Document:

<PAGE>

                                                                  EXHIBIT 10.1.7

                              DATED __________ 2005

                               BIOVEX GROUP, INC.

                                       AND

                                 [OPTION HOLDER]

                                   ----------

                             REPLACEMENT EMI OPTION
                                    AGREEMENT

                                   ----------

                (WILMER CUTLER PICKERING HALE AND DORR LLP LOGO)

                                  Alder Castle
                                 10 Noble Street
                                 London EC2V 7QJ
                            Tel: +44 (0)20 7645 2400
                            Fax: +44 (0)20 7645 2424

<PAGE>

                                TABLE OF CONTENTS

<TABLE>
<S>                                                                           <C>
1.  Definitions............................................................    3
2.  Grant of Replacement Option............................................    5
3.  Restrictions on the grant of the Replacement Option....................    6
4.  Rights to exercise the Replacement Option..............................    6
5.  Exercise of Replacement Options........................................    7
6.  Take-overs, reconstructions and winding-up.............................    8
7.  Certificate of Incorporation; Stockholders' Agreement..................    9
8.  General................................................................    9
9.  Alterations............................................................   10
10. Limitation of Liability................................................   10
11. Governing Law..........................................................   10
SCHEDULE 1.................................................................   12
Rules of the BioVex Limited Enterprise Management Incentives Scheme........   12
SCHEDULE 2.................................................................   13
Certificate of Incorporation of BioVex Group, Inc. adopted on _____ 2005...   13
SCHEDULE 3.................................................................    1
Notice of grant of EMI option..............................................    1
SCHEDULE 4.................................................................    2
Notice of Exercise.........................................................    2
SCHEDULE 5.................................................................    4
Stockholders' Agreement of BioVex Group, Inc...............................    4
</TABLE>

                                       -2-

<PAGE>

THIS DEED is made the __________ day of __________ 2005

BETWEEN:

(1)  BIOVEX GROUP, INC., a Delaware corporation, (the "Company"); and

(2)  [__________] of [__________ home address __________] (the "Option Holder").

WHEREAS:

A. The Option Holder was granted an option qualifying as an enterprise
management incentive option under Schedule 5 to the Income Tax (Earnings and
Pensions) Act 2003 by BioVex Limited, now a wholly owned subsidiary of the
Company.

B. The Option Holder has agreed with the Company, as a consequence of the
reorganisation of the BioVex group by which the Company became the holding
company of the group, to release his options over shares in the capital of
BioVex Limited in consideration for a grant of replacement options over shares
of common stock of the Company.

THIS DEED WITNESSES as follows:-

1.   DEFINITIONS

1.1  In this Deed the words and expressions set out below shall have the
     meanings specified against them unless otherwise specifically provided and
     any reference to a provision of an Act of Parliament shall include any
     modification, consolidation, re-enactment or extension of it.

     "ACQUIRING COMPANY" a company which obtains Control of the Company in
     accordance with Clause 6.1;

     "BIOVEX" BioVex Limited (a company registered in England with number
     3480520);

     "CHANGE OF CONTROL" shall mean any of (i) a consolidation, merger, or
     similar transaction or series of related transactions, including a sale or
     other disposition of stock, in which the Company is not the surviving
     corporation or which results in the acquisition of all or substantially all
     of the Company's then outstanding common stock by a single person or entity
     or by a group of persons and/or entities acting in concert, (ii) a sale or
     transfer of all or substantially all the Company's assets, or (iii) a
     dissolution or liquidation of the Company. Where a Change of Control
     involves a tender offer that is reasonably expected to be followed by a
     merger described in (i) (as determined by the Board), the Change of Control
     shall be deemed to have occurred upon consummation of the tender offer;

     "COMPANY" BioVex Group, Inc., a Delaware corporation;

     "CONTROL" the meaning given to that expression by Section 840 of the Taxes
     Act;

     "DATE OF GRANT" the date upon which the Replacement Option is granted in
     accordance with Clause 2.2;

                                       -3-

<PAGE>

     "DIRECTORS" the directors for the time being of BioVex or the directors
     present at a duly convened meeting of the board of directors or of a duly
     appointed committee of the board of directors at which a quorum is present;

     "DISQUALIFYING EVENT" has the meaning specified in sections 533-539 of the
     Income Tax Act 2003;

     "EMI SCHEME" the BioVex Limited Enterprise Management Incentives Scheme
     under which this Replacement Option has been granted;

     "EXCESS SHARES" the aggregate number of Shares comprising this Replacement
     Option in excess of the limits specified in paragraph 7 of Schedule 5 as
     applied to replacement options by paragraph 43 of Schedule 5;

     "GROUP MEMBER" the Company, BioVex and any Subsidiary;

     "INCOME TAX ACT" the Income Tax (Earnings and Pensions) Act 2003;

     "ISSUE OR RE-ORGANISATION" any issue of shares or other securities of the
     Company (other than as consideration for an acquisition) and/or any
     capitalisation, consolidation or sub-division or reduction of share capital
     in the Company and/or any other variation in the share capital of the
     Company which in the opinion of the Directors justifies a variation in the
     number of shares subject to the Replacement Option and/or the Option Price
     pursuant to the Replacement Option;

     "LISTING" the listing of some or all of the Company's shares in the
     Official List or the admission of some or all of the Company's shares to
     the Alternative Investment Market or the listing or admission of some or
     all of the Company's shares on the New York Stock Exchange, Nasdaq or any
     recognised investment exchange (as defined in the Financial Services and
     Markets Act 2000);

     "LISTING RULES" the listing rules which are made by the competent authority
     for the purposes of Part VI of the Financial Services and Markets Act 2000
     as published in the book entitled "The Listing Rules", as from time to time
     amended;

     "LONDON STOCK EXCHANGE" London Stock Exchange plc;

     "OFFICIAL LIST" the Official List of the London Stock Exchange;

     "OPTION PRICE" the acquisition price for a Share comprised in the
     Replacement Option as set out in Clause 2.2.5;

     "ORIGINAL DATE OF GRANT" the date on which the option over shares in the
     capital of BioVex was granted and which this Replacement Option replaces;

     "REDUNDANCY" dismissal by reason of redundancy for the purposes of Part XI
     of the Employment Rights Act 1996;

     "REPLACEMENT OPTION" the Replacement Option to acquire Shares granted in
     accordance with Clause 2;

                                       -4-

<PAGE>

     "RETIREMENT" retirement by the Option Holder on reaching the age of 60;

     "SALE" a Trade Sale or Change of Control;

     "SCHEDULE 5" Schedule 5 to the Income Tax Act;

     "SHARES" shares of common stock in the capital the Company par value
     $0.0001 or as the context may require shares for the time being
     representing the same whether in consequence of any Issue or Reorganisation
     or otherwise;

     "SUBSIDIARY" a company which is both under the Control of the Company and
     which is a subsidiary of the Company within the meaning of Section 736 of
     the Companies Act 1985;

     "TAXES ACT" the Income and Corporation Taxes Act 1988;

     "TRADE SALE" the sale of all or substantially all of the business assets or
     undertaking of all Group Members.

1.2  In these Rules unless the context otherwise requires words denoting the
     singular number shall include the plural number and words denoting the
     masculine gender shall include the feminine gender.

2.   GRANT OF REPLACEMENT OPTION

2.1  In consideration for the grant of the Replacement Option under Clause 2.2
     below, the Option Holder hereby releases all options granted to him prior
     to the date of this Deed under the EMI Scheme.

2.2  The Company hereby grants a Replacement Option to the Option Holder on the
     following terms:

     2.2.1 the Replacement Option is granted pursuant to the EMI Scheme and is
          subject to the rules of that scheme. A copy of the rules of the EMI
          Scheme is set out at Schedule 1 to this Agreement;

     2.2.2 the Replacement Option is granted under the provisions of Schedule 5;

     2.2.3 the Date of Grant of the Replacement Option shall be the date upon
          which this Deed is executed by the parties;

     2.2.4 the Replacement Option is over [__________] Shares;

     2.2.5 the Replacement Option Price is $_____  per Share;

     2.2.6 the Replacement Option may be exercised in accordance with Clause 4
          of this Deed;

2.3  The Replacement Option shall be personal to the Option Holder and other
     than a transfer to the Option Holder's personal representatives on death
     shall not be transferable, assignable or chargeable. Any other purported
     transfer, assignment, charge, disposal or dealing with the rights and
     interests of the Option Holder under this Deed shall render the Replacement
     Option void.

