<PAGE>

                                          
                                          
                                          
                                          
                                          
                                          
                                          
                                          
                        COLLABORATION AND LICENSE AGREEMENT
                                          
                                   BY AND BETWEEN
                                          
                                    GALAGEN INC.
                                          
                                        AND
                                          
                         AMERICAN HOME PRODUCTS CORPORATION
                                ACTING THROUGH ITS 
                         WYETH-AYERST LABORATORIES DIVISION
                                          
                                          
                                  OCTOBER 15, 1998
                                          


<PAGE>

                         COLLABORATION AND LICENSE AGREEMENT

     THIS COLLABORATION AND LICENSE AGREEMENT (the "Agreement") is entered into
as of the 15th day of October, 1998 (the "Effective Date"), by and between
GALAGEN INC., a company incorporated under the laws of the State of Delaware,
with its principal place of business at 4001 Lexington Avenue North, Arden
Hills, Minnesota  55126 USA ("GalaGen"), AND AMERICAN HOME PRODUCTS CORPORATION,
acting through its WYETH-AYERST LABORATORIES DIVISION, a company incorporated
under the laws of the State of Delaware, with its principal place of business at
555 East Lancaster Avenue, St. Davids, Pennsylvania  19087, USA
("Wyeth-Ayerst").  Both GalaGen and Wyeth-Ayerst are referred to herein
individually as a "Party" and collectively as the "Parties".

     WHEREAS,  GalaGen has developed proprietary technology with respect to
[**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE
SECURITIES AND EXCHANGE COMMISSION***]; and

     WHEREAS, GalaGen and Wyeth-Ayerst desire to collaborate with each other to
utilize GalaGen's proprietary technology to obtain [***CONFIDENTIAL TREATMENT
REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION***] and to develop Pediatric Formula Products and/or Other Products
containing such [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***]; and

     WHEREAS,  Wyeth-Ayerst desires to obtain the worldwide rights to
manufacture and sell such Pediatric Formula Products and/or Other Products.

     NOW THEREFORE, in consideration of the foregoing premises and the mutual
promises, covenants and conditions contained in this Agreement, the Parties
agree as follows:

1.   DEFINITIONS.

     For the purposes of this Agreement, the capitalized terms hereunder shall
     have the meanings defined below:

     1.1  "AFFILIATE(S)" shall mean, in the case of either Party, any
          corporation, joint venture, or other business entity which directly or
          indirectly controls, is controlled by, or is under common control with
          that Party.  "Control", as used in this Section 1.1, shall mean having
          the power to direct, or cause the direction of, the management and
          policies of an entity, whether through ownership of voting securities,
          by contract or otherwise. [**CONFIDENTIAL TREATMENT REQUESTED; PORTION


                                          1
<PAGE>

          OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***].

     1.2  "BUDGET" shall have the meaning set forth in Section 2.6.1 hereof.
     
     1.3  "CALENDAR QUARTER" shall mean the respective periods of three (3)
          consecutive calendar months ending on March 31, June 30, September 30
          or December 31, for so long as this Agreement is in effect.

     1.4  "COLLABORATION" shall mean the research and development program
          conducted jointly by the Parties hereunder for the purpose of
          optimizing the production of [***CONFIDENTIAL TREATMENT REQUESTED;
          PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***] and developing and obtaining Regulatory Approval for
          Pediatric Formula Products.

     1.5  "COMMERCIALLY REASONABLE EFFORTS" shall mean efforts and resources
          normally used by a Party for a compound or product owned by it or to
          which it has rights, which is of similar market potential at a similar
          stage in its product life, taking into account the competitiveness of
          the marketplace, the proprietary position of the compound or product,
          the regulatory structure involved, the profitability of the applicable
          products, and other relevant factors.

     1.6  "CONTROL" OR "CONTROLLED" shall mean licensed with the right to grant
          sublicenses without violating the terms of any Third Party agreement.

     1.7  "DEVELOPMENT PLAN" shall have the meaning set forth in Section 2.1.

     1.8  "FIRST COMMERCIAL SALE"  shall mean, on a Product by Product basis,
          the first sale of such Product in any country of the Territory after
          such Product has been granted Regulatory Approval by the competent
          authorities in such country.

     1.9  "GALAGEN GROSS INCOME"  shall mean all income, calculated in
          accordance with generally accepted accounting procedures, GalaGen or
          its Affiliates receives from Third Parties in connection with an Other
          Product to which GalaGen obtains rights pursuant to Section 3.3
          hereof, including, without limitation, 

          [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***]


                                          2
<PAGE>

     1.10 "GALAGEN KNOW-HOW" shall mean Know-How owned or Controlled by GalaGen
          or its Affiliates at any time during the term of this Agreement.

     1.11 "GALAGEN PATENT RIGHTS" shall mean all Patent Rights owned or
          Controlled by GalaGen.  A list of the GalaGen Patent Rights existing
          as of the Effective Date is set out in Exhibit A hereto.

     1.12 "GALAGEN TRADEMARK" shall mean the trademark(s) used by GalaGen in
          connection with the [**CONFIDENTIAL TREATMENT REQUESTED; PORTION
          OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***], including, without limitation, Proventra-TM-.

     1.13 "GOOD CLINICAL PRACTICE" OR "GCP" shall mean the then current
          standards for clinical trials for pharmaceuticals, as set forth in the
          United States Federal Food, Drug and Cosmetics Act and applicable
          regulations promulgated thereunder, as amended from time to time, and
          such standards of good clinical practice as are required by the
          European Union and other organizations and governmental agencies in
          countries in which the Products are intended to be sold, to the extent
          such standards are not inconsistent with United States GCP.

     1.14 "GOOD LABORATORY PRACTICE" OR "GLP" shall mean the then current
          standards for laboratory activities for pharmaceuticals, as set forth
          in the United States Federal Food, Drug and Cosmetics Act and
          applicable regulations promulgated thereunder, as amended from time to
          time, and such standards of good laboratory practice as are required
          by the European Union and other organizations and governmental
          agencies in countries in which the Products are intended to be sold,
          to the extent such standards are not inconsistent with United States
          GLP.

     1.15 "GOOD MANUFACTURING PRACTICE" OR "GMP" shall mean the current
          standards for the manufacture of pharmaceuticals, as set forth in the
          United States Federal Food, Drug and Cosmetics Act and applicable
          regulations promulgated thereunder, as amended from time to time, and
          such standards of good manufacturing practice as are required by the
          European Union and other organizations and governmental agencies in
          countries in which the Products are intended to be sold, to the extent
          such standards are not inconsistent with United States GMP.

     1.16 "INTELLECTUAL PROPERTY RIGHTS" shall mean all Patent Rights,
          trademarks, copyrights, Know-How and/or trade secrets which are owned
          or Controlled by one Party hereto (with the right to license) or
          jointly by the Parties, with regard to the development, manufacture,
          importing, use, marketing and/or sale of any Product.


                                          3
<PAGE>

     1.17 "INVENTION" shall mean an invention conceived in the course of the
          performance of and within the scope of this Agreement.

     1.18 "JOINT DEVELOPMENT COMMITTEE" OR "JDC" shall mean the committee
          appointed by the Parties as set forth in Section 2.2.

     1.19 "KNOW-HOW" shall mean all know-how, processes, information and data
          including any copyright relating thereto owned or Controlled by either
          Party (with the right to have or disclose) as of the Effective Date or
          acquired during the term of this Agreement relating to:
     
               (a)  [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***];

               (b)  [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***];

               (c)  any Product containing (a) or (b);

               (d)  methods of making any of (a), (b) or (c);

               (e)  any component of (a), (b) or (c);

               (f)  any method of using any of (a), (b), (c) or (e); and/or

               (g)  any use of (a), (b), (c) or (e).


          The term "Know-How", however, shall not include any know-how,
          processes, information and data which is, as of the Effective Date or
          later becomes, generally available to the public.

     1.20 [***CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***]

     1.21 "MANUFACTURING AND SUPPLY AGREEMENT" shall have the meaning set forth
          in Section 4.1 hereof.

     1.22 "NET SALES" shall mean proceeds from sales of Pediatric Formula
          Products by Wyeth-Ayerst, its Affiliates or sublicensees, as
          appropriate, to Third Parties, less the sum of (a) and (b) where (a)
          is a provision, determined under generally accepted accounting
          principles in the United States, for


                                          4
<PAGE>

          [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***].

          Sales of Pediatric Formula Products by and between a Party and its
          Affiliates are not sales to Third Parties and shall be excluded from
          Net Sales calculations for all purposes.

     1.23 "OTHER PRODUCT(S)"  shall mean any product, other than Pediatric
          Formula Products, which contains [**CONFIDENTIAL TREATMENT REQUESTED;
          PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***].  For the sake of clarity, Other Products shall include
          [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***].

     1.24 "PATENT RIGHTS" shall mean all patents or patent applications,  and
          all divisional, continuations, continuations-in-part, reissues,
          extensions, supplementary protection certificates and foreign
          counterparts thereof, existing as of the Effective Date or filed or
          issuing during the term of this Agreement, at least one claim of which
          covers:

               (a)  [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***];

               (b)  [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***];

               (c)  any Product containing (a) or (b);

               (d)  methods of making any of (a), (b) or (c);

               (e)  any component of  (a), (b) or (c);

               (f)  any method of using any of (a), (b), (c) or (e); and/or

               (g)  any use of (a), (b), (c) or (e).

     1.25 "PEDIATRIC FORMULA PRODUCT(S)" shall mean any  beverage (whether
          supplied in liquid form or as a powder to be mixed with a liquid)
          containing [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
          SEPARATELY WITH THE SECURITIES


                                          5
<PAGE>


          AND EXCHANGE COMMISSION***] for oral consumption by infants and/or
          children.

     1.26 "PREFERENTIAL OTHER PRODUCT" shall have the meaning set forth in
          Section 3.3.1 hereof.

     1.27 "PRODUCT" shall mean any Pediatric Formula Product or any Other
          Product.

     1.28 "R&D EXPENSES" shall mean the sum of (i) the reasonable out-of-pocket
          costs incurred by GalaGen in performing its obligations under the
          Collaboration and [***CONFIDENTIAL TREATMENT REQUESTED; PORTION
          OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***] per man-hour expended by GalaGen's employees who are
          performing activities pursuant to the Development Plan.

     1.29 "REGULATORY APPROVAL" shall mean all authorizations by the competent
          authorities which are required for the regular marketing, promotion,
          pricing and sale of a Product in a given country or regulatory
          jurisdiction.

     1.30 "REGULATORY AUTHORITY" shall mean any national, supra-national (e.g.,
          the European Commission, the Council of the European Union, or the
          European Agency for the Evaluation of Medicinal Products), regional,
          state or local regulatory agency, department, bureau, commission,
          council or other governmental entity involved in the granting of
          Regulatory Approval for a Product.

     1.31 [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***]

     1.32 "TERRITORY" shall mean the world.

     1.33 "THIRD PARTY(IES)" shall mean any person(s) or entity(ies) other than
          GalaGen, Wyeth-Ayerst or their Affiliates.

     1.34 "TRANSACTION AGREEMENTS" shall mean this Agreement, the Manufacturing
          and Supply Agreement and the Warrant Purchase Agreement.

     1.35 "USA" shall mean the United States of America, its territories and
          possessions and the Commonwealth of Puerto Rico.


                                          6
<PAGE>

     1.36 "VALID CLAIM" shall mean an unexpired claim of an issued patent
          forming part of the GalaGen Patent Rights, which claim has not been
          declared invalid by a court or other tribunal of competent
          jurisdiction.

     1.37 "WARRANT" OR "WARRANT PURCHASE AGREEMENT" shall have the meaning set
          forth in Section 5.3 hereof.

     1.38 "WYETH-AYERST KNOW-HOW" shall mean Know-How owned or Controlled by
          Wyeth-Ayerst.

