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                                                                     EXHIBIT 4.8

                            Collaboration Agreement



                             Dated August 9, 1999



                      Between Human Genome Sciences Inc.



                                      And



                     Cambridge Antibody Technology Ltd./1/


/1/  [***] indicates that text has been deleted, which is subject to a
     confidential treatment request. This text has been filed with the SEC on a
     supplemental basis.
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                            COLLABORATION AGREEMENT

This Collaboration Agreement (the "Agreement") is made this 9/th/ day of August
1999 ("Effective Date") by and between Cambridge Antibody Technology, Ltd.,
("CAT") an English corporation having its registered office at The Science Park,
Melbourn, Cambridgeshire SG8 6JJ, United Kingdom and Human Genome Sciences Inc.
("HGS") a Delaware corporation having its principal offices at 9410 Key West
Avenue, Rockville, Maryland, United States of America.

WHEREAS, CAT is a leader in the field of rapid human antibody discovery,
engineering and other related activities in the use of antibodies for target
validation, drug design, and the development of proprietary therapeutic
products.

WHEREAS, HGS is a leader in the field of high throughput gene discovery and
cloning and other related activities leading to the discovery and development of
novel drugs.

WHEREAS CAT and HGS wish to collaborate upon the terms and conditions as set out
in this Agreement.

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

ARTICLE 1 - DEFINITIONS

1.01  As used throughout this Agreement, the following words and phrases shall
      have the meanings ascribed to them in Sections 1.01 through 1.44.

1.02  "Affiliate(s)" means any corporation, company, partnership, joint venture
      and/or firm which controls, is controlled by or is under common control
      with a Party. "Control" means (a) in the case of corporate entities,
      direct or indirect ownership of at least fifty percent (50%) of the stock
      or shares entitled to vote for the election of directors; and (b) in the
      case of non-corporate entities, direct or indirect ownership of at least
      fifty percent (50%) of the equity interest with the power to direct the
      management and policies of such non corporate entities.

1.03  "Antibody or Antibodies" means a molecule or a gene encoding such a
      molecule comprising or containing one or more immunoglobulin variable
      domains or parts of such domains or any existing or future fragments
      variants modifications or derivatives thereof.

1.04  "Antigen(s)" means [***] or any future antigen selected by HGS pursuant to
      Article 20.

1.05  "BLA" means a Biologic License Application, or other application approving
      the marketing of Licensed Product, which is submitted to the FDA or its
      equivalent application in a Major Market.

1.06  "CAT Background IP" means Patent Rights, Know-How and Material which CAT
      owns
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       or which CAT is licensed to use which directly relate to the Target
       Antibodies at the Effective Date or Improvements which CAT owns after the
       Effective Date which directly relate to the Target Antibodies.

1.07   "CAT Antibody Patents" shall mean (1) the Winter II Patent Rights
       (European Patent Number (EPO368684/PCT/GB89/01334) and its US equivalents
       namely the Winter/Lerner Applications (US Numbers 07/933,958, 07/933,959,
       07/941,761, 07/941,762) and their European equivalents and (2) the
       McCafferty Patents Rights (European Patent Number
       EPO584877B1/PCTGB91/01134) and U.S. equivalents, and (3) the Griffiths
       Patent Rights (US Number 5,885,793) and its European equivalents all
       licensed to CAT pursuant to the license agreement dated January 7, 1997
       between CAT and the Medical Research Council ("MRC").

1.08   "CAT's Third Party Royalty Obligations" means all Royalties payable by
       CAT under license agreements with third parties as of the Effective Date
       and which cover activities conducted by CAT under the Research Programme
       including but not limited to the agreements set out in Appendix B.

1.09   "Clinical Development Antibody" means a Target Antibody which has
       achieved In-Vivo Proof of Concept within the Time Line.

1.10   "Clinical Indication" means an area of treatment of a condition in the
       Disease Area. Examples of Clinical Indications are, without limitation:
       [***].

1.11   "Competing Antibody Product" means a human Antibody owned or licensed by
       HGS or a third party which achieves In-Vivo Proof of Concept and which is
       directed to a given Target.

1.12   "Confidential Information" means any scientific, technical, trade or
       business information disclosed by one Party to the other Party which is
       (a) disclosed in writing or other tangible form and labeled
       "CONFIDENTIAL" at the time of disclosure or (b) disclosed verbally and
       identified as confidential at the time of disclosure and subsequently
       summarized and confirmed in writing as confidential within twenty (20)
       days of such oral disclosure. "Confidential Information" does not include
       information which (a) was known to the receiving Party at the time it was
       disclosed, other than by previous disclosure by the disclosing Party, as
       evidenced by written records at the time of disclosure; (b) at the time
       of disclosure or later becomes publicly known under circumstances
       involving no breach of this Agreement; (c) is lawfully and in good faith
       made available to the receiving Party by a third party who did not derive
       it from the disclosing Party and who imposes no obligation of confidence
       on the receiving Party; (d) is developed by the receiving Party
       independent of any disclosure by the disclosing Party, as evidenced by
       the receiving party's written records or (e) is required by law or
       regulation to be disclosed.

1.13   "Development Plan" means a detailed Report prepared by HGS pursuant to
       Clause 11 in
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       respect of each Clinical Development Antibody which contains estimated
       timelines for the development and commercialisation of a Licensed Product
       together with the dates by which HGS believes in good faith it can: (i)
       initiate Phase I / IIa clinical trials, (ii) initiate Phase III clinical
       trials, and (iii) file a BLA in a Major Market ("the HGS Milestones").

1.14   "Diagnostic Licensed Products" means any product in the form of a device
       compound kit or service with utility in the diagnosis prognosis
       prediction or monitoring of progress of a disorder (1) incorporating part
       of at least one variable region of a Target Antibody or (2) whose
       biological activity was identified by a Target Antibody and whose
       potential medical utility was first demonstrated by a Target Antibody.

1.15   "Disease Areas" mean (a) Malignant disease of cells of a [***], (b)
       Nonmalignant disease of cells of the [***], (c) Malignant disease of
       cells of the [***] and (d) Nonmalignant disease of cells of the [***].

1.16   "FDA" means the United States Food and Drug Administration or any
       successor United States governmental agency or any other foreign
       governmental agency performing similar regulatory functions with respect
       to pharmaceutical Licensed Products in a Major Market.

1.17   "Field" means any human therapeutic or diagnostic use.

1.18   "First Commercial Sale" means the first sale or other disposition for
       value of the Licensed Products, in a final dosage form, to an independent
       third party following regulatory approval. The term "First Commercial
       Sale" shall not include sales and disposals for experimental purposes or
       for purposes of clinically or otherwise testing any Licensed Product.

1.19   "FTE" shall mean a full time equivalent employee assigned to the Research
       Programme.

1.20   "HGS Background IP" means Patent Rights, Know-How and Material which HGS
       owns or which HGS is licensed to use which directly related to the Target
       at the Effective Date.

