<PAGE>
 
                                                                   EXHIBIT 10.42

                             BASIC LEASE PROVISIONS
                             ----------------------

     The following Basic Lease Provisions constitute a part of the
R&D Building Lease to which they are attached.

1.  Landlord:  Sorrento Tech Limited, a California limited
    partnership.

2.  Tenant:  Biosym Technologies, Inc., a California corporation.

3.  Premises:

   (a) Rentable Area:  Approximately 10,270 sq. ft.  See
       Definition of Rentable Area attached hereto as Exhibit
       "A-3".

   (b) Location:  The ground floor of the west end of the
       building located at the address specified in Item 3(c)
       below (the "Building"), as shown on the Floor Plan of
       the Premises attached hereto as Exhibit "A-1."  The
       Building is located in a certain real estate project
       commonly known as the "Naiman Tech Center" (the
       "Project"), as shown on the Site Plan of the Project
       attached hereto as Exhibit "A-2."

   (c) Address:  10065 Barnes Canyon Road, Suite A
                 San Diego, CA 92121

4.  Lease Term:

   (a) Initial Lease Term:  Five (5) years.

   (b) Option Term:  Tenant shall have the option to renew and

       extend the term of this Lease for one additional five

   (5) year period on all the same terms and conditions of

   this Lease.

5.  Target Commencement Date:  June 1, 1987. See Paragraph 3.1.

6.  Rent:

    (a) Initial Basic Annual Rent:  $11,297 per month ($1.10 per
          sq. ft.).

    (b) Adjustments to Basic Annual Rent: The Basic Annual Rent shall be
        increased annually at the rate of 5% per annum on each applicable
        anniversary of the Rent Commencement Date (as defined below). The first
        such increase shall occur on the first anniversary of the Rent
        Commencement Date. See Paragraph 4.2(b).

    (c)  Additional Rent:  See Article 5.

          (i)  Tenant's share of Building Operating Expenses:
          55 .11%

         (ii)  Tenant's share of Project Operating Expenses: 1.70%.

    (c)   Rent Abatement Period:  Tenant shall have a seven (7)
          month Rent Abatement Period, commencing on the first day
          of the first calendar month of the Lease term, and
          terminating on the last day of the seventh month of the
          Lease term. During this seven month period, Tenant shall
          not be obligated to pay Basic Annual Rent, but shall pay
          Additional Rent.


                                      (i)
<PAGE>
 
          (d)  Rent Commencement Date:

          (i) For Basic Annual Rent: February 1, 1988.

          (ii) For Additional Rent: Commencement Date.
          Additional Rent is defined in Article 5 as Tenant's pro
          rata share of Building Operating Expenses and Project
          operating Expenses.

7.   Rent Deposit: $11,297, payable in cash upon execution of
this Lease and applicable to the first monthly installment of
Basic Annual Rent.

8.  Security Deposit:  $11,297.

9.  Permitted Use:  General office purposes and purposes
    reasonably incidental thereto.

10.  Insuring Party:  Landlord.

11.  Addresses for Notices:

    (a)  If to Landlord:

               Sorrento Tech Limited
               c/o The Naiman Company
               9605 Scranton Road, Suite 300
               San Diego, CA 92121

    (b)  If to Tenant:

               (i)  Before the Commencement Date:

                   Biosym Technologies, Inc.
                   9605 Scranton Road, Suite 101
                   San Diego, CA 92121

                (ii)  After the Commencement Date: The
                Premises

12.  Address for Payments to Landlord:

         All payments payable to Landlord under this Lease shall
         be sent to Landlord at the address specified in Item
         11(a) above or such other address as Landlord may
         designate from time to time.

13.  Broker(s):  None

Addenda:  Article 21 consists of Paragraphs 21.1 through 21.3.

            /s/TS        /s/JN
            ---------    -----------
            Tenant's      Landlord's
            Initials      Initials

LAL:1618Y
 022487

                                     (ii)
<PAGE>
 
                        MEMORANDUM OF LEASE COMMENCEMENT

Whereas, Biosym Technologies, Tenant, entered into a certain lease dated
February 26, 1987 with Sorrento Tech Limited, Landlord, for the premises located
at 10065 Barnes Canyon Road.

Whereas, the parties desire to ratify the commencement date, additional rent
commencement date and basic annual rent commencement date of the term of the
said lease;

Now, THEREFORE, it is mutually agreed that:

          1)  The new commencement date of the lease is now
              August 1, 1987 and the new expiration date shall be
              July 31, 1992.

          2)  The new commencement date for additional rent shall be at
              occupancy of the premises at 10065 Barnes Canyon Road, prior to
              and until such time as Tenant takes occupancy of the 10065 Barnes
              Canyon premises, Tenant shall pay all basic and additional rent
              applicable to the premises which they currently occupy.

          3)  The new commencement date for basic annual rent shall
              be April 11, 1988.

          4)  This instrument in no way alters, changes, modifies or
              amends the lease but memorializes the agreed upon
              commencement date, additional rent commencement date
              and basic annual rent commencement date as pertaining
              to the 10065 Barnes Canyon premises.

Dated this   29   day of June, 1987.
           ------                   

LANDLORD:                                 TENANT:
SORRENTO TECH LTD.                        BIOSYM TECHNOLOGIES



By:/s/Jack Naiman                         By:/s/Todd Schmidt
   --------------                            ---------------
    Jack Naiman
<PAGE>
 
                             R & D BUILDING LEASE

                                    between

                            SORRENTO TECH LIMITED,

                                  as Landlord

                                      and

                          BIOSYM TECHNOLOGIES, INC.,

                                   as Tenant
<PAGE>
 
                               R&D BUILDING LEASE

                               TABLE OF CONTENTS

                                                                         Page
                                                                         ----
 
       ARTICLE 1        Parties.......................................    1
       ARTICLE 2        Premises......................................    1
       ARTICLE 3        Term..........................................    1
       ARTICLE 4        Basic Annual Rent.............................    2
       ARTICLE 5        Additional Rent...............................    3
       ARTICLE 6        Security Deposit..............................    7
       ARTICLE 7        Use...........................................    7
       ARTICLE 8        Maintenance, Repairs and           
                           Alterations................................    8
       ARTICLE 9        Insurance; Indemnity..........................   10
       ARTICLE 10       Damage or Destruction.........................   13
       ARTICLE 11       Payment of Taxes..............................   14
       ARTICLE 12       Utilities.....................................   15
       ARTICLE 13       Assignment and Subletting.....................   15
       ARTICLE 14       Landlord's Access.............................   17
       ARTICLE 15       Defaults; Remedies............................   17
       ARTICLE 16       Eminent Domain................................   20
       ARTICLE 17       Brokers.......................................   21
       ARTICLE 18       Estoppel Certificate, Attornment
                         and Subordination............................   21
       ARTICLE 19       Landlord's Liability..........................   22
       ARTICLE 20       Miscellaneous Provisions......................   23
       ARTICLE 21       Addenda.......................................   25
EXHIBITS

       "A-1"            Floor Plan of the Premises....................
       "A-2"            Site Plan of the Project......................
       "A-3"            Definitions of Rentable Area..................
       "B"              Schedule of Construction Responsibilities.....
       "C"              Rules and Regulations.........................
       "D"              Estoppel Certificate..........................
       "E"              Parking Agreement.............................

LAL:1618Y
 022487
<PAGE>
 
                              R & D BUILDING LEASE
                              --------------------

                              ARTICLE 1:  PARTIES

   This R & D BUILDIN1G LEASE (the "Lease"), dated for reference
purposes only as of the 26 day of February 1987, is made by and
between SORRENTO TECH LIMITED, a California limited partnership (the
"Landlord"), and BIOSYM TECHNOLOGIES, INC., a California corporation
(the "Tenant"), on the terms and conditions stated below in this
Lease and in the foregoing Basic Lease Provisions.

                              ARTICLE 2:  PREMISES

   Subject to all the terms and conditions of this Lease, Landlord
hereby leases and demises to Tenant and Tenant hires from Landlord
the "Premises" for the term and at the rental provided below in this
Lease. The Premises are more particularly described in Item 3 of
the Basic Lease Provisions.  The Premises consist of the ground
floor of the west end of the Building.  The Rentable Area of the
Premises shall, therefore, be computed pursuant to Paragraph l(a) of
Exhibit "A3"  hereto.

                                ARTICLE 3:  TERM

   3.1   Commencement Date.
         ----------------- 

      (a) General.  Subject to all the terms and conditions of
          -------                                             
this Article 3, the term of this Lease shall be as specified in Item
4(a) of the Basic Lease Provisions, unless earlier terminated or
extended as provided below in this Lease.  The parties intend that
the Lease term shall commence on the Target Commencement Date
specified in Item 5 of the Basic Lease Provisions. The date on
which the Lease term actually commences is referred to as the
"Commencement Date." The Commencement Date shall be determined as
provided below in subparagraph (b).

      (b) Definition.  The term of this Lease shall commence on
          ----------                                           
the first to occur of: (1) the date on which Landlord substantially
completes construction of the Tenant Improvements (as defined in the
Schedule of Construction Responsibilities attached hereto as Exhibit
"B"), or (2) the date on which Landlord would have substantially
completed construction of the Tenant Improvements but for delays
caused by Tenant. If Tenant takes possession of or commences use of
the Premises (or any portion thereof) for any purpose, including
construction, before the Commencement Date, the term of this Lease
shall not commence, but such occupancy shall be subject to all the
terms and conditions of this Lease and Tenant shall be obligated to
pay all items of rent under this Lease from the date Tenant takes
possession or commences use of the affected portion of the
Premises.  If Tenant takes possession of or commences use of the
Premises before the Commencement Date, Tenant shall execute an Early
Entry Indemnity Agreement in form and substance reasonably
satisfactory to Landlord.  Landlord shall be deemed to have
substantially completed construction of the Tenant Improvements when
Landlord has substantially completed construction of the Tenant
Improvements in accordance with the Schedule of Construction
Responsibilities (Exhibit "B") and a certificate of occupancy has
been issued for the Premises. Landlord shall give Tenant thirty
(30) days' prior written notice of the date on which Landlord
reasonably expects substantial completion of construction of the
Tenant improvements to occur.

      (c) Tenant's Delay.  If construction of the Tenant
          --------------                                
Improvements is delayed or postponed by Tenant's Delay (as
hereinafter defined), the start of the term of this Lease shall be
adjusted to reflect the actual amount of Tenant's Delay.  To
illustrate, if the total amount of Tenant's Delay were five days and
substantial completion of construction of the Tenant Improvements
were to occur on April 15, 1987, the Lease term would commence on
April 10, 1987.  Tenant's Delay shall be the amount of delay or time
<PAGE>
 
lost as a result of Tenant's failure to adhere to the time table set
forth in the Schedule of Approvals contained in the Schedule of
Construction Responsibilities (Exhibit "B").

   3.2   Effect of Delay in Commencement.  Notwithstanding the
         -------------------------------                      
Target Commencement Date, if for any reason the Commencement Date
occurs after the Target Commencement Date, Landlord shall not be
subject to any liability therefor, nor shall such failure affect the
validity of this Lease or the obligations of Tenant under this Lease
or extend the term of the Lease. Tenant's obligation to pay rent
shall be measured from the Commencement Date; provided, however,
that if the Commencement Date has not occurred within sixty (60)
days after the Target Commencement Date for reasons other than
Tenant's Delay, Tenant may, at Tenant's option, by written notice
sent to Landlord within ten (10) days after the end of said 60-day
period (or such longer period as the parties may mutually agree),
cancel this Lease. If Tenant so cancels this Lease, the parties
shall be discharged from all obligations hereunder.

   3.3   Option to Extend or Renew.
         ------------------------- 

      (a) Grant of Option.  Subject to all the terms and
          ---------------                               
conditions of this Lease, Tenant shall have the right (the "Option")
to extend the term of this Lease for the additional period specified
in Item 4(b) of the Basic Lease Provisions by sending written notice
to such effect to Landlord not later than one hundred eighty (180)
days before the expiration of the initial term.  Failure to timely
send such notice shall constitute a waiver of all remaining rights
under the Option and Tenant shall have no right to exercise the
Option with respect to any future option term.  Each renewal or
extension of the term of this Lease shall be on all the terms and
conditions of this Lease; provided, however, that the Basic Annual
Rent payable during each option term shall be determined as provided
in subparagraph (b) below. Notwithstanding anything in this
Paragraph 3.3 to the contrary, Tenant shall have no right to
exercise the Option if (1) Tenant is in default under this Lease
either at the time the Option is exercised or at the time any option
term is scheduled to commence; (2) Tenant is not in possession of at
least seventy-five percent (75.0%) of the Rentable Area of the
Premises either at the time the Option is exercised or the time any
option term is scheduled to commence; or (3) Tenant has assigned
this Lease in whole or in part or sublet more than twenty-five
percent (25.0%) of the Rentable Area of the Premises.

      (b) Determination of New Basic Annual Rent.  If Tenant
           -------------------------------------            
exercises the Option, the Basic Annual Rent payable during the
option term shall be increased at the same rate and with the same
frequency as during the initial term.  The first increase in the
Basic Annual Rent shall take place on the first day of the first
year of the option term.

                         ARTICLE 4:  BASIC ANNUAL RENT

   4.1   Initial Basic Annual Rent.  Subject to increase as
         -------------------------                         
provided below, Tenant shall pay to Landlord as rental for the
Premises "Basic Annual Rent" in the amount specified in Item 6 of
the Basic Lease Provisions. The initial amount of the Basic Annual
Rent shall be as specified in Item 6(a) of the Basic Lease
Provisions. The Basic Annual Rent shall be payable in equal monthly
installments, in advance, without deduction or offset, on the first
day of each month during the term of this Lease, including any
extension or renewal thereof. The date on which the first
installment of Basic Annual Rent is due and payable is hereafter
referred to as the "Rent Commencement Date." Unless otherwise
specified, the Rent Commencement Date shall be the first day of the
first month following the Commencement Date. The first installment
of Basic Annual Rent shall include any Basic Annual Rent accrued
during any partial month between the Commencement Date and the Rent
Commencement Date.


                                      -2-
<PAGE>
 
   4.2   Increases in Basic Annual Rent.
         ------------------------------ 

      (a) General. The Basic Annual Rent shall be increased at the times and in
          -------                                                              
the amounts provided below in this Paragraph 4.2.

      (b) Computation of Increase. The Basic Annual Rent shall
          -----------------------                             
be adjusted at the times specified in Item 6(b) of the Basic Lease
Provisions. The date on which the Basic Annual Rent is adjusted is
hereafter referred to as the "Rental Adjustment Date." The rate of
the increase in the Basic Annual Rent (hereafter referred to as the
"Rental Adjustment Percentage") shall be as specified in Item 6(b)
of the Basic Lease Provisions. Each such increase in the Basic
Annual Rent shall take effect on the applicable Rental Adjustment
Date. The amount of each increase in the Basic Annual Rent shall be
equal to the Basic Annual Rent (the "Reference Rent") payable during
the twelve (12) month period immediately preceding the applicable
Rental Adjustment Date multiplied by the Rent Adjustment
Percentage.  The new Basic Annual Rent shall be equal to the sum of
(1) the Reference Rent and (2) the amount of the increase in the
Basic Annual Rent computed as specified in the preceding sentence.
In no event shall the Basic Annual Rent payable during any 12-month
period be less than the Basic Annual Rent payable during the
immediately preceding 12-month period.

   4.3   Miscellaneous. The Basic Annual Rent, the Additional Rent and all other
         -------------                                                          
amounts required to be paid by Tenant under this Lease
are sometimes collectively referred to as, and shall constitute,
"rent."  The Basic Annual Rent for any period during the term hereof
which is for less than one (1) month shall be a pro rata portion of
the monthly installment then due. The Basic Annual Rent shall be
payable in lawful money of the United States to Landlord at the
address stated below or to such other persons or at such other
places as Landlord may designate in writing.

                          ARTICLE 5:  ADDITIONAL RENT

   5.1   Definition of "Additional Rent." In addition to the Basic
         ------------------------------                           
Annual Rent specified in Article 4, Tenant shall pay to Landlord as
"Additional Rent" Tenant's pro rata share of Building Operating
Expenses (as hereafter defined) and Project Operating Expenses (as
hereafter defined). Tenant's share of Building Operating Expenses
shall be equal to the ratio of the Rentable Area of the Premises to
ninety-five percent (95.0%) of the total Rentable Area of the
Building. Tenant's share of Project Operating Expenses shall be
equal to the ratio of the Rentable Area of the Premises to
ninety-five percent (95.0%) of the total Rentable Area of the
Project. The Rentable Areas of the Building and the Project are
specified in Exhibit A-3. Initially, Tenant's share of Building
Operating Expenses and Project Operating Expenses shall be as
specified in Items 6(c)(i) and 6(c)(ii), respectively, of the Basic
Lease Provisions.

   5.2   Definition of "Building Operating Expenses."  The term
         ------------------------------------------            
"Building Operating Expenses" as used herein shall include all costs
of operation and maintenance of the Building, as determined by
generally accepted accounting practices consistently applied, and
shall include the following costs by way of illustration but not limitation:
real property taxes (as defined below); Landlord's
personal property taxes; costs and expenses in contesting the amount
or validity of any property tax by appropriate proceedings; water
and sewer charges; insurance premiums; license, permit, and
inspection fees; heat; gas; light; power; water; steam; janitorial
and security services; labor; salaries; air conditioning;
landscaping; supplies; materials; equipment; tools; the cost of any
capital improvements made to the Building by Landlord that reduce
operating expenses or that are required under any governmental law
or regulation not applicable to the Building or not in effect at the
time it was constructed (such cost to be amortized over such
reasonable period as Landlord shall determine with a return on
capital at the rate paid by Landlord on funds borrowed for the

                                      -3-
<PAGE>
 
purpose of constructing such capital improvements); property
management costs; and any increases in the amount of the interest
that Landlord is required to pay to its initial permanent lender in
accordance with the terms and provisions of the note evidencing Landlord's
initial permanent financing for the Building (or if
Landlord has not then closed its initial permanent financing for the
Building, then under the note evidencing Landlord's initial
permanent financing for the Building), in the event such note
contains provisions for variable interest rates (provided, however,
that in interpreting whether or not such note contains provisions
for variable interest rates, it is agreed that if the interest rate
is fixed but such lender is entitled to any participation in the
gross or net income, revenue or cash flow from the operation of the
Building, such participation shall cause the note to be construed to
be a variable interest rate note, and payments required of Landlord
to such lender due to the provisions of such participation agreement
shall be construed to be increased payments of interest).
Notwithstanding anything in this Paragraph 5.2 to the contrary, it
is agreed that the following items shall not be included as part of
Building Operating Expenses: the cost of any Tenant Improvements
constructed in the Building; brokerage commissions; leasing and
marketing costs; costs reimbursable by insurance or third parties;
executive salaries; depreciation on the Building or other capital
improvements; and, except as expressly provided above, depreciation
on equipment located in the Building.

   5.3   Definition of "Project Operating Expenses" and Other
         ----------------------------------------------------
Terms.
----- 

      (a) Project Operating Expenses.  The term "Project Operating Expenses"
          --------------------------                                        
shall include all costs of operation and maintenance of the Common Areas (as
hereafter defined), as
determined by generally accepted accounting practices consistently applied, and
shall include the following costs by way of
illustration but not limitation: general maintenance and repairs;
pest control; resurfacing, painting, restriping, cleaning and
sweeping of parking areas; trash removal; maintenance and repair of
sidewalks, curbs and signs in the Project which tenants and/or
occupants of the Project are not obligated to repair; irrigation
systems; landscaping; painting; electrical, water, gas and other
utilities; directional signs and other traffic markers and devices;
maintenance and repair of any fire protection systems for the
Project; lighting systems; storm drainage systems and any other
utility systems; real property taxes; Landlord's personal property
taxes; the cost and expense of contesting the amount or validity of
any real property tax by appropriate means; the cost of any capital
improvements made to the Common Areas by Landlord that reduce
operating expenses or that are required under any governmental law
or regulation not applicable to the Project or not in effect at the
time it was constructed (such cost to be amortized over such
reasonable period as Landlord shall determine with a return on
capital at the rate paid by Landlord on funds borrowed for the
purpose of constructing such capital improvements); any increases in
the amount of the interest that Landlord is required to pay to its
initial permanent lender in accordance with the terms and provisions
of the note evidencing Landlord's initial permanent financing for
the Common Areas of the Project (or if Landlord has not then closed
its initial permanent financing for the Common Areas of the Project,
then under the note evidencing Landlord's initial permanent
financing of the Common Areas of the Project) in the event such note
contains provisions for variable interest rates (provided, however,
that in interpreting whether or not such note contains provisions
for variable interest rates, it is agreed that if the interest rate
is fixed but such lender is entitled to any participation in the
gross or net income, revenue or cash flow from the operation of the
Common Areas of the Project, such participation shall cause the note
to be construed to be a variable interest rate note, and payments
required of Landlord to such lender due to the provisions of such
participation agreement shall be construed to be increased payments
of interest), regular and special assessments imposed by the
                                      -4-
<PAGE>
 
Lusk/Mira Mesa industrial Park Association, a California non-profit
corporation; police and fire protection services; depreciation and
maintenance on operating machinery and equipment used in the
maintenance and repair of the Common Areas (if owned) and rental
paid for such machinery and equipment used in the maintenance and
repair of the Common Areas (if rented); rental for electric and
service rooms based upon the average rate in the Project; any
parking charges, surcharges or any other costs levied or assessed by
local, state or federal government agencies in connection with the
use of parking facilities; property management costs; the cost of
maintaining and operating the Common Area Facilities (as hereafter
defined), including without limitation all utility expenses and
salaries of all personnel employed by Landlord in the Common Area
Facilities. Such costs and expenses shall not include any allowance
for depreciation of the Common Area Facilities or other improvements
located in the Common Areas. Landlord may cause any or all of the
services described above to be provided by an independent contractor
or contractors.

      (b) Common Area Facilities.  The term "Common Area
          ----------------------                        

Facilities" sha11 include, without limitation, any swimming pools, spas, tennis
and racquetball courts, saunas, locker rooms, exercise rooms, restaurants and
other facilities available for general use by tenants/occupants of the Project.

      (c) Common Areas.  The term "Common Areas" shall include
          ------------                                        
all areas within the Project outside the exterior boundaries of
buildings (other than the Common Area Facilities) now or hereafter
situated thereon, including, but not limited to, streets, driveways,
parking areas, parking structures, truckways, delivery passages,
loading docks, sidewalks, ramps, open and closed courts, landscaped
and planted areas, exterior stairways, bus stops, retaining and
decorative walls and planters, the Common Area Facilities, and other
areas provided by Landlord and/or other owners of portions of the
Project for the common use of Landlord, such other owners and/or the
occupants of the Project, their employees, customers and invitees.
Landlord reserves the right to make changes at any time and from
time to time in the size, shape, location, number and extent of the
Common Areas, or any of them, and no such change shall entitle the
Tenant to any abatement of rent.

   5.4   Definition of Real Property Taxes.
         --------------------------------- 

      (a) General.  As used in this Lease, the term "real property taxes" shall
          -------                                                              
include any form of general or special assessment, license fee, commercial
rental tax, levy, penalty, or
tax (other than inheritance or estate taxes), unforeseen as well as
foreseen, imposed by any authority having the direct or indirect
power to tax, including any city, county, state or federal
government, or any school, agricultural, lighting, drainage or other
improvement district thereof, as against any legal or equitable
interest of Landlord in the Premises or in the Building and/or the
Project, as against Landlord's right to rent or other income
therefrom, or as against Landlord's business of leasing the Premises
or any tax imposed in substitution, partially or totally, of any tax
previously included within the definition of real property taxes, or
any additional tax the nature of which was previously included
within the definition of real property tax.

      (b) Inclusions.  The definition of "real property taxes"
          ----------                                          
set forth in subparagraph (a) includes without limitation:

          (1)  Any tax on Landlord's "right" to rent or "right"
to other income from the Premises or as against Landlord's business
of leasing the Premises.

          (2)  Any assessment, tax, fee, levy or charge in
substitution, partially or totally, of any assessment, tax, fee,
levy or charge previously included within the definition of real
property taxes, it being acknowledged by Tenant and Landlord that


                                      -5-
<PAGE>
 
Proposition 13 was adopted by the voters of the State of California
in the June 1978 Election and that assessments, taxes, fees, levies
and charges may be imposed by governmental agencies for such
services as fire protection, street, sidewalk and road maintenance,
refuse removal and for other public improvements, services or
benefits formerly provided without charge to property owners or
occupants. It is the intention of Tenant and Landlord that all such
new and increased assessments, taxes, fees, levies and charges be
included within the definition of "real property taxes" for the
purposes of this Lease.

