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                                                                    EXHIBIT 10.7

                          ASHFORD OAKS OFFICE BUILDING

                             OFFICE LEASE AGREEMENT

STATE OF TEXAS         Section
COUNTY OF BEXAR        Section

      THIS LEASE (herein so called, both in reference to this Agreement and to
the real estate transaction between Landlord and Tenant), made and entered into
by and between BUILDING ACQUISITION CORPORATION, a Texas Corporation
("Landlord"), and BioNumerik Pharmaceuticals, a Limited Liability Co.
(hereinafter called "Tenant").

                              W I T N E S S E T H:

      Effective on the execution of this Lease (even if the Commencement Date is
a later date), Landlord hereby leases to Tenant., and Tenant hereby takes from
Landlord, the Demised Premises described in this Agreement, as depicted by the
floor plan attached as Exhibit "A", in the office building named as the
"Building" below, for the Term set forth in Section 1.1(m) and on the following
terms, conditions and covenants:

                                    ARTICLE I

                    FUNDAMENTAL LEASE PROVISIONS; DEFINITIONS

      The following list sets out the Fundamental Lease Provisions and certain
other definitions pertaining to this Lease:

            1.1   Fundamental Lease Provisions.

                  (a)   "Landlord": Building Acquisition Corporation.

                  (b)   Landlord's Mailing Address: Ashford Oaks Office Bldg.,
8122 Datapoint Drive, Suite 316, San Antonio, Texas 78229; Attn: Mission City
Properties, Inc., Manager, Suite 316.

                  (c)   "Tenant": same as above

                  (d)   Tenant's Mailing Address:

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                        (i)   Before the Commencement Date: 8122 Datapoint
                              Drive, Suite 700, San Antonio, Texas 78229.

                        (ii)  After the Commencement Date: 8122 Datapoint Drive,
                              Suite 1250, San Antonio, Texas 78229.

                  (e)   "Guarantor(s)" (if applicable, Guaranty attached as
Exhibit "E"): N/A

                  (f)   Guarantor's Street Address: N/A

                  (g)   "Building" (including street address): Ashford Oaks
Office Building, 8122 Datapoint Drive, San Antonio, Texas 78229.

                  (h)   "Premises": The portion of the Building to be leased
pursuant to this Lease, as shown on the attached Exhibit "A", containing
approximately 5,464 square feet of Rentable Area. The address of the Premises is
Ashford Oaks Office Building, 8122 Datapoint Drive, Suite 1250, San Antonio.
Texas 78229.

                  (i)   "Base Rental": See Exhibit G "Addendum".

                  (j)   "Security Deposit": $ N/A

                  (k)   "Anticipated Commencement Date": May 1, 1992.

                  (l)   "Commencement Date": The date on which the Premises are
"ready for occupancy," as defined in Rider 101.

                  (m)   "Term": The period of sixty (60) months beginning with
the first day of the first full calendar month after the Commencement Date (or
beginning on the Commencement Date if that date is the first day of a calendar
month).

                  (n)   "Area of the Building": 192,472 square feet, the
stipulated total number of square feet of Rentable Area in the Building.

                  (o)   "Area of the Premises": 5,464, the stipulated number of
square feet of Rentable Area of the Premises.

                  (p)   "Landlord's Operating Cost Contribution": $ 5.00 for
each square foot in the Area of the Building.

                  (q)   "Broker": Trinity Asset Management, Inc.

                  (r)   "Use": General office purposes and basic and applied
medical research related lab facilities provided however the Premises may not be
used for any laboratory research on materials which involve infectious strains
of Human Immunodeficiency Virus.

            1.2   Certain Definitions.

                  (a)   "Rentable Area": Area computed in accordance with the
current American National Standard adopted by the Building Owners and Managers
Association International ("BOMA").

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                  (b)   "Tenant's Pro Rata Share": The Area of the Premises
divided by the Area of the Building calculated as 2.84%.

                  (c)   "Building Facilities": All equipment, machinery,
facilities and other personal property located in the Building or on the Land
(as hereinafter described) and/or used or utilized solely in connection with the
operation and/or maintenance of the Building, or any part thereof.

                  (d)   "Land": The parcel of real property more particularly
described in Exhibit "B" attached hereto, on which the Building is located.

                  (e)   "Protect": The Land and the Building, parking related
thereto, all Building Facilities and all appurtenances pertaining to the
foregoing.

                  (f)   "Common Area(s)": The portion of the Building which is
for the common use of all Tenants (and their customers, clients, invitees,
contractors), including among other facilities, corridors, tunnels, elevator
foyers, rest rooms, mechanical rooms, janitorial closets, electrical and
telephone closets, vending areas, lobby areas, drinking fountains, meeting
rooms, general tenant benefit or amenity areas, sidewalks, curbs, enclosed mall
areas, loading areas, lighting facilities, delivery passages, decks and other
parking facilities, landscaping, and other common rooms and common facilities.

                  (g)   "Service Areas": "Service Areas" will refer to areas,
spaces, facilities and equipment serving the Building (whether or not located
within the Building) but to which Tenant and other occupants of the Building
will not have access, including, but not limited to, mechanical, telephone,
electrical and similar rooms, air and water refrigeration equipment and
management areas.

                  (h)   "Lease Year": A period of twelve (12) consecutive
calendar months (during the Term) beginning on January 1 and ending on December
31, except that the first Lease Year begins on the Commencement Date of this
Lease and ends on the next following December 31 and the last Lease Year begins
on January 1 of the calendar year in which the Term ends and ends on the last
day of the Term.

                  (i)   "Rules": The Rules for the Building attached as Exhibit
"D", as modified from time-to-time in accordance with Section 4.2.

            1.3   Other Definitions. Other terms defined in this Lease have the
meanings assigned to them elsewhere in this Lease.

                                   ARTICLE II

                               MONETARY PROVISIONS

            2.1   Base Rental. Tenant shall pay to Landlord. without offset or
deduction, Base Rental for the Premises in monthly installments in advance. Rent
begins to accrue hereunder on the Commencement Date. One such monthly
installment shall be made on or before the date of

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execution of this Lease, and the first day of each calendar month during the
Term, beginning with the second month. Rent for any partial month shall be
prorated on a per diem basis.

            2.2   Tenant's Share of Certain Cost . In addition to other sums due
from Tenant under this Lease, Tenant shall pay to Landlord, in the manner and at
the times set forth below, Tenant's Pro Rata Share of Operating Costs, including
Energy Costs, for each Lease Year:

                  (a)   Operating Costs. "Operating Costs" means all costs,
charges, and expenses incurred by Landlord in connection with owning operating,
maintaining, repairing, insuring and managing the Building, and the Building's
portion of the Common Areas and Service Areas. computed on an accrual basis and
including, without limitation, costs, charges and expenses incurred with respect
to the items enumerated as "Operating Cost Examples" in Paragraph A of Exhibit
"C" to this Lease (which include amortization of certain capital improvements),
and including Energy Costs. Operating Costs do not include those items
enumerated as "Operating Cost Exclusions" to Paragraph B of Exhibit "C" to this
Lease. "Energy Costs" means the costs incurred by Landlord for (i) any and all
forms of fuel or energy utilized in connection with the operation, maintenance,
and use of the Building, Common Areas and Service Areas, (ii) sales, use, excise
and other taxes assessed by Governmental authorities on energy sources, and
(iii) other reasonable costs of providing energy to the Building, Common Areas
and Service Areas. If less than 90% of the Area of the Building is occupied
during a lease Year, then for purposes of determining the Operating Costs for
that Lease Year, Operating Costs shall be determined as if the Building had been
occupied to that extent for that Lease Year, taking into account the fixed or
variable nature of the particular costs and expenses.

                  (b)   Tenant's Pro Rata Share of Operating Costs. Tenant's Pro
Rata Share of Operating Costs for any Lease Year is computed by multiplying
Tenant's Pro Rata Share times Excess Operating Costs. "Excess Operating Costs"
means the difference between (i) the Operating Costs for a Lease Year minus (ii)
the product of (A) Landlord's Operating Cost Contribution multiplied times (B)
the Area of the Building.

                  (c)   Estimated Costs. Tenant's Pro Rata Share of Operating
Costs for the remainder of the first Lease Year and for each subsequent Lease
Year of the Term shall be estimated in good faith by Landlord, and notice of the
estimated amounts will be given to Tenant at least 10 days before the
Commencement Date or the beginning of each Lease Year, as the case may be. For
each full Lease Year of the Term, Tenant shall pay to Landlord each month, at
the same time the monthly installment of Base Rental is due, an amount equal to
one-twelfth (1/12) of the estimated Tenant's Pro Rata Share of Operating Costs
due for that year. If the first and last Lease Years are less than full calendar
years, then Tenant shall pay to Landlord, each month for those Lease Years, at
the same time the monthly installment of Base Rental is due, an amount equal to
the amount of estimated Tenant's Pro Rata Share of Operating Costs for the
partial lease Year divided by the number of full calendar months of the partial
year, as supported with a written analysis upon request by Tenant.

                  (d)   Estimate Revisions. At any time and from time to time
during the Term, Landlord may, by giving notice to Tenant, change the monthly
amount then payable by Tenant for Tenant's estimated Pro Rata Share of Operating
Costs to reflect more accurately, as supported with a written analysis upon
request by Tenant. Tenant's actual Pro Rata Share of Operating Costs for the
then current Lease Year. Tenant shall begin paying the revised estimated amount

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together with the next monthly payment of Base Rental due after receipt by
Tenant of Landlord's notice.

                  (e)   Annual Adjustments. On or before April 1 of each Lease
Year, Landlord will prepare and deliver to Tenant a statement setting forth the
calculation of the actual Tenant's Pro Rata Share of Operating Costs for the
previous Lease Year. Within 30 days after receipt of the statement of the actual
Tenant's Pro Rata Share of Operating Costs, Tenant shall pay to Landlord, or
Landlord will credit against the next rental or other payment or payments due
from Tenant, as the case may be, the difference between the actual Tenant's Pro
Rata Share of Operating Costs for the preceding Lease Year and the estimated
Tenant's Pro Rata Share of Operating Costs paid by Tenant during that year.

                  (f)   Final Partial Year. If the Term expires or this Lease
terminates before a final determination of the actual Tenant's Pro Rata Share of
Operating Costs, then the amount of adjustment between the estimated Tenant's
Pro Rata Share and the actual Tenant's Pro Rata Share of Operating Costs payable
for the preceding Lease Year and/or the final partial Lease Year of the Term
will be estimated by the Landlord based on the best data available to Landlord
at the time of the estimate. Before the scheduled last day of the Term, or as
soon as possible after an earlier termination date, an adjustment will be made
between Landlord and Tenant. The obligations set forth in the preceding sentence
shall survive expiration or earlier termination of this Lease.

            2.3   Personal Property Taxes. Tenant shall pay, before delinquency,
all taxes, fees or charges. Rates, duties and assessments that are imposed,
levied or assessed directly against Tenant, or indirectly through Landlord, and
payable during the Term hereof, on Tenant's equipment, furniture, movable trade
fixtures and other personal property located in the Premises. Tenant shall also
pay, before delinquency, business and other taxes, fees or charges, rates,
duties and assessments imposed, levied or assessed because of Tenant's occupancy
of the Premises or on the business or income of Tenant generated from the
Premises. In no event shall Tenant be required to pay taxes, fees or charges for
personal property outside of the Premises or that are part of the Common Area.

            2.4   Taxes for Leasehold Improvements. If any authority levying
real and personal property taxes against the Building includes, as a standard
practice for determining the value of the Building for tax purposes, a component
for tenant improvements or nonmovable trade fixtures of individual tenants,
Tenant shall pay to Landlord any portion of those taxes which is attributable to
the value of tenant improvements or nonmovable trade fixtures in the Premises in
excess of the value (as of the first day of the Term or as of the date of such
levying, whichever date is used by the taxing authority) of Building standard or
existing improvements (collectively, "Above Standard Improvements"). On receipt
of any such tax statement, Landlord will compute Tenant's share of taxes
attributable to Above Standard Improvements, and submit a statement to Tenant
evidencing the method of calculation. Tenant shall pay to Landlord together with
the next monthly installment of Base Rental due after the receipt of Landlord's
statement the entire amount due under this Section 2.4. The method of
calculation of the share of taxes attributable to Above Standard Improvements
will be subject to adjustment by Landlord from time to time in order to reflect
the method currently utilized by taxing authorities to calculate taxes for Above
Standard Improvements. If Tenant is assessed for taxes for Above Standard
Improvements directly by the taxing authorities, then Tenant shall pay them
before delinquency and deliver to

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Landlord copies of receipts for payment of those taxes and assessments no later
than ten (10) days before the deadline for payment without imposition of
penalty.

            2.5   Late Payments.

                  (a)   Late Charge. If any amounts due under this Lease from
Tenant to Landlord are not received by Landlord by the fifth (5th) calendar day
after the date due, then the amount past due is subject to a ten percent (10%)
late payment and service charge, payable by Tenant immediately on demand by
Landlord, to be applied to defray Landlord's administrative and other overhead
expenses.

                  (b)   Administrative Reimbursement. If Landlord performs
construction, maintenance, or repairs for Tenant under Sections 6.3, 8.2 or 13.2
of this Lease, then Tenant shall reimburse Landlord within five (5) days after
receipt of an Invoice from Landlord for the cost of those items plus an amount
equal to percent (15%) of those costs ("Administrative Reimbursement") to
reimburse Landlord for administration and overhead.

            2.6   Security Deposit. On its execution of this Lease, Tenant shall
deposit with Landlord, in addition to the advance payment of Base Rental
described to Section 2.1, the Security Deposit. The Security Deposit shall be
held by Landlord without interest as security for the performance of Tenant's
obligations under this Lease. The Security Deposit is not an advance payment of
rental or the full measure of liquidated damages on a default by Tenant. On an
Event of Default (hereinafter defined). Landlord may, from time to time and
without prejudice to any other remedy provided herein or by law, use the
Security Deposit to cure the Event of Default. After an application of the
Security Deposit, Tenant shall pay to Landlord, on demand, the amount necessary
to replenish Security Deposit to its original amount. On the expiration or
termination of the Term, any remaining, once of the Security Deposit shall be
returned by Landlord to Tenant if Tenant is not then in default.

                  Unless there has been a permitted assignment of this Lease
pursuant to Article XI, and in connection therewith Landlord receives written
notice of an assignment of the right to receive the Security Deposit or the
remaining balance thereof. Landlord may return the Security Deposit to the
original Tenant, regardless of one or more assignments of Tenant's interest in
the Security Deposit. In this event, on the return of the Security Deposit (or
balance thereof) to the original Tenant (or permitted assignee, as appropriate),
Landlord has no further liability with respect to the Security Deposit.

            On a transfer of the Premises, this Lease or the Building Landlord
may transfer the Security Deposit to the transferee, after which Landlord is
released from all liability for the return of the Security Deposit. for which
Tenant shall look solely to the transferee.

                                   ARTICLE III

                      PREMISES, COMMON AREAS, SERVICE AREAS

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            3.1   Required Condition Of Premises. Except to the extent that
Landlord is obligated to construct improvements in the Premises, as provided on
an exhibit attached to this Agreement. and except for Landlord's agreement to
complete or correct construction items, as described in the second paragraph of
this Section 3.1, the Premises are delivered to Tenant and are being leased "AS
IS" and "WITH ALL FAULTS," and Landlord makes no representation or warranty of
any kind, expressed or implied, with respect to the condition of the Premises
(including habitability, fitness or suitability for particular purpose of the
Premises, or that the Building or the improvements to the Premises have been
constructed in a good and workmanlike manner). TO THE MAXIMUM EXTENT PERMITTED
BY APPLICABLE LAW, LANDLORD HEREBY DISCLAIMS, AND TENANT WAIVES THE BENEFIT OF,
ANY AND ALL IMPLIED WARRANTIES, INCLUDING IMPLIED WARRANTIES OF HABITABILITY,
FITNESS OR SUITABILITY FOR PURPOSE, OR THAT THE BUILDING OR THE IMPROVEMENTS IN
THE PREMISES HAVE BEEN CONSTRUCTED IN A GOOD AND WORKMANLIKE MANNER. ENANT
EXPRESSLY ACKNOWLEDGES THAT LANDLORD DID NOT CONSTRUCT OR APPROVE THE QUALITY OF
CONSTRUCTION OF THE BUILDING.

            The taking of possession of the Premises by Tenant conclusively
establishes that the Premises and the Building were at the Lime of occupancy in
satisfactory order and condition except for (i) minor matters of finish
adjustments to the Premises (commonly referred to as "punch list items")
specified in reasonable detail on a list delivered by Tenant to Landlord within
fifteen (15) days after the date on which Tenant takes possession of the
Premises and (ii) defects not discoverable on inspection and about which Tenant
notifies Landlord within 90 days after taking possession of the Premises.
Landlord neither makes nor offers any other construction warranties of any kind
or nature whatsoever.

            3.2   Minor Variations in Area. The Area of the Premises contained
in Section 1.1(o) has been calculated in accordance with the foregoing
definitions and is agreed to be the Area of the Premises regardless of minor
variations resulting from construction of the Building and/or tenant
improvements.

            3.3   Ceilings, Walls, Floors. Tenant acknowledges that pipes,
ducts, conduits, wires and equipment serving other parts of the Building may be
located above acoustical ceiling surfaces, below floor surfaces or within walls
in the Premises.

            3.4   Common and Service Areas. Tenant is hereby granted a
non-exclusive right to use the Common Areas during the Term of this Lease for
their intended purposes, in common with others, subject to the terms and
conditions of this Lease, including, without limitation, the Rules.

            3.5   Delay. If the Premises are not ready for occupancy by Tenant
on the Anticipated Commencement Date, for any reason other than a delay caused
by Tenant, the obligations of Landlord and Tenant shall nevertheless continue in
full force and effect. However, except as otherwise provided in Rider 101, the
Term of this Lease shall not begin and rent shall not begin to accrue until the
actual Commencement Date. The delay in commencement of the Term and in the
accrual of rent described in the foregoing sentence constitutes full settlement
of all claims that Tenant might otherwise have by reason of the Premises not
being ready for occupancy on the Anticipated Commencement Date.

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            If the Premises are not ready for occupancy by Tenant on the
Anticipated Commencement Date due to one or more delays caused by Tenant, or
anyone acting under or for Tenant, or due to any cause other than Landlord's
fault. Landlord has no liability and the obligations of Tenant under this Lease
(including, without limitation. the obligation to pay rent) shall nevertheless
begin as of the Commencement Date.

                                   ARTICLE IV

                                       USE

            4.1   Permitted Use. The Premises shall be used and occupied only
for the purposes set forth in Section 1.1(r), and not otherwise. The Premises
are being used by Tenant for commercial business use and are not residential
property. Landlord represents that it has appropriate zoning necessary to lease
space for the uses set forth in Section 1.1 above.

            4.2   Rules. Tenant's use of the Premises and the Common Areas are
subject at all times during the Term to the Rules attached to the Lease as
Exhibit "D" and to any modifications of those Rules and any additional Rules
from time to time promulgated by Landlord. Additional Rules will not become
effective and a part of this Lease until a copy of them has been delivered to
Tenant. The inability of Landlord to cause another occupant of the Building to
comply with the Rules will neither excuse Tenant's obligation to comply with the
Rules or any other obligation of Tenant under this Lease nor cause Landlord to
be liable to Tenant for any damage resulting to Tenant. Tenant shall cause
Tenant's employees, servants and agents to comply with the Rules.

            4.3   Additional Covenants of Tenant.

                  (a)   Laws, Statutes, Etc. Tenant shall, at Tenant's sole
cost, promptly comply with all laws, statutes, ordinances, regulations,
guidelines, restrictive covenants or requirements now in force or hereafter
enacted including, without limitation, (a) the Americans With Disabilities Act
of 1990, and (b) OSHA standards, including, without limitation, 29 C. F. R.
Section 1910.1030 (dealing with bloodborne pathogens), and with the requirements
of any governmental authority having jurisdiction over the Building, board of
fire underwriters, utility company serving the Building or other similar body
now or hereafter constituted, relating to or affecting the condition, use or
occupancy of the Premises. The judgment of any court of competent jurisdiction
or the admission of Tenant in any action against Tenant, whether Landlord is a
party thereto or not, that Tenant has violated any of the foregoing is
conclusive of that fact between Landlord and Tenant.

                  (b)   Nuisance. Tenant shall not do or permit anything to be
done in or about the Premises which will in any way obstruct or interfere with
the operation of the Building or Common Areas or with the rights of other
tenants or occupants of the Building or Cannon Areas or Injure, disturb or annoy
other tenants or occupants of Building or Common Areas.

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                  (c)   Building Reputation. Tenant shall not use or permit the
Premises to be used for any objectionable purpose or any purpose which, in the
reasonable opinion of the Landlord, harms or tends to harm the business or
reputation of the Landlord or Building or reflects unfavorably on the Building,
or any part of the Building, or deceives or defrauds the public.

                  (d)   Fire Hazards. Tenant shall not cause, maintain or permit
anything to be done in the Premises nor keep anything in the Premises which
will, to the opinion of Landlord, increase the possibility of fire or other
casualty or increase the then existing premiums for or void the coverage of any
insurance on the Building or contents of the Building.

                  4.4   Control of Building and Common Areas. The Building and
Common Areas will be at all times under the exclusive control, management and
operation of Landlord. Landlord may from time to Lime (i) alter or redecorate
the Building (including the Common Areas or Service Areas) or construct
additional facilities adjoining or approximate to the Building; (ii) close
temporarily doors, entry ways, public spaces and corridors and interrupt or
suspend temporarily Building services and facilities in order to perform any
redecorating or alteration or in order to prevent the public from acquiring
prescriptive rights in the Common Areas; and (iii) change the name of the
Building.

                  4.5   Minimization of Disruption. Landlord will attempt not to
disrupt Tenant's operations in the Premises during the exercise of Landlord's
rights of Section 4.4 or 7.1, but is not required to incur extra expenses to
order to minimize the disruption. Tenant hereby waives all claims for damages or
injuries or interference with Tenant's business, loss of occupancy or quiet
enjoyment and any other laws resulting from the reasonable exercise by Landlord
of any right under Section 4.4 or 7.1. No reasonable exercise by Landlord of any
right under Sections 4.4 or 7.1 constitutes actual or constructive eviction or
breach of any expressed or implied covenant for quiet enjoyment.

