<PAGE>   1
                                                                   Exhibit 10.55


                              101 HUNTINGTON AVENUE
                                PRUDENTIAL CENTER
                           BOSTON, MASSACHUSETTS 02199

                                LEASE COVER SHEET


Lease Date:   June 16, 1997

Tenant:       Creative BioMolecules, Inc.

Floor:        24th Floor

Notice Address:              Creative BioMolecules, Inc.
                             101 HUNTINGTON AVENUE
                             Boston, MA 02199

1.       Premises Net Rentable Area:  8,665 Rentable Square Feet - (RSF)
         Building Net Rentable Area:  523,807 Square Feet

2.       Term Commencement Date:   August 1, 1997

3.       Rent Commencement Date:   The later of August 1, 1997 or the date the
                                   Work (2.1) is Substantially Complete

4.       Term:                     Five years commencing on the Rent 
                                   Commencement Date, subject to Tenant's right 
                                   to extend term for additional period of five
                                   years - Section 12.14

5.       Fixed Rents:

         Years 1 - 5 - at rate of $34.00 per RSF -

<TABLE>
              <S>                         <C> 
              Annual Amount               $294,6l0.00
              Monthly Payment Amount      $ 24,550.83
</TABLE>

6.       A. Base Operating Expense: 1997 Actuals $7.75 RSF Budgeted
         B. Real Estate Tax: Base calendar 1997 - $4.25 RSF Budgeted

                   Tenant Share:      1.65%
<PAGE>   2
7.       Use of Premises:           General Offices




LANDLORD:                                  TENANT:
THE PRUDENTIAL INSURANCE                   CREATIVE BIOMOLECULES, INC.
COMPANY OF AMERICA



By:/s/ DAVID RASZMANN                      By:/s/ WAYNE E. MAYHEW III
   -----------------------------              -----------------------------
       Vice President                             Vice President
<PAGE>   3
                                      LEASE
                                PRUDENTIAL CENTER
                              BOSTON, MASSACHUSETTS

                                TABLE OF CONTENTS


ARTICLE

1.  Description of Premises and Term of Lease

      Section        1.1   Demise
                     1.2   Easement for Utility Lines, etc.
                     1.3   Areas Outside Premises
                     1.4   Term
                     1.5   Commencement Date

2.  Finishing the Premises

      Section        2.1   Work

3.  Payment of Rent and Tenant's Share of Increased Operating Expenses

      Section        3.1   Rent
                     3.2   Increased Operating Expenses
                     3.3   Utility Charges
                     3.4   Real Estate Taxes

4.  Covenants of Landlord

      Section        4.1   Repairs by Landlord
                           Default by Landlord
                     4.2   Services by Landlord

5.  Additional Covenants by Tenant

      Section        5.1   Use of Premises
                     5.2   Tenant's Covenants
                     5.3   Assignment, Subletting
                     5.4   Excess Payments
                     5.5   Repairs by Tenant
                     5.6   Permits and Workmanship
                     5.7   Liens


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<PAGE>   4
                     5.8   Control of Premises
                     5.9   Reserved
                     5.10  Reserved
                     5.11  Tenant's Statement
                     5.12  Surrender of Premises-Removal of Trade Fixtures
                     5.13  Personal Property Tax
                     5.14  Landlord's Right to Perform Tenant's Obligations

6.  Damage or Destruction by Fire or Casualty

      Section        6.1   Total or Partial Destruction by Fire or Otherwise
                     6.2   Damage Within Last Two (2) Years
                     6.3   Apportionment

7.  Eminent Domain

      Section        7.1   Entire or Partial Taking
                     7.2   Condemnation Award
                     7.3   Rent Abatement
                     7.4   Apportionment
                     7.5   Eminent Domain Defined

8.  Default

      Section        8.1   Default by Tenant
                     8.2   Landlord's Remedies

9.  Quiet Enjoyment

10.   Landlord's Reservation of Rights

      Section        10.1  Rights Reserved to Landlord
                     10.2  Access to Premises by Landlord
                     10.3  Landlord's Safety Measures
                     10.4  Hazardous Substances
                     10.5  Interruption of Service

11. Insurance Covenants, Tenant

      Section        11.1
                     11.2
                     11.3
                     11.4
                     11.5
<PAGE>   5
                     11.6
                     11.7

12.   Miscellaneous Provisions

      Section        12.1  Waiver of Subrogation
                     12.2  Subordination
                     12.3  Landlord's Remedies Cumulative
                     12.4  Partial Invalidity
                     12.5  Successors and Assigns
                     12.6  Article Headings and Marginal Notes
                     12.7  Notices
                     12.8  Written Approvals
                     12.9  Broker's Commission
                     12.10 Entire Agreement
                     12.11 Submission of Lease-No Option
                     12.12 Massachusetts Law Governs
                     12.13 Tenant's Parking Rights
                     12.14 Tenant Extension Rights
                     12.15 Exhibits
<PAGE>   6
                                      LEASE
                                PRUDENTIAL CENTER
                              BOSTON, MASSACHUSETTS

          THIS LEASE made this 16th day of June, 1997, between THE PRUDENTIAL
INSURANCE COMPANY OF AMERICA, a New Jersey corporation, having its principal
office at Prudential Plaza, Newark, New Jersey (hereinafter called "LANDLORD"),
and Creative BioMolecules, Inc., a Delaware corporation with an office on the
24th Floor 101 Huntington Avenue, Boston, Massachusetts, (hereinafter called
"TENANT").


W I T N E S S E T H :

          In consideration of the mutual covenants herein expressed, LANDLORD
and TENANT hereby covenant and agree as follows:

                                    ARTICLE I
                    DESCRIPTION OF PREMISES AND TERM OF LEASE

1.1       DEMISE

          LANDLORD hereby leases to TENANT and TENANT hereby leases from
          LANDLORD the Premises (hereinafter called "the Premises") shaded on
          Exhibit A attached hereto and made part hereof located on the 24th
          floor, 101 Huntington Avenue, consisting of approximately 8,665
          rentable square feet (RSF) in that part of Prudential Center in
          Boston, Massachusetts which is shown on Exhibit A-1 attached hereto
          and made part hereof (whereupon the Premises are shaded), excepting
          and reserving from the Premises the roof and the exterior walls of the
          Building in which the Premises are located, and subject to all rights
          hereinafter reserved to LANDLORD and to all rights reserved to
          LANDLORD by operation of law. Said Building (as the same may from time
          to time be constituted after changes therein, additions thereto and
          eliminations therefrom pursuant to rights of LANDLORD hereinafter
          reserved) is hereinafter called "the Building." The Premises are a
          portion of those described in Certificate of Title 64667 issued to
          LANDLORD from the Suffolk Registry District of the Land Court. For all
          purposes of this Lease, the term "Prudential Center" shall refer only
          to such part of Prudential Center as is shown on said Exhibit A-1.

1.2       EASEMENT FOR UTILITY LINES, ETC.

          LANDLORD reserves the right to place (or permit any other TENANT so to
          place) in, over, below and upon the Premises (reasonable notice shall
          be given TENANT and the work shall be performed in such a manner as to
          keep to a minimum interference with TENANT'S use of the Premises and
          without affecting TENANT'S business) utility lines,
<PAGE>   7
          conduits, pipes, tunneling and the like to serve the Premises and
          other premises and to use, replace, maintain and repair (or permit any
          other TENANT so to do) such utility lines, conduits, pipes, tunneling
          and the like in, over, below and upon the Premises as may have been
          installed in the Building or Prudential Center.

1.3       AREAS OUTSIDE PREMISES

          LANDLORD reserves and excepts all rights of ownership and use in all
          respects outside the Premises, including without limitation, the
          Building and all other structures and improvements and plazas and
          common areas in Prudential Center, except that at all times during the
          term of this Lease, TENANT shall have a reasonable means of access
          from a public street to the Premises and the reasonable right to use
          said areas outside the Premises in common with other tenants. Without
          limitation of the foregoing reservation of rights by LANDLORD, it is
          understood that in its sole discretion LANDLORD shall have the right
          to change and rearrange the plazas and other common areas, to change,
          relocate and eliminate facilities therein, to erect new buildings
          thereon, to permit the use of or lease all or part thereof for
          exhibition and displays and to sell, lease or dedicate all or part
          thereof to public use; and further that LANDLORD shall have the right
          to make changes in, additions to and eliminations from the Building
          and other structures and improvements in Prudential Center, the
          Premises excepted; provided however that such changes, additions or
          eliminations do not materially affect TENANT'S Share, and TENANT, its
          employees, agents, clients, customers, and invitees shall at all times
          have reasonable access to the Building and Premises. LANDLORD is not
          under any obligation to permit individuals without proper building
          identification to enter the Building after 6:00 p.m.

1.4       TERM

          TO HAVE AND HOLD the Premises for the term of five (5) years beginning
          on the Commencement Date as hereinafter defined, (the "Term"), subject
          to TENANT'S right to extend the Term as provided in Section 12.14.

          In the event that TENANT should hold over after the expiration or
          sooner termination of the Term, TENANT shall be a lessee at sufferance
          subject to all of the terms and provisions of this Lease in effect
          immediately prior to such holdover, except that TENANT shall pay on
          account of the Rent an amount equal to 1.5 times the Rent most
          recently in effect.


                                        2
<PAGE>   8
1.5       COMMENCEMENT DATE

          The Commencement Date shall be the later of August 1, 1997 or the date
          the Premises are Substantially Complete as provided in Article 2
          hereof and the issuance of a certificate of occupancy. LANDLORD and
          TENANT agree to execute a document setting forth the Commencement Date
          after the Commencement Date has been determined.


                                    ARTICLE 2
                             FINISHING THE PREMISES

2.        WORK

          LANDLORD shall deliver the Premises in their "as is" shell condition
          as described in Exhibit B attached and made a part hereof.

          In connection with the preparation of the Premises (the Work) for
          TENANT'S use and occupancy, LANDLORD and TENANT will select three (3)
          contractors, acceptable to LANDLORD to bid on the Work. LANDLORD shall
          select a contractor (LANDLORD'S Contractor), subject to TENANT'S
          reasonable approval, whose labor will work in harmony with other labor
          working at Prudential Center. The Work will be performed in accordance
          with mutually acceptable plans and specifications (the Plans) drawn by
          LANDLORD'S architect. LANDLORD'S Contractor shall perform the Work in
          a good and workmanlike manner in accordance with all applicable codes.
          The Work shall be Substantially Complete when (1) the Work is
          Substantially Complete to TENANT'S satisfacation, and (2) permission
          has been obtained from the City of Boston Building Department to
          occupy the Premises, and (3) only minor items of finish or adjustment
          (Punch List Items) remain to be finished. LANDLORD shall complete or
          cause to be completed all Punch List Items within thirty (30) days of
          Substantial Completion.

          LANDLORD shall provide TENANT a tenant improvement allowance equal to
          $40.00 per RSF (Tenant Allowance) which shall be used to pay for the
          costs of the Tenant Improvements to the Premises performed by
          LANDLORD'S Contractor. If the cost of preparation of the Premises
          exceed the Tenant Allowance, TENANT agrees to reimburse LANDLORD for
          90% of the amount of such excess within thirty (30) days of receipt of
          LANDLORD'S invoice in reasonable detail and the balance within 10 days
          of certificate of occupancy. LANDLORD shall provide architectural and
          engineering services utilizing McMahon Architects Inc. and Erdman
          Anthony Engineering for preparation of plans and specifications for
          the Tenant Improvements, whose fees shall


                                        3
<PAGE>   9
          be paid from the Tenant Allowance.  LANDLORD'S Contract
          Manager, Premisys Real Estate Services, Inc. (Premisys), will
          be compensated by TENANT for supervision of TENANT'S Work from
          Tenant's Allowance in an amount equal to 3% of the cost of the
          Work.

