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                                                                   Exhibit 10.28


                              TERMINATION AGREEMENT


      This Termination Agreement, dated as of November 4, 1998, is made by and
between CAMBRIDGE NEUROSCIENCE, INC., a Delaware corporation having its
principal place of business at One Kendall Square, Building 700, Cambridge,
Massachusetts 02139 U.S.A. ("CNSI"), and BOEHRINGER INGELHEIM INTERNATIONAL
GmbH, a limited liability company organized under the laws of the Federal
Republic of Germany having its principal place of business at D-55216
Ingelheim/Rhein Germany ("BII").

      WHEREAS, CNSI and BII entered into a license agreement having an effective
date of March 21, 1995 (the "LICENSE AGREEMENT");

      WHEREAS, CNSI and BII desire to terminate the LICENSE AGREEMENT; and

      WHEREAS, notwithstanding any contrary terms and conditions included in the
LICENSE AGREEMENT, CNSI and BII have agreed that their respective rights and
obligations upon termination of the LICENSE AGREEMENT shall be as set forth
herein.

      NOW THEREFORE, in consideration of the foregoing premises and for good and
valuable consideration, the receipt and adequacy of which is hereby
acknowledged, CNSI and BII mutually agree as follows:

1.    USE OF DEFINED TERMS. All capitalized terms used but not expressly defined
herein shall have the meanings set forth in the LICENSE AGREEMENT.

2.    TERMINATION. CNSI and BII agree to terminate the LICENSE AGREEMENT
effective as of November 4, 1998 (the "Effective Date of Termination") according
to the terms set forth in this Termination Agreement. The termination of the
LICENSE AGREEMENT pursuant to the terms and conditions set forth herein shall be
deemed to be a termination of the LICENSE AGREEMENT "in accordance with its
terms" as described and provided in Section 6.5 of the Stock Purchase Agreement
entered into by the parties hereto and having an effective date of March 21,
1995 (the "STOCK PURCHASE AGREEMENT").

3.    RIGHTS UNDER CNSI PATENT RIGHTS AND CNSI TECHNOLOGY.

      3.1   As of the Effective date of Termination, all rights and licenses
            granted by CNSI to BII under the CNSI Patent Rights and the CNSI
            Technology shall terminate, and all rights, if any, of BII with
            respect to the Program Patent Rights and Program Technology shall be
            assigned to CNSI as provided in Section 4.2.

      3.2   The provisions of Section 3.1 notwithstanding, BII may retain a
            quantity (the amount of which shall be mutually agreed) of Licensed
            Compound on hand solely for its internal research purposes solely at
            its facilities located in Germany and solely for use by employees of
            BII and its Affiliates and who are obligated to assign all
            inventions and discoveries made through the use of the Licensed
            Compound to BII. To the extent such employees make an invention or
            discovery,


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            directly or indirectly as a result of the use of a Licensed Compound
            as permitted by this Section 3.2, including, without limitation,
            inventions or discoveries relating to the manufacture of Licensed
            Compounds or corresponding Licensed Products (hereinafter a "New
            Invention"), BII will promptly notify CNSI in writing of such New
            Invention. BII hereby grants CNSI a royalty-free, exclusive license
            to all such New Inventions, which license shall be fully paid and
            irrevocable as of the Effective Date of Termination. Such license
            shall be without additional charge to CNSI, except in the event and
            only to the extent that BII is required to make payments to the
            inventors under German Law regarding employees' inventions. CNSI
            will reimburse BII in full for all payments made by BII to such
            inventors; provided, that, CNSI shall not be required to reimburse
            BII for any payments made in excess of the payment required by law.
            CNSI shall have the sole authority and responsibility for preparing,
            filing, prosecuting, maintaining, enforcing and defending any and
            all patent applications or patents covering New Inventions, at
            CNSI's expense, provided, however, that BII shall make available to
            CNSI (or to its attorneys, agents, or representatives), at CNSI's
            expense, BII's employees, agents or consultants to the extent
            reasonably necessary or appropriate to enable CNSI to prepare, file,
            prosecute, maintain, enforce and defend such patent applications and
            patents; provided, further, that BII, its employees, agents or
            consultants shall execute all documents relating to such New
            Inventions at no charge to CNSI.

      3.3   CNSI, alone or together with one or more Third Parties, shall have
            the exclusive right to make and have made, sell and have sold, use
            and have used, market and have marketed, distribute and have
            distributed, import and have imported and export and have exported
            Licensed Products and the Licensed Compound throughout the world,
            including, without limitation, the right to grant licenses or
            sublicenses to Third Parties.

