Document:

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                                                                  EXHIBIT 10.6

                                  RULES OF THE

                                  APBIOTECH INC

                        EXECUTIVE STOCK OPTION PLAN 2000

                                    New Bridge Street Consultants
                                    20 Little Britain
                                    London  EC1A  7DH
                                    Ref: N\1021\ARUNDEL\ESTP2000 051200

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                             RULES OF THE APBIOTECH

                        EXECUTIVE STOCK OPTION PLAN 2000

      1     MEANINGS OF WORDS USED

      1.1   In these Rules:

            "Associated Company" has the meaning given to it by Section 416 of
            the U.K. Taxes Act;

            "Business Day" means a day on which NASDAQ is open for the
            transaction of business;

            "Company" means APBiotech Inc;

            "Control" has the meaning given to it by Section 840 of the U.K.
            Taxes Act;

            "Date of Grant" means the date on which the Directors resolve to
            grant an Option;

            "Directors" means the Board of Directors of the Company or a duly
            authorised committee of it;

            "Eligible Employee" means any person who is a common law employee of
            a Participating Company who devotes substantially the whole of his
            working time to his duties;

             "Employees' Share Plan" means a plan for encouraging or
            facilitating the holding of shares in the Company by or for the
            benefit of the bona fide employees or former employees of the
            Company, the Company's subsidiary or holding company or a subsidiary
            of the Company's holding company;

            "Market Value" means in relation to a Share:

            (i)   If Shares are listed on a national securities exchange or
                  traded in the over-the-counter market and sales prices are
                  regularly reported for Shares, either (a) the average of the
                  low and high prices of the Shares on the composite tape or
                  other comparable reporting system for the applicable date, or
                  if the applicable date is not a trading day, for the trading
                  day immediately preceding the applicable date or (b) the
                  closing or last price of Shares on the composite tape or other
                  comparable reporting system for the applicable date, or if the
                  applicable date is not a trading day, for the trading day
                  immediately preceding the applicable date, as the Option
                  Committee shall determine.

            (ii)  If Shares are not traded on a national securities exchange but
                  are traded on the over-the-counter market, if sales prices are
                  not regularly reported for the Shares for the trading days or
                  day referred to in clause (1), and if bid and asked prices for
                  the Shares are regularly reported, the mean between the bid
                  and the asked price for the Shares at the close of trading in
                  the over-the-counter market for the training day on which
                  Shares were traded immediately preceding the applicable date,
                  as the Option Committee shall determine; and

            (iii) If the Shares are neither listed on a national securities
                  exchange nor traded in the over-the-counter market, such value
                  as the Option Committee, in good faith, shall determine.

            "Member of the Group" means the Company and all Subsidiaries and
            Associated Companies of it from time to time;

            "Option" means a right to acquire Shares granted pursuant to the
            Plan and for the time being subsisting;

            "Option Committee" means a duly appointed committee of the Directors
            comprising Directors who:

                  (i)   do not hold any executive office with a Participating
                        Company; and

                  (ii)  will not themselves participate in the Plan;

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            "Option Exercise Date" means the date when an Option is effectively
            exercised upon compliance with the provisions of Rules 7.1;

            "Option Holder" means a person holding an Option, including, where
            the context so permits, his personal representatives;

            "Option Period" means, in respect of an Option, a period commencing
            on the Date of Grant and expiring at the close of business on the
            day preceding the 10th anniversary of the Date of Grant;

            "Option Price" means the price per Share payable on the exercise of
            an Option as determined by the Option Committee under Rule 3.1;

            "Original Shareholder" means Nycomed Amersham plc (or any subsidiary
            of Nycomed Amersham plc) or Pharmacia Corp (or any subsidiary of
            Pharmacia Corp);

            "Participating Companies" means the Company and any Subsidiary of
            the Company, direct or indirect, designated by the Option Committee
            as a Participating Company

            "Plan" means this plan known as "APBiotech Inc Executive Stock
            Option Plan 2000" in its present form or as from time to time
            altered in accordance with the Rules;