          (3)  Any assessment, tax, fee, levy or charge
allocable to or measured by the area of the Premises or the rent
payable hereunder, including, without limitation, any gross income
tax or excise tax levied by the state, city or federal government,
or any political subdivision thereof, with respect to the
possession, leasing, operating, management, maintenance, alteration,
repair, use or occupancy by Tenant of the Premises, or any portion
thereof.

          (4)  Any assessment, tax, fee, levy or charge upon
this transaction or any document to which Tenant is a party,
creating or transferring an interest or an estate in the Premises.

      (c) Exclusions.  Notwithstanding any provision of this
          ----------                                        
Paragraph 5.4 expressed or implied to the contrary, "real property
taxes" shall not include Landlord's federal or state income,
franchise, inheritance or estate taxes.

     5.5   Payment of Additional Rent.
           -------------------------- 

      (a) Time of Payment.  Tenant shall pay Additional Rent in
          ---------------                                      
monthly installments, in advance, at the same time monthly
installments of Basic Annual Rent are payable. Tenant shall be
obligated to pay Additional Rent from the Commencement Date,
notwithstanding any delay in Tenant's obligation to start paying
Basic Annual Rent. Prior to the Commencement Date and the beginning
of each calendar year thereafter, Landlord shall give Tenant a
written estimate of Building and Project Operating Expenses for the
ensuing calendar year or portion thereof. If, during the course of
any calendar year, it appears that Landlord's estimate of Building
and Project Operating Expenses was too low, Landlord may revise its
written estimate. Tenant shall pay the then current estimated
amount to Landlord as Additional Rent, in equal monthly
installments, in advance. Within thirty (30) days after receipt of
the accountant's determination, referred to in Article 5.5(c), the
parties shall make any payment or allowance necessary to adjust
Tenant's estimated payment to Tenant's actual proportionate share as
shown by the accountant's determination. Any amount due Tenant
shall be credited against installments next coming due under this
Article 5.

      (b) Adjustments for Direct Payments.  Notwithstanding anything to the
          -------------------------------                                  
contrary contained in this Article 5, as to each specific category of expense
which one or more tenants of the Building or the Project either pays directly to
third parties or specifically reimburses to Landlord (for example, separately
metered utilities, separately contracted janitorial service, property taxes
directly reimbursed to Landlord, etc.) such tenant(s)' payments with respect
thereto shall not be included in Building Operating Expenses and/or Project
Operating Expenses, as the same may be, for purposes of this Article 5. Tenant's
share of each such category of expenses shall be adjusted by excluding from the
denominator thereof the Rentable Area of all such tenants paying such category
of expenses directly to third parties or reimbursing same directly to Landlord.

      (c) Annual Determination.  Annual and other determinations of Building
          --------------------                   
and Project Operating Expenses shall be made reasonably and in good faith by
Landlord by reference to competitive market conditions as to the cost of the
items included as part of such expenses. Tenant shall have the right, after


                                      -6-
<PAGE>
 
reasonable notice, to inspect Landlord's books and records relating
to such expenses at reasonable times at Landlord's principal place
of business. The annual determination of Building and Project
Operating Expenses shall be made and certified by an independent
certified public accountant designated by Landlord. A copy of the
determination shall be made available to Tenant upon request. The
independent accountant's determination shall be final and binding
upon Landlord and Tenant.

      (d) On Termination.  Even though the Lease term has
          --------------                                 
expired and Tenant has vacated the Premises, if Tenant has not paid
all Additional Rent payable by Tenant under this Lease attributable
to a period before the termination of this Lease, Tenant shall
immediately pay any amount due from Tenant upon receipt of written
notice from Landlord. In the event of a termination of this Lease
resulting in Tenant's overpayment of Additional Rent, Landlord shall
promptly reimburse Tenant the amount of any overpayment.

                          ARTICLE 6: SECURITY DEPOSIT

     6.1   Purpose.  In addition to the Rent Deposit specified in
           -------                                               
Item 7 of the Basic Lease Provisions, Tenant has deposited with
Landlord the sum specified in Item 8 of the Basic Lease Provisions,
receipt of which is hereby acknowledged, as security for the full
performance of the obligations of Tenant to Landlord under this
Lease. If Tenant shall be in default with respect to the payment of
any item of rent or any other covenant contained herein, Landlord
may use or retain all or any part of said security deposit for the
payment of any rent or any other sum in default, or for the payment
of any amount which Landlord may spend or may become obligated to
spend by reason of Tenant's default. If any portion of said
security deposit be applied or used, Tenant shall, within five (5)
days after written notice thereof, deposit an additional amount with
Landlord sufficient to restore said security deposit to its original
amount as specified in Item 8 of the Basic Lease Provisions and
Tenant's failure to do so shall constitute a material breach of this
Lease.  If Tenant is not in default at the termination of this
Lease, Landlord shall return said security deposit to Tenant within
thirty (30) days after termination of this Lease, less any amounts
required to restore the Premises to good condition and repair,
including damage resulting from the removal by Tenant of its trade
fixtures or equipment.

     6.2   Landlord's Obligations.  Landlord's obligation with
           ----------------------                             
respect to any security deposit is that of a debtor and not as a
trustee, consequently such sums may be commingled with rental
receipts or dissipated and no interest shall accrue thereon. In the
event of the sale of the real property of which the Premises
constitute a part, Landlord or its agent shall pay over to
Landlord's successor in interest the sums held as security or
advance rent and notify Tenant in writing setting forth the details
of such transfer, including the successor's name and address. Upon
such written notification, Tenant shall have no further claim
against Landlord in that regard. In the event of foreclosure by any
mortgagee against Landlord's interest in the Premises or the Lease,
Landlord shall continue to be liable for any security deposit and
any such mortgagee shall have no liability or responsibility
therefor.

                                ARTICLE 7:  USE

     7.1   Permitted Use.  The Premises shall be used and occupied
           -------------                                          
only for the purposes specified in Item 9 of the Basic Lease
Provisions, subject, however, to any recorded covenants, conditions
and restrictions for Lusk/Mira Mesa Industrial Park (the "C,C&R's")
and applicable governmental rules and regulations; provided,
however, that, in no event shall any use of the Premises involve any
hazardous or dangerous activity not covered by the forms of
insurance required to be maintained under this Lease.


                                      -7-
<PAGE>
 
     7.2   Compliance with Law.
           ------------------- 

      (a) Warranties by Landlord. Landlord warrants to Tenant
          ----------------------                             
that the Premises, in their existing state as of the date of this
Lease and at the Commencement Date, but without regard to the use
for which Tenant will use the Premises, do not violate any
applicable building code regulation or ordinance. Landlord also
warrants that the Premises shall be in good condition as of the
Commencement Date, improved in accordance with the agreement of the
parties with respect to the construction of Tenant Improvements, as
set forth in the Schedule of Construction Responsibilities (Exhibit
B). In the event that it is determined that this Warranty has been
violated, then it shall be the obligation of Landlord, after written
notice from Tenant, to promptly, at Landlord's sole cost and
expense, rectify any such violation in the event that Tenant does
not give to Landlord written notice of the violation of this
warranty within one (1) year after the Commencement Date, it shall
be conclusively deemed that, such violation did not exist and the
correction of the same shall be the obligation of Tenant; provided,
however, that as to latent defects which are not discoverable by
reasonable diligence on the part of Tenant during said one-year
period, it is agreed that Landlord shall be responsible for
correcting such undiscoverable latent defects during the one-year
period beginning on the date Tenant discovers or should have
reasonably discovered any such latent defect.

      (b) Tenant's Duties. Tenant shall, at Tenant's expense,
          ---------------                                    
comply promptly with all applicable statutes, ordinances, rules,
regulations, orders, restrictions of record, and requirements in
effect during the term or any part of the term of this Lease
regulating the use by Tenant of the Premises. Tenant shall not use
nor permit the use of the Premises in any manner that will create
waste or a nuisance. Tenant shall comply with the Rules and
Regulations attached hereto as Exhibit "C" and with the C,C&R's.

     7.3   Condition of Premises.  Tenant hereby accepts the
           ---------------------                            
Premises in their condition existing as of the date of the execution
hereof, subject to all applicable zoning, municipal, county and
state laws, ordinances and regulations governing and regulating the
use of the Premises, and accepts this Lease subject thereto and to
all matters disclosed thereby and by any exhibits attached hereto.
Tenant acknowledges that neither Landlord nor Landlord's agent has
made any representation or warranty as to the suitability of the
Premises for the conduct of Tenant's business. The taking of
possession of the Premises by Tenant shall conclusively establish
that the Premises were at such times in good and sanitary order,
condition and repair.

                ARTICLE 8: MAINTENANCE, REPAIRS AND ALTERATIONS

     8.1   Tenant's Obligations.  Tenant shall, at Tenant's sole cost
           --------------------                                      
and expense, keep the Premises and every part thereof in good
condition and repair (except as provided in Paragraph 8.2 with
respect to Landlord's maintenance obligations), including without
limitation all decorating, remodeling, alteration and painting
required by Tenant during the term of this Lease. Tenant will pay
for any repairs to the Premises, the Building or the Project made
necessary by any negligence or carelessness of Tenant or its
assignees, subtenants, employees or their respective agents or other
persons permitted in the Building or the Project by Tenant, or any
of them, and will maintain the Premises in a safe, clean, neat and
sanitary condition. Notwithstanding anything in this Lease to the
contrary, Tenant shall be responsible for replacing any glass that
may be broken or removed at the direction of or by any negligence or
carelessness of Tenant or its assignees, subtenants, employees or
their respective agents or other persons permitted in the Building
or the Project by Tenant. Landlord is not liable to repair any
leaks in the roof of the Building or other damage to the Building
resulting from penetrations of the Building's roof made by or at the


                                      -8-
<PAGE>
 
request of Tenant, unless such penetration is made by Landlord's
contractor before the Commencement Date.

     8.2   Landlord's Obligations.
           ---------------------- 

         (a) Scope of Responsibility.  Subject to Paragraph 8.1,
             ------------------------                           
         Landlord shall make all necessary repairs to the roof, exterior and
         interior demising walls, exterior doors, windows (but not glass),
         corridors and other common areas of the Building, the Common Area
         Facilities and the Common Areas. Landlord shall keep the Building
         and the Project in a safe, clean and neat condition, and use
         reasonable efforts to keep all equipment in the Building, such as
         elevators, plumbing, and heating, air conditioning and ventilation
         ("HVAC") equipment, in good condition and repair. Landlord shall also
         maintain and repair all structural parts of the Building, which
         structural parts include, without limitation, certain items listed
         above in this subparagraph (a) and the foundations, subflooring,
         unexposed electrical, plumbing and sewage systems, including those
         portions of the said systems lying outside the Premises, and gutters
         and downspouts on the Building. There shall be no abatement of rent and
         no liability of Landlord by reason of any injury to or interference
         with Tenant's business arising from the making of any repairs,
         alterations or improvements in or to any portion of the Building (or
         fixtures, appurtenances and equipment therein) or the Project. Tenant
         specifically waives the right to make repairs at Landlord's expense
         under Section 1942 of the California Civil Code or any other law,
         statute or ordinance now or hereafter in effect, subject, however, to
         subparagraph (b) below.

         (b) Corrective Action by Tenant.  Tenant shall promptly
             ---------------------------                        
         notify Landlord in writing of any repairs which Landlord is
         obligated to effect under subsection (a). Landlord shall promptly
         effect such repairs, taking into account whether or not the nature
         of the problem presents a hazard or emergency.  If Landlord fails to
         effect such repairs within thirty (30) days after written notice
         from Tenant, Tenant may make the repairs itself in a commercially
         reasonable manner. If Tenant does so, Landlord shall reimburse
         Tenant for the cost of the repairs within fifteen (15) days after
         receipt of a reasonably detailed invoice from Tenant. If Landlord
         fails to reimburse Tenant within said 15-day period, interest shall
         accrue on the unpaid balance at the rate of interest specified in
         Paragraph 15.4(b) below from the date of disbursement by Tenant to
         the date of reimbursement by Landlord; provided, however, that no
         interest shall accrue on any disputed portion of an invoice from
         Tenant if Landlord notifies Tenant of a good faith dispute about
         such invoice within said 15-day period.  Upon resolution of such
         dispute, interest shall accrue on the amount ultimately determined
         owing to Tenant in accordance with the above provisions.

     8.3  Surrender.  On the last day of the term hereof, or on any
          ---------                                                
     earlier termination, Tenant shall surrender the Premises to Landlord
     in the same condition as when received, broom clean, ordinary wear
     and tear excepted. Tenant shall repair any damage to the Premises
     occasioned by the removal of Tenant's trade fixtures, furnishings
     and equipment, which repair shall include the patching and filling
     of holes in floors and walls and repair of structural damage.

     8.4   Landlord's Rights.  if Tenant fails to perform Tenant's
           -----------------                                      
     obligations under this Article 8, Landlord may at its option (but
     shall not be required to) enter upon the Premises, after reasonable
     notice to Tenant under the circumstances, and put the same in good
     order, condition and repair, and the cost thereof, together with
     interest thereon at the rate specified below in Paragraph 15.4 (Late
     Charges and Interest on Delinquent Payments) shall immediately
     become due and payable as Additional Rent. Landlord shall have the
     right, at any time, to change the arrangement and/or location of
     entrances or passageways, doors and doorways, and corridors,
     elevators, stairs, toilets, or other public parts of the Building
     and the configuration of the Common Areas and, upon giving Tenant


                                      -9-
<PAGE>
 
     reasonable notice thereof, to change the name, number or designation
     by which the Building and/or the Project is commonly known.

     8.5  Alterations and Additions.
          ------------------------- 

          (a) Procedure for Making Alterations.  After the
              --------------------------------            
          Commencement Date Tenant shall not, without Landlord's prior written
          consent, make or permit any alterations, improvements, additions, or
          Utility Installations (as hereafter defined) in, on or about the
          Premises, except for non-structural alterations, exceeding Five
          Thousand Dollars ($5,000) in cost in each instance. As used in this
          Paragraph 8.5, the term "Utility Installation" shall mean bus
          ducting, power panels, wiring, fluorescent fixtures, space heaters,
          conduits, air conditioning equipment and plumbing. Landlord may
          require that Tenant remove any or all of said alterations,
          improvements, additions, or Utility Installations at the expiration
          of the Lease term, and restore the Premises to their prior
          condition, ordinary wear and tear excepted. Landlord may also
          require Tenant to provide Landlord, at Tenant's sole cost and
          expense, a lien and completion bond, in an amount equal to one
          hundred fifty percent (150%) of the estimated cost of such
          improvements, to insure Landlord against any liability for
          mechanics' and materialman's liens and to insure completion of the
          work. Should Tenant make any alterations, improvements, additions
          or Utility Installations without the prior approval of Landlord,
          Landlord may require that Tenant remove any or all of the same.

          (b) Conditions to Landlord's Approval.  Any alterations,
              ---------------------------------                   
          improvements, additions or Utility Installations in or about the
          Premises that Tenant shall desire to make and which requires the
          consent of Landlord shall be presented to Landlord in written form,
          with detailed plans for the proposed work. If Landlord shall give
          its consent thereto, the consent shall be deemed conditioned upon
          Tenant's (1) acquiring a permit to do so from appropriate
          governmental agencies, (2) furnishing of a copy thereof to Landlord
          prior to the commencement of the work and (3) complying with all
          conditions of said permit in a prompt and expeditious manner.

          (c) Lien Free Construction.  Tenant shall pay when due
              ----------------------                            
          all claims for labor or materials furnished or alleged to have been
          furnished to or for Tenant at or for use in the Premises, which
          claims are or may be secured by any mechanics' or materialman's 1ien
          against the Premises or any interest therein. Tenant shall give
          Landlord not less than ten (10) days' prior written notice of the
          commencement of any work in the Premises. Landlord shall have the
          right to post notices of non-responsibility in or on the Premises as
          provided by law. If Tenant shall, in good faith, contest the
          validity of any such lien, claim or demand, then Tenant shall, at
          its sole expense, defend itself and Landlord against the same and
          shall pay and satisfy any such adverse judgment that may be rendered
          thereon before the enforcement thereof against the Landlord or the
          Premises, upon the condition that if Landlord shall require, Tenant
          shall furnish Landlord with a surety bond satisfactory to Landlord
          in an amount equal to such contested lien, claim or demand
          indemnifying Landlord against liability for the same and holding the
          Premises free from the effect of such lien or claim. In addition,
          Landlord may require Tenant to pay Landlord's reasonable attorneys'
          fees and costs incurred by Landlord in participating in such action.

          (d) Ownership Upon Expiration of Lease.  Unless Landlord
              ----------------------------------                  
          requires their removal, all alterations, improvements, additions and
          Utility Installations (whether or not such Utility Installations
          constitute trade fixtures of Tenant) which may be made on the
          Premises shall become the property of Landlord and remain upon and
          be surrendered with the Premises at the expiration of the Lease term.

                        ARTICLE 9: INSURANCE; INDEMNITY

     9.1  Insuring Party.  As used in this Article 9, the term
          --------------                                      
     "insuring party" shall mean the party designated in Item 10 of the


                                     -10-
<PAGE>
 
     Basic Lease Provisions who has the obligation to obtain the Property
     Insurance required hereunder. Whether the insuring party is
     Landlord or Tenant, Tenant shall, as additional rent for the
     Premises, pay the cost of all insurance required hereunder.  If
     Landlord is the insuring party, Tenant shall pay the cost of the
     insurance so obtained by Landlord as Additional Rent.

     9.2  Liability Insurance.  Tenant shall, at Tenant's expense,
          -------------------                                     
     obtain and keep in force during the term of this Lease a policy of
     Combined Single Limit, Bodily Injury and Property Damage Insurance
     insuring Landlord and Tenant against any liability arising out of
     the ownership, use, occupancy or maintenance of the Premises and all
     areas appurtenant thereto. Such insurance shall be a combined
     single limit policy in an amount not less than Three Million Dollars
     ($3,000,000) for personal injury and Five Hundred Thousand Dollars
     ($500,000) property damage. The liability policy shall contain
     cross liability endorsements and shall insure performance by Tenant
     of the indemnity provisions of this Article 9. The limits of said
     insurance shall not, however, limit the liability of Tenant
     hereunder. If Tenant shall fail to procure and maintain said
     insurance, Landlord may, but shall not be required to, procure and
     maintain the same, but at the expense of Tenant. Not more
     frequently than every three (3) years, if, in the reasonable opinion
     of Landlord, the amount of liability insurance required hereunder is
     not adequate, upon receipt from Landlord of a reasonably detailed
     explanation of the rationale for increasing such liability insurance
     coverage, Tenant shall increase said insurance coverage as required
     by Landlord; provided, however, that in no event shall the amount of
     the liability insurance increase be more than fifty percent (50%)
     greater than the amount thereof during the preceding three (3) years
     of the term of this Lease. However, the failure of Landlord to
     require any additional insurance coverage shall not be deemed to
     relieve Tenant from any obligations under this Lease.

     9.3  Property Insurance.
          ------------------ 

          (a) General Requirements.  The insuring party shall
              --------------------                           
          obtain and keep in force during the term of this Lease a policy or
          policies of insurance covering loss or damage to the Premises, in
          the amount of the full replacement value thereof, as the same may
          exist from time to time, against all perils included within the
          classification of fire, extended coverage, vandalism, malicious
          mischief, special extended perils (all risk), sprinkler leakage,
          earthquake sprinkler leakage, with "inflation guard" or agreed
          amount endorsement, and any other perils which Landlord deems
          necessary. Said insurance shall provide for payment of loss
          thereunder to Landlord or to the holders of any mortgages or deeds
          of trust encumbering the Premises. Tenant shall also obtain and
          keep in force during the term of this Lease a policy of business
          interruption insurance in an amount equal to the Basic Annual Rent
          and the Additional Rent for a period of at least twelve (12) months,
          with loss payable to Landlord. If such insurance coverage has a
          deductible clause, Tenant shall be liable for the deductible amount;
          provided, however, that the amount of such deductible clause shall
          not exceed One Thousand Dollars ($1,000). Tenant shall deliver to
          Landlord a certificate of such business interruption insurance.

          (b) Contents Insurance.  Tenant shall be solely
              ------------------                         
          responsible for insuring all contents of the Premises, including
          Tenant's furniture, fixtures, and equipment and improvements
          installed by Tenant.

          (c) Increases in Coverage.  Not more frequently than each
              ---------------------                                
          three (3) years during the term of this Lease, if, in the opinion of
          Landlord or the insuring party's insurance carrier, the amount of
          property insurance required hereunder is not adequate, the insuring
          party shall increase said insurance coverage. Such increase may,
          however, be more frequent than each three (3) years if required by
          the insurance carrier in order to maintain insurance for the full
          replacement cost of the Premises.


                                     -11-
<PAGE>
 
     9.4  Insurance Policies.
          ------------------ 

          (a) Requirements.  Insurance policies required under this
              ------------                                         
Article 9 shall be issued by companies holding a "General
Policyholder's Rating" of B+ or better, as set forth in the most
current issue of Best's Insurance Guide.  The insuring party shall
                 ----------------------                           
deliver to the other party copies of the policies of such insurance or
certificates evidencing the existence and amounts of such insurance
with loss payable clauses satisfactory to Landlord.  No such policy
shall be cancellable or subject to reduction of coverage or other
modification except after thirty (30) days' prior written notice to
Landlord.  If Landlord is the insuring party, Landlord shall name
Tenant as an additional insured under the policies procured by
Landlord in its capacity as the insuring party.  Any certificates of
insurance provided by Tenant shall add as additional insureds (but
                                                               ---
not "named insureds") Landlord and each of its partners, affiliates,
--------------------                                                
directors, agents and employees and shall expressly provide that the
interest of Landlord therein shall not be affected by any breach by
Tenant of any policy provision.  Insurance maintained by Tenant
under this Article 9 shall be the primary insurance as respects
Landlord (and any other additional insureds designated by Landlord)
and not contributory with any other available insurance.  Any
certificates of insurance procured by Tenant evidencing the
liability insurance coverage required under Paragraph 9.2 (Liability
Insurance) shall contain an endorsement providing, in substance,
that "such insurance as is afforded hereby for the benefit of
Landlord shall be primary and any insurance carried by Landlord
shall be excess and not contributory."

          (b) Miscellaneous.  If Tenant is the insuring party
              -------------                                  
Tenant shall, within ten (10) days prior to the expiration of such
policies, furnish Landlord with renewals or "binders" thereof, or
Landlord may order such insurance and charge the cost thereof to
Tenant, which amount shall be payable by Tenant upon demand.  Tenant
shall not do or permit to be done anything which shall invalidate
the insurance policies required under Paragraph 9.3  (Property
Insurance).  If Tenant does or permits to be done anything which
shall increase the cost of the insurance policies required under
Paragraph 9.3, then Tenant shall forthwith, upon Landlord's demand,
reimburse Landlord for any additional premiums attributable to any
act or omission or operation of Tenant causing such increase in the
cost of the insurance.  If Landlord is the insuring party, and if
the insurance policies maintained hereunder cover other improvements
in addition to the Premises, Landlord shall deliver to Tenant a
written statement setting forth the amount of any such insurance
cost increase and showing in reasonable detail the manner in which
it has been computed.

      9.5 Waiver of Subrogation.  Tenant and Landlord each hereby
          ---------------------                                  
waive any and all rights of recovery against the other, or against
the officers, employees, agents and representatives of the other,
for loss of or damage to such waiving party or its property or the
property of others under its control to the extent that such loss or
damage is insured against under any insurance policy in force at the
time of such loss or damages.  The insuring party shall, upon
obtaining the policies of insurance required hereunder, give notice
to the insurance carrier or carriers that the foregoing mutual
waiver of subrogation is contained in this Lease.

      9.6 Indemnity.  Tenant shall indemnify and hold Landlord
          ---------                                           
harmless from and against any and all claims arising from Tenant's
use of the Premises, or from the conduct of Tenant's business or
from any activity, work or things done, permitted or suffered by
Tenant in or about the Premises or elsewhere and shall further
indemnify and hold harmless Landlord from and against any and all
claims arising from any breach or default in the performance of any
obligation on Tenant's part to be performed under the terms of this
Lease, or arising from any negligence of Tenant, or any of Tenant's
agents, contractors, or employees, and from and against all costs,


                                     -12-
<PAGE>
 
attorneys' fees, expenses and liabilities incurred in the defense of
any such claim or any action or proceeding brought thereon; and in
case any action or proceeding be brought against Landlord by reason
of any such claim, Tenant upon notice from Landlord shall defend the
same at Tenant's expense by counsel satisfactory to Landlord.
Tenant, as a material part of the consideration to Landlord, hereby
assumes all risk of damage to property or injury to persons, in,
upon or about the Premises arising from any cause and Tenant hereby
waives all claims in respect thereof against Landlord; provided,
however, that nothing in this Lease shall relieve Landlord from
liability for (a) breach of this Lease by Landlord, (b) its
negligence or willful misconduct or omissions, or (c) the negligence
or willful misconduct or omissions of its employees and agents.