          In the event the total cost of the Work including architectural and
          engineering services and Premisys' supervision fee is less than $40.00
          per RSF, TENANT shall receive an annual rent credit equal to $ .25 per
          RSF for each dollar per RSF savings of Tenant Allowance. For example,
          if the total amount of Tenant Allowance spent is $38.00 per RSF, the
          rent credit would be $ .50 per RSF and the rent would be $33.50 per
          RSF.


                                    ARTICLE 3
                                 PAYMENT OF RENT
                                       AND
                 TENANT'S SHARE OF INCREASED OPERATING EXPENSES

3.1       RENT

          LANDLORD reserves and TENANT covenants and agrees, commencing on the
          commencement date, to pay to LANDLORD without notice or demand, and
          without setoff, defense, counterclaim, reduction or abatement except
          as provided herein, at the office of LANDLORD at Prudential Center or
          elsewhere as designated from time to time by written notice to TENANT
          and in the manner herein prescribed for payment thereof, rent for the
          Premises as follows:

          Commencing on the Commencement Date (the Rent Commencement Date), a
          fixed guaranteed annual rent, hereinafter called "Rent" payable in
          equal monthly installments in advance on the first day of each month
          throughout the term of this Lease, in the amounts set forth in the
          Lease Cover Sheet attached hereto and made a part hereof subject to
          any rent credit TENANT may be entitled to pursuant to Article 2.
          Simultaneously with the execution and delivery of this Lease, TENANT
          shall pay Rent due for the first month of the Term.

          Rent for any partial months at the beginning and end of the Term shall
          be a pro rata portion (based on the number of days in the particular
          month) of the monthly installment of Rent for the respective Lease
          year.

          TENANT also agrees to pay to LANDLORD, on demand, interest on all
          overdue installments of Rent commencing five (5) days from the due
          date thereof until payment thereof in full at a rate equal to twelve
          (12%) percent per year.


                                        4
<PAGE>   10
3.2       INCREASED OPERATING EXPENSES

          Commencing on January 1, 1998, TENANT also agrees to reimburse
          LANDLORD for TENANT'S Share of Increased Operating Expense in excess
          of Base Operating Expenses in accordance with Exhibit F attached
          hereto and made a part hereof.

          TENANT also agrees to pay LANDLORD, on demand, interest on all overdue
          installments of TENANT'S Share of increased operating expenses from
          the due date of written notice of overdue payment thereof until
          payment thereof in full at a rate equal to twelve (12%) percent.

3.3       UTILITY CHARGES

          TENANT shall pay directly to Boston Edison the costs of electrical
          service consumed in the Premises as measured by a separate meter.

          LANDLORD'S charges for chilled water used in supplemental HVAC units,
          if any, serving the Premises exclusively as measured by a meter
          installed by LANDLORD shall be billed to and paid for monthly by
          TENANT. LANDLORD'S charges for chilled water shall be commercially
          reasonable and shall not exceed the rates charged to other tenants of
          the Building.

3.4       REAL ESTATE TAXES

          Commencing on January 1, 1998, TENANT covenants and agrees to pay as
          Additional Rent each year of the term the amount equal on a per square
          foot basis of the increase in real estate taxes over the amount paid
          by LANDLORD in calendar 1997 as real estate taxes. TENANT shall make
          payments in its share of increased real estate taxes monthly with the
          payment of Rent and Additional Rent based upon LANDLORD'S good faith
          estimate of TENANT'S Share of increased Real Estate Taxes. TENANT'S
          monthly payment shall equal 1/12 TENANT'S estimated annual liability
          for increased taxes which LANDLORD shall adjust periodically to
          reflect tax bills received from the City of Boston. Each year at the
          time LANDLORD provides TENANT with a statement of operating costs as
          provided in Exhibit F, LANDLORD shall also provide TENANT with a
          statement of tax payments. LANDLORD shall refund to TENANT any
          overpayments at any time and TENANT shall promptly (within 30 days),
          pay any underpayment. LANDLORD shall deliver to TENANT upon request
          copies due TENANT of relevant tax bills with allocation detail.


                                        5
<PAGE>   11
          It is the intent of the LANDLORD and TENANT that, in the event the
          scheme of taxation is altered in any way, TENANT shall pay, and hereby
          covenants and agrees to pay, its proportionate Tenant's Share of such
          charges so that there will be no increased cost to LANDLORD.


                                    ARTICLE 4
                              COVENANTS OF LANDLORD

4.1       REPAIRS BY LANDLORD

          Subject to the provisions of Articles 6 and 7 and except for any loss,
          destruction or damage caused by omission, negligence or fault of
          TENANT, LANDLORD covenants and agrees at LANDLORD'S cost and expense:
          to inspect and cause the structural floor slabs, exterior walls,
          load-bearing interior walls, columns of the Premises and building
          system including the heating, ventilating, plumbing and electrical,
          that service the Premises and the rest of the Building including
          common areas (excluding all doors and interior glass, finish and
          coverings) to be kept in good order, repair and condition.

          DEFAULT BY LANDLORD

          LANDLORD shall in no event be in default in the performance of any
          obligations under this Section 4.1 unless and until LANDLORD shall
          have failed to respond within 7 days of any written notice from TENANT
          and to perform such obligations within thirty (30) days (or such
          additional time as is reasonably required to correct any such default)
          after notice by TENANT to LANDLORD properly specifying wherein
          LANDLORD has failed to perform any such obligation, and in no event
          shall LANDLORD be liable to TENANT for any indirect or consequential
          damages.

4.2       SERVICES BY LANDLORD

          LANDLORD further covenants and agrees:

          (i) LANDLORD shall subject to all governmental orders or decrees
          furnish space heating and cooling (air conditioning) as normal
          seasonal changes may require to provide reasonably comfortable space
          temperature and ventilation for occupants of the Premises under normal
          business operation, daily from 8:00 A.M. to 6:00 P.M. (Saturday to
          1:00 P.M.), Sundays and holidays excepted. Whenever machines or
          equipment are used in the Premises which affect the temperature
          otherwise maintained, LANDLORD, with TENANT'S prior approval not to be
          unreasonably withheld or delayed, reserves the right to install
          supplementary air conditioning and heating units in


                                        6
<PAGE>   12
          the Premises and the cost of such units and the installation thereof
          shall be paid by TENANT to LANDLORD upon demand. The cost of operating
          and maintaining the same shall be borne by TENANT.

          (ii) LANDLORD shall provide the cleaning services and incidental
          supplies set forth on Exhibit C attached hereto and made a part
          hereof.

          (iii) LANDLORD shall supply, for normal business office use, water for
          lavatory and toilet purposes in the Building toilet rooms.

          (iv) LANDLORD shall furnish non-exclusive use of fully automatic
          (operator less) passenger elevators for ingress to and egress from the
          floor or floors upon which the Premises are located. The service shall
          be supplied daily by passenger elevators serving such floors from 8:00
          A.M. to 6:00 P.M., Saturdays, Sundays and holidays excepted. Automatic
          freight elevator service shall be available in common with other
          tenants from 8:00 A.M. to 5:00 P.M. daily, Saturdays, Sundays and
          holidays excepted. TENANT shall have limited non-exclusive elevator
          access to the Premises (i.e. controlled by Building security services)
          24 hours a day 365 days a year, subject to disruptions caused by acts
          of God or other causes beyond LANDLORD'S control. LANDLORD reserves
          the right to program the elevator service in the Building to obtain in
          its sole discretion the most efficient and economically feasible
          method of bringing in and taking out all persons using the Building.
          TENANT agrees to cooperate in the programming of such service of those
          elevators serving the floor or floors on which the Premises are
          located.


                                    ARTICLE 5
                         ADDITIONAL COVENANTS OF TENANT

               TENANT further covenants and agrees:

5.1       USE OF PREMISES

          To use and occupy the Premises for general offices and for no other
          use whatsoever. TENANT shall not cause or permit any noise or sounds
          to emit from the Premises, into the rest of the Building, or otherwise
          disturb other tenants in the Building.

          It is expressly agreed that TENANT shall not use the Premises, or
          permit the same to be used, for any manufacturing or mechanical
          purposes or for the sale of food or alcoholic or non-alcoholic
          beverages for consumption on or off the Premises or for cooking and
          preparation of food even though any of such uses might, but for this


                                        7
<PAGE>   13
          provision, be regarded as incidental to the business of TENANT. TENANT
          may, for its own use, have microwave ovens, coffee makers, and
          refrigerators for storage and preparation of light meals for officers,
          employees and guests.

5.2       TENANT'S COVENANTS

          In connection with TENANT'S use of the Premises:

          (i) TENANT shall not conduct any auction, fire, bankruptcy, going out
          of business, liquidation or similar sales and TENANT shall not use any
          walk or passageways adjacent to Premises for business purposes.

          (ii) TENANT shall comply with all laws, orders and regulations and
          with the directions of any public officer authorized by law with
          respect to the Premises and the use and occupancy thereof and shall
          not suffer or permit any use of the Premises which directly or
          indirectly is forbidden by law, ordinance or governmental or municipal
          regulation or order or which may be dangerous to life, limb or
          property.

          (iii) TENANT shall not erect, install or maintain any sign, lettering,
          placard or similar matter if all or any part of such sign, lettering,
          placard or similar matter is painted upon or posted or otherwise
          affixed to the exterior or interior of any window or door or the glass
          thereof or is otherwise located in such manner as to be visible from
          the outside of the Premises without, in each case, obtaining
          LANDLORD'S advanced written consent not to be unreasonably withheld.
          Neither LANDLORD'S name nor the word "Prudential" alone or in any
          combination other than "Prudential Center" shall be used by the TENANT
          for any purpose whatsoever. TENANT shall not use the words "Prudential
          Center" other than as part of the business address of TENANT and then
          only in such manner as will not appear to be part of TENANT'S name.
          TENANT shall not use the words "Prudential Center" in any manner
          which is undignified, confusing, detrimental or misleading in
          LANDLORD'S opinion and shall give no greater prominence to the words
          "Prudential Center" than to any other part of the business address of
          TENANT and shall give less prominence to the words "Prudential
          Center" than to TENANT'S name. LANDLORD shall provide TENANT, at
          LANDLORD'S cost and expense, with appropriate listings in the
          Building Directory. TENANT, at its sole cost and expense, may, with
          LANDLORD'S approval not to be unreasonably withheld or delayed,
          install signage in the lobby of the floor the Premises are on
          consistent with the Building signage policy.
        
          (iv) TENANT shall not do or permit to be done any act or thing which
          will invalidate or be in conflict with fire or other insurance
          policies covering the Building or its operation or the Premises or
          part of either; or do or permit to be done anything in or


                                        8
<PAGE>   14
          about the Premises or bring or keep anything therein which shall not
          comply with all rules, orders, regulations or requirements of the
          Board of Fire Underwriters or any similar organization (and TENANT
          shall at all times comply with all such rules, orders, regulations and
          requirements); or which shall increase the rate of insurance on the
          Building, its appurtenances or contents, unless TENANT shall reimburse
          LANDLORD to the extent of such increase.

          (v) TENANT shall not install or operate any refrigerating, heating or
          air conditioning apparatus without the written permission of LANDLORD
          which permission shall not be unreasonably withheld or delayed except
          as specified in the Work.