1.21   "HGS Know-How" means all unpatented information, whether or not
       patentable, relating to Materials, methods, processes, techniques and
       data for the development, manufacture, use or sale of the Target, Target
       Antibodies or Licensed Product which is known to HGS or developed
       independently by HGS or received by HGS from a third party and not from
       CAT at any time during the Term of this Agreement and which HGS if free
       to transfer or disclose without violating contractual obligations to any
       third party.

1.22   "Improvement" means any improvements, modifications and adaptations
       (whether patentable or otherwise) to any party of either CAT Background
       IP or HGS Background IP which may arise in connection with performance of
       the Research Programme. It is recognized and agreed that a Target
       Antibody or Clinical Development Antibody and any improvements,
       modifications or adaptations to such Antibody will not be considered
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       Improvements for the purposes of this Agreement.

1.23   "In-Vivo Proof of Concept" means an objective demonstration of the
       efficacy of a Target Antibody as agreed by the JMC. In respect of Target
       1 it means demonstration of the efficacy of a Target Antibody in an
       animal model which has been specified by HGS and agreed not later than
       [***] from the Effective Date.

1.24   "Management Committee" means the Joint Management Committee established
       pursuant to the terms of Article 4.

1.25   "Know-How" means all unpatented information, whether or not patentable,
       relating to materials, methods, processes, techniques and data for the
       development, manufacture, use or sale of the Target, Target Antibodies or
       Licensed Product which is known to a Party and which a Party is free to
       transfer or disclose without violating contractual obligations to any
       third party.

1.26   "Licensed Product(s)" means Therapeutic Licensed Products, Therapeutic
       Antibody Licensed Products and Diagnostic Licensed Products.

1.27   "Insolvency Event" in relation to either Party, means any one of the
       following: (i) a notice shall have been issued to convene a meeting for
       the purpose of passing a resolution to wind up that Party or such a
       resolution shall have been passed other than a resolution for the solvent
       reconstruction or reorganisation of the Party of for the purpose of
       inclusion of any part of the share capital of that Party in the Official
       List of the London Stock Exchange or in the list of the American Stock
       Exchange or quotation of the same on the National Association of
       Securities Dealers Automated Quotation System; or (ii) a resolution shall
       have been passed by that Party's directors to seek a winding up or
       administration order or a petition for a winding up or administration
       order shall have been presented against that Party or such an order shall
       have been made; or (iii) a receiver, administrative receiver, receiver or
       manager, interim receiver, custodian, sequestrator or similar officer is
       appointed in respect of that Party or over a substantial part of its
       assets or any third party takes steps to appoint such an officer in
       respect of that Party of an encumbrance takes steps to enforce or
       enforces its security; or (iv) a proposal for a voluntary arrangement
       shall have been made in relation to that Party under Part I Insolvency
       Act 1986; or (v) a step or event shall have been taken or arisen outside
       the United Kingdom which is similar or analogous to any of the steps or
       events listed at (i) to (iv) above; or (vi) that Party takes any step
       (including starting negotiations) with a view to readjustment,
       rescheduling or deferral of any part of that Party's indebtedness, or
       proposes or makes any general assignment, composition or arrangement with
       or for the benefit of all or some of that Party's creditors or makes or
       suspends or threatens to suspend making payments to all or some of that
       Party's creditors of the Party submits to any type of voluntary
       arrangements; or (vii) where that Party is resident in the United Kingdom
       it is deemed to be unable to pay its debts within the meaning of Section
       123 Insolvency Act 1986.
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1.28   "Major Market" means United States, European Community, France, Italy,
       Germany, the United Kingdom or Japan.

1.29   "Material" means any chemical or biological substance, including but not
       limited to any: (a) organic or inorganic chemical element or compound;
       (b) nucleotide or nucleic acid sequence, including DNA and RNA sequences,
       derived by natural or synthetic means; (c) gene; (d) vector or construct,
       including but not limited to plasmids, phagemids, phages or viruses; (e)
       host organism, including bacteria, fungi, algae, protozoa and yeast; (f)
       other genetic material or micro-organism; (g) gene product, including but
       not limited to any peptide or amino acid sequence, protein, enzyme or
       antibody and any fragment thereof conferring targeting properties in
       vitro and/or in vivo; (h) eukaryotic or prokaryotic cell line or
       expression system or any development strain or produce of that cell line
       or expression system; (i) Antibody or Antibody producing cell line,
       including hybridomas; (j) drug or pro-drug; or (k) assay or reagent.

1.30   "Net Sales" means the amounts invoiced on the sales of Licensed Product
       or Non-Antibody Product by HGS, its sublicencees and Affiliates to
       independent, unrelated third parties in bona fide arms length
       transactions, less the following deductions properly documented actually
       allowed and taken by such third parties and not otherwise recovered by or
       reimbursed by HGS, its Affiliates or sublicencees: (a) trade, cash and
       quantity discounts, including charge backs; (b) taxes on sales (such as
       sales or use taxes) to the extent added to the sales price and set forth
       separately as such in the total amount invoiced; (c) freight, insurance
       and other transportation charges to the extent added to the sales prices
       and set forth separately as such in the total amount invoiced; (d)
       amounts repaid or credited by reason of rejections, defects or returns,
       or because of retroactive price reductions, or due to governmental laws
       or regulations requiring rebates; (e) import duties; and means further
       the amount of fair market value of all other consideration received by
       HGS, or its sublicencees or Affiliates in respect of the Licensed Product
       or Non-Antibody Product, whether such consideration is in cash, payments
       in kind, exchange or other forms; but does not mean sales of the Licensed
       Product or Non-Antibody Product between or among HGS and its sublicencees
       and/or Affiliates. In the event a Licensed Product or Non-Antibody
       Product is sold in combination with other active components ("Combination
       Licensed Products"), Net Sales for purposes of royalty payments on the
       Combination Licensed Products shall be calculated by multiplying the Net
       Sales of the Combination Licensed Product by the fraction A/(A+B), where
       A is the gross selling price of the Licensed Product sold separately
       (i.e. without the other active components) and B is the gross selling
       price of the other active components. In the event that no such separate
       sales are made Net Sales for royalty payments shall be calculated by
       multiplying Net Sales of the Combination Licensed Product by C/(C+D)
       where C is the fully allocated cost of the Licensed Product (not
       including the other active components) and D is the fully allocated cost
       of such other active components such costs being determined using
       generally accepted accounting procedures consistently applied.

1.31   "Non-Antibody Product" means any product in whatever form (including
       without limitation bulk active formulated or unformulated bulk, final or
       packaged and final
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       labelled forms) for any human therapeutic or diagnostic use which is not
       a Licensed Product or a Competing Antibody Product.

