Document:

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                                    AGREEMENT

                                     BETWEEN

                               LONZA BIOLOGICS PLC

                                       AND

                          AVANT IMMUNOTHERAPEUTICS INC

Confidential Treatment Requested As To Certain Information Contained In This
Exhibit

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     THIS AGREEMENT is made the _______ day of _________, 2000 BETWEEN

     1.   LONZA BIOLOGICS PLC, the registered office of which is at 228 Bath
          Road, Slough, Berkshire SL1 4DY, England ("LB"), and

     2.   AVANT IMMUNOTHERAPEUTICS INC, of 119 Fourth Avenue, Needham MA
          024942725, USA, ("the Customer").

     WHEREAS

     A.   Customer is the proprietor of the *** Confidential Treatment Requested
          as to this information *** expressing *** Confidential Treatment
          Requested as to this information *** protein and owns certain
          intellectual property rights in relation thereto, and

     B.   LB has expertise in the development of processes for and manufacture
          of products from similar cell lines, and

     C.   Customer wishes to contract with LB for Services to develop a Process
          for and manufacture Product from its proprietary cell line; and

     D.   LB is prepared to perform such Services for Customer on the terms and
          conditions set out herein.

     NOW THEREFORE it is agreed as follows:

     1.   In this Agreement, its recitals and the schedules hereto, the words
          and phrases defined in Schedule 4 hereto and in the Standard Terms for
          Contract Services set out in Schedule 5 hereto shall have the meanings
          set out therein.

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     2.   Subject to the Standard Terms for Contract Services set out in
          Schedule 5 and any Special Terms; LB agrees to perform the Services
          and the Customer agrees to pay the Price together with any additional
          costs and expenses that fall due hereunder.

     3.   3.1    Any notice or other communication to be given under this
          Agreement shall be delivered personally or sent by facsimile
          transmission, or if facsimile transmission is not available, by first
          class pre-paid post addressed as follows:

                 3.1.1   if to LB to:

                         Lonza Biologics plc
                         228 Bath Road
                         Slough Berkshire SL14DY

                         Facsimile: 01753 777001
                         For the attention of the President

                 3.1.2   if to the Customer to:

                         Avant Immunotherapeutics Inc
                         119 Fourth Avenue
                         Needham MA 02494-2725
                         USA

                         Facsimile: 001 781433 0262
                         For the attention of the President;

                 or to such other destination as either party hereto may
                 hereafter notify to the other in accordance with the provisions
                 of this clause.

          3.2    All such notices or other communications shall be deemed to
                 have been served as follows:

                 3.2.1   if delivered personally, at the time of such delivery;

                 3.2.2   if sent by facsimile, upon receipt of the transmission
                         confirmation slip showing completion of the
                         transmission;

                 3.2.3   if sent by first class pre-paid post, ten (10) business
                         days (Saturdays, Sundays and Bank or other public
                         holidays excluded) after being placed in the post.

     AS WITNESS the hands of the duly authorised representatives of the parties
hereto the day and year first above written.

Signed for and on behalf of
                                                 -------------------------

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LONZA BIOLOGICS PLC
                                                 -------------------------
                                                                          TITLE

Signed for and on behalf of

AVANT IMMUNOTHERAPEUTICS INC
                                                 -------------------------

                                                 -------------------------
                                                                          TITLE

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                                   SCHEDULE 1

     For the purposes of this document:

     "Cell Line" shall mean the *** Confidential Treatment Requested as to this
information *** created by the Customer expressing Product.

     "Product" shall mean *** Confidential Treatment Requested as to this
information *** from the Cell Line.

A.   DRAFT SPECIFICATION FOR BULK PURIFIED PRODUCT

     Lonza Biologics and the Customer will agree a draft Specification for the
     Bulk product * to be manufactured in Stage 8. Test parameters to be
     included in the Specification could be:

     ***Confidential Treatment Requested as to this information***

Note:  Lonza will release bulk Product against this draft Specification as
       outlined above.

                                       1
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A.   DRAFT SPECIFICATION FOR VIALLED PRODUCT

     Lonza Biologics and the Customer will agree a draft Specification for the
     vialled product. Test parameters to be included in the Specification could
     be:

***Confidential Treatment Requested as to this information***

Note:  Lonza will release vialled Product against this draft Specification as
       outlined above.

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B.   SPECIFICATION FOR A MASTER AND WORKING CELL BANK

     STARTING MATERIAL DEFINITION

     Master or Working Cell Bank of a cryopreserved ***Confidential
     Treatment Requested as to this information*** prepared from
     a pooled culture and stored in individual ampoules in liquid nitrogen
     refrigerators.

     GENERAL MASTER CELL BANK SPECIFICATION

     1.   The acceptance criteria for tests performed on ampoules from the cell
          bank

     ***Confidential Treatment Request as to this information***

     2.   Tests carried out on an ampoule of the cell bank or ort an ampoule of
          a cell stock linearly related to the cell bank, for example the
          Customer Stock. (The acceptance criteria to release the cells to
          Lonza's GMP facility are given in parentheses).

     ***Confidential Treatment Request as to this information***

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                               SCHEDULE 2 SERVICES

                                    CONTENTS

     1.   Supply of Customer Materials and Customer Know-How

     2.   Activities to be undertaken by Lonza

          Stage 1   -   Medium Selection, Cloning and Cell Line Selection

          Stage 2   -   Fermentation Studies

          Stage 3   -   Master and Working Cell Bank Preparation and Analysis

          Stage 4   -   Assay Transfer and Validation

          Stage 5   -   Purification Process Transfer

          Stage 6   -   Development Pilot Batch, Production of Non-GMP Product

          Stage 7   -   GMP Documentation

          Stage 8   -   Production of GMP Product at *** Confidential Treatment
          Requested as to this information ***: Creation of a Post Production
          Cell Bank

          Stage 9   -   Regulatory Documentation/Support for *** Confidential
          Treatment Requested as to this information ***

          Stage 10  -   Evaluation of Virus Clearance

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1.   SUPPLY OF CUSTOMER MATERIALS AND CUSTOMER KNOW HOW

     Customer shall supply to Lonza the following:

     i)     Sufficient information on the Cell Line and the Product to allow a
            risk assessment as required by the `Genetically Modified Organisms
            (Contained Use)' Regulations 1992 and a safety assessment by Lonza's
            Biological Safety Committee.

     ii)    At least 10 identical ampoules of viable frozen cells from the Cell
            line (Customer's Stock) containing approximately 5 x 106
            cells/ampoule.

     iii)   If available a sample of purified Product as a reference standard.

     iv)    A formulation for the Product that will be produced by the Cell
            Line. The Customer has developed a suitable formulation for the
            Product. The formulation will be supplied to Lonza Biologics to
            enable completion of the purification of the pilot material
            (Stage 6).

     v)     Detailed information on the purification procedures used to date to
            purify Product by the Customer.

     vi)    Protocols for any product specific assays that the Customer will
            transfer to Lonza such that Lonza can test the Product in
            Development Laboratories and QC (Stage 4).

     vii)   Full details including suppliers of up to four commercially
            available media prior to commencement of Stage 1.

     viii)  Documents relating to mycoplasma testing performed on the Cell Line.

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2.     ACTIVITIES TO BE UNDERTAKEN BY LONZA BIOLOGICS

1.0    STAGE 1 - MEDIUM SELECTION, CLONING AND CELL LINE SELECTION

       1.1    OBJECTIVES

              1.1.1   To assess up to four commercially available ***
                      Confidential Treatment Requested as to this information
                      *** culture media for suitability for use with the
                      incoming Cell Line.

              1.1.2   To clone the incoming Cell Line, adapt sub clones to serum
                      free suspension culture and select the most suitable Cell
                      Line for long term production.

              1.1.3   To monitor stability of production and growth
                      characteristics of selected Cell Line and one back-up Cell
                      Line.

       1.2    ACTIVITIES

              SUBSTAGE 1 a - MEDIUM SELECTION

              1.2.1   Receive details from the Customer on the cell culture
                      process conditions used to date to grow the Cell Line.

              1.2.2   Receive details including suppliers of up to four
                      commercially available media. Source media and components
                      if required from approved suppliers.

              1.2.3   Receive documents from Customer detailing Cell Line virus
                      and mycoplasma testing data. Receive ampoules of the Cell
                      Line from the tested cell bank.

              1.2.4   Review documentation from 1.2.3 and confirm that the Cell
                      Line is negative for mycoplasma. Revive cells from an
                      ampoule of the incoming Cell Line and grown in suspension
                      in up to four different commercially available ***
                      Confidential Treatment Requested as to this information
                      *** culture media. Establish criteria for routine
                      subculture of the Cell Line.

                      Note: 5uM methotrexate will be included in all cell
                      culture media used for culture expansion. Methotrexate
                      will not be included in media used in cell cultures which
                      are allowed to overgrow (until cell viability decreases).

              1.2.5   Estimate cloning efficiency (by limiting dilution) of the
                      Cell Line in the four different commercially available
                      serum free media used in 1.2.4 supplemented with
                      appropriate concentrations of serum.

              1.2.6   For those media that support good cell growth allow shake
                      flask cultures to overgrow (until cell viability
                      decreases) and measure Product accumulation by assays
                      established under Stage 4.

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                      Note: These shake flask cultures will be fed with glucose.

                      Deliver samples of cell culture supernatant (approximately
                      10ml) from the cultures taken at intervals during 1.2.6 to
                      the Customer to enable the Customer to confirm Product
                      concentrations and Product quality.

                      Note: If there is a delay in completion of these analyses
                      by the Customer at this point, there may be a delay in
                      completion of the Services

              EVALUATION POINT
              Evaluate and report the performance of the cell line in the
              commercially available *** Confidential Treatment Requested as to
              this information *** culture medium.

              Agree with the Customer which medium is selected to progress with
              for the remaining Stages.

              Discuss and agree with the Customer a series of laboratory scale
              fermentations to be performed in Stage 2.

              SUBSTAGE 1b - CLONING AND CELL LINE SELECTION

              1.2.7   Revive cells from an ampoule of the incoming Cell Line and
                      perform a single round of cloning using the capillary
                      aided cell cloning technique. The Cell Line will be
                      cultured and plated in the selected medium supplemented
                      with an appropriate concentration of serum.

                      The capillary aided cell cloning technique involves the
                      use of a capillary which delivers a droplet of a cell
                      suspension to each well of a 48 or 96 well plate. The
                      droplet is then examined under a microscope to confirm the
                      presence of a single cell before medium is added and the
                      confirmed clones grown on.

              1.2.8   Adapt up to 15 clones to serum free culture medium.
                      Perform an assessment of the productivity of the Cell
                      Lines in shake flask cultures by allowing the cultures to
                      grow to maximum cell concentration at high viability and
                      measure Product accumulation by assays established under
                      Stage 4.

                      Deliver samples of cell culture supernatant (approximately
                      10ml) from the cultures to the Customer to enable the
                      Customer to confirm Product concentrations and Product
                      quality.

                      Note: If there is a delay in completion of these analyses
                      by the Customer at this point, there may be a delay in
                      completion of the Services.

                      Select 3 candidate cloned Cell Lines for further
                      development.

                      At this point the Customer and Lonza will agreed on the
                      Lead Cell Line.

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              1.2.9   Cryopreserve pre-seed stocks (PSS) of 12 ampoules of cells
                      from each of the 3 candidate Cell Lines selected in 1.2.8.

                      Cryopreserve 2 ampoules of all other serum free adapted
                      Cell Lines.

              1.2.10  Establish criteria for routine subculture of the Cell
                      Line. Assess the stability of production of the selected
                      Cell Line and one back-up Cell Line in suspension culture
                      for 60 generations beyond the PSS in cell culture media
                      with and without methotrexate.

                      Deliver samples of cell culture supernatant (approximately
                      10ml) taken from the culture at appropriate intervals to
                      the Customer to enable the Customer to confirm Product
                      concentrations and Product quality.

              1.2.11  Issue a report of activities to Customer. This report
                      shall include the following:

                      -      Details of the key experimental data generated in
                             Stage 1.
                      -      An assessment of the performance of the Cell Line
                             at laboratory scale.

                      Note: In all reports to the Customer any techniques or
                      reagents used . which are proprietary to Lonza will be
                      described in outline only.

       1.3    TIMESCALE

              Stage 1 shall be complete with the issue of the report of
              activities and it is estimated that this report will be issued ***
              Confidential Treatment Requested as to this information *** from
              the start of Stage 1.

              Stage 2 (Cell Banking) can commence at the Customer's request any
              time after activity 1.2.9 is complete.

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       2.1    STAGE 2 - FERMENTATION STUDIES

       2.2    OBJECTIVES

              2.2.1   To assess the key fermentation parameters for the
                      Customer's Cell Line.

              2.2.2   To determine production kinetics in laboratory scale
                      fermenters *** Confidential Treatment Requested as to this
                      information ***

              2.2.3   To test if Lonza's generic fermentation Process is
                      appropriate for production of the Product in the selected
                      medium.

              SUBSTAGE 2a - FERMENTATIONS USING CUSTOMER'S MEDIUM

       2.2    ACTIVITIES

              2.2.1   Receive fermentation process details, medium and relevant
                      safety information from the Customer to enable Substage to
                      commence.

              2.2.2   Revive cells from an ampoule of the Cell Line received
                      from the Customer in the medium supplied by Customer.

              2.2.3   Carry out a time course of cell growth and Product
                      accumulation in duplicate laboratory scale stirred and
                      airlift ferementers *** Confidential Treatment Requested
                      as to this information *** using the medium supplied by
                      the Customer and fermentation conditions supplied by the
                      Customer.

