<PAGE>   1
                                                                   EXHIBIT 10.27


                                  OFFICE LEASE

                                       BY

                                       AND

                                     BETWEEN

                        CATELLUS DEVELOPMENT CORPORATION,

                             A DELAWARE CORPORATION,

                                   AS LANDLORD

                                       AND

                            ALLOS THERAPEUTICS, INC.,

                             A DELAWARE CORPORATION,

                                   AS TENANT.

                          CIRCLEPOINT CORPORATE CENTER

                              WESTMINSTER, COLORADO



<PAGE>   2

                                TABLE OF CONTENTS

<Table>
<Caption>
                                                                   Page
                                                                   ----
<S>    <C>                                                         <C>
1.     BASIC LEASE INFORMATION .......................................1

2.     PREMISES ......................................................1
       2.1    Premises ...............................................1
       2.2    Common Facilities ......................................1
       2.3    Reserved Rights ........................................1
       2.4    Parking ................................................2
       2.5    Right of First Offer ...................................2

3.     TERM ..........................................................3
       3.1    Initial Term ...........................................3
       3.2    Option to Extend .......................................4

4.     RENT ..........................................................5
       4.1    Base Rent ..............................................5
       4.2    Additional Rent ........................................6
       4.3    Late Charge and Interest ...............................6
       4.4    Security Deposit .......................................6

5.     SERVICES AND UTILITIES ........................................7
       5.1    Standard Tenant Services ...............................7
       5.2    Overstandard Tenant Use ................................8
       5.3    Interruption of Use ....................................8
       5.4    Abatement ..............................................8

6.     TAXES .........................................................9
       6.1    Real Property Taxes ....................................9
       6.2    Definition of Real Property Taxes ......................9
       6.3    Taxes on Tenant Improvements/Personal Property ........10

7.     OPERATING EXPENSES ...........................................10
       7.1    Operating Expenses ....................................10
       7.2    Definition of Operating Expenses ......................10
       7.3    Exclusions from Operating Expenses ....................11

8.     ESTIMATED EXPENSES ...........................................12
       8.1    Payment ...............................................12
       8.2    Adjustment ............................................12

9.     INSURANCE ....................................................12
       9.1    Landlord ..............................................12
       9.2    Tenant ................................................13
       9.3    General ...............................................13
       9.4    Indemnity .............................................14
       9.5    Exemption of Landlord from Liability ..................15

10.    REPAIRS AND MAINTENANCE ......................................15
       10.1   Tenant ................................................15
       10.2   Landlord ..............................................15

11.    ALTERATIONS ..................................................16
       11.1   Trade Fixtures; Alterations ...........................16
       11.2   Removal of Tenant's Property and Alterations ..........16
       11.3   Liens .................................................17
       11.4   Remodel ...............................................17

12.    USE ..........................................................17

13.    SIGNS ........................................................18

14.    DAMAGE AND DESTRUCTION .......................................18
       14.1   Landlord's Obligation to Rebuild ......................18
       14.2   Landlord's Right to Terminate .........................19
       14.3   Tenant's Right to Terminate ...........................19
       14.4   Abatement of Rent; Tenant's Fault .....................19
</Table>



                                       (v)
<PAGE>   3

<Table>
<Caption>
                                                                   Page
                                                                   ----
<S>    <C>                                                         <C>
       14.5   Damage Near End of Term ...............................19
       14.6   Insurance Proceeds ....................................19

15.    EMINENT DOMAIN ...............................................20
       15.1   Total Condemnation ....................................20
       15.2   Partial Condemnation ..................................20
       15.3   Award .................................................20
       15.4   Temporary Condemnation ................................20

16.    DEFAULT ......................................................20
       16.1   Events of Default .....................................20
       16.2   Notice ................................................21
       16.3   Remedies ..............................................21
       16.4   Cumulative ............................................22
       16.5   Mitigation of Damages .................................22

17.    DEFAULT BY LANDLORD ..........................................22

18.    ASSIGNMENT AND SUBLETTING ....................................22
       18.1   Landlord's Consent Required ...........................22
       18.2   General Provisions ....................................23
       18.3   Information to be Furnished ...........................23
       18.4   Landlord's Election ...................................23
       18.5   Termination ...........................................24
       18.6   Bonus Rental ..........................................24
       18.7   Executed Counterparts .................................24
       18.8   Permitted Transfers ...................................24
       18.9   Permitted Occupants ...................................25

19.    ESTOPPEL, ATTORNMENT AND SUBORDINATION .......................25
       19.1   Estoppel ..............................................25
       19.2   Subordination .........................................25
       19.3   Attornment ............................................25

20.    RELOCATION ...................................................25

21.    MISCELLANEOUS ................................................26
       21.1   General ...............................................26
       21.2   Waiver ................................................26
       21.3   Financial Statements ..................................27
       21.4   Limitation of Liability ...............................27
       21.5   Notices ...............................................27
       21.6   Commission ............................................27
       21.7   Authorization .........................................27
       21.8   Holding Over/Surrender ................................27
       21.9   Confidentiality .......................................28
       21.10  Covenants and Conditions ..............................28
       21.11  Use of Name, Filming and Photographs of Project .......28
       21.12  Force Majeure .........................................28
       21.13  Constant Dollars ......................................28
       21.14  Development of the Project ............................29
       21.15  Communication Equipment ...............................29
</Table>



                                      (vi)
<PAGE>   4

                                      INDEX

<Table>
<Caption>
                                                              Page(s)
                                                              -------
<S>                                                         <C>
Abatement Event ....................................................8
Abatement Notice ...................................................8
Additional Rent ....................................................6
Adjustment ........................................................12
Adjustment Dates ...................................................6
Affiliate .........................................................24
Affiliated Assignee ...............................................24
Alterations .......................................................16
Applicable Interest Rate ...........................................6
Applicable Laws ...................................................17
Approved Working Drawings ..................................Exhibit B
Architect ..................................................Exhibit B
Assignment ........................................................22
Base Rent .........................................................ii
BOMA ...............................................................1
Building ..........................................................ii
Building Hours .....................................................8
Building Specifications ....................................Exhibit B
Building Systems ..................................................17
Change Order ...............................................Exhibit B
Commencement Date .................................................ii
Common Facilities ..................................................1
Communication Equipment ...........................................29
Communication Equipment Notice ....................................29
Comparable Area ....................................................4
Condemned .........................................................20
Constant Dollars ..................................................28
Contemplated Effective Date .......................................24
Contractor .................................................Exhibit B
Control ...........................................................24
Cost Pools ........................................................11
Cost Proposal ..............................................Exhibit B
Cost Proposal Delivery Date ................................Exhibit B
Delay Notice .......................................................4
Delinquency Costs ..................................................6
Delivery Date .....................................................ii
Delivery Outside Date ..............................................3
Economic Terms .....................................................3
Effective Date .....................................................i
Eligibility Period .................................................9
Engineering Drawings .......................................Exhibit B
Engineers ..................................................Exhibit B
Estimated Delivery Date ...........................................ii
Estimated Expenses ................................................12
Event of Default ..................................................20
Expiration Date ...................................................ii
Extension Term .....................................................4
Final Space Plan ...........................................Exhibit B
Final Working Drawings .....................................Exhibit B
First Offer Notice .................................................3
First Offer Space ..................................................2
Force Majeure Event ...............................................28
Holidays ...........................................................8
Indemnified Parties ...............................................14
Intention to Transfer Notice ......................................24
Interest Rate .....................................................10
Landlord ...........................................................i
Landlord Claims ...................................................14
Landlord Indemnified Party ........................................14
Landlord Supervision Fee ...................................Exhibit B
Landlord's Work ............................................Exhibit B
Letter of Credit ...................................................6
Market Rent ........................................................4
Mortgagee .........................................................22
Objectionable Name ................................................18
</Table>

                                      (vii)


<PAGE>   5

<Table>
<Caption>
                                                              Page(s)
                                                              -------
<S>                                                         <C>
Occupant ..........................................................25
Operating Expenses ................................................10
Outside Agreement Date .............................................4
Over-Allowance Amount ......................................Exhibit B
Partial Cost Proposal ......................................Exhibit B
Permits ....................................................Exhibit B
Permitted Use .....................................................ii
Premises ...........................................................i
Project ...........................................................ii
Real Property Taxes ................................................9
Rent ...............................................................6
Rent Commencement Date ............................................ii
Repair Notice .....................................................19
Rules and Regulations .............................................18
Security Deposit ..................................................ii
Signs and graphics ................................................18
Six Month Period ..................................................24
Stated Amount ......................................................6
Subletting ........................................................23
Substantial Completion .....................................Exhibit B
Superior Leases ....................................................2
Superior Rights ....................................................3
Tenant .............................................................i
Tenant Delays ..............................................Exhibit B
Tenant Improvement Allowance ......................................ii
Tenant Improvements ........................................Exhibit B
Tenant Parties ....................................................10
Tenant Party ......................................................10
Tenant's Agents ............................................Exhibit B
Tenant's Percentage Share .........................................ii
Tenant's Percentage Share of Operating Expenses ...................10
Tenant's Percentage Share of Real Property Taxes ...................9
Tenant's Property .................................................17
Term ..............................................................ii
TI Allowance ...............................................Exhibit B
TI Allowance Items .........................................Exhibit B
time deadlines .............................................Exhibit B
Transfer Effective Date ...........................................23
Utility Installations .............................................16
Work Letter ................................................Exhibit B
Working Drawings ...........................................Exhibit B
</Table>



                                     (viii)
<PAGE>   6

CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY BRACKETS,
HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.

CA                                                              CDC#
   -----------                                                       -----------

                                  OFFICE LEASE

                             BASIC LEASE INFORMATION

Effective Date:                        April __, 2001

Landlord:                              CATELLUS DEVELOPMENT CORPORATION, a
                                       Delaware corporation

Landlord's Address for Notice:         165 South Union Street, Suite 852
                                       Lakewood, Colorado 80228
                                       Attn: Property Manager
                                       CirclePoint Corporate Center
                                       Telephone: (303) 980-3485
                                       Fax: (303) 980-3493

with a copy to:                        201 Mission Street
                                       San Francisco, CA 94105
                                       Attn: Asset Management
                                       Telephone: (415) 974-4500
                                       Fax: (415) 974-4502

and:                                   201 Mission Street
                                       San Francisco, CA 94105
                                       Attn: Office of General Counsel
                                       Telephone: (415) 974-4500
                                       Fax: (415) 974-4613

Landlord's Address for                 Catellus Commercial Group, LLC
Payment of Rent:                       c/o Cushman & Wakefield of California -
                                       Agent
                                       P. O. Box 45258
                                       San Francisco, 94145-0258

Tenant:                                Allos Therapeutics, Inc.,
                                       a Delaware corporation
Tenant's Address for Notice:
       Prior to Commencement Date:     7000 North Broadway, Suite 400
                                       Denver, CO 80221
                                       Attn: Michael E. Hart
                                       Telephone: 303-426-6262
                                       Fax: 303-412-9160

       After Commencement Date:        Two Circle Point, Suite 200
                                       Westminster, CO 80020
                                       Attn:  Michael E. Hart
                                       Telephone: [TENANT TO PROVIDE TO LANDLORD
                                       BY COMMENCEMENT DATE]
                                       Fax: [TENANT TO PROVIDE TO LANDLORD BY
                                       COMMENCEMENT DATE]

       In either case, with a copy to: Hutchinson, Black and Cook, LLC
                                       921 Walnut St., Suite 200
                                       P.O. Box 1170
                                       Boulder, CO 80306
                                       Attn: Bruce D. Dierking, Esq.
                                       Telephone: (303) 442-6514
                                       Fax: (303) 442-6593

Premises:                              Approximately 31,228 rentable square feet
                                       comprising the entire second (2nd) floor
                                       of the Building and known as Suite 200,
                                       as more particularly shown in Exhibit
                                       A-1.



                                       -i-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   7

Building:                              That certain five (5) story building
                                       consisting of approximately 150,872
                                       rentable square feet, located and
                                       addressed at Two Circle Point in the
                                       Project known as CirclePoint Corporate
                                       Center in Westminster, Colorado
                                       ("PROJECT"), as more particularly
                                       depicted as Building "2" in Exhibit A-2,
                                       attached hereto.

Delivery Date:                         The date of Substantial Completion of
                                       Landlord's Work and the Tenant
                                       Improvements (as defined in Exhibit B)
                                       and of delivery of the Premises to
                                       Tenant, which date is estimated to be
                                       September 15, 2001 ("ESTIMATED DELIVERY
                                       DATE").

Rent Commencement Date:                The Rent Commencement Date shall be the
                                       Delivery Date.

Commencement Date:                     The first day of the first full calendar
                                       month after the Delivery Date unless the
                                       Delivery Date is the first day of a
                                       calendar month, in which event the
                                       Commencement Date shall be the Delivery
                                       Date.

Expiration Date:                       The Expiration Date shall be the date
                                       that is seven (7) years and one (1) month
                                       after the Commencement Date.

Term:                                  Seven (7) years and one (1) month.

<Table>
<Caption>
Base Rent:                             Month of
                                         Term        Annual Base Rent       Monthly Base Rent
<S>                                    <C>           <C>                    <C>
                                         1-30*              [*]                    [*]

                                         31-60              [*]                    [*]

                                         61-84              [*]                    [*]

                                          85                [*]                    [*]
</Table>

                                       *Plus the period of time, if any, between
                                       the Rent Commencement Date and the
                                       Commencement Date and subject to
                                       abatement pursuant to Section 4.1 below.
                                       **Subject to adjustment based on as-built
                                       measurements pursuant to Section 2.1
                                       below.

Tenant's Percentage Share:             Twenty point seven percent (20.7%)**

Permitted Use:                         General office use (including, without
                                       limitation but subject to Applicable
                                       Laws, corporate offices, administrative
                                       offices, professional offices, and
                                       offices used for software development,
                                       engineering, research, design,
                                       development, data processing, publishing,
                                       telecommunications services, internet
                                       services and any lawful related uses) and
                                       no other uses shall be permitted without
                                       the prior written consent of Landlord,
                                       which consent may be given or withheld in
                                       Landlord's sole and absolute discretion.
                                       In no event shall Tenant be permitted to
                                       use the Premises for any laboratory or
                                       biotechnical purposes.

Security Deposit:                      [*] (Letter of Credit - See Section 4.4)

Tenant Improvement Allowance:          [*] (subject to adjustment as provided in
                                       Section 2.1 of Exhibit B)

Tenant's Broker:                       Equis Corporation



                                      -ii-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   8

EXHIBITS

       A-1    --     Premises

       A-2    --     Project

       B      --     Work Letter

       C      --     Commencement Date Memorandum

       D      --     Rules and Regulations

       E      --     Estoppel Certificate

                                      -iii-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   9

1. BASIC LEASE INFORMATION. The Basic Lease Information set forth on the
preceding pages and the Exhibits attached hereto are incorporated into and made
a part of this Lease. In the event of any conflict between the Basic Lease
Information and the other provisions of this Lease, the latter shall control.

2. PREMISES.

         2.1 Premises. Subject to the terms and conditions set forth in this
Lease, Landlord hereby leases to Tenant, and Tenant hereby leases from Landlord,
the Premises as shown on Exhibit A-1. Tenant has determined that if constructed
in accordance with this Lease, the Premises will be acceptable for Tenant's use
and Tenant acknowledges that neither Landlord nor any broker or agent has made
any representations or warranties in connection with the physical condition of
the Premises or their fitness for Tenant's use. Within thirty (30) days after
the Delivery Date, Landlord's space measurement consultant shall verify in
writing to Tenant the number of rentable square feet contained in the Premises
and the Building, and such verification shall be made in accordance with the
Standard Method for Measuring Floor Area in Office Buildings, ANSI/BOMA Z65.1 -
1996 ("BOMA"). In the event that Landlord's space measurement consultant
determines that the amounts thereof shall be different from those set forth in
this Lease, Landlord shall modify all amounts, percentages and figures appearing
or referred to in this Lease to conform to such corrected rentable square
footage (including, without limitation, the amount of Base Rent and Tenant's
Percentage Share). If such modification is made, it will be confirmed in writing
by Landlord to Tenant. Tenant's architect shall have the opportunity, but only
within ten (10) days after Landlord's written notice to Tenant of the verified
number of rentable square feet (after which time Tenant shall have no right to
object to such verification as provided hereinbelow), to consult with Landlord's
space measurement consultant regarding such verification to confirm that
Landlord's space measurement consultant's determination is accurate and in
accordance with BOMA; provided, however, that Tenant shall notify Landlord in
writing of any objection to such determination no later than three (3) days
after Tenant's consultation with Landlord's space measurement consultant.
Tenant's failure to timely object to Landlord's determination shall be deemed
Tenant's acceptance of such determination and such determination shall then be
conclusive and binding upon the parties. Tenant's objection notice, if any,
shall include the basis for Tenant's objection to such determination in
sufficient detail to allow Landlord's space measurement consultant to
investigate such objection. Landlord's space measurement consultant shall, no
later than fifteen (15) days after Landlord's receipt of Tenant's objection
notice, provide Tenant with a second determination (which may or may not be
revised from the first determination based on such consultant's reasonable
applicable of BOMA standards), which second determination shall then be
conclusive and binding upon the parties.

         2.2 Common Facilities. "COMMON FACILITIES" shall mean all areas,
facilities, utilities, equipment and services within the Building and Project
provided by Landlord for the common use or benefit of the tenants of the
Building and Project including, without limitation, pedestrian walkways, malls
and courts, parks and varas, driveways and access roads, parking facilities,
entrances and exits, truck service ways, loading docks, landscaped areas,
stairways, elevators, lobbies, common corridors and hallways, restrooms and all
offsite areas Landlord is required to maintain under the provisions of
applicable governmental requirements. Tenant and its employees and business
invitees shall be entitled to use the Common Facilities during the Term, in
common with Landlord and with other persons authorized by Landlord from time to
time, subject to the Rules and Regulations. Tenant expressly covenants that its
use of the Common Facilities shall comply with the Rules and Regulations,
including those established for shipping and receiving of goods. Anything in
this Lease to the contrary notwithstanding, it is expressly understood and
agreed that the designation or use from time to time of portions of the Common
Facilities shall not restrict Landlord's use of such areas for such purposes as
Landlord shall determine in its commercially reasonable discretion.
Notwithstanding anything to the contrary contained herein, Tenant hereby agrees
and acknowledges that because (and so long as) Tenant is leasing an entire floor
in the Building and is thereby entitled to exclusive use of the lobby located on
such floor, such lobby shall not be included in the Common Facilities and
Landlord shall have no obligation whatsoever to maintain, repair and/or
otherwise service such lobby. In the event that Tenant no longer leases an
entire floor in the Building, Tenant shall no longer have exclusive use of such
lobby area and such lobby area shall be included in the Common Facilities
hereunder.

         2.3 Reserved Rights. Landlord will operate and maintain the Common
Facilities in such manner as Landlord, in its commercially reasonable discretion
shall determine from time to time, and the cost thereof shall be included in
Operating Expenses. Notwithstanding anything to the contrary contained in this
Lease, Landlord reserves the right to do the following from time to time,
provided that such activities do not materially, adversely affect Tenant's use,
occupancy, or enjoyment of the Premises or Common Facilities or materially
increase Tenant's costs under this Lease, but subject to the requirements of
Applicable Law: (i) relocate, alter, improve, adjust or modify the size of any
Common Facilities; provided, however, that Landlord shall use reasonable efforts
not to materially and adversely affect Tenant's access to the Premises; (ii)
construct, maintain and operate lighting on the Common Facilities and in the
Project; (iii) modify the Common Facilities including, without limitation, the
parking facilities;



                                       -1-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   10
(iv) close temporarily or permanently all or any portion of the Common
Facilities and (v) do and perform such other acts in and to the Common
Facilities that Landlord determines may improve the convenience and use thereof
by tenants and their officers, agents, employees and customers. The Common
Facilities shall at all times be subject to the exclusive control and management
of Landlord and Landlord shall have the right from time to time to establish,
modify and enforce reasonable rules and regulations with respect to the Common
Facilities and any other portions of the Project; provided, however, that no
such rules or regulations shall have any material adverse impact on Tenant's
operations in the Premises or materially increase Tenant's costs under this
Lease, and further provided that Landlord shall use commercially reasonable
efforts to enforce such rules and regulations uniformly among tenants of the
Building and/or Project. Landlord reserves unto itself and its designees the
exclusive right to use the roof, exterior walls and areas beneath the floor and
above the ceiling of the Premises; provided, however, that Landlord agrees,
subject to Landlord's approval and supervision, to give Tenant reasonable access
to and use of the area above the ceiling of the Premises solely for Tenant's
installation and servicing of pipes, vents, conduits, VAV boxes and related
equipment. In addition, Landlord reserves the right to enter the Premises upon
reasonable prior notice to Tenant (except in case of an emergency or for
regularly scheduled maintenance and services, in which event no notice shall be
required) and/or to undertake the following: (a) access and inspect the Premises
to confirm the performance by Tenant of the provisions of this Lease and/or to
access mechanical installations therein; (b) install, use, maintain, repair,
alter, relocate or replace any Common Facilities and any pipes, ducts, conduits,
wires, utility lines, shafts, appurtenant meters and mechanical, electrical and
plumbing equipment and other facilities under, over or through the Premises, in
locations that will not materially interfere with Tenant's use of the Premises
for the Permitted Use; (c) record covenants, conditions and restrictions
("CC&Rs") affecting the Project and/or amendments to the CC&Rs; provided,
however, that no such CC&Rs or amendments thereto shall have any material
adverse impact on Tenant's operations in the Premises or materially increase
Tenant's costs under this Lease; (d) change the name of the Building or the
Project; (e) affix signs and displays in, on or to the Building and/or the
Project including, without limitation, signs for the rental of the Premises
and/or sale of all or any portion of the Building or the Project; and (f) show
the Premises to existing and potential Mortgagees, potential purchasers and,
during the last twelve (12) months of the Term, potential tenants.

         2.4 Parking. During the initial Lease Term and the first (1st)
Extension Term only, if any, and provided that Tenant is leasing at least the
number of rentable square feet initially leased hereunder (as such initial
square footage number may be adjusted pursuant to Section 2.1 above), Tenant
shall rent [*] parking spaces but Tenant shall not be required to pay any
monthly rental fee therefor during such initial Lease Term and the first (1st)
Extension Term only, if any (the number of parking spaces and the monthly rental
fee therefor for the second (2nd) Extension Term, if any, to be subject to
determination pursuant to Section 3.2 below). Each such parking space so rented
by Tenant shall permit Tenant's officers, agents and employees to park one (1)
passenger vehicle in the Project's parking facilities, on an unreserved,
as-available basis, and in compliance with any applicable, reasonable rules and
regulations promulgated by Landlord and/or other Applicable Laws (as defined
hereinbelow), throughout the Lease Term. Landlord reserves the right to (i)
adopt and/or discontinue a parking validation program, (ii) institute and/or
discontinue valet parking, (iii) designate or redesignate specific areas within
the Project for use by Tenant and its officers, agents and employees, and
restrict parking by Tenant and its officers, agents and employees to those
specific areas (provided, however, that any specific areas so designated for
Tenant's use shall be reasonably convenient to the Premises and of substantially
equal or better quality than the specific areas designated for the use of the
majority of other tenants of the Building), and (iv) designate or redesignate
specific parking spaces for the exclusive or non-exclusive use of specific
tenants in the Project (provided, however, that any specific areas so designated
for Tenant's use shall be reasonably convenient to the Premises and of
substantially equal or better quality than the specific areas designated for the
use of any other tenant of the Building). Tenant agrees not to overburden the
parking facilities and agrees to cooperate with Landlord and other tenants of
the Project in the use of parking facilities. Tenant agrees to assume
responsibility for compliance by its employees and agents with any applicable
rules and regulations promulgated by Landlord and/or other Applicable Laws (as
defined hereinbelow).

         2.5 Right of First Offer. Landlord hereby grants to Tenant a right of
first offer with respect to all leasable space on the [*] and [*] floors of the
Building (collectively, the "FIRST OFFER SPACE"). Notwithstanding the foregoing
(i) such first offer right of Tenant shall commence only following the
expiration or earlier termination of (A) any existing lease pertaining to the
First Offer Space, and (B) as to any First Offer Space that is vacant as of the
date of this Lease, the first lease pertaining to any portion of such First
Offer Space entered into by Landlord after the date of this Lease (collectively,
the "SUPERIOR LEASES"), including any renewal or extension of such existing or
future lease, whether or not such renewal or extension is pursuant to an express
written provision in such lease, and regardless of whether any such renewal or
extension is consummated pursuant to a lease amendment or a new lease, and (ii)
such first offer right shall be subordinate and secondary to all rights of
expansion, first refusal, first offer or similar rights granted to (A) the
tenants of the Superior Leases, (B) any other tenant of the Building or the
Project under a lease existing as of the date hereof (the rights described in
items (i) and (ii) above to be known



                                       -2-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   11

collectively as "SUPERIOR RIGHTS"). Tenant's right of first offer shall be on
the terms and conditions set forth in this Section 2.5.

                  2.5.1 Procedure for Offer. Landlord shall notify Tenant (the
"FIRST OFFER NOTICE") from time to time when Landlord determines that Landlord
shall commence the marketing of any First Offer Space because such space shall
become available for lease to third parties, where no holder of a Superior Right
desires to lease such space. The First Offer Notice shall describe the space so
offered to Tenant and shall set forth Landlord's proposed economic terms and
conditions applicable to Tenant's lease of such space, including the proposed
term (collectively, the "ECONOMIC TERMS"). Notwithstanding the foregoing,
Landlord's obligation to deliver the First Offer Notice shall not apply during
the last six (6) months of the initial Term unless Tenant has delivered a notice
to Landlord indicating Tenant's exercise of its option to extend the Lease
pursuant to Section 3.2 below.

