<PAGE>   1
                                                                    EXHIBIT 10.2



                                 LEASE AGREEMENT
                                 ---------------


                                     BETWEEN

              WARD CORPORATION, a Maryland Corporation, as Landlord

                                       AND

              Organon Teknika Corporation, a Delaware Corporation,

                                    as Tenant


<PAGE>   2
                                TABLE OF CONTENTS



<TABLE>
<CAPTION>
        Sections     Description                                                    Page No.
        --------     -----------                                                    --------
<S>                  <C>                                                            <C>
             1.      Definitions                                                       3
             2.      Rent; Additional Rent                                             3
             3.      Additional Rent                                                   3
             4.      Delivery and Condition of Premises                                4
             5.      Operation of Building and Real Property                           4
             6.      Conduct of Business by Tenant                                     4
             7.      Alterations and Tenant's Property                                 4
             8.      Repairs                                                           5
             9.      Liens                                                             5
            10.      Subordination and Modification
            11.      Inability to Perform                                              5
            12.      Destruction                                                       5
            13.      Eminent Domain                                                    5
            14.      Assignment and Subletting                                         6
            15.      Building Services                                                 6
            16.      Default; Remedies                                                 6
            17.      Insolvency or Bankruptcy                                          7
            18.      Fees and Expenses; Indemnity; Liability Insurance                 7
            19.      Access to Premises                                                8
            20.      Waiver; Release                                                   8
            21.      Tenant's Certificates                                             8
            22.      Rules and Regulations                                             8
            23.      Tax on Tenant's Personal Property                                 8
            24.      Authority                                                         8
            25.      Signage                                                           8
            26.      Parking                                                           8
            27.      Miscellaneous                                                     9


                     Exhibits "A" and "C"
                     Addendum to Lease
</TABLE>



<PAGE>   3
                                     LEASE

        THIS LEASE is made and entered into as of this 30th day of April, 1991,
by and between WARD CORPORATION, a Maryland corporation (herein called
"Landlord), and Organon Teknika Corporation, a Delaware Corporation (herein
called "Tenant").


                              W I T N E S S E T H:


      Upon and subject to the terms, covenants and conditions hereinafter set
forth, Landlord leases to Tenant and Tenant leases from Landlord the Premises
(as hereinafter defined) in the Building.

      1.    Definitions

            1.1 Additional Rent: As defined in Section 2.4, below.

            1.2 Basic Rent: As defined in Section 2.1, below.

            1.3 Building: The building located at 1300 Piccard Drive, Rockville,
Maryland 20850, upon the Real Property.

            1.4 Guarantor(s): N/A

            1.5 Lease: This Lease, as amended from time to time, and all
Exhibits attached hereto.

            1.6 Lease Commencement Date: June 1, 1991.

            1.7 Lease Year: Each period of twelve (12) calendar months during
the Term, commencing on the Lease Commencement Date and Partial Lease Year
ending on the Term Expiration Date.

            1.8 Operating Expenses Base Amount. Intentionally Deleted.

            1.9 Premises: Approximately Eight Hundred Three (803) square feet of
rentable floor area, located on the Lower Level, within the Building, and
outlined on Exhibit A, attached hereto.

            1.10 Real Estate Taxes Base Amount. Intentionally Deleted.

            1.11 Real Property: The land comprising all that certain parcel of
land situated in Montgomery County, Maryland, and identified as Lot Six (6) in a
subdivision known as "Lots Four (4), Five (5) and Six (6) and dedication of part
of Piccard Drive, 70-S Industrial Park" as per plat thereof recorded in Plat
Book 87 at plat 9281 among the land records of Montgomery County, Maryland (Tax
Account Number 4-201-1457).

            1.12 Term: The four year (4) period commencing on the Lease
Commencement Date and ending on the Term Expiration Date, unless the Term shall
sooner terminate as hereinafter provided.

            1.13 Term Expiration Date: May 31, 1995

        2. Rent; Additional Rent

            2.1 Basic Rent. Commencing on the Lease Commencement Date, Tenant
shall pay to Landlord during the Term a base rental ("Basic Rent") equal to Six
Hundred Two and 25/100 Dollars ($602.25) per month in gross. Basic Rent shall be
payable by Tenant in lawful money of the United States in equal consecutive
monthly installments of one-twelfth the Basic Rent on or before the first day of
each calendar month, in advance, at the address specified for Landlord below, or
such other place as Landlord shall designate, without any prior demand therefor
and without any deductions or setoff whatsoever. Rent for any partial month
shall be prorated at the rate of one-thirtieth (1/30th) of the monthly Basic
Rent per day.

            2.2 Above Standard Improvement Rental Rate. Intentionally Deleted.

            2.3. Adjustment of Rent. The Basic Rent set forth in Paragraph 2.1
hereinabove shall be increased as follows:

<TABLE>
<CAPTION>
                        Date          New Monthly Rent
                        ----          ----------------
<S>                                      <C>     
                        6/1/92           $ 620.32
                        6/1/93           $ 639.05
                        6/1/94           $ 658.46
</TABLE>

            2.4 Additional Rent. Tenant shall pay to Landlord as additional rent
hereunder, all charges and other amounts required under this Lease. All such
amounts and charges shall be payable to Landlord at the time and at the place
where Basic Rent is payable. Landlord shall have the same remedies for a default
in the payment of additional rent as for a default in the payment of Basic Rent.

            2.5 Late Payment Charge. If Tenant shall fail to pay any Basic Rent
or Additional Rent within five (5) days after the same is due and payable, such
unpaid amounts shall be subject to a late payment charge equal to ten percent
(10%) of such unpaid amounts in each instance to cover Landlord's additional
administrative costs resulting from Tenant's failure. Such late payment charge
shall be paid to Landlord together with such unpaid amounts.

            2.6 Returned Check Charge. A service charge of Fifty and 00/100
Dollars ($50.00) will be automatically made for each instance in which a check
is returned unpaid for any reason by the Tenant's bank.



                                        3


<PAGE>   4
      3.    Intentionally Deleted.

      4.    Delivery and Condition of Premises. Tenant agrees to accept the
Premises in their "as is" condition and further agrees to be fully responsible
for any alterations or improvements thereto. However, it is understood and
agreed that Tenant will obtain all necessary permits to construct the premises
as required by Code. Landlord shall furnish six (6) 2' X 4' fluorescent light
fixtures for installation by Tenant.