     1.39 "WYETH-AYERST PATENT RIGHTS" shall mean all Patent Rights owned or
          Controlled by Wyeth-Ayerst.  A list of the Wyeth-Ayerst Patent Rights
          existing as of the Effective Date is set out in Exhibit B hereto.

     1.40 "WYETH-AYERST TRADEMARK" shall mean the trademark(s) (other than the
          GalaGen Trademark)  used by Wyeth in connection with the marketing of
          any Product.


2.   COLLABORATION.

     2.1  GENERAL OBLIGATIONS.  The Parties have designed and agreed upon a
          joint development plan (the "Development Plan") pursuant to which they
          will conduct the Collaboration hereunder.  A copy of the Development
          Plan is attached hereto as Exhibit C.  The Development Plan may be
          updated or revised, in writing, from time to time by the JDC.  During
          the term of the Collaboration, each Party agrees to use its respective
          Commercially Reasonable Efforts to perform its obligations under the
          Development Plan and this Agreement in a timely manner.

     2.2  JOINT DEVELOPMENT COMMITTEE. The Parties agree that the Collaboration,
          including the development of the [**CONFIDENTIAL TREATMENT REQUESTED;
          PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***] and the Pediatric Formula Products, will be managed by
          a Joint Development Committee (the "JDC").

          2.2.1     COMPOSITION.  No later than thirty (30) days after the
                    Effective Date, each of the Parties will appoint two (2)
                    representatives to the JDC.  The chairperson of the JDC will
                    be one of the Wyeth-Ayerst representatives.  A Party may
                    change any of its representatives at any time by giving
                    written notice to the other Party.

          2.2.2     RESPONSIBILITIES.  The JDC will:


                                          7
<PAGE>

                    (a)  monitor the progress of and compliance with the
                         Development Plan and approve any change in the
                         Development Plan;

                    (b)  select [**CONFIDENTIAL TREATMENT REQUESTED; PORTION
                         OMITTED FILED SEPARATELY WITH THE SECURITIES AND
                         EXCHANGE COMMISSION***] studies and [**CONFIDENTIAL
                         TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
                         WITH THE SECURITIES AND EXCHANGE COMMISSION***] for
                         evaluation in animal models and/or human volunteers;

                    (c)  develop research protocols and define the primary
                         endpoint for the clinical trials; 

                    (d)  review and evaluate the results of studies performed in
                         connection with the Collaboration; and

                    (e)  determine the most appropriate regulatory pathway and
                         develop appropriate strategy to obtain Regulatory
                         Approval for the [**CONFIDENTIAL TREATMENT REQUESTED;
                         PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES
                         AND EXCHANGE COMMISSION***] and the Pediatric Formula
                         Product.

          2.2.3     MEETINGS OF THE JDC.  The chairperson of the JDC shall call
                    meetings when deemed appropriate, currently anticipated to
                    be no less frequently than once every three (3) months.  If
                    possible, the meetings shall be held in person, or where
                    appropriate, by video or telephone conference.  When held in
                    person, the location of such meetings shall alternate
                    between Wyeth-Ayerst's facilities and GalaGen's facilities. 
                    The chairperson shall determine the form of and agenda for
                    the meeting.  Additional participants may be invited by any
                    member to attend meetings where appropriate (e.g.,
                    representatives of regulatory affairs or outside
                    consultants).  Such additional participants shall have no
                    vote.  Minutes of each meeting of the JDC shall be exchanged
                    for review and comment by the members.  Thereafter, they
                    shall be signed by the chairperson and distributed to each
                    of the Parties.  Each Party shall be responsible for the
                    expenses incurred by its representatives in attending such
                    meetings.


                                          8
<PAGE>

          2.2.4     VOTING.  The JDC shall make decisions by majority vote, with
                    at least one consenting vote of each Party's JDC members. 
                    If the required majority decision cannot be found and all
                    the members of each Party take the same opposing positions
                    in a matter which either Party deems to be of major
                    importance, the matter shall be handled pursuant to Section
                    2.2.6.  Voting by proxy is permissible.  Urgent matters
                    (including regulatory and adverse event matters) may be
                    decided by unanimous vote of the chairperson and a
                    representative designated by GalaGen.

          2.2.5     ROLE OF CHAIRPERSON.  Except as explicitly set forth herein,
                    in no event shall the chairperson of the JDC have any
                    additional powers or responsibilities beyond those delegated
                    to such person by virtue of such person's membership on the
                    JDC.  Without limiting the foregoing, it is understood that,
                    except as a voting member of the JDC, the chairperson shall
                    not have the power to control or dictate decisions or to
                    veto any decisions reached by the committee under the
                    decision-making processes set forth in Section 2.2.4.

          2.2.6     DISPUTE RESOLUTION.  If the JDC is unable to resolve, after
                    thirty (30) days, a dispute regarding any issue presented to
                    it or arising in it, such dispute will be referred to
                    [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***]. 
                    If such dispute is not resolved by the end of
                    [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***]
                    period, the Parties shall be free to pursue any legal or
                    equitable remedy available to them.

     2.3  SUPPLY OF [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
          SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***].  GalaGen
          shall provide Wyeth-Ayerst with [**CONFIDENTIAL TREATMENT REQUESTED;
          PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***], from time to time and in amounts specified by
          Wyeth-Ayerst, for use by Wyeth-Ayerst, its Affiliates and sublicensees
          in the development of Products, including, without limitation, the
          manufacture of Products for use in conducting clinical trials to
          obtain Regulatory Approval for Products. [**CONFIDENTIAL TREATMENT
          REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
          EXCHANGE COMMISSION***]

     2.4  RECORDS, REPORTS, AND INFORMATION EXCHANGE.  


                                          9
<PAGE>

          2.4.1     TECHNOLOGY AND INFORMATION TRANSFER.  GalaGen will provide
                    to Wyeth-Ayerst all GalaGen Know-How as Wyeth-Ayerst deems
                    necessary to carry out its responsibilities in the
                    Collaboration and to manufacture and obtain Regulatory
                    Approval for Products.  Wyeth-Ayerst will provide to GalaGen
                    all Wyeth-Ayerst Know-How as Wyeth-Ayerst deems necessary
                    for GalaGen to carry out its responsibilities in the
                    Collaboration.  All information transferred, provided or
                    exchanged under this Section 2.4.1 will be subject to the
                    confidentiality requirements set forth in Article 12 hereof.

          2.4.2     RECORD KEEPING.  Each Party will maintain records in
                    sufficient detail and in good scientific manner appropriate
                    for Regulatory Approval and patent purposes.

          2.4.3     COMMUNICATION REGARDING THE DEVELOPMENT PROGRESS.  Within
                    [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***],
                    each Party shall provide the JDC with a written report
                    summarizing the status of the activities it conducted in
                    furtherance of the Collaboration during such [**CONFIDENTIAL
                    TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY WITH
                    THE SECURITIES AND EXCHANGE COMMISSION***].

          2.4.4     R&D EXPENSES.  Within [**CONFIDENTIAL TREATMENT REQUESTED;
                    PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
                    EXCHANGE COMMISSION***], GalaGen shall submit to
                    Wyeth-Ayerst a written report setting forth a detailed
                    accounting of the R&D Expenses incurred by GalaGen during
                    such Calendar Quarter and indicating the R&D Expenses which
                    are to be reimbursed by Wyeth-Ayerst pursuant to Section 2.6
                    hereof. [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED
                    FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
                    COMMISSION***]. 

          2.4.5     OTHER PRODUCTS.  Periodically throughout the term of this
                    Agreement, Wyeth-Ayerst shall provide the JDC with a list of
                    Other Products for which Wyeth-Ayerst has either initiated
                    development activities or plans to initiate development
                    activities.

     2.5  COMPLIANCE.  Each of the Parties shall comply with all applicable GLP,
          GCP and GMP in the conduct of the Collaboration.


                                          10
<PAGE>

     2.6  FUNDING OF THE COLLABORATION.  

          [***CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***]

     2.7  [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***]

     2.8  REGULATORY APPROVALS.  Wyeth-Ayerst shall file all regulatory dossiers
          for the [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
          SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***] and the
          Product(s) under its or its Affiliates' names.  Wyeth-Ayerst shall own
          all Regulatory Approvals for the [**CONFIDENTIAL TREATMENT REQUESTED;
          PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***] and Product(s), except for those Products to which
          GalaGen obtains rights in accordance with Section 3.3 hereof. 
          Wyeth-Ayerst shall be responsible for all communications with
          regulatory agencies with respect to the Product(s)  (other than
          Products to which GalaGen obtains rights in accordance with Section
          3.3 hereof), subject to its obligation to keep the JDC informed.   In
          the event that GalaGen obtains rights to an Other Product in
          accordance with the provisions of Section 3.3 hereof, Wyeth-Ayerst
          shall permit GalaGen to have access to such applications for
          Regulatory Approval and related documents solely as such applications
          and documents relate to the use of [**CONFIDENTIAL TREATMENT
          REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
          EXCHANGE COMMISSION***], PROVIDED, HOWEVER, that GalaGen's use of such
          applications and documents shall be limited to obtaining and
          maintaining Regulatory Approval for such Other Product.

     2.9  EXCLUSIVITY. GalaGen covenants that, except as otherwise permitted in
          accordance with the provisions of Section 3.3 hereof,  during the term
          of this Agreement, it will not conduct any research and development
          activities, either independently or with Third Parties, with respect
          to Products and that it will not provide [**CONFIDENTIAL TREATMENT
          REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
          EXCHANGE COMMISSION***] to any Third Party for the purpose of
          conducting research and development activities or commercializing any
          Product.  Notwithstanding, the foregoing, GalaGen and Wyeth-Ayerst
          each recognize that, from time to time, it may be desirable or
          necessary to retain consultants to assist the Parties in the


                                          11
<PAGE>

          Collaboration.  In such event, the Parties together shall enter into a
          consulting agreement with each such consultant, which consulting
          agreement shall, in both form and substance, be reasonably acceptable
          to each of the Parties.

     2.10 TERM OF COLLABORATION.  The term of the Collaboration shall commence
          on the Effective Date and, unless terminated earlier, shall expire
          [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***] or such later date as
          may be agreed upon by majority vote of the JDC.  The Collaboration
          shall automatically terminate upon termination of this Agreement
          pursuant to either of Sections 9.2 or 9.3 hereof.

3.   GRANT OF RIGHTS.

     3.1  EXCLUSIVE LICENSE.  

          3.1.1     PEDIATRIC FORMULA PRODUCTS.  Subject to the other provisions
                    of this Agreement, GalaGen hereby grants to Wyeth-Ayerst an
                    exclusive license (exclusive even as to GalaGen) in the
                    Territory, under GalaGen's Intellectual Property Rights and
                    GalaGen's interest in any Intellectual Property Rights
                    jointly owned by the Parties, to develop, manufacture, have
                    manufactured, import, export, use, market, offer for sale
                    and sell Pediatric Formula Products and to use the GalaGen
                    Trademarks on the packaging of and in promotional materials
                    for Pediatric Formula Products, PROVIDED, HOWEVER, that,
                    except as provided in Article 4 of the Manufacturing and
                    Supply Agreement, nothing herein shall confer upon
                    Wyeth-Ayerst any rights to manufacture [**CONFIDENTIAL
                    TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY WITH
                    THE SECURITIES AND EXCHANGE COMMISSION***] for use in
                    Pediatric Formula Products.

          3.1.2     OTHER PRODUCTS.  Subject to the other provisions of this
                    Agreement, GalaGen hereby grants to Wyeth-Ayerst an
                    exclusive license (exclusive even as to GalaGen except as
                    provided in Section 3.3 hereof) in the Territory, under
                    GalaGen's Intellectual Property Rights and GalaGen's
                    interest in any Intellectual Property Rights jointly owned
                    by the Parties, to develop, manufacture, have manufactured,
                    import, export, use, market, offer for sale and sell Other
                    Products and to use the GalaGen Trademarks on the packaging
                    of and in promotional materials for Other Products,


                                          12
<PAGE>

                    PROVIDED, HOWEVER, that, except as provided in Article 4 of
                    the Manufacturing and Supply Agreement, nothing herein shall
                    confer upon Wyeth-Ayerst any rights to manufacture
                    [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***]
                    for use in Other Products.


