<PAGE>   1

                                                                   EXHIBIT 10.40

[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



                             DATED OCTOBER 11, 2000





                           (1) EVANS VACCINES LIMITED



                           (2) AVIRON UK LIMITED



                           (3) AVIRON







                  --------------------------------------------

                               AGREEMENT FOR LEASE
                                       OF
                  AVU EXTENSION PREMISES AT GASKILL ROAD SPEKE

                  --------------------------------------------












                               CMS CAMERON MCKENNA
                                   MITRE HOUSE
                              160 ALDERSGATE STREET
                                 LONDON EC1A 4DD

                              T + 44(0)20 7367 3000
                              F + 44(0)20 7367 2000

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THIS AGREEMENT is made October 11, 2000
BETWEEN:-

(1)     EVANS VACCINES LIMITED (registered number 3970089) having its registered
        office at 216 Bath Road, Slough, Berkshire SL1 4EN (the "LANDLORD") and

(2)     AVIRON UK LIMITED (registered number 3854275) having its registered
        office at Carmelite, 50 Victoria Embankment, London EC4Y ODX (the
        "TENANT") and

(3)     AVIRON (registered in Delaware) having its registered office at 297
        North Bernardo Avenue, Mountain View, California 94043, United States of
        America (the "SURETY")

IT IS AGREED as follows:-

1.      DEFINITIONS

1.1     In this agreement unless the context otherwise requires the following
        expressions have the following meanings:-

        "ADVERSE CONDITION": a condition in or requirement of a Planning
        Agreement or a Planning Permission which the Landlord in its absolute
        discretion considers to be unacceptable

        "APPEAL PROCEEDINGS":

        (a)     any and all proceedings (other than Review Proceedings)
                instituted before the appropriate tribunal body person or forum
                in pursuance of an appeal in respect of the decision of the
                Planning Authority or the Secretary of State or relating to or
                consequent upon any Application including (without limiting the
                generality of the foregoing) all or any of the following as the
                case may be:-

                (i)     any appeal to the Secretary of State following a
                        Planning Refusal

                (ii)    any consideration by the Secretary of State of any
                        Application referred to him under section 77 of the
                        Planning Act

        (b)     any application for planning permission pursuant to section 73
                of the Planning Act for the development of the Premises without
                complying with an Adverse Condition (without which the Planning
                Permission would be a Satisfactory Planning Permission)

        "APPLICATION": an application to be made by the Landlord for detailed
        planning permission for the proposed works to the Premises requiring
        such permission and forming part of the Works and any reference to such
        application will include any amended substituted or further application
        made pursuant to this agreement

        "BUILDING CONTRACTOR": the building contractor to be employed by the
        Landlord


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



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        "COMPETENT AUTHORITY": any local authority or any other body exercising
        powers under statute or by Royal Charter or any utility service or
        supply company

        "COMPLIANCE DATE": the date on which the Conditions Precedent and the
        Planning Conditions are wholly fulfilled

        "CONDITIONS PRECEDENT":

        (a)     the grant of the Exclusion Order

        (b)     the grant of the consent of the Superior Lessor to the carrying
                out of the Works

        "CONSTRUCTION PERIOD": the period of 9 months from and including the
        date upon which the last of the Planning Conditions is satisfied or
        waived as herein provided PROVIDED THAT if on one or more occasions the
        carrying out of the Works is delayed due to any circumstances beyond the
        reasonable control of the Landlord then on each occasion the period will
        be extended by such further period as is certified by the Consultant as
        being reasonable

        "CONSULTANT": the surveyor appointed by the Landlord in connection with
        the carrying out of the Works

        "CONSENTS": all permissions licences and approvals under the Planning
        Acts the building regulations and under any other statute bye-law or
        regulation of any Competent Authority

        "DATE OF WORKS COMPLETION": the date which the Consultant certifies as
        being the date on which practical completion of the Works was achieved
        for the purposes of this agreement

        "EXCLUSION ORDER": an order of a competent court under the provisions of
        section 38(4) of the Landlord and Tenant Act 1954 (as amended by section
        5 of the Law of Property Act 1969) authorising the Landlord and the
        Tenant to agree that the provisions of sections 24-28 of that Act will
        be excluded in relation to the tenancy to be created by the Lease

        "LANDLORD'S SOLICITORS": [***]