                  2.5.2 Procedure for Acceptance. If Tenant wishes to exercise
Tenant's right of first offer with respect to the space described in the First
Offer Notice, then within ten (10) calendar days after delivery of the First
Offer Notice to Tenant, Tenant shall deliver notice to Landlord of Tenant's
intention to exercise its right of first offer with respect to the entire space
described in the First Offer Notice. If concurrently with Tenant's exercise of
the first offer right, Tenant notifies Landlord that it does not accept the
Economic Terms set forth in the First Offer Notice, Landlord and Tenant shall,
for a period of twenty- one (21) calendar days after Tenant's exercise,
negotiate in good faith to reach agreement as to such Economic Terms. If Tenant
does not so notify Landlord that it does not accept the Economic Terms set forth
in the First Offer Notice concurrently with Tenant's exercise of the first offer
right, the Economic Terms shall be as set forth in the First Offer Notice. In
addition, if Tenant does not exercise its right of first offer within the ten
(10) calendar day period, or, if Tenant exercises its first offer right but
timely objects to Landlord's determination of the Economic Terms and if Landlord
and Tenant are unable to reach agreement on such Economic Terms within said
twenty-one (21) calendar day period, then Landlord shall be free to lease the
space described in the First Offer Notice to anyone to whom Landlord desires and
Tenant's right of first offer shall terminate as to the space described in the
First Offer Notice. Notwithstanding anything to the contrary contained herein,
Tenant must elect to exercise its right of first offer, if at all, with respect
to all of the space offered by Landlord to Tenant at any particular time, and
Tenant may not elect to lease only a portion thereof.

                  2.5.3 Lease of First Offer Space. If Tenant timely exercises
Tenant's right to lease the space described in the First Offer Notice as set
forth herein, Landlord and Tenant shall execute an amendment adding such First
Offer Space to this Lease upon the same non-economic terms and conditions as
applicable to the initial Premises and the Economic Terms as provided in this
Section 2.5.

                  2.5.4 No Defaults. The rights contained in this Section 2.5
shall be personal to the original Tenant named in this Lease, and may only be
exercised by the original Tenant and any Affiliated Assignee (and not any other
assignee, sublessee or other transferee of the original Tenant's interest in
this Lease) if the original Tenant or any Affiliated Assignee physically
occupies at least eighty percent (80%) of the entire Premises as of the date of
the First Offer Notice. Tenant shall not have the right to lease First Offer
Space as provided in this Section 2.5 if, as of the date of the First Offer
Notice, or, at Landlord's option, as of the scheduled date of delivery of such
First Offer Space to Tenant, an Event of Default exists under this Lease (and
has not been cured within any applicable grace or cure period provided herein)
or if Tenant or any Affiliated Assignee does not physically occupy at least
eighty percent (80%) of the entire Premises.

3. TERM.

         3.1 Initial Term. The Term shall commence on the Commencement Date and
shall continue in full force and effect for the period of time specified as the
Term or until this Lease is terminated as otherwise provided herein. During the
period from the Delivery Date to the Commencement Date, all terms and provisions
of this Lease shall apply, except that Tenant's obligations to pay Rent shall
commence as of the Rent Commencement Date. Tenant, upon demand after
commencement of the Term, shall execute and deliver to Landlord a Commencement
Date Memorandum in the form attached hereto as Exhibit C acknowledging (a) the
Commencement Date, the Rent Commencement Date and the Expiration Date, (b) the
rentable square footage of the Premises, and (c) Tenant's acceptance of the
Premises. If for any reason the Delivery Date has not occurred by the Estimated
Delivery Date, this Lease shall remain in effect and Landlord shall not be
liable to Tenant for any loss or damage resulting therefrom; provided, however,
that if the Delivery Date has not occurred by December 31, 2001 (the "DELIVERY
OUTSIDE DATE"), as a result of any reason other than Tenant Delays or Force
Majeure Events, Tenant shall have the right to terminate this Lease upon written
notice delivered to Landlord no later than the date that is fifteen (15) days
after the Delivery Outside Date (such termination to be effective upon the date
of Tenant's notice). Notwithstanding the foregoing, if prior to commencement of
construction of the Tenant Improvements, Landlord determines in its good faith
judgment that, by utilizing commercially reasonable efforts, the Delivery Date
will not occur by the Delivery Outside Date, Landlord may give Tenant written
notice thereof prior to the date Landlord commences construction of the Tenant
Improvements (the



                                       -3-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   12

"DELAY NOTICE"), which Delay Notice shall inform Tenant of Landlord's estimate
of a revised Delivery Outside Date, as applicable. If Landlord delivers the
Delay Notice, Tenant may elect to terminate this Lease by giving Landlord
written notice thereof within ten (10) business days following delivery of the
Delay Notice. If Tenant does not so elect to terminate this Lease, then the
revised Delivery Outside Date set forth in the Delay Notice shall be substituted
for the date set forth above.

         3.2 Option to Extend.

                  3.2.1 Terms of Option. Provided that (i) an Event of Default
under this Lease does not exist at the time this extension option is exercised
or, at Landlord's option, at the scheduled commencement of the Extension Term
(and such Event of Default is not cured within any applicable cure period
provided herein), (ii) the original Tenant under this Lease (or an Affiliated
Assignee) is physically occupying at least eighty percent (80%) of the entire
Premises at the time this extension option is exercised and, at Landlord's
option, at the scheduled commencement of the Extension Term, (iii) Landlord has
not given more than two (2) notices of default in any twelve (12) month period
for nonpayment of monetary obligations and (iv) as of the date this extension
option is exercised and at the scheduled commencement of the Extension Term,
Tenant's (or any Affiliated Assignee's) net worth, as determined in accordance
with generally accepted accounting principles, is at least [*] Constant Dollars
[*], Tenant shall have the option to extend the Term (provided that the Premises
contain at least as many rentable square feet as initially leased hereunder, as
such initial square footage number may be adjusted pursuant to Section 2.1
above) for two (2) additional periods of five (5) years each (each, an
"Extension Term"). Landlord shall lease the Premises to Tenant during an
Extension Term on all the terms and conditions of this Lease, except that
Landlord shall have no additional obligation for free rent, tenant improvements
or for any other tenant inducements for the Extension Term (or for free parking
during the second (2nd) Extension Term, if any). During an Extension Term, the
Base Rent shall be increased (or decreased but in no event to an amount less
than ninety-five percent (95%) of the Base Rent in effect for the month
immediately preceding the Extension Term) to the Market Rent for the Premises
during the Extension Term as set forth below, and the Security Deposit will be
increased to reflect any increase in Base Rent payable under this Lease. There
shall be no additional extension terms beyond the Extension Terms set forth
herein. Tenant must exercise its option to extend this Lease by giving Landlord
written notice of its election to do so no later than six (6) months prior to
the end of the initial Term (or the first Extension Term, as applicable). Any
notice not given in a timely manner shall be void, and Tenant shall be deemed to
have waived its extension option hereunder. The extension option set forth
herein is personal to the original Tenant under this Lease and it shall not be
included in any assignment of Tenant's interest in this Lease (except to an
Affiliated Assignee) nor in any sublease of all or any portion of the Premises.

                  3.2.2 Determination of Base Rent During Extension Term.

                           3.2.2.1 Agreement on Base Rent. Landlord and Tenant
shall have until that date that is one hundred twenty (120) days prior to the
expiration of the initial Term, or the first Extension Term, as applicable (the
"OUTSIDE AGREEMENT DATE") in which to agree on the Base Rent during an Extension
Term (and as to the second (2nd) Extension Term only, the number of parking
spaces and the monthly rental fee therefor). Notwithstanding anything in this
Section to the contrary, in no event shall the Base Rent for an Extension Term
be less than [*] of the Base Rent in effect for the month immediately prior to
the Extension Term.

                           3.2.2.2 Arbitration. If Landlord and Tenant are
unable to agree upon the Base Rent for an Extension Term (and as to the second
(2nd) Extension Term only, the number of parking spaces and the monthly rental
fee therefor) prior to the Outside Agreement Date, then, within fifteen (15)
days following the Outside Agreement Date, each party shall submit to the other
party a separate written determination of the Market Rent (and parking
specifications, if applicable), and such determinations shall be submitted to
arbitration in accordance with clauses (A) through (G) below. Failure of Tenant
or Landlord to submit a written determination of the Market Rent within the
required period shall conclusively be deemed to be the non-determining party's
approval of the Market Rent submitted within such required period by the other
party.

                                    (A) Each party, by giving written notice to
the other party, shall appoint a real estate appraiser who is a current member
of the American Institute of Real Estate Appraisers, with at least five (5)
years of experience appraising first-class office building space comparable to
the Premises in the Comparable Area (as defined below) to determine the Market
Rent. "MARKET RENT" shall mean the monthly base rent amount per rentable square
foot in the Premises that a willing, non-equity new tenant would pay and a
willing landlord would accept at arm's length for a term comparable to and
commencing upon approximately the same time as the Extension Term for non-
sublease space in the Project or in comparable first-class office buildings with
prudent ownership (with management practices comparable with institutional
ownership), along the Boulder Turnpike from Denver to Boulder (the "COMPARABLE
AREA"), with comparable tenant improvements, in a comparable location, giving
appropriate consideration to monthly rental rates per rentable square foot, the
presence or



                                       -4-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   13

absence of rent escalation clauses such as operating expense and tax
pass-throughs, length of lease term, size and location of premises being leased,
free rent or any other similar tenant concessions or inducements, and other
generally applicable terms and conditions of tenancy for a similar building or
buildings. The determination of the appraisers shall be limited solely to the
issue of whether Landlord's or Tenant's submitted Market Rent is the closest to
the actual Market Rent as determined by such appraisers, taking into account the
definition of Market Rent as set forth above (i.e., the appraisers may only
select Landlord's or Tenant's determination but not a compromise position). Each
such appraiser shall be appointed within thirty (30) days after the Outside
Agreement Date.

                                    (B) The two (2) appraisers so appointed
shall, within ten (10) days of the date of the appointment of the last appointed
appraiser, agree upon and appoint a third appraiser who shall be qualified under
the same criteria as set forth above for qualification of the initial two (2)
appraisers.

                                    (C) The three (3) appraisers shall within
twenty (20) days after the appointment of the third appraiser reach a decision
as to whether Landlord's or Tenant's submitted Market Rent is the closest to the
actual Market Rent, and shall use the closest of Landlord's or Tenant's
submitted Market Rent as the Base Rent for the Extension Term, and shall notify
Landlord and Tenant thereof in writing.

                                    (D) The decision of the majority of the
three (3) appraisers shall be binding upon Landlord and Tenant.

                                    (E) If either Landlord or Tenant fails to
appoint an appraiser within thirty (30) days after the Outside Agreement Date,
the appraiser appointed by the other party shall reach a decision, notify
Landlord and Tenant thereof, and such appraiser's decision shall be binding upon
Landlord and Tenant.

                                    (F) If the two (2) appraisers fail to agree
upon and appoint a third appraiser within the time period provided in clause (B)
above, then Landlord and Tenant shall mutually select the third appraiser. If
Landlord and Tenant are unable to agree upon the third appraiser within ten (10)
days after the expiration of the time period in Clause (B) above, then either
party may, upon at least five (5) days' prior written notice to the other party,
request the Presiding Judge of the Jefferson County District Court, acting in
such judge's private and nonjudicial capacity, to appoint the third appraiser.
Following the appointment of the third appraiser, the panel of appraisers shall
within twenty (20) days thereafter reach a decision as to whether Landlord's or
Tenant's submitted Market Rent shall be used and shall notify Landlord and
Tenant thereof.

                                    (G) The fees of the appraisers and the costs
of the appraisal proceeding shall be paid by the non-prevailing party.

                           3.2.2.3 Amendment of Lease. Immediately after the
Base Rent for an Extension Term is determined pursuant to this Section 3.2,
Landlord and Tenant shall execute an amendment to this Lease stating the new
Base Rent in effect. In recognition that the Market Rent may not be determined
until after the commencement of an Extension Term, Tenant shall pay, during the
Extension Term until the Market Rent is determined, the amount of Rent
(including Base Rent and all other charges) in effect as of the expiration of
the initial Term of this Lease (or First Extension Term, as applicable). Under
no circumstances shall the Base Rent during an Extension Term ever be less than
[*] of such amount of Base Rent in effect as of the expiration of the initial
Term of the Lease (or First Extension Term, as applicable), regardless of the
Market Rent as determined in accordance with the foregoing provisions. If the
Market Rent is determined to be greater than such amount, Tenant shall pay
Landlord, within thirty (30) days after written request therefor, the difference
between the amount required by such determination of the Market Rent and the
amount of Base Rent theretofore paid by Tenant during the Extension Term.

4. RENT.

         4.1 Base Rent. Tenant shall pay to Landlord, at Landlord's Address for
Payment of Rent designated in the Basic Lease Information, or at such other
address as Landlord may from time to time designate in writing to Tenant for the
payment of Rent, the Base Rent, without notice, demand, offset or deduction
(except as otherwise provided herein), in advance, on the first day of each
calendar month during the Term commencing on the Rent Commencement Date. Upon
the execution of this Lease, Tenant shall pay to Landlord the Base Rent due for
the first full calendar month during the Term after the Rent Commencement Date
and any abatement period. If the Rent Commencement Date occurs on a date other
than the first day of a month or the Term ends on a date other than the last day
of a month, Base Rent shall be prorated on the basis of a thirty (30) day month.



                                       -5-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   14

         Notwithstanding anything to the contrary contained herein and provided
that Tenant faithfully performs all of the terms and conditions of this Lease,
Landlord hereby agrees to abate Tenant's obligation to pay monthly Base Rent for
the first (1st) full month of the initial Lease Term. During such abatement
period, Tenant shall still be responsible for the payment of all of its other
monetary obligations under this Lease, including Tenant's Percentage Share of
Operating Expenses and Real Estate Taxes. In the event of a default by Tenant
under the terms of this Lease that results in early termination pursuant to the
provisions of Section 16.3 of this Lease, then as a part of the recovery set
forth in such Section 16.3 of this Lease, Landlord shall be entitled to the
recovery of the monthly Base Rent that was abated under the provisions of this
Section 4.1.

         4.2 Additional Rent. All sums other than Base Rent that Tenant is
obligated to pay under this Lease, including Tenant's Percentage Share of Real
Property Taxes and Operating Expenses, shall be deemed to be "Additional Rent"
due hereunder, whether or not such sums are designated as Additional Rent. Base
Rent and Additional Rent are collectively referred to herein as "RENT."

         4.3 Late Charge and Interest. The late payment of any Rent will cause
Landlord to incur additional costs, including administration and collection
costs, processing and accounting expenses and increased debt service (the
"DELINQUENCY COSTS"). If Landlord has not received any installment of Rent
within five (5) days after such amount is due, Tenant shall pay to Landlord (a)
for the first such delinquency in any calendar year, a one-time late charge of
five percent (5%) of the delinquent amount, and (b) for the second and any
subsequent delinquencies in any calendar year, a one-time late charge of ten
percent (10%) of the delinquent amount, which amounts are agreed to represent a
reasonable estimate of the Delinquency Costs incurred by Landlord. In addition,
all such delinquent amounts shall bear interest from the date such amount was
due until paid in full at the Applicable Interest Rate. Landlord and Tenant
recognize that the damage that Landlord shall suffer as a result of Tenant's
failure to pay such amounts is difficult to ascertain and said late charge and
interest are the best estimate of the damage that Landlord shall suffer in the
event of late payment. If a late charge becomes payable for any three (3)
installments of Rent within any twelve (12) month period, then the Rent shall
automatically become due and payable quarterly in advance. "APPLICABLE INTEREST
RATE" shall mean a rate per annum equal to the lesser of (i) the maximum
interest rate permitted by law or (ii) five percent (5%) above the rate publicly
announced by Bank of America, N.A. (or if Bank of America, N.A. ceases to exist,
the largest bank then headquartered in the State of Colorado) (the "Bank") as
its "Reference Rate." If the use of the announced Reference Rate is discontinued
by the Bank, then the term Reference Rate shall mean the announced rate charged
by the Bank that is, from time to time, substituted for the Reference Rate.

         4.4 Security Deposit.

                  4.4.1 Letter of Credit. No later than May 15, 2001, Tenant
shall deliver to Landlord an unconditional, irrevocable and renewable letter of
credit ("LETTER OF CREDIT") in favor of Landlord in a form approved by Landlord,
issued by a bank approved by Landlord with a branch located in Denver, Boulder
or Westminster, Colorado, (which approval shall not be unreasonably withheld,
conditioned or delayed) in the principal amount ("STATED AMOUNT") specified
below, as security for the faithful performance and observance by Tenant of the
terms, provisions and conditions of this Lease. If Tenant fails to deliver the
Letter of Credit by May 15, 2001, and such failure is not cured within five (5)
days after written notice to Tenant, then such failure shall be an Event of
Default hereunder. If the issuer of the Letter of Credit shall become insolvent
or fail to maintain at least an "A" issuer rating under the Thomson Financial
Bank Watch or an equivalent rating service reasonably selected by Landlord, then
Tenant shall, within thirty (30) days of receipt of Landlord's written notice,
cause a replacement Letter of Credit to be issued by a bank that qualifies under
the foregoing requirements. Tenant shall pay all expenses, points and/or fees
incurred by Tenant in obtaining the Letter of Credit. The Stated Amount shall
be[*]; provided, however, that upon the dates specified below ("ADJUSTMENT
DATES"), the Stated Amount shall be reduced to the following amounts:

<Table>
<Caption>
                   Anniversary of
                 Commencement Date                    Stated Amount
                 -----------------                    -------------
<S>                      <C>
                         4th                               [*]

                         5th                               [*]

                         6th                               [*]
</Table>

         However, if (i) an Event of Default occurs under this Lease, or (ii)
circumstances exist that would, with notice or lapse of time, or both,
constitute an Event of Default, and Tenant has failed to cure such circumstance
within the time period permitted by Section 16 or such lesser time as may remain
before the relevant Adjustment Date as provided above (including, without
limitation, a failure to deposit the cash Security Deposit pursuant to Section
4.4.2 below), the Stated Amount shall not thereafter be reduced unless and until
such default or circumstance shall have been fully cured pursuant to the terms
of



                                       -6-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   15

this Lease, at which time the Stated Amount may be reduced as hereinabove
described. The Letter of Credit shall state that an authorized officer or other
representative of Landlord may make demand on Landlord's behalf for the Stated
Amount of the Letter of Credit, or any portion thereof, and that the issuing
bank must immediately honor such demand, without qualification or satisfaction
of any conditions, except the proper identification of the party making such
demand, and the signed certification of such party that (a) an Event of Default
by Tenant has occurred under the Lease and that Tenant has not cured such Event
of Default within the applicable grace or cure periods provided under this Lease
and/or (b) the term of the Letter of Credit will expire prior to thirty (30)
days following the last day of the Term and has not been extended, nor has a new
Letter of Credit for an extended period of time been substituted at least thirty
(30) days prior to the expiration of the Letter of Credit. In addition, the
Letter of Credit shall indicate that it is transferable in its entirety by
Landlord as beneficiary and that upon receiving written notice of transfer, and
upon presentation to the issuing bank of the original Letter of Credit, the
issuer or confirming bank will reissue the Letter of Credit naming such
transferee as the beneficiary. Tenant shall pay to Landlord, within thirty (30)
days following written request therefor, any transfer fee payable by Landlord to
the issuer in connection with such transfer; provided, however, that Tenant
shall not be obligated to pay for more than one (1) transfer in any twenty-four
(24) month period (Landlord to pay for any transfers subsequent to the first
such transfer in any such twenty-four (24) month period). If the term of the
Letter of Credit held by Landlord will expire prior to thirty (30) days
following the last day of the Term and it is not extended, or a new Letter of
Credit for an extended period of time is not substituted, at least thirty (30)
days prior to the expiration of the Letter of Credit, then Landlord shall be
entitled to make demand for the Stated Amount of said Letter of Credit and,
thereafter, to hold such funds in accordance with this Section 4.4. The Letter
of Credit and any such proceeds thereof shall be held by Landlord as security
for the faithful performance by Tenant of all of the terms, covenants and
conditions of this Lease. If Tenant fails to perform fully and timely all or any
of Tenant's covenants and obligations hereunder, Landlord may (but shall not be
required to) draw upon all or any portion of the Stated Amount of the Letter of
Credit, and Landlord may then use, apply or retain all or any part of the
proceeds for the payment of any sum which is in default, or for the payment of
any other amount which Landlord may spend or become obligated to spend by reason
of Tenant's failure or to compensate Landlord for any loss or damage which
Landlord may suffer by reason of Tenant's failure. If any portion of the
proceeds of the Letter of Credit are so used or applied, Tenant shall, within
ten (10) days after demand therefor, post an additional Letter of Credit in an
amount to cause the aggregate amount of the unused proceeds and such new Letter
of Credit to equal the total Stated Amount required in this Section 4.4.1 above.
Landlord shall not be required to keep any proceeds from the Letter of Credit
separate from its general funds. Should Landlord sell its interest in the
Premises during the Term, Landlord shall deposit with the purchaser thereof the
Letter of Credit or any proceeds of the Letter of Credit, and provided that such
purchaser agrees in writing to be bound by the terms of this Lease that apply to
the Letter of Credit under this Section 4.4.1 as assignee of Landlord, thereupon
Landlord shall be discharged from any further liability with respect to the
Letter of Credit and said proceeds.

                  4.4.2 Cash Security Deposit. Tenant shall deposit with
Landlord, on or before the 6th anniversary of the Rent Commencement Date, an
amount equal to the last month's Base Rent [*] (subject to adjustment based upon
the as-built measurement verification specified in Section 2.1), which amount
Landlord shall hold as a Security Deposit hereunder to secure the full and
faithful performance of each provision of this Lease to be performed by Tenant.
Landlord shall not be required to pay interest on the Security Deposit or to
keep the Security Deposit separate from Landlord's own funds. If Tenant fails to
perform fully and timely all or any of Tenant's covenants and obligations
hereunder, Landlord may, but without obligation, apply all or any portion of the
Security Deposit toward fulfillment of Tenant's unperformed covenants and/or
obligations. If Landlord does so apply any portion of the Security Deposit,
Tenant shall immediately pay to Landlord an amount sufficient to restore the
Security Deposit to an amount equal to the greater of (i) the amount of the
Security Deposit immediately before Landlord's application of a portion of the
Security Deposit or (ii) the amount of the then current Base Rent per month.
Upon any increase in Base Rent, Landlord may require Tenant to increase the
Security Deposit by the amount of the increase in Base Rent per month. Within
sixty (60) days after the later of (a) the date Tenant vacates the Premises or
(b) the expiration or sooner termination of this Lease, if Tenant is not then in
default, Landlord shall return to Tenant any unapplied balance of the Security
Deposit. Tenant hereby waives the provisions of any law, now or hereafter in
force, which provide that Landlord may claim from a security deposit only those
sums reasonably necessary to remedy defaults in the payment of rent, to repair
damage caused by Tenant or to clean the Premises, it being agreed that Landlord
may, in addition, claim those sums reasonably necessary to compensate Landlord
for any other loss or damage, foreseeable or unforeseeable, caused by the act or
omission of Tenant or any of the Tenant Parties.

5. SERVICES AND UTILITIES.

         5.1 Standard Tenant Services. Subject to the terms and provisions of
this Lease, Tenant shall be allowed to use the Premises on a twenty-four (24)
hour per day, seven (7) day per week basis.

                  5.1.1 Subject to all governmental rules, regulations and
guidelines applicable thereto, Landlord shall provide (a) heating, ventilating
and air conditioning ("HVAC") when necessary for normal



                                       -7-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   16

comfort for normal office use in the Premises and for cooling required by
customary reasonable office computer systems, from Monday through Friday, during
the period from 8:00 a.m. to 6:00 p.m., and on Saturdays during the period from
8:00 a.m. to 12:00 p.m. (collectively, the "BUILDING HOURS"), except for
nationally and locally recognized holidays as designated by Landlord
(collectively, the "HOLIDAYS"); (b) electrical wiring and facilities and power
for normal general office use as such wiring, facilities and power are specified
in the Approved Working Drawings (as defined in Exhibit B attached hereto); (c)
city water from the regular Building outlets for drinking, lavatory and toilet
purposes; (d) janitorial services five (5) days per week, except the date of
observation of the Holidays, in and about the Premises; and (e) nonexclusive
automatic elevator service. Tenant shall pay Landlord, within fifteen (15) days
after invoice, charges for replacement of lamps, starters and ballasts for
non-Building standard lighting fixtures within the Premises. Landlord shall also
have the exclusive right, but not the obligation, to provide any additional
services that may be required by Tenant, including, without limitation,
locksmithing, additional janitorial services, and additional repairs and
maintenance, provided that Tenant shall pay to Landlord, within fifteen (15)
days after billing, the actual costs incurred by Landlord to provide such
additional services plus a reasonable administration fee. Landlord shall provide
the services described in this Section 5.1.1 from the Rent Commencement Date
through the remainder of the Term, unless otherwise stated herein.

         5.2 Overstandard Tenant Use. Tenant shall not, without Landlord's prior
written consent, use heat-generating machines, machines other than normal office
machines, or equipment or lighting other than building standard lights in the
Premises, which may affect the temperature otherwise maintained by the HVAC
system or increase the water normally furnished for the Premises by Landlord
pursuant to the terms of Section 5.1 of this Lease. If Tenant uses water or HVAC
in excess of that supplied by Landlord pursuant to Section 5.1 of this Lease, or
if Tenant's consumption of electricity (exclusive of Building- standard HVAC and
Building-standard lighting) shall exceed an average of three (3) watts per
rentable square foot of the Premises, connected load, calculated on a monthly
basis during the Building Hours set forth in Section 5.1.1 above, then Tenant
shall pay to Landlord, within ten (10) days after billing, the cost of such
excess consumption, the cost of the installation, operation, and maintenance of
equipment which is installed in order to supply such excess consumption, and the
cost of the increased wear and tear on existing equipment caused by such excess
consumption; and Landlord may install devices to separately meter any increased
use and in such event Tenant shall pay the increased cost directly to Landlord,
within ten (10) days after demand, including the cost of such additional
metering devices. If Tenant desires to use HVAC during hours other than the
Building Hours, (i) Tenant shall give Landlord such prior notice, as Landlord
shall from time to time establish as appropriate, of Tenant's desired use, (ii)
Landlord shall supply such after-hours HVAC to Tenant at such hourly rate as
Landlord shall from time to time establish, and (iii) Tenant shall pay such
charges within ten (10) days after billing.