1.32   "Patent Rights" means patent applications or patents, author
       certificates, inventor certificates, utility certificates, improvement
       patents and models and certificates of addition, and all foreign
       counterparts of them and includes divisions renewals continuations,
       continuations-in-part, extensions, reissues, substitutions,
       confirmations, registrations revalidation or additions of or to them as
       well as any supplementary protection certificate or any other post patent
       expiry extension of patent protection in respect of them.

1.33   "Research Programme" shall have the meaning set forth in Article 2 with
       respect to the research and development done with respect to each Target.

1.34   "Research Programme IP" means all Patent Rights and Know-How that arises
       under the Research Programme.

1.35   "Research Programme Support Payment" shall mean the payments made by HGS
       to CAT in support of the Research Programme.

1.36   "Target" shall mean the Antigen(s) for which CAT and HGS have agreed to
       conduct a collaborative Research Programme pursuant to Article 2 of this
       Agreement.

1.37   "Target Antibodies" means an Antibody or Antibodies derived under the
       Research Programme to the Target.

1.38   "Target 1" shall mean [***].

1.39   "Target 2" and "Target 3" means the Target(s) corresponding to each
       subsequent Antigen designated by HGS pursuant to Clause 20 of the
       Agreement.

1.40   "Technical Performance Criteria" means for Target 2 and Target 3 such
       Technical Performance Criteria as shall be agreed by the JMC in respect
       of each such Target.

1.41   "Time Line" means the period agreed by the JMC by which the Clinical
       Development Antibody shall be completed. In respect to Target 1 it shall
       be 12 months from the Effective Date.

1.42   "Term" means the term of this Agreement under Article 18.

1.43   "Therapeutic Antibody Licensed Products" means all products in whatever
       form (including without limitation bulk active, formulated or
       unformulated bulk, final or packaged, and final labelled forms) for any
       human therapeutic incorporating part of at least one variable region of a
       Target Antibody.
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1.44  "Therapeutic Licensed Products" means all products in whatever form
      (including without limitations bulk active, formulated or unformulated
      bulk, final or packaged, and final labeled forms) for any human
      therapeutic whose biological activity was identified by a Target Antibody
      and whose potential medical utility was first demonstrated by a Target
      Antibody.

ARTICLE 2 RESEARCH PROGRAMME

2.01  CAT and HGS will conduct collaborative research and development with
      respect to Target 1 and to each subsequent Target designated pursuant to
      Clause 20 ("the Research Programme").

2.02  Each Party will mutually disclose all information concerning Target
      Antibodies and the Target, which is necessary for each to perform their
      duties under the Research Programme, including information relating to
      selection, derivation and assays relating to Target Antibodies and the
      Target as developed under the Research Programme. HGS shall specify the
      animal model for demonstration of In-Vivo Proof of Concept in respect of
      Target 1 not later than [***] after the Effective Date. HGS shall specify
      the animal model for demonstration of In-Vivo Proof of Concept in respect
      of Targets 2 and 3 by a date to be agreed by the JMC.

2.03  The Parties will establish a Joint Management Committee ("JMC") pursuant
      to Article 4 and each Party shall fund its own costs of the Research
      Programme. The Parties will collaborate and if required by the JMC
      employees will work with employees of the other Party at that Party's
      premises.

2.04  The purpose of the Research Programme will be to generate diverse panels
      of Target Antibodies and to use them to explore in vivo and in vitro
      biological characteristics and disease association of the Target and to
      generate a lead Target Antibody for pre-clinical and subsequent
      development of a Clinical Development Antibody.

2.05  The parties shall use reasonable efforts to fulfill their obligations as
      set out in Exhibit A to develop a Clinical Development Antibody and in
      respect of Targets 2 and 3 to meet any applicable Technical Performance
      Criteria in respect of Targets 2 and 3.

ARTICLE 3 PRE-CLINICAL DEVELOPMENT

3.01  After the development of a Clinical Development Antibody HGS shall be
      solely responsible for all further pre-clinical development costs. If HGS
      requires additional work to be done by CAT with respect to a Clinical
      Development Antibody on terms to be mutually agreed by the JMC CAT agrees
      to perform such work and HGS agrees to reimburse CAT for its costs at the
      rate of [***] per FTE for Target 1. For Targets 2 and 3 the FTE rates
      shall be mutually agreed.

ARTICLE 4 JOINT MANAGEMENT COMMITTEE
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4.01  Promptly after the Commencement Date, the Parties shall establish a JMC
      which shall oversee the Research Programme and supervise all other aspects
      of the collaboration hereunder. Certain specific functions of the JMC are
      as follows:

      (a)  to design a work plan for each Target Antibody including performance
      criteria in respect of any further Antigens selected pursuant to Clause 20
      ("Technical Performance Criteria") and to select the Time Line, the
      appropriate definition of In-Vivo Proof of Concept for Targets 2 and 3 and
      any Clinical Indications;
      (b)  allocate the work between the Parties and, if appropriate, third
      parties; oversee the performance of the Research Programme and monitor
      progress against the timetables of each Target;
      (c)  hold review meetings on progress in the Research Programme not less
      than once every three calendar months and at any time upon the mutual
      agreement of both Parties;
      (d)  provide a written report on the progress of the Research Programme
      once every three months to HGS and CAT management;
      (e)  identify any patentable inventions or other intellectual property
      requiring protection arising out of the Research Programme;
      (f)  amend the Research Programme from time to time as may be necessary or
      desirable; and
      (g)  determine when the obligations of Parties in respect of the Research
      Programme have been carried out and when that Research Programme is
      completed.

4.02  The JMC shall be established and run by the Parties as follows:

      (a)  the JMC shall be comprised of four persons ("Members") and HGS and
      CAT shall each be entitled to appoint two Members, to remove any Member
      appointed by it and to appoint any person to fill a vacancy arising from
      the removal or retirement of such Member;
      (b)  HGS and CAT shall each notify the other in writing of the identities
      of their Members from time to time. Both Parties shall use reasonable
      endeavours to keep the same Members on the JMC throughout the duration of
      the Research Programme;
      (c)  the quorum for meeting of the JMC shall be two Members, provided that
      there is at least one Member from each of HGS and CAT present;
      (d)  the JMC shall meet promptly after the Commencement Date. The venue
      for all meetings shall be agreed in advance and will generally alternate
      between the U.K. and U.S.A., unless audio and video conferences are used.
      Each Party shall be responsible for its own expenses, including travel and
      accommodation costs incurred in connection with JMC meetings;
      (e)  the Minutes of each meeting shall be kept, approved by the JMC and
      distributed to the Parties. The JMC shall appoint a secretary for each
      meeting who need not be a member of the JMC. Such appointment shall
      alternate between CAT and HGS. The Secretary shall provide an agenda seven
      days prior to the meeting and circulate minutes of the meeting within
      fourteen days after the meeting.

