<PAGE>

                                                                     EXHIBIT 4.5

THE CONFIDENTIAL PORTIONS OF THIS EXHIBIT HAVE BEEN FILED SEPARATELY WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO A CONFIDENTIAL TREATMENT REQUEST
IN ACCORDANCE WITH RULE 24B-2 OF THE SECURITIES AND EXCHANGE ACT OF 1934, AS
AMENDED. REDACTED PORTIONS OF THIS EXHIBIT ARE MARKED BY AN ***.

SHARE SALE AND PURCHASE
AGREEMENT

Relating to Ionix
Pharmaceuticals Limited

Dated ____________ 2005

The Sellers (1)

Vernalis PLC (2)

FINAL: 5 JULY 2005

<PAGE>

                                TABLE OF CONTENTS

<TABLE>
<S>                                                                           <C>
INTRODUCTION                                                                   3
OPERATIVE PROVISIONS                                                           3
1    Definitions                                                               3
2    Sale and purchase of the Shares                                          12
3    Consideration                                                            12
4    Retained Consideration Shares and Adjustment                             13
5    Conditions, Property Costs and Redundancy Costs                          15
6    Completion                                                               16
7    Sellers' Warranties                                                      17
8    Principal Warranties and Warranties generally                            18
9    Buyer Warranties                                                         18
10   Orderly Market                                                           18
11   Loans and Guarantees                                                     19
12   Protective Covenant                                                      20
13   Announcements                                                            20
14   Confidentiality                                                          21
15   Entire agreement                                                         21
16   Assignment and transfer                                                  22
17   Costs and expenses                                                       22
18   Effect of Completion                                                     22
19   Waiver                                                                   22
20   Variation                                                                22
21   Severance                                                                23
22   Further assurance                                                        23
23   Notices                                                                  23
24   Wellcome                                                                 24
25   Counterparts                                                             25
26   Governing language                                                       25
27   Governing law                                                            25
28   Jurisdiction                                                             25
29   Interpretation                                                           25
30   Rights of third parties                                                  26
31   Execution                                                                26

SCHEDULE 1                                                                    27
     Part 1: Particulars of the Company                                       27
     Part 2: Shareholders of the Company                                      27
     Part 3: Initial Consideration Shares                                     27

SCHEDULE 2                                                                    28
     Part 1: Documents which are to be delivered by the Sellers at
             Completion                                                       28
     Part 2: Documents which are to be delivered by the Buyer at Completion   28

SCHEDULE 3                                                                    29
     Part 1: Sellers' Warranties                                              29
     Part 2: Principal Warranties                                             30

SCHEDULE 4 - Buyer Warranties                                                 45

SCHEDULE 5                                                                    47
     Part 1: Limitations on Liability under the Principal Warranties          47
     Part 2: Limitations on Liability under the Sellers' Warranties and
             Buyer Warranties                                                 51
</TABLE>

<PAGE>

<TABLE>
<S>                                                                           <C>
SCHEDULE 6 - Pre Completion Covenants                                         53

SCHEDULE 7 - Completion Statement                                             56
     Part 1                                                                   56
     Part 2                                                                   56

SCHEDULE 8 - Indemnities                                                      57
     Part 1                                                                   57
     Part 2                                                                   58
     Part 3                                                                   60
</TABLE>


                                       -2-

<PAGE>

     Dated ____________ 2005

     PARTIES

(1)  THE PERSONS whose names and addresses are set out in Part 2(a) of Schedule
     1 (the "Sellers"); and

(2)  VERNALIS PLC company number 2304992 whose registered office is at Oakdene
     Court, 613 Reading Road, Winnersh, Berkshire RG41 5UA (the "Buyer").

     INTRODUCTION

(A)  The Company was incorporated in England and Wales on 16 May 2001 and is
     registered under number 04217756 as a private company limited by shares.

(B)  The Sellers have agreed to sell to the Buyer, or procure the sale to the
     Buyer (as the case may be), and the Buyer has agreed to purchase the Shares
     in consideration of the Consideration Price and otherwise in the manner and
     on and subject to the terms of this Agreement.

     OPERATIVE PROVISIONS

1    DEFINITIONS

     In this Agreement, except where a different interpretation is otherwise
     specifically required in the context, the words and expressions set out
     below shall have the following meanings:

<TABLE>
<S>                              <C>
Accounts                         the draft form of balance sheet as at the
                                 Accounts Date, and the draft form of profit and
                                 loss account for the Financial Year ended on
                                 the Accounts Date of the Company, together with
                                 the notes, reports, statements (including cash
                                 flow statements, if applicable) and other
                                 documents which are required by law to be
                                 annexed to such accounts, in each case to be
                                 audited and delivered at Completion in
                                 accordance with Schedule 2

Accounts Date                    31 December 2004

Accounts Standards               in relation to the accounts of any body
                                 corporate, the applicable requirements of the
                                 Companies Acts 1985 and 1989, together with
                                 accounting principles, standards and practices
                                 which are generally accepted in the United
                                 Kingdom, in each case as at the date of the
                                 relevant accounts or otherwise applicable at
                                 the relevant time or at the date of Completion
                                 regarding the preparation of the Completion
                                 Statement

Affiliate                        in relation to any body corporate (whether or
                                 not registered in the United Kingdom), any
                                 holding company or subsidiary of such body
                                 corporate or any subsidiary of a holding
                                 company of such body corporate in each case
                                 from time to time

this Agreement                   this agreement including the Introduction and
                                 the Schedules

Ancillary Claim                  a Property Claim and/or a Redundancy Claim, as
                                 the case may be
</TABLE>


                                       3
<PAGE>

<TABLE>
<S>                              <C>
Apax                             together Apax Europe V - A, L.P., Apax Europe V
                                 - B, L.P., Apax Europe V - C GmbH & Co. KG,
                                 Apax Europe V - D, L.P., Apax Europe V - E,
                                 L.P., Apax Europe V - F, C.V., Apax Europe V -
                                 G, C.V., Apax Europe V - 1, L.P. and Apax
                                 Europe V - 2, L.P.

Apax Loan                        the convertible loan option agreement dated 10
                                 May 2004 between the Company and Apax, as
                                 amended on 23 June 2005

Articles of Association          the articles of association of the Company
                                 adopted on 10 May 2004

Budget                           the budget and income and expenditure forecasts
                                 in the agreed form of the Company for the
                                 months of June, July and August, 2005

Business                         the business of the Company as carried on at
                                 the date hereof

Business Day                     a day other than a Saturday, Sunday or public
                                 holiday in England and Wales

Buyer Capacity Claim             a claim for breach of the Buyer Warranties

Buyer's Group                    the Buyer, any subsidiary of the Buyer, any
                                 holding company of the Buyer and any subsidiary
                                 of any holding company of the Buyer, in each
                                 case from time to time, and member of the
                                 Buyer's Group shall be construed accordingly

Buyer's Solicitors               Allen & Overy LLP, One New Change, London EC4M
                                 9QQ

Buyer's Sponsor                  JP Morgan Cazenove Limited of 20 Moorgate,
                                 London EC2R 6DA or such other sponsor as
                                 appointed by the Buyer at the relevant time

Buyer Warranties                 the warranties given by the Buyer in clause 9
                                 and Schedule 4 and each buyer warranty
                                 statement shall be a "Buyer Warranty"

Capacity Claim                   a Buyer Capacity Claim or a Sellers' Capacity
                                 Claim

Claim                            any Principal Warranty Claim, Redundancy Claim,
                                 Property Claim, Title Claim and any Seller
                                 Capacity Claim made in accordance with the
                                 terms of this Agreement and each such claim
                                 shall be a "Claim"

Company                          Ionix Pharmaceuticals Limited, short
                                 particulars of which are set out in Part 1 of
                                 Schedule 1

Completion                       completion of the sale and purchase of the
                                 Shares in accordance with the terms of clause 6

Completion Statement             the completion statement as finally agreed or
                                 determined in accordance with the provisions of
                                 Schedule 7

Conditions                       the conditions to Completion set out in clause 5
</TABLE>


                                        -4-

<PAGE>

<TABLE>
<S>                              <C>
Confidential Information         all technical, financial, commercial and other
                                 information of a confidential nature relating
                                 to the Business, including without limitation,
                                 trade secrets, know-how, inventions, product
                                 information and unpublished information
                                 relating to Intellectual Property, object code
                                 and source code of software, marketing and
                                 business plans, projections, current or
                                 projected plans or internal affairs of the
                                 Company, secret or confidential information,
                                 current and/or prospective suppliers and
                                 customers (including any customer or supplier
                                 lists) and any other person who has had
                                 material dealings with them

Consideration Price              the consideration price for the Shares stated
                                 in clause 3.1

Consultants                      those individuals who are providing services to
                                 the Company under an agreement which is not a
                                 contract of employment with the Company
                                 including, in particular, where the individual
                                 acts as a consultant or is an independent
                                 contractor on secondment, and "Consultant"
                                 shall mean any one of them

Dangerous Substance              any natural or artificial substance or thing
                                 (whether in the form of a solid, liquid, gas,
                                 vapour or any other form), which is:

                                 (a)  capable (alone or in combination) of
                                      causing harm to man or any other living
                                      organism, or capable of damaging the
                                      Environment or public health or welfare,
                                      including but not limited to controlled,
                                      special hazardous, polluting, toxic or
                                      dangerous substances and/or waste and/or
                                      radiation, electricity or heat; and/or

                                 (b)  regulated by or under Environmental Law

Deed of Assignment               a deed of assignment of the Lease together with
                                 an agreement for the sale and purchase of the
                                 Lease, a licence to assign the Lease and a
                                 notice of assignment of the Lease, in each case
                                 in the agreed form

Deferred Consideration           the sum of L5,000,000

Determined Claim                 (a)  a Principal Warranty Claim that has been
                                      determined in accordance with paragraph
                                      1.1 of Part 1 of Schedule 5;

                                 (b)  a Sellers' Capacity Claim that has been
                                      determined in accordance with paragraph
                                      1.2 of Part 2 of Schedule 5;

                                 (c)  an Ancillary Claim that has been
                                      determined in accordance with paragraph
                                      1.3 of Part 3 of Schedule 8; and

                                 (d)  a Title Claim that has been determined in
                                      accordance with paragraph 1.3 of Part 3 of
</TABLE>


                                        -5-

<PAGE>

<TABLE>
<S>                              <C>
                                      Schedule 8;

Directors                        the persons specified as directors of the
                                 Company in Part 1 of Schedule 1 (the expression
                                 "Director" meaning any of them)

Disclosure Documents             the documents attached to the Disclosure Letter
                                 as listed in the schedule annexed to the
                                 Disclosure Letter

Disclosure Letter                a letter in the agreed form from the Warrantor
                                 to the Buyer, to be dated the same date as this
                                 Agreement

Employees                        those persons (including Directors) who are
                                 employed by the Company as at the date of this
                                 Agreement, whose names appear in the list of
                                 employees included in the Disclosure Documents

Encumbrance                      any interest or equity of any person (including
                                 any right to acquire, option or right of
                                 pre-emption) or any mortgage, charge, pledge,
                                 lien, assignment, hypothecation, security
                                 interest, title retention or any licence,
                                 option, security agreement or arrangement, or
                                 any agreement to create any of the foregoing

Environment                      air (including air within buildings or other
                                 natural or man-made structures whether above or
                                 below ground), water (including surface waters,
                                 underground waters, groundwater, coastal and
                                 inland waters and water within any natural or
                                 man-made structures), land (including soil and
                                 river beds under any water, surface land and
                                 sub-surface land), buildings, structures,
                                 enclosures or other constructions, flora,
                                 fauna, man and any other living organism

Environmental Law                any and all laws, statutes, secondary and
                                 subordinate legislation, by-laws, regulations,
                                 directives, rules, codes of practice,
                                 circulars, guidance and the like, company
                                 environmental plans, codes of conduct, common
                                 law, notices, judgments, orders, decisions and
                                 interpretations of any laws by any Regulatory
                                 Authority, international and EU treaties and
                                 regulations, concerning the protection of the
                                 Environment or human health and welfare or
                                 conditions in, or in the vicinity of, the
                                 workplace or the generation, transportation,
                                 storage, treatment, disposal or presence of any
                                 Dangerous Substance

Environmental Licence            any permit, authorisation, licence (including
                                 statutory licence), consent, permission,
                                 exemption, registration or other approval
                                 required under or in relation to any
                                 Environmental Law

Estimated Completion Statement   a statement prepared by the Sellers in the same
                                 style and layout and using the same policies
                                 and practices as the statement contained in
                                 Part 2 of Schedule 7 and delivered to the Buyer
                                 on the Business Day prior to Completion
</TABLE>


                                       -6-

<PAGE>

<TABLE>
<S>                              <C>
Estimated Liability              in respect of any Claim which has not become a
                                 Determined Claim by the end of the Initial
                                 Claim Period, such estimated amount as is
                                 agreed or determined in accordance with either
                                 clause 4.2 or 4.3

Estimated Net Cash               the amount of the Net Cash as at Completion as
                                 estimated in the Estimated Completion Statement

External Cost                    any category of expenditure by the Company
                                 other than an Internal Cost

Final Issue Date                 as regards each Claim, for which Estimated
                                 Liability has been agreed or determined in
                                 accordance with either clause 4.2 or 4.3, the
                                 third Business Day following the date on which
                                 such Claim becomes a Determined Claim (if such
                                 date is later than the Second Issue Date)

Final Net Cash                   the amount of the Net Cash at Completion as
                                 determined in accordance with Schedule 7

Financial Year                   a financial year as determined in accordance
                                 with section 223 of the Companies Act 1985

First Issue Date                 the third Business Day following the first
                                 anniversary of the date of Completion

FSMA                             the Financial Services and Markets Act 2000

Independent Accountants          such firm of chartered accountants as the
                                 Sellers and the Buyer may agree in writing or
                                 failing such agreement as shall be appointed on
                                 the application of the Buyer or the Sellers by
                                 the President of the Institute of Chartered
                                 Accountants in England and Wales for the time
                                 being

Initial Claim Period             the period of 12 months following the date of
                                 Completion



Initial Consideration            the sum of L11,333,334.32 to be satisfied by
                                 the issue of the Initial Consideration Shares
                                 and the payment of L1 in accordance with
                                 clause 3


Initial Consideration Shares     17,847,769 Ordinary Shares, being such number
                                 of Ordinary Shares as shall at the Issue Price
                                 have an aggregate value of L11,333,333.32

Intellectual Property            patents, trade marks, service marks, registered
                                 designs, trade names, business names, domain
                                 names, rights in designs, copyright, computer
                                 software and database rights, rights in
                                 know-how and other intellectual property rights
                                 whether registered or unregistered and
                                 including applications for the grant of any of
                                 the foregoing

Internal Cost                    any category of expenditure which falls to be
                                 treated as an internal cost of the Company for
                                 the purposes of preparing the Management
                                 Accounts

Issue Price                      63.5p per Ordinary Share, being the average of
                                 the closing middle market prices of an Ordinary
                                 Share as shown in the London Stock Exchange
                                 Daily Official List (or in any successor
                                 publication) on the five dealing days up to and
</TABLE>


                                       -7-

<PAGE>

<TABLE>
<S>                              <C>
                                 including the dealing day prior to the date of
                                 this Agreement

ITEPA                            the Income Tax (Earnings and Pensions) Act 2003

Lease                            the underlease of the Property dated 4
                                 September 2003 between the Company and Trinity
                                 College (CSP) Limited together with all
                                 supplemental documents to that lease listed in
                                 the Disclosure Letter (other than the Deed of
                                 Assignment)

Liabilities                      all amounts owing by the Company at Completion

Listing Rules                    the prospectus rules, listing rules and
                                 disclosure rules made by the United Kingdom
                                 Listing Authority as the competent authority
                                 pursuant to Part VI of FSMA in effect as at
                                 Completion, First Issue Date, Second Issue Date
                                 or Final Issue Date (as the case may be) and
                                 including any guidance or guidance manual
                                 issued by the United Kingdom Listing Authority
                                 from time to time relating to or connected with
                                 those rules

Long Stop Date                   midnight on 4 August 2005

Management Accounts              the management accounts of the Company for the
                                 period of 5 months from the Accounts Date

Material Adverse Change          means any event or occurrence arising or
                                 occurring between the date of this Agreement
                                 and Completion which was not taken into account
                                 in preparation of the Budget or is not
                                 permitted pursuant to paragraph 2.1(a) of
                                 Schedule 6 and which is materially adverse to
                                 the:

                                 (a)  assets that are to remain in the Company
                                      following Completion (excluding for this
                                      purpose those assets that are to be
                                      transferred by the Company pursuant to the
                                      terms of the Deed of Assignment); or

                                 (b)  financial condition of the Company (when
                                      compared to the Budget);