      5.    Operation of the Building and the Real Property

            5.1 Maintenance of Building. The manner in which the Building and
the Real Property are maintained and operated and the expenditures therefor
shall be at the sole discretion of Landlord, in a manner consistent with similar
office buildings in Montgomery County.

            5.2 Alterations or Additions. Landlord hereby reserves the right, at
any time and from time to time, to make alterations or additions to the
Building and the Real Property. Landlord also reserves the right at any time and
from time to time to construct other improvements in the Building and to enlarge
same and make alterations therein or additions thereto.

      6.    Conduct of Business by Tenant

            6.1 Permitted Use. Tenant shall use and occupy the Premises during
the Term of the Lease solely for use for storage of files, as permitted by law,
and for no other use or uses without the prior written consent of Landlord.

            6.2 Uses Not Permitted. Tenant shall not use or occupy, or permit
the use or occupancy of, the Premises or any part thereof for any use other than
the use specifically set forth in Section 6.1 hereof, or in any manner that, in
Landlord's judgment, would adversely affect or interfere with any services
required to be furnished by Landlord to Tenant or to any other tenant or
occupant of the Building, or with the proper and economical rendition of any
such service, or with the use or enjoyment of any part of the Building by any
other tenant or occupant.

            6.3 Tenant's Compliance with Laws. Tenant, at Tenant's cost and
expense, shall comply with all laws, orders and regulations of federal and
municipal authorities, and with all directions, pursuant to law, of all public
officers, that shall impose any duty upon Landlord or Tenant with respect to the
Premises or the use or occupancy thereof.

            6.4 Tenant's Compliance with Insurance Requirements, etc. Tenant
shall not do anything, or permit anything to be done, in or about the Premises
which shall conflict with the provisions of any insurance policies covering the
Building or any property located therein, or result in a refusal by any
insurance company to insure the Building or any such property, in amounts
reasonably satisfactory to Landlord, or subject Landlord to any liability or
responsibility for injury to any person or property by reason of any business
operation being conducted in the Premises, or cause any increase in the
insurance rates applicable to the Building or property located therein. Tenant,
at Tenant's expense, shall comply with all rules, orders, regulations or
requirements of the American Insurance Association (formerly the National Board
of Fire Underwriters) and with any similar body that shall hereafter perform the
function of such Association.

      7.    Alterations and Tenant's Property

            7.1 Initial Improvements. Intentionally Deleted.

            7.2 Approved Alterations. Tenant shall make no alterations,
installations, additions or improvements in or to the Premises or any portion
thereof or any alteration to the mechanical systems of the Premises or any
portion thereof, including, without limitation, the plumbing and air
conditioning systems of the Premises or any portion thereof or to the apparatus
of the Premises or any portion thereof of other or like nature without
Landlord's prior written consent, which shall not be unreasonably withheld.

            7.3 Requirements for Approved Alterations. Each alteration,
installation, addition or improvement, shall be subject to the limitations that
such Alteration (a) does not adversely affect the structural strength of the
Premises or any portion thereof; (b) does not adversely affect the mechanical,
plumbing, electrical and HVAC systems of the Premises or any portion thereof;
(c) does not materially affect the external appearance or value of the Premises
or any portion thereof; and

(d) does not diminish or impair the use of the Building as a first class office
building. Prior to making any alteration, plans and specifications therefor in
such detail as Landlord may request shall be submitted to Landlord and the
mortgagees of the Building for approval.

            7.4 Standards for Approved Alterations. All Alterations made by
Tenant in the Premises or any portion thereof shall be constructed and completed
in a good and workmanlike manner at Tenant's sole cost and expense by
contractors approved by Landlord. Prompt payment shall be made by Tenant and
Tenant shall keep the Premises free of mechanics' and materialmen's liens and
cause the same to be promptly discharged or bonded. Tenant shall deliver to
Landlord written and unconditional waivers of mechanics' and materialmen's liens
upon the Real Property for all work, labor and services to be performed and
material to be furnished in connection with the proposed Alterations. Tenant
shall obtain all necessary governmental permits, licenses and approvals, and
shall promptly comply with all applicable laws. The Alterations shall be
completed in accordance with the approved plans and specifications where such
approvals are required.

            7.5 Tenant's Property. All appurtenances, fixtures, improvements,
additions and other property attached to or installed in the Premises, whether
by Landlord or by or on behalf of Tenant, and whether at Landlord's expense or
Tenant's expense, or at the joint expense of Landlord and Tenant, shall be and
remain the property of Landlord. Any furnishings and personal property placed in
the Premises that are removable without material damage to the Building or the
Premises, whether the property of Tenant or leased by Tenant, are herein called
"Tenant's Property". Any replacements of any property of Landlord, whether made
at Tenant's expense or otherwise, shall be and remain the property of Landlord.




                                        4



<PAGE>   5
              7.6    Removal of Tenant's Property. Any of Tenant's Property on
the Premises prior to the Term Expiration Date shall be removed by Tenant at
Tenant's cost and expense, and Tenant shall, at its cost and expense, repair
any damage to the Premises or the Building caused by such removal, all on or
before the Term Expiration Date. Any of Tenant's Property not removed from the
Premises prior to the expiration of the Term shall, at Landlord's option,
become the property of Landlord or Landlord may remove such Tenant's Property,
and Tenant shall pay to Landlord Landlord's costs of removal and of any repairs
in connection therewith within ten (10) days after the receipt of a bill
therefor. Tenant's obligation to pay any such costs shall survive any
termination of this Lease.

       8.     REPAIRS

              8.1    Maintenance of Premises. Tenant shall maintain the
Premises and, at Tenant's cost and expense, shall make all repairs and
replacements to preserve the Premises in good working order and in clean, safe
and sanitary condition.

              8.2    Repairs by Tenant. All repairs and replacements made by or
on behalf of Tenant or any person claiming through or under Tenant shall be
made and performed (a) at Tenant's cost and expense and at such time and in
such manner as Landlord may designate, (b) by contractors or mechanics approved
by Landlord, (c) so that same shall be at least equal in quality, value, and
utility to the original work or installation, and (d) in accordance with the
rules and regulations for the Building and the Real Property adopted by
Landlord from time to time, and in accordance with all applicable laws and
regulations of governmental authorities having jurisdiction over the Premises.
If Landlord gives Tenant notice of the necessity of any repairs or replacements
required to be made under Section 8.1 above and Tenant fails to commence
diligently to effect the same within ten (10) days thereafter, Landlord may
proceed to make such repairs or replacements and the expenses incurred by
Landlord in connection therewith shall be due and payable from Tenant upon
demand as Additional Rent; provided, that Landlord's making any such repairs or
replacements shall not be deemed a waiver of Tenant's default in failing to
make the same.