              2.2.4   Measure Product concentration using methods established
                      under Stage 4a.

              2.2.5   Harvest the cell culture supernatants and purify using
                      S-Sepharose.

              2.2.6   Deliver the material to the Customer to enable the
                      Customer to determine product quality.

              2.2.7   Issue a summary report of results to Customer.

              SUBSTAGE 2b - FERMENTATIONS USING MEDIUM SELECTED UNDER STAGE 1

              2.2.8   Revive cells from an ampoule of the Cell Line received
                      from the Customer in the medium selected in Stage 1
                      (1.2.6).

              2.2.9   Perform up to 4 pairs of laboratory scale *** Confidential
                      Treatment Requested as to this information ***
                      fermentations using the Cell Line received from the
                      Customer. These studies will be agreed with the Customer
                      and will assess the key fermentation parameters for this
                      Cell Line and Product for example:

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              -       An evaluation of Lonza's generic fermentation Process
                      operating conditions.

              -       An assessment of whether adjustment to the medium
                      formulation will be required to produce Product of similar
                      quality to previous Customer fermentations, e.g. effect of
                      sodium bicarbonate concentration, effect of feeding
                      regimes.

              2.2.10  Deliver samples of the cell culture supernatants (10ml)
                      from 2.2.8 to the Customer to enable the Customer to
                      confirm Product concentrations and Product quality.

              2.2.11  Assess Product concentrations and Product quality using
                      assays established under Stage 4.

              2.2.12  Review the results from 2.2.10 with the Customer and
                      select the optimum fermentation Process.

              2.2.13  Using the PSS of the lead Cell Line (1.2.9) perform up to
                      two pairs of laboratory scale fermentations. Monitor cell
                      growth and Product accumulation to determine the optimum
                      point to harvest culture supernatant.

              2.2.14  Deliver samples of the cell culture supernatant (10ml) to
                      the Customer to enable the Customer to confirm Product
                      concentrations and Product quality.

              2.2.15  Assess Product concentrations and Product quality using
                      assays established under Stage 4.

              2.2.16  Issue a report of activities to Customer. This report
                      shall include the following:

              -       Details of the key experimental data generated in Stage 2.
              -       An assessment of the performance of the Cell Line at
                      laboratory scale.
              -       A preliminary estimate of the expected productivity of the
                      Cell Line at production scale.

              EVALUATION POINT
              At this point the Customer and Lonza Biologics will assess whether
              the selected medium is suitable to proceed with the Services. If
              it is agreed that the selected medium is unsuitable to proceed
              with the Services, then Lonza and the Customer will agree an
              alternative work programme.

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       2.3    TIMESCALE

              Stage 2 shall be complete on the issue of the report of activities
              and it is estimated that this report will be issued ***
              Confidential Treatment Requested as to this information *** from
              the start of Stage 2.

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3.0    STAGE 3 - MASTER AND WORKINQ CELL BANK PREPARATION AND ANALYSIS

       3.1    OBJECTIVES

              3.1.1   To test the PSS created under Stage 1 (1.2.9) such that
                      sufficient test information is available for rapid
                      transfer of the Cell Line to Lonza's GMP manufacturing
                      facility. Testing for potential adventitious agents is
                      required so that all cell line and products are protected
                      for customers.

              3.1.2   To create and characterise a master cell bank (MCB) and a
                      working cell bank (WCB).

       3.2    ACTIVITIES

              3.2.1   Send an ampoule of the PSS (1.2.9) of the Lead Cell line
                      and two backup candidate Cell Lines to a testing
                      laboratory to be tested by assay for mycoplasma.

              3.2.2   Send ampoules of the Cell Line to Testing Laboratories to
                      be tested by:

                      a)      Assay for viruses:
                              *** Confidential Treatment Requested as to this
                              information ***
                      b)      Isoenzyme analysis

              3.2.3   Prepare GMP documentation, for the preparation of the cell
                      banks from the selected Cell Line.

              3.2.4   Establish a 200 ampoule MCB and a 250 ampoule WCB
                      according to the principles of GMP. The MCB will be
                      derived from one ampoule of the PSS and the WCB will be
                      derived from one ampoule of the MCB. Methotrexate will be
                      used in the cell culture medium. The cell banking system
                      has been designed with reference to the "Points to
                      Consider in the Characterisation of Cell line used to
                      Produce Biologicals" (1993 -CBER, Food and Drug
                      Administration), and the"Production and Quality Control of
                      Monoclonal Antibodies" (1995, Commission of the European
                      Communities).

              3.2.5   Establish standard maintenance, storage and release
                      procedures for the MCB and WCB at two separate Lonza
                      sites.

              3.2.6   Characterise the MCB and WCB :-

                      -       Assess sterility (21 CFR 610.12) and mycoplasma
                              (FDA PTC 1993) status.
                      -       Assess cell bank viability from 5 ampoules
                              distributed through the bank.

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                      -       Evaluate growth of cells from the MCB and WCB
                              following Lonza's generic inoculum regime to
                              measure doubling time, cell growth and split
                              ratios.

              3.2.7   Issue report of activities to Customer. The report shall
                      include:

                      -       a description of preparation of the cell banks;
                      -       details of the history of the Cell Line at Lonza;
                      -       mycoplasma and sterility test results on the cell
                              banks;
                      -       details of cell growth characteristics for the
                              Cell Line i.e. doubling time, cell concentration,
                              split ratios, viability;
                      -       details of materials and methods used for
                              activities under sections 3.2.4; 3.2.5 and 3.2.6;
                      -       a summary of Lonza's storage and control
                              procedures for the cell banks;
                      -       Testing Laboratory results.

       3.3    CELL BANK CHARACTERISATION (VIRUS TESTING)

              Additional viral characterisation of the cell banks will be
              required in order to support regulatory applications to conduct
              clinical trials, or market a product, including testing of a
              post-production cell bank (PPCB) as prepared in Stage 8 of these
              Services. Lonza can arrange for such testing at Lonza's approved
              contractors on Customer's behalf on terms to be agreed or
              alternatively deliver ampoules of the Cell Line to Customer for
              performance of this testing.

              Note: THIS PROPOSAL MAKES PROVISION FOR TESTING OF THE PSS TO
              ENABLE RAPID TRANSFER OF THE CELL LINE INTO LONZA'S MANUFACTURING
              FACILITY. THESE TESTS ON THE PSS ENABLE THE CELL BANKS TO MEET THE
              CELL BANK SPECIFICATION (SCHEDULE 1). HOWEVER FOR INITIATION OF
              PHASE I CLINICAL TRIALS THE CELL BANKS ALSO NEED TO BE TESTED.

       3.4    TIMESCALE

              Stage 3 shall be complete with the issue of the report of
              activities and it is estimated that this report will be issued ***
              Confidential Treatment Requested as to this information *** from
              the start of Stage 3. It is estimated that he 200 ampoule MCB will
              be established *** Confidential Treatment Requested as to this
              information *** from the start of Stage 3 the 250 ampoule WCB will
              be established *** Confidential Treatment Requested as to this
              information *** from the start of Stage 3 and the report will be
              complete *** Confidential Treatment Requested as to this
              information *** from the start of Stage 3. The duration of cell
              bank virus testing will depend on the range of tests chosen by the
              Customer and on the Testing Laboratory that is selected.

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4.0    STAGE 4 - ASSAY TRANSFER AND VALIDATION

       SUBSTAGE 4a - PRODUCT ELISA ASSAY TRANSFER

       4.1    OBJECTIVES

              4.1.1   To transfer an assay for measurement of Product
                      concentration in cell culture supernatants, to be used as
                      an assay in the Lonza development laboratories to support
                      the work programme.

       4.2    ACTIVITIES

              4.2.1   Receive protocols from the Customer for the Product ELISA
                      assay to be used in development. Key reagents will be
                      provided if they are not readily available commercially.

              4.2.2   Assess the performance of the assay on cell culture
                      supernatants from the Cell Line. Compare data to data
                      generated by the Customer.

              4.2.3   Validate the assay for working range, accuracy and
                      precision.

              4.2.4   Issue a report on the activities in Stage 4a to the
                      Customer.

       4.3    TIMESCALE

              Substage 4a can commence as soon as protocols and reagents and
              reference standards are received from the Customer. It is
              estimated that Stage 4 will take *** Confidential Treatment
              Requested as to this information *** to complete.

              SUBSTAGE 4b - ASSAY TRANSFER AND VALIDATION

       4.4    OBJECTIVES

              4.4.1   To establish and where appropriate validate assays for
                      determination of Product quality during the development
                      programme and for draft Specification testing.

              4.4.2   To agree with the Customer which assays to apply at which
                      stages of the work programme.

              4.4.3   To evaluate the performance of Lonza's standard QC assays
                      for the Product/Process.

              4.4.4   To establish assays as required for testing of new GMP raw
                      materials.

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       4.5    ACTIVITIES

              4.5.1   Receive protocols from the Customer for the assays to be
                      used in development and QC. Key reagents will be provided
                      if they are not readily available commercially.

              4.5.2   Assess the performance of these Customer assays with
                      Product.

              4.5.3   Evaluate the performance of Lonza Biologics' QC assays
                      with Product as appropriate.

              4.5.4   Perform validation as appropriate to this phase of the
                      clinical programme according to ICH requirements.

              4.5.5   Transfer the assays to Lonza Biologics Quality Department.

              4.5.6   Issue a report on the activities in Substage 4b to the
                      Customer.

                      Note: The timescale for this programme are estimates only
                      and make assumptions on the number of assays to be
                      transferred and that the assays are transferred smoothly
                      and no unexpected issues arise.

       4.6    TIMESCALE

              Substage 4b can commence as soon as protocols and reagents and
              reference standards are received from the Customer. The timescale
              for Substage 4b will be discussed and agreed with the Customer.

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5.0    STAGE 5 - PURIFICATION PROCESS TRANSFER

       5.1    OBIECTIVES

              5.1.1   To transfer to Lonza a one step (S-Sepharose) sample
                      purification method for use in the assessment of Product
                      quality.

              5.1.2   To establish purification process suitable for manufacture
                      of the Product at *** Confidential Treatment Requested as
                      to this information ***.

              5.1.3   To design a purification process as close as possible to
                      the Customer's process that will fit with Lonza's
                      equipment and procedures.

              5.1.4   To provide a sample of Product purified using the selected
                      process to the Customer for evaluation.

       5.2    ACTIVITIES

              5.2.1   Receive complete information from the Customer on
                      performance of the purification process at the Customer's
                      facility. Source and qualify new raw materials as
                      required. Identify changes that can be made to the
                      existing purification process.

              5.2.2   Observe the purification process at the Customer's
                      laboratories.

                      Note: If at this point difficulties in supply or
                      adaptation to Lonza's equipment and procedures are
                      identified, these will be discussed with the Customer.
                      Extra costs may be incurred if specialist equipment or
                      resins have to be sourced.

              5.2.3   Under Stage 2 of the Services provide cell culture
                      supernatant from cell cultures.

              5.2.4   Purify Product from the bulk supernatant using the
                      procedure provided by the Customer, modified to fit
                      Lonza's large scale equipment.

              5.2.5   Measure yield after each purification step.

              5.2.6   Analyse selected in Process samples and final Product for
                      purity by methods to be established under Stage 4b.

              5.2.7   Deliver a sample of the Product to the Customer for
                      evaluation.

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              EVALUATION POINT
              At this point the Customer and Lonza Biologics will assess the
              capability of the adapted purification process to produce GMP
              Product that meets the draft Specification. Agree with the
              Customer any additional work which may be needed to produce such
              Product. Any further work will be carried out at a price to be
              agreed.

              5.2.8   Issue report of activities to Customer. This report shall
                      include:

                      -       step yields for each chromatography and buffer
                              exchange operation; copies of analytical results;
                              details of materials and methods used for
                              activities under Stage 5;
                      -       an outline of the recommended manufacturing
                              process including an estimate of the expected
                              yield of Product at the chosen production scale.
                      -       a recommendation of any process modifications that
                              might be required to purify Product to meet the
                              draft Specification.

       5.3    TIME SCALE

              Stage 5 shall be complete with the issue of the, report of
              activities and it is estimated that this report will be issued
              *** Confidential Treatment Requested as to this information ***
              from the start of Stage 5.

              Stage 5 shall commence as soon as cell culture supernatant is
              available from Stage 2.

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6.0    STAGE 6 - DEVELOPMENT PILOT BATCH

       6.1    OBJECTIVES

              6.1.1   To carry out a development pilot fermentation at ***
                      Confidential Treatment Requested as to this information
                      ***

              6.1.2   To evaluate the ability of the process to produce Product
                      meeting the purity limits included in the draft
                      Specification eg *** Confidential Treatment Requested as
                      to this information *** if appropriate

              6.1.3   To produce bulk purified non-GMP Product that the Customer
                      may use for non-clinical studies.

       6.2    ACTIVITIES

              6.2.1   Recover one vial from the PSS (Stage 1) and expand culture
                      to inoculate a *** Confidential Treatment Requested as to
                      this information ***

              6.2.1   Carry out *** Confidential Treatment Requested as to this
                      information *** using process established in Stage 2.

              6.2.3   Clarify culture broth and concentrate supernatant.

                      Refine key operational parameters of this primary recovery
                      process, including the intermediate filtration step.

              6.2.4   Purify bulk concentrate by procedure established during
                      Stage 5.

              6.2.5   Test Product purity eg *** Confidential Treatment
                      Requested as to this information *** if appropriate, and
                      the *** Confidential Treatment Requested as to this
                      information *** will also be carried out on this
                      development batch.