                                       -5-

<PAGE>

2.4  The Option Holder may by notice given in writing within 30 days after its
     Date of Grant renounce his rights to the Replacement Option, in which event
     the Replacement Option will be deemed for all purposes never to have been
     granted.

2.5  The Option Holder shall within 30 days immediately following the Date of
     Grant give a declaration to the Company (in the form set out in Schedule 3
     to this Agreement or in such other form determined by the Company) that he
     meets the requirements of paragraph 26 of Schedule 5 (commitment of working
     time) in relation to the Replacement Option.

2.6  If notice of the grant of the Replacement Option is not given to HM Revenue
     and Customs within 92 days of the Date of Grant or if the HM Revenue and
     Customs conclude that the requirements of the EMI Legislation are not met
     in relation to the Replacement Option, the Replacement Option shall lapse
     and shall be deemed for all purposes never to have been granted.

3.   RESTRICTIONS ON THE GRANT OF THE REPLACEMENT OPTION

     This Clause 3 applies where the Replacement Option has been granted over
     Excess Shares.

3.1  If the Replacement Option has been granted over Excess Shares, the
     Directors shall forthwith notify the Option Holder of this fact. The
     Directors may call in this Deed for endorsement, replacement or
     cancellation (as appropriate).

3.2  If the Replacement Option has been granted over Excess Shares, the
     Replacement Option shall only take effect to the extent that the limits set
     out in paragraph 7 of Schedule 5 (as applied to replacement options by
     paragraph 43 of Schedule 5) are exceeded as an option granted otherwise
     than in accordance with Schedule 5.

4.   RIGHTS TO EXERCISE THE REPLACEMENT OPTION

4.1  Subject to the provisions of Clause 4.4 the Replacement Option shall be
     capable of being exercised in full in accordance with the provisions of
     Clause 5 immediately after a Sale or Listing becomes effective unless this
     Deed provides otherwise.

     If the Shares are admitted to Listing on the London Stock Exchange, the
     Replacement Option may not be exercised, released or surrendered at a time
     when such exercise, release or surrender would not be in accordance with
     the "Model Code on Directors' dealings in Securities" as set out in the
     Listing Rules as amended from time to time.

4.2  If the Option Holder ceases to be a director or employee of a Group Member
     (otherwise than by reason of his death), the following provisions shall
     apply:

     4.2.1 if he ceases by reason of injury, disability, sickness, Redundancy,
          Retirement, the company for which the Option Holder works ceasing to
          be a Group Member, or the business or part-business in which the
          Option Holder works being transferred to a person who is not a Group
          Member, any Replacement Option or Replacement Options held by him may
          (and subject to Clause 4.3 below must, if at all) be exercised
          (subject

                                       -6-

<PAGE>

          to Clause 4.1 above) within six months (or such longer period as the
          Directors permit) after his so ceasing;

     4.2.2 if he so ceases for any other reason, the Replacement Option may not
          be exercised at all unless the Directors so permit, in which event it
          may (and subject to Clause 4.3 below must, if at all) be exercised
          (subject to Clause 4.1 above) to the extent permitted by the Directors
          within the period mentioned in Clause 4.2.1 above (or such longer
          period as the Directors permit).

     The Option Holder shall not be treated for the purposes of this Clause 4.2
     as ceasing to be a director or employee of a Group Member until such time
     as he is no longer a director or employee of any Group Member.

4.3  If the Option Holder dies before exercising the Replacement Option and at a
     time when he is a director or employee of a Group Member the Replacement
     Option may (and must, if at all) be exercised (subject to Clause 4.1 above)
     by his personal representatives within six months after the date of his
     death.

4.4  To the extent the Replacement Option is unexercised immediately following
     the expiry of:

     4.4.1 the period of 6 months commencing immediately after a Sale becomes
          effective;

     4.4.2 any of the periods set out in Clauses 4.2.1, 4.2.2 and 4.3,

     the Replacement Option will lapse.

4.5  The personal representatives of the deceased Option Holder may not exercise
     the Replacement Option if the Option Holder was precluded from doing so at
     the time of his death.

4.6  Notwithstanding any other provision of this Deed, the Replacement Option
     may not be exercised after the expiry of the period of 10 years beginning
     with the Original Date of Grant and to the extent not exercised within that
     period shall lapse.

5.   EXERCISE OF REPLACEMENT OPTIONS

5.1  The Replacement Option may be exercised in whole or in part.

5.2  The exercise of the Replacement Option shall be effected by the delivery to
     the Company of a notice of exercise in the form set out in Schedule 4 to
     this Agreement or in such form and manner as the Directors may from time to
     time prescribe (such notice to contain such investment or securities
     representations and warranties as the Directors consider appropriate from
     time to time). Unless the Directors determine otherwise, any such notice
     shall have effect only on receipt by the Company, together with the payment
     of the aggregate Option Price in respect of the number of Shares to be
     acquired and all sums estimated by the Company due pursuant to Clause 8.2,
     such payment to be made to the Company or to such other person or body
     corporate as may be nominated by the Company at the time of exercise of the
     Replacement Option or any part thereof.

                                       -7-

<PAGE>

5.3  Subject to Clause 5.4, within 30 days after the Replacement Option has been
     exercised by the Option Holder (or his personal representative), the
     Directors on behalf of the Company shall allot to him (or his nominee) or,
     as appropriate, procure the transfer to him (or his nominee) of the number
     of Shares in respect of which the Replacement Option has been exercised,
     provided that, for the avoidance of doubt, where Shares are so allotted or
     transferred to a nominee, the beneficial interest in them must vest in the
     person who exercised the Replacement Option.

5.4  Any Shares allotted to the Option Holder pursuant to the exercise of this
     Replacement Option or any part thereof shall rank pari passu in all
     respects with the shares of the same class for the time being in issue save
     as regards any rights attaching to such shares by reference to a record
     date prior to the date of the allotment, and in the case of the transfer of
     existing Shares, the transferee shall not acquire any rights attaching to
     such Shares by reference to a record date prior to the date of the
     transfer.

6.   TAKE-OVERS, RECONSTRUCTIONS AND WINDING-UP

6.1  If an Acquiring Company:-

     6.1.1 obtains Control of the Company as a result of making:

          (a)  a general offer or otherwise to acquire the whole of the issued
               share capital of the Company which is made on a condition such
               that if it is satisfied the person making the offer will have
               Control of the Company, or

          (b)  a general offer or otherwise to acquire all the shares in the
               Company which are of the same class as the Shares which may be
               acquired by the exercise of Options granted under this Scheme, or

     6.1.2 obtains Control of the Company in pursuance of a compromise or
          arrangement sanctioned by the court under section 425 of the Companies
          Act 1985, or

     6.1.3 becomes bound or entitled to acquire shares in the Company under
          sections 428 to 430F of that Act, or

     6.1.4 acquires all the shares in the Company and the conditions specified
          in paragraph 40 of Schedule 5 are met,

     the Option Holder may at any time within the periods specified in Clause
     6.2 below by agreement with the Acquiring Company, release the Replacement
     Option to the extent it has not lapsed (the "Old Option") in consideration
     of the grant to him of an option ("the New Option") which is equivalent to
     the Old Option but relates to shares in a different company (whether the
     Acquiring Company itself or some other company) provided that the
     conditions specified in paragraph 43 of Schedule 5 are met.

6.2  The periods referred to in Clause 6.1 are as follows:

                                       -8-

<PAGE>

     6.2.1 if the Acquiring Company obtains Control of the Company in terms of
          Clause 6.1.1 the period is six months after the date on which:

          (a)  the person making the offer has obtained Control of the Company;
               and

          (b)  any condition subject to which the offer is made is met;

     6.2.2 the period of six months after the date on which the Acquiring
          Company obtained Control of the Company in terms of Clause 6.1.2;

     6.2.3 the period during which the Acquiring Company remains bound or
          entitled to acquire shares in the Company in terms of sections 428 to
          430F of the Companies Act 1985.

