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                                                                EXHIBIT 10.3.3

                          NON-QUALIFIED STOCK OPTION AGREEMENT
                               FOR NON-EMPLOYEE DIRECTORS

                               UNDER THE METABOLIX, INC.
                          2006 STOCK OPTION AND INCENTIVE PLAN

Name of Optionee:
No. of Option Shares:
Option Exercise Price per Share: $
                                 [FMV ON GRANT DATE]
Grant Date:
Expiration Date:
                      [NO MORE THAN 10 YEARS]

         Pursuant to the Metabolix, Inc. 2006 Stock Option and Incentive
Plan, as amended through the date hereof (the "Plan"), Metabolix, Inc. (the
"Company") hereby grants to the Optionee named above, who is a Director of
the Company but is not an employee of the Company, an option (the "Stock
Option") to purchase on or prior to the Expiration Date specified above all
or part of the number of shares of Common Stock, par value $0.01 per share
(the "Stock"), of the Company specified above at the Option Exercise Price
per Share specified above subject to the terms and conditions set forth
herein and in the Plan.  This Stock Option is not intended to be an
"incentive stock option" under Section 422 of the Internal Revenue Code of
1986, as amended.

    1.   EXERCISABILITY SCHEDULE.  No portion of this Stock Option may be
exercised until such portion shall have become exercisable.  Except as set
forth below, and subject to the discretion of the Committee to accelerate the
exercisability schedule hereunder, this Stock Option shall be exercisable
with respect to the following number of Option Shares on the dates indicated:

              INCREMENTAL NUMBER OF
            OPTION SHARES EXERCISABLE             EXERCISABILITY DATE
           ---------------------------            --------------------

         -------------            (---%)              ------------
         -------------            (---%)              ------------
         -------------            (---%)              ------------
         -------------            (---%)              ------------
         -------------            (---%)              ------------

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           Once exercisable, this Stock Option shall continue to be
exercisable at any time or times prior to the close of business on the
Expiration Date, subject to the provisions hereof and of the Plan.

    2.   MANNER OF EXERCISE.

         (a) The Optionee may exercise this Stock Option only in the
following manner:  from time to time on or prior to the Expiration Date of
this Stock Option, the Optionee may give written notice to the Company of his
or her election to purchase some or all of the Option Shares purchasable at
the time of such notice.  This notice shall specify the number of Option
Shares to be purchased.

         Payment of the purchase price for the Option Shares may be made by
one or more of the following methods: (i) in cash, by certified or bank check
or other instrument acceptable to the Committee; (ii) through the delivery
(or attestation to the ownership) of shares of Stock that have been purchased
by the Optionee on the open market or that are beneficially owned by the
Optionee and are not then subject to any restrictions under any Company plan
and that otherwise satisfy any holding periods as may be required by the
Committee; (iii) at the discretion of the Committee, in accordance with a
cashless exercise program established with a securities brokerage firm and
approved by the Committee, provided that in the event the Optionee chooses to
pay the option purchase price as so provided, the Optionee and the broker
shall comply with such procedures and enter into such agreements of indemnity
and other agreements as the Committee shall prescribe as a condition of such
payment procedure; or (iv) a combination of (i), (ii) and (iii) above.
Payment instruments will be received subject to collection.

         The transfer to the Optionee on the records of the Company or of the
transfer agent of the Option Shares will be contingent upon the Company's
receipt from the Optionee of full payment for the Option Shares, as set forth
above and any agreement, statement or other evidence that the Company may
require to satisfy itself that the issuance of Stock to be purchased pursuant
to the exercise of Stock Options under the Plan and any subsequent resale of
the shares of Stock will be in compliance with applicable laws and
regulations.  In the event the Optionee chooses to pay the purchase price by
previously-owned shares of Stock through the attestation method, the number
of shares of Stock transferred to the Optionee upon the exercise of the Stock
Option shall be net of the Shares attested to.  In the event that the Company
establishes, for itself or using the services of a third party, an automated
system for the exercise of Stock Options, such as a system using an internet
website or interactive voice response, then the paperless exercise of Stock
Options may be permitted through the use of such an automated system.