        "LEADING COUNSEL": such leading counsel specialising in matters relating
        to town and country planning as the parties may agree upon or in default
        of agreement as may be nominated on the application of either party by
        the President of the Law Society

        "LEASE": a lease in the form of the draft annexed hereto subject to such
        amendments as the Landlord may require and the Tenant may approve (such
        approval not to be unreasonably withheld or delayed)

        "LICENCE FOR ALTERATIONS": a licence in such form as the Landlord and/or
        the Superior Lessor may require relating to the Works


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



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        "PLANNING ACT": the Town and Country Planning Act 1990

        "PLANNING ACTS": the Town and Country Planning Act 1990 the Planning
        (Listed Buildings and Conservation Areas) Act 1990 the Planning
        (Hazardous Substances) Act 1990 the Planning (Consequential Provisions)
        Act 1990 and the Planning and Compensation Act 1991

        "PLANNING AGREEMENT":

        (a)     any planning obligation entered into or proposed to be entered
                into under section 106 of the Planning Act and/or

        (b)     any agreement concluded or proposed to be concluded between a
                party to this agreement and (i) the Planning Authority
                regulating the development and/or the use of the Premises
                (whether or not under section 106 of the Planning Act) and/or
                (ii) any other authority relating to the construction
                maintenance or adoption of or the carrying out of works on or to
                any road sewer drain or utility supply affecting or serving the
                Premises (whether or not under section 38 or section 278 of the
                Highways Act 1980 or section 104 of the Water Industry Act 1991)

        "PLANNING AUTHORITY": the local planning authority

        "PLANNING CONDITIONS":

        FIRST the grant of a Satisfactory Planning Permission prior to the
        expiry of the Relevant Period and

        SECONDLY either the expiry of the Review Period prior to the Cut Off
        Date without the institution of Review Proceedings or (if Review
        Proceedings be commenced during the Review Period) their final
        determination prior to the Cut Off Date leaving in place a Satisfactory
        Planning Permission and

        THIRDLY the completion of all Planning Agreements (if any) free from any
        Adverse Condition prior to the expiry of the Relevant Period

        "PLANNING PERMISSION": a written detailed planning permission for such
        of the Works as require a Planning permission granted by the Planning
        Authority or the Secretary of State pursuant to an Application

        "PLANNING REFUSAL": a written refusal of an Application by the Planning
        Authority (or a deemed refusal under section 78 of the Planning Act) or
        a written refusal of Appeal Proceedings or a Planning Permission granted
        subject to an Adverse Condition

        "PREMISES": the parts of the Building known as the AVU Extension
        Premises at Gaskill Road, Speke part of which is shown for
        identification purposes only hatched black on the


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



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        plan attached hereto and the remaining part of which is comprised of a
        mezzanine floor which runs part of the length of the area shown hatched
        on the plan referred to.

        "REGISTERED TITLE": the titles numbered MS134921, MS253780 and MS387854
        at HM Land Registry

        "RELEVANT PERIOD": a period comprising the aggregate of 7 months
        months from the date of this agreement and the duration of any direction
        by the Secretary of State that the Planning Authority should not
        determine an Application subject to such aggregate period not exceeding
        9 months months from the date of this agreement PROVIDED THAT if prior
        to the expiry of such aggregate period an Application shall have become
        the subject of Appeal Proceedings or Review Proceedings or a
        Satisfactory Planning Permission shall have become the subject of Review
        Proceedings instigated by a third party then such aggregate period will
        be extended until the date on which such Appeal Proceedings or Review
        Proceedings shall be finally determined PROVIDED FURTHER THAT in no
        event will the Relevant Period be extended beyond 30th June 2006.

        "RETAINED PREMISES": all parts of the Landlord's estate except the
        Premises

        "REVIEW PERIOD":

        (a)     in the case of any decision by the Secretary of State on any
                reference under section 77 of the Planning Act or on any appeal
                under section 78 of the Planning Act the period of six weeks
                from the date of his decision letter

        (b)     in any other case the period of three months from the date on
                which written notice of its decision is issued by the Planning
                Authority

        "REVIEW PROCEEDINGS": all or any of the following as the case may be in
        relation to or consequent upon an Application or a Satisfactory Planning
        Permission:-

        (a)     any application for judicial review under Order 53 of the rules
                of the Supreme Court