          (vi) TENANT shall not place any radio or television antenna on the
          roof or on or in any part of the Building other than the inside of the
          Premises; or operate or permit to be operated any musical or
          sound-producing instrument or device inside or outside the Premise
          which may be heard outside the Premises; or operate any electrical
          device from which may emanate electrical waves or any other emanations
          which interfere with or impair radio or television or telephone
          broadcasting or reception from or in the Building or elsewhere in
          Prudential Center.

          (vii) TENANT shall not place anything or allow anything to be placed
          near the glass of any door, partition or window which may be unsightly
          from outside the Premises; or obstruct any passageway, exit, stairway,
          elevator, shipping platform or truck concourse. TENANT shall lend its
          full cooperation to keep such areas free from all obstruction and in a
          clean and sightly condition and move all supplies, furniture and
          equipment as soon as received directly to the Premises and move all
          such items and waste being taken from the Premises directly to the
          loading platform designated by LANDLORD at or about the time arranged
          for removal therefrom. TENANT shall also keep the premises free of
          vermin and shall not permit any odors to emanate from the Premises.
          LANDLORD shall, at TENANT'S request and expense, provide vermin
          extermination services to the Premises.

          (viii) TENANT shall not move any safe, vault or other heavy equipment
          in or out of the Premises except in such a manner and at such time as
          LANDLORD shall in each instance authorize, not to be unreasonably
          withheld.

          (ix) TENANT shall not place a load upon the floor area of the Premises
          exceeding seventy-five (75) pounds per square foot.

          (x) TENANT shall make no material installations, alterations or
          additions in or to the Premises without LANDLORD'S prior written
          consent, not to be unreasonably


                                        9
<PAGE>   15
          withheld, and then only pursuant to plans and specifications approved
          by LANDLORD in advance in each instance.

          (xi) TENANT shall obey and comply with all rules and regulations
          promulgated by the LANDLORD pursuant to Section 10.1 hereof, so long
          as the same are applying in a non-discriminatory manner to all tenants
          in Building.

5.3       ASSIGNMENT, SUBLETTING

          TENANT shall not assign, transfer, mortgage or pledge this Lease or
          sublease (which term shall be deemed to include the granting of
          concessions and licenses and the like) all or any part of the Premises
          without first obtaining on each occasion the written consent of
          LANDLORD, which consent shall not be unreasonably withheld or delayed,
          or suffer or permit this Lease or the leasehold estate hereby created
          or any other rights arising under this Lease to be assigned,
          transferred or encumbered, in whole or in part, whether voluntarily,
          involuntarily or by operation of law, or permit the occupancy of the
          Premises by anyone other than TENANT. Any attempted assignment,
          transfer, mortgage, pledge, sublease or other encumbrance made without
          such written consent shall be void. No assignment, transfer, mortgage,
          pledge, sublease or other encumbrance shall affect the continuing
          primary liability of TENANT and no consent to any of the foregoing in
          a specific instance shall operate as a waiver in any subsequent
          instance.

          Notwithstanding the foregoing, TENANT may, without LANDLORD'S consent,
          but with written notice to LANDLORD, assign this Lease or sub-lease
          all or a portion of the Premises to any entity (i) controlled by
          TENANT, (ii) controlling TENANT and (iii) controlled by an entity
          controlling TENANT. Control for the purposes of the foregoing shall
          mean ownership directly or beneficially of greater than 50% or more of
          the stock or partnership interest in the entity.

5.4       EXCESS PAYMENTS

          In the event that the aggregate of all payments received by, or paid
          to discharge an obligation of, TENANT as a result of any assignment,
          subletting or permission to use or occupy the Premises, whether or not
          LANDLORD shall have consented hereto (it being agreed by TENANT that
          nothing herein contained shall in anyway affect the covenant contained
          herein prohibiting an assignment of subletting of the Premises without
          LANDLORD'S prior consent), shall exceed the aggregate of all payments
          less all reasonable and customary transaction costs, including but not
          limited to brokerage commission, legal fees, marketing materials,
          Tenant Improvements, Rental Holiday,


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<PAGE>   16
          payable by TENANT hereunder, then TENANT agrees to pay to LANDLORD 50%
          of the amount of any such excess.

5.5       REPAIRS BY TENANT

          TENANT shall, subject to the provisions Section by 4.1 and Articles 6
          and 7, and subject to reasonable wear and tear and any loss or damage
          from a casualty, at TENANT'S own cost and expense: keep neat and clean
          and in good order, repair and condition the Premises, including
          without limitation, all glass, windows, interior walls and doors and
          the interior of the Premises and all air conditioning, heating,
          plumbing, electrical, ventilating, lighting and other mechanical
          equipment within and serving the Premises (other than building
          standard air conditioning, heating, plumbing and electrical) and all
          the installations made by TENANT pursuant to Article 2 or otherwise,
          to the extent not covered by Landlord's repair obligations and will
          make all alterations, improvements, replacements, repairs or
          renovations to the Premises required by any laws, rules, regulations
          or requirements of all public authorities or the fire insurance rating
          association having jurisdiction after the Commencement Date; make all
          repairs and replacements and do all other work necessary for the
          foregoing purposes and also make at LANDLORD'S request all repairs to
          and replacements of the items referred to in Section 4.1 and
          LANDLORD'S property outside the Premises which are necessitated solely
          by any negligence, fault or omission of TENANT, all of the foregoing
          repairs and replacements to be at least equal in condition to the
          original condition of the item repaired or replaced. TENANT shall use
          reasonable diligence to conserve steam and hot and cold water supplied
          by LANDLORD.

5.6       PERMITS AND WORKMANSHIP

          Except as provided in Section 2, TENANT shall pay when due the entire
          cost of any work in the Premises undertaken by TENANT so that the
          Premises shall at all times be free of liens for labor and materials;
          procure all necessary permits before undertaking such work; do all of
          such work in a good and workmanlike manner, employing materials of
          good quality and complying with all governmental requirements; and
          defend, save harmless and indemnify LANDLORD from all claims, injury,
          loss or damage to any person or property occasioned by or growing out
          of such work. TENANT further agrees to employ for such work one or
          more responsible contractors whose labor will work in harmony with any
          other labor then working in Prudential Center and to cause such
          contractors employed by TENANT to carry Workmen's Compensation
          Insurance in accordance with statutory requirements and Comprehensive
          Public Liability Insurance covering such contractors on or about the
          Premises in such reasonable amounts as LANDLORD shall require and to
          submit certificates evidencing such coverage to LANDLORD prior to the
          commencement of such work.


                                       11
<PAGE>   17
5.7       LIENS

          In the event any mechanic's lien shall at any time be filed against
          the Premises by reason of work, labor, service or materials performed
          or furnished to TENANT or to anyone holding the Premises through or
          under TENANT, TENANT shall forthwith, after written notice, cause the
          same to be discharged of record. If TENANT shall fail to cause such
          lien forthwith to be discharged after being notified of the filing
          thereof, then, in addition to any other right or remedy of LANDLORD,
          LANDLORD may, but shall not be obligated to, discharge the same by
          paying the amount claimed to be due, and the amount so paid by
          LANDLORD and all costs and expenses, including reasonable attorneys'
          fees, incurred by LANDLORD in procuring the discharge of such lien,
          shall be due and payable by TENANT to LANDLORD on the first day of the
          next following month, with interest thereon at a rate equal to the
          lesser of (a) the maximum rate permitted by applicable law, or (b)
          twelve (12%) percent per year.

5.8       CONTROL OF PREMISES

          TENANT shall assume exclusive control of the Premises and all tort
          liabilities incident to the control or ownership thereof, and defend,
          save harmless and indemnify LANDLORD from all claims, damage or costs,
          including attorney's fees, arising on account of any injury or damage
          to any person or property including, without limitation, the personal
          property of TENANT and TENANT'S servants, employees, agents, guests,
          visitors and licensees, on the Premises, or otherwise resulting from
          the use or maintenance or occupancy by TENANT or anyone claiming under
          it of the Premises or of the sidewalks and ways immediately adjoining
          the Premises.

          TENANT further agrees that LANDLORD shall not be responsible or liable
          to TENANT, or to those claiming by, through or under TENANT for any
          loss or damage that may be occasioned by or through the acts or
          omissions of any person other than LANDLORD, its agents, contractors
          and employees including, without limitation, persons occupying
          premises which adjoin or are adjacent to or connect with the Premises
          or any part of the Building.

          All of the furnishings, fixtures, equipment, effects and property of
          every kind, nature and description of TENANT and of all persons
          claiming by, through or under TENANT which, during the continuance of
          this Lease or any occupancy of the Premises by TENANT or anyone
          claiming under TENANT, may be on the Premises or elsewhere in
          Prudential Center, shall be at the sole risk and hazard of TENANT, and
          if the whole or any part thereof shall be destroyed or damaged by
          fire, water or otherwise, or by the leakage or bursting of water
          pipes, steam pipes, or other pipes, by


                                       12
<PAGE>   18
          theft or from any other cause, no part of said loss or damage is to be
          charged to or to be borne by LANDLORD.

          Notwithstanding the foregoing provisions, LANDLORD shall in no event
          be indemnified or held harmless or exonerated from any liability to
          TENANT or to any other person, for injury, loss, damage, or liability
          arising from any omission, fault, negligence or other misconduct of
          LANDLORD within the meaning of the provisions of Massachusetts General
          Laws, Chapter 186, Section 15, as the same are in force at the time of
          delivery of this Lease.

5.9       (Intentionally left blank)



5.10      (Intentionally left blank)



5.11      TENANT'S STATEMENT

          TENANT agrees, subject to the conditions set forth below, from time to
          time, not more than once in twelve (12) months, upon not less than
          fifteen (15) days prior written request by LANDLORD, to execute,
          acknowledge and deliver to LANDLORD a statement in writing certifying
          that this lease is unmodified and in full force and effect (or, if
          there have been any modifications that the same is in full force and
          effect as modified and stating the modification), the dates to which
          the Operating Expenses, Rent, and any other rent and charges have been
          paid, the TENANT has accepted possession of the Premises, no Rent or
          other charges have been paid more than thirty (30) days in advance,
          the TENANT has no defenses, offsets or counterclaims against its
          obligations hereunder and whether or not the LANDLORD is in default in
          the performance of any of its obligations hereunder. Any such
          statement delivered pursuant to this Section 5.11 may be relied upon
          by any prospective purchaser or mortgagee of the Premises or any
          prospective assignee of any mortgage of the Premises.

          TENANT'S obligation under this Section 5.11 shall be subject to
          written acknowledgement by any prospective purchaser, mortgagee or
          assignee of any mortgage of the Premises that TENANT'S possession of
          the Premises under this Lease shall not be disturbed.


                                       13
<PAGE>   19
5.12      SURRENDER OF PREMISES-REMOVAL OF TRADE FIXTURES

          At the expiration or earlier termination of this Lease, TENANT shall
          remove all installations, moveable fixtures, moveable partitions and
          personal property in the Premises and such installations made under
          Article 2 or otherwise as LANDLORD shall request and all its signs
          wherever located and shall surrender all keys to the Premises and
          yield up the Premises in as good, clean and safe repair, order and
          condition, reasonable wear and tear excepted. Any property not so
          removed shall be deemed abandoned and may be removed and disposed of
          by LANDLORD in such manner as LANDLORD shall determine and TENANT
          shall pay LANDLORD the entire cost and expense incurred by it in
          effecting such removal and disposition and in making any incidental
          repairs and replacements to the Premises and Building. TENANT shall
          further indemnify LANDLORD against all loss, costs, and damage,
          including attorney's fees, resulting from TENANT'S failure and delay
          in surrendering the Premises as above provided.

