LEASE


                                 BY AND BETWEEN


                           ARE-10150 OLD COLUMBIA, LLC

                                   as Landlord

                                       and

                          NORTH AMERICAN VACCINE, INC.

                                    as Tenant



<PAGE>



                                TABLE OF CONTENTS

                                                                      PAGE

1.       LEASE OF PREMISES.............................................1

2.       BASIC LEASE PROVISIONS........................................1

3.       TERM..........................................................3

4.       POSSESSION AND COMMENCEMENT DATE..............................4

5.       RENT..........................................................5

6.       RENT ADJUSTMENTS..............................................5

7.       OPERATING EXPENSES............................................6

8.       RENTABLE AREA................................................12

9.       SECURITY DEPOSIT.............................................12

10.      USE..........................................................13

11.      BROKERS......................................................15

12.      HOLDING OVER.................................................15

13.      TAXES ON TENANT'S PROPERTY...................................16

14.      CONDITION OF DEMISED PREMISES................................16

15.      COMMON AREAS AND PARKING FACILITIES..........................16

16.      UTILITIES AND SERVICES.......................................17

17.      ALTERATIONS..................................................20

18.      REPAIRS AND MAINTENANCE......................................23

19.      LIENS........................................................23

20.      INDEMNIFICATION AND EXCULPATION..............................24


                                        i

<PAGE>




21.      INSURANCE - WAIVER OF SUBROGATION............................25

22.      DAMAGE OR DESTRUCTION........................................27

23.      EMINENT DOMAIN...............................................29

24.      DEFAULTS AND REMEDIES........................................30

25.      ASSIGNMENT OR SUBLETTING.....................................34

26.      ATTORNEYS' FEES AND COSTS....................................37

27.      BANKRUPTCY...................................................37

28.      ESTOPPEL CERTIFICATE.........................................38

29.      JOINT AND SEVERAL OBLIGATIONS................................38

30.      DEFINITION OF LANDLORD; LIMITATION OF LANDLORD'S LIABILITY...38

31.      PROJECT CONTROL BY LANDLORD..................................40

32.      QUIET ENJOYMENT..............................................41

33.      QUITCLAIM DEED...............................................41

34.      RULES AND REGULATIONS........................................41

35.      SUBORDINATION AND ATTORNMENT.................................41

36.      SURRENDER....................................................42

37.      WAIVER AND MODIFICATION......................................43

38.      WAIVER OF JURY TRIAL AND COUNTERCLAIMS.......................43

39.      TENANT'S PURCHASE OPTION.....................................43

40.      RIGHT TO EXPAND..............................................44

41.      HAZARDOUS MATERIALS..........................................47



                                       ii

<PAGE>



42.      RIGHT TO EXTEND TERM.........................................49

43.      RIGHT OF FIRST OFFER TO PURCHASE.............................50

44.      TENANT SIGNAGE...............................................51

45.      MISCELLANEOUS................................................51


EXHIBITS

EXHIBIT "A"       DEMISED PREMISES
EXHIBIT "B"       LEGAL DESCRIPTION
EXHIBIT "C"       ACKNOWLEDGMENT OF TERM COMMENCEMENT DATE
EXHIBIT "D"       WORK LETTER
EXHIBIT "E"       RULES AND REGULATIONS
EXHIBIT "F"       ESTOPPEL CERTIFICATE
EXHIBIT "G"       FORM OF AGREEMENT OF PURCHASE AND SALE
EXHIBIT "H"       EXTERIOR SIGNAGE PLAN




                                       iii

<PAGE>



                                      LEASE


     THIS LEASE is made as of March 25, 1998 ("EFFECTIVE  DATE"), by and between
ARE-10150 Old Columbia,  LLC, a Delaware limited liability company  ("LANDLORD")
and North American Vaccine, Inc., a Canadian corporation ("TENANT").

1.   LEASE OF PREMISES.

     Landlord  hereby  leases to Tenant and Tenant  hereby  leases from Landlord
upon the terms and  conditions  hereof,  those  certain  premises  (the "DEMISED
PREMISES")  within the  building  located at the  address  set forth  below (the
"BUILDING").  The Demised  Premises are  crosshatched on the floor plan attached
hereto as EXHIBIT "A". The real  property upon which the Building is located and
all landscaping,  parking  facilities and other  improvements and  appurtenances
related thereto, are hereinafter  collectively referred to as the "PROJECT", the
legal  description  for which is attached hereto as EXHIBIT "B". All portions of
the  Project  which are for the  non-exclusive  use of tenants of the  Building,
including, without limitation,  driveways,  sidewalks, parking areas, landscaped
areas, service corridors,  stairways,  elevators,  public restrooms and Building
lobbies, are hereinafter referred to as the "COMMON AREAS".

2.   BASIC LEASE PROVISIONS.

     2.1. For convenience of the parties, certain basic provisions of this Lease
are set forth  herein.  The  provisions  set forth  herein  are  subject  to the
remaining  terms and conditions of this Lease and are to be interpreted in light
of such remaining terms and conditions.

          2.1.1  Address of the Building:

                 10150 Old Columbia Road
                 Columbia, Maryland

          2.1.2  Intentionally Deleted.

          2.1.3  (a)  Rentable Area of Demised Premises: 75,500 sq. ft. (Subject
                      to confirmation pursuant to Section 8.1)

                 (b)  Rentable  Area of  Building:  75,500 sq.  ft.,  subject to
                      expansion in accordance with Section 40.

          2.1.4  Initial Basic Annual Rent:
                 (75,500 sq.ft). x ($13.00 per sq.ft.) = $981,500
                 (Subject to modification pursuant to Section 40)


<PAGE>



          2.1.5  Initial  Monthly  Rental  Installments  of Basic  Annual  Rent:
                 (75,500 sq.ft).  x ($13.00 per sq.ft.),  divided by 12 months =
                 $81,791.67 (Subject to modification pursuant to Section 40).

          2.1.6  Tenant's  Pro Rata  Share:  100% of the  Building  (Subject  to
                 modification pursuant to Section 40)

          2.1.7  (a) Term Commencement Date: As defined in Section 4.2 hereof.

                 (b)  Term Expiration Date: Ten years from the Term Commencement
                      Date,  subject  to  extension  or earlier  termination  as
                      otherwise provided herein.

          2.1.8  Security Deposit: $163,583.34.

          2.1.9  Permitted Use: Research,  development,  testing, production and
                 sale  of  biologic,   pharmaceutical   or  any  other  products
                 regulated  by the United  States  Food and Drug  Administration
                 (the  "FDA")  or  similar   foreign   regulatory   authorities,
                 including,  without limitation,  animal testing facilities, and
                 related office uses consistent with Section 10 hereof.

          2.1.10 Addresses for notices and payment of Rent:

                 Payments of Rent shall be made to:

                 135 N.  Robles Avenue, Suite 250
                 Pasadena, CA 91101
                 Attention: Corporate Secretary

                 Address for Notices to Landlord:

                 135 N.  Robles Avenue, Suite 250
                 Pasadena, CA 91101
                 Attention: Corporate Secretary

                 With a copy to:

                 11440 West Bernardo Court, Suite 170
                 San Diego, CA 92127
                 Attention: Gary A. Kreitzer, Esq.


                                        2

<PAGE>



          2.1.11 Address for Notices to Tenant:

                 Prior to July 1, 1998:

                 North American Vaccine, Inc.
                 12103 Indian Creek Court
                 Beltsville MD  20705
                 Attention:  Daniel J. Abdun-Nabi, Senior Vice President-Legal
                 Affairs & General Counsel

                 After June 30, 1998:

                 North American Vaccine, Inc.
                 10150 Old Columbia Road
                 Columbia MD  _____
                 Attention:  Daniel J. Abdun-Nabi, Senior Vice President-Legal
                 Affairs & General Counsel

                 With a copy to:

                 Arnold & Porter
                 555 Twelfth Street, N.W.
                 Washington, D.C.  20004
                 Attention:  Stephen W. Porter, Esq.

          2.1.12 The  following  Exhibits are attached  hereto and  incorporated
                 herein:

                             Exhibit "A"-Exhibit "H"

3.   TERM.

     3.1. This Lease shall take effect upon the Effective  Date,  and, except as
specifically otherwise provided within this Lease, each of the provisions hereof
shall be binding upon and inure to the benefit of Landlord and Tenant,  and each
of their  respective  successors  and  permitted  assigns,  from and  after  the
Effective Date.

     3.2. The term of this Lease (the "TERM") shall be that period from the Term
Commencement  Date as  defined  in  Section  4.2  below  and  through  the  Term
Expiration Date, as such may be terminated or extended as provided herein.

     3.3.  Notwithstanding  anything to the contrary  contained  herein,  Tenant
shall have the right,  in its sole and absolute  discretion,  to terminate  this
Lease, which termination shall be effective on the fifth anniversary of the Term
Commencement  Date,  upon not less than nine (9) months' prior written notice to


                                       3
<PAGE>


Landlord,   which  notice,   as  a  condition  to  its   effectiveness  and  the
effectiveness  of any such  termination,  shall be accompanied by the payment of
the  "Termination  Amount".  Upon the effective  date of such  termination  made
pursuant to this paragraph, this Lease shall terminate and all of the rights and
obligations  of the parties  hereunder  shall  thereafter  cease and  terminate,
except  pursuant to any  provision  which  expressly  survives  the  termination
hereof, including without limitation, the respective indemnification obligations
of  Landlord  and  Tenant  set  forth  in  Article  41 of  this  Lease,  and the
obligations  and  liabilities of Landlord and Tenant which accrue or arise prior
to the termination date of this Lease, including,  without limitation,  Tenant's
obligation to pay any and all unpaid accrued Rent as of such  termination  date.
The Termination Amount shall be [*]

4.   POSSESSION AND COMMENCEMENT DATE.

     4.1.  Landlord  shall  use  commercially   reasonable   efforts  to  tender
possession  of the Demised  Premises to Tenant on the date hereof.  In the event
Landlord fails for any reason to tender possession of the Demised Premises on or
before the close of business on May 15, 1998, Landlord shall be liable to Tenant
for the sum of any damages,  rent and holdover fees or penalties  under Tenant's
existing leases for premises at 12103 and 12031 Indian Creek Court,  Beltsville,
Maryland  20705 (as amended,  the "Existing  Leases") in excess of the rent that
would have been payable under the Existing Leases but for such holdover.  In the
event Landlord has not tendered  possession of the Demised Premises on or before
June 1, 1998,  then Tenant may, at any time  thereafter  so long as Landlord has
not tendered  possession of the Demised Premises to Tenant, by written notice to
Landlord, elect to terminate this Lease effective on the date of such notice. In
the event this Lease is  terminated  pursuant to this  Section 4.1, the Security
Deposit  shall be returned to Tenant and neither  Landlord nor Tenant shall have
any further rights,  duties or obligations under this Lease, except with respect
to  provisions  which,  by  their  terms,  survive  termination  of this  Lease.
Landlord's  obligations under this Section 4.1 shall survive termination of this
Lease by Tenant pursuant to the terms of this Section 4.1.

     4.2.  The "Term  Commencement  Date"  shall be the date of  delivery of the
Demised  Premises to Tenant.  Landlord and Tenant shall each execute and deliver
to the other written  acknowledgment  in the form attached hereto as Exhibit "C"
of the Term  Commencement  Date and the Term  Expiration  Date when the same are
established;  PROVIDED,  HOWEVER,  the  failure  to  execute  and  deliver  such
acknowledgment  shall not affect  Landlord's or Tenant's  rights or  liabilities
hereunder.

     4.3. Intentionally Deleted.

     4.4. Intentionally Deleted.

     4.5.  Tenant  shall cause the initial  improvements  to the  Building to be
constructed  pursuant  to  the  Work  Letter  attached  hereto  as  EXHIBIT  "D"
("Tenant's  Work").  Landlord  shall be  responsible  for  paying  the  costs of

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.

                                       4
<PAGE>


Tenant's  Work to the  extent  such costs do not exceed the amount of the Tenant
Improvement  Allowance  (as  defined in Section  4.5.1).  The costs  included in
Tenant's  Work  shall  include  the  costs  of  construction,   space  planning,
architectural, design, engineering and other related services, building permits,
and other planning and inspection fees.

          4.5.1  Tenant  shall be entitled to an  allowance to be used by Tenant
towards construction of Tenant's Work (the "Tenant Improvement Allowance").  The
amount of the Tenant Improvement Allowance shall be $1,432,500.00.

          4.5.2 Intentionally Deleted.

5.   RENT.

     5.1. Tenant agrees,  commencing on the forty fifth (45th) day following the
Term Commencement Date (the "Rent Commencement  Date"), to pay Landlord as Basic
Annual Rent for the Demised Premises the sum set forth in Section 2.1.4, subject
to the rental increases provided in Section 6 hereof. Basic Annual Rent shall be
paid in the equal monthly  installments  set forth in Section 2.1.5,  subject to
the rental increases provided in Section 6 hereof,  each in advance on the first
day of each and every calendar month during the Term.  Notwithstanding  anything
to the contrary set forth  herein,  Tenant shall have no obligation to pay Basic
Annual Rent for any period prior to the Rent Commencement Date.

     5.2. In addition to Basic Annual Rent,  Tenant agrees to pay to Landlord as
additional rent ("ADDITIONAL RENT") at times hereinafter specified in this Lease
(i) Tenant's pro rata share,  as set forth in Section 2.1.6  ("TENANT'S PRO RATA
SHARE"),  of  Operating  Expenses  as  provided  in Section 7 and (ii) any other
amounts that Tenant  assumes or agrees to pay under the provisions of this Lease
that are owed to Landlord, including, without limitation, any and all other sums
that may become  due under the terms of this  Lease by reason of any  Default of
Tenant or  failure  on  Tenant's  part to  comply  with the  agreements,  terms,
covenants and  conditions of this Lease to be performed by Tenant,  after notice
and lapse of  applicable  cure  period.  Except for the  payment of charges  for
utilities  supplied to the Demised Premises,  Tenant shall have no obligation to
pay Additional Rent for any periods prior to the Rent Commencement Date.

     5.3. Intentionally Deleted.

     5.4.  Basic Annual Rent and  Additional  Rent shall together be denominated
"RENT". Rent shall be paid to Landlord, without abatement, deduction, or offset,
in lawful  money of the United  States of America,  at the office of Landlord as
set forth in Section  2.1.10 or to such other  person or at such other  place as
Landlord  may from  time to time  designate  in  writing.  In the event the Term
commences  or ends on a day other than the first day of a calendar  month,  then
the Rent for such  fraction of a month shall be prorated  for such period on the
basis of a thirty (30) day month and shall be paid at the then  current rate for
such fractional month.


                                       5
<PAGE>


6.   RENT ADJUSTMENTS.

     6.1.  Basic Annual Rent shall be adjusted on the first (1)  anniversary  of
the Term  Commencement  Date,  and on the  anniversary  of such date  every year
thereafter  during the Term  (each,  a "RENT  ADJUSTMENT  DATE").  On every Rent
Adjustment  Date, Basic Annual Rent shall be increased by an amount equal to [*]
of the Basic Annual Rent  payable  immediately  preceding  the  applicable  Rent
Adjustment Date.

7.   OPERATING EXPENSES.

     7.1. As used herein, the term "OPERATING EXPENSES" shall include:

          7.1.1 Government impositions including,  without limitation,  property
tax  costs  consisting  of real and  personal  property  taxes  and  assessments
(including  amounts due under any  improvement  bond upon the  Building,  or the
parcel or  parcels  of real  property  upon  which the  Building  is  located or
assessments  levied in lieu thereof)  imposed by any  governmental  authority or
agency;  any tax on or measured  by gross  rentals  received  from the rental of
space in the  Building,  any tax  based on the  square  footage  of the  Demised
Premises, the Building or the Project as well as any parking charges,  utilities
surcharges,  or any  other  costs  levied,  assessed  or  imposed  by, or at the
direction of, or resulting  from  statutes or  regulations,  or  interpretations
thereof,  promulgated  by any  federal,  state,  regional,  municipal  or  local
government  authority in connection with the use or occupancy of the Building or
the parking facilities serving the Building;  any tax on this Lease; any fee for
a business  license to operate an office  building  and the  reasonable  cost of
attorneys or experts,  reasonably  incurred by Landlord in seeking  reduction by
the taxing  authority of the applicable  taxes,  less tax refunds  obtained as a
result of an  application  for  review  thereof.  Operating  Expenses  shall not
include  such  taxes as capital  gains,  corporation,  unincorporated  business,
income,  profit,  excess  profit,  capital  stock,  estate,  gift,  inheritance,
transfer,  recordation,  taxes which are the personal  obligation of Landlord or
another  tenant of the  Building or Project,  license  fees (except as set forth
above) or any fines,  penalties  and/or interest on late payments.  Tenant shall
not be  responsible  for more than  twelve (12)  calendar  months of real estate
taxes in any one (1) year.

          7.1.2  All other  reasonable  costs of any kind  paid or  incurred  by
Landlord in connection  with the operation and  maintenance  of the Building and
the Project  including,  by way of  examples  and not as a  limitation  upon the
generality of the foregoing,  costs of repairs and  replacements to the Building
or the other  improvements  within the Project as  appropriate  to maintain  the
Building or the Project as required  hereunder;  costs of utilities furnished to
the Common Areas;  sewer fees; trash collection;  cleaning,  including  windows;
heating;  ventilation;  air-conditioning;  maintenance of landscape and grounds;
maintenance of drives and parking areas; security services and devices; building
supplies;  maintenance for and  replacement of equipment  utilized for operation
and maintenance of the Project:  license, permit and inspection fees; sales, use
and excise taxes on goods and services  purchased by Landlord in connection with
the  operation,  maintenance  or repair of the Project and Building  systems and
equipment;  telephone,  postage, stationery supplies and other expenses incurred
in  connection  with the  operation,  maintenance,  or  repair  of the  Project;
accounting,   legal  and  other  professional  fees  and  expenses  incurred  in
connection with the operation,  maintenance  and repair of the Project;  cost of
landscaping and other customary and ordinary items of personal property provided

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.



                                       6
<PAGE>


by Landlord for use in Common Areas;  capital  expenditures;  costs of complying
with any applicable  laws or hazardous waste  remediation  rules or regulations;
costs  of  insurance,  service  contracts;  costs  of  services  of  independent
contractors  retained  to do work of the nature or type herein  referenced;  and
costs of compensation  (including  employment  taxes and fringe benefits) to the
extent equitably allocable to the Project of all persons who perform regular and
recurring duties connected with the day-to-day  operation and maintenance of the
Project,  its equipment,  the adjacent  walks,  landscaped  areas,  drives,  and
parking  areas,   including   without   limitation,   janitors,   floor  waxers,
window-washers,  watchmen,  gardeners,  sweepers,  and  handymen  and  costs  of
management services, which fee for property management services shall not exceed
[*] of the Basic Annual Rent. With respect to capital  expenditures  there shall
be  included  each  calendar  year as an  Operating  Expense  in respect of such
expenditure only the amortized cost of such item for that year [*]

          7.1.3  Operating  Expenses  shall be  determined  in  accordance  with
generally   accepted   accounting   principles.   Operating  Expenses  shall  be
appropriate for the prudent management,  operation,  maintenance,  servicing and
repair  of the  Building  and  shall be  reduced  by all cash  discounts,  trade
discounts  or quantity  discounts  received by Landlord or  Landlord's  managing
agent in the purchase of any goods, utilities or services in connection with the
prudent  operation of the Building.  If Landlord charges a user fee for use of a
building amenity or facility (including the parking facilities),  then Operating
Expenses  shall be deemed  reduced by the amount of such  fees.  Landlord  shall
equitably  prorate bills for services  rendered to the Building and to any other
property owned by Landlord.  Landlord shall  diligently and in good faith pursue
all  insurance,  breach of warranty  or other  claims  which  might  result in a
reduction  of  Operating  Expenses  payable  by  Tenant.  In no event  shall the
Building  tenants be required to pay,  in the  aggregate,  more than 100% of the
actual  Operating  Expenses of the Building for any  calendar  year,  and Tenant
shall not be required  to pay more than 100% of  Tenant's  Pro Rata Share of the
total Operating Expenses actually incurred for any calendar year.

