Document:

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                                                                    Exhibit 4.19

                                   SCHEDULE 1

                               PERFORMANCE SHARES

1.   INTRODUCTION

     This Schedule 1 shall constitute the Protherics PLC Performance Share Plan
     (the "Performance Plan"). Under the Performance Plan, the Grantor may make
     conditional awards of Shares which will be designated as Performance Shares
     on the Date of Grant. The Rules of the Protherics PLC 2005 Long Term
     Incentive Plan (the "Plan") will apply to Performance Shares granted under
     the Performance Plan except as set out below.

2.   INTERPRETATION

     Performance Shares granted under this Schedule 1 are intended to comply
     with the requirements of section 409A of Title 26 of the United States Code
     (the "Internal Revenue Code"). In the event of any conflict between the
     Plan, the Performance Plan and the Internal Revenue Code, then the
     Performance Plan and the Internal Revenue Code shall prevail.

3.   OPERATION

     Under the Performance Plan, Options shall not be granted but, instead,
     selected Eligible Employees shall be awarded a right to receive Shares at
     the end of the Performance Period, subject to the satisfaction of any
     conditions imposed in accordance with Rule 2.2.

4.   DEFINITIONS

     Words used in the Performance Plan shall have the same meaning as in the
     Plan unless amended as stated below:

<TABLE>
<S>                              <C>
"AWARD"                          means a conditional right to acquire Shares
                                 granted under the Performance Plan;
</TABLE>
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<TABLE>
<S>                              <C>
"VESTING"                        means a Participant becoming entitled to have
                                 the Shares transferred to him subject to these
                                 Rules, and the terms "Vest" and "Vests" shall
                                 be construed accordingly;

"VESTING PERIOD"                 means the period of three years from the Date
                                 of Grant by reference to which the Grantor will
                                 determine whether the conditions imposed under
                                 Rule 2.3 have been fulfilled;
</TABLE>

     the definitions of "Option" and "Option Period" shall be deleted, and any
     references thereto in the Rules shall be replaced by "Award" and "Vesting
     Period" respectively, and the Rules shall be interpreted accordingly; and

     the definition of "Option Price" shall be deleted and any references
     thereto in the Rules shall be disregarded accordingly.

5.   INTERPRETATION

     The terms "exercise" and "exercisable", where they appear in the Rules,
     should be read as "Vesting" or "Vests" as appropriate and the Rules shall
     be interpreted accordingly.

     The decision of the Grantor on the interpretation of the Rules or in any
     dispute relating to an Award or matter relating to the Performance plan
     will be final and conclusive.

6.   DEATH

     Rule 4.2 shall be amended so that if a Participant dies his Awards will
     Vest on the date of death subject to Rule 4.1.3 unless the Grantor decides
     otherwise.

7.   CESSATION OF OFFICE OR EMPLOYMENT

     Rule 4.3 shall be amended so that if a Participant ceases to hold office or
     employment with a Group Member as a result of exceptional circumstances as
     determined at the discretion of the Grantor, acting fairly and reasonably,
     an Award

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     will Vest on such cessation of office or employment, having regard to the
     extent that the conditions imposed under rule 2.3 have been met and to
     reflect the period during which the Participant continued to hold office or
     employment during the Performance Period, unless the Grantor determines
     otherwise.

8.   LAPSE

     To the extent that an Award does not vest following the occurrence of any
     of the events specified in Rules 4 and 5 it shall lapse.

9.   RESTRICTIONS ON VESTING

     No Award shall Vest at a time when such Vesting would not be in accordance
     with the Internal Revenue Code or any other applicable laws or regulations.

10.  TAKEOVER, RECONSTRUCTION AND WINDING-UP

     Rules 5.1 to 5.9 shall be replaced with the following:

     5.1  Subject to Rules 5.3, 5.4 and 5.6 below, if any person obtains Control
          of the Company as a result of making, either:

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

     5.1.2 a general offer to acquire all the shares in the Company which are of
          the same class as the Shares,

          (in either case disregarding any shares already owned by it or by any
          company associated with it), an Award shall Vest subject to Rule 5.10.

     5.2  For the purpose of this Rule 5 a person shall be deemed to have
          obtained Control of the Company if he and others acting in concert (as
          defined by the City Code on Take-overs and Mergers) with him have
          together obtained Control of it

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     5.3  If any person becomes bound or entitled to acquire Shares under
          Sections 428 to 430F of the Companies Act 1985 subject to Rules 5.6
          and 5.10 an Award shall Vest on the day that such person becomes duly
          bound or entitled.

     5.4  Subject to Rule 5.6, when under Section 425 of the Companies Act 1985
          a Court sanctions a compromise or arrangement proposed in connection
          with the acquisition of Shares an award shall Vest on the date of
          Court sanction.

          The Vesting of an Award under this Rule 5.4 shall be conditional on
          the Participant agreeing to transfer or otherwise deal with any Shares
          issued to him in order that he is placed in the same position (so far
          as possible) as would have been the case if such Shares had been
          subject to such compromise or arrangement.

     5.5  If notice is duly given of a resolution for the voluntary winding-up
          of the Company, the Company shall give notice thereof to all
          Participants and subject to Rule 5.10 an Award shall Vest upon the
          said resolution being duly passed.

     5.6  Awards shall not Vest pursuant to any of Rules 5.1, 5.3 or 5.4 above
          (where this occurs as a result of a company obtaining Control in the
          case of Rules 5.1 and 5.4 or as a result of a company becoming bound
          or entitled in accordance with Rule 5.3), any Participant may as soon
          as practicable after the relevant event, by agreement with the
          relevant company, release any Award which has not lapsed ("the Old
          Award") in consideration of the grant to him of an Award ("the New
          Award") which is equivalent to the Old Award but relates to shares in
          a different company (whether the company which has obtained Control of
          the Company itself or some other company).

     5.7  For the purposes of Rule 5.6 the provisions of the Performance Plan
          shall be construed as if:

     5.7.1 the New Award was an award granted under the Performance Plan at the
          same time as the Old Award;

     5.7.2 except for the purpose of the definition of "Participating Company"
          in Rule 1 and the reference to "the Company" in Rule 10.2, the
          reference to

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          Protherics PLC in the definition of "the Company" in Rule 1 were a
          reference to the different company mentioned in Rule 5.6;

     5.7.3 subject to Rule 5.7.4 any conditions specified pursuant to Rule 2.3
          shall not apply; and

     5.7.4 where Rule 5.8 applies, any conditions specified pursuant to Rule 2.3
          shall apply in their original form unless the Grantor determines in
          accordance with Rule 2.3.2 that it would be appropriate for such
          conditions to be varied or waived in full or in part.

     5.8  Rules 5.1, 5.3 and 5.4 above shall not apply but, instead, Awards
          shall be exchanged in accordance with Rule 5.6 where:

     5.8.1 the events form part of a scheme or arrangement whereby Control of
          the Company is obtained by another company ("the Acquiring Company");

     5.8.2 immediately after the Acquiring Company obtains Control, the issued
          equity share capital of the Acquiring Company is owned substantially
          by the same persons who were equity shareholders of the Company
          immediately prior to the Acquiring Company obtaining Control; and

     5.8.3 the Acquiring Company has agreed to grant new Awards in accordance
          with Rule 5.6 in consideration for the release of any Awards which
          have not lapsed.

     5.9  If the Company has been or will be affected by any demerger, dividend
          in specie, super dividend or other transaction which will adversely
          affect the current or future value of any Awards, the Grantor may,
          acting fairly, reasonably and objectively, allow all such Awards (but
          not some only) to Vest conditionally on such event happening. The
          Grantor will notify any Participant who is affected by this Rule.