              6.2.6   Review requirements (if any) for process modifications
                      that may be needed following this study before Stage 8.
                      Any such process modifications are subject to agreement.

              6.2.7   Deliver remainder of bulk purified Product produced from
                      the development batch to the Customer.

              6.2.8   Report on the pilot fermentation and primary recovery
                      investigations, including an estimate of the expected
                      yield from the Cell Line at production scale in the Stage
                      2 report. Report on the pilot purification and testing
                      results in the Stage 5 report

                      If requested by the Customer carry out further pilot
                      fermentations.

                                       18
<PAGE>

       6.3    TIMESCALE

              Stage 6 shall be complete upon delivery of Product from the
              development batch. It is estimated that such Product will be
              delivered *** Confidential Treatment Requested as to this
              information *** from commencement of Stage 6. Stage 6 can commence
              as soon as the purification process transfer programme is complete
              (Stage 5) and the PSS is available (Stage i ). If the Customer
              requires the Product can be shipped prior to completion of
              testing (6.2.5).

                                       19
<PAGE>

7.0    STAGE 7 - GMP DOCUMENTATION

       7.1    OBJECTIVE

              7.1.1.  To prepare GMP documentation for use in manufacture of
                      Product at *** Confidential Treatment Requested as to this
                      information ***

       7.2    ACTIVITIES

              7.2.1   Prepare GMP documentation. The documentation shall cover:

                      -       Inoculum, fermentation, primary recovery and
                              purification process manufacturing directions, and
                              in-process controls contained in the manufacturing
                              directions.
                      -       Materials specifications (as required).
                      -       Sampling protocols.
                      -       Product specifications.

       7.3    TIMESCALE

              It is estimated that Stage 7 will take *** Confidential Treatment
              Requested as to this information *** from the commencement of work
              and will be complete on notification by Lonza to the Customer that
              the documentation has been approved by Lonza's QA Department.
              Stage 7 will be scheduled such that it is not a rate limiting
              activity.

                                       20
<PAGE>

8.0    STAGE 8 - PRODUCTION OF CLINICAL MATERIAL AT *** Confidential Treatment
       Requested as to this information ***

       8.1    OBJECTIVES

              8.1.1   To manufacture clinical grade Product at *** Confidential
                      Treatment Requested as to this information *** (depending
                      on Customer requirement) in an *** Confidential Treatment
                      Requested as to this information *** in accordance with
                      the principles of Good Manufacturing Practice (GMP).

              8.1.2   To further evaluate the ability of the Process to produce
                      Product meeting the draft Specification.

       8.2    ACTIVITIES

              8.2.1   After receiving adequate virus testing data on the PSS and
                      sterility, viability and mycoplasma testing data on the
                      MCB (Stage 3), recover one vial from the MCB and expand
                      culture to inoculate a fermenter.

              8.2.2   Carry out *** Confidential Treatment Requested as to this
                      information ***.

              8.2.3   Prepare a post-production cell bank (PPCB) from the
                      fermentation. This bank is available for testing as
                      required by the Customer.

              8.2.3   Clarify culture supernatant and concentrate by the
                      procedure established in Stage 6.

              8.2.4   Purify concentrate by procedure established during
                      Stage 5.

              8.2.5   Test Product against the draft Specification.

              8.2.6   Undertake quality assurance review of lot documentation
                      and issue a Certificate of Analysis.

              8.2.7   Review requirements (if any) for process modifications in
                      order to meet Specification for manufacture of subsequent
                      lots. Any such process modifications are subject to
                      agreement.

              8.2.8   Deliver Product to the Customer.

       8.3    TIMESCALE

              Stage 8 shall commence as soon as adequate virus testing data and
              the sterility viability and mycoplasma testing data is available
              on the MCB (Stage 3).

                                       21
<PAGE>

              Stage 8 shall lid complete upon delivery of Product. It is
              estimated that Product will be delivered *** Confidential
              Treatment Requested as to this information *** from commencement
              of Stage 8.

                                       22
<PAGE>

Note: PRODUCT CAN BE SHIPPED IN QUARANTINE WITH THE CERTIFICATE OF ANALYSIS TO
FOLLOW IN ORDER TO FACILITATE THE QUICKEST DELIVERY OF PRODUCT. A LETTER IS
REQUESTED BY LONZA BIOLOGICS FROM THE CUSTOMER STATING THAT THE PRODUCT WILL NOT
BE USED IN HUMAN STUDIES UNTIL THE CERTIFICATE OF ANALYSIS IS ISSUED BY LONZA
BIOLOGICS. THE CUSTOMER MUST INFORM LONZA BIOLOGICS OF THE EXTENT OF LONZA
BIOLOGICS' IN HOUSE TESTING REQUIRED TO BE COMPLETE BEFORE THE PRODUCT IS TO BE
SHIPPED IN QUARANTINE.

                                       23
<PAGE>

9.0    STAGE 9 - REGULATORY DOCUMENTATION/SUPPORT

       9.1    OBJECTIVES

              9.1.1   To prepare regulatory documentation and regulatory support
                      as required by the Customer to support Phase III Studies.

       9.2    ACTIVITIES

              9.2.1   To provide regulatory documentation covering work under
                      all stages of these Services in a format appropriate for
                      the country of application and as requested by the
                      Customer.

              9.2.2   To attend Customer and regulatory agency meetings as
                      required by the Customer.

              9.2.3   To advise on additional studies that may be required for
                      regulatory Applications.

       9.3    TIMESCALE

              The duration of Stage 9 will depend on the extent of regulatory
              support requested by the Customer. Lonza will aim to complete the
              regulatory work as soon as possible after receiving all the
              relevant data from these Services, in anticipation of the Customer
              requiring the earliest possible filing date.

                                       24
<PAGE>

10.0   STAGE 10 - EVALUATION OF VIRUS CLEARANCE

       10.1   OBJECTIVES

              10.1.1  To obtain data for clearance of one model virus by the
                      column chromatography and virus inactivation steps used in
                      the purification of bulk Product.

       10.2   ACTIVITIES

              10.2.1  Design a scaled down process for each column
                      chromatography and inactivation step. The scaled down
                      process will mimic as closely as reasonably possible the
                      manufacturing scale process.

              10.2.2  Prepare a GLP study protocol and agree the model virus
                      with the Customer.

              10.2.3  Collect column load samples from the appropriate steps of
                      the full scale manufacturing process during Stage 8 of the
                      Services.

              10.2.4  Carry out the scaled down process for appropriate
                      chromatography steps without the virus spike. Compare the
                      elution profile, Product yield and purity with the full
                      scale manufacturing process. This is designed to
                      demonstrate that the scaled down process does mimic the
                      manufacturing process and to generate control samples to
                      test for cytotoxicity in the virus assay.

              10.2.5  Repeat the scaled down process for each column step, each
                      spiked separately with the selected virus. The virus will
                      be prepared and assayed by a suitable Testing Laboratory.
                      The column chromatography and inactivation studies will be
                      carried out by Lonza staff working in the laboratories of
                      the Testing Laboratory.

              10.2.6  Assay infectious virus recovered in Product containing
                      fractions (to allow calculation of clearance factors) and
                      in selected unbound and wash fractions to determine (where
                      possible) where infectious virus is removed and hence
                      identify critical steps in the process.

              10.2.7  Measure the rate of inactivation of virus by treating the
                      selected model virus in the inactivation steps, developed
                      in Stage 5 in the purification process for Product.

              10.2.8  Measure the clearance of the virus across the virus
                      removing filter step, if included in the process. i

              10.2.9  Calculate virus clearance factors for each step by
                      dividing total infectious virus applied by that recovered
                      with purified Product or after treatment at low pH.

                                       25
<PAGE>

              10.2.10 Issue an audited report of the activities to the Customer.

10.3   TIMESCALE

       Stage 10 shall commence once Product samples are obtained from Stage 8.
       It is estimated that Stage 10 shall be complete *** Confidential
       Treatment Requested as to this information *** from commencement.

                                       26
<PAGE>

                                   SCHEDULE 3

                           PRICE AND TERMS OF PAYMENT

1.0    PRICE

       In consideration for Lonza carrying out the Services as detailed in
Schedule 2 the Customer shall pay Lonza, as follows :-

<TABLE>
<CAPTION>
-----------------------------------------------------------------------------------------------------------
                               STAGE                                      PRICE (UK L STERLING)
-----------------------------------------------------------------------------------------------------------
<C>                                                                  <C>
1.       Substage 1 a - Media Selection                              *** Confidential Treatment Requested
                                                                     as to this information ***
-----------------------------------------------------------------------------------------------------------
         Substage 1 b - Cloning and Cell Line Selection                                "
-----------------------------------------------------------------------------------------------------------
2.       Fermentation Studies                                                          "
-----------------------------------------------------------------------------------------------------------
         Substage 2a                                                                   "
-----------------------------------------------------------------------------------------------------------
         Substage 2b                                                                   "
-----------------------------------------------------------------------------------------------------------
3.       Master and Working Cell Bank Preparation and Analysis                         "
-----------------------------------------------------------------------------------------------------------
4.       Substage 4a - Product ELISA Assay Transfer                                    "
-----------------------------------------------------------------------------------------------------------
         Sybstage 4b - Assay Transfer and Validation                                   "
-----------------------------------------------------------------------------------------------------------
5.       Purification Process Transfer                                                 "
-----------------------------------------------------------------------------------------------------------
6.       Development Pilot Batch                                                       "
-----------------------------------------------------------------------------------------------------------
7.       GMP Documentation                                                             "
-----------------------------------------------------------------------------------------------------------
8.       Production of Clinical Material(2)                                            "
-----------------------------------------------------------------------------------------------------------
9.       Regulatory Documentation Support                                              "
-----------------------------------------------------------------------------------------------------------
10.      Evaluation of Virus Clearance                                                 "
-----------------------------------------------------------------------------------------------------------
</TABLE>

Notes

(1)    This Price includes only cell bank testing as specified in Stage 3
       activities, sufficient to allow entry of the Cell Line into Lonza's GMP
       facility.

                                       27
<PAGE>

(2)    This prices may be reviewed depending on the cost of the commercial media
       selected and the costs of the resins used during the purification
       Process.

(3)    These are Lonza's cost prices for GMP batches produced in the early stage
       of a product development programme. Once a long term supply arrangement
       is entered into, it is anticipated that considerable price reductions
       could be offered.

                                       28
<PAGE>

2.0    PAYMENT

       Payment by the Customer of the Price for each Stage shall be made against
Lonza's invoices as follows:

       2.1    For
              Substage 1a
               *** Confidential Treatment Requested as to this information ***

              Substage 1b
              *** Confidential Treatment Requested as to this information ***

       2.2    For
              Stage 2
              Substage 2a
              *** Confidential Treatment Requested as to this information ***

              Substage 2b
              *** Confidential Treatment Requested as to this information ***

       2.3    For Stage 3
              *** Confidential Treatment Requested as to this information ***

       2.4    For Stage 4
              Substage 4a
              *** Confidential Treatment Requested as to this information ***

              Substage 4b
              Payment schedule to be agreed.

       2.5    For Stage 5
              *** Confidential Treatment Requested as to this information ***

       2.6    For Stage 6
              *** Confidential Treatment Requested as to this information ***

       2.7    For Stage 7
              *** Confidential Treatment Requested as to this information ***

       2.8    For Stage 8
              *** Confidential Treatment Requested as to this information ***

                                       29
<PAGE>

       2.9    For Stage 9
              *** Confidential Treatment Requested as to this information ***

       2.10   For Stage 10
              *** Confidential Treatment Requested as to this information ***

                                       30
<PAGE>

              SCHEDULE 4
1.     LB and Customer may negotiate in good faith amendments to the scope of
       the activities set out in Schedule 2 in the event that:

       a.     Customer determines that additional activities to the Services are
              required to meet its objectives or to accelerate where possible
              performance of the proposed services. Customer acknowledges that
              LB may have regard to its other third party commitments, and

       b.     Customer's requirements change resulting in certain activities to
              the Services no longer being required to meet Customer's
              objectives, Customer having regard to its obligations under
              Clause 4.3 and Clause 9.2 of. Schedule 5.

2.     The parties recognise that it may become necessary or desirable for
       Customer to manufacture *** Confidential Treatment Requested as to this
       information *** itself or through another manufacturer. LB is willing
       to effect a process transfer on commercially reasonable terms. ***
       Confidential Treatment Requested as to this information ***

                                       31
<PAGE>

                                   SCHEDULE 5
                      STANDARD TERMS FOR CONTRACT SERVICES
                          AVANT IMMUNOTHERAPEUTICS INC

1.     INTERPRETATION
       1.1    In these Standard Terms, unless the context requires otherwise
              1.1.1   "Affiliate" means any Company, partnership or other entity
                      which directly or indirectly controls, is controlled by or
                      is under common control with the relevant party to this
                      Agreement. "control" means the ownership of more than
                      fifty per cent (5096) of the issued share capital or the
                      legal power to direct or cause the direction of the
                      general management and policies of the party in question.
              1.1.2   "Agreement" means any contract between LB and a Customer
                      incorporating these Standard Terms.
              1.1.3   "Cell Line" means the cell line, particulars of which are
                      set out in Schedule 1.
              1.1.4   "cGMP" means Good Manufacturing Practices and General
                      Biologics Products Standards as promulgated under the US
                      Federal Food Drug and Cosmetic Act at 21CFR (Chapters 210,
                      211, 600 and 610) and the Guide to Good Manufacturing
                      Practices for Medicinal Products as promulgated under
                      European Directive 91/356/EEC. LB's operational quality
                      standards are defined in internal GMP policy documents.
                      Additional product-specific development documentation and
                      validation work may be required to support regulatory
                      applications to conduct clinical trials or market a
                      product.
              1.1.5   "Customer" includes any person to whom a Proposal is
                      issued by LB.
              1.1.6   "Customer information" means all technical and other
                      information not known to LB or in the public domain
                      relating to the Cell Line, the Process and the Product,
                      from time to time supplied by the Customer to LB.
              1.1.7   "Customer Materials" means the Materials supplied by
                      Customer to LB (if any) and identified as such by
                      Schedule 1 hereto.
              1.1.8   "Customer Tests" means the tests to be carried out on
                      the Product immediately following receipt of the Product
                      by the Customer, particulars of which are set out in
                      Schedule 1.
              1.1.9   "ex works" means LB has fulfilled its obligation to
                      deliver when it has made the object of delivery available
                      at its premises to the Customer or the Customer's agent
                      (or to LB's carrier if the provisions of Clause 5.1 of
                      this Schedule 5 apply). For the avoidance of doubt, unless
                      otherwise agreed in writing, LB is not responsible for
                      loading the object of delivery on to the vehicle provided
                      by the Customer or the Customers agent (or to LB's
                      nominated carrier if Clause 5.1 of this Schedule 5
                      applies) or for delaying the object of delivery for
                      export.
              1.1.10  "LB Know-How" means all technical and other information
                      relating to the Process known to LB from time to time
                      other than confidential Customer Information and
                      information in the public domain.