        (b)     any application pursuant to section 288 of the Planning Act

        (c)     any appeal to a higher court following a judgment of a lower
                court in respect of any application referred to in paragraphs
                (a) and (b) of this definition

        (d)     any reconsideration by the Planning Authority or the Secretary
                of State of any application referred to in paragraphs (a) and
                (b) of this definition upon remission to it or him

        "SATISFACTORY PLANNING PERMISSION": a Planning Permission granted
        pursuant to an Application and which is free from any Adverse Condition


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



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        "SECRETARY OF STATE": the Secretary of State for the Environment
        Transport and the Regions or other minister or authority from time to
        time having the powers now conferred upon him by sections 77 78 and 79
        of the Planning Act

        "STANDARD CONDITIONS": the Standard Conditions of Sale (Third Edition)

        "SUPERIOR LEASE": a lease dated 1st April 1948 and made between (1) The
        Lord Mayor Aldermen and Citizens of the City of Liverpool (1) and Evans
        Medical Supplies Limited (2) and a lease dated 20th February 1952 and
        made between The Lord Mayor Aldermen and Citizens of the City of
        Liverpool (1) and the Board of Trade (2) and any documents which are
        supplemental to or collateral with or entered into pursuant to such
        leases

        "SUPERIOR LESSOR": the person from time to time entitled to any
        reversion immediately or mediately expectant on the determination of the
        term granted by the Superior Lease

        "TENANT'S SOLICITORS": [***]

        "VAT": Value Added Tax and any tax or duty of a similar nature
        substituted for or in addition to it

        "WORKS": the works to the Premises to be carried out by the Landlord as
        specified in schedule 2

1.2     The definitions in the Standard Conditions also apply in this agreement

2.      GENERAL PROVISIONS

2.1     In this agreement unless the context otherwise requires references to
        clauses and schedules are to clauses of and schedules to this agreement

2.2     The headings to clauses and other parts of this agreement do not affect
        its construction

2.3     This agreement contains the whole agreement between the parties relating
        to the matters herein mentioned and supersedes previous agreements
        between them (if any) relating thereto

2.4     This agreement may only be varied in writing signed by or on behalf of
        the parties

2.5     The Tenant acknowledges that it has not entered into this agreement in
        reliance upon representations made by or on behalf of the Landlord other
        than in respect of such reliance as may be placed upon the Landlord's
        Solicitors' written replies to the Tenant's Solicitors' preliminary
        enquiries

2.6     Nothing in this agreement is to be read or construed as excluding any
        liability or remedy resulting from fraudulent misrepresentation


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



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2.7     All money payable by the Tenant under this agreement will be paid by
        direct credit transfer for the credit of the Landlord's Solicitors'
        clients' account at [***] or for the credit of any other bank account
        specified in writing by the Landlord's Solicitors

2.8     any reference to the grant of a Planning Permission or of a Satisfactory
        Planning Permission or to a Planning Refusal (other than a deemed
        refusal under section 78 of the Planning Act) will be construed as a
        reference to the date of the written notice of decision issued by the
        Planning Authority or by the Secretary of State

2.9     any reference to the final determination of any Appeal Proceedings or
        Review Proceedings will be construed as a reference to the date by which
        any appeal (or further appeal) against any determination of those Appeal
        Proceedings or Review Proceedings can be lodged has expired without any
        such appeal or further appeal being lodged

2.10    Any reference in this agreement to any enactment (whether generally or
        specifically) will be construed as a reference to that enactment as
        amended re-enacted consolidated or applied by or under any other
        enactment and will include all instruments orders plans regulations
        permissions and directions made or issued under or deriving validity
        from such enactment

2.11    Every obligation of the Tenant in this agreement to do specified acts or
        things will include an obligation to procure that they be done and every
        obligation of the Tenant in this agreement not to do specified acts or
        things will include an obligation not to permit or suffer them to be
        done

2.12    This agreement contains the whole agreement between the parties relating
        to the matters herein mentioned and supersedes previous agreements
        between them (if any) relating thereto

2.13    The Landlord may [***] on or for the benefit of the Retained Premises as
        the [***] from time to time without any [***] by the Tenant and in
        relation to [***] (but subject to [***]) the Tenant hereby licenses the
        Landlord to for such periods as are and to such extent as is reasonably
        necessary in the circumstances