4.    PROGRAM TECHNOLOGY AND PROGRAM PATENT RIGHTS; TECHNOLOGY TRANSFER.

      4.1   Within one year of the Effective Date of Termination, BII shall
            disclose to CNSI the making, conception or reduction to practice of
            any Program Technology and Program Patent Rights by its employees or
            others acting on its behalf during the term of the LICENSE
            AGREEMENT; provided, that, BII shall have no obligation to generate
            additional formal or informal reports for CNSI, except as set forth
            in Article 11. BII shall make available to CNSI, at CNSI's expense,
            BII's employees, agents or consultants to the extent reasonably
            necessary to enable CNSI to conduct a meaningful evaluation of and
            to practice any such Program Patent Rights and/or Program
            Technology.

      4.2   BII hereby assigns and transfers to CNSI all of its right, title and
            interest in and to any Program Technology and Program Patent Rights
            in existence as of the Effective Date of Termination, including,
            without limitation, Program Technology and Program Patent Rights
            relating to the manufacture of Licensed Compounds or Licensed
            Products; provided, that, BII may retain rights under the Program



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            Technology and Program Patent Rights to the limited extent necessary
            to exercise the rights set forth in Section 3.2 hereof.

      4.3   As of the Effective Date of Termination CNSI shall be solely
            responsible for the filing, prosecution, maintenance, enforcement
            and defense of the Program Patent Rights; provided, however, that
            BII shall make available to CNSI (or to its attorneys, agents, or
            representatives), at CNSI's expense, BII's employees, agents or
            consultants to the extent reasonably necessary or appropriate to
            enable CNSI to file, prosecute and maintain patent applications and
            resulting patents with respect to Program Patent Rights; and
            provided, further, that BII, its employees agents or consultants
            shall execute all documents relating to such Program Patent Rights
            at no charge to CNSI.

5.    TRADEMARK.  BII shall retain all rights to the Trademark assigned to BII
pursuant to Section 3.1.4 of the LICENSE AGREEMENT.

6.    ROYALTIES.  In the event that CNSI or any CNSI Affiliate, or any licensee
of CNSI or any CNSI Affiliate, sells the Licensed Compound or corresponding
Licensed Products, CNSI shall pay BII royalties pursuant to this Article 6.

      6.1   DEFINITIONS. For the purposes of this Termination Agreement, the
            term Net Sales means the amount received by CNSI, its Affiliates or
            licensees, in consideration for the sale, lease or other transfer of
            Licensed Products to independent customers, less: (a) credited
            allowances to such independent customers for such Licensed Product
            which was spoiled, damaged, out-dated or returned; (b) freight and
            insurance costs incurred in transporting Licensed Products to such
            customers; (c) quantity and other trade discounts actually allowed
            and taken; (d) sales, use, value added and other taxes or
            governmental charges incurred in connection with the sale,
            exportation or importation of the Licensed Products in finished
            packaged form; and (e) charge back payments and/or rebates provided
            to managed health care organizations or federal, state and local
            governments, their agencies, purchasers and reimburses, including
            reimbursements to social security organizations. The transfer of
            Licensed Products by CNSI or one of its Affiliates to (i) another
            Affiliate of CNSI, or (ii) a licensee of CNSI shall not be
            considered a sale; in such cases, Net Sales shall be determined
            based on the amount received by CNSI, its Affiliate or licensees to
            its customer, less the deductions allowed under this Section. Every
            other commercial use or disposition of Licensed Products by CNSI,
            its Affiliates or licensees, other than reasonable quantities of
            promotional samples, shall be considered a sale of the Licensed
            Products at the weighted average Net Sales price then being invoiced
            by the seller in arm's length transactions.