     3.2  SUBLICENSING.  Wyeth-Ayerst shall have the right to  sublicense all or
          any part of the rights granted to it under Section 3.1 to its
          Affiliates or Third Parties.  Wyeth-Ayerst shall notify GalaGen of its
          intent to grant a sublicense to a Third Party prior to granting such
          sublicense under this Section 3.2, but Wyeth-Ayerst shall not be
          required to obtain GalaGen's consent to grant any such sublicense
          except in the case where Wyeth-Ayerst is sublicensing, to a Third
          Party, the right to develop and commercialize an Other Product
          included in the list of Preferential Other Products established by the
          JDC in accordance with Section 3.3.1 hereof, in which event,
          Wyeth-Ayerst may grant such sublicense to such Third Party only after
          obtaining GalaGen's prior written consent, which consent shall not be
          unreasonably withheld.  In the event that GalaGen's consent is
          required, in accordance with the preceding sentence, for Wyeth-Ayerst
          to grant a sublicense to a Third Party to develop and commercialize a
          Preferential Other Product and GalaGen elects to withhold such
          consent, GalaGen shall notify Wyeth-Ayerst, in writing and within
          [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***] after Wyeth-Ayerst's
          request for such consent, that GalaGen is withholding such consent,
          which notice shall state the reason(s) such consent is being withheld
          and provide documentary or other evidence GalaGen has in support of
          its position that such reason(s) reasonably warrant the withholding of
          such consent.  If Wyeth-Ayerst does not receive such written notice
          within such [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
          SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***] period,
          GalaGen shall be deemed to have provided its consent for Wyeth-Ayerst
          to grant such sublicense. 

     3.3  GALAGEN RIGHTS TO OTHER PRODUCTS.  

          3.3.1     IDENTIFICATION OF PREFERENTIAL OTHER PRODUCTS.  GalaGen,
                    [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***], 
                    shall notify the JDC and Wyeth-Ayerst, each in writing, of
                    those Other Products that GalaGen reasonably believes it
                    would both desire and have the ability to develop and
                    commercialize, either itself or in 


                                          13
<PAGE>

                    collaboration with a Third Party, PROVIDED, HOWEVER, that
                    such list of Other Products shall not include
                    [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***]. 
                    Each such notice shall include a proposed development plan
                    for each Other Product included on such list.  Within
                    [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***]
                    after receiving the first such list the JDC shall meet to
                    consider the list and proposed development plan(s) provided
                    by GalaGen and any concerns that Wyeth-Ayerst has with the
                    inclusion of any particular Other Product(s) on such list,
                    and based on such considerations, the JDC shall establish a
                    list of Other Products for which Wyeth-Ayerst must seek
                    GalaGen's consent, in accordance with Section 3.2 hereof,
                    prior to granting to one or more Third Parties a
                    sublicense(s) to develop and commercialize such Other
                    Products (the "Preferential Other Products").  Once each
                    year the JDC shall meet [**CONFIDENTIAL TREATMENT REQUESTED;
                    PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
                    EXCHANGE COMMISSION***] (i) to review the then current list
                    of Preferential Other Products and GalaGen's progress in
                    developing such Other Product in accordance with the
                    development plan accepted by the JDC for such Other Product,
                    and (ii) to consider the list of any Other Products provided
                    by GalaGen and any concerns that Wyeth-Ayerst has with the
                    inclusion of any particular Other Product(s) on the list of
                    Preferential Other Products.  Based on such review and
                    considerations, the JDC shall revise the then current list
                    of Preferential Other Products, PROVIDED, HOWEVER, that if
                    GalaGen has failed to use reasonable efforts to develop any
                    Other Product in accordance with the development plan
                    accepted by the JDC for such Other Product, such Other
                    Product shall be removed from the list of Preferential Other
                    Products unless the JDC agrees to accept from GalaGen a
                    revised development plan for such Other Product.

          3.3.2     ACQUISITION OF SUBLICENSE BY GALAGEN.  In the event GalaGen
                    desires to develop and commercialize an Other Product
                    (whether or not such Other Product is a Preferential Other
                    Product), either itself or in collaboration with a Third
                    Party, GalaGen may, by written notice to Wyeth-Ayerst,
                    request that Wyeth-Ayerst grant to GalaGen a sublicense of
                    the rights granted to Wyeth-Ayerst under Section 3.1.2
                    hereof solely for the development and commercialization of
                    such Other Product.  After the receipt of such 


                                          14
<PAGE>

                    notice, Wyeth-Ayerst may elect whether or not to grant such
                    sublicense and will not unreasonably refuse to grant such a
                    sublicense to GalaGen, PROVIDED, HOWEVER, that in no event
                    will Wyeth-Ayerst be required to grant a sublicense to
                    GalaGen for the development and/or commercialization of such
                    an Other Product if 

                         (i)  Wyeth-Ayerst has initiated the development and/or
                              commercialization of the same or a similar Other
                              Product; 

                        (ii)  Wyeth-Ayerst has advised the JDC pursuant to
                              Section 2.4.5 hereof, that it intends to initiate
                              the development of the same or a similar Other
                              Product;

                       (iii)  Wyeth-Ayerst has, in accordance with Section 3.2
                              hereof, granted to a Third Party the right to
                              develop and/or commercialize the same or a similar
                              Other Product; 

                        (iv)  Wyeth-Ayerst reasonably believes that the
                              development and/or commercialization of such an
                              Other Product would adversely affect the
                              commercial potential of any Pediatric Formula
                              Product that Wyeth-Ayerst has developed, is
                              developing, plans to develop, is commercializing
                              or plans to commercialize; 

                         (v)  Wyeth-Ayerst is able to reasonably demonstrate
                              that the development and/or commercialization of
                              such an Other Product would have a material
                              adverse effect on the commercial potential of any
                              Other Product that Wyeth-Ayerst has developed, is
                              developing or is commercializing; 

                        (vi)  Wyeth-Ayerst is able to reasonably demonstrate
                              that the development and/or commercialization of
                              such an Other Product would have a material
                              adverse effect on the commercial potential of any
                              Other Product which Wyeth-Ayerst has advised the
                              JDC, pursuant to Section 2.4.5 hereof, that it
                              intends to initiate the development of; 

                       (vii)  Wyeth-Ayerst is able to reasonably demonstrate
                              that the development and/or commercialization of
                              such an Other Product would have a material
                              adverse 


                                          15
<PAGE>

                              effect on the commercial potential of any product
                              that is being developed or commercialized by
                              Wyeth-Ayerst in one of Wyeth-Ayerst's core
                              business areas; or 

                      (viii)  [**CONFIDENTIAL TREATMENT REQUESTED; PORTION
                              OMITTED FILED SEPARATELY WITH THE SECURITIES AND
                              EXCHANGE COMMISSION***].  Wyeth-Ayerst will notify
                              GalaGen of such election within [**CONFIDENTIAL
                              TREATMENT REQUESTED; PORTION OMITTED FILED
                              SEPARATELY WITH THE SECURITIES AND EXCHANGE
                              COMMISSION***] of receiving such notice from
                              GalaGen.  In the event that Wyeth-Ayerst elects to
                              grant such a sublicense to GalaGen the Parties
                              shall use their respective Commercially Reasonable
                              Efforts to negotiate, in good faith, a definitive
                              sublicense agreement containing terms and
                              conditions (including, without limitation, whether
                              such sublicense will be exclusive even as to
                              Wyeth-Ayerst or exclusive except as to
                              Wyeth-Ayerst) mutually acceptable to the Parties,
                              PROVIDED, HOWEVER, that such sublicense, INTER
                              ALIA, shall provide that (i) GalaGen shall pay to
                              Wyeth-Ayerst [**CONFIDENTIAL TREATMENT REQUESTED;
                              PORTION OMITTED FILED SEPARATELY WITH THE
                              SECURITIES AND EXCHANGE COMMISSION***] and (ii)
                              Wyeth-Ayerst will be granted a right of first
                              refusal to obtain the right to commercialize such
                              Other Product(s) in the event GalaGen elects to
                              license or otherwise transfer such responsibility
                              to a Third Party, PROVIDED, HOWEVER, that
                              Wyeth-Ayerst shall be required to waive its right
                              to exercise such right of first refusal if (x)
                              GalaGen, in its written notice requesting such
                              sublicense, identifies a Third Party to whom
                              GalaGen intends to further sublicense the right to
                              commercialize such Other Product and (y) GalaGen,
                              in fact, grants such a further sublicense to such
                              Third Party within [**CONFIDENTIAL TREATMENT
                              REQUESTED; PORTION OMITTED FILED SEPARATELY WITH
                              THE SECURITIES AND EXCHANGE COMMISSION***] after
                              Wyeth-Ayerst grants to 


                                          16
<PAGE>

                              GalaGen a sublicense to develop and/or
                              commercialize such Other Product. The mechanism
                              and timing for exercising such right of first
                              refusal shall be mutually agreed upon by the
                              Parties and shall be set forth in the definitive
                              sublicense agreement, provided, however, that such
                              sublicense agreement shall provide that
                              Wyeth-Ayerst's acquisition of rights under such
                              right of first refusal shall be substantially
                              equivalent to the terms and conditions that
                              GalaGen had negotiated, in good faith, with a
                              Third Party.  For purposes of this Section 3.3, a
                              material adverse effect on a product shall
                              include, without limitation, a forecasted decline
                              of [**CONFIDENTIAL TREATMENT REQUESTED; PORTION
                              OMITTED FILED SEPARATELY WITH THE SECURITIES AND
                              EXCHANGE COMMISSION***] in unit sales or revenues
                              from the sale of such product.

          3.3.3     FAILURE TO CONCLUDE NEGOTIATION OF SUBLICENSE.   If
                    Wyeth-Ayerst has used its Commercially Reasonable Efforts to
                    negotiate a sublicense agreement with GalaGen pursuant to
                    Section 3.3.2 hereof and the Parties fail to sign such a
                    definitive sublicense agreement within [**CONFIDENTIAL
                    TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY WITH
                    THE SECURITIES AND EXCHANGE COMMISSION***] after
                    Wyeth-Ayerst has notified GalaGen of its election to
                    negotiate such an agreement for the grant to GalaGen of a
                    sublicense to develop and/or commercialize such Other
                    Product (or such longer period of time as may be mutually
                    agreed upon by the Parties in writing), Wyeth-Ayerst may, by
                    written notice to GalaGen, revoke its election to negotiate
                    and/or grant such a sublicense to GalaGen.

          3.3.4     REFUSAL TO GRANT SUBLICENSE.  In the event that Wyeth-Ayerst
                    elects, for the reasons set forth in Section 3.3.2(ii)
                    and/or Section 3.3.2(vi) above, not to grant to GalaGen a
                    sublicense to develop and/or commercialize an Other Product
                    and within [**CONFIDENTIAL TREATMENT REQUESTED; PORTION
                    OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
                    COMMISSION***] making such election Wyeth-Ayerst fails to
                    either initiate the development of such Other Product or
                    sublicense to a Third Party the right to develop and/or
                    commercialize such Other Product, GalaGen, within
                    [**CONFIDENTIAL TREATMENT REQUESTED; PORTION 


                                          17
<PAGE>

                    OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
                    COMMISSION***] after the expiration of such [**CONFIDENTIAL
                    TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY WITH
                    THE SECURITIES AND EXCHANGE COMMISSION***] period, may, by
                    written notice to Wyeth-Ayerst, request that such sublicense
                    be granted and, in such event, Wyeth-Ayerst shall thereafter
                    grant to GalaGen a sublicense to develop and commercialize
                    such Other Product subject to the negotiation of a
                    definitive sublicense agreement with GalaGen as provided in
                    Section 3.3.2 hereof.