          7.1.4  The  following  costs  and  expenses  shall  be  excluded  from
Operating Expenses:

               (a) Insured losses paid by Landlord as the deductible  portion of
such losses by reason of insurance policy terms (except if and to the extent the
sums  paid  are  capital  expenditures  in which  event  such  amounts  shall be
amortized in accordance with Section 7.1.2);

               (b)  Costs,  including  permit,  license  and  inspection  costs,
associated  with  alterations  or  improvements  of the  Demised  Premises,  the
premises of other  tenants or occupants of the Building or the Project or vacant
retail  space in the  Building  or the  Project or  incurred  in  renovating  or
otherwise  improving,  decorating,  painting or  redecorating  vacant  space for
tenants or other occupants of the Building or the Project;

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       7
<PAGE>


               (c) Depreciation of the Building or the Project,  or the fixtures
or equipment therein;

               (d) Interest,  points,  fees and  principal  payments on loans to
Landlord or secured by mortgages or deeds of trust  covering the Building or the
Project or a portion  thereof and other debt costs,  if any, or  amortization on
any mortgage or mortgages or any other debt instrument  encumbering the Building
or the Project;

               (e) Payments pursuant to any ground lease or master space lease;

               (f) Expenses directly  resulting from the breach of this Lease by
Landlord, or the negligence of Landlord,  its agents,  contractors or employees,
or other tenants;

               (g)  Reimbursable  costs for which  Landlord is reimbursed by its
insurance carrier,  any tenant's carrier, any tenant, any warrantor or any other
third party;

               (h) Any bad debt loss, rent loss,  reserves for bad debts or rent
loss or legal fees incurred in collecting rent or other  obligations  from other
tenants of the Building or the Project;

               (i) The  expense  of  extraordinary  services  provided  to other
tenants of the Building or the Project, or costs incurred by Landlord in respect
of breaches of other leases in the Building or the Project;

               (j) Costs  associated  with the  operation of the business of the
person or entity which constitutes  Landlord, as distinguished from the costs of
operation  of the  Building  or the  Project,  including  accounting  and  legal
matters,  costs of defending any lawsuits with any mortgagee,  costs of selling,
syndicating,  financing,  mortgaging or hypothecating any of Landlord's interest
in the Building or the Project,  costs of any disputes  between Landlord and its
employees,  disputes of Landlord with Building management, and outside fees paid
in connection with disputes with other tenants;

               (k) The costs of  compensation  (including  employment  taxes and
fringe  benefits) of any  employee of Landlord or the  property  manager for the
Project who does not devote substantially all of his or her time to the Building
or the  Project  or the  Common  Areas,  except  to the  extent  such  costs are
reasonable,  and properly and equitably allocable to time spent by such employee
in directly servicing the Building, the Project or the Common Areas;

               (l) Fees for services  rendered to the  Building,  the Project or
the Common Areas by entities controlled by or under common control with Landlord
to the extent such fees exceed the market rate payable for  comparable  services
if rendered by unrelated third parties, except that market rate fees shall in no
event exceed [*] of the Basic Annual Rent;

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       8
<PAGE>


               (m) Fines,  penalties,  late payment charges and interest arising
from the acts or inaction of Landlord or failure timely to make tax and/or other
payments;

               (n) Legal fees,  professional fees, court costs, and consultants'
fees not directly related to the general welfare of Building or Project tenants;

               (o) Taxes other than those set forth in Section 7.1.1;

               (p) Salaries and the cost of other compensation paid to executive
employees  of  Landlord  or the  property  manager  above the  grade of  manager
(including profit sharing, bonuses and other employee benefit plans);

               (q) The rent or expenses in lieu of rent for  Landlord's  on-site
management  or  leasing  office,  or any other  offices  or other  spaces in the
Building or the Project used by Landlord or any related entity;

               (r) Costs and expenses of utilities  directly  metered to tenants
of the Building or the Project or janitorial services directly billed to tenants
of the Building or the Project and payable separately by such tenants;

               (s) Interest incurred on amounts by which any tenant's  estimated
payments exceed such tenant's proper share of Operating Expenses;

               (t) General overhead and administrative and accounting  expenses,
except to the extent reasonably and properly directly allocable to the Building;

               (u)  Charitable  or  political  contributions,   advertising  and
promotional expenditures, including costs of staging special events.

               (v) The  costs  associated  with any  concessions  or  incentives
granted  to tenants  in the  Building  or the  Project  (such as moving  expense
allowances or reimbursements);

               (w) Marketing  costs  including  rent or expenses in lieu of rent
for a marketing office,  leasing commissions,  space planners' fees,  attorneys'
fees, advertising expenses, expenses incurred in connection with the negotiation
and preparation of letters,  deal memos,  letters of intent,  leases,  subleases
and/or  assignments,  space planning costs and other costs and expenses incurred
in  connection  with  lease,   sublease  and/or   assignment   negotiations  and
transactions  with  present or  prospective  tenants or other  occupants  of the
Building or the Project; and

               (x) Costs of acquiring any antiquities or works of art;

               (y)  Increased  insurance  premiums  caused by  Landlord's or any
other tenant's hazardous, reckless, wilful or negligent acts;


                                       9
<PAGE>


               (z)  Assessments  to the  extent  paid in less  than the  maximum
permitted number of installments; and

               (aa)  Costs  and   expenses   (including,   without   limitation,
attorneys' and consultants' fees and expenses) incurred by Landlord to clean-up,
contain,  abate, remove or otherwise remediate Hazardous Materials (as such term
is hereinafter  defined) present on, about,  under or at the Project on the date
hereof;  Tenant hereby  acknowledging the delivery to it of that certain phase I
environmental audit, dated [*] prepared by [*].

     7.2. Intentionally Deleted.

     7.3. Within sixty (60) days prior to the commencement of each calendar year
during the Term, Landlord shall provide to Tenant Landlord's reasonable estimate
of the monthly  amount of Tenant's Pro Rata Share of Operating  Expenses for the
following  calendar year.  Tenant shall pay to Landlord on the first day of each
calendar month of the Term, as Additional Rent,  Landlord's estimate of Tenant's
Pro Rata Share of Operating Expenses for such month.

          7.3.1 Within  ninety (90) days after the  conclusion  of each calendar
year (or such  longer  period as may be  reasonably  required),  Landlord  shall
furnish to Tenant a statement  showing in reasonable detail the actual Operating
Expenses  and  Tenant's  Pro Rata Share of  Operating  Expenses for the previous
calendar  year  ("Annual  Statement"),  prepared in  accordance  with  generally
accepted accounting  principles,  consistently applied and otherwise prepared in
accordance  with the terms of this Lease which are applicable to the preparation
of  such  Annual  Statement  and  certified  to  be  correct  by  a  responsible
representative of Landlord. Any additional sum due from Tenant to Landlord shall
be due and payable within thirty (30) days after Landlord  provides  Tenant with
notice  thereof.  If the amounts  paid by Tenant  pursuant to Section 7.3 exceed
Tenant's Pro Rata Share of Operating  Expenses for the previous  calendar  year,
Landlord shall, at Tenant's  option,  either (i) credit the excess amount to the
next  succeeding  installments  of estimated  Additional  Rent,  or (ii) pay the
excess to Tenant within thirty (30) days after delivery of such statements.

          7.3.2 Any amount due under  Section  7.3 for any period  which is less
than a full month shall be prorated  (based on a thirty (30) day month) for such
fractional month.

     7.4. Landlord's  Annual  Statement  shall be final and binding upon Tenant
unless Tenant,  within [*] after  Tenant's  receipt  thereof,  shall
contest any item therein by giving written notice to Landlord,  specifying  each
item  contested  and the reason  therefor.  At Tenant's  request,  Landlord will
provide  Tenant with  access to  Landlord's  books and  records  relating to the
calculation of Operating  Expenses or any other Additional Rent or other charges
paid by Tenant  hereunder.  Landlord shall retain its books and records relating
to the  calculation of Operating  Expenses for any calendar year for a period of
at least six (6) years  after  such  calendar  year.  In the  event  that  after
Tenant's review of such  information,  Landlord and Tenant cannot agree upon the
amount of Tenant's Pro Rata Share of Operating Expenses,  then Tenant shall have
the right to have an  independent  public  accounting  firm  hired by Tenant (at
Tenant's sole cost and expense) and approved by Landlord  (which  approval shall

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       10
<PAGE>


not be  unreasonably  withheld or delayed)  audit and/or review such  Landlord's
books and records  for the year in  question  (the  "INDEPENDENT  REVIEW").  The
results of any such Independent  Review shall be binding on Landlord and Tenant.
If the  Independent  Review  shows that  Tenant's  Pro Rata  Share of  Operating
Expenses  actually  paid for the  calendar  year in question  exceeded  Tenant's
obligations for such calendar year, Landlord shall at Tenant's option either (1)
credit  the  excess  amount to the next  succeeding  installments  of  estimated
Additional  Rent or (2) pay the excess to Tenant  within  thirty (30) days after
delivery  of  such  statement.  In  addition,  notwithstanding  anything  to the
contrary set forth in this Section 7.4, any  inspection or audit that  discloses
that annual Operating Expenses have been overstated by more than [*] shall be at
Landlord's expense, and Landlord shall pay interest on the amount required to be
refunded,  at the  rate  of [*]  per  annum  from  the  date  Tenant  made  such
overpayments  until the date such  overpayments  are repaid by Landlord.  If any
Independent  Review shows that  Tenant's  payments of Tenant's Pro Rata Share of
Operating Expenses for such calendar year were less than Tenant's obligation for
the calendar  year,  Tenant shall pay the  deficiency to Landlord  within thirty
(30) days after delivery of such statement.

     7.5. Tenant shall not be responsible for Operating Expenses attributable to
the time period  prior to the Rent  Commencement  Date.  The  responsibility  of
Tenant for Tenant's Pro Rata Share of Operating  Expenses  shall continue to the
latest of (i) the date of  termination  of this Lease,  (ii) the date Tenant has
fully vacated the Demised Premises (including,  without limitation,  the removal
of all items  required  hereby to be removed by Tenant and the completion of all
procedures  required of Tenant  necessary  to fully  release and  terminate  any
permits or licenses  restricting the use of the Demised Premises in any manner),
or (iii) if  termination  of this Lease is due to the  default  of  Tenant,  the
earlier of (y) the date of rental  commencement  of a replacement  tenant or (z)
the Term Expiration Date.

     7.6. Operating Expenses for the calendar year in which Tenant's  obligation
to share therein  commences  and in the calendar  year in which such  obligation
ceases,  shall be prorated  based upon the actual number of days of such partial
year during which Tenant had the obligation to pay Basic Annual Rent.

     7.7.  Notwithstanding  anything  set forth herein to the  contrary,  in the
event the Building is not at least ninety-five percent (95%) occupied on average
during  any  year of the  Term,  an  adjustment  shall  be made by  Landlord  in
computing  Tenant's Pro Rata Share of  Operating  Expenses for such year so that
Tenant's Pro Rata Share of Operating Expenses shall be computed for such year as
though the  Building  had been  ninety-five  percent  (95%)  occupied on average
during such year.

     7.8.  The parties  agree that  statements  in this Lease to the effect that
Landlord is to perform certain of its  obligations  hereunder at its own or sole
cost and expense shall not be  interpreted  as excluding any cost from Operating
Expenses if such cost is otherwise  defined as an Operating  Expense pursuant to
the  terms of this  Lease.  Notwithstanding  the  foregoing,  in no event  shall
Landlord include as an Operating Expense costs and expenses incurred by Landlord
as a result of Landlord's  indemnification  obligations pursuant to Section 20.2
hereof.

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       11
<PAGE>


     7.9. Upon request by Tenant,  Landlord  shall furnish to Tenant with copies
of all proposed  assessments,  assessments,  real estate tax bills and the like.
Landlord shall also notify Tenant promptly  following the filing or commencement
of, and again  following any decision in or conclusion or settlement of, any tax
or assessment appeal, contest, reduction or challenge. On or before the 40th day
before  the  last  day to  file  an  application  to  contest  any  such  tax or
assessment,  Tenant may  request  Landlord  to notify  Tenant  whether  Landlord
intends to file such  application  and  within ten (10) days after such  request
Landlord  shall notify Tenant whether or not Landlord will do so. If within such
ten (10) day period Landlord either does not so notify Tenant or notifies Tenant
that Landlord does not intend to file such an application,  Tenant,  at its sole
cost and expense,  shall have the right (and Landlord hereby  constitutes Tenant
as Landlord's  attorney-in-fact  to the extent required by law to enable Tenant)
to challenge  and/or  appeal any tax,  assessment  or other item  includable  in
Operating Expenses. The parties hereto agree to cooperate in good faith together
in connection with any such contest, objection or litigation. Landlord shall pay
to Tenant, after deduction of Landlord's bona fide out-of-pocket costs to obtain
the same  (including,  but not limited to,  attorneys'  fees) the portion of any
refund of real estate taxes allocable to the Demised Premises.

8.   RENTABLE AREA.

     8.1. As used  herein,  the term  "RENTABLE  AREA" shall be  calculated  in
accordance  with  the  Washington   D.C.   Association  of  Realtors  Method  of
Measurement dated as of June 13, 1995. On or before the Rent Commencement  Date,
Tenant shall have the right, at its sole cost and expense,  to retain a licensed
architect to remeasure the Demised Premises. If the conclusions of the architect
retained by Tenant  differ  from the  Rentable  Area set forth in Section  2.1.3
hereof by Landlord by more than [*] of the total  square  footage of the Demised
Premises,  Landlord,  at its sole  expense,  shall (i) cause  its  architect  to
remeasure the Premises within ten (10) days of receiving notice from Tenant of a
discrepancy  or  (ii)  accept  the  determination  of  Tenant's  architect.   If
thereafter any discrepancy  remains,  the architects  shall consult and agree on
the  measurement of the Demised  Premises and Landlord and Tenant shall be bound
by such agreed to measurement.  If applicable,  Rentable Area, Basic Annual Rent
and  Tenant's  Pro Rata Share  shall be adjusted  accordingly.  If it is finally
determined that Tenant's architect was correct and the discrepancy was more than
[*]  Landlord  shall  reimburse  Tenant  for  the  reasonable  fee  of  Tenant's
architect.

9.   SECURITY DEPOSIT.

     9.1.  Tenant has deposited with Landlord the sum set forth in Section 2.1.8
(the "SECURITY  DEPOSIT"),  which Security  Deposit shall be held by Landlord as
security  for the  performance  by Tenant of all of the  terms,  covenants,  and
conditions  of this Lease to be kept and performed by Tenant during the Term. If
Tenant is in Default under this Lease,  after the  expiration of all  applicable
notice and cure periods,  Landlord may (but shall not be required to) use, apply
or retain all or any part of the Security Deposit for the payment of any Rent or
any other sum in default, or to compensate Landlord for any other loss or damage
which Landlord may suffer by reason of Tenant's  default.  If any portion of the
Security  Deposit is so used or applied,  Tenant  shall,  upon demand  therefor,

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       12
<PAGE>


deposit  cash with  Landlord in an amount  sufficient  to restore  the  Security
Deposit  to its  original  amount,  and  Tenant's  failure  to do so  shall be a
material  breach  of this  Lease.  Landlord  shall not be  required  to keep the
Security  Deposit  separate  from its  general  fund,  and  Tenant  shall not be
entitled to any interest on the Security Deposit.  In lieu of cash, Tenant shall
have the right to deposit  with  Landlord,  at any time and from time to time, a
letter of credit in the amount set forth in Section  2.1.8.  Any such  letter of
credit shall constitute the Security Deposit.  Any letter of credit so deposited
shall be an irrevocable, unconditional "clean" letter of credit having a term of
not less than two (2) years and issued by a financial institution  acceptable to
Landlord in its sole and absolute discretion. In the event that Landlord has not
received  a  replacement  letter of credit on or before the date that is 45 days
prior to the  expiration  date of the  letter of credit  then held by  Landlord,
Landlord  shall have the right to draw upon the letter of  credit.  If  Landlord
draws upon the  letter of credit  for any  purpose  permitted  pursuant  to this
Section 9.1, Tenant shall,  upon demand by Landlord,  deposit cash with Landlord
in an amount  sufficient to restore the Security Deposit to its original amount,
and Tenant's failure to do so shall be a material breach of this Lease.

     9.2.  In the  event  of  bankruptcy  or other  debtor-creditor  proceedings
against Tenant,  the Security Deposit shall be deemed to be applied first to the
payment of Rent and other  charges due  Landlord  for all  periods  prior to the
filing of such proceedings.

     9.3.  Landlord  may  deliver  the  Security  Deposit  to any  purchaser  of
Landlord's  interest in the Demised Premises provided that Landlord obtains such
purchaser's  written agreement to be bound by Landlord's  obligations under this
Lease from and after the date of the  transfer  of  Landlord's  interest  in the
Demised Premises and provides a copy of such written  agreement to Tenant.  Upon
fulfilling  such  conditions,  Landlord  shall be  discharged  from any  further
liability with respect to the Security Deposit.  This provision shall also apply
to any subsequent transfers.

     9.4. If Tenant  shall fully  perform  every  provision  of this Lease to be
performed by Tenant,  the Security  Deposit,  or any balance  thereof,  shall be
returned  to Tenant  within  thirty  (30) days after the  expiration  or earlier
termination of this Lease.

10.  USE.

     10.1.  Tenant  shall use the Demised  Premises for the purpose set forth in
Section  2.1.9 and shall not use the Demised  Premises,  or permit or suffer the
Demised  Premises to be used,  for any other  purpose  without the prior written
consent of Landlord which may be withheld in Landlord's reasonable discretion.

     10.2.  Tenant shall not use or occupy the Demised  Premises in violation of
any federal, state and local laws and regulations,  zoning ordinances, or of the
certificate of occupancy issued for the Building, and shall, upon five (5) days'
written notice from Landlord,  discontinue any use of the Demised Premises which
is finally decided by any  governmental  authority  having  jurisdiction to be a
violation  of  law,  regulation  or  zoning  ordinance  or  the  certificate  of
occupancy.  Tenant shall comply with any direction of any governmental authority


                                       13
<PAGE>


having  jurisdiction  which  shall,  by reason of the nature of Tenant's  use or
occupancy of the Demised Premises,  impose any duty upon Tenant or Landlord with
respect  to the  Demised  Premises  or with  respect  to the  use or  occupation
thereof.   Notwithstanding   the   foregoing,   any   inspectional   reports  or
observations,  establishment inspection reports, complaints,  warning letters or
any other similar document (including without limitation any Form 483) issued by
the FDA or comparable foreign  regulatory  authority which in any way relates to
the conduct of Tenant's  business in the Demised Premises shall not be deemed to
be a violation of the terms of this Lease by Tenant.