            CNSI, its Affiliates or licensees shall be deemed to have sold a
            "Bundled Product" if the Licensed Products are sold by CNSI, its
            Affiliates or licensees pursuant to an agreement with an independent
            customer specifying, for a combination of products or services, (i)
            a single price, (ii) other terms of purchase not separately



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            identifying either a price per product or the effective deductions
            referred to above per product, or (iii) a price for units of the
            Licensed Products which is discounted below CNSI's or its
            Affiliates' or licensees' standard invoice price per unit of the
            Licensed Products by at least five percentage points more than the
            amount that any other product or service in the Bundled Product is
            discounted below such other product's or service's standard invoice
            price. In order to calculate the Net Sales of the Licensed Products
            included in a Bundled Product (a) in the case of the foregoing
            clauses (i) and (ii), the total Net Sales of the Bundled Product
            shall be multiplied by a fraction, the numerator of which shall be
            the product of the number of units of the Licensed Products sold
            multiplied by the standard invoice price per unit of the Licensed
            Products and the denominator of which shall be the sum, for all
            products or services included in the Bundled Product, of the
            products of the number of units sold for each product or service in
            the Bundled Product multiplied by the standard invoice price per
            unit for each such product or service, and (b) in the case of the
            foregoing clause (iii), the parties will determine whether an
            adjustment to Net Sales is appropriate and, if so, a mutually
            agreeable method of calculation.

      6.2   ROYALTIES RECEIVED BY CNSI AND CNSI AFFILIATES ON THE NET SALES OF
            LICENSED PRODUCTS BY THIRD PARTY LICENSEES.

            6.2.1   Subject to Section 6.4, CNSI shall pay BII a percentage of
                    the royalty received by CNSI on the Net Sales of Licensed
                    Products by CNSI's Third Party licensees at the following
                    rates:

                                                            PERCENT OF ROYALTIES
                    ROYALTY PAID TO CNSI BY THIRD PARTY     RECEIVED BY CNSI
                    LICENSEE                                OWED TO BII
                    -----------------------------------     --------------------

                    Ten percent (10%) or less                     10%

                    Greater than ten percent (10%) and
                    less than twenty percent (20%)                15%

                    Twenty percent (20%) or greater               20%

            CNSI will pay the above percentage of royalties to BII for the
            duration of any royalty payments received by CNSI from a Third Party
            licensee.

            6.2.2   Subject to Section 6.4, to the extent that CNSI also
                    receives consideration in the form of up-front licensing
                    fees or milestone payments, or payments for the purchase of
                    outstanding shares of the capital stock of CNSI which are in
                    excess of the fair market value of such shares, but
                    excluding reimbursement of research and development costs
                    actually incurred by CNSI (hereinafter "Other Licensing
                    Income"), CNSI shall pay BII a percentage of such Other
                    Licensing Income actually received by CNSI



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                    according to the schedule for royalties received in the same
                    transaction as set forth in Section 6.2.1. By way of
                    example, but not limitation, if CNSI enters into an
                    agreement with a Third Party licensee for the development of
                    Licensed Products and the agreement provides that CNSI shall
                    receive an up-front license fee of Five Hundred Thousand
                    Dollars ($500,000.00) and a royalty of twelve percent (12%)
                    on the Net Sales of Licensed Products by such Third Party
                    licensee, CNSI shall owe BII fifteen percent (15%) of the
                    up-front license fee received from such Third Party and
                    fifteen percent (15%) of the royalties on Net Sales received
                    from such Third Party.

      6.3   ROYALTIES ON THE NET SALES OF LICENSED PRODUCTS SOLD DIRECTLY BY
            CNSI OR CNSI AFFILIATES. CNSI shall pay BII a royalty of three
            percent (3%) on the Net Sales of Licensed Products sold directly to
            Third Parties other than Third Party licensees by CNSI or its
            Affiliates.

      6.4   PAYMENTS ON SALES OF LICENSED COMPOUND OR LICENSED PRODUCTS BY CNSI
            OR CNSI AFFILIATES. In the event CNSI supplies Licensed Compounds or
            Licensed Products to a Third Party licensee, CNSI shall pay BII
            three percent (3%) of the Net Sales of Licensed Products related
            thereto by such Third Party licensee only if such three percent (3%)
            of Net Sales is greater than the royalties and other amounts CNSI
            would have owed BII on the Net Sales of Licensed Products by such
            Third Party licensee pursuant to Sections 6.2.1 and 6.2.2 above, and
            in such case, CNSI shall not owe BII the royalty set forth in
            Sections 6.2.1 and 6.2.2.

      6.5   OTHER. In the event CNSI is acquired, is merged with a Third Party,
            is disposed of by a receiver in bankruptcy, or in the event that
            CNSI sells or otherwise disposes of the program relating to the
            Licensed Compounds or Licensed Products, such that the provisions of
            Section 6.2, 6.3 and 6.4 do not apply, then CNSI's successor shall,
            as a condition to the consummation of such transaction, assume
            CNSI's obligations under those provisions.