7.   CERTIFICATE OF INCORPORATION; STOCKHOLDERS' AGREEMENT

7.1  Any Shares acquired on the exercise of the Replacement Option are subject
     to the provisions of the Certificate of Incorporation of the Company. A
     copy of the said Certificate as at the date of this Agreement is set out in
     Schedule 2 to this Agreement.

7.2  As a condition to exercise of this Replacement Option, the Option Holder
     will be required to become a party to, and to become bound as a "Common
     Holder" under, the Stockholders' Agreement of the Company dated 30 August
     2005, substantially in the form attached as Schedule 5 to this Agreement,
     as the same is amended from time to time.

8.   GENERAL

8.1  Any rights conferred on the Option Holder under this Deed are entirely
     separate from any pension right or entitlement he may have and from his
     terms or conditions of employment with any Group Member and the terms of
     this Deed shall in no respects whatever affect in any way the Option
     Holder's pension rights or entitlement or terms or conditions of employment
     with any Group Member. In particular (but without limiting the generality
     of the foregoing words) if the Option Holder leaves employment with any
     Group Member he shall not be entitled to any compensation for any loss of
     any right or benefit or prospective right or benefit under this Deed which
     he might otherwise have enjoyed whether such compensation is claimed by way
     of damages for wrongful dismissal or breach of contract or by way of
     compensation for loss of office or otherwise howsoever.

8.2  If the Company, Biovex or any Group Member is required to account for any
     amount of tax, duties and/or National Insurance Contributions (both
     employer and employee) as a result of or in connection with the exercise of
     the Replacement Option or the acquisition or disposal of the Shares arising
     on or after the exercise of the Replacement Option, the Option Holder shall
     indemnify the Company, BioVex, or the relevant Group Member, as the case
     may be, in respect of the amount of all tax, duties and National Insurance
     Contributions (employee and, to the extent lawful, employer) accounted for
     or to be accounted for.

                                       -9-

<PAGE>

9.   ALTERATIONS

9.1  Subject to Clauses 9.2 and 9.3 below, the Directors may at any time alter
     or add to all or any of the provisions of this Deed, or the terms of the
     Replacement Option, in any respect.

9.2  No alteration or addition to the disadvantage of the Option Holder shall be
     made under Clause 9.1 above, unless the alteration or addition is approved
     by the Option Holder.

9.3  No alteration or addition to the material advantage of the Option Holder
     shall be made under Clause 9.1 above without the prior approval of the
     Remuneration Committee.

9.4  As soon as reasonably practicable after making any alteration or addition
     under Clause 9.1 above, the Directors shall give notice in writing thereof
     to the Option Holder.

10.  LIMITATION OF LIABILITY

     Nothing in this Deed nor in the EMI Scheme nor anything said or done by the
     Company or its agents may be taken as representing that the Replacement
     Option qualifies or will continue to qualify under Schedule 5. The Company
     will not be liable to the Option Holder for any loss whatsoever, arising
     from its failure to qualify, or from any failure to notify the Option
     Holder of any Disqualifying Event.

11.  GOVERNING LAW

     This Deed and its interpretation are governed by English law.

                                      -10-

<PAGE>

IN WITNESS whereof this document has been executed and delivered as a Deed the
day and year first above written

SIGNED                            )
as a deed by                      )
in the presence of:               )

Witness signature:
                   ------------------------------------

Witness name:
              -----------------------------------------

Witness occupation:
                    -----------------------------------

Witness address:
                 --------------------------------------

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

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

EXECUTED                          )
as a deed by BIOVEX GROUP, INC.   )
acting by ________ and ________   )

Director
                   ------------------------------------

Director/Secretary
                   ------------------------------------

                                      -11-

<PAGE>

                                   SCHEDULE 1

       RULES OF THE BIOVEX LIMITED ENTERPRISE MANAGEMENT INCENTIVES SCHEME

<PAGE>

                                   SCHEDULE 2

 CERTIFICATE OF INCORPORATION OF BIOVEX GROUP, INC. ADOPTED ON __________ 2005
<PAGE>

                                   SCHEDULE 3

                          NOTICE OF GRANT OF EMI OPTION

                        ENTERPRISE MANAGEMENT INCENTIVES
       NOTICE OF THE GRANT OF AN OPTION UNDER SCHEDULE 5 TO THE INCOME TAX
                        (EARNINGS AND PENSIONS) ACT 2003

--------------------------------------------------------------------------------
1.   DETAILS OF THE COMPANY WHOSE SHARES ARE THE SUBJECT OF THE AGREEMENT:

Name: ____________________________________

Registered number: _______________________

Address of registered office: ____________

__________________________________________

__________________________________________

Name of the Tax Office to which the company's accounts are sent for Corporation
Tax assessment:

__________________________________________

Corporation Tax reference ________________

--------------------------------------------------------------------------------
2.   DETAILS OF THE EMPLOYER COMPANY GIVING THIS NOTICE:

Name: ____________________________________

Name of the Tax Office to which the company's accounts are sent for Corporation
Tax assessment:

__________________________________________

Corporation Tax reference ________________

Name and reference of the Tax Office which deals with the tax liabilities of
this company's employees:

__________________________________________

PAYE tax reference _______________________

--------------------------------------------------------------------------------
3.   DETAILS OF THIS OPTION, AND THIS EMPLOYEE'S OTHER OPTIONS:

Date of grant: __/__/____

Total market value (at date of this grant) of this employee's unexercised EMI
options, including this option: L___________________

Total market value (at date of grant) of this employee's unexercised CSOP and
EMI Options in employee's employer company, or any other group company: L______

Select one:

     The market value of the shares under this option at the date of its grant
     has been agreed with SVD as L__________ per share, OR

     The market value has not been agreed with SVD, OR

     The company's shares were listed on a Recognised Stock Exchange at L______
     per share, at date of grant.

--------------------------------------------------------------------------------
4.   DETAILS OF AND DECLARATION BY THE EMPLOYEE TO WHOM THIS OPTION HAS BEEN
     GRANTED:

Name in full: ____________________________

National Insurance number: __/__/__/_

I declare that I am committed to working for the Qualifying Company whose shares
are the subject of this option, and/or for Qualifying Subsidiaries of that
company, for: (select one)

At least 25 hours a week, OR              At least 75% of my Working Time.

Signature:                                Date: __/__/____
           ----------------------------

--------------------------------------------------------------------------------
5.   DECLARATION BY A DIRECTOR OR THE SECRETARY OF THE EMPLOYER COMPANY:

Name in full: ____________________________

I ATTACH A COPY OF THE OPTION AGREEMENT.

I declare that the option set out in the attached agreement satisfies the
requirements of the Schedule in respect of: (select one)

     All the shares, or ____________ shares (enter number)

I also declare that to the best of my knowledge and belief, all the information
given above is correct and complete.

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

<PAGE>

                                   SCHEDULE 4

                               NOTICE OF EXERCISE

             BIOVEX LIMITED ENTERPRISE MANAGEMENT INCENTIVES SCHEME
                                 (THE "SCHEME")

                    NOTICE OF EXERCISE (REPLACEMENT OPTIONS)

This notice is to be completed by the option holder named below when exercising
a replacement option to acquire some or all of the shares shown on the option
holder's replacement option agreement dated _________________ (insert date of
relevant replacement option agreement) and made between BioVex Group, Inc. and
the option holder ("Option Agreement"). It should be returned to the Company
Secretary.

To:  BioVex Group, Inc.