     3.4  [***CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***]

4.   MANUFACTURE, SUPPLY AND COMMERCIALIZATION OF PRODUCTS.

     4.1  MANUFACTURE AND SUPPLY OF [**CONFIDENTIAL TREATMENT REQUESTED; PORTION
          OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***].  GalaGen shall manufacture or have manufactured and
          supply to Wyeth-Ayerst and Wyeth-Ayerst shall purchase from GalaGen
          its requirements of the [**CONFIDENTIAL TREATMENT REQUESTED; PORTION
          OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***], for use in manufacturing Products to be sold to Third
          Parties, in accordance with the terms and provisions of the
          Manufacturing and Supply Agreement signed by the Parties on even date
          with the Effective Date, which agreement shall be substantially in the
          form which is attached hereto as Exhibit F.   

     4.2  MANUFACTURE OF PRODUCTS.  Wyeth-Ayerst, either directly or through a
          Third Party manufacturer of its choosing, shall be responsible for
          manufacturing its requirements of the Products using the
          [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***] supplied by GalaGen
          pursuant to Section 4.1 hereof.  

     4.3  REGISTRATION AND COMMERCIALIZATION OF PRODUCTS.  Wyeth-Ayerst shall
          use its Commercially Reasonable Efforts to obtain Regulatory Approval
          for, and to promote, market and sell a Pediatric Formula Product in
          those countries of the Territory where Wyeth-Ayerst, in its sole
          discretion, deems it commercially reasonable to do so.  If within


                                          18
<PAGE>

          [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***], an application for
          Regulatory Approval has not been filed seeking Regulatory Approval for
          the sale of a Pediatric Formula Product in the United States, the
          Parties, upon GalaGen's written request, shall meet to discuss
          Wyeth-Ayerst's plans for obtaining Regulatory Approval for and
          commercializing (either directly or through one or more Affiliates,
          sublicensees or distributors) Pediatric Formula Products in the United
          States, PROVIDED, HOWEVER, that if there has been a delay in either
          (a) the completion of the research and development activities to be
          performed under the Development Plan or (b) the supply by GalaGen to
          Wyeth-Ayerst of Wyeth-Ayerst's requirements of the [**CONFIDENTIAL
          TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE
          SECURITIES AND EXCHANGE COMMISSION***] for use in the development of
          Pediatric Formula Products, such [**CONFIDENTIAL TREATMENT REQUESTED;
          PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***].  In addition, if, after having had the discussions
          described in the preceding sentence, Wyeth-Ayerst, [**CONFIDENTIAL
          TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE
          SECURITIES AND EXCHANGE COMMISSION***], fails to either 

               (i)  file an application seeking Regulatory Approval for at least
                    one (1) Pediatric Formula Product in the United States, or 

              (ii)  grant a sublicense to one or more Third Parties to develop
                    and/or commercialize at least one (1) Pediatric Formula
                    Product in the United States, 

          Wyeth-Ayerst shall, upon GalaGen's written request, grant to GalaGen
          an exclusive (exclusive, except as to Wyeth-Ayerst) sublicense of the
          rights granted to Wyeth-Ayerst hereunder, to develop, make, have made,
          use, import, market, promote, offer for sale, and sell Pediatric
          Formula Products (and not any Other Products) in the United States,
          PROVIDED, HOWEVER, that if  there has been a delay [**CONFIDENTIAL
          TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE
          SECURITIES AND EXCHANGE COMMISSION***] in either (x) the completion of
          the research and development activities to be performed under the
          Development Plan or (y) the supply by GalaGen to Wyeth-Ayerst of
          Wyeth-Ayerst's requirements of [**CONFIDENTIAL TREATMENT REQUESTED;
          PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***] for use in the development of Pediatric Formula
          Products such [**CONFIDENTIAL TREATMENT 


                                          19
<PAGE>

          REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
          EXCHANGE COMMISSION***].  Further, if Wyeth-Ayerst has not made its
          First Commercial Sale of a Pediatric Formula Product in the United
          States within [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED
          FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***] after
          obtaining Regulatory Approval for the first Pediatric Formula Product
          in the United States, Wyeth-Ayerst shall, upon GalaGen's written
          request, grant to GalaGen an exclusive (exclusive, even as to
          Wyeth-Ayerst) sublicense of the rights granted by GalaGen to
          Wyeth-Ayerst hereunder, to use GalaGen's Intellectual Property Rights
          and GalaGen's interest in any Intellectual Property Rights jointly
          owned by the Parties to develop, make, have made, use, import, market,
          promote, offer for sale, and sell Pediatric Formula Products (and not
          any Other Products) in the United States only.   In the event that
          Wyeth-Ayerst is required, in accordance with this Section 4.3, to
          grant a sublicense to GalaGen the Parties shall within the
          [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***] after GalaGen's
          written request, use their respective Commercially Reasonable Efforts
          to negotiate, in good faith, a definitive sublicense agreement
          containing terms and conditions mutually acceptable to the Parties,
          provided, however, that in no event will Wyeth-Ayerst be required to
          grant to GalaGen a license under any of Wyeth-Ayerst's Intellectual
          Property Rights..


5.   CONSIDERATION TO GALAGEN.

     5.1  LICENSE FEE.  [***CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED
          FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***]

     5.2  ADDITIONAL LICENSE FEES.  [***CONFIDENTIAL TREATMENT REQUESTED;
          PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***]

     5.3  PURCHASE OF WARRANTS.  Simultaneously with the execution of this
          Agreement, GalaGen will issue to Wyeth-Ayerst a stock purchase
          warrant(the "Warrant" or the "Warrant Purchase Agreement") permitting
          Wyeth-Ayerst to purchase up to two hundred thousand (200,000) shares
          of GalaGen's common stock at the price set forth therein.  The Warrant
          shall be in the form that is attached hereto as Exhibit G.


                                          20
<PAGE>

     5.4  METHOD OF PAYMENT. [**CONFIDENTIAL TREATMENT REQUESTED; PORTION
          OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***].


6.  ACCOUNTS AND RECORDS; WITHHOLDING TAX.

     6.1  RECORD KEEPING BY GALAGEN.  GalaGen shall keep accurate books and
          accounts of record in connection with the activities conducted by it
          as part of the Collaboration in sufficient detail to permit accurate
          determination of all figures necessary for verification of the R&D
          Expenses incurred by GalaGen in the Collaboration hereunder.  GalaGen
          shall maintain such records for a period of [**CONFIDENTIAL TREATMENT
          REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
          EXCHANGE COMMISSION***] after the end of the year in which they were
          generated.

     6.2  AUDIT BY WYETH-AYERST.  Wyeth-Ayerst, through an independent certified
          public accountant reasonably acceptable to GalaGen, shall have the
          right, at its own expense, to access the books and records of GalaGen
          for the sole purpose of verifying the statements furnished by GalaGen
          pursuant to Section 2.4.4.  Such access shall be conducted after
          reasonable prior written notice to GalaGen and during ordinary
          business hours and shall not be more frequent than once per calendar
          year.  Wyeth-Ayerst agrees to keep in strict confidence all
          information learned in the course of such audit, except when it is
          necessary to reveal such information in order to enforce its rights
          under this Agreement.  Wyeth-Ayerst's right to have such records
          examined shall survive termination or expiration of this Agreement. 
          In the event such audit reveals an overpayment GalaGen shall promptly
          refund to Wyeth-Ayerst the amount of such overpayment.  In the event
          such audit reveals an overpayment of [**CONFIDENTIAL TREATMENT
          REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
          EXCHANGE COMMISSION***] of the amount actually due, GalaGen shall also
          promptly reimburse Wyeth-Ayerst for the reasonable out-of-pocket
          expenses incurred by Wyeth-Ayerst in conducting such audit.

     6.3  RECORD KEEPING BY WYETH-AYERST.  Wyeth-Ayerst shall keep accurate
          books and accounts of record in connection with the sale by or for it
          of the Products in sufficient detail to permit accurate determination
          of all figures necessary for verification of payments required to be
          paid hereunder.  Wyeth-Ayerst shall maintain such records for a period
          of [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
          SEPARATELY WITH THE SECURITIES AND 


                                          21
<PAGE>

          EXCHANGE COMMISSION***] after the end of the year in which they were
          generated.

     6.4  AUDIT BY GALAGEN.  GalaGen, through an independent certified public
          accountant reasonably acceptable to Wyeth-Ayerst, shall have the
          right, at its own expense, to access the books and records of
          Wyeth-Ayerst for the sole purpose of determining whether a payment
          under either Section 5.1 or Section 5.2 has become due.  Such access
          shall be conducted after reasonable prior written notice to GalaGen
          and during ordinary business hours and shall not be more frequent than
          once per calendar year.  Wyeth-Ayerst may require such independent
          certified public accountant to sign a customary confidential
          disclosure agreement prior to permitting such independent certified
          public accountant to have access to its books, records or facilities. 
          The Parties agree that such independent certified public accountant
          shall disclose to GalaGen only whether the payments due under Section
          5.1 or Section 5.2 hereof were made on time in accordance with the
          provisions of Article 5 hereof and the specific details concerning any
          late payments.  GalaGen agrees to keep in strict confidence all
          information learned in the course of such audit, except when it is
          necessary to reveal such information in order to enforce its rights
          under this Agreement.  GalaGen's right to have such records examined
          shall survive termination or expiration of this Agreement.  In the
          event that such an audit reveals that a payment by Wyeth-Ayerst to
          GalaGen under Section 5.1 or Section 5.2 hereof was paid to GalaGen
          more than [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
          SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***] to GalaGen
          in accordance with Article 5 hereof, Wyeth-Ayerst shall reimburse
          GalaGen for the reasonable out-of-pocket expenses incurred by GalaGen
          in conducting such audit.

     6.5  WITHHOLDING.  All taxes, assessments and fees of any nature levied or
          incurred on account of any payments accruing under this Agreement, by
          national, state or local governments, will be assumed and paid by
          Wyeth-Ayerst, except taxes levied thereon as income to GalaGen and if
          such taxes are required to be withheld by Wyeth-Ayerst they will be
          deducted from payments due to GalaGen and will be timely paid by
          Wyeth-Ayerst to the proper taxing authority for the account of
          GalaGen.  A receipt or other proof of payment therefor shall be
          secured and sent to GalaGen as soon as practicable.

     6.6  FOREIGN EXCHANGE.  For the purpose of computing Net Sales for Products
          sold in a currency other than United States Dollars, such currency
          shall be converted into United States Dollars in accordance with
          Wyeth-Ayerst's customary and usual translation procedures,
          consistently applied.


                                          22
<PAGE>

7.   TRADEMARKS.

     7.1  TRADEMARKS FOR PRODUCTS.  Wyeth-Ayerst shall select and own the
          Wyeth-Ayerst Trademarks for marketing Products in the Territory.  All
          expenses for (i) registration of such Trademarks and (ii) bringing,
          maintaining and prosecuting any action to protect or defend such
          Trademarks shall be borne by Wyeth-Ayerst and Wyeth-Ayerst shall
          retain all recoveries therefrom.  At the termination of this
          Agreement, Wyeth-Ayerst shall continue to have unrestricted ownership
          of such Trademark(s) in the Territory.