     10.3.  Tenant  shall  not do or  permit  to be  done  anything  which  will
invalidate any fire,  environmental,  extended  coverage or any other  insurance
policy  covering  the  Building  and  Project  and shall  comply with all rules,
orders,  regulations,  and  requirements  of the  insurers of the  Building  and
Project  and Tenant  shall  promptly  upon  demand  reimburse  Landlord  for any
additional  premium  charged  for such  insurance  policy by reason of  Tenant's
taking any action that  proximately  causes an increase in the premiums  payable
for any environmental,  extended coverage or other insurance policy covering the
Building.

     10.4.  Tenant shall,  upon termination of this Lease return to Landlord all
keys to offices and  restrooms,  either  furnished to, or otherwise  procured by
Tenant.  In the event any key so furnished is lost, Tenant shall pay to Landlord
the cost of  replacing  the same or of changing the lock or locks opened by such
lost key if Landlord shall deem it necessary to make such change.

     10.5. No awnings or other  projection shall be attached to any outside wall
of the building.

     10.6.   Subject  to  Article  44  and  Section  16.1,   hereof,   no  sign,
advertisement, or notice shall be exhibited, painted or affixed by Tenant on any
external part of the Demised  Premises or the Building without the prior written
consent  of  Landlord,   which  consent  shall  not  be  unreasonably  withheld,
conditioned or delayed. Tenant may install on floors of the Building on which it
is the sole Tenant,  without obtaining Landlord's consent, signs in the interior
of the Demised Premises,  including  elevator lobbies,  provided that such signs
are not visible from the exterior of the Building.

     10.7.  Tenant shall cause any office equipment or machinery to be installed
in the Demised Premises so as to not unreasonably cause hazardous  conditions in
the Common Areas.

     10.8.  Tenant  shall not do or permit  anything  to be done in or about the
Demised Premises which shall in any way unreasonably  obstruct or interfere with
the rights of other tenants or occupants of the Building, or injure them, or use
or allow the Demised  Premises to be used for  immoral,  unlawful  purpose,  nor
shall Tenant knowingly  cause,  maintain or permit any nuisance or waste in, on,
or about the Demised Premises, Building or Project.

     10.9.  Tenant shall be responsible for all liabilities,  costs and expenses
arising out of or in connection with the compliance of the Demised Premises with
the Americans with Disabilities Act, 42 U.S.C. ss. 12101, et seq. (together with
regulations   promulgated   pursuant  thereto,  the  "ADA"),  and  Tenant  shall


                                       14
<PAGE>


indemnify,  defend and hold harmless  Landlord from and against any loss,  cost,
liability or expense  (including  reasonable  attorneys fees and  disbursements)
arising out of any failure of the Demised Premises to comply with the ADA.

11.  BROKERS.

     11.1.  Tenant  represents and warrants that it has had no dealings with any
real estate broker or agent in  connection  with the  negotiation  of this Lease
other  than  Julien J.  Studley,  Inc.  and Smithy  Braedon-Oncor  International
(together,  "BROKER"),  as has been  disclosed  in writing to Landlord  and that
Tenant knows of no other real estate broker or agent who is or might be entitled
to a commission in connection with this Lease.

     11.2.  Tenant hereby  indemnifies and shall defend,  hold and save Landlord
harmless  from and  against  any and all claims for any  commissions  or fees in
connection  with this  Lease  made by any  broker or finder  having  worked,  or
claiming to have worked, on behalf of Tenant, other than Broker.

     11.3.  Tenant  represents and warrants that no broker or agent has made any
representation  or warranty relied upon by Tenant in Tenant's  decision to enter
into this Lease other than as contained in this Lease.

     11.4.  Tenant  acknowledges  and agrees that the  employment  of brokers by
Landlord is for the purpose of solicitation of offers of lease from  prospective
tenants and no authority is granted to any broker to furnish any  representation
(written or oral) or warranty from Landlord unless  expressly  contained  within
this Lease.  Landlord in executing  this Lease does so in reliance upon Tenant's
representations and warranties contained within Sections 11.1 and 11.3 hereof.

     11.5.  All  commissions  and fees owing to Broker in  connection  with this
Lease including,  without  limitation,  Tenant's  exercise of expansion  rights,
rights to purchase the Project and rights to develop the Project,  shall be paid
by Landlord in accordance with a separate agreement. Landlord hereby indemnifies
and agrees to defend, hold and save Tenant harmless from and against any and all
claims  for any  commission  or fees in  connection  with this Lease made by any
broker or  finder  having  worked,  or  claiming  to have  worked,  on behalf of
Landlord, including Broker.

12.  HOLDING OVER.

     12.1. If, with Landlord's express written consent,  Tenant holds possession
of all or any part of the  Demised  Premises  after the  expiration  or  earlier
termination of the Term, Tenant shall become a tenant from  month-to-month  upon
the date of such  expiration  or earlier  termination,  and in such case  Tenant
shall  continue to pay Basic Annual Rent in the amount  payable upon the date of
the expiration or earlier  termination of this Lease, and all other  provisions,
representations,  covenants and  agreements  contained  herein,  other than with
respect to the Term and any  extensions  thereof,  but  specifically  including,
without  limitation,  the  adjustment of Basic Annual Rent pursuant to Article 6
hereof, shall remain in full force and effect.


                                       15
<PAGE>


     12.2. Notwithstanding the foregoing, if Tenant remains in possession of the
Demised Premises after the expiration or earlier termination of the Term without
the  express  written  consent  of  Landlord,  Tenant  shall  become a tenant at
sufferance upon the terms of this Lease except that the monthly rental shall be,
for the initial [*] period following such expiration or earlier termination,  an
amount  equal to [*] of the Basic  Annual Rent in effect  during the last thirty
(30) days of the Term, and thereafter an amount equal to [*] of the Basic Annual
Rent in effect  during  the last  thirty  (30) days of the Term,  together  with
Additional  Rent,  and Tenant shall be responsible  for all damages  suffered by
Landlord resulting from or occasioned by Tenant's holding over.

     12.3.  Acceptance  by  Landlord  of Rent after such  expiration  or earlier
termination of the Term shall not result in a renewal or  reinstatement  of this
Lease.

     12.4. The foregoing provisions of this Article 12 are in addition to and do
not  affect  Landlord's  right to  re-entry  or any  other  rights  of  Landlord
hereunder or as otherwise provided by law.

13.  TAXES ON TENANT'S PROPERTY.

     13.1.  Tenant  shall pay,  prior to  delinquency,  any and all taxes levied
against any personal property or trade fixtures placed by Tenant in or about the
Demised Premises.

     13.2. If any such taxes on Tenant's personal property or trade fixtures are
levied against Landlord or Landlord's  property or, if the assessed valuation of
the Building is increased by the inclusion  therein of a value  attributable  to
Tenant's  personal  property or trade fixtures,  and if Landlord,  after written
notice to  Tenant,  pays the taxes  based  upon such  increase  in the  assessed
valued,  then  Tenant  shall upon demand  repay to Landlord  the taxes so levied
against Landlord.

14.  CONDITION OF DEMISED PREMISES.

     Tenant  acknowledges that, other than as expressly set forth in this Lease,
neither  Landlord  nor any  agent of  Landlord  has made any  representation  or
warranty with respect to the  condition of the Demised  Premises or the Building
or  Project,  or with  respect to the  suitability  for the  conduct of Tenant's
business.  Tenant  shall  accept the  Demised  Premises  AS-IS WHERE IS with all
faults.

15.  COMMON AREAS AND PARKING FACILITIES.

     15.1.  So long as Tenant is the sole tenant of the  Building,  Tenant shall
have exclusive use of the Common Areas of the Building and  nonexclusive  use of
the Common Areas of the Project that are not also Common Areas of the  Building.
At such time as Tenant is not the sole tenant of the Building, Tenant shall have
the  non-exclusive  right,  in common with other tenants of the Building and the
Project, to use the Common Areas. In any event, Tenant's use of the Common Areas
shall be subject to the rules and  regulations  adopted by Landlord and attached

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       16
<PAGE>


hereto as EXHIBIT "E" together with such other reasonable and  nondiscriminatory
rules and regulations as are hereafter promulgated by Landlord in its discretion
(the "RULES AND REGULATIONS").

     15.2.  As an  appurtenance  to the Demised  Premises,  Tenant  shall have a
non-exclusive  revocable license to use parking facilities within the Project on
a  non-reserved  basis up to a  maximum  of three  (3)  parking  spaces  per one
thousand  (1,000) square feet of Rentable  Area.  Landlord shall not assign more
parking  rights to tenants of the Project than the number of parking spaces that
actually exist in the Common Areas.

     15.3. So long as Tenant is the sole tenant of the Building,  Landlord shall
not have the right to modify Common Areas of the Building without Tenant's prior
consent. At such time as Tenant is not the sole Tenant of the Building, Landlord
reserves the right to modify Common Areas.

     15.4. Notwithstanding any other provision herein to the contrary,  Landlord
shall be responsible for all  liabilities,  costs and expenses arising out of or
in  connection  with the  compliance of the Common Areas of the Project with the
ADA.

16.  UTILITIES AND SERVICES.

     16.1. ACCESS;  SECURITY.  Tenant shall have access to the Demised Premises,
the roof of the Demised Premises and the parking  facilities serving the Demised
Premises 24 hours per day, 7 days per week  throughout  the Term.  Tenant  shall
have the right to install a modern,  electronic security system for the Building
and the Project which will control external and internal ingress to the Building
and the  Project  at all  points,  including  programmable  selective  access to
elevators and other  secured areas of the Building.  Tenant shall have the right
to install or provide  for (a)  Tenant-only  elevator  access,  (b)  Tenant-only
access from the fire  stairwells  to floors of the Building  occupied  solely by
Tenant,  (c) continuous video  surveillance of areas of ingress and egress,  all
portions of the  parking  facilities,  the  Building  perimeter  and the Project
perimeter and (d) (24) hour per day security guards to monitor video cameras and
ingress and egress to and from the Building and the Project.  Tenant, subject to
the terms of Article 17 and  Exhibit  "D",  shall be  permitted  to  construct a
perimeter  fence to restrict  access to the Building and the Project and to take
such  other  security   measures  as  are  determined  in  Tenant's   reasonable
discretion.

     16.2. OTHER SERVICES.

          16.2.1 Landlord, as Operating Expenses, shall provide snow removal and
landscaping services.

          16.2.2 Tenant shall employ its own  contractor or personnel to provide
maintenance and repair services to Tenant's  bio-waste and security  systems and
to furnish window-cleaning,  trash removal,  recycling and janitorial service to
the Demised  Premises,  and Landlord  shall have no  obligation  to furnish such
services to the  Demised  Premises,  unless  subsequently  requested  by Tenant.
Tenant shall pay for such services directly to the contractor employed by Tenant



                                       17
<PAGE>


for such  purpose,  and  Operating  Expenses  shall not  include  any expense of
furnishing such services to the Demised Premises.

     16.3.  EMERGENCY  MAINTENANCE.  Landlord shall use commercially  reasonable
efforts to have its Building maintenance  personnel,  if any, or outside service
contractors,  as  appropriate,  respond  within a  reasonable  period of time to
Tenant's  request to repair  Building  equipment or systems  malfunctions  which
Landlord is  obligated to repair and such  personnel  shall  promptly  repair or
replace any such damaged  equipment  subject to availability of parts.  Landlord
shall take the foregoing  requirement  into account in procuring  warranties and
service contracts for the Building.

     16.4.  Tenant  shall pay for all  water,  (including  the cost to  service,
repair and replace  reverse  osmosis,  deionized and other  treated  water) gas,
heat,  light,  power,  telephone  and other  utilities  supplied  to the Demised
Premises,  together with any fees,  surcharges  and taxes  thereon.  If any such
utility  is not  separately  metered to Tenant,  Tenant  shall pay a  reasonable
proportion  to be  determined  by Landlord of all charges  jointly  metered with
other premises as part of Tenant's Pro Rata Share of Operating  Expenses,  or in
the  alternative,  Landlord  may,  at its  option,  monitor  the  usage  of such
utilities by Tenant and charge  Tenant with the cost of  purchasing,  installing
and  monitoring  such  metering  equipment,  which  shall be paid by  Tenant  as
Additional Rent.

     16.5.  Landlord  shall not be liable for,  nor shall any eviction of Tenant
result from,  the failure to furnish any such utility or service  whether or not
such  failure is caused by accident,  breakage,  repairs,  strikes,  lockouts or
other  labor  disturbances  or labor  disputes  of any  character,  governmental
regulation,  moratorium  or other  governmental  action,  inability  despite the
exercise of  reasonable  diligence or by any other  cause,  other than the gross
negligence or wilful misconduct of Landlord. In the event of such failure (other
than a failure caused by the gross negligence or wilful misconduct of Landlord),
Tenant  shall not be entitled to any  abatement  or  reduction  of Rent,  nor be
relieved from the operation of any covenant or agreement of this Lease.

     16.6. Intentionally Deleted.

     16.7.  Tenant  shall pay  directly  to the  applicable  utility  or service
provider,  prior  to  delinquency,  for any  separately  metered  utilities  and
services  which may be  furnished to Tenant or the Demised  Premises  during the
Term.

     16.8. Intentionally Deleted.

     16.9. INTERRUPTION OF SERVICES.

          16.9.1  INTERRUPTION  OF SERVICES --  TENANT'S  RIGHT TO CURE.  In the
event of a material  interruption  of  services or  utilities  to be provided by
Landlord or to perform any repairs or maintenance  required under this Lease and
such  failure  materially  impairs  Tenant's  use and  enjoyment  of the Demised
Premises,  then if such  failure is not cured by  Landlord  within a  reasonable
period after  Landlord is first given  notice of such failure by Tenant,  Tenant
may deliver to Landlord and to Landlord's  lender(s) written notice stating that


                                       18
<PAGE>


Tenant  intends to obtain such  service or utility or to perform  such repair or
maintenance. Prior to Tenant undertaking any action to cure or remedy such event
or condition,  Tenant shall first allow  Landlord and  Landlord's  lender(s) ten
(10) business days  following  receipt by Landlord and  Landlord's  lender(s) of
such  written  notice to cure or  remedy  the event or  condition  specified  in
Tenant's notice;  PROVIDED,  HOWEVER,  that if such event or condition cannot be
cured within the ten (10)-day business period, such period shall be extended for
a  reasonable  additional  time,  so long as  Landlord or  Landlord's  lender(s)
commence to cure such event or condition within the ten (10)-business day period
and proceed diligently thereafter to effect such cure. If Landlord or Landlord's
lender(s)  fail to cure or  remedy  such  event or  condition  within  such time
period,  then  Tenant  may cure or remedy  such event or  condition.  Tenant may
deliver an invoice to Landlord for such costs and expenses,  and Landlord  shall
pay to Tenant the amount of such invoice  within thirty (30) days after delivery
by Tenant,  and the amount of such  expenses,  when paid by  Landlord,  shall be
included within  Operating  Expenses,  to the extent such costs and expenses are
not excluded  from the  definition  of  Operating  Expenses  herein.  The phrase
"material  interruption  of  services  or  utilities"  shall  mean the  total or
substantial failure of the supply of electricity, gas, water or sewer service to
the Building or other Building systems (excluding telephone service).

          16.9.2  MANNER IN WHICH TENANT MAY CURE.  In the event Tenant seeks to
cure or remedy any event or condition which gives rise to Tenant's  remedies set
forth in  Section  16.9.1,  Tenant  shall (i)  proceed  in  accordance  with the
applicable  provisions  of  this  Lease  and  all  applicable  rules,  laws  and
governmental regulations; (ii) use only such contractors, suppliers, etc. as are
duly  licensed in the State of Maryland  and insured to effect such  repairs and
who perform such repairs on first class  buildings in the normal course of their
business;  (iii) promptly effect such repairs in a good workmanlike  quality and
in a first class  manner:  (iv) use new  materials;  and (v)  indemnify and hold
Landlord  and its  lender(s)  harmless  from any and all  liability,  damage and
expense  arising from injury to persons or personal  property  arising out of or
resulting from Tenant's exercise of such rights.

          16.9.3 FIRE, CASUALTY.  Notwithstanding the foregoing,  the provisions
of this  Section  16.9  shall not apply in the event the  Demised  Premises  are
damaged by fire, casualty or other event described in Section 22.

          16.9.4  AVAILABILITY  OF OTHER RELIEF.  Notwithstanding  anything else
contained  in this  Section  16.9,  Tenant shall in all events have the right to
seek  declaratory  and  injunctive  relief in the event  Landlord  breaches  its
obligation  to  furnish  services  and  utilities  as,  when,  and in the manner
required hereunder.


                                       19
<PAGE>


17.  ALTERATIONS.

     17.1. Other than Tenant's Work and subject to Section 17.11 hereof,  Tenant
shall  make no  alterations,  additions  or  improvements  in or to the  Demised
Premises without  Landlord's prior written consent,  which approval shall not be
unreasonably  withheld,  conditioned  or delayed,  and then only by  architects,
contractors,   suppliers  or  mechanics   approved  by  Landlord  in  Landlord's
reasonable  discretion.  The  foregoing  notwithstanding,  Tenant shall have the
right without  Landlord's  prior written  consent or approval to make  interior,
non-structural  alterations,  additions  and/or  improvements not materially and
adversely  affecting the Building systems or the Common Areas and not, as to any
particular  project,  exceeding  [*] in hard costs in the event that the subject
project  is  undertaken  prior  to the [*] of the  Term  Commencement  Date  and
exceeding [*] in hard costs in the event that the subject  project is undertaken
thereafter;  provided,  however, that Tenant shall nevertheless furnish Landlord
with prior written notice thereof in accordance with Section 17.5 below and with
a copy of any preliminary plans and  specifications,  working drawings and final
"as-built"  drawings  obtained  therefor.  In all events Tenant shall deliver to
Landlord a copy of all documents,  plans and drawings  submitted to governmental
authorities in connection with any alteration, addition or improvement.

     17.2.  Unless  permitted  without  the need to  obtain  Landlord's  consent
pursuant to Section 17.11,  Tenant agrees that there shall be no construction of
partitions  or other  obstructions  which  might  interfere  with free access to
mechanical  installation or service facilities of the Building or interfere with
the moving of Landlord's  equipment to or from the  enclosures  containing  said
installations or facilities.

     17.3. Tenant agrees that any work by Tenant shall be accomplished in such a
manner as to permit any fire  sprinkler  system and fire water  supply  lines to
remain fully operable at all times.

     17.4.  Tenant  covenants  and agrees that all work done by Tenant  shall be
performed  in  full  compliance  with  all  laws,  rules,  orders,   ordinances,
directives, regulations, and requirements of all governmental agencies, offices,
departments, bureaus and boards having jurisdiction, and in full compliance with
the rules, orders, directions,  regulations,  and requirements of any applicable
fire rating bureau.  Tenant shall provide Landlord with "as-built" plans showing
any material change in the Demised Premises.  Deliveries to Landlord pursuant to
this Section shall be subject to the terms of Section 45.13 hereof.