11.  MANNER OF EXERCISE

     Rule 6 shall not apply except that in the event that any Tax Liability
     becomes due on the Vesting of an Award, the Participant will be deemed to
     have given irrevocable instructions to the Company's brokers (or any other
     person acceptable to the Company) for the sale of sufficient Shares
     acquired on the Vesting of the Award to

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     realise an amount equal to the Tax Liability and the payment of the Tax
     Liability to the Relevant Company, unless:

11.1 the Relevant Company is able to deduct an amount equal to the whole of the
     Tax Liability from the Participant's net pay for the relevant pay period;
     or

11.2 the Participant has paid to the Relevant Company an amount equal to the Tax
     Liability; or

11.3 the Grantor determines otherwise.

12.  ISSUE OR TRANSFER OF SHARES

     Rule 7 shall apply except to the extent that the Grantor will procure
     (subject to Rule 6) the allotment or transfer of the relevant number of
     Shares subject to the Award to the Participant within 30 days following the
     date on which the Award Vests.

13.  RIGHTS

     Notwithstanding Rule 8.2 of the Plan, Participants will not be entitled to
     any rights whatsoever attaching to the Shares subject to an Award until
     such time as the Award has Vested and full and unconditional title to the
     Shares is transferred to the Participant.<PAGE>

                                                                    Exhibit 4.20

                                                                           FINAL

                                   ----------

                                  RULES OF THE
                                 PROTHERICS PLC
                            2005 DEFERRED BONUS PLAN

                                   ----------

APPROVED BY SHAREHOLDERS OF THE COMPANY AT AN EXTRAORDINARY GENERAL MEETING HELD
ON 27 JANUARY 2005

APPROVED BY THE BOARD AT A MEETING HELD ON 17 FEBRUARY 2005

                                (DELOITTE LOGO)

                                4 BRINDLEY PLACE
                                BIRMINGHAM B1 2HZ

                               Tel: 0121 632 6000

                                                                               1

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                                    CONTENTS

<TABLE>
<S>                                                                          <C>
1.    DEFINITIONS AND INTERPRETATION......................................     3
2.    OPERATION OF THE PLAN...............................................     9
3.    MAKING OF DEFERRED AWARDS...........................................    10
4.    CONDITIONS..........................................................    11
5.    OPTION AWARDS.......................................................    11
6.    LIMIT ON SHARE ISSUE................................................    12
7.    TERMINATION OF EMPLOYMENT...........................................    13
8.    TERMINATION OF EMPLOYMENT BEFORE THE RELEASE DATE...................    13
9.    RECONSTRUCTION OR TAKEOVER AND OTHER EVENTS BEFORE THE RELEASE
      DATE................................................................    14
10.   TERMINATION OF EMPLOYMENT, RECONSTRUCTION AND TAKEOVER, AND OTHER
      EVENTS..............................................................    14
11.   VARIATION OF SHARE CAPITAL..........................................    14
12.   RIGHTS OF EXERCISE AND LAPSE OF OPTION AWARDS.......................    15
13.   TAKEOVER, RECONSTRUCTION AND WINDING-UP.............................    17
14.   EXERCISE OF OPTION AWARDS...........................................    21
15.   ISSUE OR TRANSFER OF SHARES.........................................    22
16.   ADJUSTMENTS TO OPTION AWARDS........................................    22
17.   ADMINISTRATION OF THE PLAN..........................................    23
18.   ALTERATIONS.........................................................    24
19.   LEGAL ENTITLEMENT...................................................    26
20.   GENERAL.............................................................    27
</TABLE>

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                                  RULES OF THE

                                 PROTHERICS PLC
                            2005 DEFERRED BONUS PLAN

1.   DEFINITIONS AND INTERPRETATION

1.1  In this Plan, the following words and expressions shall have, where the
     context so admits, the meanings set forth below.

<TABLE>
<S>                              <C>
"ANNUAL REMUNERATION"            The higher of:

                                 (A)  the annual rate of the Participant's
                                      remuneration (exclusive of bonuses and
                                      commissions in the form of cash, Shares or
                                      other assets and of benefits-in-kind, from
                                      all Participating Companies at the Date of
                                      Grant); and

                                 (B)  the remuneration (exclusive of bonuses and
                                      commissions in the form of cash, Shares or
                                      other assets and of benefits-in-kind) paid
                                      or payable to the Participant by all
                                      Participating Companies in, or in respect
                                      of, the 12 months immediately preceding
                                      the Date of Grant

"BOARD"                          The board of directors for the time being of
                                 the Company or a duly authorised committee
                                 thereof.

"COMMITTEE"                      Either:

                                 (A)  in relation to the grant of a Deferred
                                      Award to executive directors of the
                                      Company, the remuneration committee; or

                                 (B)  in relation to the grant of a Deferred
                                      Award to other directors and employees,
                                      such other duly authorised committee of
                                      the Board as may be appointed from time to
                                      time.
</TABLE>

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<TABLE>
<S>                              <C>
"COMPANY"                        Protherics PLC registered in England and Wales
                                 under No. 02459087.

"CONTROL"                        The meaning given by Section 840 of the Taxes
                                 Act.

"DAILY OFFICIAL LIST"            The register of listed securities and the
                                 prices of transactions published by the London
                                 Stock Exchange.

"DATE OF GRANT"                  The date on which an Option Award is granted.

"DEALING DAY"                    Any day on which the London Stock Exchange is
                                 open for the transaction of business.

"DEFERRED AWARD"                 An award of cash or Option Awards made to an
                                 Eligible Employee in a form specified in Rule 3
                                 under the Plan

"ELIGIBLE EMPLOYEE"              Any person who at the Date of Grant is:

                                 (A)  an employee of a Participating Company,
                                      who is not a director, or

                                 (B)  an executive director of a Participating
                                      Company who devotes substantially the
                                      whole of his working time to the business
                                      of a Participating Company; and

                                 (C)  more than six months from his anticipated
                                      date of Retirement.

"EMPLOYEES' SHARE SCHEME"        The meaning given by Section 743 of the
                                 Companies Act 1985.

"EXECUTIVE SHARE OPTION PLAN"    A share option plan in which participation is
                                 discretionary (for the avoidance of doubt,
                                 excluding any Sharesave Plan).

"GRANT PERIOD"                   The period of 42 days commencing on the day
                                 after any of the following days:
</TABLE>

                                                                               4

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<TABLE>
<S>                              <C>
                                 (A)  the day on which the Plan is adopted by
                                      the Company;

                                 (B)  the day on which the Company makes an
                                      announcement of its results for the last
                                      preceding financial year, half-year or
                                      other period;

                                 (C)  any day on which the Grantor resolves that
                                      exceptional circumstances exist which
                                      justify the grant of Options;

                                 (D)  any day on which any change to the
                                      legislation affecting Executive Share
                                      Option Plans is proposed or made;

                                 (E)  the date of commencement of an Eligible
                                      Employee's employment with a Participating
                                      Company provided that the Eligible
                                      Employee is not already employed by a
                                      Participating company, but only in respect
                                      of that Eligible Employee;

                                 PROVIDED THAT if by reason of primary or
                                 secondary legislation, regulation or government
                                 directive or by reason of any agreement to
                                 which the Company is or may be a party, the
                                 Grantor is restricted from granting Deferred
                                 Awards under the Plan during the period
                                 specified above the relevant Grant Period shall
                                 be 42 days commencing on the day after the
                                 restriction is lifted.