     7.2  TRADEMARKS [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
          SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***].  Subject
          to the license granted to Wyeth-Ayerst under Section 3.1 hereof,
          GalaGen, in consultation with Wyeth-Ayerst, shall select and own the
          GalaGen Trademarks for marketing the [**CONFIDENTIAL TREATMENT
          REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
          EXCHANGE COMMISSION***] in the Territory.  All expenses for (i)
          registration of such Trademarks and (ii) bringing, maintaining and
          prosecuting any action to protect or defend such GalaGen Trademarks
          shall be borne by GalaGen and GalaGen shall retain all recoveries
          therefrom.  If permitted by applicable laws and regulations
          Wyeth-Ayerst shall signify that the Product includes a [**CONFIDENTIAL
          TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE
          SECURITIES AND EXCHANGE COMMISSION***] by including the GalaGen
          Trademark, in a visible and readable form, on the label or package for
          the Product and GalaGen shall provide Wyeth-Ayerst with camera ready
          artwork of such GalaGen Trademark for such purpose.  The location and
          size of the GalaGen Trademark on such label or package shall be
          determined by Wyeth-Ayerst.  Wyeth-Ayerst shall not and shall not
          authorize any of its Affiliates or sublicensees to (i) use the GalaGen
          Trademarks on any product other than Products or (ii) use any
          trademark that is confusingly similar to the GalaGen Trademarks, in
          either case without the prior written consent of GalaGen.  Each Party
          agrees to notify the other Party, in writing, of any claim or action
          for infringement or unfair competition relating to the GalaGen
          Trademarks which are threatened or brought against such Party by a
          Third Party, and of any conflicting uses of, applications or
          registrations for, or acts of infringement or unfair competition
          involving the GalaGen Trademarks promptly after such Party learns of
          any such matter.  The Parties shall cooperate in the defense or
          prosecution of any 


                                          23
<PAGE>

          such claims, which cooperation shall include, without limitation,
          providing to the other Party all records, documents and specimens in
          its possession relating to such claim or action and causing its
          employees to give testimony relating to such claim or action, 


8.   PROSECUTION, MAINTENANCE AND INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS.

     8.1  PATENTABLE INVENTIONS.

          8.1.1     OWNERSHIP OF PATENTABLE INVENTIONS.  Wyeth-Ayerst shall own
                    all Inventions made solely by its employees and agents, and
                    all patent applications and patents claiming such
                    Inventions.  GalaGen shall own all Inventions made solely by
                    its employees and agents, and all patent applications and
                    patents claiming such Inventions.  All Inventions made
                    jointly by employees or agents of GalaGen and employees or
                    agents of Wyeth-Ayerst and all patent applications and
                    patents claiming such Inventions shall be owned jointly by
                    GalaGen and Wyeth-Ayerst.  All determinations of
                    inventorship under this Section 8.1.1 shall be in accordance
                    with United States law.

          8.1.2     PATENT PROCUREMENT.  Wyeth-Ayerst and GalaGen shall each
                    disclose to the other and discuss any Inventions and the
                    desirability of filing a United States patent application
                    covering the Invention, as well as any foreign counterpart
                    patent applications.  The Party owning the Invention shall
                    make the final decision with respect to any such filings and
                    shall have the right to select patent counsel and to take
                    such other actions as are reasonably appropriate to prepare,
                    file, prosecute and maintain patent protection with respect
                    to its Inventions arising under this Section 8.1.  With
                    respect to jointly owned Inventions, the Parties shall meet
                    to determine in what countries, if any, patent applications
                    claiming such joint Inventions should be filed.  In the
                    event that either Party does not wish to share in the
                    expenses of both filing and prosecuting patent applications
                    claiming such joint Inventions in any country of the
                    Territory, such Party shall promptly assign or cause to be
                    assigned to the other Party all of its right, title and
                    interest in and to such joint Invention and thereafter such
                    joint Invention shall be treated as an Invention solely
                    owned by such other Party for all purposes of this
                    Agreement.  In the event both Parties desire to share in the
                    expenses of applying for, obtaining and maintaining patents
                    claiming such a joint Invention in one or more countries of
                    the 


                                          24
<PAGE>


                    Territory Wyeth-Ayerst shall file and prosecute any patent
                    applications thereon in such countries and the out-of-pocket
                    expenses incurred by Wyeth-Ayerst in preparing, filing, and
                    prosecuting such joint patent applications and in
                    maintaining any patents issued therefrom shall be shared
                    equally by the Parties.  GalaGen shall reimburse
                    Wyeth-Ayerst for its share of such expenses pursuant to
                    invoices submitted to GalaGen by Wyeth-Ayerst and shall pay
                    to Wyeth-Ayerst the amount due for each such invoice within
                    [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***]
                    of GalaGen's receipt of such invoice.

     8.2  PROSECUTION AND MAINTENANCE OF PATENT RIGHTS.   Each Party shall be
          responsible for prosecuting and maintaining its own Patent Rights
          throughout the Territory, subject to Section 8.1.2.  To facilitate
          such decision-making, each Party will appoint a "patent coordinator",
          who will have the authority to make such decision on behalf of such
          Party.  Except as otherwise provided in Section 8.1.2, all expenses
          for filing, prosecuting and maintaining a Party's Patent Rights shall
          be borne in full by such Party.

     8.3  PATENT EXTENSIONS.  The Party holding a Patent Right, if requested by
          and with the assistance of the other Party, shall apply in a timely
          manner for such patent term extensions or patent term restoration
          certificates for such Patent Right as are available under the Federal
          Drug Price Competition and Patent Term Restoration Act of 1984 (Pub.
          L. No. 98-417), and any amendments thereof or any successor acts
          thereto in the USA or similar legislation in other countries of the
          Territory.  All expenses incurred in connection with such patent term
          extensions or patent restoration certificates shall be borne in full
          by the Party holding such Patent Right.

     8.4  COOPERATION.  Each of the Parties shall execute or have executed by
          its appropriate employees, representatives, agents and contractors
          such documents as may be necessary to obtain, perfect or maintain any
          Patent Rights filed or to be filed pursuant to this Agreement, and to
          cooperate with the other Party so far as reasonably necessary with
          respect to furnishing all information and data in its possession
          reasonably necessary to obtain or maintain such Patent Rights.

     8.5  INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS.

          8.5.1     PROSECUTION OF INFRINGEMENT.

                    (a)  If either Party should become aware of any infringement
                         or


                                          25
<PAGE>

                         threatened infringement or misappropriation, as the
                         case may be, in any country of the Territory, of any
                         Intellectual Property Rights of the other Party, it
                         shall promptly notify such other Party in writing.  As
                         soon as practicable the Parties shall confer on the
                         particulars of such infringement or misappropriation
                         and the possible courses of action to be taken.  The
                         Party holding the affected Intellectual Property Rights
                         shall have the right, but not the obligation, to
                         institute, prosecute and control any legal proceedings
                         in its own name by its own counsel and at its own
                         expense, subject to Section 8.5.1(d), to prevent or
                         restrain such infringement, and the other Party shall
                         have the right, at its own expense, to be represented
                         in such action by its own counsel.  If one Party brings
                         any such action or proceeding, the other Party hereby
                         consents to being joined as a party plaintiff where
                         necessary and, in case of  joining, such other Party
                         agrees to give the first Party reasonable assistance
                         and authority to file and to prosecute such suit, at
                         the expense of the Party bringing such suit.

                    (b)  Notwithstanding the foregoing, the Parties shall
                         jointly determine which Party shall have the primary
                         right and responsibility (but not the obligation) to
                         institute, prosecute, and control any action or
                         proceeding with respect to infringement or
                         misappropriation of jointly owned Intellectual Property
                         Rights and the other Party shall have the right, at its
                         expense, to be represented by its counsel.  Each Party
                         hereby consents to the filing of any such action by the
                         other Party with respect to any jointly owned Patent
                         Rights in accordance with this Section 8.5.1(b).

                    (c)  If one Party alone prosecutes an infringement or
                         misappropriation of Intellectual Property Rights, after
                         payment of its legal costs and expenses, any damages
                         and costs recovered in any proceedings or by way of
                         settlement under Sections 8.5.1(a) and 8.5.1(b) above
                         or Section 8.5.2 shall belong to the Party bringing
                         such action, subject to payment therefrom to the other
                         Party of a reasonable sum to compensate the latter for
                         loss of profits, as applicable.
                    
                    (d)  If both Parties participate in prosecuting an
                         infringement or misappropriation of Intellectual
                         Property Rights, any damages and costs recovered in any
                         proceedings or by way 


                                          26
<PAGE>

                         of settlement under this Section 8.5.1 shall be shared
                         by the Parties as follows:

                    [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***]

          8.5.2     OTHER PARTY'S RIGHT TO PROSECUTE INFRINGEMENT.  If the Party
                    having the primary right to institute, prosecute, and
                    control such infringement or misappropriation action under
                    Section 8.5.1 fails to do so within a period of
                    [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
                    SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***]
                    after receiving notice of the infringement, or if that
                    Party, after initiating an action, determines to discontinue
                    such action, the other Party shall have the right, but not
                    the obligation, to bring and control or take over any such
                    action by counsel of its own choice, and its own expense,
                    subject to Section 8.5.1(c) unless prevented from doing so
                    by the laws of the country where the infringement or
                    misappropriation occurred or is threatened.

          8.5.3     SETTLEMENTS.  In connection with any proposed settlement in
                    respect of any infringement or threatened infringement of
                    any Intellectual Property Rights, the Party intending to
                    settle shall notify and consult with the other Party as to
                    the terms of settlement, whose written consent shall be
                    required prior to any such settlement, such consent not to
                    be unreasonably withheld.

          8.5.4     COOPERATION.  In connection with any action taken by either
                    Party against a Third Party to protect or enforce any
                    Intellectual Property Rights, the other Party shall, if
                    requested, consult with the Party taking such action, and
                    make available as witnesses its employees or as evidence any
                    materials, and/or data as are reasonably necessary for the
                    furtherance of such action.  The expenses in connection with
                    the providing of witnesses and/or the making available of
                    any materials and/or data shall be borne by the Party
                    incurring them, and reimbursed pursuant to Section 8.5.1(d).

     8.6  INFRINGEMENT OF THIRD PARTY PATENT RIGHTS.

          8.6.1     INFRINGEMENT OF THIRD PARTY PATENTS.  If Wyeth-Ayerst should
                    be of the opinion that it cannot make, import, use, market
                    and/or sell a Product in any country of the Territory under
                    its own Intellectual Property Rights or those licensed to it
                    by GalaGen under this 


                                          27
<PAGE>

                    Agreement without infringing a Third Party's patent, it
                    shall notify GalaGen.  Both Parties then shall seek an
                    opinion of patent counsel acceptable to both Parties.  If
                    such patent counsel concurs with Wyeth-Ayerst's opinion,
                    they shall, at Wyeth-Ayerst's sole option, jointly or
                    independently endeavor to secure a license from the Third
                    Party on terms that are reasonably acceptable to both
                    Parties.

          8.6.2     OPINION OF COUNSEL.  If, in the opinion of patent counsel
                    selected under Section 8.6.1, the Third Party patent, if
                    litigated, would be found invalid or not infringed by the
                    manufacture, use or sale of Product or if the Parties
                    otherwise mutually agree to obtain a license to such Third
                    Party patent, the Parties shall proceed in accordance with
                    the terms of this Agreement, unless an action for
                    infringement is brought against one or both Parties.

          8.6.3     DEFENSE AGAINST CLAIM OF INFRINGEMENT.  If either Party is
                    sued for infringement of any Third Party patents arising out
                    of the manufacture, use, sale or importation of a Product in
                    any country of the Territory, the Parties shall promptly
                    meet to discuss the course of action to be taken to resolve
                    or defend any such infringement litigation.  Each Party
                    shall provide the other with such assistance as is
                    reasonably necessary and shall cooperate in the defense of
                    any such action.  If the allegation of infringement is due
                    to or based on the use of [**CONFIDENTIAL TREATMENT
                    REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE
                    SECURITIES AND EXCHANGE COMMISSION***] in a Product then,
                    the cost/expense of defending such action incurred by
                    Wyeth-Ayerst and any damages and/or other compensation
                    imposed on Wyeth-Ayerst, by settlement or otherwise, in such
                    country shall be shared equally by the Parties.  GalaGen
                    shall pay its share of such amounts pursuant to invoices
                    submitted periodically by Wyeth-Ayerst which invoices shall
                    be due and payable within thirty (30) days of GalaGen's
                    receipt thereof.  In the event that Wyeth-Ayerst has not
                    made all payments due to GalaGen under this Agreement,
                    Wyeth-Ayerst may deduct amounts due to Wyeth-Ayerst from
                    GalaGen under this Section 8.6.3  from any amounts otherwise
                    due GalaGen under this Agreement.