                                    ARTICLE V

                             SERVICES AND UTILITIES

            5.1   Services by Landlord. So long as Tenant is not in default
under this Lease, and subject to the conditions and standards contained in this
Lease and to standards, limitations and guidelines imposed by governmental
authorities and utility companies, Landlord will furnish or cause to be
furnished, while Tenant is occupying the Premises, the following services and
utilities:

                  (a)   Water at the normal temperature of the supply of water
to the Building for lavatory and drinking purposes, through fixtures installed
by Landlord or by Tenant with Landlord's consent; including office trash removal
trail the Premises

                  (b)   Janitorial cleaning services including office trash
removal from the Premises to those portions of the Premises used solely for
office purposes, five (5) days per week (except on holidays observed by the
Building), in accordance with the standards of service provided to other tenants
in the Building;

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                  (c)   Heated and refrigerated air conditioning, at such
temperatures and in such quantities as Landlord determines are reasonably
necessary for the reasonably comfortable use and occupancy of the Premises for
general office purposes; current hours of service extend from 7:00 am to 7:00 pm
every day and may only be amended upon 30 day written notice to Tenant;

                  (d)   Routine maintenance in the Common Areas;

                  (e)   Electric current to the Premises for Building standard
office lighting and office machines that consume electric current within the
limits set forth in Section 5.3(.))(1);

                  (f)   Twenty-four (24) hour, non-exclusive. passenger elevator
service and. when scheduled through the Building management. non-exclusive
freight elevator service to the floors) on which the Premises are located; and

                  (g)   Replacement of Building standard light bulbs, and
fluorescent tubes in the Premises.

            Landlord is in no event responsible for the removal from the
Premises of medical waste of any nature or of any contaminated or otherwise
environmentally sensitive materials.

            5.2   Tenant's Obligations. Tenant shall pay for, before
delinquency, all telephone charges and the cost charge for all other materials
and services not expressly the obligation of Landlord that are furnished to or
used on, in or about the Premises during the Term of this Lease.

            5.3   Tenant's Additional Service Requirements.

                  (a)   Additional Services Requiring Landlord's Consent. Except
as otherwise expressly provided elsewhere in this Lease (including any exhibit
attached to this Lease). Tenant shall not, without Landlord's prior consent to
writing. do the following:

                        (i)   Install or use special lighting beyond building
standard, or any equipment machinery, or device in the Premises which requires a
nominal voltage of more than 120 volts, single phase, or which. in Landlord's
reasonable judgment, exceeds the capacity of existing feeders, conductors,
risers, or wiring in or to the Premises or Building, or which requires amounts
of water in excess of that usually furnished or supplied for use in office
space. or which will decrease the amount or pressure of water or the amperage or
voltage of electricity that Landlord can furnish to other occupants of the
Building;

                        (ii)  Install or use any heat or cold-generating
equipment, machinery, or device that affects the temperature otherwise
maintainable by tire heat or air conditioning system of the Building;

                        (iii) Use portions of the Premises for special purposes
requiring greater or more difficult cleaning work than office areas, such as,
but without limitation, kitchens, reproduction rooms, interior glass partitions,
and non-Building standard materials or finishes; or laboratory areas

                        (iv)  Accumulate refuse or rubbish (A) in excess of that
ordinarily accumulated to business office occupancy. or (8) at times other than
Building standard cleaning times.

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                  (b)   Providing Additional Services. If, in the reasonable
opinion of Landlord, additional services to Tenant are necessary, Landlord may:

                        (i)   Require that Tenant cease the activity or remove
the item (or Landlord may refuse to permit the activity or installation of the
item), causing (or which will cause) the need for the additional service. If
Landlord and Tenant are not able to agree on a mutually satisfactory method for
providing the additional services, or in Landlord's reasonable judgment,
providing the additional service is not operationally or economically feasible;

                        (ii)  With respect to additional utility consumption,
install and maintain separate metering devices, or cause periodic usage surveys
to be prepared by an engineer employed by Landlord for that purpose. Cost of the
additional utility consumption plus, if Landlord installs and maintains separate
meters, the costs of the meters and of their installation, maintenance and
repair, or it Landlord orders usage surveys, the cost of those surveys, is the
obligation of Tenant;

                        (iii) With respect to heat or cold-generating equipment,
furnish additional heat or air conditioning to the Premises, or install
supplementary heating or air conditioning units in the Premises or elsewhere in
the Building or modify the existing heating or air conditioning system in the
Premises. The cost of additional heat or air conditioning. supplementary units,
or modifications to the existing system is the obligation of Tenant;

                        (iv)  With respect to lighting beyond Building standard,
purchase and replace, at Tenant's expense, light bulbs and ballasts and/or
fixtures: and/or

                        (v)   With respect to additional cleaning work. instruct
Landlord's janitorial contractor to provide the services, the cost of which is
the obligation of Tenant; provided however, should Landlord require Tenant to
independently contract for all janitorial services in those areas requiring such
additional cleaning (i.e., laboratory areas), Landlord agrees to credit Tenant's
monthly Base Rental by the proportionate cost of the services that Landlord
would ordinarily provide for those office areas.

                  (c)   After Hours Heat or Air Conditioning. Landlord shall, on
request and at Tenant's expense, provide after hours heat or air conditioning.
The cost of after hours heat or air conditioning will be determined from time to
time by Landlord and, on request, confirmed in writing to Tenant.

                  (d)   Payment. Tenant shall pay to Landlord the cost of any
additional service and any other costs for which Tenant is obligated under
Section 5.3(b) or (c) within five (5) days after receipt of an invoice from
Landlord.

            5.4   Interruption of Utility Service. Landlord will use its
reasonable efforts to provide or cause to be provided the services required of
Landlord under this Lease. However, Landlord reserves the right, without any
liability to Tenant and without affecting Tenant's covenants and obligations
under this Lease, to stop or interrupt or reduce any of the services listed in
Section 5.1 or to stop, interrupt or reduce any other services required of
Landlord under this Lease, whenever and for so long as may be necessary, in
Landlord's reasonable judgment, by reason of (i) accidents or emergencies, (ii)
the making of repairs or changes that Landlord in good faith considers necessary
or which it is required or permitted by this Lease or by law to make, (iii)

                                       11
<PAGE>

difficulty in securing proper supplies of fuel, water, electricity, labor or
supplies, (iv) the compliance by Landlord with governmental, quasi-governmental
or utility company energy conservation measures, or (v) the exercise by Landlord
of any right contained in Section 4.4. Landlord shall, on an interruption of a
utility service, use its reasonable efforts to cause the service to be resumed
as soon as practicable. However, no interruption or stoppage of any services
shall ever be construed as an eviction of Tenant nor will interruption or
stoppage cause an abatement of the rent payable under this Lease or in any
manner relieve Tenant from any of Tenant's obligations under this Lease;
provided however, should such interruption or stoppage of any such services
continue for a period exceeding five consecutive days, Tenant shall be entitled
to rent abatement of rent due hereunder for each day after said period on that
portion of the Premises so effected. Landlord is not liable for any interruption
or stoppage of any services or for any damage to persons or property resulting
from that stoppage.

                                   ARTICLE VI

                             REPAIRS AND MAINTENANCE

            6.1   Landlord's Repair Obligations. Landlord will, subject to the
casualty provisions of Article VIII. maintain the (i) Common Areas and Service
Areas, (ii) roof, foundation, exterior windows and load-bearing items of the
Building; (iii) exterior (located outside the Premises) surfaces of walls; (iv)
plumbing, pipes and conduits located in the Common Areas or Service Areas of the
Building; and (v) the Building central heating, ventilation and air
conditioning, electrical, mechanical and plumbing systems. Landlord is not
required to make any repair in connection with or resulting from (1) any
alteration or modification to the Premises or to Building equipment performed
by, for or because of Tenant or to special equipment or systems installed by,
for or because of Tenant, (2) the installation, use or operation of Tenant's
property, fixtures and equipment, (3) the moving of Tenant's property in or out
of the Building or in and about the Premises, (4) Tenant's use or occupancy of
the Premises in violation of Article IV or in a manner not contemplated by the
parties at the time of execution of this Lease (e.g., subsequent installation of
special use rooms), (5) the acts or omissions of Tenant and Tenant's employees,
agents, invitees, subtenants, licensees or contractors, or (6) fire or other
casualty, except as provided in Article VIII. Depending on the nature of repairs
undertaken by Landlord, the cost of the repairs will be borne solely by Landlord
or will be reimbursed to Landlord either by a particular tenant or tenants or by
all tenants as an Operating Cost.

            6.2   Tenant's Obligations. Except for janitorial services provided
by Landlord and Landlord's obligations under Sections 3.1 and 6.1. Tenant, at
Tenant's expense, through Landlord or contractors approved by Landlord, shall
maintain the Premises in good order, condition and repair including, without
limitation, the interior surfaces of the windows, walls and ceilings; floors;
wall and floor coverings; window coverings; doors; interior windows; and all
switches. fixtures and equipment in the Premises. On receipt of reasonable
notice from Tenant, Landlord will perform, at the expense of Tenant, all repairs
and maintenance to plumbing, pipes and electrical wiring located within walls,
above ceiling surfaces and below floor surfaces resulting from the use of the
Premises by Tenant. Tenant is not responsible for any plumbing, pipes and
electrical wiring. Switches, fixtures and equipment located in the Premises but
serving another tenant or for portions of the central heat, ventilation and air
conditioning, electrical, mechanical and plumbing systems of the Building which
are located in the Premises, except for (i) repairs resulting from the acts of
Tenant and Tenant's employees, agents, invitees, subtenants, licensees

                                       12
<PAGE>

or contractors, (ii) modifications made to any of those systems by, for, or
because of Tenant. and (iii) special equipment installed by, for, or because of
Tenant.

            6.3   Rights of Landlord. If Tenant fails, in Landlord's reasonable
judgment. to maintain the Premises in good order, condition and repair. then
Landlord may perform the maintenance. repairs, refurbishing or repairing at
Tenant's expense.(if at Landlord's refit, Tenant's obligation shall. be limited
to a maximum of $5,000)

            6.4   Condition on Surrender. On the expiration or earlier
termination of this Lease, or on the exercise by Landlord of Landlord's right to
re-enter the Premises without terminating this Lease. Tenant shall surrender the
Premises in the same condition as received or as subsequently improved by
Landlord or Tenant, except for (i) ordinary wear and tear, and (ii) damage by
fire, earthquake, acts of God or the elements for which damage Landlord has
received all insurance proceeds, and shall deliver to Landlord all keys for the
Premises and combinations to safes located in the Premises. Tenant shall, at
Landlord's option, remove, or cause to be removed, from the Premises or the
Building, at Tenant's expense (if at Landlord's request, Tenant's obligation
shall be limited to a maximum of $5,000) and as of the expiration or termination
of this Lease, ail signs. notices, displays, millwork. nonmovable trade
fixtures. or, subject to Subsection 6.5(d) of this Lease, any non-Building
standard tenant improvements placed in the Premises or the Building. Tenant
shall repair, at Tenant's expense, any damage to the Premises or the Building
resulting from the removal of any item, including without limitation, repairing
the floor and patching and painting the walls where reasonably required by
Landlord. Tenant's obligations under this Section 6.4 shall survive the
expiration or earlier termination of this Lease. If Tenant fails to remove any
item of property permitted or required to be removed at the expiration or
earlier termination of the Term. Landlord may. at Landlord's option, (a) remove
that property from the Premises or Building at Tenant's expense and sell or
dispose of It in a manner that Landlord considers advisable, or (b) place that
property in storage at Tenant's expense. Any property of Tenant remaining in the
premises ten (10) days after the expiration or termination of this Lease will be
deemed to have been abandoned by Tenant.

            6.5   Alterations by Tenant.

                  (a)   Approval Required. Tenant shall not make. or cause or
permit to be made, any additions. alterations. installations or improvements in
or to the Premises (collectively, "Alternations"). without the prior written
consent of Landlord. Together with Tenant's request for approval of an
Alteration, Tenant must also submit details with respect to design concept,
plans and specifications. names of and financial and other pertinent information
about proposed contractors (including without limitation. the labor organization
affiliation or lack of affiliation of any contractors), certificates of
Insurance to be maintained by Tenant's contractors, hours of construction,
proposed construction methods, details with respect to the quality of the
proposed work and reasonable evidence of security (such as payment and
performance bonds) to assure timely completion and payment of the costs of the
work by the contractor. With respect to an Alteration that is visible from
outside the Premises, which must be approved as determined in Landlord's sale
discretion, the alteration must, in the opinion of Landlord, also be
architecturally and aesthetically harmonious with the remainder of the Building.

                  (b)   Complex Alterations. If the nature, volume or complexity
of any proposed Alteration will affect the basic heat, ventilation and air
conditioning or other Building

                                       13
<PAGE>

Facilities or systems or the Building. Tenant shall furnish to Landlord
Information reasonably required by Landlord to insure Landlord that the
Alterations meet Landlord's reasonable requirements so as not to adversely
affect the Building or Building Facilities or systems; otherwise. Landlord may
require that the work be designed by consultants designated by Landlord and be
performed by Landlord or Landlord's contractors. Any work described in this
Section 6.5(a) must be approved as determined in Landlord's sole discretion,
which will not be reasonably withheld.

                  (c)   Standard of Work. All work to be performed by or for
Tenant pursuant hereto will be performed diligently and in a first-class,
workmanlike manner, and in compliance with all applicable laws, ordinances,
regulations and rules of any public authority having jurisdiction over the
Building and/or Tenant and, so long as communicated in writing to Tenant,
Landlord's insurance carriers. Landlord has the right, but not the obligation,
to inspect periodically the work on the Premises and may make required changes
to the method or quality of the work.

                  (d)   Ownership of Alterations. All Alterations made by or for
Tenant (other than Tenant's movable trade fixtures), immediately become the
property of Landlord, without compensation to Tenant, but Landlord has no
obligation to repair, maintain or insure those Alterations. Carpeting. shelving
and cabinetry are considered improvements of the Premises and not movable trade
fixtures, regardless of how or where affixed. No Alterations will be removed by
Tenant from the Premises either during or at the expiration or earlier
termination of the Term, and they shall be surrendered as a part of the Premises
unless the Alteration is not Building-standard and Landlord has requested that
Tenant remove it. Tenant may request at the time of submission to Landlord of
Tenant's information in connection with a proposed Alteration that Landlord
designate which non-Building standard Tenant improvements resulting from the
Alteration are subject to removal at the end of the Term. In the absence of such
a request. all non-Building standard improvements resulting from the Alteration
are subject to removal in accordance with the provisions of this Lease.

            6.6   Payment of Costs: Mechanic's Liens. Except for costs that
Landlord agrees with Tenant in writing to pay (including in an Exhibit or Rider
attached to this Lease). Tenant shall pay for all costs incurred or arising out
of alterations. additions or improvements in or to the Premises and shall not
permit a mechanic's or materialman's lien to be asserted against the Premises.
On Landlord's request, Tenant shall deliver to Landlord proof of payment
reasonably satisfactory to Landlord of all costs incurred or arising out of any
such alterations, additions or improvements.

            If Tenant contracts with a third party for the construction of
improvements in the Premises, or for the supply of materials relating thereto.
Tenant shall obtain validly executed and acknowledged lien waivers from any
party who might assert a mechanic's or materialmen's lien as a result of
Tenant's contract, regardless of the probable or ultimate validity of that lien.
If a lien is filed against the Premises or any interest of Landlord or Tenant in
the Building, then Tenant shall cause same to be discharged of record within ten
(10) days after its filing. If Tenant fails to obtain that discharge, then, to
addition to any other right or remedy of Landlord, Landlord may (but is not
obligated to) discharge the lien, either by paying the amount claimed to be due
or by procuring a bond. or by any other means. Any amount paid by Landlord to
obtain the discharge of the lien. with interest on that amount at the lesser of
eighteen percent (18%) per

                                       14
<PAGE>

annum or the highest lawful rate, from the date of Landlord's payment to the
date of repayment to Landlord, shall be paid by Tenant to Landlord on demand.

                                   ARTICLE VII

                            LANDLORD'S RIGHT OF ENTRY

            In addition to its re-entry rights under Section 13.2, Landlord and
its authorized agents may. during reasonable hours. enter the Premises (i) to
inspect their general condition and state of repair, (ii) to make repairs
required or permitted under this Lease, (iii) to show the Premises to any
prospective tenant. purchaser or mortgagee, or (iv) for any other reasonable
purpose.

                                  ARTICLE VIII

                            FIRE AND CASUALTY DAMAGE

            8.1   Casualty Reparable by Landlord. If the Building, or any part
thereof, is damaged or destroyed by any peril that would be covered by a
standard Texas fire and extended coverage insurance policy, then Tenant shall
give immediate notice thereof to Landlord, and Landlord shall at its sole cost
and expense proceed with reasonable diligence to rebuild and repair the damaged
areas to substantially the condition in which they existed before the damage or
destruction. except that Landlord is not required to rebuild. repair or replace
any part of the partitions. tenant improvements, fixtures, additions or other
improvements placed in. on or about the Premises by Tenant. Rental payable by
Tenant under this Lease shall be abated to the extent that the Premises are
rendered uninhabitable by the casualty.

            8.2   Casualties Not Reparable By Landlord. If the Premises, or any
part thereof, are damaged or destroyed by a casualty other than a peril covered
by a standard Texas fire and extended coverage insurance policy, or if any other
improvements situated on the Premises are damaged or destroyed, then Tenant
shall at its sole cost and expense proceed with reasonable diligence to rebuild
and repair the damaged improvements to substantially the condition in which they
existed before the damage or destruction, subject to Landlord's approval of the
plans and specifications and the contractor for the rebuilding and repairing.

            8.3   Tenant's Property Insurance. Tenant shall maintain insurance
on all alterations, additions, portions and improvements erected by or on behalf
of Tenant in, on or about the Premises in an amount not less than 80% (or such
greater percentage as necessary to comply with co-insurance requirements of the
policy) the "replacement cost" thereof, as defined in the Replacement Cost
Endorsement to be attached to the policy. Written evidence of the required
insurance coverage or certified copies of policies and receipts evidencing
payment of the premiums therefor shall be delivered to Landlord before the
Commencement Date. Not less than ten (10) days before the expiration date of any
such policies, written evidence of insurance or certified copies of renewals
thereof (bearing notations evidencing the payment of renewal premiums) shall be
delivered to Landlord. All policies shall be procured by Tenant from financially
responsible insurance companies acceptable to Landlord. Each policy shall
provide

                                       15
<PAGE>

for not less than thirty (30) days' written notice to Landlord before a policy
may be cancelled and shall name Landlord. and any other parties reasonably
designated by Landlord, as "additional insureds.

            8.4   Mortgagee Requirements. Notwithstanding anything herein to the
contrary, if the holder of any indebtedness of Landlord secured by a mortgage or
deed of trust covering the Premises requires that insurance proceeds payable to
Landlord be applied to that indebtedness. then Landlord may terminate this Lease
by delivering written notice of termination to Tenant within thirty (30) days
after the requirement is made by the lienholder, whereupon all further rights
and obligations of each party hereunder shall cease and terminate.

            8.5   Termination of Lease. Notwithstanding anything contained to
the contrary in this Article VIII, if the Building or the Premises is destroyed
by a fire or other casualty to the extent that, in Landlord's reasonable
judgment the Building or the Premises cannot practically be rebuilt to its
pre-existing condition within one hundred twenty (120) days, or in any event
during the last twelve (12) months of the Term, then Landlord may, at Landlord's
sole option, terminate this Lease within ninety (90) days from the date of
destruction. by delivering written notice thereof to Tenant, in which case
neither party hereto shall have any further obligations hereunder to the other.

            8.6   Waiver of Subrogation. Each of Landlord and Tenant waives any
and every claim in its favor against the other during the Term of this Lease for
any and all loss of, or damage to, any of its property located within or upon,
or constituting a part of. the Premises, which loss or damage is covered by
valid and collectible fire and extended coverage insurance policies. These
mutual waivers are 1n addition to, and not in limitation or derogation of, any
other waiver or release contained to this Lease with respect to any loss of, or
damage to, property of Tenant. Because the mutual waivers will preclude the
assignment of a claim by way of subrogation or otherwise to an insurance company
(or any other person), each party hereto shall immediately give to each
insurance company which has issued to it policies of fire and extended coverage
insurance, written notice of the terms of the waiver. and shall cause those
insurance policies to be properly endorsed. if necessary, to prevent the
invalidation of insurance coverages by reason of the waiver.

                                   ARTICLE IX

                    INDE14NITY AND PUBLIC LIABILITY INSURANCE

            9.1   Indemnity. Landlord is not liable to Tenant or Tenant's
employees, agents. patrons or visitors. or to any other person whomsoever. for
any injury to person or damage to property on or about the Premises. if caused
by the action or inaction of Tenant, its agents, servants or employees, or of
any other person entering upon the Premises under the expressed or implied
invitation of Tenant. including without limitation. action or inaction required
of Tenant by Section 4.3(a) of this Lease. or caused by the Building or the
improvements located on the Premises becoming out of repair, or caused by
leakage of gas, oil. water or steam or by electricity emanating from the
Premises. or due to any cause whatsoever, including Landlord's own negligence.
Tenant hereby indemnifies Landlord and agrees to hold it harmless from any

                                       16
<PAGE>

loss. expense or claims. including attorney's fees, arising out of any such
damage or injury. except injury to persons or damage to property the sole cause
of which is the gross negligence or willful misconduct of Landlord.

            9.2   Liability Insurance. Tenant shall procure and maintain
throughout the Term at its sole cost and expense. a policy or policies of
comprehensive general liability insurance. for bodily injury or death or
property damage. insuring Landlord and Tenant against all claims. demands. or
actions relating to the Premises on an occurrence basis with a minimum combined
single limit with policy limits of not less than $1,000,000 per occurrence for
Injury to persons (including death). and for property damage or destruction.
including loss of use. All policies shall be procured by Tenant from financially
responsible insurance companies acceptable to Landlord, and shall name Landlord.
and any other party reasonably designated by Landlord, as "additional insureds."
Written evidence of the required insurance coverage or certified copies of
policies and receipts evidencing payment of premiums therefor shall be delivered
to Landlord before the Commencement Date. Not less than ten (10) days before the
expiration date of any policies, written evidence of insurance or certified
spies of the renewals thereof (bearing notations evidencing the payment of
renewal premiums) shall be delivered to Landlord. Ail policies shall provide
that not less than thirty (30) days' written notice shall be given to Landlord
before a policy may be cancelled.