      9.7 Exemption of Landlord from Liability.  Tenant hereby
          ------------------------------------                
agrees that Landlord shall not be liable for injury to Tenant's
business or any loss of income therefrom or for damage to the goods,
wares, merchandise or other property of Tenant, Tenant's employees,
invitees, customers, or any other person in or about the Premises,
nor shall Landlord be liable for injury to the person of Tenant,
Tenant's employees, agents or contractors, whether such damage or
injury is caused by or results from fire, steam, electricity, gas,
water or rain, or from the breakage, leakage, obstruction or other
defects of pipes, sprinklers, wires, appliances, plumbing, air
conditioning or lighting fixtures, or from any other cause, whether
the said damage or injury results from conditions arising upon the
Premises or upon other portions of the Buildings of which the
Premises are a part, or from other sources or places, and regardless
of whether the cause of such damage or injury or the means of
repairing the same is inaccessible to Tenant; provided, however,
that nothing in this Lease shall relieve Landlord from liability for
(a) breach of this Lease by Landlord, (b) its negligence or willful
misconduct or omissions or (c) the negligence or willful misconduct
or omissions of its employees and agents.  Landlord shall not be
liable for any damages arising from any act or neglect of any other
tenant, if any, of the Building, the Project or of any subtenant of Tenant.

                       ARTICLE 10:  DAMAGE OR DESTRUCTION

      10.1  Reconstruction.  If the Premises are damaged or destroyed
            --------------                                           
during the term of this Lease, Landlord shall, except as hereinafter
provided, diligently repair or rebuild them to substantially the
condition in which they existed immediately prior to such damage or
destruction; provided, however, that Tenant shall repair any damage
which is estimated in good faith by Landlord to be under Five
Thousand Dollars ($5,000).  Landlord shall reimburse Tenant upon
demand for expenses incurred by Tenant in such repair work.

      10.2  Rent Abatement.  Basic Annual Rent, but not Additional
            --------------                                        
Rent, shall be abated proportionately; provided, however, that if
the damage or destruction is not caused by or the result of Tenant's
acts, omissions or willful misconduct (or that of its agents,
employees or invitees), all rent shall abate as of the date on which
payments under the policy of business interruption insurance
required to be maintained by Tenant under Paragraph 9.3(a) cease (or
in the event Tenant fails to procure such insurance, on the date
such payments would have ceased had Tenant obtained such
insurance).  Such rent abatement shall be in proportion to the ratio
of the portion of the Premises rendered unusable to the total
Rentable Area of the Premises.  Such abatement shall continue for
the period commencing with such damage or destruction and ending
with substantial completion by Landlord of the work or repair or
reconstruction which Landlord is obligated or undertakes to do.  If
it is determined that continuation of Tenant's business is not
practical pending reconstruction, Basic Annual Rent due and payable
hereunder shall abate until reconstruction is substantially
completed or until business is totally or partially resumed,
whichever is the earlier.


                                     -13-
<PAGE>
 
      10.3  Excessive Damage or Destruction.  If the Premises are
            -------------------------------                      
damaged or destroyed to the extent that Landlord determines that
they cannot, with reasonable diligence, be fully repaired or
restored by Landlord within one hundred eighty (180) days after the
date of the damage or destruction, either Landlord or Tenant shall
have the right to terminate this Lease.  Landlord shall determine
whether the Premises can be fully repaired or restored within said
180 day period, and Landlord's determination shall be conclusive on
Tenant.  Landlord shall send Tenant written notice of Landlord's
determination within thirty (30) days after the date of the damage
or destruction.  If Landlord determines that the Premises can be
fully repaired or restored within said 180-day period, or if it is
determined that such repair or restoration cannot be made within
said period but neither party elects to terminate this Lease within
thirty (30) days after the date of said determination, this Lease
shall remain in full force and effect and Landlord shall diligently
repair and restore the damage as soon as reasonably possible.

      10.4  Uninsured Casualty.  Notwithstanding anything in this
            ------------------                                   
Lease to the contrary, in the event of damage to or destruction of
all or any portion of the Premises which is not fully covered by the
insurance proceeds received by Landlord or which has not been
insured under the insurance policies required under Article 9,
Landlord may terminate this Lease by written notice to Tenant, given
within thirty (30) days after the date of notice to Landlord that
said damage or destruction is not so covered.  If Landlord does not
elect to terminate this Lease, this Lease shall remain in full force
and effect and the Premises shall be repaired and rebuilt in
accordance with the provisions for repair set forth in Paragraph
10.1 (Reconstruction).

      10.5  Waiver.  With respect to any destruction which Landlord is
            ------                                                    
obligated to repair or may elect to repair under the terms of this
Article 10, Tenant hereby waives all right to terminate this Lease
pursuant to rights otherwise presently or hereafter accorded by law
to tenants, except as expressly otherwise provided herein.

      10.6  Damage Near End of Term.  If the Premises are destroyed or
            -----------------------                                   
damaged such that the reasonable cost of repair would exceed
Twenty-five Thousand Dollars ($25,000.00) during the last twelve
(12) months of the term of this Lease, Landlord may, at Landlord's
option, cancel and terminate this Lease as of the date of occurrence
of such damage by giving written notice to Tenant of Landlord's
election to do so within thirty (30) days after the date of
occurrence of such damage.

                    ARTICLE 11:  TAXES ON TENANT'S PROPERTY

      11.1  Tenant's Obligation.  Tenant shall be liable for and shall
            -------------------                                       
pay ten (10) days before delinquency all taxes, levies and
assessments levied against any personal property or trade fixtures
placed by Tenant in or about the Premises.  If any such taxes,
levies and assessments on Tenant's personal property or trade
fixtures are levied against Landlord or Landlord's property or if
the assessed value of the Building or the Project is increased by
the inclusion therein of a value placed upon such personal property
or trade fixtures of Tenant and if Landlord pays the taxes, levies
and assessments based upon such increased assessment, which Landlord
shall have the right to do regardless of validity thereof, but only
under proper protest if requested by Tenant, Tenant shall, upon
demand, repay to Landlord the taxes, levies and assessments so
levied against Landlord, or the proportion of such taxes, levies and
assessments resulting from such increase in the assessment; provided
that, in any such event Tenant shall have the right, in the name of
Landlord and with Landlord's full cooperation but without any cost
to Landlord, to bring suit in any court of competent jurisdiction to
recover the amount of any such taxes, levies and assessments so paid
under protest, any amount so recovered to belong to Tenant.


                                     -14-
<PAGE>
 
      11.2  Additional Taxes Payable by Tenant.  If the Tenant
            ----------------------------------                
Improvements in the Premises, whether installed and/or paid for by
Landlord or Tenant and whether or not affixed to the real property
so as to become a part thereof, are assessed for real property tax
purposes at a valuation higher than the valuation at which tenant
improvements conforming to Landlord's "building standard" in other
space in the Building are assessed, then the real property taxes
levied against Landlord or the property by reason of such excess
assessed valuation shall be deemed to be taxes levied against
personal property of Tenant and shall be governed by the provisions
of Paragraph 11.1.  If the records of the County Assessor are
available and sufficiently detailed to serve as a basis for
determining whether said Tenant Improvements are assessed at a
higher valuation than Landlord's "building standard," such records
shall be binding on both Landlord and Tenant; otherwise the actual
cost of construction shall be the basis for such determination.

                             ARTICLE 12:  UTILITIES

      Tenant shall be solely responsible for and shall promptly pay
for all water, gas, heat, light, power, telephone and other
utilities and services supplied to the Premises, together with any
taxes thereon.  Landlord shall not be responsible for providing any
utilities or services to Tenant.  If any such services are not
separately metered to Tenant, Tenant shall pay as Additional Rent,
its pro rata share thereof as provided above.  Landlord shall not be
liable to Tenant for interruption in or curtailment of any utility
service, nor shall any such interruption or curtailment constitute a
constructive eviction or grounds for rental abatement in whole or in
part hereunder.

                     ARTICLE 13:  ASSIGNMENT AND SUBLETTING

      13.1  Landlord's Consent Required.  Tenant shall not voluntarily
            ---------------------------                               
or involuntarily assign, sublet, mortgage, or otherwise encumber all
or any portion of its interest in this Lease or in the Premises
without obtaining the prior written consent of Landlord, which
consent shall not be unreasonably withheld, and any such attempted
assignment, subletting, mortgage or other encumbrance without such
consent shall be null and void and of no effect.

      13.2  No Release of Tenant.  No permitted assignment,
            --------------------                           
subletting, mortgage or other encumbrance of Tenant's interest in
this Lease shall relieve Tenant of its obligation to pay the rent
and to perform all of the other obligations to be performed by
Tenant hereunder.  The acceptance of rent by Landlord from any other
person shall not be deemed to be a waiver by Landlord of any
provision of this Lease or to be a consent to any subletting,
assignment, mortgage or other encumbrance.  Consent to one sublease,
assignment, mortgage or other encumbrance shall not be deemed to
constitute consent to any subsequent subletting, assignment,
mortgage or other encumbrance.

      13.3  Notice to Landlord.  If Tenant desires at any time to
            ------------------                                   
assign this Lease or to sublet the Premises or any portion thereof,
it shall first notify Landlord of its desire to do so and shall send
Landlord a written notice (the "Transfer Notice"), specifying (a)
the name of the proposed subtenant or assignee; (b) the nature of
the proposed subtenant's or assignee's business to be carried on in
the Premises; (c) all the terms and provisions of the proposed
sublease or assignment; and (d) such financial information as
Landlord may reasonably request concerning the proposed subtenant or
assignee.

      13.4  Landlord's Option.  At any time within thirty (30) days
            -----------------                                      
after Landlord's receipt of the Transfer Notice, Landlord may by
written notice to tenant elect (a) to sublease the Premises or the
portion thereof so proposed to be subleased by Tenant, or to take an
assignment of Tenant's leasehold estate hereunder, or such part


                                     -15-
<PAGE>
 
thereof as shall be specified in said notice, on the same terms
stated in this Lease and in turn sublease or assign to the proposed
subtenant or assignee on the same terms as those offered by Tenant
to the proposed subtenant or assignee, as the case may be; or (b) to
terminate this Lease as to the portion (including all) of the
Premises so proposed to be subleased or assigned, with a
proportionate abatement in the rent payable hereunder.  If Landlord
does not exercise any option set forth in this Paragraph 13.4 within
said thirty (30) day period, Tenant may thereafter within ninety
days (90) after the expiration of said 30-day period enter into a
valid assignment or sublease of the Premises or portion thereof,
upon the terms and conditions set forth in the Transfer Notice.  If
Tenant does not do so within ninety (90) days after the date of the
Transfer Notice, any assignment or sublease shall be deemed a new
transaction and will require a new Transfer Notice in compliance
with Paragraph 13.3 (Notice to Landlord).

      13.5  Involuntary Transfers.  If this Lease is assigned to any
            ---------------------                                   
person or entity pursuant to the provisions of the Bankruptcy Code,
11 U.S.C. (S)101 et seq. (the "Bankruptcy Code"), any and all monies
                 -- ---                                             
or other consideration payable or otherwise to be delivered in
connection with such assignment shall be paid or delivered to
Landlord, shall be the exclusive property of Landlord and shall not
constitute property of Tenant or of the estate of Tenant within the
meaning of the Bankruptcy Code.  Any and all monies or other
consideration constituting Landlord's property under the preceding
sentence not paid or delivered to Landlord shall be held in trust
for the benefit of Landlord and be promptly paid or delivered to
Landlord.  Any person or entity to which this Lease is assigned
pursuant to the provisions of the Bankruptcy Code shall be deemed
without further act or deed to have assumed all of the obligations
arising under this Lease on and after the date of such assignment.
Any such assignee shall upon demand execute and deliver to Landlord
an instrument confirming such assumption.

      13.6  Related Matters.
            --------------- 

          (a) No Merger.  The voluntary or other surrender of this
              ---------                                           
Lease by Tenant or a mutual cancellation hereof shall not work a
merger, and shall at the option of Landlord, terminate all or any
existing subleases or subtenancies or shall operate as an assignment
to Landlord of such subleases or subtenancies.

          (b) Transfer of Stock.  If Tenant is a corporation which,
              -----------------                                    
under the then current guidelines published by the Commissioner of
Corporations of the State of California, is not deemed a public
corporation, or is an unincorporated association or partnership, the
transfer, assignment or hypothecation of any stock or interest in
such corporation, association or partnership in the aggregate in
excess of twenty-five percent (25%) shall be deemed an assignment
within the meaning and provisions of this Article 13.

          (c) Reimbursement of Costs.  Tenant agrees to pay
              ----------------------                       
Landlord Three Hundred Dollars ($300.00) to reimburse Landlord for
Landlord's reasonable costs and attorneys' fees incurred in
conjunction with the processing and documentation of any such
requested assignment, subletting, transfer, change of ownership or
hypothecation of this Lease or Tenant's interest in and to the
Premises.

          (d) Excess Rent.  In the event that an assignment or
              -----------                                     
sublease, which is otherwise permitted under the terms of this
Lease, results in the payment of rent by the occupant in excess of
the Basic Annual Rent imposed on Tenant hereunder, then fifty
percent (50.0%) of such excess rent shall be paid to Landlord as
rent hereunder.  Tenant shall furnish Landlord with whatever
information Landlord may reasonably require to determine whether
such excess rent may be payable.


                                     -16-
<PAGE>
 
                         ARTICLE 14:  LANDLORD'S ACCESS

      Landlord and Landlord's agents shall have the right to enter the
Premises at reasonable times, upon twenty-four (24) hours notice
(except in the case of an emergency or the performance of routine
maintenance or repair work), for the purpose of inspecting the same,
showing the same to prospective purchasers, or lenders, or lessees,
and making such alterations, repairs, improvements or additions to
the Premises or to the Building of which they are a part as Landlord
may deem necessary or desirable.  Landlord may at any time place on
or about the Premises any ordinary "For Sale" signs and Landlord may
at any time during the last one hundred twenty (120) days of the
term hereof place on or about the Premises any ordinary "For Lease"
signs.  Notwithstanding anything in this Lease, including the Rules
and Regulations (Exhibit C), to the contrary, it is agreed that
Tenant may install its own locks on the computer equipment room in
the Premises and that Landlord shall have no right to access to such
computer equipment room, except in an emergency.  Tenant agrees that
Landlord shall not be liable for any damages or injury resulting
from Landlord's being denied access to such computer equipment room.

                        ARTICLE 15:  DEFAULTS; REMEDIES

      15.1  Events of Defaults.  The occurrence of any one or more of
            ------------------                                       
the following events shall constitute a material default and breach
of this Lease by Tenant:

          (a) Vacation or Abandonment.  The vacating or abandonment
              -----------------------                              
of the Premises by Tenant.

          (b) Late Payment.  The failure by Tenant to make any
              ------------                                    
payment of rent or any other payment required to be made by Tenant
hereunder, as and when due, where such failure shall continue for a
period of five (5) days after said payment is due.

          (c) Non-Performance.  The failure by Tenant to observe or
              ---------------                                      
perform any of the covenants, conditions or provisions of this Lease
to be observed or performed by Tenant (other than those involving
payment of money), where such failure shall continue for a period of
thirty (30) days after written notice from Landlord to Tenant;
provided, however, that if the nature of Tenant's default is such
that more than thirty (30) days are reasonably required for its
cure, then Tenant shall not be deemed to be in default if Tenant
commenced such cure within said thirty (30) day period and
thereafter diligently pursues such cure to completion.

          (d) Insolvency.  The occurrence of any of the following
              ----------                                         
events of insolvency:

          (1) Assignment.  The making by Tenant of any general
              ----------                                      
assignment, or general arrangement for the benefit of creditors;

          (2) Bankruptcy.  The filing by or against Tenant of
              ----------                                     
a petition to have Tenant adjudged a bankrupt or a petition for
reorganization or arrangement under any law relating to bankruptcy
(unless, in the case of an involuntary petition filed against
Tenant, the same is dismissed within thirty (30) days);

          (3) Receivership.  The appointment of a trustee or
              ------------                                  
receiver to take possession of substantially all of Tenant's assets
located at the Premises or of Tenant's interest in this Lease, where
possession is not restored to Tenant within thirty (30) days; or

          (4) Attachment.  The attachment, execution or other
              ----------                                     
judicial seizure of substantially all of Tenant's assets located at
the Premises or of Tenant's interest in this Lease, where such
seizure is not discharged within thirty (30) days.

          (e) Misrepresentation.  The discovery by Landlord that
              -----------------                                 
any financial statement given to Landlord by Tenant, any assignee of


                                     -17-
<PAGE>
 
Tenant, any subtenant of Tenant, any successor in interest of Tenant 
or any guarantor of Tenant's obligations hereunder, and any of them, was
materially false.

     15.2  Remedies.  In the event of any default or breach by Tenant
           --------                                                  
     under this Lease within the meaning of Paragraph 15.1 (Events of
     Default) Landlord may at any time thereafter, with or without notice
     or demand and without limiting Landlord in the exercise of any right
     or remedy which Landlord may have by reason of such default or
     breach, exercise the remedies listed below in this Paragraph 15.2
     and such other remedies Landlord may have at law or in equity.  If
     Tenant causes or threatens to cause a breach of any of the
     covenants, agreements, terms or conditions contained in this Lease,
     Landlord shall be entitled to obtain all sums held by Tenant, by any
     trustee or in any account provided for herein, to enjoin such breach
     or threatened breach, and to invoke any right and remedy allowed at
     law or in equity or by statute or otherwise as though re-entry,
     summary proceedings and other remedies were not provided for in this
     Lease.

          (a) Termination by Landlord.  Landlord shall have the right to
              -----------------------                                   
     terminate Tenant's right to possession of the Premises by any lawful means,
     in which case this Lease shall terminate and Tenant shall immediately
     surrender possession of the Premises to Landlord. In the event that
     Landlord shall elect to so terminate the Lease, then Landlord may recover
     from Tenant:

               (1) The worth at the time of award of any unpaid rent
               which had been earned at the time of such termination; plus

               (2) The worth at the time of award of the amount by
               which the unpaid rent which would have been earned after
               termination until the time of award exceeds the amount of such
               rental loss Tenant proves reasonably could have been reasonably
               avoided; plus

               (3) 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 such rental loss that Tenant
               proves could be reasonably avoided; plus

               (4) Any other amount necessary to compensate Landlord
               for all the detriment proximately caused by Tenant's failure to
               perform his obligations under this Lease or which in the ordinary
               course of things would be likely to result therefrom; and

               (5) At Landlord's election, such other amounts in
               addition to or in lieu of the foregoing as may be permitted from
               time to time by applicable California law.

          (b) Definitions.  As used in subparagraphs (a)(1) and
              -----------                                      
          (a)(2) above, the "worth at the time of award" is computed by
          allowing interest at the maximum rate permitted under applicable
          law.  As used in subparagraph (a)(iii) above, the "worth at the time
          of award" is 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%).

          (c) Re-Entry.  In the event of any such default by
              --------                                      
          Tenant, Landlord shall also have the right, with or without
          terminating this Lease, to re-enter the Premises and remove all
          persons and property from the Premises; such property may be removed
          and stored in a public warehouse or elsewhere at the cost of and for
          the account of Tenant.

          (d) Reletting Premises.  In the event of the vacation or
              ------------------                                  
          abandonment of the Premises by Tenant or in the event that Landlord
          shall elect to re-enter as provided above or shall take possession
          of the Premises pursuant to legal proceeding or pursuant to any
          notice provided by law, then if Landlord does not elect to terminate
          this Lease as provided in this Paragraph 15.2, Landlord may from



                                     -18-
<PAGE>
 
          time to time, without terminating this Lease, either recover all
          rental as it becomes due or relet the Premises or any part thereof
          for such term or terms and at such rental or rentals and upon such
          other terms and conditions as Landlord in its sole discretion may
          deem advisable with the right to make alterations and repairs to the
          Premises.

          (e) Application of Proceeds of Reletting.  In the event
              ------------------------------------               
          that Landlord shall elect to so relet, then rentals received by
          Landlord from such reletting shall be applied:  first, to the payment
          of any indebtedness other than rent due hereunder from Tenant to
          Landlord, second, to the payment of any cost of such reletting;
          third, to the payment of the cost of any alterations and repairs to
          the Premises; fourth, to the payment of rent due and unpaid
          hereunder; and the residue, if any, shall be held by Landlord and
          applied to payment of future rent hereunder.  If upon any reletting
          Landlord should receive less rent than the amount due from Tenant
          under this Lease, then Tenant shall pay any deficiency to Landlord
          immediately upon demand therefor by Landlord.  Such deficiency shall
          be calculated and paid monthly.  Tenant shall also pay to Landlord
          as soon as ascertained, any costs and expenses incurred by Landlord
          in such reletting or in making such alterations and repairs not
          covered by the rentals received from such reletting.

          (f) Conditions for Termination.  No re-entry or taking
              --------------------------                        
          possession of the Premises by Landlord pursuant to this Paragraph
          15.2 shall be construed as an election to terminate this Lease
          unless a written notice of such intention be given to Tenant or
          unless the termination thereof be decreed by a court of competent
          jurisdiction.  Notwithstanding any reletting without termination by
          Landlord because of any default by Tenant, Landlord may at any time
          after such reletting elect to terminate this Lease for any such
          default.

          (g) Cumulative Remedies.  Each right and remedy of
              -------------------                           
          Landlord provided for in this Lease shall be cumulative and shall be
          in addition to every other right or remedy provided for in this
          Lease or now or hereafter existing at law or in equity or by statute
          or otherwise.  The exercise or beginning of the exercise by Landlord
          of any one or more of the rights or remedies provided for in this
          Lease, or now or hereafter existing at law or in equity or by
          statute or otherwise, shall not preclude the simultaneous or later
          exercise by Landlord of any or all other rights or remedies provided
          for in this Lease or now or hereafter existing at law or in equity
          or by statute or otherwise.

          (h) No Waiver.  No failure by Landlord to insist upon the
              ---------                                            
          strict performance of any term hereof or to exercise any right or
          remedy consequent upon a breach thereof, and no acceptance of full
          or partial payment of rent during the continuance of any such
          breach, shall constitute a waiver of any such breach or of any such
          term.  Efforts by Landlord to mitigate the damages caused by
          Tenant's breach of this Lease shall not be construed to be a waiver
          of Landlord's right to recover damages under this Paragraph 15.2.
          Nothing in this Paragraph 15.2 affects the right of Landlord to
          indemnification by Tenant in accordance with Paragraph 9.6 for
          liability arising prior to the termination of this Lease for
          personal injuries or property damage.

15.3  Default by Landlord.  Landlord shall not be in default
      -------------------                                   
under this Lease unless Landlord fails to perform obligations
required of Landlord within a reasonable time, but in no event later
than thirty (30) days after written notice by Tenant to Landlord and
to the holder of any first mortgage or deed of trust covering the
Premises whose name and address shall have theretofore been
furnished to Tenant in writing, specifying in reasonable detail how
Landlord has failed to perform such obligations; provided, however,
that if the nature of Landlord's 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


                                     -19-
<PAGE>
 
thirty (30) day period and thereafter diligently prosecutes the same
to completion.

      15.4  Late Charges and Interest on Delinquent Payments.
            -------------------------------------------------

          (a) Late Charges.  Tenant hereby acknowledges that late
              ------------                                       
payment by Tenant to Landlord of rent and other sums due hereunder
will cause Landlord to incur costs not contemplated by this Lease,
the exact amount of which will be extremely difficult to ascertain.
Such costs include, but are not limited to, processing and
accounting charges, and late charges which may be imposed on
Landlord by the terms of any mortgage or trust deed covering the
Premises.  Accordingly, if any installment of rent or any other sum
due from Tenant shall not be received by Landlord or Landlord's
designee within ten (10) days after such amount shall be due, Tenant
shall pay to Landlord a late charge equal to six percent (6.0%) of
such overdue amount; provided, however, that in no event shall the
amount of such late charge exceed Two Hundred Fifty Dollars ($250).
The parties hereby agree that such late charge represents a fair and
reasonable estimate of the costs Landlord will incur by reason of
late payment by Tenant.  Acceptance of such late charge by Landlord
shall in no event constitute a waiver of Tenant's default with
respect to such overdue amount, nor prevent Landlord from exercising
any of the other rights and remedies granted hereunder.

