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                                                                  Exhibit 10.2.2

                      NON-QUALIFIED STOCK OPTION AGREEMENT

                                 METABOLIX, INC.

     AGREEMENT made as of the __ day of _________ 200_, between Metabolix, Inc.
(the "Company"), a Delaware corporation, and _______________ (the
"Participant").

     WHEREAS, the Company desires to grant to the Participant an Option to
purchase shares of its common stock, $.01 par value per share (the "Shares"),
under and for the purposes set forth in the Company's 2005 Stock Plan (the
"Plan");

     WHEREAS, the Company and the Participant understand and agree that any
terms used and not defined herein have the same meanings as in the Plan; and

     WHEREAS, the Company and the Participant each intend that the Option
granted herein shall be a Non-Qualified Option.

     NOW, THEREFORE, in consideration of the mutual covenants hereinafter set
forth and for other good and valuable consideration, the parties hereto agree as
follows:

     1.      GRANT OF OPTION.

     The Company hereby grants to the Participant the right and option to
purchase all or any part of an aggregate of _______________ Shares, on the terms
and conditions and subject to all the limitations set forth herein, under United
States securities and tax laws, and in the Plan, which is incorporated herein by
reference. The Participant acknowledges receipt of a copy of the Plan.

     2.      PURCHASE PRICE.

     The purchase price of the Shares covered by the Option shall be $_____ per
Share, subject to adjustment, as provided in the Plan, in the event of a stock
split, reverse stock split or other events affecting the holders of Shares (the
"Purchase Price"). Payment shall be made in accordance with Paragraph 9 of the
Plan.

     3.      EXERCISABILITY OF OPTION.

     Subject to the terms and conditions set forth in this Agreement and the
Plan, the Option granted hereby shall become exercisable as follows:

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                                          [TO BE COMPLETED BY COMPANY FOR EACH
                                          PARTICIPANT]


     The foregoing rights are cumulative and are subject to the other terms and
conditions of this Agreement and the Plan.

     4.      TERM OF OPTION.

     The Option shall terminate ten years from the date of this Agreement, but
shall be subject to earlier termination as provided herein or in the Plan.

     If the Participant ceases to be an employee, director or consultant of the
Company or of an Affiliate (for any reason other than the death or Disability of
the Participant or termination of the Participant for "cause" (as defined in the
Plan)), the Option may be exercised, if it has not previously terminated, within
three months after the date the Participant ceases to be an employee, director
or consultant of the Company or an Affiliate, or within the originally
prescribed term of the Option, whichever is earlier, but may not be exercised
thereafter. In such event, the Option shall be exercisable only to the extent
that the Option has become exercisable and is in effect at the date of such
cessation of employment, directorship or consultancy.

     Notwithstanding the foregoing, in the event of the Participant's Disability
or death within three months after the termination of employment, directorship
or consultancy, the Participant or the Participant's Survivors may exercise the
Option within one year after the date of the Participant's termination of
employment, directorship or consultancy, but in no event after the date of
expiration of the term of the Option.

     In the event the Participant's employment, directorship or consultancy is
terminated by the Company or an Affiliate for "cause" (as defined in the Plan),
the Participant's right to exercise any unexercised portion of this Option shall
cease immediately as of the time the Participant is notified his or her
employment, directorship or consultancy is terminated for "cause," and this
Option shall thereupon terminate. Notwithstanding anything herein to the
contrary, if subsequent to the Participant's termination, but prior to the
exercise of the Option, the Board of Directors of the Company determines that,
either prior or subsequent to the Participant's termination, the Participant
engaged in conduct which would constitute "cause," then the Participant shall
immediately cease to have any right to exercise the Option and this Option shall
thereupon terminate.

     In the event of the Disability of the Participant, as determined in
accordance with the Plan, the Option shall be exercisable within one year after
the Participant's termination of service or, if earlier, within the term
originally prescribed by the Option. In such event, the Option shall be
exercisable:

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     (a)     to the extent that the Option has become exercisable but has not
             been exercised as of the date of Disability; and

     (b)     in the event rights to exercise the Option accrue periodically, to
             the extent of a pro rata portion through the date of Disability of
             any additional vesting rights that would have accrued on the next
             vesting date had the Participant not become Disabled. The proration
             shall be based upon the number of days accrued in the current
             vesting period prior to the date of Disability.