            "Plan Period" means the period commencing on the date of the
            approval of the Plan by the Directors and ending on the 10th
            anniversary of that date;

            "Rules" means these rules as amended from time to time;

            "Shares" means shares in the Company's common stock, US$0.01 - par
            value

            "Subsidiary" means a company which is:

                  (i)   a subsidiary of the Company within the meaning given
                        thereto by Section 736 of the U.K. Companies Act 1985,
                        and

                  (ii)  under the Control of the Company;

            "Taxes Act" means the UK Income and Corporation Taxes Act 1988; and

            "Year" means a year beginning on any January 1 and ending the
            following December 31.

      1.2   Where the context so admits or requires, the singular includes the
            plural and the masculine includes the feminine and vice versa;
            references to any statutory provision shall include any modification
            or re-enactment.

      1.3   Headings shall be ignored in construing the Rules. Footnotes and
            expressions in italics do not form part of the rules and are for
            guidance only.

2 GRANT OF OPTIONS

      2.1   GRANT OF OPTIONS

            Subject to Rule 2.10 below, the Option Committee may during the Plan
            Period in its absolute discretion grant to any Eligible Employee an
            Option to acquire such number of Shares as the Option Committee may
            determine (or such lesser number as may be the case following an
            adjustment under Rule 2.8) at the Option Price.

      2.2   TIME WHEN OPTIONS MAY BE GRANTED

            Options shall only be granted at such times as may be permitted by
            applicable securities laws.

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      2.3    CONDITIONS ON EXERCISE

             The Option Committee may grant an Option on the basis that it may
             not be exercised, in whole or in part, until certain conditions
             have been satisfied.

             The Option Committee may in its discretion waive, vary or amend any
             such condition. Such discretion shall only be exercised if events
             happen which cause the Option Committee to consider that a waived,
             varied or amended condition would be a fairer measure of
             performance and would be no more difficult to satisfy.

      2.4   OPTION CERTIFICATES

            Each Option Holder shall be issued an option certificate (executed
            as a deed), on or as soon as practicable after the Date of Grant, in
            such form as the Option Committee shall prescribe.

      2.5   NO PAYMENT

            No payment to the Company shall be required on the grant of an
            Option.

      2.6   DISCLAIMER OF OPTION

            Any Option Holder may, by notice in writing to the Secretary of the
            Company, within 30 days after the Date of Grant, disclaim in whole
            his Option and in such case the Option shall be deemed never to have
            been granted under the Plan. No consideration shall be payable for
            any disclaimer.

      2.7   DISPOSAL RESTRICTIONS

            Except for the transmission of an Option on the death of an Option
            Holder to his personal representatives, neither an Option nor any
            rights in respect of it may be transferred, assigned or otherwise
            disposed of by an Option Holder to any other person, and if an
            Option Holder purports to transfer, assigns or disposes of any such
            Option or rights, whether voluntarily or involuntarily, then the
            relevant Option shall immediately lapse.

      2.8   BLUE PENCIL PROVISION

            If any Option is purported to be granted on terms which are not in
            accordance with the provisions of these Rules, including the
            limitations on participation and the calculation of the Option
            Price, the Option Committee shall vary the terms of such Option to
            bring the Option within the Rules and any such variation shall take
            effect from the Date of Grant.

      2.9   LIMITS ON SHARES AVAILABLE

            2.9.1 Subject to Rules 2.9.2 and 2.9.3 below, no Options shall be
                  granted under the Plan which would, at the time they are
                  granted, cause the number of Shares which may be issued in
                  pursuance of Options granted under the Plan, or in pursuance
                  of options or other awards made under any other Employees'
                  Share Plan of the Company, to exceed such number as represents
                  3% of the ordinary share capital of the Company from time to
                  time.

            2.9.2 The limit at Rule 2.9.1 above shall apply from the date of
                  adoption of the Plan by the Company until such date as
                  determined by the Directors, which shall not be before 1 June
                  2002 at the earliest.