              8.3    Maintenance of Common Areas. Landlord shall operate and
maintain the common or public areas of the Real Property and the Building in a
manner deemed by Landlord, in its sole discretion, in a manner consistent with
similar office buildings in Montgomery County.

       9.     Liens. Intentionally Deleted.

      10.     Subordination and Modification

              10.1   Subordination of Lease. Without the necessity of any
additional document being executed by Tenant for the purpose of effecting a
subordination, Tenant agrees that this Lease and Tenant's tenancy hereunder are
and shall be automatically subject and subordinate at all times to (a) all
ground leases or underlying leases that may now exist or hereafter be executed
affecting the Building or the Real Property or both, (b) the lien of any
mortgage deed of trust or similar security instrument that may now exist or
hereafter be executed in any amount for which the Building, the Real Property,
ground leases or underlying leases, or Landlord's interest or estate in any of
said items is specified as security, and (c) all renewals, modifications,
consolidations, replacements and extensions of any of the foregoing.

                     Tenant covenants and agrees to execute and deliver, upon
demand by Landlord and in the form requested by Landlord, any additional
documents evidencing the subordination of this Lease with respect to any such
ground lease or underlying lease, or the lien of any such mortgage or deed of
trust. If Tenant fails to execute such instruments within fifteen (15) days
after written request therefor, Landlord is hereby appointed Tenant's
attorney-in-fact to execute, acknowledge and deliver any and all such
instruments for and on behalf of Tenant.

              10.2   Attornment. In the event that any ground lease or
underlying lease terminates for any reason or any mortgage or deed of trust is
foreclosed or a conveyance in lieu of foreclosure is made for any reason,
Tenant shall, notwithstanding any subordination of any ground lease, underlying
lease or lien to this Lease, attorn to and become the Tenant of the successor
in interest to Landlord at the option of such successor in interest.

              10.3   Amendment or Modification. If, in connection with any loan
secured by a mortgage or deed of trust affecting the Building, Real Property or
both, the lender should require any amendment or modification of the terms
hereof, Tenant shall duly execute and deliver any instrument reasonably
requested by such lender to affect such amendment or modification; provided,
that such amendment or modification shall not enlarge the term hereof or
increase the amount of Basic Rent payable hereunder.

       11.    Inability to Perform; No Delay to Constitute Eviction.
Intentionally Deleted.

       12.    Destruction

              12.1   Intentionally Deleted.

              12.2   Intentionally Deleted.
       
              12.3   Intentionally Deleted.

              12.4   Intentionally Deleted.

              12.5   No Abatement of Rent if Damage Caused by Tenant. If any
such damage is due to the fault or neglect of Tenant, any person claiming
through or under Tenant, or any of their servants, employees, agents,
contractors, visitors or licensees, then there shall be no abatement of Basic
Rent by reason of such damages, unless Landlord is reimbursed for such
abatement of Basic Rent pursuant to any rental insurance policies that Landlord
may, in its sole discretion, elect to carry.

       13.    Eminent Domain. Intentionally Deleted.



                                       5
<PAGE>   6

     14.  Assignment and Subletting

               14.1  No Assignment or Subletting Permitted. Tenant shall not
directly or indirectly, voluntarily or by operation of law, sell, assign,
sublease, pledge or otherwise transfer or hypothecate all or any part of the
Premises or Tenant's leasehold estate hereunder, without first obtaining
Landlord's prior written consent, which consent will not be unreasonably
withheld. A transfer of fifty percent (50%) or more of the ownership interests
of Tenant within any twelve (12) month period shall be deemed equivalent to an
assignment or subletting requiring the consent of Landlord. Notwithstanding the
foregoing, a corporate reorganization within the meaning of Section 368 of the
Internal Revenue Code of 1986 shall not be considered an assignment or
subletting within the meaning of this Section 14.1. Tenant agrees that any
permitted assignment or subletting hereunder may be conditioned upon payment of
consideration to be agreed upon by Landlord and Tenant.

               14.2  Procedure for Assignment, Subletting. If Tenant desires at
any time to assign, sublease or otherwise transfer the Premises or any portion
thereof, it shall send a written notice to Landlord, which notice shall contain
(a) the name of the proposed occupant or subtenant, (b) the nature of the
proposed occupant's or subtenant's business to be carried on in the Premises,
(c) the portion(s) of the Premises to be subject to such assignment or sublease
and the other terms and provisions of the proposed assignment or sublease, (d)
such financial information as Landlord may reasonably request concerning the
proposed occupant or subtenant, and (e) a true copy of a proposed assignment or
sublease.

               14.3  No Release of Tenant. No assignment or sublease by Tenant
shall relieve Tenant of any obligation to be performed by Tenant under this
Lease, whether arising before or after the assignment or sublease. Any
assignment or sublease that is not in compliance with this Section 14 shall be
void and, at the option of Landlord, shall constitute a default by Tenant under
this Lease.

     15.  Building Services.

               15.1  Standard Services. Landlord shall furnish reasonably
adequate electrical power for all normal office machines and lighting, and
water without additional cost to Tenant. Landlord shall furnish hot and cold
water at those points of supply provided for the general use of all of the
tenants in the Building. Landlord shall provide routine maintenance, painting
and electrical lighting service for all public areas and special service areas
of the Building, in the manner and to the extent deemed by the Landlord to be
standard. In the event an air conditioner unit or units (in excess of Building
Standard Improvements), for the purposes of cooling computers or other office
machinery, are installed by Tenant, the operation of the unit(s) shall be under
Tenant's control, and the maintenance costs shall be the obligation of Tenant.
Failure by Landlord to any extent to furnish these defined services unless
caused by Landlord's gross negligence, or any cessation thereof, or delay
thereof caused by breakdown, maintenance, repairs, strikes, scarcity of labor
or materials, acts of God or from any other cause, shall not render Landlord
liable in any respect for damages to either person or property, nor shall such
events be construed an eviction of Tenant, nor work an abatement of Basic Rent
or Additional Rent, nor relieve Tenant from the fulfillment of any term,
condition, covenant or agreement contained in this Lease. Should any of the
Building equipment or machinery break down, or for any cause or reason cease to
function properly, Landlord shall use reasonable diligence to repair the same
promptly, but Tenant shall have no claim for rebate of Basic Rent or Additional
Rent or for any damages on account of any interruptions in service occasioned
thereby or resulting therefrom. Where the Landlord does not pursue said cause
diligently, Tenant may, upon written notice to Landlord, have said repairs or
maintenance performed by Landlord's approved contractors and deduct the
reasonable cost for same from the amount owed to Landlord thereafter.