I, __________________________ (insert full name), refer to the replacement
option ("Option") grantEd to me pursuant to the Scheme and the Option Agreement
at the price of $_______________ (insert per share option price) and now:

     -    have been advised by the Secretary that my immediate income tax and
          employer and employee national insurance liability is L____________
          with a dollar equivalent of $___________;

     -    exercise the Option in respect of _____________________ (insert
          number) shares of common Stock of BioVex Group, Inc.;

     -    meet my payment obligations by enclosing a cheque for $______________
          in favour of "BioVex Group, Inc.";

     The total amount you need to pay will be your option price multiplied by
     the number of shares in respect of which you are now exercising your
     Replacement Option. You may then need to add your immediate income tax and
     national insurance liability (employer and employee). All sterling amounts
     need to be converted to US dollars at the prevailing exchange rate.

     -    return the original Replacement Option Agreement and all copies which
          I hold for endorsement and return to me or, if no Shares remain under
          this Option following this exercise, for retention by the Company;

     -    represent and warrant as follows:

          -    I am purchasing the Shares for my own account for investment
               only, and not with a view to, or for sale in connection with, any
               distribution of the Shares in violation of the Securities Act of
               1933 (the "Securities Act") or any rule or regulation under the
               Securities Act.

          -    I have had such opportunity as I have deemed adequate to obtain
               from representatives of the Company such information as is
               necessary to permit me to evaluate the merits and risks of my
               investment of the Company.

<PAGE>

          -    I have sufficient experience in business, financial and
               investment matters to be able to evaluate the risks involved in
               the purchase of the Shares and to make an informed investment
               decision with respect to such purchase.

          -    I can afford a complete loss of the value of the Shares and am
               able to bear the economic risk of holding such Shares for an
               indefinite period.

          -    I understand that (i) the Shares have not been registered under
               the Securities Act and are "restricted securities" within the
               meaning of Rule 144 under the Securities Act, (ii) the Shares
               cannot be sold, transferred or otherwise disposed of unless they
               are subsequently registered under the Securities Act or an
               exemption from registration is then available, (iii) in any
               event, the exemption from registration under Rule 144 will not be
               available for at least one year and even then will not be
               available unless a public market then exists for the Common
               Stock, adequate information concerning the Company is then
               available to the public, and other terms and conditions of Rule
               144 are complied with; and (iv) there is now no registration
               statement on file with the Securities and Exchange Commission
               with respect to any stock of the Company and the Company has no
               obligation or current intention to register the Shares under the
               Securities Act.

and request that I be registered as the holder of such shares and a definitive
certificate for such shares be sent by registered post to me at the address
below or delivered by hand to me at my usual place of work.

BLOCK CAPITALS PLEASE

FULL NAME                                 SIGNATURE OF OPTION HOLDER

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

ADDRESS
        -------------------------------

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

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

Your rights under the Scheme are governed by the Rules which may be inspected
upon request to the Company Secretary and your replacement option agreement. In
the event of any conflict between (i) the Rules, your replacement option
agreement and any applicable legislation and (ii) this notice of exercise, the
Rules, your replacement option agreement and legislation (as appropriate) take
precedence. References made to taxation consequences are for guidance only.

<PAGE>

                                   SCHEDULE 5

                  STOCKHOLDERS' AGREEMENT OF BIOVEX GROUP, INC.<PAGE>

                                                                  Exhibit 10.3.1

          Confidential Materials omitted and filed separately with the
         Securities and Exchange Commission. Asterisks denote omissions.

                                LICENSE AGREEMENT

                                 by and between

                           WYETH HOLDINGS CORPORATION

                                       and

                                 BIOVEX LIMITED

                                   dated as of

                                  April 1, 2005

<PAGE>

                                LICENSE AGREEMENT

THIS AGREEMENT is made as of April 1, 2005 (the "Effective Date") by and between
Wyeth Holdings Corporation, having a place of business at Five Giralda Farms,
Madison, New Jersey, 07940 ("Licensor"), and Biovex Limited, (company number
3480520), having its registered office at 70 Milton Park, Abingdon, Oxford OX14
4RX England ("Licensee").

     Licensor is the owner of the Licensed Patents, as defined below.

     Licensee wishes to obtain a license under the Licensed Patents, to develop,
have developed, make, have made, use, offer to sell, sell and have sold, import
and have imported, Licensed Products and perform Licensed Services, as defined
below.

     Licensor is willing to grant such a license to Licensee on the terms and
conditions of this Agreement.

     Licensor and Licensee have therefore agreed as follows.

1. DEFINITIONS

     The following terms shall have the meanings indicated in this Agreement:

     1.1. "Agreement" means this Agreement, including all Schedules hereto.

     1.2. "Affiliate" means any Person controlled by, controlling, or under
common control with either Licensee or Licensor. For this purpose, "control"
means direct or indirect beneficial ownership of at least fifty percent (50%)
interest in the voting stock (or the equivalent) of such Person or having the
right to direct, appoint or remove a majority or more of the members of its
board of directors (or their equivalent), or having the power to control the
general management of such Person, by contract, law or otherwise.
Notwithstanding the foregoing, the term "Affiliate" shall not include Persons in
which a Party or its Affiliates owns a majority of the ordinary voting power to
elect a majority of the board of directors or other governing body, but is
restricted from electing such majority by contact or otherwise, until such time
as such restrictions are no longer in effect.

     1.3. "Applicable Percentage" means [**] percent ([**]%).

     1.4. "Bankruptcy Event" means, with respect to a specified Person, (a) the
filing by such Person in any court or agency, pursuant to any statute or
regulation of any state or country, a petition in bankruptcy or insolvency or
for reorganization or for the appointment of a receiver or trustee of such
Person or of its assets, (b) the filing against such Person of an involuntary
petition for any bankruptcy or insolvency proceeding which petition is not
dismissed within ninety (90) days after filing, (c) the making by such Person of
an assignment for the benefit of its creditors, (d) the taking of possession of
any material part of the assets of such Person by a lien holder or other
encumbrancer, or (e) the levy or enforcement of any distress, execution or other
process upon or against any of the material assets of such Person.

                                       1

<PAGE>

     1.5. "Confidential Information" means, with respect to any Party
("Disclosing Party"), any information relating to the Licensed Product(s) or
Improvements that is disclosed in writing or by email to the other Party
("Receiving Party") during the term of this Agreement, but shall not include
information that:

          1.5.1. the Receiving Party or an Affiliate owned or controlled prior
     to receipt from the Disclosing Party, or

          1.5.2. is or becomes public through no breach of this Agreement by the
     Receiving Party or any Affiliate thereof, or

          1.5.3. is hereafter developed by the Receiving Party or an Affiliate
     independent of any disclosure from the Disclosing Party as evidenced by
     competent written evidence, or

          1.5.4. the Receiving Party or an Affiliate obtains from a third Person
     not under a confidentiality obligation to the Disclosing Party.

     1.6. "Effective Date" has the meaning given to it in the Preamble.

     1.7. "Improvements" means any information, patentable or otherwise,
developed or acquired (by license or otherwise, provided in the case of
acquisition that the terms of the acquisition do not prohibit Licensee from
making the grant set forth in Section 2.1.5) by Licensee during the term of this
Agreement and which relates to improvements to inventions disclosed in the
Licensed Patents as follows:

          "Improvements in Area A" means patentable and non-patentable [**] to
     regions of the HSV-1 and/or HSV-2 genome other than regions represented by
     the [**] gene or between the [**] and [**] sites on the [**] corresponding
     to [**] that result in improved [**] in and [**] neoplastic cells conceived
     under and/or reduced to practice by BioVex during the term of this
     Agreement;

          "Improvements in Area B" means patentable and non-patentable [**]
     within regions of the HSV-1 and/or HSV-2 genome represented by the [**]
     gene or between the [**] and [**] sites on the [**] corresponding to [**]
     that result in improved [**] in and [**] neoplastic cells conceived under
     and/or reduced to practice by BioVex during the term of this Agreement.

     1.8. "Licensed Patents" means United States patent application Serial
Number 08/686631 filed July 24, 1996 and any divisional, continuation or
continuation-in-part thereof or substitute therefor, any foreign patent
applications corresponding to any such patent applications claiming priority
from such patents and applications, and any U.S. or foreign patent or the
equivalent thereof issuing therefrom and any reissue, re-examination, renewal,
supplementary protection certificate or extension thereof.