4.03  Decisions of the JMC shall be made by unanimous agreement of all the
      Members present at the meeting at which there is a quorum. If agreement
      cannot be reached then the
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      Parties shall discuss the position in good faith in an effort to resolve
      their differences. If it is not possible to obtain agreement, then either
      Party may require that the outstanding matters requiring resolution shall
      be deferred to the CEOs of the Parties (or their nominees) for resolution,
      who together shall use reasonable efforts to resolve such matters
      promptly.

ARTICLE 5 INTELLECTUAL PROPERTY OWNERSHIP

5.01  Nothing in this Agreement transfers or licenses any right, title or
      interest to CAT Background IP or HGS Background IP save as expressly set
      out herein.

5.02  Any and all Research Programme IP shall be owned by HGS from the moment of
      its development or other origination, and CAT hereby assigns and will
      assign any and all rights, title and interest in Research Programme IP to
      HGS.

5.03  Provided however that any and all Improvements shall be owned by the Party
      who owns the underlying technology to which the Improvements are made
      regardless of which Party makes the Improvement.

ARTICLE 6 GRANTS, RESERVED RIGHTS AND EXCLUSIVITY

6.01  CAT grants to HGS a royalty free non-exclusive worldwide license under the
      CAT Background IP solely to carry out the Research Programme.

6.02  CAT grants to HGS an option ("the Option") to a world-wide royalty bearing
      exclusive sub-licensable license under the CAT Background IP to develop,
      make, have made, use and have used, import, sell and have sold Licensed
      Product for use in the Field. Subject to 6.03 if CAT develops a Clinical
      Development Antibody then HGS shall exercise its option provided that HGS
      had paid the Research Programme Support Payment pursuant to Article 7.
      However if (1) CAT does not develop a Clinical Development Antibody or (2)
      if HGS has not exercised its Option within the Time Line then the Option
      shall lapse.

6.03  In the event the [***] then there shall be no obligation for the parties
      to be exclusive to each other and in the event that HGS does not exercise
      its Option then the obligations of Article 11 shall not apply.

6.04  Subject to Clause 6.03 if CAT develops a Clinical Development Antibody
      then neither party shall develop Antibodies against the Target for the
      Clinical Indication identified by the JMC in the In-Vivo Proof of Concept
      with any third parties and shall be exclusive to each other in the future
      development and commercialisation of Target Antibodies to that Target for
      the Clinical Indication identified by the JMC.

6.05  Subject to Clause 6.03 if CAT develops a Clinical Development Antibody
      then both parties shall use their good faith effort to assess whether the
      Clinical Development Antibody may be appropriate for a different Clinical
      Indication pursuant to the provisions
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      of Clause 3.01. In the event that the [***] then the parties shall have no
      obligation to be exclusive to each other in respect of the development and
      commercialization for that different Clinical Indication. In assessing
      whether a Competing Antibody Product performs better the JMC shall base
      its decision on objective criteria such as [***] of the Clinical
      Development Antibody and the Competing Antibody Product as deemed
      appropriate. If the JMC cannot agree within [***] they shall refer the
      decision to the Chief Executive Officers of the parties or their appointed
      representative. If they cannot agree within [***] from the referral to the
      CEOs then the parties shall appoint an expert whose decision shall be
      binding on both the parties.

6.06  In the event a Clinical Development Antibody does not achieve a mutually
      agreed pre-defined clinical endpoint and HGS stops development of the
      Clinical Development Antibody in that Clinical Indication then HGS's
      license shall be converted to a non-exclusive license and the parties
      shall no longer be exclusive to each other in respect of that Clinical
      Development Antibody in that Clinical Indication.

6.07  HGS grants to CAT a royalty free non exclusive worldwide license under the
      HGS Background IP and Research Programme IP solely to carry out the
      Research Programme for the benefit of HGS.

6.08  Except for the research right granted under 6.01 HGS shall have the right
      to sublicense any and all of the rights provided that it shall notify CAT
      within [***] of the grant of any sublicense and that HGS shall not have
      the right to sublicense the right to select or engineer Target Antibodies.

ARTICLE 7 RESEARCH PROGRAMME SUPPORT, ROYALTIES AND MILESTONES

7.01  HGS shall pay to CAT a Research Programme Support Payment which in respect
      of Target 1 shall be [***] for the support required to fulfil its
      obligations, deemed equivalent to at least [***] FTEs. Payment shall be
      made in advance on a monthly basis for the first [***] from the Effective
      Date at a rate of [***] per month. Thereafter the balance due shall be
      payable [***].

7.02  In the event that HGS in its sole discretion notifies CAT that it wishes
      to designate a Target Antibody candidate as a Clinical Development
      Antibody at any time prior to achievement of In-Vivo Proof of Concept HGS
      shall pay CAT the balance of any unpaid Research Programme Payment
      Support. In no event shall CAT receive more than [***] by operation of
      this clause.

7.03  CAT shall have the sole responsibility for payment, and shall pay all of
      CAT's Third Party Royalty Obligations owed on Licensed Products under this
      Agreement.

7.04  HGS shall pay to CAT the following milestones with respect to Therapeutic
      Licensed Products and Therapeutic Antibody Licensed Products for the
      following events in a
<PAGE>

      Major Market:

          -  Initiation of the first Phase I/IIa clinical trial   [***]
          -  Initiation of the first Phase III clinical trial     [***]
          -  Filing of a BLA for the first Clinical
             Indication in the first Disease Area                 [***]
          -  Approval by the FDA of the first Clinical
             Indication in the first Disease Area                 [***]
          -  Approval by the FDA of a Clinical
             Indication in a second Disease Area                  [***]

      HGS shall pay to CAT royalty payments of [***] of Net Sales of Therapeutic
      Antibody Licensed Products by HGS or its Affiliates or sublicensees. HGS
      shall pay to CAT royalty payments of [***] of Net Sales of Therapeutic
      Licensed Products by HGS or its Affiliates or sublicensees.

7.05  If the parties agree that royalties should be paid to third parties other
      than CAT's Third Party Royalty Obligations to practise or have practised
      the technology claimed in the CAT Antibody Patents such royalties will be
      borne equally by HGS and CAT and HGS shall be able to offset its share of
      such third party royalties against the royalties owed to CAT under Clause
      7.04 provided however that the royalties payable to CAT on Therapeutic
      Antibody Licensed Products pursuant to Clause 7.04 shall not be reduced
      below [***] of Net Sales in any year for which a royalty is owed to CAT.
      It is agreed and acknowledged that the provisions of this section shall
      not apply to third party royalty payments outside the scope of the CAT
      Antibody Patents nor shall it apply to royalties payable in respect of
      Therapeutic Licensed Products, Diagnostic Licensed Products or Non-
      Antibody Products.

7.06  HGS shall pay to CAT the following milestones with respect to Diagnostic
      Licensed Products for the following events in a Major Market:

      -    Filing of PMA or 510k               US$ [***]
      -    Approval by the FDA                 US$ [***]

7.07  HGS shall pay to CAT royalty payments in respect of Net Sales of
      Diagnostic Licensed Products equal to the amount of [***].