     17.5.  In seeking Landlord's  approval,  Tenant shall provide Landlord,  at
least [*] in advance of any proposed construction,  with plans,  specifications,
bid proposals,  work contracts and such other information  concerning the nature
and cost of the  alterations  as may be  reasonably  requested by Landlord,  and
shall,  if  reasonably  required by  Landlord,  secure at Tenant's  own cost and
expenses  a  completion  and lien  indemnity  bond  reasonably  satisfactory  to
Landlord for said work. Deliveries to Landlord pursuant to this Section shall be
subject to the terms of Section 45.13 hereof.  Landlord  shall be deemed to have
approved  Tenant's  submissions  if Landlord  fails to respond  within [*] after
receipt thereof.

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       20
<PAGE>


     17.6. Intentionally Deleted.

     17.7.  Tenant  shall  repair any damage to the Demised  Premises  caused by
Tenant's  removal of any  property  from the Demised  Premises.  During any such
restoration  period,  Tenant shall pay Rent to Landlord as provided herein as if
said space were otherwise occupied by Tenant.

     17.8.  Notwithstanding anything to the contrary set forth elsewhere in this
Lease,  (a) Tenant  shall have the right to remove  items  moved to the  Demised
Premises  from  Tenant's  premises  at  12103  and  12031  Indian  Creek  Court,
Beltsville, Maryland, [*] provided, however, that Tenant shall repair any damage
caused by the  removal  thereof;  (b) Tenant  shall have the right to remove [*]
purchased  and  installed  by Tenant  with funds  other than those  provided  by
Landlord as tenant improvement  allowance or as a loan; provided,  however, that
Tenant shall repair any damage caused by the removal  thereof;  (c) Tenant shall
not have the  right to  remove  [*] and (d)  Tenant  shall not have the right to
remove [*]  purchased or installed by Tenant with funds  provided by Landlord as
tenant  improvement  allowance or as a loan.  In any event,  Tenant shall not be
permitted  to  remove  (i) any part of the  Building's  systems,  (ii)  anything
purchased or paid for by Landlord directly or through the payment by Landlord to
Tenant of any  construction or improvement  allowance or loan, or (iii) anything
that could result in significant damage to the Building. If Tenant shall fail to
remove all of its effects from the Demised  Premises  prior to the expiration or
earlier termination of this Lease, then Landlord may, at its option,  remove the
same in any manner that  Landlord  shall choose,  or store said effects  without
liability to Tenant for loss thereof or damage thereto, and Tenant agrees to pay
Landlord  upon  demand any  expenses  incurred  by such  removal  and storage or
Landlord may, at its option,  without  notice,  sell said property or any of the
same, at private sale and without legal process,  for such price as Landlord may
obtain and apply the  proceeds  of such sale  against any amounts due under this
Lease from Tenant to Landlord and against any expenses  incident to the removal,
storage and sale of said personal property.

     17.9. Intentionally Deleted.

     17.10.  Tenant  shall  pay to  Landlord  within 30 days  after  substantial
completion of any alterations, additions or improvements to the Demised Premises
(other than Tenant's Work pursuant to Exhibit "D" hereto) an amount equal to [*]
of all "hard" costs (but in no event more than [*] in respect of any  individual
alteration, addition or improvement project) incurred by Tenant in connection 

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       21
<PAGE>


with such  alterations,  additions or improvements to cover Landlord's  overhead
and expenses for plan review, coordination,  scheduling and supervision thereof.
Tenant shall provide to Landlord promptly upon Landlord's  request copies of all
bills, invoices, and statements covering the costs of such charges. Tenant shall
reimburse  Landlord  for any extra  expense  incurred  by  Landlord by reason of
faulty work done by Tenant or its contractors,  or by reason of delays caused by
such work, or by reason of inadequate cleanup.

     17.11.  Landlord acknowledges that the conduct of Tenant's business and the
use of the Demised Premises in connection with Tenant's  business are subject to
the rules and regulations of the FDA and other governmental  agencies,  offices,
departments,  bureaus and boards.  Notwithstanding  anything to the contrary set
forth in this Lease, Tenant shall have the right to make alterations,  additions
or improvements  to the Demised  Premises to the extent the same are required to
cause Tenant or the Demised  Premises to be in compliance with all laws,  rules,
orders,   ordinances,   directives,   regulations,   and   requirements  of  all
governmental  agencies,   offices,   departments,   bureaus  and  boards  having
jurisdiction over the same ("Legal Requirement"). Nothing in this Lease shall be
construed to require Tenant to violate any Legal Requirement and all obligations
of Tenant and all  rights of  Landlord  hereunder  shall be subject to any Legal
Requirement  applicable to Tenant or the Demised Premises.  Tenant shall deliver
to Landlord  copies of any rule,  regulation,  correspondence  or other document
evidencing  Tenant's  obligation to comply with a Legal  Requirement  materially
affecting Tenant's use of the Demised Premises.  Notwithstanding  the provisions
of the immediately preceding sentence,  Tenant shall not be obligated to deliver
to  Landlord  copies  of  any  written   material  that  Tenant   determines  is
confidential, sensitive or secret. Tenant shall make such material available for
Landlord's review but Landlord shall not be permitted to copy the same.

          17.11.1  Prior to initiating any  alterations or  improvements  to the
Demised  Premises  pursuant to Section  17.11,  Tenant shall deliver to Landlord
detailed plans showing such proposed  alterations or improvements  ("Improvement
Plans").  Landlord shall respond to Tenant's request to complete the alterations
within [*] of Landlord's  receipt of the  Improvement  Plans.  Landlord shall be
deemed to have  approved  the  Improvement  Plans if  Landlord  fails to respond
within such [*] period. Deliveries to Landlord pursuant to this Section shall be
subject to the terms of Section 45.13 hereof.

          17.11.2  All   alterations,   if  approved  by   Landlord,   or  other
alterations, additions or improvements not requiring Landlord's consent pursuant
to Section 17.11, shall be completed only by architects,  contractors, suppliers
or mechanics approved by Landlord in Landlord's reasonable discretion.

     17.12.  Notwithstanding  anything to the contrary  contained in this Lease,
Landlord  shall not  require,  as a  condition  to  granting  its consent to any
alteration,  that Tenant make any monetary  payment to Landlord  (other than the
payment required  pursuant to Section 17.10),  or that Tenant deposit any sum of
money or provide other additional security to Landlord.

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.



                                       22
<PAGE>



18.  REPAIRS AND MAINTENANCE.

     18.1.  Landlord  shall  keep and  maintain  in good  order and  repair  the
Building and Project structure and systems,  including the foundation,  roof and
roof covering materials, exterior walls, elevators,  electrical,  plumbing, fire
and safety  systems,  security  systems,  HVAC.  systems,  entrance,  sidewalks,
lobbies,  stairways,  landscaped areas,  parking  facilities,  lobbies and other
common areas and  facilities of the Building (and the full cost thereof shall be
included as a part of Operating Expenses,  unless expressly excluded pursuant to
Article 7). In  addition,  Landlord  covenants  with Tenant to proceed  with due
diligence to remedy,  as promptly as is feasible  under the  circumstances,  any
material  interruption  of services.  Landlord  shall in no event be required to
make repairs to leasehold improvements made by Tenant, or another tenant. Tenant
agrees to deliver  notice to Landlord,  as promptly as is  reasonable  under the
circumstances, of any defective condition in or about the Demised Premises known
to Tenant which  Landlord is required to repair  hereunder;  provided,  however,
that Tenant's  failure to report to Landlord any such defective  condition shall
not  relieve  Landlord of  Landlord's  obligation  to repair any such  defective
condition  promptly upon  learning of the need for such repair.  Notwithstanding
the foregoing,  in the event of any of the foregoing  maintenance or repairs are
required  by  reason  of any act or  omission  of  Tenant,  Tenant  shall pay to
Landlord the cost of such maintenance and repairs.

     18.2.  Except for services of Landlord,  if any,  required by Section 18.1,
Tenant  shall at Tenant's  sole cost and expense  keep the Demised  Premises and
every part thereof in good  condition and repair,  damage  thereto from ordinary
wear and tear and damage by casualty excepted. Tenant shall, upon the expiration
or earlier termination of this Lease, surrender the Demised Premises to Landlord
in good condition, ordinary wear and tear and damage by casualty excepted.

     18.3.  Repairs under this Article 18 which are  obligations of Landlord are
subject to allocation among Tenant and other tenants as Operating Expenses.

     18.4.  This  Article 18 relates to repairs and  maintenance  arising in the
ordinary  course of  operation  of the  Building,  the  Project  and any related
facilities.  In the event of fire, earthquake,  flood, hurricane or other act of
God, vandalism, war, or similar cause of damage or destruction,  this Article 18
shall  not be  applicable  and the  provisions  of  Article  22 shall  apply and
control.

19.  LIENS.

     19.1.  Tenant  shall keep the Demised  Premises,  the Building and the real
property  upon which the Building is situated free from any liens arising out of
work performed,  materials furnished or obligations  incurred by Tenant.  Tenant
further  covenants and agrees that any mechanic's lien filed against the Demised
Premises  or against the  Building or the Project for work  claimed to have been
done for,  or  materials  claimed  to have been  furnished  to  Tenant,  will be
discharged  by  Tenant,  by bond or  otherwise,  within  ten (10) days after the
filing thereof, at the sole cost and expense of Tenant.



                                       23
<PAGE>


     19.2.  Should Tenant fail to discharge any lien of the nature  described in
Section 19.1,  Landlord may at Landlord's election pay such claim or post a bond
or otherwise provide security to eliminate the lien as a claim against title and
the cost thereof shall be immediately due from Tenant as Additional Rent.

     19.3. In the event Tenant shall lease or finance the  acquisition of office
equipment,  furnishings, or other personal property which are Tenant's Property,
Tenant warrants that any Uniform Commercial Code Financing Statement executed by
Tenant will upon its face or by exhibit  thereto  indicate  that such  Financing
Statement  is  applicable  only to such  Tenant's  Property  located  within the
Demised Premises.  In no event shall the address of the Building be furnished on
the statement without  qualifying  language as to applicability of the lien only
to such Tenant's Property.  Should any holder of a Financing  Statement executed
by Tenant  record or place of record a  Financing  Statement  which  appears  to
constitute a lien against any interest of Landlord or against equipment owned by
Landlord  which may be located  other than within the Demised  Premises,  Tenant
shall within ten (10) days after  filing such  Financing  Statement  cause (i) a
copy of the Security  Agreement or other documents to which Financing  Statement
pertains  to be  furnished  to  Landlord  to  facilitate  Landlord's  being in a
position to show such lien is not  applicable to Landlord's  interest,  and (ii)
cause  Tenant's  lender to amend any  documents  of record so as to clarify that
such lien is not  applicable  to any interest of Landlord in the Building or the
Project.

20.  INDEMNIFICATION AND EXCULPATION.

     20.1.  Tenant  hereby  indemnifies  and  agrees  to  defend,  hold and save
Landlord  harmless  from and against any and all demands,  claims,  liabilities,
losses, costs, expenses,  actions,  causes of action, damages or judgments,  and
all  reasonable  expenses  incurred  in  investigating  or  resisting  the  same
(including,   without  limitation,   reasonable  attorneys'  fees,  charges  and
disbursements),  for injury or death to person or injury to  property  occurring
within or about the Demised  Premises,  arising  directly or  indirectly  out of
Tenant's,  its  employees',  agents' or guests' use or  occupancy of the Demised
Premises  or a breach or  default  by Tenant  in the  performance  of any of its
obligations hereunder,  unless caused solely by the willful act or negligence of
the Landlord.

     20.2.  Landlord  hereby  indemnifies  and agrees to  defend,  hold and save
Tenant  harmless  from and against  any and all  demands,  claims,  liabilities,
losses, costs, expenses,  actions,  causes of action, damages or judgments,  and
all  reasonable  expenses  incurred  in  investigating  or  resisting  the  same
(including,   without  limitation,   reasonable  attorneys'  fees,  charges  and
disbursements),  suffered by or claimed against Tenant,  directly or indirectly,
based on or arising out of any act or omission of  Landlord,  its  employees  or
agents or any breach by Landlord of its obligations under this Lease.

     20.3. Intentionally Deleted.

     20.4.  Landlord  shall not be liable for any damages  arising from any act,
omission or neglect of any other tenant in the Building or the Project or of any
other third party other than Landlord's agents, employees or contractors.



                                       24
<PAGE>



     20.5. Security devices and services,  if any, while intended to deter crime
may not in  given  instances  prevent  theft  or  other  criminal  acts.  Tenant
acknowledges and agrees that Landlord shall not be liable for injuries or losses
caused by criminal  acts of third  parties,  and Tenant  assumes the risk that a
criminal may circumvent any security device or service or that a security device
or service may  malfunction.  Tenant shall, at Tenant's cost,  obtain  insurance
coverage to the extent Tenant desires protection against such criminal acts.

21.  INSURANCE - WAIVER OF SUBROGATION.

     21.1. Landlord,  as part of Operating Expenses,  shall carry insurance upon
the  Building,  in an amount equal to full  replacement  cost  (exclusive of the
costs of  excavation,  foundations,  and  footings,  and  without  reference  to
depreciation  taken by  Landlord  upon its books or tax  returns) or such lesser
coverage  as  Landlord  may elect  provided  such  coverage is not less than one
hundred  percent  (100%) of such  full  replacement  cost or the  amount of such
insurance  Landlord's  mortgage lender requires Landlord to maintain,  providing
protection against any peril generally included within the classification  "Fire
and Extended  Coverage"  together with insurance  against  sprinkler  damage (if
applicable), vandalism and malicious mischief. Landlord, subject to availability
thereof and, as part of Operating Expenses,  shall further insure against flood,
environmental  hazard and  earthquake,  loss or failure of  building  equipment,
rental  loss  during the  period of repair or  rebuild,  workmen's  compensation
insurance and fidelity  bonds for employees  employed to perform  services.  All
insurance  procured by Landlord  shall be maintained  with an insurance  company
authorized to do business in the State of Maryland with a then current Alfred M.
Best Company,  Inc. (or if it no longer  exists,  a comparable  rating  service)
general  policy  maker's  rating of A or better and  financial  size category of
Class XII or higher. Landlord shall promptly deliver to Tenant written notice of
(i) any substitution of such company or companies,  and (ii) any change in their
Alfred M. Best Company,  Inc.  general policy maker's rating of any such company
or  substituted  company.  Landlord  shall also  maintain  boiler and  machinery
coverage in a type and amount normally maintained by prudent owners of buildings
managed and operated in a first class manner.  The  deductible on Landlord's All
Risk  Coverage   Insurance  shall  not  exceed  One  Hundred   Thousand  Dollars
($100,000.00) or such greater amount as shall be commercially  reasonable and as
may  customarily  be accepted  from time to time by prudent  owners of buildings
managed  in a first  class  manner.  Any  insurance  required  to be  carried by
Landlord under this Lease shall be  noncontributory  and primary over any policy
that  might be  carried  by  Tenant.  Landlord  shall  provide  certificates  of
insurance on ACORD form 27 evidencing all insurance  required under this Section
21.1.

     21.2.  Landlord,  as  part  of  Operating  Expenses,  shall  further  carry
commercial general liability insurance with a single loss limit of not less than
Ten Million  Dollars  ($10,000,000.00)  for death or bodily injury,  or property
damage with  respect to the Project.  Landlord's  commercial  general  liability
insurance policy shall name Tenant as an additional insured. No insurance policy
required  under this Lease to be  obtained by Landlord  shall be  cancelable  or
subject to reduction of coverage or other  modification or  cancellation  except
after thirty (30) days prior written notice to Tenant from the insurer.


                                       25
<PAGE>


     21.3.  Tenant at its own cost shall procure and continue in effect from the
Term  Commencement  Date and  continuing  throughout  the Term (and occupancy by
Tenant,  if any,  after the  expiration  or earlier  termination  of this Lease)
commercial general liability  insurance with limits of not less than Ten Million
Dollars  ($10,000,000.00)  per occurrence for combined single limit for death or
bodily injury and property damage with respect to the Demised Premises.

     21.4.  Tenant  shall have the right,  upon sixty (60) days'  prior  written
notice to Landlord,  to obtain any insurance policy required under this Lease to
be obtained by Landlord,  provided  that Tenant names  Landlord as an additional
insured with respect to such insurance  policy or policies.  In the event Tenant
obtains insurance pursuant to this Section 21.4, Landlord shall reimburse Tenant
for the cost of the premiums for such  insurance  within  thirty (30) days after
delivery by Tenant of evidence of payment  therefor,  and Landlord shall then be
permitted to pass through the costs of such insurance premiums to tenants of the
Building or the Project as Operating Expenses.

     21.5. The insurance required of Tenant in Section 21.3 shall name Landlord,
its officers,  employees and agents,  as an additional  insured.  Said insurance
shall be with companies having a rating of not less than policyholder  rating of
A and  financial  category  rating of at least  Class XII in  "Best's  Insurance
Guide."  Tenant shall obtain for Landlord from the insurance  companies or cause
the insurance companies to furnish certificates of coverage to Landlord. No such
policy  shall be  cancelable  or  subject  to  reduction  of  coverage  or other
modification or cancellation  except after thirty (30) days prior written notice
to Landlord  from the  insurer.  All such  policies  shall be written as primary
policies, not contributing with and not in excess of the coverage which Landlord
may carry. Tenant's policy may be a "blanket policy" which specifically provides
that the amount of insurance  shall not be prejudiced by other losses covered by
the policy.  Tenant shall,  at least twenty (20) days prior to the expiration of
such policies,  furnish Landlord with renewals or binders. Tenant agrees that if
Tenant does not take out and maintain  such  insurance,  Landlord may (but shall
not be required to) procure said insurance on Tenant's behalf and require Tenant
to pay for the additional cost of such insurance as Additional Rent.

     21.6. Tenant assumes the risk of damage to any fixtures,  goods, inventory,
merchandise,  equipment,  and leasehold improvements,  and Landlord shall not be
liable for injury to Tenant's business or any loss of income therefrom  relative
to such damage all as more particularly  heretofore set forth within this Lease.
Tenant at  Tenant's  cost  shall  carry such  insurance  as Tenant  desires  for
Tenant's  protection  with  respect to  personal  property of Tenant or business
interruption.

     21.7. In each instance where insurance is to name Landlord as an additional
insured,  Tenant  shall upon  written  request of Landlord  also  designate  and
furnish  certificates so evidencing Landlord as an additional insured to (i) any
lender of Landlord holding a security  interest in the Building or real property
upon which the  Building is situated,  and/or (ii) the landlord  under any lease
wherein  Landlord  is tenant of the real  property  whereupon  the  Building  is
located if the  interest of Landlord is or shall become that of a tenant under a
ground  lease  rather  than that of a fee  owner,  and/or  (iii) any  management
company retained by Landlord to manage the Building or the Project.