                                       32
<PAGE>

              1.1.11  "Patent Rights" means all patents and patent applications
                      of any kind throughout the world relating to the Process
                      which from time to time LB Is the owner of or is entitled
                      to use.
              1.1.12  "Price" means the price specified in Schedule 3 for the
                      Services.
              1.1.13  "Process" means the process for the production of the
                      Product from the Cell Line, including any improvements
                      thereto from time to time.
              1.1.14  "Product" means all or any part of the product (including
                      any sample thereof), particulars of which are set out in
                      Schedule 1.
              1.1.15  "Proposal" means any proposal or quotation issued by LB.
              1.1.16  "Services" means all or any part of the services the
                      subject of the Agreement or Proposal (including, without
                      limitation, cell culture evaluation, purification
                      evaluation, master, working and extended cell bank
                      creation, and sample and bulk production), particulars of
                      which are set out In Schedule 2.
              1.1.17  "Special Term" means any term additional or supplemental
                      to these Standard Terms from time to time agreed In
                      writing between LB and the Customer. Particulars of any
                      Special Terms at the date of the Agreement are set out in
                      Schedule 4.
              1.1.18  "Specification" means the specification for Product,
                      particulars of which are set out in Schedule 1. '
              1.1.19  "Terms of Payment" means the terms of payment specified in
                      Schedule 3.
              1.1.20  "Terms means any third party instructed by LB to cant'
                      out tests on the Cell Line or the Product.
       1.2    Unless the context requires otherwise, words and phrases defined
              in any other part of the Agreement shall bear the same meanings in
              these Standard Terms, references to the singular number include
              the plural and vice versa, references to Schedules are references
              to schedules to the Agreement, and references to Clauses are
              references to clauses of these Standard Terms.
       1.3    In the event of a conflict between a Special Term and these
              Standard Terms, the Special Term shall prevail.

2.     APPLICABILITY OF STANDARD TERMS
       2.1    Unless agreed otherwise, these Standard Terms shall apply to every
              Proposal and Agreement, and to any services additional to the
              Services requested by a Customer: LB shall not be bound by any
              terms which may be inconsistent with these Standard Terms and the
              Special Terms. No variation of or addition to these Standard Terms
              and the Special Terms or any other term of an Agreement shall be
              effective unless in writing and signed for and on behalf of LB and
              Customer. For the avoidance of doubt, amendments to the draft
              Specification or Specification for Product shall be effective if
              reduced to writing and signed by the regulatory representative of
              both Parties, which regulatory representative shall be nominated
              from time to time by the parties.
       2.2    Unless previously withdrawn, a Proposal is open for acceptance
              within the period stated therein. Where no period is stated, the
              Proposal shall be open for acceptance within thirty (30) days from
              the date it is issued unless withdrawn in the meantime. Any
              acceptance by a Customer of a Proposal shall not create a binding
              contract.

                                       33
<PAGE>

       2.3    A binding contract shall only be created when LB has accepted in
              writing an offer placed by a Customer.

3.     SUPPLY BY CUSTOMER
       3.1    Prior to or immediately following the date of the Agreement the
              Customer shall supply to LB the Customer Information, together
              with full details of any hazards relating to the Cell Line and/or
              the Customer Materials, their storage 'and use. On review of this
              Customer Information, the Cell Line and/or the Customer Materials
              shall be provided to LB at LB's request. Property in the Cell Line
              and/or the Customer Materials supplied to LB shall remain vested
              in the Customer.
       3.2    The Customer hereby grants LB the non-exclusive right to use the
              Cell Line, the Customer Materials and the Customer Information for
              the purpose of the Agreement. LB hereby undertakes not to use the
              Cell Line, the Customer Materials or the Customer Information (or
              any part thereof) for any other purpose.
              3.3 LB shall:
              3.3.1   at all times use all reasonable endeavours to keep the
                      Cell Line and/or the Customer Materials secure and safe
                      from loss and damage in such manner as LB stores its own
                      material of similar nature;
              3.3.2   not part with possession of the Cell Line and/or the
                      Customer Materials or the Product, save for the purpose
                      of tests at the Testing Laboratories; and
              3.3.3   procure that all Testing Laboratories are subject to
                      obligations of confidence substantially in the form of
                      those obligations of confidence imposed on B under these
                      Standard Terms.
       3.4    The Customer warrants to LB that
              3.4.1   the Customer is and shall at all times throughout the
                      duration of the Agreement remain entitled to supply the
                      Cell Line, the Customer Materials and Customer Information
                      to LB;
              3.4.2   to the best of the Customer's knowledge and belief the use
                      by LB of the Cell Line, the Customer Materials or and the
                      Customer Information for the Services will not infringe
                      any rights (including, without limitation, any
                      Intellectual or industrial property rights) vested in any
                      third party; and
              3.4.3   the Customer will notify LB, in writing, immediately it
                      knows or ought to know that it is no longer entitled to
                      supply the Cell Line, the Customer Materials and/or the
                      Customer Information to LB or that the use by LB of the
                      Cell Line, the Customer Materials or the Customer
                      Information for the Services infringes or is alleged to
                      infringe any rights (including, without limitation, any
                      intellectual or industrial property rights) vested in
                      any third party.
       3.5    The Customer undertakes to indemnify and to maintain LB promptly
              indemnified against any loss, damage, costs and expenses of any
              nature (including court costs and legal fees on a full indemnity
              basis), whether direct or consequential, and whether or not
              foreseeable or in the contemplation of LB or the Customer, that LB
              may suffer arising out of or incidental to any breach of the
              warranties given by the Customer under Clause 3.4 above or any
              claims alleging LB's use of the Cell Line, the Customer Materials
              or the Customer Information infringes any rights (including,
              without limitation, any intellectual or industrial property
              rights)

                                       34
<PAGE>

              vested in any third party (whether or not the Customer knows or
              ought to have known about the same).
       3.6    The obligations pf the Customer under this Clause 3 shall survive
              the termination for whatever reason of the Agreement.

4.     PROVISION OF THE SERVICES
       4.1    LB shall diligently carry out the Services as provided in
              Schedule 2 and shall use all reasonable efforts to achieve the
              estimated timescales therefor.
       4.2    Due to the unpredictable nature of the biological processes
              involved in the Services, the timescales set down for the
              performance of the Services (including without limitation the
              dates for production and delivery of Product) and the quantities
              of Product for delivery set out in Schedule 2 are estimated only.
       4.3    Subject to Clause 4.1. the Customer shall not be entitled to
              cancel any unfulfilled part of the Services or to refuse to accept
              the Services on grounds of late performance, late delivery or
              failure to produce the estimated quantities of Product for
              delivery. LB shall not be liable for any loss, damage, costs or
              expenses of any nature, whether direct or consequential,
              occasioned by 4.3.1 any delay in performance or delivery howsoever
              caused; or 4.3.2 any failure to produce the estimated quantities
              of Product for delivery.
       4.4    LB shall comply with the regulatory requirements from time to time
              applicable to the Services as set out in Schedule 2 hereto. If the
              Customer requests LB to comply with any other regulatory or
              similar legislative requirements LB shall use all reasonable
              commercial endeavours to do so provided that:
              4.4.1   the Customer shall be responsible for informing LB in
                      writing of the precise foreign requirements which the
                      Customer is requesting LB to observe;
              4.4.2   such foreign requirements do not conflict with any
                      mandatory requirements under the laws of England;
              4.4.3   LB shall be under no obligation to ensure that such
                      written information complies with the applicable
                      requirements of any foreign jurisdiction; and
              4.4.4   all costs and expenses incurred by LB in complying with
                      such foreign requirements shall be charged to the Customer
                      in addition to the Price.
         4.5  Delivery of Product shall be ex-works LB's premises (Incoterms
              1990). Risk in and title to Product shall pass on delivery.
              Transportation of Product, whether or not under any arrangements
              made by LB on behalf of the Customer. shall be made at the sole
              risk and expense of the Customer.
         4.6  Unless otherwise agreed, LB shall package and label Product for
              delivery ex-works in accordance with its standard operating
              procedures. It shall be the responsibility of the Customer to
              inform LB in writing in advance of any special packaging and
              labelling requirements for Product. All additional costs and
              expenses of whatever nature incurred by LB in complying with such
              special requirements shall be charged to the Customer in addition
              to the Price.

                                       35
<PAGE>

5.     TRANSPORTATION OF PRODUCT AND CUSTOMER TESTS
       5.1    If requested by the Customer, LB will (acting as agent of the
              Customer for such purpose) arrange the transportation of Product
              on issue of certificate of analysis or otherwise whichever is the
              earlier to occur from LB's premises to the destination indicated
              by the Customer together with insurance cover for Product in
              transit at its invoiced value. All additional costs and expenses
              of whatever nature incurred by LB in arranging such transportation
              and insurance shall be charged to the Customer in addition to the
              Price.
       5.2    Where LB has made arrangements for the transportation of Product,
              the Customer shall diligently examine the Product as soon as
              practicable after receipt. Notice of all claims (time being of the
              essence) arising out of:
              5.2.1   damage to or total or  partial loss of Product in transit
                      shall be given in writing to LB and the carrier within
                      three (3) working days of delivery; or
              5.2.2   non-delivery shall be given in writing to LB within ten
                      (10) days after the date of LB's despatch notice.
       5.3    The Customer shall make damaged Product available for inspection
              and shall comply with the requirements of any insurance policy
              covering the Product notified by LB to the Customer. LB shall
              offer the Customer all reasonable assistance (at the cost and
              expense of the Customer) in pursuing any claims arising out of the
              transportation of Product.
       5.4    Promptly following receipt of Product, the Customer shall carry
              out the customer Tests.
              PROVIDED ALWAYS the Specification for such Product is not stated
              to be in draft form, if the Customer Tests show that the Product
              fails to meet Specification, the Customer shall give LB written
              notice thereof within forty-five (45) days from the date of
              delivery of the Product ex works and shall return such Product to
              LB's premises for further testing. In the absence of such written
              notice Product shall be deemed to have been accepted by the
              Customer as meeting Specification. If LB Is satisfied  that
              Product  returned to LB fails to meet Specification and that such
              failure Is not due (in whole or in part) to acts or omissions of
              the Customer or any third party after delivery of such Product
              ex-works, LB shall at Customer's discretion refund that part of
              the Price that relates to the production of such Product or
              replace such Product at its own cost and expense. In the event
              Customer requires LB to replace such Product, LB shall be entitled
              to have regard to its commercial commitments to third parties in
              the timing of such replacement. Customer acknowledges that there
              may, therefore, be a delay in the timing of the replacement of
              such Product.
              FOR THE AVOIDANCE OF DOUBT, WHERE THE SPECIFICATION IS STATED TO
              BE IN DRAFT FORM LB SHALL BE OBLIGED ONLY TO USE ITS REASONABLE
              ENDEAVORS TO PRODUCE PRODUCT THAT MEETS SPECIFICATION.
       5.5    If there is any dispute concerning whether Product returned to LB
              fails to meet Specification or whether such failure Is due (in
              whole or in part) to acts or omissions of the Customer or any
              third party after delivery of such Product ex-works. such dispute
              shall be referred for decision to an independent expert (acting as
              an expert and not as an arbitrator) to be appointed by agreement
              between LB

                                       36
<PAGE>

              and the Customer or, in the absence of agreement by the President
              for the time being of the Association of the British
              Pharmaceutical Industry. The costs of such independent expert
              shall be borne equally between LB and the Customer. The decision
              of such independent expert shall be in writing and, save for
              manifest error on the face of the decision, shall be binding on
              both LB and the Customer.
       5.6    The provisions of Clauses 5.4 and 5.5 shall be the sole remedy
              available to the Customer in respect of Product that fails to meet
              Specification.