            9.3   Tenant's 's Failure to Maintain Insurance. If Tenant fails to
comply with the foregoing insurance requirements, then Landlord may (in addition
to having available to it all other remedies provided herein on the occurrence
of an Event of Default) obtain such insurance, and Tenant shall pay to Landlord
on demand, as additional rent hereunder, the premium cost thereof plus interest
at the lesser of eighteen percent (18%) per annum or the highest lawful rate.
from the date of payment by Landlord until payment by Tenant.

                                    ARTICLE X

                                  CONDEMNATION

            10.1  Total or Substantial Condemnation. If all or a substantial
part of the Premises is taken for any public or quasi-public use under any
governmental law, ordinance or regulation or by right of eminent domain, or is
sold to the condemning authority under threat of condemnation. then this Lease
shall terminate and the rent shall be abated during the unexpired portion of the
Term, effective from the date of taking of the Premises by the condemning
authority.

            10.2  Partial Condemnation. If less than a substantial part of the
Premises Is taken for public or quasi-public use under any governmental law.
ordinance or regulation, or by right of eminent domain, or is sold to the
condemning authority under threat of condemnation, then Landlord, at its option,
may by written notice to Tenant terminate this Lease or shall forthwith at its
sole expense restore and reconstruct the building in which the Premises are
located and improvements therein (other than leasehold improvements or other
improvements made by Tenant or any assignee, subtenant or other occupant of the
Premises) to make the same reasonably suitable for the uses for which the
Premises are leased. as provided in Section 4.1.

                                       17
<PAGE>

            10.3  Disposition of Awards. All awards arising from a total or
partial taking of the Premises, of Tenants leasehold estate, or a taking for
temporary use shall belong to and be the property of Landlord without any
participation by Tenant. Tenant hereby assigns to Landlord any share of any such
award that might otherwise be payable to Tenant.

                                   ARTICLE XI

                  ASSIGNMENT, TRANSFER AND SUBLEASING BY TENANT

            11.1  Landlord's Consent Required.

                  (a)   No Assignment or Subletting. Tenant shall not assign or
in any manner transfer this Lease or any estate or interest therein. or sublet
the Premises or any part thereof, or grant any license, concession or other
right of occupancy of any portion of the Premises without the prior written
consent of Landlord, which shall not be unreasonably withheld. However, Tenant
may assign this Lease without Landlord's prior approval to a wholly-owned
subsidiary. Consent by Landlord to one or more assignments or sublettings shall
not operate as a waiver of Landlord's right to any subsequent assignments and
sublettings. All assignments and sublettings shall be subject to the use
limitations stated in Section All assignments will transfer the and privileges
of Tenant

                  (b)   Required Information. If Tenant desires to design the n
this Lease or to sublet all or part of the Premises, then Tenant shall notify
Landlord at least thirty (30) days in advance of the date on which Tenant
desires to make the assignment or enter into the sublease. Tenant shall provide
Landlord with a copy of the proposed assignment or sublease, and sufficient
information concerning the proposed assignee or subtenant to low Landlord to
make informed judgments as to the financial condition. reputation, operations
and general irability of the proposed assignee or subtenant.

                  (c)   Landlord's Options. Within fifteen (15) days after
Landlord's receipt of the documents and information described in Subsection (b)
above, Landlord has the following options, as elected in its sole discretion:

                        (i)   cancel the Lease as to all of the Premises if
Tenant proposes to assign the Lease or sublet more than fifty percent (50%) of
the Premises, or cancel the Lease as to the portion of the Premises proposed be
sublet if Tenant proposes to sublet less than fifty percent (50%) of the
Premises; or

                        (ii)  consent to the proposed assignment or sublease,
subject to the other provisions contained in this Article XI; or

                        (iii) refuse to consent to the proposed assignment or
sublease but allow Tenant to continue its search for an assignee or subtenant
that will be acceptable to Landlord, which option will be deemed to have been
elected by Landlord unless Landlord gives Tenant written notice to the contrary.

                                       18
<PAGE>

                  (d)   Legal Fees and Other Expenses. To reimburse Landlord for
administrative and legal expenses associated with its review and/or preparation
of legal documents relating to a proposed assignment or sublease, Tenant shall
pay to Landlord the amount of all reasonable legal fees and expenses incurred by
Landlord in connection with its review of Tenant's request, plus any legal fees
and disbursements incurred in the preparation and review of any documentation.
Tenant shall pay these amounts within five (5) days after its receipt of an
invoice from Landlord, as additional rent.

            11.2  Transfer of Voting Interest. If Tenant is a corporation or
partnership and if at any time during the Term of this Lease (including
extensions, those persons who own a majority of either the outstanding voting
shares or all outstanding shares of capital stock or the controlling partnership
interests of Tenant at the time of the execution of this Lease, cease to own a
majority of those shares or partnership interests (except as the result of
transfers by devise or descent), then the change in ownership of a majority of
those shares or partnership interests is deemed an assignment of this Lease by
Tenant and therefore subject in ail respects to the provisions of Section 11.1.
The previous sentence shall not apply. however, if at the time of the execution
of this Lease the outstanding voting shares of capital stock or partnership
interests of Tenant are listed on a recognized security exchange or
over-the-counter market.

            11.3  No Release. Notwithstanding any assignment or subletting,
Tenant and any Guarantor of Tenant's obligations under this Lease shall remain
fully responsible and liable for the payment of the rent herein specified and
for compliance with all of Tenant's other obligations under this Lease (even if
future assignments and sublettings occur after the assignment or subletting by
Tenant, and regardless of whether or not Tenant's approval has been obtained for
those future assignments and sublettings). Moreover, if the rental due and
payable by a sublessee (or a combination of the rental payable by the sublessee
plus any bonus or other consideration relating thereto) exceeds the rental
payable under this Lease, or if with respect to a permitted assignment,
permitted license or other transfer by Tenant permitted by Landlord. the
consideration payable to Tenant by the assignee, licensee or other transferee
exceeds the rental payable under this Lease, then Tenant shall pay to Landlord
the excess amounts within ten (10) days after receipt thereof by Tenant.
Finally, on an assignment or subletting, it is understood and agreed that all
rentals paid to Tenant by an assignee or sublessee are received by Tenant in
trust for Landlord, to be forwarded immediately to Landlord without offset or
reduction of any kind. On Landlord's election, those rentals shall be paid
directly to Landlord as specified under this Lease (to be applied as a credit
against Tenant's accrued rental obligations, with any excess being the sole
property of Landlord).

            11.4  No Mortgage. Tenant shall not mortgage, pledge or otherwise
encumber its interest in this Lease or in the Premises.

            11.5  Transfer of Landlord's Interest. On a transfer and assignment
by Landlord of its interest in this Lease, or all or part of the Building,
Landlord shall thereby be released from any further obligations hereunder, and
Tenant shall look solely to the successor in interest of Landlord for
performance, of those obligations. Any security given by Tenant to secure
performance of Tenant's obligations hereunder may be transferred by Landlord to
the successor in interest, and Landlord shall thereby be discharged of any
further obligation relating thereto. On a transfer of its interest in the
Building or Premises, Landlord may become a mortgagee for purposes of Article
XIV.

                                       19
<PAGE>

            11.6  Bankruptcy. If this Lease is assigned in connection with a
bankruptcy proceeding, the provisions of Article XIV apply.

                                   ARTICLE XII

                                  HOLDING OVER

            Without in any way affecting Landlord's rights and remedies under
this Lease, if Tenant holds over after the expiration or termination of this
Lease, then Tenant shall pay as monthly rent during each month of the holdover
period an amount equal to 150% of the amount of monthly rent due for the last
month of the Term. No holding over by Tenant after the Term of this Lease,
either with or without the consent and acquiescence of Landlord. shall extend
the Term for a period longer than one month unless that Term is extended in a
writing executed by Landlord. Any holding over without the written consent of
Landlord shall be on a vacancy-at-sufferance basis. On an unauthorized holding
over, Tenant shall indemnify Landlord against all claims for damages with
respect to any other lessee or prospective lessee to whom Landlord has leased
all or any part of the Premises.

                                  ARTICLE XIII

                     DEFAULT BY TENANT; LANDLORD'S REMEDIES

            13.1  Events of Default. The following events (individually, an
"Event of Default," and collectively, "Events of Default") constitute defaults
under this Lease:

                  (a)   Failure of Tenant to pay when due an installment of the
rent or any other amount payable to Landlord hereunder.

                  (b)   Failure of Tenant to comply with any term, condition or
covenant of this Lease.

                  (c)   Insolvency of, or the making of a transfer in fraud of
creditors or a general assignment for the refit of creditors by, Tenant or a
Guarantor of Tenant's obligations under this Lease.

                  (d)   Filing of a petition under any section or chapter of the
United States Bankruptcy Code, as needed. or under any similar law or statute of
the United States or any State thereof, by Tenant or by a guarantor of Tenant's
obligations under this Lease, or entry of an order for relief in a bankruptcy
proceeding against Tenant or a Guarantor.

                  (e)   Appointment of a receiver, trustee or liquidator of
Tenant or of a Guarantor or for alt or substantially all of the assets of Tenant
or of a Guarantor of Tenant's obligations under this Lease.

                  (f)   Abandonment by Tenant of any substantial portion of the
Premises or cessation of use of the remises for the purpose leased.

                  (h)   Assignment of Tenant's interest to this Lease by
operation of law.

                                       20
<PAGE>

            13.2  Remedies of Landlord. On the occurrence of an Event of Default
listed in Section 13.1, Landlord may pursue any one or more of the following
remedies without any notice or demand whatsoever except as otherwise indicated
(and, further, Tenant is liable for damages as provided in Section 13.3):

                  (a)   Termination. Terminate this Lease by giving written
notice of termination to Tenant, in which event Tenant shall immediately
surrender the Premises to Landlord. If Tenant fails to so surrender the
Premises, then Landlord may, without, prejudice to any other remedy it has for
possession of the Premises or arrearages in rent or other damages, re-enter and
take possession of the Premises and expel or remove Tenant and any other person
occupying the Premises or any part thereof, by any lawful means, without being
liable for prosecution or claim for damages whether caused by the negligence of
Landlord or otherwise.

                  (b)   Continuation of Lease: Reletting of Premises. Landlord
may continue this Lease in full force and effect, in which case Tenant is liable
for all rents and other amounts payable under this Lease. Landlord may,
nevertheless. re-enter and take possession of the Premises. by any lawful means,
without terminating this Lease and without being liable for prosecution or for
any claim for damages therefor. and relet the Premises and apply the rent
received to the account of Tenant. No reletting by Landlord is considered to be
for its own account unless Landlord has notified Tenant that this Lease has been
terminated. Landlord may relet the Premises for a period or periods of time
equal to, lesser or greater than the remainder of the Term, and on whatever
terms and conditions Landlord, in its sole discretion. deems advisable.
Landlord's action under this subsection (b) is not considered an acceptance of
Tenant's surrender of the Premises unless Landlord expressly so notifies or
agrees with Tenant in writing.

                  (c)   Act for Tenant. Re-enter the Premises by any lawful
means, without terminating this Lease and without being liable for any
prosecution or for any claim for damages therefore, and do whatever Tenant is
obligated to do under the terms of this Lease. Tenant shall pay to Landlord, on
demand. expenses incurred by Landlord in effecting compliance with Tenant's
obligations under this Lease, plus interest thereon at the lesser of 18% per
annum or the highest lawful rate, from the date expended until repaid. Landlord
is not liable for any damages resulting to Tenant from such action, whether
caused by negligence of Landlord or otherwise.

                  (d)   Change Locks. Landlord may change the locks on doors
permitting entry into the Premises and deny Tenant's access thereto until all
Events of Default have been cured. Landlord has no obligation to advise Tenant
of the change of locks other than to provide written notice at Premises of the
person whom Tenant may contact, during the normal business hours for the
Premises of which Tenant has advised Landlord in writing, to acquire additional
Information. Tenant waives all rights under Chapter 93 of the Texas Property
Code to which it is otherwise entitled.

                  (e)   Recapture of Advance Benefits. In addition to the
remedies set forth in Sections 13.2(a)-(d), inclusive, on the occurrence of an
Event of Default by Tenant under this Lease with respect to which Landlord
elects either to terminate this Lease or, without terminating this Lease, to
terminate Tenant's possession of the Premises. (i) Tenant shall pay to Landlord
in cash on demand an amount equal to all "Reimbursable Costs" (as defined below)
for which Tenant has not yet vested (as defined below). and (ii) any remaining
rental abatement and/or other concessions that have not yet accrued under this
Lease shall terminate. As used herein. the

                                       21
<PAGE>

term "Reimbursable Costs" means the total of (i) the aggregate dollar value of
all rental abatements that Tenant has received under this Lease; and (iii) the
aggregate dollar amount which has been paid to or on behalf of Tenant under this
Lease, including. without limitation. any brokerage commission paid and/or
payable by Landlord in connection with the execution of this Lease. Because the
Reimbursable Costs were incurred by Landlord in reliance on Tenant's fully
performing Tenant's obligations under this Lease. Tenant hereby acknowledges
that Landlord will be damaged on a default by Tenant in an amount equal to the
aggregate dollar value of the Reimbursable Costs for which Tenant has not yet
vested. in addition to (and not 1n lieu of) any other damages suffered by
Landlord. Tenant shall vest as to Reimbursable Costs at the rate of (A) 100%
divided by the number of months in the initial Term for which Tenant is
obligated to pay full rent, (B) multiplied by the number of months for which
Tenant has paid full rent and is not otherwise in default hereunder. No vesting
shall occur with respect to any month for which Tenant has not paid rent or in
which Tenant is otherwise in default hereunder. For example, if Tenant is
obligated to pay full rent for 50 months, then Tenant shall vest hereunder at
the rate of 2% for each month for which it pays full rent.

                  (f)   Lease Remedies Not Exclusive; Lease Supersedes Property
Code. Pursuit of any of the foregoing remedies does not constitute an
irrevocable election of remedies nor preclude pursuit of any other remedy
provided elsewhere in this Lease or by applicable law, and none is exclusive of
another unless so provided in this Lease or by applicable law. Likewise,
forbearance by Landlord to enforce one or more of the remedies available to it
on an Event of Default does not constitute a waiver of that default or of the
right to exercise at remedy later or of any rent, damages or other amounts due
to Landlord hereunder. In the case of a inflict. and to the extent that Chapter
93 of the Texas Property Code applies to this Lease, the terms of this Lease
supersede and control the provisions of Chapter 93 of the Texas Property Code.

            13.3  Tenant's Liability For Landlord's Damages.

                  (a)   In General. In all events, Tenant is liable for all
damages of whatever kind or nature, direct or indirect, suffered by Landlord as
a result of the occurrence of an Event of Default. If Tenant fails to promptly
pay Landlord for the damages suffered, Landlord may pursue a monetary recovery
from Tenant. Included among those damages are all expenses incurred by Landlord
to repossessing the Premises (including, among other expenses, increased
insurance premiums resulting from Tenant's vacancy). all expenses incurred by
Landlord in reletting the Premises (including, among other expenses. those
Incurred for repairs. remodeling, replacements, advertisements and brokerage
fees), all concessions granted to a new tenant on a reletting, all losses
incurred by Landlord as a result of Tenant's default (including among other
losses, any adverse reaction by Landlord's mortgagee or by other tenants or
prospective tenants of the Building) and a reasonable allowance for Landlord's
administrative efforts, salaries and overhead attributable directly or
indirectly to Tenant's default and landlord's pursuit of the rights and remedies
provided under this Lease or by applicable law.

                  (b)   Termination of Lease. If Landlord terminates this Lease
            under Section 13.2(a). then Tenant shall pay to Landlord on demand
            the amount of all loss and damage suffered by Landlord by reason of
            the termination, to be determined by one or a combination of the
            following measures of damages:

                                       22
<PAGE>

                        (i)   Until Landlord is able, through good faith efforts
(the nature of which shall be at Landlord's sole discretion), to relet the
Premises. Tenant shall pay to Landlord on or before the first day of each
calendar month. the amounts required to be paid by Tenant under this Lease.
After the Premises have been relet by Landlord, Tenant shall pay to Landlord on
the 20th day of each calendar month, the difference between the amount required
to be paid by Tenant under this Lease for that calendar month and the amount
actually collected by Landlord for that month. If it becomes necessary for
Landlord to bring suit to collect a Deficiency. Landlord may allow the
deficiency to accumulate and may bring an action on several or all of the
accrued deficiencies at one time. No suit shall prejudice to any way Landlord's
right to bring a similar action for any deficiency or deficiencies that arise
later. Any amount collected by Landlord from subsequent tenants for any calendar
month which exceeds the amounts required to be paid by Tenant under this Lease
shall be credited to reduce Tenant's liability for any calendar month for which
the amount collected by Landlord is less than the amount required to be paid by
Tenant, as Tenant's sole right to that excess.

                        (ii)  When Landlord desires to do so. including after it
has elected to proceed under subparagraph (i) immediately above (that election
not being exclusive under this Lease). Landlord may demand a final settlement.
On that demand, Landlord is entitled to receive from Tenant the difference
between the total of all amounts required to be paid by Tenant under this Lease
for the remainder of the Term minus the reasonable rental value of the Premises
for that period, with such difference to be discounted to a present value based
on a rate equal to the rate of interest allowed by law in Texas when the parties
to a contract have not agreed on a particular rate of interest (or, in the
absence of such a stipulated rate. at the rate of 10% per annum).

                        (iii) Landlord's election to proceed under subsection
(i) above shall not prejudice its right thereafter to cancel that election in
favor of the remedy described in subsection (ii) above, so long as at the time
of that cancellation, Tenant is still in default.

                  (c)   Continuation of Lease: Reletting of Premises. If
Landlord elects to continue this Lease in effect, then Tenant is liable for the
rent and other amounts due hereunder. If Landlord relets the Premises for the
account of Tenant, then the amounts actually received by Landlord shall be
credited to the amounts owed by Tenant under this lease (including the amounts
described in Section 17.3(a)).

                                   ARTICLE XIV

                       BANKRUPTCY OR INSOLVENCY OF TENANT

            14.1  Liquidation. If Tenant becomes a debtor under Chapter 7 of the
federal Bankruptcy Code. 11 U. S. C. Sections 101 et seq. (the "Bankruptcy
Code"), and Tenant's trustee or Tenant elects to assume this Lease for the
purpose of assigning it, or otherwise, then that election and assignment may be
made only if the provisions of Sections 14.2 and 14.4 are satisfied. If Tenant
or Tenant's trustee fails to elect to assume this Lease within 60 days after an
order for relief is entered against Tenant, or such additional time as is
provided by the court within that 60-day period, then this Lease shall be deemed
to have been rejected. Immediately after that

                                       23
<PAGE>

rejection, Landlord may repossess the Premises without further obligation to
Tenant or Tenant's trustee and this Lease shall terminate, but Landlord's right
to be compensated for damages (including. without limitation. liquidated damages
provided for under this Lease) in any such proceeding shall survive.

            14.2  Reorganization. If a petition for reorganization or adjustment
of debts is filed concerning Tenant under Chapter 11 of the Bankruptcy Code, or
a proceeding is filed under Chapter 7 of the Bankruptcy Code and is converted to
a Chapter 11 case, then Tenant's trustee or Tenant, as debtor-in-possession.
must elect to assume this Lease within 120 days after an order for relief is
entered against Tenant, or Tenant's trustee or the debtor-in-possession shall be
deemed to have rejected this Lease. If Tenant. Tenant's trustee or the
debtor-in-possession fails to perform all of Tenant's obligations under this
Lease within the time periods (excluding grace periods) required for that
performance, then no election by Tenant's trustee or the debtor-in-possession to
assume this Lease, whether under Chapter 7 or Chapter 11, is effective unless
each of the following conditions has been satisfied:

                  (a)   Defaults Cured. Tenant's trustee or the
debtor-in-possession cures all defaults under the Lease. or provides Landlord
with Assurance (as defined below) that it will cure. (i) all defaults that can
be cured by the payment of money within 10 days from the date of such assumption
and (ii) all other defaults under this Lease that can be cured by the
performance of the act needed to effect the cure promptly after the date of
assumption.

                  (b)   Compensation For Damages. Tenant's trustee or the
debtor-in-possession and, if this Lease has been guaranteed, Guarantor
compensates, or provides Landlord with Assurance that within 10 days from the
date of such assumption it will compensate. Landlord for any actual pecuniary
loss incurred by Landlord arising from the default of Tenant, Tenant's trustee,
or the debtor- in-possession as indicated in any statement of actual pecuniary
loss sent by Landlord to Tenant's trustee or the debtor-In-possession.

                  (c)   Assurance of Future Performance. Tenant's trustee or the
debtor-in-possession provides Landlord with Assurance of the future performance
of the obligations of Tenant under the Lease. Lessee's trustee or the
debtor-In-possession, and if that Assurance has been provided, Tenant's trustee
or the debtor-in-possession shall also (i) deposit with Landlord, as security
for the timely payment of rent under this Lease, an amount equal to three (7)
months' Base Rental, and (ii) pay in advance to Landlord on the date that Base
Rental is due and payable, one-twelfth (1/12) of Tenant's annual obligations for
any other purpose (e.g., taxes and insurance) pursuant to this Lease. The
obligations imposed on Tenant's trustee or the debtor- in-possession all
continue with respect to Tenant or any assignee of this Lease after the
completion of bankruptcy proceedings.

                  (d)   No Breach of Other Obligations. The assumption will not
breach or cause a default under any provision of any other lease, mortgage,
financing agreement or other agreement by which Landlord is bound relating to
the Premises or any larger development of which the Premises are a part.