     1.9. "Licensed Product(s)" means any product which would, or the
development, manufacture, use, sale or importation of which product would,
absent the license granted by

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<PAGE>

Licensor to Licensee herein, infringe any Valid Claim in any Licensed Patent in
a country where a Licensed Patent subsists.

     1.10. "Licensed Service(s)" means any commercial research, development or
manufacturing services provided to a third Person, the provision of which
utilizes or embodies any process, product or discovery claimed by one or more
Valid Claims of any Licensed Patent in a country where a Licensed Patent
subsists.

     1.11. "Net Sales" shall mean the actual gross amount invoiced by Licensee
or its Affiliate or any sublicensee (as defined in Section 2.1.1(d)) for sales
or other commercial disposition of a Licensed Product, or provision of a
Licensed Service, to a third Person customer (including any distributor as
defined in Section 2.1.1 (b)), less the following deductions with respect to
such sales or services:

               a) any rebates, quantity, trade and cash discounts, and other
          usual and customary discounts to customers;

               b) compulsory payments and rebates, actually paid or deducted;

               c) retroactive price reductions, credits or allowances actually
          granted upon rejections or returns of Licensed Products, including for
          recalls or damaged goods;

               d) freight, postage, shipping and insurance charges actually
          allowed or paid for delivery of Licensed Products, to the extent
          included in the gross sales price;

               e) sales taxes, excise taxes, use taxes, import/export duties or
          other governmental charges actually due or incurred with respect to
          such sales, including without limitation value-added taxes;

               f) discounts and performance discounts to the extent that such
          discounts are associated with the Licensed Products together with
          other products of Licensee and its Affiliates, and to the extent that
          such discounts cannot be attributed only to the Licensed Products.
          Such discounts and performance discounts will be allocated to the
          Licensed Products on a reasonable pro rata basis (based on the amount
          of the sales of products by Licensee and its Affiliates prior to
          discount); and

               g) charge-back payments and rebates granted to managed health
          care organizations or to federal, state and local governments, their
          respective agencies, purchasers or reimbursers;

all as incurred in the ordinary course of business in type and amount consistent
with good industry practice and determined in accordance with generally accepted
accounting principles on a basis consistent with Licensee's audited consolidated
financial statements.

                                        3

<PAGE>

For sake of clarity and avoidance of doubt, sales by Licensee, its Affiliates or
any sublicensee defined in Section 2.1.1 (d) of a Licensed Product to a
distributor defined in Section 2.1.1 (b) of such Licensed Product in a given
country shall be considered a sale to a third Person customer.

Any Licensed Products used as samples or used for clinical or other research
purposes and for donations shall not be included in Net Sales.

     1.12. "Party" means each party to this Agreement and their respective
successors and permitted assigns.

     1.13. "Person" means any natural person or legal entity.

     1.14. "Phase II" means any controlled clinical study involving the use of a
Licensed Product in human patients designed primarily to obtain preliminary data
on the effectiveness of a specific therapy involving the use of a Licensed
Product in human patients.

     1.15. "Phase III" means any Phase IIb/III clinical study involving a
Licensed Product designed to have adequate statistical power to meet the
requirements for regulatory approval by regulatory authorities either in the
United States, European Union, or Japan.

     1.16. "Royalty Payments" is defined in Section 3.1.4.

     1.17. "Territory" means all countries in the world.

     1.18 "Valid Claim" means any claim of any issued and unexpired patent that
has not been held permanently revoked, deemed unenforceable or invalid by a
decision of a court or other government agency of competent jurisdiction, which
decision is unappealable or unappealed within the time allowed for appeal.

2. LICENSE

     2.1. Grant of License. Licensor hereby grants to Licensee for the term of
this Agreement a non-exclusive, royalty bearing license under the Licensed
Patents, with the limited right to grant sublicenses only as set forth in
Section 2.1.1, to develop, have developed, make, have made, use, offer to sell,
sell, have sold, import and have imported, Licensed Products and to provide
Licensed Services in the Territory. In addition to the other terms and
conditions of this Agreement, the license granted hereby is subject to the
following:

          2.1.1. Sublicensing. Notwithstanding anything herein to the contrary,
     Licensee shall have the right to grant sublicenses only to (a) Licensee's
     Affiliates, (b) any distributor of Licensed Products pursuant to a bona
     fide arm's length distribution agreement between such distributor and
     Licensee, (c) any subcontractor that performs all or a portion of the
     manufacturing of Licensed Products pursuant to a bona fide arm's length
     manufacturing agreement between such subcontractor and Licensee, or (d) any
     third Person that enters into a bona fide license agreement with Licensee
     to make, use, sell or promote Licensed Products; provided, however, that
     Licensee shall be responsible for the operations of any sublicensee
     relevant to this Agreement as if such operations were carried out by
     Licensee itself, including

                                        4

<PAGE>

     (without limitation) the payment of any royalties or other payments
     provided for hereunder. All sublicenses granted hereunder shall be
     consistent with and subject to the terms and conditions of this Agreement.
     Licensee shall notify Licensor of any such sublicense and provide Licensor
     with a copy of any such sublicense agreement within ten (10) days of the
     execution thereof.

          2.1.2. Restriction on other Rights. No right or license is granted to
     Licensee in or to any right or interest of Licensor that is not
     specifically set forth in this Agreement.

          2.1.3. Due Diligence. Licensee shall comply with all applicable laws
     and regulations. Licensee shall be responsible for obtaining all regulatory
     approvals required for the manufacture and sale of Licensed Products.
     Licensee shall provide Licensor (i) prompt written notice of all regulatory
     approvals for Licensed Products in the Territory, and (ii) on an annual
     basis with a summary of the development status of the Licensed Products and
     Licensed Services. Licensee shall use reasonable commercial efforts to
     research, develop and bring to market Licensed Products and Licensed
     Services; provided that Licensee shall always be free to stop development
     or put development of any Licensed Product or Licensed Service on hold
     without termination of this Agreement. In case Licensee provides written
     notice to Licensor that the development of all Licensed Products and
     Licensed Services is stopped or put on hold, all obligations of the
     Licensee hereunder shall cease or shall be suspended respectively, until
     such time as Licensee restarts development of a Licensed Product, except
     for the following: Section 2.1.3 first and third sentences, Sections, 3, 5,
     6, 7 and 8.

          2.1.4. Licensee shall inform Licensor within ten (10) business days
     upon achievement of any milestone described in Section 3.1.3.

          2.1.5. Improvements. Licensee hereby grants to Licensor (i) a [**]
     non-exclusive, [**] license [**] to the Improvements in Area A, and (ii) a
     [**] license [**] to the Improvements in Area B. Licensee shall keep
     Licensor currently and generally advised in writing of all Improvements,
     and shall provide Licensor with a written report thereof not less than once
     each calendar year. Upon request of Licensor, Licensee shall finish to
     Licensor one copy of all available documents relating to such Improvements.

3. PAYMENTS

     3.1. Payments. Licensee shall make the following payments to Licensor as
consideration for the rights granted by Licensor hereunder:

          3.1.1. Licensing Fee. Upon execution of this Agreement, Licensee shall
     pay within ten (10) days to Licensor a non-refundable licensing fee of [**]
     U.S. Dollars (U.S. $[**]) in immediately available funds to an account
     designated in writing by Licensor.

          3.1.2. Annual Maintenance Fee. Within thirty (30) days of each annual
     anniversary of the Effective Date, Licensee shall pay to Licensor [**] U.S.
     Dollars

                                        5

<PAGE>

     (U.S. $[**]) creditable against payments under Section 3.1.4 in the
     Calendar year in which such annual maintenance fee is paid.