6.     PRICE AND TERMS OF PAYMENT
       6.1    The Customer shall pay the Price in accordance with the Terms of
              Payment.
       6.2    Unless otherwise indicated in writing by LB, all prices and
              charges are exclusive of Value Added Tax or of any other
              applicable taxes, levies, imposts, duties and fees of whatever
              nature imposed by or under the authority of any government or
              public authority, which shall be paid by the Customer (other than
              taxes on LB's income). All invoices are strictly net and payment
              must be made within thirty (30) days of date of invoice. Payment
              shall be made without deduction, deferment, set-off, lien or
              counterclaim of any nature.
       6.3    In default of payment on due date:
              6.3.1   interest shall accrue on any amount overdue at the rate
                      of two per cent (2%) above the base lending rate from time
                      to time of HSBC Bank plc, interest to accrue on a day to
                      day basis both before and after judgment; and
              6.3.2   LB shall, at its sole discretion, and without prejudice to
                      any other of its accrued rights, be entitled to suspend
                      the provision of the Services or to treat the Agreement as
                      repudiated by notice in writing to the Customer exercised
                      at any time thereafter.

7.     WARRANTY AND LIMITATION OF LIABILITY
       7.1    LB warrants that:
              7.1.1   the Services shall be performed in accordance with
                      Clause 4.1; and
              7.1.2   the Product shall meet Specification, save where the
                      Specification is stated to be in draft form when LB shall
                      be obliged only to use its reasonable endeavors to produce
                      Product that meets Specification.
       7.2    Clause 7.1 is in lieu of all conditions, warranties and statements
              in respect of the Services and/or the Product whether expressed or
              implied by statute, custom of the trade or otherwise (including
              but without limitation any such condition, warranty or statement
              relating to the description or quality of the Product, its fitness
              for a particular purpose or use under any conditions whether or
              not known to LB) and any such condition, warranty or statement is
              hereby excluded.
       7.3    Without prejudice to the terms of Clauses 5.6, 7.1, 7.2, 7.4 and
              7.6. the liability of LB for any loss or damage suffered by the
              Customer as a direct result of any breach of the Agreement or of
              any other liability of LB (including misrepresentation and
              negligence) in respect of the Services (including without
              limitation the production and/or supply of the Product) shall be
              limited to the payment by LB of damages which shall not exceed
              pounds sterling one million four hundred and thirty four thousand
              (L1,434,000). The aforementioned financial

                                       37
<PAGE>

              cap in respect of LB's liability shall not apply where damages are
              incurred due to willful misconduct or gross negligence on the part
              of LB.
       7.4    Subject to Clause 7.6, LB shall not be liable for the following
              loss or damage howsoever caused (even if foreseeable. or in the
              contemplation of LB or the Customer)
              7.4.1   loss of profits, business or revenue whether suffered by
                      the Customer or any other person; or
              7.4.2   special, indirect or consequential loss, whether suffered
                      by the Customer or any other person; and
              7.4.3   any loss arising from any claim made against the Customer
                      by any other person.
       7.5    The Customer shall indemnify and maintain LB promptly indemnified
              against all claims, actions, costs, expenses (including court
              costs and legal fees on a full indemnity basis) or other
              liabilities whatsoever in respect of
              7.5.1   any liability under the Consumer Protection Act 1987,
                      unless such liability is caused by the negligent act or
                      omission of LB in the production and/or supply of the
                      Product; and
              7.5.2   any product liability (other than that referred to in
                      Clause 7.5.1) in respect of Product, unless such liability
                      is caused by the negligent act or omission of LB in the
                      production and/or supply of Product; and
              7.5.3   any negligent or willful act or omission of the Customer
                      in relation to the use, processing, storage or sale of the
                      Product.
       7.6    Nothing contained In these Standard Terms shall purport to exclude
              or restrict any liability for death or personal injury resulting
              directly from negligence by LB in carrying out the Services or any
              liability for breach of the implied undertakings of LB as to
              title.
       7.7    The obligations of the Customer under this Clause 7 shall survive
              the termination for whatever reason of the Agreement.

8.     CUSTOMER INFORMATION, LB KNOW-HOW AND PATENT RIGHTS
       8.1    The Customer acknowledges that LB Know-How and LB acknowledges
              that Customer ' Information with which it is supplied by the other
              pursuant to the Agreement is supplied, subject to Clause 8.4, in
              circumstances imparting an obligation of confidence and each
              agrees to keep such LB Know-How or such Customer Information
              secret and confidential and to respect the other's proprietary
              rights therein and not at any time for any reason whatsoever to
              disclose or permit such LB Know-How or such Customer Information
              to be disclosed to any third party save as expressly provided
              herein.
       8.2    The Customer and LB shall each procure that all their respective
              employees, consultants and contractors having access to
              confidential LB Know-How or confidential Customer Information
              shall be subject to the same obligations of confidence as the
              principals pursuant to Clause 8.1 and shall enter into secrecy
              agreements in support of such obligations. Insofar as this is not
              reasonably practicable, the principals shall take all reasonable
              steps to ensure that any such employees, consultants and
              contractors are made aware of such obligations.
       8.3    LB and the Customer each undertake not to disclose or permit to be
              disclosed to any third party, or otherwise make use of or permit
              to be made use of, any trade

                                       38
<PAGE>

              secrets or confidential information relating to the technology,
              business affairs or finances of the other, any subsidiary, holding
              company or subsidiary or any such holding company of the other, or
              of any suppliers, agents, distributors, licensees or other
              customers of the other which comes into its possession under this
              Agreement.
       8.4    The obligations of confidence referred to in this Clause 8 shall
              not extend to any information which
              8.4.1   is or becomes generally available to the public otherwise
                      than by reason of a breach by the recipient party of the
                      provisions of this Clause 8;
              8.4.2   is known to the recipient party and is at its free
                      disposal prior to its receipt from the other;
              8.4.3   is subsequently disclosed to the recipient party without
                      being made subject to an obligation of confidence by a
                      third party; or
              8.4.4   LB or the Customer may be required to disclose under any
                      statutory, regulatory or similar legislative requirement,
                      subject to the imposition of obligations of secrecy
                      wherever possible in that relation.
       8.5    The Customer acknowledges that
              8.5.1   LB Know-How and the Patent Rights are vested in LB or LB
                      is otherwise entitled thereto; and
              8.5.2   the Customer shall not at any time have any right, title,
                      license or interest In or to LB Know-How, the Patent
                      Rights or any other intellectual property rights relating
                      to the Process which are vested in LB or to which LB is
                      otherwise entitled.
       8.6    LB acknowledges that
              8.6.1   Customer has undertaken that the Customer Information is
                      vested in the Customer or the Customer is otherwise
                      entitled thereto and LB has no right to use the same save
                      to the extent those granted by Customer to LB under
                      Clause 3.2;
              8.6.2   save as provided herein LB shall not at any time have any
                      right, title, license or interest in or to the Customer
                      Information or any other Intellectual Property rights
                      vested in Customer or to which the Customer is entitled;
                      and
              8.6.3   LB will provide to the Customer such information relating
                      to the Process and Product as contained in the Batch
                      record as requested by the Customer for the performance of
                      Customer's regulatory requirements subject to the
                      obligations of confidentiality outlined in Clause 8.
       8.7    The obligations of LB and the Customer under this Clause 8 shall
              survive the termination for whatever reason of the Agreement.

9.     TERMINATION
       9.1    If it becomes apparent to either LB or the Customer at any stage
              in the provision of the Services that it will not be possible to
              complete the Services for scientific or technical reasons, a
              sixty (60) day period shall be allowed for discussion to resolve
              such problems. If such problems are not resolved within such
              period, LB and the Customer shall each have the right to terminate
              the Agreement forthwith by notice in writing. In the event of such
              termination, the Customer shall pay to LB -a termination sum
              calculated by reference to all the Services performed by

                                       39
<PAGE>

              !,B prior to such termination (including a pro rata proportion of
              the Price for any stage of the Services which Is in process at the
              date of termination) and all expenses reasonably incurred by LB in
              giving effect to such termination, including the costs of
              terminating any commitments' entered into under the Agreement,
              such termination sum not to exceed the Price.
       9.2    Customer shall be entitled to terminate this Agreement at any time
              for any reason by sixty (60) days' notice to LB in writing. In the
              event of Customer serving notice to terminate this Agreement which
              notice is expressed to be given pursuant to this Clause 9.2.
              Customer shall
              9.2.1   pay LB a termination sum calculated in accordance with the
                      principles of Clause 9.1 above, and
              9.2.2   i.    in the event notice to terminate this Agreement
                            pursuant to this Clause 9.2 is issued to LB within
                            four (4) months of LB's then estimated start date
                            for any stage of the Services which includes cGMP
                            fermentation activities, Customer shall pay LB a sum
                            equal to forty percent (40%) of the full Price of
                            that stage, or those stages, in question which
                            payment shall fall due to LB on or before the date
                            of termination of the Services.
                      ii.   in the event notice to terminate this Agreement
                            pursuant to this Clause 9.2 is issued to LB within
                            one (1) month of LB's then estimated start date for
                            any stage of the Services which includes cGMP
                            fermentation activities, Customer shall pay LB a sum
                            equal to eighty percent (80%) of the full Price of
                            that stage, or those stages, in question which
                            payment shall fall due to LB on or before the date
                            of termination of the Services.
                      iii.  in the event notice to terminate this Agreement
                            pursuant to this Clause 9.2 is issued to LB after
                            the start of a stage or stages of the Services
                            which includes cGMP fermentation activities,
                            Customer shall pay LB a sum equal to one hundred
                            percent (100%) of the full Price of that stage, or
                            those stages, in question which payment shall fall
                            due to LB on or before the date of termination of
                            the Services.
              For the avoidance of doubt activities relating to cGMP
              fermentation shall be deemed to commence with the date of removal
              of the vial of cells for the performance of the fermentation from
              frozen storage.
       9.3    In the event that notice to terminate is served by Customer under
              Clause 9.2 and LB Is successful In allocating Customer's
              production slot to a third party customer the provisions of
              Clause 9.2.2. shall not apply.
       9.4    LB and the Customer may each terminate the Agreement forthwith by
              notice in writing to the other upon the occurrence of any of the
              following events
              9.4.1   if the other commits a breach of the Agreement which (in
                      the case of a breach capable of remedy) is not remedied
                      within thirty (30) days of the receipt by the other of
                      notice identifying the breach and requiring its remedy; or
              9.4.2   if the other ceases for any reason to carry on business or
                      compounds with or convenes a meeting of its creditors or
                      has a receiver or manager

                                       40
<PAGE>

                      appointed in respect of all or any part of its assets or
                      is the subject of an application for an administration
                      order or of any proposal for a voluntary arrangement or
                      enters into liquidation (whether compulsorily or
                      voluntarily) or undergoes any analogous act or proceedings
                      under foreign law
       9.5    Upon the termination of the Agreement for whatever reason
              9.5.1   LB shall promptly return all Customer Information to the
                      Customer and shall dispose of or return to the Customer
                      the Customer Materials (and where supplied by Customer the
                      Cell Line) and any materials therefrom, as directed by the
                      Customer;
              9.5.2   the Customer shall promptly return to LB all LB Know-How
                      it has received from LB;
              9.5.3   the Customer shall not thereafter use or exploit the
                      Patent Rights or the LB Know-How in any way whatsoever;
              9.5.4   LB may thereafter use or exploit the Patent Rights or the
                      LB Know-How in any way whatsoever without restriction; and
              9.5.5   LB and the Customer shall do all such acts and things and
                      shall sign and execute all such deeds and documents as the
                      other may reasonably require to evidence compliance with
                      this Clause 9.5.
       9.6    Termination of the Agreement for whatever reason shall not affect
              the accrued rights of either LB or the Customer arising under or
              out of this Agreement and all provisions which are expressed to
              survive the Agreement shall remain in full force and effect.

10.    FORCE MAJEURE
       10.1   If LB is prevented or delayed in the performance of any of its
              obligations under the Agreement by Force Majeure and shall give
              written notice thereof to the Customer specifying the matters
              constituting Force Majeure together with such evidence as LB
              reasonably can give and specifying the period for which it is
              estimated that such prevention or delay will continue, LB shall be
              excused from the performance or the punctual performance of such
              obligations as the case may be from the date of such notice for so
              long as such cause of prevention or delay shall continue.
       10.2   The expression "Force Majeure" shall be deemed to include any
              cause affecting the performance by LB of the Agreement arising
              from or attributable to acts, events, acts of God, omissions or
              accidents beyond the reasonable control of LB.

11.    GOVERNING, LAW. JURISDICTION AND ENFORCEABILITY
       11.1   The construction, validity and performance of the Agreement shall
              be governed by the laws of England, to the jurisdiction of whose
              courts LB and the Customer submit.
       11.2   No failure or delay on the part of either LB or the Customer to
              exercise or enforce any rights conferred on it by the Agreement
              shall be construed or operate as a waiver thereof nor shall any
              single or partial exercise of any right, power or privilege or
              further exercise thereof operate so as to bar the exercise or
              enforcement thereof at any time or times thereafter.

                                       41
<PAGE>

       11.3   The illegality or invalidity of any provision (or any part
              thereof) of the Agreement or these Standard Terms shall not affect
              the legality, validity or enforceability of the remainder of its
              provisions or the other parts of such provision as the case may
              be.

12.    MISCELLANEOUS
       12.1   Neither party shall be entitled to assign, transfer, charge or in
              any way make over the benefit and/or the burden of this Agreement
              without the prior written consent of the other which consent shall
              not be unreasonably withheld or delayed, save that either party
              shall be entitled without the prior written consent of the other
              to assign, transfer, charge, subcontract, deal with or in any
              other manner make over the benefit and/or burden of this Agreement
              to an Affiliate or to any 50/50 joint venture company of which the
              party in question is the beneficial owner or fifty per cent (50%)
              of the issued  share capital thereof or to any company with which
              the party in question may merge or to any company to which that
              party may transfer its assets and undertakings.
       12.2   The text of any press release or other communication to be
              published by or in the media concerning the subject matter of the
              Agreement shall require the prior written approval of LB and the
              Customer.
       12.3   The Agreement embodies the entire understanding of LB and the
              Customer and there are no promises, terms, conditions or
              obligations, oral or written, expressed on implied, other than
              those contained in the Agreement. The terms of the Agreement shall
              supersede all previous agreements (if any) which may exist or have
              existed between LB and the Customer relating to the Services.