5.13      PERSONAL PROPERTY TAX

          TENANT shall pay promptly when due all taxes which may be imposed upon
          personal property (including, without limitation, fixtures and
          equipment) in the Premises to whomever assessed, and shall pay all
          license and similar fees and taxes which may be imposed on the
          business of TENANT conducted upon the Premises.

5.14      LANDLORD'S RIGHT TO PERFORM TENANT'S OBLIGATIONS

          If TENANT shall at anytime default in the performance of any
          obligation under this Lease, after reasonable written notice from
          LANDLORD, LANDLORD shall have the right, but shall not be obligated,
          to perform such obligation notwithstanding the fact that no specific
          provision for such substituted performance by LANDLORD is made in this
          Lease with respect to such default. In performing such obligation,
          LANDLORD may make any payment of money or perform any other act. All
          sums so paid by LANDLORD and all necessary incidental costs and
          expenses in connection with the performance of any such act by
          LANDLORD, shall be payable to LANDLORD immediately on demand, and, if
          not paid within ten (10) days after demand, shall accrue interest at a
          rate equal to the lesser of (a) the maximum rate permitted by
          applicable law, or (b) twelve (12%) percent. LANDLORD may exercise the
          foregoing rights without waiving any other of its rights or releasing
          TENANT from any of its obligations under this Lease.


                                       14
<PAGE>   20
                                    ARTICLE 6
                    DAMAGE OR DESTRUCTION BY FIRE OR CASUALTY

6.1       TOTAL OR PARTIAL DESTRUCTION BY FIRE OR OTHERWISE

          If the Building is damaged and made substantially untenantable by fire
          or casualty, whether or not the Premises are damaged, LANDLORD may by
          written notice to TENANT given within sixty (60) days after such
          occurrence terminate this Lease. Such termination shall be effective
          as of the date of such damage if the Premises have been made
          untenantable by said casualty, otherwise as of a date sixty (60) days
          following the giving of such notice of termination, subject to the
          option hereby given TENANT to advance said effective date of
          termination, such option to be exercised by written notice specifying
          such earlier effective date of termination.

          Unless this Lease is terminated under the foregoing provisions of this
          Section 6.1, if the Premises are made partially or wholly untenantable
          by fire or casualty, LANDLORD shall use reasonable dispatch to restore
          that part thereof originally constructed by LANDLORD or any prior
          owner thereof (including any work described in Article 2) to
          substantially the same condition of such part at the time of such
          damage, subject, however, to zoning laws and building codes then in
          force, and only to the extend of insurance proceeds recovered by
          LANDLORD. LANDLORD shall not be responsible for any delay in the
          performance of the foregoing obligation which may result from
          governmental regulations, inability to obtain labor or materials or
          any other cause beyond LANDLORD'S reasonable control. There shall be a
          reasonable abatement of Rent and Operating Expenses, parking charges
          and all other amounts payable under this Lease from the later of the
          time of any such damage to the Premises or the date the conduct of
          TENANT'S business at the Premises is substantially impaired as a
          result of damage to the Building (provided, in the later instance,
          TENANT has vacated the Premises) until completion of restoration as
          aforesaid by LANDLORD. LANDLORD shall endeavor to locate temporary
          alternate space for TENANT'S use and occupancy. Notwithstanding
          anything to the contrary, in this Article 6, if, within 120 days of
          the fire or casualty, (i) LANDLORD shall not have completed the
          restoration or (ii) LANDLORD shall not have sufficiently repaired the
          damage to the Building and the conduct of TENANT'S business continues
          to be substantially impaired or the Premises are not reasonably
          accessible, TENANT shall have the right, by notice to LANDLORD to
          terminate this Lease effective as of the date of the notice.

6.2       DAMAGE WITHIN LAST TWO YEARS

          Notwithstanding the foregoing provisions of Section 6.1, if any
          substantial damage to or destruction of the Premises (i.e. 50% or
          more of the Premises) shall occur within the


                                       15
<PAGE>   21
          last two (2) years of the term, and shall be of such a character that
          the Premises cannot reasonably be expected to be repaired and restored
          within one hundred twenty (120) days from such damage or destruction,
          then either party may elect to terminate this Lease by written notice
          given to the other party within thirty (30) days after such damage or
          destruction and in such event this Lease shall terminate as of the
          date of such damage or destruction.

6.3       APPORTIONMENT

          In the event of any termination under the provisions of this Article
          6, Rent and other payments shall be apportioned as of the termination
          date.


                                    ARTICLE 7
                                 EMINENT DOMAIN

7.1       ENTIRE OR PARTIAL TAKING

          If the entire Premises, or such portion thereof as would substantially
          impair the conduct of TENANT'S business, shall be taken by right of
          eminent domain, either party may terminate this Lease by written
          notice given to the other party within thirty (30) days after TENANT
          has been deprived of possession, such termination to be effective as
          of the date on which TENANT has been deprived of possession. If the
          Building or any substantial part thereof, whether or not including the
          Premises, is taken by right of eminent domain, LANDLORD may terminate
          this Lease by written notice given to TENANT within thirty (30) days
          after such taking, such termination to be effective as of the date on
          which TENANT has been deprived of possession if TENANT has so been
          deprived, otherwise as of the date specified in such notice which
          shall be not less than fifteen (15) nor more than thirty (30) days
          after the giving of such notice. Should any part of the Premises be
          taken and this Lease is not terminated in accordance with the
          foregoing provisions, LANDLORD covenants and agrees promptly to
          restore that part of the Premises originally constructed by LANDLORD
          to an architectural unit as nearly like the condition of such part
          prior to such taking as shall be practicable, but only to the extent
          of the condemnation proceeds received by LANDLORD.

7.2       CONDEMNATION AWARD

          LANDLORD shall have, and hereby reserves and excepts, and TENANT
          hereby grants and assigns to LANDLORD, exclusive rights to recover and
          retain the award for any taking of or damage done to the Premises or
          any part thereof (including, without limitation, all such
          installations made by TENANT under Article 2 or otherwise except


                                       16
<PAGE>   22
          for TENANT'S trade fixtures) or the leasehold estate hereby created or
          to any other premises of LANDLORD over, under and in the vicinity of
          the Premises. TENANT shall have and LANDLORD hereby grants and assigns
          to TENANT exclusive rights to recover and retain any amounts which may
          be specifically awarded to it for any taking or damage by public
          authority to any of TENANT'S trade fixtures.

7.3       RENT ABATEMENT

          In the event of any such taking of the Premises, the Rent or a fair
          and just proportion thereof according to the nature, duration and
          extent of the damage sustained, shall be suspended or abated until the
          Premises or what may remain thereof shall be restored by LANDLORD
          pursuant to Article 7.1.

7.4       APPORTIONMENT

          In the event of any termination under the provision of the Article 7,
          rent and other payments shall be apportioned as of the termination
          date.

7.5       EMINENT DOMAIN DEFINED

          The term "eminent domain" shall include the exercise of any similar
          governmental power and any purchase or other acquisition by
          governmental authority in lieu of condemnation.


                                    ARTICLE 8
                                     DEFAULT

8.1       DEFAULT BY TENANT

          If at any time after the date hereof (whether the term of this Lease
          is then in force or has not yet begun) any of the following shall
          occur:

                           a.   TENANT shall be in default in the performance of
                  any of its obligations set forth in Articles 3 continuing for
                  seven (7) days after written notice from LANDLORD (provided,
                  however, that there shall be no grace period if TENANT has
                  received two (2) notices of default under Article 3 in any
                  twelve (12) month period); or TENANT shall be in default in
                  the performance of any other obligation, warranty or agreement
                  by TENANT set forth herein continuing for thirty (30) days
                  after notice from LANDLORD (or if any such default is
                  non-monetary and cannot reasonably be cured within such


                                       17
<PAGE>   23
                  time period, such period shall be extended for so long as it
                  takes to cure such default as long as TENANT has commenced
                  curing within such time period and thereafter diligently
                  prosecutes the curing of the defect); or

                           b.   any assignment, trust or other arrangement for
                  the benefit of creditors is made by TENANT; or

                           c.   the leasehold interest hereunder is taken on
                  execution or is subjected to any lien and such levy or
                  lien is not removed or reasonable security for its
                  removal is not provided, in either case within ten (10)
                  days after such levy or lien becomes effective; or

                           d.   a petition is filed by TENANT or those claiming
                  through or under TENANT, for adjudication as a bankrupt or for
                  reorganization or an arrangement or for any other relief under
                  the Bankruptcy Reform Act or other federal or state insolvency
                  laws, or, any involuntary petition under any of the provisions
                  of said Act or laws is filed against TENANT or those claiming
                  through or under TENANT and said involuntary petition is not
                  dismissed within ninety (90) days of filing; or

                           e.   the Premises are vacated or abandoned (whether
                  or not keys have been returned or rent is paid); or

                           f.   within a period of thirty (30) days after 
                  written notice from LANDLORD to TENANT, specifying any other
                  default or defaults in the performance of any other
                  obligation of TENANT, TENANT has not corrected or commenced
                  to correct, to LANDLORD'S reasonable satisfaction, the
                  default or defaults so specified;

          then, in any such case, LANDLORD may lawfully, immediately or at any
          time thereafter, and without notice, demand (subject to applicable law
          including any statute relating to summary process and section of the
          Bankruptcy Code, if applicable), either enter into and upon the
          Premises or any part thereof and expel TENANT and those claiming
          through or under TENANT and remove their goods, effects and fixtures
          and store them at TENANT'S expense without liability for prosecution
          or damage thereof or mail a notice of termination to TENANT, and upon
          such entry or mailing, this Lease and TENANT'S possessions and all
          rights relating to the Premises shall terminate, cease and be at an
          end, including all of TENANT'S statutory rights of redemption, said
          rights being hereby waived by TENANT.


                                       18
<PAGE>   24
          The failure of LANDLORD at any time to exercise any of its options to
          forfeit and terminate this Lease in case of a default shall not waive
          the right of forfeiture or termination of this Lease as herein
          provided. Any right accruing to LANDLORD hereunder to forfeit or
          terminate this Lease shall not be waived or defeated except by the
          written waiver of LANDLORD, and acceptance of rent shall not, in any
          event, be construed as a waiver.

8.2       LANDLORD'S REMEDIES

          In the event that this Lease is terminated under any of the provisions
          contained in Section 8.1 or shall be otherwise terminated for breach
          of any obligation of TENANT, TENANT covenants to pay forthwith to
          LANDLORD, as compensation, the excess of the total rent reserved for
          the residue of the term over the rental value of the Premises for said
          residue of the term. In calculating the rent reserved there shall be
          included in addition to the Rent and Operating Expenses, the value of
          all other considerations agreed to be paid or performed by TENANT for
          said residue.

          TENANT further covenants as an additional and cumulative obligation
          after any such ending to pay punctually to LANDLORD all the sums and
          perform all the obligations which TENANT covenants in this Lease to
          pay and perform in the same manner and to the same extent and at the
          same time as if this Lease had not been terminated. In calculating the
          amounts to be paid by TENANT under the next foregoing covenant TENANT
          shall be credited with any amount paid to LANDLORD as compensation as
          in this Section 8.2 provided and also with the net proceeds of any
          rent obtained by LANDLORD by reletting the Premises, after deducting
          all LANDLORD'S expenses in connection with such reletting, including,
          without limitation, all repossession cost, brokerage commissions, fees
          for legal services and expenses of preparing the Premises for such
          reletting.