          3.1.3. Milestone Payments. Licensee shall pay to Licensor the
     following non-refundable milestone payments, to be paid only once, at the
     time when a Licensed Product reaches a milestone described below:

               (i) upon initiation of the first Phase II clinical trial by or on
          behalf of Licensee (for the purposes of this Section, initiation shall
          mean the first administration of the first Licensed Product in a
          clinical trial): [**] U.S. Dollars (U.S. $[**]);

               (ii) upon initiation of the first Phase II clinical trial by or
          on behalf of Licensee (for the purposes of this Section, initiation
          shall mean the first administration of the second and each subsequent
          Licensed Product in a clinical trial): [**] U.S. Dollars (U.S. $[**]);

               (iii) upon initiation of a Phase III clinical trial of each
          Licensed Product by or on behalf of Licensee (for the purposes of this
          Section, initiation shall mean the first administration of each
          Licensed Product in such a trial): [**] U.S. Dollars (U.S. $[**]); and

               (iv) upon receiving an approval for marketing anywhere in the
          Territory of each Licensed Product: [**] U.S. Dollars (U.S. $[**]).

     Each such milestone payment shall be due and payable to Licensor within
     thirty (30) days of the date such milestone is achieved (whether achieved
     by or on behalf of Licensee or any of its Affiliates or sublicensees).
     Licensee shall remit to Licensor each such milestone payment in immediately
     available funds to an account designated in writing by Licensor.

          3.1.4. Royalties. Licensee shall pay or cause to be paid to Licensor a
     royalty equal to the Applicable Percentage of all Net Sales of any Licensed
     Product or Licensed Service by Licensee or any of its Affiliates, or
     permitted sublicensees ("Royalty Payments") on a country-by-country basis.
     No multiple royalties shall be payable because a Licensed Product or
     Licensed Service, its manufacture, use or sale is or shall be covered by
     more than one Valid Claim of a patent included in the Licensed Patents or
     more than one patent under the Licensed Patents. Royalty shall only be
     payable once in respect of each Licensed Product. Royalty Payments shall be
     made in accordance with Sections 3.4 and 3.5.

     3.2. Records. During the Term of this Agreement and for three (3) years
thereafter, Licensee shall (and shall cause its Affiliates and permitted
sublicensees to) keep complete and accurate records of sales of Licensed
Products and Licensed Services and such other matters as may affect the
determination of any amount payable to Licensor hereunder in sufficient detail
to enable a recognized international firm of certified public or chartered
accountants engaged by Licensor to determine any amounts payable to Licensor
under this Agreement.

                                        6

<PAGE>

Licensee shall (and shall cause its Affiliates and permitted sublicensees to)
permit certified public accountants engaged by Licensor, at Licensor's expense
(except as provided below), to examine not more than once in any twelve-month
period per Person its books, ledgers, and records during regular business hours
for the purpose of and to the extent necessary to verify any report required
under this Agreement or the accuracy of any amount payable hereunder for a three
(3) year period after the royalty period to which such records relate. Should
any examination conducted by Licensor or its representatives pursuant to the
provisions of this paragraph result in an increase of more than five percent
(5%) of any payment due Licensor hereunder, Licensee, in addition to any amounts
that may be due Licensor, shall be obligated to reimburse any out-of-pocket
expenses incurred by Licensor with respect to such examination within thirty
(30) days after receipt of an invoice therefor from Licensor.

     3.3. Royalty Reports. Within sixty (60) days after March 31, June 30,
September 30 and December 31 of each year, Licensee shall deliver to Licensor a
true and accurate report, giving such particulars of the business conducted by
Licensee, its Affiliates and permitted sublicensees during the preceding quarter
under this Agreement as are pertinent to an accounting for any Royalty Payments
hereunder. Each such report will contain at least the following information: the
number and kind of Licensed Products and Licensed Services (including where
permitted the identity of each Person to whom Licensed Services are sold) sold
in each country, total gross invoice amounts for each such Licensed Product and
Licensed Service, deductions applicable to Net Sales thereof, a calculation of
total amount due to Licensor for the relevant period, the exchange rate used to
convert gross invoice amounts and deductions applicable to Net Sales thereof in
each country. All payments shall be made in United States dollars.

     3.4. Payments. Within sixty (60) days of the end of each calendar quarter
in which any Net Sales occur, Licensee shall calculate the Royalty Payments owed
to Licensor and shall remit to Licensor the amount owed to Licensor in
immediately available funds to an account designated in writing by Licensor. For
purposes of determining when a sale of Licensed Product occurs, the sale shall
be deemed to occur on the date of invoice to the purchaser of the Licensed
Product.

     3.5 Taxes. If laws or regulations require withholding with respect to
payments made by Licensee of any taxes imposed upon Licensor on account of any
royalties and advance payments, paid under this Agreement, such taxes shall be
deducted by Licensee as required by law from such remittable royalty and advance
payment and shall be paid by Licensee to the proper tax authorities. Official
receipts of payment of any withholding tax shall be secured and sent to Licensor
as evidence of such payment. The Parties shall exercise their best efforts to
ensure that any withholding taxes imposed are reduced as far as possible under
the provisions of any relevant tax treaty.

     3.6 Overdue Payments. Payments not paid within seven (7) days of the
respective time period set forth in this Section 3 shall bear interest at a rate
of two percent (2%) above the London Interbank Offered Rate (LIBOR) from the due
date until paid in full.

                                        7

<PAGE>

4. PROTECTION OF INTELLECTUAL PROPERTY RIGHTS

     4.1. Patent Prosecution/Patent Costs. Licensor shall be responsible for the
prosecution, maintenance, renewal, extension and defense of all Licensed Patents
in its sole discretion and at its expense.

     4.2. Infringement by Third Persons. Licensee shall promptly advise Licensor
in writing of any infringement or suspected infringement of any of the rights
under the Licensed Patents. In the case of any infringement of any Licensed
Patent by any third Person (an "Infringer") during the term of this Agreement,
Licensor shall have the right under Licensor's control and at Licensor's expense
to prosecute any third Person infringement of the Licensed Patents. Subject to
Licensor's control of any such proceeding, Licensee shall have the right, at its
own expense and using counsel of its choosing, to participate in such
proceeding. Licensee shall assist as reasonably requested in taking any such
action against any such Infringer at Licensor's expense, unless Licensee has
stopped the development of all Licensed Products or has put the development of
all Licensed Products on hold. Any amount recovered by or reimbursed to Licensor
as a result of any action taken by Licensor under this Section 4.2 (including,
without limitation, from any settlement or other voluntary disposition thereof)
shall be retained by Licensor.

     4.3. Patent Marking. Licensee shall use appropriate patent marking on
Licensed Products where legally permissible. Licensee shall register or record
this Agreement in any country if Licensor's legal or beneficial interest in the
Licensed Patents would be prejudiced in such country by a failure to register.

     4.4. Patent Term Restoration. Licensor and Licensee shall cooperate in
obtaining patent term restoration in the United States or its equivalent in the
Territory where applicable to the Licensed Patents, including 35 U.S.C. 156 and
its foreign counterparts.

5. INDEMNIFICATION; ETC.

     5.1. Indemnification.

          5.1.1. Except as provided in Section 5.1.2, Licensee shall indemnify,
     defend and hold harmless Licensor, its Affiliates, and their respective
     directors, officers, managers, employees and agents and their respective
     successors, heirs and assigns (each a "Licensor Indemnitee"), against any
     liability, damage, deficiency, loss, cost or expense of any kind (including
     reasonable attorneys' fees and expenses of litigation) (each a "Liability")
     incurred by or imposed upon any Licensor Indemnitee as a result of any
     third party claim made or suit brought against a Licensor Indemnitee to the
     extent the same is relating to (a) any death, illness, personal injury,
     property damage or improper business practices arising out of the
     development, manufacture, sale, use or other disposition of any Licensed
     Product or provision of any Licensed Service (whether based on negligence
     or other tort, warranty, strict liability, or any other theory) or (b) any
     breach of this Agreement by Licensee.

          5.1.2. Except as provided in Section 5.1.1, Licensor shall indemnify,
     defend and hold harmless Licensee, its Affiliates, and their respective
     directors, officers,

                                        8

<PAGE>

     managers, employees and agents and their respective successors, heirs and
     assigns (each a "Licensee Indemnitee"), against any liability, damage,
     deficiency, loss, cost or expense of any kind (including reasonable
     attorney's fees and expenses of litigation) (each a "Liability") incurred
     by or imposed upon any Licensee Indemnitee as a result of any third party
     claim made or suit brought against a Licensee Indemnitee to the extent the
     same is relating to any breach of this Agreement by Licensor.