            2.9.3 Only those Shares which are capable of being issued before 1
                  June 2002 (or such later date as determined by the Directors
                  pursuant to Rule 2.9.2 above) on the exercise of any options
                  or other awards will be relevant for the purposes of
                  calculating the limit in rule 2.9.1 above, and Shares shall
                  not be regarded as being capable of being issued by reason of
                  any provisions in the relevant Employees' Share Plans under
                  which such options or awards are

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                  granted allowing a person to exercise an option or award in
                  circumstances of leaving employment or a change of control of
                  the Company.

      2.10  LIMIT ON INDIVIDUAL PARTICIPATION

            The maximum number of shares over which Options can be granted to an
            Eligible Employee in any year is 1,000,000 Shares.

        3   OPTION PRICE

      3.1   DETERMINATION OF OPTION PRICE

            The Option Committee shall determine the Option Price which shall be
            stated at the Date of Grant and shall not be less than the Market
            Value of a Share on the Date of Grant.

       4.   VARIATIONS IN SHARE CAPITAL

      4.1   ADJUSTMENT OF OPTIONS

            In the event (a "Relevant Event") of any variation in the equity
            share capital of the Company in consequence of a capitalisation or
            rights issue, sub-division, consolidation or reduction of share
            capital or other variation in the share capital:

            4.1.1 the number or nominal amount of Shares comprised in each
                  Option, and/or

            4.1.2 the Option Price, and/or

            4.1.3 the aggregate Option Price in relation to any Option,

            may be adjusted in such manner as the Directors consider appropriate
            (including retrospective adjustments where such Relevant Event or
            the variation in the equity share capital of the Company as a
            consequence of the Relevant Event occurs after the Option Exercise
            Date but the relevant record date precedes such Option Exercise
            Date). If and to the extent a Relevant Event is a change in the
            number or kind of Shares effected solely by application of a
            mathematical formula (e.g., a 2-for-1 stock split), the adjustment
            described in this Rule 4.1 shall be made and shall occur
            automatically by application of such formula, without further action
            by the Directors.

      4.2   OTHER RELEVANT EVENTS

            Options may be adjusted following variations in the share capital of
            the Company other than those specified in Rule 4.1. Any such
            adjustments shall be made in accordance with Rule 4.1.

      4.3   NOTICE

            The Directors may take such steps as they consider necessary to
            notify Option Holders of any adjustment made under this Rule 4.

        5   EXERCISE AND LAPSE - GENERAL RULES

      5.1   EXERCISE - GENERAL RULE

            Unless otherwise specified in these Rules an Option shall only be
            exercisable:

             5.1.1 on or after the dates specified in the option certificate

             5.1.2 on the satisfaction or waiver of any condition imposed under
                   Rule 2.3;

             5.1.3 except as provided in Rules 6 and 7, while the Option Holder
                   is an employee of a Member of the Group.

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      5.2   CESSATION OF EMPLOYMENT - GENERAL RULE

            Unless any of the provisions in Rule 6 apply, when an Option Holder
            ceases to be an employee of a Member of the Group, all his Options
            shall lapse.

      5.3   LAPSE
            Options shall lapse on the expiry of the Option Period.

        6   RIGHTS OF EXERCISE - PARTICULAR CASES

      6.1   CESSATION OF EMPLOYMENT

            6.1.1 If an Option Holder ceases to be in the employment of any
                  Member of the Group (except for any reason specified in 6.1.2
                  or 6.1.3 below), then:

                  6.1.1.1 all Options which are otherwise exercisable, shall
                          lapse unless exercised within the earlier of the
                          expiry of the Option Period or three months after the
                          date of cessation of the Option Holder's employment;
                          and

                  6.1.1.2 all Options, which are not otherwise exercisable,
                          shall lapse and determine immediately upon such
                          cessation.

            6.1.2 If an Option Holder ceases to be in the employment of any
                  Member of the Group by reason of death or disability, then all
                  Options, whether or not otherwise exercisable, shall become
                  exercisable and shall lapse unless exercised within the
                  earlier of the expiry of the Option Period or twelve months
                  after the cessation of the Option Holder's employment

            6.1.3 If an Option Holder ceases to be in the employment of any
                  Member of the Group by reason of dismissal for cause, then all
                  Options, whether or not otherwise exercisable, shall lapse and
                  determine immediately.