               15.2  Additional Services. Intentionally Deleted.

     16.  Default; Remedies

               16.1  Events of Default.  The following shall constitute an
event of default under this Lease:

                     (a) The failure to pay any amount of Basic Rent or
Additional Rent in full within five (5) days after the same is due.

                     (b) The failure to perform or honor any other covenant or
condition made under this Lease, provided Tenant shall have a grace period of
ten (10) days from the date of written notice from Landlord within which to
cure any such failure governed by this subparagraph but not specifically by the
other subparagraphs of this Section 16-1; provided however, that with respect
to any such default, that cannot reasonably be cured within such ten (10) day
grace period, Tenant shall not be deemed in default if Tenant commences to cure
within ten (10) days from Landlord's notice and continues to prosecute
diligently the curing thereof to completion within a reasonable time; and
provided, further, that if any such failures which would be deemed defaults
hereunder upon expiration of such grace period occur more often than twice in
any twelve month period, the foregoing requirements of written notice and a
grace period shall be deemed waived with respect to any such subsequent
failures for the remainder of the Term.

                    (c) If any representation or warranty made by Tenant, or
others on behalf of Tenant, under or pursuant to the Lease shall prove to have
been false or misleading in any material respect (including by way of material
omissions) as of the date on which such representation or warranty was made.

                    (d) If Tenant makes or consents to an assignment for the
benefit of creditors or a common law composition of creditors, or a receiver of
Tenant's assets is appointed, or Tenant files a voluntary petition in any
bankruptcy or insolvency proceeding, or an involuntary petition in bankruptcy
or insolvency proceeding is filed against Tenant and not discharged or
dismissed within thirty (30) days, or Tenant is adjudicated bankrupt or
admits in writing its inability to pay its debts or that it is insolvent.

                    (e) Final judgment for the payment of money in excess of
Ten Thousand Dollars ($10,000) shall be rendered against Tenant and Tenant
shall not discharge the same or cause it to be discharged within ten (10) days
from the entry thereof, or shall not appeal therefrom or from the order,
judgment, decree or process.

                    (f) If Tenant shall dissolve or liquidate, and such
dissolution or liquidation is not in connection with a reorganization, merger
or consolidation approved in writing by Landlord.


                                       6

<PAGE>   7
          16.2 Landlord's Remedies. Upon the occurrence of an Event of Default
which is not cured by Tenant within the grace periods specified in Section 16.1
hereof, Landlord shall have all rights or remedies available to Landlord in law
or equity.

               (a) Landlord may terminate this Lease by notice to Tenant (and
Tenant hereby expressly waives any other or additional notice to quit or notice
of Landlord's intention to re-enter), whereupon this Lease and the Term shall
terminate, Tenant shall quit, vacate and surrender the Premises and all amounts
accrued and unpaid Basic Rent and Additional Rent shall be due and payable in
full.

               (b) Intentionally Deleted.

               (c) Intentionally Deleted.

               (d) Intentionally Deleted.
     
     17. Insolvency or Bankruptcy. Intentionally Deleted.

     18. Fees and Expenses; Indemnity; Liability Insurance.

               18.1 Performance by Landlord. If Tenant shall default in the
performance of its obligations under this Lease, Landlord, at any time
thereafter and without notice, may remedy such default for Tenant's account and
at Tenant's expense, without thereby waiving any other rights or remedies of
Landlord with respect to such default.

               18.2 Indemnification by Tenant. Tenant agrees to indemnify
Landlord, its employees, agents, contractors, mortgagees and successors in
interest against and save Landlord, its employees, agents, contractors,
mortgagees and successors in interest harmless from any and all loss, cost,
liability, damage and expense including without limitation, penalties, fines
and reasonable counsel fees, incurred in connection with or arising from any
cause whatsoever in, on or about the Premises, including, without limiting the
generality of the foregoing (a) any default by Tenant in the observance or
performance of any of the terms, covenants or conditions of this Lease on
Tenant's part to be observed or performed, or (b) the use or occupancy or
manner of use or occupancy of the Premises by Tenant or any person or entity
claiming through or under Tenant contrary to the permitted use provided in
6.1, or (c) intentionally deleted, or (d) any acts, omissions or negligence of
Tenant or any person or entity claiming through or under Tenant, or of the
contractors, agents, servants, employees, visitors or licensees of Tenant or
any such person or entity, in, or about the Premises or the Building, either
prior to, during, or after the expiration of the Term, including without
limitation, any acts, omissions or negligence in the making or performing of
any Alterations. Tenant further agrees to indemnify and save harmless Landlord,
Landlord's agents, and the lessor or lessors under all ground or underlying
leases, from and against any and all loss, cost, liability, damage and expense
including, without limitation, reasonable counsel fees, incurred in connection
with or arising from any claims by any persons by reason of injury to persons
or damage to property occasioned by any negligent act or omission referred to
in the preceding sentence.
          
               18.3 Liability Insurance. Tenant shall procure at its cost and
expense and keep in effect during the Term comprehensive general liability
insurance including contractual liability naming Landlord as an additional
insured thereunder, with a minimum combined single limit of liability of One
Million Dollars ($1,000,000.00). Such insurance shall specifically include the
liability assumed hereunder by Tenant (provided that the amount of such
insurance shall not be construed to limit the liability of Tenant hereunder),
and shall provide that it is primary insurance, and not excess over or
contributory with any other valid, existing and applicable insurance in force
for or on behalf of Landlord, and shall provide that Landlord shall receive
thirty (30) days' written notice from the insurance prior to any cancellation
or change of coverage. Tenant shall provide such additional insurance as
Landlord may require in connection with the storage of any items subject to the
special provisions of Section 6.1 hereof.