     In the event of the death of the Participant while an employee, director or
consultant of the Company or of an Affiliate, the Option shall be exercisable by
the Participant's Survivors within one year after the date of death of the
Participant or, if earlier, within the originally prescribed term of the Option.
In such event, the Option shall be exercisable:

     (x)     to the extent that the Option has become exercisable but has not
             been exercised as of the date of death; and

     (y)     in the event rights to exercise the Option accrue periodically, to
             the extent of a pro rata portion through the date of death of any
             additional vesting rights that would have accrued on the next
             vesting date had the Participant not died. The proration shall be
             based upon the number of days accrued in the current vesting period
             prior to the Participant's date of death.

     5.      METHOD OF EXERCISING OPTION.

     Subject to the terms and conditions of this Agreement, the Option may be
exercised by written notice to the Company or its designee, in substantially the
form of EXHIBIT A attached hereto. Such notice shall state the number of Shares
with respect to which the Option is being exercised and shall be signed by the
person exercising the Option. Payment of the purchase price for such Shares
shall be made in accordance with Paragraph 9 of the Plan. The Company shall
deliver such Shares as soon as practicable after the notice shall be received,
provided, however, that the Company may delay issuance of such Shares until
completion of any action or obtaining of any consent, which the Company deems
necessary under any applicable law (including, without limitation, state
securities or "blue sky" laws). The Shares as to which the Option shall have
been so exercised shall be registered in the Company's share register in the
name of the person so exercising the Option (or, if the Option shall be
exercised by the Participant and if the Participant shall so request in the
notice exercising the Option, shall be registered in the Company's share
register in the name of the Participant and another person jointly, with right
of survivorship) and shall be delivered as provided above to or upon the written
order of the person exercising the Option. In the event the Option shall be
exercised, pursuant to Section 4 hereof, by any person other than the
Participant, such notice shall be accompanied by appropriate proof of the right
of such person to exercise the Option. All Shares that shall be purchased upon
the exercise of the Option as provided herein shall be fully paid and
nonassessable.

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     6.      PARTIAL EXERCISE.

     Exercise of this Option to the extent above stated may be made in part at
any time and from time to time within the above limits, except that no
fractional share shall be issued pursuant to this Option.

     7.      NON-ASSIGNABILITY.

     The Option shall not be transferable by the Participant otherwise than by
will or by the laws of descent and distribution or pursuant to a qualified
domestic relations order as defined by the Code or Title I of the Employee
Retirement Income Security Act or the rules thereunder. Except as provided in
the previous sentence, the Option shall be exercisable, during the Participant's
lifetime, only by the Participant (or, in the event of legal incapacity or
incompetency, by the Participant's guardian or representative) and shall not be
assigned, pledged or hypothecated in any way (whether by operation of law or
otherwise) and shall not be subject to execution, attachment or similar process.
Any attempted transfer, assignment, pledge, hypothecation or other disposition
of the Option or of any rights granted hereunder contrary to the provisions of
this Section 7, or the levy of any attachment or similar process upon the Option
shall be null and void.

     8.      NO RIGHTS AS STOCKHOLDER UNTIL EXERCISE.

     The Participant shall have no rights as a stockholder with respect to
Shares subject to this Agreement until registration of the Shares in the
Company's share register in the name of the Participant. Except as is expressly
provided in the Plan with respect to certain changes in the capitalization of
the Company, no adjustment shall be made for dividends or similar rights for
which the record date is prior to the date of such registration.

     9.      ADJUSTMENTS.

     The Plan contains provisions covering the treatment of Options in a number
of contingencies such as stock splits and mergers. Provisions in the Plan for
adjustment with respect to stock subject to Options and the related provisions
with respect to successors to the business of the Company are hereby made
applicable hereunder and are incorporated herein by reference.

     10.     TAXES.

     The Participant acknowledges that upon exercise of the Option the
Participant will be deemed to have taxable income measured by the difference
between the then fair market value of the Shares received upon exercise and the
price paid for such Shares pursuant to this Agreement. The Participant
acknowledges that any income or other taxes due from him or her with respect to
this Option or the Shares issuable pursuant to this Option shall be the
Participant's responsibility.