7.08  Subject to Clause 7.04 in the event that HGS, its affiliates or
      sublicensees require additional licenses from third parties in order to
      develop manufacture or commercialise a Licensed Product or a Non-Antibody
      Product any consideration or royalties payable shall be the sole
      responsibility of HGS, its Affiliates or Sublicensees and shall not be
      creditable against any royalty or other payments due to CAT under this
      Agreement.

7.09  All royalties shall be payable until the later of 10 years from the date
      of the First Commercial Sale or until the expiry of the last of the
      patents in the CAT Background IP
<PAGE>

      which patents would be infringed by a Licensed Product.

ARTICLE 8 PAYMENTS

8.01  HGS shall make payments to CAT with respect to the sale of Licensed
      Product by HGS, its sublicensees and its affiliates, on a country-by-
      country basis, commencing six months after the First Commercial Sale and
      to continue every six months thereafter. Such payments shall be due forty-
      five days after the close of each six month period.

8.02  Each payment or credit shall be accompanied by a report setting forth the
      calculations of the amounts to be paid or credited on a country-by-country
      basis.

8.03  All payments shall be in United States dollars. Payments due on Net Sales
      made in currency other than United States dollars shall first be
      calculated in the foreign currency and then converted to United States
      dollars on the basis of the monthly average exchange rate for the
      preceding six months in effect in the purchase of United States dollars
      with such foreign currency as set forth in the Key Currency Cross Rates
      Tables of the Wall Street Journal (or comparable publication if not quoted
      in the Wall Street Journal) with respect to the currency of the country of
      origin of such payment prior to the date of payment.

8.04  HGS shall maintain true and complete books of account for a period of 3
      years containing an accurate record of all data necessary for the proper
      computation of payments due from it or charges made by it under this
      Agreement.

8.05  Upon request by CAT, HGS agrees to make such books of account available,
      upon reasonable notice and at reasonable times, for inspection by an
      independent Certified Public Accounting firm which is acceptable to both
      parties. Such inspection may take place at any time within 3 years after
      the date of payment or charges to which they relate (but not more than
      once in each calendar year) for the sole purpose of verifying the amount
      of such payments or charges and the accuracy of such books of account.

8.06  The fees and expenses of the audit shall be borne by CAT, unless a net
      discrepancy of more than [***] in CAT's favor is discovered in which case
      HGS shall bear the fees and expenses. If any such audit shows any
      underpayment or overpayment, a correcting payment or credit, respectively,
      shall be made within thirty days after receipt of the written statement of
      the audit.

8.07  Any income or other tax that HGS, its Affiliates or sublicensees are
      required by law to withhold and pay on behalf of CAT with respect to
      Royalties paid to CAT under this Agreement shall be deducted from said
      Royalties prior to remittance to CAT; provided however, that in regard to
      any such tax so deducted, HGS, its Affiliates or sublicensees shall give
      or cause to be given to CAT such assistance as may reasonably be necessary
      to enable CAT to claim exemption therefrom or credit therefor, and in each
      case shall furnish CAT proper evidence of such taxes paid on its behalf.
<PAGE>

8.08 All payments made to CAT under the Agreement shall be made to the account
     of Cambridge Antibody Technology Limited at [***] by telephonic transfer.

8.09 If HGS fails to make any payments to CAT hereunder within 15 days on the
     due date for payment, without prejudice or any other right or remedy
     available to CAT, CAT shall be entitled to charge HGS interest (both before
     and after judgement) on the amount unpaid at the rate or LIBOR [***]
     calculated on a daily basis until payment in full is made without prejudice
     to CAT's right to receive payment on the due date.

ARTICLE 9  LIABILITY

9.01 Each Party (the "Indemnifying Party") shall be responsible for and
     indemnify the other Party and its Affiliates and their officers, servants
     and agents (collectively the "Indemnified Party") against any and all
     liability, loss, damage, cost or expense incurred or suffered by the
     Indemnified Party as a result of a claim that use of any Licensed Product
     or Non-Antibody Product supplied or made available by the Indemnifying
     Party has caused death or bodily injury except where the claim arises
     through the negligence or intentional wrongdoing of the Indemnified Party.
     An Indemnified Party that intends to claim indemnification under this
     Clause shall promptly notify the Indemnifying Party of any claim, loss,
     damage, or expense in respect of which the Indemnified Party intends to
     claim indemnification reasonably promptly after the Indemnified Party
     becomes aware of its claim.  The Indemnifying Party shall assume the
     defense of any related third-party action, suit or proceedings with counsel
     mutually satisfactory to the Parties; provided, however, that an
     Indemnified Party shall have the right to retain its own counsel with the
     fees and expenses to be paid by the Indemnifying Party, if representation
     of that Indemnified Party by the counsel retained by the Indemnifying Party
     would be inappropriate due to actual or potential differing interests
     between the Indemnified Party and any other party represented by that
     counsel in the proceedings.  The indemnity in this Clause shall not apply
     to amounts paid in settlement of any claim, loss, damage or expense if that
     settlement is effected without the consent of the Indemnifying Party, which
     consent shall not be unreasonably withheld.  The failure of an Indemnified
     Party to deliver notice to the Indemnifying Party within a reasonable time
     after becoming aware of any claim, loss, damage or expense in respect of
     which it intends to claim indemnification under this Clause, if prejudicial
     to the Indemnifying Party's ability to defend the action, shall relieve the
     Indemnifying Party of any liability to the Indemnified Party under this
     Clause.  The Indemnifying Party shall not have any liability to any
     Indemnified Party otherwise than under this Clause.  The Indemnified Party
     and its employees and agents shall cooperate fully with the Indemnifying
     Party and its legal representatives in the investigation of any matter
     covered by this indemnification.

9.02 Neither Party shall be liable to the other in contract, tort, negligence,
     breach of statutory duty or otherwise for any economic loss or other loss
     or turnover, profits, business or goodwill or any loss, damages, costs or
     expenses of any nature whatsoever incurred or suffered by the other or its
     Affiliates of an indirect or consequential nature arising out of or in
     connection with this Agreement.
<PAGE>

9.03 The maximum limit of CAT's liability under this Agreement shall be the
     amounts paid by HGS to CAT hereunder provided however that this clause will
     not be applicable if CAT receives a licence from HGS pursuant to the
     provisions of Clause 11.03.

9.04 During the term of this Agreement and for a period of [***] following the
     expiration or earlier termination of this Agreement HGS shall maintain
     adequate liability insurance, including Licensed Product liability and
     contractual liability insurance each with coverage of [***] for each claim
     and in the aggregate to cover HGS's obligations under this Agreement.  Such
     insurance cover shall be maintained with a nationally recognised insurance
     carrier reasonably acceptable to CAT.

