any other covenant
or condition herein contained, and the consent or approval by either party to
any act by the other, which act requires the consent or approval of the other
party, shall not be deemed to waive or render unnecessary the future requirement
of consent or approval to the same or similar act; and the subsequent acceptance
of rent or other charges hereunder shall not be deemed to be a waiver of any
preceding breach by Tenant, other than the failure of Tenant to pay the
particular rent or other charges so accepted, regardless of Landlord's knowledge
of such preceding breach at the time of acceptance of said rent or other
charges. No express covenant, term or condition of this Lease shall be deemed to
have been waived by either party, unless such waiver be in writing.

         N. Landlord's Fire Insurance. At all times during the Term, Landlord
shall cause to be maintained a policy or policies of fire and extended coverage
insurance, issued by and binding upon some licensed insurance company, covering
the Building, including the Leased Premises and Leasehold Improvements
(exclusive of contents), in an amount equal to not less than eighty percent
(80%) of the replacement cost thereof. Such insurance shall insure Landlord (and
other persons, firms or corporations as may be designated by Landlord) against
the losses provided for in said policy or policies subject to the terms and
provisions of this Lease and any first mortgage or deed of trust covering the
Building; and Tenant shall have no interest in said policy or policies or
proceeds therefrom. Landlord shall not be obligated to insure any furnishings,
equipment, trade fixtures, or other personal property which Tenant may place or
cause to be placed upon the Leased Premises, or any improvements which Tenant
may construct therein.

         O. Landlord's Liability Insurance. Likewise, Landlord shall cause to be
maintained a policy or policies of comprehensive general liability insurance
issued by and binding upon some licensed insurance company, insuring Landlord
(and such other persons, firms or corporations as may

                                      -14-
<PAGE>   15
be designated by Landlord) against loss of life, bodily injury and/or property
damage with respect to the Common Areas and the operation of the Center, subject
to the terms and provision of this Lease and any first mortgage or deed of trust
covering the Center; and Tenant shall have no interest in said policy or
policies or proceeds therefrom.

         P. Tenant's Fire Insurance. At all times during the Term, Tenant shall
keep the trade fixtures, equipment, furnishings, fixtures, improvements and any
other personal property furnished and installed by Tenant insured against loss
or damage by fire or other casualty, with fire and extended coverage insurance
in an amount equal to ninety percent (90%) of the replacement cost thereof,
written by one or more responsible insurance companies approved by Landlord and
licensed to do business in the State of Texas, which insurance companies shall
be rated not less than A+10 by Best Guide Rating, insurance Tenant, and naming
as additional insured Landlord and such other persons, firms or corporations as
are designated by Landlord. Each such policy shall be noncancellable for any
cause without first giving Landlord ten (10) days prior written notice.

         Q. Tenant's Liability Insurance. Likewise, Tenant shall maintain in
force during the Term a policy or policies of comprehensive public liability
insurance, including property damage, written by one or more responsible
insurance companies approved by Landlord and licensed to do business in Texas,
which insurance companies shall be rated not less than A+10 by Best Guide
Rating, insurance Tenant, and naming as additional insured Landlord and such
other persons, firms, or corporations as are designated by Landlord, against
loss of life, bodily injury and/or property damage with respect to the Leased
premises and the business operated therein by Tenant, in which the limit of
public liability shall not be less than FIVE HUNDRED THOUSAND AND NO/100 DOLLARS
($500,000.00) single limit bodily injury and in which the limit of property
damage liability shall be not less than ONE HUNDRED THOUSAND AND NO/100 DOLLARS
($100,000.00). Each such policy shall be noncancellable for any cause without
first giving Landlord ten (10) days prior written notice.

         R. Policies. Tenant shall deliver a copy of each such policy, or a
certificate or said insurance, to Landlord on or before the commencement date of
the Term.

         S. Hold Harmless. Tenant shall indemnify and save Landlord harmless
from and against (i) any and all costs, liability or expense arising out of the
claim of any person or persons on account of any occurrence in, on or at the
Leased Premises, Building, Other Buildings or Center resulting from the
occupancy or use of the Leased Premises by Tenant, or by any person or persons
holding under Tenant (including, without limitation and for purposes of this
Paragraph S of Article V, Tenant's guests, invitees, agents, contractors,
employees, servants, subtenants or assignees), except however, for losses or
damage caused by Landlord's gross negligence or willful misconduct; (ii) any
penalty, damage or charge incurred or imposed by reason of any violation of law
or ordinance by Tenant or any person or persons holding under Tenant; and (iii)
any and all costs, liability or expense arising out of the claim of Tenant or
any person or persons holding under tenant on account of any occurrence in, or
on or at the Leased Premises, Building, Other Buildings or Center, except
however, for losses or damage caused by Landlord's gross negligence or willful
misconduct. Further, Landlord shall not be liable or responsible to Tenant for
any loss or damage to any property or person resulting from theft, fire, act of
God, public enemy, injunction, riot, strike, insurrection, war, court order,

                                      -15-
<PAGE>   16
requisition or order of governmental body or authority, or from the acts or
omissions of occupants of other space in the Building or Other Buildings; or for
any damage or inconvenience which may arise through repair or alteration of any
part of the Building, Other Buildings or Center, or failure to make any such
repairs, or through operations in the construction of any public or quasi-public
work.