      6.6   PAYMENTS TO THIRD PARTIES.

            6.6.1   If CNSI, its Affiliates or licensees can demonstrate that,
                    in order to manufacture or sell Licensed Products or
                    Licensed Compounds in any country they must make payments
                    (including without limitation royalties, option fees or
                    license fees) to one or more Third Parties to obtain a
                    license or similar right in the absence of which the
                    Licensed Compound and/or the Licensed Products could not be
                    legally manufactured or sold in such country, CNSI may
                    deduct from the royalty thereafter payable to BII on Net
                    Sales in such country an amount equal to fifty percent (50%)
                    of the payment to such Third Party, other than the
                    University of Oregon, subject to the limitations of Section
                    6.6.2 below.



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            6.6.2.  It is specifically understood and agreed that an aggregate
                    total sum of the reduction under Section 6.6.1 of royalty
                    payments described in Sections 6.2 and 6.3 shall not reduce
                    the royalty to be paid to BII by more than fifty percent
                    (50%) in any given quarter under any circumstance; provided,
                    however, that in the event that royalties paid by CNSI for
                    the use of Third Party patents, including, without
                    limitation, royalties payable to the University of Oregon,
                    together with the royalties paid to BII under this
                    Termination Agreement, are so significant a factor in the
                    return realized by CNSI as to diminish CNSI's ability to
                    respond to competitive pressures in the market, BII agrees
                    to negotiate a reasonable reduction in the royalty paid to
                    BII for the period during which such market condition
                    exists. Factors determining the size of the reduction will
                    include CNSI's profit margin on Licensed Products or
                    Licensed Compounds, as the case may be, and on analogous
                    products and prevailing prices for competitive products.

      6.7   ROYALTY REPORTS, EXCHANGE RATES. During the term of this Termination
            Agreement, following the First Commercial Sale of the Licensed
            Products in any country, CNSI shall, (a) within thirty (30) days
            after each calendar quarter in the case of Licensed Products sold
            directly by CNSI or its Affiliates, or (b) within fifteen (15)
            business days after receipt by CNSI of the applicable quarterly
            report (as described below) in the case of the sale of Licensed
            Products by a Third Party licensee, furnish to BII a written
            quarterly report showing, on a country by country basis and as
            applicable: (i) the gross sales of the Licensed Products sold, as
            the case may be, by CNSI and its Affiliates or by CNSI's licensees,
            during the reporting period and the calculation of Net Sales from
            such gross sales; (ii) withholding taxes, if any, required by law to
            be deducted in respect of such sales; (iii) the dates of the First
            Commercial Sales of the Licensed Products in any countries during
            the reporting period; and (iv) the exchange rates used in
            determining the amount of United States dollars. If no royalty is
            due for any royalty period hereunder, CNSI shall so report. CNSI
            shall keep complete and accurate records in sufficient detail to
            properly reflect all gross sales and Net Sales of Licensed Compounds
            and Licensed Products to enable the royalties payable hereunder to
            be determined. For the purposes of this Termination Agreement, the
            term "First Commercial Sale" means the first sale for use or
            consumption by the general public of the Licensed Products in the
            applicable country based on the required marketing and pricing
            approval granted by the governing health authority of such country.

      6.8   AUDITS. Upon the written request of BII, CNSI shall permit an
            independent public accountant selected by BII and acceptable to
            CNSI, which acceptance shall not be unreasonably withheld, to have
            access during normal business hours to such records of CNSI as may
            be reasonably necessary to verify the accuracy of the royalty
            reports described herein, in respect of any fiscal year ending not
            more than thirty-six (36) months prior to the date of such request.
            All such verifications shall be conducted at BII's expense and not
            more than once in each calendar year.



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            In the event such BII representative concludes that additional
            royalties were owed to BII during such period, the additional
            royalty shall be paid by CNSI within thirty (30) days of the date
            BII delivers to CNSI such representative's written report so
            concluding. The fees charged by such representative shall be paid by
            BII unless the audit discloses that the royalties payable by CNSI
            for the audited period are incorrect by more than five percent (5%),
            in which case CNSI shall pay the reasonable fees and expenses
            charged by such representative. CNSI shall include in each Third
            Party license granted by it a provision requiring the licensee to
            make reports to CNSI, to keep and maintain records of sales made
            pursuant to such license and to grant access to such records by
            BII's representatives to the same extent required of CNSI under this
            Termination Agreement. BII agrees that all information subject to
            review under this Section 6.8 or under any sublicense agreement is
            confidential and that BII shall cause its representatives to retain
            all such information in confidence and to treat such confidential
            information with the same care that it treats its own confidential
            information.