                                       26
<PAGE>


     21.8.  Landlord and Tenant each hereby waive any and all rights of recovery
against the other or against the officers,  directors,  employees,  agents,  and
representatives  of the other,  on account of loss or damage  occasioned 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 fire and extended
coverage  insurance  policy  which  either may have in force at the time of such
loss or damage. Such waivers shall continue as long as their respective insurers
so  permit.  Any  termination  of such a waiver  shall be by  written  notice of
circumstances  as hereinafter set forth.  Landlord and Tenant upon obtaining the
policies of insurance  required or permitted  under this Lease shall give notice
to the  insurance  carrier  or  carriers  that the  foregoing  mutual  waiver of
subrogation is contained in this Lease. If such policies shall not be obtainable
with  such  waiver  or  shall  be so  obtainable  only at a  premium  over  that
chargeable  without such waiver,  the party seeking such policy shall notify the
other thereof,  and the latter shall have ten (10) days thereafter to either (i)
procure such insurance with companies reasonably satisfactory to the other party
or (ii) agree to pay such  additional  premium  (in the  Tenant's  case,  in the
proportion which the area of the Demised Premises bears to the insured area). If
neither (i) nor (ii) are done,  this  Section  21.8 shall have no effect  during
such time as such policies shall not be obtainable or the party in whose favor a
waiver of subrogation is desired refuses to pay the additional  premium. If such
policies  shall  at  any  time  be  unobtainable,   but  shall  be  subsequently
obtainable,  neither party shall be subsequently  liable for a failure to obtain
such insurance until a reasonable time after  notification  thereof by the other
party.  If the release of either  Landlord or Tenant,  as set forth in the first
sentence  of this  Section  21.8  shall  contravene  any  law  with  respect  to
exculpatory  agreements,  the liability of the party in question shall be deemed
not released but shall be secondary to the other's insurer.

     21.9.  Landlord may require insurance policy limits to be raised to conform
with requirements of Landlord's lender and/or to bring coverage limits to levels
then being required of new tenants within the Project.

22.  DAMAGE OR DESTRUCTION.

     22.1. If the Demised Premises or any part thereof shall be damaged by fire,
casualty  or any other  cause,  Tenant  shall  give  prompt  notice  thereof  to
Landlord.

     22.2.  If the Building or Demised Premises are damaged by fire, casualty or
other  cause  thereby  rendering  the  Demised  Premises  totally  or  partially
inaccessible  or  untenantable  for Tenant's  purposes,  Landlord  shall provide
notice  to  Tenant  within  [*]  after  the date of such  damage  of  Landlord's
reasonable  estimate  of the time  required  to  restore  the  Demised  Premises
("Restoration  Notice"). If less than [*] of the insurable value of the Building
was destroyed by such damage and Landlord sets forth in the  Restoration  Notice
that  the  Demised  Premises  can be  restored  within  [*] from the date of the
damage,  Landlord, at Landlord's sole expense (which shall not be passed through
as an Operating Expense (except to the extent of any insurance deductible amount
paid by Landlord  that is a capital  expenditure),  shall repair such damage and
this Lease shall continue in full force and effect.

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       27
<PAGE>


     22.3.  If more than [*]of the insurable  value of the Building is destroyed
by fire,  casualty or any other cause and Landlord sets forth in the Restoration
Notice that the Demised Premises can not be repaired within [*] from the date of
the damage,  Landlord shall have the right to terminate this Lease by delivering
notice of  termination to Tenant,  and this Lease shall be terminated  effective
[*] after delivery of such notice.

     22.4.  Notwithstanding  anything to the contrary in this Article 22, if the
Demised Premises is damaged and (i) [*] or more of the space then used by Tenant
exclusively for office  purposes,  or (ii) [*] or more of the space then used by
Tenant for research and development and production purposes or (iii) [*] or more
of the space then used by Tenant for  warehouse  purposes,  is thereby  rendered
untenantable  or not  reasonably  usable by Tenant for its  purposes,  or if the
Building shall be so damaged that Tenant is deprived of reasonable  access to or
reasonable use of the appropriate percentage of any of (i), (ii) or (iii) above,
and Landlord's  Restoration Notice indicates that repair of the Demised Premises
will require more than [*] from the date of such damage,  then Tenant shall have
the right to  terminate  this Lease by giving  notice to Landlord not later than
[*] following  Tenant's receipt of the Restoration  Notice. In addition,  if the
restoration  is not actually  substantially  complete by the  estimated  date of
completion set forth in the Restoration  Notice,  Tenant shall have the right to
terminate  this Lease by giving notice to Landlord not later than [*] after such
estimated  date of  completion.  If Tenant  delivers to  Landlord a  termination
notice pursuant to the terms of the preceding two sentences, this Lease shall be
deemed to have  terminated  as of the date of the  receipt  by  Landlord  of the
termination notice.

     22.5.  Landlord  shall give written notice to Tenant of its election not to
repair,  reconstruct or restore the Building or Project pursuant to the terms of
Section 22.3 within the [*] period following the date of damage or destruction.

     22.6.  Upon any  termination  of this Lease under any of the  provisions of
this Article,  the parties shall be released thereby without further  obligation
to the other from the date possession of the Demised  Premises is surrendered to
the Landlord except for items which have theretofore occurred.

     22.7.  If  the  Demised   Premises  or  any  portion  thereof  is  rendered
untenantable or inaccessible by reason of fire, casualty or other similar cause,
then Rent shall  abate for such  period  with  respect to such  untenantable  or
inaccessible  portion of the Demised  Premises,  PROVIDED,  HOWEVER,  that,  for
purposes of determining  the amount of such abatement,  if such  untenantable or
inaccessible  portion of the  Demised  Premises  shall be (i) space then used by
Tenant for research and  development  or production  purposes,  the Basic Annual
Rent per square  foot with  respect to such space  shall be deemed to be [*] per
square  foot,  (ii) space then used by Tenant  for  office  purposes,  the Basic
Annual  Rent per square foot shall be deemed to be [*] per square foot and (iii)
space then used by Tenant for  warehouse  purposes,  the Basic  Annual  Rent per
square  foot  shall be deemed to be [*] per  square  foot.  Notwithstanding  the
foregoing, if Tenant vacates portions of the Demised Premises not rendered

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       28
<PAGE>


untenantable or inaccessible by such damage,  then Rent shall abate with respect
to such  portion so vacated,  but only so long as, and to the  extent,  Landlord
recovers insurance proceeds pursuant to its rental interruption insurance policy
with respect to the same.

     22.8.  Notwithstanding  anything to the contrary contained in this Article,
should   Landlord  be  delayed  or  prevented  from  completing  the  repair  or
restoration  of the damage to the Demised  Premises after the occurrence of such
damage  or  destruction   by  reason  of  acts  of  God  or  war,   governmental
restrictions, inability to procure the necessary labor or materials, strikes, or
other uses beyond the control of Landlord,  the time for Landlord to commence or
complete  repairs  shall be  extended,  provided,  at the  election of Landlord,
Landlord shall be relieved of its obligation to make such repairs or restoration
and Tenant shall be released from all obligations under this Lease as of the end
of one year from date of destruction,  if repairs required to provide Tenant use
of the Demised Premises are not then substantially complete.

     22.9.  If Landlord is obligated to or elects to repair or restore as herein
provided,  Landlord  shall be obligated to make repairs or  restoration  only of
those portions of the Building and the Demised  Premises  which were  originally
provided at  Landlord's  expense or were paid for out of the Tenant  Improvement
Allowance.  The  repair  and  restoration  of  Tenant's  Property  shall  be the
obligation of Tenant.

     22.10.  Notwithstanding  anything  set  forth  in  this  Article  22 to the
contrary,  in the event that,  during the final [*] of the Term,  if the Demised
Premises  is  damaged  and  (i) [*] or more of the  space  then  used by  Tenant
exclusively  for  office  purposes,  (ii) [*] or more of the space  then used by
Tenant for research and development and production purposes or (iii) [*] or more
of the space then used by Tenant for  warehouse  purposes,  is thereby  rendered
untenantable  or not  reasonably  usable by Tenant for its  purposes,  or if the
Building shall be so damaged that Tenant is deprived of reasonable  access to or
reasonable use of the appropriate  percentage of any of (i), (ii) or (iii) above
for a period of at least [*] Tenant may, by notice to Landlord  within [*] after
the occurrence of such damage, elect to (x) terminate this Lease, (y) extend the
term of this Lease pursuant to Section 42, or (z) purchase the Project  pursuant
to Section  39. If Tenant  elects to  terminate  this  Lease,  this Lease  shall
terminate on the date of Tenant's notice. If Tenant elects to extend the term of
this Lease,  the terms of Sections 22.2 and 22.3 shall be applicable.  If Tenant
elects to purchase the Project,  Landlord shall have no obligation to repair the
damage and Landlord, at the closing of the sale of the Project,  shall assign to
Tenant all of the casualty  insurance  proceeds  paid and payable in  connection
with such damage.  If Tenant fails to make any election within the aforesaid [*]
period,  Landlord may terminate  this Lease by notice to Tenant within [*] after
the expiration of the first [*] period following the occurrence of such damage.

23.  EMINENT DOMAIN.

     23.1.  Landlord  shall  give  Tenant  notice  of  the  commencement  of any
condemnation  or  eminent  domain  proceeding  affecting  the  Demised  Premises
promptly following  Landlord's  obtaining  knowledge  thereof.  In the event the

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       29
<PAGE>


whole of the  Demised  Premises,  or such part  thereof  as shall,  in  Tenant's
reasonable   determination,   substantially  interfere  with  Tenant's  use  and
occupancy  of the  Demised  Premises  for its  purposes,  shall be taken for any
public or  quasi-public  purpose by any lawful power or authority by exercise of
the right of  appropriation,  condemnation or eminent domain, or sold to prevent
such taking,  Tenant or Landlord may  terminate  this Lease  effective as of the
date possession is required to be surrendered to said authority.

     23.2.  In the event of a  partial  taking of the  Building,  or of  drives,
walkways,  and parking areas serving the Building for any public or quasi-public
purpose by any lawful power or authority by exercise of right of  appropriation,
condemnation,  or eminent domain,  or sold to prevent such taking,  then without
regard as to whether any portion of the Demised Premises  occupied by Tenant was
so taken,  Landlord may elect to terminate  this Lease as of such taking if such
taking is, in the reasonable  discretion of Landlord,  of a material nature such
as to make it uneconomical to continue use of the unappropriated portion for the
purposes set forth in Section 2.1.9.

     23.3. Tenant shall be entitled to any award or other  compensation which is
specifically awarded as compensation for the taking of Tenant's Property and for
the costs of Tenant  moving to a new location.  Except as before set forth,  any
award for such taking shall belong to Landlord.

     23.4.  If upon any taking of the nature  described  in this Article 23 this
Lease  continues in effect,  the Landlord shall promptly  proceed to restore the
Demised Premises, Building and the Project to substantially their same condition
prior to such partial  taking.  To the extent such  restoration  is feasible (as
determined  by  Landlord  in its  sole  discretion),  the Rent  shall be  abated
proportionately  based  upon the  extent to which  Tenant's  use of the  Demised
Premises has decreased on the basis of the percentage of the rental value of the
Demised  Premises after such taking and the rental value of the Demised Premises
prior to such taking and taking into account the different rental values for the
laboratory, warehouse and office portions of the Demised Premises.

24.  DEFAULTS AND REMEDIES.

     24.1.  Late  payment by Tenant to  Landlord of Rent and other sums due will
cause Landlord to incur costs not  contemplated by this Lease,  the exact amount
of which will be extremely difficult and impracticable 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 Demised  Premises.  Therefore,  if any installment of Rent due
from Tenant is not  received by Landlord  within [*] after the date such payment
is due,  Tenant  shall pay to Landlord an  additional  sum of [*] of the overdue
Rent as a late charge, PROVIDED, HOWEVER, that on up to [*] occasions in any [*]
period,  unless  Landlord  shall have given  written  notice of such  failure to
Tenant and Tenant shall not have made the payment  within [*] after such written
notice, Tenant shall not be obligated to pay such late charge. The parties agree
that this late charge  represents  a fair and  reasonable  estimate of the costs
that Landlord will incur by reason of late payment by Tenant. In addition to the
late charge,  Rent not paid when due shall bear  interest from the 5th day after
the due date until  paid at the lesser of (i) [*] per annum or (ii) the  maximum
rate permitted by law.

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       30
<PAGE>


     24.2.  No payment by Tenant or receipt by Landlord of a lesser  amount than
the Rent payment herein  stipulated  shall be deemed to be other than on account
of the Rent,  nor shall any  endorsement or statement on any check or any letter
accompanying any check or payment as Rent be deemed an accord and  satisfaction,
and Landlord may accept such check or payment  without  prejudice to  Landlord's
right to recover the balance of such Rent or pursue any other  remedy  provided.
If at any time a dispute shall arise as to any amount or sum of money to be paid
by Tenant to  Landlord,  Tenant  shall  have the  right to make  payment  "under
protest"  and such  payment  shall not be regarded as a voluntary  payment,  and
there  shall  survive  the  right on the part of Tenant  to  institute  suit for
recovery of the payment paid under protest.

     24.3.  If Tenant  fails to pay any sum of money  (other  than Basic  Annual
Rent)  required to be paid by it  hereunder,  or shall fail to perform any other
act on its part to be performed  hereunder,  Landlord  may,  without  waiving or
releasing Tenant from any obligations of Tenant,  but shall not be obligated to,
make such  payment or perform  such act if Tenant does not cure such  failure to
pay within [*] after delivery of written notice by Landlord. All sums so paid or
incurred by Landlord,  together with interest  thereon,  from the date such sums
were paid or incurred, at the annual rate equal to [*] per annum or highest rate
permitted by law,  whichever is less,  shall be payable to Landlord on demand as
Additional Rent.

     24.4.  The  occurrence  of any one or more of the  following  events  shall
constitute a "DEFAULT" hereunder by Tenant:

          24.4.1 The abandonment or vacation of the Demised  Premises by Tenant,
unless  Tenant  shall  continue  to pay  Rent  and  perform  all  of  its  other
obligations in accordance with the terms of this Lease;

          24.4.2 The  failure by Tenant to make any  payment of Rent as and when
due, and such failure continues for more than [*] following receipt by Tenant of
written notice of such failure (provided,  however, that no such notice shall be
required in the event that  Landlord has given [*] such notices to Tenant within
the preceding 365 day period);

          24.4.3 The failure by Tenant to observe or perform any  obligation  or
covenant contained herein (other than described in Section 24.4.1 and 24.4.2) to
be performed by Tenant,  where such failure  shall  continue for a period of [*]
after written  notice  thereof from Landlord to Tenant.  Such notice shall be in
lieu of, and not in  addition  to,  any  notice  required  under  Maryland  law;
provided  that if the  nature of  Tenant's  Default  is such that it  reasonably
requires more than [*] to cure, then Tenant shall not be deemed to be in Default
if Tenant  shall  commence  such cure  within  said [*]  period  and  thereafter
diligently prosecutes the same to completion;

          24.4.4 Tenant makes an assignment for the benefit of creditors;

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.

                                       31
<PAGE>


          24.4.5 A receiver, trustee or custodian is appointed to, or does, take
title, possession or control of all, or substantially all, of Tenant's assets;

          24.4.6 Tenant files a voluntary petition under the Bankruptcy Code (or
any similar law) or an order for relief is entered  against Tenant pursuant to a
voluntary  or  involuntary   proceeding  commenced  under  any  chapter  of  the
Bankruptcy Code;

          24.4.7 Any involuntary  petition is filed against the Tenant under any
chapter of the Bankruptcy Code and is not dismissed within ninety (90) days; or

          24.4.8 Tenant's interest in this Lease is attached,  executed upon, or
otherwise  judicially  seized and such action is not released within ninety (90)
days of the action.

Notices  given under this  Section  24.4 shall  specify the alleged  Default and
shall demand that Tenant  perform the  provisions  of this Lease or pay the Rent
that is in arrears, as the case may be, within the applicable period of time, or
quit the Demised  Premises.  No such notice  shall be deemed a  forfeiture  or a
termination of this Lease unless Landlord elects otherwise in such notice.

     24.5. In the event of a Default by Tenant, and 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, Landlord shall be entitled to terminate
Tenant's  right to  possession of the Demised  Premises by any lawful means,  in
which case this Lease shall  terminate  and Tenant shall  immediately  surrender
possession of the Demised  Premises to Landlord.  In such event,  Landlord shall
have the immediate  right to re-enter and remove all persons and  property,  and
such  property  may be removed and stored in a public  warehouse or elsewhere at
the cost of, and for the  account of Tenant,  all  without  service of notice or
resort to legal process and without being deemed guilty of trespass, or becoming
liable for any loss or damage which may be occasioned thereby. In the event that
Landlord shall elect to so terminate this Lease, then Landlord shall be entitled
to recover  from Tenant all  damages  incurred by Landlord by reason of Tenant's
default, including:

          24.5.1  The worth at the time of award of any  unpaid  Rent  which had
been earned at the time of such termination;

          24.5.2  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 that  portion of such rental loss which Tenant  proves could have
been reasonably avoided; plus

          24.5.3  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  which  Tenant  proves  could  have been or can be
reasonably avoided; plus

          24.5.4 Any other amount  necessary to compensate  Landlord for all the
detriment proximately caused by Tenant's failure to perform its obligation under
this Lease or which in the  ordinary  course of things would be likely to result


                                       32
<PAGE>


therefrom,  including,  but not  limited to, the cost of  restoring  the Demised
Premises to the condition required under the terms of this Lease.

As used in Sections 24.5.1 and 24.5.2 above,  "worth at the time of award" shall
mean an award of money damages by a court of competent jurisdiction and shall be
computed by  allowing  interest at the rate  specified  in the last  sentence of
Section 24.1. As used in Section  24.5.3,  "worth at the time of award" shall be
computed by taking the present value of such amount,  by using the discount rate
of the Federal  Reserve Bank of San  Francisco at the time of the award plus [*]
percentage points.

     24.6.  If Landlord  does not elect to  terminate  this Lease as provided in
this  Section,  then  Landlord  may,  from time to time,  recover all Rent as it
becomes  due under this Lease.  At any time  thereafter,  Landlord  may elect to
terminate this Lease and to recover damage to which Landlord is entitled.

     24.7. In the event  Landlord  elects to terminate  this Lease and relet the
Demised Premises, it may execute any new lease in its own name. Tenant hereunder
shall  have no right or  authority  whatsoever  to  collect  any Rent  from such
tenant. The proceeds of any such reletting shall be applied as follows:

          FIRST,  to the  payment  of  any  indebtedness  other  than  Rent  due
     hereunder from Tenant to Landlord  pursuant to this Lease,  including,  but
     not limited to, storage charges or brokerage  commissions owing from Tenant
     to Landlord as the result of such reletting;

          SECOND,  to the  payment of the costs and  expenses of  reletting  the
     Demised  Premises,  including  alterations and repairs which Landlord deems
     reasonably necessary and advisable and reasonable  attorneys' fees, charges
     and  disbursements  incurred by Landlord in connection with the retaking of
     the Demised Premises and such reletting;

          THIRD,  to the  payment  of Rent  and  other  charges  due and  unpaid
     hereunder; and

          FOURTH,  to the  payment of future Rent and other  damages  payable by
     Tenant under this Lease.

     24.8. All rights, options, and remedies of Landlord contained in this Lease
shall be construed and held to be nonexclusive  and  cumulative.  Landlord shall
have the right to pursue any one or all of such rights,  options and remedies or
any other remedy or relief  which may be provided by law,  whether or not stated
in this  Lease.  No waiver of any default of Tenant  hereunder  shall be implied
from any  acceptance by Landlord of any Rent or other  payments due hereunder or
any  omission by Landlord to take any action on account of such  default if such
default  persists or is repeated,  and no express  waiver shall affect  defaults
other than as specified in said waiver. Landlord hereby waives all statutory and
common law rights of distraint available under applicable law.

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.



                                       33
<PAGE>


     24.9.  Termination  by Landlord of (i) this Lease or (ii) Tenant's right to
possession of the Demised  Premises  shall not relieve Tenant from any liability
to Landlord which has theretofore accrued or shall arise based upon events which
occurred prior to the last to occur of (y) the date of Lease  termination or (z)
the date possession of Demised Premises is surrendered.