         5.3 Interruption of Use. Except as otherwise provided hereinbelow,
Tenant agrees that Landlord shall not be liable for damages, by abatement of
Rent or otherwise, for failure to furnish or delay in furnishing any service
(including telephone and telecommunication services), or for any diminution in
the quality or quantity thereof, and such failures or delays or diminution shall
never be deemed to constitute an eviction or disturbance of Tenant's use and
possession of the Premises or relieve Tenant from paying Rent or performing any
of its obligations under this Lease. Furthermore, Landlord shall not be liable
under any circumstances for a loss of, or injury to, property or for injury to,
or interference with, Tenant's business, including, without limitation, loss of
profits, however occurring, through or in connection with or incidental to a
failure to furnish any of the services or utilities as set forth in this Lease.

         5.4 Abatement. An "ABATEMENT EVENT" shall be defined as an event that
prevents Tenant from using the Premises or any portion thereof, as a result of
any failure to provide services or access to the Premises, where (i) Tenant does
not actually use the Premises or such portion thereof, and (ii) such event is
caused by the negligence or willful misconduct of Landlord, its agents,
employees or contractors. Tenant shall give Landlord and any mortgagee of
Landlord (of whom Tenant is notified) notice ("ABATEMENT NOTICE") of any such
Abatement Event, and if such Abatement Event continues beyond the "Eligibility
Period" (as that term is defined below), then the Base Rent and Tenant's Share
of Operating Expenses and Real Property Taxes shall be abated entirely or
reduced, as the case may be, after expiration of the Eligibility Period for such
time that Tenant continues to be so prevented from using, and does not use, the
Premises or a portion thereof, in the proportion that the rentable area of the
portion of the Premises that Tenant is prevented from using, and does not use,
bears to the total rentable area of the Premises; provided, however, in the
event that Tenant is prevented from using, and does not use, a portion of the
Premises for a period of time in excess of the Eligibility Period and the
remaining portion of the Premises is not sufficient to allow Tenant to
effectively conduct its business therein, and if Tenant does not conduct its
business from such remaining portion, then for such time after expiration of the
Eligibility Period during which Tenant is so prevented from effectively
conducting its business therein, the Base Rent and Tenant's Share of Operating
Expenses and Real Property Taxes for the entire Premises shall be abated
entirely for such time as Tenant continues to be so prevented from using, and
does not use, the Premises. If, however, Tenant reoccupies any portion of the
Premises during such period, the Base Rent and Tenant's Share of Operating
Expenses and Real Property Taxes allocable to such reoccupied portion,



                                       -8-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   17

based on the proportion that the rentable area of such reoccupied portion of the
Premises bears to the total rentable area of the Premises, shall be payable by
Tenant from the date Tenant reoccupies such portion of the Premises.
Notwithstanding anything to the contrary contained herein, if Landlord is
diligently pursuing the repair of such utilities or services and Landlord
provides substitute services reasonably suitable for Tenant's purposes as
reasonably determined by Landlord, for example bringing in portable air
conditioning or heating equipment, then there shall be no abatement of Base Rent
and Tenant's Share of Operating Expenses and Real Property Taxes. The term
"Eligibility Period" shall mean a period of five (5) consecutive business days
after Landlord's and Landlord's mortgagee's (if applicable), receipt of the
applicable Abatement Notice. Such right to abate Base Rent and Tenant's Share of
Operating Expenses and Real Property Taxes shall be Tenant's sole and exclusive
remedy at law or in equity for an Abatement Event and such abatement shall not
apply in case of damage to, or destruction of, the Premises or the Building, or
any eminent domain proceedings which shall be governed by separate provisions of
this Lease.

6. TAXES.

         6.1 Real Property Taxes. Tenant shall pay to Landlord in the manner set
forth in Section 8 below, and as Additional Rent, Tenant's Percentage Share of
Real Property Taxes attributable to the tax parcel within which the Building is
located and the portion of Real Property Taxes attributable to the developed
Common Facilities in the Project (including, but not limited to, common
detention ponds, the central park area, Building and Project roads, Building and
Project landscaping, etc.) allocated by Landlord to the Building based on the
Building's pro rata share thereof (as such pro rata share is reasonably
determined by Landlord) (collectively, "TENANT'S PERCENTAGE SHARE OF REAL
PROPERTY TAXES"). Landlord shall not allocate to Tenant any portion of any Real
Property Taxes attributable to undeveloped portions of the Project, developed
portions of the Project held for lease (excluding the Building), or developed
portions of the Project that are not Common Facilities. Tenant's obligation to
pay Tenant's Percentage Share of Real Property Taxes during the Term shall
survive the expiration or early termination of this Lease provided that Landlord
invoices Tenant for such amounts no later than two (2) years after such
expiration or early termination. If this Lease shall commence or terminate on a
day other than the first or last day of a calendar year, respectively, the
amount of Tenant's Percentage Share of Real Property Taxes payable by Tenant for
such calendar year shall be prorated on the basis of a 365 day year and shall be
due and payable when rendered notwithstanding termination of this Lease provided
that Landlord invoices Tenant for such amounts no later than two (2) years after
such expiration or early termination. Tenant's Percentage Share of Real Property
Taxes allocable to the calendar year in which this Lease commences or terminates
shall be deemed to have been incurred evenly over the entire twelve (12) month
period of such calendar year.

         6.2 Definition of Real Property Taxes. The term "REAL PROPERTY TAXES"
shall mean the sum of the following: all real property taxes, mill levies, metro
district charges, including ad valorem taxes (including all components thereof,
such as amounts payable to any public or quasi-public authority or agency,
including school districts) and special taxes, possessory interest taxes,
business or license taxes or fees, service payments in lieu of such taxes or
fees, annual or periodic license or use fees, excises, common or community
facilities district assessments and any other assessments, bonds, levies, fees,
penalties (if a result of Tenant's delinquency), exactions or charges, general
and special, ordinary and extraordinary, unforeseen as well as foreseen
(including fees "in-lieu" of any such tax or assessment) that are assessed,
levied, charged, conferred or imposed by any public authority or quasi-public
authority upon the Project (or any real property comprising any portion thereof)
or its operations, together with all taxes, assessments or other fees imposed by
any public authority upon or measured by any Rent or other charges payable
hereunder, including any gross receipts tax or excise tax levied with respect to
receipt of rental income, or upon, with respect to or by reason of the
development, possession, leasing, operation, management, maintenance,
alteration, repair, use or occupancy by Tenant of the Premises or any portion
thereof, or documentary transfer taxes upon this transaction or any document to
which Tenant is a party creating or transferring an interest in the Premises,
together with any tax imposed in substitution, partially or totally, of any tax
previously included within the aforesaid definition or any additional tax the
nature of which was previously included within the aforesaid definition,
together with the costs and expenses (including attorneys' and expert witness'
fees and costs) of challenging any of the foregoing, seeking a reduction in or
abatement, redemption or return of any of the foregoing or contesting the
validity or applicability of any governmental enactments that may affect Real
Property Taxes but only to the extent of any actual reduction, abatement,
redemption or return achieved unless such challenge or contest is requested by
Tenant. All references to Real Property Taxes during a particular year shall be
deemed to refer to taxes accrued during such year, including supplemental tax
bills, regardless of when they are actually assessed and without regard to when
such taxes are payable. The obligation of Tenant to pay for supplemental taxes
shall survive for two (2) years after the expiration or early termination of
this Lease. Nothing contained in this Lease shall require Tenant to pay any
franchise, corporate, estate or inheritance tax of Landlord, or any income or
profits tax. In no event shall Tenant or any of Tenant's officers, directors,
employees, agents, representatives, customers, visitors, invitees, licensees,
contractors, assignees and/or subtenants (collectively, "TENANT PARTIES" and
individually, a "TENANT PARTY") be entitled to file any real property tax
assessment appeal.



                                       -9-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   18

         6.3 Taxes on Tenant Improvements/Personal Property. Notwithstanding any
other provision hereof, Tenant shall pay, not less than ten (10) days before
delinquency, (a) the full amount of any increase in Real Property Taxes during
the Term resulting from any and all alterations and tenant improvements
(exclusive of the Tenant Improvements but including any increases resulting from
the Tenant Improvements to the extent of the Over-Allowance Amount) of any kind
whatsoever placed in, on or about or made to the Premises for the benefit of, at
the request of, or by Tenant, to the extent the same exceed Building standard
allowances for leasehold improvements as reasonably determined by Landlord and
(b) all taxes and assessments levied upon Tenant's Property. Upon Landlord's
request, Tenant shall provide Landlord copies of receipts for payment of all
such taxes. To the extent any such taxes are not separately assessed or billed
to Tenant, Tenant shall pay to Landlord the amount thereof as invoiced by
Landlord with thirty (30) days following delivery of such invoice. Landlord
agrees that in no event shall Additional Rent hereunder include any amounts
specified in this Section 6.3 (or amounts specified in substantially similar
provisions in other leases or agreements) payable by other tenants of the
Building.

7. OPERATING EXPENSES.

         7.1 Operating Expenses. Tenant shall pay to Landlord, in the manner set
forth in Section 8 below, and as Additional Rent, Tenant's Percentage Share of
Operating Expenses attributable to Landlord's operation, management, repair and
maintenance of the Building and the portion of Operating Expenses attributable
to the operation, management, repair and/or maintenance of the developed Common
Facilities of the Project (including, but not limited to, common detention
ponds, the central park area, Building and Project roads, Building and Project
landscaping, etc.) allocated by Landlord to the Building based upon the
Building's pro rata share thereof (as such pro rata share is reasonably
determined by Landlord) (collectively, "TENANT'S PERCENTAGE SHARE OF OPERATING
EXPENSES"). Landlord shall not allocate to Tenant any portion of Operating
Expenses attributable to undeveloped portions of the Project, developed portions
of the Project held for lease (excluding the Building), or developed portions of
the Project that are not Common Facilities. Tenant's obligation to pay Tenant's
Percentage Share of Operating Expenses during the Term shall survive the
expiration or any earlier termination of this Lease provided that Landlord
invoices Tenant for such amounts no later than two (2) years after such
expiration or early termination. If this Lease shall commence or terminate on a
day other than the first or last day of a calendar year, respectively, the
amount of Tenant's Percentage Share of Operating Expenses payable by Tenant for
such calendar year shall be prorated on the basis of a 365 day year and shall be
due and payable when rendered notwithstanding termination of this Lease.
Tenant's Percentage Share of Operating Expenses allocable to the calendar year
in which this Lease commences or terminates shall be deemed to have been
incurred evenly over the entire twelve (12) month period of such calendar year.
"TENANT'S PERCENTAGE SHARE" is a percentage equal to the rentable square footage
of the Premises divided by the rentable square footage of the Building (as set
forth in the Basic Lease Information).

       7.2 Definition of Operating Expenses. The term "OPERATING EXPENSES" shall
mean (except as otherwise excluded below) the total costs and expenses
reasonably paid or incurred by Landlord in the operation, management, repair and
maintenance of the Building and developed Common Facilities of the Project
(including, but not limited to, common detention ponds, the central park,
Building and Project roads, Building and Project landscaping, etc.), including,
but not limited to, all costs of: (i) maintenance, repair and replacement of
HVAC, electricity, steam, water, gas, sewer, mechanical, telephone and
telecommunications systems, escalator and elevator systems and all other
utilities and systems; (ii) landscaping, gardening and site maintenance; (iii)
security, life safety and fire protection; (iv) general maintenance, trash
removal, cleaning and service contracts and the cost of all supplies, tools and
equipment required in connection therewith; (v) all deductibles, self-insured
retentions, premiums and other costs relating to the insurance carried by
Landlord or Landlord's agent for the Project, and the costs of any
self-insurance as reasonably determined by Landlord; (vi) wages, salaries,
payroll taxes and other labor costs and employee benefits of employees directly
employed and working at the Building and/or Project (or a pro-rata share of such
amounts for employees indirectly employed and working at the Building and/or
Project); (vii) fees, charges and other costs of all independent contractors
engaged by Landlord to provide operations, maintenance, or repair service at or
with respect to the Building and/or Project; (viii) directory revisions at the
Building; (ix) charges on or surcharges imposed by any governmental agencies on
or with respect to transit or automobile usage or parking facilities; (x) costs
incurred in connection with any private transit association; (xi) amortization
over the useful life (together with interest at a rate equal to the floating
commercial loan rate announced from time to time by Bank of America, N.A., or
its successor, as its prime rate, plus two percent (2%) per annum (the "INTEREST
RATE") on the unamortized balance) of all of the following costs of a capital
nature (including, without limitation, improvements, replacements, repairs and
equipment): (1) reasonably intended to produce a reduction in operational
charges or energy consumption; or (2) required by Applicable Laws enacted or
first applicable after the Commencement Date; or (3) replacement of exterior
perimeter windows (except during the initial Term); or (4) minor capital
expenditures or improvements where the total cost of all such expenditures or
improvements is less than Fifty Thousand Constant Dollars ($50,000) in any
twelve- month period in the aggregate, and the cost of capital tools not in
excess of Ten Thousand Constant Dollars ($10,000) in any twelve (12) month
period in the aggregate or (5) the refurbishment or replacement of improvements
when repair is no longer feasible; (xii) the cost of contesting the validity or



                                      -10-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   19

applicability of any governmental enactments which may affect Operating
Expenses; (xiii) reasonable and customary association fees and costs assessed
under the CC&Rs and/or in connection with any property owners or maintenance
association; and (xiv) any other expenses of any kind whatsoever incurred in
connection with the operation, management, repair and maintenance of the
Building and Project. Operating Expenses shall also include either (a) an
administrative fee to Landlord for accounting and project management services
relating to the Project in an amount equal to three percent (3%) of Base Rent
and Additional Rent from all tenants of the Project (other than the
administrative fee), or (b) all costs and fees incurred by Landlord in
connection with the management of this Lease and the Building and Project,
including the costs of those services customarily performed by a property
management services company whether performed internally or through an outside
management company. If the Building and/or Project are not fully occupied during
any year, an adjustment shall be made in computing the Operating Expenses for
such year so that Operating Expenses include an equitable portion of all
variable items of Operating Expenses, as reasonably determined by Landlord.
Landlord shall have the right, from time to time, to equitably allocate and
prorate some or all of the Operating Expenses among different tenants and/or
different buildings of the Project and/or on a building-by-building basis (the
"COST POOLS"). Such Cost Pools may include, without limitation, the office space
tenants and retail space tenants of the buildings in the Project.

         7.3 Exclusions from Operating Expenses. Notwithstanding Section 7.2 to
the contrary, Operating Expenses shall exclude the following:

                  (i) Costs of repairs, replacements or other work occasioned by
fire, windstorm or other casualty to the extent of the greater of the amount
actually covered by insurance or the amount of insurance that Landlord is
required to maintain under this Lease (excluding commercially reasonable
deductibles), or by the exercise by governmental authorities of the right of
eminent domain.

                  (ii) Leasing commissions, attorney's fees, costs,
disbursements and other expenses incurred by Landlord or its agents in
connection with leases with other tenants, other occupants or prospective
tenants or other occupants of the Building and the Project, and similar costs
incurred in connection with and/or enforcement of any leases with other tenants,
other occupants, or prospective tenants or other occupants of the Building and
the Project.

                  (iii) "Tenant allowances," "tenant concessions," work letters,
and other costs or expenses (including permit, license and inspection fees but
not including such costs or expenses incurred in connection with any Common
Facilities) incurred in completing, fixturing, furnishing, renovating or
otherwise improving, decorating or redecorating space for other tenants or other
occupants of the Building and the Project, or vacant, leasable space in the
Building, including space planning/interior design fees for same.

                  (iv) Costs of correcting material defects, including any
allowances for same, in the original construction of the Building (including
latent defects) or equipment used therein (or the replacement of defective
equipment).

                  (v) Costs (including fines, penalties and legal fees) incurred
due to the knowing and willful violation by Landlord, its employees, agents
and/or contractors, of any terms and conditions of this Lease or of the leases
of the other tenants in the Building or the Project, and/or of any Applicable
Laws that would not have been incurred but for such violation by Landlord, its
employees, agents and/or contractors.

                  (vi) Payments in respect of overhead and/or profit to any
subsidiary or affiliate of Landlord as a result of a non-competitive selection
process for services (other than property and construction management fees) on
or to the Building or the Project, or for goods, supplies or other materials, to
the extent that the costs of such services, goods, supplies and/or materials
exceed the costs that would have been paid had the services, goods, supplies or
materials been provided by parties unaffiliated with Landlord of similar skill,
competence and experience, on a competitive basis.

                  (vii) Payments of principal, finance charges or interest on
debt or amortization on any mortgage or deed of trust encumbering the Building
or the Project, and rental payments (or increases in same) under any ground or
underlying lease or leases (except to the extent the same may be made to pay or
reimburse, or may be measured by, Real Property Taxes).

                  (viii) Except for property and construction management fees,
and the administrative fee to Landlord set forth in Section 7.2, costs of
Landlord's general overhead and general administrative expenses (individual,
partnership or corporate, as the case may be), which costs would not be
chargeable to Operating Expenses of the Building or the Project in accordance
with generally accepted accounting principles, including, without limitation,
all costs related to accounting and audit services by certified public
accountants for Landlord and its affiliates (excepting accounting and audit
services necessary to satisfy normal property management requirements).



                                      -11-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   20

                  (ix) Compensation paid to clerks, attendants or other persons
in commercial concessions (such as a snack bar, restaurant or newsstand), if
any, operated by Landlord or any subsidiary or affiliate of Landlord.

                  (x) Advertising and promotional expenses.

                  (xi) Costs for which Landlord is directly reimbursed by
insurance.

                  (xii) Depreciation on the Building, the Project or any
equipment or materials used by Landlord or Landlord's manager in conjunction
therewith, except on equipment or materials purchased by Landlord to enable
Landlord to supply services Landlord might otherwise contract for with a third
party, where such depreciation would otherwise have been included in the charge
for such third party's services, all as determined in accordance with generally
accepted accounting principles, consistently applied, and when depreciation is
permitted or required, the item shall be amortized over its reasonably
anticipated useful life.

                  (xiii) Costs of capital improvements except those set forth in
Section 7.2(xi).

8. ESTIMATED EXPENSES.

         8.1 Payment. The term "ESTIMATED EXPENSES" for any particular calendar
year during the Term shall mean Landlord's estimate of Tenant's Percentage Share
of Operating Expenses and Tenant's Percentage Share of Real Property Taxes which
are payable by Tenant for such calendar year. Before the commencement of each
calendar year during the Term or as soon thereafter as is reasonably
practicable, Landlord shall notify Tenant in writing of the Estimated Expenses
for such calendar year (and upon Tenant's written request, Landlord shall
provide an annual budget supporting such Estimated Expenses). Tenant shall pay
to Landlord monthly, in advance, one-twelfth (1/12) of the Estimated Expenses;
provided, however, that if Landlord fails to notify Tenant of the Estimated
Expenses for any particular calendar year before the start of such calendar
year, Tenant shall be required to continue to pay to Landlord, each month in
advance, the amount of the Estimated Expenses due for the immediately prior
month until Landlord notifies Tenant of the amount of the Estimated Expenses for
such calendar year, whereupon Tenant shall (i) thereafter commence to pay
one-twelfth (1/12) of such newly determined Estimated Expenses and (ii) pay,
with its next installment of Estimated Expenses, a fraction of the Estimated
Expenses for the then-current calendar year (reduced by any amounts paid with
respect to the then-current calendar year pursuant to the immediately preceding
sentence), which fraction shall have as its numerator the number of months which
have elapsed in such current calendar year (including the month of such payment)
and twelve (12) as its denominator. If at any time Landlord determines that
Tenant's Percentage Share of Operating Expenses and Tenant's Percentage Share of
Real Property Taxes are projected to vary from the then Estimated Expenses,
Landlord may, by notice to Tenant, revise the Estimated Expenses, and Tenant's
monthly installments for the remainder of such year shall be adjusted so that by
the end of such calendar year Tenant has paid to Landlord the revised Estimated
Expenses for such year.

         8.2 Adjustment. The term "ADJUSTMENT" shall mean for any calendar year
the difference between (i) the Estimated Expenses and (ii) the sum of (a)
Tenant's Percentage Share of Real Property Taxes, and (b) Tenant's Percentage
Share of Operating Expenses. After the end of each calendar year, Landlord shall
deliver to Tenant a statement of Tenant's Percentage Share of Operating Expenses
and Tenant's Percentage Share of Real Property Taxes for such calendar year,
accompanied by a computation of the Adjustment. If Tenant's payments of
Estimated Expenses are less than Tenant's Percentage Share of Operating Expenses
and Tenant's Percentage Share of Real Property Taxes, then Tenant shall pay the
difference within thirty (30) days after receipt of such statement. Tenant's
obligation to pay such amount shall survive the termination of this Lease
provided that Landlord invoices Tenant for such amounts no later than two (2)
years after such termination. If Tenant's payments of Estimated Expenses exceed
Tenant's Percentage Share of Operating Expenses and Tenant's Percentage Share of
Real Property Taxes, then, provided that Tenant is not in default hereunder,
Landlord shall credit such excess amount to future installments of Estimated
Expenses for the next calendar year. If Tenant is in default, Landlord may, but
shall not be required to, credit such amount to Rent arrearage. In no event
shall Tenant be entitled to any credit in the event that Tenant's Percentage
Share of Real Property Taxes and/or Tenant's Share of Operating Expenses are
less than such amounts for the Base Year.

9. INSURANCE.

         9.1 Landlord. Landlord, either directly or through its agent, shall
maintain "all risk" or "Special Form" property insurance, including boiler and
machinery comprehensive form, if applicable, through individual or blanket
policies insuring the Building against fire and other casualties, including all
alterations, additions and improvements, whether owned by Landlord or by Tenant
(but excluding the cost of Tenant's Property and the cost of the Tenant
Improvements or Alterations in excess of Building- standard), in amounts equal
to the full replacement value thereof, with deductibles and the form and



                                      -12-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   21

endorsements of such coverage as selected by Landlord in a commercially
reasonable manner. Landlord may also carry such other insurance as Landlord may
deem prudent or advisable, in such amounts, with such deductibles and upon such
terms as Landlord shall determine in a commercially reasonable manner. The cost
of the insurance obtained by Landlord under this Section 9.1 shall be included
in Operating Expenses.

         9.2 Tenant. Tenant shall, at Tenant's expense, obtain and keep in force
at all times the following insurance (and any other form(s) of insurance
Landlord may reasonably require from time to time) in the following coverage
amounts, which coverage amounts Landlord may reasonably increase from time to
time but upon prior written notice to Tenant, and all such coverage shall be
primary without right of contribution by Landlord:

                  9.2.1 Commercial General Liability Insurance (Occurrence
Form). A policy of commercial general liability insurance (occurrence form)
having a combined single limit of not less than One Million Dollars ($1,000,000)
per occurrence and Two Million Dollars ($2,000,000) aggregate per location if
Tenant has multiple locations, and Two Million Dollars ($2,000,000)
products/completed operations aggregate, providing coverage for, among other
things, blanket contractual liability, premises, host liquor, products/completed
operations with an "Additional Insured-Managers or Lessors of Premises
Endorsement" and containing the "Amendment of the Pollution Exclusion
Endorsement" for damage caused by heat, smoke or fumes from a hostile fire, and
personal and advertising injury coverage, with deletion of the exclusion for
explosion, collapse or underground hazard, if applicable, and, if necessary,
Tenant shall provide for restoration of the aggregate limit, and provided that
the policy shall include coverage for liability assumed under this Lease as an
"insured contract" for the performance of Tenant's indemnity obligations under
this Lease.

                  9.2.2 Automobile Liability Insurance. Business automobile
liability insurance having a combined single limit of not less than One Million
Dollars ($1,000,000) per occurrence and insuring Tenant against liability for
claims arising out of ownership, maintenance or use of any owned, hired or
non-owned automobiles (but only as applicable based on Tenant's actual
ownership, maintenance or use of any such automobiles);

                  9.2.3 Workers' Compensation and Employer's Liability
Insurance. Workers' compensation insurance having limits not less than those
required by state statute and federal statute, if applicable, and covering all
persons employed by Tenant in the conduct of its operations on the Premises
(including the all states endorsement and, if applicable, the volunteers
endorsement), together with employer's liability insurance coverage in the
amount of at least One Million Dollars ($1,000,000) for bodily injury by
accident and One Million Dollars ($1,000,000) for bodily injury;

                  9.2.4 Property Insurance. "Special Form" or "all risk"
property insurance, including boiler and machinery comprehensive form, if
applicable, on a replacement cost basis, each covering damage to or loss of any
of Tenant's Property and/or any Tenant Improvements or Alterations in excess of
Building-standard. Tenant's property insurance deductible shall not exceed
Twenty-Five Thousand Dollars ($25,000.00);

                  9.2.5 Business Interruption. Loss of income and extra expense
insurance and contingent business income insurance in amounts as will reimburse
Tenant for direct or indirect loss of earnings attributable to all perils
commonly insured against by prudent lessees in the business of Tenant, or
attributable to prevention of access to the Premises as a result of such perils.
Such insurance will provide for an extended period of indemnity to be not less
than one hundred eighty (180) days/six (6) months; and

                  9.2.6 Umbrella/Excess Insurance. An umbrella liability policy
or excess liability policy having a limit of not less than Ten Million Dollars
($10,000,000.00), which policy shall be in "following form" and shall provide
that if the underlying aggregate is exhausted, the excess coverage will drop
down as primary insurance. Such umbrella liability policy or excess liability
policy shall include coverage for additional insureds.