                                 in each case (excluding any material adverse
                                 event, circumstance, effect, occurrence or
                                 state of affairs in financial, banking, capital
                                 markets or general economic conditions or that
                                 has a similar impact on any business that is
                                 similar to the Business) it being acknowledged
                                 by the parties that any matters arising from
                                 the proposed programme of redundancy (including
                                 the Redundancy Costs) and/or arising in respect
                                 of any of the Employees (including without
                                 limitation, the resignation or acceptance of
                                 redundancy by any of the Employees) or the
                                 proposed assignment of the Property (including
                                 the Property Costs and proposed re-location of
                                 equipment and moveable assets and equipment
                                 located at the Property prior to Completion) or
                                 any matters undertaken with the prior written
                                 consent of the Buyer pursuant to paragraph 2 of
</TABLE>


                                       -8-

<PAGE>

<TABLE>
<S>                              <C>
                                 Schedule 6 shall not constitute a Material
                                 Adverse Change for the purpose of this Agreement

Minority Shareholders            those Other Members who have not signed in
                                 person the stock transfer forms in respect of
                                 the transfer of their Shares to the Buyer
                                 pursuant to this Agreement and any person
                                 claiming to be entitled to any interest in such
                                 Shares

Minority Shareholder Claim       any claim brought by a Minority Shareholder
                                 against either the Buyer or the Company in
                                 respect of:

                                 (a)  the implementation by the Company of the
                                      provisions of Articles 2.4 and 6 of the
                                      Articles of Association in respect of the
                                      transfer of Shares pursuant to this
                                      Agreement; or

                                 (b)  the transfer of such Minority
                                      Shareholder's Shares by an attorney acting
                                      under power of attorney

Net Cash                         the amount of the cash, cash equivalents and
                                 certain debtors of the Company (including
                                 Residual Cash and RB Debts) less the
                                 Liabilities, in each case as determined in
                                 accordance with Schedule 7

Non-Disclosable Information      all information (including but not limited to
                                 Confidential Information) which relates to:

                                 (a)  the Company;

                                 (b)  any of the Sellers and/or their respective
                                      Affiliates;

                                 (c)  any aspect of the Business;

                                 (d)  the provisions of this Agreement;

                                 (e)  the negotiations relating to this
                                      Agreement;

                                 (f)  the subject matter of this Agreement; or

                                 (g)  the Buyer and any of its Affiliates from
                                      time to time

Ordinary Shares                  ordinary shares of 5 pence each in the capital
                                 of the Buyer

Other Members                    the persons whose names and addresses are set
                                 out in Part 2(b) of Schedule 1

Pensionable Employee             a director or employee of the Company

Principal Warranties             the warranties given by the Warrantor in clause
                                 8 and Part 2 of Schedule 3 and each such
                                 warranty statement shall be a "Principal
                                 Warranty"

Principal Warranty Claim         a claim for breach of the Principal Warranties

Property                         the leasehold property at Unit 418, Phase VI
                                 Cambridge Science Park, Milton Road, Cambridge
                                 CB4 0PA

Property Claim                   a claim in respect of Property Costs under the
                                 indemnity set
</TABLE>


                                       -9-

<PAGE>

<TABLE>
<S>                              <C>
                                 out in paragraph 1 of part 2 of Schedule 8

Property Costs                   all costs and liabilities in connection with
                                 the Property, including without limitation
                                 business rates, property insurance, property
                                 maintenance, equipment maintenance, utilities,
                                 maintenance costs related to the fixed assets
                                 and equipment to be divested to the landlord
                                 upon termination of the Lease, and all costs in
                                 connection with the termination of the Lease

RB Contract                      the contract relating to intranasal
                                 buprenorphine dated 22 February 2005 between
                                 the Company and Reckitt Benckiser Healthcare
                                 (UK) Limited

RB Debts                         any amount owed at Completion by Reckitt
                                 Benckiser Healthcare (UK) Limited to the
                                 Company under the RB Contract in reimbursement
                                 of money paid by the Company to Archimedes
                                 Development Limited for services rendered prior
                                 to Completion

Redundancy Claim                 a claim in respect of Redundancy Costs under
                                 the indemnity set out in paragraph 1 of part 2
                                 of Schedule 8

Redundancy Costs                 any liabilities, payment, award, compensation,
                                 fine, loss, order, penalty, payment by way of
                                 settlement and/or costs and expenses incurred
                                 by the Company in connection with a claim
                                 (including reasonable legal costs and expenses)
                                 arising out of or in relation to the
                                 termination of employment of any Redundant
                                 Employee, including (i) any liabilities arising
                                 as a result of any failure to comply with the
                                 requirements of section 188 of the Trade Union
                                 and Labour Relations (Consolidation) Act 1992
                                 and (ii) any sum payable following the date of
                                 Completion to or in connection with any
                                 Redundant Employee in respect of his or her
                                 employment

Redundant Employees              the person named in Disclosure Document
                                 3.12.12.02 (as referred to in paragraph 3.A.8
                                 of the Disclosure Letter) and those Employees
                                 whose positions are made redundant by the
                                 Company with the agreement of the Buyer

Regulatory Authority             any court, authority, agency, department
                                 (including but not limited to any government
                                 department or agency) or other person or legal
                                 entity having authority and/or jurisdiction in
                                 respect of Environmental Laws

Relevant Land                    any land now or at any time owned, used,
                                 occupied, leased or controlled by the Company

Relevant Proportions             ***% for Apax and ***% for Wellcome Trust

Residual Cash                    cash and cash equivalents of the Company at the
                                 date of Completion, but if the Milestone
                                 Payment payable on the first dose administered
                                 in the first Phase II Clinical Trial for
                                 IX-1003 (as such terms are defined in the RB
                                 Contract) pursuant to clause 7.1 of the RB
                                 Contract has been paid
</TABLE>


                                      -10-

<PAGE>

<TABLE>
<S>                              <C>
                                 then such Milestone Payment shall be deducted
                                 from Residual Cash, as set out in the
                                 Completion Statement

Retained Consideration           the sum of L1,166,667.08 to be satisfied by
                                 the issue and allotment of the Retained
                                 Consideration Shares in accordance with and
                                 subject to clauses 3 and 4 and Schedules 5
                                 and 8

Retained Consideration Shares    1,837,271 Ordinary Shares, being such number
                                 of Ordinary Shares as shall at the Issue Price
                                 have an aggregate value equal to the Retained
                                 Consideration

Retirement Benefit               any benefits payable by reference to reaching
                                 or expecting to reach retirement or a
                                 particular age or payable by reason of serious
                                 ill-health, incapacity or death and any other
                                 retirement benefit with the meaning of section
                                 255 of the Pensions Act 2004

Second Issue Date                the third Business Day following the date
                                 falling 13 months following the date of
                                 Completion

Sellers' Capacity Claim          a Claim for breach of the Sellers' Warranties

Sellers' Warranties              the warranties given severally by the Sellers
                                 in clause 7 and Part 1 of Schedule 3 and each
                                 such warranty statement shall be a "Sellers'
                                 Warranty"

Shares                           the entire issued share capital of the Company
                                 as at Completion, including any shares issued
                                 to Apax on conversion of the Apax Loan, as set
                                 out in Schedule 1, each such share being a
                                 "Share" and having the those rights attributed
                                 to them in the Articles of Association

Short Form Agreement             the agreement in the agreed form to be executed
                                 by the parties at Completion and filed with
                                 form 88(2) at Companies House

Taxation                         all forms of taxation, duties, rates, levies,
                                 contributions, withholdings, deductions,
                                 liabilities to account, charges and imposts in
                                 the nature of Taxation whether imposed in the
                                 United Kingdom or elsewhere in the world, and
                                 any interest, penalty, surcharge or fine
                                 relating thereto

Taxes Act 1988                   the Income and Corporation Taxes Act 1988

Taxing Authority                 H M Revenue & Customs and any other
                                 governmental, state, federal, provincial, local
                                 governmental or municipal authority, body or
                                 official competent to impost, administer or
                                 collect any Taxation and whether of the United
                                 Kingdom or elsewhere in the world

The Wellcome Trust Limited       The Wellcome Trust Limited (Company Number
                                 2711000) whose Registered Office is at 215
                                 Euston Road, London, NW1 2BE

Title Claim                      means a claim by the Buyer under paragraph 1 of
                                 part 1 of Schedule 8

VAT                              Value Added Tax
</TABLE>


                                      -11-

<PAGE>

<TABLE>
<S>                              <C>
Warrantor                        Andrew Peter Sandham of ***

Warranties                       the Principal Warranties and the Sellers'
                                 Warranties and each of the Principal Warranties
                                 and the Sellers' Warranties shall be a
                                 "Warranty"

Warranty Claim Limit             L***

Warranty Claim Ratio             a ratio of *** (Retained Consideration Shares:
                                 Deferred Consideration)

Wellcome Trust                   the Wellcome Trust a Registered Charity, Number
                                 210183, also of 215 Euston Road, London, NW1
                                 2BE acting by its trustee The Wellcome Trust
                                 Limited
</TABLE>

2    SALE AND PURCHASE OF THE SHARES

2.1  Subject to the Conditions being satisfied or, where applicable, waived,
     each of the Sellers shall sell free from all Encumbrances and with effect
     from Completion, and the Buyer shall purchase all of the Shares held by
     them together with all rights attaching to them at Completion. Without
     limitation to the foregoing, the Sellers shall jointly procure the delivery
     at Completion to the Buyer of duly executed stock transfer forms in respect
     of all of the Shares held by the Other Members together with, where
     relevant, copies of the authority under which such stock transfer forms
     were executed. Title to the Shares shall transfer pursuant to the Short
     Form Agreement.

2.2  The Buyer shall not be obliged to complete the purchase of any of the
     Shares unless the purchase and/or transfer of all the Shares is completed
     simultaneously in accordance with this Agreement.

2.3  Each of the Sellers hereby waives and shall procure the waiver by his or
     its (as the case may be) nominee(s) of any and all rights of pre-emption
     over the Shares which he or it or they (as the case may be) has or have
     conferred either by the Articles of Association or other constitutional
     documents of the Company or in any other way necessary to effect the sale
     of the Shares to the Buyer pursuant to this Agreement.

3    CONSIDERATION

3.1  The Consideration Price for the sale of the Shares shall (subject to
     adjustment as provided in this Agreement) be the Initial Consideration, the
     Retained Consideration and the Deferred Consideration.

3.2  The Initial Consideration shall be satisfied by:

     (a)  the allotment and issue of the Initial Consideration Shares, credited
          as paid in full, by the Buyer to Apax and Wellcome Trust or their
          respective nominees in the Relevant Proportions on Completion (as
          shown in the relevant columns in the table set out in Part 3 of
          Schedule 1); and

     (b)  the payment of the aggregate sum of L1 to Apax (or, to the extent
          required by article 6.4 of the Articles of Association, the Company)
          for all of the Shares held by the Warrantor and the Other Members.

3.3  The Retained Consideration shall be satisfied by the allotment and issue of
     the Retained Consideration Shares, credited as paid in full, by the Buyer
     to Apax and Wellcome Trust or their respective nominees in the Relevant
     Proportions in accordance with and subject to the provisions of clause 4
     and Schedules 5 and 8.


                                      -12-
<PAGE>

3.4  For the purposes of clauses 3.2 and 3.3, each of the Initial Consideration
     Shares and the Retained Consideration Shares shall rank pari passu in all
     respects with the Ordinary Shares in issue at the date of allotment, save
     that they shall not rank for any dividend or other distribution declared
     made or paid before, or by reference to a record date before such date.

3.5  The Buyer shall be entitled to elect to satisfy its obligation to allot and
     issue Initial Consideration Shares and/or Retained Consideration Shares
     pursuant to clauses 3.2 and 3.3 by instead paying a proportion of such
     Initial Consideration or Retained Consideration calculated at the Issue
     Price in cash to Apax and Wellcome Trust in the Relevant Proportions in
     circumstances where to allot and issue such Initial Consideration Shares or
     Retained Consideration Shares would, in the reasonable opinion of the
     Buyer's Sponsor (having consulted with the UK Listing Authority), require
     the Buyer to publish listing particulars or a prospectus in accordance with
     the Listing Rules.

3.6  Subject to the provisions of clause 4 and Schedules 5 and 8, within five
     Business Days following receipt by the Company or an Affiliate of the
     Company under the RB Contract of the final Milestone Payment payable on the
     first grant of Marketing Authorisation for IX-1003 (as such terms are
     defined in the RB Contract) pursuant to clause 7.1 of the RB Contract the
     Buyer shall:

     (a)  notify the Sellers in writing of such receipt; and

     (b)  make payment of the Deferred Consideration to Apax and Wellcome Trust
          in the Relevant Proportions,

     but less an amount equal to the aggregate amount of any Determined Claims
     and Estimated Liability that has not previously been settled by a reduction
     in the number of Retained Consideration Shares issued pursuant to clause 4
     (but not (subject to paragraph 3 of Part 2 of Schedule 5) exceeding ***).

3.7  The Sellers acknowledge that the payment of the Consideration Price by the
     Buyer in the Relevant Proportions to Apax and Wellcome Trust in accordance
     with this Agreement shall satisfy and discharge, and be deemed to satisfy
     and discharge, in each case in accordance with the Articles of Association
     and any other agreements or other arrangement in place between the Sellers
     and the Other Members, any obligation whatsoever (implied or otherwise) on
     the Buyer to pay any element of consideration to any legal or beneficial
     owner of the Shares (other than Apax and Wellcome Trust) under this
     Agreement.

4    RETAINED CONSIDERATION SHARES AND ADJUSTMENT

4.1  Subject to the remainder of this clause 4, clause 3.5 and Schedules 5 and
     8, on each of the First Issue Date, Second Issue Date and Final Issue Date
     the Buyer shall:

     (a)  subject only to the UK Listing Authority and the London Stock Exchange
          respectively agreeing to admit all such Retained Consideration Shares
          to the Official List and to trading on the London Stock Exchange
          subject only to allotment, allot and issue to Apax and Wellcome Trust
          or their respective nominees in the Relevant Proportions the
          appropriate number of Retained Consideration Shares determined in
          accordance with the following provisions of this clause 4;

     (b)  deliver duly executed share certificates in the names of Apax and
          Wellcome Trust or their respective nominees for such Retained
          Consideration Shares; and

     (c)  update the register of members of the Buyer with the names of Apax and
          Wellcome Trust or their respective nominees entered as being members
          of the Buyer in respect of such Retained Consideration Shares.

4.2  Where a Claim has been notified by the Buyer to the Sellers under the
     relevant provision of this Agreement at any point during the Initial Claim
     Period and such Claim has not become a


                                      -13-

<PAGE>

     Determined Claim on or before the expiry of such Initial Claim Period, the
     Sellers and the Buyer shall agree an estimate of the amount of such claim
     (which shall be the Estimated Liability) or, in the absence of such
     agreement within 3 days of the First Issue Date, appoint an Expert (in
     accordance with Clause 4.3) to determine the Estimated Liability.

4.3  If Clause 4.2 applies and the parties are unable to agree on the amount of
     the Estimated Liability within the 3 day period referred to therein, the
     Sellers and the Buyer shall within 10 days of the First Issue Date (the
     "Appointment Date") agree the appointment of an independent practising
     solicitor or barrister admitted in England and Wales for a continuous
     period of at least 10 years as at the date of commencement of the
     appointment or in the absence of such agreement, such person as may be
     nominated (at the request of either party) by the President of The Law
     Society of England and Wales (the "Expert") to determine the amount of such
     Claim for which the relevant Seller(s) are liable. In making his
     determination under this clause the following procedures shall apply:

     (a)  within 7 days of the Appointment Date each party shall submit to the
          Expert (with a copy to the other party) written representations in
          support of the Claim (in the case of the Buyer) and the defence to the
          Claim (in the case of the Sellers) specifying in reasonable detail the
          specific matter(s) in respect of which the Claim or defence is made
          and the calculation of the amount which that party considers should be
          the Estimated Liability;

     (b)  within 7 days of receipt of such representations:

          (i)  either party may submit further written representations to the
               Expert (with a copy to the other party) addressing any matters
               raised in the other party's representations; and

          (ii) the Expert may request further written submissions from either
               party to be delivered to the Expert (and copied to the other
               party) within that 7 day period;

     (c)  the Expert shall determine the amount of the Estimated Liability and
          notify the parties in writing of such determination by no later than
          one month following the end of the Initial Claim Period;

     (d)  the Expert may impose such additional procedures and/or deadlines as
          he considers necessary or expedient in order to determine the amount
          of the Estimated Liability within the period referred to in (c) above.

4.4  The Expert shall act as an expert and not as an arbitrator and his
     determination shall (for the purposes of determining the Estimated
     Liability only) in the absence of manifest error be final and binding on
     the Sellers and the Buyer. In the absence of fraud, the Expert shall be
     under no liability to any person by reason of his determination. The costs
     of the determination, including fees and expenses of the Expert, shall be
     borne as the Expert shall determine.