          5.1.3. A party's obligation to defend, indemnify and hold harmless is
     conditioned upon the indemnified party providing to the indemnifying party
     immediate notice of any such liability and providing all reasonable
     assistance in defending against such Liability.

          5.1.4. This Section 5.1 shall survive expiration or termination of
     this Agreement.

     5.2. Warranty Disclaimer. EXCEPT AS EXPRESSLY SET FORTH IN THIS AGREEMENT,
LICENSOR MAKES NO EXPRESS OR IMPLIED WARRANTY INCLUDING, WITHOUT LIMITATION, ANY
IMPLIED WARRANTY OF MERCHANTABILITY OR ANY IMPLIED WARRANTY OF FITNESS FOR A
PARTICULAR PURPOSE WITH RESPECT TO ANY OF THE LICENSED PATENTS OR ANY LICENSED
PRODUCTS OR LICENSED SERVICES OR OTHERWISE AND HEREBY DISCLAIMS THE SAME. EXCEPT
AS PROVIDED BELOW, LICENSOR MAKES NO EXPRESS OR IMPLIED WARRANTY THAT THE
MANUFACTURE, USE OR SALE OF ANY LICENSED PRODUCT OR PROVISION OF ANY LICENSED
SERVICE WILL NOT INFRINGE ANY PATENT OR OTHER RIGHT OF ANY PARTY OR THIRD PERSON
AND HEREBY DISCLAIMS THE SAME.

     5.3. Representations and Warranties of Licensor.

          5.3.1. Licensor hereby represents, warrants and covenants to Licensee
     that Licensor has the full right and authority to execute and perform this
     Agreement and the execution and performance of this agreement by Licensor
     will not conflict with, cause a default under or violate any existing
     contractual obligation that may be owed by Licensor to any third Person.

          5.3.2. Licensor has not previously assigned, transferred, conveyed or
     otherwise encumbered its right, title and interest in the Licensed Patents.

          5.3.3. Licensor shall maintain the Licensed Patents for the duration
     of this Agreement

          5.3.4. To Licensor's knowledge as of the Effective Date, each of the
     Licensed Patents is valid.

     5.4. Representations and Warranties of Licensee. Licensee hereby
represents, warrants and covenants to Licensor that Licensee has the full right
and authority to execute and perform this Agreement and the execution and
performance of this agreement by Licensee

                                        9

<PAGE>

will not conflict with, cause a default under or violate any existing
contractual obligation that may be owed by Licensee to any third Person.

     5.5. Insurance. In the event that Licensee is conducting clinical trials
using Licensed Products or manufacturing and supplying Licensed Products,
Licensee shall obtain product liability insurance citing Licensor as an
interested party under terms which are similar to that obtained by other
companies comparable to Licensee for products similar to such Licensed Products
and used in similar circumstances.

6. TERM AND TERMINATION

     6.1. Term. This Agreement will be effective as of the Effective Date and
will remain in effect until all Valid Claims in all Licensed Patents have
expired on a country-by country basis. Licensee shall have no obligation to make
Royalty Payments with respect to the Net Sales of a Licensed Product or
provision of a Licensed Service if (a) all Valid Claims in all Licensed Patents
applicable to the development, manufacture, use, sale or importation of such
Licensed Product or provision of such Licensed Service have expired in each
country in which such Licensed Product is used, sold or imported or such
Licensed Service is provided and (b) all Valid Claims in all Licensed Patents
applicable to the development, manufacture, use, sale or importation of such
Licensed Product or provision of such Licensed Service have expired in each
country in which such Licensed Product is manufactured or such Licensed Service
is provided. For the avoidance of doubt, Licensee shall be obligated to make
Royalty Payments with respect to products that are Licensed Products in
countries in which they are manufactured even if such products are used, sold or
imported in or into countries in which they are not Licensed Products.

     6.2. Termination by Licensor.

          6.2.1. Termination for Cause. Licensor shall have the right to
     terminate this Agreement and the license granted hereunder upon the
     happening of the following events:

               (i) Licensee fails to pay or cause to be paid any payment which
          has become due to Licensor under this Agreement and has not cured such
          non-payment within thirty (30) days after written notice from Licensor
          to Licensee specifying such non-payment.

               (ii) Licensee is in breach of or default under any material
          provision of this Agreement other than a payment obligation referred
          to in Section 6.2.1 (i) and has not cured such breach or default
          within sixty (60) days after written notice from Licensor to Licensee
          specifying the nature of such breach or default.

          6.2.2. Termination after Challenge. If Licensee or any of its
     Affiliates directly or indirectly makes, files, maintains or supports any
     claim, demand, lawsuit, cause of action or other action or proceeding,
     including without limitation by reexamination, opposition, interference,
     declaratory judgment proceeding or invalidity or nullity proceeding,
     alleging that a Licensed Patent is invalid or

                                       10

<PAGE>

     unenforceable, Licensor may immediately upon written notice to Licensee
     terminate this Agreement.

     Notwithstanding anything to the contrary in this Agreement, and provided
     that the discovery request, subpoena or court order was not initiated by or
     on behalf of Licensee or any of its Affiliates and does not result from
     legal proceedings that were initiated or supported by or on behalf of the
     Licensee or any of its Affiliates, if Licensee or any of its Affiliates or
     sublicensees is subject to a discovery request, subpoena or court order
     relating to one or more of the Licensed Patents that might be violative, or
     might lead to any action or proceeding that might be a violation, of this
     Section 6.2.2, Licensee, such Affiliate or such sublicensee shall provide
     prompt notice to Licensor of such discovery request, subpoena or court
     order such that Licensor may take any steps necessary to obtain a
     protective or other order. If reasonable efforts to obtain such protective
     or other order are unsuccessful, of if further delay in compliance with
     such discovery request, subpoena or court order is reasonably likely to
     result in a finding of contempt, Licensee, such Affiliate or such
     sublicensee may comply with such discovery request, subpoena or court
     order.

     6.3. Bankruptcy Event. Licensor may, at its option, terminate this
Agreement immediately upon notice to Licensee if a Bankruptcy Event occurs with
respect to the Licensee.

     6.4. Termination by Licensee. Licensee shall have the right to terminate
this agreement immediately upon one hundred and twenty (120) days written notice
to Licensor given after the complete and final cessation of, with the intention
never to resume, any and all activities relating to the development,
manufacture, commercialization, marketing or sale of Licensed Products and
Licensed Services by Licensee, its Affiliates, distributors, subcontractors or
permitted sublicensees.

     6.5. Effect of Termination.

          6.5.1. Upon termination of this Agreement for any reason, nothing
     herein shall be construed to release either Party from any obligation that
     matured prior to the effective date of such termination.

          6.5.2. Upon termination of this Agreement for any reason, any
     sublicense granted hereunder with respect to which the sublicensee is not
     then in breach or default shall continue as a direct license between the
     sublicensee and the Licensor on the terms of this Agreement, provided that
     the sublicensee agrees in writing, within thirty (30) days after
     termination of this Agreement, to be bound by the terms of this Agreement.

          6.5.3. The provisions of Sections 3.2 (Records), 3.5 (Taxes), 3.6
     (Overdue Payments), 4.2 (Infringement by Third Persons) (but only with
     respect to infringement occurring prior to termination), 5.1
     (Indemnification), 5.2 (Warranty Disclaimer), and 8 (General) shall survive
     termination of this Agreement for any reason.

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<PAGE>

          6.5.4. Licensee may, after termination of this Agreement, sell all
     Licensed Products which are in inventory at the time of termination, and
     complete and sell Licensed Services which Licensee can clearly demonstrate
     were in the process of being provided at the time of such termination,
     provided that Licensee shall pay to Licensor any Royalty Payments due on
     the sale of such Licensed Products or provision of such Licensed Services
     and shall submit reports, in accordance with this Agreement.

7. CONFIDENTIALITY

     7.1. Confidentiality. Subject to Section 7.2. below, during the term of
this Agreement neither Party shall use or disclose any Confidential Information
received by it pursuant to this Agreement without the prior written consent of
the other.