         9.3 General.

                  9.3.1 Insurance Companies. Insurance required to be maintained
by Tenant shall be written by companies licensed to do business in the state in
which the Premises are located and having a "General Policyholders Rating" of at
least A-VIII (or such higher rating as may be required by any Mortgagee) as set
forth in the most current issue of "Best's Insurance Guide."

                  9.3.2 Certificates of Insurance. Tenant shall deliver to
Landlord certificates of insurance for all insurance required to be maintained
by Tenant in the form of the ACORD 27 (Evidence of Property Insurance) and the
ACORD 25-5 (Certificate of Liability Insurance) (or in a form acceptable to
Landlord in its sole discretion), no later than seven (7) days before the date
on which Tenant is to take



                                      -13-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   22

possession of the Premises. Tenant shall, at least ten (10) days before the
expiration of the policy, furnish Landlord with certificates of renewal or
"binders" thereof. Each certificate shall expressly provide that such policies
shall not be cancelable or otherwise subject to modification except after sixty
(60) days' prior written notice to the parties named as additional insureds in
this Lease (except in the case of cancellation for nonpayment of premium in
which case cancellation shall not take effect until at least ten (10) days'
notice has been given to Landlord). If Tenant fails to procure or maintain any
insurance required in this Lease, Tenant shall be liable for all losses and
costs suffered or incurred by Landlord (including litigation costs and
attorneys' fees and expenses) resulting from said failure. In addition, if
Tenant shall fail to procure or maintain such insurance, or to deliver such
certificates, within the time periods set forth above, Landlord may, at its
option, in addition to all of its other rights and remedies under this Lease,
and without regard to any notice and cure periods set forth in Section 16 below,
procure such policies for the account of Tenant, and the cost thereof shall be
paid to Landlord as Additional Rent within ten (10) days after delivery of bills
therefor.

                  9.3.3 Additional Insured. Landlord, as well as any property
management company of Landlord for the Building or the Project, each Mortgagee
and any other interested party having an insurable interest reasonably
designated by Landlord in writing to Tenant shall be named as additional
insureds under all of the policies required by Section 9.2.1 and 9.2.6, and such
endorsement shall be included with the certificates to be provided to Landlord
pursuant to Section 9.3.2 above. The policies required under Section 9.2.1 shall
provide for severability of interest. Landlord is to be insured as its interests
may appear and is to be designated as a loss payee on the insurance required to
be maintained by Tenant pursuant to Section 9.2.4.

                  9.3.4 Limits of Insurance. The limits of insurance maintained
by the parties hereunder shall not limit such parties' respective liability
under this Lease.

                  9.3.5 Mutual Waiver of Subrogation. Landlord and Tenant each
waive any right to recover against the other for claims for damages to each
parties' respective property required to be insured hereunder. This provision is
intended to waive fully, and for the benefit of the parties, any rights and/or
claims which might give rise to a right of subrogation in favor of any insurance
carrier. This waiver extends to any business interruption or loss of earnings
coverage of Tenant whether such coverage is purchased as part of Tenant's
property insurance policy or as a separate policy.

                  9.3.6 Notification of Incidents. Tenant shall notify Landlord
within twenty-four (24) hours after the occurrence of any accidents or incidents
in the Premises, the Building, the Common Facilities or other portions of the
Project which, in Tenant's reasonable opinion, could give rise to a claim
against Landlord.

         9.4 Indemnity.

                  9.4.1 By Tenant. Tenant shall indemnify, protect, defend (by
counsel reasonably acceptable to Landlord) and hold harmless Landlord and
Landlord's affiliated entities, and each of their respective members, managers,
partners, directors, officers, employees, shareholders, lenders, agents,
contractors, successors and assigns (collectively, the "LANDLORD INDEMNIFIED
PARTIES" and each, a "LANDLORD INDEMNIFIED PARTY") from and against any and all
claims, judgments, causes of action, damages, penalties, costs, liabilities, and
expenses, including all costs, attorneys' fees, expenses and liabilities
reasonably incurred in the defense of any such claim or any action or proceeding
brought thereon (collectively, "LANDLORD CLAIMS") arising from any cause
whatsoever in the Premises (but excluding Landlord Claims to the extent caused
by a Landlord Indemnified Party's negligence or willful or criminal misconduct).
In addition, Tenant shall further indemnify, protect, defend (by counsel
reasonably acceptable to Landlord) and hold harmless the Landlord Indemnified
Parties from and against any and all Landlord Claims arising from (i) any
default in the performance of any obligation on Tenant's part to be performed
under the terms of this Lease; (ii) Tenant's use of the Premises, the conduct of
Tenant's business or any activity, work or things done, permitted or suffered by
Tenant or any Tenant Party in or about the Premises, the Building, the Common
Facilities or other portions of the Project and/or (iii) any acts, omissions or
negligence of Tenant or any Tenant Party. The obligations of Tenant under this
Section 9.4 shall survive the termination of this Lease with respect to any
Claims or liability attributable to events which occurred before such
termination.

                  9.4.2 By Landlord. Landlord shall indemnify, protect, defend
(by counsel reasonably acceptable to Tenant) and hold harmless Tenant and Tenant
Parties (collectively, the "TENANT INDEMNIFIED PARTIES" and each, an "TENANT
INDEMNIFIED PARTY") from and against any and all claims, judgments, causes of
action, damages, penalties, costs, liabilities, and expenses, including all
costs, attorneys' fees, expenses and liabilities reasonably incurred in the
defense of any such claim or any action or proceeding brought thereon
(collectively, "TENANT CLAIMS") arising from any cause whatsoever in the Common
Facilities but only to the extent that such Tenant Claims are covered by the
insurance maintained, or required to be maintained hereunder, by Landlord (but
excluding Tenant Claims to the extent caused by a Tenant Indemnified Party's
negligence or willful or criminal misconduct). In addition,



                                      -14-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   23

Landlord shall further indemnify, protect, defend (by counsel acceptable to
Tenant) and hold harmless the Tenant Indemnified Parties from and against any
and all Tenant Claims arising from any negligence or willful misconduct of
Landlord or its employees, agents or contractors. The obligations of Landlord
under this Section 9.4.2 (a) shall survive the termination or expiration of this
Lease with respect to any Tenant Claims or liability attributable to events
which occurred before such termination or expiration and (b) are subject to
Section 9.3.5.

         9.5 Exemption of Landlord from Liability. Tenant, as a material part of
the consideration to Landlord, (i) hereby assumes all risk of damage to property
including, but not limited to, Tenant's fixtures, equipment, furniture,
improvements and alterations or injury to persons in, upon or about the
Premises, the Building, the Common Facilities or other portions of the Project
arising from any cause, and (ii) hereby expressly releases Landlord and waives
all claims in respect thereof against Landlord and all other Landlord
Indemnified Parties, except that clauses 9.5(i) and (ii) above will not apply
with respect to damage or injury (a) caused by the negligence or willful or
criminal misconduct of a Landlord Indemnified Party that is of a type not
covered by the insurance maintained, or required to be maintained hereunder, by
Tenant or (b) covered by Landlord's indemnity under Section 9.4.2 above. Tenant
hereby agrees that neither Landlord nor any other Indemnified Party shall be
liable for injury to Tenant's business or any loss of income therefrom. Tenant
further agrees that neither Landlord nor any other Landlord Indemnified Party
shall be liable for damage to the property of Tenant, or injury to or death or
illness of Tenant, Tenant's employees, invitees, customers, agents or
contractors or any other person in or about the Premises, the Building, the
Common Facilities or the Project, except for any loss, damage or injury
attributable in whole or in part to the act, omission or negligence of any
Landlord Indemnified Party or the willful or criminal misconduct of such
Landlord Indemnified Party that is of a type not covered by the insurance
maintained, or required to be maintained hereunder, by Tenant, whether such
damage, illness or injury is caused by fire, steam, electricity, gas, water or
rain, or from the breakage, leakage or other defects of sprinklers, wires,
appliances, plumbing, ventilation, air conditioning or lighting fixtures, or
from any other cause, and whether such damage, illness or injury results from
conditions arising upon the Premises, or from other sources or places, and
regardless of whether the cause of such damage, illness or injury or the means
of repairing the same is inaccessible to Tenant. Landlord shall not be liable to
Tenant for any damages arising from any act or neglect of any other tenant, if
any, of the Building or the Project or Landlord's failure to enforce the terms
of any agreements with parties other than Tenant.

10. REPAIRS AND MAINTENANCE.

         10.1 Tenant. Except as set forth in Section 10.2 below, Tenant shall
keep and maintain the Premises and every part thereof, including, but not
limited to, floors and floor coverings, interior plumbing, interior walls and
ceilings, including electrical wiring, appliances and devices using or
containing refrigerants, fixtures and equipment in good repair and in a clean
and safe condition, and repair and/or replace any and all of the foregoing in a
good and workmanlike manner. Without limiting the foregoing, but subject to the
provisions of Section 14 below, Tenant shall, at Tenant's sole expense, repair
any area of the Premises damaged by Tenant or any Tenant Party or by any other
cause. If Tenant, in the reasonable judgment of Landlord, fails to maintain the
Premises in accordance with the terms of this Lease and correct such failure
within ten (10) days following Tenant's receipt of written notice from Landlord
stating the nature of the failure, Landlord shall have the right to enter the
Premises and perform such maintenance, repairs or replacements at Tenant's sole
cost and expense (including a sum for overhead to Landlord equal to ten percent
(10%) of the cost of the maintenance, repairs or replacements). Tenant shall
maintain written records of maintenance and repairs, as required by any
Applicable Law, and shall use certified technicians to perform such maintenance
and repairs, as so required. Landlord shall have the right to approve all
service maintenance contractors hired by Tenant which approval shall not be
unreasonably withheld, conditioned or delayed. Upon Landlord's request, Tenant
shall deliver to Landlord full and complete copies of all service or maintenance
contracts entered into by Tenant for the Premises within one hundred twenty
(120) days after the Commencement Date and, thereafter, within ten (10) days
after entering into any new or materially amending any existing service or
maintenance contract.

         10.2 Landlord. Landlord shall, at its sole cost and expense or as an
Operating Expense if permitted under Section 7 above, repair damage to
structural portions, foundations, roofs, and exterior walls of the Building and
the Project; provided that, if such damage is caused by the negligence or
willful or criminal misconduct of Tenant or a Tenant Party, then such repairs
shall be at Tenant's sole expense but only to the extent such damage is not
covered by insurance carried by Landlord hereunder. There shall be no abatement
of Rent during the performance of such work provided that Landlord makes
commercially reasonable efforts to minimize any adverse impact on Tenant's use
and enjoyment of the Premises for the conduct of Tenant's business. Landlord
shall not be liable to Tenant for injury or damage that may result from any
defect in the construction or condition of the Building or the Premises unless
the same is the result of the negligence or willful or criminal misconduct of
Landlord or any of its agents, employees or contractors that is of a type not
covered by the insurance maintained, or required to be maintained hereunder, by
Tenant, nor (except as otherwise provided herein) for any damage that may result
from interruption of Tenant's use of the Premises during any repairs by
Landlord. Nevertheless,



                                      -15-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   24

Landlord shall use commercially reasonable efforts to enforce any applicable
construction warranties pertaining to any defect in the construction or
condition of the Building or the Premises. Tenant waives any right to repair the
Premises, the Building, the Project and/or the Common Facilities at the expense
of Landlord under any Applicable Law.

11. ALTERATIONS.

         11.1 Trade Fixtures; Alterations. Tenant may, without any further
consent or approval by Landlord but subject to all other requirements of this
Section 11 (e.g., Tenant's insurance, delivery of as- built drawings to
Landlord, etc.), install trade fixtures, equipment, data and telephone cable and
conduit, furniture, and office decorations in the Premises (collectively,
"UTILITY INSTALLATIONS"), provided that such Utility Installations are installed
and are removable without structural or other damage to the Premises, the
Building, the Common Facilities or the Project, subject to the other provisions
of this Section 11. Tenant shall not construct, nor allow to be constructed, any
alterations, improvements or physical additions other than Utility Installations
(collectively, "ALTERATIONS") in, about or to the Premises without obtaining the
prior written consent of Landlord, which will not be unreasonably withheld,
conditioned, or delayed; provided, however, Landlord shall have the right, in
Landlord's sole discretion, to withhold its consent to any Alteration that would
adversely affect the structural portions of the Building or any Building Systems
or which would be visible from the exterior of the Premises or the Building.
Landlord may impose, as a condition of its consent to all Alterations, such
requirements as Landlord may reasonably deem appropriate, including, but not
limited to, the requirement that Tenant utilize only contractors, materials,
mechanics and materialmen reasonably approved by Landlord; however, a contractor
of Landlord's selection shall perform all mechanical, electrical, plumbing,
structural and heating, ventilation and air conditioning work, provided that
Landlord's contractor is willing to perform such work at commercially reasonable
and competitive rates and in a commercially reasonable timeframe. If such
Alterations trigger a legal requirement upon Landlord to make any Alterations or
improvements to the Building or Common Facilities and if Tenant elects to
proceed with such Alterations after receipt of written notice from Landlord of
such requirements, Tenant shall, as Additional Rent, reimburse Landlord for the
cost thereof within thirty (30) days following receipt of an invoice therefor.
The construction of the initial improvements to the Premises shall be governed
by the terms of Exhibit B attached hereto and not by the terms of this Section
11.1. Tenant shall submit plans and specifications to Landlord with Tenant's
request for approval to construct Alterations. If Landlord does not approve
Tenant's proposed Alterations, Landlord shall notify Tenant of such disapproval
in writing and shall specify with reasonable specificity the reasons for such
disapproval and the changes to the proposed Alterations that Landlord reasonably
requires in order to grant its approval. Landlord's approval of the plans,
specifications (and working drawings, if reasonably requested by Landlord for
Alterations necessitating such working drawings) for Alterations shall create no
responsibility or liability on the part of Landlord for their completeness,
design sufficiency, or compliance with Applicable Laws. If Landlord does not
respond within ten (10) business days to Tenant's written request for Landlord's
approval, then Landlord shall be deemed to disapprove such request; provided,
however, if Landlord has not responded to Tenant's written request within such
ten (10) business day period, Tenant may give Landlord an additional written
request containing the following phrase (or a phrase substantially similar to
the following phrase) on page 1 of such additional request in capital letters
and 12-point boldface type (in the absence of which it shall not be deemed
validly delivered to Landlord) "YOUR FAILURE TO APPROVE OR DISAPPROVE OF THE
MATTERS REQUESTED IN THIS NOTICE WITHIN TEN (10) BUSINESS DAYS SHALL CONSTITUTE
YOUR APPROVAL THEREOF," and if Landlord does not respond to such request within
such additional ten (10) business day period, then Landlord shall be deemed to
have approved such request. Tenant shall reimburse Landlord for all costs which
Landlord incurs in responding to Tenant's request and reviewing Tenant's plans
and specifications (and working drawings, if applicable) including any costs or
expenses that Landlord may incur in having outside architects and engineers
review said matters (such costs not to exceed Two Thousand Five Hundred Constant
Collars ($2,500.00) for cosmetic, non-structural Alterations in the Premises
initially leased hereunder only), together with a fee in the amount of four
percent (4%) of the total hard costs of construction and installation of the
Alterations. All Alterations shall be diligently constructed to completion and
shall be completed at Tenant's expense, in compliance with all Applicable Laws,
in strict accordance with any design or construction procedures reasonably
established by Landlord for the Building and/or the Project and in a good and
workmanlike manner. Tenant agrees to carry "Builder's All Risk" insurance in an
amount approved by Landlord covering the construction of Alterations, and such
other insurance as Landlord may require of Tenant or its contractors. Tenant
shall file a notice of completion after completion of such work and provide
Landlord with a copy thereof. Tenant shall provide Landlord with a set of
"as-built" drawings for any such work. Except as provided in Section 11.2, all
Alterations shall remain the property of Tenant until the expiration or earlier
termination of this Lease, at which time they shall be and become the property
of Landlord.

         11.2 Removal of Tenant's Property and Alterations. All Utility
Installations and articles of movable personal property installed in the
Premises by or for the account of Tenant (except for ceiling and related
fixtures, HVAC equipment and floor coverings), and that can be removed without
structural or other damage to the Premises or the Building (collectively,
"TENANT'S PROPERTY") shall be and remain



                                      -16-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   25

the property of Tenant and may be removed by it at any time during the Term;
provided, however, that any equipment or other property for which Landlord has
granted any allowance or credit to Tenant or which is a replacement for items
originally provided by Landlord at Landlord's expense shall not be considered
Tenant's Property, and provided further that Landlord, in Landlord's sole
discretion, shall have the right to reserve ownership of any telecommunications
cabling and/or conduit installed by Tenant. Upon the expiration or earlier
termination of this Lease, Tenant shall have removed from the Premises all of
Tenant's Property except such items as the parties have agreed are to remain and
to become the property of Landlord and, upon the request of Landlord, Tenant, at
its sole cost and expense, shall also remove any Alterations designated in
writing by Landlord at the time Landlord gave its consent for the
construction/installation of such Alterations (provided that Tenant requested
Landlord's consent for such Alterations and if Tenant did not request such
consent, Tenant, at its sole cost and expense, shall remove any Alterations
designated by Landlord upon the expiration or earlier termination of this Lease
to be removed, and except for any data and telephone cable and/or conduit, of
which Landlord may require removal upon the expiration or earlier termination of
this Lease). If Landlord requires any such removal, Tenant shall be given a
reasonable period of time after any early termination of this Lease in which to
accomplish such removal and repair, but in no event shall such removal and
repair period extend for more than fifteen (15) days after such early
termination and provided that Tenant shall pay to Landlord, no later than ten
(10) days after Landlord's invoice, the Base Rent specified in Section 21.8(a)
below for Tenant's use of the Premises during such removal/repair period. Tenant
shall repair or pay the cost of repairing any damage to the Premises or the
Project resulting from such removal. Tenant's obligations under this Section
11.2 shall survive the termination of this Lease. Any items of Tenant's Property
which shall remain in the Premises after the Expiration Date or earlier
termination of this Lease may, at the option of Landlord, be deemed abandoned
and in such case may either be retained by Landlord as its property or be
disposed of, without accountability, at Tenant's expense in such manner as
Landlord may reasonably deem fit.

         11.3 Liens. Tenant shall promptly pay and discharge all claims for
labor performed, supplies furnished and services rendered at the request of
Tenant and shall keep the Premises free of all mechanics' and materialmen's
liens in connection therewith. Tenant shall provide at least ten (10) days'
prior written notice to Landlord before any labor is performed, supplies
furnished or services rendered on or at the Premises and Landlord shall have the
right to post on the Premises notices of non-responsibility. If any lien is
filed, Tenant shall cause such lien to be released and removed (by bonding or
otherwise) within ten (10) days after the date of filing, and if Tenant fails to
do so, Landlord may take such action as may be reasonably necessary to remove
such lien and Tenant shall pay Landlord the amounts expended by Landlord
together with interest thereon at the Applicable Interest Rate from the date of
expenditure.

         11.4 Remodel. Landlord reserves the right, at any time , to make
alterations, additions, repairs or improvements to or in, or to increase or
decrease the size or area of, all or any part of the Building or the Project and
the fixtures and equipment therein including, without limitation, the HVAC,
plumbing, electrical, fire protection, life safety, security and other
mechanical, electrical and communications systems of the Premises, the Building
and the Project (collectively, the "BUILDING SYSTEMS"); provided that any such
alterations, additions, repairs, improvements or increases/decreases in the size
of the Building or the Project shall not materially and adversely affect
Tenant's use and enjoyment of the Premises or materially increase Tenant's costs
under this Lease.

12. USE. The Premises shall be used only for the Permitted Use set forth in the
Basic Lease Information and for no other use (including laboratory use) without
Landlord's prior written consent, which consent may be granted or denied in
Landlord's commercially reasonable discretion, and Tenant shall not cause or
permit, nor allow any of Tenant Parties to cause or permit, any hazardous
materials (as defined under Applicable Laws, as defined below) to be brought
upon, stored, manufactured, recycled, disposed or used in, on, under or about
the Premises, the Building, the Common Facilities or any other portion of the
Project. Tenant's use of the Premises shall be in compliance with and subject to
all laws, codes, ordinances, statutes, orders, rules, regulations, conditions of
approval and requirements of all federal, state, county, municipal and other
governmental authorities and all administrative or judicial orders or decrees
and all permits, licenses, approvals and other entitlements issued by
governmental entities, and rules of common law, relating to or affecting the
Project or any portion thereof or the use or operation thereof, whether now
existing or hereafter enacted, as the same may be amended from time to time, and
all covenants, conditions and restrictions of record, including the CC&Rs and
any supplement thereto, now or hereafter recorded in any official or public
records that are applicable to the Project or any portion thereof ("APPLICABLE
LAWS"). Tenant shall be responsible for obtaining any permit, business license,
certificate of occupancy, or other permits or licenses required by any
governmental agency permitting Tenant's use or occupancy of the Premises (except
that Landlord shall obtain all necessary permits or licenses with respect to the
base, shell and core of the Premises to be delivered to Tenant pursuant to
Exhibit "B" attached hereto). Tenant shall comply with the rules and regulations
(the "RULES AND REGULATIONS") attached hereto as Exhibit C, together with such
additional and/or modifications to such Rules and Regulations as Landlord may
from time to time prescribe; provided, however, that no such additional or
modified Rules and Regulations shall have any material adverse impact on
Tenant's use and enjoyment of the Premises or materially increase Tenant's costs
to conduct business in the Premises.



                                      -17-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   26

Tenant shall not commit waste, overload the floors or structure of the Building,
subject the Premises, the Building, the Common Facilities or any other portion
of the Project to any use which would damage the same or increase the risk of
loss or violate any insurance coverage, permit any unreasonable odors, smoke,
dust, gas, substances, noise or vibrations to emanate from the Premises, take
any action which would constitute a nuisance or would disturb, obstruct or
endanger Landlord or any third party, take any action which would abrogate any
warranties, or use or allow the Premises to be used for any unlawful purpose.
Landlord shall not be responsible for non-compliance by any other tenant or
occupant with, or Landlord's failure to enforce, any of the Rules and
Regulations or any other terms or provisions of such tenant's or occupant's
lease. Tenant shall promptly comply with the reasonable requirements of any
board of fire insurance underwriters or other similar body now or hereafter
constituted. Tenant shall not do any act which shall in any way encumber the
title of Landlord in and to the Premises, the Building or any other portion of
the Project.

13. SIGNS. Provided Tenant is not in default under this Lease, Tenant shall be
entitled to, at Tenant's sole cost and expense and subject to the provisions of
this Section 13, (a) Building-standard signage on the Building lobby directory
and (b) one strip on the Building's monument sign (at a location to be
determined by Landlord and in a size to be determined by Landlord based
equitably on the square footage of the Premises in relation to the square
footage of the premises of other tenants designated on such sign) identifying
the name of the original Tenant signing this Lease or any Affiliated Assignee;
provided that the name of any such Affiliated Assignee is not an "Objectionable
Name," as that term is defined below. In addition, should the name of the Tenant
originally signing this Lease change, Tenant shall be entitled to modify, at
Tenant's sole cost and expense, Tenant's signage to reflect Tenant's new name,
but only if Tenant's new name is not an "Objectionable Name." The term
"OBJECTIONABLE NAME" shall mean any name that relates (i) to an entity that is
of a character or reputation, or is associated with a political orientation or
faction that is materially inconsistent with the quality of the Project, or that
would otherwise reasonably offend a landlord of a building or project comparable
to the Project, taking into consideration the level and visibility of Tenant's
signage, or (ii) conflicts with any covenants in other leases of space in the
Building or the Project. In connection with Section 13(b) hereinabove, Landlord
agrees that only in the event Landlord allows other tenants that lease
approximately the same number of square feet in the Building as Tenant leases
hereunder to place their logo and/or personalized typeface on the Building's
monument sign, Tenant shall be entitled to place its logo and/or personalized
typeface thereon, provided that such logo and/or typeface shall be subject to
Landlord's approval as further provided in this Section 13. All signs and
graphics of every kind visible in or from public view or corridors, the Common
Facilities or the exterior of the Premises, whether located inside or outside
the Premises, Building or Project, shall be subject to Landlord's prior written
approval, which approval may be given or withheld in Landlord's commercially
reasonable discretion, and shall be subject to all Applicable Laws and in
compliance with Landlord's signage program. Landlord hereby consents to the
design and specifications for Tenant's standard corporate name and Landlord
further agrees that, subject to all Applicable Laws and Landlord's signage
program, such name may be used for all Tenant signage in accordance with this
Section 13. For purposes hereof, the term "SIGNS AND GRAPHICS" includes, without
limitation, all signs, designs, monuments, logos, banners, projected images,
pennants, decals, advertisements, pictures, notices, lettering, graphics and
decorations. Tenant shall keep all such signs and graphics in good condition and
repair during the Term and shall remove all such signs and graphics before the
termination of this Lease. Such installations and removals shall be made in such
manner, to the extent reasonably practicable, as to avoid injury or defacement
of the Premises or the Project and Tenant shall repair any injury or defacement,
including without limitation, discoloration caused by such installation or
removal. Subject to the requirements of Applicable Laws, any signs and graphics
that are installed and that have not been separately approved by Landlord may be
removed without notice by Landlord at the sole expense of Tenant. Except as
otherwise provided herein, Tenant may not install any signs and graphics on the
exterior or roof of the Building, the Common Facilities or other portions of the
Project. Any signs and graphics, window coverings, or blinds (even if the same
are located behind the Landlord-approved window coverings for the Building), or
other items visible from the exterior of the Premises or Building, shall be
subject to the prior written approval of Landlord, in accordance with this
Section 13.