3.      STANDARD CONDITIONS

        This agreement incorporates the Standard Conditions as varied by
        schedule 1 and so far as they apply to a letting and are not varied by
        or inconsistent with the other provisions of this agreement (which will
        prevail in case of conflict)

4.      CONDITIONS PRECEDENT


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
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COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



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4.1     The performance by the Landlord of its obligations in relation to the
        Works and the grant of the Lease are conditional on the Conditions
        Precedent being wholly fulfilled and the performance by the Landlord of
        its obligations in relation to the Works is additionally conditional on
        the Planning Conditions being wholly fulfilled

4.2

        4.2.1   The parties will apply for and use all reasonable endeavours but
                at the cost of [***] to procure that the Conditions Precedent
                and the Planning Conditions are wholly fulfilled provided that
                the Landlord will not be obliged to institute court proceedings
                against the Superior Lessor in respect of any consent needed
                from the Superior Lessor unless [***] considers such proceedings
                appropriate and [***] agrees to indemnify [***] against all
                costs claims proceedings and other expenses resulting or
                associated directly or indirectly with such proceedings

        4.2.2   The Tenant will enter into such Planning Agreements in such form
                as may be reasonable in the circumstances

        4.2.3   In the event of a Planning Refusal the Landlord may (but without
                obligation to do so and in any event [***], institute and
                prosecute Appeal Proceedings or Review Proceedings

        4.2.4   In the event of an Application or a Satisfactory Planning
                Permission becoming the subject of Review Proceedings instigated
                by any party not being the Landlord the Landlord shall have
                absolute discretion as to its involvement or otherwise in such
                proceedings

        4.2.5   Without prejudice to clause 4.2.1 the Tenant will [***] and
                [***] as may be reasonably required by the Superior Lessor

        4.2.6   If so required by the Landlord and/or the Superior Lessor the
                Tenant will:-

                (a)     [***]

                (b)     [***]

        4.2.7   In consideration of the Landlord (at the request of the Surety)
                having agreed to grant the Lease to the Tenant the Surety hereby
                agrees with the Landlord that the Surety will execute the
                Licence for Alterations or other deed containing such covenants
                by the Surety in favour of the Superior Lessor as the Superior
                Lessor may require


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



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        4.2.8   Any obligation undertaken by [***] the Surety to [***] or [***]
                with the Superior Lessor includes an obligation to ensure that
                there is no delay in the approval of a draft of such [***] and
                that the duly executed engrossment thereof is returned
                unconditionally to the Landlord's Solicitors within five working
                days from its receipt by [***]

5.      THE WORKS

5.1     Subject to proper payment of its costs and other expenses pursuant to
        clause 13.1 hereof the Landlord will use its reasonable endeavours to
        obtain any necessary Planning Permission and practically complete the
        Works within the Construction Period.

5.2     The Landlord and the Tenant will as soon as possible after the date
        hereof meet to discuss the detail of the Works and an associated project
        plan.

5.3     Following such meeting the Landlord will as soon as reasonably possible
        produce to the Tenant for approval a project plan together with plans
        and specifications showing the detail of the Works (such approval not to
        be unreasonably withheld or delayed).

5.4     If requested to do so by the Tenant the Landlord will procure that the
        Tenant is provided with copies of all Applications including all
        accompanying drawings.

5.5     The Landlord may not make any material variation to the Works without
        the Tenant's prior written consent (such consent not to be unreasonably
        withheld or delayed) but otherwise may make such modifications as it may
        reasonably require.

5.6     The Landlord shall permit the Tenant at all reasonable times to inspect
        the progress of the Works and shall take proper account of reasonable
        representations made by or on behalf of the Tenant in relation to the
        Works.

5.7     The Landlord shall procure that the Tenant is given not less than 10
        days notice of the intention of the Consultant to inspect the Works with
        a view to the issue of a certificate that the Works are practically
        completed.

5.8     The notice shall state the date and time of such inspection.

5.9     The Tenant's representative shall be permitted to accompany the
        Consultant on the inspection if he attends at such date and time but not
        otherwise.

5.10    The Consultant shall take proper account of any representations made by
        the Tenant's representative during such inspection.

5.11    The Landlord will procure that a copy of the Consultant's certificate
        that the Works are practically completed (together with any schedule
        listing any defects) is given to the Tenant of the Tenant's solicitors
        as soon as is reasonably practicable following its issue.