         (b) The shares of Stock purchased upon exercise of this Stock Option
shall be transferred to the Optionee on the records of the Company or of the
transfer agent upon compliance to the satisfaction of the Committee with all
requirements under applicable laws or regulations in connection with such
transfer and with the requirements hereof and of the Plan.  The determination
of the Committee as to such compliance shall be final and binding on the
Optionee.  The Optionee shall not be deemed to be the holder of, or to have
any of the rights of a holder with respect to, any shares of Stock subject to
this Stock Option unless and until this Stock Option shall have been
exercised pursuant to the terms hereof, the Company or the transfer agent
shall have transferred the shares to the Optionee, and the Optionee's name
shall have been

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entered as the stockholder of record on the books of the Company.  Thereupon,
the Optionee shall have full voting, dividend and other ownership rights with
respect to such shares of Stock.

         (c) The minimum number of shares with respect to which this Stock
Option may be exercised at any one time shall be 100 shares, unless the
number of shares with respect to which this Stock Option is being exercised
is the total number of shares subject to exercise under this Stock Option at
the time.

         (d) Notwithstanding any other provision hereof or of the Plan, no
portion of this Stock Option shall be exercisable after the Expiration Date
hereof.

    3.   TERMINATION AS DIRECTOR. If the Optionee ceases to be a Director of
the Company, the period within which to exercise the Stock Option may be
subject to earlier termination as set forth below.

         (a) TERMINATION BY REASON OF DEATH.  If the Optionee ceases to be a
Director by reason of the Optionee's death, any exercisable portion of this
Stock Option outstanding on such date may be exercised by his or her legal
representative or legatee for a period of 12 months from the date of death or
until the Expiration Date, if earlier.

         (b) OTHER TERMINATION.  If the Optionee ceases to be a Director for
any reason other than the Optionee's death, any exercisable portion of this
Stock Option outstanding on such date may be exercised for a period of six
months from the date of termination or until the Expiration Date, if earlier.

    4.   INCORPORATION OF PLAN.  Notwithstanding anything herein to the
contrary, this Stock Option shall be subject to and governed by all the terms
and conditions of the Plan, including the powers of the Committee set forth
in Section 2(b) of the Plan.  Capitalized terms in this Agreement shall have
the meaning specified in the Plan, unless a different meaning is specified
herein.

    5.   TRANSFERABILITY.  This Agreement is personal to the Optionee, is
non-assignable and is not transferable in any manner, by operation of law or
otherwise, other than by will or the laws of descent and distribution.  This
Stock Option is exercisable, during the Optionee's lifetime, only by the
Optionee, and thereafter, only by the Optionee's legal representative or
legatee.

    6.   NO OBLIGATION TO CONTINUE AS A DIRECTOR.  Neither the Plan nor this
Stock Option confers upon the Optionee any rights with respect to continuance
as a Director of the Company.

    7.   NOTICES.  Notices hereunder shall be mailed or delivered to the
Company at its principal place of business and shall be mailed or delivered
to the Optionee at the address on file with the Company or, in either case,
at such other address as one party may subsequently furnish to the other
party in writing.

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                                       METABOLIX, INC.

                                       By:  __________________________________
                                            Title:

The foregoing Agreement is hereby accepted and the terms and conditions
thereof hereby agreed to by the undersigned.

Dated: _________________________       _______________________________________
                                       Optionee's Signature

                                       Optionee's name and address:

                                       ______________________________________

                                       ______________________________________

                                       ______________________________________

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WHENEVER CONFIDENTIAL INFORMATION IS OMITTED HEREIN (SUCH OMISSIONS ARE DENOTED
BY AN ASTERISK*), SUCH CONFIDENTIAL INFORMATION HAS BEEN SUBMITTED SEPARATELY TO
THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO A REQUEST FOR CONFIDENTIAL
TREATMENT.