          (b) Interest on Past-Due Obligations.  Except as
              --------------------------------            
expressly herein provided, any amount due Landlord not paid within
ten (10) business days after written notice shall bear interest at
the maximum rate permitted under applicable law.  Payment of such
interest shall not excuse or cure any default by Tenant under this
Lease; provided, however, that interest shall not be payable on late
charges incurred by Tenant.  The parties agree that the payment of
late charges and the payment of interest provided for in this
Paragraph 15.4 are distinct and separate from one another in that
the payment of interest is to compensate Landlord for the use of
Landlord's money by Tenant, while the payment of late charges is to
compensate Landlord for the additional administrative expense
incurred by Landlord in handling and processing delinquent payments.

                          ARTICLE 16:  EMINENT DOMAIN

      16.1  Total Condemnation.  If the whole of the Premises is
            ------------------                                  
acquired or condemned by eminent domain, inversely condemned or sold
in lieu of condemnation, for any public or quasi-public use or
purpose ("condemned"), then the Lease term shall terminate as of the
date of title vesting in such proceeding and the rent shall be
adjusted to the date of termination.  Tenant shall immediately
notify Landlord of any such occurrence.

      16.2  Partial Condemnation.  If any part of the Premises is
            --------------------                                 
partially condemned, and such partial condemnation renders the
Premises unusable for the business of the Tenant, then the term of
this Lease shall terminate as of the date of title vesting in such
proceeding and Rent shall be adjusted to the date of termination.
If such condemnation is not extensive enough to render the Premises
unusable for the business of Tenant, then Landlord shall promptly
restore the Premises to a condition comparable to its condition
immediately prior to such condemnation proceeds recovered by
Landlord less 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 the Basic Annual Rent shall be
reduced in proportion that the floor area taken bears to the total
Rentable Area of the Premises.  If any parking areas are condemned,
Landlord has the option, but not the obligation, to supply Tenant
with alternative parking.

      16.3  Landlord's Award.  If the Premises are wholly or partially
            ----------------                                          
condemned, then, subject to the provisions of Paragraph 16.4
(Tenant's Award), Landlord shall be entitled to the entire award



                                     -20-
<PAGE>
 
paid for such condemnation, and Tenant waives any right or claim in
any part thereof from the Landlord or the condemning authority.

      16.4  Tenant's Award.  Tenant shall have the right to claim and
            --------------                                           
recover from the condemning authority, but not from Landlord, such
compensation as may be separately awarded or recoverable by Tenant's
own right on account of any and all costs or loss (including loss of
business) to which Tenant might be put in removing Tenant's
merchandise, furniture, fixtures, leasehold improvements and
equipment to a new location.

      16.5  Temporary Condemnation.  If the whole or any part of the
            ----------------------                                  
Premises shall be condemned for any temporary public or quasi-public
use or purpose, this Lease shall remain in effect and Tenant shall
be entitled to receive for itself such portion or portions of any
award made for such use with respect to the period of the taking
which is within the term.  If a temporary condemnation remains in
force at the expiration or earlier termination of this Lease, Tenant
shall pay to Landlord a sum equal to the reasonable cost of
performing any obligations required of Tenant by this Lease with
respect to the surrender of the Premises, including, without
limitation, repairs and maintenance required, and upon such payment
Tenant shall be excused from any such obligations.  If a temporary
condemnation is for an established period which extends beyond the
term, this Lease shall terminate as of the date of occupancy by the
condemning authority, and the damages shall be as provided in
Paragraphs 16.3 and 16.4 and Basic Annual Rent shall be adjusted to
the date of occupancy.

      16.6  Notice and Execution.  Landlord shall, immediately upon
            --------------------                                   
service of process in connection with any condemnation or potential
condemnation, give Tenant notice in writing thereof.  Tenant shall
immediately execute and deliver to the Landlord all instruments that
may be required to effect the provisions of this Article 16.

                              ARTICLE 17: BROKERS

      Tenant warrants that it has had no dealings with any real estate
broker or agents in connection with the negotiation of this Lease
and the Sublease, excepting only the broker identified in Item 13 of
the Basic Lease Provisions, and it knows no other real estate broker
or agent who is entitled to a commission in connection with this
Lease.  Landlord shall pay any commission due such broker.

                       ARTICLE 18: ESTOPPEL CERTIFICATE,
                          ATTORNMENT AND SUBORDINATION

      18.1  Estoppel Certificate.  Tenant shall at any time upon not
            --------------------                                    
less than ten (10) business days' prior written notice from Landlord
execute, acknowledge and deliver to Landlord an Estoppel Certificate
substantially in the form attached hereto as Exhibit "D." Any
Estoppel Certificate executed by Tenant may be conclusively relied
upon by any prospective purchaser or encumbrancer of the Premises.
Tenant's failure to deliver such Estoppel Certificate within such
time shall conclusively establish that (a) this Lease is in full
force and effect, without modification except as may be represented
by Landlord; (b) there are no uncured defaults in Landlord's
performance, and (c) not more than one month's rent has been paid in
advance.  Such failure by Tenant, if willful, may, at Landlord's
option, be treated by Landlord as a material default by Tenant under
this Lease.  If Landlord desires to finance or refinance the
Premises, or any part thereof, Tenant hereby agrees to deliver to
any lender designated by Landlord such financial statements of
Tenant and such other information about Tenant as may be reasonably
required by such lender.  Such statements shall include the past
three (3) years' financial statements of Tenant.  All such financial
statements shall be received in confidence and shall be used only
for the purposes herein set forth.


                                     -21-
<PAGE>
 
      18.2  Subordination
            -------------

          (a) Priority of Lease.  This Lease, at Landlord's option,
              -----------------                                    
shall be subordinate to any ground lease, mortgage, deed of trust,
or any other hypothecation for security now or hereafter placed upon
the real property of which the Premises are a part and to any and
all advances made on the security thereof and to all renewals,
modifications, consolidations, replacements and extensions thereof.
Notwithstanding such subordination, Tenant's right to quiet
possession of the Premises shall not be disturbed if Tenant is not
in default and so long as Tenant shall pay the rent and observe and
perform all of the provisions of this Lease, unless this Lease is
otherwise terminated pursuant to its terms.  If any mortgagee,
trustee or ground lessor shall elect to have this Lease prior to the
lien of its mortgage, deed of trust or ground lease, and shall give
written notice thereof to Tenant, this Lease shall be deemed prior
to such mortgage, deed of trust, or ground lease, whether this Lease
is dated prior or subsequent to the date of said mortgage, deed of
trust or ground lease or the date of recording thereof.

          (b) Execution of Documents.  Tenant agrees to execute any
              ----------------------                               
documents required to effectuate such subordination or to make this
Lease prior to the lien of any mortgage, deed of trust or ground
lease, as the case may be, and failing to do so within ten (10) days
after written demand, does hereby make, constitute and irrevocably
appoint Landlord as Tenant's attorney in fact and in Tenant's name,
place and stead, to do so.

      18.3  Attornment.  Tenant shall, in the event any proceedings
            ----------                                             
are brought for the foreclosure of, or in the event of exercise of
the power of sale under, any mortgage or deed of trust made by the
Landlord, its successors or assigns, encumbering the Premises, or
any part thereof, if any, and if so requested, attorn to the
purchaser upon such foreclosure or sale or upon any grant of a deed
in lieu of foreclosure and recognize such purchaser as the Landlord
under this Lease.

                        ARTICLE 19: LANDLORD'S LIABILITY

      19.1  Scope of Liability.  If Landlord is a limited partnership,
            ------------------                                        
it is understood and agreed that any claims by Tenant shall be
limited to the assets of such limited partnership.  Tenant also
expressly waives any and all rights to proceed against the
individual partners or the officers, directors or shareholders of
any corporate partner in such limited partnership, except to the
extent of such partners' interests in such limited partnership.

      19.2  Transfer by Landlord; Landlord's Liability.
            ------------------------------------------ 

          (a) Landlord shall have the right to assign, hypothecate
or otherwise transfer this Lease and Landlord's interest hereunder
at any time at Landlord's option.

          (b) The term "Landlord" as used herein shall mean only the
owner or owners at the time in question of the fee title or a
Tenant's interest in a ground lease of the Premises, and except as
expressly provided in Article 15, in the event of any transfer of
such title or interest, Landlord herein named (and in case of any
subsequent transfers the then grantor) shall be relieved from and
after the date of such transfer of all liability as respects
Landlord's obligations thereafter to be performed, provided that any,
funds in the hands of Landlord or the then grantor at the time of
such transfer, in which Tenant has an interest, shall be delivered
to the grantee.  The obligations contained in this Lease to be
performed by Landlord shall, subject as aforesaid, be binding on
Landlord's successors and assigns, only during their respective
periods of ownership.


                                     -22-
<PAGE>
 
                     ARTICLE 20:  MISCELLANEOUS PROVISIONS

      20.1  Use of Common Areas; Parking.  Tenant shall have the
            ----------------------------                        
non-exclusive right, in common with others, to the use of the Common
Areas and common entrances, lobbies, elevators, ramps, drives,
stairs, and similar access and serviceways, parking areas and the
other common facilities in and adjacent to the Building and the
Project, subject to such nondiscriminatory rules and regulations as
may be adopted by the Landlord.  Tenant shall have the right to
designate thirty-five (35) reserved parking spaces in the parking
areas for its exclusive use, and will do so in writing to Landlord
within 120 days of the execution of this Lease.

      20.2  Severability.  The invalidity of any provision of this
            ------------                                          
Lease as determined by a court of competent jurisdiction, shall in
no way affect the validity of any other provision hereof.

      20.3  Time of Essence.  Time is of the essence of each and every
            ---------------                                           
provision of this Lease.

      20.4  Captions.  Article and paragraph captions are used for
            --------                                              
convenience of reference and are not a part of this Lease.

      20.5  Incorporation of Prior Agreements; Amendments.  This Lease
            ---------------------------------------------             
contains all agreements of the parties with respect to any matter
mentioned herein.  No prior agreement or understanding pertaining to
any such matter shall be effective.  This Lease may be modified in
writing only, signed by the parties in interest at the time of the
modification.  Except as otherwise stated in this Lease, Tenant
hereby acknowledges that neither any real estate broker listed in
Item 13 of the Basic Lease Provisions hereof nor any cooperating
broker on this transaction nor the Landlord or any employees or
agents of any of said persons has made any oral or written
warranties or representations to Tenant relative to the condition or
use by Tenant of the Premises.  Tenant acknowledges that Tenant
assumes all responsibility regarding the effect of and the necessity
of complying with (a) the Occupational Safety Health Act and all
similar or successor state and federal statutes and (b) all other
applicable laws and regulations in force during the term of this
Lease, except as otherwise specifically stated in this Lease.

      20.6  Notices.  Any notice required or permitted to be given
            -------                                               
under this Lease shall be in writing and may be given by personal
delivery or by certified mail, and if given personally or by mail,
shall be deemed sufficiently given if addressed to Tenant or to
Landlord at the addresses specified in Item 11 of the Basic Lease
Provisions.  Either party may by notice to the other specify a
different address for notice purposes except that upon Tenant's
taking possession of the Premises, the Premises shall constitute
Tenant's address for notice purposes.  A copy of all notices
required or permitted to be given to Landlord hereunder shall be
concurrently transmitted to such party or parties at such addresses
as Landlord may from time to time hereafter designate by notice to
Tenant.

      20.7  Waivers.  No waiver by one party of any provision hereof
            -------                                                 
shall be deemed a waiver of any other provision hereof or of any
subsequent breach by the other party of the same or any other
provision.  A party's consent to or approval of any act shall not be
deemed to render unnecessary the obtaining of that party's consent
to or approval of any subsequent act by the other party.  The
acceptance of rent hereunder by Landlord shall not be a waiver of
any preceding breach by Tenant of any provision hereof, other than
the failure of Tenant to pay the particular rent so accepted,
regardless of Landlord's knowledge of such preceding breach at the
time of acceptance of such rent.

      20.8  Recording.  Tenant shall not record this Lease or a short
            ---------                                                
form memorandum thereof without Landlord's prior written consent,


                                     -23-
<PAGE>
 
and such recordation shall, at the option of Landlord, constitute a
non-curable default by Tenant under this Lease.

      20.9  Holding Over.  If Tenant remains in possession of the
            ------------                                         
Premises or any part thereof after the expiration of the term hereof
without the express written consent of Landlord, such occupancy
shall be a tenancy from month to month at a rental in an amount
equal to one hundred twenty-five percent (125.0%) of the Basic
Annual Rent then payable, plus all other charges payable hereunder,
and upon all the terms hereof applicable to a month-to-month tenancy.

      20.10  Cumulative Remedies.  No remedy or election hereunder
             -------------------                                  
shall be deemed exclusive but shall, wherever possible, be
cumulative with all other remedies at law or in equity.

      20.11  Covenants and Conditions.  Each provision of this Lease
             ------------------------                               
to be performed by Tenant shall be deemed both a covenant and a
condition.

      20.12  Binding Effect; Choice of Law.  Subject to any provisions
             -----------------------------                            
hereof restricting assignment or subletting by Tenant and subject to
Article 19 (Landlord's Liability), this Lease shall bind the
parties, their personal representatives, successors and assigns.
This Lease shall be governed by and construed in accordance with the
laws of the State of California.

      20.13  Attorneys' Fees.  If either party brings an action to
             ---------------                                      
enforce the terms hereof or declare rights hereunder, the prevailing
party in any such action, on trial or appeal, shall be entitled to
its reasonable attorneys' fees to be paid by the losing party as
fixed by the court.

      20.14  Signs and Auctions.  Tenant shall not place any sign upon
             ------------------                                       
the Premises or conduct any auction thereon without Landlord's prior
written consent.

      20.15  Corporate Authority.  If Tenant is a corporation, each
             -------------------                                   
individual executing this Lease on behalf of said corporation
represents and warrants that he is duly authorized to execute and
deliver this Lease on behalf of said corporation, in accordance with
a duly adopted resolution of the Board of Directors of said
corporation or in accordance with the Bylaws of said corporation,
and that this Lease is binding upon said corporation in accordance
with its terms.  If Tenant is a corporation Tenant shall within
thirty (30) days after execution of this Lease, deliver to Landlord
a certified copy of a resolution of the Board of Directors of said
corporation authorizing or ratifying the execution of this Lease.

      20.16  Consents.  Wherever in this Lease the consent of one
             --------                                            
party is required to an act of the other party, such consent shall
not be unreasonably withheld.

      20.17  Guarantor.  In the event that there is a guarantor of
             ---------                                            
this Lease, said guarantor shall have the same obligations as Tenant
under Paragraph 18.1 (Estoppel Certificate) and 20.15 (Consents) of
this Lease.

      20.18  Quiet Possession.  Subject to Tenant's paying the Basic
             ----------------                                       
Annual Rent and other items of rent reserved hereunder and observing
and performing all of the covenants, conditions and provisions on
Tenant's part to be observed and performed hereunder, Tenant shall
have quiet possession of the Premises for the entire term hereof
subject to all of the provisions of this Lease.

      20.19  Force Majeure.
             ------------- 

          (a) Events of Force Majeure.  Notwithstanding anything to
              -----------------------                              
the contrary contained in this Lease, each party shall be excused
from performing any obligation or undertaking provided in this
Lease, and any delay in the performance of any obligation under this


                                     -24-
<PAGE>
 
Lease shall be excused, so long as the performance of such
obligation is prevented, delayed, retarded, hindered or prohibited
by any act of God, such as earthquake, flood, inclement weather or
other action of the elements; fire; explosion; war; invasion; civil
insurrection; riot; mob violence; sabotage; malicious mischief;
inability to procure or unavailability of or general shortage of
labor, equipment, facilities, materials or supplies in the open
market; general inability to obtain transportation; moratorium on
the payment of financial obligations; lockouts (by persons other
than the party invoking the benefits of this provision); strike or
other action of labor unions or trade organizations; condemnation;
pending litigation or appeal thereof or therefrom; laws or orders of
any governmental authority whatever, whether civil, military, naval,
environmental, municipal, state or federal authority; or any other
cause (financial inability excepted), whether similar or dissimilar
to the foregoing, which is not reasonably within the control of the
party invoking the benefits of this Paragraph (hereafter, "event of
force majeure").

          (b) Notices.  Any Party (the "affected party") whose
              -------                                         
performance under this Lease is prevented or delayed by the
occurrence of any event of force majeure shall notify the other
party (the "other party") in writing of the occurrence of the event
of force majeure and the cessation of the same within fifteen (15)
days after such occurrence or cessation.  The failure to so notify
the other party shall be deemed to constitute a waiver of the
benefits of this Paragraph.  Each day of delay due to the occurrence
of an event of force majeure shall result in one day's extension of
the time for performance by the affected party.  If such an
extension of time is granted to the affected party, the time for
performance by the other party shall be extended to the same extent.

          (c) Excessive Delay.  Notwithstanding anything in this
              ---------------                                   
Paragraph to the contrary, if the cumulative amount of any delay(s)
permitted or excused by reason of the occurrence(s) of an event of
force majeure exceeds six (6) months, the other party shall have the
right to cancel and terminate this Lease without penalty at any time
by sending the affected party written notice to such effect.

                              ARTICLE 21:  ADDENDA
                                        
      21.1  Effect of Addenda.  The provisions of this Article 21, if
            -----------------                                        
any, shall supersede and override any other provision in this Lease
to the extent the same are inconsistent.  This Article 21 shall
consist of this Paragraph 21.1 and the following paragraphs which
are also identified in Item 14 of the Basic Lease Provisions as
being part of this Article 21.

      21.2  Expansion Space.  One year after the Rent Commencement
            ---------------                                       
Date, provided Tenant is not in default under any of the terms or
conditions of this Lease, Landlord agrees that Tenant shall have the
right to relocate to other space in the Project or other space
located in the City of San Diego which is owned by Landlord or The
Naiman Company (the "New Space") on the following terms and
conditions:

      (1)  The New Space shall be at least fifty percent (50.0%)
larger than the Premises;

      (2)  Tenant provides Landlord with a sixty (60) day written
notice of Tenant's desire to relocate to the New Space;

      (3)  Any and all costs of both Landlord and Tenant, including
without limitation legal fees incurred by Landlord in drafting a new
lease for the New Space (which legal fees shall not exceed $1,000),
all of Tenant's moving and relocation expenses and any brokerage
commissions that may become payable to third parties by reason of
Tenant's relocation shall be paid solely by Tenant;


                                     -25-
<PAGE>
 
      (4)  Tenant continues to make payment of all items of rent, both
Basic Annual Rent and Additional Rent, and any other payment
required to be made under the Lease until Tenant is released from
liability under this Lease;

      (5)  The rent for the New Space shall be equal to the greater of
(i) the Basic Annual Rent then payable under this Lease or (ii) the
then current rental rate for the building or project in which the
New Space is located as published in Landlord's schedule of rental
rates;

      (6)  Tenant executes a new lease on terms and conditions
reasonably acceptable to Landlord; and

      (7)  Effective as of the commencement date of the lease for the
New Space, Tenant shall be released from liability under this Lease,
except for liabilities or obligations arising from or relating to
events or circumstances occurring prior to such date.

      21.3  Right of First Refusal.  If, during the term of the Lease
            ----------------------                                   
Landlord decides to lease additional space in the Building to a
third party, Landlord shall send written notice to such effect to
Tenant.  Tenant shall have the right of first refusal to lease the
space described in such notice on the same terms and conditions
offered to the third party.  Tenant shall exercise its right of
first refusal within two business days of receipt of such notice.
Failure to timely exercise such right of first refusal shall
constitute a waiver of the right of first refusal under this Lease.

      IN WITNESS WHEREOF, the parties hereto have executed this R&D
Building Lease at the place and on the date specified immediately
adjacent to their respective signatures below.

LANDLORD:

Executed at San Diego, California on February __, 1987.


                         SORRENTO TECH LIMITED, a
                         California limited partnership


                         By:/s/Jack Naiman
                            --------------------
                               Jack Naiman,
                         Title:  General Partner


TENANT:

Executed at San Diego, California on February 26, 1987.


                         BIOSYM TECHNOLOGIES, INC., a
                         California corporation


                         By: /s/Todd Schmidt
                             -----------------------------

                         Title: /s/
                                --------------------------


                         By: /s/ Arnie Hagler
                             ----------------------------- 

                         Title: CEO
                                --------------------------
LAL:  1618Y
      022487


                                     -26-
<PAGE>
 
                           FLOOR PLAN OF THE PREMISES
                           --------------------------
                                        



                                [to be provided]




















                                 EXHIBIT "A-1"
<PAGE>
 
                            SITE PLAN OF THE PROJECT
                            ------------------------






















                                 EXHIBIT "A-2"
                                        
<PAGE>
 
                          DEFINITION OF RENTABLE AREA
                          ---------------------------

      1.  Definition.  The term "Rentable Area" as used in this
          ----------                                           
R&D Building Lease shall mean:

          (a) Single Tenant Floor.  As to each floor of each
              -------------------                           
building in the Project on which the entire space rentable to a
tenant is or will be leased to one tenant (hereinafter referred
to as "single Tenant Floor"), Rentable Area shall be the entire
area bounded by the inside surface of the four exterior glass
walls (or the inside surface of the permanent exterior wall
where there is no glass) on such floor, including all areas
used for elevator lobbies, corridors, special stairways, or
elevators, common restrooms (if any), mechanical rooms,
electrical rooms and telephone closets without deduction for
columns and other structural portions of each building or
vertical penetrations that are included for the special use of
a tenant, but excluding the area contained within the exterior
walls of each building's stairs, fire towers, vertical ducts,
elevator shafts, flues, vents, stacks and pipe shafts.
Rentable Area for a Single Tenant Floor shall include a prorata
portion of any ground floor elevator lobby areas.

          (b) Multi-Tenant Floor.  As to each floor of each
              ------------------                           
building in the Project on which space is or will be leased to
more than one tenant (hereinafter referred to as "Multi-Tenant
Floor"), Rentable Area attributable to each such tenant shall
be the total of (1) the entire area included within the
premises covered by such tenant's lease, being the area bounded
by the inside surface of any exterior glass walls (or the
inside surface of the permanent exterior walls where there
is no glass) bounding such premises, the exterior of all walls
separating such premises from any public corridors or other
public areas on such floor, and the centerline of all walls
separating such premises from other areas leased or to be
leased to other tenants on such floor, and (2) a pro rata
portion of the area covered by the elevator lobbies, corridors,
common restrooms (if any), mechanical rooms, electrical rooms
and telephone closets situated on such floor and on the ground
floor of a building (but only to the extent any of the same
serve all tenants of the building).

      2.  Certification.  Landlord's architect shall determine
          -------------                                       
the Rentable Area of each tenant's premises and such
determination shall be binding and conclusive.  A certified
copy of such determination shall be delivered to Landlord and
each tenant.  Landlord reserves the right to have its architect
redetermine the Rentable Areas of the Premises, the Building
and/or the Project from time to time during the term of this
Lease.  A certified copy of any such redetermination shall be
delivered to Landlord and each affected tenant.  In the event
of any such redetermination, each tenant's share of Building
Operating Expenses or Project Operating Expenses, as the case
may be, shall be recomputed.

      3.  Rentable Area of Building.  Total Rentable Area of
          -------------------------                         
the building is approximately 19,617 square feet.

      4.  Rentable Area of Project.  Total Rentable Area of the
          ------------------------                             
Project is 635,000 sq. ft.



                                 EXHIBIT "A-3"

                                  Page 1 of 1
<PAGE>
 
                   SCHEDULE OF CONSTRUCTION RESPONSIBILITIES



      1.  Construction of Tenant Improvements.  Landlord shall
          -----------------------------------                 
construct certain improvements (the "Tenant Improvements") in
the Premises.  The Tenant Improvements shall consist of all
interior improvements constructed in the Building which are not
part of The Building's structure or shell and shall include by
way of illustration, floor coverings, interior partitions,
doors, ceilings, lighting fixtures, wall coverings, electrical
and telephone outlets and fire sprinklers.  The Tenant
Improvements shall be constructed in accordance with plans and
specifications prepared by Landlord's architect and approved by
Landlord and Tenant.  Landlord's architect shall prepare such
plans and specifications in accordance with a space plan for
the Premises prepared by Landlord's space planning firm and
approved by Tenant as provided in Paragraph 4 below.  Landlord
shall pay for up to twenty (20) hours of such space planning
work and the amount so paid by Landlord shall not be included
as part of Landlord's Maximum Contribution (as defined below).
As of the date of signing this Lease, Tenant has used more than
20 hours of space planning time.  It is understood and agreed
that the Tenant Improvements shall be constructed in all
portions of the Premises to a level acceptable to Landlord.
Landlord's contractor shall construct the Tenant Improvements.