      6.2   LEAVE OF ABSENCE

            No Options that are not exercisable at the beginning of an
            authorized leave of absence shall become exercisable during such
            leave of absence.

      6.3   TAKEOVERS ETC.

            6.3.1 Subject to Rule 6.3.4 below if, in consequence of any offer
                  made to the holders of Shares, the Directors become aware that
                  the right to cast more than 50 per cent of the votes which may
                  ordinarily be cast on a poll at a general meeting of the
                  Company has or will become vested in the offeror and/or any
                  company controlled by the offeror and/or any person associated
                  with or acting in concert with the offeror, the Directors
                  shall, within 30 days of becoming so aware, notify every
                  Option Holder accordingly.

            6.3.2 Each Option Holder shall be entitled at any time during the
                  Change of Control Period to exercise all his Options (whether
                  or not otherwise exercisable) in whole or in part. The Options
                  shall not lapse on the expiry of the Change of Control Period
                  but all Options not exercisable immediately prior to the
                  beginning of the Change of Control Period shall cease to be
                  exercisable on the expiry of the Change of Control Period.

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            6.3.3 For the purposes of this Rule 6.3, "Change of Control Period"
                  means the period commencing on the date of the giving of the
                  Directors' notification under this Rule 6.3 and ending three
                  months after that.

            6.3.3 Unless the Directors decide otherwise the provisions of this
                  Rule 6.3 shall not apply if an Original Shareholder shall
                  become entitled to cast more than 50% of the votes which may
                  ordinarily be case on a poll at a general meeting of the
                  Company.

      6.4   DISSOLUTION OR LIQUIDATION

            In the event of the proposed dissolution or liquidation of the
            Company, all outstanding Options will terminate immediately prior to
            the consummation of such proposed action, unless otherwise provided
            by the Option Committee; provided, however, that if the rights of a
            Option Holder (or his personal representatives if appropriate) have
            not otherwise terminated and expired, the Option Holder (or his
            personal representatives if appropriate) will have the right to
            exercise his Options immediately prior to such dissolution or
            liquidation, and the Option Committee may, in the exercise of its
            sole discretion in such instances, accelerate the date on which any
            Option becomes exercisable or fully vests and/or declare that any
            Option shall terminate as of a specified date.

      6.5   LOSS OF OWNERSHIP

            Where the Option Holder is deprived of the legal or beneficial
            ownership of the Option by operation of law, or does anything or
            omits to do anything which causes him to be so deprived or becomes
            bankrupt, all his Options shall lapse.

      6.6   OVERSEAS TRANSFER

            If an Option Holder, whilst continuing to be employed by a Member of
            the Group is transferred to work in another country and as a result
            of that transfer the Option Holder will either:

            6.6.1 become subject to tax on his remuneration in the country to
                  which he is transferred and the Option Committee are satisfied
                  that as a result he will suffer a tax disadvantage upon
                  exercising an Option; or

            6.6.2 become subject to restrictions on his ability to exercise his
                  Option or to hold or deal in the Shares or the proceeds of the
                  sale of the Shares he may acquire upon the exercise of that
                  Option by reason of or in consequence of the securities laws
                  or exchange control laws of the country to which he is
                  transferred;

            the Option Committee (or its delegate) may allow the Option Holder
            to exercise the Option in a period specified by the Option Committee
            or its delegate. The Options will become exercisable again in the
            ordinary course if not so exercised.

      6.7   PRIORITY

            In the event of any conflict between any of the provisions of Rules
            5 and 6, the provision which results in the earliest lapsing of the
            Option in question shall prevail.

        7   EXERCISE OF OPTIONS

      7.1   LIMIT ON EXERCISE

            An Option may only be exercised during the periods specified in
            Rules 5 and 6.