ARTICLE 10 CONFIDENTIALITY

10.01 The receiving party will retain all of the Confidential Information in
          confidence during the term of this Agreement and for a period of five
          years after termination of this Agreement and will not, without the
          prior written permission of the other party or pursuant to Article 10
          hereof, disclose it to third parties, or use it for any purpose other
          than in accordance with the terms of this Agreement.

10.02 Each party shall have the right to disclose to others Confidential
          Information to the extent such disclosure is reasonably necessary, in
          filing or prosecuting patent applications, prosecuting or defending
          litigation, complying with governmental regulations, conducting
          preclinical or clinical trials, or seeking approval from or complying
          with the FDA, provided that if a party is required to make any non-
          confidential disclosure of the other party's Confidential Information,
          the disclosing party will give reasonable advance notice to the other
          party of such disclosure requirement, and will use reasonable efforts
          to secure confidential treatment of such Confidential Information
          required to be disclosed.

ARTICLE 11 DUE DILIGENCE

11.01 Subsequent to the development of a Clinical Development Antibody HGS will
          prepare and deliver a Development Plan to CAT. HGS will use reasonable
          efforts to meet the HGS Milestones set out in the Development Plan and
          to develop marketable Licensed Products of good merchantable quality,
          including reasonable efforts to develop Licensed Products in multiple
          Clinical Indications of a Disease Area, and to bring those Licensed
          Products to market within the time set out in the Development Plan and
          to satisfy market demand for those Licensed Products.

11.02 Subsequent to the development of a Clinical Development Antibody if HGS
          its Affiliate or sublicensee does not file an application with the FDA
          for permission to test in humans (or where a filing is not required
          has not initiated human Clinical trials) and HGS its Affiliates or
          sublicensees by itself or with a third party develops a Non-Antibody
          Product which is a competing antagonist of [***] action in a Clinical
          Indication then HGS shall pay to CAT the following milestone payments:
<PAGE>

          -  Initiation of the first Phase III clinical trial    US$[***]
          -  Filing for approval of a BLA in the first Clinical
             Indication                                          US$[***]
          -  Approval of the first Clinical Indication           US$[***]
          -  Approval of a Clinical Indication in
             subsequent Disease Area                             US$[***]

      In addition HGS shall pay CAT Royalties on Net Sales of Non-Antibody
      Products of [***]

11.03 If HGS (a) within [***] from the delivery of a Clinical Development
          Antibody does not file an application with the FDA for permission to
          test in humans a Licensed Product or a Non-Antibody Product in the
          field of antagonists to action of the Antigen or where a filing is not
          required has not initiated human clinical trials or (b) notifies CAT
          that it is not initiating or terminating all clinical trials in the
          field of an antagonist to a Target then the Licenses granted to HGS
          shall terminate and HGS shall grant to CAT under HGS Background IP,
          Research Programme IP and HGS Know How a world-wide royalty bearing
          exclusive sub-licensable license to develop, make, have made, use and
          have used, import, sell and have sold the Licensed Product
          incorporating such Clinical Development Antibody for use in the Field
          and provide CAT with all Material and related data to the Clinical
          Development Antibody.

11.04 If the Licenses referred to above are granted then CAT shall pay to HGS
          any future applicable milestones as set out in Article 7 and a Royalty
          of [***] on Therapeutic Licensed Products and [***] on Net Sales of
          Diagnostic Licensed Products.

ARTICLE 12 PUBLICATIONS

12.01 The parties agree that any proposed publications (including, but not
          limited to abstracts posters and the like) or public disclosure on the
          research conducted under this Agreement shall be submitted to the
          other party at least thirty days prior to submission to a journal or
          other third party. A proposed submission or disclosure shall be
          reviewed promptly; however, where necessary, submission of disclosure
          may be delayed for an additional ninety days following the initial
          thirty day period for the purposes of preparing related patent
          applications and for deleting particularly Confidential Information
          from said proposed disclosure if in the reasonable judgment of the
          other party such patent applications are considered necessary and
          disclosure would jeopardize potential protection.

ARTICLE 13 GOVERNING LAW

13.01 This Agreement shall be governed by and construed in accordance with the
          law of England.

ARTICLE 14 PATENT PROSECUTION AND INFRINGEMENT
<PAGE>

14.01 HGS shall have the sole right and responsibility, at its sole discretion
          and with reasonable assistance from CAT, for the filing of and any
          prosecution and maintenance of patents and any other rights related to
          the Research Programme IP and for the conduct of any claims or
          proceedings relating to them in all countries, including any
          interference or opposition proceedings. All applicable costs,
          including that of the patent attorneys retained by HGS, shall be the
          responsibility of HGS.

14.02 Each Party shall promptly report in writing to the other during the term
          of this Agreement any (i) known infringement or suspected infringement
          of any of the Research Programme IP or (ii) unauthorised use or
          misappropriation of the Confidential Information by a third party of
          which it becomes aware, and shall provide the other party with all
          available evidence supporting said infringement, suspected
          infringement or unauthorised use or misappropriation.

14.03 If during the term of this Agreement if a third party in any country where
          the Licensed Product is being imported, manufactured, used, or sold,
          notifies any of the Parties, their Affiliates or licensees that such
          activity infringes or is alleged to infringe any issued patent either
          assigned to or licensed to such third party, then the Party so
          notified shall promptly notify the other Party in writing.

14.04 Each Party shall co-operate with the other Party, to the extent reasonably
          requested, in any legal action brought by or against the other Party
          or both of them or against their Affiliates or sublicensees in
          connection with the making, using or selling of Licensed Product(s)
          ("Action").

14.05 HGS shall have the sole responsibility at its sole expense to defend or
          prosecute any Action. CAT shall provide all reasonable assistance in
          connection with any Action at HGS expenses (including CAT's reasonable
          attorneys' fees). If HGS finds it necessary to join CAT in such suit
          or action. CAT shall execute all papers and perform such other acts as
          may be reasonably required. Unless HGS and CAT otherwise agree any
          amount recovered in any such action or suit whether by judgement or
          settlement shall be retained by HGS. In the event HGS fails to take
          action within ninety days of learning of such infringement, CAT shall
          have the sole right, but not obligation, to bring, defend and maintain
          any appropriate suit or action involving infringement of such a patent
          by manufacture, use or sale of the Licensed Product. If CAT finds it
          necessary to join HGS in such suit or action, HGS shall execute all
          papers and perform such other acts as may be reasonably required. HGS
          may, at its option, join as a party in such suit and, at its expense,
          be represented by counsel of its choice. Unless HGS and CAT otherwise
          agree, any amount recovered in any such action or suit, whether by
          judgement or settlement, [***].

14.06 HGS shall mark the Licensed Products or Non-Antibody Products sold in the
          United States with all applicable patent numbers. All Licensed
          Products or
<PAGE>

          Non-Antibody Products shipped to and/or sold in other countries shall
          be marked and labelled in such a manner as to conform with all
          applicable laws of the country where the Licensed Products or Non-
          Antibody Products are sold.

