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                                                                   Exhibit 10.53





September 17, 1997

Carl M. Cohen, Ph.D.
15 Magnolia Avenue
Newton, MA 02158


Dear Carl,

It is with pleasure that I extend to you an offer to join Creative BioMolecules,
Inc. The terms of this offer are summarized below.



Title and Duties:       Vice President of Research, reporting to President and
                        CEO. Your duties will be determined by the President,
                        consistent with your position.

Term:                   Commencing on November 3, 1997, and continuing
                        thereafter until terminated by either you or the Company
                        under the provisions of this letter agreement.

Salary:                 Base salary of $14,666.67 per month, which is an
                        annualized salary of $176,000.00 payable in accordance
                        with the Company's standard payroll practices. You will
                        be eligible for your first merit increase in January
                        1999 for the fourteen month period November 1997 -
                        December 1998.

Sign-on Bonus:          You will be eligible for a $10,000 sign-on bonus,
                        payable after the completion of 30 days starting with
                        your commencement of employment ("Commencement Date").

Bonus:                  You will be eligible for a first year bonus up to 20% of
                        your base salary. The payment of a bonus will reflect
                        substantial completion of reasonable goals and
                        objectives which we will mutually determine. A bonus
                        will not be paid even if objectives have been achieved,
                        if the Company decides not to pay Company bonuses in a
                        given year. Future bonus arrangements will be determined
                        on an annual basis by mutual agreement.


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Carl M. Cohen, Ph. D.
September 17, 1997
Page Two




Equity Participation:   Subject to the approval of the Board of Directors, you
                        will be granted stock options under the Company's 1987
                        Stock Plan to purchase an aggregate of 100,000 shares of
                        Common Stock, with the exercise price to be the fair
                        market value of the Common Stock on the date of grant as
                        determined by the Board of Directors. The options will
                        vest annually over a four year period and will be
                        subject to the other terms and conditions of the option
                        agreement(s) to be entered into between you and the
                        Company. Such agreement(s) will include a provision
                        permitting exercise of the options with payment made by
                        you through a loan from the Company. The agreement(s)
                        will also include a provision for acceleration of the
                        vesting of the options, substantially as follows:

                        "In case of (i) any consolidation or merger of the
                        Company with or into any other corporation or
                        corporations (other than a merger with a wholly-owned
                        subsidiary or a merger in which stockholders of the
                        Company have beneficial ownership of more than 50% of
                        the share capital of the surviving company, (ii) a sale
                        of all or substantially all of the assets of the Company
                        or (iii) the acquisition by a third party (together with
                        its affiliates or persons acting in concert with) of
                        beneficial ownership of more than fifty percent (50%) of
                        the share capital of the Company, then immediately prior
                        to the consummation of any such transaction this option
                        shall become fully exercisable."

Benefits:               Benefits to include:
                        -group health and dental insurance
                        -group life and AD&D insurance
                        -group short and long term disability insurance
                        -401(k) savings plan
                        -3 weeks vacation, under the Company's standard policy




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Carl M. Cohen, Ph. D.
September 17, 1997
Page Three




                        The Company will also reimburse you for any reasonable
                        out-of-pocket business expenses you incur in the course
                        of your employment, subject to documentation in
                        accordance with Company policies.

Severance Package:      If your employment with the Company is terminated at any
                        time during the 12-month period after the Commencement
                        Date, for any reason other than your resignation or
                        termination by the Company for "cause" (as defined
                        below), the Company will continue to pay your base
                        salary and provide you with health, dental, and life
                        insurance benefits for 6 months after the effective date
                        of such employment termination. As used in this letter
                        agreement, "cause" shall mean (i) illegal, dishonest or
                        negligent conduct which constitutes a breach of your
                        obligations under this agreement, or which involves an
                        improper use of the funds or assets of the Company, or
                        (ii) any conduct which is likely to have a material
                        adverse impact on the goodwill, reputation or business
                        of the Company.

                        In addition, upon acceleration of the vesting of your
                        stock options as set forth in this letter agreement, the
                        Company will pay you a severance package which is
                        consistent with severance paid to other officers of the
                        Company.

Confidentiality and
Inventions Assignment:  You agree to be bound by the terms of the Company's
                        confidentiality and inventions assignment provisions,
                        pursuant to a separate agreement to be signed by the
                        Company prior to the Commencement Date. You also hereby
                        represent and warrant that you have no commitments or
                        obligations inconsistent with this agreement, including
                        such confidentiality and inventions assignment
                        provisions, and you hereby agree to indemnify and hold
                        the Company harmless against any claim based upon
                        circumstances alleged to be inconsistent with such
                        representation and warranty.


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Carl M. Cohen, Ph. D.
September 17, 1997
Page Four

Governing Law and
Miscellaneous
Provisions:             This agreement shall be governed by and construed under
                        the laws of the Commonwealth of Massachusetts, without
                        application of the conflicts of law provisions thereof.
                        This agreement, including the above-referenced stock
                        option agreement and the confidentiality and inventions
                        assignment agreement, embodies the entire agreement and
                        understanding between you and the Company regarding the
                        subject matter hereof. This agreement shall not be
                        modified or amended except by an instrument in writing
                        signed by you and the Company. The Company may assign
                        its rights and obligations under this agreement to any
                        person or entity who succeeds to all of the Company's
                        business or that aspect of the Company's business in
                        which you are principally involved. Your rights and
                        obligations under this agreement may not be assigned
                        without the prior written consent of the Company.
                        Subject to the foregoing, this agreement shall be
                        binding upon and inure of the benefit of the Company and
                        any parent, subsidiary or other affiliate, and their
                        respective successors and assigns and shall be binding
                        upon and inure to the benefit of you and your heirs,
                        executors, administrators and assigns. This agreement
                        may be executed in one or more counterparts each of
                        which shall be deemed to be an original, but all of
                        which together shall constitute one and the same
                        instrument.

Should you wish to discuss any aspect of this employment offer, please feel free
to contact me. If the terms of employment are acceptable, please sign this
letter (a copy for your files is enclosed) and return it to me by Monday,
September 22, 1997.

We believe that Creative BioMolecules will provide an exciting and stimulating
work environment, and look forward to your arrival.

Sincerely,
                                                 Agreed to:

/s/ Michael Tarnow
Michael M. Tarnow                                /s/ Carl M. Cohen
-------------------------------                  -------------------------------
President & CEO                                  Carl M. Cohen, Ph. D.

Enclosure