     The Participant agrees that the Company may withhold from the Participant's
remuneration, if any, the minimum statutory amount of federal, state and local
withholding taxes attributable to such amount that is considered compensation
includable in such person's gross income. At the Company's discretion, the
amount required to be withheld may be withheld in

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cash from such remuneration, or in kind from the Shares otherwise deliverable to
the Participant on exercise of the Option. The Participant further agrees that,
if the Company does not withhold an amount from the Participant's remuneration
sufficient to satisfy the Company's income tax withholding obligation, the
Participant will reimburse the Company on demand, in cash, for the amount
under-withheld.

     11.     PURCHASE FOR INVESTMENT.

     Unless the offering and sale of the Shares to be issued upon the particular
exercise of the Option shall have been effectively registered under the
Securities Act of 1933, as now in force or hereafter amended (the "1933 Act"),
the Company shall be under no obligation to issue the Shares covered by such
exercise unless and until the following conditions have been fulfilled:

     (a)     The person(s) who exercise the Option shall warrant to the Company,
             at the time of such exercise, that such person(s) are acquiring
             such Shares for their own respective accounts, for investment, and
             not with a view to, or for sale in connection with, the
             distribution of any such Shares, in which event the person(s)
             acquiring such Shares shall be bound by the provisions of the
             following legend which shall be endorsed upon the certificate(s)
             evidencing the Shares issued pursuant to such exercise:

                       "The shares represented by this certificate have been
                       taken for investment and they may not be sold or
                       otherwise transferred by any person, including a pledgee,
                       unless (1) either (a) a Registration Statement with
                       respect to such shares shall be effective under the
                       Securities Act of 1933, as amended, or (b) the Company
                       shall have received an opinion of counsel satisfactory to
                       it that an exemption from registration under such Act is
                       then available, and (2) there shall have been compliance
                       with all applicable state securities laws;" and

     (b)     If the Company so requires, the Company shall have received an
             opinion of its counsel that the Shares may be issued upon such
             particular exercise in compliance with the 1933 Act without
             registration thereunder. Without limiting the generality of the
             foregoing, the Company may delay issuance of the Shares until
             completion of any action or obtaining of any consent, which the
             Company deems necessary under any applicable law (including without
             limitation state securities or "blue sky" laws).

     12.     RESTRICTIONS ON TRANSFER OF SHARES.

     12.1    The Shares acquired by the Participant pursuant to the exercise of
the Option granted hereby shall not be transferred by the Participant except as
permitted herein.

     12.2    In the event of the Participant's termination of service for any
reason, the Company shall have the option, but not the obligation, to repurchase
all or any part of the Shares issued pursuant to this Agreement (including,
without limitation, Shares purchased after termination of employment, Disability
or death in accordance with Section 4 hereof). In the event the Company does
not, upon the termination of service of the Participant (as described

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above), exercise its option pursuant to this Section 12.2, the restrictions set
forth in the balance of this Agreement shall not thereby lapse, and the
Participant for himself or herself, his or her heirs, legatees, executors,
administrators and other successors in interest, agrees that the Shares shall
remain subject to such restrictions. The following provisions shall apply to a
repurchase under this Section 12.2:

     (i)     The per share repurchase price of the Shares to be sold to the
             Company upon exercise of its option under this Section 12.2 shall
             be equal to the Fair Market Value of each such Share determined in
             accordance with the Plan as of the date of termination of service,
             provided, however, in the event of a termination by the Company for
             "cause" (as defined in the Plan), the per share repurchase price of
             the Shares to be sold to the Company upon exercise of its option
             under this Section 12.2 shall be equal to the Purchase Price.

     (ii)    The Company's option to repurchase the Participant's Shares in the
             event of termination of service shall be valid for a period of 18
             months commencing with the date of such termination of service.

     (iii)   In the event the Company shall be entitled to and shall elect to
             exercise its option to repurchase the Participant's Shares under
             this Section 12.2, the Company shall notify the Participant, or in
             case of death, his or her Survivor, in writing of its intent to
             repurchase the Shares. Such written notice may be mailed by the
             Company up to and including the last day of the time period
             provided for in Section 12.2(ii) for exercise of the Company's
             option to repurchase.