     24.10.  The occurrence of any of the following shall constitute a "Landlord
Default" hereunder:

          24.10.1  Landlord shall have failed to pay when due any sum owing from
Landlord to Tenant  hereunder,  and such failure shall  continue for a period of
more than [*] after Tenant delivers notice to Landlord of such failure; or

          24.10.2 Except as otherwise  specifically  excused as provided in this
Lease,  the  neglect  or failure of  Landlord  to perform or observe  any of the
terms,  covenants or conditions contained in this Lease on Landlord's part to be
performed or observed which is not remedied by Landlord  within [*] after Tenant
shall have given to Landlord notice specifying such neglect or failure, provided
that,  for any neglect or failure  which cannot  reasonably be cured within such
[*], the cure period  therefor  shall be extended for such time as is reasonably
necessary to effect a cure of such neglect or failure,  on the  conditions  that
Landlord immediately commences and diligently pursues such cure to completion.

          24.10.3  In the  event  of any  Landlord  Default,  Tenant  shall,  in
addition to any other remedy  available  hereunder or at law or in equity,  have
the right of injunction  and the right to invoke any remedy allowed at law or in
equity, including specific performance, injunctive relief, reasonable attorneys'
fees and damages arising from all damages incurred by Tenant as a result of such
Landlord Default  (including costs of mitigation),  and mention in this Lease of
any particular  remedy shall not preclude Tenant from any other remedy at law or
in equity.  Tenant  shall not have the right to offset  against  or deduct  from
installments of Rent any amounts  allegedly owed to Tenant pursuant to any claim
of Tenant against Landlord.

     24.11.  In the event of any  Landlord  Default,  Tenant will give notice by
registered or certified mail to any  beneficiary of a deed of trust or mortgagee
of a mortgage  covering the Demised Premises and to any landlord of any lease of
any building in which Demised  Premises is located whose address shall have been
furnished, and Tenant shall offer such beneficiary,  mortgagee and/or landlord a
reasonable opportunity to cure the default,  including time to obtain possession
of the  Building  by power of sale or a  judicial  action if such  should  prove
necessary  to effect a cure,  provided  that  Landlord  shall have  furnished to
Tenant in writing the names and addresses of all such persons who are to receive
such notices.

25.  ASSIGNMENT OR SUBLETTING.

     25.1. Except as hereinafter provided,  Tenant shall not, either voluntarily
or by operation  of law,  directly or  indirectly,  sell,  hypothecate,  assign,
pledge,  encumber  or  otherwise  transfer  this  Lease,  or sublet the  Demised

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       34
<PAGE>


Premises or any part  thereof,  or permit or suffer the Demised  Premises or any
part  thereof to be used or  occupied  as work  space,  storage  space,  mailing
privileges,  concession  or  otherwise  by anyone  other than Tenant or Tenant's
employees, without the prior written consent of Landlord in each instance, which
consent shall not be unreasonably withheld, conditioned or delayed.

     25.2.  In the event  Tenant  desires to assign,  sublease,  hypothecate  or
otherwise transfer this Lease or sublet the Demised Premises, then at least [*],
but not more than [*],  prior to the date when Tenant  desires the assignment or
sublease to be effective (the "ASSIGNMENT  DATE"),  Tenant shall give Landlord a
notice (the "ASSIGNMENT NOTICE") containing  information  (including references)
concerning the character of the proposed  assignee or sublessee,  the Assignment
Date, any ownership or commercial  relationship  between Tenant and the proposed
assignee or sublessee,  and the  consideration  and all other material terms and
conditions  of the  proposed  assignment  or  sublease  along  with  such  other
information as Landlord may reasonably  require,  all in such detail as Landlord
shall reasonably require.

     25.3.  Landlord in making its determination as to whether consent should be
given to a proposed  assignment  or sublease,  shall give  consideration  to the
financial  strength of such successor  (notwithstanding  the assignor  remaining
liable for  Tenant's  performance)  and any  change in use which such  successor
proposes to make of the Demised  Premises.  In no event shall Landlord be deemed
to be  unreasonable  for declining to consent to transfer to a successor of poor
reputation, lacking financial qualifications,  or seeking a change in use of the
Demised Premises.

     25.4. As conditions  precedent to Landlord  considering a request by Tenant
to Tenant's transfer of rights or subletting of the Demised  Premises,  Landlord
may require any or all of the following:

          25.4.1  Tenant  shall  remain fully liable under this Lease during the
unexpired Term;

          25.4.2 Tenant shall reimburse Landlord for Landlord's actual costs and
expenses, including, without limitation, reasonable attorneys' fees, charges and
disbursements   incurred  in  connection   with  the  review,   processing   and
documentation of such request;

          25.4.3 Written agreement from any sublessee that in the event Landlord
gives such third party notice that Tenant is in Default  under this Lease,  such
third party shall,  during the  continuance  of such Default,  make all payments
otherwise due Tenant  directly to Landlord,  which  payments will be received by
Landlord without any liability on Landlord except to credit such payment against
those due under the Lease,  and any such third  party  shall  agree to attorn to
Landlord or its  successors  and assigns should this Lease be terminated for any
reason;

          25.4.4  Any such  transfer  and  consent  shall be  effected  on forms
reasonably approved by Landlord;

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       35
<PAGE>

          25.4.5 Tenant shall not then be in Default hereunder;

          25.4.6 Such third party's  proposed use of the Demised  Premises shall
be substantially the same as Tenant's use;

          25.4.7 Any agreement  pertaining to Tenant's transfer of this Lease or
subletting of any portion of the Demised  Premises shall be in a form reasonably
acceptable to Landlord,  and Landlord shall not be bound by any  modification or
amendment made without  Landlord's prior written consent,  which may be withheld
in Landlord's reasonable discretion;

          25.4.8 Tenant shall deliver to Landlord one original  executed copy of
any and all written  instruments  evidencing or relating to Tenant's transfer of
rights or subletting of the Demised Premises; and

          25.4.9  A list  of  Hazardous  Materials,  certified  by the  proposed
sublessee to be true and correct, which the proposed sublessee intends to use or
store in the Demised Premises.  Additionally,  Tenant shall deliver to Landlord,
on or before the date any  proposed  sublessee  takes  occupancy  of the Demised
Premises,  all of the items  relating to Hazardous  Materials  of such  proposed
sublessee as described in Article 41 below.

          25.4.10 Evidence with respect to the business  experience,  reputation
and financial responsibility of the third party concerned.

     25.5.  Any sale,  assignment,  hypothecation  or  transfer of this Lease or
subletting of the Demised Premises that is not in compliance with the provisions
of this Article 25 shall be void.

     25.6.  The consent by Landlord to an  assignment  or  subletting  shall not
relieve  Tenant or any  assignees  of this  Lease or  sublessee  of the  Demised
Premises  from  obtaining  the consent of Landlord to any further  assignment or
subletting  nor shall it release  Tenant or any  assignee or sublessee of Tenant
from full and primary liability under this Lease.

     25.7.  In the  event of any  subletting,  Tenant  shall  remain  fully  and
primarily  liable for the  payment of all Rent and other sums due,  or to become
due hereunder, and for the full performance of all other terms, conditions,  and
covenants to be kept and  performed  by Tenant.  The  acceptance  of Rent or any
other sum due  hereunder,  or the  acceptance of  performance of any other term,
covenant,  or  condition  thereof,  from any other person or entity shall not be
deemed to be a waiver of any of the provisions of this Lease or a consent to any
subletting of the Demised Premises.

     25.8.  Notwithstanding  anything to the  contrary set forth in this Article
25, Tenant shall have the right,  upon prior written  notice to Landlord in each
instance  but without the  necessity  of obtaining  Landlord's  consent,  to (i)
assign or otherwise  transfer  this Lease or any of its rights  hereunder,  (ii)
sublet the Demised  Premises or any part  thereof,  (iii)  permit the use of the
Demised  Premises or any part  thereof by any  persons  other than Tenant or its
employees,  agents or invitees, and (iv) permit the assignment or other transfer


                                       36
<PAGE>


of this Lease or any of Tenant's  rights  hereunder by operation of law, in each
case if the proposed  assignee or subtenant is an Affiliate or Successor  Entity
of Tenant.  "Affiliate"  shall mean any entity  which,  directly or  indirectly,
controls  or is  controlled  by or is under  common  control  with  Tenant.  For
purposes  of the  definition  of  "Affiliate,"  the  word  "Control"  (including
"Controlling",  "Controlled  by" and "under common Control with") shall mean the
possession,  directly  or  indirectly,  of the  power to  direct  or  cause  the
direction of the management and policy of a particular  entity,  whether through
the  ownership  of voting  securities,  by contract or  otherwise.  A "Successor
Entity" shall mean (x) an entity into which or with which Tenant, its successors
or assigns, is merged,  amalgamated or consolidated,  or (y) an entity acquiring
this Lease for the term hereby demised,  the good will and all or  substantially
all of the other property and assets of Tenant,  its successors or assigns,  and
assuming all or substantially  all of the liabilities of Tenant,  its successors
and assigns.

     25.9.  Notwithstanding anything to the contrary in this Lease, Tenant shall
have  the  right,   without  obtaining  the  consent  of  Landlord,   to  permit
office-sharing  arrangements  pursuant  to which  clients or  subcontractors  of
Tenant may use space in the Premises.

26.  ATTORNEYS' FEES AND COSTS.

     26.1. If either party  commences an action  against the other party arising
out of or in connection with this Lease,  the prevailing party shall be entitled
to have and recover from the  non-prevailing  party reasonable  attorneys' fees,
charges and disbursements and costs of suit.

27.  BANKRUPTCY.

     27.1. In the event a debtor,  trustee,  or debtor in  possession  under the
Bankruptcy  Code, or other person with similar  rights,  duties and powers under
any other law,  proposes  to cure any  default  under this Lease or to assume or
assign this Lease,  and is obliged to provide  adequate  assurances  to Landlord
that (i) a default will be cured,  (ii)  Landlord  will be  compensated  for its
damages arising from any breach of this Lease, or (iii) future performance under
this Lease will occur, then adequate  assurances shall include any or all of the
following:

          27.1.1  Those acts  specified in the  Bankruptcy  Code or other law as
included within the meaning of adequate  assurance,  even if this Lease does not
concern a shopping center or other facility described in such laws;

          27.1.2 A prompt cash payment to  compensate  Landlord for any monetary
defaults or actual damages arising directly from a breach of this Lease;

          27.1.3 A cash  deposit  in an  amount at least  equal to the  Security
Deposit as referenced in Section 2.1.8.


                                       37
<PAGE>


          27.1.4 The  assumption or  assignment of all of Tenant's  interest and
obligations under this Lease.

28.  ESTOPPEL CERTIFICATE.

     Tenant  shall  within  [*]  of  written  notice  from  Landlord,   execute,
acknowledge  and  deliver  a  statement  in  writing  substantially  in the form
attached  to this  Lease as EXHIBIT  "F" with the  blanks  filled in, and on any
other  form  reasonably  requested  by  a  proposed  lender  or  purchaser,  (i)
certifying  that this Lease is  unmodified  and in full force and effect (or, if
modified, stating the nature of such modification and certifying that this Lease
as so  modified  is in full force and  effect) and the dates to which the rental
and other charges are paid in advanced,  if any, (ii)  acknowledging  that there
are not, to  Tenant's  knowledge,  any uncured  defaults on the part of Landlord
hereunder,  or  specifying  such  defaults if any are claimed and (iii)  setting
forth  such  further  information  with  respect  to this  Lease or the  Demised
Premises as may  reasonably  be requested  thereon.  Any such  statement  may be
relied upon by any  prospective  purchaser or encumbrancer of all or any portion
of the real property of which the Demised Premises are a part.  Tenant's failure
to deliver  such  statement  within such time shall,  at the option of Landlord,
constitute a Default  under this Lease,  and, in any event,  shall be conclusive
upon Tenant that the Lease is in full force and effect and without  modification
except as may be represented by Landlord in any certificate prepared by Landlord
and delivered to Tenant for execution.

29.  JOINT AND SEVERAL OBLIGATIONS

     29.1. If more than one person or entity executes this Lease as Tenant,

          29.1.1 Each of them is jointly and  severally  liable for the keeping,
observing and performing of all of the terms, covenants, conditions,  provisions
and agreements of this Lease to be kept, observed and performed by Tenant, and

          29.1.2 The term  "TENANT" as used in this Lease shall mean and include
each of them jointly and severally.  The act of, notice from,  notice to, refund
to, or the signature of, any one or more of them, with respect to the tenancy of
this Lease, including, but not limited to, any renewal,  extension,  expiration,
termination or modification of this Lease, shall be binding upon each and all of
the persons  executing this Lease as Tenant with the same force and effect as if
each and all of them had so acted, so given or received such notice or refund or
so signed.

30.  DEFINITION OF LANDLORD; LIMITATION OF LANDLORD'S LIABILITY.

     30.1.  The term  "LANDLORD"  as used in this Lease,  so far as covenants or
obligations on the part of Landlord are concerned,  shall be limited to mean and
include only Landlord or the  successor-in-interest of Landlord under this Lease
at the  time in  question.  In the  event  of any  transfer,  assignment  or the
conveyance of Landlord's fee title or leasehold  interest,  the landlord  herein
named (and in case of any subsequent transfers or conveyances, the then grantor)
shall be  automatically  freed  and  relieved  from,  and after the date of such

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       38
<PAGE>


transfer,  assignment or conveyance, of all liability for the performance of any
covenants or obligations  contained in this Lease  thereafter to be performed by
Landlord  and,  without  further  agreement,  the  transferee  of such  title or
leasehold  shall be deemed to have assumed and agreed to observe and perform any
and all obligations of Landlord  hereunder  during its ownership or ground lease
of the Demised  Premises.  Subject to Tenant's  rights under  Section 43 hereof,
Landlord may transfer its interest in the Demised Premises or this Lease without
the consent of Tenant and such  transfer  or  subsequent  transfer  shall not be
deemed a violation  on the part of  Landlord  or the then  grantor of any of the
terms or  conditions  of this Lease.  If on the date of transfer,  assignment or
conveyance of Landlord's fee title interest in the Project all or any portion of
the Tenant Improvement Allowance (as such term is defined in EXHIBIT "D") or the
Loan Amount has not been disbursed by Landlord to Tenant, Landlord shall, on the
date of such transfer, deposit such undisbursed Tenant Improvement Allowance and
Loan Amount with an escrow agent reasonably  satisfactory to Tenant which escrow
agent   shall   enter  in  to  an  escrow   agreement   with   Tenant   and  the
successor-in-interest  to Landlord pursuant to which the escrowed funds shall be
disbursed to Tenant in  accordance  with and subject to the terms of EXHIBIT "D"
and the Loan Agreement which shall be incorporated  into the escrow agreement by
reference.

     30.2. If Landlord is in default of this Lease, and as a consequence, Tenant
recovers a money  judgment  against  Landlord,  such judgment shall be satisfied
only out of the proceeds of sale  received on execution of the judgment and levy
against the right,  title and  interest of Landlord in the Building and Project,
and out of rent or other income from such real  property  receivable by Landlord
or out of the  consideration  received  by  Landlord  from the sale,  financing,
refinancing, or other disposition of all or any part of Landlord's right, title,
and interest in the Building and Project.

     30.3.  Landlord  shall not be  personally  liable  for any  deficiency.  If
Landlord is a partnership  or joint  venture,  the partners of such  partnership
shall not be personally liable and no partner of Landlord shall be sued or named
as a party in any suit or action or  service  of  process  be made  against  any
partner of Landlord  except as may be  necessary to secure  jurisdiction  of the
partnership or joint venture.  If Landlord is a corporation,  the  shareholders,
directors,  officers,  employees, and/or agents of such corporation shall not be
personally liable and no shareholder,  director,  officer,  employee or agent of
Landlord  shall be sued or named as a party in any suit or action or  service of
process made against any shareholder,  director,  officer,  employee or agent of
Landlord.  No partner,  shareholder,  director,  employee,  or agent of Landlord
shall be required to answer or otherwise  plead to any service of process and no
judgment  will be  taken  or writ  of  execution  levied  against  any  partner,
shareholder,  director, employee or agent of Landlord. Nothing contained in this
Section 30.3 shall  restrict  Tenant from  commencing a legal action against any
person  described in this Section 30.3 seeking to obtain a return of any amounts
distributed to or otherwise received by such person from and after the date that
Tenant  first  made a  written  demand  upon  Landlord  for  such  amounts.  The
immediately  preceding sentence shall not be applicable to shareholders or other
owners (in such capacity) so long as the stock of Landlord is publicly traded.


                                       39
<PAGE>


     30.4.  Each of the  covenants  and  agreements  of this Article 30 shall be
applicable to any covenant or agreement either expressly contained in this Lease
or imposed by statute or by common law and shall survive the termination of this
Lease.

31.  PROJECT CONTROL BY LANDLORD.

     31.1.  Landlord  reserves full control over the Building and the Project to
the extent not inconsistent with Tenant's enjoyment of the Demised Premises, the
obligations of Landlord to Tenant under the terms of this Lease, or Section 31.4
below.  This  reservation  includes  but is not limited to,  subject to Tenant's
rights under this Lease,  the right of Landlord to expand the  Project,  and the
right to grant  easements  and  licenses to others.  Landlord's  reservation  of
rights  does not  include  the rights to  subdivide  the Project or the right to
convert the Building to condominium units.

     31.2. Tenant shall, should Landlord so request, promptly join with Landlord
in  execution  of such  documents  as may be  reasonably  appropriate  to assist
Landlord to implement any such action, provided that Tenant need not execute any
document  which is of nature  wherein  liability  is created in Tenant or, if by
reason of the  terms of such  document,  Tenant  will be  deprived  of the quiet
enjoyment and use of the Demised Premises as granted by this Lease.