               18.4 Delivery of Policies. Tenant shall deliver policies of all
required insurance, or certificates thereof, to Landlord on or before the Lease
Commencement Date, and thereafter at least thirty (30) days before the
expiration dates of expiring policies. In the event Tenant shall fail to
procure such insurance, or to deliver such policies or certificates, Landlord
may, at its option, procure same for the account of Tenant, and the cost
thereof shall be paid to Landlord as Additional Rent within five (5) days after
delivery to Tenant of bills therefor. Tenant's compliance with the provisions
of this Section 18.5 shall in no way limit Tenant's liability under any of the
other provisions of this Section.

               18.5 Landlord Not Liable. Landlord shall not be responsible for
or liable to Tenant for any loss or damage that may be occasioned by or through
the acts or omissions of persons occupying adjoining premises or any part of
the premises adjacent to or in connection with the Premises or any part of the
Building or of third parties either legally or illegally within the Premises or
the Building or for any loss or damage resulting to Tenant or its property from
burst, stopped or leaking water, gas, sewer or steam pipes or for any damage or
loss or property within the Premises from any causes whatsoever, including
theft or vandalism, except that Landlord shall indemnify Tenant for any
negligent acts or omissions.

               18.6 Payment by Tenant. Except as specifically provided to the
contrary in this Lease, Tenant shall pay to Landlord, within five (5) days
after notice by Landlord to Tenant of the amount thereof: (a) sums equal to all
expenditures made and monetary obligations incurred by Landlord including,
without limitation, expenditures made and obligations incurred for reasonable
counsel fees, in connection with the remedying by Landlord for Tenant's account
pursuant to the provisions of Section 18.1 hereof; (b) sums equal to all
losses, costs, liabilities, damages and expenses referred to in Section 18.2
hereof; and (c) sums equal to all expenditures made and monetary obligations
incurred by Landlord, including, without limitation, expenditures made and
obligations incurred for reasonable counsel fees, in collecting or attempting
to collect the Basic Rent, Additional Rent or any other sum of money accruing
under this Lease or in enforcing or attempting to enforce any rights of
Landlord under this Lease or pursuant to law. Any sum of money (other than
Basic Rent) accruing from Tenant to Landlord pursuant to any provision of this
Lease, whether prior to or after the Lease Commencement Date, may, at Landlord's
option, be deemed Additional Rent. Tenant's obligations under this 18.7 shall
survive the expiration or earlier termination of the Term.

                                       7
<PAGE>   8
 19.  Access to Premises; Landlord's Right to Enter. Landlord reserves and shall
have the right to enter the Premises at all reasonable times during normal
business hours with Landlord providing forty-eight (48) hours advance notice to
Tenant, except in the case of an emergency, to inspect same, to show the
Premises to prospective purchasers, mortgagees or tenants, to post notices of
nonresponsibility, and to alter, improve or repair the Premises, adjacent
premises and any other portion of the Building or any systems serving any of the
same, without abatement of Basic Rent or Additional Rent, and may for that
purpose erect, use and maintain scaffolding, pipes, conduits and other necessary
structures in and through the Premises where reasonably required by the
character of the work to be performed; provided that the entrance to the
Premises shall not be blocked thereby. Landlord and its agents shall also have
unrestricted access to the Premises at any time in the event of an emergency,
without abatement of Basic Rent or Additional Rent. Tenant hereby waives any
claim for damages for any injury or inconvenience to or interference with
Tenant's business, any loss of occupancy or quiet enjoyment of the Premises or
any other loss occasioned thereby. For each of the aforesaid purposes, Landlord
shall at all times have and retain a key with which to unlock all of the doors
in, upon and about the Premises, and Landlord shall have the right to use any
and all means that Landlord may deem necessary or proper to open said doors in
an emergency, in order to obtain entry to any portion of the Premises, and any
entry to the Premises or portions thereof obtained by Landlord by any of said
means, or otherwise, shall not under any circumstances be construed or deemed to
be a forcible or unlawful entry into, or a detainer of, the Premises, or an
eviction, actual or constructive, of Tenant from the Premises or any portion
thereof. Landlord shall also have the right at any time, without same
constituting an actual or constructive eviction and without incurring any
liability to Tenant therefor, to change the arrangement and/or location of
entrances or passageways, doors and doorways, and corridors, elevators, stairs,
toilets and other public parts of the Building.

     20.  Waiver; Release

          20.1 No Waiver. No failure by Landlord to insist upon the strict
performance of any obligation of Tenant under this Lease or to exercise any
right, power or remedy consequent upon a breach thereof, no acceptance of full
or partial Basic Rent or Additional Rent during the continuance of any such
breach, and no acceptance of the keys to or possession of the Premises prior to
the termination of the Term by any employee of Landlord shall constitute a
waiver of any such breach or of such term, covenant or condition or operate as
a surrender of this Lease. No payment by Tenant or receipt by Landlord or a
lesser amount than the aggregate of all Basic Rent and Additional Rent then due
under this Lease shall be deemed to be other than on account of the first
items of such Basic Rent and Additional Rent then accruing or becoming due,
unless Landlord elects otherwise; and no endorsement or statement on any check
and no letter accompanying any check or other payment of Basic Rent or
Additional Rent in any such lesser amount and no acceptance of any such check
or other such payment by Landlord shall constitute an accord and satisfaction,
and Landlord may accept such check or payment without prejudice to Landlord's
right to recover the balance of such Basic Rent or Additional Rent or to pursue
any other legal remedy.

          20.2 Modifications in Writing. Neither this Lease nor any term or
provision hereof may be changed, waived, discharged or terminated orally, and
no breach thereof shall be waived, altered or modified, except by a written
instrument signed by the party against which the enforcement of the change,
waiver, discharge or termination is sought. No waiver of any breach shall
affect or alter this Lease, but each and every term, covenant and condition of
this Lease shall continue in full force and effect with respect to any other
then existing or subsequent breach thereof.