"GRANTOR"                        The Committee (acting on behalf of the Company)
                                 or the Board or the Trustees acting on the
                                 recommendation of, or with the consent of, the
                                 Committee, as the case may be.
</TABLE>

                                                                               5

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<TABLE>
<S>                              <C>
"GROUP MEMBER"                   A Participating Company or a body corporate
                                 which is (within the meaning of Section 736 of
                                 the Companies Act 1985) the Company's holding
                                 company or a Subsidiary of the Company's
                                 holding company.

"ITEPA"                          The Income Tax (Earnings and Pensions) Act
                                 2003.

"LONDON STOCK EXCHANGE"          London Stock Exchange PLC or any successor body
                                 carrying on the business of London Stock
                                 Exchange PLC.

"MARKET VALUE"                   In relation to a Share on any day:

                                 (A)  if and so long as the Shares are listed on
                                      the London Stock Exchange, their closing
                                      middle market quotation (as derived from
                                      the Daily Official List) for the
                                      immediately preceding Dealing Day, or if
                                      the Grantor determines, the average of the
                                      closing middle market quotations over the
                                      three immediately preceding Dealing Days,
                                      or

                                 (B)  in any other case, their market value as
                                      determined by the Committee.

"MODEL CODE"                     Means the UK Listing Authority Model Code for
                                 transactions in securities by directors,
                                 certain employees and persons connected with
                                 them.

"OPTION AWARD"                   A right to acquire Shares under the Plan
                                 pursuant to a Deferred Award which is either
                                 subsisting or is proposed to be granted.

"OPTION PRICE"                   The price per Share, as determined by the
                                 Grantor at the Date of Grant, at which a
                                 Participant may acquire Shares upon the
                                 exercise of an Option Award granted to him
                                 being not less than their nominal value if the
</TABLE>

                                                                               6

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<TABLE>
<S>                              <C>
                                 Shares are to be subscribed; but subject to any
                                 adjustment pursuant to Rule 16.

"PARTICIPANT"                    Any Eligible Employee to whom an Option has
                                 been granted, or (where the context so admits)
                                 the personal representative of any such person.

"PARTICIPATING COMPANY"          (A)  The Company; and

                                 (B)  any other company which is under the
                                      Control of the Company, and is a
                                      Subsidiary of the Company except one which
                                      the Grantor has designated shall not be a
                                      Participating Company.

"PERFORMANCE TARGET"             Means any target or targets specified for a
                                 financial year in relation to a Deferred Award.

"PLAN"                           The Protherics PLC 2005 Deferred Bonus Plan in
                                 its present form or as from time to time
                                 amended in accordance with the provisions
                                 hereof.

"RECOGNISED INVESTMENT           The meaning given by the Financial Services and
EXCHANGE"                        Markets Act 2000.

"RECONSTRUCTION OR TAKEOVER"     Means any takeover, merger or internal
                                 reconstruction, however effected, including a
                                 reverse takeover, partial offer, reorganisation
                                 or scheme of arrangement sanctioned by the
                                 court.

"RELEASE DATE"                   Means the date on which the Grantor determines
                                 the extent to which Deferred Awards vest under
                                 Rule 2.5.

"RETIREMENT"                     Retirement on or after the date specified in
                                 the Participant's contract of employment.

"RULES"                          The rules of the Plan as amended from time to
                                 time.

"SHARE"                          A fully paid ordinary share in the capital of
                                 the Company.
</TABLE>

                                                                               7
<PAGE>

<TABLE>
<S>                              <C>
"SHARESAVE PLAN"                 A savings related share option plan approved
                                 under Schedule 3 to ITEPA.

"SUBSIDIARY"                     The meaning given by Section 736 of the
                                 Companies Act 1985.

"TAX LIABILITY"                  A liability to account for any tax, national
                                 insurance, social security or other levy in
                                 respect of a Deferred Award by the Company or
                                 any Participating Company ("the Relevant
                                 Company"), whether by reason of grant, exercise
                                 or otherwise, including for the avoidance of
                                 doubt:

                                      (A) any liability to pay secondary Class
                                      1 National Insurance Contributions for
                                      which an agreement or election has been
                                      entered into under paragraph 3A or 3B of
                                      Schedule 1 to the Social Security
                                      Contributions and Benefits Act 1992
                                      ("National Insurance Election"); and

                                      (B) any liability arising after
                                      termination of a Participant's employment
                                      for whatever reason and which may arise or
                                      be incurred in any jurisdiction whatever,
                                      and by the law of the same jurisdiction
                                      may or shall be recovered from the person
                                      entitled to the Deferred Award,

                                 but subject to (A) above, not including any
                                 secondary Class 1 National Insurance
                                 Contributions.

"TAXES ACT"                      The Income and Corporation Taxes Act 1988.

"TREASURY SHARES"                Any shares bought and held by the Company in
                                 accordance with Section 162A(3) of the
                                 Companies Act 1985 (as amended).

"TRUSTEES"                       The trustee or trustees for the time being of
                                 any
</TABLE>

                                                                               8

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<TABLE>
<S>                              <C>
                                 employee benefit trust established for the
                                 benefit of all or substantially all of the
                                 Eligible Employees.

"VESTING DATE"                   Means the date on which an Option Award becomes
                                 exercisable.
</TABLE>

1.2  Words and expressions not otherwise defined herein have the same meaning
     they have in the Taxes Act or ITEPA (as the case may be).

1.3  Where the context so admits or requires words importing the singular shall
     include the plural and vice versa and words importing the masculine shall
     include the feminine.

1.4  Reference in the Rules of the Plan to any statutory provisions are to those
     provisions as amended, extended or re-enacted from time to time, and shall
     include any regulations made thereunder. The Interpretation Act 1978 shall
     apply to these Rules on the same basis as if they were an Act of
     Parliament.

1.5  The headings in the Rules of the Plan are for the sake of convenience only
     and should be ignored when construing the Rules.

2.   OPERATION OF THE PLAN

2.1  The Grantor may decide at any time and at its discretion when the Plan
     shall be operated.

2.2  In relation to any operation of the Plan, the Grantor may select any
     employees or executive directors of any Participating Company to be
     Participants in the Plan.

2.3  The Grantor will make a Deferred Award on the basis that it will not vest
     until a Performance Target has been satisfied.

2.4  Deferred Awards may on determination take the form of cash or Option
     Awards, or a combination of cash and Option Awards, as the Grantor may
     determine. A Deferred Award, comprising cash or Option Awards or both, will
     not exceed 50% of Annual Remuneration.

                                                                               9

<PAGE>

2.5  As soon as practicable after the end of the financial year, the Performance
     Target together with any other conditions (if any) attaching to Deferred
     Awards shall be evaluated and the amount of each Participant's Deferred
     Award shall be calculated. The date on which the Grantor makes these
     determinations is the Release Date. Deferred Awards payable in cash shall
     be paid as soon as practicable after the Release Date by the Company or,
     where relevant, the Participating Company employing the Participant. The
     Grantor may also on or following the Release Date, but during a Grant
     Period, grant an Option Award in respect of the vested Deferred Award. The
     Grantor will notify each Participant of the Date of Grant, the Vesting
     Date, the Option Price (if relevant) and the number of Shares subject to
     the Option Award (calculated in accordance with Rule 5.2). The Grantor will
     execute a deed on the grant of an Option Award.

2.6  The Grantor may consult with any Participant before determining the type of
     Deferred Award to be made, but shall not be bound by any views expressed by
     the Participant.