     (iv)    The written notice to the Participant shall specify the address at,
             and the time and date on, which payment of the repurchase price is
             to be made (the "Closing"). The date specified shall not be less
             than ten days nor more than 60 days from the date of the mailing of
             the notice, and the Participant or his or her successor in interest
             with respect to the Shares shall have no further rights as the
             owner thereof from and after the date specified in the notice. At
             the Closing, the repurchase price shall be delivered to the
             Participant or his or her successor in interest and the Shares
             being purchased, duly endorsed for transfer, shall, to the extent
             that they are not then in the possession of the Company, be
             delivered to the Company by the Participant or his or her successor
             in interest.

     12.3    It shall be a condition precedent to the validity of any sale or
other transfer of any Shares by the Participant that the following restrictions
be complied with (except as hereinafter otherwise provided):

     (i)     No Shares owned by the Participant may be sold, pledged or
             otherwise transferred (including by gift or devise) to any person
             or entity, voluntarily, or by operation of law, except in
             accordance with the terms and conditions hereinafter set forth.

             (ii)   Before selling or otherwise transferring all or part of the
                    Shares, the Participant shall give written notice of such
                    intention to the Company, which notice shall include the
                    name of the proposed transferee, the proposed purchase price
                    per share, the terms of payment of such purchase

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                    price and all other matters relating to such sale or
                    transfer and shall be accompanied by a copy of the binding
                    written agreement of the proposed transferee to purchase the
                    Shares of the Participant. Such notice shall constitute a
                    binding offer by the Participant to sell to the Company such
                    number of the Shares then held by the Participant as are
                    proposed to be sold in the notice at the monetary price per
                    share designated in such notice, payable on the terms
                    offered to the Participant by the proposed transferee
                    (provided, however, that the Company shall not be required
                    to meet any non-monetary terms of the proposed transfer,
                    including, without limitation, delivery of other securities
                    in exchange for the Shares proposed to be sold). The Company
                    shall give written notice to the Participant as to whether
                    such offer has been accepted in whole by the Company within
                    sixty days after its receipt of written notice from the
                    Participant. The Company may only accept such offer in whole
                    and may not accept such offer in part. Such acceptance
                    notice shall fix a time, location and date for the closing
                    on such purchase ("Closing Date") which shall not be less
                    than ten nor more than sixty days after the giving of the
                    acceptance notice, provided, however, if any of the Shares
                    to be sold pursuant to this Section 12.3 have been held by
                    the Participant for less than six months, then the Closing
                    Date may be extended by the Company until no more than ten
                    days after such Shares have been held by the Participant for
                    six months. The place for such closing shall be at the
                    Company's principal office. At such closing, the Participant
                    shall accept payment as set forth herein and shall deliver
                    to the Company in exchange therefor certificates for the
                    number of Shares stated in the notice accompanied by duly
                    executed instruments of transfer.

     (iii)   If the Company shall fail to accept any such offer, the Participant
             shall be free to sell all, but not less than all, of the Shares set
             forth in his or her notice to the designated transferee at the
             price and terms designated in the Participant's notice, provided
             that (i) such sale is consummated within six months after the
             giving of notice by the Participant to the Company as aforesaid,
             and (ii) the transferee first agrees in writing to be bound by the
             provisions of this Section 12 so that such transferee (and all
             subsequent transferees) shall thereafter only be permitted to sell
             or transfer the Shares in accordance with the terms hereof. After
             the expiration of such six months, the provisions of this Section
             12.3 shall again apply with respect to any proposed voluntary
             transfer of the Participant's Shares.

     (iv)    The restrictions on transfer contained in this Section 12.3 shall
             not apply to (a) transfers by the Participant to his or her spouse
             or children or to a trust for the benefit of his or her spouse or
             children, (b) transfers by the Participant to his or her guardian
             or conservator, and (c) transfers by the Participant, in the event
             of his or her death, to his or her executor(s) or administrator(s)
             or to trustee(s) under his or her will (collectively, "Permitted
             Transferees"); provided however, that in any such event the Shares
             so transferred in the hands of each such Permitted Transferee shall
             remain subject to this Agreement, and each such Permitted
             Transferee shall so acknowledge in writing as a condition precedent
             to the effectiveness of such transfer.