     21.  Tenant's Certificates. Tenant, at any time and from time to time upon
not less than fifteen (15) days' prior written notice from Landlord, will
execute, acknowledge and deliver to Landlord and, at Landlord's request, to any
prospective purchaser, ground or underlying lessor or mortgagee of any part of
the Building and Real Property, a certificate of Tenant stating: (a) that
Tenant has accepted the Premises (or, if Tenant has not done so, that Tenant
has not accepted the Premises and specifying the reasons therefor), (b) the
Commencement and Term Expiration Dates of this Lease, (c) that this Lease is
unmodified and in full force and effect (or, if there have been modifications,
that same is in full force and effect as modified and stating the
modifications), (d) whether or not there are then existing any defenses against
the enforcement of any of the obligations of Tenant under this Lease (and, if
so, specifying same), (f) the dates, if any, to which the Basic Rent and
Additional Rent and other charges under this Lease have been paid, and (g) any
other information that may reasonably be required by any of such persons,
including but not limited to current financial statements for Tenant (and any
Guarantors of Tenant's obligation hereunder). It is intended that any such
certificate of Tenant delivered pursuant to this Section 21 may be relied upon
by Landlord and any prospective purchaser, ground or underlying lessor or
mortgagee of any part of the Real Property.

     22.  Rules and Regulations. Tenant, its agents, employees, invitees,
licensees, customers, clients and guests shall at all times faithfully observe
and comply with the rules and regulations attached hereto as Exhibit C, and
such other rules and regulations as may be promulgated from time to time by
Landlord, and all modifications thereof and additions thereto, from time to
time, put into effect by Landlord. Landlord shall not be responsible for the
nonperformance by any other tenant or occupant of the Building of any said
rules and regulations. In the event of an express and direct conflict between
the terms, covenants, agreements and conditions of this Lease and the terms,
covenants, agreements and conditions of such rules and regulations, as modified
and amended from time to time by Landlord, this Lease shall control.

     23.  Tax on Tenant's Personal Property. At least ten (10) days prior to
delinquency, Tenant shall pay all taxes levied or assessed upon Tenant's
equipment, furniture, fixtures and other personal property located in or about
the Premises. If the assessed value of Landlord's property is increased by the
inclusion therein of a value placed upon Tenant's equipment, furniture,
fixtures or other personal property, Tenant shall pay to Landlord, upon demand,
the taxes so levied against Landlord, or the portion thereof resulting from
said increase in assessment.

     24.  Authority. The persons executing this Lease on behalf of Tenant
hereby covenant and warrant that Tenant is a duly authorized and existing
entity, that Tenant has and is qualified to do business in the State of
Maryland and Delaware, that Tenant has full right and authority to enter into
this Lease, and each person signing on behalf of Tenant is authorized to do so.
Upon Landlord's request, Tenant shall provide Landlord with evidence reasonably
satisfactory to Landlord confirming the foregoing covenants and warranties.

     25.  Signage. Intentionally Deleted.

     26.  Parking. Intentionally Deleted.


                                       8
<PAGE>   9
     27.  Miscellaneous

               27.1 Notices. Except as otherwise expressly provided in this
Lease, any bills, statements, notices, demands, requests or other
communications given or required to be given under this Lease shall be
effective only if rendered or given in writing, sent by mail or delivered
personally as follows:

               to Tenant:     Organon Teknika Corporation
                              1330-A Piccard Drive
                              Rockville, MD 20850-4373
                              Attention: Richard J. James

               to Landlord:   Ward Corporation
                              1300 Piccard Drive
                              Rockville, MD 20850
                              Attention: Richard E. Ward

or to such other address as either Landlord or Tenant may designate as its new
address for such purpose by notice to the other in accordance with the
provisions of this Section. Any such bill, statement notice, demand, request or
other communication shall be deemed to have been rendered or given two (2) days
after the date when it shall have been mailed as provided in this Section if
sent by registered or certified mail, or upon the date personal delivery is
made. If Tenant is notified of the identity and address of Landlord's mortgagee
or ground or underlying lessor, Tenant shall give to such mortgagee or ground
or underlying lessor notice of any default by Landlord under the terms of this
Lease in writing sent by registered or certified mail, and such mortgagee or
ground or underlying lessor shall be given a reasonable opportunity to cure such
default prior to Tenant's exercising any remedy available to it.

               27.2 Interpretation. The words "Landlord" and "Tenant" as used
herein shall include the plural as well as the singular. The words used in the
neuter gender include the masculine and the feminine. The captions preceding
the articles of this Lease have been inserted solely as a matter of
convenience and such captions in no way define or limit the scope or intent of
any provision of this Lease.

               27.3 Successors and Assigns. The terms, covenants and conditions
contained in this Lease shall bind and inure to the benefit of Landlord and
Tenant and, except as otherwise provided herein, their respective personal
representatives and successors and assigns; provided, however, upon the sale,
assignment or transfer by the Landlord named herein (or by any subsequent
landlord) of its interest in the building as owner or lessee, including any
transfer by operation of law, the Landlord (or subsequent landlord) shall be
relieved from all subsequent obligations or liabilities under this Lease, and
all obligations subsequent to such sale, assignment or transfer (but not any
obligations or liabilities that have accrued prior to the date of such sale,
assignment or transfer) shall be binding upon the grantee, assignee or other
transferee of such interest, and any such grantee, assignee or transferee, by
accepting such interest, shall be deemed to have assumed such subsequent
obligations and liabilities.

               27.4 Severability. If any provision of this Lease or the
application thereof to any person or circumstance shall, to any extent, be
invalid or unenforceable, the remainder of this Lease, or the application of
such provisions to persons or circumstances other than those as to which it is
invalid or unenforceable, shall not be affected thereby, and each provision of
this Lease shall be valid and be enforced to the full extent permitted by law.

               27.5 Applicable Law. This Lease shall be construed and enforced
in accordance with the laws of the State of Maryland.

               27.6 No Option to Lease. Intentionally Deleted.

               27.7 Entire Agreement. This instrument, including the Exhibits
hereto, which are made a part of this Lease, contains the entire agreement
between the parties and all prior negotiations and agreements are merged
herein. Neither Landlord nor Landlord's agents have made any representations or
warranties with respect to the Premises, the Building, the Real Property or
this Lease except as expressly set forth herein, and no rights, easements or
licenses are or shall be acquired by Tenant by implication or otherwise unless
expressly set forth herein.

               27.8 Inspection by Landlord. The review, approval, inspection or
examination by Landlord of any item to be reviewed, approved, inspected or
examined by Landlord under the terms of this Lease or the Exhibits attached
hereto shall not constitute the assumption of any responsibility by Landlord
for either the accuracy or sufficiency of any such item or the quality or
suitability of such item for its intended use. Any such review, approval,
inspection or examination by Landlord is for the sole purpose of protecting
Landlord's interests in the Building and under this Lease, and no third
parties, including, without limitation, Tenant or any person or entity claiming
through or under Tenant, or the contractors, agents, servants, employees,
visitors or licensees of Tenant or any such person or entity, shall have any
rights hereunder.