4.5  The number of Retained Consideration Shares to be issued on the First Issue
     Date shall be the total number of Retained Consideration Shares, less such
     number of Retained Consideration Shares as at the Issue Price have an
     aggregate value equivalent to:

     (a)  the amount of any Determined Claims as at the expiry of the Initial
          Claim Period;

     (b)  the amount of any Claim that has not at the expiry of the Initial
          Claim Period become a Determined Claim; and

     (c)  the amount of Retained Consideration that the Buyer elects to pay in
          cash on the First Issue Date in substitution for the relevant number
          of Retained Consideration Shares (if any) pursuant to clause 3.5.


                                      -14-

<PAGE>

4.6  The number of Retained Consideration Shares to be issued on the Second
     Issue Date shall be the balance of any Retained Consideration Shares not
     issued on the First Issue Date, less such number of Retained Consideration
     Shares as at the Issue Price have an aggregate value equivalent to:

     (a)  the amount of any Claims which have become Determined Claims since the
          expiry of the Initial Claim Period;

     (b)  the Estimated Liability in respect of any Claims which have not become
          Determined Claims at the Second Issue Date; and

     (c)  the amount of Retained Consideration that the Buyer elects to pay in
          cash on the Second Issue Date in substitution for the relevant number
          of Retained Consideration Shares (if any) pursuant to clause 3.5.

4.7  Subject to paragraph 3 of Part 2 of Schedule 5 the number of Retained
     Consideration Shares to be issued on each Final Issue Date (if any) shall
     be such number of the balance (if any) of Retained Consideration Shares not
     issued on the First Issue Date or the Second Issue Date that at the Issue
     Price have an aggregate value equivalent to the amount by which the
     relevant Determined Claim is less than the Estimated Liability of such
     Claim (if any). If however the amount of the relevant Determined Claim is
     greater than the amount of the Estimated Liability of such Claim, Apax and
     Wellcome Trust shall on the relevant Final Issue Date pay to the Buyer the
     difference in cash (in the Relevant Proportions) for same day value to an
     account notified by the Buyer for that purpose.

4.8  The provisions of Schedule 8 shall apply.

5    CONDITIONS

5.1  The sale and purchase of the Shares is conditional on:

     (a)  the Sellers giving a Selling Notice to the Company and the Company
          giving a Compulsory Sale Notice to the Other Members (as each such
          term is defined in the Articles of Association and in each case in
          agreed form) and not less than 14 days having elapsed since the giving
          of those notices;

     (b)  notice in the agreed form of the sale and purchase of the Shares being
          given to holders of options over the Company's shares, and no holder
          of options over, or rights of conversion into, shares in the capital
          of the Company having given (and not withdrawn) notice to exercise any
          of such options or rights between the date of this Agreement and
          Completion (save in connection with the Apax Loan);

     (c)  the Sellers delivering to the Buyer not less than 2 Business Days
          prior to Completion transfers in respect of all the Shares duly
          executed by or on behalf of each registered holder in favour of the
          Buyer or its nominee as it may direct together with such number of
          certificates for the Shares (or such number of indemnities in respect
          of the loss thereof in the agreed form) as the Sellers have obtained
          (including certificates and/or indemnities from each of the Sellers);

     (d)  the Apax Loan being converted into *** Shares in accordance with the
          terms disclosed in the Disclosure Letter;

     (e)  the contracts of employment relating to the Redundant Employees being
          terminated in accordance with their terms or in accordance with
          compromise agreements entered into by those employees in agreed form;

     (f)  the Lease being assigned in accordance with the Deed of Assignment;


                                      -15-

<PAGE>

     (g)  the UK Listing Authority and the London Stock Exchange respectively
          agreeing to admit all the Initial Consideration Shares to the Official
          List and to trading on the London Stock Exchange, subject only to
          allotment;

     (h)  no fact or circumstance having occurred prior to Completion which
          would amount to a Material Adverse Change;

     (i)  no notice having been given or received by the Company or the Sellers
          to terminate (or indicating an intention to terminate) the RB Contract
          and no circumstances having arisen as at Completion (excluding for
          this purpose any such circumstances arising from or in connection with
          the implementation of this Agreement) giving rise to a right by either
          party to terminate the RB Contract (other than by reason of the Buyer
          breaching its obligations under the confidentiality agreement between
          the Buyer and the Company dated 18 December 2004);

     but the Buyer may waive all or any of Conditions (a) to (i) above (either
     in whole or in part) at any time by giving notice to the Sellers.

5.2  Each party shall use all reasonable endeavours to procure (so far as it is
     so able to procure) that each of the Conditions is satisfied on or before
     the Long Stop Date or earlier termination of this Agreement under cluase
     5.3.

5.3  If any of the Conditions are not satisfied or waived on or before the Long
     Stop Date and the Buyer elects not to complete the purchase of the Shares
     all the provisions of this Agreement shall lapse and cease to have effect
     except this sub-clause and clauses 1, 5.1, 5.2, 13-17, 19, 20, 23-30
     provided that if the Agreement is terminated prior to the Long Stop Date,
     neither party shall be liable for any breach of, or failure to comply with,
     clauses 5.1 or 5.2 occurring after the earlier of termination and the Long
     Stop Date.

6    COMPLETION

6.1  Subject to the provisions of this Agreement, Completion shall take place at
     the offices of the Buyer's Solicitors at 8 a.m. on the second Business Day
     after the date on which the last of the Conditions in clauses 5.1(a),
     5.1(c), 5.1(e) and 5.1(g) is satisfied or waived in accordance with clause
     5, provided that the other Conditions have been satisfied or so waived
     prior to Completion (or at such other place, at such other time and/or on
     such other date as the Buyer and the Sellers may agree).

6.2  Until Completion the provisions of Schedule 6 shall apply.

6.3  At Completion the Sellers and the Buyer shall deliver or cause to be
     delivered to the other the items listed in Parts 1 and 2 of Schedule 2
     respectively to the extent not already delivered prior to Completion.

6.4  At Completion the Sellers shall procure that a board meeting of the Company
     shall be held at which it is resolved that:

     (a)  approval is given for the registration of the transfers of the Shares
          and the entry of the Buyer or its nominee in the register of members
          of the Company (subject only to the transfers being represented duly
          stamped);

     (b)  Tony Weir and John Slater are appointed as directors and John Slater
          as secretary of the Company;

     (c)  the Company's registered office is changed to Oakdene Court, 613
          Reading Road, Winnersh, Berkshire, RG41 5UA;

     (d)  the Company's bank mandates are revised in such manner as the Buyer
          requires.


                                      -16-

<PAGE>

6.5  At Completion, the Buyer shall:

     (a)  allot and issue to Apax and Wellcome Trust or their respective
          nominees in the Relevant Proportions the Initial Consideration Shares
          credited as paid in full in accordance with clause 3;

     (b)  deliver duly executed share certificates in the names of Apax and
          Wellcome Trust or their respective nominees for the Initial
          Consideration Shares;

     (c)  update the register of members of the Buyer with the names of Apax and
          Wellcome Trust or their respective nominees entered as being members
          of the Buyer in respect of the Initial Consideration Shares;

     (d)  pay the sum of L1 to Apax (or, to the extent required by article 6.4
          of the Articles of Association, the Company) in respect of the
          consideration to be paid to Other Members and the Warrantor; and

     (e)  pay an amount of cash equal to the Estimated Net Cash (if a positive
          number) into the understated bank account:

               Barclays Bank, Corporate Banking Centre, 8-9 Hanover Square,
               London, W1A 4ZW

               Sterling Client A/C No: ***

               Sort Code: ***

               Ref: ***

6.6  If for any reason the Sellers do not do or procure to be done all those
     things set out in clause 6.4 and deliver or cause to be delivered to the
     Buyer the items listed in Part 1 of Schedule 2 as contemplated by clause
     6.3, the Buyer may elect (in addition and without prejudice to all other
     rights or remedies available to it) to fix a new time and date for
     Completion.

6.7  Following Completion, the amount of the Final Net Cash shall be agreed or
     determined in accordance with Schedule 7.

6.8  If:

     (a)  the Final Net Cash (if a positive number) exceeds the Estimated Net
          Cash, the Buyer shall pay to Apax and Wellcome Trust the difference in
          cash (in the Relevant Proportions) as soon as reasonably practicable
          and in any event within 5 Business Days of the date the Final Net Cash
          is agreed or determined in accordance with Schedule 7; and

     (b)  the Estimated Net Cash was a positive number and exceeds the Final Net
          Cash Apax and Wellcome Trust shall pay to the Buyer the difference in
          cash (in the Relevant Proportions) as soon as reasonably practicable
          and in any event within 5 Business Days of the date the Final Net Cash
          is agreed or determined in accordance with Schedule 7; and

     (c)  both the Estimated Net Cash and Final Net Cash are negative numbers,
          Apax and Wellcome Trust shall pay to the Buyer the amount of the Final
          Net Cash (in the Relevant Proportions) as soon as reasonably
          practicable and in any event within 5 Business Days of the date the
          Final Net Cash is agreed or determined in accordance with Schedule 7.

7    SELLERS' WARRANTIES

7.1  On the date of this Agreement each of the Sellers severally warrant to the
     Buyer for itself or himself only in the terms of the Sellers' Warranties
     subject to the limitations and qualifications set out in Part 2 of Schedule
     5.


                                      -17-

<PAGE>

7.2  The Sellers acknowledge that the Buyer has entered into this Agreement in
     reliance on the Sellers' Warranties and the Principal Warranties.

8    PRINCIPAL WARRANTIES AND WARRANTIES GENERALLY

8.1  On the date of this Agreement the Warrantor warrants to the Buyer in the
     terms of the Principal Warranties subject to:

     (a)  any matter fairly disclosed in the Disclosure Letter or the Disclosure
          Documents; and

     (b)  the limitations and qualifications set out in Part 1 of Schedule 5.

8.2  Where any Principal Warranty is qualified by the expression "so far as the
     Warrantor is aware" or "to the best of the knowledge, information and
     belief of the Warrantor" or words having similar effect, such knowledge and
     awareness shall be confined to the actual knowledge of the Warrantor at the
     date of this Agreement having made reasonable enquiry of each of Nigel Low,
     C Michael Perkins and Kelly Chessum.

8.3  Each of the Warranties is separate and independent and, except as expressly
     provided to the contrary in this Agreement, is not limited:

     (a)  by reference to any other Warranty; or

     (b)  by any other provision of this Agreement.

9    BUYER WARRANTIES

9.1  On the date of this Agreement the Buyer warrants to the Sellers in the
     terms of the Buyer Warranties subject to the limitations and qualifications
     set out in Part 2 of Schedule 5.

9.2  The Buyer acknowledges that the Sellers have entered into this Agreement in
     reliance on the Buyer Warranties.

10   ORDERLY MARKET

10.1 For the purposes of this clause 10:

     (a)  INTEREST shall have the meaning given to it in section 208 of the
          Companies Act 1985 excluding section 209 thereof;

     (b)  CONTROLLED SHARES means any of the Initial Consideration Shares
          allotted and issued to Apax or Wellcome Trust or their respective
          nominees;

     (c)  CONTROLLED PERIOD means the period of 12 months following Completion.

10.2 Subject to clauses 10.3 and 10.4, each of Apax and Wellcome Trust covenants
     to the Buyer that during the Controlled Period it will, and will procure
     that its or his (as the case may be) nominees will:

     (a)  notify the Buyer and its nominated broker in writing prior to the
          disposal of any Controlled Shares; and

     (b)  not dispose of any Controlled Shares other than through the Buyer's
          nominated broker (provided that if Apax or Wellcome Trust (as the case
          may be) receive an unsolicited offer to acquire Controlled Shares then
          the preceding provision of this sub-paragraph (b) shall not apply to a
          disposal to the person who made such offer but such Seller shall be
          obliged to notify the Buyer's nominated broker in writing prior to
          such disposal).

10.3 The provisions of this clause 10 shall not apply to:

     (a)  a disposal pursuant to a court order;


                                      -18-

<PAGE>

     (b)  a renunciation of a right to subscribe for shares where such right is
          derived from the Controlled Shares or a failure to take up any such
          right;

     (c)  if the Buyer makes an offer to its shareholders to purchase its own
          shares or proposes a scheme of arrangement, a disposal or agreement to
          dispose of any Controlled Shares to the Buyer pursuant to that offer
          or scheme;

     (d)  the acceptance by Apax or Wellcome Trust or their respective nominees
          of a general offer made for all the issued share capital of the Buyer
          provided such offer is recommended by the board of directors of the
          Buyer;

     (e)  the execution by Apax or Wellcome Trust of an irrevocable commitment
          to accept a general offer made for all the issued share capital of the
          Buyer provided such offer is recommended by the board of directors of
          the Buyer;

     (f)  a transfer or purported transfer of the legal and/or beneficial
          interest of any Controlled Shares by way of the grant of security for
          borrowing by Apax or Wellcome Trust; or

     (g)  a disposal by each of Apax and Wellcome Trust in their absolute
          discretion of no more than *** Controlled Shares in aggregate to
          Andrew Sandham, Nigel Low and/or Lennart Bruce and/or their respective
          family members and/or their respective trustees as they see fit and on
          such terms as each of Apax and Wellcome Trust see fit.

10.4 Notwithstanding the provisions of clauses 10.2 and 10.3, in the event that
     either of Apax and Wellcome Trust intends to dispose of Controlled Shares
     in order to fund a payment pursuant to clauses 4.7, 6.8(b), 6.8(c), 7.1 and
     paragraph 1 of Part 1 of Schedule 8, the following provisions shall apply:

     (a)  for as long as Apax or Wellcome Trust (as relevant) holds ***% or more
          of the issued share capital of the Buyer, the relevant Seller shall:

          (i)  firstly notify the Buyer and its nominated broker of its
               intention to dispose of such shares; and;

          (ii) provide the Buyer's nominated broker with reasonable details of
               the proposed trade; and

          (iii) not dispose of any Controlled Shares other than through the
               Buyer's nominated broker, provided that if the Buyer's nominated
               broker cannot effect the trade at a price or within timescales
               acceptable to Apax or Wellcome Trust (as the case may be), Apax
               or Wellcome Trust (as the case may be) shall be entitled to
               effect such trade with another broker of their choice and shall
               advise the Buyer of the relevant broker's details and the
               progress of such trade; and.

     (b)  for as long as Apax or Wellcome Trust (as relevant) holds less than
          ***% of the issued share capital of the Buyer, the provisions of
          clause 10.2 shall not apply to the disposal of Controlled Shares for
          that purpose.

10.5 The provisions of this clause shall also apply to any other securities for
     the time being representing or derived from the Controlled Shares (whether
     by way of consolidation, sub division, capitalisation or rights issue or
     otherwise), other than any such securities as may be acquired for cash by
     way of rights or other issue, and references in this clause to the
     Controlled Shares shall be construed accordingly.

11   LOANS AND GUARANTEES

11.1 Each Seller shall procure that on Completion:


                                      -19-

<PAGE>

     (a)  all indebtedness owing immediately before Completion from that Seller
          or any person connected with that Seller to the Company (other than
          amounts owing by way of trade credit in the ordinary course of trading
          as a result of goods or services supplied on normal arm's length
          terms) is or has been satisfied in full together with all interest
          accruing on it up to (but excluding) Completion; and

     (b)  all indebtedness owing immediately before Completion by the Company to
          that Seller or any person connected with that Seller (other than
          amounts owing by way of trade credit in the ordinary course of trading
          as a result of goods or services supplied on normal arm's length terms
          or pursuant to any service agreement with any Employee or Redundant
          Employee) is or has been satisfied in full together with all interest
          accruing on it up to (but excluding) Completion.

11.2 The parties acknowledge that the Consideration Price has been agreed on the
     basis that no indebtedness of any kind (whether or not then presently
     payable) will be owing to or by the Company immediately after Completion by
     or to any Seller or person connected with any Seller other than any amounts
     owing by way of trade credit in the ordinary course of trading as a result
     of goods or services supplied on normal arm's length terms or pursuant to
     any service agreement with any such Seller.

11.3 The Sellers shall procure that on Completion the Company is released from
     all guarantees and indemnities given by the Company in respect of any
     liability or obligation of any Seller or any person connected with any
     Seller.

12   PROTECTIVE COVENANT

12.1 Each Seller covenants with the Buyer and the Company that he or it (as the
     case may be) shall not for a period of 12 months after Completion:

     (a)  induce or attempt to induce any person who is at the date of
          Completion a director or employee of the Company to leave the
          employment of the Company; or

     (b)  employ or attempt to employ any person who is at the date of
          Completion a director or employee of the Company.

12.2 If the restriction in clause 12.1 is void but would be valid if some part
     of the restriction were deleted or amended, the restriction shall apply
     with such modification as may be necessary to make it valid.

12.3 The Sellers acknowledge that the provisions in clause 12.1 are no more
     extensive than is reasonable to protect the Buyer as the purchaser of the
     Shares.