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     (v)     The provisions of this Section 12.3 may be waived by the Company.
             Any such waiver may be unconditional or based upon such conditions
             as the Company may impose.

     12.4    In the event that the Participant or his or her successor in
interest fails to deliver the Shares to be repurchased by the Company under this
Agreement, the Company may elect (a) to establish a segregated account in the
amount of the repurchase price, such account to be turned over to the
Participant or his or her successor in interest upon delivery of such Shares,
and (b) immediately to take such action as is appropriate to transfer record
title of such Shares from the Participant to the Company and to treat the
Participant and such Shares in all respects as if delivery of such Shares had
been made as required by this Agreement. The Participant hereby irrevocably
grants the Company a power of attorney which shall be coupled with an interest
for the purpose of effectuating the preceding sentence.

     12.5    If the Company shall pay a stock dividend or declare a stock split
on or with respect to any of its Common Stock, or otherwise distribute
securities of the Company to the holders of its Common Stock, the number of
shares of stock or other securities of Company issued with respect to the shares
then subject to the restrictions contained in this Agreement shall be added to
the Shares subject to the Company's rights to repurchase pursuant to this
Agreement. If the Company shall distribute to its stockholders shares of stock
of another corporation, the shares of stock of such other corporation,
distributed with respect to the Shares then subject to the restrictions
contained in this Agreement, shall be added to the Shares subject to the
Company's rights to repurchase pursuant to this Agreement.

     12.6    If the outstanding shares of Common Stock of the Company shall be
subdivided into a greater number of shares or combined into a smaller number of
shares, or in the event of a reclassification of the outstanding shares of
Common Stock of the Company, or if the Company shall be a party to a merger,
consolidation or capital reorganization, there shall be substituted for the
Shares then subject to the restrictions contained in this Agreement such amount
and kind of securities as are issued in such subdivision, combination,
reclassification, merger, consolidation or capital reorganization in respect of
the Shares subject immediately prior thereto to the Company's rights to
repurchase pursuant to this Agreement.

     12.7    The Company shall not be required to transfer any Shares on its
books which shall have been sold, assigned or otherwise transferred in violation
of this Agreement, or to treat as owner of such Shares, or to accord the right
to vote as such owner or to pay dividends to, any person or organization to
which any such Shares shall have been so sold, assigned or otherwise
transferred, in violation of this Agreement.

     12.8    The provisions of Sections 12.1, 12.2 and 12.3 shall terminate upon
the effective date of the registration of the Shares pursuant to the Securities
Exchange Act of 1934.

     12.9    If, in connection with a registration statement filed by the
Company pursuant to the 1933 Act, the Company or its underwriter so requests,
the Participant will agree not to sell any Shares for a period not to exceed 180
days following the effectiveness of such registration.

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     12.10   The Participant acknowledges and agrees that neither the Company,
its shareholders nor its directors and officers, has any duty or obligation to
disclose to the Participant any material information regarding the business of
the Company or affecting the value of the Shares before, at the time of, or
following a termination of the employment of the Participant by the Company,
including, without limitation, any information concerning plans for the Company
to make a public offering of its securities or to be acquired by or merged with
or into another firm or entity.

     12.11   All certificates representing the Shares to be issued to the
Participant pursuant to this Agreement shall have endorsed thereon a legend
substantially as follows: "The shares represented by this certificate are
subject to restrictions set forth in a Non-Qualified Stock Option Agreement
dated ________, 200__ with this Company, a copy of which Agreement is available
for inspection at the offices of the Company or will be made available upon
request."