                                       24
<PAGE>

                  For purposes of this Article XIV, Landlord and Tenant
acknowledge that "Assurance" means no less than (i) Tenant's trustee or the
debtor-in-possession has and will continue to have sufficient unencumbered
assets after the payment of all secured obligations and administrative expenses
to assure Landlord that sufficient funds will be available to fulfill the
obligations of Tenant under this Lease and there has been deposited with
Landlord. or the Bankruptcy Court has entered an order segregating. sufficient
cash payable to Landlord, and/or Tenant's trustee or the debtor-in-possession
shall have been granted a valid and perfected first lien and security interest
and/or mortgage in property of Tenant, Tenant's trustee or the
debtor-in-possession, acceptable as to value and kind to Landlord, to secure to
Landlord the obligation of Tenant, Tenant's trustee or the debtor-in-possession
to cure the defaults under this Lease, monetary and/or non-monetary, within the
time periods set forth above, and (if this Lease has been guaranteed) (ii)
Guarantor has cured all defaults under this Lease that can be cured by the
payment of money and has undertaken to promptly cure all other :faults under
this Lease that can be cured by the performance of any act and, if this Lease
has been guaranteed, Landlord has received a duly authorized and binding
undertaking of Guarantor that Guarantor remains obligated under its Guaranty to
the same extent as if the circumstances giving rise to the requirement that
Assurance be provided had not occurred. together with a statement of Guarantor's
certified public accountants certifying that the net worth of Guarantor, on a
consolidated basis but exclusive of any net worth of Lessee, is in excess of
$250,000.00. For an individual Guarantor, there shall be excluded from that
Guarantor's net worth for purposes hereof any equity in the Guarantor's
principal residence. For a non-individual Guarantor, there shall be excluded
from that Guarantor's net worth for purposes hereof its basis in Its fixed
assets, including land and buildings.

            14.3  Subsequent Liquidation or Petition. If this Lease is assumed
in accordance with Section 14.2 and hereafter Tenant is liquidated or files a
petition for reorganization or adjustment of debts under Chapter 11 of the
Bankruptcy Code, Landlord may, at its option, terminate this Lease and all
rights of Tenant hereunder, by giving Tenant notice of its election so to
terminate within 30 days after the occurrence of either of such events.

            14.4  Assignment.

                  (a)   Adequate Assurance of Future Performance. If Tenant's
trustee or the debtor-in-possession assumes this Lease pursuant to the terms and
provisions of Sections 14.1 or 14.2 for the purpose of assigning (or otherwise
elects to assign) this Lease to an assignee other than Guarantor, then this
Lease may be so assigned only if the proposed assignee provides adequate
assurance of future performance of all of the terms, covenants and conditions of
this Lease to be performed by Tenant including, without limitation, the
obligation to pay Base Rental. As used herein, "adequate assurance of future
performance" means that no less than each of the following conditions has been
satisfied:

                        (i)   The proposed assignee has furnished Landlord with
either (A) a current financial statement audited by a certified public
accountant indicating a net worth and working capital in amounts that Landlord
reasonably determines are sufficient to assure the future performance by the
assignee of Tenant's obligations under this Lease or (B) a guaranty, or
guaranties, in form and substance satisfactory to Landlord from one or more
persons with a net worth and working capital in amounts that Landlord reasonably
determines are sufficient to assure the future performance of Tenant's
obligations under this Lease.

                                       25
<PAGE>

                        (ii)  The proposed assignment will not release or impair
any guaranty of the obligations of Tenant (including Guarantor and the proposed
assignee) under this lease.

                        (iii) The proposed assignee and its guarantors have a
demonstrated financial condition and operating performance similar or superior
to that of Tenant and any Guarantor of Tenant's obligations under this Lease at
the date that Tenant became a tenant hereunder.

                  (b)   Any and all monies or other considerations payable or
otherwise to be delivered in connection with the assignment referred to in
subparagraph (i) next above shall be paid or delivered to Landlord, shall be and
remain the exclusive property of Landlord and shall not constitute property of
Tenant or of the estate of Tenant within the meaning of the Bankruptcy Code. Any
and all monies or other considerations constituting Landlord's property under
the preceding sentence not paid or delivered to Landlord shall be held in trust
for e benefit of Landlord and be promptly paid to or turned over to Landlord.

                  (c)   Any person or entity to which this Lease is assigned
pursuant to the provisions of the Bankruptcy Code shall be deemed without
further act or deed to have assumed all of the obligations arising under this
Lease on and after the date of such assignment. Any such assignee shall on
demand execute and deliver to Landlord an instrument confirming the assumption.

            14.5  Reasonable Charges. When, pursuant to the Bankruptcy Code,
Tenant's trustee or the debtor- in-possession is obligated to pay reasonable use
and occupancy charges for the use of the Premises, the charges shall not be less
than the Base Rental and all other amounts payable by Tenant under this Lease.

            14.6  Consent. Neither the whole nor any portion of Tenant's
interest in this Lease or its estate in the Premises shall pass to any trustee,
receiver, assignee for the benefit of creditors, or any other person or entity,
or otherwise by operation of law under the laws of any state having jurisdiction
of the person or property of Tenant unless Landlord has consented to the
transfer in writing. No acceptance by Landlord of Base Rental or any other
payments from a trustee, receiver, assignee, person or other entity shall be
deemed to constitute such consent by landlord, nor shall it be deemed a waiver
of Landlord's right to terminate this lease for transfer of Tenant's interest
under this Lease without such consent.

            14.7  Intent. Landlord and Tenant acknowledge, for themselves and
for each of their successors and assigns, their intent to have the applicable
provisions of Section 365 of the Bankruptcy Code, or any successor provisions,
apply to this Lease.

                                   ARTICLE XV

                                  LIEN FOR RENT

            IN CONSIDERATION OF THE MUTUAL BENEFITS ARISING UNDER THIS LEASE
TENANT HEREBY GRANTS TO LANDLORD A LIEN AND SECURITY INTEREST IN STANDARD OFFICE
EQUIPMENT OWNED BY TENANT (INCLUDING,

                                       26
<PAGE>

BUT NOT LIMITED TO, ALL FIXTURES, MACHINERY, EQUIPMENT, FURNISHINGS, AND OTHER
ARTICLES OF PERSONAL PROPERTY NOW OR HEREAFTER PLACED IN OR ON THE PREMISES BY
TENANT, TOGETHER WITH THE PROCEEDS FROM THE DISPOSITION OF THOSE ITEMS) [THE
"COLLATERAL"], NOW OR HEREAFTER PLACED IN OR UPON TILE PREMISES, AS SECURITY FOR
PAYMENT OF ALL RENT AND OTHER SUMS AGREED TO BE PAID BY TENANT HEREIN. THE
PROVISIONS OF THIS ARTICLE XV CONSTITUTE A SECURITY AGREEMENT UNDER THE TEXAS
UNIFORM COMMERCIAL CODE, AND LANDLORD HAS AND MAY ENFORCE A SECURITY INTEREST IN
THE COLLATERAL. THE COLLATERAL SHALL NOT BE MOVED WITHOUT THE CONSENT OF
LANDLORD UNTIL ALL ARREARAGES IN RENT AND OTHER SUMS OF MONEY THEN CUE TO
LANDLORD HEREUNDER HAVE BEEN PAID AND DISCHARGED. ON OR BEFORE THE COMMENCEMENT
DATE. TENANT SHALL EXECUTE, AS DEBTOR. TWO OR MORE FINANCING STATEMENTS. IN THE
FORMS OF EXHIBIT "F" ATTACHED HERETO, TO PERFECT THIS SECURITY INTEREST PURSUANT
TO THE TEXAS UNIFORM COMMERCIAL CODE. LANDLORD MAY AT ITS ELECTION AT ANY TIME
FILE A COPY OF THIS LEASE AS A FINANCING STATEMENT. LANDLORD, AS SECURED PARTY,
HAS ALL OF THE RIGHTS AND REMEDIES AFFORDED A SECURED PARTY UNDER THE TEXAS
UNIFORM COMMERCIAL CODE 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 XVI

                          SUBORDINATION AND ATTORNMENT

            Landlord may transfer, assign, mortgage and convey to whole or to
part the Building or the Land, and any and all of its rights under this Lease,
and nothing herein shall be construed as a restriction on Landlord's right to do
so. Tenant hereby subordinates this Lease and all rights of Tenant hereunder to
the lien of any mortgage or deed of trust now or hereafter placed against the
Premises. and all renewals, substitutions and extensions thereof, and all such
liens are superior to and prior to this Lease. If a mortgagee or other
lienholder acquires the Premises as a purchaser at a foreclosure sale (any such
mortgagee or other lienholder of purchaser at a foreclosure sale being each
hereinafter referred to as the "Purchaser at Foreclosure"), then cant shall (at
the sole and absolute election of the Purchaser at Foreclosure) thereafter
remain bound to the same effect as if a new and identical Lease between the
Purchaser at Foreclosure, as Landlord, and Tenant, as Tenant, had been entered
into for the remainder of the Term of the Lease in effect at the time of the
foreclosure. Tenant shall, on request. execute any certificate or instrument
necessary or desirable further to effect the subordination of this Lease to the
mortgage or deed of trust liens, or to confirm a lienholder's election to
continue the Lease in effect after foreclosure. as above provided. Tenant shall
attorn and pay rent to the Purchaser at Foreclosure as if that party were a
signatory to this Agreement. Tenant hereby constitutes and appoints Landlord as
Tenant's attorney-in-fact to execute any such certificate or instrument for and
on behalf of Tenant. Any lienholder with a lien that covers the Premises has the
absolute right at any time to subordinate its lien to this Lease and to Tenant's
rights hereunder such that a foreclosure of that lien will result in the
purchase of the affected property subject to the rights of Tenant hereunder, and

                                       27
<PAGE>

Tenant has no right or ability to unilaterally prevent that result. On an act or
omission by Landlord which might allow Tenant to terminate this Lease or to
claim a partial or total eviction, Tenant shall not exercise any such right
until (i) it has given written notice to the holder of any mortgage. deed of
trust or other lien on the Premises. of the act or omission, and (ii) a
reasonable period for remedying the act or omission has elapsed following the
giving of notice.

                                  ARTICLE XVII

                             TENANT ESTOPPEL LETTER

            On the request of Landlord made from time-to-time with at least five
(5) business days' notice, Tenant shall execute and deliver to Landlord, or to a
mortgagee or prospective purchaser as directed by Landlord, a statement in
writing certifying, to the extent true, that. among other things, (i) alt of the
construction work in or relating to the Premises has been satisfactorily
completed, (ii) Tenant has accepted the work in or relating to. and is in
possession of. the Premises, (iii) the Lease is in full force and effect and has
not been amended, modified or superseded, (iv) there is no existing default on
Landlord's or Tenant's part, (v) rent has begun to accrue but has not been paid
more than one month in advance. (vi) Tenant has no claim against Landlord which
might be offset against accruing rent. and (vii) Tenant has no knowledge of any
pledge or assignment by Landlord of the Lease or rentals due thereunder, except
for the assignment to Landlord's lenders. If any of the foregoing matters is not
true at the time that Landlord requests the written statement. then Tenant shall
specify in detail any differences.

                                  ARTICLE XVIII

                                 QUIET ENJOYMENT

            Landlord has neither made nor authorized any other person (including
Broker or any other brokers) to make any representations, covenants or
warranties with respect to the Premises except as expressly set forth to this
Lease. Landlord warrants that it has full right and power to execute and perform
this Lease and to grant the estate demised herein and that Tenant, on payment of
the rent and performance of the covenants herein contained, shall peaceably and
quietly have. hold and enjoy the Premises during the full Term of this Lease.
Subject to the rights of lienholders under Article XVI.

                                   ARTICLE XIX

                                NO IMPLIED WAIVER

            Landlord's failure to insist at any time on the strict performance
of any covenant or agreement. or its failure to exercise any option, right,
power or remedy contained to this Lease, shall not be construed as a waiver or a
relinquishment thereof for the future. The waiver of or redress for any
violation of any term, covenant, agreement, or condition contained in this Lease
shall not prevent a subsequent act being a violation. Landlord shall be
considered to have waived

                                       28
<PAGE>

a provision of this Lease only if specifically expressed in a writing signed by
Landlord. No expressed waiver shall affect any matter other than the one
specified in the waiver and only for the time and in the manner specifically
stated. Landlord's receipt of rent with knowledge of the breach of a covenant or
agreement contained in this Lease shall not be deemed a waiver of the breach. No
payment by Tenant or acceptance by Landlord of a lesser amount than the monthly
Installment of rent due under this Lease shall be considered other than on
account of the earliest rent due hereunder. nor shall any endorsement or
statement on any check or any letter accompanying any check or payment as rent
be deemed an accord and satisfaction. Landlord may accept a check or payment
without prejudice to Landlord's right to recover the balance of the rent due or
to pursue any other remedy provided in this Lease.

                                   ARTICLE XX

                                     NOTICES

            Each provision of this Lease, or any applicable governmental laws,
ordinances, regulations, and other requirements with reference to the sending
mailing or delivery of any notice, communication, request, reply or advice
(hereinafter severally and collectively called "notice"), or with reference to
the making of any payment by Tenant to Landlord. shall have been compiled with
when and if the following steps are taken:

            20.1  Payments Due Landlord. All rent and other payments required to
be made by Tenant to Landlord hereunder shall be payable to Landlord in the
County in which the Building is located, at the address set out in Section 1.1.
or at such other address as Landlord specifies from time to time. All such
payments shall, for the purposes of this Lease, notwithstanding the provisions
of Section 20.2 be deemed paid only when actually received by Landlord. Except
as may be provided otherwise in this Lease. all amounts payable under this Lease
will be payable in coin or currency of the United States of America which at the
time of payment is legal tender for public and private debts.

            20.2  Notices. Any notice or document required to be delivered
hereunder. or any notice given by either party hereto to the other party shall
be deemed to be delivered if actually received or. whether or not received, on
deposit in the United States mail, postage prepaid, certified or registered mail
(with or without return receipt requested). addressed to the appropriate party
at its respective address set out in Section 1.1 or at such other address as
that party has theretofore specified in accordance with Section 20.3. Notice
given in any other manner is effective only if and when received by the party to
be notified. If a party intentionally avoids receipt of notice. then notice is
deemed received if given by any means by which service of process can be
effected under applicable law.

            20.3  Change in Addresses. The parties hereto and their respective
heirs. successors. legal representatives, and assigns may from time to time
change their respective addresses by giving at least fifteen (15) days' written
notice to the other party, delivered In compliance with this Article XX.

                                       29
<PAGE>

                                   ARTICLE XXI

                              SUBSTITUTION OF SPACE

                           [Section Not Part of Lease]

                                  ARTICLE XXII

                                  MISCELLANEOUS

            22.1  Attorney's Fees. If, as a result of any breach or default by
Tenant of its respective obligations under this Lease, Landlord employs an
attorney to enforce or defend any of its rights or remedies hereunder, and if
Landlord prevails, then Tenant shall pay to Landlord the reasonable attorney's
fees incurred by Landlord.

            22.2  Broker's Commission. Tenant and Landlord hereby indemnify each
other, and shall hold each other harmless from and against. all liabilities
arising from any claim for a "broker's or leasing agent's" commission, other
than with respect to the commissions which the indemnified party has agreed. in
writing. To pay, including any agreed to be paid to the Broker(s) named to
Section 1.1(g)

            22.3  Force Majeure. If the performance by Landlord of any provision
of this Lease is delayed or prevented by any act of God. Strike, lockout,
shortage of material or labor, restriction by any governmental authority, civil
riot, flood, and any other cause not within the control of Landlord, then the
period for Landlord's performance of the provision shall be automatically
extended for the same amount of time that Landlord is so delayed or hindered.

            22.4  Use of Language. Words of any gender used to this Lease
include any other gender, and words in the singular include the plural. unless
the context otherwise requires.

            22.5  Captions. The captions or headings of paragraphs in this lease
are inserted for convenience only, and shall not be considered in construing the
provisions hereof if any question of intent arises.

            21.6  Successors. The terms, conditions and covenants contained in
this Lease inure to the benefit of, and are binding on, the parties hereto and
their respective successors in interest, assigns and legal representatives,
except as otherwise herein expressly provided. All rights, powers, privileges,
immunities and duties of Landlord under this Lease, including without
limitation, notices required or permitted to be delivered by Landlord to Tenant
hereunder, may, at Landlord's option, be exercised or performed by Landlord's
agent or attorney.

            22.7  Sublease. If this Lease is to fact a sublease, then Tenant
accepts this Lease subject to all of the terms and conditions of the lease under
which Landlord holds the Premises as lessee. Tenant shall do no act or thing
that would constitute a violation by Landlord of its obligation under such
lease.

                                       30
<PAGE>

            22.8  Severability. If any provision of this Lease 1s finally held
by a court of competent jurisdiction to be invalid or unenforceable. then the
invalid or unenforceable provision shall be deemed severed from this Lease and
the validity and enforceability of the remaining provisions of this Lease shall
be unaffected.

            22.9  Charges For Services. Any amount payable by Tenant to Landlord
hereunder is considered to be rent due and shall be included in any lien for
rent. The non-payment of any such amounts due is an Event of Default hereunder
giving rise to Landlord's exercise of any remedies available hereunder or at
law.

            22.10 Personal Liability. Landlord's liability to Tenant for any
default by Landlord under this Lease is limited to Landlord's interest fn the
Building and the Land, and Tenant agrees to look solely to landlord's interest
therein for the recovery of any judgment against Landlord. it being intended
that neither Landlord nor any of its partners, shareholders, agents, affiliates,
officers or directors shall be personally liable for any judgment or deficiency.

            22.11 Damage From Certain Causes. Landlord is not liable or
responsible to Tenant for any loss or damage to any property or person
occasioned by theft, fire, act of God, public enemy, injunction, riot, strike,
insurrection, war, court order, requisition, or order of governmental body or
authority, or for any damage or inconvenience that may arise through repair or
alteration of any part of the Land, the Building or the Premises, or a failure
to make any such repairs.

            22.12 Notice And Cure to Landlord and Mortgagee. On any act or
omission by Landlord which might give, or which Tenant claims or intends to
claim gives, Tenant the right to damages from Landlord or the right to terminate
this Lease by reason of a constructive or actual eviction from all or part of
the Premises, or otherwise, Tenant shall not sue for damages or attempt to
terminate until it has given written notice of the act or omission to Landlord
and to the holders) of the indebtedness or other obligations secured by any
mortgage or deed of trust affecting the Premises, and a reasonable period of
time for remedying the act or omission has elapsed following the giving of the
notice, during which time Landlord and the lienholder(s), or either of them.
their agents or employees, may enter upon the Premises and do therein whatever
is necessary to remedy the act or omission. During the period after the giving
of notice and during the remedying of the act omission, the Base Rental payable
by Tenant shall not be abated and apportioned except to the extent that a
Premises are untenantable.

            22.13 Governing Law. This Lease and the rights and obligations of
the parties hereto shall be interpreted. construed, and enforced 1n accordance
with the local laws of the State of Texas.

            22.14 No Reduction Of Rental. Except as otherwise expressly and
unequivocally provided in this Agreement. Tenant shall not for any reason
withhold or reduce the amounts payable by Tenant under this Lease, it being
understood that the obligations of Landlord hereunder are independent of
Tenant's obligations. Furthermore, if Landlord is required by a governmental
authority to reduce energy consumption, to impose a parking or similar charge
with respect to the Building, to restrict the hours of operation of, limit
access to or reduce parking spaces available at the Building, or take other
limiting actions, then Tenant is not entitled to rent abatement or to terminate
this Lease.

                                       31
<PAGE>

            22.15 No Oral Changes. This Lease may not be changed or terminated
orally. but only in writing executed by both parties hereto.

            22.16 Lease Provisions Confidential. Each and every term and
provision contained in this Lease that is not generic (e.g. the Area of the
Building) is confidential and shall not. without the written consent of the
other party, be disclosed to any person outside the organizations of the parties
to this Lease, or to Landlord's property management company, or to professional
advisers (e.g. lawyers and accountants) who have a "need to know" relationship
with the disclosing party.

            22.17 ENTIRETY: NO REPRESENTATIONS AND WARRANTIES. THIS LEASE,
INCLUDING ONLY THE ATTACHMENTS HERETO SPECIFIED IN SECTION 22.18, EMBODIES THE
ENTIRE AGREEMENT BETWEEN THE PARTIES AND SUPERSEDES ALL PRIOR AGREEMENTS AND
UNDERSTANDINGS, INCLUDING ANY LETTERS OF INTENT, IF ANY, RELATING TO THE SUBJECT
MATTER HEREOF, LANDLORD HAS NOT MADE, AND TENANT MAY NOT RELY ON. ANY
REPRESENTATIONS OR WARRANTIES WITH REGARD TO THE BUILDING, PREMISES OR
OTHERWISE. EXPRESSED OR IMPLIED, EXCEPT AS STATED IN THIS LEASE. IN PARTICULAR,
LANDLORD HAS NOT AUTHORIZED ANY AGENT OR BROKER TO MAKE A REPRESENTATION OR
WARRANTY INCONSISTENT WITH THE TERMS OF THIS LEASE AND TENANT MAY NOT RELY ON
ANY SUCH NCONSISTENT REPRESENTATION OR WARRANTY.

                      [THIS SPACE INTENTIONALLY LEFT BLANK]

                                       32
<PAGE>

            22.18 Attachments. If the box next to any of the following documents
is marked, then the document is attached to this Lease, and it, as well as all
drawings and documents prepared pursuant thereto, are a part of this Lease:

         Exhibit  "A" - Floor Plan                   [X]

                  "B" - Legal Description            [X]

                  "C" - Operating Cost
                           Computation               [X]

         '        "D" - Rules                        [X]

                  "E' - Guaranty of Lease
                           Agreement                 [ ]

                  "F" - Financing Statements         [ ]

                  "G" - Addendum                     [X]

     Rider 101    Work Letter - As Is                [X]

        201A            Parking Agreement            [X]

        301             Option to Extend             [ ]

THIS LEASE is executed and effective this 1st day of May, 1992.

                                           LANDLORD:

                                           BUILDING ACQUISITION CORPORATION,
                                           a Texas corporation,

                                           By: /s/ TIM LYLES
                                               Printed Name: Tim Lyles
                                               Title: Secretary

                                           TENANT:

                                           BioNumerik Pharmaceuticals
                                           a Limited Liability Company

                                       33
<PAGE>

                                           By:  /s/ FREDERICK H. HAUSHEER
                                                -------------------------------

                                                Printed Name:  Fred Hausheer

                                                Title:  Chief Executive Officer

                                       34
<PAGE>

                                   EXHIBIT "A"

                           ATTACHED TO AND MADE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                        Floor Plan of Premises (graphic)

                                       35
<PAGE>

                                   RIDER 201A

                           ATTACHED TO AND MADE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                                Parking Agreement

            1.    (a)   Parking Spaces - Tenant's Obligation. Landlord shall
permit Tenant to use, and Tenant shall pay Landlord for, at all times during the
term of this Lease, parking spaces in the parking facility associated with the
Building ('Parking Garage") in the following quantities and for the Basic
Parking Charge (herein so called) set forth below for each parking space:

<TABLE>
<CAPTION>
                                             Basic Parking
Number of Spaces                            Charge per Space
----------------                            ----------------
<S>                                         <C>
Eleven (11)                                 $  N/A per month
</TABLE>

                  (b)   Parking Spaces - Tenant's Option. In addition to the
parking spaces in the Building Garage, Landlord shall permit Tenant to use five
(5) surface parking spaces such that the total number of spaces available to
Tenant from time to time equals one space for each 350 square feet of Rentable
Area of the Premises.