      7.2   MANNER OF EXERCISE

            To exercise an Option in whole or in part, an Option Holder must
            deliver to the Secretary of the Company or other duly appointed
            agent:

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            7.2.1 the option certificate covering the Shares over which the
                  Option is being exercised;

            7.2.2 notice in writing, in the prescribed form, duly completed and
                  signed by the Option Holder or by his duly appointed agent;
                  and

            7.2.3 payment in full of the Option Price for the total number of
                  Shares in respect of which the Option is being exercised.

            The Option Holder shall pay the Option Price for an Option as
            specified by the Option Committee (x) in cash, (y) with the approval
            of the Option Committee, by delivering Shares owned by the Option
            Holder (including Shares acquired in connection with the exercise of
            an Option, subject to such restrictions as the Option Committee
            deems appropriate) and having a Market Value on the Option Exercise
            Date equal to the Option Price or (z) by such other method as the
            Option Committee may approve, including attestation (on a form
            prescribed by the Option Committee) to ownership of Shares having a
            Market Value on the Option Exercise Date equal to the Option Price,
            or payment through a broker in accordance with procedures permitted
            by Regulation T of the United States Federal Reserve Board. Shares
            used to exercise an Option shall have been held by the Option Holder
            for the requisite period of time to avoid adverse accounting
            consequences to the Company with respect to the Option. The Option
            Holder shall pay the Option Price and the amount of any withholding
            tax due at the time of exercise. Shares shall not be issued upon
            exercise of an Option until the Option Price is fully paid and any
            required withholding is made.

            If the Option Committee so permits, an Option Holder subject to
            United States tax may elect to satisfy the Company's income tax
            withholding obligation with respect to an Option by having Shares
            withheld having a Market Value up to an amount that does not exceed
            the Option Holder's minimum applicable withholding tax rate for
            federal (including FICA), state and local tax liabilities. The
            election must be in a form and manner prescribed by the Option
            Committee and shall be subject to the prior approval of the Option
            Committee.

            The date of receipt by the Company of the items listed in Rules
            7.2.1 to 7.2.3 shall constitute the Option Exercise Date. If any
            conditions must be fulfilled before an Option may be exercised, the
            receipt of such documents shall not be treated as effecting the
            exercise of an Option unless and until the Directors are satisfied
            that the conditions have been fulfilled, in which case the Option
            Exercise Date shall be the date on which the Directors declare that
            they are so satisfied. The Directors must use reasonable endeavours
            to ensure that they obtain evidence as to the satisfaction of any
            conditions within seven days after the date of receipt by the
            Company of the items listed at Rules 7.2.1 to 7.2.3 above and shall
            make a declaration within seven days of receipt of the evidence.

      7.3   TRANSFER

            Subject to Rules 7.6 and 7.7, the Directors shall allot the Shares
            to be issued or shall procure the transfer of Shares to be
            transferred following the exercise of an Option within 30 days of
            the Option Exercise Date.

      7.4   RIGHTS

            In respect of Shares issued or transferred on the exercise of an
            Option, Option Holders are entitled to all rights attaching to such
            Shares by reference to a record date after the Option Exercise Date.
            They shall not be entitled to rights before such date.

      7.5   PART EXERCISE

            Other than on exercise of an Option to the full extent then
            exercisable, no Option shall be capable of exercise in part except
            in multiples of 100 Shares.

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      7.6   CONSENTS

            All allotments, issues and transfers of Shares will be subject to
            any necessary consents or other applicable requirements or
            restrictions under any relevant enactments or regulations for the
            time being in force in the United Kingdom and the United States or
            elsewhere, and it shall be the responsibility of the Option Holder
            to comply with any requirements to be fulfilled in order to obtain
            or obviate the necessity for any such consent.