     31.3. Except in the event of an emergency,  Landlord or its designees shall
be permitted to enter the Demised Premises upon at least twenty-four (24) hours'
prior written notice to Tenant,  accompanied by an agent of Tenant designated by
Tenant for such purpose to (a) inspect the same and to determine  whether Tenant
is in compliance with its obligations hereunder, (b) supply any service Landlord
is required to provide  hereunder,  (c) show the Demised Premises to prospective
lenders, insurers,  investors,  purchasers or, during the last year of the Term,
tenants,  (d) post  notices  of  nonresponsibility,  (e)  access  the  telephone
equipment,  electrical  substation  and fire risers,  and (f) alter,  improve or
repair any  portion of the  Building  other than the Demised  Premises,  but for
which access to the Demised  Premises is necessary.  In connection with any such
alteration, improvement or repair, Landlord may erect in the Demised Premises or
elsewhere  in the  Building  or the  Project  scaffolding  and other  structures
reasonably  required for the work to be  performed.  In no event shall  Tenant's
Rent  abate  as a result  of any such  entry  or  work;  PROVIDED,  HOWEVER,  in
connection with any such entry,  Landlord shall  coordinate with Tenant in order
to minimize the disruption to Tenant's use of the Demised Premises. In the event
of an  emergency,  Landlord or its  designees  shall be  permitted  to enter the
Demised Premises unaccompanied and without notice;  provided that Landlord shall
have, prior to such entry, used diligent efforts to have a Tenant representative
accompany Landlord or its designee;  Landlord hereby acknowledging that Tenant's
use of the Demised  Premises  includes  the storage  and  handling of  Hazardous
Materials  and  biologic  agents  and that  Landlord's  entry  into the  Demised
Premises  without  a  Tenant   representative   will  be  at  Landlord's  peril.
Notwithstanding  anything to the contrary set forth in this Lease, Landlord will
not be permitted access to areas  previously  designated in writing by Tenant as
security  areas,  unless Landlord or its  representatives  are accompanied by an
agent of Tenant  designated  by Tenant for such purpose.  Landlord  shall at all
times  retain  a key with  which  to  unlock  all of the  doors  in the  Demised
Premises. If an emergency necessitates immediate access to the Demised Premises,
Landlord may use whatever  force is necessary to enter the Demised  Premises and


                                       40
<PAGE>


any such entry to the  Demised  Premises  shall not  constitute  a  forcible  or
unlawful  entry to the Demised  Premises,  an  unlawful  detainer of the Demised
Premises,  or an eviction of Tenant  from the Demised  Premises,  or any portion
thereof. Any access by Landlord or its agents and invitees hereunder,  including
access in the event of an emergency,  shall be subject to  compliance  with such
reasonable  confidentiality and security procedures as are reasonably imposed on
Tenant's  business  operations  and  Tenant's  standard  operating   procedures.
Landlord reserves the right,  after consultation with Tenant, to stop service of
a Building  system when  necessary  by reason of accident  or  emergency.  It is
expressly understood and agreed that any covenants on Landlord's part to furnish
any  service or system or to  perform  any act shall not be deemed  breached  if
Landlord is unable to do so by reason of unavoidable delays.

     31.4. Notwithstanding anything contained in this Article 31, Landlord shall
not  commence  construction  of the  Expansion  Space (as defined in Section 40)
during the initial [*] of the Term without the prior written  consent of Tenant,
which  consent  shall be granted in Tenant's  sole and absolute  discretion.  If
Landlord  desires to develop the  Expansion  Space at any time after the initial
[*] of the Term, Landlord may do so subject to the terms of Article 40 hereof.

32.  QUIET ENJOYMENT.

     So long as Tenant is not in Default,  Landlord  covenants  that Landlord or
anyone acting through or under Landlord will not disturb  Tenant's  occupancy of
the Demised Premises except as permitted by the provisions of this Lease.

33.  QUITCLAIM DEED.

     Tenant shall  execute and deliver to Landlord on the  expiration or earlier
termination  of this Lease,  immediately  on Landlord's  request,  in recordable
form,  a  quitclaim  deed to the Demised  Premises  or such other  documentation
reasonably requested by Landlord evidencing termination of this Lease.

34.  RULES AND REGULATIONS.

     Tenant shall  faithfully  observe and comply with the Rules and Regulations
attached  hereto  as  Exhibit  "E"  and  all  reasonable  and  nondiscriminatory
modifications thereof and additions thereto from time to time put into effect by
Landlord.  Landlord  shall not be  responsible  to Tenant for the  violation  or
non-performance by any other tenant or any agent, employee or invitee thereof of
any of said Rules and Regulations.

35.  SUBORDINATION AND ATTORNMENT.

     35.1.  This  Lease  shall be  subject  and  subordinate  to the lien of any
mortgage,  deed of trust,  ground  lease,  master  lease or other lease in which
Landlord is tenant  which may  hereafter  encumber  the Project or the  Building
(collectively,  "Mortgages"),  and to all advances  made or hereafter to be made

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       41
<PAGE>


upon the  security  thereof,  provided  that Tenant  receives a  non-disturbance
agreement  from any holder of a Mortgage (a  "Mortgagee")  in form and substance
reasonably  satisfactory to Tenant. In the event that Landlord does not secure a
Nondisturbance  Agreement  from a future  Mortgagee,  this Lease shall be deemed
senior in priority to such future Mortgage held by such future Mortgagee.

     35.2.  Notwithstanding  Section 35.1, Tenant shall execute and deliver upon
demand such further  instrument or instruments  evidencing such subordination of
this Lease to any such  Mortgage  as may be  reasonably  required  by  Landlord.
However,  if any such  Mortgagee  or landlord  under lease  wherein  Landlord is
tenant so elects,  this Lease shall be deemed prior in lien to any such lease or
mortgage,  regardless  of date and Tenant will execute a statement in writing to
such effect at  Landlord's  request.  If Tenant  fails to execute  any  document
required from Tenant under this Section  within  fifteen (15) days after written
request therefor, Tenant hereby constitutes and appoints Landlord or its special
attorney-in-fact  to execute and deliver any such  document or  documents in the
name of Tenant. Such power is coupled with an interest and is irrevocable.

     35.3. In the event any proceedings are brought for  foreclosure,  or in the
event of the  exercise  of the  power of sale  under  any  Mortgage  made by the
Landlord  covering  the Demised  Premises,  Tenant  shall at the election of the
purchaser  at such  foreclosure  or sale attorn to the  purchaser  upon any such
foreclosure or sale and recognize such purchaser as Landlord under this Lease.

     35.4. Landlord hereby represents and warrants to Tenant that as of the date
hereof there is no Mortgage,  ground lease, master lease or other lease in which
Landlord is tenant.

36.  SURRENDER.

     36.1. No surrender of possession of any part of the Demised  Premises shall
release  Tenant  from  any of  its  obligations  hereunder  unless  accepted  by
Landlord.

     36.2.  The  voluntary or other  surrender of this Lease by Tenant shall not
work a merger,  unless  Landlord  consents and shall, at the option of Landlord,
operate as an assignment to it of any or all subleases or subtenancies.

     36.3.  The voluntary or other  surrender of any ground or underlying  lease
that now exists or may  hereafter  be  executed  affecting  the  Building or the
Project, or a mutual  cancellation,  thereof, or of Landlord's interest therein,
shall not work a merger and shall,  at the option of the successor of Landlord's
interest in the Building or Project, operate as an assignment of this Lease.

     36.4.  Upon the  expiration or earlier  termination  of this Lease,  Tenant
shall surrender the Demised Premises to Landlord broom clean and free of debris;
with all of Tenant's  personal  property and effects  removed  therefrom and all
damage as a result of or caused by such removal repaired; and with all licenses,
permits  and  similar  items  which  restrict  or affect the use of the  Demised
Premises released and fully terminated.


                                       42
<PAGE>


37.  WAIVER AND MODIFICATION.

     No provision  of this Lease may be modified,  amended or added to except by
an  agreement  in  writing.  The waiver by  Landlord  of any breach of any term,
covenant or condition herein contained shall not be deemed to be a waiver of any
subsequent  breach of the same or any other term,  covenant or condition  herein
contained.

38.  WAIVER OF JURY TRIAL AND COUNTERCLAIMS.

     THE  PARTIES  HERETO  SHALL AND THEY  HEREBY DO WAIVE  TRIAL BY JURY IN ANY
ACTION,  PROCEEDING  OR  COUNTERCLAIM  BROUGHT BY EITHER OF THE  PARTIES  HERETO
AGAINST  THE  OTHER  ON ANY  MATTERS  WHATSOEVER  ARISING  OUT OF OR IN ANY  WAY
CONNECTED WITH THIS LEASE, THE RELATIONSHIP OF LANDLORD AND TENANT, TENANT'S USE
OR OCCUPANCY OF THE DEMISED PREMISES, AND OR ANY CLAIM OF INJURY OR DAMAGE.

39.  TENANT'S PURCHASE OPTION.

     Tenant shall have the option (the "PURCHASE OPTION") during the Term of the
Lease and any  extensions  thereto,  to purchase the Project upon the  following
terms and conditions:

     39.1. The price for the Project  payable by Tenant to Landlord  pursuant to
the  Purchase  Option shall be equal to [*]

     39.2.  In the event that Tenant  desires to purchase  the  Project,  Tenant
shall  deliver to  Landlord  written  notice (the  "OPTION  NOTICE") of Tenant's
intent to buy the  Project.  Landlord  and Tenant  shall  within  [*]  following
determination  of the [*]  pursuant  to  Section  39.2.1  enter  into a  written
purchase  agreement in  substantially  the form  attached as EXHIBIT "G" hereto,
with respect to the Project  incorporating  the terms  described in Section 39.1
and providing for a closing date that is neither more than [*] nor less than [*]
after the date of the  execution of the purchase  agreement by both Landlord and
Tenant. If Landlord does not timely (i) execute and deliver a purchase agreement
as contemplated by this Section 39.2 or (ii) perform under the terms of any such
purchase agreement, Tenant shall have the right to pursue all remedies available
to  Tenant  at  law or in  equity,  including  specific  performance  and  other
injunctive relief.

          39.2.1 For purposes of determining  the [*] to be employed in Section
39.1, each of Landlord and Tenant shall designate an independent,  licensed real
estate  appraiser  within ten (10) days after  delivery  by Tenant of the Option
Notice.  Each such real  estate  appraiser  shall have more than five (5) years'
experience as a real estate appraiser specializing in commercial leasing and who
shall be familiar with the commercial real estate

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       43
<PAGE>


market in which the  Project  is  located.  Said  appraisers  shall  each make a
determination  of the  appropriate  [*] within [*] after being  designated.  [*]
Landlord and Tenant shall each bear the cost of its appraiser.

     39.3. Notwithstanding the above, the Purchase Option shall not be in effect
and may not be exercised by Tenant during [*];  provided,  however,  that in the
event that  Tenant  extends  the  maturity  date of the loan made by Landlord to
Tenant pursuant to the Loan Agreement,  the date on and after which the Purchase
Option may be exercised by Tenant shall be extended [*] for every [*]  extension
of the loan maturity date.

     39.4.  The Purchase  Option shall  terminate  and be of no further force or
effect upon the expiration or earlier termination of the Lease.

     39.5. Upon request by Tenant,  Landlord shall execute and deliver to Tenant
a memorandum  of purchase  option (the  "Memorandum")  in recordable  form.  The
Memorandum  shall not set forth the method to be used to determine  the purchase
price and shall  otherwise be in form and substance  reasonably  satisfactory to
Landlord. Tenant shall have the right, at its sole cost and expense, to have the
Memorandum recorded in the appropriate governmental records.

40.  RIGHT TO EXPAND.

     Tenant shall have the right, but not the obligation,  to expand the Demised
Premises (the "EXPANSION  RIGHT") to include the as yet  undeveloped  additional
space which may be  constructed  in the Project on land adjacent to the Building
(the "EXPANSION SPACE"), upon the following terms and conditions:

     40.1. In the event that Landlord desires to lease all or any portion of the
Expansion Space, Landlord shall deliver to Tenant written notice (the "EXPANSION
NOTICE") of the  availability of such portion of the Expansion  Space,  together
with the terms and conditions upon which Landlord is prepared to lease to Tenant
such portion of the Expansion Space and reasonably  detailed  architectural  and
engineering  reports with respect to the proposed Expansion Space.  Tenant shall
have [*]  following  delivery  of the  Expansion  Notice to deliver to  Landlord
written  notification  ("Expansion  Notice  Response")  of either  (i)  Tenant's
exercise  of the  Expansion  Right and  agreement  to lease such  portion of the
Expansion  Space upon the terms and  conditions  of the Expansion  Notice,  (ii)
Tenant's  election to develop the Expansion Space itself as more fully described
in Section  40.2 below  ("Tenant's  Development  Election"),  or (iii)  Tenant's
rejection of the Expansion  Notice.  In the event Tenant fails to timely deliver
the Expansion Notice Response or pursuant thereto rejects the Expansion  Notice,
or if Landlord and Tenant are unable to agree upon any of the terms of the lease
or sale agreement for such portion of the Expansion  Space after  negotiating in
good faith,  Landlord shall have the right,  for a period of [*] thereafter,  to
lease the Expansion Space to a third

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       44
<PAGE>


party upon any terms and conditions which Landlord desires,  PROVIDED,  HOWEVER,
that,  such terms and  conditions are no more favorable to such third party than
the terms and  conditions  offered to Tenant.  If Landlord does not enter into a
lease  with  respect to the  Expansion  Space  within the [*] period  referenced
above,  Tenant shall again have all rights to lease  Expansion  Space under this
Section 40.1.

     40.2.

          40.2.1 Landlord shall not cause the commencement of any development or
construction  activity with respect to the  Expansion  Space until the date (the
"Option Date") that is the later of (i) the [*] of the Term Commencement Date or
(ii) the date on which  Tenant  shall  first  have  the  right to  exercise  the
purchase option pursuant to Section 39.

          40.2.2 At any time after the Option Date,  provided that Tenant is not
then in Default  under this Lease and  Tenant is  occupying  the entire  Demised
Premises,  Tenant may deliver to Landlord  written notice  ("TENANT'S  EXPANSION
NOTICE") of Tenant's desire to lease the Expansion Space,  together with (i) the
terms and conditions  upon which Tenant is prepared to lease the Expansion Space
and  (ii) a  reasonably  detailed  proposal  setting  forth  the  design  of the
Expansion Space.  Landlord shall notify Tenant in writing within [*] of delivery
of Tenant's  Expansion Notice as to whether Landlord wishes to develop and lease
the  Expansion  Space to Tenant on the  terms  set forth in  Tenant's  Expansion
Notice or whether Landlord  declines to develop and lease the Expansion Space to
Tenant ("Development  Notice"). If Landlord sets forth in its Development Notice
that it does not wish to go forward with  developing  and leasing the  Expansion
Space to Tenant, or if Landlord does not timely deliver the Development  Notice,
then Tenant shall have the rights set forth in Section 40.2.3 below. If Landlord
sets forth in its  Development  Notice  that it wishes to develop  and lease the
Expansion  Space to Tenant,  then  Landlord and Tenant  shall  negotiate in good
faith the terms upon which Landlord shall develop and lease the Expansion  Space
to Tenant,  including  without  limitation  the  specifications  of the building
constituting the Expansion Space  (construction of which shall be of the same or
better  quality than the  Building),  the condition of the Expansion  Space upon
delivery to Tenant,  the timing of delivery  and the terms of the lease and work
letter  applicable to the Expansion  Space. If Landlord and Tenant are unable to
agree on the terms upon which  Landlord  will  develop  and lease the  Expansion
Space to Tenant  within the [*] period  immediately  following  delivery  of the
Development  Notice,  then  Tenant  shall  have the  rights set forth in Section
40.2.3 below.

          40.2.3 In the event that (i)  Tenant  exercises  Tenant's  Development
election under Section 40.1, (ii) Landlord does not timely deliver a Development
Notice, (iii) Landlord indicates in the Development Notice that it does not wish
to develop and lease the  Expansion  Space to Tenant or (iv) Landlord sets forth
in the  Development  Notice  that it wishes to develop  and lease the  Expansion
Space to Tenant,  and Landlord and Tenant are thereafter  unable to agree on the
terms upon which  Landlord will develop and lease the Expansion  Space to Tenant
during the [*] period following delivery of the Development Notice, Tenant shall

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.



                                       45
<PAGE>


have the right to elect at any time  thereafter  during the Term to (a) purchase
the entire Project in accordance with the terms of Section 39 or (b) develop the
Expansion Space at Tenant's sole cost and expense.

          40.2.4  If Tenant  wishes  to elect to  develop  the  Expansion  Space
pursuant to Section  40.2.3,  Tenant shall  deliver to Landlord  written  notice
indicating  Tenant's desire to construct the Expansion Space, which notice shall
include a reasonably detailed proposal setting forth the design of the Expansion
Space. The following shall apply to Tenant's development and construction of the
Expansion Space.

          (a)  Tenant's  plans for  construction  of the  Expansion  Space shall
provide for construction of a minimum of [*] square feet of gross rentable area,
and the Expansion  Space shall be constructed  with materials of equal or better
quality than the existing Building.

          (b)  Landlord  shall  have the right to  review  Tenant's  design  and
construction  plans  and to  approve  the  same,  which  approval  shall  not be
unreasonably  withheld,  conditioned or delayed. If in addition to the Expansion
Space  proposed to be  constructed by Tenant,  the then  applicable  zoning laws
would  permit  further  expansion,  Landlord  shall  be  deemed  to  have  acted
reasonably in not approving Tenant's design and construction plans if such plans
would make it  impractical  to further  expand the  Building.  The design of the
Expansion Space must be architecturally compatible with the existing Building.

          (c) Upon  completion of construction of the Expansion Space by Tenant,
this Lease shall be amended to include the Expansion  Space,  except that Tenant
shall have no obligation  to pay rent with respect to the Expansion  Space other
than Operating Expenses.

          (d) Landlord must be reasonably  assured that the  construction of the
Expansion Space will be completed in a timely fashion.

          (e) Tenant shall indemnify and hold Landlord harmless from and against
any and all liabilities,  losses, costs, expenses,  claims, demands, damages and
judgments  (including,  without limitation,  reasonable attorneys' fees, charges
and  disbursements)  arising  directly or indirectly out of the  construction by
Tenant of the Expansion Space,  unless caused by the wilful act or negligence of
Landlord.

     40.3. In the event Tenant elects to exercise the Expansion  Right  pursuant
to the Expansion  Notice  Response,  within [*] Tenant and Landlord  shall enter
into a written  amendment to the Lease (the "EXPANSION  AMENDMENT")  which shall
provide,  unless otherwise agreed in writing,  (i) the commencement  date of the
Expansion  Space;  (ii) that the  Demised  Premises  under this  Lease  shall be
increased to include the rentable square feet of the Expansion Space;  (iii) the
new Basic Annual Rent;  (iv) Tenant's new Pro Rata Share based upon the addition
of the Expansion Space to the Demised Premises;  (v) the proportionate  increase
to the Security Deposit (which shall be payable upon execution of the Expansion

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       46
<PAGE>


Amendment);  and (vi) any other terms contained in the Expansion  Notice. In all
other  respects,  this Lease shall  remain in full force and  effect,  and shall
apply to the Expansion Space.

     40.4. Notwithstanding the above, the Expansion Right shall not be in effect
and may not be exercised  by Tenant  during any period of time that Tenant is in
Default under any provision of the Lease.

41.  HAZARDOUS MATERIALS.

     41.1.  PROHIBITION/COMPLIANCE.   Tenant  shall  not  cause  or  permit  any
Hazardous Materials (as hereinafter defined) to be brought upon, kept or used in
or about the Demised  Premises,  the  Building or the  Project in  violation  of
applicable law by Tenant,  its agents,  employees,  contractors or invitees.  If
Tenant  breaches  the  obligation  stated  in  the  preceding  sentence,  or  if
contamination of the Demised Premises, the Building, the Project or any adjacent
property by Hazardous  Materials  otherwise occurs during the term of this Lease
or any extension or renewal hereof or holding over hereunder as a result of acts
or omissions of Tenant or its agents, Tenant hereby indemnifies and shall defend
and hold Landlord, its officers,  directors,  employees,  agents and contractors
harmless from any and all claims, judgments,  damages,  penalties, fines, costs,
liabilities,  or losses (including,  without limitation,  diminution in value of
the Demised Premises or any portion of the Building or the Project,  damages for
the loss or  restriction on use of rentable or usable space or of any amenity of
the Demised  Premises,  the  Building or the Project,  damages  arising from any
adverse  impact on marketing of space in the Demised  Premises,  the Building or
the Project, and sums paid in settlement of claims,  attorneys' fees, consultant
fees and expert  fees) which arise  during or after the Lease term to the extent
resulting from such  contamination.  This  indemnification of Landlord by Tenant
includes,   without   limitation,   costs   incurred  in  connection   with  any
investigation  of  site  conditions  or  any  cleanup,  remedial,   removal,  or
restoration work required by any federal,  state or local governmental agency or
political subdivision because of Hazardous Materials present in the air, soil or
ground  water  above,  on or under the Demised  Premises.  Without  limiting the
foregoing,  if the presence of any Hazardous  Materials on the Demised Premises,
the  Building,  the Project or any  adjacent  property,  caused or  permitted by
Tenant results in any contamination of the Demised Premises,  the Building,  the
Project or any adjacent property,  Tenant shall promptly take all actions at its
sole expense as are necessary to return the Demised Premises,  the Building, the
Project  or any  adjacent  property,  to the  condition  existing  prior to such
contamination,  provided that Landlord's  approval of such action shall first be
obtained,  which  approval  shall not  unreasonably  be withheld so long as such
actions would not potentially have any material adverse  long-term or short-term
effect on the Demised Premises, the Building or the Project.