                  (c)   Reclamation of Excess Parking spaces. If Tenant is at
any time during the Term of the Lease using more parking spaces ("Excess
Spaces") than the number to which it would be entitled by multiplying the Area
of the Premises times the ratio of the total Area of the Building divided by the
total number of parking spaces available in the Parking Garage ("Parking
Ratio"), then on thirty (30) days' notice Landlord may reclaim from use by
another tenant of the Building enough of the Excess Spaces to allow the other
tenant sufficient parking spaces to equal the Parking Ratio, based on the Area
of the Premises leased by the other tenant.

            2.    Basic Parking Charge. Tenant shall pay to Landlord during the
term of this Lease, as additional rental hereunder, the Basic Parking Charge
specified above for each of the parking spaces (i) required to be paid for
pursuant to paragraph 1(a) above, and (ii) actually used by Tenant pursuant to
paragraph 1(b), such amount to be payable monthly in advance on the first day of
each and every calendar month during the term of this Lease. The applicable
Basic Parking Charge may be adjusted periodically (but no more often than every
six (6) months throughout the Term of this Lease beginning on the first day of
January of the first Lease Year after the date on which this Lease commences
(and on the first day of each July and January thereafter) to equal the then
prevailing market rate for parking spaces in the Parking Garage. In

                                       36
<PAGE>

no event shall any adjustment in the prevailing market rate decrease the Basic
Parking Charge below that in effect in the immediately preceding Lease Year. A
pro rata portion of the Basic Parking Charge shall be payable for the first
partial calendar month if the Term of this Lease commences on a date other than
the first day of a calendar month. Default by Tenant in the payment of any Basic
Parking Charge is a default in the payment of rent, giving to Landlord all
rights and remedies available to it in such event.

            3.    Other Parking Provisions.

                  (a)   Landlord may, at its option, provide a reasonable means
of controlling access to the Parking Garage, but no specific, designated parking
spaces within the Parking Garage are to be provided to Tenant.

                  (b)   Landlord may relocate any parking areas or spaces from
time to time, and may also use portions of the Parking Garage outside of the
designated areas for free, visitor, or other parking needs of Landlord.

                  (c)   Landlord may make, modify and enforce rules and
regulations relating to the parking of automobiles in the Parking Garage, and
Tenant shall observe those rules and regulations. Landlord also may change the
size of the Parking Garage.

                  (d)   Tenant is responsible for ensuring that its employees
and agents do not park their automobiles in visitor parking areas or spaces, if
any, established by Landlord. or in parking spaces or areas, if any, reserved or
designated by Landlord for the use of other tenants of the Building, or for
other purposes (such as for retail tenants) so long as such designation does not
result in there being fewer than the number of spaces in the Parking Garage
specified in paragraph 1(b) above available for Tenant's use. Tenant shall
furnish to Landlord the state automobile license numbers of automobiles of
Tenant and its employees who will occupy Tenant's parking spaces from time to
time, within five (5) days from Tenant's receipt of written notice from Landlord
requesting that information.

                  (e)   Landlord is not liable or responsible for any loss of or
to any automobile or vehicle or equipment or other property therein, or damage
to property or injury to person, unless the loss, damages, or injury is
proximately caused by the gross negligence of Landlord or its employees.

                  (f)   Landlord may, in its sole discretion from time to time
designate parking spaces in any parking areas for the exclusive use of specified
tenants of the Building. The location and the number of those spaces shall be
determined by Landlord in its sole discretion. and Landlord may from time to
time change the location and number of those spaces.

                  (g)   This Parking Agreement is not deemed to create a
bailment between the parties. It being agreed and understood that the
relationship created between Landlord and Tenant with regard to the parking
spaces and Parking Garage is that of licensor and licensee, respectively.

                                       37
<PAGE>

                  (h)   If fifty percent (50%) or more of the Parking Garage is
damaged by fire or other casualty or if the insurance proceeds payable as a
result of the casualty to the Parking Garage are applied by Landlord's mortgagee
to Landlord's mortgage debt against the Building and/or Parking Garage, or if
there is a material, until ed loss to the Parking Garage, then Landlord may, at
its option, terminate this Parking Agreement by notifying Tenant in writing of
the termination within thirty (30) days of the date of the casualty. If this
Parking Agreement is not so terminated by Landlord. then Landlord shall either
(i) proceed to restore the Parking Garage and provide Tenant with alternative
parking during the restoration, or (ii) not restore the Parking Garage, but
provide Tenant with alternate parking throughout the remainder of the Term of
this Parking Agreement.

                                       38
<PAGE>

                                   EXHIBIT "B"

                           ATTACHED TO AND MADE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                          Legal Description of the Land

                            ASHFORD OAKS SUBDIVISION

                              VOLUME 9400, PAGE 37

                              N.C.B. 14595, LOT 19

                           2,703 ACRES 117,743 SQ. FT.

                                       39
<PAGE>

                                                                             (A)

                                   EXHIBIT "C"

                           ATTACHED TO AND MADE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                           Operating Cost Computation

A.    Operating Cost Examples. The following are, without limitation, examples
of costs included in the computation of Operating Costs:

      (1) all taxes, assessments, and other governmental charges, whether
federal. state, county or municipal, and whether they be by taxing districts or
authorities presently taxing the Premises and Building or by others.
subsequently created or otherwise, and any other taxes and assessments levied or
assessed against the Land, the Building and other associated improvements
situated on the Land, and the Building Facilities, including interest on
installment payments, and including all costs and fees (including attorney's
fees) incurred by Landlord in contesting or negotiating with taxing authorities;

      (2) all reasonable costs and expenses of operating, maintaining and
repairing (including replacing components of) Building Facilities, including
elevators, escalators, heat, ventilation, and air conditioning systems, and all
other mechanical or electrical systems serving the Building;

      (3) all reasonable costs and expenses incurred in cleaning the Building;

      (4) costs of all utilities for the Project. including without limitation.
the cost of water and power, heating, lighting, air conditioning, ventilating
and sewer rents or charges for the Project;

      (5) all supplies and materials reasonably used in the operation and
maintenance of the Project;

      (6) costs of all insurance relating to the Project, including the cost of
casualty and liability insurance applicable to the Project and Landlord's
personal property used in connection therewith;

      (7)   using generally accepted accounting principles amortization of costs
of or rental expenses for any machinery, equipment or other capital improvements
installed by Landlord to maintain or upgrade the Project for the benefit of
Tenant and other Building tenants or to conform to any law, ordinance, rule,
regulation. or order of any governmental authority having

                                       40
<PAGE>

jurisdiction over the Project which was enacted or promulgated after
construction on the Project began, or for the purpose and in reasonable
anticipation of reducing energy costs in the Project or other Operating costs:

      (8)   expenses and fees (including attorney's fees) incurred in contesting
the validity or applicability of any governmental enactments that may affect
Operating Costs:

      (9)   general maintenance costs and expenses reasonably incurred in
connection with the Project (including, but not limited to, security,
maintenance of all exterior and interior landscaping, garbage and other waste
removal, non-tenant alterations and decorations, heating and air conditioning
repairs, Parking Garage or surface parking repairs or replacements and all labor
utilized and supplies consumed with respect to any general Project maintenance);

      (10)  janitorial service and window cleaning for the Building, including
the Common Areas and Service Areas (including materials, supplies, Building
standard light bulb, equipment and tools therefor and rental and appreciation
costs related to the foregoing), or contracts with third parties to provide the
same:

      (11)  the cost of providing security to the Building and Parking Garage:

      (12)  reasonable management cost: of the Project (including, but not
limited to, any management fee payable by Landlord with respect to the Project.
audit and accounting expenses and legal fees), and Landlord's overhead expenses
directly attributable to Project management; and

      (13)  wages, salaries, fees, pension benefits, taxes, unemployment and
disability insurance, worker's compensation insurance, social security benefits
and any other expenses reasonably incurred with respect to all personnel engaged
in the operation, maintenance, leasing or security of the Project. The term
"personnel" shall include. but not be limited to, employees such as
superintendents, engineers, electricians, clerks, mechanics, helpers, security
officers, porters, cleaners, window washers, as well as contract laborers
performing services with respect to the Project.

      Operating Cost Exclusions. The following are, without limitation, examples
of costs excluded from the computation of Operating Costs:

      (1)   leasing commissions, attorney's fees, costs and disbursements and
other expenses incurred in leasing, renovating or improving space for tenants or
prospective tenants of the Building;

      (2)   costs incurred by Landlord in the discharge of its obligations under
the Work Letter;

      (3)   costs (including permit, license and inspection fees) incurred in
renovating or otherwise improving or decorating, painting or redecorating space
for tenants of vacant space:

      (4)   Landlord's costs of any services sold to tenants for which Landlord
is entitled to be reimbursed by such tenants as an additional charge or rental
over and above the Base Rental and Operating Costs payable under the lease with
the tenant or other occupant;

                                       41
<PAGE>

      (5)   any depreciation and amortization on the Building, except as
expressly permitted herein;

      (6)   interest on debt or amortization payments on any mortgages or deeds
of trust or any other debt for borrowed money:

      (7)   all items and services for which Tenant reimburses Landlord outside
of Operating Costs or pays third provisions or which Landlord provides
selectively to one or more tenants or occupants of the Building (other than
Tenant) without reimbursement;

      (8)   advertising and promotional expenditures; and

      (9)   repairs or other work occasioned by fire. windstorm or other work
paid for through insurance or condemnation proceeds.

                                       42
<PAGE>

                                   EXHIBIT "D"

                           ATTACHED TO AND MADE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                                      Rules

      1.    Tenant, its agents, servants, and employees shall not block or
obstruct any of the entries, passages, doors, hallways or stairways of the
Building, or place, empty or throw any rubbish, litter, trash or material of any
nature into those areas, or permit those areas to be used at any time except for
ingress and egress of Tenant, its agents, servants, employees, visitors or
invitees. No tenant and no employee, agent or invitee of a tenant shall go onto
the roof of the Building.

      2.    Tenant shall refer all contractors. contractor's representatives and
installation technicians rendering any service to Tenant to Landlord for
Landlord's supervision, approval and control before performance of any
contractual service. This provision applies to all work performed in the
Building, including, without limitation, installation of telephones, telegraph
equipment, electrical devices and attachments and installations of any nature
affecting floors, walls, woodwork, trim, windows, ceilings, equipment or any
other physical portion of the Building.

      3.    Movement in and out of the Building of furniture, office equipment
or other bulky materials, or movement through Building entrances or lobbies, or
dispatch or receipt by Tenant of any merchandise or materials which requires use
of elevators or stairways shall be restricted to reasonable hours designated by
Landlord. All such movement shall be under the supervision of Landlord and in
the manner agreed between Tenant and Landlord by prearrangement before
performance of any movement. Prearrangements initiated by Tenant shall include
determination by Landlord, and subject to Landlord's decision and control, of
the time, method and routing of movement. and limitations imposed by safety or
other reasonable concerns which may prohibit any article, equipment or any other
item from being brought into the Building. Tenant shall assume all risk as to
damage to articles moved and injury to persons or public engaged or not engaged
in the movement, including equipment. property and personnel of Landlord if
damaged or inured as a result of acts by Tenant or Tenant's employees, agents or
contractors in connection with carrying out this service for Tenant from the
time of ring property to completion of work; and Landlord is not liable for any
such act. or any damage or loss to of the property or persons resulting from any
such act in connection with such service performed for Tenant, and Tenant hereby
agrees to indemnify, defend and hold Landlord harmless from

                                       43
<PAGE>

and against any and all such damage, injury or loss, including attorney's fees
arising with respect thereto.

      4.    No signs, advertisements or notices are allowed in any form on
windows or doors inside or outside the Premises or any other part of the
Building, and no signs except in uniform location and uniform styles fixed by
Landlord are permitted on exterior identification pylons, if any, in the public
corridors or on corridor doors or entrances to the Premises. All signs shall be
contracted for by Landlord for Tenant at the reasonable rate fixed by Landlord
from time to time, and Tenant shall be billed and pay for such service
accordingly on demand. Following move-in, no nails, hooks or screws shall be
driven or inserted in any part of the Building (other than for the handling of
pictures. diplomas or other items of a like nature), except by the maintenance
personnel of the Building, nor shall any part be defaced by tenants.

      5.    No draperies, shutters, or other window coverings shall be installed
on exterior windows or walls or windows and doors facing public corridors
without Landlord's written approval. Landlord may require installation and
continued use of uniform window coverings for such windows.

      6.    No portion of the Premises or any other part of the Building may at
any time be used or occupied as sleeping or lodging quarters.

      7.    Tenant shall not place, install or operate in the Premises or in any
other part of the Building any engine, stove or machinery, or conduct mechanical
operations or cook thereon or therein (except for coffee machines, microwave
ovens and other breakroom appliances of a residential nature), or place or use
in or about the Premises any explosive, gasoline, kerosene, oil, acids, caustics
or any other inflammable, explosive or hazardous materials, fluid or substance
without the prior written consent of Landlord. If such chemicals are permitted
by Landlord, Tenant must supply Landa MSDS forms in compliance with all
applicable laws to which Landlord is subject. The preceding sentence does not
prohibit the storage of photocopier or other typical office supplies within the
Premises.

      8.    Any directory of the Building provided by Landlord shall be
exclusively for the display of the name and location of tenants in the Building,
and Landlord may exclude any other names therefrom and may limit the number of
listings per tenant. Tenant shall pay Landlord's standard charge for Tenant's
listing thereon and for any changes by Tenant.

      9.    Landlord is not responsible for lost or stolen personal property,
equipment, money or any article taken from the Premises or the Building, whether
or not any such area is locked against entry.

      10.   Tenant shall keep and shall cooperate with Landlord and Landlord's
employees and agents in keeping, the Premises in a clean and tidy condition at
all times.

      11.   No curtains, blinds or screens may be attached to or hung, or used
in connection with, any window or door of the Premises without the prior written
approval of Landlord as to the quality, type, design, color and manner of
attaching the same. No protective screen, grating, shade or other enclosing
device may be used on the portion of the Premises abutting the Common Areas,
courts, atria or public corridors without Landlord's prior written approval as
to

                                       44
<PAGE>

the quality, type, design, color and manner of attaching the same, to the end
that all portions of the Premises facing those Common Areas shall be compatible
to appearance.

      12.   Tenant, its agents, servants or employees shall not bring into the
Building or the Premises or keep on the Premises any dog bird or animal. Tenant,
its agents, servants or employees shall not bring into the Building or keep on
the Premises any bicycle or other vehicle without the prior written consent of
Landlord.

      13.   No additional locks shall be placed on any door in or providing
access to the Premises without the prior written consent of Landlord. A
reasonable number of keys to the Premises and security access cards for the
building (if that method is used) will be furnished by Landlord and neither
Tenant. its agents, servants, or employees, shall have any duplicate keys made.
Landlord may at all times keep a pass key to the Premises. All keys shall be
returned to Landlord promptly on termination of this Lease. Tenant shall pay a
reasonable amount fixed by Landlord from time to time for each key and security
access card issued by Landlord in replacement of one previously issued.

      14.   Tenant shall give Landlord prompt notice of all accidents to or
defects in air conditioning equipment, plumbing, electrical facilities or any
part or appurtenance of the Premises.

      15.   Landlord will not permit entrance to Tenant's offices by use of pass
keys controlled by Landlord to person at any time without permission by Tenant
except employees, contractors, janitorial staff, or police personnel directly
supervised by Landlord or employees of the United States Postal Service.

      16.   Employees of Landlord shall not receive or carry messages for or to
any Tenant or other person, and shall not contract with or render free or paid
services to any Tenant or Tenant's agents, employees or invitees. If Landlord's
employees perform any such services, then those employees are solely the agents
of Tenant regardless of whether or how payment is arranged for services, and
Landlord is expressly relieved from any and all liability in connection with any
such services and any associated injury or damage to person or property.

      17.   Landlord may exclude or expel from the Building any person who, in
the judgment of the Landlord, is intoxicated or under the influence of liquor or
drugs, or who in any manner acts in violation of the Rules of the Building.

      18.   Tenant shall not use the plumbing facilities of the Premises for any
purpose other than that for which they were constructed. Tenant shall not
dispose of any substances in such facilities which may clog, erode, or damage
the plumbing pipes, lines, or conduits of the Building whether through the
utilization of "garbage disposal" units or otherwise. Tenant shall pay for all
damages resulting to any fixtures or appliances from misuse by Tenant, or
Tenant's agents or employees, and Landlord is in no way responsible therefor.

      19.   Landlord may prescribe the weight and position of safes, computers
and other heavy equipment which shall, in all cases, in order to distribute
their weight, stand on supporting devices approved by Landlord. All damage done
to the Premises or to the Building by placing in or taking out any property of
Tenant unless caused by the negligence or willful misconduct of

                                       45
<PAGE>

Landlord or Landlord's employees or agents or done by Tenant's property while in
the Premises or the Building, shall be repaired immediately at the sole expense
of Tenant.

      20.   To ensure orderly operation of the Building, no ice, minerals or
other water, towels, newspapers, etc. shall be delivered to the Premises except
by persons approved by Landlord in advance in writing.

      21.   Landlord may refuse admittance to the Building from 7 p.m. to 7 a.m.
daily, or on Sundays or on legal holidays, to any person or persons who cannot
furnish satisfactory identification, or to any person or persons who for any
other reason in Landlord's judgment. should be denied access to the Premises.
Landlord, for the protection of the tenants and their effects, may prescribe
hours and intervals during the night, on Sundays and Holidays, when all persons
entering and departing the Building are required to enter their names, the
offices to which they are going or from which they are leaving, and the time of
entrance or departure in a register provided for that purpose by Landlord.

      22.   Canvassing, soliciting and peddling in the Building are prohibited,
and each Tenant shall cooperate to prevent the same.

      23.   Alterations and miscellaneous job orders shall at all times be
directed to the Building manager's office to facilitate the orderly and
otherwise proper processing of that work in accordance with any covenants of the
Lease applicable thereto.

      24.   Landlord may waive any one or more of these Rules for the benefit of
any particular tenant or tenants, but no waiver by Landlord shall be construed
as a waiver of such Rules in favor of any other tenant or tenants, or prevent
Landlord from thereafter enforcing all Rules against any or all of the tenants
of the Building.

      25.   Landlord may rescind or amend any of these Rules and make other and
further reasonable rules as in its judgment are from time to time necessary and
desirable.

      26.   These Rules are in addition to, and shall not be construed to in any
way modify, alter, or amend, in whole or in part, the terms, covenants,
agreements and conditions of any lease of Premises in the Building.

                                       46
<PAGE>

                                   EXHIBIT "G"

                           ATTACHED TO AND MADE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                                    Addendum

A.    Article 1.1(i) "Base Rental": payable monthly in advance in installments
      according to the following schedule.

      $1,593.67      Month 1

      $3,187.33      Month 2

      $4,781.00      Months 3-24

      $5,008.67      Months 25-36

      $5,236.33      Months 37-48

      $5,464.00      Months 49-60

B.    Option to Terminate:

      So long as Tenant is not in default under the terms of this lease, Tenant
      shall have the option of terminating this lease on the second, third or
      fourth anniversary of the commencement date of this lease by providing
      Landlord sixty (60) days prior written notice. In the event Tenant
      exercises this option for the purpose of leasing other premises within the
      Building and a new lease for said premises is fully executed by both
      parties, Tenant shall not be required to remove tenant alterations after
      the Commencement Date of the Lease as stipulated in Section 6.4.

                                       47
<PAGE>

                                    RIDER 101

                           ATTACHED TO AND MADE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                                   Work Letter

      Landlord leases the Premises to Tenant in "as-is" condition and Landlord
will have no obligation to make improvements therein except as set forth herein.
Landlord shall at Landlord's sole cost and expense provide Building Standard
Signage at the entry to Tenant's space and on the Building Directory, balance
the heating, ventilation and air conditioning system throughout the Premises,
shampoo all carpeted flooring, disconnect all sprinkler heads servicing Tenant's
computer room facility (subject to necessary approval by those authorities
having jurisdiction over such matters) and install new vinyl flooring in the
existing restroom facilities.

      Landlord agrees that Tenant may install two (2) 220 volt, 3 phase outlets
in the Premises at Tenant's sole cost and expense, with electric service to said
outlets not to be separately metered by Landlord. Further, Tenant shall be
allowed to install two (2) auxiliary air units with separate electrical meter in
the Premises at Tenant's sole cost and expense electrical service to which will
be separately metered by Landlord and paid by Tenant as Additional Rent.

      Landlord hereby approves Tenant's future installation of lab facilities,
subject to landlord's reasonable approval of Tenant's plans and specifications
and installation procedures outlined in Section 6.5 and further subject to local
building and fire codes.

                                       48
<PAGE>

                            FIRST AMENDMENT TO LEASE

      This First Amendment to Lease (the "Amendment") is entered into this 28th
day of June, 1993 by and between Building Acquisition Corporation, a Texas
Corporation ("Landlord") and BioNumerik Pharmaceutical, Inc., a Delaware
corporation ("Tenant").