     7.7    TAX WITHHOLDING

            In a case where a Member of the Group is obliged to (or would suffer
            a disadvantage if it were not to) account for any tax (in any
            jurisdiction) for which a person exercising an Option is liable by
            virtue of the exercise of the Option and/or for any social security
            contributions recoverable from the person in question (together, the
            "Tax Liability"), no Shares shall be issued or transferred following
            the exercise of the Option unless that person has either:

            (i)   made a payment to the Member of the Group of an amount equal
                  to the Tax Liability; or

            (ii)  entered into arrangements acceptable to that or another Member
                  of the Group to secure that such a payment is made (whether by
                  authorising the sale of some or all of the shares on his
                  behalf and the payment to the Member of the Group of the
                  relevant amount out of the proceeds of sale or otherwise).

      7.8   ARTICLES OF ASSOCIATION

            Any Shares acquired upon the exercise of Options shall be subject to
            the Articles of Incorporation and the By-Laws of the Company from
            time to time in force.

        8   GENERAL

      8.1   NOTICES

            Any notice or other document required to be given under or in
            connection with the Plan may be delivered to an Option Holder or
            sent by post to him at his home address according to the records of
            his employing company or such other address as may appear to the
            Company to be appropriate. Notices sent by post shall be deemed to
            have been given on the day following the date of posting. Any notice
            or other document required to be given to the Company under or in
            connection with the Plan may be delivered or sent by post to it at
            its registered office (or such other place or places as the
            Directors may from time to time determine and notify to Option
            Holders).

      8.2   DOCUMENTS SENT TO SHAREHOLDERS

            The Company shall send to Option Holders copies of any documents or
            notices sent to the holders of its Shares, concurrently with issuing
            the same to the holders of its Shares.

      8.3   AVAILABILITY OF SHARES

            The Company shall procure that sufficient Shares are available for
            transfer to satisfy all Options under which Shares may be acquired.

      8.4   DIRECTORS' DECISIONS FINAL AND BINDING

            The decision of the Directors in any dispute relating to an Option
            or matter relating to the Plan shall be final and conclusive.

      8.5   COSTS

            The costs of introducing and administering the Plan shall be borne
            by the Company.

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      8.6   REGULATIONS

            The Directors shall have power from time to time to make or vary
            regulations for the administration and operation of the Plan
            provided that the same are not inconsistent with these Rules.

      8.7   LIMITATION OF LIABILITY

            The rights and obligations of an Option Holder under the terms and
            conditions of his office or employment shall not be affected by his
            participation in the Plan or any right he may have to participate in
            the Plan. An individual who participates in the Plan waives all and
            any rights to compensation or damages in consequence of the
            termination of his office or employment with any company for any
            reason whatsoever insofar as those rights arise, or may arise, from
            his ceasing to have rights under or be entitled to exercise any
            Option under the Plan as a result of such termination or from the
            loss or diminution in value of such rights or entitlements. If
            necessary the Option Holder's terms of employment shall be varied
            accordingly.

        9   AMENDMENTS AND TERMINATION

      9.1   DIRECTORS' POWERS OF AMENDMENT

            The Directors may at any time alter or add to all or any of the
            provisions of the Plan or any previously granted Option in any
            respect; provided that no such amendment shall materially impair the
            rights of any Option Holder under any previously granted Option
            unless the amendment is required by applicable law, or

            9.1.1 the Directors shall have invited every relevant Option Holder
                  to give an indication as whether or not he approves of the
                  amendment; and

            9.1.2 the alteration is approved by a majority of those Option
                  Holders who have given such an indication.

      9.2   OVERSEAS EMPLOYEES

            Notwithstanding any other provision of the Plan the Directors may,
            in respect of Options granted to Eligible Employees who are or who
            may become subject to taxation outside the United States on their
            remuneration, amend or add to the provisions of the Plan and the
            terms of Options as they consider necessary or desirable to take
            account of or to mitigate or to comply with relevant overseas
            taxation, securities, exchange control and/or other overseas laws,
            provided that the terms of Options granted to such Eligible
            Employees are not overall more favourable than the terms of Options
            granted to other Eligible Employees.

      9.3   NOTICE

            As soon as reasonably practicable after making any alteration or
            addition, the Directors shall give written notice to any Option
            Holder affected by the alteration or addition.