          In lieu of any other damages or indemnity and in lieu of full recovery
          by LANDLORD of all sums payable under the provisions of the next
          preceding paragraph, LANDLORD at any time after such termination and
          before such full recovery by LANDLORD under the provisions of the next
          preceding paragraph may, by written notice to TENANT, elect to recover
          as liquidated damages an amount equal to the aggregate of the annual
          Rent and Operating Expenses accrued under Article 3 in the twelve (12)
          months ended next prior to such termination plus the amount of any
          Rent of any kind accrued and unpaid at the time of termination and
          less the amount of any recovery by LANDLORD under the provisions of
          the next preceding paragraph up to the time of payment of such
          liquidated damages.


                                       19
<PAGE>   25
                                    ARTICLE 9
                                 QUIET ENJOYMENT

          QUIET ENJOYMENT

          LANDLORD covenants that it has full authority to make this Lease for
          the full term thereof and that TENANT, paying the Rent reserved and
          performing and observing the agreements and conditions herein on its
          part to be performed and observed, shall and may during the term
          hereof peaceably and quietly have, hold and enjoy the Premises,
          subject, however, to all provisions of this Lease.


                                   ARTICLE 10
                        LANDLORD'S RESERVATION OF RIGHTS

10.1      RIGHTS RESERVED TO LANDLORD

          Without limitation of any of the rights LANDLORD would otherwise have
          and without effecting an eviction or disturbance of TENANT'S use or
          possession of the Premises or giving rise to any claim or set-off or
          abatement of rent or assuming any obligation by the reservation or
          exercise of any such rights, LANDLORD may exercise any and all of the
          following rights:

                           (i)   To designate the time, manner and sources of
                  furnishing refuse and garbage collections and further to
                  designate the times and the routes of incoming and outgoing
                  freight and the removal routes of all garbage and refuse.

                           (ii)  To have passkeys to the Premises to be used 
                  only in the event of an emergency and TENANT cannot be
                  located, or pursuant to Section 10.2 hereof.

                           (iii) At any time or times, upon reasonable written
                  notice, to decorate and to make, at its own expense, repairs,
                  alterations, additions and improvements, structural or
                  otherwise, in or to the Building or part thereof, and during
                  such operations to take into and through the Premises or any
                  part of the Building all materials required, and to close or
                  temporarily suspend operation of entrances, doors, corridors,
                  elevators and other facilities. LANDLORD may do any such work
                  during ordinary business hours provided that if TENANT shall
                  pay LANDLORD for overtime or premium wages and for other
                  additional expenses incurred, such work shall be done during
                  other hours if TENANT so


                                       20
<PAGE>   26
                  requests. LANDLORD agrees that it will endeavor to carry out
                  work under this subparagraph so as to keep to a minimum
                  interference with TENANT'S use of the Premises.

                           (iv)   To modify, alter or relocate facilities 
                  utilized in common with other tenants in the Building or
                  Prudential Center.

                           (v)    To adopt and from time to time amend rules and
                  regulations for the protection and welfare of Prudential
                  Center and for the maintenance of high standards of conduct,
                  safety, care and cleanliness therein, with which TENANT agrees
                  to comply provided they apply to a majority of the other
                  tenants of the Prudential Center. LANDLORD shall not be
                  responsible to TENANT for noncompliance with said rules and
                  regulations by any other occupant of Prudential Center.

                           (vi)   To install and maintain signs on the exterior 
                  of the Building which do not obstruct the windows in the
                  Premises and to install and maintain signs in the interior
                  of the Building outside the Premises.

                           (vii)  To approve all sources from which TENANT is to
                  obtain sign painting and lettering, ice and mineral or
                  drinking water and vending machines.

                           (viii) To require all persons entering or leaving the
                  Building's or the banks of elevators servicing the Building
                  between the hours of 6:00 P.M. and 7:00 A.M. on weekdays, and
                  at all hours on Saturday, Sunday and holidays to identify
                  themselves by signature registration and supporting evidence
                  with the designated representative of LANDLORD if any.

10.2      ACCESS TO PREMISES BY LANDLORD

          Without limitation of any other rights which are reserved by or
          granted to LANDLORD in this Lease or which LANDLORD would otherwise
          enjoy, LANDLORD and persons authorized by it may on reasonable notice
          or except in an emergency and at time(s) convenient to TENANT'S
          business operations enter into the Premises for the purposes of (a)
          inspecting the same, (b) making timely repairs which LANDLORD is
          obligated to make under the provisions of this Lease, (c) making
          repairs to the Premises which TENANT is obligated to make and has
          failed to make within thirty (30) days after written demand by
          LANDLORD and performing any other duty which TENANT is obliged to
          perform by the provisions of this Lease and has failed to perform
          after like demand (the reasonable cost and expense of which repairs
          and performance TENANT covenants and agrees to pay upon demand of
          LANDLORD


                                       21
<PAGE>   27
          along with interest thereon from the date of expenditure until payment
          is made in full at a rate equal to the lesser of (a) the maximum rate
          permitted by applicable law, or (b) eighteen (18%) percent), and (d)
          performing any acts related to the safety, protection and preservation
          of the Premises and the Building. LANDLORD may, during the progress of
          any work on or in the Premises, keep and store in the Premises all
          necessary materials, tools and equipment and, except in the event of
          LANDLORD's negligence or wilful misconduct, LANDLORD shall not be
          liable for inconvenience, annoyance, disturbance, loss of business or
          other damage to TENANT by reason of the exercise of any of the
          aforesaid rights or on account of bringing materials, supplies and
          equipment into or through the Premises during the course thereof and
          the obligations of TENANT under this Lease shall not thereby be
          affected in any manner. The foregoing right of entry does not impose,
          nor does LANDLORD assume (except as provided in Section 4.1) any
          responsibility or liability for the repair, maintenance or supervision
          of the Premises or of any of the fixtures or appurtenances therein
          contained or therewith connected or of any of TENANT'S property.

10.3      LANDLORD'S SAFETY MEASURES

          TENANT agrees without any diminution or abatement of Rent to observe
          and be bound by such measures as may directly or indirectly affect the
          Premises which LANDLORD may take, in connection with the prosecution
          by LANDLORD of any construction work in or adjacent to Prudential
          Center, for the safety of the general public, the preservation and
          protection of Prudential Center and any and all persons having access
          thereto. It is agreed, however, that pedestrian ingress and egress
          shall be available at all times during such construction.

10.4      HAZARDOUS SUBSTANCES

          TENANT shall not cause or permit any Hazardous Substances to be used,
          stored, generated or disposed of on or in the Premises by TENANT,
          TENANT's agents, employees or contractors, without first obtaining in
          each instance, LANDLORD'S written consent. TENANT may, without
          LANDLORD'S consent, but with written notice to LANDLORD as to amount
          and location, store and use (for all but minimal quantities of one
          gallon or less) Hazardous Substances normally used in TENANT'S
          business operations conducted on the Premises, as long as (a) such
          operations are within the scope of the uses permitted under this Lease
          and (b) in doing so, TENANT complies with all provisions of this
          Section 10.4. Any such use, storage, generation or disposal of
          Hazardous Substances shall comply with all applicable federal, state
          and local laws and regulations. If TENANT or TENANT'S agents,
          employees or contractors use, store, generate or dispose of Hazardous
          Substances on or in the Premises, or if the Premises become
          contaminated in any manner for which TENANT


                                       22
<PAGE>   28
          is legally liable, TENANT shall indemnify and hold harmless the
          LANDLORD from any and all claims, damages, fines, judgment, penalties,
          costs, liabilities or losses arising during or after the term and
          arising as a result of such contamination by TENANT. This
          indemnification includes, without limitation, any and all costs
          incurred due to any investigation of the site or any cleanup, removal
          or restoration mandated by a federal, state or local agency or
          political subdivision. Without limitation of the foregoing, if TENANT
          causes or permits the presence of any Hazardous Substance on the
          Premises and such results in contamination, TENANT shall promptly, at
          its sole expense, take any and all necessary actions to return the
          Premises to the condition existing prior to the presence of any such
          Hazardous Substance on the Premises. Except in the case of an
          emergency, TENANT shall first obtain LANDLORD's approval for any such
          remedial action, which approval shall not be unreasonably withheld or
          delayed and which, in any event, shall be granted if the regulatory
          authorities with jurisdiction have approved the proposed remedial
          action. TENANT shall not have any responsibility or liability (a) for
          any Hazardous Substance brought upon, generated or disposed of on or
          from the Premises or Building by any party other than TENANT or
          TENANT'S agents, employees or contractors, or (b) for any Hazardous
          Substance on the Premises or Building on or prior to the Commencement
          Date of the term of this Lease.

          As used herein, "Hazardous Substance" means any substance which is
          toxic, ignitable, reactive, or corrosive and which is regulated by a
          local government, the Commonwealth of Massachusetts, or the United
          States government. "Hazardous Substances" includes any and all
          materials or substances which are defined as "hazardous waste",
          "extremely hazardous waste" or a "hazardous substance" pursuant to
          state, federal or local governmental law. "Hazardous Substance"
          includes but is not restricted to asbestos, polchlorobiphenyls
          ("PCB's") and petroleum.

          LANDLORD has replaced the asbestos containing fireproofing originally
          installed in the Premises with non-asbestos containing fireproofing.

          To the best of LANDLORD'S knowledge and belief, LANDLORD represents
          and warrants to TENANT that (i) no investigative order, settlement,
          agreement, enforcement order or litigation with respect to Hazardous
          or Toxic Materials or Substances is proposed, threatened, anticipated
          or in existence with respect to the Premises or the Building; and (ii)
          no notice, demand, claim, citation, complaint, request for information
          or similar communication has been received by LANDLORD with respect to
          Hazardous or Toxic Materials or Substances in, on, under or at the
          Building, the Premises or Prudential Center.


                                       23
<PAGE>   29
          LANDLORD agrees, subject to the provisions of this Lease, to be
          responsible for the cost of removal, remediation or cure of Hazardous
          Substances or Toxic Materials or Substances or conditions resulting
          from the presence or release of the same at the Building, the Premises
          or Prudential Center to the extent not the responsibility of TENANT or
          any other person, but only to the extent, LANDLORD is required and
          liable under Applicable Environmental Laws.

10.5      INTERRUPTION OF SERVICE

          LANDLORD shall not be required to supply any service to the Premises
          except as expressly stipulated in this Lease and, except in the case
          of LANDLORD'S negligence or wilfull misconduct, LANDLORD shall not be
          liable under any circumstances for interruption of any service due to
          accident, to making repairs, alterations or additions, to labor
          difficulties, to trouble in obtaining fuel, electricity, service or
          supplies or to any cause beyond LANDLORD'S reasonable control.


                                   ARTICLE 11
                                    INSURANCE

11.1      INSURANCE

          TENANT hereby agrees to indemnify, defend and hold harmless LANDLORD,
          its subsidiaries, directors, officers, agents and employees from and
          against any and all damage, loss, liability or expense including but
          not limited to, attorneys' fees and legal costs suffered by same
          directly or by reason of any claim, suit or judgment brought by or in
          favor of any person or persons for damage, loss or expense due to, but
          not limited to, bodily injury, including death resulting anytime
          therefrom, and property damage sustained by such person or persons
          which occurs on the Premises by the TENANT or otherwise, the acts or
          omissions of the TENANT, its agents, employees or any contractors
          brought onto the Premises by the TENANT, or the failure by TENANT to
          perform, fulfill or observe any obligation or liability of TENANT set
          forth herein, except that caused by the negligence, acts of omission
          of LANDLORD or its employees, agents, customers and invitees. Such
          loss or damage shall include, but not be limited to, any injury or
          damage to LANDLORD'S personnel (including death resulting anytime
          therefrom) or premises. TENANT agrees that the obligations assumed
          herein shall survive this Lease.