                               W I T N E S S E T H

      WHEREAS, Landlord and Tenant executed that certain lease (the "Lease")
dated as of May 1, 1992, covering approximately 5,464 square feet of Rentable
Area in the Ashford Oaks Office Building located at 8122 Datapoint Drive, in the
City of San Antonio, Bexar County, Texas, and further identified as Suite 1250;
and

      WHEREAS, Tenant, formerly known as BioNumerik Pharmaceutical, a Limited
Liability Company, organized and existing under the laws of the State of Texas
having merged with and into BioNumerik Pharmaceutical, Inc., a Delaware
Corporation, hereby affirms the terms of the Lease and further attorns to,
assumes and agrees to be bound by all of the terms of the Lease, except where
specifically amended herein; and

      WHEREAS, Landlord and Tenant desire to amend said lease;

      NOW, THEREFORE, in consideration of the Premises and the mutual benefits
to accrue to Landlord and Tenant, both parties agree that effective June 28,
1993, the following designated sections of the above described Lease shall be,
and hereby are, amended as follows:

      1.    Section 1.1(c) "Tenant" is amended to read BioNumerik
Pharmaceutical, Inc., a Delaware Corporation.

      2.    Section 1.1(h) "Premises" is amended so that the Premises shall
contain approximately 5,275 square feet of Rentable Area on the 12th floor (the
"Original Premises") of the Building to be identified as Suite 1250 in the
location indicated on Exhibit "A" and approximately 7,757 square feet of
Rentable Area on the 4th floor of the Building to be identified as Suite 400 in
the location indicated on the attached Exhibit "A-1" (the "Expanded Premises").
The Expanded Premises together with the Original Premises sometimes hereinafter
referred to as the "Entire Premises".

      3.    Section 1.1(j) "Base Rental" is amended so that Tenant's Base Rental
payable hereunder for the Entire Premises shall be paid monthly in advance, in
installments of Base Rental in accordance with the amounts set forth in the
following schedule:

<TABLE>
<CAPTION>
                               Monthly Base                 Monthly Base               Monthly Base
Monthly Period              Rental Suite 1250             Rental Suite 400             Rental Total
--------------              -----------------             ----------------             ------------
<S>                         <C>                           <C>                          <C>
1 - 12                          $4,615.63                     $7,757.00                 $12,372.63
13 - 24                          4,837.18                      8,067.35                  12,904.53
25 - 36                          5,053.45                      8,455.13                  13,508.58
37- 48                           5,275.00                      8,782.47                  14,057.47
49 - 60                          5,496.55                      9,108.27                  14,604.82
</TABLE>

      4.    The following shall be added to Section 1.1(k) "Anticipated
Commencement Date": The Anticipated Commencement Date for the Expanded Premises
is amended to be six (6) months after the full execution of this Amendment.

      5.    The following shall be added to section 1.1(l) "Commencement Date":
The Commencement Date for the Original Premises shall remain the date Tenant
took occupancy of the Original Premises and the Commencement Date for the Entire
Premises shall mean the date which is the earlier of (i) the date the Premises
are

<PAGE>

"ready for occupancy", as defined in Rider 301, or (ii) six (6) months after the
full execution of this Amendment (the "Second Commencement Date").

      6.    The following shall be added to Section 1.1(m) "Term" so that the
Term of the Original Premises shall begin at the Commencement Date for such
Premises and the Term for the Entire Premises shall be for an additional period
of sixty (60) months beginning on the Commencement Date as defined in Paragraph
5 of this Amendment. In the event the commencement Date is not the first day of
a calendar month, this Lease will nevertheless continue for a period not to
exceed sixty (60) months (subject to Tenant's right to renew as provided in this
Amendment), and Tenant's Base Rental will be prorated accordingly.

      7.    Section 1.1(n) "Area of the Building" is amended so that the
stipulated number of square feet of Rentable Area in the Building is 190,819
square feet.

      8.    Section 1.1(o) "Area of the Premises" is amended for the Entire
Premises so that the stipulated number of square feet of Rentable Area in the
Entire Premises upon the completion of Suite 400 is 13,032 square feet.

      9.    Section 1.1(p) "Landlord's Operating Cost Contribution" is amended
for the Entire Premises to be $5.25 for each square foot in the Area of the
Building.

      10.   Section 1.2(b) "Tenant's Pro Rata Share" in amended for the entire
Premises to be 6.8295%.

      11.   Exhibit "G" is deleted in its entirety.

      12.   Rider 201A Paragraph 1.(a) is amended so that the number of spaces
Tenant may use in the parking facility shall be twenty-five (25). Three (3) of
the above spaces shall be designated reserved parking spaces in the Building
garage in locations to be determined by Landlord from time-to-time.

      13.   "Non-disturbance". In connection with any mortgage executed after
the date hereof, provided that (i) so long as Tenant is in compliance with the
provisions of this Lease, Tenant's use and occupancy of the Premises and its
rights under this Lease shall not be disturbed or affected by any foreclosure or
other action (or by the delivery or acceptance of a deed or other conveyance or
transfer in lieu thereof) which may be instituted or undertaken in order to
enforce any right or remedy available to such holder, (ii) Tenant shall not be
named as a party defendant in any foreclosure, summary or any other action
commenced by any such secured party, and (iii) any party succeeding to the
interest of Landlord as a result of any such enforcement action or otherwise
shall be bound to Tenant, and Tenant shall be bound to it, under all the terms,
covenants and conditions of this Lease with the same force and effect as if such
party were the original Landlord under this Lease. Landlord will use its best
efforts to obtain any such written non-disturbance agreement from any such
mortgagee.

      14.   "Hazardous Materials". Notwithstanding anything herein to the
contrary, Landlord represents and warrants to the best of Landlord's knowledge
(i) that no hazardous materials, wastes, or substances as those terms are
defined by current applicable laws and regulations and no other materials
intended for use at or generated on such Building or the Premises have been or
are used, stored or treated or otherwise disposed of in violation of current
applicable laws and regulations; (ii) the Premises are now in condition that is
clean, healthful, environmentally safe and free of all environmental
contamination; and (iii) Landlord is not in violation of (at the commencement of
this Lease) and has no existing or potential obligation to take corrective
action pursuant to any applicable zoning, ordinance or other law, regulation or
requirement relating to the operation of the use of the Building and Premises,
including without limitation, applicable building codes and environmental
protection and occupational health and safety laws and regulations.

      15.   The following shall be added to the Lease as Section 22.18
"Guarantee": within three (3) weeks of the full execution of this Lease, Tenant
shall provide Landlord an irrevocable Letter of Credit to be issued by Texas
Commerce Bank of San Antonio acceptable to Landlord naming Landlord beneficiary
therein (hereinafter defined as the "Letter of Credit") in an amount equal to
$93,084.00. Upon an occurrence of a monetary Event of Default by Tenant under
the Lease and after written notice and a reasonable time to cure, Landlord may
draw against the Letter

<PAGE>

of Credit to the extent of such default. In the event Tenant has not so
defaulted, the amount of the Letter of credit may be reduced during the term of
this Lease by Tenant in accordance with the following schedule:

<TABLE>
<CAPTION>
                   Required Amount of Letter of
Monthly             Credit per square foot of             Required Amount of Letter of
Period            Rentable Area on the 4th floor            Credit in total dollars
------            ------------------------------            -----------------------
<S>               <C>                                     <C>
1-20                       $12.00                                $93,084.00
21-40                      $10.00 *                              $77,570.00
41-50                      $ 8.00 **                             $62,056.00 **
51-60                      $ 5.00 ***                            $38,785.00 ***
</TABLE>

*     This amount may be further reduced by $0.10 per square foot of Rentable
Area as each month in this particular monthly period passes.

**    This amount may be further reduced by $0.30 per square foot of Rentable
Area as each month in this particular monthly period passes.

***   This amount may be further reduced by $0.50 per square foot of Rentable
Area as each month in this particular monthly period passes.

      16.   Rider 301 attached hereto is added to the Lease.

      17.   Rider 401 attached hereto is added to the Lease.

      18.   Rider 501 attached hereto is added to the Lease.

      BioNumerik Pharmaceutical, Inc., a Delaware Corporation hereby affirms the
terms of the Lease and further attorns to, assumes and agree to be bound by all
the terms of the Lease; and except as specifically amended herein, the Lease
dated May 1, 1992 (all its Exhibits and Riders) by and between Landlord and
Tenant, shall remain in full force and effect in accordance with its terms and
provisions.

      IN WITNESS WHEREOF, the parties herein have hereunto met their hand the
day and year first above written.

TENANT:                                        LANDLORD:

BioNumerik Pharmaceutical, Inc.,               Building Acquisition Corporation,
a Delaware corporation                         a Texas corporation

By:    /s/ FREDERICK H. HAUSHEER               By:      /s/ TIM LYLE
Printed Name:  Frederick H. Hausheer           Printed: Thomas W. Lyles, Jr.
Title: Chairman & CEO                          Title:   Secretary
Date:  7-14-93                                 Date:    7-16-93

<PAGE>

                                   EXHIBIT A-1

                           ATTACHED TO AND MADE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                FOURTH FLOOR PORTION OF THE PREMISES (SUITE 400)

Fourth floor Premises

Expansion space

Building lease area graphic image of floor plan representing 6,750 USF/7,757 RSF
of fourth floor premises and 3,446 USF/3,960 RSF expansion space.

<PAGE>

                                    EXHIBIT H

                           ATTACHED TO AND HAVE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                          LANDLORD FURNISHED MATERIALS

<TABLE>
<S>                                                  <C>
Light Fixtures                                       208

Raco Doors
3x9 RH                                                13
3x9 LH                                                37

Door Headers                                          39

Ceiling Tile (Cases)
735                                                    4
770                                                  280

Frames (box)
LH                                                    51
RH                                                    12

Insulation
54 sf bundles                                         16
48 sf bundles                                         11
Owens 28 of rolls                                    143

Door jams (box)
LH                                                     1

Passage Sets
LH                                                    45
RH                                                    18

Electrical
Duplex Outlets (each)                                296
outlet Covers (each)                                 518

Single switches (each)                                95
Single covers (each)                                 221

Door Stops (each)                                     58

Sprinkler covers (each)                              207

Hinges (each)
LH                                                    63
</TABLE>

<PAGE>

                                    RIDER 301

                            ATTACHED AND MADE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                                   WORKLETTER

1.    Plans and Specifics

      (a)   Within 21 days of the execution of this Amendment, Tenant shall
submit to Landlord for Landlord's approval complete plans and specifications,
including finish schedules, for the layout, improvement and finish of the
Leasehold Improvements (herein so called) required by Tenant in the Premises
(consistent with the design and construction of office space in the Building
(collectively "Tenant's Plans"). Tenant's Plans shall be prepared by a licensed
architect and engineer reasonably satisfactory to Landlord. To the extent
necessary, Tenant's architect shall coordinate with Landlord's architect or
engineers to assure that Tenant's Plans are consistent with the plans and
specifications of office space in the Building.

      (b)   Tenant's Plans must be approved by Landlord. If Landlord disapproves
Tenant's Plans, or any portion hereof, then Landlord shall promptly notify
Tenant of that and of the revisions that Landlord reasonably requires before it
will approve them. As promptly as reasonably possible thereafter, but in no
event later than ten (10) days after Landlord's notice, Tenant shall submit to
Landlord for Landlord's approval plans and specifications incorporating the
required revision. The final plans and specifications approved by Landlord are
referred to as the "Final Plans." Tenant shall pay to Landlord, upon demand, all
fees of any consultants Landlord employees in connection with its review and
approval of Tenant's Final Plans, not to exceed $1,000.00. If Tenant requests
any change, addition or alteration (a "Change") to the Final Plans or in the
construction of the Leasehold Improvements, Landlord shall either approve or
disapprove in writing the proposed change within five (5) business days of
Tenant's request.

Under no circumstances is Landlord's approval of Tenant's Plans to be considered
approval of their correctness, of their compliance with applicable building and
fire codes and all other requirements of any governmental authority having
jurisdiction over the Premises, or of other sufficiency or adequacy for Tenant's
purposes, and Tenant shall save and hold Landlord, its officers, employees,
legal representatives and assigns harmless from all liability, claim, cost and
expense incurred in connection with the failure of any Leasehold improvements
constructed in accordance with the Final Plans to comply with said requirements
and codes. The Leasehold Improvements constructed as a part of the Final Plans
shall be the property of Landlord and shall remain upon and a part of and be
surrendered with the Premises upon the expiration of the Term of the Lease.

2.    Building Permit, Certificate of Occupancy. Tenant shall be responsible for
obtaining all necessary building and other permits for construction of the
Leasehold Improvements and for obtaining a certificate of occupancy permitting
unconditional occupancy and use of the Premises (for the purpose stipulated in
Section 1.1(r)) after completion of the Leasehold Improvements.

3.    Payment for Work. Landlord shall provide to Tenant an allowance not to
exceed $15.00 per square foot of Rentable Area of the fourth (4th) floor portion
of the Premises plus $2.50 per square foot of Rentable Area of the twelfth
(12th) floor of the Premises (the "Allowance") to be applied to pay only for
those actual coats of the Leasehold improvements, including, without limitation,
architectural and engineering fees relating to the construction of the Leasehold
Improvements to the Premises. The Allowance shall be provided only upon receipt
of paid invoices from Tenant.

<PAGE>

In the event the cost of constructing the Leasehold Improvements to the Premises
described on the Final Plans exceeds the Allowance (the "Excess") Tenant shall
pay any such Excess. The Allowance for each floor shall be treated separately
and in the event Tenant does not fully utilize all the Allowance on one
particular floor, such remaining portion of the Allowance may not be applied to
the other floor. Tenant shall promptly pay any such Excess and shall comply
fully with any contract or other agreement therefor, to the end that there is no
basis for a mechanic's or materialman's lien claim against the Premises or the
Building.

If Tenant requests any changes in the Final Plans, then any of those changes
that are approved by Landlord shall become part of the Final Plans, and the
costs of revising the Final Plans and the costs resulting from the changes shall
be added to the Excess, and shall be paid in accordance with the provisions set
out in this Rider 301.

If the actual construction costs are less than the Allowance, Tenant shall not
be entitled to any portion of the unexpended Allowance, which shall belong to
Landlord.

4.    Construction. Construction of the Leasehold Improvements shall be
performed by Tenant's contractors. In selecting Tenant's contractor, Tenant must
competitively bid the Final Plans to at least three (3) qualified contractors. A
Qualified Contractor shall be defined as one which meets the insurance
requirements and reasonable approvals of Landlord. Landlord shall apply the
Allowance only to the amount stipulated in the lowest qualifying bid and no
portion of the Allowance may be applied to pay any construction cost of any
other Qualified Contractor which is in excess of the lowest bid, reasonable
change order cost excepted.

5.    Delay. Tenant shall pay any and all costs and expenses incurred by
Landlord in connection with any delay in the commencement or completion of the
Leasehold Improvements caused by (i) Tenant's failure to timely prepare and
submit Tenant's Plans; (ii) Tenant's specification of non-building standard
improvements or finishes; (iii) any change, additions or alteration to the Final
Plans (or the Leasehold improvements covered thereby) that are requested by
Tenant; and (iv) any other delay requested or caused by Tenant.

6.    Commencement Date/"Ready for occupancy". For the purpose of this First
Amendment to Lease, the Premises are "ready for occupancy" on the first to occur
of (i) the date that the Leasehold Improvements to the Premises- described on
the Final Plane are substantially completed except for any minor punch-list
items to be performed by Tenant's contractor, or (ii) on the date on which
Tenant begins occupancy of the Premises, or (iii) the date on which substantial
completion would have occurred, but for delays of the nature described in
Paragraph 5 of this Rider 301, but in no event later than six (6) months after
the full execution of this Amendment. Once the Premises are deemed "ready for
occupancy", Tenant shall sign a letter, in a form and fashion satisfactory to
Landlord, acknowledging that the Premises have been completed in accordance with
the Final Plans and stating the Commencement Date and expiration date of the
Term of the Lease. However, Tenant's failure to execute or deliver such a letter
shall not delay or otherwise change the Commencement Date.

7.    Default. A default by Tenant under this Work Letter is an Event of Default
under the Lease and entitles Landlord to any remedies under the Lease
(notwithstanding that tile Term thereof has not commenced).

8.    Indemnity. Tenant shall indemnify, defend, and hold Landlord harmless from
and against any damages suffered by Landlord as a result of Tenant's failure to
comply with the terms of this workletter.

9.    Landlord Furnished Materials. In addition to the Allowance provided by
Landlord above, Landlord shall make available to Tenant (for the construction of
the initially leased Premises only) at no additional cost, "stockpiled
materials" which may be currently stored in the vacant spaces of the Building.
Any such materials not actually used in the construction of the Premises shall
be returned to Landlord's inventory. Such inventory of remaining "stockpiled
materials" is attached as Exhibit "H".

<PAGE>

                                    RIDER 401

                           ATTACHED TO AND MADE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                      EXPANSION OPTION/RIGHT OF FIRST OFFER

1. "Expansion Option". So long as Tenant is in possession of the Premises and
has not committed an Event of Default under this Lease and Tenant's financial
condition, as determined by Landlord is comparable to Tenant's financial
condition at the time of the full execution of this Amendment, during the first
eighteen (18) months after the commencement Date referenced in Paragraph 4 of
this Amendment, Tenant shall have the option (hereinafter defined as the
"Expansion Option") to lease an additional 3,960 square feet of Rentable Area on
the fourth (4th) floor of the Building where indicated on Exhibit "A-1" attached
to be identified as part of Suite 400 (hereinafter defined as the "Expansion
Space").

      (a)   To exercise the Expansion Option (i) Tenant must give written notice
(hereinafter defined as the "Expansion Notice") of its intention to lease the
Expansion Space at least sixty (60) days prior to the date Tenant anticipates
occupying the Expansion Space, (ii) Tenant must lease the entire Expansion
Space, and (iii) such anticipated occupancy date must not be later than eighteen
(18) months after the Commencement Date referenced in Paragraph 4 of this
Amendment.

      (b)   Upon receipt of the Expansion Notice from Tenant, Landlord shall
submit to Tenant an amendment within fifteen (15) business days setting forth
the terms and conditions of such expansion. Such amendment shall establish the
effective date of the changes to the Lease and shall set forth the increases in
the Area of the Premises, Tenant's Pro Rata share and Tenant's Base Rental. In
the event Tenant does not fully execute the amendment in a final form and
fashion that is satisfactory to both parties, Landlord shall be free to market
the Expansion Space unconditionally and this Expansion Option shall be of no
further force or effect.

      (c)   Once the Expansion Space is "ready for occupancy" (as defined in
Rider 301) Tenant's Base Rental for the entire Premises including the Expansion
Space shall be increased to the amounts set forth in the following schedule:

<TABLE>
<CAPTION>
                                  Monthly Base Rental for the entire
Monthly Period                 Premises (including the Expansion Space)
--------------                 ----------------------------------------
<S>                            <C>
1-12                                         $16,332.63
13-24                                         17,022.93
25-36                                         17,824.98
37-48                                         18,540.98
49-60                                         19,254.65
</TABLE>

For purposes of example only, in the event the Expansion Space is "ready for
occupancy" on month five (5) of the Term of the Lease, Tenant's Base Rental as
increased by the leasing of the Expansion Space would be $16,332.63 and continue
in accordance with the remainder of the schedule above.

      (d)   In the event Tenant exercises this Expansion Option and the
Expansion Space is not "ready for occupancy" within eighteen (18) months after
the Commencement Date referenced in Paragraph 4 of this Amendment for any reason
whatsoever, Tenant's Base Rental as increased by the leasing of the Expansion
Space

<PAGE>

shall nevertheless become due and payable on the nineteenth (19th) month of the
Term of the Lease in accordance with the amounts set forth in the above
schedule.

      (e)   Leasehold Improvements to the Expansion Space shall be constructed
in accordance with Rider 301 attached hereto, provided, however, anything
contained in Rider 301 to the contrary notwithstanding the following shall
apply:

      (i)   Tenant shall submit its plans and specifications (for the Expansion
            Space) referenced in Paragraph 1(a) of said rider to Landlord for
            approval no later than ten (10) days after Landlord and Tenant fully
            execute an amendment to the Lease as referenced above; and

      (ii)  the Allowance for the Expansion space shall not exceed $59,400.00
            and such Allowance shall be proportionately reduced by the ratio
            which the remaining Term of the Lease bears to the Term as
            stipulated in Paragraph 5 of this Amendment.

      (f)   As consideration for Landlord providing Tenant this Expansion Option
right, until such time as the Expansion Option expires or Tenant has elected to
exercise the Expansion Option and has subsequently begun paying the increased
Base Rental in accordance with the schedule of Base Rental set forth in 1(c)
above, Tenant shall pay as additional Base Rental, the amounts set forth in the
following schedule:

<TABLE>
<CAPTION>
                           Additional Base Rental for Tenant's
Monthly Period                   Expansion Option Rights
--------------                   -----------------------
<S>                        <C>
1-6                                     $    0.00
7-12                                     1,524.60
13-18                                    1,980.00
</TABLE>

      2.    "Right of First Offer". Provided there has not been an occurrence of
an Event of Default by Tenant and Tenant is in possession of the Premises,
Tenant shall have the right to lease the balance of the fourth (4th) floor and
all of the sixth (6th) and the seventh (7th) floors should they become available
for lease to a third party tenant during tile Term of the Lease (hereinafter
defined as the "Right of First Offer"). Landlord shall notify Tenant in writing
of the availability of such space and the terms and conditions under which
Tenant shall be able to lease such space prior to marketing said space to a
third party. Upon such notice Tenant shall have twenty (20) days to either lease
such space on the terms and conditions that Landlord has presented to Tenant or
counter Landlord with terms and conditions acceptable to Tenant and Landlord. In
the event Landlord and Tenant agree to such expansion Landlord and Tenant shall
execute an amendment to this Lease in a form and fashion satisfactory to both
parties, setting forth the terms and conditions of such expansion. In the event
Tenant does not respond or an agreement is not reached within ten (10) days of
Landlord's receipt of any counter offer from Tenant, Landlord shall be free to
market such space unconditionally.

<PAGE>

                                    RIDER 501

                            ATTACHED AND MADE A PART
                                       OF
                             OFFICE LEASE AGREEMENT

                          ASHFORD OAKS OFFICE BUILDING

                                OPTION TO EXTEND

Tenant shall have one (1) option (the "Option") to renew and extend the Term of
this Lease for sixty (60) months (the "Renewal Term"), which option shall follow
consecutively on the expiration of the Term of this Lease, provided that at the
time that the option to renew is exercised, this Lease is in full force and
effect, Tenant is not in default hereunder and has not vacated the Premises. The
option shall be exercised by Tenant's giving to Landlord written notice of its
intention to renew and extend the Term of this Lease at least twelve (12) months
and no more than fifteen (15) months before the expiration date of the initial
Term of this Lease. The renewal and extension of this Lease for the Renewal Term
shall be on and under the same covenants, agreement, terms, provisions, and
conditions as are contained herein for the initial Term of this Lease, including
those providing for adjustments to the rent; provided however, that the rent for
the Renewal Terms shall be at the then prevailing rental rate for comparable
office space. In determining the then prevailing rental rate, Landlord will take
into consideration Tenant's creditworthiness, recent leases in the Building and
in comparable office buildings in a comparable geographic area, provided
however, in the determination of the then prevailing rental rate any recent
leases containing previously negotiated rental discounts (i.e. renewal rate
ceilings established at the time of initial lease execution, etc.) shall be
excluded. A legal document satisfactory to both parties shall be executed by
both parties that reflects the terms and conditions of such Renewal Term. Any
assignment or subletting by Tenant in violation or breach of Section 11.1 of
this Lease or vacating the Premises, shall terminate the Option to Tenant set
forth herein. Any termination of this Lease during the initial Term shall
terminate all rights of renewal and extension set forth in this Rider 301. In
the event Tenant elects to lease less Rentable Area than the initially leased
Premises, this option to renew will become null and void.