      9.4   TERMINATION OF THE PLAN

            The Directors may terminate the Plan at any time, and it shall
            terminate on the 10th anniversary of its adoption by the Directors,
            but Options granted prior to such termination shall continue to be
            valid and exercisable in accordance with these Rules.

       10   GOVERNING LAW

            The Plan and all Options shall be governed by and construed in
            accordance with [Applicable US State] law.

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                                   SCHEDULE 1
                 APBIOTECH INC EXECUTIVE STOCK OPTION PLAN 2000

This Schedule 1 constitutes the US approved part of the APBiotech Inc Executive
Stock Option Plan 2000 (THE "US ISO PLAN"). The terms of the US ISO Plan are
identical to the APBiotech Inc Executive Stock Option Plan 2000 (the "Plan") to
which the US ISO Plan is appended except as follows:

1.    For purposes of the US ISO Plan, options otherwise granted in accordance
      with the Plan may be designated as "Incentive Stock Options" ("ISOS")
      within the meaning of section 422 of the United States Internal Revenue
      code of 1986, as amended (the "US TAX CODE").

2.    The aggregate number of shares for which ISOs may be granted under the US
      ISO Plan shall not exceed 14,500,000. The price at which shares may be
      acquired by the exercise of an option under the US ISO Plan shall be not
      less than the fair market value of such shares as of the Grant Date as
      determined by the Board.

3.    The class of persons who may receive ISOs shall, in addition to the
      limitations imposed by the Plan, be limited to those persons who are
      employees of the Company or its "parent" or "subsidiary" corporations
      within the meaning of Sections 424(e) and (f), respectively, of the US Tax
      Code.

4.    In addition to any other restrictions contained in the Plan, ISOs shall
      not be transferable otherwise than by will or the laws of descent and
      distribution. During the lifetime of the person to whom the ISO is
      granted, the ISO shall be exercisable only by such person.

5.    To the extent that the aggregate market value of shares with respect to
      which ISOs are exercisable for the first time by a Participant during any
      calendar year (under all plans or schemes of the Company or its "parent"
      and "subsidiary" corporations within the meaning of section 424(e) and (f)
      respectively of the US tax Code) exceed US$100,000 such option shall to
      the extent of such excess be treated as options which are not ISOs. For
      the purpose of the preceding sentence, the market value of any shares
      subject to an ISO shall be determined at the time such ISO is granted.

6.    For purposes of any ISO grants, the terms of the Plan shall be deemed to
      be incorporated by reference to this schedule.

7.    No options may be granted as ISOs under the US ISO Plan after the earlier
      of the tenth anniversary of (a) the date of adoption of the US ISO Plan by
      the Board, or (b) the date the US ISO Plan is approved by the Company's
      stockholders.

<PAGE>   12

8.    If any option is exercised in accordance with Rules 5 and 6 of the Plan
      more than three (3) months after the date that the Participant was last
      employed by the Company (or by its parent or a subsidiary as defined in
      Rule 3 of this Schedule above) or in the case of either death or "total
      disability" (as defined by section 422(c)(6) of the US Tax Code) more than
      twelve (12) months after the date that the Participant was last employed
      by the Company (or by its parent or a subsidiary as defined in Rule 3 of
      this Schedule above) then such option shall be treated as a nonqualified
      stock option for purposes of the US Tax Code.

9.    If an option is granted to an individual who, at the time the option is
      granted, owns stock possessing more than 10% of the total combined voting
      power of all classes of stock of the Company (or its parent or any
      subsidiary as defined in Rule 3 of this Schedule above) then the option
      exercise price shall be not less than 110% of the fair market value of the
      shares which may be acquired by the exercise of the option and such option
      by its terms shall not be exercisable after the expiration of 5 years from
      the date such option is granted.<PAGE>   1
                                                                   Exhibit 10.12

                              COMMITMENT AGREEMENT

                                                              September 28, 2000

TO APBIOTECH, INC. AND AMERSHAM PHARMACIA BIOTECH LIMITED:

     Nycomed Amersham plc ("NA") and Pharmacia Corporation ("PHA" and,
collectively with NA and PHA, the "Shareholders") hereby agree that if (i) the
Supported Party (as defined below) is unable to satisfy its debts to
Unaffiliated Parties (as defined below) and/or to repay on-demand debt issued by
NA to Amersham-Pharmacia Biotech Limited or any of it subsidiaries as and when
they fall due, and (ii) the Supported Party is unable to obtain alternative
sources of financing, then the Shareholders shall provide to the Supported Party
up to $500,000,000 in funding by electing, in their sole discretion, either to
extend to the Supported Party a loan or to subscribe for ordinary shares or
shares of common stock of the Supported Party, as the case may be, in either
case on the terms set forth below.