                      MASSACHUSETTS INSTITUTE OF TECHNOLOGY

                                LICENSE AGREEMENT

                                   (EXCLUSIVE)

                                                             Date: July 15, 1993

*    CONFIDENTIAL TREATMENT REQUESTED

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                                TABLE OF CONTENTS

                                                                            Page

PREAMBLE 1                                                                     1

ARTICLE 1 - DEFINITIONS                                                        1

ARTICLE 2 - GRANT                                                              4

ARTICLE 3 - DUE DILIGENCE                                                      5

ARTICLE 4 - ROYALTIES                                                          6

ARTICLE 5 - REPORTS AND RECORDS                                                8

ARTICLE 6 - PATENT PROSECUTION                                                 9

ARTICLE 7 - INFRINGEMENT                                                      10

ARTICLE 8 - PRODUCT LIABILITY                                                 13

ARTICLE 9 - EXPORT CONTROLS                                                   14

ARTICLE 10 - NON-USE OF NAMES                                                 14

ARTICLE 11 - ASSIGNMENT                                                       15

ARTICLE 12 - DISPUTE RESOLUTION                                               16

ARTICLE 13 - TERMINATION                                                      16

ARTICLE 14 - PAYMENTS, NOTICES AND OTHER COMMUNICATIONS                       17

ARTICLE 15 - MISCELLANEOUS PROVISIONS                                         18

*    CONFIDENTIAL TREATMENT REQUESTED

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                                    PREAMBLE

     This Agreement is made and entered into this 15th day July, 1993, (the
"Effective Date") by and between MASSACHUSETTS INSTITUTE OF TECHNOLOGY, a
corporation duly organized and existing under the laws of the Commonwealth of
Massachusetts and having its principal office at 77 Massachusetts Avenue,
Cambridge, Massachusetts 02139, U.S.A. (hereinafter referred to as "M.I.T."),
and METABOLIX, INC., a corporation duly organized under the laws of the
Commonwealth of Massachusetts and having its principal office at 285
Commonwealth Avenue, Boston, Massachusetts 02115, U.S.A. (hereinafter referred
to as "LICENSEE").

                                   WITNESSETH

     WHEREAS, M.I.T. is the owner of certain PATENT RIGHTS (as later defined
herein) relating to M.I.T. Case No. 4403, "Method for Producing Novel Polyester
Biopolymers" by Oliver P. Peoples and Anthony J. Sinskey, USSN 566,535, USSN
700,109 and related technology, and has the right to grant licenses under said
PATENT RIGHTS, subject only to a royalty-free, nonexclusive license heretofore
granted to the United States Government.

     WHEREAS, M.I.T. desires to have the PATENT RIGHTS utilized in the public
interest and is willing to grant a license thereunder;

     WHEREAS, LICENSEE has represented to M.I.T., to induce M.I.T. to enter into
this Agreement, that LICENSEE is knowledgeable with respect to the subject
matter related to the LICENSED PRODUCT(s) (as later defined herein) and/or the
use of the LICENSED PROCESS(es) (as later defined herein) and that it shall
commit itself to a thorough, vigorous and diligent program of exploiting the
PATENT RIGHTS so that public utilization shall result therefrom; and

     WHEREAS, LICENSEE desires to obtain a license under the PATENT RIGHTS upon
the terms and conditions hereinafter set forth.

     NOW, THEREFORE, in consideration of the premises and the mutual covenants
contained herein, the parties hereto agree as follows:

                             ARTICLE 1 - DEFINITIONS

     For the purposes of this Agreement, the following words and phrases shall
have the following meanings:

     1.1 "LICENSEE" shall include a related company of METABOLIX, INC. the
voting stock of which is directly or indirectly at least fifty percent (50%)
owned and controlled by

*    CONFIDENTIAL TREATMENT REQUESTED

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METABOLIX, INC., an organization which directly or indirectly controls more than
fifty percent (50%) of the voting stock of METABOLIX, INC. and an organization
the majority ownership of which is directly or indirectly common to the
ownership of METABOLIX, INC.

     1.2 "PATENT RIGHTS" shall mean all of the following M.I.T. intellectual
property:

          (a)  The United States and foreign patents and/or patent applications
               and invention disclosures listed in Appendix A;

          (b)  United States and foreign patents issued from the application and
               invention disclosures listed in Appendix A and from divisionals
               and continuations of these applications and invention
               disclosures;

          (c)  claims of United States and foreign continuation-in-part
               applications and of the resulting patents which are directed to
               subject matter specifically described in the United States and
               foreign applications and invention disclosures listed in Appendix
               A;

          (d)  claims of all foreign patent applications and of the resulting
               patents which are directed to subject matter specifically
               described in the United States patents and/or patent applications
               and invention disclosures described in (a), (b), (c) or (d)
               above; and

          (e)  any reissues of United States patents described in (a), (b), (c)
               or (d) above.