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



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6.      TITLE

        Title to the Premises will not be deduced but the Tenant will
        nevertheless be deemed to take the Lease with full knowledge of the
        terms and contents of and of any matter referred to in or deriving from
        the Registered Title and will raise no requisition on them

7.      MATTERS SUBJECT TO WHICH THE PREMISES ARE LET

7.1     The Premises are let subject to and as the case may be with the benefit
        of the matters contained or referred to in the Lease

7.2     The Premises are also let subject to:

        7.2.1   all matters registrable by any Competent Authority pursuant to
                statute

        7.2.2   all requirements notices orders or proposals (whether or not
                subject to confirmation) of any Competent Authority

        7.2.3   all matters disclosed or reasonably to be expected to be
                disclosed by [***] or as the result of [***] and whether made in
                person by writing or orally by or for the Tenant or which a
                [***]

        7.2.4   all notices served by [***]

8.      THE LEASE

8.1     The Landlord will grant or procure the grant of and the Tenant will
        accept the Lease or the later of:

        8.1.1   [***] from and including the Date of Works Completion

        8.1.2   [***] from and including the Compliance Date

8.2     The Lease will be for a term of approximately 5 years from and including
        the date of completion and expiring upon 30th June 2006

8.3     The initial annual rent first reserved by the Lease will be [***] which
        will be payable from and including the Date of Works Completion

8.4     The Tenant will on the date for completion of the Lease in accordance
        with clause 8.1 pay to the Landlord:

        8.4.1   the proportion of the rent first reserved by and then payable
                under the Lease for the period from and including the Date of
                Works Completion


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



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        8.4.2   any other rents reserved by or money payable and then due under
                the Lease calculated from and including the Date of Works
                Completion

8.5

        8.5.1   Engrossments of the Lease and counterpart will be prepared by
                the Landlord's Solicitors and within three working days of being
                called upon to do so the Tenant and the Surety will execute the
                counterpart and return it unconditionally to the Landlord's
                Solicitors

        8.5.2   Without prejudice to any other provision of this agreement the
                Tenant will indemnify the Landlord against any loss suffered by
                the Landlord resulting from any failure by the Tenant or the
                Surety to comply with the provisions of clause 8.6.1

9.      POSSESSION

9.1     Vacant possession of the Premises will be given to the Tenant on
        completion of the Lease

9.2     This agreement is an executory agreement only and will not operate or be
        deemed to operate as a demise of the Premises

10.     ALIENATION

        The benefit of this agreement is [***] and the [***] will not [***] its
        interest under this agreement or any part thereof or otherwise dispose
        of such interest or any part thereof and the Tenant named herein will
        [***] the Lease

11.     ACKNOWLEDGMENT AND INTEREST

        The Tenant acknowledges and agrees that:

11.1    The obligations of the Landlord contained in this agreement are personal
        to Evans Vaccines Limited and to any other party giving written notice
        to the Tenant at any time that such party has personally assumed those
        obligations

11.2    Without prejudice to any other right remedy or power of the Landlord if
        any sums have become due from the Tenant to the Landlord under this
        agreement but remain unpaid for a period exceeding [***] the Tenant will
        pay [***] to the Landlord [***] at [***] rate ([***] any judgment) from
        the date when they become due until payment thereof calculated on a
        daily basis and [***]


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



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12.     TERMINATION

        If:

12.1    there is any breach of the obligations of the Tenant and/or the Surety
        under this agreement which (if capable of remedy) is not remedied by the
        Tenant and/or the Surety within such reasonable period as the Landlord
        stipulates or

12.2    the Tenant and/or the Surety (being a body corporate) is unable to pay
        its debts (as defined in section 123 of the Insolvency Act 1986) or has
        a winding-up petition or petition for an administration order presented
        against it or passes a winding-up resolution (other than in connection
        with a members' voluntary winding-up for the purposes of an amalgamation
        or reconstruction which has the prior written approval of the Landlord)
        or calls a meeting of its creditors to consider a resolution that it be
        wound up voluntarily or resolves to present its own winding-up petition
        or is wound up (whether in England or elsewhere) or the directors or
        shareholders of the Tenant or the Surety resolve to present a petition
        for an administration order in respect of the Tenant or the Surety (as
        the case may be) or an administrative receiver or a receiver or a
        receiver and manager is appointed in respect of the property or any part
        thereof of the Tenant or the Surety or