     13.     NO OBLIGATION TO MAINTAIN RELATIONSHIP.

     The Company is not by the Plan or this Option obligated to continue the
Participant as an employee, director or consultant of the Company or an
Affiliate. The Participant acknowledges: (i) that the Plan is discretionary in
nature and may be suspended or terminated by the Company at any time; (ii) that
the grant of the Option is a one-time benefit which does not create any
contractual or other right to receive future grants of options, or benefits in
lieu of options; (iii) that all determinations with respect to any such future
grants, including, but not limited to, the times when options shall be granted,
the number of shares subject to each option, the option price, and the time or
times when each option shall be exercisable, will be at the sole discretion of
the Company; (iv) that the Participant's participation in the Plan is voluntary;
(v) that the value of the Option is an extraordinary item of compensation which
is outside the scope of the Participant's employment contract, if any; and (vi)
that the Option is not part of normal or expected compensation for purposes of
calculating any severance, resignation, redundancy, end of service payments,
bonuses, long-service awards, pension or retirement benefits or similar
payments.

     14.     NOTICES.

     Any notices required or permitted by the terms of this Agreement or the
Plan shall be given by recognized courier service, facsimile, registered or
certified mail, return receipt requested, addressed as follows:

If to the Company:

             Metabolix, Inc.
             21 Erie Street
             Cambridge, MA 02139-4260
             Attention:

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If to the Participant:

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

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

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

or to such other address or addresses of which notice in the same manner has
previously been given. Any such notice shall be deemed to have been given upon
the earlier of receipt, one business day following delivery to a recognized
courier service or three business days following mailing by registered or
certified mail.

     15.     GOVERNING LAW.

     This Agreement shall be construed and enforced in accordance with the law
of the State of Delaware, without giving effect to the conflict of law
principles thereof. For the purpose of litigating any dispute that arises under
this Agreement, the parties hereby consent to exclusive jurisdiction in the
Commonwealth of Massachusetts and agree that such litigation shall be conducted
in the courts of Middlesex County, Massachusetts or the federal courts of the
United States for the District of Massachusetts.

     16.     BENEFIT OF AGREEMENT.

     Subject to the provisions of the Plan and the other provisions hereof, this
Agreement shall be for the benefit of and shall be binding upon the heirs,
executors, administrators, successors and assigns of the parties hereto.

     17.     ENTIRE AGREEMENT.

     This Agreement, together with the Plan, embodies the entire agreement and
understanding between the parties hereto with respect to the subject matter
hereof and supersedes all prior oral or written agreements and understandings
relating to the subject matter hereof. No statement, representation, warranty,
covenant or agreement not expressly set forth in this Agreement shall affect or
be used to interpret, change or restrict, the express terms and provisions of
this Agreement, provided, however, in any event, this Agreement shall be subject
to and governed by the Plan.

     18.     MODIFICATIONS AND AMENDMENTS.

     The terms and provisions of this Agreement may be modified or amended as
provided in the Plan.

     19.     WAIVERS AND CONSENTS.

     Except as provided in the Plan, the terms and provisions of this Agreement
may be waived, or consent for the departure therefrom granted, only by written
document executed by the party entitled to the benefits of such terms or
provisions. No such waiver or consent shall be deemed to be or shall constitute
a waiver or consent with respect to any other terms or provisions of this
Agreement, whether or not similar. Each such waiver or consent shall be
effective only in

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the specific instance and for the purpose for which it was given, and shall not
constitute a continuing waiver or consent.

     20.     DATA PRIVACY.

     By entering into this Agreement, the Participant: (i) authorizes the
Company and each Affiliate, and any agent of the Company or any Affiliate
administering the Plan or providing Plan recordkeeping services, to disclose to
the Company or any of its Affiliates such information and data as the Company or
any such Affiliate shall request in order to facilitate the grant of options and
the administration of the Plan; (ii) waives any data privacy rights he or she
may have with respect to such information; and (iii) authorizes the Company and
each Affiliate to store and transmit such information in electronic form.

     21.     CONSENT OF SPOUSE.

     If the Participant is married as of the date of this Agreement, the
Participant's spouse shall execute a Consent of Spouse in the form of EXHIBIT B
hereto, effective as of the date hereof. Such consent shall not be deemed to
confer or convey to the spouse any rights in the Shares that do not otherwise
exist by operation of law or the agreement of the parties. If the Participant
marries or remarries subsequent to the date hereof, the Participant shall, not
later than 60 days thereafter, obtain his or her new spouse's acknowledgement of
and consent to the existence and binding effect of Section 12.2 of this
Agreement by such spouse's executing and delivering a Consent of Spouse in the
form of Exhibit B.