9.   TERM AND TERMINATION.

     9.1  TERM. This Agreement shall be effective as of the Effective Date and
          unless terminated earlier by mutual written agreement of the Parties
          or pursuant to Sections 9.2 or 9.3 below, the Term of this Agreement
          shall 


                                          28
<PAGE>

          continue in effect until the later of (i) expiration of the last to
          expire GalaGen Patent Right incorporating a Valid Claim which, but for
          the license granted under Section 3.1.1 hereof, would be infringed by
          the manufacture, use or sale of a Product by Wyeth-Ayerst hereunder or
          (ii) ten (10) years after the First Commercial Sale of a Product. Upon
          the expiration of this Agreement pursuant to this Section 9.1,
          Wyeth-Ayerst's licenses pursuant to Section 3.1 shall become fully
          paid-up, perpetual, exclusive licenses subject only to any sublicenses
          granted by Wyeth-Ayerst that are in effect at such time, including,
          without limitation, any sublicenses granted to GalaGen under either
          Section 3.3 or 4.3 hereof, which sublicenses shall also survive the
          expiration of this Agreement in accordance with their respective
          terms.  The right of GalaGen to obtain additional sublicenses with
          respect to Other Products in accordance with Section 3.3 hereof shall
          also survive the expiration of this Agreement.

     9.2  TERMINATION FOR CAUSE. 

          9.2.1     TERMINATION FOR CAUSE.  This Agreement may be terminated by
                    written notice by either Party at any time during the Term
                    of this Agreement:

                    (a)  for material breach by the other Party, which breach
                         remains uncured for [**CONFIDENTIAL TREATMENT
                         REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE
                         SECURITIES AND EXCHANGE COMMISSION***] in the case of
                         nonpayment of any amount due and [**CONFIDENTIAL
                         TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
                         WITH THE SECURITIES AND EXCHANGE COMMISSION***] for all
                         other breaches, each measured from the date written
                         notice of such breach is given to the breaching Party,
                         or, if such breach is not susceptible of cure within
                         such [**CONFIDENTIAL TREATMENT REQUESTED; PORTION
                         OMITTED FILED SEPARATELY WITH THE SECURITIES AND
                         EXCHANGE COMMISSION***] and the breaching Party uses
                         diligent good faith efforts to cure such breach, for
                         [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED
                         FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
                         COMMISSION***] after written notice to the breaching
                         Party; or

                    (b)  upon the filing or institution of bankruptcy,
                         reorganization, liquidation or receivership
                         proceedings, or upon an assignment of a substantial
                         portion of the assets for the 


                                          29
<PAGE>

                         benefit of creditors by the other Party, or in the
                         event a receiver or custodian is appointed for such
                         Party's business, or if a substantial portion of such
                         Party's business is subject to attachment or similar
                         process; PROVIDED, HOWEVER, that in the case of any
                         involuntary bankruptcy proceeding such right to
                         terminate shall only become effective if the proceeding
                         is not dismissed within [**CONFIDENTIAL TREATMENT
                         REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE
                         SECURITIES AND EXCHANGE COMMISSION***] after the filing
                         thereof.

          9.2.2     EFFECT OF TERMINATION FOR CAUSE ON LICENSE.

                    (a)  In the event Wyeth-Ayerst terminates this Agreement
                         under Section 9.2.1(a), Wyeth-Ayerst's licenses
                         pursuant to Section 3.1 shall become fully paid-up,
                         perpetual licenses.  

                    (b)  In the event that GalaGen terminates this Agreement
                         under Section 9.2.1(a), then the rights and licenses
                         granted to Wyeth-Ayerst under Section 3.1 of this
                         Agreement shall terminate and all rights to the GalaGen
                         Patent Rights and [**CONFIDENTIAL TREATMENT REQUESTED;
                         PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES
                         AND EXCHANGE COMMISSION***] shall revert to GalaGen. 
                         Additionally, the Parties will negotiate, in good
                         faith, the grant by Wyeth-Ayerst of a license to
                         GalaGen, on appropriate commercial terms, of any of
                         Wyeth-Ayerst's Patent Rights or Know-How solely as such
                         Patent Rights or Know-How relate to GalaGen's rights to
                         manufacture and sell the [**CONFIDENTIAL TREATMENT
                         REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE
                         SECURITIES AND EXCHANGE COMMISSION***] for use in
                         Products.  

                    (c)  In the event Wyeth-Ayerst terminates this Agreement
                         under Section 9.2.1(b) or this Agreement is otherwise
                         terminated under Section 9.2.1(b), the Parties agree
                         that Wyeth-Ayerst, as a licensee of rights to
                         intellectual property under this Agreement, shall
                         retain and may fully exercise all of its rights and
                         elections under Title 11 (as such term is defined in
                         Section 9.6.1 hereof), including as set forth in
                         Section 9.6 hereof.

     9.3  UNILATERAL TERMINATION BY WYETH-AYERST. Wyeth-Ayerst shall have the
          right to unilaterally terminate this Agreement, on a country by
          country and 


                                          30
<PAGE>

          Product by Product basis, upon [**CONFIDENTIAL TREATMENT REQUESTED;
          PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***] written notice to GalaGen.  In the event of such
          termination by Wyeth-Ayerst, all Wyeth-Ayerst's rights to use the
          [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***] in such Products in
          such country shall revert to GalaGen.  If Wyeth-Ayerst terminates this
          Agreement with respect to Pediatric Formula Products, Wyeth-Ayerst
          shall not be obligated to make any other payments under Section 5.1 of
          this Agreement for events which occur after the effective date of such
          termination and, in such event payments made by Wyeth-Ayerst to
          GalaGen under Article 5 hereof prior to such date shall be
          non-refundable.



     9.4  GENERAL CONDITIONS OF EXPIRATION AND TERMINATION.

          9.4.1     EFFECT ON SUBLICENSEES.  Any permitted sublicenses granted
                    by Wyeth-Ayerst hereunder shall automatically terminate or
                    expire at the same time as this Agreement expires (insofar
                    as they have not already terminated), except where, and to
                    the extent, any license granted hereunder survives
                    expiration of this Agreement, as expressly provided in this
                    Agreement.  Upon early termination of this Agreement, for
                    any reason, with respect to a particular Product in a given
                    country or countries if any permitted sublicensee of such
                    Product in such country(ies) is not then in default under
                    its sublicense agreement with Wyeth-Ayerst, then such
                    sublicensee shall automatically have a license under this
                    Agreement as a direct licensee of GalaGen with respect to
                    such Product in such country(ies), on economic terms as are
                    set forth herein with respect to Wyeth-Ayerst and otherwise
                    with the same rights and obligations as Wyeth-Ayerst under
                    this Agreement.

          9.4.2     EFFECT ON RIGHTS TO OTHER PRODUCTS.  Except for a
                    termination of this Agreement by GalaGen pursuant to Section
                    9.2.1(a) hereof, the expiration or termination of this
                    Agreement shall not affect the rights of GalaGen or
                    Wyeth-Ayerst under Section 3.3 of this Agreement or under
                    any sublicense granted to GalaGen under Section 4.3 of this
                    Agreement.

          9.4.3     SURVIVAL.  The provisions of Articles 6, 10, 12 and Sections
                    2.6.3, 2.8, 3.3, 7.1, 8.1, 9.4, 13.6, 13.7, and 13.11 shall
                    survive termination or expiration of this Agreement.


                                          31
<PAGE>

          9.4.4     PRIOR OBLIGATIONS; REMEDIES.  Termination or expiration of
                    this Agreement shall not operate to deprive either Party of
                    any rights or remedies either at law or in equity or to
                    relieve either Party of any of its obligations incurred
                    prior to the effective date of such termination or
                    expiration.

     9.5  NO LIMIT ON REMEDIES.  Nothing herein shall exclude or limit any
          remedies or entitlements whatsoever which the law confers to either
          Party in the event of a breach of contractual obligations by the other
          Party.

     9.6  INSOLVENCY.  

          9.6.1     EFFECT ON LICENSES.  All rights and licenses granted under
                    or pursuant to this Agreement by GalaGen to Wyeth-Ayerst
                    are, for all purposes of Section 365(n) of Title 11 of the
                    United States Code ("Title 11"), licenses of rights to
                    "intellectual property" as defined in Title 11.  GalaGen
                    agrees that Wyeth-Ayerst, as licensee of such rights under
                    this Agreement shall retain and may fully exercise all of
                    its rights and elections under Title 11.  GalaGen agrees
                    during the Term of this Agreement to create and maintain
                    current copies or, if not amenable to copying, detailed
                    descriptions or other appropriate embodiments, to the extent
                    feasible, of all such intellectual property.  If a case is
                    commenced by or against GalaGen under Title 11, GalaGen (in
                    any capacity, including debtor-in-possession) and its
                    successors and assigns (including, without limitation, a
                    Title 11 Trustee) shall,

                         (i)  as Wyeth-Ayerst may elect in a written request,
                              immediately upon such request:

                                (A)     perform all of the obligations provided
                                        in this Agreement to be performed by
                                        GalaGen including, where applicable and
                                        without limitation, providing to
                                        Wyeth-Ayerst portions of such
                                        intellectual property (including
                                        embodiments thereof) held by GalaGen and
                                        such successors and assigns or otherwise
                                        available to them; or 

                                (B)     provide to Wyeth-Ayerst all such
                                        intellectual property (including all
                                        embodiments thereof) held by GalaGen and
                                        such successors and assigns or otherwise
                                        available to them; and


                                          32
<PAGE>

                         (ii) not interfere with the rights of Wyeth-Ayerst
                              under this Agreement, or any agreement
                              supplemental hereto, to such intellectual property
                              (including such embodiments), including any right
                              to obtain such intellectual property (or such
                              embodiments) from another entity.

          9.6.2     RIGHTS TO INTELLECTUAL PROPERTY.  If a Title 11 case is
                    commenced by or against GalaGen, and this Agreement is
                    rejected as provided in Title 11, and Wyeth-Ayerst elects to
                    retain its rights hereunder as provided in Title 11, then
                    GalaGen (in any capacity, including debtor-in-possession)
                    and its successors and assigns (including, without
                    limitation, a Title 11 Trustee) shall provide to
                    Wyeth-Ayerst all such intellectual property (including all
                    embodiments thereof) held by GalaGen and such successors and
                    assigns, or otherwise available to them, immediately upon
                    Wyeth-Ayerst's written request.  Whenever GalaGen or any of
                    its successors or assigns provides to Wyeth-Ayerst any of
                    the intellectual property licensed hereunder (or any
                    embodiment thereof) pursuant to this Section 9.6,
                    Wyeth-Ayerst shall have the right to perform the obligations
                    of GalaGen hereunder with respect to such intellectual
                    property, but neither such provision nor such performance by
                    Wyeth-Ayerst shall release GalaGen from any such obligation
                    or liability for failing to perform it.

          9.6.3     WYETH-AYERST'S RIGHTS.  All rights, powers and remedies of
                    Wyeth-Ayerst provided herein are in addition to and not in
                    substitution for any and all other rights, powers and
                    remedies now or hereafter existing at law or in equity
                    (including, without limitation, Title 11) in the event of
                    the commencement of a Title 11 case by or against GalaGen. 
                    Wyeth-Ayerst, in addition to the rights, power and remedies
                    expressly provided herein, shall be entitled to exercise all
                    other such rights and powers and resort to all other such
                    remedies as may now or hereafter exist at law or in equity
                    (including, without limitation, Title 11) in such event. 
                    The Parties agree that they intend the foregoing
                    Wyeth-Ayerst rights to extend to the maximum extent
                    permitted by law, including, without limitation, for
                    purposes of Title 11:

                         (i)  the right of access to any intellectual property
                              (including all embodiments thereof) of GalaGen, or
                              any Third Party with whom GalaGen contracts to
                              perform an obligation of GalaGen under this
                              Agreement, and, in the case of the Third Party,
                              which is necessary for the development,


                                          33
<PAGE>

                              registration, manufacture and marketing of
                              [**CONFIDENTIAL TREATMENT REQUESTED; PORTION
                              OMITTED FILED SEPARATELY WITH THE SECURITIES AND
                              EXCHANGE COMMISSION***] and/or Products; and 

                        (ii)  the right to contract directly with any Third
                              Party described in (i) to complete the contracted
                              work.