                                       42<PAGE>

                            STOCK PURCHASE AGREEMENT

                             DATED DECEMBER 1, 2000

                                 BY AND BETWEEN

                         AVANT IMMUNOTHERAPEUTICS, INC.

                                       AND

                                   PFIZER INC

                                       1
<PAGE>

                                TABLE OF CONTENTS

                                                                            Page
                                                                            ----

1.   DEFINITIONS...............................................................4
2.   PURCHASE AND SALE; PURCHASE PRICE.........................................5
     2.1    Sale and Purchase of the Shares....................................5
     2.2    Closing............................................................6
3.   REPRESENTATIONS, WARRANTIES, COVENANTS, ETC. OF PFIZER....................6
     3.1    Due Authorization..................................................6
     3.2    Non-Contravention..................................................6
     3.3    Own Account........................................................7
     3.4    Legend.............................................................7
     3.5    Financial Experience...............................................7
     3.6    Brokers and Finders................................................7
4.   REPRESENTATIONS, WARRANTIES, COVENANTS, ETC. OF THE COMPANY...............7
     4.1    Organization and Authority.........................................7
     4.2    Enforceability.....................................................8
     4.3    Capitalization.....................................................8
     4.4    Authorization of the Shares........................................8
     4.5    Non-contravention..................................................8
     4.6    Consents and Approvals.............................................9
     4.7    Business of Company................................................9
     4.8    Securities Laws...................................................10
     4.9    Investments in Other Entities.....................................10
     4.10   Licenses and Other Rights; Compliance with Laws...................10
     4.11   Reliance; "Knowledge".............................................10
5.   COVENANTS OF THE COMPANY.................................................11
     5.1    Nasdaq; Reporting Status..........................................11
     5.2    State Securities Laws.............................................11
     5.3    Confidentiality...................................................11
     5.4    Removal of Legend.................................................11
6.   REGISTRATION.............................................................11
     6.1    Registration Statement Covering Resale of Common Stock............12
     6.2    Registration Obligations..........................................12
     6.3    Reports...........................................................13
     6.4    Indemnification...................................................13
7.   CONDITIONS TO THE COMPANY'S OBLIGATION TO SELL...........................13
8.   CONDITIONS TO PFIZER'S OBLIGATION TO PURCHASE............................14
9.   INDEMNIFICATION..........................................................15
10.  MISCELLANEOUS............................................................16
     10.1   Governing Law.....................................................16
     10.2   Headings..........................................................16

                                       2
<PAGE>

     10.3   Severability......................................................16
     10.4   Notices...........................................................16
     10.5   Counterparts......................................................17
     10.6   Entire Agreement; Benefit.........................................17
     10.7   Waiver............................................................18
     10.8   Amendment.........................................................18
     10.9   Further Assurances................................................18
     10.10 Assignment.........................................................18
     10.11 Expenses...........................................................18
     10.12 Survival...........................................................18
     10.13 Public Statements, Press Releases, etc.............................18
     10.14 Construction.......................................................19

                                       3
<PAGE>

      THIS STOCK PURCHASE AGREEMENT, dated December 1, 2000 (this "Agreement"),
by and between AVANT IMMUNOTHERAPEUTICS, INC., a Delaware corporation, with
headquarters located at 119 Fourth Avenue, Needham, MA 02494 (the "Company"),
and Pfizer Inc ("Pfizer").

                              W I T N E S S E T H:

WHEREAS,

(A)  Pfizer desires to purchase, and the Company desires to sell, upon the terms
     and conditions set forth in this Agreement, shares (the "Shares") of common
     stock, $.001 par value per share, of the Company (the "Common Stock"), that
     will result in the receipt by the Company of aggregate gross proceeds of
     approximately $3 million; and

(B)  Pfizer wishes to purchase, upon the terms and conditions stated in this
     Agreement, 285,877 Shares.

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
contained herein and other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties agree as follows:

1.   DEFINITIONS

     1.1 The following terms used in this Agreement shall have the following
meanings (such meanings to be equally applicable to both the singular and plural
forms of the terms defined):

     "AMEX" means the American Stock Exchange.

     "Closing Date" means 4:00 p.m., Boston time, three (3) days after the date
hereof, or such other time and date as the parties hereto may agree on.

     "Disclosure Schedule" means the Disclosure Schedule prepared by the Company
and furnished to Pfizer prior to the date of execution and delivery of this
Agreement by Pfizer. Items disclosed in response to a particular Section of this
Agreement in the Disclosure Schedule will be deemed disclosed for purposes of
other Sections as applicable without cross-references.

     "Executory Agreement" means the agreement entitled same entered into by the
Company and Pfizer on November 17, 2000.

                                       4
<PAGE>

     "Material Adverse Effect" means any material adverse effect on the
business, operations, assets, condition (financial or other) or prospects of the
Company and its Subsidiaries taken as a whole.

     "Megan Health Transaction" means the Company's merger with Megan Health,
Inc.

     "Nasdaq" means the Nasdaq Stock Market.

     "NYSE" means the New York Stock Exchange.

     "1933 Act" means the Securities Act of 1933, as amended.

     "1934 Act" means the Securities Exchange Act of 1934, as amended.

     "Person" means any natural person, corporation, partnership, limited
liability company, trust or unincorporated organization, incorporated
government, governmental agency or political subdivision.

     "Polmerix" means Polmerix, Inc., a Delaware corporation.

     "Registration Statement" means a registration statement with respect to the
Shares, together with any necessary amendments or supplements thereto and any
prospectus forming a part thereof.

     "Rule 144" means Rule 144 under the 1933 Act.

     "SEC" means the United States Securities and Exchange Commission.

     "SEC Reports" means all periodic and other reports filed by the Company
with the SEC pursuant to the 1933 Act and 1934 Act subsequent to January 1, 2000
and prior to the date hereof, in each case as filed with the SEC and including
the information and documents (other than exhibits) incorporated therein by
reference.

     "Securities Laws" means the 1933 Act, the 1934 Act, or any state securities
or "blue sky" law.

     "Subsidiary" has the meaning set forth in Section 4.1.

                                       5
<PAGE>

2.   PURCHASE AND SALE; PURCHASE PRICE

     2.1  SALE AND PURCHASE OF THE SHARES. Subject to all of the terms and
conditions hereof and in reliance on the representations and warranties set
forth or referred to herein, at the Closing the Company agrees to sell to Pfizer
and Pfizer hereby agrees to purchase, 285,877 Shares of Common Stock at a price
per share of $10.494, representing the average closing price as reported by
Nasdaq for the sixty (60) trading days ending on the trading day two (2) days
preceding the date of the execution of the Executory Agreement, plus a ten
percent (10%) premium, for an aggregate consideration of 2,999,993.20 (the
"Purchase Price").

     2.2  CLOSING. The closing of the purchase and sale of the Shares (the
"Closing") will take place at the offices of Goodwin, Procter & Hoar LLP,
Boston, Massachusetts on the Closing Date or at such other place as the parties
hereto may agree upon. The Closing shall occur when (a) the Company shall have
delivered to Pfizer share certificates representing the Shares to be issued to
Pfizer; and (b) Pfizer has delivered an amount equal to the Purchase Price.

3.   REPRESENTATIONS, WARRANTIES, COVENANTS, ETC. OF PFIZER

     Pfizer represents and warrants to, and covenants and agrees with, the
Company as follows:

     3.1  DUE AUTHORIZATION. Pfizer has all requisite power and authority,
corporate or otherwise, to execute, deliver and perform its obligations under
this Agreement and the other agreements executed by Pfizer in connection
herewith and to consummate the transactions contemplated hereby and thereby.
This Agreement has been duly and validly authorized, duly executed and delivered
by Pfizer and, assuming due execution and delivery by the Company, is a valid
and binding agreement of Pfizer enforceable in accordance with its terms, except
as the enforceability hereof may be limited by bankruptcy, insolvency,
reorganization, moratorium, fraudulent conveyance or other similar laws now or
hereafter in effect relating to or affecting creditors' rights generally and
general principles of equity, regardless of whether enforcement is considered in
a proceeding in equity or at law.

     3.2  NON-CONTRAVENTION. The execution, delivery and performance of this
Agreement by Pfizer and the consummation of any of the transactions contemplated
hereby by Pfizer will not (a) conflict with or result in a breach of any of the
terms and provisions of, or constitute a default (or an event which with notice
or lapse of time, or both, would constitute a default) under, or result in the
creation or imposition of any lien, charge or encumbrance upon any property or
assets of Pfizer pursuant to any agreement, instrument, franchise, license or
permit to which Pfizer is a party or by which any of its properties or assets
may be bound or (b) violate or conflict with any judgment, decree, order,
statute, rule or regulation of any court or any public, governmental or
regulatory agency or body applicable to Pfizer or any of its properties or
assets, other than such breaches, defaults or violations that are not reasonably
expected to materially impair the ability of Pfizer to consummate the
transactions contemplated by this Agreement. The execution, delivery and
performance of this Agreement by Pfizer and

                                       6
<PAGE>

the consummation of the transactions contemplated hereby by Pfizer does not and
will not violate or conflict with any provision of the organizational documents
of Pfizer, as currently in effect. No consent, approval, authorization, order,
registration, filing, qualification, license or permit of or with any court or
any government agency or body applicable to Pfizer is required for the
execution, delivery and performance of this Agreement or the consummation of the
transactions contemplated hereby other than those, if any, which have been
obtained on or prior to the Closing Date.

     3.3  OWN ACCOUNT. Pfizer is acquiring the Shares for its own account, for
investment and not with a view to the distribution thereof in violation of the
1933 Act.

     3.4  LEGEND. Pfizer agrees that the Company may place a legend on the stock
certificates delivered hereunder stating that the Shares have not been
registered under the 1933 Act and, therefore, cannot be offered, sold or
transferred unless they are registered under the 1933 Act or an exemption from
such registration is available.

     3.5.  FINANCIAL EXPERIENCE. Pfizer has such knowledge and experience in
business and financial matters so as to enable it to understand and evaluate the
risks of Pfizer's investment in the Shares and form an investment decision with
respect thereto.

     3.6  BROKERS AND FINDERS. No agent, broker, investment banker, financial
advisor or other firm or person engaged by Pfizer is or will be entitled to any
broker's or finder's fee or any other commission or similar fee in connection
with any of the transactions contemplated by this Agreement.

4.   REPRESENTATIONS, WARRANTIES, COVENANTS, ETC. OF THE COMPANY

     The Company represents and warrants to Pfizer that, except as specifically
set forth in the Disclosure Schedule, the following matters are true and correct
on the date of execution and delivery of this Agreement and will be true and
correct on the Closing Date, and the Company covenants and agrees with Pfizer as
follows:

     4.1  ORGANIZATION AND AUTHORITY. The Company and each of its Subsidiaries
(as defined in Rule 405 under the 1933 Act) is a corporation duly organized,
validly existing and in good standing under the laws of the jurisdiction of its
incorporation, and has all requisite corporate power and authority to (i) own,
lease and operate its properties and to carry on its business as described in
the SEC Reports and as currently conducted and (ii) to execute, deliver and
perform its obligations under this Agreement and to consummate the transactions
contemplated hereby and thereby. The Company is duly qualified to do business as
a foreign corporation and is in good standing in all jurisdictions where such
qualification is necessary and where failure so to qualify could have a Material
Adverse Effect.

     4.2  ENFORCEABILITY. The execution, delivery and performance by the Company
of this Agreement and the issuance and sale by the Company of the Shares will
result in legally binding obligations of the Company, enforceable against it in
accordance with the respective

                                       7
<PAGE>

terms and provisions hereof and thereof, except as limited by bankruptcy,
insolvency, and other laws affecting the enforcement of creditors' rights
generally or by its equitable principles in any action (legal or equitable).

     4.3  CAPITALIZATION.

          (a)  The authorized capitalization of the Company is as set forth in
the Disclosure Schedule.

          (b)  Except as set forth in this Section 4.3, or in the Disclosure
Schedule, there are: (i) no outstanding warrants, options, agreements,
convertible securities or other commitments or instruments pursuant to which the
Company or any Subsidiary is or may become obligated to issue, sell, repurchase
or redeem any shares of capital stock or other securities of the Company or any
Subsidiary; (ii) no preemptive, contractual or similar rights to purchase or
otherwise acquire shares of capital stock of the Company or any Subsidiary
pursuant to any provision of law, the Certificate of Incorporation or By-Laws of
the Company or any Subsidiary or any agreement to which the Company or any
Subsidiary is a party, or otherwise; (iii) no restrictions on the transfer of
capital stock of the Company or any Subsidiary imposed by the Certificate of
Incorporation or By-Laws of the Company or any Subsidiary, any agreement to
which the Company or any Subsidiary is a party, any order of any court or any
governmental agency to which the Company or any Subsidiary is subject, or any
statute other than those imposed by relevant state and federal securities laws;
(iv) no cumulative voting rights for any of the Company's capital stock; (v) no
registration rights under the 1933 Act with respect to shares of the Company's
capital stock; (vi) no shares of capital stock of the Company reserved for
issuance for any purpose; (vii) to the best of the Company's knowledge and
belief after due inquiry, no options or other rights to purchase shares of
capital stock from stockholders of the Company or any Subsidiary granted by such
stockholders; and (viii) no agreements, written or oral, between the Company or
any Subsidiary and any holder of its securities, or, to the best of the
Company's knowledge and belief, among holders of its securities, relating to the
acquisition, disposition or voting of the securities of the Company or any
Subsidiary.