      6.9   ROYALTY PAYMENT TERMS. Royalties shown to have accrued by each
            royalty report provided for under this Termination Agreement shall
            be due, (i) within thirty (30) days of the end of each calendar
            quarter in the case of the sale of Licensed Products by CNSI or its
            Affiliates, or (ii) within fifteen (15) business days of CNSI's
            receipt of payment from a Third Party licensee in the case of sales
            of Licensed Products by a Third Party licensee. Payment of royalties
            in whole or in part may be made in advance of such due date.
            Royalties determined to be owing with respect to any prior quarter
            shall be added, together with interest thereon accruing at the rate
            set forth in Section 6.11, from the date of the report for the
            quarter for which such amounts are owing, to the next quarterly
            payment hereunder.

      6.10  WITHHOLDING TAXES. CNSI shall deduct any withholding taxes from the
            payments agreed upon under this Article 6 and pay them to the proper
            tax authorities required by the laws of the United States of America
            applicable at the date of payment. CNSI shall not deduct any other
            withholding or any other governmental charges from the payments
            agreed upon under this Termination Agreement, including but not
            limited to any such taxes or charges incurred as a result of an
            assignment or sublicense by CNSI to any Affiliate or any Third
            Party, except as noted above. CNSI shall maintain official receipts
            of payment of any withholding taxes and forward these receipts to
            BII. The parties will exercise their best efforts to ensure that any
            withholding taxes imposed are reduced as far as possible under the
            provisions of the current or any future double taxation agreement
            between the United States and the Federal Republic of Germany. BII
            shall provide CNSI with completed Form 1001 "Ownership, Exemption,
            or Reduced Rate Certificate," or Form 4224 "Exemption From
            Withholding of Tax on Income Effectively Connected With the Conduct
            of a Trade or Business in the United States," as applicable.



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      6.11  INTEREST ON LATE PAYMENTS. Any payments by CNSI to BII that are not
            paid on or before the date such payments are due under this
            Termination Agreement shall bear interest, to the extent permitted
            by applicable law, at two (2) percentage points above the Prime Rate
            of interest declared from time to time by BankBoston, N.A., in
            Boston, Massachusetts, calculated on the number of days payment is
            delinquent.

      6.12  EXPIRATION OF ROYALTY OBLIGATION. CNSI's obligation to pay BII
            royalties under this Section 6 shall expire twelve (12) years from
            the Effective Date of Termination.

7.    DEVELOPMENT COSTS. Within fifteen (15) business days of the Effective Date
of Termination, CNSI shall pay BII One Million Four Hundred and Seventy-Eight
Thousand Dollars ($1,478,000.00), which represents all outstanding amounts owed
BII pursuant to Section 4.2 of the LICENSE AGREEMENT. Such payment will be made
to BII's account at the Citibank, Frankfurt am Main, Account No. 120 3497 004,
Swift Code: CITIDEFF.

8.    BULK DRUG SUPPLY. For a period of two (2) years after the execution of
this Agreement (the "Purchase Period"), CNSI shall have the right to purchase
some or all of the existing quantity of Licensed Compound from BII at a price of
9,500 DM/kg. of Licensed Compound. As of the Effective Date of Termination, the
amount of Licensed Compound in stock is 56.831 kg., and CNSI may purchase up to
a total of 54 kg. hereunder. CNSI shall purchase such Licensed Compounds in
amounts of 2kg. or greater. At the conclusion of the Purchase Period, BII may
destroy any quantities of Licensed Compound in stock; provided, that BII shall
provide CNSI with at least thirty (30) days advance written notice thereof, and
provided, further, that CNSI shall have the right to request that instead such
remaining quantity of Licensed Compound be purchased by CNSI on the above terms.

9.    RIGHT TO DESIGNATE DIRECTOR.

      9.1   The termination of the LICENSE AGREEMENT pursuant to the terms and
            conditions set forth herein shall cause the termination of Section
            6.0 of the STOCK PURCHASE AGREEMENT, including, without limitation,
            BII's right to designate a nominee for election to CNSI's Board of
            Directors.