         T. Waiver of Subrogation. Anything in this Lease to the contrary
notwithstanding, Landlord and Tenant each hereby waives any and all rights of
recover, claim, action or cause of action, against the other, its agents,
officers or employees for any loss or damage to or loss of any part of the
Leased Premises or any improvements thereto, or for damage to or loss of any
personal property of such party therein, by reason of fire, the elements, or any
other perils to the extent against which such matters are insured under the
terms of the standard fire and extended coverage insurance policies required
hereunder, regardless of cause or origin, including negligence of the other
party hereto, its agents, officers or employees, and each party hereto covenants
that to the extent permitted by the laws and insurance regulations of the State
of Texas, without penalty or extra premium charge on account thereof, no insurer
shall hold any right of subrogation against such other party, but only to the
extent that such waiver would not have the effect of invalidating any insurance
coverage of Landlord or Tenant.

         U. Landlord's Lien. In consideration of the mutual benefits arising
under this Lease, Tenant hereby grants to Landlord a lien and security interest
in all property of Tenant now or hereafter placed in or on the Leased Premises,
including, but not limited to, all fixtures, equipment, furnishings and other
articles of personal property and such property shall be and remain subject to
such lien and security interest of Landlord for payment of all rent and other
sums agreed to be paid by Tenant herein; provided however, that Landlord hereby
subordinates its lien and security interest to any lien or security interest
which may attached Tenant's personal property in favor of any third party
providing financing to Tenant. Landlord will provide Subordination Agreements
reasonably acceptable to all such third party creditors. Said lien and security
interest shall in addition to and cumulative of Landlord's liens provided by
law. This Lease shall constitute a security agreement under the Texas Uniform
Commercial Code so that Landlord shall have and may enforce said security
interest and Tenant agrees to execute, as debtor, such financing statement or
statements as Landlord, as secured party, may now or hereafter reasonably
request in order that such security interest or interests may be perfected
pursuant to said Code. Landlord may at its election at any time file a copy of
this Lease as a financing statement for this purpose, the addresses given in
Paragraph D of Article VI hereof shall be deemed to be the addresses of Landlord
and Tenant. Landlord, as secured party shall be entitled to all of the rights
and remedies afforded a secured party under the Texas Uniform Commercial Code,
which rights and remedies shall be in addition to and cumulative of the
Landlord's liens and rights provided by law or by the other terms and provisions
of this Lease.

                                   ARTICLE VI

         Landlord and Tenant further covenant and agree as follows:

         A. Successors and Assigns. This Lease shall be binding upon and inure
to the benefit of the successors and assigns of Landlord, and shall be binding
upon and inure to the benefit of Tenant,

                                      -16-
<PAGE>   17
its successors, heirs, executors, administrators or legal representatives, and
to the extent assignment may be approved by Landlord, hereunder, Tenant's
assigns.

         B. Certifications. Landlord and Tenant respectively agree at any time
and from time to time during the Term, upon not less than ten (10) days prior
written request therefor from the other said party, to execute, acknowledge and
deliver unto the requesting party a statement or statements, in writing,
certifying (if such be true) that this Lease is unmodified and in good standing
(or if modified, then in good standing as modified, stating the modification),
and the date or dates, if any, to which Base Rental, additional rent or other
charges hereunder, if any, have been paid in advance, it being the intention of
the parties hereto that any such statement may be relied upon by any prospective
purchaser, mortgagee or assignee of any mortgagee of the Leased Premises, the
Building, Other Buildings, Center or any part thereof, by any other tenant in
the Building or by any approved assignee or subtenant of the Tenant herein.

         C. Memorandum of Lease. Promptly after the commencement date of the
Term, Landlord and Tenant may, in accordance with Paragraph A of Article II,
execute a memorandum or short form of this Lease Agreement, in recordable form,
acknowledging Tenant's acceptance of the Leased Premises for all purposes herein
provided and specifying the commencement date and the termination date of the
Term, and said agreement shall be recorded, at Landlord's option, in the Office
of the County Clerk of Harris County, Texas, but this Lease itself shall not be
recorded.