          (c)  Prior to the date of this Agreement, the Company has reserved a
number of authorized but unissued shares of Common Stock sufficient for issuance
pursuant to this Agreement.

          (d)  All of the outstanding capital stock of the only Subsidiary,
Polmerix, is owned by the Company.

     4.4  AUTHORIZATION OF THE SHARES. The issuance, sale and delivery of the
Shares to Pfizer have been duly authorized by all requisite action of the
Company, and the Shares are authorized, validly issued and outstanding, fully
paid and nonassessable and not subject to preemptive or any other similar rights
of the stockholders of the Company or others.

     4.5  NON-CONTRAVENTION. The execution and delivery of this Agreement by the
Company and the consummation by the Company of the offer and sale of the Shares
and the other

                                       8
<PAGE>

transactions contemplated by this Agreement do not and will not, with or without
the giving of notice or the lapse of time, or both (i) result in any violation
of any provision of the Certificate of Incorporation or By-laws of the Company
or any of its Subsidiaries; (ii) conflict with or result in a breach by the
Company or any of its Subsidiaries of any of the terms or provisions of, or
constitute a default under, or result in the modification of, or result in the
creation or imposition of any lien, security interest, charge or encumbrance
upon any of the properties or assets of the Company or any of its Subsidiaries
pursuant to, any indenture, mortgage, deed of trust or other agreement or
instrument to which the Company or any of its Subsidiaries is a party or by
which the Company or any of its Subsidiaries or any of their respective
properties or assets are bound or affected; (iii) violate or contravene any
applicable law, rule or regulation or any applicable decree, judgment or order
of any court, United States federal or state regulatory body, administrative
agency or other governmental body having jurisdiction over the Company or any of
its Subsidiaries or any of their respective properties or assets; or (iv)
violate or contravene any permit, certification, registration, approval,
consent, license or franchise necessary for the Company or any of its
Subsidiaries to own or lease and operate any of their respective properties and
to conduct any of their respective business or the ability of the Company or any
of its Subsidiaries to make use thereof.

     4.6  CONSENTS AND APPROVALS. No authorization, consent, approval or other
order of, or declaration to or filing with, any governmental agency or body
(other than filings required to be made under applicable federal and state
securities laws, which have been made) or any third party is required for (a)
the valid authorization, execution, delivery and performance by the Company of
this Agreement or (b) the valid authorization, reservation, issuance, sale and
delivery of the Shares by the Company to Pfizer.

     4.7  BUSINESS OF THE COMPANY.

          (a) Except as provided in the Disclosure Schedule: (i) there are no
actions, suits, arbitrations, claims, investigations or legal or administrative
proceedings pending or, to the best of the Company's knowledge and belief after
due inquiry of the executive officers of the Company, threatened, against the
Company or any Subsidiary, whether at law or in equity, before or by any
federal, state, municipal or other governmental department, commission, agency,
instrumentality, or arbitrator, domestic or foreign; and (ii) there are no
judgments, decrees, injunctions, orders or awards of any court, governmental
department, commission, agency, instrumentality or arbitrator entered or
existing against the Company or any Subsidiary or any of its assets or
properties.

          (b) The Disclosure Schedule lists each SEC Report filed by the Company
with the SEC under the 1933 Act or the 1934 Act since September 30, 1998. The
Company has delivered to Pfizer copies of the SEC Reports, other than exhibits
and material incorporated by reference which have not been requested by Pfizer.
The SEC Reports as filed comply with the applicable requirements of the 1933 Act
or the 1934 Act, as the case may be, and the rules and regulations thereunder,
and as of the respective dates thereof did not contain an untrue statement of a
material fact or omit to state any material fact required to be stated therein
or necessary to make the statements therein, in light of the circumstances under
which they were made, not misleading. Except as set forth in the Disclosure
Schedule, the Company has filed

                                       9
<PAGE>

on a timely basis all SEC Reports, required to be filed by it pursuant to the
1933 Act or the 1934 Act.

          (c) Except as set forth in the Disclosure Schedule, since
September 30, 1998, there has not been any material adverse change in the
business, operations, properties, assets, condition or prospects of the
Company or any Subsidiary or any event, condition or contingency that could
reasonably be expected to result in such a material adverse change.

     4.8  SECURITIES LAWS. Neither the Company nor anyone acting on its behalf
has offered securities of the Company for sale to, or solicited any offers to
buy the same from, or sold securities of the Company to, any person or
organization, in any case so as to subject the Company, its promoters, directors
or officers to any liability under the Securities Laws. The offer, sale and
issuance of the Shares to Pfizer hereunder is in compliance with the Securities
Laws and is exempt from the registration requirements of the 1933 Act.

     4.9  INVESTMENTS IN OTHER ENTITIES. Except as set forth in the Disclosure
Schedule, (a) neither the Company nor any Subsidiary has made any loan or
advance to any person or entity which is outstanding on the date hereof, nor is
it committed or obligated to make any such loan or advance, and (b) neither the
Company nor any Subsidiary has ever owned or controlled and does not currently
own or control any capital stock or other ownership interest, directly or
indirectly, in any corporation, association, partnership, trust, joint venture
or other entity, other than Polmerix.

     4.10  LICENSES AND OTHER RIGHTS; COMPLIANCE WITH LAWS. The Company or the
Subsidiary, as the case may be, is in compliance under each franchise, permit,
license and other rights and privileges necessary to permit them to own their
respective properties and to conduct business as presently conducted, and the
transactions contemplated by this Agreement will not cause a violation under
any, of such franchises, permits, licenses and other rights and privileges. The
Company and the Subsidiary is in compliance with all applicable laws, rules,
regulations, orders, judgements, decrees and any bring-downs except when the
failure to so comply would not have a Material Adverse Effect.

     4.11  RELIANCE; "KNOWLEDGE". The Company understands that the foregoing
representations and warranties shall be deemed material and to have been relied
upon by Pfizer. No representation or warranty by the Company in this Agreement,
and no written statement contained in any document, certificate or other writing
delivered by the Company to Pfizer contains any untrue statement of material
fact or omits to state any material fact necessary to make the statements herein
or therein, in light of the circumstances under which they were made, not
misleading.

                                       10
<PAGE>

5.   COVENANTS OF THE COMPANY

     5.1  NASDAQ; REPORTING STATUS. The Company shall use its best efforts to
take all such actions as may be necessary and as soon as practicable and in no
event later than 30 days after the Closing Date to file with Nasdaq an
application or other document required by Nasdaq for the listing of the Shares
with Nasdaq and shall provide evidence of such filing to Pfizer. So long as
Pfizer beneficially owns any portion of the Shares, the Company will use its
best efforts to maintain the inclusion of the Common Stock on Nasdaq or the
listing of the Common Stock on the AMEX or the NYSE; PROVIDED, HOWEVER, that
this will not restrict the Company from engaging in any transaction which
results in all of the capital stock of the Company being acquired in a business
combination or other acquisition transaction.

     5.2  STATE SECURITIES LAWS. On or before the Closing Date, the Company
shall take such action as shall be necessary to qualify, or to obtain, an
exemption for the Shares under such of the securities laws of United States
jurisdictions as shall be necessary to qualify, or to obtain an exemption from,
the sale of the Shares. The Company shall furnish Pfizer with copies of all
filings, applications, orders and grants or confirmations of exemptions relating
to such securities laws on or before the Closing Date.

     5.3  CONFIDENTIALITY. Except as necessary for governmental notification
purposes or to comply with applicable laws and regulations, and except as
otherwise agreed to by the parties in writing, the parties agree to keep the
existence of this Agreement and the transactions contemplated hereby and
thereby, until public disclosure is made pursuant to Section 11.13 hereof,
strictly confidential; PROVIDED, HOWEVER that the existence of this Agreement
and the transactions contemplated hereby or portions thereof may be disclosed to
those third parties who agree to be bound by the terms of this confidentiality
provision. In the event that the Company is required by law to provide a copy of
this Agreement to any third party, the Company shall ensure that such document
is redacted, to the extent permitted by law, to eliminate all confidential
information. Pfizer shall have the right to review and approve each such
document prior to its submission to any third party

     5.4  REMOVAL OF LEGEND. The legend on the stock certificates delivered
hereunder which is referenced in Section 3.4 hereof shall be removed and the
Company shall issue unlegended certificates to Pfizer if Pfizer provides the
Company with an opinion of counsel to Pfizer (which may be in-house counsel)
which is reasonably acceptable to the Company to the effect that such legend is
no longer required or if Pfizer has met or complied with the conditions for a
permissible sale or transfer pursuant to Rule 144 under the 1933 Act (as such
rule may be amended from time to time).

6.   REGISTRATION

     6.1  REGISTRATION STATEMENT COVERING RESALE OF COMMON STOCK. As soon as
reasonably practicable after the closing of the Megan Health Transaction, the
Company will file a registration statement (the "Shelf Registration Statement")
under Rule 415 under the 1933 Act covering the resale of the Shares. Thereupon,
the Company shall use commercially reasonable

                                       11
<PAGE>

efforts to cause such Shelf Registration Statement to be declared effective
by the SEC for all Shares covered thereby. The Company agrees to use
commercially reasonable efforts to keep the Shelf Registration Statement
continuously effective, with respect to Pfizer's Shares, until the earlier of
(i) the date on which Pfizer has disposed of all of its Shares, or (ii) the
date on which Pfizer may sell all of the Shares under Rule 144 of the 1933
Act (the "Terminal Date").

     6.2  REGISTRATION OBLIGATIONS. Whenever the Company includes any Shares in
a registration statement or similar document pursuant to this Agreement, the
Company shall, as expeditiously as reasonably possible:

          (a) Prepare and file with the SEC a Registration Statement, and use
its best efforts to cause such Registration Statement to become effective;

          (b) Notify Pfizer, promptly after the Company receives notice thereof,
of the effective date of the Registration Statement, or if any amendment or
supplement to the Registration Statement is filed, the date of such filing;

          (c) Notify Pfizer promptly of any request by the SEC for additional
information or an amendment or supplement to the Registration Statement;

          (d) Advise Pfizer of any order by the SEC suspending the effectiveness
of the Registration Statement and of the initiation or threat of any proceeding
for that purpose, and use its best efforts to prevent the issuance of any stop
order and to promptly obtain its withdrawal if such stop order is issued;

          (e) Prepare and file with the SEC such amendments and supplements to
the Registration Statement as may be necessary to keep the Registration
Statement effective until the Terminal Date, and comply with the provisions of
the 1933 Act during such period with respect to the disposition of all
securities covered by the Registration Statement;

          (f) Provide Pfizer with copies of the Registration Statement
(including preliminary prospectuses) in conformity with the requirements of the
1933 Act and such other documents as Pfizer may reasonably request in order to
facilitate the disposition of the Shares;

          (g) Use its commercially reasonable efforts to register and qualify
the Shares under the securities and blue sky laws of those jurisdictions
selected by Pfizer or any underwriter, and take any and all other action
reasonably necessary or advisable to enable Pfizer to sell the Shares in such
jurisdictions; PROVIDED, HOWEVER, that the Company shall not be required to
qualify to do business or consent to service of process in any jurisdiction in
which it is not now so qualified or has not so consented;

          (h) Promptly notify Pfizer of the occurrence of any event, the result
of which is to cause the Registration Statement to contain an untrue statement
of a material fact or to omit to state any material fact required to be reported
therein or necessary to make the statements therein not misleading in light of
the circumstances then existing, and prepare a supplement or

                                       12
<PAGE>

amendment to the Registration Statement which shall correct such untrue
statement or eliminate such omission;

          (i) Cause the registered Shares to be listed or approved for trading
on each securities exchange or through any facility on which similar securities
issued by the Company are then listed or traded;

          (j) Provide a transfer agent and registrar for the registered Shares
not later than the effective date of the Registration Statement;

          (k) In the event of an underwritten public offering, enter into such
customary agreements (including an underwriting agreement in customary form) and
take such other actions as Pfizer or the underwriters, may reasonably request in
order to expedite or facilitate the sale of the Shares;

          (l) Make available for inspection by Pfizer, any participating
underwriter, attorney, accountant or other agent retained by Pfizer or such
underwriter, all financial and other records and pertinent corporate documents
of the Company, and cause the Company's officers, directors and employees to
supply all information reasonably requested by Pfizer, the underwriter,
attorney, accountant or agent in connection with the Registration Statement;

          (m) Use its commercially reasonable efforts to obtain cold comfort
letters from the Company's independent public accountants, in customary form and
covering such matters of the type customarily covered by cold comfort letters,
as Pfizer may reasonably request; and

          (n) Use its commercially reasonable efforts to cause counsel to the
Company to provide legal opinions reasonably requested by Pfizer in connection
with the Registration Statement.

     6.3  REPORTS. The Company shall at all times timely file all information
and reports required to be filed by it under the 1933 Act and the 1934 Act and
the rules and regulations adopted by the SEC thereunder. Upon request, the
Company shall deliver to Pfizer a written statement as to whether it has
complied with such requirements, and the Company shall take such further action
as Pfizer may reasonably request, to enable Pfizer to be eligible to sell
restricted securities pursuant to Rule 144 under the 1933 Act or any similar
rule or regulation hereafter adopted by the SEC.