11.2      TENANT hereby agrees to maintain in full force and effect at all times
          during the term of this Lease, at its own expense, for the protection
          of TENANT and LANDLORD, as their interest may appear, policies of
          insurance issued by a carrier or carriers licensed


                                       24
<PAGE>   30
          to do business in Massachusetts and acceptable to LANDLORD
          affording the following coverage:

             a)    Worker's Compensation   -     Statutory
                   Employer's Liability    -     Not less than $100,000
                   Comprehensive General   -     Not less than $1,000,000
                   Liability Insurance           Combined Single Limit
                   including Blanket,            for both bodily injury
                   Contractual Liability,        and property damage
                   Broad Form Property

11.3      LANDLORD shall insure the Building, including all Leasehold 
          improvements installed pursuant to Article 2 for its full
          insurable replacement cost value and shall maintain Commercial
          General Liability Insurance in an amount that is commercially
          reasonable and at least equal to that other owners of high-rise
          office buildings of comparable quality in Boston maintain.

11.4      The TENANT shall deliver to LANDLORD at least thirty (30) days prior
          to the time such insurance is first required to be carried by TENANT,
          Certificates of Insurance evidencing the above coverage. Such 
          Certificates, with the exception of Worker's Compensation, shall name
          LANDLORD, its subsidiaries, directors, agents and employees, and
          LANDLORD'S property manager (Premisys Real Estate Services, Inc.), as
          additional insureds and shall expressly provide that the interest of
          same therein shall not be affected by any breach by TENANT of any 
          policy provision for which such Certificates evidence coverage.  All
          Certificates shall provide that no less than thirty (30) days prior
          written notice shall be given LANDLORD in the event of material
          alteration to or cancellation of the coverages evidenced by such
          Certificates.

11.5      Upon demand, TENANT shall provide LANDLORD, at TENANT'S expense with
          such increased amount of insurance coverage, as LANDLORD may require
          of all other tenants in the Building. Any increase requested by
          LANDLORD in the amount of TENANT'S insurance shall not exceed the
          amounts and types of coverages required by Landlords in other 
          first-class high-rise buildings in Boston for similar risks. 

11.6      If, on account of the failure of TENANT to comply with the foregoing
          provisions, LANDLORD is adjudged a co-insurer by its insurance 
          carrier, then any loss or damage LANDLORD shall sustain by reason
          thereof shall be borne by TENANT and shall be immediately paid by
          TENANT upon receipt of a bill thereof and evidence of such loss.


                                       25
<PAGE>   31
11.7      LANDLORD makes no representation that the limits of liability
          specified to be carried by TENANT under the terms of this Lease are
          adequate to protect TENANT against TENANT'S undertaking under this
          Article.


                                   ARTICLE 12
                            MISCELLANEOUS PROVISIONS

12.1      WAIVER OF SUBROGATION

          The parties agree that all insurance carried by either party with
          respect to the Premises, whether or not required by this Lease, if
          either party so requests and it can be so written, and if it does not
          result in additional premium or if the requesting party agrees to pay
          any additional premium, shall include provisions which either
          designate the requesting party as one of the insureds or deny to the
          insurer acquisition by subrogation of rights of recovery against the
          requesting party to the extent such rights have been waived by the
          insured party prior to the occurrence of loss or injury. The
          requesting party shall be entitled to have duplicates or certificates
          of any policies containing such provisions. Each party hereby waives
          any rights of recovery against the other for loss or injury against
          which the waiving party is protected by insurance containing
          provisions denying to the insurer acquisition by subrogation of rights
          of recovery, reserving, however, any rights with respect to any excess
          of loss or injury over the amount recovered by such insurance. TENANT
          shall not acquire as insured under any fire or extended coverage
          insurance on the Premises any right to participate in the adjustment
          of loss or to receive insurance proceeds and agrees upon request
          promptly to endorse any checks or other instruments in payment of loss
          in which TENANT is named as payee.

12.2      SUBORDINATION

          This Lease shall at the election of LANDLORD be subject and
          subordinate to all mortgages which may now or hereafter affect the
          real estate of which the Premises form a part, and to all renewals,
          modifications, consolidations, replacements and extensions thereof.
          LANDLORD shall obtain a subordination agreement from any holder of any
          such mortgage which shall bind and benefit the respective parties and
          their successors and provide in substance that (i) such holder shall
          not disturb the possession and other rights of TENANT under this Lease
          and shall acknowledge that the Lease is enforceable, so long as this
          Lease remains in full force and effect, (ii) in the event of
          acquisition of title by such holder, through foreclosure proceedings
          or otherwise, such holder shall accept TENANT as TENANT of the
          Premises under the terms and conditions of this Lease and shall
          perform the obligations of LANDLORD hereunder


                                       26
<PAGE>   32
          (but only such as accrue while such holder is owner of the Premises),
          and (iii) TENANT shall recognize such holder or any other person
          acquiring title to the Premises as LANDLORD. LANDLORD and TENANT agree
          to execute and deliver any appropriate instruments necessary to carry
          out the foregoing provisions of this Section 12.2. Any such mortgage
          to which this Lease shall be subordinate may contain such other terms,
          provisions and conditions as are usual or customary.

12.3      LANDLORD'S REMEDIES CUMULATIVE

          The specific remedies to which LANDLORD may resort under the terms of
          this Lease are cumulative and are not intended to be exclusive of any
          other remedies or means of redress to which LANDLORD may be lawfully
          entitled in case of any breach or threatened breach by TENANT of any
          provision of this Lease. The failure of LANDLORD to insist in any one
          or more cases upon the strict performance of any of the provisions of
          this Lease or to exercise any option herein contained shall not be
          construed as a waiver or relinquishment for the future of such
          provision or option. Consent, approval or permission by LANDLORD in
          any instance where required shall not waive or render unnecessary like
          consent, approval or permission in any subsequent instance. A receipt
          of rent by LANDLORD or the holder of any mortgage upon the Premises
          with knowledge of the breach of any obligation of TENANT under this
          Lease shall not be deemed a waiver of such breach except as to the
          payment of such rent.

12.4      PARTIAL INVALIDITY

          If any of the terms, provisions or conditions 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 and
          the application of such term, provision or condition to persons or
          circumstances other than those as to which it is held invalid or
          unenforceable shall not be affected thereby and each of the other
          terms, provisions and conditions of this Lease shall be valid and
          enforceable to the fullest extent permitted by law.

12.5      SUCCESSORS AND ASSIGNS

          Unless repugnant to the context, the words "LANDLORD" and "TENANT"
          shall be construed to mean the original parties and their respective
          successors and assigns and those claiming through or under them
          respectively. The agreements and conditions contained in this Lease to
          be performed and observed on the part of TENANT shall be binding upon
          TENANT and its successors and assigns and shall inure to the benefit
          of LANDLORD and its successors and assigns, and the agreements and
          conditions contained in this Lease to be performed and observed on the
          part of LANDLORD shall be binding upon LANDLORD and its successors and
          assigns and shall inure to the


                                       27
<PAGE>   33
          benefit of TENANT and its permitted successors and assigns. TENANT
          agrees that at all times on and after the Commencement Date of this
          Lease the sole liability for performance of all obligations of
          LANDLORD hereunder shall be that of the owner from time to time of the
          Premises and that such liability with respect to each owner shall
          exist only for breaches of such obligations as are committed during
          the period of its ownership. To the fullest extent permitted by law,
          TENANT further agrees that LANDLORD'S liability for any negligence,
          claims, causes of action, damages arising hereunder shall be limited
          to the value of LANDLORD'S interest in Prudential Center and no other
          assets of LANDLORD. The term "owner" shall not include the holder of
          any mortgage prior to the taking of possession by such holder for the
          purpose of foreclosure of its mortgage.

          Except as otherwise specifically provided by statute, no recourse
          shall be made on any of TENANT obligations under this Lease or for any
          claim based thereon or otherwise in respect thereof against any
          incorporator of TENANT, subscriber to TENANT'S capital stock,
          shareholder, employee, agent, officer or director, past, present or
          future, of any corporation or counsel, which shall be TENANT hereunder
          of included in the term "TENANT" or any successor of any such
          corporation, partnership or association, or against any principal,
          disclosed or undisclosed, of any such corporation, or against any
          principal, disclosed or undisclosed, of any affiliate of any party
          which shall be TENANT or included in the term "TENANT" whether
          directly or indirectly or through TENANT or through any receiver,
          assignee, agent, trustee in bankruptcy or through any receiver,
          assignee, agent, trustee in bankruptcy or through any other person,
          firm or corporation, whether by virtue of any constitution, statute or
          rule of law or by enforcement of any assessment or penalty or
          otherwise.

12.6      ARTICLE HEADINGS AND MARGINAL NOTES

          The headings of Articles and marginal notes are inserted only as a
          matter of convenience and for reference and in no way define, limit or
          describe the scope or intent of this Lease nor in any way affect it.

12.7      NOTICES

          Every notice and demand required or permitted to be given under this
          Lease shall be in writing and deemed to have been duly given when
          mailed by certified mail, addressed in the case of notice to or demand
          upon LANDLORD to it at Prudential Tower, Boston, MA 02199, attention
          Boston Realty Group Office with a copy to Premisys Real Estate
          Services, Inc., Suite 450, Prudential Center, Boston, MA 02199 and in
          the case of notice to or demand upon TENANT to it at the Premises with
          a copy to Michael


                                       28
<PAGE>   34
          Tarnow, CEO, or to such other address as the party may upon notice to
          the other request.

12.8      WRITTEN APPROVALS

          Except as provided in Section 5.3, all approvals required of LANDLORD
          and TENANT under this Lease shall be in writing and shall not be
          unreasonably withheld or delayed.

12.9      BROKER'S COMMISSION

          TENANT and LANDLORD represent and warrant to each other that they have
          not directly or indirectly dealt, with respect to the leasing of space
          in Prudential Center, with any broker other than R. M. Bradley & Co.,
          Inc. and McCall & Almy, Inc. and covenant and agree to defend, save
          harmless and indemnify each other against any claims for a commission
          arising out of the execution and delivery of this Lease or out of any
          negotiations between LANDLORD and TENANT with respect to the leasing
          of space within Prudential Center, except that TENANT'S
          indemnification shall not apply to any claims by R. M. Bradley & Co.,
          Inc. and McCall & Almy, Inc., it being understood that LANDLORD shall
          pay any commissions due such brokers. The indemnification provided in
          this section shall apply to claims arising out of the acts of the
          indemnifying party.

12.10     ENTIRE AGREEMENT

          This instrument contains all the agreements made between the parties
          hereto and may not be modified in any other manner than by instrument
          in writing executed by the parties or their respective successors in
          interest.

12.11     SUBMISSION OF LEASE-NO OPTION

          The submission of this Lease or a summary of some or all of its
          provisions for examination does not constitute a reservation of or
          option for the Premises or an offer of lease.

12.12     MASSACHUSETTS LAW GOVERNS

          This lease shall be construed in accordance with and governed by the
          Laws of the Commonwealth of Massachusetts.