2.7  The Grantor may not resolve to make a Deferred Award more than ten years
     after the Plan has been adopted by the Board.

3.   MAKING OF DEFERRED AWARDS

3.1  Deferred Awards are subject to the rules of the Plan. Participants shall be
     notified in writing that they have been selected for participation in the
     Plan. The notice shall include:

     (i)  details of the Performance Target and any other conditions attaching
          to the Deferred Award;

     (ii) the maximum percentage of Annual Remuneration that may be awarded;

     (iii) the nature of the Deferred Award; and

     (iv) if appropriate, the Option Price

3.2  No payment by the Participant shall be required on receiving notice of a
     Deferred Award.

3.3  Subject to the rights of the Participant's personal representatives
     pursuant to Rule 12.2, every Deferred Award shall be personal to the
     Participant to whom it is made and shall not be transferable or in any way
     without the prior written agreement of the Grantor and

                                                                              10
<PAGE>

     such transfer shall be subject to such conditions as the Grantor may
     prescribe at that time.

4.   CONDITIONS

4.1  When making a Deferred Award, the Grantor will make vesting subject to a
     Performance Target being met. A Performance Target must be objective and
     specified in the notice given to Participants under Rule 3.1. The Grantor
     may waive or change a Performance Target in accordance with its terms if
     anything happens which causes the Grantor reasonably to consider it
     appropriate.

4.2  In addition to the Performance Target, the Grantor may impose such
     additional condition or conditions on the vesting of a Deferred Award or
     exercise of an Option Award as it may determine. Any condition relating to
     a Deferred Award must be objective, be specified in the notice given to
     Participants under Rule 3.1 and may provide that a Deferred Award will not
     vest if it is not satisfied. Any condition relating to an Option Award must
     also be objective, be specified in the certificate or statement given to
     Participants under Rule 5.1 and may provide that an Option Award will not
     be exercisable if it is not satisfied. The Grantor may waive or change a
     condition in accordance with its terms or in any way they see fit.

4.3  Without prejudice to the generality of Rule 4.2, the Grantor may make the
     exercise of an Option Award conditional upon an Eligible Employee agreeing
     to enter into a National Insurance Election (or its overseas equivalent to
     the extent this is lawful).

5.   OPTION AWARDS

5.1  As soon as practicable following the Release Date and the grant of Option
     Awards (in accordance with Rule 2.5) each Participant will receive a
     certificate setting out the terms of the Option Award. The certificate will
     either be the deed referred to in Rule 2.5 or a statement. The Grantor will
     set the form of the certificate, but the certificate must be consistent
     with these Rules.

5.2  The number of Shares subject to an Option Award will be calculated by
     reference to the Market Value of a Share on the Date of Grant, or such
     other date which the Grantor may

                                                                              11

<PAGE>

     decide but excluding a date which falls during a prohibited period under
     the Model Code.

5.3  If any option certificate is lost or damaged the Grantor may replace it on
     such conditions as it may wish to set.

5.4  Participants are not required to pay for the grant of any Option Award.

5.5  A Participant may surrender his Option Award in whole or in part within the
     period of 30 days immediately following the Date of Grant and if an Option
     Award, or any part of an Option Award, is so surrendered, it shall be
     deemed for all purposes not to have been granted.

6.   LIMIT ON SHARE ISSUE

6.1  The number of Shares which may be allocated under the Plan on any day shall
     not, when added to the aggregate of the number of Shares which have been
     allocated during that and the previous nine years under the Plan and under
     any other Employees' Share Scheme (including a Sharesave plan) adopted by
     the Company or any other company when it is under the Company's Control,
     exceed such number as represents ten per cent of the ordinary share capital
     of the Company in issue immediately prior to that day.

6.2  In determining the above limit:

     6.2.1 any Shares allocated to the Trustees under the Plan and any other
          Employees' Share Scheme adopted by the Company shall be included;

     6.2.2 no account shall be taken of any Shares where the right to acquire
          such Shares was released or lapsed without being exercised, including
          pursuant to Rule 5.5 above; and

     6.2.3 no account shall be taken of any Shares where the right to acquire
          such Shares has been or is to be satisfied other than by the issue or
          allotment of any part of the share capital of the Company.

6.3  For the avoidance of doubt, references in this Rule 6 to the "allocation"
     of Shares shall mean, in the case of any share option plan, the placing of
     unissued Shares or Treasury

                                                                              12
<PAGE>

     Shares under option, and, in relation to other types of Employees' Share
     Scheme, shall mean the issue and allotment of Shares or Treasury Shares.

7.   TERMINATION OF EMPLOYMENT

7.1  For the purpose of this Plan, no person shall be treated as ceasing to hold
     an office or employment with a Group Member by virtue of which that person
     is eligible to participate in the Plan until that person ceases to hold any
     office or employment with any Group Member.

8.   TERMINATION OF EMPLOYMENT BEFORE THE RELEASE DATE

8.1  This Rule 8 applies if a Participant ceases to hold office or employment
     with a Group Member before determination of the Performance Target at the
     end of the financial year to which the Deferred Award relates.

8.2  If a Participant ceases to hold office or employment with a Group Member as
     a result of exceptional circumstances (as determined within three months of
     the cessation, at the sole discretion of the Grantor, acting fairly and
     reasonably), he (or his personal representatives) may at the discretion of
     the Grantor receive the cash comprised in his Deferred Award or be entitled
     within 6 months of cessation to exercise an Option Award in respect of such
     number of Shares as the Grantor may determine (but such number of Shares
     when added to any cash paid or to be paid is not to exceed in value 50% of
     the Participant's Annual Remuneration).

8.3  For the purposes of this Rule 8, in determining the amount of cash to be
     paid or the number of Shares exercisable under an Option Award the Grantor
     will have regard to the extent that the conditions imposed under Rule 4
     have been met and the length of the period to which the Performance Target
     relates during which the Participant continued to hold office or
     employment, unless the Grantor determines otherwise.

                                                                              13

<PAGE>

9.   RECONSTRUCTION OR TAKEOVER AND OTHER EVENTS BEFORE THE RELEASE DATE

9.1  In the event of a Reconstruction or Takeover before the Release Date, the
     Grantor may determine the extent to which a Deferred Award will vest,
     having regard to the length of time that it has been held and the extent to
     which the Performance Target has been satisfied.

9.2  The Grantor has discretion to take such action as it may think appropriate
     if other events happen which may have an effect on Deferred Awards.

10.  TERMINATION OF EMPLOYMENT, RECONSTRUCTION AND TAKEOVER, AND OTHER EVENTS

10.1 This Rule 10 applies if following determination of the Performance Target
     but before the Date of Grant in respect of an Option Award arising from a
     vested Deferred Award:

          (i)  a Participant ceases to hold office or employment with a Group
               Member for any reason;

          (ii) there is a Reconstruction and Takeover; or

          (iii) other events happen which may have an effect on vested Deferred
               Awards.

10.2 If an event specified in Rule 10.1 occurs, the Grantor has discretion to
     take such action as it may think appropriate in relation to vested Deferred
     Awards and related Option Awards which have not yet been granted.

11.  VARIATION OF SHARE CAPITAL

11.1 The Grantor may vary the terms of a Deferred Award or Option Award to take
     account of any variation of the share capital of the Company, or any
     special dividend or other transaction which might adversely affect the
     value of the Shares, to ensure that the Participant is not disadvantaged.