         D. Notices. All notices required or permitted to be given hereunder by
either party hereto to the other said party, shall be deemed sufficiently given
or made as of the date when mailed by United States Registered Mail, Return
Receipt Requested, adequate postage prepaid, to their respective addresses as
follows:

        Landlord                                      Tenant
--------------------------------------------------------------------------------

Sam H. Hawkins / dba                         Introgen Therapeutics, Inc.
Plaza del Oro Business Center                8080 North Stadium Blvd.
8012 El Rio                                  Suite 1200
Houston, Texas 88054                         Houston, Texas 77054
                                             Attn:  David Enloe

         Either party hereto may, by notice to the other party in the manner
hereinabove provided, change its mailing address.

         E. Payments. No payment made by Tenant or received by Landlord in an
amount less than the monthly installment of Base Rental, any additional rent or
other charges payable by Tenant hereunder shall be deemed to be other than on
account of the earliest stipulated Base Rental, additional rent or other charges
payable by Tenant hereunder, nor shall any endorsement or statement on any check
or any letter accompanying any check or payment as such sum be deemed an accord
and satisfaction, and Landlord may accept any such check or payment without
prejudice to Landlord's

                                      -17-
<PAGE>   18
right to recover the balance of such sum or to pursue any other remedy in this
Lease or by law provided Landlord. All payments due hereunder shall be deemed
made on the date received by Landlord and not on the date mailed.

         F. Entire Agreement. This Lease, together with the Exhibits aforesaid,
and the rider or riders, if any, attached hereto and forming a part hereof,
contain and set forth the entire agreement and understanding between the parties
hereto concerning the Leased Premises, and there are no covenants, promises,
agreements, conditions or understandings either oral or written, between said
parties other than as herein expressly set forth. Except as herein otherwise
provided, no subsequent alteration, amendment, change or addition to this Lease
shall be binding upon either party hereto, unless reduced to writing and signed
by both Landlord and Tenant.

         G. No Partnership. Landlord does not become a partner of Tenant in the
conduct of its business or otherwise, or a joint venturer or a member of a joint
enterprise with Tenant by virtue of this Lease.

         H. Force Majeure. In the event either party hereto shall be delayed,
hindered or prevented from the performance of any act required hereunder by
reason of strike, lockouts, labor disputes, labor troubles, inability to procure
materials, failure of power, restrictive governmental laws or regulations,
riots, insurrection, war or other reason of like nature not the fault of the
party so delayed, then the performance of such acts shall be excused for the
period of the delay and the period for the performance of any such act shall be
extended for a period equivalent to the period of such delay; provided that if
for any reasons set forth in this Article VI (H), Landlord should be unable to
provide peaceful occupancy of the premises together with the services Landlord
is obligated to provide herein, then Tenant shall be excused from paying rent
for so long as such occupancy or services are not available.

         I. Captions. The captions, paragraph numbers and article numbers
appearing in this Lease are inserted only as a matter of convenience and in no
way define, limit, construe or describe the scope or intent of such sections or
articles, nor in anyway affect this Lease.

         J. Pronouns. The word "Tenant" shall be deemed and taken to mean each
and every person or party mentioned as a Tenant herein, be the same one or more;
and if there shall be more than one Tenant any notice required or permitted by
the terms of this Lease may be given by or to any one thereof and shall have the
same force and effect as if given by or to all thereof. The use of the neuter
singular pronoun to refer to Landlord or Tenant shall be deemed a proper
reference even though Landlord or Tenant may be an individual, a partnership, a
corporation, or group of two or more individuals or corporations. The necessary
grammatical changes required to make the provisions of this Lease apply in the
plural sense where there is more than on Landlord or Tenant, and to either
corporations, associations, partnerships or individuals, males or females, shall
in all instances be assumed as though in each case fully expressed.

         K. Brokerage. Each party hereto represents and warrants unto the other
that there are no claims of brokerage commissions or finder's fees in connection
with the negotiation or execution of

                                      -18-
<PAGE>   19
this Lease except that agreement between Tenant and Colliers Appelt Womack dated
the 26th of May, 1996, and each of the parties hereto agrees to indemnify and
save the other harmless from and against all liabilities arising from any other
claim, including without limitation, cost of attorney's fees in connection
therewith.

         L. Severability. If any provision, covenant or condition of this Lease
or the application thereof to any person or circumstance shall, to any extent,
be invalid or unenforceable, the remainder of this Lease, or the application of
such provision, covenant or condition to person or circumstances other than
those as to which it is held invalid or unenforceable, shall not be affected
thereby and each provision, covenant or condition of this Lease shall be valid
and shall be enforced to the fullest extent permitted by law.

         M. Survival. Any representation, warranty, covenant or agreement
contained herein which contemplated performance after the expiration or
termination of this Lease shall be deemed to survive such expiration or
termination.

         N. No Personal Liability. Tenant agrees to look solely to Landlord's
interest in the Development for the recovery of any judgement from Landlord, it
being agreed that Landlord shall never be personally liable for any such
judgement.