12.3    the Tenant and/or the Surety (being a body corporate) calls or a nominee
        calls on its behalf a meeting of its creditors or any of them or makes
        an application to the court under section 425 of the Companies Act 1985
        or submits to its creditors or any of them a proposal pursuant to Part I
        of the Insolvency Act 1986 or enters into any arrangement scheme
        compromise moratorium or composition with its creditors or any of them
        (whether pursuant to Part I of the Insolvency Act 1986 or otherwise) or

12.4    the Tenant and/or the Surety (being an individual) makes an application
        to the court for an interim order under Part VIII of the Insolvency Act
        1986 or convenes a meeting of his creditors or any of them or enters
        into any arrangement scheme compromise moratorium or composition with
        his creditors or any of them (whether pursuant to Part VIII of the
        Insolvency Act 1986 or otherwise) or has a bankruptcy petition presented
        against him or is adjudged bankrupt (whether in England or elsewhere)

        THEN and in any such case the Landlord may by notice in writing to the
        Tenant at any time thereafter terminate this agreement (without
        prejudice to any right or remedy of any party in respect of any
        antecedent breach of this agreement and without prejudice to any
        continuing obligations of the Surety under this agreement)

12.5    the Conditions Precedent and Planning Conditions are not satisfied by
        30th June 2006

13.     COSTS AND INDEMNITY

13.1    The [***] will pay to the [***] forthwith upon demand all proper costs
        and expenses (including professional fees) of the [***] associated with
        [***]


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COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



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13.2    The Tenant will indemnify the Landlord against all actions proceedings
        claims demands losses costs expenses damages and liability (including
        any liability for any injury to any person or damage to any land or
        other property) arising directly or indirectly from any obligation of
        the Landlord or any breach of any obligation of the Tenant under this
        agreement or any act or omission of the Tenant or [***]

14.     [***]

14.1    All sums payable under the terms of this agreement are [***] in respect
        thereof howsoever arising and the Tenant will pay to the Landlord all
        [***] for which the Landlord is liable to [***] in relation to any
        supply made or deemed to be made for [***] purposes pursuant to this
        agreement

14.2    The Tenant does not intend or expect the Premises to be occupied by it
        or a person that is connected with the Tenant as determined in
        accordance with section [***] other than wholly or mainly for eligible
        purposes (within the meaning of paragraph [***])

14.3    The Tenant represents warrants and undertakes to and with the Landlord
        that the statement in clause 14.2 is at the date of this agreement and
        will be at the date of completion of the Lease true and correct in all
        respects

15.     SURETY

15.1    In consideration of the Landlord entering into this agreement at the
        request of the Surety the Surety will procure the observance and
        performance of all the obligations of the Tenant under this agreement
        and in the case of any default the Surety will observe and perform such
        obligations as if the Surety instead of the Tenant were liable therefor
        as a principal obligor and not merely as a surety and the Surety agrees
        with the Landlord as a primary obligation to keep the Landlord
        indemnified on demand against all losses damages costs and expenses
        incurred by the Landlord as a result of any failure by the Tenant to
        observe and perform such obligations or as a result of any obligation of
        the Tenant under this agreement being or becoming unenforceable

15.2    If this agreement is disclaimed by or on behalf of the Tenant or is
        terminated in relation to the Tenant pursuant to clause 12 the Surety
        will (if so required by the Landlord by written notice within three
        months after such disclaimer or after the date of the Landlord's notice
        of termination under clause 12 (as the case may be)) enter into a new
        agreement with the Landlord containing the same conditions and
        provisions as this agreement (except this clause 15) and the new
        agreement will take effect from the date of the disclaimer or such
        notice of termination and in such case the Surety will [***] pay the
        Landlord's [***] in connection with such agreement

15.3    The insolvency of the Tenant will not affect the liability of the Surety
        under this agreement and any money received or recovered by the Landlord
        from the Surety may be placed in a separate or suspense account by the
        Landlord without any obligation on the Landlord to apply it in or
        towards the discharge of the Tenant's obligations under this


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



                                       12
<PAGE>   14

        agreement so as to preserve the Landlord's right to prove in any
        insolvency of the Tenant in respect of the whole of the Tenant's
        indebtedness to the Landlord under this agreement

15.4    The obligations of the Surety under this agreement are in addition to
        any other right or remedy of the Landlord and will not be discharged
        diminished or in any way affected by:-

        15.4.1  any time or indulgence granted by the Landlord to the Tenant or
                any neglect or forbearance of the Landlord in enforcing the
                obligations of the Tenant under this agreement

        15.4.2  any variation of this agreement or other act omission matter or
                thing (other than a release by deed given by the Landlord) by
                which but for this provision the obligations of the Surety under
                this agreement would have been so discharged diminished or
                affected

16.     DISPUTES

        Any dispute arising under this Agreement is to be resolved by means of
        the dispute resolution procedure set out in the Shared Services
        Agreement dated on or about the date of this Agreement and made between
        the Landlord and the Tenant.