      9.2   The provisions of Section 9.1 notwithstanding, BII and CNSI agree
            that Burkhard Blank, M.D., heretofore a designee of BII pursuant to
            Section 6.1 of the STOCK PURCHASE AGREEMENT, shall serve on CNSI's
            Board of Directors through March 31, 1999, and thereafter upon the
            mutual agreement of the parties.

10.   ASSIGNMENT OF REGULATORY APPROVALS, PRE-CLINICAL AND CLINICAL DATA AND
      MANUFACTURING DATA.

      10.1  Within sixty (60) days of the Effective Date of Termination, BII
            shall provide to CNSI a copy of all correspondence to regulatory
            agencies relating to the termination of their clinical
            investigations of the Licensed Compound. BII shall



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            also provide to CNSI copies of technical documentation related to
            the manufacture, quality, purity and testing of the Licensed
            Compound and the corresponding Licensed Products. The foregoing
            notwithstanding, BII shall have no obligation to generate additional
            formal or informal reports for CNSI, except as provided in Article
            11.

      10.2  BII shall retain the raw data and biological samples generated by
            BII during the Program in industry standard archives for a period of
            three (3) years after the Effective Date of Termination. If
            requested by CNSI, BII shall provide such data and samples to CNSI
            so as not to jeopardize any regulatory filings, and to assist CNSI
            in completing, maintaining or supplementing, to the extent necessary
            or desirable, any regulatory filings.

      10.3  BII shall use reasonable efforts to cooperate with CNSI so as not to
            jeopardize any regulatory proceedings or approvals or delay any
            future regulatory filings undertaken by CNSI. BII agrees to make its
            employees and non-employee consultants reasonably available at their
            respective places of employment to consult with CNSI (at CNSI's
            expense) in connection with any request from CNSI or from any
            regulatory agency pertaining to any aspect of the development or
            manufacture of Licensed Compounds or Licensed Products performed by
            BII or under contract to BII during the Program, including
            toxicology, pre-clinical data, clinical testing and manufacturing
            issues.

11.   THE FINAL ANALYSIS REPORT; PUBLICATIONS AND OTHER COMMUNICATIONS REGARDING
CLINICAL STUDY 534.11. The parties agree that BII shall prepare a Final Analysis
Report and publication regarding Phase III Clinical Study 534.11 on or before
December 31, 1999, and that CNSI shall have the right to review and provide
comments on the Final Analysis Report and any publications or disclosures
regarding Clinical Study 534.11 for a period of (30) business days after its
receipt thereof, which date shall be at least thirty (30) business days prior to
the release thereof to third parties who are not employees of BII or its
Affiliates. Until such review occurs, and CNSI has had the opportunity to
provide comments on the contents of the Final Analysis Report, publication or
other disclosure, the Final Analysis Report and any such publication or other
disclosure shall be treated as the Confidential Information of CNSI.

12.   Each of CNSI and BII hereby release the other from any and all claims,
actions or causes of action by it and arising from or related to the LICENSE
AGREEMENT, the transactions contemplated thereby or the termination thereof;
provided, that, this Section shall not be interpreted to release either CNSI or
BII from any obligation expressly set forth in this Termination Agreement,
including, without limitation, their respective continuing obligations pursuant
to Section 13 hereof.

13.   SURVIVAL. The following Articles and Sections of the LICENSE AGREEMENT
shall survive its termination: Articles 1, 11 and 13 and Sections 4.3, 5.3, 6.5,
8.1.2, 9.1, 9.3, 9.4 and 9.5.



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14.   MISCELLANEOUS.

      14.1  APPLICABLE LAW. This Termination Agreement shall be governed by and
            construed in accordance with the laws of the Commonwealth of
            Massachusetts, without giving affect to the choice of law provisions
            thereof.

      14.2  ASSIGNMENT. This Termination Agreement may be assigned by either
            party without the consent of the other party, provided, that, any
            assignee shall assume all obligations of its assignor under this
            Termination Agreement.

      14.3  SEVERABILITY. Each party hereby agrees that it does not intend to
            violate any public policy, statutory or common laws, rules,
            regulations, treaty or decision of any government agency or
            executive body thereof of any country or community or association of
            countries. Should one or more provisions of this Termination
            Agreement be or become invalid, the parties hereto shall substitute,
            by mutual consent, valid provisions for such invalid provisions
            which valid provisions in their economic effect are sufficiently
            similar to the invalid provisions that it can be reasonably assumed
            that the party would have entered into this Termination Agreement
            with such valid provision. In case such valid provisions cannot be
            agreed upon, the invalidity of one or several provisions of this
            Termination Agreement shall not affect the validity of this
            Termination Agreement as a whole, unless the invalid provisions are
            of such essential importance to this Termination Agreement that it
            is to be reasonably assumed that the parties would not have entered
            into this Termination Agreement without the invalid provisions.