10.  INDEMNIFICATION AND INSURANCE.

     10.1 INDEMNIFICATION BY WYETH-AYERST.  Wyeth-Ayerst shall indemnify, defend
          and hold harmless GalaGen and its Affiliates, and each of its and
          their respective employees, officers, directors and agents (each, a
          "GalaGen Indemnified Party") from and against any and all liability,
          loss, damage, cost, and expense (including reasonable attorneys' fees)
          (collectively, a "Liability") which the GalaGen Indemnified Party may
          incur, suffer or be required to pay resulting from or arising in
          connection with (i) the breach by Wyeth-Ayerst of any representation
          or warranty contained in this Agreement; (ii) the manufacture,
          promotion, distribution, use, testing, marketing, sale or other
          disposition of Products by Wyeth-Ayerst, its Affiliates or
          sublicensees; or (iii) the successful enforcement by a GalaGen
          Indemnified Party of its rights under this Section 10.1. 
          Notwithstanding the foregoing, Wyeth-Ayerst shall have no obligation
          under this Agreement to indemnify, defend or hold harmless any GalaGen
          Indemnified Party with respect to claims, demands, costs or judgments
          which result from either (x) the failure of [**CONFIDENTIAL TREATMENT
          REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
          EXCHANGE COMMISSION***] supplied by GalaGen or its Affiliates or
          subcontractors to comply with the specifications as set forth in the
          Manufacturing and Supply Agreement or the applicable Regulatory
          Approvals or (y) the willful misconduct or negligent acts or omissions
          of GalaGen, its Affiliates, or any of their respective employees,
          officers, directors or agents.

     10.2 INDEMNIFICATION BY GALAGEN.  GalaGen shall indemnify, defend and hold
          harmless Wyeth-Ayerst and its Affiliates, and each of its and their
          respective employees, officers, directors and agents (each, a
          "Wyeth-Ayerst Indemnified Party") from and against any Liability which
          the Wyeth-Ayerst Indemnified Party may incur, suffer or be required to
          pay resulting from or arising in connection with (i) the breach by
          GalaGen of any representation or warranty contained in this Agreement;
          (ii) the 


                                          34
<PAGE>

          discovery, development, manufacture, promotion, sale or use of
          [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***] or Other Products by
          GalaGen, its Affiliates or their subcontractors or permitted
          sublicensees; or (iii) the successful enforcement by a Wyeth-Ayerst
          Indemnified Party of its rights under this Section 10.2. 
          Notwithstanding the foregoing, GalaGen shall have no obligation under
          this Agreement to indemnify, defend, or hold harmless any Wyeth-Ayerst
          Indemnified Party with respect to claims, demands, costs or judgments
          which result from willful misconduct or negligent acts or omissions of
          Wyeth-Ayerst, its Affiliates, or any of their respective employees,
          officers, directors or agents.

     10.3 CONDITIONS TO INDEMNIFICATION.  The obligations of the indemnifying
          Party under Sections 10.1 and 10.2 are conditioned upon the delivery
          of written notice to the indemnifying Party of any potential Liability
          promptly after the indemnified Party becomes aware of such potential
          Liability, PROVIDED, HOWEVER, that the failure to give such notice
          promptly shall not impair a Party's rights to indemnification under
          this Article 10 unless the delay in providing such notice has a
          material adverse effect on the ability of the indemnifying Party to
          defend against such Liability.  The indemnifying Party shall have the
          right to assume the defense of any suit or claim related to the
          Liability if it has assumed responsibility for the suit or claim in
          writing; however, if in the reasonable judgment of the indemnified
          Party, such suit or claim involves an issue or matter which could have
          a materially adverse effect on the business operations or assets of
          the indemnified Party, the indemnified Party may waive its rights to
          indemnity under this Agreement and control the defense or settlement
          thereof, but in no event shall any such waiver be construed as a
          waiver of any indemnification rights such Party may have at law or in
          equity.  If the indemnifying Party defends the suit or claim, the
          indemnified Party may participate in (but not control) the defense
          thereof at its sole cost and expense.

     10.4 SETTLEMENTS.  Neither Party may settle a claim or action related to a
          Liability without the consent of the other Party, if such settlement
          would impose any monetary obligation on the other Party or require the
          other Party to submit to an injunction or otherwise limit the other
          Party's rights under this Agreement.  Any payment made by a Party to
          settle any such claim or action shall be at its own cost and expense
          except in the event that such payment was made with the prior written
          consent of the indemnifying Party, in which case such payment will be
          subject to the indemnification obligations of the Parties as set forth
          in this Article 10.


                                          35
<PAGE>

     10.5 INSURANCE.  Each Party further agrees to use reasonable commercial
          efforts to obtain and maintain, during the term of this Agreement,
          Comprehensive General Liability Insurance, including Products
          Liability Insurance, with reputable and financially secure insurance
          carriers to cover its indemnification obligations under Sections 10.1
          or 10.2, as applicable, or, in the case of Wyeth-Ayerst,
          self-insurance, in each case with limits of not less than
          [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***].

11.  REPRESENTATIONS AND WARRANTIES.

     11.1 REPRESENTATIONS AND WARRANTIES OF EACH PARTY.  Each of GalaGen and
          Wyeth-Ayerst hereby represents, warrants and covenants to the other
          Party hereto as follows:

          (a)  it is a corporation or entity duly organized and validly existing
               under the laws of the state or other jurisdiction of
               incorporation or formation;

          (b)  the execution, delivery and performance of this Agreement by such
               Party has been duly authorized by all requisite corporate action
               and does not require any shareholder action or approval;

          (c)  it has the power and authority to execute and deliver this
               Agreement and to perform its obligations hereunder;

          (d)  the execution, delivery and performance by such Party of this
               Agreement and its compliance with the terms and provisions hereof
               does not and will not conflict with or result in a breach of any
               of the terms and provisions of or constitute a default under (i)
               a loan agreement, guaranty, financing agreement, agreement
               affecting a product or other agreement or instrument binding or
               affecting it or its property; (ii) the provisions of its charter
               or operative documents or bylaws; or (iii) any order, writ,
               injunction or decree of any court or governmental authority
               entered against it or by which any of its property is bound; and

          (e)  it shall comply with all applicable material laws and regulations
               relating to its activities under this Agreement.

     11.2 REPRESENTATIONS AND WARRANTIES OF GALAGEN.  In addition to the
          representations and warranties made by GalaGen under Section 11.1


          above, GalaGen hereby further represents and warrants to Wyeth-Ayerst
          that:


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<PAGE>

          (a)  As of the Effective Date, the GalaGen Patent Rights and Know-How
               are existing and, to the best of its knowledge, are not invalid
               or unenforceable, in whole or in part;

          (b)  it has the full right, power and authority to grant all of the
               right, title and interest in the licenses granted under Article 3
               hereof;

          (c)  it has not, prior to the Effective Date, previously assigned,
               transferred, conveyed or otherwise encumbered its right, title
               and interest in any of the [**CONFIDENTIAL TREATMENT REQUESTED;
               PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
               COMMISSION***], Products, the GalaGen Patent Rights or Know-How
               or the GalaGen Trademarks, with respect to which Wyeth-Ayerst has
               been granted a license or other rights hereunder;

          (d)  it is the sole and exclusive owner of the GalaGen Patent Rights
               and  Know-How and GalaGen Trademarks existing as of the Effective
               Date, all of which are free and clear of any liens, charges and
               encumbrances, and no other person, corporate or other private
               entity, or governmental entity or subdivision thereof, has or
               shall have any claim of ownership with respect to the GalaGen
               Patent Rights or Know-How or the GalaGen Trademarks existing as
               of the Effective Date, whatsoever;

          (e)  to the best of its knowledge the GalaGen Patent Rights and
               Know-How, and the development, manufacture, use, distribution,
               marketing, promotion and sale of [**CONFIDENTIAL TREATMENT
               REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES
               AND EXCHANGE COMMISSION***] or Products do not, as of the
               Effective Date, interfere or infringe on any intellectual
               property rights owned or possessed by any Third Party;

          (f)  as of the Effective Date, there are no claims, judgments or
               settlements against or owed by GalaGen or, to the best of its
               knowledge, pending or threatened claims or litigation relating to
               [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
               SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***], the
               GalaGen Patent Rights or Know-How and the GalaGen Trademarks;




                                          37
<PAGE>

          (g)  during the Term of this Agreement it will use diligent efforts
               not to diminish the rights under the GalaGen Patent Rights and
               Know-How and the GalaGen Trademarks licensed to Wyeth-Ayerst
               hereunder, including without limitation, by not committing or
               permitting any actions or omissions which would cause the breach
               of any agreements between itself and Third Parties which provide
               for Intellectual Property Rights applicable to the development,
               manufacture, use or sale of [**CONFIDENTIAL TREATMENT REQUESTED;
               PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
               COMMISSION***] and/or Products, that it will provide Wyeth-Ayerst
               promptly with notice of any such alleged breach, and that as of
               the Effective Date, it is in compliance in all material respects
               with any agreements with Third Parties relating to the GalaGen
               Patent Rights and Know How,  the GalaGen Trademarks, the
               [**CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED
               SEPARATELY WITH THE SECURITIES AND EXCHANGE COMMISSION***] and/or
               the Products.

     11.3 REPRESENTATIONS AND WARRANTIES OF WYETH-AYERST.  In addition to the
          representations and warranties made by Wyeth-Ayerst under Section 11.1
          above, Wyeth-Ayerst hereby further represents and warrants to GalaGen
          that the Products manufactured and sold by Wyeth-Ayerst hereunder,
          which Products contain [**CONFIDENTIAL TREATMENT REQUESTED; PORTION
          OMITTED FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
          COMMISSION***], manufactured by GalaGen in accordance with the
          Specifications (as such term is defined in the Manufacturing and
          Supply Agreement) and supplied to Wyeth-Ayerst by GalaGen under the
          Manufacturing and Supply Agreement, shall:

          (a)  be manufactured, stored and shipped in accordance with GMPs, as
               applicable and all other applicable material laws, rules,
               regulations or requirements in effect at the time of the
               manufacture of such Product; and

          (b)  not be adulterated or misbranded as provided for under any
               applicable law, order or regulation then in effect in the country
               in which such Product is being sold as of the time that
               Wyeth-Ayerst sells such Product to a Third Party.

     11.4 [***CONFIDENTIAL TREATMENT REQUESTED; PORTION OMITTED FILED SEPARATELY
          WITH THE SECURITIES AND EXCHANGE COMMISSION***]


                                          38
<PAGE>

     11.5 NO INCONSISTENT AGREEMENTS.  Except as otherwise provided in Section
          11.4 above, neither Party has in effect and after the Effective Date
          neither Party shall enter into any oral or written agreement or
          arrangement that would be inconsistent with its obligations under this
          Agreement.

     11.6 REPRESENTATION BY LEGAL COUNSEL.  Each Party hereto represents that it
          has been represented by legal counsel in connection with this
          Agreement and acknowledges that it has participated in the drafting
          hereof.  In interpreting and applying the terms and provisions of this
          Agreement, the Parties agree that no presumption shall exist or be
          implied against the Party which drafted such terms and provisions.