12.4 The covenant in this clause may with the prior written consent of the Buyer
     be enforced by the Company against the Sellers or any of them under the
     Contracts (Rights of Third Parties) Act 1999. The provisions of this clause
     may be varied or terminated by agreement between the Sellers and the Buyer
     (and the Buyer may also release or compromise in whole or in part any
     liability in respect of rights or claims contemplated by this clause)
     without the consent of the Company.

13   ANNOUNCEMENTS

13.1 Except to the extent otherwise expressly permitted by this Agreement, the
     parties shall not make any public announcement or issue a press release or
     respond to any enquiry from the press or other media concerning or relating
     to this Agreement or its subject matter or any ancillary matter.

13.2 Notwithstanding any other provision in this Agreement, any party may, after
     consultation with the other parties whenever practicable, make or permit to
     be made an announcement concerning or


                                      -20-

<PAGE>

     relating to this Agreement or its subject matter or any ancillary matter if
     and to the extent required by:

     (a)  law; or

     (b)  any securities exchange on which its securities are listed or traded;
          or

     (c)  any regulatory or governmental or other authority with relevant powers
          to which that party is subject or submits, whether or not the
          requirement has the force of law.

14   CONFIDENTIALITY

14.1 Each of the Sellers and the Buyer hereby undertakes that they shall
     preserve the confidentiality of the Non-Disclosable Information which
     relates to the other, this Agreement and the Company and its Business, and
     except to the extent otherwise expressly permitted by this Agreement, not
     directly or indirectly reveal, report, publish, disclose or transfer or use
     for its own or any other purposes such Non-Disclosable Information provided
     that nothing in this clause shall prevent the Buyer from using any
     Non-Disclosable Information after Completion in connection with carrying on
     business of the Company or the Buyer's Group after Completion.

14.2 Notwithstanding any other provision in this Agreement and without prejudice
     to the above, the Buyer may, after consultation with the Sellers whenever
     practicable, and any Seller may, after consultation with the Buyer and each
     other Seller whenever practicable, disclose Non-Disclosable Information if
     and to the extent:

     (a)  required by law; or

     (b)  required by any securities exchange on which its securities are listed
          or traded; or

     (c)  required by any regulatory or governmental or other authority with
          relevant powers to which it is subject or submits (whether or not the
          authority has the force of law); or

     (d)  required to vest the full benefit of this Agreement in that party or
          to enforce any of the rights of that party in this Agreement; or

     (e)  required by its professional advisers, officers, employees,
          consultants, subcontractors or agents to provide their services (and
          subject always to similar duties of confidentiality); or

     (f)  that information is in or has come into the public domain through no
          fault of that party; or

     (g)  the other party has given prior written consent to the disclosure; or

     (h)  it is necessary to obtain any relevant tax clearances from any
          appropriate tax authority.

14.3 The restrictions contained in this clause 14 shall continue to apply after
     Completion without limit in time.

15   ENTIRE AGREEMENT

15.1 This Agreement and the documents referred to or incorporated in it
     constitute the entire agreement between the parties relating to the subject
     matter of this Agreement and supersede and extinguish any prior drafts,
     agreements, undertakings, representations, warranties and arrangements of
     any nature whatsoever, whether or not in writing, between the parties in
     relation to the subject matter of this Agreement. Notwithstanding that the
     Short Form Agreement will be executed after the date of this Agreement, in
     the event of any dispute in relation to, or differences to the terms or
     interpretation of, the Short Form Agreement, the provisions of this
     Agreement shall prevail.

15.2 Each of the parties acknowledges and agrees that it has not entered into
     this Agreement in reliance on any statement or representation of any person
     (whether a party to this Agreement or not) other than as expressly
     incorporated in this Agreement.


                                      -21-

<PAGE>

15.3 Nothing in this Agreement or in any other document referred to herein shall
     be read or construed as excluding any liability or remedy as a result of
     fraud.

15.4 Without limiting the generality of the foregoing, each of the parties
     irrevocably and unconditionally waives any right or remedy it may have to
     claim damages and/or to rescind this Agreement by reason of any
     misrepresentation (other than a fraudulent misrepresentation) having been
     made to it by any person (whether party to this Agreement or not) and upon
     which it has relied in entering into this Agreement.

16   ASSIGNMENT AND TRANSFER

     This Agreement is personal to the parties and no party may assign,
     transfer, subcontract, delegate, charge or otherwise deal in any other
     manner with this Agreement or any of its rights or obligations nor grant,
     declare, create or dispose of any right or interest in it without the prior
     written consent of all other parties save The Wellcome Trust Limited may
     assign its rights under this Agreement to any successor trustee of the
     Wellcome Trust and the Buyer may assign the benefit of this Agreement to
     any member of the Buyer's Group. In the event such assignee ceases to be a
     member of the Buyer's Group, the benefit of this Agreement shall be
     transferred back to an entity within the Buyer's Group with immediate
     effect. Save as expressly stated in this Agreement, this Agreement and its
     terms shall be binding on the personal representatives and the estate of
     the Warrantor. Any purported assignment, transfer, subcontracting,
     delegation, charging or dealing in contravention of this clause shall be
     ineffective.

17   COSTS AND EXPENSES

     Except as otherwise stated in this Agreement, each party shall pay its own
     costs and expenses in relation to the negotiation, preparation, execution,
     performance and implementation of this Agreement and each document referred
     to in it and other agreements forming part of the transaction, save that
     this clause shall not prejudice the right of either party to seek to
     recover its costs in any litigation or dispute resolution procedure which
     may arise out of this Agreement.

18   EFFECT OF COMPLETION

     This Agreement shall, to the extent that it remains to be performed,
     continue in full force and effect notwithstanding Completion.

19   WAIVER

19.1 A waiver of any right, power, privilege or remedy provided by this
     Agreement must be in writing and may be given subject to any conditions
     thought fit by the grantor. For the avoidance of doubt, any omission to
     exercise, or delay in exercising, any right, power, privilege or remedy
     provided by this Agreement shall not constitute a waiver of that or any
     other right, power, privilege or remedy.

19.2 A waiver of any right, power, privilege or remedy provided by this
     Agreement shall not constitute a waiver of any other breach or default by
     the other party and shall not constitute a continuing waiver of the right,
     power, privilege or remedy waived or a waiver of any other right, power,
     privilege or remedy.

19.3 Any single or partial exercise of any right, power, privilege or remedy
     arising under this Agreement shall not preclude or impair any other or
     further exercise of that or any other right, power, privilege or remedy.

20   VARIATION

     Any variation of this Agreement or of any of the documents referred to in
     it is valid only if it is in writing and signed by or on behalf of every
     party to this Agreement or such document as the case may be.


                                      -22-

<PAGE>

21   SEVERANCE

21.1 If any provision of this Agreement is held to be invalid or unenforceable
     by any judicial or other competent authority, all other provisions of this
     Agreement will remain in full force and effect and will not in any way be
     impaired.

21.2 If any provision of this Agreement is held to be invalid or unenforceable
     but would be valid or enforceable if some part of the provision were
     deleted, or the period of the obligation reduced in time, or the range of
     activities or area covered, reduced in scope, the provision in question
     will apply with the minimum modifications necessary to make it valid and
     enforceable.

22   FURTHER ASSURANCE

22.1 Each of the Sellers shall from time to time on or following Completion, on
     being requested to do so by the Buyer, use all reasonable endeavours to do
     or procure the doing of all such acts and/or execute or procure the
     execution of all such documents in a form reasonably satisfactory to the
     Buyer at the cost and expense of the relevant Seller necessary to transfer
     good title to the Shares held by such Seller to the Buyer.

22.2 For so long after Completion as the Seller or any nominee of it or him (as
     the case may be) remains the registered holder of any Share, it or he (as
     the case may be) shall hold (or direct the relevant nominee to hold) that
     Share and any distributions, property and rights deriving from it in trust
     for the Buyer and shall deal with that Share and any distributions,
     property and rights deriving from it as the Buyer directs; in particular,
     each Seller shall exercise all voting rights as the Buyer directs or shall
     execute or procure the execution of an instrument of proxy or other
     document which enables the Buyer or its representative to attend and vote
     at any meeting of the Company.

23   NOTICES

23.1 Any communication to be given in connection with this Agreement shall be in
     writing in English except where expressly provided otherwise and shall
     either be delivered by hand or sent by first class prepaid post or fax or
     (in the case of the Warrantor) by email (but if by email with a copy by
     hand or first class pre-paid post to the postal address). Delivery by
     courier shall be regarded as delivery by hand.

23.2 Such communication shall be sent to the address of the relevant party
     referred to in this Agreement or the fax number or email address set out
     below or to such other address or fax number or email address as may
     previously have been communicated to the other party in accordance with
     this clause 23. Each communication shall be marked for the attention of the
     relevant person.

<TABLE>
<CAPTION>
Party            Fax Number/Email      Address                            For the attention of
-----            -------------------   --------------------------------   -----------------------
<S>              <C>                   <C>                                <C>
Buyer            +44 (0)118 989 9300   Oakdene Court, 613 Reading Road,   Chief Financial
                                       Winnersh, Berkshire, RG41 5UA      Officer/General Counsel

Wellcome Trust   ***                   215 Euston Road                    ***
                                       London NW1 2BE

Apax             ***                   15 Portland Place                  ***
                                       London WIB 1PT

Andrew Sandham   ***                   ***                                ***
</TABLE>

23.3 A communication shall be deemed to have been served:

     (a)  if delivered by hand at the address referred to in clause 23.2, at the
          time of delivery;


                                      -23-

<PAGE>

     (b)  if sent by first class prepaid post to the address referred to in
          clause 23.2, at the expiration of two clear days after the time of
          posting; and

     (c)  if sent by facsimile to the number referred to in clause 23.2 or sent
          by email to the email address specified in that clause, at the time of
          completion of transmission by the sender.

     If a communication would otherwise be deemed to have been delivered outside
     normal business hours (being 9:30 a.m. to 5:30 p.m. on a Business Day)
     under the preceding provisions of this clause 23.3, it shall be deemed to
     have been delivered at the next opening of such business hours.

23.4 In proving service of the communication, it shall be sufficient to show
     that delivery by hand was made or that the envelope containing the
     communication was properly addressed and posted as a first class prepaid
     letter or that the fax was despatched and a confirmatory transmission
     report received or that the email was transmitted to the correct email
     address, whether or not opened or read by the recipient.

23.5 A party may notify the other parties to this Agreement of a change to its
     name, relevant person, address or fax number or email address for the
     purposes of clause 23.2 or 23.7 as the case may be provided that such
     notification shall only be effective on:

     (a)  the date specified in the notification as the date on which the change
          is to take place; or

     (b)  if no date is specified or the date specified is less than five clear
          Business Days after the date on which notice is deemed to have been
          served, the date falling five clear Business Days after notice of any
          such change is deemed to have been given.

23.6 For the avoidance of doubt, the parties agree that the provisions of
     clauses 23.1, 23.2, 23.3, 23.4 and 23.5 shall not apply in relation to the
     service of any claim form, application notice, order, judgment or other
     document relating to or in connection with any proceeding, suit or action
     arising out of or in connection with this Agreement.

23.7 In this Agreement:

     (a)  where the consent, approval or agreement of all of the Sellers
          collectively is required, such consent, approval or agreement shall be
          deemed to have been validly given if given in writing signed by or on
          behalf of both Apax and Wellcome Trust; and

     (b)  where notice requires to be served or a matter intimated to all of the
          Sellers collectively it shall be sufficient for such notice to be
          served or such intimation given to both Apax and Wellcome Trust.

24   WELLCOME

     The Wellcome Trust Limited represents and warrants that it is, and each of
     the other parties to this Agreement acknowledge and agree that The Wellcome
     Trust Limited is, entering into this Agreement solely in its capacity as
     the trustee of Wellcome Trust and it is hereby agreed and declared that
     notwithstanding anything to the contrary contained or implied in this
     Agreement:

     (a)  the obligations incurred by The Wellcome Trust Limited under or in
          consequence of this Agreement shall be enforceable against it or the
          other trustees of Wellcome Trust from time to time; and

     (b)  the liabilities of The Wellcome Trust Limited (or such other trustees
          as are referred to in clause (a) above) in respect of such obligations
          shall be limited to such liabilities as can and may lawfully and
          properly be met out of the Retained Consideration Shares and the
          Deferred Consideration or out of the assets of Wellcome Trust for the
          time being in the hands or under the control of The Wellcome Trust
          Limited or such other trustees from time to time.


                                      -24-

<PAGE>

25   COUNTERPARTS

     This Agreement may be executed in any number of counterparts, each of which
     shall constitute an original, and all the counterparts shall together
     constitute one and the same agreement.

26   GOVERNING LANGUAGE

26.1 Each notice, instrument, certificate or other communication to be given by
     one party to another in this Agreement or in connection with this Agreement
     shall be in English (being the language of negotiation of this Agreement)
     and in the event that such notice, instrument, certificate or other
     communication or this Agreement is translated into any other language, the
     English language text shall prevail.

27   GOVERNING LAW

     This Agreement is governed by and is to be construed in accordance with
     English law.

28   JURISDICTION

     The parties irrevocably agree that the courts of England and Wales shall
     have exclusive jurisdiction to settle any dispute which may arise out of or
     in connection with this Agreement.

29   INTERPRETATION

29.1 The clause and paragraph headings and the table of contents used in this
     Agreement are inserted for ease of reference only and shall not affect
     construction.

29.2 References in this Agreement and the Schedules to the parties, the
     Introduction, Schedules and clauses are references respectively to the
     parties, the Introduction and Schedules to and clauses of this Agreement.

29.3 References to documents "in the agreed form" are to documents in terms
     agreed between the parties prior to execution of this Agreement and
     initialled for the purposes of identification by or on behalf of each of
     the parties.

29.4 References to "writing" or "written" includes any other non-transitory form
     of visible reproduction of words.

29.5 References to times of the day are to that time in London and references to
     a day are to a period of 24 hours running from midnight.

29.6 References to any English legal term or legal concept shall in respect of
     any jurisdiction other than England be deemed to include that which most
     approximates in that jurisdiction to such English legal term or legal
     concept.

29.7 References to persons shall include bodies corporate, unincorporated
     associations and partnerships, in each case whether or not having a
     separate legal personality.

29.8 References to the word "include" or "including" (or any similar term) are
     not to be construed as implying any limitation and general words introduced
     by the word "other" (or any similar term) shall not be given a restrictive
     meaning by reason of the fact that they are preceded by words indicating a
     particular class of acts, matters or things.

29.9 Save where the context specifically requires otherwise, words importing one
     gender shall be treated as importing any gender, words importing
     individuals shall be treated as importing corporations and vice versa,
     words importing the singular shall be treated as importing the plural and
     vice versa, and words importing the whole shall be treated as including a
     reference to any part thereof.


                                      -25-

<PAGE>

29.10 References to statutory provisions, enactments or EC Directives shall
     include references to any amendment, modification, extension,
     consolidation, replacement or re-enactment of any such provision, enactment
     or Directive (whether before or after the date of this Agreement), to any
     previous enactment which has been replaced or amended and to any
     regulation, instrument or order or other subordinate legislation made under
     such provision, enactment or Directive, unless any such change imposes upon
     any party any liabilities or obligations which are more onerous than as at
     the date of this Agreement.

29.11 A company or other entity shall be a "holding company" for the purposes of
     this Agreement if it falls within either the meaning attributed to that
     term in section 736 and 736A of the Companies Act 1985 (as amended) or the
     meaning attributed to the term "parent undertaking" in section 258 of such
     Act, and a company or other entity shall be a "subsidiary" for the purposes
     of this Agreement if it falls within any of the meanings attributed to a
     "subsidiary" in section 736 and 736A of the Companies Act 1985 (as amended)
     or the meaning attributed to the term "subsidiary undertaking" in section
     258 of such Act, and the terms "subsidiaries" and "holding companies" are
     to be construed accordingly.

29.12 Section 839 Income and Corporation Taxes Act 1988 is to apply to determine
     whether one person is connected with another for the purposes of this
     Agreement.

29.13 The rights and obligations of the Sellers under this Agreement are, save
     to the extent that they are expressly stated to be joint rights or
     obligations of the Sellers, their several rights and obligations and,
     subject thereto, no Seller shall have any liability to the Buyer in respect
     of any act or omission of or default or breach of, this Agreement by any
     other Seller. The liability of the Apax and Wellcome Trust in respect of
     any reduction in the amount of Retained Consideration Shares or Deferred
     Consideration to which they would otherwise be entitled under this
     Agreement as a result of any Claims shall be several.

30   RIGHTS OF THIRD PARTIES

     Except as otherwise expressly stated, this Agreement does not confer any
     rights on any person or party (other than the parties to this Agreement)
     pursuant to the Contracts (Rights of Third Parties) Act 1999.

31   EXECUTION

     This Agreement is entered into by the parties on the date at the beginning
     of this Agreement.