14. DAMAGE AND DESTRUCTION.

         14.1 Landlord's Obligation to Rebuild. If the Premises and/or the
Building are damaged or destroyed, Landlord shall promptly and diligently repair
or restore the Premises and/or the Building subject to the provisions of this
Section 14 unless Landlord or Tenant duly and timely elects, if so entitled
pursuant to this Section 14 to terminate this Lease by written notice to the
other party. Landlord's obligation, should Landlord elect or be obligated to
repair or rebuild, shall be limited to the shell of the Building, the Building
first floor lobby, all Common Facilities reasonably required for Tenant's access
to and use of the Premises, and any improvements, additions or alterations
constructed in the Premises; provided, however that Landlord shall not be
obligated to repair or rebuild any such improvements, additions or alterations
in the Premises that are in excess of Building-standard unless Tenant pays to
Landlord, within ten (10) days after Landlord's invoice therefor and prior to
Landlord's commencement of



                                      -18-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   27

any such repairs or rebuilding, all costs for such repairs or rebuilding.
Tenant, at its sole cost and expense, shall replace or fully repair Tenant's
Property to the extent deemed necessary or desirable.

         14.2 Landlord's Right to Terminate. Landlord shall have the option to
terminate this Lease if the Premises or the Building is destroyed or damaged by
fire or other casualty, regardless of whether the casualty is insured against
under this Lease, if (i) Landlord reasonably determines that there are
insufficient insurance proceeds to pay all of the costs of the repair or
restoration, (ii) the holder of any indebtedness secured by the Building or all
or any portion of the Premises requires that the insurance proceeds be applied
to such indebtedness, or (iii) Landlord reasonably determines that the repair or
restoration of the Premises or the Building cannot be completed within three
hundred (300) days after the date of the issuance of permits for the necessary
repair or restoration of the portion of the Building or Premises which was
damaged. If Landlord elects to exercise the right to terminate this Lease as a
result of a casualty, Landlord shall exercise the right by written notice to
Tenant of its election to terminate this Lease within forty-five (45) days after
the date Landlord learns of the necessity for repairs as a result of the
casualty, in which event this Lease shall terminate fifteen (15) days after the
date of the notice, provided that Tenant shall be given a reasonable period of
time thereafter to remove its property from the Premises but in no event shall
such removal period extend for more than fifteen (15) days after such early
termination and provided that Tenant shall pay to Landlord, no later than ten
(10) days after Landlord's invoice, the Base Rent specified in Section 21.8(a)
below for Tenant's use of the Premises during such removal period.

         14.3 Tenant's Right to Terminate. Tenant shall have the option to
terminate this Lease if the Premises or the Building is destroyed or damaged by
fire or other casualty to an extent that materially and adversely impacts
Tenant's use and enjoyment of the Premises, regardless of whether the casualty
is insured against under this Lease, and Landlord reasonably determines that the
repair or restoration of the Premises or the Building cannot be substantially
completed within three hundred (300) days after the date of the issuance of
permits for the necessary repair or restoration of the portion of the Premises
which was damaged. Within thirty (30) days after Landlord learns of the
necessity for repairs as a result of the casualty, Landlord shall notify Tenant
in writing ("REPAIR NOTICE") as to Landlord's determination of the number of
days required to repair or restore the Premises after the receipt of such
permits. If Tenant elects to exercise its right to terminate this Lease as a
result of a casualty, Tenant shall exercise the right by written notice to
Landlord within fifteen (15) days after delivery of the Repair Notice, in which
event this Lease shall terminate fifteen (15) days after the delivery of
Tenant's termination notice. Except as otherwise expressly provided in this
Section 14.3, Tenant waives all rights it may have to terminate this Lease as a
result of damage to the Premises or Building pursuant to rights presently or
hereafter accorded by law, equity or otherwise.

         14.4 Abatement of Rent; Tenant's Fault. If the Premises are damaged or
destroyed by other than Tenant's or a Tenant Parties' negligence or willful or
criminal misconduct, the Base Rent shall be temporarily abated proportionately
to the degree the Premises are rendered untenantable as a result of the damage
or destruction. Such abatement shall commence on the date of the damage or
destruction and shall continue through the period required by Landlord to
substantially complete the repair and restoration of the Premises or until such
time as the Premises are tenantable for the operation of Tenant's business,
whichever is earlier. Except for the rent abatement provided above or as
otherwise provided in this Lease, Tenant shall not be entitled to any
compensation or damages from Landlord for loss of the use of the Premises,
damage to Tenant's Property or any inconvenience occasioned by any damage,
repair or restoration. If the Premises or any portion of the Building is damaged
as a result of the negligence or willful or criminal misconduct by Tenant or any
Tenant Parties, Base Rent shall not be abated during the repair of such damage
and Tenant shall be liable to Landlord for the cost of the repair necessitated
thereby to the extent such cost is not covered by insurance proceeds received by
Landlord.

         14.5 Damage Near End of Term. In addition to Landlord's right to
terminate this Lease under Section 14.2, Landlord shall have the right to
terminate this Lease upon thirty (30) days' prior written notice to Tenant if
the Premises or Building is damaged or destroyed during the last twelve (12)
months of the Term and Landlord reasonably determines that the repair or
restoration of the Premises or the Building cannot be completed within thirty
(30) days after the date Landlord learns of the necessity for repairs as a
result of the casualty. Landlord shall notify Tenant in writing of its election
to terminate this Lease under this Section 14.5, if at all, within forty-five
(45) days after the date of the casualty. If Landlord does not elect to
terminate this Lease pursuant to this Section 14.5, the repair of the Premises
or Building shall be governed by Section 14.1.

         14.6 Insurance Proceeds. If this Lease is duly terminated pursuant to
this Section 14, Landlord may keep all the insurance proceeds resulting from the
damage, and Tenant does hereby assign to Landlord and agrees to deliver to
Landlord the proceeds of Tenant's insurance policies covering the Tenant
Improvements, any Alterations and any other installation or property located in
the Premises that is to become Landlord's property upon the expiration or
earlier termination of this Lease (or the proceeds that would have been
available to Tenant [and, in turn, to Landlord] had Tenant properly maintained
the insurance required to be carried on such property pursuant to this Lease).
Any insurance proceeds from



                                      -19-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   28

Tenant's insurance policies not otherwise due and payable to Landlord under the
foregoing sentence shall be and remain the property of Tenant.

15. EMINENT DOMAIN.

         15.1 Total Condemnation. If the entire Premises is condemned by eminent
domain, inversely condemned or sold under threat of condemnation for any public
or quasi-public use or purpose ("CONDEMNED"), this Lease shall terminate as of
the earlier of the date title vests in the condemning authority or the date an
order of immediate possession is issued, and Rent shall be adjusted to the date
of termination.

         15.2 Partial Condemnation. If only a portion of the Premises or the
Building is Condemned and such partial condemnation materially and adversely
impacts Tenant's ability to use and enjoy the Premises for the conduct of
Tenant's business, Landlord shall have the option of either (i) relocating
Tenant to comparable space within the Building reasonably acceptable to Tenant
or (ii) terminating this Lease as of the earlier of the date title vests in the
condemning authority or the date an order of immediate possession is issued, and
Rent shall be adjusted to the date of termination. If such partial condemnation
does not materially and adversely impact Tenant's ability to use and enjoy the
Premises for the conduct of Tenant's business, Landlord shall fully and promptly
restore the Premises and the Building to the extent of any condemnation proceeds
recovered by Landlord, excluding the portion thereof lost in such condemnation,
and this Lease shall continue in full force and effect except that after the
date of such title vesting or order of immediate possession, Rent shall be
reasonably and equitably prorated.

         15.3 Award. If the Premises are wholly or partially Condemned, Landlord
shall be entitled to the entire award paid for such condemnation, and Tenant
waives any claim to any part of the award from Landlord or the condemning
authority; provided, however, that Tenant shall have the right to recover from
the condemning authority such compensation as may be separately awarded to
Tenant in connection with any taking of Tenant's Property and for costs in
moving Tenant's Property to a new location. No condemnation of any kind shall be
construed to constitute an actual or constructive eviction of Tenant or a breach
of any express or implied covenant of quiet enjoyment. Tenant hereby waives any
rights at law or equity now or hereafter existing to terminate this Lease as a
result of a condemnation except to the extent expressly granted herein.

         15.4 Temporary Condemnation. Upon a temporary condemnation not
extending beyond the Term, this Lease shall remain in effect, Tenant shall
continue to pay Rent and Tenant shall receive any award made for such
condemnation with respect to the Premises except damages to any of Landlord's
property. If a temporary condemnation is for a period which extends beyond the
Term, this Lease shall terminate as of the date of such temporary taking by the
condemning authority and any such award shall be distributed in accordance with
Section 15.3 above. If a temporary condemnation remains in effect at the
expiration or earlier termination of this Lease, Tenant shall pay Landlord the
reasonable cost of performing any obligations required of Tenant with respect to
the surrender of the Premises.

16. DEFAULT.

         16.1 Events of Default. The occurrence of any of the following events
shall, at Landlord's option, constitute an "EVENT OF DEFAULT":

                  16.1.1 Failure to pay Rent within three (3) days after
Landlord's written notice to Tenant that such payment is due;

                  16.1.2 Failure to perform any of Tenant's covenants and
obligations hereunder (other than a default described in Sections 16.1.1,
16.1.3, 16.1.4, 16.1.5, 16.1.6, and 16.1.7) where such failure continues for a
period of thirty (30) days after written notice from Landlord; provided,
however, if the nature of the default is such that more than thirty (30) days
are reasonably required for its cure, Tenant shall not be deemed to be in
default if Tenant promptly commences the cure within ten (10) days after receipt
of notice and diligently and continuously prosecutes such cure to completion;

                  16.1.3 The making of a general assignment by Tenant for the
benefit of creditors; the filing of a voluntary petition by Tenant or the filing
of an involuntary petition by any of Tenant's creditors seeking the
rehabilitation, liquidation or reorganization of Tenant under any law relating
to bankruptcy, insolvency or other relief of debtors and, in the case of an
involuntary action, the failure to remove or discharge the same within ninety
(90) days of such filing; the appointment of a receiver or other custodian to
take possession of substantially all of Tenant's assets or this leasehold;
Tenant's insolvency or inability to pay Tenant's debts or failure generally to
pay Tenant's debts when due; any court entering a decree or order directing the
winding up or liquidation of Tenant or of substantially all of Tenant's assets;
Tenant's taking any action toward the dissolution or winding up of Tenant's
affairs; the cessation or suspension of Tenant's use of the Premises; or the
attachment, execution or other judicial seizure of substantially all of Tenant's
assets or this leasehold;



                                      -20-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   29

                  16.1.4 Knowingly making any material misrepresentation by
Tenant or any successor-in-interest of Tenant in any materials delivered by or
on behalf of Tenant to Landlord or any Mortgagee pursuant to this Lease;

                  16.1.5 Tenant's failure to comply with the provisions
contained in Section 19; r

                  16.1.6 Any assignment by Tenant of its interest in this Lease
or sublease by Tenant of all or any portion of the Premises in violation of the
provisions contained in Section 18; or

                  16.1.7 Tenant's failure to deliver the Letter of Credit by May
15, 2001, which failure is not cured within five (5) days following written
notice thereof to Tenant.

         16.2 Notice. Any notice required to be given by Landlord under this
Lease in connection with a default by Tenant hereunder shall be in lieu of, and
not in addition to, any notice required under Section 13-40.104 of the Colorado
Revised Statutes (1999). Tenant shall pay to Landlord the amount of Five Hundred
Constant Dollars ($500.00) for each notice of default given to Tenant under this
Lease, which is the amount the parties reasonably estimate will compensate
Landlord for the cost of giving such notice of default.

         16.3 Remedies. Upon the occurrence of any Event of Default, if such
Event of Default has not been cured within any applicable grace or cure periods
provided hereunder, Landlord shall have all rights and remedies available at law
and/or in equity, including the following:

                  16.3.1 Termination. Landlord shall have the right to terminate
this Lease by written notice to Tenant and, on the date specified in such
notice, this Lease shall terminate.

                           16.3.1.1 Repossession. Following termination, without
prejudice to other remedies Landlord may have, Landlord may: (i) reenter the
Premises upon voluntary surrender by Tenant or remove Tenant therefrom and any
other persons occupying the Premises, using such legal proceedings as may be
available; (ii) repossess the Premises or relet the Premises or any part thereof
for such term (which may be for a term extending beyond the Term), at such
rental and upon such other terms and conditions as Landlord in Landlord's sole
discretion shall determine, with the right to make reasonable alterations and
repairs to the Premises; and/or (iii) remove all personal property therefrom.

                           16.3.1.2 Unpaid Rent. Upon such termination, Landlord
shall have all the rights and remedies of a landlord provided by Applicable Law,
including the right to recover from Tenant: (i) the worth, at the time of award,
of the unpaid Rent that had been earned at the time of termination, (ii) the
worth, at the time of award, of the amount by which the unpaid Rent that would
have been earned after the date of termination until the time of award exceeds
the amount of loss of rent that Tenant proves could have been reasonably
avoided, (iii) the worth, at the time of award, of the amount by which the
unpaid Rent for the balance of the Term after the time of award exceeds the
amount of the loss of rent that Tenant proves could have been reasonably
avoided, and (iv) any other amount, and court costs, necessary to compensate
Landlord for all detriment proximately caused by Tenant's default. The phrase
"worth, at the time of award," as used in (i) and (ii) above, shall be computed
at the Applicable Interest Rate, and as used in (iii) above, shall be computed
by discounting such amount at the discount rate of the Federal Reserve Bank of
San Francisco at the time of award plus one percent (1%).

                  16.3.2 Continuation. Even though an Event of Default may have
occurred, this Lease shall continue in effect for so long as Landlord does not
terminate Tenant's right to possession; and Landlord may enforce all of
Landlord's rights and remedies under this Lease, including the right to recover
Rent as it becomes due. Landlord, without terminating this Lease, may, during
the period Tenant is in default, enter the Premises and relet the same, or any
portion thereof, to third parties for Tenant's account and Tenant shall be
liable to Landlord for all costs Landlord incurs in reletting the Premises,
including, without limitation, brokers' commissions, expenses of repairing any
damage in the Premises (beyond ordinary wear and tear), remodeling the Premises
and like costs to the extent such costs relate to the remainder of the Term
hereunder, less any excess Rent or other consideration received or to be
received by Landlord in connection with such reletting over the Rent otherwise
due and owing from Tenant hereunder. Reletting may be for a period shorter or
longer than the remaining Term. Tenant shall continue to pay the Rent on the
date the same is due provided that Landlord shall credit Tenant's account for
all amounts received directly by Landlord in connection with such reletting
(less Landlord's expenses incurred in connection with such reletting), which
credits Landlord may apply monthly or otherwise and which credits may be
reflected on invoices to Tenant for remaining amounts due or may be reflected in
a lump sum payment to Tenant within thirty (30) days after the termination of
this Lease. No act by Landlord hereunder, including acts of maintenance,
preservation or efforts to lease the Premises or the appointment of a receiver
upon application of Landlord to protect Landlord's interest under this Lease,
shall terminate this Lease unless Landlord notifies Tenant that Landlord elects
to terminate this Lease. If Landlord relets the Premises, the rent that Landlord
receives from reletting shall be applied to the payment of, first, any
indebtedness from Tenant to Landlord under this Lease (other than Base Rent,



                                      -21-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   30

Tenant's Percentage Share of Operating Expenses and Tenant's Percentage Share of
Real Property Taxes); second, all costs, including maintenance, incurred by
Landlord in reletting as provided herein; and, third, Base Rent and Tenant's
Percentage Share of Operating Expenses and Tenant's Percentage Share of Real
Property Taxes under this Lease. After deducting the payments referred to above,
any sum remaining from the rental Landlord receives from reletting shall be held
by Landlord and applied in payment of future Rent as Rent becomes due under this
Lease. In no event, and notwithstanding anything in this Section 16 to the
contrary, shall Tenant be entitled to any excess rent received by Landlord. If,
on the date Rent is due under this Lease, the rent received from the reletting
is less than the Rent due on that date, Tenant shall pay to Landlord, in
addition to the remaining Rent due, all costs, including maintenance, which
Landlord incurred in reletting the Premises that remain after applying the rent
received from reletting as provided hereinabove. So long as this Lease is not
terminated, Landlord shall have the right to remedy any default of Tenant, to
maintain or improve the Premises, to cause a receiver to be appointed to
administer the Premises and new or existing subleases and to add to the Rent
payable hereunder all of Landlord's reasonable costs in so doing, with interest
at the Applicable Interest Rate from the date of such expenditure.

         16.4 Cumulative. Each right and remedy of Landlord provided for herein
or now or hereafter existing at law, in equity, by statute or otherwise shall be
cumulative and shall not preclude Landlord from exercising any other rights or
remedies provided for in this Lease or now or hereafter existing at law or in
equity, by statute or otherwise. No payment by Tenant of a lesser amount than
the Rent nor any endorsement on any check or letter accompanying any check or
payment as Rent shall be deemed an accord and satisfaction of full payment of
Rent; and Landlord may accept such payment without prejudice to Landlord's right
to recover the balance of such Rent or to pursue other remedies.

         16.5 Mitigation of Damages. Notwithstanding anything to the contrary
contained in this Lease, Landlord shall, but only as may be required under
Applicable Law, make commercially reasonable efforts to mitigate its damages in
case of any Event of Default by Tenant.

17. DEFAULT BY LANDLORD. Landlord shall not be in default under this Lease
unless Landlord fails to perform an obligation required of Landlord within
thirty (30) days after written notice by Tenant to Landlord and to each
Mortgagee of which Tenant has received prior written notice, specifying the
nature of the alleged default; provided, however, that if the nature of the
obligation is such that more than thirty (30) days are required for performance,
then Landlord shall not be in default if Landlord commences performance within
such thirty (30) day period and thereafter diligently prosecutes the same to
completion. Tenant agrees to give each Mortgagee, at the same time Tenant
delivers written notice to Landlord, by registered or certified mail or
nationally recognized overnight delivery service, a copy of any notice of
default served upon Landlord by Tenant, provided that, prior to such notice,
Tenant has been notified in writing (by way of service on Tenant of a copy of
assignment of rents and leases or otherwise) of the address of such Mortgagee.
Tenant further agrees that if Landlord shall have failed to cure such default
within thirty (30) days after such notice to Landlord (or if such default cannot
be cured or corrected within that time, then such additional time as may be
necessary if Landlord has commenced within such thirty (30) day period and is
diligently pursuing the remedies or steps necessary to cure or correct such
default), then any Mortgagee shall have an additional thirty (30) days within
which to cure or correct such default (or if such default cannot be cured or
corrected within that time, then such additional time as may be necessary if
such Mortgagee has commenced within such thirty (30) day period and is
diligently pursuing the remedies or steps necessary to cure or correct such
default). Notwithstanding the foregoing, in no event shall any Mortgagee have
any obligation to cure any default of Landlord. "MORTGAGEE" shall mean the
holder of any mortgage or deed of trust secured by the Building or the real
property on which the Building is located, the master lessor under any master
lease affecting the Building or the real property on which the Building is
located, and/or the ground lessor under any ground lease affecting the Building
or the real property on which the Building is located. If any event of default
by Landlord has not been cured within the time periods provided for herein,
Tenant shall have all rights and remedies afforded under Applicable Law in
connection therewith.

18. ASSIGNMENT AND SUBLETTING.

         18.1 Landlord's Consent Required. Except as otherwise provided herein,
Tenant may not voluntarily or by operation of law, sell, assign or otherwise
transfer all or any part of its interest in or rights with respect to the
Premises or its leasehold or subleasehold estate hereunder (collectively,
"ASSIGNMENT"), or (subject to Section 18.9 below) permit all or any portion of
the Premises to be occupied by anyone other than itself, its employees, agents,
and contractors, or sublet all or any portion of the Premises (collectively,
"SUBLETTING") without Landlord's prior written consent in each instance, which
shall not be unreasonably withheld, conditioned or delayed. Any sale or transfer
of Tenant's stock or other securities through any initial public offering or on
any nationally-recognized stock exchange shall not be deemed an Assignment or
Subletting hereunder. Under no circumstances shall Tenant mortgage, encumber,
pledge or hypothecate this Lease or any interest in the Premises. Without
limiting the circumstances in which it may be reasonable for Landlord to
withhold its consent to an Assignment or Subletting, Landlord and Tenant
acknowledge that it shall be reasonable for Landlord to withhold its



                                      -22-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   31

consent in the following instances: (i) the proposed assignee or subtenant is a
governmental agency; (ii) the use of the Premises by the proposed assignee or
subtenant would not be permitted under this Lease, would entail any alterations
which would lessen the value of the leasehold improvements in the Premises,
would require increased services by Landlord or would violate any Applicable
Law; (iii) the financial condition of the proposed assignee or subtenant does
not meet the credit standards applied by Landlord for other tenants under leases
in the Project with comparable terms; (iv) the Premises, or the relevant part
thereof, will be used in a manner that will violate any negative covenant as to
use contained in any other lease of space in the Building or Project; (v)
Landlord has experienced previous defaults by or is in litigation with the
proposed assignee or subtenant; (vi) the proposed assignment or sublease
involves a party who is a tenant in the Building or Project or involves a party
with whom Landlord has negotiated for other space in the Building or Project
within the six (6) months immediately preceding Tenant's notice to Landlord of a
proposed Assignment or Subletting; (vii) Tenant is in default of any obligation
of Tenant under this Lease, or Tenant has defaulted under this Lease on two (2)
or more occasions during the Term; or (viii) in the case of a Subletting of less
than the entire Premises, if the Subletting would result in the division of the
Premises into more than two subparcels or would require access to be provided
through space leased or held for lease to another tenant or improvements to be
made outside of the Premises.

         18.2 General Provisions. The merger of Tenant with any other entity or
the transfer of any controlling or managing ownership or beneficial interest in
Tenant (as a consequence of a single transaction or a number of multiple
transactions), or the assignment or sale of a substantial portion of the assets
of Tenant, whether or not located at the Premises, that does not satisfy the
requirements of Section 18.8, shall constitute an Assignment hereunder. Except
in the event Landlord elects to terminate this Lease pursuant to Section 18.4
below, no Assignment or Subletting by Tenant shall relieve Tenant or any
guarantor of any obligation under this Lease, including Tenant's obligation to
pay Rent hereunder, and Tenant shall continue to be liable as a principal and
not as a guarantor or surety to the same extent as though no Assignment or
Subletting had been made. Any purported Assignment or Subletting contrary to the
provisions of this Lease without Landlord's prior written consent shall be null
and void and shall constitute an Event of Default hereunder. The consent by
Landlord to any Assignment or Subletting shall not constitute a waiver of the
necessity of obtaining Landlord's consent to any subsequent Assignment or
Subletting. Landlord may consent to any subsequent Assignment or Subletting, or
any amendment to or modification of this Lease with the assignees of Tenant,
without notifying Tenant or any successor of Tenant, and without obtaining its
or their consent thereto, and such action shall not relieve Tenant or any
successor of Tenant of any liability under this Lease but such action shall in
no event materially increase Tenant's obligations hereunder.

         18.3 Information to be Furnished. If Tenant desires to assign this
Lease or sublet any or all of the Premises, Tenant shall give Landlord written
notice thereof with copies of all documents and agreements associated with the
Assignment or Subletting, including without limitation, the name and address of
the proposed assignee or subtenant, the nature of the business proposed to be
carried on in the Premises, the effective date of the Assignment or Subletting
(the "TRANSFER EFFECTIVE DATE"), and such financial statements and other
documents as Landlord may reasonably require, not later than forty-five (45)
days prior to the anticipated effective date of the Assignment or Subletting.
Tenant shall pay Landlord's reasonable attorneys' fees incurred in the review of
such documentation, not to exceed Two Thousand Five Hundred Constant Dollars
($2,500.00). Tenant shall also pay, in advance, an administrative fee of Five
Hundred Constant Dollars ($500.00) for each proposed transfer.

         18.4 Landlord's Election. At any time within fifteen (15) days after
Landlord's receipt of Tenant's notice of its proposed Assignment or Subletting
and the information specified in Section 18.3, Landlord may, by written notice
to Tenant, elect to (i) consent to the proposed Assignment or Subletting by
Tenant or (ii) reasonably withhold its consent to the proposed Assignment or
Subletting by Tenant (however, if the foregoing fifteen (15) day period will
expire prior to the expiration of the thirty (30) day period following Tenant's
delivery of the Intention to Transfer Notice pursuant to the following
paragraph, then such fifteen (15) day period shall be extended to be coterminous
with such thirty (30) day period). If Landlord fails to notify Tenant in writing
of such election, Landlord shall be deemed to have disapproved of such
Assignment or Subletting. Notwithstanding anything to the contrary contained
herein, if Tenant claims that Landlord has unreasonably withheld or delayed its
consent under this Section 18 or otherwise has breached or acted unreasonably
under this Section 18, Tenant's sole remedies shall be a declaratory judgment
and an injunction for the relief sought without monetary damages, and Tenant
hereby waives all other remedies, including, without limitation, any right at
law or equity to terminate this Lease.

         Notwithstanding anything to the contrary contained in this Section
18.4, if Tenant contemplates a proposed Assignment of its entire interest in
this Lease or the Subletting of the entire Premises, then



                                      -23-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   32

Tenant shall give Landlord notice (the "INTENTION TO TRANSFER NOTICE") of such
contemplated transfer (whether or not the contemplated transferee or the terms
of such contemplated transfer have been determined). The Intention to Transfer
Notice shall specify the contemplated date of commencement of the contemplated
transfer, which shall not be earlier than thirty (30) days following Landlord's
receipt of the Intention to Transfer Notice (the "CONTEMPLATED EFFECTIVE DATE").
Thereafter, Landlord shall have the option, by giving written notice to Tenant
within thirty (30) days after Landlord's receipt of the Intention to Transfer
Notice, to terminate this Lease and release Tenant and any guarantor hereunder
from all obligations first occurring under this Lease as of the Contemplated
Effective Date (except those obligations that expressly survive the expiration
or earlier termination of this Lease). If Landlord declines, or fails to elect
in a timely manner to terminate this Lease under this Section 18.4 within such
thirty (30) day period, then, provided Landlord has consented to the proposed
transfer, Tenant shall be entitled to proceed with the proposed transfer and
Landlord shall not have any right to recapture with respect to any transfer
thereof consummated within a period of six (6) months (the "SIX MONTH PERIOD")
commencing on the expiration of such thirty (30) day period; provided, however,
that any such transfer shall be subject to other terms of this Section 18. If
such a transfer is not so consummated within the Six Month Period (or if a
transfer is so consummated, then upon the expiration of the term of any transfer
consummated within such Six Month Period), Tenant shall again be required to
submit a new Intention to Transfer Notice to Landlord with respect to any
proposed Assignment of its entire interest in this Lease or any Subletting of
the entire Premises.