               27.9 Legal Fees Paid by Prevailing Party. In the event that
either Landlord or Tenant fails to perform any of its obligations under this
Lease or in the event a dispute arises concerning the meaning or interpretation
of any provision of this Lease, the defaulting party or the party not
prevailing in such dispute, as the case may be, shall pay any and all costs and
expenses incurred by the other party in enforcing or establishing its rights
hereunder, including, without limitation, court costs and reasonable counsel
fees.

               27.10 Surrender of Premises. Upon the expiration or sooner
termination of the Term, Tenant will quietly and peacefully surrender to
Landlord the Premises in the condition in which they are required to be kept as
provided hereunder, ordinary wear and tear excepted.

               27.11 Quiet Enjoyment. Upon Tenant paying the Basic Rent and
Additional Rent and performing all of Tenant's obligations under this Lease,
Tenant may peacefully and quietly enjoy the Premises during the Term as against
all persons or entities lawfully claiming by or through Landlord; subject,
however, to the provisions of this Lease and to any mortgages, ground or
underlying lease referred to herein.


                                       9
<PAGE>   10
          27.12 No Reduction in Rent. Tenant covenants and agrees that no
diminution of light, air or view by any structure that may hereafter be erected
(whether or not by Landlord) shall entitle Tenant to any reduction of Basic
Rent or Additional Rent under this Lease, result in any liability of Landlord
to Tenant, or in any other way affect this Lease or Tenant's obligations
hereunder.

          27.13 Holding Over by Tenant. Any holding over after the Term
Expiration Date or the termination of the Term if sooner with the consent of
Landlord shall be construed to be a tenancy from month to month at a rental
equal to one hundred twenty-five percent (125%) of the Basic Rent herein
specified unless Landlord shall specify a different rent in its sole
discretion, together with an amount estimated by Landlord for the monthly
Additional Rent payable under this Lease, and shall otherwise be on the terms
and conditions herein specified so far as applicable. Any holding over without
Landlord's consent shall constitute a default by Tenant and entitle Landlord to
reenter the Premises as provided in Section 16 hereof.

          27.14 Broker; Indemnification Therefor. Intentionally Deleted.

          27.15 No Recordation of Lease by Tenant. Tenant will not record this
Lease or any memorandum or short form hereof, but at the request of Landlord,
Tenant shall execute, acknowledge and deliver to Landlord in proper form for
recordation a memorandum of this Lease, setting forth the terms and provisions
hereof in summary form.

          27.16 No Merger of Estates. The fee title of Landlord and the
leasehold estate of Tenant shall at all times be separate and apart, and shall
in no event be merged, notwithstanding the fact that this Lease or the leasehold
estate created hereby, or any interest in either thereof, may be held directly
or indirectly by or for the account of any person who shall own the fee estate
in the Premises or any portion thereof; and no such merger of estates shall
occur by operation of law, or otherwise, unless and until all persons at the
time having any interest in the fee estate and all persons having any interest
in the Lease or the leasehold estate, including any mortgagee or leasehold
mortgagee, shall join in the execution of a written instrument affecting such
merger of estates.

          27.17 Security Deposit. Simultaneously with the execution of this
Lease, Tenant shall deposit with Landlord the sum of Six Hundred and 00/100
Dollars ($600.00), as a security deposit for the performance by Tenant of the
provisions of this Lease. Such deposit shall be considered as security for the
payment and performance by Tenant of all Tenant's obligations, covenants,
conditions and agreements under this Lease. In the event of any default by
Tenant hereunder, Landlord shall have the right, but shall not be obligated to
apply all or any portion of the deposit to cure such default, in which event
Tenant shall be obligated to promptly deposit with Landlord the amount
necessary to restore the deposit to its original amount. If Tenant is not in
default at the expiration of the Term, Landlord shall return the security
deposit to Tenant. Landlord shall not be required to pay Tenant interest on the
security deposit.

          27.18 Right to Relocate. Landlord shall have the right, exercisable by
giving Tenant reasonable notice, and without liability to Tenant for damage or
injury to property, person or business, all claims for damage being hereby
released by Tenant, and without affecting an eviction or disturbance of Tenant's
use or possession or giving rise to any claim for set offs, or abatement of rent
to relocate Tenant to another location of equal size within the Building at
Landlord's expenses; provided however, that such other location shall have at
least as many square feet of exterior windows as the Premises, and shall contain
improvements that are at least equal in quality, function, etc. to those to be
contained in the Premises, and provided further that Landlord shall use every
reasonable effort to minimize disturbance that any such relocation might cause.

          27.19 Additional Documents. Intentionally Deleted.

          IN WITNESS WHEREOF, Landlord and Tenant have executed this Lease
Agreement as of the day and year first above written.

LANDLORD:                               TENANT:

WARD CORPORATION                         ORGANON TEKNIKA CORPORATION


By: /s/ RICHARD E. WARD                 By: /s/ MICHAEL G. HANNA, Ph.D.
    -------------------                     ---------------------------
    Richard E. Ward                         Michael G. Hanna, Ph.D.
    Its President                           Its Vice President

          
ATTEST:                                 ATTEST:

By: /s/ MARIA M. INGLESBY               By: /s/ RICHARD J. JAMES
    ---------------------                   --------------------------      
    Maria M. Inglesby                       Richard J. James
    Commercial Leasing                      Its Witness

    [Corporate Seal]                        [Corporate Seal]


                                       10
             

           
<PAGE>   11
                                    ADDENDUM

        THIS ADDENDUM is incorporated in and made a part of the foregoing and
annexed Lease dated April 30th, 1991 (the "Lease") between Ward Corporation (the
"Landlord") and Organon Teknika Corporation, (the "Tenant") covering Eight
Hundred Three (803) net rentable square feet in Landlord's building known by the
street address of 1300 Piccard Drive, Rockville, MD 20850, the provisions of
this Addendum being as follows:

1.      The Lease is hereby amended by adding a new Section 28 as follows:

        28. Cancellation Option. Tenant shall have the option to terminate this
        Lease at the end of the thirty-six (36) month of the Lease Term provided
        Tenant has notified Landlord in writing on or before the thirtieth
        (30th) month of the Lease Term, of its election to terminate this Lease.