                                                                              14
<PAGE>

12.  RIGHTS OF EXERCISE AND LAPSE OF OPTION AWARDS

12.1 An Option Award:

     12.1.1 save as provided in Rules 12.2, 12.3 and 13 below, can only be
          exercised:

          12.1.1.1 on or after the Vesting Date;

          12.1.1.2 if not prohibited by any statute, regulations or any code
               adopted by the Company based on the Model Code; and

          12.1.1.3 if not prevented under Rule 13 (Takeover, Reconstruction and
               Winding-Up);

     12.1.2 save as provided in Rules 12.2, 12.3 and 13 below, may only be
          exercised by a Participant while he is a director or employee of a
          Group Member,

     12.1.3 may only be exercised if the conditions upon exercise (as waived,
          varied or amended) imposed pursuant to Rule 4 have been fulfilled to
          the satisfaction of the Grantor unless the Grantor, in its absolute
          discretion, determines otherwise.

12.2 An Option Award may be exercised in the period of one year following the
     death of a Participant subject to Rule 12.1.3 unless the Grantor determines
     otherwise.

12.3 If a Participant ceases to hold office or employment with a Group Member as
     a result of exceptional circumstances (as determined within three months of
     the cessation, at the discretion of the Grantor, acting fairly and
     reasonably), an Option Award may be exercised subject to Rule 12.1.3 as the
     Grantor may direct from the date of cessation until six months thereafter.

12.4 An Option Award shall lapse upon the occurrence of the earliest of the
     following events:

     12.4.1 the tenth anniversary of the Date of Grant

     12.4.2 the expiry of either of the periods specified in Rules 12.2 and 12.3
          (save that if at the time any of the applicable periods under Rules
          12.3 expire, time is

                                                                              15

<PAGE>

          running under the period in Rule 12.2, the Option Award shall not
          lapse by reason of this Rule 12.4.2 until the expiry of the period
          specified in Rule 12.2);

     12.4.3 the expiry of any of the periods specified in Rules 13.1, 13.3, 13.4
          and 13.5 save where an Option Award is released in consideration of
          the grant of a New Award (during one of the periods specified in Rules
          13.1, 13.3 or 13.4) pursuant to Rule 13.6;

     12.4.4 the Participant ceasing to hold an office or employment or giving or
          being given notice to terminate employment with a Group Member in any
          circumstances other than:

          12.4.4.1 where the cessation of office or employment arises on any of
               the grounds specified in Rules 12.2, or 12.3 provided that an
               Option Award shall not be regarded as having lapsed pursuant to
               this Rule 12.4.4.1 if the Grantor determines within three months
               of the Participant ceasing to hold his office or employment that
               the Participant ceased to hold the office or employment in
               accordance with Rule 12.3; or

          12.4.4.2 where the cessation of office or employment arises on any
               ground whatsoever during any of the periods specified in Rule 13
               save where an Option Award is released in consideration of the
               grant of a New Award (during one of the periods specified in
               Rules 13.1, 13.3 or 13.4) pursuant to Rule 13.6;

     12.4.5 subject to Rule 13.5 the passing of an effective resolution, or the
          making of an order by the Court, for the winding-up of the Company;

     12.4.6 the Participant being deprived of the legal or beneficial ownership
          of the Option Award by operation of law, or doing or omitting to do
          anything which causes him to be so deprived or being declared
          bankrupt; and

     12.4.7 the Participant purporting to transfer or dispose of the Option
          Award or any rights in respect of it other than as permitted under
          Rule 3.3.

                                                                              16

<PAGE>

12.5 No Option Award may be granted, exercised, released or surrendered at a
     time when such grant, exercise, release or surrender would not be in
     accordance with the "Model Code on Directors' Dealings in Securities"
     issued by the UK Listing Authority as amended from time to time.

12.6 For the purpose of this Plan, no person shall be treated as ceasing to hold
     an office or employment with a Group Member by virtue of which that person
     is eligible to participate in the Plan until that person ceases to hold any
     office or employment with any Group Member.

12.7 If there is any conflict between any of the provisions of this Rule 12 the
     provision which results in the shortest exercise period of the Option will
     prevail. However, the Grantor may permit an Option holder to exercise his
     Options within any applicable longer period set out in rules 12.2 and 12.3.

13.  TAKEOVER, RECONSTRUCTION AND WINDING-UP

13.1 Subject to Rules 13.3, 13.4 and 13.6 below, if any person obtains Control
     of the Company as a result of making, either:

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

     13.1.2 a general offer to acquire all the shares in the Company which are
          of the same class as the Shares,

     (in either case disregarding any shares already owned by it or by any
     company associated with it), an Option Award may, subject to Rule 13.10, be
     exercised within six months (or such earlier date as the Grantor may
     determine) of the earliest of:

     (a)  the date, being prior to the date on which the person making the offer
          under Rule 13.1.lor 13.1.2 obtains Control of the Company, on which
          the Board resolves that, in its reasonable opinion, to do otherwise
          would result in a loss of a corporation tax deduction pursuant to
          Schedule 23 of the Finance Act 2003; or

                                                                              17

<PAGE>

     (b)  the time when the person making the offer has obtained Control of the
          Company and any condition subject to which the offer is made has been
          satisfied.

     In each case, the Grantor shall notify Participants in writing as soon as
     possible and in any event with sufficient time to exercise their Option
     Awards. Such exercise of Option Awards shall be done in accordance with any
     procedure set down by the Grantor.

13.2 For the purpose of Rule 13.1 a person shall be deemed to have obtained
     Control of the Company if he and others acting in concert (as defined by
     the City Code on Take-overs and Mergers) with him have together obtained
     Control of it.

13.3 If any person becomes bound or entitled to acquire Shares under Sections
     428 to 430F of the Companies Act 1985 subject to Rule 13.6 and 13.10 an
     Option Award may be exercised within a period of four weeks beginning with
     the date on which that person becomes so bound or entitled.

13.4 Subject to Rule 13.6, if under Section 425 of the Companies Act 1985 it is
     proposed that the Court sanctions a compromise or arrangement proposed for
     the purposes of or in connection with a plan for the reconstruction of the
     Company or its amalgamation with any other company or companies, the
     following apply:

     13.4.1 the Company shall give notice thereof to all Participants at the
          same time as it sends notices to members of the Company calling the
          meeting to consider such a compromise or arrangement;

     13.4.2 the Participant may then, subject to Rule 13.10 exercise the Option
          Award subject to the terms of this Rule 13.4 before the earlier of the
          expiry of six months from the date of such notice and the date on
          which the Court sanctions the compromise or arrangement;

     13.4.3 the exercise of an Option Award under this Rule 13.4 shall be
          conditional on:

          13.4.3.1 such compromise or arrangement being sanctioned by the Court
               and;

          13.4.3.2 the Participant agreeing to transfer or otherwise deal with
               any Shares issued to him in order that he is placed in the same
               position (so far as

                                                                              18

<PAGE>

               possible) as would have been the case if such Shares had been
               subject to such compromise or arrangement;

     13.4.4 the Option Award shall then lapse conditionally on such compromise
          or arrangement sanctioned by the Court becoming effective.

13.5 If notice is duly given of a resolution for the voluntary winding-up of the
     Company, the Company shall give notice thereof to all Participants. Subject
     to Rule 13.6, and subject to Rule 13.10 an Option Award may then be
     exercised until the resolution is duly passed or defeated or the meeting
     concluded or adjourned sine die provided that any such exercise of an
     Option Award pursuant to this Rule 13.5 shall be conditional upon the said
     resolution being duly passed. If such resolution is duly passed all Option
     Awards shall, to the extent that they have not been exercised, lapse
     immediately.