      2.  Payment of Construction Costs.  The term
          -----------------------------           
"Construction Costs" shall mean and include the cost and
expense of constructing the Tenant Improvements, including
without limitation the cost of labor and materials, space
planning and architectural fees, the cost of moving Tenant's
current HVAC equipment to the Premises, and the cost of any
governmental permits and fees.  Landlord shall pay a portion of
the Construction Costs not to exceed Fifteen Dollars ($15.00)
per sq. ft. of Rentable Area in the Premises ("Landlord's
Maximum Contribution").  Tenant shall be solely responsible for
paying any Construction Costs in excess of Landlord's Maximum
Contribution.  Before starting construction, Landlord shall
provide Tenant with a written estimate of the Construction
Costs.  Tenant shall have the right to approve such estimate as
provided in Paragraph 4 below.  If Tenant disapproves of such
cost estimate and the plans and specifications for the Tenant
Improvements are changed as a result, the time expended in
revising the plans and specifications and obtaining new cost
estimates shall be included as part of Tenant's Delay.

      3.  Performance of Construction Work.  Landlord shall
          --------------------------------                 
cause to be obtained all necessary approvals and permits from
all governmental agencies having authority over construction of
the Tenant Improvements.  All work performed by Landlord's
contractor shall be done in a good and workmanlike manner in
accordance with the approved plans and specifications.














                                  EXHIBIT "B"
                                  Page 1 of 2
<PAGE>
 
      4.    Schedule of Approvals.
            ----------------------

          (a) Tenant shall approve the matters listed in the
"Event" column below by the corresponding time specified in the
"Time" column as follows:

              Event                                 Time
                                                    ----
 
      (1)        Space Plan Approval Date           February 27, 1987
 
      (2)        Deadline for Tenant's              Five (5) days after receipt
                 approval of working draw-          of working drawings and
                 ings and specifications            specifications
 
      (3)        Deadline for Tenant's              Three (3) days
                 approval of Construction           after receipt of cost
                 Costs                              estimate from Landlord

          (b) If Tenant fails to approve such matters by the times
indicated, the delay in obtaining Tenant's approval shall be
included as part of Tenant's Delay.


















                                  EXHIBIT "B"
                                  Page 2 of 2
<PAGE>
 
              RULES AND REGULATIONS ATTACHED TO AND MADE A PART OF
              ----------------------------------------------------
                               R&D BUILDING LEASE
                               ------------------
                                        

      1.  No sign, placard, picture, advertisement, name or
notice shall be inscribed, displayed or printed or affixed on
or to any part of the Building without the written consent of
Landlord, first had and obtained, and Landlord shall have the
right to remove any such sign, placard, picture, advertisement,
name or notice without notice to and at the expense of Tenant.
All signs or lettering on doors shall conform to Landlord's
sign criteria for the Building.  Tenant shall not place
anything or allow anything to be placed near the glass of any
window, door, partition or wall which may appear unsightly from
outside the Premises.

      2.  Tenant shall not alter any lock or install any new or
additional locks or any bolts on any door of the Premises.

      3.  Toilet rooms, urinals, wash bowls and other apparatus
shall not be used for any purpose other than that for which
they were constructed and no foreign substance of any kind
whatsoever shall be thrown therein, and the expense of any
breakage, stoppage or damage resulting from the violation of
this rule shall be borne by Tenant or those employees or
invitees of Tenant who shall have caused it.

      4.  Tenant shall not use, keep or permit to be used or
kept, any foul or noxious gas or substance in the Premises, or
permit or suffer the Premises to be occupied or used in a
manner offensive or objectionable to Landlord or other
occupants of the Building by reason of noise, odors and/or
vibrations, or interfere in any way with other tenants or those
having business therein, nor shall any animals or birds be
brought in or kept in or about the Premises or the Building.

      5.  Tenant shall not use or keep in the Premises any
inflammable or combustible fluid or material, including, but
not limited to, kerosene or gasoline.  Tenant shall not use any
method of heating or air conditioning other than that supplied
by Landlord.

      6.  Upon the termination of its tenancy, Tenant shall
deliver to Landlord the keys for all offices, rooms and toilet
rooms which shall have been furnished to Tenant or which Tenant
shall have had made, and in the event of loss of any keys so
furnished, shall pay Landlord therefor.

      7.  Tenant shall not lay linoleum, tile, carpet or any
other similar floor covering so that the same shall be affixed
to the floor of the Premises in any manner except as approved
by Landlord.  The expense of repairing any damage resulting
from a violation of this rule or removal of any floor covering
shall be borne by Tenant, or by the contractors, employees or
invitees of Tenant who caused the damage.

      8.  Landlord reserves the right to exclude or expel from
the Buildings 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 any of the rules
and regulations of the Building.

      9.  Landlord shall have the right, exercisable without
notice and without liability to Tenant, to change the name and
the street address of the Building of which the Premises are a
part.









                                  EXHIBIT "C"
                                  Page 1 of 2
<PAGE>
 
      10. Tenant shall not disturb, solicit, or canvas any
occupant of The Building and shall cooperate to prevent same.

      11. Without the written consent of Landlord, Tenant shall
not use the name of the Building or the Project in connection
with or in promotion or advertising the business of Tenant
except as Tenant's address.

      12. The word "Building" as used herein means the building
occupied by Tenant pursuant to the R&D Building Lease to which
this Exhibit C is attached.

      13. Landlord reserves the right to promulgate reasonable
rules and regulations relating to the use of parking areas,
including assignment of specific parking areas by number, and
such limitations as may in the opinion of Landlord be necessary
and desirable.  Tenant and Tenant's employees shall park their
cars only in those portions of the parking areas designated by
Landlord for employee parking.

      14. All exterior window coverings, whether curtains,
blinds or otherwise, used by Tenant shall be approved in
writing by Landlord.  Landlord intends that all window
coverings in the Project be uniform and standard in color,
texture and appearance and Tenant shall have no right to
deviate from or change the exterior window coverings approved
by Landlord.



                                  EXHIBIT "C"
                                  Page 2 of 2
<PAGE>
 
                              ESTOPPEL CERTIFICATE

                          Statement of Tenant Release



Date:                                           , 19
     ------------------------------------------     --

Re:   Address:
              ----------------------------------------  
 
              ----------------------------------------  

For Premises in:
                --------------------------------------
 
                --------------------------------------

Gentlemen:

      It is our understanding that you have made certain
commitments to the Landlord of the subject premises and, as a
condition thereof, have required this certification by the
undersigned.

      The undersigned, as Tenant under that certain Office Lease
dated __________________, 19___, made and entered into
between Sorrento Tech Limited, as Landlord, and the
undersigned, as Tenant, hereby ratified said Lease and
certified that the undersigned has accepted possession and
entered into occupancy of the Premises described in said Lease
and the minimum rental in the monthly amount of $ ______________
was payable from that or an earlier date; that said Lease is in
full force and effect and has not been assigned, modified,
supplemented or amended in any way; that the same represents
the entire agreement between the parties as to the leasing;
that the terms of said Lease to be performed by the Landlord
have been fully satisfied, including without limitation, that
the improvements and space required to be furnished according
to said Lease have been completed in all respects, that
Landlord has fulfilled all of its duties of an inducement
nature, that all required contributions by Landlord to Tenant
on account of Tenant's improvements have been paid and
received; and that on this date there are no existing defenses
or offsets which the undersigned has against the enforcement of
said Lease by Landlord; that rental has not been paid in
advance except as provided by the Lease terms, and that
security in the sum of $ ________ has been deposited with
Landlord; and that all minimum rental due as of this date has
been paid.


                         Very truly yours,

                         __________________________________

                         __________________________________
                                       TENANT












                                  EXHIBIT "D"
<PAGE>
 
                               PARKING AGREEMENT


      Subject to compliance with the following Rules and
Regulations, so long as the Lease to which this Parking
Agreement is attached remains in effect, Tenant or persons
designated by Tenant shall be entitled to park, on a
non-exclusive basis, in the Project parking facilities, and on
surface parking areas located on the Project.

      All persons utilizing the Project parking facilities shall
comply with this Parking Agreement.  The following Rules and
Regulations are in effect until Landlord notifies Tenant of any
change. Landlord reserves the right to modify and/or adopt
such other reasonable and non-discriminatory rules and
regulations for the Project parking as it deems necessary.
Landlord may refuse to permit any person who violates this
Parking Agreement to park in the Project parking facilities.
Any violation of this Parking Agreement shall subject the
violator's car to removal from the Project parking facilities
at the violator's expense.


                             Rules and Regulations


     1.   Cars must be parked entirely within the stall lines
          painted on the floor.

     2.   All directional signs and arrows must be observed.

     3.   The speed limit shall be 5 miles per hour.

     4.   Parking is prohibited:

          (a)  In areas not striped for parking,

          (b)  In fire lanes,

          (c)  Where "no parking" signs are posted,

          (d)  In cross-hatched areas, or

          (e)  In such other areas as may be designated by
               Landlord.

     5.   Every parker is required to park and lock his or her
          own car.  All responsibility for damage to cars or
          persons is assumed by the parker.

     6.   No more than one vehicle may be parked in any one
          parking space.  Washing, waxing, cleaning or servicing
          of any vehicle by a parker and/or his agents is
          prohibited.

     7.   Tenant shall acquaint all its officers and employees
          with these Rules and Regulations.



                                  EXHIBIT "E"
CJM: 1665G
P: 0049G
080984
<PAGE>
 
                            FIRST AMENDMENT OF LEASE
                            ------------------------

     This First Amendment of Lease is between SORRENTO TECH LIMITED ("Landlord")
and BIOSYM TECHNOLOGIES, INC. ("Tenant").

                                   Recitals:
                                   ---------

A.   On February 26, 1997,  Landlord  and  Tenant  entered into a lease 
     agreement for approximately 10,270 square feet in the Naiman Tech Center at
     10065 Barnes Canyon Road, San Diego, California ("New Premises").

B.   Pursuant to the terms of said lease agreement, the Target Commencement Date
     of the New Premises was June 1, 1987, and the Rent Commencement Date for
     Initial Basic Annual Rent is February 1, 1988.

     The  parties  hereto  wish to amend the lease agreement as follows:

     1.  The term "Target Commencement Date" shall be deleted from the lease
agreement. Paragraphs 3.1(a) - (c), paragraph 3.2, and paragraphs 4(a) and (b)
of Exhibit "B" to the lease agreement shall be deleted in their entirety. The
term "Commencement Date" as used in the lease agreement shall mean October 1,
1987, provided Landlord delivers possession of the premises to Tenant, pursuant
to approved plans and specifications, no later than November 1, 1987. For each
day that Landlord delivers possession of the premises to Tenant after November
1, 1987, one day shall be added to the "Commencement Date" and Rent Commencement
Date for Initial Basic Annual Rent as defined herein. By way of example only, if
the Landlord delivers possession to Tenant on October 15, 1987, the
"Commencement Date" remains October 1, 1987, and the Rent Commencement Date for
Initial Basic Annual Rent remains May 1, 1988. If the Landlord delivers
possession to Tenant on November 5, 1987, the "Commencement Date" shall be
October 5, 1987, and the Rent Commencement Date for Initial Basic Annual Rent
shall be May 5, 1988.

     2.  The Rent Commencement Date for Initial Basic Annual Rent shall be May
1, 1988, subject to modification as set forth in paragraph 1 hereof and further
subject to modification as follows:

      The cost of all Tenant Improvements in excess of Landlord's Maximum
Contribution shall be credited against the seven (7) month Rent Abatement Period
provided in paragraph 6(c) of the Basic Lease Provisions. Landlord estimates
such excess to be in the amount of Forty-nine Thousand Two Hundred Eighty-seven
Dollars ($49,287.00) pursuant to approved plans and specifica-tions. Such credit
shall be in lieu of a cash payment required by Tenant to pay for Construction
Costs in excess of Landlord's Maximum Contribution. By way of example, if the
monthly basic rent is 
<PAGE>
 
Eleven Thousand Two Hundred Ninety-seven Dollars ($11,297.00) and the total
excess Construction Costs of Tenant Improvements is Forty-nine Thousand Two
Hundred Eighty-seven Dollars ($49,287.00), the credit against rent abatement is
4.36 months, or 4 months and 11 days ($49,287.00 divided by $11,297.00).
Therefore, the reduced Rent Abatement Period shall commence on October 1, 1987,
and continue for 2.64 months or 2 months and 20 days. Rent payable for a partial
month shall be prorated based on a 30-day month. The cost of Tenant Improve-
ments in excess of Landlord's Maximum Contribution may increase or decrease
pursuant to written change orders executed by Landlord and Tenant and the credit
against the Rent Abatement Period may therefore increase or decrease.

     3.  Tenant shall continue to pay all amounts due under the terms of its
existing lease agreement for 9605 Scranton Road pursuant to the terms of the
Lease Termination Agreement between Landlord and Tenant dated September 10,
1987.

     4.  Landlord shall construct the System #1, Basic System Wall in the New
Premises as outlined in a letter to Tenant from Landlord dated August 5, 1987.
The total cost to Tenant of said Basic System Wall shall be no more than Fifty-
five Thousand Five Hundred Thirty-nine Dollars ($55, 539.00).*

         4.1  Notwithstanding paragraph 8.5(d) of the lease agreement, Tenant
may remove the System #1, Basic System Wall from the New Premises and the same
shall remain the property of Tenant upon termination or expiration of the lease
agreement.

     5.  Except as specifically amended herein, all the terms of the lease
agreement, including defined terms, shall remain unchanged and in full force and
effect.

     6.  This Amendment of Lease may be executed in counter-parts, each of which
shall be deemed an original but all of which shall constitute one and the same
instrument.

     7.  This Amendment of Lease supersedes all prior lease negotiations,
understandings, amendments or modifications, whether written or verbal, with
respect to the subject matter hereof.

     Landlord:

     Executed at San Diego, California, on September 15, 1987.
                                           ------------       

                       SORRENTO TECH LIMITED, a
                       California Limited Partnership

                       By:
                          
                       /s/Jack Naiman
                       ---------------------------------
                       Jack Naiman,  General Partner


                                      -2-
<PAGE>
 
                    AMENDMENT NO. 2 TO R & D BUILDING LEASE

                                    BETWEEN

                             SORRENTO TECH LIMITED

                                      AND

                           BIOSYM TECHNOLOGIES, INC.

        This AMENDMENT NO. 2 to R & D BUILDING LEASE ("Amendment No. 2") is made
this 31st day of July 1988, by and between SORRENTO TECH LIMITED, a California
limited partnership ("Landlord") and BIOSYM TECHNOLOGIES, INC., a California
corporation ("Tenant").

                                   RECITALS
                                   --------

        A. Landlord and Tenant are parties to a certain R & D Building Lease
dated February 26, 1987, as amended by that certain First Amendment of Lease
dated September 15, 1987 (collectively, the "Lease"). Under the Lease, Tenant is
leasing from Landlord approximately 10,270 square feet of space (the "Original
Premises")in a building (the "Building") owned by Landlord and located at 10065
Barnes Canyon Road, Suite A, City of San Diego, San Diego County, California
92121. The Original Premises and the Building are more particularly described in
the Lease.


        B.  The purpose of this Amendment No. 2 is to amend the Lease in order
to reflect the parties' agreement concerning (i) the leasing by Landlord to
Tenant of the Additional Premises (as defined below) pursuant to the terms and
conditions of that certain proposal letter dated June 30, 1988 from Landlord to
Tenant and (ii) Landlord's grant of a right of first refusal to Tenant with
regard to Tenant's leasing of the remaining space in the Building.

                                   AGREEMENT
                                   ---------

        NOW, THEREFORE, in consideration of the above Recitals and other good
and valuable consideration, receipt of which is hereby acknowledged, the parties
do hereby agree as follows:

        1.1  Addition of New Article 22.  A new Article 22 is hereby added to 
             --------------------------                      
the Lease to read as follows:



                        ARTICLE 22:  ADDITIONAL PREMISES

        22.1  Lease of Additional Premises.  Landlord hereby leases to Tenant 
              ----------------------------           
and Tenant hereby leases from Landlord the "Additional Premises" on all the
terms and conditions of the Lease, except as otherwise expressly provided in
this Article 22. The Additional Premises are more particularly described in
Subparagraph 22.1(a) below.

        (a)  Additional Premises.   The Additional
             -------------------                  
Premises shall consist of the following:
<PAGE>
 
                      (1)  Rentable Area: Approximately 6,000 sq. ft.
                           --------------     

                      (2)  Location.  That certain 6,000 square feet
                           --------       
immediately adjacent to and contiguous with the Premises as shown on the Floor
Plan of the Premises attached to the Lease as Exhibit "A-1."

                      (3)  Address: 10055 Barnes Canyon Road, San Diego, CA 
                           -------
92121.
        
                (b) Term:  The lease term (the "Expansion Lease Term") for the
                    ----                      
Additional Premises shall commence on the "Expansion Commencement Date" (as
defined in Paragraph 22.2 below). Notwithstanding anything to this Lease to the
contrary, the Lease term for the Premises and the Expansion Lease Term shall
terminate as of July 31, 1992.

                (c) Target Expansion Commencement Date. The Target Expansion 
                    ----------------------------------
Commencement Date is October 1, 1988.

                (d) Rent.
                    ---- 

                      (1)  Basic Annual Rent. The base monthly rent (the "Base 
                           ----------------- 
Monthly Rent") for the Additional Premises shall be $1.00 triple-net ("NNN") per
square foot per month. Notwithstanding the foregoing, the Base Monthly Rent for
the first twelve months of Tenant's occupancy of the Additional Premises shall
be as follows:

                   Month                    Rental Rate
                   -----                    -----------

                   Months 1-4           $-0- per sq. ft.
                   Months 5-8           $0.30 NNN per sq.ft.
                   Months 9-12          $0.50 NNN per sq.ft.

                      (2)  Building and Project Operating Expenses:  Building 
                           ----------------------------------------     
Operating Expenses and Project Operating Expenses as provided by Paragraph 6(c)
of the Basic Lease Provisions shall accrue and be payable by Tenant for the
Additional Premises beginning on the Expansion Commencement Date.

                      (3)  Adjustment to Base Monthly Rent: The Base Monthly 
                           --------------------------------     
Rent shall be increased annually at the rates specified in Paragraph 6(b) of the
Basic Lease Provisions on each successive anniversary of the Expansion Rent
Commencement Date as defined by Paragraph 22.1(d)(4) below, commencing on the
first anniversary of the Expansion Rent Commencement Date.

                      (4)  Expansion Rent Commencement Date:  Base Monthly Rent
                           ---------------------------------     
shall commence on the first calendar day (the "Expansion Rent Commencement
Date") of the fifth month after the Expansion Commencement Date.

                 (e)  Security Deposit.  Prior to the construction of the 
                      ----------------               
Expansion Tenant Improvements (as defined in Paragraph 22.2(b) below). Tenant
shall pay 



                                      -2-
<PAGE>
 
to the Landlord the sum of $6,000 as a security deposit for the Additional
Premises.

                       22.2  Expansion Commencement Date.
                             --------------------------- 

                              (a) General.  Subject to all terms and conditions
                                  -------                                      
       of this Paragraph 22.2, the Expansion Lease Term shall be as specified in
       Paragraph 22.1(b) above unless earlier terminated or extended as provided
       in the Lease. The parties intend that the Expansion Lease Term shall
       commence on the Target Expansion Commencement Date. The date on which the
       Expansion Lease Term actually commences is referred to as the "Expansion
       Commencement Date."

                              (b)      Definition.  The Expansion Commencement
                                       ----------                
       Date shall be the date which is the first to occur of: (1) the date on
       which Landlord substantially completes construction of the tenant
       improvements for the Additional Premises (the "Expansion Tenant
       Improvements") and a certificate of occupancy is issued for the
       Additional Premises by the City of San Diego or (2) the date on which
       Landlord would have substantially completed construction of the Expansion
       Tenant Improvements but for Tenant's Delay (as defined below). If Tenant
       takes possession of or commences use of the Additional Premises (or any
       portion thereof) for any purpose, including construction, before the
       Expansion Commencement Date, the Expansion Lease Term shall not commence,
       but such occupancy shall be subject to all the terms and conditions of
       the Lease and Tenant shall be obligated to pay all items of rent under
       the Lease from the date Tenant takes possession or commences use of the
       affected portion of the Additional Premises.

                              (c) Tenants Delay.  If construction of the
                                  -------------                         
       Expansion Tenant Improvements is delayed or postponed by any delay caused
       by Tenant ("Tenant's Delay"), the Expansion Commencement Date shall be
       adjusted in accordance with the provisions of Paragraph 22.2(b)(2) above
       by the actual number of days by which Landlord`s substantial completion
       of the Expansion Tenant Improvements is delayed due to Tenant's delay.

                              (d) Effect of Delay in Expansion Commencement 
                                  -----------------------------------------
       Date.    Notwithstanding the Target Expansion Commencement Date, if for 
       ----- 
       any reason the Expansion Commencement Date occurs after the Target
       Expansion Commencement Date, Landlord shall not be subject to any
       liability therefor, nor shall such failure affect the validity of the
       Lease or the obligations of Tenant under the Lease or extend the Lease
       Term for the Premises or the Expansion Lease Term. Tenant's obligations
       to pay the Base Monthly Rent shall be measured from the Expansion
       Commencement Date.

                              (e) Construction of Expansion Tenant Improvements.
                                  ----------------------------------------------
       The Expansion Tenant Improvements shall be constructed by Landlord in
       accordance with plans and specifications approved by Landlord and Tenant.
       The Expansion Tenant Improvements shall


                                      -3-
<PAGE>
 
       include the construction of certain interior improvements for use by
       Tenant in the course of its business. Landlord shall contribute a total
       of $20.00 per square foot ("Landlord`s Maximum Contribution") toward the
       cost of the Expansion Tenant Improvements. In the event the cost of the
       Expansion Tenant Improvements is less than Landlord`s Maximum
       Contribution, the difference shall be credited toward Tenant's first
       rental payments. Conversely, in the event the cost of the Expansion
       Tenant Improvements exceeds Landlord`s Maximum Contribution, the
       difference shall be paid by Tenant as the construction of the Expansion
       Tenant Improvements progresses, with the balance to be paid to Landlord
       by Tenant prior to Tenant's taking occupancy of the Additional Premises.

                       22.3  Right of First Refusal.  Provided Tenant is not 
                             -----------------------   
       in default under the terms of the Lease, Tenant shall have the right of
       first refusal to lease approximately 3,347 sq. ft. of remaining unleased
       space (the "Vacant Space") in the building. Landlord shall notify Tenant
       in writing no later than five (5) business days following Landlord's
       receipt of any bona fide offer to lease the Vacant Space to a third
       party. Such written notice shall specify the terms of said offer, and
       Tenant shall have five (5) business days after receipt of such written
       notice within which to exercise its right of first refusal by providing
       written notice to Landlord of Tenant's intent to lease the Vacant Space
       upon the same terms and conditions offered by the third party.

                  1.2  Security Deposit and Additional Rent. It is understood 
                       ------------------------------------- 
and agreed that as additional consideration for this Amendment No. 2 Tenant has
paid to Landlord the sum of $11.297 representing the Security Deposit payable to
Landlord by Tenant as provided by Paragraph 8 of the Base Lease Provisions.
Tenant has also paid to Landlord the sum of $18,890 representing accrued
Building Operating Expenses and Project Operating Expenses applicable to the
Original Premises as provided by Paragraph 6(c) of the Basic Lease Provisions.

                  1.3  Effect of Amendment.  Terms used in this Amendment
                       -------------------                
No. 2 with initial capital letters are defined terms which shall have the same
meaning ascribed to them in the Lease, unless the context of this Amendment No.
2 expressly provides otherwise. Except as amended by this Amendment No. 2, the
Lease shall remain in full force and effect as to both the Original Premises and
the Additional Premises. In the event of a conflict between provisions of the
Lease and those of this Amendment No. 2, this Amendment No. 2 shall control.


                                      -4-
<PAGE>
 
        IN WITNESS WHEREOF, the parties hereto have executed this AMENDMENT NO.
2 to R & D BUILDING LEASE, as of the date first above written.