     7.2. Permitted Disclosure. Nothing contained in this Section shall be
construed to restrict the Parties from disclosing Confidential Information to
the extent that is reasonably required: (i) for legal, regulatory, tax, or
customs reasons, (ii) for audit purposes, (iii) by court or other government
order, or (iv) from using such Confidential Information as is reasonably
necessary to perform acts permitted by, or to exploit rights granted under this
Agreement.

8. GENERAL

     8.1. Assignment. This Agreement shall be binding upon and shall inure to
the benefit of each Party and each Party's respective transferees, successors
and assigns, provided, however, that Licensee shall not have the right to assign
this Agreement or its rights or obligations hereunder to any other Person
without the prior written consent of the Licensor other than as set forth in the
next sentence. Licensee may assign this Agreement and all of its rights and
obligations under this Agreement to any third Person who acquires all or
substantially all of Licensee's assets (or those of a separate business unit of
Licensee by merger, sale of assets or stock, or otherwise, or to any third
Person who acquires all or substantially all of Licensee (or a separate business
unit of Licensee) by merger, sale of assets or stock, or otherwise. Licensee
shall provide Licensor with a copy of any such executed assignment agreement.
Any purported assignment in violation of the provisions of this Section 8.1
shall be null and void.

     8.2. Publicity. Neither Party shall issue any news release or other public
announcement relating to this Agreement, including any of its terms, without the
prior written approval of the other Party. Once the text or substance of any
announcement has been so approved, it may be repeated without further approval.

     8.3. Use of Name. Except as may be agreed to by the Parties pursuant to
Section 8.2, neither Party shall use the name of the other in connection with
this Agreement, the Licensed Patents, the Licensed Products the Licensed
Services or any related matter in any press releases, public announcements or
other publicity or advertising materials without the prior written approval of
the other Party.

                                       12

<PAGE>

     8.4. Entire Agreement/Amendments. This Agreement constitutes the entire and
only agreement between the Parties relating to Licensed Patents, and all prior
negotiations, representations, agreements and understandings are superseded
hereby. No agreements amending, altering or supplementing the terms hereof may
be made except by means of a written document signed by a duly authorized
representative of each Party.

     8.5. Notices. Any notice, communication or payment required or permitted to
be given or made hereunder shall be in writing and, except as otherwise
expressly provided in this Agreement, shall be deemed given or made and
effective (i) when delivered personally; or (ii) when delivered by telex or
telecopy (if not a payment); or (iii) when received if sent by overnight
express; or (iv) upon confirmation of receipt if mailed by certified or
registered mail, postage prepaid and return receipt requested, in each case
addressed to Parties at their address stated below, or to such other address as
such Party may designate by written notice in accordance with the provisions of
this Section 8.5.

LICENSEE:     Biovex Limited
              70 Milton Park
              Abingdon, Oxford
              OX14 4RX
              England
              Fax: +44 1235 441901
              Attention: Vice President, Business Development

LICENSOR:     Wyeth Holdings Corporation
              Five Giralda Farms
              Madison, New Jersey 07940
              Fax: (973) 660-7050
              Attention: General Counsel

with copy to: Wyeth Pharmaceuticals
              500 Arcola Road, CC-3
              Collegeville, PA 19426
              Fax: (484) 865-9301
              Attention: Senior Vice President, Global Business Development

     8.6. Governing Law; Jurisdiction. This Agreement shall be construed and
enforced in accordance with the domestic substantive laws of The State of New
York and the United States of America without regard to any choice or conflict
of laws rule or principle that would result in the application of the domestic
substantive law of any other jurisdiction other than, in regard to any question
affecting the construction or effect of any patent, the law of the jurisdiction
under which such patent is granted. This Agreement shall not be subject to (a)
the United Nations Conventions on Contracts for the International Sale of Goods;
(b) the 1974 Convention on the Limitation Period in the International Sale of
Goods (the "1974 Convention"); or (c) the Protocol amending the 1974 Convention,
done at Vienna April 11, 1980. Any legal or other action hereunder shall be
brought exclusively in the U.S. Federal courts of New York. The Parties consent
to the personal jurisdiction and venue of such courts in the event of such
action. The

                                       13

<PAGE>

Parties hereby consent to waive any constitutional, statutory or common law
right of trial by jury and of forum non-conviens.

     8.7. Limitation of Liability. EXCEPT FOR THE LIABILITY ARISING OUT OF
SECTION 5.1, EACH PARTY'S AGGREGATE LIABILITY FOR ALL DAMAGES OF ANY KIND
RELATING TO THIS AGREEMENT OR ITS SUBJECT MATTER SHALL NOT EXCEED THE AMOUNT
PAID OR PAYABLE BY LICENSEE TO LICENSOR UNDER THIS AGREEMENT. The foregoing
limitations shall apply to all claims and actions of any kind, whether based on
contract, tort (including but not limited to negligence), or any other grounds.

     8.8. Headings. Headings included herein are for convenience only, and shall
not be used to construe this Agreement.

     8.9. Independent Contractors. For the purposes of this Agreement and all
services to be provided hereunder, each Party shall be, and shall be deemed to
be, an independent contractor and not an agent, partner, joint venturer or
employee of the other Party. Neither Party shall have authority to make any
statements, representations or commitments of any kind, or to take any action
which shall be binding on the other Party, except as may be explicitly provided
for herein or authorized in writing.

     8.10. Severability. If any provision of this Agreement shall be found by a
court of competent jurisdiction to be void, invalid or unenforceable, the same
shall either be reformed to comply with applicable law or stricken if not so
conformable, so as not to affect the validity or enforceability of this
Agreement.

     8.11. Force Majeure. Neither Party shall be responsible or liable to the
other Party for nonperformance or delay in performance of any terms or
conditions of this Agreement due to acts or occurrences beyond the control of
the nonperforming or delayed Party, including, but not limited to, acts of God,
acts of government, wars, riots, strikes or other labor disputes, shortages of
labor or materials, fires, and floods, provided the nonperforming or delayed
Party provides to the other Party written notice of the existence of and the
reason for such nonperformance or delay.

     8.12. No Waiver. Failure of either Party to enforce a right under this
Agreement shall not act as a waiver of that right or the ability to later assert
that right relative to the particular situation involved or to terminate this
Agreement arising out of any subsequent default or breach.

                                       14

<PAGE>

     8.13. Counterparts. This Agreement may be executed in any number of
counterparts, each of which shall constitute an original document, but all of
which shall constitute the same agreement.

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

BIOVEX LIMITED                          WYETH HOLDINGS CORPORATION

By: /s/ Robert Coffin                   By: /s/ Robert F. Smith
    ---------------------------------       ------------------------------------
Name: Robert Coffin                     Name: Robert F. Smith
Title: Chief Scientific Officer         Title: Vice President

By: /s/ Tony Mills
    ---------------------------------
Name: Tony Mills
Title: Vice President, Business Development

                                       15

<PAGE>

                                   Schedule 1

                                LICENSED PATENTS

<TABLE>
<CAPTION>
     COUNTRY        APPLICATION   Filing Date      Patent                      Issue Date
     -------        -----------   -----------      ------                      ----------
<S>                 <C>           <C>              <C>                         <C>
USA                 60/001602     July 27, 1995
USA                 08/686631     July 24, 1996    5,824,318                   October 20, 1998
PCT                 96/12281      July 24, 1996
Australia           67139/96      July 25, 1996    725557                      January 25, 2001
Canada              2227860       July 25, 1996    Application still pending
Europe*             96927257.4    July 25, 1996    841943                      September 3, 2003
Israel              118942        July 24, 1996    118942                      December 15, 2002
Israel-divisional   135726        April 18, 2000   Application still pending
S. Africa           96/6287       July 26, 1996    96/6287                     May 27, 1998
Taiwan              85/09120      July 26, 1996    Abandoned
</TABLE>

*    Nationalized patents in Austria, Belgium, Denmark, Finland, France,
     Germany, Great Britain, Greece, Ireland, Italy, Luxembourg, Netherlands,
     Portugal, Spain, Sweden & Switzerland

                                      -16-

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