      At any time during the forty-five (45) day period immediately preceding
the date by which Tenant is required to exercise a renewal option, Tenant may
request in writing a quote from Landlord of the rent that will be applicable for
the Renewal Term. Landlord shall respond to a timely written request by
providing Tenant a written quote of the rent within fifteen (15) business days
after Landlord's receipt of Tenant's request.

<PAGE>

                            SECOND AMENDMENT TO LEASE

      This Second Amendment to Lease (the "Amendment") is entered into this 28th
day of February, 1995, by and between Building Acquisition Corporation, a Texas
Corporation ("Landlord") and BioNumerik Pharmaceuticals, Inc., a Delaware
Corporation ("Tenant").

                               W I T N E S S E T H

      WHEREAS, Landlord and Tenant executed that certain lease (the "Lease")
dated as of May 1, 1992, covering approximately 5,464 square feet of Rentable
Area in the Ashford Oaks Office Building (the "Building") located at 8122
Datapoint Drive, in the City of San Antonio, Bexar County, Texas, and further
identified as Suite 1250; and

      WHEREAS, Tenant, formerly known as BioNumerik Pharmaceuticals, L.C., a
Limited Liability Company, organized and existing under the laws of the State of
Texas having merged with and into BioNumerik Pharmaceuticals, Inc., a Delaware
Corporation, hereby affirms the terms of the Lease and further attorns to,
assumes and agrees to be bound by all of the terms of the Lease, except where
specifically amended herein; and

      WHEREAS, Landlord and Tenant have previously executed that certain First
Amendment to extend the term of the Lease and to expand the space covered by the
Lease to certain areas of the fourth floor of the Building including Exhibit
"A-1", "H", Rider 301, 401 & 501, dated July 16, 1993 (the "First Amendment");
and

      WHEREAS, Landlord and Tenant desire to further amend said Lease;

      NOW THEREFORE, in consideration of the Leased Premises and the mutual
benefits to accrue to Landlord and Tenant, both parties agree that effective May
1, 1992, the following designated sections of the above described Lease shall
be, and hereby are amended as follows:

      1.    Section 1.1 (j) "Base Rental" shall be as follows:

<TABLE>
<CAPTION>
                                           Suite 1250                      Suite 400
                            Suite 1250    Base Rental       Suite 400     Base Rental          Total
Monthly                       Monthly         Rate            Monthly         Rate            Monthly
Period           Month      Base Rental    (Monthly)       Base Rental     (Monthly)        Base Rental
------           -----      -----------    ---------       -----------     ---------        -----------
<S>           <C>           <C>           <C>              <C>            <C>               <C>
1-12          5/92-4/93      $4,615.63       $ .875                                         $ 4,615.63
13-24         5/93-4/94       4,837.18         .917                                           4,837.18
25-26         5/94-6/94       5,053.45         .958                                           5,053.45
27-36         7/94-4/95       5,053.45         .958         $ 7,757.00      $  1.00          12,810.45
37-38         5/95-6/95       5,275.00         1.00           7,757.00         1.00          13,032.00
39-48         7/95-4/96       5,275.00         1.00           8,067.35         1.04          13,342.35
49-50         5/96-6/96       5,496.55        1.042           8,067.35         1.04          13,563.90
51-60         7/96-4/97       5,496.55        1.042           8,455.13         1.09          13,951.68
61-62         5/97-6/97       5,712.83        1.083           8,455.13         1.09          14,167.96
63-72         7/97-4/98       5,712.83        1.083           8,782.47       1.1322          14,495.30
73-74         5/98-6/98       5,934.37        1.125           8,782.47       1.1322          14,716.84
76-84         7/98-4/99       5,934.37        1.125           9,108.27       1.1742          15,042.64
85-86         5/99-6/99       6,155.92        1.167           9,108.27       1.1742          15,264.19
87-96         7/99-4/00       6,155.92        1.167           9,742.79        1.256          15,898.71
97-98         5/00-6/00       6,372.20        1.208           9,742.79        1.256          16,114.99
99-108        7/00-4/01       6,372.20        1.208          10,371.11        1.337          16,743.31
109-110       5/01-6/01       6,593.75        1.250          10,371.11        1.337          16,964.86
111-120       7/01-4/02       6,593.75        1.250          11,038.21        1.423          17,631.96
</TABLE>

<PAGE>

Total Base Rental payable during the ten (10) year term is $1,530,354.16.

      2.    Section 1.1(l) "Commencement Date" shall be May 1, 1992 for Suite
            1250 and July 1, 1994 for Suite 400.

      3.    Section 1.1 (m) "Term" shall commence May 1, 1992 and end April 30,
            2002.

      4.    If the Expansion Option is exercised before December 31, 1995 the
            Base Rental Rates for Suite 400 described above shall also apply to
            the Expansion Space as defined in the Expansion Option contained in
            Rider 401 attached to the First Amendment. Such Expansion Option
            shall be extended and remain available to Tenant through December
            31, 1995, provided, however, if Tenant has not exercised said
            Expansion Option by July 1, 1995, Tenant shall commence paying a
            Retention Fee in the amount of $1,524.00 per month to retain such
            Expansion Option rights through December 31, 1995. Should Tenant
            fail to timely remit such Retention Fee, Tenant shall forfeit
            Tenant's rights under the Expansion Option. The Retention Fee
            provides Tenant no additional rights other than to exercise the
            rights set forth in Rider 401 and to require Landlord not enter into
            a lease with another party for the Expansion Space prior to December
            31, 1995. This provision supercedes the payment schedule set forth
            in Paragraph 1 (f) of Rider 401 to the Lease.

            Paragraph 1 (c) of Rider 401 shall be deleted in its entirety and
            the schedule of Base Rental amounts set forth in Paragraph 1 of this
            Amendment shall be increased in accordance with the following
            schedule once the Expansion Space is "ready for occupancy" (as
            defined in Rider 301):

<TABLE>
<CAPTION>
                                                  MONTHLY BASE RENTAL FOR
   MONTHLY PERIOD                                  THE EXPANSION SPACE*
   --------------                                  --------------------
<S>                                               <C>
7-1-94 thru 6-30-95                                     $3,960.00
7-1-95 thru 6-30-96                                     $4,118.40
7-1-96 thru 6-30-97                                     $4,316.40
7-1-97 thru 6-30-98                                     $4,483.51
7-1-98 thru 6-30-99                                     $4,649.83
7-1-99 thru 6-30-00                                     $4,973.76
7-1-00 thru 6-30-01                                     $5,294.52
7-1-01 thru 4-30-02                                     $5,635.08
</TABLE>

            *This amount shall be added to Total Monthly Base Rental shown in
            Paragraph 1 of this Amendment upon exercise of the Expansion Option.

      5.    Should Tenant exercise its Right of First Offer as described in
            Paragraph 2 of Rider 401 before March 31, 1995, then the Base Rental
            Rates for Suite 400 shall apply to the areas covered by the Right of
            First Offer of the 4th floor. Failure to exercise this Right of
            First Offer prior to March 31, 1995 shall relieve Landlord of any
            obligation to offer the predetermined Base Rental Rate but shall not
            cause the Right of First Offer to terminate in regards to the
            remaining 4th, 6th and 7th floor space. Additionally, Landlord and
            Tenant do hereby agree that in regard to the remaining 4th floor
            space, Tenant is hereby notified said space is available for lease
            to Tenant. Except as limited above to defined rental rates, Tenant
            may lease said area under the same conditions as the Expansion Space
            and in accordance with the notice provisions contained in Rider 401.

      6.    Tenant may elect to terminate this Lease as of June 30, 1999,
            provided however, Tenant has provided Landlord a minimum of six (6)
            months prior written notice and a maximum of twelve (12) months
            prior written notice of its intention to exercise said option. To
            exercise said option Tenant shall remit to Landlord at that time,
            along with said notice, a Termination Fee payable to Landlord in the
            amount of $46,855.80. Notwithstanding such option, Tenant shall
            remain obligated to pay for any sums which it is liable under the
            Lease including, but not limited to, any and all of its Prorata
            Share of Operating

<PAGE>

            Costs which may not have matured as of the effective date of
            termination plus any remaining unpaid sums (i.e. separate utility
            charges, past due rentals, late fees, etc.). All such sums remaining
            due from Tenant shall be payable within thirty (30) days of receipt
            of Landlord's invoice therefore. In the event the Premises is
            expanded during the initial term of the Lease and Tenant exercises
            this option to terminate in accordance with the terms stipulated
            above, Tenant shall remit an Additional Termination Fee. Such
            Additional Termination Fee shall be based on the following formula:

                                        34
            Total Expenses    X   --------------------     =     Additional
                                  Remaining Lease Term           Termination Fee

            Total Expenses are defined as those expenses incurred by Landlord in
            connection with the leasing of any such expanded area(s) to include,
            but not be limited to, architectural fees, consulting fees, finish
            allowances, etc., but not to include leasing commissions. Remaining
            Lease Term is defined as the months and days remaining in the term
            of the Lease at the time such expanded area is "ready for occupancy"
            through April 30, 2002.

      7.    The following provision "Supplemental Chiller" is hereby added to
            the Lease: In the interest of Landlord and Tenant, Landlord has
            installed a supplemental chilled water system (the "Supplemental
            Chiller") to provide supplemental cooling to the Building and
            Tenant's 4th floor Premises. Tenant shall be provided use of the
            Supplemental Chiller in a quantity not to exceed eighty (80) tons of
            its one hundred and forty (140) ton capacity (equal to 192 gallons
            per minute). Tenant shall be responsible for all costs of accessing
            the chilled water supplied by the Supplemental Chiller to the fourth
            floor in the location identified by Landlord. In consideration of
            Landlord's installation of the above system Tenant agreed to pay,
            and has paid to Landlord eighty thousand three hundred and eighty
            eight no/100 dollars ($80,388.00).

            All utility costs, routine maintenance and repairs and all other
            costs associated with the use of the Supplemental Chiller shall be
            borne by Landlord and Tenant on a prorata basis based upon the
            actual ratio of BTU's consumed by each party. To measure Tenant's
            use, a BTU metering device shall be installed by Tenant, at Tenant's
            sole cost and expense, in the 4th floor janitor's closet near the
            point of supply of the chilled water to the 4th floor Premises. To
            measure Landlord's use (which for the proposes hereunder shall
            include other tenant's usage but shall not include Tenant's usage),
            a BTU metering device(s) shall be installed by Landlord so that any
            and all such usage of the Supplemental Chiller can be accurately
            measured. Such metering device(s) shall, at a minimum, measure the
            temperature differential between the supply and return chilled water
            lines and record the flow rate of chilled water in gallons per
            minute (GPM) serving the Premises and other areas served by the
            Supplemental Chiller, process this data and display the total heat
            used in BTU's.

            Utility costs for this service shall be based on the then applicable
            rate assessed by the local utility company, City Public Service, or
            its successor, for such service actually used by Tenant and paid for
            by Landlord. Such cost shall be calculated based on 1 kilowatt hour
            per 3413 BTU's of consumption.

      8.    Paragraph B Option to Terminate as contained in the Addendum to this
            Lease is hereby deleted in its entirety and Tenant shall have no
            rights to terminate or cancel this Lease, except as otherwise
            provided in the Lease or subsequent amendments.

      9.    The parties hereto do hereby agree that the previous Second
            Amendment to Lease dated the 28th day of February, 1994 was never
            fully executed or accepted by either party and shall be considered
            null and void and shall not be legally binding on either party to
            this Lease.

      10.   Notwithstanding anything contained in Paragraph 15 of the First
            Amendment to Lease, the Letter of Credit shall be provided for the
            period starting July 1, 1994 and ending June 30, 1999.

<PAGE>

      11.   Section 22.18 "Guarantee" is hereby amended so that Tenant's
            delivery of said irrevocable Letter of Credit shall be due within
            one (1) week of full execution of this Amendment. The monthly
            periods referenced in Paragraph 15 of the First Amendment to Lease
            shall be deemed to have commenced July 1, 1994, and as such the
            amount of said Letter of Credit initially provided to Landlord may
            be reduced in accordance with the provisions contained in Section
            22.18. Tenant hereby acknowledges and agrees that Landlord shall
            have no responsibility to disburse any portion of the Allowance
            referenced in Rider 301 of the Lease until such time as Landlord has
            received said Letter of Credit in a form that is reasonably
            acceptable to Landlord. Tenant shall be solely responsible for any
            late fees, charges or expenses incurred in the discharging of any
            mechanics liens on the property or Building occasioned or caused by
            any potential payment delays resulting from Landlord's withholding
            of the Allowance or otherwise.

      BioNumerik Pharmaceuticals, Inc., a Delaware Corporation hereby affirms
the terms of the Lease, the First Amendment and this Second Amendment, Exhibits
and Riders, and further attorns to, assumes and agree to be bound by all the
terms of the Lease. This Second Amendment to Lease supercedes the Lease and
First Amendment to Lease and if there shall be a conflict or an inconsistency
between any of these agreements, the Second Amendment to Lease shall govern and
control. Except as specifically amended herein, the Lease dated May 1, 1992,
(all its Exhibits and Riders) by and between Landlord and Tenant, shall remain
in full force and effect in accordance with its terms and provisions.

      IN WITNESS WHEREOF, the parties herein have hereunto set forth their hands
this 28th day of February, 1995.

      TENANT:                                 LANDLORD:

      BioNumerik Pharmaceuticals, Inc.,       Building Acquisition Corporation,
      a Delaware Corporation                  a Texas Corporation

      By:  /s/ FREDERICK H. HAUSHEER          By: /s/ DANIEL E. LEININGER
         -------------------------               ------------------------------
      Printed                                 Printed
      Name:  Frederick H. Hausheer            Name:  Daniel E. Leininger
      Title: Chairman & C.E.O.                Title: President
      Date:                                   Date:

<PAGE>

                            THIRD AMENDMENT TO LEASE

      This Third Amendment to Lease (the "Amendment") is entered into this 28th
day of October, 1998, by and between Building Acquisition Corporation, a Texas
Corporation ("Landlord") and BioNumerik Pharmaceuticals, Inc., a Texas
Corporation ("Tenant").

                               W I T N E S S E T H

      WHEREAS, Landlord and Tenant executed that certain lease (the "Lease")
dated as of May 1, 1992, the First Amendment to Lease dated June 28, 1993 (the
"First Amendment"), and the Second Amendment to Lease dated February 28, 1995
(the "Second Amendment") regarding Rentable Area in the Ashford Oaks Office
Building (the "Building") located at 8122 Datapoint Drive, in the City of San
Antonio, Bexar County, Texas, and further identified as Suites 1250 and 400; and

      WHEREAS, Tenant, hereby affirms the terms of the Lease and the First and
Second Amendments thereto and further attorns to, assumes and agrees to be bound
by all of the terms of the Lease and the First and Second Amendments thereto,
except where specifically amended herein; and

      WHEREAS, Landlord and Tenant desire to further amend said Lease;

      NOW THEREFORE, in consideration of the Leased Premises and the mutual
benefits to accrue to Landlord and Tenant, both parties agree that the above
described Lease, as amended by the First Amendment and the Second Amendment,
shall be further amended as follows:

1.    Term Extension

      The Lease Term shall be extended for a total of forty-four (44) months
("Extension Term") from the current expiration date of April 30, 2002 to a new
expiration date of December 31, 2005.

      Base Rental during the Extension Term shall be as follows:

<TABLE>
<CAPTION>
   MONTH                        NO. OF MONTHS                MONTHLY RATE                  ANNUAL RATE
   -----                        -------------                ------------                  -----------
<S>                             <C>                          <C>                           <C>
5/02 - 12/03                          20                       $ 1.4166                      $ 17.00
1/04 - 12/04                          12                       $   1.50                      $ 18.00
1/05 - 12/05                          12                       $ 1.5833                      $ 19.00
</TABLE>

<PAGE>

2.    Expansion Option

            Tenant shall have the option to lease the balance of the space on
      the fourth floor of the Building ("Expansion Option") as shown on the
      attached floor plan ("Expansion Space") by providing Landlord written
      notice on or before December 31, 1998.

            The Expansion Space shall be deemed to contain 8,001 rentable sq.
      ft. If the Expansion Option is exercised, the Leased Premises when
      combined with the Expansion Space, shall contain 21,033 rentable sq. ft.

            Landlord will provide the Expansion Space in an "as is" condition
      and: a) allow Tenant access to and use of any building materials stored
      therein; b) provide a base buildout allowance of $15.00 per rentable sq.
      ft. or $120,015.00; c) provide an architectural and engineering allowance
      of $.50/rentable sq. ft. or $4000.50; and d) provide, at Tenant's option,
      an additional buildout allowance of $6.00 per rentable sq. ft. or
      $48,006.00 to be amortized monthly over the term of the Lease at 10%
      interest (collectively, the "Buildout Allowances"). Tenant shall have the
      right to construct improvements in the Expansion Space without paying a
      construction management fee to Landlord or Landlord's agent, subject only
      to Landlord's approval of the Expansion Space construction documents, as
      such approval is described in Rider 301 of the First Amendment to Lease
      ("Workletter").

            Tenant shall pay a Base Rental for the Expansion Space as follows:

<TABLE>
<CAPTION>
    TERM                    MONTHLY RATE                ANNUAL RATE
    ----                    ------------                -----------
<S>                         <C>                         <C>
7/99 - 12/03                  $ 1.5416                    $ 18.60
1/04 - 12/04                    1.6333                      19.60
1/05 - 12/05                    1.7166                      20.60
</TABLE>

            Whether or not Tenant has completed the buildout of the Expansion
      Space, the Base Rental shall commence one hundred eighty (180) days after
      delivery of Tenant's written notice to exercise the Expansion Option but
      in no event later than July 1, 1999. The lease term on the Expansion Space
      shall expire on December 31, 2005.

            For purposes of calculating Tenant's Pro Rata Share of Operating
      Costs attributable to the Expansion Space, the actual Operating Costs for
      calendar year 1999 shall be Landlord's Operating Cost contribution.
      Tenant's Pro Rata Share attributable to the Expansion Space is 4.193% and
      if this Expansion Option is exercised, 11.02% for the combined Leased
      Premises.

            Tenant will be provided a total of twenty-four (24) additional
      parking spaces. These additional parking spaces will be at no charge for
      the term of the Lease, and will be unreserved and will be provided as
      eighteen (18) covered and six (6) open spaces.

<PAGE>

3.    Termination Option

            Upon execution of this Amendment, Tenant will be deemed to have
      canceled its existing Termination Option as described in item number 6 in
      the Second Amendment. Tenant may elect to terminate the Lease, as amended
      ("Termination Option") as of December 31, 2002 by providing Landlord a
      minimum of six (6) months prior written notice to exercise this
      Termination Option. If the Expansion Option has been exercised, Tenant
      shall remit to Landlord a payment ("Termination Fee") equal to the
      unamortized Buildout Allowance on the Expansion Space only, as calculated
      on a straight line basis over the total potential term (i.e., until
      December 31, 2005). If the Termination Option is allowed to expire and is
      not exercised, Landlord agrees to pay Cross & Company or its successors or
      assigns, a cash, lump sum leasing commission equal to four percent (4%) of
      the gross rent to be paid by Tenant on the Leased Premises over the
      remaining uncancelable term no later than thirty (30) days after June 30,
      2002.

4.    Tenant or Tenant's officers shall not be required to provide a Letter of
      Credit or Guarantee as described in the Lease Agreement, First or Second
      Amendment.

5.    Tenant's Right of First Offer to Lease any and all space as it becomes
      available on the sixth and seventh floor of the Property, as contained in
      section 2 of Rider 401 of the First Amendment to Lease shall continue in
      full force and effect. Should Tenant not exercise the Expansion Option,
      the Tenant shall have a Right of First Refusal on the balance of the
      fourth floor. Landlord shall provide written notification of the bona fide
      intent of a third party tenant to lease any or all of this fourth floor
      space and the terms and conditions which the third party tenant is willing
      to accept. Tenant shall then have ten (10) business days in which to
      either accept this space on the same terms and conditions as the third
      party or to allow Landlord to enter into a lease with the third party.
      Should the Landlord and the third party fail to execute a lease or should
      the space again become available for lease during Tenant's term, this
      Right of First Refusal will still be valid and applicable to this space.

6.    Tenant shall have the right to lease any or all of the shell space on the
      fourth floor of the building at a monthly rate of 54.167(cent) per square
      foot for storage. This space shall be used solely for the purposes of
      storing Tenant's equipment, furniture and files only, and for no other
      purpose. This agreement, as it applies to this storage space only, may be
      terminated by either party providing fifteen (15) day written notice to
      the other party.

      Except as described in this Amendment, the terms of which shall control if
in conflict with the Lease or the First or Second Amendment to Lease, all other
terms and conditions of the Lease, First or Second Amendments to Lease shall
remain in full force and effect. Except as otherwise defined herein, all
capitalized terms used but not defined herein shall have the same meanings
assigned to such terms in the Lease, as amended by the First and Second
Amendment.

AGREED AND ACCEPTED this 28th day of October , 1998.

Tenant:                                        Landlord:
BioNumerik Pharmaceuticals, Inc.               Building Acquisition Corporation

By:  /s/ DAVID R. MARGRAVE                     BY:  /s/ DANIEL LEININGER
   -----------------------                        ----------------------
Its: Vice President &                          Its: President
     Chief Administrative Officer

<PAGE>

                                 EXPANSION SPACE

Building lease area graphic image of floor plan representing fourth floor
premises and expansion space.