      14.4  NOTICES. Any consent, notice or report required or permitted to be
            given or made under this Termination Agreement by one of the parties
            thereto to the other shall be in writing, delivered personally or by
            facsimile (and promptly confirmed by telephone, personal delivery or
            courier) or courier, postage prepaid (where applicable), addressed
            to such other party at its address indicated below, or to such other
            address as the addressee shall have last furnished in writing to the
            addressor and shall be effective upon receipt by the addressee.

            If to CNSI:      Cambridge NeuroScience, Inc.
                             One Kendall Square
                             Cambridge, Massachusetts 02139
                             Attention: President
                             Telephone:(617) 225-0600
                             Telecopy: (617) 225-0613



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            with a copy to:  Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
                             One Financial Center
                             Boston, Massachusetts 02111
                             Attention: William T. Whelan, Esq.
                             Telephone:(617) 542-6000
                             Telecopy: (617) 542-2241

            If to BII:       Boehringer Ingelheim International GmbH
                             Postbox 200
                             D-55216 Ingelheim, Rhein
                             Germany
                             Attention: Corporate Licensing
                             Telephone: 011 49 61 32 77 34 08
                             Telecopy: 011 49 61 32 77 35 83

            with a copy to:  Boehringer Ingelheim International GmbH
                             Postbox 200
                             D-55216 Ingelheim, Rhein
                             Germany
                             Attention: Head of Legal Department
                             Telephone: 011 49 61 32 77 21 06
                             Telecopy: 011 49 61 32 77 35 83

      14.5  DISPUTE RESOLUTION; CHOICE OF FORUM. Any disputes arising between
            the parties relating to, arising out of or in any way connected with
            this Termination Agreement or any term or condition hereof, or the
            performance by either party of its obligations hereunder, whether
            before or after the expiration or termination of this Termination
            Agreement, shall be promptly presented to the Chief Executive
            Officer of CNSI and the Member of the Corporate Board of BII
            responsible for Pharmaceuticals for resolution and if they or their
            designees cannot promptly resolve such disputes, then either party
            shall have the right to bring an action to resolve such dispute
            before a court of competent jurisdiction. The parties hereby submit
            to the jurisdiction of the federal or state courts located within
            the Commonwealth of Massachusetts for the conduct of any suit,
            action or proceeding arising out of or relating to this Termination
            Agreement.

      14.6  HEADINGS. The captions to the several Articles and Sections hereof
            are not a part of this Termination Agreement, but are merely guides
            or labels to assist in locating and reading the several Articles and
            Sections hereof.

      14.7  WAIVER. The waiver by either party hereto of any right hereunder or
            the failure to perform or a breach by the other party shall not be
            deemed a waiver of any other right hereunder or of any other breach
            or failure by said other party whether of a similar nature or
            otherwise.



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      14.8  COUNTERPARTS. This Termination Agreement may be executed in two or
            more counterparts, each of which shall be deemed an original, but
            all of which together shall constitute one and the same instrument.

15.   This Termination Agreement together with the STOCK PURCHASE AGREEMENT,
contains the entire understanding of the parties with respect to the subject
matter hereof and, except where the LICENSE AGREEMENT is expressly referenced,
supersedes the LICENSE AGREEMENT. All express or implied agreements and
understandings, either oral or written, heretofore made are expressly merged in
and made a part of this Termination Agreement. This Termination Agreement may be
amended, or any term hereof modified, only by a written instrument duly executed
by both parties hereto.




                  [Remainder of page intentionally left blank.]




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      IN WITNESS WHEREOF, the parties have executed this Termination Agreement
as of the date first set forth above.


CAMBRIDGE NEUROSCIENCE, INC.
  
     /s/ Harry W. Wilcox
By: ___________________________________

        President & CEO
Title: ________________________________




BOEHRINGER INGELHEIM INTERNATIONAL GMBH
     ppa
     /s/ David Mitchard 
By: ___________________________________

        Authorized Signatory
Title: ________________________________


     ppa
     /s/ Peter Muller
By: ___________________________________

        Authorized Signatory
Title: ________________________________




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