         18.5 Termination. If Landlord elects to terminate this Lease pursuant
to Section 18.4 above, this Lease shall terminate effective as of the
Contemplated Effective Date and Tenant and any guarantor shall be released from
all obligations first accruing under the Lease as of such Contemplated Effective
Date (except those obligations that expressly survive the expiration or earlier
termination of this Lease).

         18.6 Bonus Rental. If Tenant receives rent or other consideration in
connection with any Assignment or Subletting in excess of the Rent, or in case
of the Subletting of a portion of the Premises, in excess of such Rent that is
fairly allocable to such portion (after deducting the reasonable expenses
incurred by Tenant for (1) any changes, alterations or improvements to the
Premises paid for by Tenant in connection with the transfer, (2) any other
out-of-pocket monetary concessions provided by Tenant to the transferee, and (3)
any brokerage commissions and/or reasonable attorneys' fees paid for by Tenant
in connection with the transfer), Tenant shall pay Landlord fifty percent (50%)
of the difference between each such payment of rent or other consideration and
the Rent required hereunder. If Tenant is in default hereunder, Landlord may,
without waiving any rights or remedies, collect rent from the subtenant or
occupant and apply the net amount collected to the Rent herein reserved and
apportion any excess rent so collected in accordance with the terms of the
preceding sentence.

         18.7 Executed Counterparts. No permitted Assignment or Subletting shall
be effective until there has been delivered to Landlord a written counterpart of
the assignment agreement or sublease reasonably satisfactory in form and
substance to Landlord in which the assignee or subtenant agrees to be and remain
jointly and severally liable with Tenant for the payment of Rent pertaining to
the Premises and for the performance of all the terms and provisions of this
Lease relating thereto arising on or after the date of the Assignment or
Subletting.

         18.8 Permitted Transfers. The term "AFFILIATE" shall mean (i) any
entity that is controlled by, controls or is under common control with, Tenant
or (ii) any entity that merges with, is acquired by, or acquires Tenant through
the purchase of stock or assets, and where the net worth of such entity (as to
(i) above) and the net worth of the surviving entity (as to (ii) above) as of
the date such transfer or transaction, as applicable, is completed is not less
than [*] Constant Dollars [*], except in the event of any transaction pursuant
to (ii) above in which (a) Tenant is not the surviving entity, and (b) the net
worth of the surviving entity is less than Tenant's net worth immediately prior
to such transaction calculated under generally accepted accounting principles,
in which case the net worth of the surviving entity as of the date such
transaction is completed shall not be less than [*] Constant Dollars [*].
Notwithstanding anything to the contrary contained in this Section 18, an
Assignment or Subletting of all or a portion of the Premises to an affiliate
("AFFILIATE") of Tenant shall not be deemed a transfer requiring Landlord's
consent under this Section 18, provided that (1) Tenant notifies Landlord of any
such assignment or sublease and promptly supplies Landlord with any documents or
information requested by Landlord regarding such assignment or sublease or such
Affiliate (including evidence of the assignee's assumption of Tenant's
obligations under this Lease in the event of an assignment), (2) such assignment
or sublease is not a subterfuge by Tenant to avoid its obligations under this
Lease, and (3) such assignment or sublease does not cause Landlord to be in
default under any existing lease at the Building or Project. An assignee of
Tenant's entire interest in this Lease pursuant to the immediately preceding
sentence may be referred to herein as an "AFFILIATED ASSIGNEE." "CONTROL," as
used in this Section 18.8, shall mean the ownership, directly or indirectly, of
greater than fifty percent (50%) of the voting securities of, or possession of
the right to vote, in the ordinary direction of its affairs, of greater than
fifty percent (50%) of the voting interest in, an entity



                                      -24-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   33

         18.9 Permitted Occupants. Notwithstanding the provisions of Section
18.1 above, Tenant may allow any Affiliate, or any person or company that is an
agent or contractor of Tenant to occupy certain portions of the Premises for the
primary purpose of furthering the business conducted by Tenant at the Premises
without such occupancy being deemed an Assignment or Subletting and without
Landlord's consent (for purposes of this Section 18.9 each such person or
company is referred to as an "OCCUPANT"), provided the following conditions are
satisfied: (a) such occupancy is not a subterfuge to avoid the provisions of
Section 18.1 concerning an Assignment or Subletting; (b) Tenant shall have
provided Landlord with the name and address of the Occupant and a copy of the
agreement, if any, under which such Occupant is occupying the Premises prior to
such Occupant's occupancy of the Premises; and (c) the aggregate amount of
rentable square feet occupied by all Occupants in the Premises does not, at any
one time, exceed twenty percent (20%) of the total rentable square feet in the
Premises. If an occupancy does not satisfy all of the foregoing conditions, then
such occupancy shall constitute a Subletting and shall be subject to the
provisions of Section 18.1.

19. ESTOPPEL, ATTORNMENT AND SUBORDINATION.

         19.1 Estoppel. Within ten (10) days after request by Landlord, Tenant
shall deliver to any Mortgagee, proposed Mortgagee, proposed purchaser and/or
Landlord an estoppel certificate duly executed (and acknowledged if required by
Landlord or any Mortgagee, proposed Mortgagee or proposed purchaser), in the
form attached hereto as Exhibit E, or in such other form as may be reasonably
acceptable to any existing or proposed Mortgagee or purchaser which form may
include some or all of the provisions contained in Exhibit E, to the extent the
certifications contained in such form are true and within the knowledge of
Tenant. Tenant's failure to deliver said statement in such time period shall be
an Event of Default hereunder unless Tenant delivers such statement within five
(5) days after Landlord's written notice to Tenant of such failure, and shall be
conclusive upon Tenant that (i) this Lease is in full force and effect, without
modification except as may be represented by Landlord; (ii) there are no uncured
defaults in Landlord's performance and Tenant has no right of offset,
counterclaim or deduction against Rent hereunder; and (iii) no more than one
month's Base Rent has been paid in advance. If any Mortgagee or proposed
Mortgagee should require that this Lease be amended (except as will materially
and adversely affect the rights of Tenant), Landlord shall give written notice
thereof to Tenant and Tenant shall, within ten (10) days after the receipt of
Landlord's notice, execute and deliver to Landlord the required Lease amendment.

         19.2 Subordination. This Lease shall be subject and subordinate to all
present and future ground leases, master leases and underlying leases, and to
the lien of all mortgages, deeds of trust and other encumbrances now or
hereafter in force against the Building, or any part thereof, or Landlord's
interest therein, and to all renewals, extensions, modifications, consolidations
and replacements thereof, and to all advances made or hereafter to be made upon
the security of such mortgages, deeds of trust or other encumbrances, all
without the necessity of Tenant's executing any further instrument to effect
such subordination, unless the holders of such mortgages, deeds of trust or
other encumbrances, or the lessors under such ground leases, master leases or
underlying leases, require that this Lease be superior thereto. Landlord's
interest herein may be assigned as security at any time to any lienholder.
Tenant shall, within ten (10) days following request by Landlord, execute such
further instruments or assurances as Landlord may reasonably deem necessary or
as may be reasonably required by any Mortgagee or proposed Mortgagee to evidence
or confirm the subordination or superiority of this Lease to any such mortgages,
deeds of trust, ground leases, master leases or underlying leases, Tenant's
failure to deliver said documentation in such time period shall be an Event of
Default hereunder. As a condition precedent to this Lease being subject and
subordinate to any future ground leases, master leases and underlying leases,
and to the lien of any future mortgages, deeds of trust and other encumbrances
hereafter in force against the Building, Landlord shall have delivered to Tenant
a commercially reasonable non-disturbance agreement in favor of Tenant.

         19.3 Attornment. Tenant hereby agrees that Tenant will recognize as its
landlord under this Lease, and shall attorn to, any person succeeding to the
interest of Landlord in the Building or the land upon which the Building is
located upon any foreclosure of any mortgage or deed of trust upon the Building
or the land upon which the Building is located, upon the execution of any deed
in lieu of foreclosure with respect to any deed of trust encumbering the
Building or such land, or upon the expiration or termination of any ground
lease, master lease or underlying lease encumbering the Building or such land,
if requested to do so by such successor or lienholder or ground lessor, master
lessor or underlying lessor. If requested, Tenant shall execute and deliver a
commercially reasonable instrument or instruments confirming its attornment as
provided for herein. Notwithstanding anything to the contrary contained herein,
as a condition precedent to Tenant's agreement to attorn to any holder of a
superior ground lease, master lease, underlying lease, mortgage, deed of trust
or other encumbrance, Tenant shall have received a commercially reasonable
non-disturbance agreement in favor of Tenant.

20. RELOCATION. Landlord shall have the right, upon reasonable prior notice to
Tenant, to require Tenant to relocate the Premises to other substantially
similar premises in the Building designated by Landlord. If such relocation
becomes necessary, Landlord agrees that it will pay Tenant's reasonable



                                      -25-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   34

expenses for architectural fees and construction costs to build tenant
improvements comparable to those located in the original Premises; and
relocation of Tenant's fixtures and equipment, telephone and utility services.
Landlord and Tenant agree to adjust the rental, to the extent necessary, to
reflect any increase or decrease in the aggregate number of rentable square feet
contained in such substitute premises. Notwithstanding anything to the contrary
contained herein but provided that (a) Tenant leases and occupies space in the
Building that contains at least one-half (1/2) the number of rentable square
feet as Tenant initially leases hereunder (as such initial square footage number
may be adjusted pursuant to Section 2.1 above) and (b) Tenant has a net worth,
as determined in accordance with generally accepted accounting principles, of at
least [*] Constant Dollars [*], Landlord shall not exercise its relocation right
under this section 20 as to the original Tenant or an Affiliated Assignee
hereunder only (i.e., Landlord's covenant to not relocate the original Tenant,
provided the conditions of this Section 20(a) and (b) above are met, shall be
personal to the original Tenant and may not be assigned or otherwise transferred
except to an Affiliated Assignee and any other transfer of Tenant's interest
shall be subject to Landlord's right to relocate the Tenant under this Section
20).

21. MISCELLANEOUS.

         21.1 General.

                  21.1.1 Entire Agreement. This Lease and the Exhibits hereto
set forth all the agreements between Landlord and Tenant concerning the Premises
and there are no agreements either oral or written other than as set forth
herein.

                  21.1.2 Time of Essence. Time is of the essence of this Lease.

                  21.1.3 Attorneys' Fees. In any action or proceeding which
either party brings against the other to enforce its rights hereunder, the
unsuccessful party shall pay all costs incurred by the prevailing party,
including reasonable attorneys' fees, which amounts shall be a part of the
judgment in said action or proceeding.

                  21.1.4 Severability. If any provision of this Lease or the
application of any such provision shall be held by a court of competent
jurisdiction to be invalid, void or unenforceable to any extent, the remaining
provisions of this Lease and the application thereof shall remain in full force
and effect and shall not be affected, impaired or invalidated.

                  21.1.5 Law. This Lease shall be construed and enforced in
accordance with the laws of the State of Colorado.

                  21.1.6 No Option. Submission of this Lease to Tenant for
examination or negotiation does not constitute an option to lease, offer to
lease or a reservation of, or option for, the Premises. This document shall
become effective and binding only upon the execution and delivery hereof by
Landlord and Tenant.

                  21.1.7 Successors and Assigns. This Lease shall be binding
upon and inure to the benefit of the successors and assigns of Landlord and
shall be binding upon and, subject to compliance with the terms of Section 18,
inure to the benefit of the successors and assigns of Tenant.

                  21.1.8 Third Party Beneficiaries. Nothing herein is intended
to create any third party beneficiaries.

                  21.1.9 Memorandum of Lease. Tenant shall not record this Lease
or a short form memorandum hereof.

                  21.1.10 Agency, Partnership or Joint Venture. Nothing
contained herein nor any acts of the parties hereto shall be deemed or construed
by the parties hereto, nor by any third party, as creating the relationship of
principal and agent or of partnership or of joint venture by the parties hereto
or any relationship other than the relationship of landlord and tenant.

                  21.1.11 Merger. The voluntary or other surrender of this Lease
by Tenant or a mutual cancellation thereof or a termination by Landlord shall
not constitute a merger and shall, at the option of Landlord, terminate all or
any existing subtenancies or may, at the option of Landlord, operate as an
assignment to Landlord of any or all of such subtenancies.

                  21.1.12 Headings. Section headings have been inserted solely
as a matter of convenience and are not intended to define or limit the scope of
any of the provisions contained therein.

         21.2 Waiver. No waiver of any default or breach hereunder shall be
implied from any omission to take action on account thereof, notwithstanding any
custom and practice or course of dealing. No waiver by either party of any
provision of this Lease shall be effective unless in writing and signed by



                                      -26-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   35

such party. No waiver shall affect any default other than the default specified
in the waiver and then such waiver shall be operative only for the time and to
the extent therein stated. Waivers of any covenant shall not be construed as a
waiver of any subsequent breach of the same covenant.

         21.3 Financial Statements. Tenant shall provide to any Mortgagee,
purchaser, potential Mortgagee or purchaser, and/or Landlord, within ten (10)
days after request, a current, accurate, certified financial statement for
Tenant and Tenant's business prepared under generally accepted accounting
principles consistently applied and such other certified financial information
or tax returns as may be reasonably requested by Landlord, any existing or
proposed Mortgagee, and/or any purchaser or any lender of such purchaser;
provided, however, that Landlord may not request such information from Tenant
more than once in any calendar year (except as may be more frequently required
in connection with any sale or financing of the Building or Project). Further,
with regard to any such financial statements and related documents conspicuously
marked "confidential" by Tenant, Landlord agrees to use commercially reasonable
efforts to prevent disclosure of any financial statements and related documents
so marked to parties other than (a) Landlord's employees, agents, outside
financial or legal consultants, Mortgagee(s) and/or lender(s) who have a
reasonable need to access such financial statements or related documents, (b)
any prospective purchasers of the Building or Project and their employees,
agents, financial or legal consultants, and/or lender(s) who have a reasonable
need to access such financial statements or related documents or (c) as required
by Applicable Laws. In no event shall Tenant be required to disclose any
information or statements in violation of applicable securities laws or other
Applicable Laws and in no event shall Landlord be liable to Tenant in connection
with any "confidential" information provided to Landlord by Tenant.

         21.4 Limitation of Liability. The obligations of Landlord under this
Lease are not personal obligations of the individual members, managers,
partners, directors, officers, shareholders, agents or employees of Landlord and
Tenant shall look solely to Landlord's interest in the Building (including,
without limitation, any insurance proceeds, condemnation proceeds, accounts,
claims, causes of action, personal property, contracts, leases, and other assets
of Landlord solely related to the Building or Project) for satisfaction of any
liability of Landlord and shall not look to other assets of Landlord nor seek
recourse against the assets of the individual members, managers, partners,
directors, officers, shareholders, agents or employees of Landlord. Whenever
Landlord transfers its interest in the Building, provided that the transferee of
Landlord's interest agrees in writing to be bound by all of the terms and
conditions of the Lease arising after the date of the transfer, Landlord shall
be automatically released from further performance under this Lease arising from
and after the date of transfer and from all further liabilities and expenses
hereunder arising from and after the date of transfer, and the transferee of
Landlord's interest shall assume all liabilities and obligations of Landlord
hereunder arising from and after the date of such transfer. Nothing contained
herein shall be construed to release Landlord from liabilities hereunder that
accrued or that arose prior to the date of any such transfer.

         21.5 Notices. All notices to be given hereunder shall be in writing and
sent via a method capable of being traced (mailed postage prepaid by USPS
certified or registered mail, return receipt requested, or delivered by a
nationally-recognized overnight delivery service (e.g., Federal Express, UPS)),
or sent by facsimile, electronically confirmed (immediately followed by one of
the preceding methods), to Landlord's Address and Tenant's Address set forth in
the Basic Lease Information or to such other place as Landlord or Tenant may
designate in a written notice given to the other party or, in the case of
Tenant, delivered to Tenant at the Premises. Notices shall be deemed served upon
the first attempted delivery by the U.S. Postal Service, the courier or a
nationally recognized overnight delivery service, or upon receipt of the
facsimile before 5 p.m. on any business day, or, if receipt is after 5 p.m., on
the next business day.

         21.6 Commission. Landlord shall pay a brokerage commission to Tenant's
Broker specified in the Basic Lease Information in accordance with a separate
agreement between Landlord and Tenant's Broker. Landlord shall have no further
or separate obligation for payment of any commissions or fees to any other
broker or finder. Subject to the first sentence of this Section 21.6, Tenant
agrees to indemnify and hold harmless Landlord from any claims, including
reasonable attorneys' fees, in connection with a claim by any person for a real
estate broker's commission, finder's fee or other compensation based upon any
statement, representation or agreement of Tenant, and Landlord agrees to
indemnify and hold Tenant harmless from any such claims or liability, including
reasonable attorneys' fees, based upon any statement, representation or
agreement of Landlord.

         21.7 Authorization. Each individual executing this Lease on behalf of
the respective parties represents and warrants that to the best of his or her
respective knowledge, he or she is duly authorized to execute and deliver this
Lease on behalf of such party and that such execution is binding upon such
party.

         21.8 Holding Over/Surrender. If Tenant holds over the Premises or any
part thereof after expiration of the Term, such holding over shall be considered
to be at sufferance only, at a rent equal to (a) for the first thirty (30) days
after such expiration, the Base Rent in effect immediately preceding the
expiration and (b) thereafter, one hundred fifty percent (150%) of the Base Rent
in effect immediately



                                      -27-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   36

preceding the expiration and shall otherwise be on all the other terms and
conditions of this Lease. This paragraph shall not be construed as Landlord's
permission for Tenant to hold over. Acceptance of Rent by Landlord following
expiration or termination shall not constitute a renewal of this Lease or
extension of the Term except as specifically set forth above. If Tenant fails to
surrender the Premises upon expiration or earlier termination of this Lease,
Tenant shall indemnify and hold harmless Landlord from and against all loss or
liability proximately resulting from or arising out of Tenant's failure to
surrender the Premises, including, but not limited to, lost profits and any
amounts required to be paid to any tenant or prospective tenant who was to have
occupied the Premises after the expiration or earlier termination of this Lease
and any related attorneys' fees and brokerage commissions. Subject to the terms
and conditions hereof, upon the termination of this Lease or Tenant's right to
possession of the Premises, Tenant will surrender the Premises, together with
all keys, in good condition and repair, reasonable wear and tear excepted.
Conditions existing because of Tenant's failure to perform maintenance, repairs
or replacements shall not be deemed "reasonable wear and tear."

         21.9 Confidentiality. Tenant acknowledges that the economic terms of
this Lease are confidential information. Tenant shall use commercially
reasonable efforts to keep such confidential information strictly confidential
and shall not disclose such confidential information to any person or entity
other than (a) Tenant's Architect, Tenant's financial, legal and space planning
consultants and any proposed subtenants or assignees and/or (b) as may be
required by Applicable Laws.

         21.10 Covenants and Conditions. Each provision to be performed by a
party hereunder shall be deemed to be both a covenant and a condition.

         21.11 Use of Name, Filming and Photographs of Project. Tenant
acknowledges and agrees that the names Catellus, CirclePoint Corporate Center,
and all variations thereof, are proprietary to Landlord. Tenant shall not use
any such name or any variation thereof or identify Landlord in any promotional
advertising or other promotional materials to be disseminated to the public or
any portion thereof or use any trademark, service mark, trade name or symbol of
Landlord or that is associated with it, without Landlord's prior written
consent, which may be given or withheld in Landlord's sole discretion.
Notwithstanding the foregoing, Tenant may use the term "CirclePoint Corporate
Center" only to identify the location of the Premises. Further, Tenant shall not
film or photograph the Premises, Building or Project (or allow or permit any
third party to so film or photograph) without Landlord's prior written consent,
which, consent in Landlord's sole and absolute discretion, may be withheld, or
conditioned upon Tenant's payment of a fee.

         21.12 Force Majeure. If either party is delayed in the performance of
any obligation hereunder, except for the payment of money, by reason of a Force
Majeure Event, then the performance of the obligation shall be excused for the
period of the delay and the period for performing the obligation shall be
extended for a period equivalent to the period of the delay. Nothing contained
in this Section shall excuse Tenant from the obligation to pay Rent when due
without regard to the occurrence of any Force Majeure Event, or extend the
Commencement Date or the Rent Commencement Date. "FORCE MAJEURE EVENT" shall
mean and include any delay caused by fire, flood, inclement weather, strikes,
lockouts or other labor or industrial disturbance (whether or not on the part of
agents or employees of either party hereto engaged in the construction of the
Premises), civil disturbance, order of any government, court or regulatory body
claiming jurisdiction or otherwise, act of public enemy, war, riot, sabotage,
blockade, embargo or failure or inability to secure materials, supplies or labor
through ordinary sources by reason of shortages or priority that are beyond the
reasonable control of the party claiming the occurrence of a Force Majeure Event
or any other event that is beyond the reasonable control of the party claiming
the occurrence of a Force Majeure Event.

         21.13 Constant Dollars. Certain dollar amounts set forth in this Lease
are referred to as being Constant Dollars. The term "CONSTANT DOLLARS" shall
mean the present value of the dollars to which such phrase refers, and an
adjustment shall occur on each anniversary of the Commencement Date as
hereinafter set forth. Constant Dollars shall be determined by multiplying the
dollar amount to be adjusted by a fraction, the numerator of which is the
Current Index Number and the denominator of which is the Base Index Number (as
such terms are hereinafter defined). The "Base Index Number" shall be the level
of the Index (as hereinafter defined) for the calendar month in which the
Commencement Date occurs; the "Current Index Number" shall be the level of the
Index for the calendar month in which the adjustment is to take place; and the
"Index" shall be the Consumer Price Index - All Urban Consumers
(Denver-Boulder-Greeley, CO.) All Items Base 1982-84=100) or any successor index
thereto as hereinafter provided. If publication of the Index is discontinued, or
if the basis of calculating the Index is materially changed, then Landlord shall
substitute for the Index comparable statistics as computed by an agency of the
United States Government or, if none, by a periodical or publication of
recognized authority closely approximating the result which would have been
achieved by the Index.



                                      -28-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   37

         21.14 Development of the Project.

                  21.14.1 Subdivision. Tenant acknowledges that the Project has
been, or is in the process of being, subdivided. Landlord reserves the right to
further subdivide all or a portion of the Project. Tenant agrees to execute and
deliver, within ten (10) days after request by Landlord and in the form
reasonably requested by Landlord, any additional commercially reasonable
documents needed to conform this Lease to the circumstances resulting from a
subdivision and any all maps in connection therewith, provided Tenant shall not
be required to incur any unreasonable costs, undue burden or diminution of
Tenant's rights hereunder in connection therewith.

                  21.14.2 Multiple Ownership. If portions of the Project are
owned by an entity other than Landlord, Landlord, at its option, may enter into
an agreement with the owner or owners of such portion(s) to provide (i) for
reciprocal rights of access, use and/or enjoyment of the Project, (ii) for the
common management, operation, maintenance, improvement and/or repair of all or
any portion of the Project, (iii) for the allocation of Operating Expenses for
Common Facilities, and (iv) for any other matter which Landlord reasonably deems
necessary. Tenant agrees that this Lease shall be subordinate to any such
agreement, and agrees to execute and deliver, within ten (10) days after request
by Landlord, and in the form reasonably requested by Landlord, any additional
commercially reasonable documents designated by Landlord to further evidence the
subordination of this Lease to such agreement, provided Tenant shall not be
required to incur any unreasonable costs, undue burden or diminution of Tenant's
rights hereunder as a result thereof, and provided that no such document or
agreement shall have any material adverse effect on Tenant's use and enjoyment
of the Premises for the conduct of its business.

                  21.14.3 Construction of Project. Tenant acknowledges that
portions of the Project may be under construction following Tenant's occupancy
of the Premises, and that such construction may result in levels of noise, dust,
and obstruction of access, which are in excess of that present in a fully
constructed project. Provided that such levels of noise, dust, and obstruction
of access do not commercially unreasonably prevent or impair Tenant's ability to
use and enjoy the Premises for the conduct of its business, Tenant hereby waives
any and all Rent offsets or claims of constructive eviction which may arise in
connection with such construction, and further provided that Landlord shall take
all reasonable measures to minimize any interference or disruption to Tenant's
use of the Premises.

                  21.14.4 Site Plan. Tenant acknowledges that the purpose of the
site plan set forth on Exhibit A-2 is to show the general location of the
Building and other proposed improvements within the Project, and is not meant to
constitute an agreement, representation or warranty as to the precise location,
size or configuration of any of the improvements shown thereon, nor shall it
constitute an agreement, representation or warranty that any such improvements
will be constructed, except as otherwise expressly provided herein with respect
to Landlord's Work.

                  21.14.5 Expansion of Project. Tenant acknowledges that
Landlord may from time to time include within the Project additional land by
annexing the same into the CC&Rs, whereupon such annexed land will constitute a
portion of the Project.