<PAGE>

                            FOURTH AMENDMENT TO LEASE

      This Fourth Amendment to Lease (the "Amendment") is entered into this 13th
day of October, 1999, by and between Ashford Building, Ltd., a Texas limited
partnership, ("Landlord") and BioNumerik Pharmaceuticals, Inc., a Texas
Corporation ("Tenant").

                                   WITNESSETH

      WHEREAS, Landlord and Tenant executed that certain lease (the "Lease")
dated as of May I, 1992, the First Amendment to Lease dated June 28, 1993 (the
"First Amendment"), the Second Amendment to Lease dated February 28, 1995 (the
"Second Amendment") and the Third Amendment to Lease dated October 28, 1998 (the
"Third Amendment") regarding Rentable Area in the Ashford Oaks Office Building
(the "Building") located at 8122 Datapoint Drive, in the City of San Antonio,
Bexar County, Texas, and further identified as Suites 1250 and 400; and

      WHEREAS, Tenant, hereby affirms the terms of the Lease, the First, Second
and Third Amendments thereto and further attorns to, assumes and agrees to be
bound by all of the terms of the Lease and the First, Second and Third
Amendments thereto, except where specifically amended herein; and

      WHEREAS, Landlord and Tenant desire to further amend said Lease;

      NOW THEREFORE, in consideration of the Leased Premises and the mutual
benefits to accrue to Landlord and Tenant, both parties agree that the above
described Lease, as amended by the First, Second and Third Amendments, shall be
further amended as follows:

1.    Lease Space Expansion

      The Leased Premises shall be expanded by 8,001 rentable square feet or
      from 13,032 rentable square feet prior to the execution of this Fourth
      Amendment to a new total of 21,033 rentable square feet. The 8,001
      rentable square feet represents the balance of the fourth floor of the
      Building, as shown on the attached floor plan, and shall be known as the
      Second Expansion Space ("Second Expansion Space").

2.    Expansion Space Tenant Finish

      Landlord shall provide an allowance of $15.00 per rentable square foot or
      a total of $120,015 towards Tenant's interior finish in the Second
      Expansion Space. Landlord will also provide an additional allowance of
      $.50 per rentable square foot or $4,000.50 for architectural and
      engineering services applicable to the Second Expansion Space. Landlord
      shall also provide, subject to Tenant's sole option, up to an additional
      $5.00 per rentable square foot allowance or $40,005.00 to be amortized
      monthly over the term of the lease at an annual interest rate of 12%
      (collectively "Tenant Finish Allowances").

      Tenant shall have the right to manage the construction of the interior
      finish in the Second Expansion Space without a fee to be paid to Landlord
      or Landlord's agent. Landlord will fund the Tenant Finish Allowances upon
      receipt of paid invoices and lien waiver from Tenant. Any cost in excess
      of the Tenant Finish Allowances shall be Tenant's sole responsibility.
      Should Tenant use the additional allowance of $5.00 per rentable sq. ft.,
      as described above, Tenant agrees to execute a memorandum to the lease
      documenting the amount amortized and the resulting monthly payment. In no
      event shall leasing commissions be calculated on any portion of any such
      additional Base Rental attributable to the amortization of these costs.

<PAGE>

3.    Expansion Space Base Rental

      Base Rental for the Second Expansion Space shall be structured as follows:

<TABLE>
<CAPTION>
                                                    Annual Base Rental
Monthly Period                                     Per Rentable Sq. Ft.
--------------                                     --------------------
<S>                                                <C>
Start date to 12/31/03                                   $19.00
1/1/04 to 12/31/04                                       $20.00
1/1/05 to 12/31/05                                       $21.00
</TABLE>

      Therefore, the Monthly Base Rental for the existing leased premises and
      the Second Expansion Space shall be as follows:

<TABLE>
<CAPTION>
                              Existing               Second Expansion
                           Leased Premises                Space                     Total
Monthly Period            (13,032 sq. ft.)           (8,001 sq. ft.)*         (21,033 sq. ft.)
--------------            ----------------           ----------------         ----------------
<S>                       <C>                        <C>                      <C>
1/00 - 4/00                  $15,898.71                 $12,668.25               $28,566.96
5/00 - 6/00                   16,114.99                  12,668.25                28,783.24
7/00 - 4/01                   16,743.31                  12,668.25                29,411.56
5/01 - 6/01                   16,964.86                  12,668.25                29,633.11
7/01 - 4/02                   17,631.96                  12,668.25                30,300.21
5/02 - 12/03                  18,461.13                  12,668.25                31,129.38
1/04 - 12/04                  19,548.00                  13,335.00                32,883.00
1/05 - 12/05                 $20,633.57                 $14,001.75               $34,635.32
</TABLE>

      *Base Rental for the Second Expansion Space shall commence on the earlier
      of substantial completion of the interior finish or one hundred fifty
      (150) days after the execution of this Fourth Amendment whether or not
      Tenant has completed the interior finish in the Second Expansion Space.
      ("Second Expansion Space Commencement Date")

4.    Other

      a.    For purposes of calculation of Tenant's Pro Rata Share of Operating
            Costs attributable to the Second Expansion Space, the actual
            Operating Costs for calendar year 2000 shall be Landlord's Operating
            Cost contribution. Tenant's Pro Rata Share attributable to the
            Second Expansion Space is 4.193% and 11.02% for the combined leased
            premises.

      b.    The lease term on the Second Expansion Space shall expire on
            December 31, 2005, except as hereafter provided. Tenant shall have
            the right to terminate the Lease, as amended, ("Second Expansion
            Space Termination Option") for the area contained in the Second
            Expansion Space as of the end of the thirty-sixth (36th) month after
            the Second Expansion Space Commencement Date. Tenant shall exercise
            this Second Expansion Space Termination Option by providing Landlord
            a minimum of six (6) months prior written notice. The Termination
            Option, as described in the Third Amendment to Lease, Section #3, is
            hereby adjusted so as to be exercisable and effective in the same
            manner and as of the same date as this Second Expansion Space
            Termination Option. If such termination option is allowed to expire
            and is not exercised, Landlord agrees to pay Cross & Company or its
            successors or assigns, a cash, lump sum leasing commission equal to
            four percent (4%) of the Total Base Rental to be paid by Tenant on
            the Leased Premises over the remaining uncancelable term. This
            commission shall be paid no later than August 31, 2002. Except as
            amended hereby, Tenant's existing Termination Option with respect to
            the Lease, as amended, for the area of the Leased Premises, other
            than the Second Expansion Space, shall remain and continue as
            provided in the Third Amendment.

<PAGE>

      c.    Landlord shall provide Tenant a total of twenty-four (24) additional
            parking spaces at no charge for the term of the Lease to be taken as
            eighteen (18) in-garage spaces and six (6) surface spaces.

Except as described in this Fourth Amendment, the terms of which shall control
if in conflict with the Lease or the First, Second or Third Amendments to the
Lease, all other terms and conditions of the Lease, First, Second and Third
Amendments to the Lease shall remain in full force and effect. Except as
otherwise defined herein, all capitalized terms used but not defined herein
shall have the same meanings assigned to such terms in the Lease, as amended by
the First, Second and Third Amendments.

AGREED AND ACCEPTED THIS 13th DAY OF OCTOBER 1999.

TENANT                                      LANDLORD
BioNumerik Pharmaceuticals, Inc.            ASHFORD BUILDING, LTD.

By  /s/ FREDERICK H. HAUSHEER, M.D.         By   /s/ DANIEL LEININGER
  ---------------------------------           ----------------------------------
Its Chief Executive Officer                 Its  President

<PAGE>

                                  ATTACHMENT A

                                 EXPANSION SPACE

Building lease area graphic image of floor plan representing fourth floor
premises and expansion space.

<PAGE>

                            FIFTH AMENDMENT TO LEASE

      This Fifth Amendment to Lease (the "Fifth Amendment") is entered into this
29th day of June, 2001, by and between Ashford Building, Ltd., a Texas limited
partnership, ("Landlord") and BioNumerik Pharmaceuticals, Inc., a Texas
Corporation ("Tenant").

                                   WITNESSETH

      WHEREAS, Landlord and Tenant executed that certain lease (the "Lease")
dated as of May 1, 1992, the First Amendment to Lease dated June 28, 1993 (the
"First Amendment"), the Second Amendment to Lease dated February 28, 1995 (the
"Second Amendment"), the Third Amendment to Lease dated October 28, 1998, (the
"Third Amendment") and the Fourth Amendment to Lease dated October 13, 1999 (the
Fourth Amendment) regarding Rentable Area in the Ashford Oaks Office Building
(the "Building") located at 8122 Datapoint Drive, in the City of San Antonio,
Bexar County, Texas, and further identified as Suites 1250 and 400; and

      WHEREAS, Tenant, hereby affirms the ten terms of the Lease, the First,
Second, Third and Fourth Amendments thereto and further attorns to, assumes and
agrees to be bound by all of the terms of the Lease and the First, Second, Third
and Fourth Amendments thereto, except where specifically amended herein; and

      WHEREAS, BioNumerik Pharmaceuticals, L.C., a limited liability company,
merged with and into BioNumerik Pharmaceuticals, Inc., a Delaware corporation,
which merged with and into BioNumerik Pharmaceuticals, Inc., a Texas
corporation. By way of the foregoing mergers and by way of various rounds of
financing during the term of the Lease, Tenant has undergone several changes in
ownership ("Changes in Ownership"); and

      WHEREAS, Landlord and Tenant desire to further amend said Lease;

      NOW THEREFORE, in consideration of the Leased Premises and the mutual
benefits to accrue to Landlord and Tenant, both parties agree that the above
described Lease, as amended by the First, Second, Third and Fourth Amendments,
shall be further amended as follows:

      1.    Lease Space Expansion

            The Leased Premises shall be expanded by 9,523 rentable square feet
            (the "Third Expansion Space") or from 21,033 rentable square feet
            prior to the execution of this Fifth Amendment to a new total of
            30,556 rentable square feet. The Third Expansion Space will be taken
            as 4,761.5 rentable square feet on July 1, 2001 and the balance of
            the Third Expansion Space on May 1, 2002. The 9,523 rentable square
            feet represents the remaining office space on the twelfth (12th)
            floor of the Building, in the location depicted on the floor plan
            attached hereto as Exhibit "A".

      2.    Third Expansion Space Tenant Finish

            Landlord shall provide an allowance of $10.00 per rentable square
            foot (prorated as appropriate for the Third Expansion Space portion
            to be taken in May 2002) or a total of $92,190.74 towards Tenant's
            interior finish in the Third Expansion Space ("Tenant Finish
            Allowance"). Tenant shall be responsible for the cost of performing
            all work desired by Tenant in the Third Expansion Space to include,

                                       1
<PAGE>

            but not be limited to, obtaining all necessary fees and permits,
            construction management supervision fees, demolition, new
            construction, and any and all modifications both above and below the
            ceiling. Landlord will fund the Tenant Finish Allowance upon receipt
            of paid invoices and lien waivers from Tenant. Any cost in excess of
            the Tenant Finish Allowance shall be Tenant's sole responsibility.

      3.    Expansion Space Base Rental

            Base Rental for the Third Expansion Space shall be structured as
            follows:

<TABLE>
<CAPTION>
Monthly Period               Annual Base Rental Per Rentable Sq. Ft.
--------------               ---------------------------------------
<S>                          <C>
7/01/01 to 12/31/05                        $19.00
</TABLE>

            Therefore the Monthly Base Rental for the existing Leased Premises
            and the Third Expansion Space shall be as follows:

<TABLE>
<CAPTION>
                             EXISTING                 THIRD
MONTHLY                      PREMISES               EXPANSION              TOTAL
PERIOD                    21,033 SQ. FT.          9,523 SQ. FT.*       30,556 SQ. FT.
------                    --------------          --------------       --------------
<S>                       <C>                     <C>                  <C>
07/01 - 01/02               $30,300.21              $ 7,539.04           $37,839.25
02/02 - 04/02                30,300.21                7,539.04            37,839.25
05/02 - 12/03                31,129.38               15,078.08            46,207.46
01/04 - 12/04                32,883.00               15,078.08            47,961.08
01/05 - 12/05                34,635.32               15,078.08            49,713.40
</TABLE>

            * reflects 4,761.5 rentable square feet leased on July 1, 2001 and
            the same amount leased on May 1, 2002.

            Base rental for the Third Expansion Space shall commence as
            stipulated on the above schedule regardless of the completeness of
            any leasehold improvements to be constructed by Tenant.

      4.    Other

            a.      For purposes of calculation of Tenant's Pro Rata Share of
                    Operating Costs attributable to the Third Expansion Space,
                    the actual Operating Costs for calendar year 2001 shall be
                    Landlord's Operating Cost contribution. Tenant's Pro Rata
                    Share is 4.991% for the Third Expansion Space and 16.013%
                    for the combined leased premises.

            b.    The lease term on the Third Expansion Space shall expire on
                  December 31, 2005, except as hereafter provided. Tenant shall
                  have the right to terminate the Lease, as amended, ("Third
                  Expansion Space Termination Option") for the area contained in
                  the Third Expansion Space as of December 31, 2003. To exercise
                  this Termination Option, Tenant must provide Landlord a
                  minimum of six (6) months prior written notice. The
                  Termination Option, as described in the Third Amendment to
                  Lease, Section #3 and the Second Expansion Space Termination
                  Option, as described in the Fourth Amendment, Section 4.b are
                  hereby amended so as to be exercisable and effective in the
                  same manner and as of the same date (as of 12/31/03) as this
                  Third

                                       2
<PAGE>

                  Expansion Space Termination Option; provided however, the
                  parties hereto agree that in the event Tenant elects to
                  exercise the foregoing termination options, the aggregate
                  termination fee shall be $86,814.90. If such termination
                  option is allowed to expire and is not exercised, Landlord
                  agrees to pay Cross & Company or its successors or assigns, a
                  cash, lump sum leasing commission equal to four percent (4%)
                  of the Total Base Rental to be paid by Tenant on the Leased
                  Premises over the remaining uncancelable term. This commission
                  shall be paid no later than January 31, 2004.

            c.    Landlord shall provide Tenant a total of twenty-nine (29)
                  additional parking spaces at no charge for the term of the
                  Lease to be taken as twenty one (21) in-garage spaces and
                  eight (8) surface spaces resulting in an aggregate of
                  sixty-nine (69) total parking spaces, fifty (50) in garage
                  spaces and nineteen (19) surface spaces.

            d.    Landlord recognizes and accepts that Tenant has entered into a
                  short term space sublease with the existing tenant in the
                  Third Expansion Space, subject to Landlord's approval of the
                  sublease document. Said sublease shall expire on June 30,2001.

            e.    Section 11.2 of the Lease is deleted in its entirety and
                  replaced with the following: "Notwithstanding anything to the
                  contrary in this Lease, Tenant may, without obtaining
                  Landlord's prior written consent, sublet the Premises or
                  assign the Lease to (a) an entity controlled by or under
                  common control with Tenant, (b) a successor entity related to
                  Tenant by merger, consolidation, non-bankruptcy
                  reorganization, or governmental action, or (c) a purchaser of
                  substantially all of Tenant's assets located in the Premises
                  (a "Permitted Transfer"). A sale or transfer of Tenant's
                  capital stock, including pursuant to an initial public
                  offering, shall not be deemed an assignment, subletting or any
                  other transfer of the Lease or Premises. No such Permitted
                  Transfer shall be subject to any rights of recapture or rent
                  profit-sharing provisions."

            f.    Section 22.16 is hereby modified by the addition of the
                  following sentence to the end of the paragraph:
                  "Notwithstanding the foregoing, Tenant may disclose, without
                  prior written consent of the Landlord, the terms and
                  provisions of this Lease as required by law, including as part
                  of any initial public offering of Tenant's stock."

            g.    Landlord consents to the Changes in Ownership.

            h.    This Agreement, together with the Lease, as amended,
                  constitutes the entire agreement between Landlord and Tenant
                  regarding the Lease and the subject matter contained herein
                  and supersedes any and all prior and/or contemporaneous oral
                  or written negotiations, agreements or understandings. This
                  Fifth Amendment shall be binding upon and inure to the benefit
                  of Landlord and Tenant and their respective heirs, legal
                  representatives, successors and assigns. No subsequent change
                  or addition to this Fifth Amendment shall be binding unless in
                  writing and duly executed by both Landlord and Tenant. Except
                  as specifically amended hereby, all of the terms and
                  conditions of the Lease, as amended, are and shall remain in
                  full force and effect and are hereby ratified and confirmed.
                  This Fifth Amendment may be executed in two or more
                  counterparts, each of which shall constitute an original, but
                  all of which, taken together, shall constitute but one
                  Agreement. An executed facsimile copy of this Fifth Amendment
                  shall be considered an original.

                                       3
<PAGE>

Except as described in this Fifth Amendment, the terms of which shall control if
in conflict with the Lease or the First, Second, Third or Fourth Amendments to
the Lease, all other terms and conditions of the Lease, as amended by the First,
Second, Third and Fourth Amendments to the Lease shall remain in full force and
effect. Except as otherwise defined herein, all capitalized terms used but not
defined herein shall have the same meanings assigned to such terms in the Lease,
as amended by the First, Second, Third and Fourth Amendments.

Agreed to and Accepted on the day first above mentioned.

TENANT                                        LANDLORD
BIONUMERIK PHARMACEUTICALS, INC.              ASHFORD BUILDING, LTD.
a Texas corporation                           a Texas Limited Partnership
                                              By:      Ashford GP Corp.,
                                                       a Texas corporation
                                                       General Partner

By:    /s/ FREDERICK H. HAUSHEER              By:    /s/ DANIEL E. LEININGER
Printed Name:  Frederick H. Hausheer, M.D.    Printed Name:  Daniel E. Leininger
Title  Chief Executive Officer                Title:  President

                                       4
<PAGE>

                                   EXHIBIT "A"

Building lease area graphic image of floor plan representing twelfth floor
premises and expansion space.

                                       5
<PAGE>

                            SIXTH AMENDMENT TO LEASE

      This Sixth Amendment to Lease (the "Sixth Amendment") is entered into
effective as of June 29, 2002, by and between Ashford Building, Ltd., a Texas
limited partnership, ("Landlord") and BioNumerik Pharmaceuticals, Inc., a Texas
corporation ("Tenant").

                                   WITNESSETH

      WHEREAS, Landlord and Tenant executed that certain lease (the "Lease")
dated as of May 1, 1992, the First Amendment to Lease dated June 28, 1993 (the
"First Amendment"), the Second Amendment to Lease dated February 28, 1995 (the
"Second Amendment"), the Third Amendment to Lease dated October 28, 1998, (the
"Third Amendment"), the Fourth Amendment to Lease dated October 13, 1999 (the
"Fourth Amendment") and the Fifth Amendment to Lease dated June 29, 2001 (the
"Fifth Amendment") regarding Rentable Area in the Ashford Oaks Office Building
(the "Building") located at 8122 Datapoint Drive, in the City of San Antonio,
Bexar County, Texas, and further identified as Suites 1250, 1200 and 400; and

      WHEREAS, Tenant, hereby affirms the terms of the Lease, the First, Second,
Third, Fourth and Fifth Amendments thereto and further attorns to, assumes and
agrees to be bound by all of the terms of the Lease and the First, Second,
Third, Fourth and Fifth Amendments thereto, except where specifically amended
herein; and

      WHEREAS, Landlord and Tenant desire to further amend said Lease;

      NOW THEREFORE, in consideration of the Leased Premises and the mutual
benefits to accrue to Landlord and Tenant, both parties agree that the above
described Lease, as amended by the First, Second, Third, Fourth and Fifth
Amendments, shall be further amended as follows:

      1.    Landlord agrees to extend the availability date for Tenant to use
            the Tenant Finish Allowance described in the Fifth Amendment to
            Lease dated June 29, 2001, provided, however, that if Tenant, after
            the date hereof, elects to draw on any of the remaining finish out
            funds to be provided by Landlord under such Tenant Finish Allowance,
            then Tenant's existing early termination options to terminate the
            Lease (or any portion thereof) prior to December 31, 2005
            (consisting of the Termination Option, as amended, the Second
            Expansion Space Termination Option, as amended, and the Third
            Expansion Space Termination Option, all as described in Section 4.b.
            of the Fifth Amendment) shall immediately terminate and thereafter
            be of no force and effect. Subject to the condition described in the
            previous sentence, the Tenant Finish Allowance may be used by Tenant
            at any time during the remaining term of the Lease, provided that in
            no event shall the Tenant Finish Allowance be used during the last
            12 months of the Lease term. Accordingly, the Tenant Finish
            Allowance may not be used after December 31, 2004.

      2.    Except as specifically amended hereby, all of the existing terms and
            conditions of the Lease, as amended, are and shall remain in full
            force and effect and are hereby ratified and confirmed.

                                       1
<PAGE>

This Agreement, together with the Lease, as amended, constitutes the entire
agreement between Landlord and Tenant regarding the Lease and the subject matter
contained herein and supersedes any and all prior and/or contemporaneous oral or
written negotiations, agreements or understandings. This Sixth Amendment shall
be binding upon and inure to the benefit of Landlord and Tenant and their
respective heirs, legal representatives, successors and assigns. No subsequent
change or addition to this Sixth Amendment shall be binding unless in writing
and duly executed by both Landlord and Tenant. This Sixth Amendment may be
executed in two or more counterparts, each of which shall constitute an
original, but all of which, taken together, shall constitute but one agreement.
An executed facsimile copy of this Sixth Amendment shall be considered an
original.

Except as described in this Sixth Amendment, the terms of which shall control if
in conflict with the Lease or the First, Second, Third, Fourth or Fifth
Amendments to the Lease, all other terms and conditions of the Lease, as amended
by the First, Second, Third, Fourth and Fifth Amendments to the Lease shall
remain in full force and effect. Except as otherwise defined herein, all
capitalized terms used but not defined herein shall have the same meanings
assigned to such terms in the Lease, as amended by the First, Second, Third,
Fourth and Fifth Amendments.

Agreed to and Accepted as of the day first above mentioned.

TENANT                                        LANDLORD

BIONUMERIK PHARMACEUTICALS, INC.              ASHFORD BUILDING, LTD.
a Texas corporation                           a Texas Limited Partnership
                                              By:    Ashford GP Corp.,

By:   /s/ FREDERICK H. HAUSHEER               By:    /s/ DANIEL E. LEININGER
Printed Name: Frederick H. Hausheer, M.D.     Printed Name: Daniel E. Leininger
Title Chief Executive Officer                 Title: President

                                       2