13.6 If an Option Award becomes exercisable pursuant to any of Rules 13.1, 13.3
     or 13.4 above (where this occurs as a result of a company obtaining Control
     in the case of Rules 13.1 and 13.4 or as a result of a company becoming
     bound or entitled in accordance with Rule 13.3), any Participant may, by
     agreement with the relevant company, release any Option Award which has not
     lapsed ("the Old Award") in consideration of the grant to him of a new
     award ("the New Award") which is equivalent to the Old Award but relates to
     shares in a different company (whether the company which has obtained
     Control of the Company itself or some other company).

13.7 For the purposes of Rule 13.6 the provisions of the Plan shall be construed
     as if:

     13.7.1 the New Award was an award granted under the Plan at the same time
          as the Old Award;

     13.7.2 except for the purpose of the definition of "Participating Company"
          in Rule 1 and the reference to "the Company" in Rule 18.2, the
          reference to Protherics PLC in the definition of "the Company" in Rule
          1 were a reference to the different company mentioned in Rule 13.6;

     13.7.3 subject to Rule 13.7.4 any conditions specified pursuant to Rules
          4.2 and 4.3 shall not apply, and

                                                                              19

<PAGE>

     13.7.4 where Rule 13.8 applies, any conditions specified pursuant to Rules
          4.2 and 4.3 shall apply in their original form unless the Grantor
          determines in accordance with Rule 4.1 that it would be appropriate
          for such conditions to be varied or waived in full or in part.

13.8 Rules 13.1, 13.3 and 13.4 above shall not apply where:

     13.8.1 the events form part of a scheme or arrangement whereby Control of
          the Company is obtained by another company ("the Acquiring Company");

     13.8.2 immediately after the Acquiring Company obtains Control, the issued
          equity share capital of the Acquiring Company is owned substantially
          by the same persons who were equity shareholders of the Company
          immediately prior to the Acquiring Company obtaining Control; and

     13.8.3 the Acquiring Company has agreed to grant new awards in accordance
          with Rule 13.6 in consideration for the release of any Option Awards
          which have not lapsed.

13.9 If the Company has been or will be affected by any demerger, dividend in
     specie, super dividend or other transaction which will adversely affect the
     current or future value of any Option Awards, the Grantor may, acting
     fairly, reasonably and objectively, allow all such Option Awards (but not
     some only) to be exercised conditionally on such event happening. The
     Grantor will specify the period of exercise of such Option Awards. The
     Grantor will notify any Participant who is affected by this Rule.

13.10 Where Rules 13.1, 13.3, 13.4 or 13.5 apply in deciding whether and to what
     extent Options Awards will vest, the Grantor shall have regard as
     appropriate to the extent to which time has elapsed since the Date of Grant
     and any conditions specified pursuant to Rule 4 have been met.

13.11 Where Rules 13.1, 13.3, 13.4 or 13.5 apply, Option Awards shall lapse to
     the extent not already exercised following the expiry of any specified
     period.

                                                                              20

<PAGE>

14.  EXERCISE OF OPTION AWARDS

14.1 An Option Award may be exercised by the delivery to the Company Secretary
     (as agent for the Grantor), or his duly appointed agent, of an award
     certificate covering at least all the Shares over which the Option Award is
     then to be exercised, with the notice of exercise in the prescribed form
     duly completed and signed by the Participant (or by his duly authorised
     agent) together with a remittance for, or authorisation for the payment of,
     the total Option Price (if applicable) payable to the Company (as agent for
     the Trustees where the Trustees have agreed to satisfy the Option) in
     respect of the Shares over which an Option Award is to be exercised, unless
     the Grantor determines that a difference exercise procedure should apply.

14.2 If any conditions must be fulfilled before an Option Award may be
     exercised, the delivery of the certificate shall not be treated as
     effecting the exercise of the Option Award unless and until the Grantor is
     satisfied that the conditions have been fulfilled.

14.3 The effective date of exercise shall be the later of the date of delivery
     of the notice of exercise and the date that the Grantor states that the
     conditions imposed by Rule 4 have been fulfilled, if applicable. For the
     purposes of this Plan a notice of exercise shall be deemed to be delivered
     when it is received by the Company.

14.4 In the event that any Tax Liability becomes due on the exercise of an
     Option Award, the Participant will be deemed to have given irrevocable
     instructions to the Company's brokers (or any other person acceptable to
     the Company) for the sale of sufficient Shares acquired on the exercise of
     the Option Award to realise an amount equal to the Tax Liability and the
     payment of the Tax Liability to the Relevant Company, unless:

     14.4.1 the Relevant Company is able to deduct an amount equal to the whole
          of the Tax Liability from the Participant's net pay for the relevant
          pay period; or

     14.4.2 the Participant has paid to the Relevant Company an amount equal to
          the Tax Liability; or

     14.4.3 the Grantor determines otherwise.

                                                                              21

<PAGE>

15.  ISSUE OR TRANSFER OF SHARES

15.1 Subject to Rule 15.3 Shares to be issued pursuant to the exercise of Option
     Awards shall be allotted to the Participant (or his nominee) within 30 days
     following the date of effective exercise of the Option Award.

15.2 Subject to Rule 15.3, the Grantor shall procure the transfer of any Shares
     or Treasury Shares to be transferred to a Participant (or his nominee)
     pursuant to the exercise of an Option Award within 30 days following the
     date of effective exercise of the Option Award.

15.3 The allotment or transfer of any Shares under the Plan shall be subject to
     obtaining any such approval or consent as is mentioned in Rule 20.3 below.

15.4 Shares issued pursuant to the Plan will rank pari passu in all respects
     with the Shares then in issue, except that they shall not rank for any
     right attaching to Shares by reference to a record date preceding the date
     of exercise.

15.5 If Shares or Treasury Shares are transferred pursuant to the Plan the
     Participant shall not be entitled to any rights or dividends attaching to
     such shares by reference to a record date preceding the date of exercise.

15.6 If and so long as the Shares are listed on the London Stock Exchange, the
     Company shall apply for listing of any Shares issued pursuant to the Plan
     as soon as practicable after the allotment thereof.

15.7 The Grantor may at any time determine not to procure the transfer or issue
     of Shares or Treasury Shares to a Participant who exercises his Option
     Award, but instead to pay to him (subject to the withholding provisions in
     Rule 14.4) a cash amount. This cash amount must be equal to the amount by
     which the Market Value of the Shares on the day of exercise, in respect of
     which the Option is exercised, exceeds the Option Price.

16.  ADJUSTMENTS TO OPTION AWARDS

16.1 The number of Shares over which an Option Award is granted, the conditions
     of exercise and, if relevant, the Option Price thereof (and where an Option
     Award has been

                                                                              22

<PAGE>

     exercised but no Shares have been allotted or transferred pursuant to such
     exercise, the number of Shares which may be so allotted or transferred and
     the price at which they may be acquired) shall be adjusted in such manner
     as the Grantor shall determine following any capitalisation issue,
     demerger, any offer or invitation made by way of rights, subdivision,
     consolidation, reduction, other variation in the share capital of the
     Company or any other exceptional event which in the reasonable opinion of
     the Grantor justifies such an adjustment, to the intent that (as nearly as
     may be without involving fractions of a Share) the aggregate Option Price
     payable in respect of an Option shall remain unchanged.