                                      -26-

<PAGE>

                                   SCHEDULE 3

                           PART 1: SELLERS' WARRANTIES

A.   GENERAL/COMMERCIAL

1    CAPACITY AND AUTHORITY

1.1  The relevant Seller has the requisite power, capacity and authority to
     enter into and perform this Agreement and all other documents entered into
     by that Seller pursuant to or in connection with this Agreement.

1.2  This Agreement and all other documents entered into by the relevant Seller,
     pursuant to or in connection with this Agreement, constitute binding
     obligations of the relevant Seller enforceable in accordance with their
     respective terms, subject to:

     (a)  limitations arising from the laws of bankruptcy, administration,
          liquidation, insolvency, receivership or similar laws affecting
          generally the enforcement of creditors' rights;

     (b)  the effect of general principles of law and equity;

     (c)  where any obligations of any person are to be performed or observed
          outside England and Wales, or by a person subject to the laws of a
          jurisdiction outside England and Wales, the possibility that such
          obligations may not be enforceable under English law to the extent
          that performance or observance thereof would be illegal or contrary to
          public policy under the laws of any such jurisdiction;

     (d)  the effect of the Limitation Act 1980; and

     (e)  the laws of any jurisdiction outside England.

2    NO BREACH

2.1  Neither the entry into of this Agreement by the relevant Seller nor the
     implementation by that Seller of the transactions contemplated by it will
     result in:

     (a)  breach of any provision of any constitutional document of the relevant
          Seller (if appropriate); or

     (b)  a breach of, or give rise to a default under, any contract or other
          instrument to which the relevant Seller is a party or by which it is
          bound; or

     (c)  breach of any applicable laws or regulations or of any order, decree
          or judgment of any court, or any governmental, regulatory or other
          authority applicable to the relevant Seller.

3    THE SHARES

3.1  The Shares constitute at the date of this Agreement and will at Completion
     (including in respect of any Shares issued to Apax in connection with the
     conversion of the Apax Loan prior to Completion) constitute the entire
     issued share capital of the Company at Completion, are and will be fully
     paid or credited as fully paid and have been or will be duly and validly
     authorised and issued.

3.2  The relevant Seller is the sole legal and beneficial owner of those of the
     Shares set against its name in part 2 of Schedule 1 or is otherwise able to
     sell and transfer the entire legal and beneficial ownership of such Shares
     to the Buyer.

3.3  As regards the relevant Seller in respect of the Shares held by it, there
     is no Encumbrance on, over or affecting such Shares.


                                      -29-

<PAGE>

                          PART 2: PRINCIPAL WARRANTIES

1    THE COMPANY

     The Company is duly incorporated and validly existing under the laws of the
     jurisdiction in which it is incorporated.

2    ARRANGEMENTS WITH THE COMPANY

     There are not currently outstanding any contracts or agreements to which
     the Company is a party which are otherwise than on arm's length normal
     commercial terms.

3    CONSTITUTIONAL DOCUMENTS, STATUTORY BOOKS AND RETURNS

     The copies of the Memorandum and Articles of Association of the Company
     attached to the Disclosure Letter are complete and accurate in all material
     respects. The register of members and other statutory books and registers
     of the Company have been properly kept and no notice or allegation that any
     of them is incorrect or should be rectified has been received. All returns,
     particulars, resolutions and other documents which the Company is required
     by law to file with or deliver to the registrar of companies have been
     correctly made up and duly filed or delivered.

4    ACCOUNTS, MANAGEMENT ACCOUNTS AND GRANTS

4.1  The Accounts have been prepared in accordance with the Accounts Standards
     and give a true and fair view of the state of affairs of the Company at the
     Accounts Date and of the profits and losses for the period covered by the
     Accounts and at Completion will be audited.

4.2  The Accounts have been prepared and will be audited on a basis consistent
     with the accounting policies used in the preparation of the audited
     accounts of the Company for the preceding financial year.

4.3  The Company is not subject to any arrangement for receipt or repayment of
     any grant, subsidy or financial assistance from any governmental department
     or other body.

4.4  The Management Accounts have been prepared applying and adopting policies,
     principles, bases, conventions, rules, practices, techniques, methods and
     procedures consistent with those employed in preparing the management
     accounts of the Company for each of the 12 months in the Financial Year
     2004 and enable a reasonable judgement to be made as to the income and
     expenditure of the Company for the period to which they relate.

5    EVENTS SINCE THE ACCOUNTS DATE

     Since the Accounts Date:

     (a)  the Company has not allotted or issued or agreed to allot or issue any
          share capital;

     (b)  the Company has not redeemed or purchased or agreed to redeem or
          purchase any of its share capital;

     (c)  no resolution of the Company in general meeting has been passed other
          than resolutions relating to ordinary business at annual general
          meetings;

     (d)  the Company has not declared, made or paid a dividend or other
          distribution except as provided for in the Accounts;

     (e)  no change in the accounting reference period of the Company has been
          made;

     (f)  the Company has not acquired or disposed of or agreed to acquire or
          dispose of any material business or asset (other than in the ordinary
          course of business);


                                      -30-

<PAGE>

     (g)  the Company has not assumed or incurred, or agreed to assume, any
          material liability (including any contingent liability), obligation,
          commitment or expenditure involving an amount in excess of L10,000
          that is not included within the Budget or set out in the Management
          Accounts; and

     (h)  the Company has not repaid any borrowing or indebtedness in advance of
          its stated maturity.

6    TRADING ARRANGEMENTS AND RB CONTRACT

6.1  The Company is not a party to any contract, arrangement or commitment which
     is:

     (a)  otherwise than in the ordinary course of business;

     (b)  of a long-term nature (that is to say, unlikely to have been fully
          performed, in accordance with its terms, more than 12 months after the
          date on which it was entered into); or

     (c)  which is incapable of termination in accordance with its terms by the
          Company on 12 months' notice or less.

6.2  In relation to the RB Contract (all clause references and defined terms in
     this sub-paragraph are to clauses and defined terms in the RB Contract):

     (a)  the Company has not consented to any sub-licence or sub-contract under
          clause 3.5.2;

     (b)  no notice has been given under 3.5.8;

     (c)  the West Agreement has not been novated to Reckitt Benckiser
          Healthcare (UK) Limited;

     (d)  the Company has not sub-licensed or sub-contracted any rights under
          the RB Contract;

     (e)  Reckitt Benckiser Healthcare (UK) Limited has not exercised its option
          under clause 3.10;

     (f)  the Disclosure Letter contains a summary of the clinical status and
          formulation development status of IX-1003 as at 15 June 2005;

     (g)  the Company is not in breach of its obligation to transfer Know How to
          Reckitt Benckiser Healthcare (UK) Limited pursuant to clause 4.1 of
          the RB Contract;

     (h)  the joint steering committee under the RB Contract has not embarked on
          the development of any products other than IX-1003, IX-1004 and
          IX-1005;

     (i)  West provides the services described in clause 10.4 and the Warrantor
          has no reason to believe that West intends to cease providing those
          services; and

     (j)  the Company has not exercised Option provided for in clause 13.1.

6.3  Copies of all agreements to which the Company is party and which in any one
     Financial Year carry a financial liability or financial benefit for the
     Company of L50,000 or more are contained in the Disclosure Letter (with the
     exception of employee service contracts and lease agreements relating to
     premises occupied by the Company). The Company has complied in all material
     respects with, and so far as the Warrantor is aware, the other parties have
     complied in all material respects with, the terms of all such contracts. No
     notice to terminate any of such contracts has either been served or
     received by the Company and the Warrantor is not aware of any intention on
     the part of any party to any such material contract to serve a notice to
     terminate.

7    LICENCES TO OPERATE

7.1  The Company has complied with all material statutory, municipal,
     governmental, court and other requirements applicable to:


                                      -31-

<PAGE>

     (a)  the formation, continuance in existence, creation and issue of
          securities; and

     (b)  the management, property and operations of the Company.

7.2  The Company has not received any written notice in the 12 months prior to
     the date of this Agreement alleging that any licences, consents and other
     permissions and approvals required for or in connection with the carrying
     on of the Business have not been obtained.

8    LITIGATION

8.1  The Company is not at present engaged in, nor has been engaged in during
     the 12 months prior to the date of this Agreement, any action or proceeding
     (whether civil or criminal), arbitration or mediation (whether formal or
     informal), investigation or inquiry other than any matter in which the
     Company is a claimant in the collection of debts arising in the ordinary
     course of business none of which individually exceeds L15,000 and which do
     not exceed L30,000 in aggregate.

8.2  The Company has not received notice in writing of:

     (a)  any actual, pending or threatened governmental, regulatory
          investigation or inquiry, whether formal or otherwise, which is
          connected with the Company and the Warrantor is not aware of any facts
          or circumstances which are likely to give rise to any such action
          against the Company; or

     (b)  any claim in damages connected with the Company (whether liquidated or
          unliquidated), or of an injunction or other order or an application
          for such an injunction or other order, either as a party or non-party
          to proceedings, arbitration, investigation, inquiry or other action,
          formal or otherwise, which is connected with the Company.

8.3  There is no judgment, award, order or decision outstanding or, so far as
     the Warrantor is aware, pending against the Company or its assets.

9    INSURANCE

9.1  The Disclosure Letter sets out a list of all material insurance policies
     maintained by or on behalf of the Company and full details of any claims
     made in the 24 months prior to the date of this Agreement under such
     insurance policies, or prior policies in respect of similar insured risks.
     All premiums due and payable on the insurance polices have been paid and so
     far as the Warrantor is aware the Company has not received any written
     notice that the policies relating to them are not in full force and effect
     or void or voidable.

9.2  No claim in excess of L10,000 has been made and is outstanding either by
     the insurer or the insured under any of the said policies.

10   ASSETS

10.1 The Company owns or is entitled to use all material tangible assets and
     property which the Warrantor considers necessary for the purposes of
     carrying on the Business as it is currently carried on.

10.2 No material tangible asset or property is the subject of any Encumbrance
     (excepting any lien arising by operation of law in the ordinary course of
     trading) or, save as disclosed in the Disclosure Letter, the subject of any
     leasing, hire, hire-purchase, conditional sale or credit sale agreement.

10.3 There are disclosed in the Disclosure Letter a list of material tangible
     assets and property subject to leasing, hire, hire-purchase, conditional
     sale or credit sale agreement terms.


                                      -32-

<PAGE>

11   BORROWINGS AND LENDINGS

     Borrowings

11.1 The Company does not have any bank borrowings.

     Loans

11.2 Other than in the ordinary course of business, the Company has not lent any
     money which has not been repaid, and does not own the benefit of any debts
     (whether or not due for payment), other than debts which have arisen in the
     ordinary course of business.

12   INSOLVENCY

12.1 The Company has not:

     (a)  entered into any arrangement or composition for the benefit of its
          creditors or any of them nor has it (or its agent or nominee) convened
          a meeting of its creditors;

     (b)  submitted to its creditors or any of them a proposal under Part I of
          the Insolvency Act 1986;

     (c)  entered into any arrangement, scheme, compromise, moratorium or
          composition with any of its creditors (whether under Part I of the
          Insolvency Act 1986 or otherwise);

     (d)  made an application to the Court under section 425 of the Companies
          Act 1985 or resolved to make such an application;

     (e)  presented a petition for winding up nor has a petition for winding up
          been presented against it which has not been withdrawn within 14 days,
          nor has a winding up order been made against it or a provisional
          liquidator appointed;

     (f)  been the subject of a resolution for voluntary winding up (other than
          a voluntary winding up while solvent for the purposes of an
          amalgamation or reconstruction which has the prior written approval of
          the other party) nor has a meeting of its shareholders been called to
          consider a resolution for winding up;

     (g)  had an administrative receiver or receiver appointed in respect of all
          or any of its assets or the assets of any guarantor;

     (h)  had a written demand for the payment of sums due served upon it in
          accordance with Section 123(1)(a) of the Insolvency Act 1986 which has
          not been settled or disputed.

12.2 The Company is not:

     (a)  the subject of an interim order under Schedule 1B of the Insolvency
          Act 1986 nor has it made an application to Court for such an order;

     (b)  the subject of an administration order, nor has a resolution been
          passed by the Directors or shareholders for the presentation of a
          petition for such an order nor has a petition for such an order been
          presented or come into force;

     (c)  subject to a resolution passed by the Directors or the shareholders
          for notice of appointment of an administrator to be filed with the
          Court, nor has a notice of appointment of an administrator been filed
          with the Court by the holder of a floating charge or by the Company or
          its Directors.


                                      -33-

<PAGE>

B    EMPLOYMENT AND PENSIONS

1    EMPLOYEES

     Employment contracts for Directors and Employees

1.1  The Disclosure Letter contains the following:

     (a)  an accurate list of all Employees together with their job title and
          salary; and

     (b)  accurate and complete copies of the Directors' current service
          agreements and of the current service agreements for all other
          Employees.

     Incentive Schemes

1.2  The Disclosure Letter contains details of all share incentive, share
     option, profit sharing or other incentive or benefit schemes between the
     Company and any of its Employees which are now in force and there are no
     other such schemes.

     Notice periods

1.3  All contracts of service or services with Directors, Employees or
     Consultants can be terminated by 12 months' notice or less without giving
     rise to any claim for damages or compensation (other than a statutory
     redundancy payment or statutory compensation for unfair dismissal or other
     statutory right, if applicable).

     Pay reviews

1.4  No remuneration reviews or negotiations for an increase in the remuneration
     or benefits of an Employee are current or due to take place within the next
     three months.

     Assurances etc

1.5  No assurances or undertakings (whether legally binding or not) have been
     given to any of the Employees as to the continuation, introduction,
     increase or improvement of any terms and conditions, remuneration, benefits
     or other bonus or incentive between the Company and any of its Employees.

     Loans

1.6  There are no outstanding loans between the Company and an Employee (other
     than loans not individually exceeding L5,000 relating to travel
     arrangements).

     Property

1.7  No employee resides in or occupies or is entitled to reside in or occupy
     any property belonging to the Company.

     Secondments

1.8  The Company has not entered into any secondment arrangements relating to
     any Employee.

     Redundancy

1.9  The Company has no obligation to make any payment, on the redundancy of any
     Employee, in excess of the statutory redundancy payment.

     Trade Union

1.10 The Company does not recognise a trade union nor does it have any works or
     supervisory council or other body representing Employees.


                                      -34-

<PAGE>

1.11 The Company has not received any application for recognition from a trade
     union.

2    PENSIONS

2.1  Other than in respect of the Norwich Union Stakeholder Pension Scheme the
     Company has not paid, provided or contributed towards and the Company is
     not under any obligation (whether or not legally enforceable) to pay,
     provide or contribute towards, any relevant benefit as defined in section
     612, Taxes Act 1988 for or in respect of any Pensionable Employee or any
     spouse, child or dependent of any Pensionable Employee.

2.2  The Company is not or has not since 27 April 2004 been an associate of or
     connected with (within the meaning of sections 435 and 239 respectively of
     the Insolvency Act 1986) any person who is an employer in relation to any
     occupational pension scheme, other than a scheme that provides for money
     purchase benefits only (as defined in section 181(1) of the Pension Schemes
     Act 1993).

2.3  The Company is compliant with the stakeholder pension employer requirements
     referred to in Part IV of the Stakeholder Pension Schemes Regulations 2000
     and section 3 of the Reform and Pensions Act 1999.


                                      -35-

<PAGE>

C    INTELLECTUAL PROPERTY AND INFORMATION TECHNOLOGY

1    INTELLECTUAL PROPERTY

1.1  All Intellectual Property which is used by the Company is owned by, or
     licensed to, the Company.

     Registered IP

1.2  Details of all registered Intellectual Property, including applications
     made for registration, owned by the Company are set out in the Disclosure
     Letter (REGISTERED IPR).

1.3  The Company is the exclusive legal and beneficial owner of the Registered
     IPR free from all Encumbrances. So far as the Warrantor is aware, no
     challenge by a third party has been made in respect of the Company's
     applications to register its Intellectual Property.

1.4  All fees payable in respect of the maintenance of the Registered IPR have
     been paid. No third party has challenged any of the Registered IPR and, so
     far as the Warrantor is aware, there are no proceedings (including any
     oppositions or allegations) that might result in any of the registrations
     of the Registered IPR being cancelled or revoked or being subject to a
     compulsory licence, and so far as the Warrantor is aware the Registered IPR
     is valid.

1.5  All material research and development activity conducted by or on behalf of
     the Company has been conducted by employees of the Company acting in the
     course of their employment or pursuant to written agreements complete and
     accurate copies of which are contained in the Disclosure Letter.

1.6  The Company has disclosed in the Disclosure Letter its processes in place
     to document inventions and protect against unauthorised disclosure of its
     Confidential Information, and operates in accordance with those processes.

     Licensed IP

1.7  Complete and accurate copies of all licences of Intellectual Property
     granted to or by the Company, or which otherwise relate to any Intellectual
     Property owned by the Company, are set out in the Disclosure Letter (with
     the exception of basic material transfer agreements and routine software or
     research reagent licenses).