"LANDLORD"                              "TENANT"

SORRENTO TECH LIMITED,                  BIOSYM TECHNOLOGIES, INC.
a California limited                    a California corporation        
partnership                                                     

By:  /s/Jack Naiman                     By:  /s/Don Miller
   ----------------------                  -----------------------------
Title:  General Partner                 Title:  Vice President, Finance
                                              --------------------------
                                        By:  /s/Arnie Hagler

                                        Title:  Chairman
                                              --------------------------

                                      -5-
<PAGE>
 
                    AMENDMENT NO. 3 TO R & D BUILDING LEASE

                                    BETWEEN

                             SORRENTO TECH LIMITED

                                      AND

                           BIOSYM TECHNOLOGIES, INC.

     This AMENDMENT NO. 3 TO R & D BUILDING LEASE ("Amendment No. 3") is made
this 28th day of July 1989, by and between SORRENTO TECH LIMITED, a California
limited partnership ("Landlord"), and BIOSYM TECHNOLOGIES, INC., a California
corporation ("Tenant").

                                    RECITALS
                                    --------

     A.  Landlord and Tenant are parties to a certain R & D Building Lease dated
February 26, 1987, as amended by (1) a certain First Amendment of Lease dated
September 15, 1987 and (2)  a certain Amendment No. 2 to R & D Building Lease
dated July 31, 1998 (collectively, the "Lease").  Under the Lease, Tenant is
leasing from Landlord approximately 16,270 square feet of space (the "Original
Premises") in a building (the "Building") owned by Landlord and located at 10065
Barnes Canyon Road, Suite A, City of San Diego, San Diego County, California
92121.  The Original Premises and the Building are more particularly described
in the Lease.

     B.  The purpose of this Amendment No. 3 is to amend the Lease in order to
reflect the parties' agreement concerning the leasing by Landlord to Tenant of
the Expansion Premises (as defined below) pursuant to Tenant's right of first
refusal to lease the Vacant Space (as defined in the Lease).

                                   AGREEMENT
                                   ---------

     NOW, THEREFORE, in consideration of the above Recitals and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties do hereby agree as follows:

     1.1  Addition of New Article 23.   A  new  Article 23   is hereby added to
          --------------------------                                           
the Lease to read as follows:

                        ARTICLE 23:   EXPANSION PREMISES

         23.1  Lease of Expansion Premises.  Pursuant to Paragraph 22.3 of the
               ---------------------------                                    
    Lease, Landlord hereby leases to Tenant and Tenant hereby leases from
    Landlord the Vacant Space on all the terms and conditions of the Lease,
    except as otherwise expressly provided in this Article 23.  For purposes of
    this Amendment, the Vacant Space shall be referred to as the "Expansion
    Premises."  The Expansion Premises are more particularly described in
    Paragraph 23.1(a) below.

              (a)  Expansion Premises.  The Additional Premises shall consist of
                   ------------------                                           
    the following:

                   (1)  Rentable Area:   Approximately 3,347 sq. ft.
<PAGE>
 
              (2)  Location:    That certain 3,347 square feet adjacent to and
                   --------                                                   
    contiguous with the Original Premises as shown on the Floor Plan of the
    Original  Premises  attached  to  the  Lease as Exhibit "A-1."

              (3)  Address:   10065 Barnes Canyon Road, San Diego, California
                   -------                                                   
    92121.

              (b)  Term.  The Lease term (the "Expansion Lease Term") for the
                   ----                                                     
    Expansion Premises shall  commence  on  the  "Expansion  Commencement  Date"
    (as defined  in  Paragraph 23.2  below).   Notwithstanding anything  in
    this  Lease to the contrary, the Lease term  for the Original Premises and
    the Expansion Lease Term shall terminate as of July 31, 1992.

              (c)  Target  Expansion Commencement Date.  The Target Expansion
                   -----------------------------------                       
    Commencement Date is October 1, 1989.

              (d)  Rent.
                   ---- 

              (1)  Basic Annual Rent:   The Basic Annual Rent for the Expansion
                   -----------------                                           
    Premises shall be $1.00 triple-net  (NNN) per square foot per month.  The
    Basic Annual Rent for the Expansion Premises shall be payable beginning on
    the Expansion Rent Commencement Date (as defined in Paragraph 23.1(d) (4)
    below.)  Beginning July 1, 1998, the Basic Annual Rent for the Original
    Premises shall be $1.00 triple-net (NNN) per square foot per month.

              (2) Building and Project Operating Expenses:   Building Operated
                  ---------------------------------------                     
    Expenses and Project Operating Expenses as provided under Article 5 of the
    Lease shall accrue and be payable by Tenant for the Original Premises
    beginning on the Expansion Commencement Date.

              (3)  Adjustments to Base Monthly Rent:  The Base  Monthly Rent for
                   --------------------------------                             
    the Expansion Premises shall be increased annually at the rates specified in
    Paragraph 6(b) of the Basic Lease Provisions of the Lease on each successive
    anniversary of the Expansion Rent   Commencement   Date   as   defined  by
    Paragraph 23.1(d) (4) below, commencing on the first anniversary of the
    Expansion Rent Commencement Date.

              (4)  Expansion Commencement Date:  Basic Annual Rent for the
                   ---------------------------                            
    Expansion Premises shall commence on the first calendar day (the "Expansion
    Rent Commencement Date") of the fifth month after the Expansion Commencement
                                    -----                                       
    Date.

         23.2  Expansion Commencement Date.
               --------------------------- 

              (a) General. Subject to all the terms and conditions  of this
                  -------                                                  
    Paragraph 23.2, the Expansion Lease Term shall be as specified in Paragraph
    23.1(b) above, unless earlier terminated or extended as provided in the
    Lease.  The parties intend that the Expansion Lease Term shall commence on
    the Target Expansion Commencement Date.  The date on which the Expansion
    Lease Term 


                                      -2-
<PAGE>
 
    actually commences is referred to as the "Expansion Commencement Date."

              (b) Definition. The Expansion Commencement Date shall be the date
                  ----------                                                   
    which is the first to occur  of:  (1) the date which Landlord substantially
    completes construction of the tenant improvements for the Expansion Premises
    (the "Expansion Tenant Improvements") or (2) the date on which Landlord
    would have substantially completed construction of  the Expansion Tenant
    Improvements but for Tenant's Delay (as defined below).  If Tenant takes
    possession of or commences use of the Expansion Premises (or any portion
    thereof) for any purpose, including construction, before the Expansion
    Commencement Date, the Expansion Lease Term shall not commence, but such
    occupancy shall be subject to all the terms and conditions of the Lease and
    Tenant shall be obligated to pay all items of rent under the Lease from the
    date Tenant takes possession or commences use of the affected portion of the
    Expansion Premises.

              (c) Tenant's Delay. If construction of the Expansion Tenant
                  --------------                                         
    Improvements is delayed or postponed by any delay caused by Tenant
    ("Tenant's Delay"), the Expansion Commencement Date shall be adjusted in
    accordance    with    the    provisions    of Paragraph 23.2(b) (2) above by
    the actual number of days by which Landlord's substantial completion of  the
    Expansion Tenant Improvements is delayed due to Tenant's Delay.

              (d)  Effect of Delay in Expansion Commencement Date.
                   ----------------------------------------------   
    Notwithstanding the Target Expansion Commencement Date, if for any reason
    the Expansion Commencement Date occurs after the Target Expansion
    Commencement Date, Landlord shall not be subject to any liability therefor,
    nor shall such failure affect the validity of the Lease or the obligations
    of Tenant under the Lease or extend the Lease Term for the Premises or the
    Expansion Lease Term.  Tenant's obligation to pay Basic Annual Rent shall be
    measured from the Expansion Commencement Date.

              (e)  Construction of Expansion Tenant Improvements.   The
                   ---------------------------------------------       
    Expansion Tenant Improvements shall be construed by Landlord in accordance
    with plans and specifications approved by Landlord and Tenant.  The
    Expansion Tenant Improvements shall include the construction of certain
    interior improvements for use by Tenant in the course of its business.
    Landlord shall contribute a total of $20.00   per   square   foot
    ("Landlord's  Maximum Contribution")  toward the cost of the Expansion
    Tenant Improvements.  In the event the cost of the Expansion Tenant
    Improvements is less than Landlord's Maximum  Contribution, the difference
    shall be credited toward Tenant's first rental payment.  Conversely, in the
    event the cost of the Expansion Tenant Improvements exceeds Landlord's
    Maximum Contribution, the difference shall be paid 


                                      -3-
<PAGE>
 
    by Tenant as the construction of the Expansion Tenant Improvements
    progresses, with the balance to be paid to Landlord by Tenant prior to
    Tenant's taking occupancy of the Additional Premises.

    1.2  Security Deposit.  It is understood and agreed that Tenant shall pay to
         ----------------                                                       
Landlord upon execution of this Amendment  No. 3, the sum of $3,347 representing
the Security Deposit for the Expansion Premises payable to Landlord by Tenant.

    1.3  Effect of Amendment.  Terms used in this Amendment    No. 3  with
         -------------------                                               
initial capital letters are defined terms which shall  have the same meaning
ascribed to them in the Lease, unless the context of this Amendment No. 3
expressly provides otherwise.  Except as amended by this Amendment No. 3, the
Lease shall remain in full force and effect as to both the Original Premises and
the Expansion Premises.  In the event of   a conflict  between  the provisions
of the Lease and those of this Amendment No. 3, this Amendment No. 3 shall
control.

    IN WITNESS WHEREOF, the parties hereto have executed this AMENDMENT NO. 3 TO
R & D BUILDING LEASE, as of the date first written above.

"LANDLORD"                                      "TENANT"

SORRENTO TECH LIMITED                           BIOSYM TECHNOLOGIES, INC.,
a California Limited                            a California corporation
partnership

By:   /s/Jack Naiman                            By:   /s/Don Miller
   -----------------                               ----------------
     Jack Naiman
   General Partner                              Title:   Vice President, Finance
                                                      --------------------------

                                                By:   /s/Robert Enoch
                                                   ------------------

                                                 Title:  President and Chief
                                                       ----------------------
                                                         Operating Officer
                                                       ----------------------





                                      -4-
<PAGE>
 
                            AMENDMENT NO. 4 TO R & D BUILDING LEASE
                
                                            BETWEEN

                                     SORRENTO TECH LIMITED

                                              AND

                                   BIOSYM TECHNOLOGIES, INC.

                     This Amendment No. 4 to R & D BUILDING LEASE ("Amendment
                  No. 4") is made this 26th day of November 1990, by and between
                  SORRENTO TECH LIMITED, a California limited partnership
                  ("Landlord") and BIOSYM TECHNOLOGIES, INC., a California
                  corporation ("Tenant").

                                            RECITALS
                                            --------

                     A.  Landlord and Tenant are parties to a certain R & D
                  Building Lease dated February 26, 1987, as amended by (1) a
                  certain First Amendment of Lease dated September 15, 1987, (2)
                  a certain Amendment No. 2 dated July 31, 1988, and (3) a
                  certain Amendment No. 3 dated July 28, 1989 (collectively, the
                  "Lease").  Under the Lease, Tenant is leasing from Landlord
                  approximately 19,617 square feet of space (the "Original
                  Premises")in a building (the "Building") owned by Landlord
                  and located at 10065 Barnes Canyon Road, Suite A, City of San
                  Diego, San Diego County, California 92121.  The Original
                  Premises and the Building are more particularly described in
                  the Lease.

                     B.  The purpose of this Amendment No. 4 is to amend the
                  Lease in order to reflect the parties' agreement concerning
                  the leasing by Landlord to Tenant of Additional Premises (as
                  defined below).

                                           AGREEMENT
                                           ---------

                     NOW, THEREFORE, in consideration of the above Recitals and
                  other good and valuable consideration, the receipt and
                  sufficiency of which are hereby acknowledged, the parties do
                  hereby agree as follows:

                     1.1  Addition of New Article 24.  A new Article 24 is
                          --------------------------                      
                  hereby added to the Lease to read as follows:

                                ARTICLE 24:  ADDITIONAL PREMISES

                     24.1    Lease of Additional Premises.  Landlord hereby
                             ----------------------------                  
                  leases to Tenant and Tenant hereby leases from Landlord the
                  "Additional Premises" on all the terms and conditions of the
                  Lease, except as otherwise expressly provided in this Article
                  24.  The Additional Premises are more particularly described
                  in Paragraph 24.1 (a) below.

                     (a)  Additional Premises.   The Additional Premises shall
                          -------------------                                 
                  consist of the following:

                       (1) Rentable Area: Approximately 1,520 square feet.
                           -------------                                  

                       (2) Location.  That certain 1,520 square feet known as
                           --------                                          
                  Suite E and F within the building located at 10055 Barnes
                  Canyon Road.

                       (3) Address:  10055 Barnes Canyon Road, San Diego, 
                           -------                            
                  California 92121.

                     (b) Term:  The Lease term (the "Additional Premises Lease
                         ----                                                 
                  Term") for the Additional Premises shall commence on the
                  "Additional Premises Commencement Date" (as defined in
                  paragraph 24.2 below).  Notwithstanding anything to this Lease
                  to the contrary, the Lease term for the Original Premises
                  shall terminate on July 31, 1992.  The Lease Term for the
                  Additional Premises 


                                      -1-
<PAGE>
 
                  contained in this Amendment No. 4 shall terminate as of April
                  7, 1991.

                     (c) Additional Premises Commencement Date.  The Additional
                         -------------------------------------                 
                  Premises Commencement Date is October 8, 1990.

                     (d)  Rent.
                          ---- 

                       (1)  Basic Annual Rent.  The Basic Annual Rent for the
                            -----------------                                
                  Additional Premises shall be $0.99 triple-net (NNN) per square
                  foot per month.  The Basic Annual Rent for the Additional
                  Premises shall be payable beginning on the Additional Premises
                  Commencement Date (as defined in Paragraph 24.2 below).

                       (2) Building and Project Operating Expenses:  Building
                           ---------------------------------------           
                  Operating Expenses and Project Operating Expenses as provided
                  under Article 5 of the Lease shall accrue and be payable by
                  Tenant for the Additional Premises beginning on the Additional
                  Premises Commencement Date.

                       (3) Adjustment to Base Monthly Rent:  The Base Monthly
                           -------------------------------                   
                  Rent for the Additional Premises shall be increased annually
                  at the rates specified in Paragraph 6(b) of the Basic Lease
                  Provisions of the Lease on each successive anniversary of the
                  Additional Premises Rent Commencement Date as defined by
                  Paragraph 24.2 below, commencing on the first anniversary of
                  the Additional Premises Rent Commencement Date.

                     24.2  Additional Premises Commencement Date.
                           ------------------------------------- 

                            (a) General.  Subject to all terms and conditions of
                                -------                                         
                  this Paragraph 24.2, the Additional Premises Lease Term shall
                  be as specified in Paragraph 24.1 above, unless earlier
                  terminated or extended as provided in the Lease.  The parties
                  intend that the Additional Premises Lease Term shall commence
                  on the Additional Premises Commencement Date.

                     1.2  Effect of Amendment.  Terms used in this Amendment No.
                          -------------------                                   
                  4 with initial capital letters are defined terms which shall
                  have the same meaning ascribed to them in the Lease, unless
                  the context of this Amendment No. 4 expressly provides
                  otherwise.  Except as amended by this Amendment No. 4, the
                  Lease shall remain in full force and effect as to both the
                  Original Premises, the Expansion Premises and the Additional
                  Premises.  In the event of a conflict between provisions of
                  the Lease and those of this Amendment No. 4, this Amendment
                  No. 4 shall control.

                     IN WITNESS WHEREOF, the parties hereto have executed this
                  AMENDMENT NO. 4 to R & D BUILDING LEASE, as of the date first
                  written above.

                 "LANDLORD"                       "TENANT"
                 SORRENTO TECH LIMITED,           BIOSYM TECHNOLOGIES, INC.
                 a California limited             a California corporation
                 partnership                      
                                                  
                 By:  /s/Jack Naiman              By:  /s/Todd Schmidt
                    -------------------              --------------------
                                                  
                                                  Title:  Vice President
                                                        -----------------
                                                  By:
                                                     --------------------
                                                  Title:
                                                        -----------------


                                      -2-
<PAGE>
 
                    AMENDMENT NO. 5 TO R & D BUILDING LEASE

                                    BETWEEN

                             SORRENTO TECH LIMITED

                                      AND

                           BIOSYM TECHNOLOGIES, INC.

                This Amendment No. 5 to R & D BUILDING LEASE ("Amendment No. 5")
            is made this 7th day of May 1991, by and between SORRENTO TECH
            LIMITED, a California limited partnership ("Landlord") and BIOSYM
            TECHNOLOGIES, INC., a California corporation ("Tenant").

                                    RECITALS
                                    --------

                A.  Landlord and Tenant are parties to a certain R & D Building
            Lease dated February 26, 1987, as amended by (1) a certain First
            Amendment of Lease dated September 15, 1987, (2) a certain Amendment
            No. 2 dated July 31, 1988, and (3) a certain Amendment No. 3 dated
            July 28, 1989 and (4) a certain Amendment No. 4 dated November 26,
            1990 (collectively, the "Lease"). Under the Lease, Tenant is leasing
            from Landlord approximately 19,617 square feet of space (the
            "Original Premises")in a building (the "Building") owned by Landlord
            and located at 10065 Barnes Canyon Road, Suite A, and approximately
            1,520 square feet of space in a building owned by Landlord located
            at 10055 Barnes Canyon Road, Suites E and F, City of San Diego, San
            Diego County, California 92121. The Original Premises and the
            Building are more particularly described in the Lease.

                B.  The purpose of this Amendment No. 5 is to amend the Lease in
            order to reflect the parties' agreement concerning the leasing by
            Landlord to Tenant of Additional Premises (as defined below).

                                   AGREEMENT
                                   ---------

                NOW, THEREFORE, in consideration of the above Recitals and other
            good and valuable consideration, the receipt and sufficiency of
            which are hereby acknowledged, the parties do hereby agree as
            follows:

                1.1  Article 24.  A new Article 24 is hereby amended as follows:
                     ----------                                                 

                (a) Extension of Termination Date for Additional Premises Suites
                    ------------------------------------------------------------
            E and F. The Lease Term for the 1,520 square feet in Suites E and F
            -------
            as outlined in Amendment No. 4 to the Lease shall be extended and
            shall terminate as of October 8, 1991.

                (b)  Basic Annual Rent.  The Basic Annual Rent for the
                     -----------------                                
            Additional Premises Suites E and F shall be $0.99 triple-net (NNN)
            per square foot per month for the extension period.

                1.2  Addition of New Article 25:  A new Article 25 is hereby
                     --------------------------                             
            added to the Lease to read as follows:
<PAGE>
 
                ARTICLE 25 ADDITIONAL PREMISES - SUITES G AND H

                25.1  Lease of Additional Premises Suites G and H.  Landlord
                      -------------------------------------------           
            hereby leases to Tenant and Tenant hereby leases from Landlord the
            "Additional Premises" on all the terms and conditions of the Lease,
            except as otherwise expressly provided in this Article 25. The
            Additional Premises are more particularly described in Paragraph
            25.1 (a), as described below..

                    (a)  Additional Premises. The Additional Premises shall
                         -------------------                               
            consist of the following:

                  (1)  Rentable Area:  Approximately 1,453 square feet.
                       -------------                                   

                    (2)  Location:  That certain 1,453 square feet known as
                         --------                                          
            Suite G and H within the building located at 10055 Barnes Canyon
            Road.

                    (b) Additional Premises Commencement Date.  The Additional
                        -------------------------------------                 
            Premises Commencement Date is April 15, 1991.

                    (c)  Rent.
                         ---- 

                      (1) Basic Annual Rent.  The Basic Annual Rent for the
                          -----------------                                
            Additional Premises Suites G and H shall be $0.99 triple-net (NNN)
            per square foot per month. The Basic Annual Rent for the Additional
            Premises shall be payable beginning on the Additional Premises Rent
            Commencement Date (as defined below).

                    (2) Building and Project Operating Expenses:  Building
                        ---------------------------------------           
            Operating Expenses and Project Operating Expenses as provided under
            Article 5 of the Lease shall accrue and be payable by Tenant for the
            Additional Premises beginning on the Additional Premises
            Commencement Date.

                (b)  Term.  The Lease term (the "Additional Premises Lease
                     ----                                                 
            Term") for the Additional Premises shall commence on the "Additional
            Premises Commencement Date" (as defined in paragraph 25.2 below).
            Notwithstanding anything in this Lease to the contrary, the Lease
            term for the Original Premises shall terminate on July 31, 1992. The
            Lease Term for the Additional Premises Suites E and F shall be
            extended to terminate as of October 8, 1991. The Lease Term for the
            Additional Premises Suites G and H shall terminate as of October 31,
            1991.

                25.2  Additional Premises Commencement Date.
                      ------------------------------------- 

                (a) General.  Subject to all terms and conditions of
                    -------                                         
            this Paragraph 25.2, the Additional Premises Lease Term shall be as
            specified in Paragraph 25.1 above, unless earlier terminated or
            extended as provided in the Lease. The parties intend that the
            Additional Premises Lease Term shall commence on the Additional
            Premises Commencement Date.


                                      -2-
<PAGE>
 
                1.2  Effect of Amendment.  Terms used in this Amendment No. 5
                     -------------------                                     
            with initial capital letters are defined terms which shall have the
            same meaning ascribed to them in the Lease, unless the context of
            this Amendment No. 5 expressly provides otherwise. Except as amended
            by this Amendment No. 5, the Lease shall remain in full force and
            effect as to both the Original Premises, the Expansion Premises and
            the Additional Premises. In the event of a conflict between
            provisions of the Lease and those of this Amendment No. 5, this
            Amendment No. 5 shall control.

                IN WITNESS WHEREOF, the parties hereto have executed this
            AMENDMENT NO. 5 to R & D BUILDING LEASE, as of the date first
            written above.

LANDLORD

Dated:  May 7, 1991            SORRENTO TECH LIMITED
      ----------------         a California limited partnership
                               By:   The Walters Management Co., Inc.
                                     Court Appoint Receiver

                               By:  /s/John Alioto
                                  -------------------------------------
                               Its:  Senior Vice President
                                   ------------------------------------

TENANT:                        BIOSYM TECHNOLOGIES, INC.
                               a California corporation 
Dated:  May 7, 1991            
      ----------------         By:  /s/Todd Schmidt
                                  -------------------------------------
                               Name: Todd Schmidt  
                                    -----------------------------------
                               Title: Vice President
                                     ----------------------------------


                                      -3-
<PAGE>
 
                    AMENDMENT NO. 6 TO R & D BUILDING LEASE

                                    BETWEEN

                             SORRENTO TECH LIMITED
                                      AND
                           BIOSYM TECHNOLOGIES, INC.


     This Amendment No. 6 to R & D BUILDING LEASE ("Amendment No. 6") is made
this 17th day of July 1991, by and between SORRENTO TECH LIMITED, a California
limited partnership ("Landlord") and BIOSYM TECHNOLOGIES, INC., a California
corporation ("Tenant").

                                    RECITALS
                                    --------

     A.     Landlord and Tenant are parties to a certain R & D Building Lease
dated February 26, 1987, as amended by (1) a certain First Amendment of Lease
dated September 15, 1987, (2) Amendment No. 2 dated July 31, 1988, (3) Amendment
No. 3 dated July 28, 1989, (4) Amendment  No. 4 dated November 26, 1990, and (5)
Amendment No. 5 dated May 7, 1991 (collectively, the "Lease").  Under the Lease,
Tenant is leasing from Landlord approximately 19,617 square feet of space (the
"Original Premises") in a building (the "Building") owned by Landlord and
located at 10065 Barnes Canyon Road, and approximately 2,973 square feet of
space in a building owned by Landlord located at 10055 Barnes Canyon Road,
Suites E,  F,  G  &  H, City of San Diego, San Diego County, California  92121.
The Original Premises and the Buildings are more particularly described in the
Lease.

     B.     The purpose of this Amendment No. 6 is to amend the Lease in order
to reflect the parties' agreement concerning the leasing by Landlord to Tenant
of Additional Premises (as defined below).

                                   AGREEMENT
                                   ---------

     NOW, THEREFORE, in consideration of the above Recitals and other good and
valuable consideration, the receipt and sufficiency of which  are hereby
acknowledged, the parties do hereby agree as follows:

     1.1  Articles 24 and 25.  Articles 24 and 25 are hereby amended as follows:
          ------------------                                                    

       (a)  Extension of Termination Date for Additional Premises Suites E, F, G
            --------------------------------------------------------------------
and H.  The Lease Term for the 2,973 square feet in  Suites E, F, G and H at
------                                                                      
10055 Barnes Canyon Road is hereby extended and shall terminate as of December
31, 1991.