     41.2.  BUSINESS.  Landlord  acknowledges  that it is not the intent of this
Article 41 to prohibit  Tenant from  operating  its  business  as  described  in
Section 2.1.9 above.  Tenant may operate its business according to the custom of
the industry so long as the use or presence of  Hazardous  Materials is strictly
and properly monitored according to all applicable governmental requirements. As
a material  inducement to Landlord to allow Tenant to use Hazardous Materials in
connection with its business,  Tenant agrees to deliver to Landlord prior to the
Rent Commencement Date a list identifying each type of Hazardous Materials to be


                                       47
<PAGE>


present on the  Demised  Premises  and  setting  forth any and all  governmental
approvals or permits  required in connection with the presence of such Hazardous
Materials on the Demised Premises  ("HAZARDOUS  MATERIALS  LIST").  Tenant shall
deliver to Landlord an updated Hazardous Materials List at least once a year and
shall also deliver an updated list before any new Hazardous Materials is brought
onto the Demised  Premises.  Tenant shall  deliver to Landlord  true and correct
copies of the following  documents (the  "DOCUMENTS")  relating to the handling,
storage,  disposal  and  emission  of  Hazardous  Materials  prior  to the  Term
Commencement  Date, or if unavailable at that time,  concurrent with the receipt
from or submission to a governmental  agency:  permits;  approvals;  reports and
correspondence;  written storage and management  plans,  notice of violations of
any  laws;  plans  relating  to the  installation  of any  storage  tanks  to be
installed in or under Building or the Project  (provided,  said  installation of
tanks  shall only be  permitted  after  Landlord  has given  Tenant its  written
consent to do so, which consent may be withheld in Landlord's  sole and absolute
discretion);  and all closure plans or any other  documents  required by any and
all  federal,  state and local  governmental  agencies and  authorities  for any
storage  tanks  installed  in, on or under the  Building  or the Project for the
closure of any such tanks. Tenant is not required,  however, to provide Landlord
with any  portion(s) of the Documents  containing  information  of a proprietary
nature which, in and of themselves,  do not contain a reference to any Hazardous
Materials  or  hazardous  activities.  It is not the  intent of this  Section to
provide  Landlord  with  information  which  could be  detrimental  to  Tenant's
business should such information  become possessed by Tenant's  competitors.  At
the  written  request of  Landlord,  Tenant  agrees  that it shall  enter into a
written  agreement  with other tenants at the Building (if any)  concerning  the
equitable  allocation of fire control areas (as defined in the Uniform  Building
Code, and adopted by the City of Columbia  ("UBC"))  within the Building for the
storage of  Hazardous  Materials.  In the event that  Tenant's  use of Hazardous
Materials is such that it utilizes  fire control areas in the Building in excess
of Tenant's Pro Rata Share of the Building as set forth in Section  2.1.6 above,
Tenant agrees that it shall, at its own expense, and upon the written request of
Landlord,  establish  and  maintain  a  separate  area of the  Demised  Premises
classified  by the UBC as an "H"  occupancy  area,  for the use and  storage  of
Hazardous  Materials,  or take such  other  action so that its share of the fire
control areas of the Building is not greater than Tenant's Pro Rata Share of the
Building.

     41.3.  TESTING. At any time, and from time to time, prior to the expiration
or  earlier  termination  of the Term (but not more  often  than [*]  during the
initial  Term and [*]  during  each  Extension  Term,  unless  Landlord,  in its
reasonable  judgment,  has a  demonstrable  basis  upon  which to  believe  that
contamination   has  occurred),   Landlord  shall  have  the  right  to  conduct
appropriate  tests of the  Demised  Premises,  the  Building  and the Project to
demonstrate that  contamination  has occurred as a result of Tenant's use of the
Demised  Premises.  Tenant  shall be solely  responsible  for and shall  defend,
indemnify and hold the Landlord,  its agents and  contractors  harmless from and
against any and all claims,  costs and liabilities  including actual  attorneys'
fees,  charges  and  disbursements,  arising  out of or in  connection  with any
removal,  clean up,  restoration and materials  required hereunder to return the
Demised  Premises and any other property of whatever  nature to their  condition
existing prior to the time of any contamination by reason of Tenant's use of the
Demised  Premises.  Tenant  shall pay for the cost of the  tests of the  Demised
Premises.

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       48
<PAGE>


     41.4.  UNDERGROUND  TANKS.  If  underground  or other storage tanks storing
Hazardous  Materials are located on the Demised Premises or are hereafter placed
on the Demised  Premises at the request of or for the benefit of Tenant,  Tenant
shall  monitor  the  storage  tanks,  maintain  appropriate  records,  implement
reporting procedures,  properly close any underground storage tanks, and take or
cause to be taken all other steps  necessary  or required  under all  applicable
local, state and federal laws and regulations as they now exist or may hereafter
be  adopted  or  amended   including  without   limitation,   Code  of  Maryland
Regulations, Title 26, Subtitle 10, Chapters 2 through 12.

     41.5.  TENANT'S  OBLIGATIONS.  Tenant's  obligations  under this Article 41
shall survive the  expiration or earlier  termination  of the Lease.  During any
period of time  employed by Tenant or  Landlord  after the  termination  of this
Lease to  complete  the  removal  from the  Demised  Premises  of any  Hazardous
Materials  brought upon,  kept or used by Tenant on the Demised  Premises during
the Term, and the release and termination of any licenses or permits restricting
the use of the Demised  Premises,  Tenant shall continue to pay the full Rent in
accordance with this Lease, which Rent shall be prorated daily.

     41.6.  DEFINITION  OF  "HAZARDOUS  MATERIALS."  As used  herein,  the  term
"HAZARDOUS  MATERIALS"  means any  pollutant,  contaminant,  hazardous  or toxic
substance,  material or waste, including,  without limitation, those that are or
become regulated by any local governmental authority,  the State of Maryland, or
the United States government.  The term "Hazardous  Material" includes,  without
limitation,  any material or substance  which is (i)  designated as a "hazardous
substance"  pursuant to Section 311 of the Federal Water  Pollution  Control Act
(33 U.S.C.  Section  1317),  (ii)  defined as a  "hazardous  waste"  pursuant to
Section 1004 of the Federal  Resource  Conversation  and Recovery Act, 42 U.S.C.
Section 6901, ET. SEQ. (42 U.S.C.  Section 6903),  (iii) defined as a "hazardous
substance" pursuant to Section 101 of the Comprehensive  Environmental  Response
Compensation  and  Liability  Act, 42 U.S.C.  Section  9601 ET. SEQ.  (42 U.S.C.
Section  9601),  (iv)  defined  as "oil"  pursuant  to Section  4-401(g)  of the
Maryland  Environmental  Code Annotated  (1993), or (v) designated as "hazardous
substance" or "hazardous  waste" pursuant to Maryland  Environmental  Code Ann.,
Title 7,  Subtitle 2 (1993),  all as amended from time to time and together with
the rules and regulations promulgated thereunder.

42.  RIGHT TO EXTEND TERM.

     Tenant  shall  have the  right to  extend  the Term of the  Lease  upon the
following terms and conditions:

     42.1.  Tenant shall have two (2)  consecutive  rights (each,  an "EXTENSION
RIGHT ") to extend  the term of this  Lease for five (5) years  each  (each,  an
"EXTENSION  TERM") on the same terms and  conditions  as the  Lease.  During any
Extension Term,  Basic Annual Rent shall be adjusted on the commencement of each
Extension Term and on each one (1) year  anniversary of the commencement of such
Extension Term in accordance with Section 6 above.


                                       49
<PAGE>


     42.2. Extension Rights are personal to North American Vaccine, Inc. and are
not  assignable  separate  and apart from this Lease  except that the  Extension
Rights shall be deemed to have been transferred to any assignee of this Lease.

     42.3.  Extension Rights are conditional upon Tenant giving Landlord written
notice of its election to exercise  each  Extension  Right at least one (1) year
prior to the end of the  expiration  of the  initial  term of this  Lease or the
expiration of any Extension Term.

     42.4.  Notwithstanding anything set forth above to the contrary,  Extension
Rights shall not be in effect and Tenant may not  exercise any of the  Extension
Rights  during any period of time that Tenant is in Default  under any provision
of this Lease.

     42.5. The period of time within which any Extension Rights may be exercised
shall  not be  extended  or  enlarged  by reason of the  Tenant's  inability  to
exercise the Extension Rights because of the provisions of Section 42.4 above.

43.  RIGHT OF FIRST OFFER TO PURCHASE.

     Tenant shall have the right (the "PURCHASE  RIGHT") to purchase the Project
upon the following terms and conditions:

     43.1.  In the event that  Landlord  desires to sell the  Project,  Landlord
shall deliver to Tenant written notice (the "SALE NOTICE") of Landlord's  intent
to sell the Project, together with the terms and conditions under which Landlord
is prepared to sell the Project. Tenant shall have [*] following delivery of the
Sale Notice to deliver to Landlord written  notification  ("Tenant's  Response")
exercising  one of the following  options (i) Tenant's  exercise of the Purchase
Right upon the terms and conditions of the Sale Notice,  (ii) Tenant's rejection
of its Purchase Right or (iii) Tenant's  desire to purchase the Project on terms
other  than those  offered  by  Landlord.  In the event  Tenant  fails to timely
deliver  such  notice,  or if  Tenant's  Response is a  rejection,  or if Tenant
indicated  that it desired to  purchase  the  Project on terms  other than those
offered by Landlord, and on the date which is [*] after the delivery of Tenant's
Response  Landlord  and Tenant have failed to agree upon any of the terms of the
purchase  agreement for the Project after  negotiating  in good faith,  Landlord
shall  thereafter  have the right to market the  Project,  and the right,  for a
period  of [*]  after the  expiration  of [*]  following  delivery  of  Tenant's
Response,  to sell the Project to a third party on terms and  conditions no more
favorable  to the  third  party  than  those set  forth in the Sale  Notice.  If
Landlord  does not  consummate  the sale of the  Project  within  the [*] period
referenced above, Tenant shall again have the Purchase Right.

     43.2. In the event that Tenant and Landlord enter into a purchase agreement
following the timely  exercise of the Purchase  Right,  the purchase and sale of
the Project  shall close no sooner than the date which is [*], and no later than
the date which is [*],  following  receipt by Landlord  of Tenant's  election to
exercise the Purchase Right.

________________________

[*}  Confidential  information  has been omitted and filed  separately  with the
Commission.


                                       50
<PAGE>


     43.3.  Notwithstanding the above, the Purchase Right shall not be in effect
and may not be exercised  by Tenant  during any period of time that Tenant is in
Default under any provision of the Lease.

     43.4. The Purchase Right is personal to North  American  Vaccine,  Inc. and
may not be  transferred  separate  and apart from this  Lease,  except  that the
Purchase Right shall be deemed to have been  transferred to any assignee of this
Lease.

     43.5.  The Purchase  Right shall  terminate  and be of no further  force or
effect upon the expiration or earlier termination of the Term.

     43.6.  The Purchase  Right is in addition to, and is not to be construed to
limit in any way, Tenant's Purchase Option pursuant to Section 39 hereof.

44.  TENANT SIGNAGE.

     Subject to Section 16.1,  Tenant shall have the right to place signs on the
exterior of the  Building  as set forth in EXHIBIT  "H".  Tenant  shall have the
right to place signs in the interior of the Demised  Premises on floors occupied
solely by Tenant without first  obtaining the consent of Landlord.  Fabrication,
installation,  insurance,  and  maintenance of such signage shall be at Tenant's
sole cost and expense.  Tenant covenants and agrees that all work done by Tenant
shall be performed in full compliance with all laws, rules, orders,  ordinances,
directions, regulations, and requirements of all governmental agencies, offices,
departments, bureaus and boards having jurisdiction, and in full compliance with
the rules, orders, directions,  regulations,  and requirements of any applicable
fire rating bureau. Except for the foregoing,  no sign,  advertisement or notice
visible from the exterior of the Building shall be inscribed, painted or affixed
by Tenant on any part of the  Project  without  the prior  consent of  Landlord,
which consent shall not be unreasonably withheld, conditioned or delayed. Tenant
shall  remove  such  signage  promptly   following  the  expiration  or  earlier
termination  of this Lease.  Any such removal shall be at Tenant's sole expense,
and Tenant shall bear the cost of any resulting repairs to the Building that are
reasonably  necessary  due to the  removal.  Should  Tenant  fail to remove such
signage  within ten (10) days  following the  termination  of this Lease,  or if
Tenant sooner requests that Landlord  remove the signage,  Landlord shall effect
the removal and repair at Tenant's expense.

45.  MISCELLANEOUS.

     45.1.  TERMS AND HEADINGS.  Where  applicable  in this Lease,  the singular
includes the plural and the masculine or neuter includes the masculine, feminine
and neuter.  The section headings of this Lease are not a part of this Lease and
shall have no effect upon the construction or interpretation of any part hereof.


                                       51
<PAGE>


     45.2.  EXAMINATION OF LEASE.  Submission of this instrument for examination
or signature by Tenant does not constitute a reservation of or option for lease,
and it is not effective as a lease or otherwise  until execution by and delivery
to both Landlord and Tenant.

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

     45.4.  CONSENTS.  Whenever consent or approval of either party is required,
that party shall not unreasonably  withhold,  delay or condition such consent or
approval, except as may be expressly set forth to the contrary.

     45.5. ENTIRE AGREEMENT. The terms of this Lease are intended by the parties
as a final  expression  of their  agreement  with  respect  to the  terms as are
included  herein,  and may not be  contradicted  by  evidence  of any  prior  or
contemporaneous  agreement.  The  Lease  and the  Exhibits  constitute  a single
document.

     45.6.  SEVERABILITY.  Any provision of this Lease which shall provide to be
invalid,  void, or illegal in no way affects,  impairs or invalidates  any other
provision  hereof,  and such  other  provisions  shall  remain in full force and
effect.

     45.7.  RECORDING.  Neither  party shall  record this Lease or a  memorandum
hereof.

     45.8. IMPARTIAL CONSTRUCTION. The language in all parts of this Lease shall
be in all cases  construed  as a whole  according  to its fair  meaning  and not
strictly for or against either Landlord or Tenant.

     45.9.  INUREMENT.  Each of the covenants,  conditions and agreements herein
contained  shall inure to the benefit of and shall apply to and be binding  upon
the parties hereto and their respective heirs,  legatees,  devisees,  executors,
administrators, successors, assigns, sublessees, or any person who may come into
possession  of  said  Demised  Premises  or  any  part  thereof  in  any  manner
whatsoever.  Nothing in this Section 45.9  contained  shall in any way alter the
provisions against assignment or subletting in this Lease provided.

     45.10.  NOTICES. Any notice,  consent,  demand, bill,  statement,  or other
communication required or permitted to be given hereunder must be in writing and
may be given by personal delivery,  reputable  overnight courier or by mail, and
if given by mail shall be deemed sufficiently given two (2) days after time when
deposited in United States Mail is sent by registered or certified  mail, and if
given by other means shall be deemed given when received, addressed to Tenant or
Landlord at the addresses shown in Sections 2.1.10 and 2.1.11. Either party may,
by notice to the other given  pursuant to this  Section,  specify  additional or
different addresses for notice purposes.

     45.11.  MARYLAND  JURISDICTION.  This Lease has been negotiated and entered
into in the State of Maryland and shall be governed by,  construed  and enforced
in accordance with the laws of the State of Maryland,  applied to contracts made
in Maryland for Maryland domiciliaries to be wholly performed in Maryland.


                                       52
<PAGE>


     45.12.  AUTHORITY.  That individual or those individuals signing this Lease
guarantee,  warrant and represent that said  individual or individuals  have the
power,  authority and legal capacity to sign this Lease on behalf of and to bind
all entities, corporations, partnerships, joint venturers or other organizations
and/or entities on whose behalf said individual or individuals have signed.

     45.13.   CONFIDENTIALITY.   Landlord   agrees  that  any   information   or
documentation  furnished  to  Landlord  by Tenant  pursuant to the terms of this
Lease, or any information or documentation  that Landlord  otherwise  obtains in
connection  with its  rights to access  the  Demised  Premises  under this Lease
(collectively,  "Confidential  Information")  shall be used by Landlord only for
the purposes expressly set forth in this Lease.  Landlord shall not disclose any
Confidential  Information to any third party unless expressly permitted to do so
under the terms of this  Lease.  In the event that  Landlord  is required in any
proceeding to disclose any Confidential Information,  Landlord shall give Tenant
immediate  oral  notice  of such  request  so that  Tenant  may  challenge  such
disclosure requirement or seek a protective order. Landlord shall cooperate with
Tenant in seeking the same.  Landlord  agrees that money  damages would not be a
sufficient  remedy for any breach of this Section 45.13, and that in addition to
all  other  remedies,  Tenant  shall be  entitled  to seek  injunctive  or other
equitable relief as a remedy for any such breach,  and Landlord hereby agrees to
waive any  requirement  that Tenant post a bond or other  security in connection
with  seeking such remedy.  The terms of this  Section  45.13 shall  survive the
expiration or earlier termination of this Lease.

     45.14.  REAL  ESTATE  INVESTMENT  TRUST.  Notwithstanding  anything  to the
contrary set forth  herein,  nothing in this Lease shall be construed to require
Landlord  to take any action or fail to take any  action  if, in the  opinion of
Landlord's  counsel, a copy of which shall be provided to Tenant, such action or
inaction  would be  likely to result in  Landlord  losing  its  status as a real
estate  investment trust, as defined in Section 856 of the Internal Revenue Code
(as amended).

     45.15. This Lease may be executed in two or more counterpart copies, all of
which counterparts shall have the same force and effect as if all parties hereto
had executed a single copy of this Lease.


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<PAGE>



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

                                       Landlord:

                                       ARE - 10150 OLD COLUMBIA, LLC,
                                       a Delaware limited liability company

                                       By: Alexandria Real Estate Equities, L.P.

                                       By: ARE-QRS CORP.


                                       By: /s/ Joel Marcus
                                          --------------------------------------
                                       Name:  JOEL MARCUS
                                       Its:   CHIEF EXECUTIVE OFFICER



                                       Tenant:

                                       NORTH AMERICAN VACCINE, INC. a
                                       Canadian corporation


                                       By: /s/ Daniel J. Abdun-Nabi
                                           -------------------------------------
                                       Name: DANIEL J. ABDUN-NABI
                                       Its:  Senior Vice President-Legal Affairs
                                             & GENERAL COUNSEL




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