1.8  The Company has complied in all material respects with the terms of, and so
     far as the Warrantor is aware the other parties have complied with the
     material terms of, licences and other agreements referred to in warranty
     1.7 and the Warrantor is not aware of any intention on the part of any
     party to any such licences or agreements to serve a notice to terminate.

     Infringement

1.9  The Company has not received any written notice in the 24 months prior to
     the date of this Agreement alleging that the principal processes employed
     and the principal products and services dealt in by the Company infringe
     the Intellectual Property of any third party.

2    INFORMATION TECHNOLOGY

2.1  Other than as set out in the Disclosure Letter, the information technology
     systems of the Company have not been the subject of failure or breakdown in
     the 12 months prior to the date of this Agreement that has caused any
     material disruption to the business of the Company.

2.2  The Company has protected the information technology systems used by it
     against viruses, Trojan horses and other damaging programming code using
     preventative measures consistent with those commonly used in the drug
     discovery business. The Company has procedures in place designed to prevent
     any unauthorised access to the information technology systems used by it
     and the data


                                      -36-

<PAGE>

     stored on those information technology systems consistent with those
     commonly used in the drug discovery business.

2.3  Details of the Company's security procedures and disaster recovery plans
     are set out in, or attached to, the Disclosure Letter. The Company has
     complied with such procedures and plans for the 12 months prior to the date
     of this Agreement. The Company maintains back-up capabilities which back up
     data after the close of business on each Business Day.

2.4  The Company is notified to the Information Commissioner and has not
     knowingly breached the Data Protection Act 1998 or any applicable data
     protection legislation in England or Wales. The Company's data protection
     policies are set out in, or attached to, the Disclosure Letter.


                                      -37-

<PAGE>

D    PROPERTY AND ENVIRONMENT

1    PROPERTY

     GENERAL

1.1  The Company does not own, control, use or occupy or have any interest in
     any land or building and the Company has not entered into any legally
     binding agreement for the purchase of any such interest.

1.2  All original surrender, release, or indemnity documents relating to any
     Relevant Land (including the Property) are in the possession of the
     Company.

1.3  The Company has not received any written notice or order affecting any
     Relevant Land (including the Property) from any government department, any
     authority or any third party.

1.4  The Company is not a guarantor of the tenant's covenants in any lease,
     including under any authorised guarantee agreement.

1.5  The Company has not surrendered the lease of any leasehold property to the
     reversioner without first investigating the reversioner's title and without
     receiving from the reversioner an absolute release from the tenant's
     covenants in the relevant lease and from all liability arising under the
     lease.

1.6  The Company has not assigned or transferred any leasehold property of which
     it was the original tenant or in respect of which it entered into a
     covenant with the landlord to observe and perform the tenant's covenants
     under that lease without receiving a full and effective indemnity in
     respect of its liability under that lease or that covenant (as the case may
     be).

1.7  The Company has not conveyed or transferred any freehold property in
     respect of which it entered into any covenant (including an indemnity
     covenant) which continues to bind it without receiving a full and effective
     indemnity in respect of its liability under that covenant.

1.8  The Company has not conveyed or transferred any property, whether freehold
     or leasehold, which at the time of conveyance or transfer was subject to a
     lease, tenancy, licence or agreement for occupation or use without
     receiving a full and effective indemnity in respect of its liability under
     each relevant lease, tenancy, licence or agreement or under each indemnity
     covenant given by it in respect of any occupation lease.

2    ENVIRONMENT

2.1  The Company has not received any written notice of any actual, pending or
     threatened actions by Regulatory Authorities or third parties in respect of
     any alleged non-compliance with Environmental Law and has at all times
     complied in all material respects with all applicable Environmental Laws.

2.2  The Company has at all times held all requisite Environmental Licences (all
     of which are (where still required) valid and subsisting) and has at all
     times complied with the terms and conditions of such Environmental Licences
     in all material respects. So far as the Warrantor is aware, no
     Environmental Licence is personal to the Company. So far as the Warrantor
     is aware, there are no circumstances likely to give rise to any,
     suspension, revocation or material modification of any Environmental
     Licence, or which is likely to prejudice the renewal, extension or, where
     necessary, transfer of, any such licence.

2.3  So far as the Warrantor is aware, no Dangerous Substance has been used,
     disposed of, stored, generated, released, buried, transported, or emitted
     at, on, from, under or to any Relevant Land nor, so far as the Warrantor is
     aware, has the Company or any other person or entity for which the Company
     can be liable, used, disposed of, stored, generated, released, buried,
     transported, or


                                      -38-

<PAGE>

     emitted any Dangerous Substance at, on, from or under any other place, in
     each case except where such Dangerous Substances are used, disposed of,
     stored, generated, released, buried, transported or emitted in the ordinary
     course of the Company's business in accordance with any applicable
     Environmental Laws and/or Environmental Licences.


                                      -39-

<PAGE>

E    TAXATION AND TAX RETURNS

     TAXATION

1    As far as the Warrantor is aware, the Company has made all returns and
     given or delivered all notices, accounts and information which ought to
     have been made to any Taxing Authority and all returns, notices, accounts
     and information submitted to any Taxing Authority were when made true and
     accurate in all material respects and the Company is not involved in any
     dispute with any Taxing Authority concerning any matter likely to
     materially affect in any way the liability (whether accrued, contingent or
     future) of it to Taxation and the Warrantor is not aware of any matter
     which may lead to such dispute.

2    As far as the Warrantor is aware, the Company has duly paid or fully
     provided for all Taxation for which it is liable and the Warrantor is not
     aware of any circumstances in which interest or penalties in respect of
     Taxation not duly paid could be charged against the Company in respect of
     any period prior to Completion.

3    No liability of the Company to Taxation, or to account for Taxation, has
     arisen since the Accounts Date or will arise up to Completion save for:

     (a)  corporation tax payable in respect of normal trading profits earned;

     (b)  income tax deducted or accounted for under PAYE regulations;

     (c)  national insurance contributions in respect of emoluments; or

     (d)  value added tax for which it is accountable to any Taxing Authority,

     and which has where appropriate been deducted or charged and where due paid
     to the appropriate Taxing Authority.

4    The Company has not entered into or been a party to any schemes or
     arrangements designed partly or wholly for the purpose of it or (so far as
     the Warrantor is aware) any other person avoiding Taxation.

     DISTRIBUTIONS AND OTHER PAYMENTS

5    The rents, annual payments and other sums of an income nature paid or
     payable by the Company since the Accounts Date, or which the Company is
     under an obligation incurred since the Accounts Date to pay in the future
     and which are not wholly allowable as deductions or charges in computing
     income for the purposes of Corporation Tax (except to the extent that
     payments of a similar nature were made prior to the Accounts Date and were
     not treated as allowable in preparing the Accounts) do not exceed L500,000.

6    All interest, discounts or premiums payable by the Company in respect of
     its loan relationships within the meaning of Chapter II of Part IV of the
     Finance Act 1996 are capable of being brought into account by the Company
     as a debit for the purposes of that Chapter as and to the extent that they
     are from time to time recognised in the Company's accounts (assuming that
     the accounting policies and methods adopted for the purpose of the Accounts
     continue to be so adopted).

     CAPITAL ALLOWANCES AND CAPITAL GAINS

7    No balancing charge under the Capital Allowances Act 1990 or the Capital
     Allowances Act 2001 (or other legislation relating to any capital
     allowances or charge to corporation tax on capital gains) not provided for
     or taken into account in computing any provisions in the Accounts would be
     made on the Company on the disposal of any pool of assets (that is to say
     all those assets expenditure relating to which would be taken into account
     in computing whether a balancing charge would arise on a disposal of any
     other of those assets) or of any asset not in such a pool, on the
     assumption


                                      -40-

<PAGE>

     that the disposals are made for a consideration equal to the book value
     shown in or adopted for the purpose of the Accounts for the assets in the
     pool or (as the case may be) for the asset.

8    No event has occurred since the Accounts Date otherwise than in the
     ordinary course of business by reason of which any balancing charge will
     fall to be made against or any disposal value will fall to be brought into
     account by the Company under the Capital Allowances Act 1990 or the Capital
     Allowances Act 2001 (or other legislation relating to any capital
     allowances).

9    The Company has not claimed any research and development tax relief or tax
     credit under the Finance Act 2000 or the Finance Act 2002.

     CAPITAL GAINS

     INTANGIBLE ASSETS

10   In this section references to intangible fixed assets mean intangible fixed
     assets and goodwill within the meaning of schedule 29 to the Finance Act
     2002 and to which the provisions of that Schedule apply and references to
     an intangible fixed asset shall be construed accordingly.

11   The Disclosure Letter sets out the basis on which debits relating to
     expenditure on intangible fixed assets have been taken into account in the
     Accounts and, so far as the Warrantor is aware, in relation to any such
     expenditure (on intangible fixed assets) incurred since the Accounts Date
     debits will, on the basis of facts and circumstances known at the date of
     this Agreement be available to the Company. So far as the Warrantor is
     aware no circumstances have arisen since the Accounts Date by reason of
     which that basis might change.

12   The Company does not own an asset which has ceased to be a chargeable
     intangible asset since the Accounts Date in the circumstances described in
     paragraph 108 of schedule 29 to the Finance Act 2002 and, so far as the
     Warrantor is aware, no circumstances have arisen since the Accounts Date
     which have required, or will (on the basis of the facts and circumstances
     known at the date of this Agreement) require, a credit to be brought into
     account by the Company on a revaluation of an intangible fixed asset.

     CLOSE COMPANIES

13   The Company is not and has not at any time since incorporation been a close
     investment holding company as defined in section 13A Taxes Act 1988.

14   No distribution within section 418 Taxes Act 1988 has been made by the
     Company since incorporation.

15   No loan or advance made by or debt incurred to or assigned to the Company
     falling within the provisions of section 419 Taxes Act 1988 (as extended by
     section 422 thereof) is outstanding or has been waived since the Accounts
     Date.

     GROUPS OF COMPANIES

16   The Company is not and has not since incorporation been a member of a group
     of companies as defined in section 170 TCGA 1992 or part 8 of schedule 29
     to the Finance Act 2002.

     OVERSEAS INTERESTS

17   UK Residence

     The Company is and has since incorporation been resident in the United
     Kingdom for corporation tax purposes and is not and has not been treated as
     resident in any other jurisdiction for any Taxation purpose. The Company
     has not nor has had a branch, agency or permanent establishment outside the
     United Kingdom.


                                      -41-

<PAGE>

18   Controlled foreign companies and offshore funds

     The Company does not have and has not since incorporation had any interest
     in a controlled foreign company as defined in Chapter IV Part XVII Taxes
     Act 1988 nor any material interest in an offshore fund as defined in
     section 759 Taxes Act 1988.

19   Agency for non-residents

     The Company has not been and is not assessable to Taxation under section 78
     Taxes Management Act 1970 (including that section as modified and applied
     for stamp duty reserve tax), section 126 Finance Act 1995, schedule 26
     Finance Act 2003 or under section 42A Taxes Act 1988.

     SECONDARY LIABILITY

20   The Company is not liable to reimburse or indemnify any person (including a
     Taxing Authority) an amount in respect of a Taxation liability (other than
     in respect of VAT insurance premium tax and air passenger duty) which is
     the primary liability of any other person and which arose as a result of a
     transaction, event, act or omission occurring on or before Completion
     (including those deemed to have occurred for Taxation purposes on or before
     Completion) or by reference to any profits earned on or before Completion.

     TAX AVOIDANCE, TRANSACTIONS REQUIRING CLEARANCE ETC.

21   Transactions between persons under common control

     No transactions or arrangements involving the Company have taken place or
     are in existence which are such that any of the provisions of section 770
     to section 773 or schedule 28AA Taxes Act 1988 or part 12 of schedule 29 to
     the Finance Act 2002 have been or could be applied to it so as to give rise
     to a liability to Taxation of the Company not provided for in the Accounts.

22   Pension scheme refunds

     Since the Accounts Date no payment has been made to the Company to which
     section 601 Taxes Act 1988 applies.

     STAMP DUTY AND STAMP DUTY LAND TAX (SDLT)

23   All documents to which the Company is a party and which are required to be
     stamped with United Kingdom stamp duty in order:

     (a)  to establish the Company's title to an asset owned by it at
          Completion; or

     (b)  to enable their enforcement by any Group Company,

     have been duly stamped.

24   All SDLT payable by the Company has been paid within the periods prescribed
     by law, all land transaction returns have been correctly completed, are
     true and accurate and not the subject of any dispute with or enquiry from
     any Taxing Authority.

     VALUE ADDED TAX

25   Registration

     The Company is duly registered for the purposes of Value Added Tax with
     monthly prescribed accounting periods and no such registration is subject
     to any conditions imposed by or agreed with the relevant Taxing Authority
     and the Company is not (nor are there any circumstances by virtue of which
     it may become) under a duty to make monthly payments on account under the
     Value Added Tax (Payments on Account) Order 1993.


                                      -42-

<PAGE>

26   VAT group

     The Company is not nor has it been treated for Value Added Tax purposes as
     a member of any group of companies and there has been no transfer of a
     business as a going concern in respect of which the Company could become,
     or has at any time since the Accounts Date been, liable under section 44
     VATA 1994 nor since the Accounts Date has there been any supply of goods or
     services by the Company in respect of which section 43(1) VATA 1994 is
     disapplied by sub-section (2A) of that section. No direction has been given
     to the Company under paragraph 1 of schedule 9A to VATA 1994 either to the
     Company or in circumstances where the Company may be liable for any Value
     Added Tax assessed by that direction.

27   Secondary liability

     No act or transaction has been effected in consequence of which the Company
     is or may be held liable for any Value Added Tax under section 29, section
     47, section 48 or section 55 VATA 1994.

28   Compliance

     The Company has complied with all statutory provisions, rules, regulations,
     orders and directions concerning Value Added Tax.

29   Exemption

     The Company is not nor was it partially exempt in its current or preceding
     value added tax year and so far as the Warrantor is aware there are no
     circumstances by reason of which either regulation 107 or 108 Value Added
     Tax Regulations 1995 might apply (or have since the Accounts Date applied)
     to the Company.

30   Valuation

     No direction has been or so far as the Warrantor is aware could have been
     made to the Company under paragraph 1 of schedule 6 or paragraph 1 of
     schedule 7 to VATA 1994.

31   Security

     The Company has not at any time been required to give security under
     paragraph 4 of schedule 11 to VATA 1994.

32   Option to charge VAT on supplies by the Company

     The Disclosure Letter contains particulars of any elections to waive
     exemption made under schedule 10 to VATA 1994 by (i) the Company or (ii)
     any person who is a relevant associate (as defined in paragraph 3(7) of
     that schedule) in relation to the Company and all such elections have
     effect. The Company has not made an exempt supply in relation to any
     property such that it did or (if it wished to elect in future) would need
     permission to elect to waive exemption and there is no land or building in
     which the Company has an interest where any election to waive exemption is
     or may become ineffective by virtue of paragraph 2(3A) or 2(3AA) of the
     schedule.

33   Capital Goods Scheme

     There is no capital item within the meaning of Part XV of the Value Added
     Tax Regulations 1995 (S.I. 1995/2518) in relation to which a liability
     under Part XV has arisen or could in future arise on the Company.

34   Interest in the case of official error and repayment supplement

     No claims have been made by the Company under section 78 or section 79 VATA
     1994. So far as the Warrantor is aware there are no circumstances by virtue
     of which an assessment under section 78A VATA 1994 has been or could be
     made on the Company.


                                      -43-
<PAGE>

35   Bad debt relief

     The Company has not made any claim under section 36 VATA 1994. So far as
     the Warrantor is aware, there are no circumstances by virtue of which there
     could be a clawback of input tax from the Company under section 26A VATA
     1994.

36   Inheritance Tax

     So far as the Warrantor is aware, there are not in existence any
     circumstances whereby any such power as is mentioned in section 212(1)
     Inheritance Tax Act 1984 that could so far as the Warrantor is aware be
     exercised in relation to any shares, securities or assets of the Company.


                                      -44-

<PAGE>

                                   SCHEDULE 4

                                BUYER WARRANTIES

1    The Buyer is a company duly incorporated and validly existing under the
     laws of England and Wales and has the requisite power, capacity and
     authority to enter into and perform this Agreement.

2    This Agreement constitutes valid and legally binding obligations of the
     Buyer enforceable in accordance with their terms subject to:

     (a)  limitations arising from the laws of bankruptcy, administration,
          liquidation, insolvency, receivership or similar laws affecting
          generally the enforcement of creditors' rights;

     (b)  the effect of general principles of law and equity;

     (c)  where any obligations of any person are to be performed or observed
          outside England and Wales, or by a person subject to the laws of a
          jurisdiction outside England and Wales, the possibility that such
          obligations may not be enforceable under English law to the extent
          that performance or observance thereof would be illegal or contrary to
          public policy under the laws of any such jurisdiction;

     (d)  the effect of the Limitation Act 1980; and

     (e)  the laws of any jurisdiction outside England.