         O. Option to Extend. Tenant is hereby granted an option to extend the
term of this lease for a six (6) month period upon the same terms and conditions
as herein contained, provided, Tenant gives Landlord written notice at lease
sixty (60) days prior to the expiration of the initial term of its election to
exercise the option. If the term hereof is so extended then the rental to be
paid for the six (6) month option term shall be an amount equal to the rental
provided to be paid for the initial terms hereunder.

         P. Leasehold Repairs: Landlord agrees to patch existing holes in walls,
touch up paint and replace existing carpet prior to occupancy by Tenant.

                                      -19-
<PAGE>   20
         EXECUTED, as of the day, month and year first hereinabove written.

                                            Sam H. Hawkins, dba
                                            PLAZA DEL ORO BUSINESS CENTER

                                            By:  /s/ SAM H. HAWKINS
                                               -------------------------------
                                                   Landlord

                                            INTROGEN THERAPEUTICS, INC.

                                            By:  /s/ DAVID NANCE
                                               -------------------------------
                                                   Name:  David Nance
                                                   Title:  President

                                      -20-
<PAGE>   21
                                    EXHIBIT A

SURVEY OF 464,366 SQUARE FEET OR 10.6604 ACRES OUT OF UNRESTRICTED RESERVE "A"
OF PLAZA DEL ORO, SECTION 6, AS RECORDED IN VOLUME 264, PAGE 51, HARRIS COUNTY
MAP RECORDS; SAID 10.6604 ACRES BEING PART OF A CERTAIN 6.6135 ACRE TRACT
DESCRIBED IN DEED RECORDED UNDER HARRIS COUNTY CLERK'S FILE NO. H161823, ALL OF
A CERTAIN 2.6474 ACRE TRACT DESCRIBED IN DEED RECORDED UNDER CLERK'S FILE NO.
J157466, AND PART OF A CERTAIN 7.9752 ACRE TRACT DESCRIBED IN DEED RECORDED
UNDER CLARK'S FILE NO. H161825, OFFICIAL PUBLIC RECORDS OF REAL PROPERTY,
LOCATED IN THE P.W. ROSE SURVEY, ABSTRACT NO. 645, HARRIS COUNTY, TEXAS:

BEGINNING at a 5/8 iron rod found for the northwest corner of Unrestricted
Reserve "A" of Plaza Del Oro Section 6 and the southwest corner of Lot 8, Block
42 of Institute Place as recorded in Volume 4, Page 32, Harris County Map
Records, said point being in the east line of a 100 foot wide Houston and Great
Northern Railroad Company easement as described in Volume 10, Page 612, Harris
County Deed Records, and the north line of a 60 foot wide railroad easement as
described in Volume 2646, Page 414, Harris County Deed Records;

THENCE S 72 deg 16 min. 04 sec. E, along a common line, being the south line of
Block 42 and 43 of said Institute Place and the north lines of Unrestricted
Reserve "A" of Plaza Del Oro Section 6 and said 60 foot wide railroad easement,
458.34 feet to a 1/2 inch iron rod set for the northeast corner of the herein
described tract;

THENCE S 17 deg. 43 min. 56 sec. W, 404.82 feet to a 1/2 inch iron rod set in
the north line of El Camino (60 feet wide);

THENCE in a southwesterly direction with the north line of El Rio along a curve
to the left having a radius of 85.00 feet and a central angle of 70 deg. 55 min.
30 sec., for an arc distance of 105.22 feet to a 1/2 inch iron rod set for the
point of tangency;

THENCE S 17 deg. 25 min. 00 sec. W, along the west line of El Rio 612.34 feet to
a 5/8 inch iron rod found for the southeast corner of the herein described
tract;

THENCE N 72 deg. 35 min. 00 sec. W, along the north line of a certain 3.365 acre
tract described in deed dated December 11, 1981 to State Farm Mutual Automobile
Insurance Company recorded under Clerk's File No. H261112, 400.00 feet to a 5/8
inch iron rod found in the common line between the above mentioned Houston and
Great Northern Railroad Company 100 foot wide easement and Unrestricted Reserve
"A" of Plaza Del Oro Section 6 for the southwest corner of the herein described
tract;

THENCE N 17 deg. 25 min. 00 sec. E, along the east line of said 100 foot
railroad easement, 940.53 feet to a 1/2 inch iron rod set for the point of
curvature of a curve to the right;

THENCE in a northeasterly direction with said common line along a curve to the
right having a radius of 11,409.22 feet and a central angle of 0 deg. 48 min. 03
sec., for an arc distance of 159.47 feet to the POINT OF BEGINNING and
containing 464,366 square feet or 10.6604 acres of land.
<PAGE>   22
                                    EXHIBIT B

                               [PLAN OF PREMISES]
<PAGE>   23
                                    EXHIBIT C

                               [PLAN OF PREMISES]

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