ARTICLE 15 DISPUTE RESOLUTION

15.01 All other disputes between the Parties arising out of the circumstances
          and relationships contemplated by this Agreement including disputes
          relating to the validity, construction or interpretation of this
          Agreement and including disputes relating to pre-contractual
          representations shall be in the first instance referred to the
          respective Chief Executive Officers of the Parties. If they fail to
          agree then any dispute shall be settled by arbitration as follows:

15.02 The arbitration shall be conducted in the English language in accordance
          with the Commercial Arbitration Rules of the International Chamber of
          Commerce (ICC). The arbitration shall be conducted by one arbitrator
          chosen by mutual agreement of the parties. If the parties are unable
          to agree on an arbitrator, they shall each pick one arbitrator and the
          two arbitrators shall choose a third arbitrator. The parties will
          cooperate with each other in using the arbitration to be held in as
          efficient and expeditious a manner as practicable. Any arbitration
          proceeding instituted under this Agreement shall be brought in London,
          England if instituted by HGS and in Washington D.C. if instituted by
          CAT.

15.03 Any award rendered by the arbitrator(s) shall be final and binding upon
          the parties hereto. Judgement upon the award may be entered in any
          court of record of competent jurisdiction. Each party shall pay its
          own expenses of arbitration and the expenses of the arbitrator(s)
          shall be equally shared unless the arbitrator(s) assesses as part of
          his, her or their award all or any part of the arbitration expenses of
          one party (including reasonable attorney's fees) against the other
          party.

ARTICLE 16 WARRANTIES

16.01 Each Party represents and warrants to the others as follows:-

     (a)  HGS represents and warrants that it is a corporation, duly organised,
     validly existing and in good standing under the laws of the Delaware, and
     has all requisite corporate power and authority to execute, deliver and
     perform this Agreement.  CAT represents and warrants that it is a
     corporation, duly organised, validly existing and in good standing under
     the laws of England and Wales and has all requisite corporate power and
     authority to execute, delivery and perform this Agreement;

     (b)  This Agreement when executed and delivered by the Parties will be
     legal, valid and binding obligation of such Party, enforceable against such
     Party in accordance with its terms; and

     (c)  The execution, delivery and performance of this Agreement by either
     Party does not
<PAGE>

      conflict with, or constitute a breach or default under, (i) the charter
      documents of such party, (ii) any law, order, judgement or governmental
      rule or regulation applicable to such Party or its property, or, (iii) any
      provision of any agreement, contact, commitment or instrument to which it
      is a Party (and the execution, delivery and performance of this Agreement
      by the Party does not require the consent, approval or authorisation of,
      or notice, declaration, filing or registration with, any governmental or
      regulatory authority).

16.02 CAT represents to HGS that to the best of its belief as of the Effective
          Date the CAT Antibody Patents are the main patents required from CAT
          to operate CAT's antibody phage display technology.

ARTICLE 17 NOTICES

17.01 All notices or other communications required or permitted to be given by
          either party under this Agreement shall be in writing and shall,
          unless otherwise specifically set forth herein, be sufficiently given
          by either party when deposited in the mail, registered or certified,
          postage prepaid, or by telefacsimile, and addressed as hereinafter set
          forth or to such other addressee and/or address as or shall
          subsequently be designated by either party by notice given in
          accordance with this Section.

      To HGS:

      Human Genome Sciences

      9410 Key West Avenue

      Rockville

      Maryland

      Attn: General Counsel

      Fax (1) 301 309 8439


      To CAT:

      Cambridge Antibody Technology Ltd.

      The Science Park

      Melbourn, Cambridgeshire SG8 6JJ

      Attn:  Company Secretary
<PAGE>

      Fax: (44) 1763 263413

17.02 Either party may change the address or the recipient to which notice is to
          be provided by written notice pursuant to this Clause.

ARTICLE 18 TERM AND TERMINATION

18.01  Unless and until earlier terminated as provided in this Article this
          Agreement shall commence on the Effective Date and shall continue
          until the last to expire of the patents in the CAT Background IP which
          patents would be infringed by a Licensed Product or the expiry of ten
          years from the date of First Commercial Sale of a Licensed Product by
          HGS or its Affiliates or sublicensees (whichever is the later).

18.02  If either party breaches or defaults in the performance or observance of
          any of its material obligations under this Agreement, and such breach
          or default is not cured within 30 days after receipt by such party of
          a written notice from the non-breaching party specifying the breach or
          default (or such longer period as is reasonably necessary if the
          breach is of such a nature that it cannot be reasonably cured within
          30 days) then the non-breaching party shall have the right to
          terminate this Agreement.

18.03  If CAT has failed to provide to HGS a Clinical Development Antibody, HGS
          may terminate this agreement upon written notice to CAT. If HGS has
          failed to provide an animal model for the In-Vivo Proof of Concept
          within [***] in respect of Target 1 and within the time period as
          agreed by the JMC in respect of Target 2 and 3 or has failed to
          indicate a Clinical Indication within [***] of the Effective Date in
          respect of Target 1 and within the time period agreed by the JMC in
          respect of Target 2 and 3 then CAT may terminate this Agreement upon
          written notice to HGS provided that termination based on Target 2 or
          Target 3 shall be effective only with respect to that Target.

18.04  Either party may terminate this Agreement by written notice to the other
          party in the event the other party shall have become subject to an
          Insolvency Event.

18.05  No exercise by CAT or HGS of any right of termination shall constitute a
          waiver of any right of CAT or HGS for recovery of any monies then due
          to it hereunder or any other right or remedy may have at law, in
          equity or under this Agreement.

ARTICLE 19 CONSEQUENCES OF TERMINATION

19.01  The provisions of Articles 5 8 9 10 12 and 14 shall survive the
          termination for any reason of this Agreement.

19.02  In addition the obligation to make payments under this Agreement with
          respect to any
<PAGE>

          period prior to its termination shall survive the termination of this
          Agreement. Termination of this Agreement is to be without prejudice to
          rights of either party which have accrued and are due prior to
          termination.

ARTICLE 20 ADDITIONAL PROGRAMMES & AREAS OF EXCLUSIVITY

20.01  CAT agrees to conduct additional Research Programmes directed to 2
          further Targets in addition to the Target on behalf of HGS on the
          terms specified in this Agreement, adding the new Target(s) to the
          definition of the Antigen in Clause 1.04 and throughout this
          Agreement, and defining a Research Programme for each such Target 2
          and Target 3 pursuant to Article 2, with the following limitations:

       (a) The JMC shall agree that Target 2 and Target 3 is suitable to enter a
       Research Programme. In reaching such a determination the JMC shall give
       weight to the fact that any new Target shall meet similar criteria to the
       Antigen in terms of availability of the Antigen and relevant assay,
       supporting background biology and empirical support for an antibody based
       therapeutic intervention. In addition the JMC shall be satisfied that the
       Time Line is appropriate and that CAT is aware of any competing
       technologies that HGS has initiated or is considering initiating in
       respect of any new Target.