       (b)  Option to Extend.  Tenant shall have the option to extend the lease
            ----------------                                                   
term on a month-to-month basis upon thirty (30) days written notification
through July 31, 1992, which is co-terminus with the lease for the Original
Premises.


                                       1
<PAGE>
 
       (c)  Basic Annual Rent.  The Basic Annual Rent for Suites E, F, G and H
            -----------------                                                 
shall be $0.75 triple-net (NNN) per square foot per month for the extension
period and for any month-to-month extension.

     1.2  Addition of New Article 26.  A new Article 26 is hereby added to the
          --------------------------                                          
Lease to read as follows:

       ARTICLE 26:  ADDITIONAL PREMISES - 9725 Scranton Road

     26.1  Lease of Additional Premises.  Landlord hereby leases to Tenant and
           ----------------------------                                       
Tenant hereby leases from Landlord the "Additional Premises" on all the terms
and conditions of the Lease, except as otherwise expressly provided in this
Article 26.  The Additional Premises are more particularly described in
Paragraph 26.1 (a), as described below.

       (a)  Additional Premises.  The Additional Premises shall consist of the
            -------------------                                               
following:

              (1)  Rentable Area:  Approximately 4,762 square feet.
                   -------------                
              
              (2)  Location:  That certain 4,762 square feet at 9725 Scranton 
                   --------                     
Road, known as Building 3 within the Naiman Tech Center.

       (b)  Additional Premises Commencement Date.  The Additional Premises
            -------------------------------------                          
Commencement Date is July 8, 1991.

       (c)  Rent.
            -----

          (1)  Basic Annual Rent.  The Basic Annual Rent for the Additional
               -----------------                                           
Premises shall be $0.75 triple-net (NNN) per square foot per month.  The Basic
Annual Rent for the Additional Premises shall be payable beginning on the
Additional Premises Rent Commencement Date (as defined below).

          (2)  Building and Project Operating Expenses and Utilities:  Building
               -----------------------------------------------------           
Operating Expenses and Project Operating Expenses  as provided under Article 5
of the Lease shall accrue and be payable by Tenant for the Additional Premises
beginning on the Additional Premises Commencement Date.  Tenant shall make
necessary arrangements with San Diego Gas & Electric for service to the
Additional Premises.

       (d)  Term:  The lease term (the "Additional Premises Lease Term") for the
            ----                                                                
Additional Premises shall commence on the "Additional Premises Commencement
Date" (as defined in paragraph 26.2 below).  Notwithstanding anything in this
Lease to the contrary, the Lease term for the Original Premises shall terminate
on July 31, 1992.  The Lease Term for the Additional Premises shall terminate as
of December 31,  1991.

       (e)  Option to Extend.  Tenant shall have the option to extend the lease
            ----------------                                                   
term on a month-to-month basis upon thirty (30) days written notification
through July 31, 1992, which is co-terminus with the lease


                                       2
<PAGE>
 
for the Original Premises.

     26.2  Additional Premises Commencement Date.
           ------------------------------------- 

       (a)  General.  Subject to all terms and conditions of this Paragraph
            -------                                                        
26.2, the Additional Premises Lease Term shall be as specified  in Paragraph
26.1 above, unless earlier terminated or extended as provided in the Lease.  The
parties intend that the Additional Premises Lease Term shall commence on the
Additional Premises Commencement Date.

     1.3  Effect of Amendment.  Terms used in this Amendment No. 6 with initial
          -------------------                                                  
capital letters are defined terms which shall have the same meaning ascribed to
them in the Lease, unless the context of this Amendment No. 6 expressly provides
otherwise.  Except as amended by this Amendment No. 6, the Lease shall remain in
full force and effect as to both the Original Premises, the Expansion Premises
and the Additional Premises.  In the event of a conflict between provisions of
the Lease  and those of this Amendment No. 6, this Amendment No. 6 shall
control.

     IN WITNESS WHEREOF, the parties hereto have executed this AMENDMENT NO. 6
to R & D BUILDING LEASE, as of the date first written above.

LANDLORD:

Dated:  July 17, 1991                     SORRENTO TECH LIMITED,
        -------                           a California limited partnership 
                                          
                                          By:  The Walters Management Co., Inc.
                                            Court Appoint Receiver

                                          By:  /s/William Borsari
                                               -------------------------

                                          Its: President
                                               -------------------------


TENANT:

Dated: July 3, 1991                       BIOSYM TECHNOLOGIES, INC.,
       ------                             a California corporation       
                                          
                                          By: /s/Todd Schmidt
                                              ------------------------

                                          Name: Todd Schmidt
                                                ----------------------


                                       3
<PAGE>
 
                    AMENDMENT NO. 7 to R & D BUILDING LEASE

                                    BETWEEN

                             SORRENTO TECH LIMITED

                                      AND

                           BIOSYM TECHNOLOGIES, INC.

  This Amendment No. 7 to R & D BUILDING LEASE ("AMENDMENT NO. 7")is made this
9th day of September 1991, by and between SORRENTO TECH LIMITED, a California
corporation ("Tenant").

                                    RECITALS
                                    --------

  A.  Landlord and Tenant are parties to a certain R & D Building Lease dated
February 26, 1987, as amended by (1) a certain First Amendment of Lease dated
September 15, 1987, (2) Amendment No. 2 dated July 31, 1988, (3) Amendment No. 3
dated July 28, 1989, (4) Amendment No. 4 dated November 26, 1990, (5) Amendment
No. 5 dated May 7, 1991, and(6) Amendment No.6 dated July 17, 1991
(collectively, the "Lease").  Under the Lease, Tenant is leasing from Landlord
approximately 19,617 square feet of space (the "Original Premises") in a
building (the "Building") owned by Landlord and located at 10065 Barnes Canyon
Road, approximately 2,973 square feet of spaced in a building owned by Landlord
located at 10055 Barnes Canyon Road, Suites E, F, G & H, and approximately 4,762
square feet of space in a building owned by Landlord located at 9725 Scranton
Road, City of San Diego, San Diego County, California 92121.  The Original
Premises and the Buildings are more particularly described in the Lease.

  B.  The purpose of this Amendment No. 7 is to amend the Lease in order to
reflect the parties' agreement concerning the leasing by Landlord to Tenant of
Additional Premises (as defined below).

                                   AGREEMENT
                                   ---------

  NOW, THEREFORE, in consideration of the above Recitals and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties do hereby agree as follows:

 1.1  Articles 26.   Articles 26 is hereby amended as follows:
      -----------                                             

   ARTICLE 26:  ADDITIONAL PREMISES  -  9725 Scranton Road

  26.1  Lease of Additional Premises.  Landlord hereby leases to Tenant and
        ----------------------------                                       
Tenant hereby leases from Landlord the "Additional Premises" on all the terms
and conditions of the Lease, except as otherwise expressly provided in this
Article 26.  The Additional Premises are more particularly described in
paragraph 26.1 (a), as described below.


                                       1
<PAGE>
 
       (a) Additional Premises. The additional Premises shall consist of the 
           -------------------     
following:

           (1)  Rentable Area: Approximately 2,218 square feet.
                -------------               

           (2)  Location.  That certain 2,218 square feet at 9725 Scranton Road,
                --------                     
 known as Building 3 within the Naiman Tech Center.

       (b) Additional Premises Commencement Date.  The additional premises 
           -------------------------------------
Commencement Date is September 1, 1991.

       (c) Rent.
           ---- 

          (1) Basic Annual Rent. The Basic Annual Rent for the Additional
              -----------------                                          
Premises shall be $0.75 triple-net(NNN) per square foot per month.  The Basic
Annual Rent for the Additional Premises shall be payable beginning on the
Additional premises Rent Commencement Date (as defined below).

          (2) Building and Project Operating Expenses and Utilities: Building
              ------------------------------------------- ---------          
Operating Expenses and Project Operating Expenses as provided under Article 5 of
the Lease shall accrue and be payable by Tenant for the Additional Premises
beginning on the Additional Premises Commencement Date.  Tenant shall make
necessary arrangements with San Diego Gas & Electric for service to the
Additional Premises.

          (d) Term:  The lease terms (the "Additional premises Lease Term") for
              ----                                                             
the Additional Premises shall commence on the "Additional Premises Commencement
Date" (as defined in paragraph 26.2 below).  Notwithstanding anything in this
Lease to the contrary, the Lease term for the Original Premises shall terminate
on July 31, 1992.  The Lease Term for the Additional Premises shall terminate as
of December 31, 1991.

          (e) Option to Extend. Tenant shall have the option to extend the lease
              ----------------                                                  
term on a month-to-month basis upon thirty (30) days written notification
through July 31, 1992, which is co-terminus with the lease for the Original
Premises.

                       26.2  Additional Premises Commencement Date.
                             ------------------------------------- 

          (a)  General.  Subject to all terms and conditions of this Paragraph
               -------                                                        
26.2, the Additional Premises Lease Term shall be as specified in Paragraph 26.1
above, unless earlier terminated or extended as provided in the Lease.  The
parties intend that the Additional Premises Lease Term shall commence on the
Additional Premises Commencement Date.

          1.3  Effect of Amendment. Terms used in this Amendment No. 7 with
               -------------------                                         
initial capital letters are defined terms which shall have the same meaning
ascribed to them in the Lease, unless the context of this Amendment No. 7
expressly provides otherwise.  Except as amended by this Amendment No. 7, the
Lease shall remain in full force and effect


                                       2
<PAGE>
 
as to both the Original Premises, the Expansion Premises and the Additional
Premises.  In the event of a conflict between provisions of the Lease and those
of this Amendment No. 7, this Amendment No. 7 shall control.

LANDLORD:

Dated: 9/5  , 1991                        SORRENTO TECH LIMITED,
      ------                              a California limited partnership

                                          By: The Walters Management Co. Inc.
                                              Court Appoint Receiver

                                          By: /s/William Borsari
                                              -------------------------

                                          Its: President
                                               ------------------------

TENANT:

Dated: 8/9  , 1991                        BIOSYM TECHNOLOGIES, INC.,
      ------                              a California corporation        
                                          
                                          By: /s/Kelly B. Cole
                                              -------------------------

                                          Name: Kelly B. Cole
                                                -----------------------

                                          Title: Manager, Purchasing and
                                                -----------------------
                                                 Facilities
                                                -----------


                                       3
<PAGE>
 
                                AMENDMENT NO. 8

                                       to

                              R & D BUILDING LEASE

                                    between

                             SORRENTO TECH LIMITED

                                      and

                           BIOSYM TECHNOLOGIES, INC.



     This Amendment No. 8 to R & D BUILDING LEASE ("Amendment  No. 8") is made
this 6th day of September, 1991, by and between SORRENTO TECH LIMITED, a
California limited partnership ("Landlord"), and BIOSYM TECHNOLOGIES, INC., a
California corporation ("Tenant"), with reference to the facts set forth in the
Recitals below.

                                    RECITALS
                                    --------
                                        
     A.   Landlord and Tenant are parties to a certain R & D Building Lease
dated February 26, 1987, as amended by (1) a certain First Amendment of Lease
dated September 15, 1987; (2) a certain Amendment No. 2 to R & D Building Lease
dated July 31, 1988; (3) a certain Amendment No. 3 to R & D Building Lease dated
July 28, 1989; (4) a certain Amendment No. 4 to R & D Building Lease dated
November 26, 1990; (5) a certain Amendment No. 5 to R & D Building Lease dated
May 7, 1991; (6) a certain Amendment No. 6 to R & D Building Lease dated July
17, 1991; and (7) a certain Amendment No. 7 to R & D Building Lease dated August
____, 1991 (collectively, the "Lease"). Under the Lease, Tenant is leasing from
Landlord approximately 29,570 square feet of space (the "Existing Premises")
consisting of (i) approximately 19,617 square feet of space in a building
located at 10065 Barnes Canyon Road, (ii) approximately 2,973 square feet of
space in a building located at 10055 Barnes Canyon Road, Suites E, F, G & H in
the City of San Diego; and (iii) approximately 6,980 square feet of space in a
building owned by Landlord located at 9725 Scranton Road, in the City of San
Diego, San Diego County, California 92121. The Existing Premises are more
particularly described in the Lease.

     B.  The purpose of this Amendment No. 8 is to amend the Lease in order to
reflect the parties' agreement concerning the relocation of Tenant to and the
leasing by Landlord to Tenant of the New Premises and the surrender of the
Existing Premises to Landlord.

                                   AGREEMENT
                                   ---------

     NOW, THEREFORE, in consideration of the Recitals above, the mutual
covenants and conditions below and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the parties agree as
follows:

     1.1  Relocation to the New Premises.  Subject to the terms and conditions
          ------------------------------                                      
below, Landlord shall relocate Tenant to the New Premises (as more fully
described below) identified as the first and second


                                      -1-
<PAGE>
 
floors of the building (the "New Building") located   at 9685 Scranton Road, San
Diego, California 92121.

     1.2  New Basic Lease Provisions.  Paragraphs 3(a), (b) and (c), 4(a), 5,
          --------------------------                                         
6(a), (b) (c) and (d), 8, 11 and 13 of the Basic Lease Provisions for the Lease
are deleted in their entirety and substituted with the following:

                       3.  Premises:
                           -------- 

                    (a)  Rentable Area:  Approximately 51,635 sq.   ft.  See the
          Definition of Rentable Area attached    as Exhibit "A-3."

                    (b)  Location:  The first and second floors    of the
          existing building located at 9685 Scranton Road (commonly known as
          "Building 3D"), San Diego, California (the "New Premises"), as shown
          on the Floor Plan of the Premises attached as Exhibit "A-1." The New
          Premises are located in a certain real estate project commonly known
          as the Naiman Tech Center (the "Project"), as shown on the Site Plan
          of the Project attached as Exhibit "A-2."

                    (c)  Address:  9685 Scranton Road, San Diego, California
          92121.

                    4. Lease Term:  The Lease Term shall be eight (8) years
                       ----------                                               
          beginning on the Commencement Date.

                    5. Commencement Date:  The Commencement Date   shall be the
                       -----------------                                       
          date which the Tenant Improvements are substantially completed subject
          only to certain "punch list" items and minor adjustments.
          "Substantial completion," for purposes of this Section 5, shall mean
          Landlord's architect or project manager has certified that the Tenant
          Improvements have been substantially completed and the City of San
          Diego Building Inspection Department has made its final inspection and
          approval   of the Tenant Improvements.  Landlord shall complete   all
          "punch list" items and minor adjustments not later than ninety (90)
          days after substantial completion of the Tenant Improvements.  In the
          event the Tenant


                                      -2-
<PAGE>
 
          Improvements shall not be substantially completed on or before May 1,
          1992, Tenant shall have the right to terminate this Amendment No. 8
          and, upon such termination, the parties shall have no further
          obligations hereunder.

                    6.  Rent:
                        ---- 

                    (a) New Premises.  Basic Annual Rent for    the New premises
                        ------------                                            
          shall be payable beginning on the Commencement Date as follows:

<TABLE> 
<CAPTION> 

Lease                                       $(NNN)per                     Basic Annual Rent
Period                                       Sq. Ft.                       (NNN) per Month
-------------------------------  --------------------------------  --------------------------------
<S>                              <C>                               <C>
Months 1-12                                   $0.30                            $15,490.50
Months 13-24                                  $0.50                            $25,817.50
Months 25-36                                  $0.70                            $36,144.50
Months 37-48                                  $0.75                            $38,726.25
Months 49-60                                  $0.80                            $41,308.00
Months 61-72                                  $0.85                            $43,889.75
Months 73-84                                  $0.95                            $49,053.25
Months 85-96                                  $1.00                            $51,635.00

</TABLE>

                (c)  Additional Rent:  Tenant shall pay, as Additional Rent 
                     ---------------   
          during the entire Lease Term, Tenant's share of Building Operating
          Expenses and Project Operating Expenses as provided in Article 5 of
          the Lease. Tenant's share of Building Operating Expenses shall be 100%
          and Tenant's share of Project Operating Expenses shall be 8.56%.
          Notwithstanding the foregoing, combined Building and Project Operating
          Expenses shall not exceed $.24 per square foot per month for the first
          three (3) years of the Lease Term. Thereafter, (i) increases in
          Building Operating Expenses shall not exceed four percent (4%) per
          annum, and (ii) increases in Project Operating Expenses shall not
          exceed four percent (4%) per annum. Upon written request, Landlord
          shall provide Tenant with an Operating Expenses projection.

                (d)  Utilities:  Tenant shall have the sole responsibility to 
                     ---------   
          secure utilities services for the New Premises. Tenant shall make
          necessary arrangements with San Diego Gas & Electric Company to (i)
          supply utilities for (ii) bill Tenant separately utilities. shall make
          necessary the New Premises and for all such arrangements with San
          Diego Gas & Electric Company to (i) supply utilities for the New
          Premises and (ii) bill Tenant separately for all such utilities.


                                      -3-
<PAGE>
 
     8.   Security Deposit:  Upon execution of this Amendment No. 8, Tenant
          ----------------                                                 
          shall pay $17,049 to Landlord to increase the Security Deposit to
          $37,694.

                11.  Addresses for Notices:
                     --------------------- 

                     (a)    If to Landlord:
                            Sorrento Tech Limited
                            c/o Naiman Tech Center
                            9605 Scranton Road, Suite 102
                            San Diego, CA  92121
                            Attn:  Property Management

                     (b)    If to Tenant:

                            Biosym Technologies, Inc.
                            9685 Scranton Road
                            San Diego, CA  92121
                            Attn:  Accounts Payable

                13. Broker: Grubb & Ellis (Steve Scott)
                            8880 Rio San Diego Dr., #200
                            San Diego, CA  92108

             Broker commissions payable to Grubb & Ellis or to The Walters
        Management Co. shall be paid by Landlord. Landlord and Tenant represent
        and warrant that they are unaware of any additional brokerage
        commissions or fees payable to any other broker for the subject
        transaction.

     1.3  Tenant Improvement Allowance.  Exhibit "B" to the Lease  shall be
          ----------------------------                                     
deleted in its entirety and shall be replaced by this Section 1.3 and Exhibit
"B" attached to this Amendment.  Landlord shall construct certain tenant
improvements (the "Tenant Improvements") in the Premises, pursuant to this
Section 1.3 and   the attached Exhibit "B".  Landlord shall provide Tenant with
a tenant improvement allowance (the "Allowance") of $21.50 per    square foot.
The terms and conditions of the Allowance are more fully set forth in Exhibit
"B".  The Allowance shall include the  cost of space planning, plans, permits
and other fees associated  with the Tenant Improvements.  Landlord has approved
the firm Krommenhoek, McKeown & Associates to prepare the space plans.       If
Tenant does not use all of the Allowance, Basic Annual Rent     for the New
Premises shall be reduced by $0.0125 per square foot   per month for each unused
$1.00 throughout the Lease Term or pro  rata part thereof.  As more fully set
forth in Exhibit "B", the Tenant Improvements shall be constructed by Landlord's
contractor   in accordance with plans and specifications prepared by Tenant's
architect and approved by Landlord and Tenant.  The Tenant Improvements shall be
constructed in accordance with all    applicable government codes, regulations
and permits.



                                      -4-
<PAGE>
 
     1.4 First Right of Refusal for Expansion Space.  Pursuant to the terms and
         ------------------------------------------                            
conditions of this Section 1.4 and Exhibit "C" attached to this Amendment,
Landlord shall grant Tenant a right of first refusal to lease adjacent space in
Building 3 (the "Expansion Space") during the Lease Term. The Expansion Space is
more fully described in Exhibit "C." Tenant's right of refusal shall remain
effective provided such rights have not been previously granted to tenants
located in Building 3 as of the Commencement Date as to Torrey Science
Technologies and as of the date of this Amendment No. 8 as to all other parties.
Landlord shall notify Tenant in writing within thirty (30) days after the
Expansion Space (or portion thereof) becomes legally available to lease, or at
Landlord's option, such earlier time as Landlord shall be in a position to
estimate when the Expansion Space will be legally available to lease, advising
Tenant of such estimated date. Expansion Space shall be "available" only to the
extent it is not subject to expansion, extension, first offer, first refusal and
any other rights of other tenants in the Building as of the Commencement Date as
to Torrey Science Technologies and as of the date of this Amendment No. 8 as to
all other parties. Tenant shall then have the right of first refusal (in the
event that Tenant is not then in default under the Lease, with any applicable
cure period having expired), exercisable by written notice to Landlord within
ten (10) business days thereafter, to add any such available space to the New
Premises immediately as it may become available. Any such available space shall
be leased to Tenant at the Prevailing Rental Rate (as defined in Exhibit "C")
for a term coterminous with the balance of the Lease Term remaining on Tenant's
lease of the New Premises (or such shorter term as may be necessary to prevent
any conflict with such other tenants' rights to such space).

     1.5  Signage.  Tenant may erect building top signage, entry door signage,
          -------                                                             
and directory signage (collectively, "Signage"). Signage shall conform to the
Naiman Tech Center sign standards, the provisions of the City of San Diego
Municipal Code relating to signage, and the Lusk Mira Mesa CC&Rs.

     1.6  Parking.  Landlord shall provide Tenant with three and  one half (3.5)
          -------                                                               
parking spaces per one thousand (1,000) usable square foot of the New Premises.
Landlord shall not charge Tenant a parking fee for such parking privileges.

     1.7  Reduction of Rent for Existing Premises.  Subject to the terms and
          ---------------------------------------                              
conditions of this Amendment, upon execution of this Amendment No. 8, Landlord
shall reduce (the "Reduction") Tenant's obligation to pay rent under the Lease
for the Existing Premises to $0.70 per square foot per month for the entire
Existing Premises and any interim expansion space that Tenant may occupy prior
to Tenant's occupancy of the New Premises. The Reduction shall be for the period
commencing on the date hereof until the Commencement Date. Tenant shall continue
paying all Building and Project Operating Expenses for the New Premises,
including without limitation, janitorial and utility expenses.


                                      -5-
<PAGE>
 
     1.8  Amendment No. 8 Contingent Upon Relocation of Other Tenants.  This
          -----------------------------------------------------------       
Amendment No. 8 is subject to and contingent upon Landlord's ability to relocate
the existing tenants of the New Premises in the New Building to alternate
locations within the  Naiman Tech Center.  In the event the existing tenant in
the New Premises has not executed a lease amendment or other relocation
agreement to Tenant's reasonable satisfaction on or before   September 6, 1991,
Tenant shall have the right to terminate this Amendment No. 8, provided Tenant
shall exercise its right to terminate this Amendment No. 8 on or before
September 20, 1991.

     1.9  Quiet Enjoyment.  Landlord covenants and agrees that Tenant, upon
          ---------------                                                  
making all of Tenant's payments as and when due under the Lease, and upon
performing, observing and keeping the covenants, agreements and conditions of
this Lease on its part to be kept, shall peaceably and quietly hold, occupy and
enjoy the New Premises during the term of this Lease subject to the terms and
provisions of this Lease.

     1.10  Option to Renew.
           --------------- 

     (a)  Grant of Option.  Subject to all of the terms and conditions of the
          ---------------                                                    
Lease as amended by this Amendment No. 8, Tenant shall have the right (the
"Option") to extend the Lease Term for one (1) additional term of five (5) years
(the "Option Term") by sending written notice to such effect to Landlord not
later than one hundred eighty (180) days prior to the expiration of the Lease
Term. Failure to timely send such notice shall constitute a waiver of all
remaining rights as to the Option and Tenant shall have no right to exercise the
Option. The extension of the Lease Term shall be on all of the same terms and
conditions of the Lease as amended by this Amendment No. 8, provided that Basic
Annual Rent payable during the Option Term shall be determined as provided in
Section 1.10(b) below. Notwithstanding anything in this Section 1.10 to the
contrary, Tenant shall have no right to exercise the Option if (i) Tenant is in
default under this Lease either at the time the Option is exercised or at the
time the Option Term is scheduled to commence; (ii) Tenant is not in possession
of at least seventy- five percent (75%) of the Rentable Area of the New Premises
either at the time the Option is exercised or at the time the Option Term is
scheduled to commence; or (iii) Tenant has assigned this Lease in whole or in
part or sublet more than twenty-five percent (25%) of the Rentable Area of the
Premises either at the time the Option is exercised or at the time the Option
Term is scheduled to commence.