3    Neither the entry into this Agreement nor the implementation of the
     transactions contemplated by it will result in:

     (a)  a breach of any provision of the memorandum and articles of
          association of the Buyer;

     (b)  a breach of, or give rise to a default under, any contract or other
          instrument to which the Buyer is a party or by which it is bound; or

     (c)  a breach of any applicable laws or regulations or of any order, decree
          or judgment of any court, governmental agency or regulatory authority
          applicable to the Buyer.

4    With the exception of those matters referred to in clause 5 no consent or
     approval of, authorisation or order of any court or any governmental,
     regulatory or other authority which has not been obtained or made at the
     date of this Agreement is required by the Buyer for the execution or
     implementation of this Agreement.

5

5.1  The Buyer has not:

     (a)  entered into any arrangement or composition for the benefit of its
          creditors or any of them nor has it (or its agent or nominee) convened
          a meeting of its creditors;

     (b)  submitted to its creditors or any of them a proposal under Part I of
          the Insolvency Act 1986;

     (c)  entered into any arrangement, scheme, compromise, moratorium or
          composition with any of its creditors (whether under Part I of the
          Insolvency Act 1986 or otherwise);

     (d)  made an application to the Court under section 425 of the Companies
          Act 1985 or resolved to make such an application;


                                      -45-

<PAGE>

     (e)  presented a petition for winding up nor has a petition for winding up
          been presented against it which has not been withdrawn within 14 days,
          nor has a winding up order been made against it or a provisional
          liquidator appointed;

     (f)  been the subject of a resolution for voluntary winding up (other than
          a voluntary winding up while solvent for the purposes of an
          amalgamation or reconstruction which has the prior written approval of
          the other party) nor has a meeting of its shareholders been called to
          consider a resolution for winding up;

     (g)  had an administrative receiver or receiver appointed in respect of all
          or any of its assets or the assets of any guarantor;

     (h)  had a written demand for the payment of sums due served upon it in
          accordance with section 123(1)(a) of the Insolvency Act 1986 which has
          not been settled or disputed.

5.2  The Buyer is not:

     (a)  the subject of an interim order under Schedule 1B of the Insolvency
          Act 1986 nor has it made an application to Court for such an order;

     (b)  the subject of an administration order, nor has a resolution been
          passed by the Directors or shareholders for the presentation of a
          petition for such an order nor has a petition for such an order been
          presented or come into force;

     (c)  subject to a resolution passed by the Directors or the shareholders
          for notice of appointment of an administrator to be filed with the
          Court, nor has a notice of appointment of an administrator been filed
          with the Court by the holder of a floating charge or by the Company or
          its Directors.

5.3  No member of the Buyer's Group is:

     (a)  a party to any litigation, arbitration or administrative proceedings
          which are in progress or of which it has been notified in writing by
          or against or concerning it or any of its assets; nor

     (b)  so far as the directors of the Buyer are aware, the subject of any
          governmental, regulatory or official investigation or enquiry which is
          in progress or of which it has been notified in writing,

which in each case has or is likely to have a material adverse effect on the
Buyer's ability to execute, deliver and perform its obligations under this
Agreement.

5.4  The Buyer has available sufficient authorised and unissued share capital to
     permit the issue of the Initial Consideration Shares and the Retained
     Consideration Shares in accordance with the terms of this Agreement.


                                      -46-

<PAGE>

                                   SCHEDULE 5

         PART 1: LIMITATIONS ON LIABILITY UNDER THE PRINCIPAL WARRANTIES

The following limitations only relate to Principal Warranty Claims:-

1    SCOPE

1.1  The Warrantor shall only be liable in respect of a Principal Warranty Claim
     if such Principal Warranty Claim becomes a Determined Claim which shall
     mean a claim:

     (a)  which has been resolved by written agreement between the Sellers and
          the Buyer; or

     (b)  which is the subject of an order as to both liability and quantum made
          by a court or tribunal of competent jurisdiction or arbitration.

1.2  Nothing in this Schedule shall have the effect of excluding, limiting or
     restricting any liability of the Warrantor in respect of a Principal
     Warranty Claim arising as a result of fraud or wilful non-disclosure on the
     part of the Warrantor.

2    CAP ON WARRANTOR'S LIABILITY

2.1  The aggregate liability of the Warrantor in respect of all and any
     Principal Warranty Claims shall not exceed the Warranty Claim Limit.

2.2  In the event that the Buyer brings a Principal Warranty Claim against the
     Warrantor and such Principal Warranty Claim becomes a Determined Claim,
     then such Principal Warranty Claim shall be satisfied (and shall only be
     capable of being satisfied) at the Warranty Claim Ratio by both a reduction
     in the number of Retained Consideration Shares to be allotted and issued to
     Apax and Wellcome Trust by the Buyer (calculated in accordance with clause
     4) and by a reduction in the Deferred Consideration (calculated in
     accordance with Clause 3.6), provided that the aggregate amount available
     to satisfy all Principal Warranty Claims shall always be limited to:

     (a)  a reduction in the number of Retained Consideration Shares to be
          allocated and issued to Apax and the Wellcome Trust equal to such
          number of Retained Consideration Shares, which at the Issue Price have
          an aggregate value of no more than L***; plus

     (b)  a reduction in the Deferred Consideration of no more than L***,
          and

     provided further that the aggregate amount available to satisfy all
     Principal Warranty Claims, and any Ancillary Claims to be satisfied
     pursuant to paragraph 4 of Part 2 of Schedule 8, shall not exceed the
     Warranty Claim Limit.

     Accordingly the Warrantor shall have no financial liability for, and the
     Buyer shall not be able to seek any financial payment from the Warrantor
     (or his estate or personal representatives) in respect of, any Principal
     Warranty Claim.

3    TIME LIMITS FOR MAKING CLAIMS

3.1  No Principal Warranty Claim may be made against the Warrantor unless notice
     (complying with the provisions of paragraph 3.2 below) of such Principal
     Warranty Claim is served on the Warrantor (but not his estate or personal
     representatives, if relevant) and Apax and Wellcome Trust in writing as
     soon as practicable after the Buyer becomes aware of the circumstances
     giving rise to a Principal Warranty Claim and, in any event before the day
     falling on the first anniversary of Completion provided that, save in
     respect to a Principal Warranty Claim to which subparagraph 4 applies, the
     liability of the Warrantor shall cease absolutely unless within six months
     of service of such notice legal proceedings in respect of such Principal
     Warranty Claim have been properly issued and validly served on the
     Warrantor.


                                      -47-

<PAGE>

3.2  A notice of Principal Warranty Claim shall specify in reasonable detail the
     specific matter in respect of which the Principal Warranty Claim is made
     and a calculation of the amount claimed.

4    CONTINGENT LIABILITIES

     No Principal Warranty Claim may be made against the Warrantor based upon a
     liability which is contingent unless and until such contingent liability
     becomes an actual liability.

5    THRESHOLD AND DE MINIMIS

5.1  The Warrantor shall not be liable in respect of any Principal Warranty
     Claim unless the aggregate liability for all Principal Warranty Claims
     exceeds L150,000 (THE THRESHOLD), in which case the Buyer shall be
     entitled to all amounts resulting from those Principal Warranty Claims and
     not just the excess over the Threshold.

5.2  In calculating liability for Principal Warranty Claims for the purposes of
     paragraph 5.1 above, any Principal Warranty Claim which is less than
     L*** shall be disregarded and the Warrantor shall not be liable for
     any such disregarded Claims.

5.3  If more than one Principal Warranty Claim arises from, or is caused by, the
     same or substantially the same matter, matters, circumstance or
     circumstances and the aggregate amount of damages to which the Buyer would
     be entitled as a result of those Principal Warranty Claims is equal to or
     exceeds the sum specified in subparagraph 5.2, subparagraph 5.2 shall not
     apply to any of those Principal Warranty Claims.

6    CHANGES IN LEGISLATION

     The Warrantor shall not be liable in respect of a Principal Warranty Claim
     if such Principal Warranty Claim would not have arisen but for, or to the
     extent it is increased directly or indirectly as a result of:

     (a)  a change in legislation or law announced after the date of this
          Agreement; or

     (b)  an increase in the Taxation rates or an imposition of Taxation in each
          case not actually or prospectively in force at the date of this
          Agreement; or

     (c)  any change or withdrawal after the date of this Agreement of any
          published practice or concession of any Taxing Authority; or

     (d)  a change after Completion in the accounting policies adopted by the
          Company (other than a change made in order to comply with the Accounts
          Standards in force at the date of this Agreement) including any change
          to the date to which its accounts are prepared.

7    ACTS OF BUYER

     The Warrantor shall not be liable in respect of a Principal Warranty Claim
     to the extent that such Principal Warranty Claim is directly attributable
     to, or to the extent it is increased directly or indirectly as a result of:

     (a)  any act, omission, transaction or arrangement carried out at the
          request of or with the approval of the Buyer before or at Completion;
          or

     (b)  any act, omission, transaction or arrangement carried out by or on
          behalf of the Buyer or by or on behalf of a member of the Buyer's
          Group outside the ordinary course of business after Completion.


                                      -48-

<PAGE>

8    MITIGATION

     Nothing in this Agreement shall be deemed to relieve the Buyer from any
     common law duty to take reasonable steps to mitigate any loss or damage
     suffered or incurred by it as a result of any of the Principal Warranties
     being untrue or inaccurate.

9    RECOVERY FROM ANOTHER PERSON

9.1  If the Buyer or any member of the Buyer's Group receives (whether by
     payment, discount, credit, relief or otherwise) from a third party a sum
     which would not have been received but for the matter or circumstance
     giving rise to the relevant Principal Warranty Claim before the Principal
     Warranty Claim is settled, such sum (less any reasonable costs incurred in
     obtaining such sum and less any Taxation attributable to the recovery after
     taking account of any tax relief available in respect of any matter giving
     rise to the Principal Warranty Claim) shall to that extent reduce or
     satisfy, as the case may be, such Principal Warranty Claim.

9.2  If the Sellers resolve a Principal Warranty Claim in accordance with
     paragraph 1.1(a) which results in the number of Retained Consideration
     Shares being reduced in accordance with clauses 4.5-4.7 and the Buyer
     subsequently within six months of the Principal Warranty Claim being so
     determined (the last day of such 6 month period being the "Settlement
     Date") receives from a third party a sum which would not have been received
     but for the matter or circumstance giving rise to the relevant Principal
     Warranty Claim and receipt of this amount was not taken into account when
     settling the Principal Warranty Claim, then the Buyer shall within 5
     Business Days of the Settlement Date issue such number of the balance (if
     any) of the Retained Consideration Shares as is equal to the number
     obtained by dividing such sum received by the Buyer (less any reasonable
     costs incurred in obtaining such sum and less any Taxation attributable to
     the recovery after taking account of any tax relief available in respect of
     any matter giving rise to the Principal Warranty Claim) (subject to a
     maximum amount equal to the Principal Warranty Claim settled) by the Issue
     Price.

10   COMPLETION STATEMENT

     No matter or circumstance shall be subject to a Principal Warranty Claim to
     the extent that such matter has been taken into account in the Completion
     Statement.

11   NOTICE OF CLAIMS

     If a member of the Buyer's Group becomes aware of or is notified in writing
     of circumstances giving rise to a claim or of an entitlement to recover
     (whether by payment, discount, credit, relief or otherwise) from a third
     party an amount which relates to the subject matter of a Principal Warranty
     Claim the Buyer shall as soon as reasonably practicable give written notice
     to and consult with the Sellers in respect of the claim, circumstance or
     entitlement and continue to give the Sellers reasonably regular updates on
     the progress of such claim. Such notice to the Sellers shall specify in
     reasonable detail the specific matter in respect of which the claim,
     circumstance or entitlement has arisen and a calculation of the amount
     claimed or recoverable from the relevant third party. The Buyer will keep
     the Sellers informed of any material developments relating to the claim,
     circumstance or entitlement.

12   TAXATION

12.1 No Principal Warranty Claim may be made against the Warrantor:

     (a)  to the extent that the Principal Warranty Claim is in respect of
          Taxation and comprises Taxation payable on income, profits or gains
          actually earned, accrued or received in the ordinary course of
          business of the Company between the Accounts Date and Completion; or


                                      -49-

<PAGE>

     (b)  to the extent that the Principal Warranty Claim is in respect of
          Taxation and such Taxation arises from a transaction in the ordinary
          course of business of the Company between the Accounts Date and
          Completion; or

     (c)  to the extent that the Principal Warranty Claim is in respect of
          Taxation and such Taxation would not have arisen but for:

          (i)  a disclaimer, claim or election made or notice or consent given
               after Completion by a member of the Buyer's Group otherwise than
               at the request of the Warrantor; or

          (ii) a failure or omission by the Company to make any claim, election,
               surrender or disclaimer or give any notice or consent or do any
               other thing after Completion the making or giving or doing of
               which was taken into account or assumed in computing the
               provision for Taxation (including the provision for deferred
               Taxation) in the Accounts and in respect of which the Warrantor
               had provided to the Buyer written details of such claims,
               elections, surrenders or disclaimers, notices or consents, or
               doing of any other thing not less than 10 Business Days before
               the expiry of any relevant time limits in respect of the same; or

     (d)  to the extent that the Principal Warranty Claim is in respect of
          Taxation and such Taxation could be relieved or mitigated by any loss,
          relief, allowance, exemption, set off or credit (other than any loss,
          relief, allowance, exemption, set off or credit or right to repayment
          of Taxation (including any repayment supplement) which is not
          available to the Company before Completion but is available to the
          Company after Completion as a result of any event or transaction
          occurring after Completion) in computing or against income, profits,
          gains or Taxation; or

     (e)  to the extent that the Principal Warranty Claim is in respect of
          Taxation and such Taxation was discharged (whether by payment or by
          the utilisation of any relief, allowance or credit in respect of
          Taxation) prior to Completion; or

     (f)  to the extent that the Principal Warranty Claim is in respect of VAT
          which has been charged and a tax invoice issued but which is not yet
          due to HM Revenue and Customs; or

     (g)  to the extent that the Principal Warranty Claim arises as a result of
          unutilised reliefs, allowances or credits (if any) of the Company as
          at or arising before Completion proving to be unavailable or otherwise
          incapable of being utilised in reducing the income, profits or gains
          of the Company earned, accrued or received on or after Completion or
          the Taxation liabilities of the Company in respect of any period after
          Completion.

12.2 In calculating the liability of the Warrantor for any Principal Warranty
     Claim in respect of Taxation, there shall be taken into account the amount
     by which any Taxation for which the Buyer or any member of the Buyer's
     Group is now or may in the future be accountable or liable to be assessed
     is reduced or extinguished as a result of the matter giving rise to such
     liability and any repayment of Taxation which would not have arisen but for
     the matter giving rise to such liability.

13   NO DOUBLE RECOVERY

     The Buyer shall not be entitled to recover in respect of the Principal
     Warranties more than once for the same loss.


                                      -50-

<PAGE>

     PART 2: LIMITATIONS ON LIABILITY UNDER THE SELLERS' WARRANTIES AND BUYER
     WARRANTIES

1    SCOPE

1.1  No party to this Agreement shall be entitled to claim under the Sellers'
     Warranties or Buyer Warranties for any indirect or consequential loss or
     loss of profit.

1.2  A party to this Agreement shall only be liable in respect of a Buyer
     Capacity Claim or Sellers' Capacity Claim if and to the extent that such
     Capacity Claim becomes a Determined Claim which shall mean a Capacity
     Claim:

     (a)  which has been resolved by written agreement between the relevant
          Seller(s) and the Buyer; or

     (b)  which is the subject of an order as to both liability and quantum made
          by a court or tribunal of competent jurisdiction or arbitration.

1.3  Nothing in this Schedule shall have the effect of excluding, limiting or
     restricting any liability of the relevant party in respect of a Claim under
     either the Buyer Warranties or the Sellers' Warranties arising as a result
     of fraud by that party.

2    CAP ON BUYER'S LIABILITY

2.1  The aggregate liability of the Buyer to the Sellers in respect of all and
     any Buyer Capacity Claims (together with the proper and reasonable costs of
     recovery of any damages for breach of warranty incurred by or on behalf of
     the Sellers, including stamp duty in respect of the transfer of any shares)
     shall not exceed an amount equal to the amount of the Consideration Price
     (calculated, where relevant, by reference to the Issue Price) paid by the
     Buyer at the time such Claim becomes a Determined Claim.

3    CAP ON SELLERS' LIABILITY

3.1  The aggregate liability of each of Apax and Wellcome Trust in respect of
     all and any Sellers' Capacity Claims (when aggregated with any other
     Claims) shall, save as provided below, not exceed the amount of the
     Consideration Price (calculated, where relevant, by reference to the Issue
     Price) paid by Buyer to the relevant Seller at the time such Seller's
     Capacity Claim becomes a Determined Claim (the "Paid Amount").