     If both Shareholders elect to extend a loan, the Shareholders shall loan to
the Supported Party up to an aggregate of $500,000,000. The rate of interest and
terms of such loan shall be customary for credits similar to the Supported Party
at the time of such loan, and such loan shall be evidenced by documentation
containing terms customary for loans to such credits made by financial
institutions.

     If one Shareholder wishes to elect to extend a loan pursuant to the
previous paragraph and the other Shareholder wishes to elect to subscribe for
ordinary shares or shares of common stock, then neither Shareholder shall
subscribe for ordinary shares or shares of common stock and the Shareholders
shall instead extend a loan. If both Shareholders elect to subscribe for
ordinary shares or shares of common stock of the Supported Party, as the case
may be, the Shareholders shall subscribe for:

(1)  If the Supported Party is APBiotech, Inc. (the "Company"), an aggregate
     number of shares of common stock of the Company equal to the Company
     Number, as defined below, at an aggregate subscription price of up to
     $500,000,000 (such price, up to such maximum price, the "Company Aggregate
     Price") and a per share subscription price equal to the Reference Price.
     "Company Number" means the quotient of the Company Aggregate Price
     divided by the Reference Price (as defined below). "Reference Price" means
     a per share price equal to volume-weighted average sales price of the
     Company's common stock on the Nasdaq National Market for the twenty trading
     days prior to the date on which the subscription price is paid (or, if
     fewer than twenty trading days have elapsed between the completion of the
     IPO (as defined below) and such date of payment, such number of trading
     days as have so elapsed), as determined by Bloomberg Financial Markets.

<PAGE>   2
(2)  If the Supported Party is Amersham Pharmacia Biotech Limited ("Limited"), a
     number of ordinary shares of Limited mutually agreed by the Shareholders,
     for an aggregate subscription price of up to $500,000,000.

Such subscription shall be evidenced by documentation containing terms customary
for private placements entered into in the United States in the biotechnology
industry.

     "Supported Party" means (i) prior to the completion of the initial public
offering of shares of common stock of the Company (the "IPO"), Limited, and (ii)
following the completion of the IPO, the Company.

     "Unaffiliated Parties" means persons or entities other than the Company,
Limited, the Shareholders and their respective affiliates.

     The obligations of the Shareholders under this letter agreement are
several and not joint.  Any funds provided to the Company pursuant to this
Agreement shall be provided by each Shareholder ratably based on the percentage
of outstanding shares of capital stock of the Supported Party held by such
Shareholder at the date of this letter agreement.  This letter agreement shall
terminate automatically upon the earliest to occur of (i) the successful
completion of the IPO and the repayment of aggregate principal amount of demand
debt issued by NA to Limited or any of its subsidiaries, (ii) the day after the
first anniversary of the effective date of the SEC registration statement
pertaining to the IPO, and (iii) December 31, 2001.

     This letter agreement is governed by and shall be construed in accordance
with the laws of the State of New York.  This letter agreement may be executed
in any number of counterparts, each of which shall be an original and all of
which collectively shall constitute one and the same agreement.

                                         NYCOMED AMERSHAM plc

                                         By: /s/ Giles Kerr
                                            ------------------------------
                                            Name:  Giles Kerr
                                            Title: Finance Director

                                         PHARMACIA CORPORATION

                                         By: /s/ Christopher J. Coughlin
                                            ------------------------------
                                            Name:  Christopher J. Coughlin
                                            Title: Chief Financial Officer

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