     (b)  Rent During Option Term.  Provided Tenant shall validly exercise the
          -----------------------                                             
Option, the Basic Annual Rent payable during the Option Term shall be the fair
market rent for the New Premises for the entire Option Term (e.g., fair market
value for the base year subject to annual increases at a fixed rate over the
five-year term). In the event the parties are unable to


                                      -6-
<PAGE>
 
agree on the Basic Annual Rent for the Option Term within sixty (60)days after
the exercise of the Option by Tenant, either party may request that the fair
market rent for the New Premises during the Option Term be determined by
appraisal as provided below. Each party shall select a disinterested member of
the American Institute of Real Estate Appraisers ("MAI Appraiser(s)") with at
least five years of experience in appraising fair market rent in the San Diego
market. Each party shall designate an appraiser within seven (7) days after such
60-day period. In the event that either party shall fail to designate an MAI
Appraiser designate within such 7-day period, the appraiser selected by the
other party shall be the sole appraiser to determine the fair market rent. Upon
the designation of the MAI Appraisers, the appraiser shall have seven (7) days
in which to designate a third MAI Appraiser. If the two appraisers are unable to
agree on a third appraiser, either party may request the President of the
Executive Committee of the San Diego Chapter of the American Institute of Real
Estate Appraisers to appoint such third MAI Appraiser. The three appraisers
shall each appraise the fair market rent for the entire Option Term taking into
account appropriate indicators of the value of the leasehold interest and shall
report their findings to Landlord and Tenant in writing. If the appraisers fail
to deliver a determination of the fair market rent within thirty (30) days after
the appointment of the third appraiser, either party may dismiss the appraisers
and reinitiate the appraisal procedure set forth above. In recognition that the
fair market rent of the New Premises during the Option Term may not be
determined until after the commencement of the Option Term, Tenant shall pay, as
Basic Annual Rent for the New Premises until the fair market rent for the New
Premises is determined, the amount of Basic Annual Rent then in effect under the
Lease. In the event the fair market rent for the New Premises during the Option
Term is determined to be greater than such amount, Tenant shall pay Landlord,
within thirty (30) days after written request, the difference between the amount
required by such determination of the fair market rent for the New Premises
during the Option Term, and the amount previously paid by Tenant for the New
Premises during the Option Term.

     1.11  Non-Disturbance.  The parties agree that the effect of this Amendment
           ---------------                                                      
No. 8 is contingent upon receipt of a non- disturbance agreement recognizing
Tenant's interest in the Lease from HomeFed Bank in a form acceptable to Tenant
(or other similar instrument) on or before September 6, 1991. In the event such
non-disturbance agreement (or similar instrument) is not received by Tenant on
or before September 6, 1991, Tenant shall have the right to terminate this
Amendment No. 8, provided that Tenant shall exercise its right to terminate this
Amendment No. 8 on or before September 20, 1991.

     1.12  Effect of Amendment.  Terms used in this Amendment     No. 8 with
           -------------------                                              
initial capital letters are defined terms which shall have the same meaning
ascribed to them in the Lease, unless the


                                      -7-
<PAGE>
 
context of this Amendment No. 8 expressly provides otherwise. Except as amended
by this Amendment No. 8, the Lease shall remain in full force and effect as to
the New Premises. In the event of a conflict between provisions of the Lease and
those of this Amendment No. 8, this Amendment No. 8 shall control.

     IN WITNESS WHEREOF, the parties hereto have executed this AMENDMENT NO. 8
to R & D BUILDING LEASE, as of the date first written above.

"LANDLORD:"
Dated: 9/5 , 1991                       SORRENTO TECH LIMITED,
      -----                             a California limited partnership

                                        By:  The Walters Management Co.,
                                             Inc., as Court-Appointed
                                             Receiver

                                        By:    /s/William Borsari
                                               ------------------
                                        Name:  William Borsari
                                               ---------------
                                        Title: President
                                               ---------

"TENANT:"

Dated:  August 23, 1991                 BIOSYM TECHNOLOGIES, INC.,
        ---------                       a California corporation

                                        By:    /s/Todd Schmidt
                                               ---------------
                                        Name:  Todd Schmidt
                                               ------------
                                        Title: Vice President
                                               --------------


                                      -8-
<PAGE>
 
                                 EXHIBIT "A-1"

                           FLOOR PLAN OF THE PREMISES
                           --------------------------
                                        

                                        
                                        
                             [Diagram appears here]
<PAGE>
 
                                 EXHIBIT "A-2"

                            SITE PLAN OF THE PROJECT
                            ------------------------
                                        



                             [Diagram appears here]
<PAGE>
 
                                 EXHIBIT "A-3"

                          DEFINITION OF RENTABLE AREA
                          ---------------------------

     1.  Definition.  The term "Rentable Area" as used in this  Lease shall
         ----------                                                        
mean:

     a.  Single Tenant Floor.  As to each floor of each building in the Project
         -------------------                                                   
on which the entire space rentable to a tenant is or will be leased to one
tenant (hereinafter referred to as "Single Tenant Floor"), Rentable Area shall
be the entire area bounded by the inside surface of the four exterior glass
walls (or the inside surface of the permanent exterior wall where there is no
glass) on such floor, including all areas used for elevator lobbies, corridors,
special stairways, or elevators, common restrooms (if any), mechanical rooms,
electrical rooms and telephone closets without deduction for columns and other
structural portions of each building or vertical penetrations that are included
for the special use of a tenant, but excluding the area contained within the
exterior walls of each building's stairs, fire towers, vertical ducts, elevator
shafts, flues, vents, stacks and pipe shafts. Rentable Area for a Single Tenant
Floor shall include a pro rata portion of any ground floor elevator lobby areas.

     b.  Multi-Tenant Floor.  As to each floor of each building in the Project
         ------------------                                                   
on which space is or will be leased to more than one tenant (hereinafter
referred to as "Multi-Tenant Floor"), Rentable Area attributable to each such
tenant shall be the total of (1) the entire area included within the premises
covered by such tenant's lease, being the area bounded by the inside surface of
any exterior glass walls (or the inside surface of the permanent exterior walls
where there is no glass) bounding such premises, the exterior of all walls
separating such premises from any public corridors or other public areas on such
floor, and the centerline of all walls separating such premises from other areas
leased or to be leased to other tenants on such floor, and (2) a pro rata
portion of the area covered by the elevator lobbies, corridors, common restrooms
(if any), mechanical rooms, electrical rooms and telephone closets situated on
such floor and on the ground floor of a building (but only to the extent any of
the same serve all tenants of the building).

     2.  Certification.  Landlord's architect shall determine the Rentable
         -------------                                                        
Area of each tenant's premises and such determination shall be binding and
conclusive. A certified copy of such determination shall be delivered to
Landlord and each tenant. Landlord reserves the right to have its architect
redetermine the Rentable Areas of the Premises, the Building and/or the Project
from time to time during the Initial Term and, if extended, any option term of
this Lease. A certified copy of any such redetermination shall be delivered to
Landlord and each affected tenant.
<PAGE>
 
                                  EXHIBIT "B"

                    TENANT IMPROVEMENT ALLOWANCE MEMORANDUM
                    ---------------------------------------
                                        
     In addition to the mutual covenants contained in the Lease, Landlord and
Tenant further mutually agree as follows:

     1.  Tenant Improvement Allowance.  Landlord shall pay     $21.50 per square
         ----------------------------                                           
foot of Usable Area (as defined below) in the Premises (the "Allowance") for the
work to be performed by Tenant and Landlord under this Tenant Improvement
Allowance Memorandum (the "Memorandum"). Such work shall include the
construction of the tenant improvements described below and the preparation of
all space plans, working drawings, plans for such construction and building
permits and fees associated with such work.

     2.  Plans and Specifications for the Premises.
         ----------------------------------------- 

     a.  Tenant shall prepare detailed space plans and specifications and
working drawings for the Premises which shall include, but not be limited to,
locations of doors, partitioning, reflected ceiling, electrical fixtures,
outlets and switches, telephone outlets, plumbing fixtures, extraordinary floor
loads, and other special requirements. Tenant shall coordinate and develop such
space plans and working drawings and shall use its reasonable best efforts to
obtain all required governmental permits ("Permits") on or before the dates set
forth in the Schedule of Approvals below. Landlord shall use its reasonable best
efforts to assist Tenant in obtaining the Permits. Tenant shall have the right
to apply the Allowance to the payment of its contractors for the preparation of
space plans, specifications and working drawings and to applicable governmental
entities for permit applications, provided (i) Tenant shall first deliver to
landlord invoices or receipts from such contractors or completed applications
for Permits to governmental entities and (ii) payment of the same shall be made
in a timely manner by Landlord directly to such contractors and governmental
entities. Landlord shall be entitled in all respects to rely upon all plans,
drawings and information supplied by Tenant. The Tenant improvement work to be
done pursuant to such plans and specifications shall be referred to as the
"Tenant Improvements."

     b.  Tenant's plans and specifications shall not be in conflict with the 
building codes for the city of San Diego or with insurance regulations for a
fire resistive Type I building. All plans and specifications shall be in a form
satisfactory to appropriate governmental authorities responsible for issuing
permits and licenses required for construction.

     3.  Definition of Usable Area.  The term Usable Area shall  mean the
         -------------------------                                       
Rentable Area of the Premises (as defined in Exhibit "A-3"), less the area of
elevator lobbies, public restrooms, mechanical rooms, electrical rooms,
telephone closets and other
<PAGE>
 
common areas of the Building and vertical penetrations not constructed or
provided for the special use of Tenant.

     4.  Work at Tenant's Cost and Expense.  After Tenant has performed its
         ---------------------------------                                 
obligations under Sections 7(a), (c) and (e) below, Landlord shall cause the
Tenant Improvements to be installed by Landlord's contractor, but at Tenant's
sole cost and expense, subject only to Landlord's paying the Allowance set forth
above. Prior to commencing any Tenant Improvements, Landlord shall submit to
Tenant a written cost estimate of the Tenant Improvements by the date specified
in Section 7(d) below and Tenant shall approve or disapprove such cost estimate
by the date specified in Section 7(e) below. In the event Tenant disapproves the
cost estimate, Landlord shall resubmit revised cost estimates until Tenant shall
approve the same. In the event Tenant shall not approve Landlord's revised cost
estimates, if any, on or before November 1, 1991, either party shall have the
right to terminate this Amendment No. 8. Tenant shall have the right, upon
reasonable advance notice, to audit Landlord's records which relate specifically
to the Tenant Improvements. After approval by Tenant, Landlord's contractor
shall then proceed with constructing the Tenant Improvements. At the time
specified in Paragraph 7(f), Tenant shall pay Landlord, in full, the amount of
such cost less the Allowance. In the event the total cost of the Tenant
Improvements shall be less than the Allowance, such amount shall be credited
against Tenant's first installment of Basic Annual Rent for the New Premises.

     5.  Building Standard Materials.  The following items are Building Standard
         ---------------------------                                            
and must be used in order to maintain the Building's integrity. These items are
exterior window blinds, suite entry and interior doors and hardware, acoustical
ceilings, suite plaques and directory strips, HVAC and electrical systems, metal
studs and carpeting. However, Tenant may request different materials or require
work different from or in addition to the Building Standard. In such event any
materials, drawings, plans or specifications requested shall be subject to the
written approval of Landlord. Such approval shall not be unreasonably withheld
or delayed.

     6.  Completion and Rent Commencement Date.  It is understood that
         -------------------------------------                            
Tenant shall be liable for the delay and increased cost, if any, in completing
the Tenant Improvements if caused by any event listed in Sections 6(a), (b) and
(c). It is further understood that the Commencement Date shall not be affected
by any such delay on the part of Tenant. Neither the Commencement Date nor the
obligation to pay rent as set forth in Section 4.1 of the Lease and in the new
Item 6 incorporated into the Basic Lease Provisions by this Amendment No. 8
shall be delayed by any of the following:

     a.   Tenant's failure to approve or furnish its space plans and 
specifications, working drawings and to apply for and diligently pursue
obtaining the Permits by the times specified in the Schedule of Approvals,
below, or

     b.   Delays of any nature, whether or not within Tenant's control,
resulting from Tenant's decision to use any materials, finishes or installations
other than Building Standard, provided Landlord shall promptly notify Tenant of
any anticipated delay due to Tenant's selection of non-building standing
materials, or
<PAGE>
 
     c.   A delay in construction of the Tenant Improvements as a result of
Tenant's failure to approve written costs of such Tenant Improvements in
accordance the Sections 4 and 5 above.

     d.   Any change requested by Tenant in the scope of Tenant Improvements
approved and contracted for by Landlord. 

Notwithstanding anything in this Amendment No. 8 to the contrary, either party
shall have the right to terminate the Lease in the event a building permit for
the Tenant Improvements shall not be obtained on or prior to February 14, 1992,
provided such terminating party shall not be the cause of any delay in obtaining
a building permit.
 
     7.    Schedule of Approvals.
           ----------------------

     Event
     -----
        Event                                Time
        -----                                ----   

        a.   "Space Plan Approval            September 9, 1991
             Date;" i.e., submittal
             of preliminary plans
             and specifications for
             Tenant Improvements
             and electrical and
             HVAC requirements by
             Tenant

        b.   Approval of Tenant's            September 16, 1991
             preliminary plans by
             Landlord
<PAGE>
 
        c.   Deadline for Tenant's           October 22, 1991
             submittal of final
             space plans and
             working drawings,
             including electrical
             and HVAC requirements
             and completion of
             applications for
             Permits by Tenant

        d.   Submission of cost              November 4, 1991
             estimate for Tenant
             Improvements by
             Landlord
        
        e.   Deadline for Tenant's           November 11, 1991
             approval for Landlord's
             cost estimate for
             Tenant Improvements

        f.   Deadline for payment            Prior to the
             of Tenant's share of            Commencement Date
             cost of Tenant
             Improvements
<PAGE>
 
                                  Exhibit "C"

                             RIGHT OF FIRST REFUSAL
                             ----------------------

     During the Lease Term, Tenant shall have a right of
     first refusal to lease the space adjacent to the New Premises
     shown on the floor plan attached hereto as Schedule 1, and known
     as (i) building 3, Suite B, containing approximately 16,670
     square feet of rentable area; and (ii) Building 3, Suite A
     containing approximately 11,590 square feet of rentable area (the
     "Expansion Space") prior to the Expansion Space being offered to
     any person or entity not then occupying the Expansion Space in
     its "then as is" condition, when the same becomes legally
     available to lease, on the same terms and provisions then in
     effect under the Lease, except that the rental rate for the
     Expansion Space shall be increased to reflect the prevailing
     Rental Rate.  "Prevailing Rental Rate" means the average per
     square foot rental rate per month for all leases for comparable
     space and approximately the same number of months, executed by
     existing tenants in the Project for space expansions during the
     immediately preceding 24-month period prior to the date upon
     which such Prevailing Rental Rate is to become effective and
     payable under the terms of this Lease.  If no such comparable
     space has been leased during such twenty-four (24) month period,
     the rental rates used for purposes of this provision shall be
     adjusted to the amounts Landlord would have used had leases for
     such comparable space been entered.  In all cases, such rates
     shall be determined without regard to any free rent periods,
     tenant improvement allowances, takeover lease obligations, or
     other economic incentives; provided, however, that any such
     economic incentives generally provided by Landlord in such com-
     parable expansion leases shall also be provided to Tenant.

     Landlord shall notify Tenant in writing within thirty
     (30) days after the Expansion Space (or portion thereof) becomes
     legally available to lease, or at Landlord's option, such earlier
     time as Landlord shall be in a position to estimate when the
     Expansion Space will be legally available to lease, advising
     Tenant of such estimated date.  Tenant shall then have ten (10)
     business days in which to notify Landlord in writing exercising
     Tenant's right of first refusal to lease the Expansion Space on
     the terms described above.  If Tenant exercises the right of
     first refusal to lease the Expansion Space, such lease shall
     commence the later of sixty (60) days after Tenant's notice
     exercising the right of first refusal, or the date the Expansion
     Space is available for occupancy, and shall continue for the
     duration of the term of the Lease.  After Tenant validly
     exercises the right of first refusal provided herein, the parties
     shall execute an amendment to the Lease, adding the Expansion
     Space, or a new lease for the Expansion Space, or such other
     documentation as Landlord shall require, promptly after Landlord
     shall prepare the same, in order to confirm the leasing of the
     Expansion Space to Tenant, but an otherwise valid exercise of the
<PAGE>
 
     right of first refusal contained herein shall be fully effec-
     tive, whether or not such confirmatory documentation is executed.

     If the parties are unable to agree on the Prevailing
     Rental Rate within sixty (60) days after the commencement of the
     lease for the Expansion Space, either party may request that the
     Prevailing Rental Rate be determined by arbitration under the
     Commercial Arbitration Rules of the American Arbitration
     Association then in effect.  In recognition that the Prevailing
     Rental Rate may not be determined until after the commencement
     of the lease for the Expansion Space, Tenant shall pay, as Rent
     for the Expansion space, until the Prevailing Rental Rate is
     determined, the amount of Rent then in effect under the Lease on
     a per rentable square foot basis (including Rental, and all other
     charges).  Under no circumstances shall Rent under the Lease ever
     be less than such amount of Rent then in effect under the Lease,
     on a per rentable square foot basis, regardless of the Prevailing
     Rental Rate, as determined in accordance with the foregoing
     provisions.  If the Prevailing Rental Rate 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 
     Prevailing Rental Rate, and the amount theretofore paid by Tenant 
     for the Expansion Space.

     If Tenant shall fail to exercise such right of first
     refusal, after notice by Landlord of the availability of the
     Expansion Space, as provided herein, such right of first refusal
     shall be deemed to have lapsed and expired, and shall be of no
     further force or effect.  Landlord may thereafter freely lease
     all or a portion of the Expansion Space to any other party, at
     any time, on any terms, in Landlord's sole discretion.
     Notwithstanding the foregoing, if the Expansion Space is
     currently legally available to lease, the parties shall be deemed
     to have agreed that the right of first refusal granted herein
     shall only apply after the Expansion Space has been leased, and
     thereafter becomes available to lease.  If the Expansion Space
     is currently not legally available to lease, the foregoing right
     of first refusal shall be subject to the existing tenants or
     occupants thereof renewing their existing leases and/or
     exercising any options to extend, and in all events is subject
     and subordinate to any other rights of any other person or entity
     to lease the Expansion Space, if such rights have already been
     granted prior to the date of this Lease.

     If Tenant shall exercise the right of first refusal
     granted herein, Landlord does not guarantee that the Expansion
     Space will be available on the commencement date for the lease
     thereof, if the then existing occupants of the Expansion Space
     shall hold-over, or for any other reason beyond Landlord's
     reasonable control.  In such event, rent with respect to the
     Expansion Space shall be abated until Landlord legally delivers
     the same to Tenant, as Tenant's sole recourse.  Tenant's exercise
     of such right of first refusal shall not operate to cure any
     default by Tenant of any of the terms of provisions in the Lease
     nor to extinguish or impair any rights or remedies of Landlord
     arising by virtue of such default.  The right of first refusal
     herein shall, at Landlord's election, be null and void, if Tenant
     is in default under the Lease on the date Tenant exercises its
     rights hereunder or at any time thereafter and prior to commencement
     of the Lease for the Expansion Space.  If the lease
<PAGE>
 
     or Tenant's right to possession of the New Premises shall
     terminate in any manner whatsoever before Tenant shall exercise
     the right herein provided, or if Tenant shall have subleased or
     assigned all or any portion of the New Premises, then immediately
     upon such termination, sublease or assignment, the right of first
     refusal to lease the Expansion Space herein granted shall
     simultaneously terminate and become null and void.  Such right
     of first refusal is personal to Tenant.  Under no circumstances
     whatsoever shall the assignee under a complete or partial
     assignment of the Lease, or a subtenant under a sublease of the
     Premises, have any right to exercise the right of first refusal
     granted herein.  Tenant agrees that time is of the essence of
     this provision.
<PAGE>
 
                                  EXHIBIT "C"

                                EXPANSION SPACE
                                ---------------



                             [Diagram appears here]
<PAGE>
 
                    AMENDMENT NO. 9 TO R & D BUILDING LEASE

                                    BETWEEN

                             SORRENTO TECH LIMITED
                                      AND
                           BIOSYM TECHNOLOGIES, INC.

     This Amendment No. 9 to R & D BUILDING LEASE ("Amendment No. 8") is made
this 20 day  of April 1992, by and between SORRENTO TECH LIMITED, a California
limited partnership ("Landlord") and BIOSYM TECHNOLOGIES, INC., a California
corporation ("Tenant").

                                    RECITALS
                                    --------

     A.  Landlord and Tenant are parties to a certain R&D Building Lease dated
February 26, 1987, as amended by (1) a certain First Amendment of Lease dated
September 15, 1987, (2) Amendment No. 2 dated July 31, 1988, (3) Amendment No. 3
dated July 28, 1989, (4) Amendment No. 4 dated November 26, 1990, (5) Amendment
No. 5 dated May 7, 1991, (6) Amendment No. 6 dated July 17, 1991, (7) Amendment
No. 7 dated _______, 1991 and Amendment No. 8 dated September 6, 1991
(collectively, the "Lease").  Under the Lease, Tenant is leasing from Landlord
approximately 19,617 square feet of space (the "Original Premises") in a
building (the "Building") located at 10065 Barnes Canyon Road; approximately
2,973 square feet of space in a building located at 10055 Barnes Canyon Road,
Suites E, F,G & H; and approximately 6,980 square feet of space in a building
owned by Landlord located at 9725 Scranton Road, City of San Diego, San Diego
County, California 92121.

In addition certain modifications to the lease plus additional space was added
per Amendment No. 8. The Original Premises and the Buildings are more
particularly described in the Lease.

     B.  The purpose of this Amendment No. 9 is to amend the Lease in order to
reflect the parties' agreement concerning the leasing by Landlord to Tenant of
New Premises (as defined below).

                                   AGREEMENT
                                   ---------

     NOW, THEREFORE, in consideration of the above Recitals and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties do hereby agree as follows:

     1.1  Landlord agrees to lease, on a temporary basis, additional space
located at 9725 Scranton Road under the same terms and conditions as specified
in Amendment No. 8.


                                       1
<PAGE>
 
     1.  PREMISES:
         -------- 

       (a)    Rentable Area: +1,160 sq. ft.  See Definition of Rentable Area
attached to the Lease as Exhibit "A-3."

       (b)    Location:  The first floor of the existing building located at
9725 Scranton Road, San Diego, California, as shown on the Floor Plan of the
premises attached hereto as Exhibit "A-1."  The New Premises located in a
certain real estate project commonly known as the Naiman Tech Center (the
"Project"), as shown on the Site Plan of the Project attached to the Lease as
Exhibit "A-2."

     2.  Lease Term:  March 1, 1992.
        -----------                 

     3.  Target Commencement Date:  October 24, 1991.
         ------------------------                    

     4.  Rent:
         ---- 

        (a) The initial Basic Monthly Rent shall be $.70/sf.

     5.  Security Deposit:  None
         -----------------      

     6.  Addresses for Notices:
         --------------------- 

       (a)  If to Landlord:

        Sorrento Tech Limited
        c/o Naiman Tech Center
        9605 Scranton Road, Suite 102
        San Diego, CA 92121
       (b)  If to Tenant:

        Biosym Technologies, Inc.
        9685 Scranton Road
        San Diego, CA 92121

     7.  Broker:  None.
         ------        

     8.  Tenant Improvement Allowance: None.
         ----------------------------       

     1.2  Effect of Amendment.  Terms used in this Amendment No. 9 with initial
          -------------------                                                  
capital letters are defined terms which shall have the same meaning ascribed to
them in the Lease, unless the context of this Amendment No. 9 expressly provides
otherwise. Except as amended


                                       2
<PAGE>
 
by this Amendment No. 9, the Lease shall remain in full force and effect as to
both the Original Premises, the Expansion Premises and the Additional Premises.
In the event of a conflict between provisions of the Lease and those of this
Amendment No. 9, this Amendment No. 9 shall control.

     IN WITNESS WHEREOF, the parties hereto have executed this AMENDMENT NO. 9
to R&D BUILDING LEASE, as of the date first written above.

LANDLORD:

Dated: April 20, 1992                   SORRENTO TECH LIMITED
                                        a California limited partnership

                                        By: The Walters Management Co. Inc.
                                            Court Appoint Receiver

                                        By: /s/ William Borsari 
                                            ----------------------              

                                        Title: President
                                               -------------------


TENANT:

Dated: April 20, 1992                   BIOSYM TECHNOLOGIES, INC.,
                                        a California corporation

                                        By: /s/ Todd Schmidt
                                           ---------------------------

                                        Title: Vice President - Finance
                                               ------------------------






                                       3
<PAGE>
 
                                 Attachment A


                            [Diagram appears here]