17.     JURISDICTION

17.1    This agreement will in all respects be governed by and construed in
        accordance with English law and the parties irrevocably submit to the
        exclusive jurisdiction of the English courts

17.2    The address for service upon the Surety in England and Wales is c/o
        [***]

18.     THIRD PARTY RIGHTS

        Nothing in this agreement is intended to confer on any person any right
        to enforce any term of this agreement which that person would not have
        had but for the [***]

IN WITNESS whereof this agreement has been duly executed as a deed (but not
delivered until) the day and year first before written


[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.


                                       13
<PAGE>   15

                                   SCHEDULE 1

                               STANDARD CONDITIONS

1.      Throughout the conditions references to property being sold are to be
        construed as references to the Premises

2.      Conditions 1.4 2.2 3.4 4.2 4.3.2 4.5.2 4.5.5 5 6.3.2 6.5 6.7 6.8.2(b)
        8.2.4 8.3 and 9 do not apply

3.      Condition 1.1.1(f) is deleted and wherever the word "contract" appears
        in the Standard Conditions (save where followed by the word "rate") it
        is replaced by the word "agreement"

4.      In condition 1.1.1(g) the "contract rate" is [***] per annum above the
        base rate from time to time of Lloyds TSB Bank Plc

5.      In condition 1.3.5 "5.00 pm" is substituted for "4.00 pm" and the words
        "before 5.00 pm" are added after the words "treated as having been
        received

6.      In condition 1.3.6 "5.00 pm" is substituted for "4.00 pm" and the words
        "(d) by fax: if sent before 5.00 pm on a working day the day of despatch
        but otherwise on the first working day after despatch" are added at the
        end

7.      In condition 3.1.2 the words "(f) overriding interests (as defined in
        Section 70(l) of the Land Registration Act 1925)" are added at the end

8.      In condition 4.1 the words "4.1.5 If the buyer persists in any valid
        requisition with which the seller is unable or unwilling on reasonable
        grounds to deal satisfactorily and does not withdraw it within five
        working days of being required so to do the seller may by notice to the
        buyer and notwithstanding any intermediate negotiation or litigation
        rescind the agreement" are added at the end

9.      In conditions 6.1.2 and 6.1.3 "12 noon" is substituted for "2.00 pm"

10.     In condition 7.1.1 the words "or in the negotiations leading to it" and
        "or was" are deleted





[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



                                    Sch. 1-1
<PAGE>   16

                                   SCHEDULE 2

                                    THE WORKS

Such works as are necessary to:

1.      Create a goods lift and staircase to first floor level within the
        Premises; and

2.      Re-configure corridor and office space at first floor level within the
        Premises.





[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.



                                    Sch. 2-1
<PAGE>   17

EXECUTED as a Deed by EVANS    )
VACCINES LIMITED               )
in the presence of:-           )



                                       Director           /s/ ALAN JARVIS

                                       Director/Secretary /s/ C.S.W. SWINGLAND








[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.
<PAGE>   18

EXECUTED as a Deed by AVIRON    )
UK LIMITED in the presence of:- )



                                       Director               /s/ Ray Prasad

                                       Director/Secretary     /s/ Fred Kurland


EXECUTED as a Deed by AVIRON    )
in the presence of:-            )



                                       Director               /s/ Fred Kurland

                                       Director/Secretary     /s/ Ray Prasad








[***] - CERTAIN CONFIDENTIAL INFORMATION CONTAINED IN THIS DOCUMENT, MARKED BY
[***] HAS BEEN OMITTED AND FILED SEPARATELY WITH THE SECURITIES AND EXCHANGE
COMMISSION PURSUANT TO RULE 24B-2 OF THE SECURITIES EXCHANGE ACT OF 1934, AS
AMENDED.