                  [Remainder of Page Intentionally Left Blank]

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     IN WITNESS WHEREOF, the Company has caused this Agreement to be executed by
its duly authorized officer, and the Participant has hereunto set his or her
hand, all as of the day and year first above written.

                                           METABOLIX, INC.


                                           By:
                                              ----------------------------------
                                              Name:
                                              Title:


                                           -------------------------------------
                                              Participant

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                                                                       EXHIBIT A

                NOTICE OF EXERCISE OF NON-QUALIFIED STOCK OPTION

                         [FORM FOR UNREGISTERED SHARES]

To:  Metabolix, Inc.

Ladies and Gentlemen:

     I hereby exercise my Non-Qualified Stock Option to purchase __________
shares (the "Shares") of the common stock, $.01 par value, of Metabolix, Inc.
(the "Company"), at the exercise price of $_____ per share, pursuant to and
subject to the terms of that certain Non-Qualified Stock Option Agreement
between the undersigned and the Company dated ________, 200_.

     I am aware that the Shares have not been registered under the Securities
Act of 1933, as amended (the "1933 Act"), or any state securities laws. I
understand that the reliance by the Company on exemptions under the 1933 Act is
predicated in part upon the truth and accuracy of the statements by me in this
Notice of Exercise.

     I hereby represent and warrant that (1) I have been furnished with all
information which I deem necessary to evaluate the merits and risks of the
purchase of the Shares; (2) I have had the opportunity to ask questions
concerning the Shares and the Company and all questions posed have been answered
to my satisfaction; (3) I have been given the opportunity to obtain any
additional information I deem necessary to verify the accuracy of any
information obtained concerning the Shares and the Company; and (4) I have such
knowledge and experience in financial and business matters that I am able to
evaluate the merits and risks of purchasing the Shares and to make an informed
investment decision relating thereto.

     I hereby represent and warrant that I am purchasing the Shares for my own
personal account for investment and not with a view to the sale or distribution
of all or any part of the Shares.

     I understand that because the Shares have not been registered under the
1933 Act, I must continue to bear the economic risk of the investment for an
indefinite time and the Shares cannot be sold unless the Shares are subsequently
registered under applicable federal and state securities laws or an exemption
from such registration requirements is available.

     I agree that I will in no event sell or distribute or otherwise dispose of
all or any part of the Shares unless (1) there is an effective registration
statement under the 1933 Act and applicable state securities laws covering any
such transaction involving the Shares or (2) the Company receives an opinion of
my legal counsel (concurred in by legal counsel for the

                                       A-1
<Page>

Company) stating that such transaction is exempt from registration or the
Company otherwise satisfies itself that such transaction is exempt from
registration.

     I consent to the placing of a legend on my certificate for the Shares
stating that the Shares have not been registered and setting forth the
restriction on transfer contemplated hereby and to the placing of a stop
transfer order on the books of the Company and with any transfer agents against
the Shares until the Shares may be legally resold or distributed without
restriction.

     I understand that at the present time Rule 144 of the Securities and
Exchange Commission (the "SEC") may not be relied on for the resale or
distribution of the Shares by me. I understand that the Company has no
obligation to me to register the sale of the Shares with the SEC and has not
represented to me that it will register the sale of the Shares.

     I understand the terms and restrictions on the right to dispose of the
Shares set forth in the 2004 Employee, Director and Consultant Stock Plan and
the Non-Qualified Stock Option Agreement, both of which I have carefully
reviewed. I consent to the placing of a legend on my certificate for the Shares
referring to such restriction and the placing of stop transfer orders until the
Shares may be transferred in accordance with the terms of such restrictions.

     I have considered the Federal, state and local income tax implications of
the exercise of my Option and the purchase and subsequent sale of the Shares.