                                       29
<PAGE>   35
12.13     TENANT'S PARKING RIGHTS

          TENANT may, provided it is not in default hereunder beyond any
          applicable grace/cure period, contract with the Prudential Center
          garage operator for up to ten (10) monthly unassigned parking spaces
          in the Prudential Center at such rates as may be charged for
          unassigned monthly parking spaces from time to time during the term
          hereof. The rate for such spaces as of January 1, 1997 shall be $270
          per month. In addition, LANDLORD and TENANT shall enter into a parking
          license agreement to provide TENANT with an additional ten (10)
          parking spaces in the Prudential Center through June 30, 2001 or at
          such later date LANDLORD requires such spaces for an office building
          to be constructed.

12.14     TENANT'S EXTENSION RIGHTS

          If TENANT is not then in default of its obligations hereunder beyond
          any applicable grace or cure periods, or if in default, is diligently
          pursuing the cure of such default TENANT may by giving LANDLORD twelve
          (12) months advance written notice to LANDLORD, extend the term of
          this Lease Agreement for one (1) additional period of five (5) years
          (Extended Term) on all terms and conditions hereof, except that the
          rent shall be 95% of the then current fair market rent, including
          without limitation then current renewal rates for comparable space
          discounts and common allowances. In the event LANDLORD and TENANT
          cannot agree within six (6) months prior to commencement of the
          Extended Term as to the amount of rent to be paid, the LANDLORD shall
          provide TENANT, within fifteen (15) days of the end of such six (6)
          month period, a written statement setting forth LANDLORD'S position as
          to the amount of rent for the ensuing period and containing the name
          of a qualified Broker nominated by LANDLORD to determine the rent.
          TENANT may, within fifteen (15) days of receipt of LANDLORD'S
          statement, submit to LANDLORD and the qualified Broker nominated by
          LANDLORD a written response setting forth TENANT'S position as to the
          rent to be charged and, if TENANT elects to, the name of a qualified
          Broker nominated by TENANT, the two qualified Brokers so nominated
          shall determine the rent within thirty (30) days of the nomination of
          the second qualified Broker. In the event the two Brokers so named
          cannot agree upon the rent to be charged within the thirty (30) days
          period, they shall jointly promptly select a third qualified Broker
          who shall with the other two qualified Brokers determine the rent
          within twenty (20) days of the third Broker being named. A decision of
          any two of the three qualified Brokers so named shall be binding upon
          the parties. The cost of the two or three qualified Brokers shall be
          shared equally between LANDLORD and TENANT.


                                       30
<PAGE>   36
          Qualified Brokers for the purpose of this Section shall mean a
          licensed Massachusetts Real Estate Broker with at least seven (7)
          years experience in commercial brokerage in the downtown Boston and
          Back Bay markets who has been a broker in leases totaling at least
          15,000 RSF in Downtown and Back Bay within two years prior to
          appointment.

          In the event either TENANT or LANDLORD does not nominate a qualified
          Broker, the rent shall be determined solely by the other's qualified
          Broker and the costs of such qualified Broker shall be borne by the
          party who appointed the qualified Broker.

          During the Extended Term, until determination of the amount of rent,
          TENANT shall pay rent at the rate including escalations as at end of
          the then current term subject to adjustment after determination of
          rent.

12.15 EXHIBITS

          Exhibits A, A-1, B, C, and F are hereby incorporated herein and made a
          part hereof.

          IN WITNESS WHEREOF, LANDLORD and TENANT have caused this Lease to be
executed by their duly authorized officers and their respective seals to be
hereto affixed, the day and year first above written.


                                    LANDLORD:
                                    THE PRUDENTIAL INSURANCE
                                    COMPANY OF AMERICA


                                    By:/s/ David Raszmann
                                       -------------------------------------   
                                       Vice President


                                    TENANT:
                                    CREATIVE BIOMOLECULES, INC.


                                    By:/s/ Wayne E. Mayhew III
                                       -------------------------------------
                                       Vice President

                                       
                                       31
<PAGE>   37









                                  EXHIBIT A
                       24th FLOOR 101 HUNTINGTON AVENUE
                                 (floor plan)










<PAGE>   38










                                 EXHIBIT A-1
                        PRUDENTIAL CENTER, BOSTON, MA
                                    (plan)








<PAGE>   39
                                    EXHIBIT B
                       ATTACHED TO AND MADE PART OF LEASE
                    DATED JUNE 16,1997 BETWEEN THE PRUDENTIAL
                   INSURANCE COMPANY OF AMERICA, LANDLORD AND
                           CREATIVE BIOMOLECULES, INC.

                         DESCRIPTION OF SHELL CONDITION

          The Premises shall be deemed completed "in shell condition" upon
LANDLORD'S furnishing and installing the following:

          WINDOWS: Multi and Full Floor Tenant -- Delivered with building
standard venetian blinds and solar reflective film. Building standard blinds are
levelor energy conservation reflective type.

          FLOORS: Multi and Full Floor Tenant -- Delivered in rough condition,
ready to accept leveling and fill where appropriate. The floors are cellular
type with concrete composite fill on a metal decking. Electrical and telephone
closets delivered with rough concrete floor.

          COLUMNS: Multi and Full Floor Tenant -- Delivered with unpainted
concrete or hard surface fireproofing on interior columns. The exterior columns
shall be delivered ready to accept finishes.

          ELEVATOR LOBBIES:  Full Floor Tenant -- Passenger and Service 
Elevator Lobbies - Delivered in rough concrete floor and walls ready for
construction.  Multi Tenant Floor-Delivered in finished condition.

          HVAC INTERIOR SYSTEMS:  Multi and Full Floor Tenant -- Delivered with
VAV boxes (one per 5,000 sq. ft. approximate) per floor for tenant use.  
LANDLORD shall provide the main duct take-offs with fire dampers.  Tenant work 
to include all duct work "downstream" of the fire damper.

          HVAC PERIMETER SYSTEM: Multi and Full Floor Tenant -- Existing
perimeter HVAC induction system shall be maintained. The existing thermostats
shall be maintained. Perimeter induction units shall be delivered with covers
ready to accept paint.

          CEILING: Multi and Full Floor Tenant -- Delivered unfinished with
exposed nonasbestos containing fireproofing on structural steel and deck of
floor above.


                                       B-1
<PAGE>   40
          CODE:  Multi and Full Floor Tenant -- All building core space will 
be delivered in compliance with code including, but not limited to A.D.A. and 
Mass. Architectural Access Board (MABB).

          ELECTRIC: Multi and Full Floor Tenant -- Premises to be delivered with
primary service utility lines. Electric feeds to be delivered with floor
disconnect switch in place. Tenant to be responsible for all electric wiring
"downstream" of the floor disconnect switch. All primary feeds and switches to
be sized for a maximum power load of 5 Watts/USF of floor space.

          LIFE SAFETY: Multi and Full Floor Tenant -- Premises to include at
LANDLORD'S expense, sprinklers and life safety systems to comply with building
standard systems. In lieu of the above, Tenant may elect to have LANDLORD
provide a monetary allowance of $1.00/New York USF to be used by the Tenant to
install the Life Safety System.

          TOILET ROOMS: Multi and Full Floor Tenant -- Delivered with a ceramic
tile floor and walls with a suspended acoustical tile ceiling and plumbing
fixtures installed and in operating condition. Toilet rooms will be delivered in
compliance with current A.D.A. and MABB requirements.

          JANITOR'S CLOSET:  Multi and Full Floor Tenant -- Delivered with 
tiled floor and utility sink in operating order.


                                       B-2
<PAGE>   41
                                    EXHIBIT C
                       ATTACHED TO AND MADE PART OF LEASE
                   DATED JUNE 16, 1997 BETWEEN THE PRUDENTIAL
                   INSURANCE COMPANY OF AMERICA, LANDLORD, AND
                           CREATIVE BIOMOLECULES, INC.


LANDLORD shall furnish at LANDLORD'S own expense the following services:

(1)       Daily Services (Monday through Friday, holidays excepted):

          a.      Empty wastebaskets and ashtrays in office areas;

          b.      Damp sweep entire tile floor area or vacuum carpet;

          c.      Clean toilet rooms, fixtures, mirrors and mop toilet room
                  floors, and furnish paper products and soap.

(2)       Weekly Services

          Dust office area including furniture, tops of files and windowsills.

(3)       Services Every Month

          Spot wash finger markings from door frames and light switch plates.

(4)       Other Periodic Services

          a.      Wash all exterior windows every two months unless weather
                  does not permit the safe use of LANDLORD'S exterior
                  window washing equipment;

          b.      Tile floors (other than ceramic tile) will be cleaned of
                  wax and rewaxed three (3) times per year; and

          c.      Clean fluorescent fixtures once a year.


                                       C-1
<PAGE>   42
                                    EXHIBIT F

                 TENANT'S SHARE OF INCREASED OPERATING EXPENSES
                              101 HUNTINGTON AVENUE
                      ATTACHED TO AND MADE A PART OF LEASE
                   DATED JUNE 16, 1997 BETWEEN THE PRUDENTIAL
                     INSURANCE COMPANY OF AMERICA, LANDLORD
                     AND CREATIVE BIOMOLECULES, INC., TENANT


I.        DEFINITIONS

          TENANT shall reimburse LANDLORD for TENANT'S proportionate share
("Tenant's Share") of increased "Operating Expenses" (as herein defined) in
excess of Base Operating Expenses as follows:

          A.  "Tenant's Share" of the amount of Operating Expenses in
              excess of Base Operating Expenses equals 1.65%.

                8,665 R.S.F. (PREMISES NET RENTABLE AREA)
              523,807 s.f. (Building Net Rentable Area)


          B.  Base Operating Expenses equal calendar year 1997 Actual
              Operating Expenses

          C.  "Operating Expenses" shall mean any and all costs and
              expenses adjusted for 100% occupancy [except those listed
              in subparagraphs (a) through (e) below] actually paid or
              incurred by LANDLORD in connection with the ownership,
              management, operating, servicing, and maintenance of the
              Building, its utility services from the property line to
              the Building including, without limitation, the cost and
              expense of the following: salaries, wages, medical,
              surgical and general welfare and other so-called "fringe"
              benefits (including group insurance and retirement
              benefits) for employees of LANDLORD or any contractor of
              LANDLORD engaged in the cleaning, operation, maintenance
              or management of the Building, and payroll taxes, and
              worker's compensation insurance premiums relating thereto
              as it relates to the Building, gas, steam, fuel oil,
              water, sewer rental, electricity (exclusive of TENANT'S
              Electrical Usage), utility taxes, rubbish removal, fire,
              casualty, liability, rent and other insurance carried by
              LANDLORD, repairs, repainting, replacement, building
              supplies, uniforms, and cleaning thereof, window
              cleaning, service contracts with independent contractors
              for any of the foregoing (including, but not limited to
              elevator and


                                       F-1
<PAGE>   43
                  air conditioning maintenance), management fees at market rates
                  based on management fees for similar office buildings in
                  Boston (whether or not paid to any person, firm or corporation
                  having an interest in or under common ownership with LANDLORD
                  or any of the persons, firms or corporations comprising
                  LANDLORD), legal fees and expenses incurred in connection with
                  any application or proceeding brought for reduction of the
                  assessed valuation of the Building or any part thereof, but
                  only if brought to have the effect of reducing TENANT'S cost,
                  auditing fees and all other costs and expenses actually
                  incurred in connection with the operation, maintenance and
                  management of the Building and an allocated share of the
                  "Center's Common Area Expenses" (as herein defined). Included
                  in the foregoing will be the cost or portion thereof properly
                  allocatable to the property (amortized over such reasonable
                  period as LANDLORD shall determine together with the interest
                  on the unamortized balance as the greater of 10% or the six
                  month Treasury Bill rate for the date upon which funds for the
                  project are committed) of any capital improvements made to the
                  Building by the LANDLORD which result in appropriate reduction
                  of Operating Expenses or made to the Building by the LANDLORD
                  after the date of this Lease that are required under any
                  governmental law or regulation that was not applicable to the
                  Building on the date of this Lease. Operating Expenses shall
                  be computed on an accrual basis and shall be determined in
                  reasonable detail in accordance with generally accepted
                  accounting principles consistently applied. They may be
                  incurred directly or by way of reimbursement, and shall
                  include taxes applicable thereto. The following shall be
                  excluded in calculating Operating Expenses:

                           (a) Depreciation or capital expenditures on the
                  Building or any part thereof, except as included above;

                           (b) Expenses incurred directly in leasing or in
                  procuring any tenants, including advertising, promotion,
                  public relations, sales, brokers' commissions, and expenses
                  for tenant alterations or renovating space for new tenants;

                           (c) Amortization and interest on indebtedness;

                           (d) Real estate taxes or payments in lieu of real
                  estate taxes except as provided for in Section 3.4
                  hereof;

                           (e) The net amount of any insurance proceeds,
                  reimbursements, discounts or allowances received by LANDLORD
                  in connection with those "Operating Expenses" which are
                  included.