         21.15 Communication Equipment. If Tenant desires to use the roof of the
Building to install communication equipment to be used from the Premises in
connection with Tenant's business at the Premises only, Tenant may so notify
Landlord in writing ("COMMUNICATION EQUIPMENT NOTICE"), which Communication
Equipment Notice shall generally describe the specifications for the equipment
desired by Tenant. If at the time of Landlord's receipt of the Communication
Equipment Notice, Landlord reasonably determines that space is available on the
roof of the Building for such equipment, then subject to all governmental laws,
rules and regulations, Tenant and Tenant's contractors (which shall first be
reasonably approved by Landlord) shall have the right and access to install,
repair, replace, remove, operate and maintain one (1) so-called "satellite dish"
or other similar device, such as antennae no greater than one (1) meter in
diameter, together with all cable, wiring, conduits and related equipment
(collectively, "COMMUNICATION EQUIPMENT"), for the purpose of receiving and
sending radio, television, computer, telephone or other communication signals,
at a location on the roof of the Building designated by Landlord. Landlord shall
have the right to require Tenant to relocate the Communication Equipment at any
time to another location on the roof of the Building reasonably approved by
Tenant. Tenant shall retain Landlord's designated roofing contractor to make any
necessary penetrations and associated repairs to the roof in order to preserve
Landlord's roof warranty. Tenant's installation and operation of the
Communication Equipment shall be governed by the following terms and conditions:

                  (a) Tenant's right to install, replace, repair, remove,
operate and maintain the Communication Equipment shall be subject to all
governmental laws, rules and regulations and Landlord makes no representation
that such laws, rules and regulations permit such installation and operation.

                  (b) All plans and specifications for the Communication
Equipment shall be subject to Landlord's reasonable approval.



                                      -29-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   38

                  (c) All costs of installation, operation and maintenance of
the Communication Equipment and any necessary related equipment (including,
without limitation, costs of obtaining any necessary permits and connections to
the Building's electrical system) shall be borne by Tenant.

                  (d) It is expressly understood that Landlord retains the right
to use the roof of the Building for any purpose whatsoever provided that
Landlord shall not unduly interfere with Tenant's use of the Communication
Equipment.

                  (e) Tenant shall use the Communication Equipment so as not to
cause any interference to other tenants in the Building or to other tenants of
the Building or with any other tenant's Communication Equipment, and not to
damage the Building or interfere with the normal operation of the Building.

                  (f) Landlord shall not have any obligations with respect to
the Communication Equipment. Landlord makes no representation that the
Communication Equipment will be able to receive or transmit communication
signals without interference or disturbance (whether or not by reason of the
installation or use of similar equipment by others on the roof of the Building)
and Tenant agrees that Landlord shall not be liable to Tenant therefor.

                  (g) Tenant shall (i) be solely responsible for any damage
caused as a result of the Communication Equipment, (ii) promptly pay any tax,
license or permit fees charged pursuant to any laws or regulations in connection
with the installation, maintenance or use of the Communication Equipment and
comply with all precautions and safeguards recommended by all governmental
authorities, and (iii) pay for all necessary repairs, replacements to or
maintenance of the Communication Equipment.

                  (h) The Communication Equipment shall remain the sole property
of Tenant. Tenant shall remove the Communication Equipment and related equipment
at Tenant's sole cost and expense upon the expiration or sooner termination of
this Lease or upon the imposition of any governmental law or regulation which
may require removal, and shall repair the Building upon such removal to the
extent required by such work of removal. If Tenant fails to remove the
Communication Equipment and repair the Building within fifteen (15) days after
the expiration or earlier termination of this Lease, Landlord may do so at
Tenant's expense. The provisions of this Section 21.15 shall survive the
expiration or earlier termination of this Lease.

                  (i) The Communication Equipment shall be deemed to constitute
a portion of the Premises for purposes of Section 9 of this Lease.

         IN WITNESS WHEREOF, the parties have executed this Lease as of the date
first set forth above.

"Landlord"                             CATELLUS DEVELOPMENT CORPORATION,
                                       a Delaware corporation

                                       By:  Catellus Commercial Group, LLC, a
                                            Delaware limited liability company
                                            Its: Agent

                                            By: /s/ Ted Antenucci
                                               ---------------------------------
                                               Name: Ted Antenucci
                                                    ----------------------------
                                               Its:  E.V.P.
                                                   -----------------------------

"Tenant"                               ALLOS THERAPEUTICS, INC.,
                                       a Delaware corporation

                                            By: /s/ Michael E. Hart
                                               ---------------------------------
                                               Name: Michael E. Hart
                                                    ----------------------------
                                               Its:  Chief Financial Officer and
                                                     Sr. VP, Operations
                                                   -----------------------------

                                            By:
                                               ---------------------------------
                                               Name:
                                                    ----------------------------
                                               Its:
                                                   -----------------------------



                                      -30-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   39

                                   EXHIBIT A-1

                                    PREMISES



                                  [FLOOR PLAN]



                                       -1-
<PAGE>   40

                                   EXHIBIT A-2

                                     PROJECT



                                  [FLOOR PLAN]



                                   EXHIBIT A-2
                                        1
<PAGE>   41

                                    EXHIBIT B

                                   WORK LETTER

         This Work Letter ("WORK LETTER") is attached to the Lease as Exhibit B
and incorporated into the Lease by reference. Capitalized terms used herein and
not defined herein shall have the respective meanings set forth in the Lease.

         1. Landlord's Work. Landlord shall arrange for the construction the
Building in the Project in accordance with the plans and specifications
described in Schedule 1, attached hereto and incorporated herein by reference
(collectively, "LANDLORD'S WORK"), which Landlord's Work shall include
construction of the lobby and restrooms located on the second (2nd) floor of the
Building, as further detailed on the plans attached hereto as Schedule 2.

         2. Tenant Improvements.

                  2.1 TI Allowance. Tenant shall be entitled to a one-time
tenant improvement allowance (the "TI ALLOWANCE") in the amount of [*] for the
costs relating to the initial design and construction of Tenant's improvements
that are permanently affixed to the Premises (the "TENANT IMPROVEMENTS"). In no
event shall Landlord be obligated to make disbursements pursuant to this Work
Letter in a total amount which exceeds the TI Allowance. Tenant shall not be
entitled to any credit for any unused portion of the TI Allowance. The parties
hereto agree that, in the event the number of rentable square feet of the
Premises is adjusted from 31,228 pursuant to Section 2.1 of the Lease, the TI
Allowance shall be reduced or increased (as the case may be) by the product of
(a) Twenty-Eight Dollars ($28.00) and (b) the difference between such adjusted
number of rentable square feet in the Premises and 31,228 (and in the event of
such increase or reduction, the parties shall promptly execute an amendment to
the Lease reflecting such adjusted TI Allowance amount).

                  2.2 Disbursement of the TI Allowance. Except as otherwise set
forth in this Work Letter, the TI Allowance shall be disbursed by Landlord (each
of which disbursements shall be made pursuant to Landlord's disbursement
process), only for the following items and costs (collectively, the "TI
ALLOWANCE ITEMS"): (a) payment of the fees of the "Architect" and the
"Engineers," as those terms are defined in Section 2.3 of this Work Letter
(including fees for one "test fit"), and payment of the fees incurred by, and
the cost of documents and materials supplied by, Landlord and Landlord's
consultants in connection with the preparation and review of the "Working
Drawings," as that term is defined in Section 2.3 of this Work Letter; (b) the
payment of plan check, permit and license fees relating to construction of the
Tenant Improvements; (c) the cost of construction of the Tenant Improvements;
(d) the cost of any changes in the base, shell and core of the Building when
such changes are required by the Working Drawings (including if such changes are
due to the fact that such work is prepared on an unoccupied basis) or are
otherwise required by Applicable Law as a result of the construction of the
Tenant Improvements, such cost to include all direct architectural and/or
engineering fees and expenses incurred in connection therewith; (e) the cost of
any changes to the Working Drawings or Tenant Improvements required by
Applicable Law; (f) sales and use taxes and/or applicable fees; (g) "Landlord's
Supervision Fee," as that term is defined in Section 2.10 of this Work Letter;
(h) all other costs to be expended by Landlord in connection with the
construction of the Tenant Improvements; and (i) one-half (1/2) of the costs of
the demising walls between the Premises and the Building's second (2nd) floor
lobby, which one-half (1/2) of the costs shall not exceed Four Thousand Dollars
($4,000.00). However, in no event shall more than Ninety Thousand Dollars
($90,000.00) of the TI Allowance be used for the items described in (a) above;
any additional amount incurred as a result of (a) above shall be deemed to
constitute an Over-Allowance Amount.

                  2.3 Building Specifications. Landlord may establish
specifications for the Building-standard components to be used in the
construction of the Tenant Improvements in the Premises (collectively, the
"BUILDING SPECIFICATIONS"), which shall be available to Tenant upon request.
Tenant shall utilize materials and finishes that comply with the Building
specifications and Tenant shall not substitute any such materials or finishes
without Landlord's prior written consent. Landlord may make changes to the
Building Specifications from time to time.

                           2.3.1 Selection of Architect/Working Drawings.
Conditioned upon Landlord's reasonable approval of a contract for services,
Tenant shall retain Gray Design (the "ARCHITECT") to prepare the "Working
Drawings," as that term is defined in this Section 2.3.1 below. Landlord shall
retain Landlord's designated engineering consultants (the "ENGINEERS") to
prepare all plans and engineering working drawings relating to the structural,
mechanical, HVAC/lifesafety, electrical, plumbing, and sprinkler work in the
Premises. The plans and drawings to be prepared by the Architect hereunder shall
be known collectively as the "WORKING DRAWINGS" and the plans and drawings to be
prepared by the Engineers hereunder shall be known collectively as the
"ENGINEERING DRAWINGS." Notwithstanding that Landlord has retained the Engineers
to prepare the Engineering Drawings and that

                                    EXHIBIT B
                                       -1-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



<PAGE>   42

Landlord shall review the Working Drawings required hereunder, Landlord shall
have no liability whatsoever in connection therewith and shall not be
responsible for any omissions or errors contained in the Working Drawings or the
Engineering Drawings.

                           2.3.2 Selection of Contractor. Landlord shall also
retain a contractor ("CONTRACTOR") designated by Landlord and reasonably
approved by Tenant to construct the Tenant Improvements. The Contractor shall
subcontract with Landlord's designated subcontractors for any and all
mechanical, electrical plumbing, HVAC/lifesafety, and sprinkler systems. Tenant
shall be permitted to participate with Landlord in the process of selecting the
Contractor; provided, however, that if Landlord and Tenant have not reasonably
agreed on the selection of the Contractor by May 1, 2001, such failure to agree
shall be deemed a Tenant Delay as further provided in Section 3.2 below.

                  2.4 Final Space Plan. Tenant and the Architect shall prepare
the final space plan for Improvements in the Premises (collectively, the "FINAL
SPACE PLAN"), which Final Space Plan shall include a layout and designation of
all offices, rooms and other partitioning, their intended use, and equipment to
be contained therein, and shall deliver the Final Space Plan to Landlord for
Landlord's approval or reasonable disapproval, which approval or reasonable
disapproval shall be delivered by Landlord to Tenant no later than five (5)
business days after Landlord's receipt of such Final Space Plan. If Landlord
reasonably disapproves of any portion of the Final Space Plan, the parties shall
meet, within five (5) days after Landlord's disapproval, to agree upon revisions
to be made to the Final Space Plan to meet the reasonable satisfaction of
Landlord. The Architect shall then revise the Final Space Plan to the form
agreed upon in such meeting and Landlord shall then approve or reasonably
disapprove the revised Final Space Plan in writing no later than five (5)
business days after Landlord's receipt of such revised Final Space Plan. If
Landlord shall again reasonably disapprove the revised Final Space Plan, the
parties will revise and review the Final Space Plan again in accordance with the
procedure set forth above until Landlord's reasonable approval is obtained.

                  2.5 Final Working Drawings. Tenant and the Architect shall
complete the architectural drawings for the Premises, and the Architect shall
compile a fully coordinated set of architectural working drawings in a form
which is complete to allow subcontractors to bid on the work and to obtain all
applicable permits (collectively, the "FINAL WORKING DRAWINGS") and shall submit
the same to Landlord for Landlord's approval or reasonable disapproval, which
approval or reasonable disapproval shall be delivered by Landlord to Tenant no
later than five (5) business days after Landlord's receipt of such Final Working
Drawings. If Landlord reasonably disapproves of any portion of the Final Working
Drawings, the parties shall meet, within five (5) days after Landlord's
disapproval, to agree upon revisions to be made to the Final Working Drawings to
meet the reasonable satisfaction of Landlord. The Architect shall then revise
the Final Working Drawings to the form agreed upon in such meeting. Landlord
shall then approve or reasonably disapprove the revised Final Working Drawings
no later than five (5) business days after Landlord's receipt of such revised
Final Working Drawings. If Landlord shall again reasonably disapprove the
revised Final Working Drawings, the parties will revise and review the Final
Working Drawings again in accordance with the procedure set forth above until
Landlord's reasonable approval is obtained.

                  2.6 Approved Working Drawings. The Final Working Drawings
approved by Landlord and Tenant and the Engineering Drawings shall be referred
to herein collectively as (the "APPROVED WORKING DRAWINGS") and Tenant shall
submit the same to the appropriate governmental entities for all applicable
building permits necessary to allow the Contractor to commence and fully
complete the construction of the Tenant Improvements (the "PERMITS"). If Tenant
desires any change, modification or alteration in the Approved Working Drawings,
Tenant must first obtain the prior written consent of Landlord, provided that
Landlord may withhold its consent, in its sole discretion, to any change in the
Approved Working Drawings, if such change would directly or indirectly delay the
Substantial Completion of the Premises. Prior to commencing any change requested
by Tenant to the Approved Working Drawings, Landlord shall prepare and deliver
to Tenant, for Tenant's approval, a change order ("CHANGE ORDER") setting forth
the additional time required to perform the change and the total cost of such
change, which shall include associated architectural, engineering and
Contractor's fees. If Tenant fails to approve such Change Order in writing
within two (2) business days after such delivery by Landlord, Tenant shall be
deemed to have withdrawn the Change Order and Landlord shall not proceed to
perform the change but will continue with construction in accordance with the
Approved Working Drawings.

                  2.7 Time Deadlines. Tenant shall cooperate with (i) the
Architect, the Engineers, and Landlord to complete all phases of the Working
Drawings, the Engineering Drawings and the permitting process and Tenant shall
exercise its best efforts to obtain the Permits no later than May 15, 2001, and
(ii) the Contractor, for approval of the "Cost Proposal," as that term is
defined in Section 2.8, below, in accordance with the dates set forth herein.
Tenant shall meet with Landlord on a weekly basis to discuss Tenant's progress
in connection with the same. The applicable dates for approval of items, plans
and drawings and selection of a contractor as described in this Work Letter are
referred to herein as the "TIME DEADLINES." Tenant agrees to comply with the
time deadlines.



                                    EXHIBIT B
                                       -2-
<PAGE>   43

                  2.8 Cost Proposal. After the Approved Working Drawings are
approved by Landlord and Tenant, Landlord shall provide Tenant with a cost
proposal in accordance with the Approved Working Drawings, which cost proposal
shall include, as nearly as possible, the cost of all TI Allowance Items to be
incurred by Tenant in connection with the construction of the Tenant
Improvements (the "COST PROPOSAL"). Landlord does not guaranty the accuracy of
the Cost Proposal. Notwithstanding the foregoing, portions of the cost of the
Tenant Improvements may be delivered to Tenant as such portions of the Tenant
Improvements are priced by Contractor (on an individual item-by-item or
trade-by-trade basis), even before the Approved Working Drawings are completed
(the "PARTIAL COST PROPOSAL"). Tenant shall either (i) approve and deliver the
Cost Proposal to Landlord within five (5) business days of the receipt of the
same (or, as to a Partial Cost Proposal, within two (2) business days of receipt
of the same), or (ii) notify Landlord within five (5) business days after
Tenant's receipt of the Cost Proposal (or Partial Cost Proposal, as the case may
be) that Tenant desires to revise the Approved Working Drawings to reduce the
amount of the Cost Proposal (or Partial Cost Proposal, as the case may be), in
which case such changes shall be made to the Approved Working Drawings only in
accordance with Section 2.7 above and the revised Working Drawings shall be
provided to the Contractor for repricing whereupon Landlord shall revise the
Cost Proposal (or Partial Cost Proposal, as the case may be) for Tenant's
approval. This procedure shall be repeated until the Cost Proposal (or Partial
Cost Proposal, as the case may be) is approved by Tenant. The date by which
Tenant has approved the Cost Proposal, or the last Partial Cost Proposal, as the
case may be, shall be known hereafter as the "COST PROPOSAL DELIVERY DATE." The
total of all Partial Cost Proposals, if any, shall be known as the Cost
Proposal.

                  2.9 Over-Allowance Amount. The amount that is equal to the
difference between (i) the amount of the Cost Proposal and (ii) the amount of
the TI Allowance (less any portion thereof already disbursed by Landlord, or in
the process of being disbursed by Landlord, on or before the Cost Proposal
Delivery Date that is not otherwise included within the Cost Proposal) shall be
referred to herein as the "OVER-ALLOWANCE AMOUNT." Tenant shall pay to Landlord
(a) one-half (1/2) of such Over- Allowance Amount no later than ten (10) days
after the Cost Proposal Delivery Date and (b) the other one-half (1/2) of such
Over-Allowance Amount on or before August 15, 2001. The Over-Allowance Amount
shall be disbursed by Landlord prior to the disbursement of any then remaining
portion of the TI Allowance, and such disbursement shall be pursuant to the same
procedure as the TI Allowance. In the event that after the Cost Proposal
Delivery Date, any revisions, changes, or substitutions shall be made to the
Construction Drawings or the Tenant Improvements, any additional costs which
arise in connection with such revisions, changes or substitutions shall be paid
by Tenant to Landlord as an addition to the Over-Allowance Amount as follows:
(1) one-half (1/2) of such additional amount within five (5) days after
Landlord's invoice therefor and (2) the remaining one-half (1/2) of such
additional amount upon Tenant's receipt of Landlord's written notice that the
work to which the change order applies is complete but in no event later than
August 15, 2001. In the event any such revisions, changes or substitutions occur
after August 15, 2001, Tenant shall pay for such additional amounts within five
(5) days after Landlord's invoice therefor. In addition, upon Landlord's
determination of the actual costs incurred by or on behalf of Landlord for the
TI Allowance Items, Tenant shall pay Landlord the amount, if any, by which such
actual costs exceed the sum of the TI Allowance and the Over-Allowance Amount
within fifteen (15) days after being billed therefor, or Landlord may, at its
election, require that Tenant deposit with Landlord the full amount of such
excess prior to Landlord's delivery of the Premises to Tenant. No portion of the
TI Allowance shall be used to pay Tenant or Tenant's agents, contractors or
employees, unless and until Landlord's contractors and any other persons and
entities employed by or under contract with Landlord have been paid in full.

                  2.10 Landlord Supervision. Landlord shall independently retain
Contractor to construct the Tenant Improvements in accordance with the Approved
Working Drawings and the Cost Proposal and Landlord shall supervise the
construction by Contractor, and Tenant shall pay a construction supervision and
management fee (the "LANDLORD SUPERVISION FEE") to Landlord (or its agent) in an
amount equal to the product of (i) [*] and (ii) the Over-Allowance Amount.

                  2.11 Contractor's Warranties and Guaranties. Landlord hereby
assigns to Tenant all warranties and guaranties by Contractor relating to the
Tenant Improvements, and Tenant hereby waives all claims against Landlord
relating to, or arising out of the construction of, the Tenant Improvements.

         3. Completion of the Tenant Improvements; Delivery Date.

                  3.1 Substantial Completion. "SUBSTANTIAL COMPLETION" of the
Premises shall occur upon completion of construction of the Tenant Improvements
in the Premises pursuant to the Approved Working Drawings, with the exception of
any punch list items and any Tenant fixtures, work-stations, built-in furniture,
or equipment to be installed by Tenant or under the supervision of Contractor.

                  3.2 Delay of Substantial Completion of the Premises. Except as
provided in this Section 3, the Delivery Date shall occur as set forth in the
Basic Lease Information. If there shall be a delay or there are delays in the
Substantial Completion of the Premises (based upon the anticipated date of the
occurrence of the Delivery Date as set forth in the Lease) or in the occurrence
of any of the other

                                    EXHIBIT B
                                       -3-

[*] = CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
BRACKETS, HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.


<PAGE>   44

conditions precedent to the Delivery Date, as set forth in the Lease, as a
direct, indirect, partial, or total result of any of the following
(collectively, "TENANT DELAYS"): (a) Tenant's failure to comply with the time
deadlines (including the failure to obtain the Permits by May 15, 2001 and the
failure to agree upon the selection of the Contractor by May 1, 2001); (b)
Tenant's failure to timely approve any matter requiring Tenant's approval; (c) a
breach by Tenant of the terms of this Work Letter or the Lease; (d) changes in
the Final Space Plan or the Final Working Drawings requested by Landlord (but
only as such changes are required to preserve the integrity of Landlord's Work
or structural portions of the Building) or Tenant after Tenant's initial
submission thereof to Landlord; (e) Tenant's request for changes in the Approved
Working Drawings (including, without limitation, any changes made in order to
reduce the amount of the Cost Proposal (or Partial Cost Proposal, as the case
may be); (f) Tenant's requirement for materials, components, finishes or
improvements that are not available in a reasonable time (based upon the
anticipated Delivery Date) or that are different from, or not included in, the
Building Specifications and Tenant's refusal to reasonably accept substitute
materials, components, finishes and improvements proposed by Landlord; (g)
changes to the base, shell and core of the Building required by the Approved
Working Drawings; (h) Tenant's failure to timely deliver the second (2nd) Letter
of Credit as required under Section 4.4.1 of the Lease; or (i) any other acts or
omissions of Tenant, or its agents, or employees (including Tenant's Architect);
then, notwithstanding anything to the contrary set forth in this Lease and
regardless of the actual date of the Substantial Completion of the Premises, the
date of Substantial Completion and delivery of the Premises to Tenant (for
purposes of determining the Delivery Date) shall be deemed to be the date
Substantial Completion and delivery of the Premises to Tenant would have
occurred if no Tenant Delays, as set forth above, had occurred.

                  3.3 Tenant's Entry Into the Premises Prior to Substantial
Completion. Provided that Tenant and its agents do not interfere with, or delay,
Contractor's work in the Building and the Premises, Contractor shall allow
Tenant access to the Premises prior to the Substantial Completion of the
Premises for the purpose of Tenant installing overstandard equipment or fixtures
(including Tenant's data and telephone equipment) in the Premises. Prior to
Tenant's entry into the Premises as permitted by the terms of this Section 3.3,
Tenant shall submit a schedule to Landlord and Contractor, for their approval,
which schedule shall detail the timing and purpose of Tenant's entry. Tenant
shall hold Landlord harmless from and indemnify, protect and defend Landlord
against any loss or damage to the Building or Premises and against injury to any
persons caused by Tenant's actions pursuant to this Section 3.3.

                  3.4 Tenant's Representative. Tenant has designated Rhonda
Gardner and Kurt Vanderslice as its sole representatives with respect to the
matters set forth in this Work Letter, each of whom shall have full authority
and responsibility to act on behalf of the Tenant as required in this Work
Letter.

                  3.5 Landlord's Representative. Landlord has designated Lance
Kitt and Greg Weaver as its sole representatives with respect to the matters set
forth in this Work Letter, each of whom, until further notice to Tenant, shall
have full authority and responsibility to act on behalf of the Landlord as
required in this Work Letter.

                  3.6 Time of the Essence. Unless otherwise indicated, all
references herein to a "number of days" shall mean and refer to calendar days.
In all instances where Tenant is required to approve or deliver an item, if no
written notice of approval is given or the item is not delivered within the
stated time period, at Landlord's sole option, at the end of said period the
item shall automatically be deemed approved or delivered by Tenant and the next
succeeding time period shall commence.

                  3.7 Tenant's Lease Default. Notwithstanding any provision to
the contrary contained in this Lease, if an Event of Default as described in
Section 16 of the Lease or this Work Letter has occurred at any time on or
before the Substantial Completion of the Premises or if a circumstance exists
that with the giving of notice, the lapse of time, or both, would constitute an
Event of Default under the Lease, then (i) in addition to all other rights and
remedies granted to Landlord pursuant to this Lease, Landlord shall have the
right to withhold payment of all or any portion of the TI Allowance and/or
Landlord may cause Contractor to cease the construction of the Premises (in
which case, Tenant shall be responsible for any delay in the Substantial
Completion of the Premises caused by such work stoppage as set forth in Section
3.2 of this Work Letter), and (ii) all other obligations of Landlord under the
terms of this Work Letter shall be forgiven until such time as such default is
cured pursuant to the terms of this Lease.

                  3.8 Tenant's Agents. All of Tenant's agents, contractors, and
subcontractors performing work in, or in connection with, the Premises
(collectively as "TENANT'S AGENTS"), shall be subject to Landlord's reasonable
approval and, if deemed necessary by Landlord to maintain harmony among other
labor at the real property or if required by law or any agreement to which
Landlord is bound, shall be union labor.

                  3.9 Tenant's Architect's Insurance. Prior to Tenant's
Architect performing any services in connection with the Tenant Improvements,
the Final Space Plan, or the Working Drawings,



                                    EXHIBIT B
                                       -4-
<PAGE>   45

Tenant shall deliver to Landlord certificates evidencing that Tenant's Architect
has in force, with insurance companies reasonably acceptable to Landlord, (i)
Professional Liability Insurance with limits of not less than Five Million
Dollars ($5,000,000) per claim and annual aggregate, with a retention of not
more than Fifty Thousand Dollars ($50,000) per claim and an inception date or a
retroactive date coinciding with or prior to the earlier of the Effective Date
or the date of first performance of Tenant's Architect's services, (ii) Workers
Compensation Insurance as required by state and federal statutes with Employer's
Liability Insurance with limits of not less than One Million Dollars
($1,000,000) for bodily injury by accident and One Million Dollars ($1,000,000)
for bodily injury by disease, (iii) Commercial General Liability Insurance in
the amount of not less than One Million Dollars ($1,000,000) per occurrence, One
Million Dollars ($1,000,000) annual general aggregate, and (iv) Commercial
Automobile Liability Insurance for all owned and non-owned automobiles utilized
in connection with the services performed under the Tenant's Architect contract
in the amount of not less than One Million Dollars ($1,000,000) combined single
limit for bodily injury and property damage combined. All such insurance
required by this Section 3.9 shall be maintained for the entire period during
which services are performed under Tenant's Architect's contract, with the
exception of the Professional Liability Insurance policy which shall be
maintained in force for at least one (1) year following Substantial Completion
of the Tenant Improvements. Thereafter, during the second (2nd) and third (3rd)
years following Substantial Completion of the Tenant Improvements, Tenant's
Architect shall maintain Professional Liability Insurance with limits of not
less than One Million Dollars ($1,000,000.00) annual aggregate, on a claims made
basis, during such second (2nd) and third (3rd) years after Substantial
Completion of the Tenant Improvements, so long as such insurance is reasonably
available under standard policies at rates comparable to those in effect as of
the date of such Substantial Completion. Landlord shall be named as an
additional insured on all required Commercial General Liability policies of
Tenant's Architect, and the required certificate of insurance shall include an
additional insured endorsement ISO form number CG 20 10 11 85, or equivalent,
evidencing such additional insured status. All insurance of Tenant's Architect
will be primary as respects any insurance of Landlord, which insurance shall be
non-contributing.