16.2 Apart from pursuant to this Rule 16.2 no adjustment under Rule 16.1 above
     may have the effect of reducing the Option Price to less than the nominal
     value of a Share. Where an Option Award subsists over both issued and
     unissued Shares any such adjustment may only be made if the reduction of
     the Option Price of Option Awards over both issued and unissued Shares can
     be made to the same extent. Any adjustment made to the Option Price of
     Option Awards over unissued Shares shall only be made if and to the extent
     that the Board shall be authorised to capitalise from the reserves of the
     Company a sum equal to the amount by which the nominal value of the Shares
     in respect of which the Option Award is exercisable exceeds the adjusted
     Option Price and to apply such sum in paying up such amount on such Shares
     so that on exercise of any Option Award in respect of which such a
     reduction shall have been made the Board shall capitalise such sum (if any)
     and apply the same in paying up such amount as aforesaid.

16.3 The Grantor may take such steps as it may consider necessary to notify
     Participants of any adjustment made under this Rule 16 and to call in,
     cancel, endorse, issue or reissue any certificate consequent upon such
     adjustment.

17.  ADMINISTRATION OF THE PLAN

17.1 Any notice or other communication under or in connection with the Plan may
     be given by personal delivery or by sending the same by electronic means or
     post, in the case of a company to its registered office, and in the case of
     an individual to his last known address, or, where he is a director or
     employee of a Group Member, either to his last known address or to the
     address of the place of business at which he performs the whole or
     substantially the whole of the duties of his office or employment, and
     where a notice

                                                                              23

<PAGE>

     or other communication is given by post, it shall be deemed to have been
     received 72 hours after it was put into the post properly addressed and
     stamped, and if by electronic means, when the sender receives electronic
     confirmation of delivery or if not available, 24 hours after sending the
     notice.

17.2 The Company may distribute to Participants copies of any notice or document
     normally sent by the Company to the holders of Shares.

17.3 In the case of partial exercise of an Option Award, the Grantor may in
     consequence call in, endorse, cancel and reissue, as it considers
     appropriate, any certificate for the balance of the Shares over which the
     Option Award was granted.

17.4 If any certificate shall be worn out, defaced or lost, it may be replaced
     on such evidence being provided as the Grantor may require.

17.5 The Company shall at all times keep available for allotment unissued Shares
     at least sufficient to satisfy all Option Awards under which Shares may be
     subscribed or the Grantor shall procure that sufficient are available for
     transfer to satisfy all Option Awards under which Shares may be acquired.

17.6 The Plan shall be administered by the Board. The Board shall have full
     authority, consistent with the Plan, to administer the Plan, including
     authority to interpret and construe any provision of the Plan, to amend the
     Plan to correct any errors or mistakes of procedure, and to adopt such
     regulations for administering the Plan and such forms of exercise as it may
     deem necessary or appropriate. Decisions of the Board shall be final and
     binding on all parties.

17.7 The costs of introducing and administering the Plan shall be borne by the
     Participating Companies.

18.  ALTERATIONS

18.1 Subject to Rules 18.2 and 18.4, the Grantor may at any time alter or add to
     all or any of the provisions of the Plan in any respect.

                                                                              24

<PAGE>

18.2 Subject to Rule 18.3, no alteration or addition to the material advantage
     of Participants or employees shall be made under Rule 18.1 to:

     18.2.1 the definition of "Eligible Employee";

     18.2.2 the limits in Rules 2 and 6;

     18.2.3 any rights attaching to the Options and the Shares;

     18.2.4 the rights of Participants under Rules 8, 9, 10, 11, 12 and 13; and

     18.2.5 the terms of this Rule 18.2,

     without the prior approval by ordinary resolution of the members of the
     Company in general meeting.

18.3 Rule 18.2 shall not apply to any minor alteration or addition which is to
     benefit the administration of the Plan, or to take account of any change in
     legislation or to obtain or maintain favourable taxation, exchange control
     or regulatory treatment for the Company, or any Subsidiary of the Company
     or any Participant.

18.4 No alteration or addition shall be made under Rule 18.1 which would
     materially abrogate or adversely affect the subsisting rights of a
     Participant unless it is made:

     18.4.1 with the consent in writing of such number of Participants as hold
          Deferred Awards under the Plan to acquire 75 per cent of the Shares
          which would be issued or transferred if all Option Awards granted and
          subsisting under the Plan were exercised; or

     18.4.2 by a resolution at a meeting of Participants passed by not less than
          75 per cent of the Participants who attend and vote either in person
          or by proxy,

     and for the purpose of this Rule 18.4 the provisions of the Articles of
     Association of the Company relating to shareholder meetings shall apply
     mutatis mutandis.

18.5 Notwithstanding any other provision of the Plan other than Rule 18.1 the
     Grantor may at any time in respect of Deferred Awards granted to Eligible
     Employees who are or who may become subject to taxation outside the United
     Kingdom on their remuneration amend or add to the provisions of the Plan
     and the terms of Deferred Awards (whether

                                                                              25

<PAGE>

     by way of the establishment of further Plans to apply in overseas
     territories or otherwise) as it considers necessary or desirable to take
     account of or to mitigate or to comply with relevant overseas taxation,
     securities or exchange control laws, provided that:

     18.5.1 the terms of Deferred Awards granted to such Eligible Employees are
          not overall more favourable than the terms of Deferred Awards granted
          to other Eligible Employees; and

     18.5.2 any Shares made available in respect of such Deferred Awards shall
          be treated as counting against the limits contained in Rules 6.

18.6 As soon as reasonably practicable after making any alteration or addition
     under Rule 18.1, the Board shall give written notice thereof to any
     Participant materially affected thereby.

18.7 No alteration shall be made to the Plan if following the alteration the
     Plan would cease to be an Employees' Share Scheme.

18.8 No alteration to the Plan under this Rule 18 shall require the consent of
     any person unless expressly provided in the Rules.

19.  LEGAL ENTITLEMENT

19.1 Nothing in the Plan or in any instrument executed pursuant to it will
     confer on any person any right to continue in employment nor will it affect
     the right of any Group Member to terminate the employment of any person
     without liability at any time with or without cause, nor will it impose
     upon the Grantor or any other person any duty or liability whatsoever
     (whether in contract, tort or otherwise) in connection with:

     19.1.1 the lapsing of any Option Award pursuant to the Plan;

     19.1.2 the failure or refusal to exercise any discretion under the Plan;
          and/or

     19.1.3 a Participant ceasing to be a person who has a service relationship
          for any reason whatever.

                                                                              26
<PAGE>

19.2 Deferred Awards shall not (except as may be required by taxation law) form
     part of the emoluments of individuals or count as wages or remuneration for
     pension or other purposes.

19.3 Nothing in the Plan shall be deemed to give any employee of any
     Participating Company any right to participate in the Plan.

19.4 Any person who ceases to have the status or relationship of an employee
     with any Group Member as a result of the termination of his employment for
     any reason and however that termination occurs, whether lawfully or
     otherwise, shall not be entitled and shall be deemed irrevocably to have
     waived any entitlement by way of damages for dismissal or by way of
     compensation for loss of office or employment or otherwise to any sum,
     damages or other benefits to compensate that person for the loss of
     alteration of any rights, benefits or expectations in relation to any
     Deferred Award, the Plan or any instrument executed pursuant to it.

19.5 The benefit of this Rule 19 is given to the Company for itself and as
     trustee and agent of each Group Member.

20.  GENERAL

20.1 The Plan shall terminate upon the tenth anniversary of its approval by the
     Company or at any earlier time by the passing of a resolution by the Board
     or an ordinary resolution of the Company in general meeting. Termination of
     the Plan shall be without prejudice to the subsisting rights of
     Participants.