                                       F-2
<PAGE>   44
                           (f) Also excluded are the following:

                                    (i) cost of repairs or replacements 
                    incurred by reason of fire or other casualty or by the
                    exercise or the right of eminent domain;

                                    (ii) advertising and promotional 
                    expenditures;

                                    (iii) legal fees incurred in disputes with
                    tenants, matters in connection with any underlying lease
                    including, but not limited to, the conveyance or financing
                    or refinancing thereof, negotiation of leases with
                    prospective or current tenants, financing or refinancing of
                    mortgages, disputes with mortgagees not caused by TENANT and
                    other legal and auditing fees, other than legal and auditing
                    fees reasonable incurred in connection with the preparation
                    of statements required pursuant to additional rent or rental
                    escalation provisions;

                                    (iv) costs incurred in performing work or
                    furnishing services to or for individual tenants (including
                    TENANT) other than work or services of a kind and scope
                    which LANDLORD would be obligated to furnish TENANT without
                    charge if such work were required in the Demised Premises
                    pursuant to applicable law or codes as required by the
                    governmental authority having jurisdiction;

                                    (v) the cost incurred by LANDLORD in
                    performing work or furnishing any services to or for a
                    tenant of space in the building (including TENANT) for which
                    a separate charge is made, including without limitation, the
                    supply of overtime air-conditioning, ventilation and heating
                    at LANDLORD'S cost and expense, regardless of the amount
                    billed or received by LANDLORD for performing such work or
                    furnishing such service;

                                    (vi) franchise and income taxes of LANDLORD;

                                    (vii) real estate taxes on land and/or
                    Building to the extent included in this Lease;

                                    (viii) the costs of providing overtime heat
                    and air-conditioning to tenants of the Building to the
                    extent that the same are payable by the tenants for whom
                    such services are provided;

                                    (ix) rent under ground leases (if any)


                                       F-3
<PAGE>   45
                                    (x) all costs incurred in connection with or
                  directly related to the original construction of the Building
                  (as distinguished from operating expenses and the repair,
                  maintenance and operations thereof);

                                    (xi) financing and refinancing costs,
                  interest on debt or amortization payments on any mortgage or
                  mortgages, and rental under any ground or underlying lease or
                  leases;

                                    (xii) a bad debt loss, rent loss or any
                  reserves;

                                    (xiii) all interest or penalties incurred as
                  a result of LANDLORD'S failure to pay any costs or taxes as
                  the same shall become due provided such failure shall not have
                  been caused by TENANT;

                                    (xiv) any and all costs associated with the
                  operation of the business of the entity which constitutes
                  LANDLORD; excluded items shall specifically include, but shall
                  not be limited to, formation of the entity, costs of defending
                  any lawsuits with any mortgagee (except as the actions of
                  TENANT may be in issue), costs of selling, syndication,
                  financing, mortgaging or hypothecating any of the LANDLORD'S
                  interest in the Building, costs of any disputes between
                  LANDLORD and its employees (if any) not engaged in the
                  operation of the Building, disputes between LANDLORD and
                  managers of the Building;

                                    (xv) (i) costs of printing and decorating
                  for any tenant's space; (ii) the cost of providing overtime
                  heat and air-conditioning to tenants of the Building to the
                  extent that the same are payable by the tenants for whom such
                  services are provided; and (iii) rent under ground leases (if
                  any);

                                    (xvi) amounts for which LANDLORD has been
                  reimbursed by insurance proceeds;

                                    (xvii) costs incurred in renovating or
                  otherwise improving or decorating or redecorating space for
                  tenants or other occupants in the Building or vacant space in
                  the Building or costs related thereto;

                                    (xviii) LANDLORD'S costs of electricity,
                  incremental air-conditioning and other services sold to
                  tenants for which LANDLORD is


                                       F-4
<PAGE>   46
                  entitled to be reimbursed by tenants (whether or not
                  actually collected by LANDLORD) as a separate additional
                  charge or rental;
      
                                    (xix) any cost or expense incurred as a
                  result of painting, decorating, carpet shampooing, drapery
                  cleaning and wall washing within the rentable areas of the
                  Building for a specific tenant as opposed to that performed
                  for all tenants or common areas.
      
              D.  "Center's Common Area Expenses" is defined as those costs
                  and expenses incurred for the open areas, public areas
                  and amenities within the Prudential Center which become a
                  cost center to receive expenses reasonably deemed by the
                  LANDLORD to be chargeable thereto which are accumulated
                  and prorated against the income-generating elements of
                  the Center by a formula predicated on a rentable area
                  basis consistently applied annually. (The portion
                  chargeable during 1997 to the Building is 14.3%, subject
                  to change as rentable areas may change.)
      
              E.  "Calendar Year" is defined as any consecutive twelve (12)
                  month period commencing January lst, provided that LANDLORD,
                  upon written notice to TENANT, may change from time to time to
                  any other consecutive 12-month period, and in that event
                  Tenant's Share of Operating Expenses shall be adjusted pro
                  rata.
      
    II.       PAYMENT OF TENANT'S SHARE

              A.  LANDLORD shall on or after January 1 in each year give to
                  TENANT a statement of Tenant's Estimated Share of
                  Operating Expenses (Estimate) for the current calendar
                  year.  Tenant's Estimated Share of Operating Expenses
                  shall be the product of Tenant's Share times the amount
                  by which LANDLORD'S Estimate of Operating Expenses for
                  the Calendar Year exceed Base Operating Expenses.  TENANT
                  shall reimburse LANDLORD monthly with each rent payment
                  an amount equal to 1/12th of Tenant's Estimated Share of
                  Operating Expenses.  LANDLORD reserves the right during
                  any year to adjust Tenant's Estimated Share of Operating
                  Expenses in any year to reflect increases of 5% or more
                  by which actual Operating Expenses are exceeding
                  Estimated Operating Expenses.

              B.  LANDLORD shall on or before May 1, in each calendar year
                  provide a Statement of Operating Expenses (Statement) for the
                  prior calendar year prepared by an independent Certified
                  Public Accountant which shall show in reasonable detail all
                  items of Operating Expense for the prior year and Tenant's
                  Share of such Operating Expenses with the amount of any
                  difference due to

                                       F-5

<PAGE>   47



                  LANDLORD or TENANT between Tenant's Estimated Share of
                  Operating Expenses and Tenant's Share of Operating Expense for
                  such year. The amount of any difference due TENANT shall
                  accompany the Statement when delivered to TENANT. TENANT shall
                  reimburse LANDLORD the amount of any difference due LANDLORD
                  within thirty (30) days of receipt of LANDLORD'S Statement.

              C.  If any part of the original lease term or any extended lease
                  term is less than a calendar year, the TENANT shall reimburse
                  LANDLORD for Tenant's Share of Operating Expenses due in
                  accordance with this Section II hereof as the number of days
                  of the term or extended term contained in a calendar year
                  bears to 365 days.

              D.  Upon expiration or termination of the Lease or extensions
                  thereof, all reimbursements due under this Exhibit shall
                  become due coincident with rent payments due LANDLORD for the
                  last month of the lease term or any extended term thereof.

              E.  LANDLORD shall notify TENANT of any adjustment of
                  Tenant's Share upon expiration or termination of Lease
                  which shall be an estimate, computed by LANDLORD based
                  upon the most recent figures available to and prepared by
                  LANDLORD.  LANDLORD shall notify TENANT after the end of
                  the calendar year of any overpayment or underpayment
                  resulting from such calculation of the Tenant's Share of
                  Operating Expenses and TENANT and LANDLORD shall within
                  thirty (30) days of receipt of said notice make
                  appropriate payment to adjust overpayment or underpayment
                  previously made.

              F.  TENANT'S obligation to reimburse LANDLORD for Tenant's Share
                  of Operating Expenses under this Exhibit and LANDLORD'S and
                  TENANT'S obligation to make adjustments referred to above
                  shall survive expiration or termination of this Lease.


    III.      AVAILABILITY OF RECORDS

              A.  Within thirty (30) days after receipt by TENANT of
                  LANDLORD'S Statement of Operating Expenses, TENANT may
                  notify LANDLORD in writing of any cost items for which
                  TENANT requests to see supporting data.  Promptly upon
                  receipt of such notice, LANDLORD will make available to
                  TENANT or its agents for examination, at such place in
                  Metropolitan Boston as LANDLORD may reasonably designate,
                  at TENANT'S expense, such appropriate accounting


                                       F-6
<PAGE>   48
                  books and records of LANDLORD as shall relate to the items so
                  designated by TENANT. TENANT shall cause all information so
                  obtained to be held in strict confidence. Notwithstanding the
                  giving of said notice, TENANT shall make payment of all
                  amounts indicated in LANDLORD'S Estimate or Statement within
                  thirty (30) days of said notice.

                  At any time within sixty (60) days after LANDLORD'S accounting
                  books and records relating to the designated cost items shall
                  have been made available to TENANT as aforesaid, TENANT may
                  dispute in writing any specific, significant (i.e., having an
                  effect of an increase of over 5%) item or items included by
                  LANDLORD. If such dispute is not amicably settled between
                  LANDLORD and TENANT within thirty (30) days after TENANT'S
                  notice thereof, either party may during the next succeeding
                  thirty (30) days (upon written notice to the other party
                  accompanied by a copy of its letter of submission setting
                  forth the items of dispute) refer such disputed item or items
                  to an independent, nationally-recognized Certified Public
                  Accounting firm (to be selected by LANDLORD and to be other
                  than the firm that issued the certification of Estimate or
                  Statement) for decision and the decision of such accounting
                  firm shall be conclusive and binding upon LANDLORD and TENANT.
                  The expenses involved in such determination shall be borne by
                  the party against whom a decision is rendered by said
                  accounting firm provided that if more than one item is
                  disputed and a decision shall be rendered against each party
                  in respect to any item or number of items so disputed, then
                  the expenses shall be apportioned according to the amounts
                  decided against each party. Within thirty (30) days after the
                  rendering of such decision, LANDLORD shall make any
                  adjustments required thereby to the Estimate or Statement.


                                       F-7