                  3.10 Insurance Requirements. All of Tenant's Agents shall
carry liability and Products and Completed Operation Coverage insurance, each in
amounts not less than One Million Dollars ($1,000,000.00) per incident, One
Million Dollars ($1,000,000.00) in aggregate, and in form and with companies as
are required to be carried by Tenant as set forth in Section 9.2 of the Lease,
and the policies therefor shall insure Landlord and Tenant, as their interests
may appear, as well as Landlord's contractor, and shall name as additional
insureds all mortgagees of the real property or any other party designated by
Landlord. All insurance maintained by Tenant's Agents shall preclude subrogation
claims by the insurer against anyone insured thereunder. Such insurance shall
provide that it is primary insurance as respects the Landlord and that any other
insurance maintained by Landlord is excess and noncontributing with the
insurance required hereunder.



                                    EXHIBIT B
                                       -5-
<PAGE>   46

                             SCHEDULE 1 TO EXHIBIT B

                        BUILDING PLANS AND SPECIFICATIONS

                                   WESTMINSTER

                          BASE BUILDING CORE AND SHELL

PARKING STALLS:                     Parking is provided at 4.1 spaces per 1,000
                                    square feet of rentable building area.

PARKING LOT LIGHTING:               Parking lot lighting is provided, designed
                                    to supply an average to minimum ratio of
                                    approximately 1.0 foot candles/SF.

SITEWORK:                           Asphalt concrete paving in all traffic and
                                    parking areas, concrete curb and gutter per
                                    approved development plans.

LANDSCAPING:                        Landscape planting materials and irrigation
                                    of all planting areas per approved
                                    development plans.

BUILDING STRUCTURE:                 Precast concrete frame with precast concrete
                                    floor and roof structure and approximately
                                    4-inch concrete topping slab.

FLOOR LOADING CRITERIA:             Live load is approximately 50 psf in general
                                    office area, with approximately 100 psf at
                                    corridor and interior office area
                                    immediately adjacent to corridor. Partition
                                    load is approximately 20 psf.

CEILING HEIGHTS:                    Clear ceiling heights are approximately
                                    12'-2" feet at ground floor tenant areas,
                                    and approximately 9'-2" at floors 2, 3, 4
                                    and 5 tenant areas. Typical structure to
                                    structure clearance is approximately 14.5
                                    feet at ground floor 14'-8" from floor to
                                    bottom of "T" at ground floor, and 11'- 8"
                                    approximately 11.5 feet from floor to bottom
                                    of "T" at floors 2, 3, 4 and 5. Clearances
                                    may be 12 inches less at beam locations.

BUILDING SKIN:                      Precast architectural concrete spandrel
                                    panels with continuous glazing in between.
                                    Full height glazing at most locations. See
                                    elevation drawings for detail.

ROOFING:                            60 mil EPDM roof membrane, ballasted, over
                                    2.6" rigid polyisocyanruate board. R-value
                                    of 19.

PERIMETER WALLS:                    Perimeter, exterior walls to be insulated
                                    only, no drywall.

CORE SERVICE AREAS:                 1.  Sound attenuation is provided to meet
                                        NC35 levels.

                                    2.  Janitor's closet provided on each floor.

                                    3.  Finished doors provided for all service
                                        rooms.

                                    4.  Door frames to be anodized aluminum for
                                        all core doors.

                                    5.  One drinking fountain location each
                                        floor, with two fountains, one meeting
                                        ADA requirements.

REST ROOMS:                         Rest rooms to have ceramic tile on floors,
                                    and full height on wet walls. Toilet
                                    partitions to be ceiling hung stainless
                                    steel. Vanity tops to be granite. Restrooms
                                    to be ADA compliant.

SHOWER FACILITIES:                  Ground floor restrooms to include two shower
                                    stalls each in men's and women's. One shower
                                    stall in each to be ADA compliant.

TELEPHONE ROOM:                     Main telephone/fiber optic room provided at
                                    ground floor, approximately 20 feet by 10
                                    feet. Conduit to be stubbed into room for
                                    telephone and 3 possible fiber optic
                                    providers. Approximately 6 foot by 9 foot
                                    communications rooms provided on floors 2,
                                    3, 4 and 5.



                                  SCHEDULE 1 TO
                                    EXHIBIT B
                                       -1-
<PAGE>   47

ELEVATORS:                          Hydraulic elevators, 3,500 lb. capacity
                                    provided. Interior cab height to be
                                    approximately 10 feet, with suspended
                                    ceiling at approximately 9 feet. Finishes
                                    will be compatible with main lobby. Freight
                                    elevator to be supplied with protective
                                    blankets. Waiting time will be average of
                                    27-29 seconds, with 5 minute handling
                                    capacity of 13% of building population
                                    (upper floors only). Elevators to be ADA
                                    compliant, and provided with emergency
                                    telephones.

FIRE PROTECTION:                    Complete fire sprinkler system in accordance
                                    with applicable codes for office occupancy.
                                    Fireproofing of the Building's structural
                                    steel as specified on the structural plans
                                    for the Building as approved by the City of
                                    Westminster (a copy of which plans Tenant
                                    acknowledges receiving).

PLUMBING SYSTEMS:                   Complete plumbing system for domestic water
                                    service, sanitary sewer service, and roof
                                    drainage. Water and sanitary systems will be
                                    accessible to tenant areas for future
                                    connections for convenience sinks and other
                                    uses.

HVAC:                               HVAC system is provided with rooftop units,
                                    total capacity approximately 460 tons, of
                                    approximately 350 sf per ton. Primary trunk
                                    ducts and exterior zone VAV boxes provided
                                    at approximately 1 per 1,100 SF. Exterior
                                    zone VAV boxes are provided with electric
                                    reheat. No distribution ducting or diffusers
                                    are included at these exterior zone boxes.

                                    Energy management system provided, with
                                    remote computer monitoring capability.
                                    Tenant metering capability also included in
                                    system.

                                    HVAC Design criteria for cooling load
                                    allowed include the following:

                                    2 watts per SF for lighting;
                                    1.5 watts per SF for office equipment
                                    150 SF per person.

ELECTRICAL SERVICE:                 The building is provided with primary
                                    electrical service, 277/480 volts, 3 phase,
                                    with main disconnects in the main electrical
                                    room on the first floor. Electrical
                                    distribution panel rooms are provided two
                                    per floor adjacent to stairwells.

                                    Electrical service will provide total
                                    capacity of 27 watts per square foot,
                                    generally allocated as follows:

                                    15 watts per SF for HVAC loads;
                                    3 watts per SF for lighting;
                                    6.5 watts per SF for tenant equipment loads;
                                    2.5 watts per SF spare power;
                                    A pad area for a future generator to be
                                    included in the building shell.

FIRE ALARM:                         Fire alarm panel is provided, including fire
                                    alarm devices as required by code in core
                                    and common areas.

SECURITY:                           A card access system to be provided at the
                                    main entry doors of the building. Elevator
                                    card access also to be available based on
                                    tenant needs (but at Tenant's sole cost and
                                    expense).



                                  SCHEDULE 1 TO
                                    EXHIBIT B
                                       -2-
<PAGE>   48

                                    EXHIBIT C

                          COMMENCEMENT DATE MEMORANDUM

         With respect to that certain lease ("Lease") dated ___________________,
____, between ______________________________________, a
__________________________ ("Tenant"), and CATELLUS DEVELOPMENT CORPORATION, a
Delaware corporation ("Landlord"), whereby Landlord leased to Tenant and Tenant
leased from Landlord approximately ______________ rentable square feet of the
building located at _______________________________ ("Premises"), Tenant hereby
acknowledges and certifies to Landlord as follows:

         (1) The Commencement Date is ____________ and the Expiration Date is
____________;

         (2) The Rent Commencement Date is ____________;

         (3) The Premises contain ___________ rentable square feet of space; and

         (4) Tenant has accepted and is currently in possession of the Premises
and the Premises are acceptable for Tenant's use.

         IN WITNESS WHEREOF, this Commencement Date Memorandum is executed this
____ day of ________, ____.

"Tenant"                                                                       ,
                                       ----------------------------------------
                                       a
                                         ---------------------------------------

                                       By:
                                          --------------------------------------
                                          Name:
                                               ---------------------------------
                                          Its:
                                              ----------------------------------

                                       By:
                                          --------------------------------------
                                          Name:
                                               ---------------------------------
                                          Its:
                                              ----------------------------------



                                    EXHIBIT C
                                       -1-
<PAGE>   49

                                    EXHIBIT D

                              RULES AND REGULATIONS

         1. The sidewalks, entrances, passages and courts of the Project,
including the parks, and the sidewalks, entrances, passages, courts, elevators,
vestibules, stairways, corridors or halls of the Building shall not be
obstructed or used for any purpose other than ingress and egress.

         2. No awning or other projection shall be displayed or attached to the
outside walls of the Building without the prior written consent of Landlord. The
standard window blinds specified by Landlord shall not be removed from the
windows, and no other curtains, blinds, shades or screens shall be attached to
or hung in, or used in connection with, any window or door of the Premises,
without the prior written consent of Landlord. Such awnings, projections,
curtains, blinds, shades, screens or other fixtures must be of a quality, type,
design and color, and attached in the manner approved by Landlord.

         3. No sign, advertisement, or notice shall be exhibited, painted,
inscribed or affixed by any tenant on any part of, or so as to be seen from the
outside of, the Premises or the Building without the prior written consent of
Landlord. In the event of the violation of the foregoing by any tenant, Landlord
may remove same without any liability, and may charge the expense incurred in
such removal to the tenant violating this rule. Interior signs on doors and
directory tablet shall be inscribed, painted or affixed for each tenant by
Landlord at the expense of such tenant, and shall be of a size, color, and style
acceptable to Landlord and consistent with Landlord's signage program.

         4. Except in connection with the initial Tenant Improvements (which
shall be governed by the Approved Working Drawings), electric wiring of every
kind and telephone outlets shall be installed in a manner as will be prescribed
by Landlord. The location of convenience outlets, electric light outlets, power
outlets and telephone outlets shall be approved by Landlord, prior to
installation, but the cost shall be paid by tenant. No electrical wall or
ceiling fixture shall be installed unless first approved by Landlord. All
electric work must be done by electricians so licensed by the State in which the
Premises are located pursuant to proper governmental permits.

         5. The sashes, sash doors, windows, and doors that reflect or admit
light and air into the halls, passageways or other public places in the Building
shall not be covered or obstructed by any tenant, nor shall any bottles, parcels
or other articles be placed on the windowsills, except Landlord shall have the
right to require Tenant to keep the drapes closed at all times or some of the
time.

         6. The toilets, wash bowls and other plumbing fixtures shall not be
used for any purpose other than those for which they were constructed, and no
sweepings, rubbish, rags or other substances shall be thrown therein. All
damages resulting from any misuse of the fixtures shall be borne by the tenant
who, or whose servants, employees, agents, visitors or licensees shall have
caused the same.

         7. Except for Utility Installations (which are subject to Section 11 of
the Lease), no tenant shall mark, paint, drill into, or in any way deface any
part of the Premises or the Building. No boring, cutting or stringing of wires
or laying of carpeting, linoleum or other similar floor coverings shall be
permitted, except with the prior written consent of Landlord and as Landlord may
direct.

         8. No bicycles, vehicles or animals of any kind shall be brought into
or kept in or about the Premises, and no cooking shall be done or permitted by
any tenant on the Premises, except for the microwaving of foods, preparation of
coffee, tea, hot chocolate and similar items for tenants and their employees and
catered events (subject to Landlord's reasonable approval). No tenant shall
cause or permit any unusual or objectionable odors to be produced upon or
permeate the Premises.

         9. The Premises shall not be used for manufacturing or for the storage
of merchandise except as such storage may be incidental to the use of the
Premises for general office purposes. No tenant shall occupy or permit any
portion of its Premises to be occupied for the manufacture or sale of liquor,
narcotics, or tobacco in any form. No tenant shall engage or pay any employees
on the Premises except those actually working for such tenant on the Premises
nor advertise for laborers giving an address at the Premises. The Premises shall
not be used for lodging or sleeping or for any immoral or illegal purposes.

         10. No tenant shall use, keep or permit to be used or kept any foul or
noxious gas or substances in the Premises or the Building or permit or suffer
the Premises to be occupied or used in a manner offensive or objectionable to
Landlord or other tenants of the Building or of neighboring buildings by reason
of noise, odors and/or vibrations, including, without limitation, by the use of
any musical instrument, radio, phonograph, sound-producing instrument or device
that can be heard outside the Premises.



                                    EXHIBIT D
                                       -1-
<PAGE>   50

         11. No tenant shall place any radio or television antenna on the roof
or on any part of the inside or outside of the Building other than inside the
Premises. No tenant shall operate any electrical device from which may emanate
electrical waves which may interfere with or impair radio or television
broadcasting or reception from or in the Building or any part of the Project. No
tenant shall throw anything out of the doors, windows or down the passageways.
Landlord reserves the right to exclude or expel from the Building or any part of
the Project any person who, in the judgment of Landlord, is intoxicated or under
the influence of liquor or drugs or who shall in any manner do any act in
violation of these Rules and Regulations.

         12. Except for office/cleaning supplies typically used in the ordinary
course of business, no tenant, nor any of tenant's servants, employees, agents,
visitors or licensees, shall at any time keep or permit to be kept upon the
Premises any inflammable, combustible or explosive fluid, chemical or substance.

         13. No additional locks or bolts of any kind shall be placed upon any
of the doors or windows by any tenant, nor shall any changes be made in existing
locks or the mechanism thereof. All keys to the Premises, and any other parts of
the Building, shall be obtained by Tenant only from Landlord. Landlord shall
furnish Tenant, without charge, two keys or magnetic cards to the primary
entrance door to the Premises. Tenant shall obtain any additional keys only from
Landlord and shall not make or otherwise procure any additional sets of keys.
Each tenant must, upon the termination of its tenancy, return to Landlord all
such keys, and in the event of the loss of any keys so furnished, such tenant
shall pay to Landlord the cost of replacing the same or of changing the lock or
locks opened by such lost key if Landlord shall deem it necessary to make such
change.

         14. Except for the initial Tenant Improvements, the weight, size and
position of all safes and other unusually heavy objects used or placed in the
Building shall be prescribed by Landlord, and Landlord reserves the right to
require such safes or other objects to be placed upon supports approved by
Landlord to distribute the weight. The repair of any damage done to the Building
or property therein by putting in or taking out or maintaining such safes or
other unusually heavy objects shall be made and paid for by Tenant. All
removals, or the carrying in or out of the Building or moving within the
Building of any safes, freight, furniture, fixtures or bulky matter of any
description must take place during the hours which Landlord may determine from
time to time. The moving of safes, furniture or other fixtures or bulky matter
of any kind must be made upon previous notice to the superintendent of the
Building and under his supervision, and the persons employed by any tenant for
such work must be acceptable to Landlord. Landlord reserves the right to inspect
all safes, furniture, fixtures, freight or other bulky articles to be brought
into the Building and to exclude from the Building all safes, freight or other
bulky articles which violate any of these Rules and Regulations or the Lease of
which these Rules and Regulations are a part.

         15. No tenant shall purchase janitorial, maintenance or other like
service from any company or persons unless the written consent of Landlord is
first obtained.

         16. Tenant shall not use the name of the Building or Landlord in its
advertising.

         17. Access to the Building between the hours of 6 P.M. in the evening
and 7 A.M. in the morning on weekdays and at all hours on Saturdays and Sundays
and usual holidays is controlled by a card key system. Landlord will furnish
card keys to persons for whom any tenant requests the same in writing. Each
tenant shall be responsible for all persons for whom it requests card keys and
shall be liable to Landlord for all acts of such persons. In the case of mob,
riot, public disorder or other commotion or invasion, Landlord reserves the
right to prevent access to the Building or to any other part of the Project
during the continuance of the same by closing the entrances to the Building or
any other part of the Project, blocking ingress or egress to the Building or any
other part of the Project or by closing the doors, or otherwise, for the safety
of the tenants of the Building or protection of the Building and property in the
Building.

         18. Any persons employed by any tenant to do janitorial work shall,
while in the Building and outside of the Premises, be subject to and under the
control and direction of the superintendent of the Building (but not as an agent
or servant of said superintendent or of Landlord, and the tenant shall be
responsible for all acts of such persons).

         19. All doors opening onto public corridors shall be kept closed,
except when in use for ingress or egress.

         20. The requirements of tenants will be attended to only upon
application to the Office of the Building.

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



                                    EXHIBIT D
                                       -2-
<PAGE>   51

         22. All office equipment of any electrical or mechanical nature shall
be placed by tenants in the Premises in settings approved by Landlord, to absorb
or prevent any vibration, noise or annoyance.

         23. No air conditioning unit or other similar apparatus shall be
installed or used by any tenant without the written consent of Landlord.

         24. There shall not be used in any space or in the public halls of the
Building, either by any tenants or others, any hand trucks except those equipped
with rubber tires and side guards.

         25. The expense of repairing any damage resulting from a violation of
any Rule or Regulation herein shall be borne by the tenant by whom, or by whose
contractors, employees or invitees, the damage shall have been caused.

         26. Tenant shall not smoke in the Premises or the Project, and shall
not allow any smoking by any Tenant Party or any visitor to the Premises or the
Project. Tenant, Tenant Parties and/or any visitors to the Project may smoke
only in areas designated by Landlord.



                                    EXHIBIT D
                                       -3-
<PAGE>   52

                                    EXHIBIT E

                           TENANT ESTOPPEL CERTIFICATE

To:      [Insert name of party to rely on document] ("Relying Party")

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

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

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

         Attn:
              -------------------------------------------------------

Re:      Lease Dated:
                     ------------------------------------------------
         Current Landlord:
                          -------------------------------------------
         Current Tenant:
                        ---------------------------------------------
         [RENTABLE] Square Feet: Approximately
                                               ----------------------
         Floor(s):
                  ---------------------------------------------------
         Located at:
                    -------------------------------------------------
         ____________________________________________ ("Tenant") hereby
certifies that as of _________, ____:

         1. Tenant is the present owner and holder of the tenant's interest
under the lease described above, as it may be amended to date (the "Lease") with
______________________ as Landlord (who is called "Landlord" for the purposes of
this Certificate). (USE THE NEXT SENTENCE IF THE LANDLORD OR TENANT NAMED IN THE
LEASE IS A PREDECESSOR TO THE CURRENT LANDLORD OR TENANT.) [The original
landlord under the Lease was _______________, and the original tenant under the
Lease was _______________.] The Lease covers the premises commonly known as
_______________ (the "Premises") in the building (the "Building") at the address
set forth above.

                (CHOOSE ONE OF THE FOLLOWING SECTION 2(a)s BELOW)

         [2. (a) A true, correct and complete copy of the Lease (including all
modifications, amendments, supplements, side letters, addenda and riders of and
to it) is attached to this Certificate as Exhibit A.]

         [2 (a) The attached Exhibit A accurately identifies the Lease and all
modifications, amendments, supplements, side letters, addenda and riders of and
to it.]

                  (b) (IF APPLICABLE) [The Lease provides that in addition to
the Premises, Tenant has the right to use or rent during the term of the Lease
_______________ [assigned/unassigned] parking spaces near the Building or in the
parking structure of the Project most proximately located to the Premises.]

                  (c) The term of the Lease commenced on _______________, _____,
and will expire on _______________, _____, including any presently exercised
option or renewal term. (CHOOSE ONE OF THE FOLLOWING TWO SENTENCES.) [Tenant has
no option or right to renew, extend or cancel the Lease, or to lease additional
space in the Building or the Project, or to use any parking (IF APPLICABLE)
[other than that specified in Section 2(b) above].] [Except as specified in
Section(s) ____________ of the Lease (copy attached), Tenant has no option or
right to renew, extend or cancel the Lease, or to lease additional space in the
Building or the Project, or to use any parking (IF APPLICABLE) [other than that
specified in Section 2(b) above].]

(CHOOSE ONE OF THE FOLLOWING SECTION 2(d)s)

                  [(d) Tenant has no option or preferential right to purchase
all or any part of the Premises (or the land of which the Premises are a part).
Tenant has no right or interest with respect to the Premises or the Building
other than as Tenant under the Lease.]

                  [(d) Except as specified in Section(s) _____________ of the
Lease (copy attached), Tenant has no option or preferential right to purchase
all or any part of the Premises (or the land of which the Premises are a part).
Except for the foregoing, Tenant has no right or interest with respect to the
Premises or the Building other than as Tenant under the Lease.]

                  (e) The annual minimum rent currently payable under the Lease
is $ _____________ and such rent has been paid through _____________, ____.

                  (f) (IF APPLICABLE) [Additional rent is payable under the
Lease for (i) operating, maintenance or repair expenses, (ii) property taxes
(including CFD special taxes), and/or (iii) consumer price index cost of living
adjustments. Such additional rent has been paid in accordance with Landlord's



                                    EXHIBIT E
                                       -1-
<PAGE>   53

rendered bills through _____________, _______. The base year amounts for
additional rental items are as follows: (1) operating, maintenance or repair
expenses $_____________, (2) property taxes $_____________, and (3) consumer
price index _____________ (please indicate base year CPI level).]

                  (g) Tenant has made no agreement with Landlord or any agent,
representative or employee of Landlord concerning free rent, partial rent,
rebate of rental payments or any other similar rent concession (IF APPLICABLE)
[except as expressly set forth in Section(s) ______ of the Lease (copy
attached)].

                  (h) Landlord currently holds a security deposit in the amount
of $__________ which is to be applied by Landlord or returned to Tenant in
accordance with Section(s) ____ of the Lease. Tenant acknowledges and agrees
that Relying Party shall have no responsibility or liability for any security
deposit, except to the extent that any security deposit shall have been actually
received by Relying Party.

         3. (a) The Lease constitutes the entire agreement between Tenant and
Landlord with respect to the Premises, has not been modified, changed, altered
or amended, and is in full force and effect in the form (CHOOSE ONE) [attached
as/described in] Exhibit A. There are no other agreements, written or oral,
which affect Tenant's occupancy of the Premises.

                  (b) All insurance required of Tenant under the Lease has been
provided by Tenant and all premiums have been paid.

                  (c) To the best knowledge of Tenant, no party is in default
under the Lease. To the best knowledge of Tenant, no event has occurred which,
with the giving of notice or passage of time, or both, would constitute such a
default.

                  (d) The interest of Tenant in the Lease has not been assigned
or encumbered. Tenant is not entitled to any credit against any rent or other
charge or rent concession under the Lease except as set forth in the Lease. No
rental payments have been made more than one month in advance.

         4. All contributions required to be paid by Landlord to date for
improvements to the Premises have been paid in full and all of Landlord's
obligations with respect to tenant improvements have been fully performed.
Tenant has accepted the Premises, subject to no conditions other than those set
forth in the Lease.

         5. Neither Tenant nor any guarantor of Tenant's obligations under the
Lease is the subject of any bankruptcy or other voluntary or involuntary
proceeding, in or out of court, for the adjustment of debtor-creditor
relationships.

         6. (a) As used here, "Hazardous Substance" means any substance,
material or waste (including petroleum and petroleum products) which is
designated, classified or regulated as being "toxic" or "hazardous" or a
"pollutant," or which is similarly designated, classified or regulated, under
any federal, state or local law, regulation or ordinance.

                  (b) Tenant represents and warrants that it has not used,
generated, released, discharged, stored or disposed of any Hazardous Substances
on, under, in or about the Building or the land on which the Building is located
(IF APPLICABLE) [, other than Hazardous Substances used in the ordinary and
commercially reasonable course of Tenant's business in compliance with all
applicable laws]. (IF APPLICABLE) [Except for such commercially reasonable use
by Tenant,] Tenant has no actual knowledge that any Hazardous Substance is
present, or has been used, generated, released, discharged, stored or disposed
of by any party, on, under, in or about such Building or land.

         7. Tenant hereby acknowledges that Landlord intends to [discuss action
to be taken vis-a-vis Relying Party]. Tenant acknowledges the right of Landlord,
Relying Party and any and all of Landlord's present and future lenders,
purchasers and their successors and assigns to rely upon the statements and
representations of Tenant contained in this Certificate and further acknowledges
that any action taken by such parties will be made and entered into in material
reliance on this Certificate.



                                    EXHIBIT E
                                       -2-
<PAGE>   54

         8. Tenant hereby agrees to furnish Relying Party with such other and
further estoppel as Relying Party may reasonably request.

"Tenant"                                                                       ,
                                       ----------------------------------------
                                       a
                                         ---------------------------------------

                                       By:
                                          --------------------------------------
                                          Name:
                                               ---------------------------------
                                          Its:
                                              ----------------------------------

                                       By:
                                          --------------------------------------
                                          Name:
                                               ---------------------------------
                                          Its:
                                              ----------------------------------



                                    EXHIBIT E
                                       -3-