3.2  If, and to the extent that, at the time such Sellers' Capacity Claim
     becomes a Determined Claim:

     (a)  any of the Retained Consideration or the Deferred Consideration
          remains to be paid by the Buyer; and

     (b)  the amount of the Determined Claim exceeds the Paid Amount,

     then (i) firstly, the number of Retained Consideration Shares remaining to
     be issued to each of Apax and Wellcome Trust pursuant to this Agreement,
     and (ii) then, the amount of the Deferred Consideration, shall be reduced
     accordingly.

3.3  The aggregate liability of the Warrantor in respect of all and any Sellers'
     Capacity Claims (when aggregated with any other Claims) shall not exceed
     the amount of the Consideration Price received by the Warrantor as at the
     date the Seller's Capacity Claim becomes a Determined Claim.

4    TIME LIMITS FOR MAKING CLAIMS

4.1  No claim in respect of the Buyer Warranties and the Sellers' Warranties may
     be made against any party to this Agreement unless notice (complying with
     the provisions of paragraph 4.2 below) of such claim is served on the
     relevant party in writing as soon as practicable after the circumstances


                                      -51-

<PAGE>

     giving rise to a claim become apparent and, in any event, before the date
     falling 12 months following the date of Completion provided that the
     liability of such party shall cease absolutely unless within six months of
     service of such notice legal proceedings in respect of such claim in
     respect of the Buyer Warranties and the Sellers' Warranties have been
     properly issued and validly served on the relevant party and/or such claim
     has been pursued with reasonable diligence.

4.2  A notice of claim in respect of the Buyer Warranties and the Sellers'
     Warranties shall specify in reasonable detail the specific matter in
     respect of which the claim is made and a calculation of the amount claimed.


                                      -52-

<PAGE>

                                   SCHEDULE 6

                            PRE COMPLETION COVENANTS

1    ACCESS

     From the date of this Agreement until Completion the Sellers shall:

     (a)  procure that the Buyer, its agents and representatives are given full
          access to the Property and to the books and records (excluding minutes
          of the Board Meetings of the Company) of the Company during normal
          business hours on any Business Day and on reasonable notice to the
          Sellers; and

     (b)  provide such information regarding the Business and affairs of the
          Company as the Buyer may reasonably require.

2    CONDUCT OF BUSINESS

2.1  From the date of this Agreement until Completion each Seller shall exercise
     all rights and powers available to him or it (as the case may be) so as to
     procure that, except with the written consent of the Buyer, the Company
     shall not:

          (a)  incur any expenditure in respect of:

               (i)  any Internal Cost in excess of L20,000 per item or L100,000
                    in aggregate other than

                    a)   expenditure expressly specified in the Budget in
                         respect of any Internal Cost; and

                    b)   any expenditure incurred pursuant to obligations under
                         the RB Contract; and

                    c)   expenditure relating to the Property Costs directly
                         associated with the termination of the Lease.

               (ii) any External Cost in excess of L50,000 per item; or

          (b)  dispose of or grant any licence in respect of any interest in its
               Intellectual Property other than pursuant to an agreement
               relating to the transfer of materials or a confidentiality
               agreement entered into in the ordinary course of its business; or

          (c)  dispose of or create any Encumbrance in respect of any part of
               its assets except in the ordinary course of trading; or

          (d)  borrow any money or make any payments out of or drawings on its
               bank account(s) (except routine payments or drawings); or

          (e)  enter into any unusual or abnormal contract or commitment or:

               (i)  grant any lease or third party right in respect of the
                    Property or transfer or otherwise dispose of the Property
                    other than as specifically contemplated by this Agreement;
                    or

               (ii) make or prepay any loan; or

               (iii) enter into any leasing, hire purchase or other agreement or
                    arrangement for payment on deferred terms; or


                                      -53-

<PAGE>

               (iv) fail to observe and perform any term or condition of, or
                    waive any rights under, any contract or arrangement; or

               (v)  contravene any statute, order, regulation or the like; or

               (vi) do or omit to do anything which might result in the
                    termination, revocation, suspension, modification or
                    non-renewal of any licence or consent held by it; or

               (vii) grant any power of attorney; or

     (f)  declare, make or pay any dividend or other distribution; or

     (g)  grant, issue or redeem any mortgage, charge, debenture or other
          security or give any guarantee or indemnity; or

     (h)  make any change in the terms and conditions of employment of any of
          its Directors or Employees or employ or terminate (except for good
          cause) the employment of any person other than as specifically
          contemplated by this Agreement; or

     (i)  make, or announce to any person any proposal to make, any change or
          addition to any Retirement Benefit of or in respect of any of its
          directors, employees, former directors or former employees (or any
          dependant of any such person) other than any change required by law or
          proposed change of which full and accurate particulars are set out in
          the Disclosure Letter; or

     (j)  grant or create, or announce to any person any proposal to grant or
          create, any additional Retirement Benefit; or

     (k)  permit any of its insurances to lapse or do anything which would make
          any policy of insurance void or voidable; or

     (l)  create, issue, purchase or redeem any class of share or loan capital
          other than in accordance with the terms of conversion of the Apax
          Loan; or

     (m)  pass any resolution of its shareholders or any class of shareholders,
          whether in general meeting or otherwise; or

     (n)  form any subsidiary or acquire shares in any company or participate
          in, or terminate any participation in, any partnership or joint
          venture; or

     (o)  agree, conditionally or otherwise, to do any of the foregoing; or

     (p)  in any other way depart from the ordinary course of its day-to-day
          trading.

2.2  Until Completion the Sellers shall jointly exercise all powers available to
     them so as to procure that the Company shall maintain the policies for the
     payment of creditors and the collection of debts of the Company which have
     been applied during the Financial Year ended on the Accounts Date and, in
     particular, shall procure that:

     (a)  there is no unusual postponement of the payment of creditors or
          unusual acceleration of the collection of debts in either case having
          regard to the policies applied for such payment and collection
          prevailing in the Financial Year ended on the Accounts Date; and

     (b)  no discounts or other forms of inducements or incentives whatsoever
          are offered or made available by the Company to debtors in relation
          to, or on account of, early payment other than pursuant to
          arrangements in place as at the date of this Agreement (if any) which
          have been notified to the Buyer.


                                      -54-

<PAGE>

2.3  From the date of this Agreement Apax will not exercise any powers or rights
     whether contained in the Articles of Association or otherwise to appoint
     any person as a director of the Company or to remove any Director.

2.4  From the date of this Agreement the Sellers shall not convert, consolidate
     or sub-divide any share capital of the Company or otherwise pass any
     resolution in connection with the share capital of the Company (save in
     connection with the conversion of the Apax Loan).


                                      -55-

<PAGE>

                                   SCHEDULE 8

                                   INDEMNITIES

                                     PART 1

TITLE INDEMNITY

1    Apax and Wellcome Trust each hereby agrees to indemnify the Buyer in the
     Relevant Proportions against all costs, liabilities, claims, demands and
     expenses (including all reasonable legal and other professional fees and
     expenses) which may be sustained or suffered by the Buyer or the Company in
     respect of any Minority Shareholder Claim.

2    The aggregate liability of Apax and Wellcome Trust in respect of all and
     any Title Claims shall be limited in the Relevant Proportions to an amount
     equal to 'X' per cent of L*** where 'X' is calculated as follows:

                          A
               X = 100 x ---
                          B

     Where:

     A = the number of Shares held by the Minority Shareholders immediately
     prior to Completion

     B = the number of Shares in issue at Completion

3    No Title Claim may be made against either Apax or Wellcome Trust unless
     notice (complying with the provisions of paragraph 4 below) of such claim
     is served on both Apax and Wellcome Trust in writing as soon as reasonably
     practicable after the circumstances giving rise to such claim become known
     to the Buyer and, in any event, before the expiry of 6 months from the date
     of Completion provided that the liability of Apax and Wellcome Trust in
     respect of such claim shall cease absolutely unless within six months of
     service of such notice legal proceedings in respect of such claim have been
     properly issued and validly served on both Apax and Wellcome Trust.

4    A notice of claim under paragraph 1 shall specify in reasonable detail the
     specific matter in respect of which the claim is made and a calculation of
     the amount claimed.

5    The conduct of all claims under this Part 1 shall be governed by the terms
     of Part 3 below.

6    In the event that the Buyer brings a Title Claim against Apax and/or
     Welcome Trust, such Title Claim shall be satisfied first by a reduction in
     the number of Retained Consideration Shares, calculated in accordance with
     clause 4.


                                      -57-

<PAGE>

                                     PART 2

PROPERTY AND REDUNDANCY INDEMNITY

1    Apax and Wellcome Trust each hereby agrees to indemnify the Buyer in the
     Relevant Proportions against all reasonable costs, liabilities claims,
     demands and expenses (including all reasonable legal and other professional
     fees and expenses) which may be sustained or suffered by the Buyer or the
     Company to the extent not taken into account in the Completion Statement:

     (a)  in relation to Property Costs; and

     (b)  as a result of Redundancy Costs.

2    The aggregate liability of Apax and Wellcome Trust in respect of all and
     any Ancillary Claims shall be limited to a maximum amount equal to L***
     but subject to the provisions of paragraph 4 below.

3    In the event that the Buyer brings an Ancillary Claim against Apax and
     Wellcome Trust, such claim shall be satisfied in the following order:

     (a)  firstly, by a reduction in the number of Retained Consideration Shares
          to be allotted and issued to Apax and Wellcome Trust by the Buyer
          calculated in accordance with clause 4, up to a maximum reduction of
          number of Retained Consideration Shares which at the Issue Price are
          of a value equivalent to L***; and

     (b)  then as provided in paragraph 4 below.

     Accordingly Apax and Wellcome Trust shall have no direct payment obligation
     for, and the Buyer shall not be able to seek any financial payment from
     Apax and Wellcome Trust in respect of, any such Ancillary Claim.

4    To the extent that the aggregate liability of Apax and Wellcome Trust in
     respect of Ancillary Claims exceeds L***, Apax and Wellcome Trust agree to
     satisfy any such Ancillary Claim first by a reduction in the number of
     Retained Consideration Shares to be allotted to Apax and Wellcome Trust
     calculated in accordance with Clause 4 and thereafter by a reduction in the
     Deferred Consideration be paid to Apax and Wellcome Trust in accordance
     with Clause 3.5 of no more than L***;

     Provided that, the aggregate amount available to satisfy all Principal
     Warranty Claims together with any such Ancillary Claims to be satisfied
     pursuant to this paragraph 4 shall not exceed the Warranty Claim Limit.

5    No Ancillary Claim may be made against Apax and Wellcome Trust unless
     notice (complying with the provisions of paragraph 6 below) of such claim
     is served on each of Apax and Wellcome Trust in writing as soon as
     reasonably practicable after the circumstances giving rise to a Ancillary
     Claim become known to the Buyer and, in any event, before:

     (a)  in respect of any claim in relation to Property Costs, the day falling
          12 months from the date of Completion; and

     (b)  in respect of any claim in relation to Redundancy Costs, the day
          falling 14 days from the later of:

          (i)  3 months from the date of Completion;

          (ii) 3 months from the date of termination of the relevant Employee's
               employment; and

          (iii) such other time and date as is determined by an employment
               tribunal to be the final date for service of proceedings on the
               Company by the relevant Employee,


                                      -58-
<PAGE>

     provided that the liability of Apax and Wellcome Trust shall cease
     absolutely unless within six months of service of such notice legal
     proceedings in respect of such Ancillary Claim have been properly issued
     and validly served on each of Apax and Wellcome Trust.

6    A notice of Ancillary Claim shall specify in reasonable detail the specific
     matter in respect of which the Ancillary Claim is made and a calculation of
     the amount claimed.

7    The conduct of all claims under this Part 2 shall be governed by the terms
     of Part 3 below.


                                      -59-
<PAGE>

                                     PART 3

CONDUCT OF TITLE CLAIMS AND ANCILLARY CLAIMS

1    For so long as, and to the extent that, the Buyer is entitled to make a
     Title Claim or Ancillary Claim under this Agreement, if a member of the
     Buyer's Group becomes aware of any claim or any matter or circumstance
     which might give rise to a Title Claim or an Ancillary Claim or of an
     entitlement to recover (whether by payment, discount, credit, relief or
     otherwise) from a third party an amount which relates to the subject matter
     of such a claim:

     (a)  the Buyer shall promptly give written notice to and consult with both
          Apax and Wellcome Trust in respect of the claim, matter, circumstance
          or entitlement;

     (b)  the Buyer shall, and shall procure that each member of the Buyer's
          Group shall:

          (i)  at the written request and the cost of both Apax and Wellcome
               Trust take such action or (at Apax and Wellcome Trust's option)
               permit Apax and Wellcome Trust to take such action as they
               consider appropriate to avoid, dispute, resist, appeal, defend,
               compromise or settle the claim (including, without limitation,
               making any counterclaims or other claims against third parties)
               and any related adjudication or proceedings, and to conduct
               matters relating thereto including negotiations or appeals,
               subject to the Buyer and/or the relevant member of the Buyer's
               Group being indemnified for all reasonable costs and expenses;

          (ii) provide to Apax and Wellcome Trust and its advisers reasonable
               access to premises and personnel and to relevant assets,
               documents and records within each member of the Buyer's Group's
               power or control that are reasonably required for the purposes of
               investigating the matter or entitlement which allegedly gives
               rise to the claim (save for documents which are privileged from
               production to the Sellers); and

          (iii) (use reasonable efforts to preserve all documents, records,
               correspondence, accounts, electronically stored data and other
               information relevant to a matter which has given rise to a claim.

     (c)  Apax and Wellcome Trust (at their cost) may, subject to providing
          reasonable notice to the Buyer and complying with the reasonable
          requests of the Buyer and subject to any duty of confidentiality owed
          by the Buyer to any other person, examine and take copies of the
          documents or records, and photograph the premises or assets to which
          they are permitted access under paragraph 1.1(b)(ii) above.

2    If a claim is as a result of, or in connection with, a claim by or a
     liability to a third party then the Buyer shall and shall procure that each
     member of the Buyer's Group shall make no admission of liability in respect
     of, or compromise, dispose of or settle, such claim without the written
     consent of both Apax and Wellcome Trust.

3    Apax and Wellcome Trust shall only be liable in respect of a claim under
     either paragraph 1 of part 1 or paragraph 1 of part 2 of this schedule if
     and to the extent that such claim becomes a Determined Claim which shall
     mean a claim:

     (a)  which has been resolved by written agreement between each of Apax and
          Wellcome Trust and the Buyer; or

     (b)  which is the subject of an order as to both liability and quantum made
          by a court or tribunal of competent jurisdiction or arbitration.


                                      -60-

<PAGE>

     ATTESTATIONS

EXECUTED by Apax Partners Europe Managers Ltd on behalf of APAX EUROPE V - A,
L.P. acting by


-------------------------------------
Signatory

-------------------------------------
Print name of signatory


EXECUTED by Apax Partners Europe Managers Ltd on behalf of APAX EUROPE V - B,
L.P. acting by


-------------------------------------
Signatory

-------------------------------------
Print name of signatory


EXECUTED by Apax Partners Europe Managers Ltd on behalf of APAX EUROPE V - C
GmbH & Co. KG acting by


-------------------------------------
Signatory

-------------------------------------
Print name of signatory


EXECUTED by Apax Partners Europe Managers Ltd on behalf of APAX EUROPE V - D,
L.P. acting by


-------------------------------------
Signatory

-------------------------------------   ----------------------------------------
Print name of signatory                 Print name of signatory


                                      -61-

<PAGE>

EXECUTED by Apax Partners Europe Managers Ltd on behalf of APAX EUROPE V - E,
L.P. acting by


-------------------------------------
Signatory

-------------------------------------
Print name of signatory


EXECUTED by Apax Partners Europe Managers Ltd on behalf of APAX EUROPE V - F,
C.V. acting by


-------------------------------------
Signatory

-------------------------------------
Print name of signatory


EXECUTED by Apax Partners Europe Managers Ltd on behalf of APAX EUROPE V - G,
C.V. acting by


-------------------------------------
Signatory

-------------------------------------
Print name of signatory


EXECUTED by Apax Partners Europe Managers Ltd on behalf of APAX EUROPE V - 1,
L.P. acting by


-------------------------------------
Signatory

-------------------------------------
Print name of signatory


                                      -62-

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EXECUTED by Apax Partners Europe Managers Ltd on behalf of APAX EUROPE V - 2,
L.P. acting by


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Signatory

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EXECUTED by The Wellcome Trust Limited as trustee for and on behalf of the
Wellcome Trust acting by


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its Attorney Sandra Robertson

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Signed by:


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For and on behalf of VERNALIS PLC


Signed by:


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ANDREW PETER SANDHAM


Signed by:


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For and on behalf of SILVERADO PLC



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