        Except as hereinafter amended, the Lease remains in full force and
        effect, unmodified. In the event of any conflict between a provision of
        this Addendum or the Lease, the provisions of the Addendum shall
        prevail.

        IN WITNESS WHEREOF, Landlord and Tenant have executed this Addendum as
of the day and year first above written.

LANDLORD:                                TENANT:

WARD CORPORATION                         ORGANON TEKNIKA CORPORATION


By: /s/ RICHARD E. WARD                  By: /s/  MICHAEL G. HANNA, PH.D.
   ---------------------------              -----------------------------
   Richard E. Ward                          Michael G. Hanna, Ph.D.
   Its President                            Its Vice President



ATTEST:                            ATTEST:


By: /s/ MARIA M. INGLESBY                By: /s/ RICHARD J. JAMES
   ---------------------------              -----------------------------
   Maria M. Inglesby                        Richard J. James
   Commercial Leasing                       Its Witness


                                         (Corporate Seal]
(Corporate Seal]

                                       1

<PAGE>   12
                                        SECOND ADDENDUM


        THIS SECOND ADDENDUM is incorporated in and made a part of the foregoing
and annexed Lease dated April 30, 1991 (the "Lease") between Ward Corporation
(the "Landlord") and Organon Teknika Corporation, (the "Tenant") covering Eight
Hundred Three (803) net rentable square feet in Landlord's building known by the
street address of 1300 Piccard Drive, Rockville, MD 20850, the provisions of
this Second Addendum being as follows:

1.      Section 1.9 of the Lease is hereby amended by adding the following
        sentence at the end thereof:

        "Commencing November 15, 1991, the Premises shall contain an additional
        One Thousand One Hundred Fifty-One (1,151) net rentable square feet
        (hereinafter the "Additional Lease Space") which space is shown on
        Attachment "A", thereby causing the entire leased premises to contain a
        total of One Thousand Nine Hundred Twenty-Four (1,924) net rentable
        square feet."

2.      Section 2.1 of the Lease is hereby amended by adding the following
        sentence at the end thereof:

        "Commencing November 15, 1991, Tenant shall pay to Landlord during the
        Term a base rental ("Basic Rent") for the Additional Lease Space equal
        to Nine Hundred Fifty-Nine and 17/100 Dollars ($959.17) per month in
        gross."

3.      Section 2.3 of the Lease is hereby amended by adding the following
        sentence at the end thereof:

        "The Basic Rent for the Additional Lease Space (as defined in Item 2
        hereinabove) shall be increased as follows:

<TABLE>
<CAPTION>
                 Date                        New Monthly Rent
                 ----                        ----------------
<S>                                            <C>      
                6/1/92                         $  987.94
                6/1/93                         $1,017.68
                6/1/94                         $1,048.37
</TABLE>

4.      Section 4 of the Lease is hereby amended by adding the following
        sentence at the end thereof:

        "Tenant agrees to accept the Additional Lease Space in their "as-is"
        condition and further agrees to be fully responsible for any alterations
        or improvements thereto. However, it is understood and agreed that
        Tenant will obtain all necessary permits to construct the premises as
        required by Code. Landlord shall furnish ten (10) 2' X 4' fluorescent
        light fixtures for installation by Tenant."

5.      Section 6.1 of the Lease is hereby amended by adding the following
        sentence at the end thereof:

        "Tenant shall use and occupy the Additional Lease Space during the term
        of the Lease solely for use as storage of non-hazardous research
        supplies, as permitted by law, and for no other use or uses without the
        prior written consent of Landlord."




                        [signatures appear on next page]



                                        1

<PAGE>   13
                                 THIRD ADDENDUM

        THIS THIRD ADDENDUM is incorporated in and made a part of the foregoing
and annexed Lease dated April 30, 1991 (the "Lease") between Ward Corporation
(the "Landlord") and Organon Teknika Corporation, (the "Tenant") covering Eight
Hundred Three (803) of net rentable square feet of storage space ("Leased
Premises") in Landlord's building known by the street address of 1300 Piccard
Drive, Rockville, MD 20850, the provisions of this Third Addendum being as
follows:

1.      Section 1.2 of the Lease is hereby amended by deleting "May 31, 1995"
        and replacing with the following:

        "May 31, 1997".

2.      Section 1.12 of the Lease is hereby amended by deleting "The four year
        (4) period" and replacing with the following:

        "The six year (6) period."

3.      Section 2.1 of the Lease is hereby amended:

        "Rent for the Leased Premises shall be increased as follows:

<TABLE>
<CAPTION>
                        Date       803 sf     New Monthly Amount
                        ----       ------     ------------------
<S>                                <C>            <C>    
                       6/1/95      $10.13         $677.87
                       6/1/96      $10.43         $697.94
                       6/1/97      $10.74         $719.69
</TABLE>

4.      The Lease is hereby amended by adding a new Section 29 as follows:

        Section 29. Renewal Option.   Tenant shall have the right to renew this
        Lease for two (2) two (2) year periods by giving Landlord six (6) months
        written notice prior to the expiration of the then current Lease term. A
        three percent (3%) escalator will follow this Lease throughout the
        Renewal periods. If Tenant should choose not to exercise those options
        Landlord may begin to show the space to prospective tenants ninety (90)
        days prior to the Lease Expiration Date.

        Except as hereinafter amended, the Lease remains in full force and
        effect, unmodified. In the event of any conflict between a provision of
        this Third Addendum or the Lease, the provisions of the Third Addendum
        shall prevail.

        IN WITNESS WHEREOF, Landlord and Tenant have executed this Third
Addendum as of the ____ day of_______________, 1995.

LANDLORD:                                   TENANT:

WARD CORPORATION                            PERIMMUNE, INC.

By: /s/     RICHARD E. WARD                 By: /s/ MICHAEL G. HANNA, JR.
   -------------------------------             ---------------------------------
   Richard E. Ward                             Michael G. Hanna, Jr., Ph.D.
   Its President                               President & CEO


                                            By: 
                                               ---------------------------------
                                               
                                               

ATTEST:                                     WITNESS:


By:    [SIG]                                By:  /s/  RICHARD JAMES
   -------------------------------             ---------------------------------

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