20.2 By participating in the Plan, a Participant consents to the holding and
     processing of personal data provided by the Participant to the Company for
     all purposes relating to the operation of the Plan, including, but not
     limited to administering and maintaining Participant records, providing
     information to the Trustees, registrars, brokers, savings carrier or other
     third party administrators of the Plan, providing information to future
     purchasers of the Company or the business in which the Participant works
     and transferring information about the Participant to a country or
     territory outside the European Economic Area.

                                                                              27

<PAGE>

20.3 All allotments, issues and transfers of Shares will be subject to obtaining
     any approval or consent required under any applicable laws, regulations of
     governmental authority and the requirements of the London Stock Exchange
     and any other Recognised Investment Exchange on which the Shares are
     traded.

20.4 The Company and any Subsidiary of the Company may provide money to the
     Trustees or any other person to enable them or him to acquire Shares to be
     held for the purposes of the Plan, or enter into any guarantee or indemnity
     for those purposes, to the extent permitted by Section 153 of the Companies
     Act 1985. In addition, the Company may require any Subsidiary to enter into
     such other agreement or agreements as it shall deem necessary to oblige
     such Subsidiary to reimburse the Company for any other amounts paid by the
     Company hereunder, directly or indirectly in respect of such Subsidiary's
     employees.

20.5 These Rules shall be governed by and construed in accordance with the laws
     of England and Wales.

                                                                              28

<PAGE>

                                 PROTHERICS PLC
                      2005 DEFERRED BONUS PLAN (THE "PLAN")

                            NOTICE OF DEFERRED AWARD

I am pleased to confirm, that you have been selected to participate in this
year's operation of the Plan. This means that, subject to the performance of the
Company during the financial year ending on [date] you will receive a Deferred
Award, comprising cash and options. The terms of the Deferred Award are subject
to the rules of the Plan, a copy of which is available from [contact]. In the
event of any conflict between the terms of this letter and the rules of the
Plan, the rules of the Plan will prevail.

DEFERRED AWARD

Subject to the full satisfaction of the Performance Target relating to the
financial year ending [date] and other conditions outlined below, you will
receive:

     (i)  a cash payment amounting to up to [25%] of your annual remuneration;
          and

     (ii) a grant of options over shares in the Company ("Option Awards").

CASH

If the Performance target is met, you will receive a cash payment as soon as
practicable after the [Remuneration Committee] meets around [month] next year.
The amount you receive will be calculated by reference to your annual
remuneration as at [year end].

OPTION AWARD

In addition to the cash payment, you will be granted an Option Award. The number
of shares under option will be calculated by reference to a percentage (up to
[25]%) of your annual remuneration as at [year end] divided by the market value
of the shares at or around the time the grant is made to you. The Option Award
will not be granted to you before the [Remuneration Committee] has met and
determined the extent, if any, that the Performance Target has been satisfied.

The Option Award will not be immediately exercisable. Rather, it will not be
exercisable until about [2] years after grant. Further details of the Option
Award will be given to you after it has been granted.

PERFORMANCE TARGET

[Insert details of Performance Target].

CONDITIONS

It will be a condition of the exercise of an Option Award that you satisfy any
liability for PAYE and employees' class 1 national insurance contributions that
may arise in connection with the grant of the Option Award or its exercise,
assignment or release. You agree to enter into any arrangements required by the
Company in relation to such liability.

                                                                              29

<PAGE>

Participation in, and the operation of, the Plan will not form part of or affect
your contract of employment or your employment relationship, nor will they give
you the right to continued employment. Participation in one operation of the
Plan does not indicate that you will participate, or be considered for
participation, in any later operations. Specific provisions are included in the
rules of the Plan relating to the exclusions of rights and waiver of claims for
the operation of the Plan. You are not entitled to any compensation or other
benefit in respect of the Plan. You should therefore read the rules of the Plan
before you decide whether to participate.

If you have any questions in relation to the Plan and the operation of Deferred
Awards then please contact [name] for further information.

In the meantime, I should like to thank you for the continued support you have
given to the Company.

------------------------------------
[Authorised signatory]

                                                                              30

<PAGE>

                                 PROTHERICS PLC

               (Registered in England and Wales: Number 02459087)

Certificate No: [___]

                                  PROTHERICS PLC
                            2005 DEFERRED BONUS PLAN

                            OPTION AWARD CERTIFICATE

THIS IS TO CERTIFY
That

NAME
Of
Address

is the holder of an Option Award over:

-    [____] [Ordinary Shares] of [____] each in the capital of the Company at an
     exercise price of L[____] per share in accordance with the Rules of the
     Protherics PLC 2005 Deferred Bonus Plan

The Date of Grant of this Option Award is [date].

The Vesting Date of this Option Award is [date].

This Option Award is not transferable to any person and shall lapse if any
attempt is made to transfer, assign or charge it.

The Option Award shall in any event lapse on [tenth anniversary or any earlier
date] to the extent that it has not been exercised.

Exercise of this Option Award is subject to the conditions imposed by the Board
as attached to this Certificate.

This Option Award is an Unapproved Option for UK tax purposes.

If you do not wish to accept this Option Award you may surrender it in writing
to the Company Secretary within 30 days of the Date of Grant.

EXECUTED as a DEED by Protherics PLC acting by

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

THIS IS AN IMPORTANT DOCUMENT: PLEASE KEEP IT IN A SAFE PLACE.

                                                                              31

<PAGE>

                                 PROTHERICS PLC
                            2005 DEFERRED BONUS PLAN

                        NOTICE OF EXERCISE - OPTION AWARD

TO: The Company Secretary
    Protherics PLC
    The Heath Business and Technical Park
    Runcorn
    WA7 4QF

I HEREBY exercise the Option Award evidenced by the Certificate attached in
respect of _________ Ordinary Shares of [____] each in the capital of the
Company

1.   I enclose a cheque for L[____] being the aggregate Option Price in respect
     of those shares. OR

     I enclose completed Instructions to the Company's brokers in respect of the
     exercise of the Option and the sale of Shares to meet the aggregate Option
     Price in respect of those shares. (Delete as appropriate)(1)

2.   I enclose a cheque payable to [the Company] for L____ in respect of the
     estimated Tax Liability arising in connection with the exercise of my
     Option. If my Tax Liability is greater than the amount I have paid I
     authorise you to deduct any outstanding Tax Liability in relation to the
     Option from my salary. OR

     I authorise the Company or its duly appointed agent to sell such number of
     the Shares registered in my name as will enable it (after payment of all
     necessary selling expenses and commissions) to recover and retain for
     itself from the sale proceeds an amount equal to such Tax Liability and
     then account to me for any cash balance remaining and generally to sign any
     stock transfer form or other document or documents which may be required.
     (Delete as appropriate)(2)

3.   I understand that no Shares will be issued or transferred to me until ALL
     of my Tax Liability has been satisfied in full.

4.   I request that you issue or transfer to me such number of [Ordinary Shares]
     and I agree to accept the same subject to the Memorandum and Articles of
     Association of the Company. I authorise you to place my name on the
     Register of Members in respect of the shares so issued or transferred to
     me.

5.   Please send the share certificate for the said shares, when ready, to me by
     post at my risk to the address below.

SIGNED:                                 DATE:
        -----------------------------         -----------------------
NAME IN FULL
             ------------------------

----------
(1)  You can choose whether you wish to provide your own funds to pay the Option
     Price or whether you wish to make use of the broker-assisted exercise
     method.

(2)  You must choose one of these methods for satisfying the Tax Liability.

                                                                              32

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