     6.4  INDEMNIFICATION. The Company shall indemnify and hold harmless Pfizer,
the officers and directors of Pfizer, and each underwriter of Shares sold by
Pfizer pursuant to this Section 6 (and any person who controls Pfizer or the
underwriter within the meaning of Section 15 of the 1933 Act) against all
claims, losses, damages, liabilities and expenses (including reasonable
attorneys' fees) arising out of or based on any untrue statement or alleged
untrue statement of a material fact contained in the Registration Statement or
in any related prospectus, notification or similar document, or from any
omission or alleged omission of a material fact required to be stated therein or
necessary to make the statements therein, in light of the circumstances under
which they were made, not misleading (a "Misstatement or

                                       13
<PAGE>

Omission") except insofar as such Misstatement or Omission is based on
information furnished in writing to the Company by Pfizer relating to Pfizer and
expressly for use therein, and used in accordance with such writing. Pfizer
shall furnish the Company with such information concerning Pfizer and the
intended method of disposition of the Shares as shall be necessary to effect the
registration of the Shares pursuant to this Section 6. In the event that the
Shares are registered pursuant to this Agreement, Pfizer shall indemnify and
hold harmless the Company, its officers and directors and each of its
underwriters (and any person who controls the Company or such underwriters
within the meaning of Section 15 of the 1933 Act) against all claims, losses,
damages, liabilities and expenses (including reasonable attorneys' fees)
arising out of or based on any Misstatement or Omission, but only insofar as
such Misstatement or Omission is based on information furnished in writing to
the Company by Pfizer relating to Pfizer and expressly for use in connection
with such registration, and used in accordance with such writing. In no event
shall the liability of Pfizer under this Section 6.4 be greater in amount than
the dollar amount of the proceeds received by Pfizer upon the sale of the Shares
giving rise to such indemnification obligation.

7.   CONDITIONS TO THE COMPANY'S OBLIGATION TO SELL

     Pfizer understands that the Company's obligation to sell the Shares to
Pfizer pursuant to this Agreement is conditioned upon satisfaction of the
following conditions precedent on or before the Closing Date (any or all of
which may be waived by the Company in its sole discretion):

          (a)  the delivery by Pfizer to the Company of an amount equal to the
               Purchase Price;

          (b)  on the Closing Date, no legal action, suit or proceeding shall be
               pending or threatened which seeks to restrain or prohibit the
               transactions contemplated by this Agreement;

          (c)  the representations and warranties of Pfizer contained in this
               Agreement shall have been true and correct on the date of this
               Agreement and on the Closing Date as if made on the Closing Date
               and on or before the Closing Date Pfizer shall have performed all
               covenants and agreements of Pfizer required to be performed by
               Pfizer on or before the Closing Date;

          (d)  the Company and/or Megan and Pfizer shall have entered into a
               License and Royalty Agreement and a Collaborative Research and
               Development Agreement; and

          (e)  the closing of the Megan Health Transaction.

8.   CONDITIONS TO PFIZER'S OBLIGATION TO PURCHASE

     The Company understands that Pfizer's obligation to purchase the Shares is
conditioned upon satisfaction of the following conditions precedent on or before
the Closing Date (any or all of which may be waived by Pfizer in its sole
discretion):

                                       14
<PAGE>

          (a)  delivery by the Company to Pfizer of the share certificates
               representing the Shares in accordance with this Agreement;

          (b)  on the Closing Date, no legal action, suit or proceeding shall be
               pending or threatened which seeks to restrain or prohibit the
               transactions contemplated by this Agreement;

          (c)  the representations and warranties of the Company contained in
               this Agreement shall have been true and correct on the date of
               this Agreement and shall be true and correct on the Closing Date
               as if given on and as of the Closing Date (except for
               representations given as of a specific date, which
               representations shall be true and correct as of such date), and
               on or before the Closing Date the Company shall have performed
               all covenants and agreements of the Company contained herein
               required to be performed by the Company on or before the Closing
               Date;

          (d)  the Company shall have delivered to Pfizer its certificate, dated
               the Closing Date, duly executed by its Chief Executive Officer to
               the effect set forth in subparagraphs (b) and (c) of this Section
               8;

          (e)  the receipt by Pfizer of a certificate, dated the Closing Date,
               of the Secretary or Assistant Secretary of the Company certifying
               (i) the Certificate of Incorporation and By-laws of the Company
               as in effect on the Closing Date, (ii) all resolutions of the
               board of directors (and committees thereof) of the Company
               relating to this Agreement and the transactions contemplated
               hereby and thereby, (iii) the incumbency of officers and
               directors of AVANT, and (iv) such other matters as are reasonably
               requested by Pfizer;

          (f)  on the Closing Date, Pfizer shall have received an opinion of
               Goodwin, Procter & Hoar LLP, counsel for the Company, dated the
               Closing Date, addressed to Pfizer, in form, scope and substance
               reasonably satisfactory to Pfizer; and

          (h)  on the Closing Date, (i) trading in securities on the NYSE, Inc.,
               the AMEX or Nasdaq shall not have been suspended or materially
               limited and (ii) a general moratorium on commercial banking
               activities in the Commonwealth of Massachusetts shall not have
               been declared by either federal or state authorities.

9.   INDEMNIFICATION

          (a)  INDEMNIFICATION. The Company shall indemnify, defend and hold
Pfizer harmless against any and all claims, losses, damages, liabilities and
expenses (including reasonable attorneys' fees) arising out of or based on the
untruth, inaccuracy or breach of any statements, representations, warranties or
covenants of the Company contained herein.

                                       15
<PAGE>

          (b)  INDEMNIFICATION PROCEDURE. Any party (the "Indemnified Party")
that may be entitled to indemnification under this Agreement shall give notice
to the party obligated to indemnify ("Indemnifying Party") reasonably promptly
after the assertion by a third party of a claim against the Indemnified Party in
respect of which the Indemnified Party intends to seek indemnification, but the
delay in notifying the Indemnifying Party shall not relieve it of any
obligations hereunder except to the extent that such delay adversely affects the
ability of the Indemnifying Party to conduct the defense of such claim. The
Indemnified Party shall be entitled to participate in such defense, but shall
not be entitled to indemnification with respect to the expenses of such defense
incurred after the date the Indemnifying Party shall have assumed the defense of
the claim with counsel satisfactory to the Indemnified Party. The Indemnifying
Party may not settle any claim without the consent of the Indemnified Party
(which consent shall not be unreasonably withheld). If notice is given to an
Indemnifying Party of the assertion by a third party of a claim against the
Indemnified Party and the Indemnifying Party does not, within ten (10) days
after the Indemnified Party's notice is given, give notice to the Indemnified
Party of its election to assume the defense thereof, the Indemnified Party may,
at the Indemnifying Party's expense, select counsel to defend such claim, and
defend such claim in such manner as it may deem appropriate, and the
Indemnifying Party shall be bound by any determination made with respect to such
claim or any compromise or settlement thereof effected by the Indemnified Party.
Notwithstanding the foregoing, if an Indemnified Party determines in good faith
that there is a reasonable probability that a claim may adversely affect it
other than as a result of monetary damages or that the Indemnified Party may
have claims or interests opposed to that of the Indemnifying Party, such
Indemnified Party may, by notice to the Indemnifying Party, assume the exclusive
right to defend, compromise or settle such claim, but the Indemnifying Party
shall not be bound by any determination of a claim so defended or any compromise
or settlement thereof effected without its consent (which shall not be
unreasonably withheld).

10.  MISCELLANEOUS

     10.1  GOVERNING LAW. THIS AGREEMENT SHALL BE GOVERNED BY AND INTERPRETED IN
ACCORDANCE WITH THE LAWS OF THE COMMONWEALTH OF MASSACHUSETTS OF THE UNITED
STATES.

     10.2  HEADINGS. The headings and captions used in this Agreement are for
convenience of reference and shall not form part of, or affect the
interpretation of, this Agreement.

     10.3  SEVERABILITY. If any provision of this Agreement shall be invalid or
unenforceable in any jurisdiction, such invalidity or unenforceability shall not
affect the validity or enforceability of the remainder of this Agreement or the
validity or enforceability of this Agreement in any other jurisdiction.

     10.4  NOTICES. Any notice or other communication required or permitted to
be given or made hereunder shall be in writing in the English language and shall
be deemed to have been duly given if sent by registered air mail (return receipt
requested), facsimile letter or delivered by hand to the party to whom such
notice or communication is required or permitted to be given. Any such notice or
other communication, if mailed, shall be considered given or made

                                       16
<PAGE>

when mailed, as evidenced by the postmark at point of mailing. If sent by
facsimile letter such notice shall be deemed to have been given on the date that
it is sent; provided, that a confirmatory copy of the facsimile letter is mailed
on the same day as the facsimile letter is sent to the receiving party. If
delivered by hand, any such notice or communication shall be considered given
when delivered.

     All notices to the Company shall be addressed as follows:

                       AVANT Immunotherapeutics, Inc.
                       119 Fourth Avenue
                       Needham, MA 02194
                       U.S.A.
                       Facsimile: (781) 433-3191
                       Attention: Chief Executive Officer

     With a copy to:

                       Goodwin, Procter & Hoar LLP
                       Exchange Place
                       Boston, MA 02109
                       Facsimile: (617) 523-1231
                       Attention: Stuart M. Cable, P.C.

     All notices to Pfizer shall be addressed as follows:

                       Pfizer Inc.
                       Global Research & Development
                       Eastern Point Road
                       Groton, CT 06340
                       Attention: Mark Dellaporta, Esq.

     10.5  COUNTERPARTS. This Agreement may be executed in counterparts and by
the parties hereto on separate counterparts, each of which shall be deemed to be
an original but all of which together shall constitute one and the same
instrument. A telephone line facsimile transmission of this Agreement bearing a
signature on behalf of a party hereto shall be legal and binding on such party.

     10.6  ENTIRE AGREEMENT; BENEFIT. This Agreement together with the
Disclosure Schedule, constitute the entire agreement among the parties hereto
with respect to the subject matter hereof. There are no restrictions, promises,
warranties or undertakings other than those set forth or referred to herein and
therein. This Agreement, including the Annexes hereto and Disclosure Schedule,
supersede all prior agreements and understandings, whether written or oral,
between the parties hereto with respect to the subject matter hereof. This
Agreement and the terms and provisions hereof are for the sole benefit of only
the Company, Pfizer and their respective successors and permitted assigns.

                                       17
<PAGE>

     10.7  WAIVER. Failure of any party to exercise any right or remedy under
this Agreement or otherwise, or delay by a party in exercising such right or
remedy, or course of dealing between the parties shall not operate as a waiver
thereof or an amendment hereof, nor shall any single or partial exercise of any
such right or power, or any abandonment or discontinuance of steps to enforce
such a right or power, preclude any other or further exercise thereof or
exercise of any other right or power.

     10.8  AMENDMENT. No amendment, modification, waiver, discharge or
termination of any provision of this Agreement or consent to any departure by
Pfizer or the Company therefrom shall in any event be effective unless the same
shall be in writing and signed by the party to be charged with enforcement, and
then shall be effective only in the specific instance and for the purpose for
which given. No course of dealing between the parties hereto shall operate as an
amendment of this Agreement.

     10.9  FURTHER ASSURANCES. Each party to this Agreement will perform any and
all acts and execute any and all documents as may be necessary and proper under
the circumstances in order to accomplish the intents and purposes of this
Agreement and to carry out its provisions.

     10.10  ASSIGNMENT. Except as otherwise provided herein, the provisions
hereof shall inure to the benefit of, and be binding upon, the successors,
assigns, heirs, executors and administrators of the parties hereto; PROVIDED,
HOWEVER, that the right of Pfizer to purchase Shares shall not be assignable
(other than to a wholly-owned subsidiary) without the consent of the Company
(such consent not to be unreasonably withheld).

     10.11  EXPENSES. Each of the Company and Pfizer shall bear its own expenses
in connection with the preparation and negotiation of this Agreement and the
consummation of the transactions contemplated hereby.

     10.12  SURVIVAL. The respective representations, warranties, covenants and
agreements of the Company and Pfizer contained in this Agreement and the
documents delivered in connection with this Agreement shall survive the
execution and delivery of this Agreement and the closing hereunder and delivery
of and payment for the Shares, and shall remain operative and in full force and
effect regardless of any investigation made by or on behalf of Pfizer or any
Person controlling or acting on behalf of Pfizer or by the Company or any Person
controlling or acting on behalf of the Company.

     10.13  PUBLIC STATEMENTS, PRESS RELEASES, ETC. The Company and Pfizer shall
have the right to approve before issuance any press releases or any other public
statements with respect to the transactions contemplated hereby; PROVIDED,
HOWEVER, that the Company shall be entitled, without the prior approval of
Pfizer, to make any press release or other public disclosure with respect to
such transactions as is required by applicable law and regulations, including
the 1933 Act and the rules and regulations promulgated thereunder and the rules
and regulations of the Nasdaq National Market (although Pfizer and its counsel
shall be consulted and provided with a draft press release by the Company in
connection with any such press

                                       18
<PAGE>

release or other public disclosure prior to its release and shall be provided
with a final copy thereof promptly following the release thereof).

     11.14  CONSTRUCTION. The language used in this Agreement will be deemed to
be the language chosen by the parties to express their mutual intent, and no
rules of strict construction will be applied against any party.

                                       19
<PAGE>

     IN WITNESS WHEREOF, the parties have caused this Agreement to be duly
executed by their respective officers hereunto duly authorized as of the date
first set forth above.

                                              AVANT IMMUNOTHERAPEUTICS, INC.

                                              By:  /s/ Una S. Ryan
                                                 -------------------------------
                                                   Name: Una S. Ryan
                                                   Title: President and CEO

                                              PFIZER INC

                                              By:  /s/ Pfizer Inc
                                                 -------------------------------
                                                   Name:
                                                   Title:

                                       20

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