       (b)  CAT shall have the right to reject a proposed Target 2 or 3 within
       [***] of the date of said proposal if:

       [***]

       In the case of any Target rejected by CAT, HGS shall have a right but not
       an obligation to propose a substitute Target.

20.02  CAT shall use reasonable endeavours to commence a Research Programme
          promptly after agreement of the JMC to accept a Target.

20.03  HGS's right to initiate any subsequent Research Programme hereunder shall
          terminate [***] from the Effective Date.

20.04  Royalty payments, milestone payments and other terms for Target 2 and
          Target 3 will be as specified herein except that the set of milestone
          payments with respect to Target 2 and Target 3 shall be increased from
          the milestone payments specified herein for the Target by [***] for
          each subsequent twelve month period between the Effective Date and the
          initiation of the Research Programme directed to such subsequent
          Target.

ARTICLE 21 FORCE MAJEURE

21.01  Each of the parties hereto shall be excused from the performance of its
          obligations
<PAGE>

             (except the obligations of confidentiality and non-disclosure
             imposed in Article 10 above) hereunder in the event such
             performance is prevented by force majeure. For the purpose of this
             Agreement, force majeure is defined as follows:

       a) Strikes, lockouts, or other industrial action taken by the employees
          of any party or any third party (whether or not the party against whom
          such action is taken could have avoided the same by acceding to the
          demands of the employees responsible for such action);

       b) Civil commotion, embargo, governmental legislation or regulation,
          riot, invasion, war, threat of or preparation of war;

       c) Fire, explosion, storm, flood, earthquake, subsidence, epidemic or
          other natural physical disaster.

       If the period of force majeure extends beyond six months then this
       Agreement may be terminated by either party upon written notice.

ARTICLE 22 WAIVER AND ASSIGNMENT

22.01  The right of either party at any time to require strict performance by
          the other party hereto of all the terms and conditions hereof shall
          not in any way be affected or impaired by prior waiver, forbearance or
          course of dealing.

22.02  This Agreement shall not be assigned by either party without the prior
          written consent of the other party, such consent not to be
          unreasonably withheld, provided however that a party may assign this
          Agreement or any of its rights or obligations hereunder to any
          affiliate or to any third party with which it may merge or consolidate
          or to which it may transfer all or substantially all of its assets to
          which this agreement relates, without obtaining the consent of the
          other party, provided that the assigning party remains liable under
          this agreement and that the third party, assignee or surviving entity
          assumes in writing all of its obligations under this agreement.

22.03  This Agreement shall be binding upon any permitted assignee of either
          party.

ARTICLE 23 ANNOUNCEMENTS

23.01  Subject to Clause 23.02 no press release announcement or other
          communication to any third party concerning the transaction
          contemplated by this Agreement or the financial terms of this
          Agreement or any ancillary matters shall be made or permitted or
          authorised to be made by either Party without the prior written
          approval of the other, such approval not to be unreasonably withheld
          or delayed.

23.02  Either Party may make an announcement concerning the transactions
          contemplated by this Agreement or any ancillary matter if required by:
<PAGE>

       (a) law or regulation
       (b) existing contractual obligations; or
       (c) any Securities Exchange or Regulatory Authority or governmental body
           to which either party is subject or submits, wherever situated,
           including (without limitation) the US Securities Exchange Commission,
           The UK Stock Exchange or The Panel on Take-overs and Mergers, whether
           or not the requirement has the force of law

ARTICLE 24 MISCELLANEOUS

24.01  If any provision of this Agreement is held by a court of competent
          jurisdiction to be invalid or unenforceable, it shall be modified, if
          possible, to the minimum extent necessary to make it valid and
          enforceable or, if such modification is not possible, it shall be
          stricken and the remaining provisions shall remain in full force and
          effect; provided, however, that if a provision is stricken as to
          materially affect the economic benefits of this Agreement, the party
          adversely affected may terminate this Agreement upon sixty days prior
          written notice to the other party.

24.02  The headings set forth at the beginning of the various Articles and
          Sections of this Agreement are for reference and convenience and shall
          not affect the meanings of the provisions of this Agreement.

24.03  If so advised the parties shall co-operate in notification of this
          Agreement to the Commission of the European Community pursuant to
          Council Regulation 17/62 of the Council of Ministers of the European
          Community as soon as reasonably practicable after the Commencement
          Date. Each Party shall be responsible for its own costs and expenses
          related to such notification. Each Party will give the other full and
          prompt co-operation in providing any information which the other may
          require in order to prepare such notification.

24.04  Nothing herein shall be deemed to establish a relationship of principal
          and agent between CAT and HGS, not any of their agents or employees
          for any purpose whatsoever. This Agreement shall not be construed as
          constituting CAT and HGS as partners, or as creating any other form of
          legal association or arrangement with could impose liability upon one
          party for the act or failure to act of the other party.

24.05  Nothing contained in this Agreement shall be construed as conferring any
          right to use in advertising, or other promotional activities, any
          name, trade name, trademark, or
<PAGE>

          other designation of either party thereto.

24.06  This Agreement may be executed in multiple counterparts, each of which
          shall be deemed an original and which together shall constitute one
          and the same instrument.

IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be executed
by their duly authorized officers as of the Effective Date.

Human Genome Sciences, Inc.


By:_________________________________________________

Title:______________________________________________


Cambridge Antibody Technology Ltd.


By:_________________________________________________

Title:______________________________________________
<PAGE>

                                   EXHIBIT A


In the course of the Research Programme pertaining to the Target, the Parties
shall have the following obligations as modified from time to time by agreement
of the JMC.



                             Human Genome Sciences
                                     [***]


                         Cambridge Antibody Technology
                                     [***]
<PAGE>

                                   EXHIBIT B
                  EXISTING CAT THIRD PARTY ROYALTY OBLIGATIONS


1.   License Agreement, dated January 7, 1997, between CAT and MRC, with certain
     royalty rates, as may be amended from time to time which shall include all
     royalty payments due to The Scripps Research Institute and Stratagene
     pursuant to an agreement dated 25 June 1999 (the "MRC License").

2.   Therapeutic Antibodies Agreement, dated December 31, 1997, between CAT and
     Dyax Corp., with a royalty rate of [***], as may be amended from time to
     time (the "Dyax License").

3.   Diagnostic Antibodies Agreement, dated December 31, 1997, between CAT and
     Dyax Corp., with a royalty rate of [***], as may be amended from time to
     time (the "Dyax License").

1/   [***] indicates that text has been deleted, which is subject to a
confidential treatment request. This text has been filed with the SEC on a
supplemental basis.