     I am paying the option exercise price for the Shares as follows:

                                   ----------

     Please issue the stock certificate for the Shares (check one):

     / / to me; or

     / / to me and ________________, as joint tenants with right of survivorship

and mail the certificate to me at the following address:


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

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

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

     My mailing address for shareholder communications, if different from the
address listed above is:

                                       A-2
<Page>

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

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

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

                                       Very truly yours,


                                       -----------------------------------------
                                       Participant (signature)


                                       -----------------------------------------
                                       Print Name


                                       -----------------------------------------
                                       Date


                                       -----------------------------------------
                                       Social Security Number

                                      A-3
<Page>

                                                                       EXHIBIT A

                NOTICE OF EXERCISE OF NON-QUALIFIED STOCK OPTION

IMPORTANT NOTICE: This form of Notice of Exercise may only be used at such time
as the Company has filed a Registration Statement with the Securities and
Exchange Commission under which the issuance of the Shares for which this
exercise is being made is registered and such Registration Statement remains
effective.

TO:  Metabolix, Inc.

Ladies and Gentlemen:

     I hereby exercise my Non-Qualified Stock Option to purchase _________
shares (the "Shares") of the common stock, $.01 par value, of Metabolix, Inc.
(the "Company"), at the exercise price of $________ per share, pursuant to and
subject to the terms of that certain Non-Qualified Stock Option Agreement
between the undersigned and the Company dated _______________, 200_.

     I understand the nature of the investment I am making and the financial
risks thereof. I am aware that it is my responsibility to have consulted with
competent tax and legal advisors about the relevant national, state and local
income tax and securities laws affecting the exercise of the Option and the
purchase and subsequent sale of the Shares.

     I am paying the option exercise price for the Shares as follows:

                                   ----------

     Please issue the Shares (check one):

     / / to me; or

     / / to me and____________________________, as joint tenants with right of
                   survivorship,

     at the following address:


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

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

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

                                       A-1
<Page>

     My mailing address for shareholder communications, if different from the
address listed above, is:


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

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

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


                                       Very truly yours,


                                       -----------------------------------------
                                        Participant (signature)


                                       -----------------------------------------
                                        Print Name


                                       -----------------------------------------
                                        Date


                                       -----------------------------------------
                                        Social Security Number

                                      A-2
<Page>

                                                                       EXHIBIT B

                                CONSENT OF SPOUSE

     I, ____________________________, spouse of _____________________________,
acknowledge that I have read the Non-Qualified Stock Option Agreement dated as
of _______________, 200__ (the "Agreement") to which this Consent is attached as
Exhibit B and that I know its contents. Capitalized terms used and not defined
herein shall have the meanings assigned to such terms in the Agreement. I am
aware that by its provisions the Shares granted to my spouse pursuant to the
Agreement are subject to a right of repurchase in favor of Metabolix, Inc. (the
"Company") and that, accordingly, the Company has the right to repurchase up to
all of the Shares of which I may become possessed as a result of a gift from my
spouse or a court decree and/or any property settlement in any domestic
litigation.

     I hereby agree that my interest, if any, in the Shares subject to the
Agreement shall be irrevocably bound by the Agreement and further understand and
agree that any community property interest I may have in the Shares shall be
similarly bound by the Agreement.

     I agree to the repurchase right described in Section 12.2 of the Agreement
and I hereby consent to the repurchase of the Shares by the Company and the sale
of the Shares by my spouse or my spouse's legal representative in accordance
with the provisions of the Agreement. Further, as part of the consideration for
the Agreement, I agree that at my death, if I have not disposed of any interest
of mine in the Shares by an outright bequest of the Shares to my spouse, then
the Company shall have the same rights against my legal representative to
exercise its rights of repurchase with respect to any interest of mine in the
Shares as it would have had pursuant to the Agreement if I had acquired the
Shares pursuant to a court decree in domestic litigation.

     I AM AWARE THAT THE LEGAL, FINANCIAL AND RELATED MATTERS CONTAINED IN THE
AGREEMENT ARE COMPLEX AND THAT I AM FREE TO SEEK INDEPENDENT PROFESSIONAL
GUIDANCE OR COUNSEL WITH RESPECT TO THIS CONSENT. I HAVE EITHER SOUGHT SUCH
GUIDANCE OR COUNSEL OR DETERMINED AFTER REVIEWING THE AGREEMENT CAREFULLY THAT I
WILL WAIVE SUCH RIGHT.

     Dated as of the _______ day of ________________, 200__.



                                    --------------------------------------------
                                    Print name:

                                      B-1