12.  CONFIDENTIAL INFORMATION; PUBLICATIONS; PUBLICITY

     12.1 NONDISCLOSURE OBLIGATION.  Each of GalaGen and Wyeth-Ayerst shall use
          only in accordance with this Agreement and shall not disclose to any
          Third Party any information received by it from the other Party (the
          "Information"), without the prior written consent of the other Party. 
          The foregoing obligations shall survive [**CONFIDENTIAL TREATMENT
          REQUESTED; PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
          EXCHANGE COMMISSION***].  These obligations shall not apply to
          Information that: 

               (i)  is known by the receiving Party at the time of its receipt,
                    and not through a prior disclosure by the disclosing Party,
                    as documented by business records;

              (ii)  is at the time of disclosure or thereafter becomes published
                    or otherwise part of the public domain without breach of
                    this Agreement by the receiving Party;

             (iii)  is subsequently disclosed to the receiving Party by a Third
                    Party who has the right to make such disclosure;

              (iv)  is developed by the receiving Party independently of  the
                    Information received from the disclosing Party and such
                    independent development can be documented by the receiving
                    Party;

               (v)  is disclosed to any institutional review board of any entity
                    conducting clinical trials or any governmental or other
                    regulatory agencies in order to obtain patents or to gain
                    approval to conduct clinical trials or to market
                    [**CONFIDENTIAL TREATMENT REQUESTED; 


                                          39
<PAGE>

                    PORTION OMITTED FILED SEPARATELY WITH THE SECURITIES AND
                    EXCHANGE COMMISSION***] and/or Products, but such disclosure
                    may be made only to the extent reasonably necessary to
                    obtain such patents or authorizations; and, in which case
                    reasonable effort shall be taken to maintain the
                    confidentiality of such Information, or

            (vi)    is required by law, regulation, rule, act or order of any
                    governmental authority or agency to be disclosed by a Party,
                    PROVIDED that notice is promptly delivered to the other
                    Party in order to provide an opportunity to seek a
                    protective order or other similar order with respect to such
                    Information and thereafter the disclosing Party discloses to
                    the requesting entity only the minimum Information required
                    to be disclosed in order to comply with the request, whether
                    or not a protective order or other similar order is obtained
                    by the other Party.

     12.2 PERMITTED DISCLOSURES.  Information may be disclosed to employees,
          agents, consultants, sublicensees or suppliers of the recipient Party
          or its Affiliates, but only to the extent required to accomplish the
          purposes of this Agreement and only if the recipient Party obtains
          prior agreement from its employees, agents, consultants, sublicensees
          or suppliers to whom disclosure is to be made to hold in confidence
          and not make use of such Information for any purpose other than those
          permitted by this Agreement.  Each Party will use at least the same
          standard of care as it uses to protect proprietary or confidential
          information of its own to ensure that such employees, agents,
          consultants, sublicensees or suppliers do not disclose or make any
          unauthorized use of the Information.

     12.3 DISCLOSURE OF AGREEMENT.  Neither GalaGen nor Wyeth-Ayerst shall
          release to any Third Party or publish in any way any non-public
          information with respect to the terms of this Agreement or concerning
          their cooperation without the prior written consent of the other,
          which consent will not be unreasonably withheld or delayed, PROVIDED,
          HOWEVER, that either Party may disclose the terms of this Agreement to
          the extent required to comply with applicable laws, including without
          limitation the rules and regulations promulgated by the United States
          Securities and Exchange Commission and the Party intending to disclose
          the terms of this Agreement shall provide the nondisclosing Party an
          opportunity to review and comment on the intended disclosure which is
          reasonable under the circumstances.  Notwithstanding any other
          provision of this Agreement, each Party may disclose the terms of this
          Agreement to lenders, investment bankers and other financial
          institutions of its choice solely for purposes of financing the
          business operations of such Party 


                                          40
<PAGE>

          either (i) upon the written consent of the other Party or (ii) if the
          disclosing Party uses reasonable efforts to obtain a signed
          confidentiality agreement with such financial institution with respect
          to such information on terms substantially similar to those contained
          in this Article 12.

     12.4 PUBLICITY.  Subject to Section 12.3, all publicity, press releases and
          other announcements relating to this Agreement or the transactions
          contemplated hereby shall be reviewed in advance by, and shall be
          subject to the approval of, both Parties.

     12.5 PUBLICATION.  The Parties shall cooperate in appropriate publication
          of the results of research and development work performed pursuant to
          this Agreement, but subject to their predominating interest in
          obtaining patent protection for any patentable subject matter.  The
          determination of authorship for any paper shall be in accordance with
          accepted scientific practice.  Notwithstanding anything in this
          Section 12.5 to the contrary, all publication and presentations of the
          results of research and development work performed pursuant to this
          Agreement  must be approved in advance by both Parties.

13.  MISCELLANEOUS.

     13.1 FORCE MAJEURE.  Neither Party shall be liable to the other for delay
          or failure in the performance of the obligations on its part contained
          in this Agreement if and to the extent that such failure or delay is
          due to circumstances beyond its control which it could not have
          avoided by the exercise of reasonable diligence.  It shall notify the
          other Party promptly should such circumstances arise, giving an
          indication of the likely extent and duration thereof, and shall use
          all Commercially Reasonable Efforts to resume performance of its
          obligations as soon as practicable.

     13.2 ASSIGNMENT.  

          13.2.1    ASSIGNMENT BY GALAGEN.  GalaGen may assign any of its rights
                    or obligations under this Agreement in any country to any of
                    its Affiliates, for so long as they remain Affiliates. 
                    GalaGen may also assign its rights and obligations under
                    this Agreement in connection with a merger or similar
                    reorganization or the sale of all or substantially all of
                    its assets.  GalaGen shall not otherwise assign any of its
                    rights or obligations under this Agreement without the prior
                    written consent of Wyeth-Ayerst, which consent may be
                    provided or withheld in Wyeth-Ayerst's sole discretion.  Any
                    assignment under this Section 13.2.1 by GalaGen of its
                    rights and/or obligations under this Agreement shall not
                    relieve GalaGen 


                                          41
<PAGE>

                    of its responsibilities for the performance of its
                    obligations under this Agreement.

          13.2.2    ASSIGNMENT BY WYETH-AYERST.  Wyeth-Ayerst may assign any of
                    its rights or obligations under this Agreement in any
                    country to any of its Affiliates or to one or more Third
                    Parties.  Wyeth-Ayerst shall notify GalaGen, in writing,
                    upon making any such assignment.  In the event Wyeth-Ayerst
                    assigns any of its rights or obligations under this
                    Agreement in connection with a merger or similar
                    reorganization or the sale of all or substantially all of
                    its assets or a sale of that part of its business relating
                    to the subject matter of this Agreement, no intellectual
                    property rights of the acquiring corporation shall be
                    included in the technology licensed hereunder.  Any
                    assignment under this Section 13.2.2 by Wyeth-Ayerst shall
                    not relieve Wyeth-Ayerst of its responsibilities for the
                    performance of its obligations under this Agreement.

          13.2.3    BINDING NATURE OF ASSIGNMENT.  This Agreement shall be
                    binding upon and inure to the benefit of the successors and
                    permitted assigns of the Parties.  Any assignment not in
                    accordance with this Section 13.2 shall be void.

          13.3 NO WAIVER.  The failure of either Party to require performance by
               the other Party of any of that other Party's obligations
               hereunder shall in no manner affect the right of such Party to
               enforce the same at a later time.  No waiver by any Party hereto
               of any condition, or of the breach of any provision, term,
               representation or warranty contained in this Agreement, whether
               by conduct or otherwise, in any one or more instances, shall be
               deemed to be or construed as a further or continuing waiver of
               any such condition or breach, or of any other condition or of the
               breach of any other provision, term, representation or warranty
               hereof.

          13.4 SEVERABILITY.  If a court or other tribunal of competent
               jurisdiction should hold any term or provision of this Agreement
               to be excessive, or invalid, void or unenforceable, the offending
               term or provision shall be deleted, and, if possible, replaced by
               a term or provision which, so far as practicable achieves the
               legitimate aims of the Parties.

          13.5 RELATIONSHIP BETWEEN THE PARTIES.   Both Parties are independent
               contractors under this Agreement.  Nothing herein contained shall
               be deemed to create an employment, agency, joint venture or
               partnership relationship between the Parties hereto or any of
               their agents or employees, or any other legal arrangement that
               would impose liability upon one Party for the act or failure to
               act of the other Party.  Neither Party shall have any express or
               implied power to enter into any contracts 



                                          42
<PAGE>

               or commitments or to incur any liabilities in the name of, or on
               behalf of, the other Party, or to bind the other Party in any
               respect whatsoever.

          13.6 CORRESPONDENCE AND NOTICES.

               13.6.1    ORDINARY NOTICES.  Correspondence, reports,
                         documentation, and any other communication in writing
                         between the Parties in the course of ordinary
                         implementation of this Agreement shall be delivered by
                         hand, sent by facsimile, or by airmail to any one
                         member of the JDC appointed by the Party which is to
                         receive such written communication, or any other way as
                         the JDC deems appropriate.

               13.6.2    EXTRAORDINARY NOTICES.  Extraordinary notices and
                         communications (including, without limitation, notices
                         of termination, force majeure, material breach, change
                         of address) shall be in writing and sent by prepaid
                         registered or certified air mail, or by facsimile
                         confirmed by prepaid registered or certified air mail
                         letter, and shall be deemed to have been properly
                         served to the addressee upon receipt of such written
                         communication.

               13.6.3    ADDRESSES FOR NOTICES.  In the case of GalaGen, the
                         proper address for communications and for all payments
                         shall be:

                              GalaGen Inc.
                              4001 Lexington Avenue North
                              Arden Hills, Minnesota  55126  USA
                              Attn:  Chief Executive Officer
                              Fax:  (612) 481-2380

                         and in the case of Wyeth-Ayerst, the proper address for
                         communications and for all payments shall be:
               
                              Wyeth-Ayerst Laboratories
                              555 East Lancaster Avenue
                              St. Davids, Pennsylvania  19087
                              Attn:  Senior Vice President, Global Business
                              Development
                              Fax:  (610) 688-9498
               
                              With a copy to: 
     
                                   American Home Products Corporation
                                   5 Giralda Farms
                                   Madison, New Jersey  07940


                                          43
<PAGE>

                                   Attn:  Senior Vice President and General
                                   Counsel
                                   Fax: (973) 660-7156
          
     13.7 CHOICE OF LAW.  This Agreement is subject to and governed by the laws
          of the State of Delaware, excluding its conflict of laws provisions.
          
     13.8 ENTIRE AGREEMENT; AMENDMENT. This Agreement, together with the other
          Transaction Agreements, including the Exhibits and Schedules hereto
          and thereto and all the covenants, promises, agreements, warranties,
          representations, conditions and understandings contained herein and
          therein sets forth the complete, final and exclusive agreement between
          the Parties and supersedes and terminates all prior and
          contemporaneous agreements and understandings between the Parties,
          whether oral or in writing.  There are no covenants, promises,
          agreements, warranties, representations, conditions or understandings,
          either oral or written, between the Parties other than as are set
          forth in the Transaction Agreements.  No subsequent alteration,
          amendment, change, waiver or addition to this Agreement shall be
          binding upon the Parties unless reduced to writing and signed by an
          authorized officer of each Party.  No understanding, agreement,
          representation or promise, not explicitly set forth herein, has been
          relied on by either Party in deciding to execute this Agreement. 
          
     13.9 HEADINGS. The headings and captions used in this Agreement are solely
          for the convenience of reference and shall not affect its
          interpretation.

   13.10  COUNTERPARTS.  This Agreement may be executed in one or more
          counterparts each of which shall be an original and all of which shall
          constitute together the same document.
          
   13.11  FURTHER ACTIONS.  Each Party agrees to execute, acknowledge and
          deliver such further instruments, and to do all other acts, as may be
          necessary or appropriate in order to carry out the purposes and intent
          of this Agreement including, without limitation, any filings with any
          antitrust agency which may be required.

     IN WITNESS WHEREOF, this Agreement has been executed by the duly authorized
representatives of the Parties as of the date first set forth above.


AMERICAN HOME PRODUCTS CORPORATION      GALAGEN INC.



/s/ Tuan Ha-Ngoc                        /s/ Robert A. Hoerr              
-----------------------------------     ----------------------------------
Name:  Tuan Ha-Ngoc                     Name:  Robert A. Hoerr
Title: Vice President - Strategic       Title: President & CEO     
       Development



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