     1.3 A "LICENSED PRODUCT" shall mean any product or part thereof which:

          (a)  is covered in whole or in part by an issued, unexpired valid
               claim or a pending claim contained in the PATENT RIGHTS in the
               country in which any such product or part thereof is made, used
               or sold; or

          (b)  is manufactured by using a process or is employed to practice a
               process which is covered in whole or in part by an issued,
               unexpired valid claim or a pending claim contained in the PATENT
               RIGHTS in the country in which a LICENSED PROCESS is used or in
               which such product or part thereof is used or sold.

     1.4 A "LICENSED PROCESS" shall mean any process which:

          (a)  is covered in whole or in part by an issued, unexpired valid
               claim or a pending claim contained in the PATENT RIGHTS in the
               country in which such process is used or in which the LICENSED
               PRODUCT made thereby is used or sold.

*    CONFIDENTIAL TREATMENT REQUESTED

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     1.5 "NET SALES" shall mean LICENSEE's (and its sublicensees') billings for
LICENSED PRODUCTS and LICENSED PROCESSES produced hereunder less the sum of the
following:

          (a)  discounts allowed in amounts customary in the trade;

          (b)  sales, tariff duties and/or use taxes directly imposed and with
               reference to particular sales;

          (c)  outbound transportation prepaid or allowed; and

          (d)  amounts allowed or credited on returns.

     No deduction shall be made for commissions paid to individuals whether they
be with independent sales agencies or regularly employed by LICENSEE and on its
payroll, or for cost of collections. LICENSED PRODUCTS shall be considered
"sold" when billed out or invoiced. "NET SALES" shall not include LICENSED
PRODUCTS sold for clinical testing, research or development purposes.

     Where the LICENSED PRODUCT is a combination product consisting of polymer
whose composition or manufacture is covered by the PATENT RIGHTS plus other
materials which are not covered by the PATENT RIGHTS, the "NET SALES" shall mean
the NET SALES of the full product multiplied by the fully loaded manufacturing
cost of the polymer divided by the total fully loaded manufacturing cost of the
total combination material. When the LICENSED PRODUCT consists of a combination
product consisting of a component made from the polymer, plus other components,
then "NET SALES" shall mean NET SALES of the total product multiplied by the
fully loaded manufacturing cost of the polymer component divided by the fully
loaded manufacturing cost of the total product. By "fully loaded" is meant the
cost of goods sold plus overhead allocated to production and the sale thereof.

*    CONFIDENTIAL TREATMENT REQUESTED

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                               ARTICLE 2 - GRANT

     2.1 M.I.T. hereby grants to LICENSEE the worldwide right and license to
make, have made, use, lease and sell the LICENSED PRODUCTS and to practice the
LICENSED PROCESSES to the end of the term for which the PATENT RIGHTS are
granted unless this Agreement shall be sooner terminated according to the terms
hereof.

     2.2 LICENSEE agrees that to the extent possible LICENSED PRODUCTS leased or
sold in the United States shall be manufactured substantially in the United
States and that in those cases where domestic manufacture is impractical it will
request appropriate waivers from the Department of Commerce pursuant to 37
C.F.R. Sec. 401.14(i).

     2.3 In order to establish a period of exclusivity for LICENSEE, M.I.T.
hereby agrees that it shall not grant any other license to make, have made, use,
lease and sell LICENSED PRODUCTS or to utilize LICENSED PROCESSES during the
term of this agreement.

     2.4 M.I.T. reserves the right to practice under the PATENT RIGHTS for its
own noncommercial research purposes.

     2.5 M.I.T. further grants to LICENSEE a ninety (90) day first option to
negotiate for an exclusive license to new inventions dominated by the claims of
the PATENT RIGHTS as originally licensed which arise from the laboratory of
Prof. Anthony Sinskey at M.I.T. within four (4) years of the Effective Date of
this Agreement. Such option shall be subject to any rights granted in
sponsorship agreements to sponsors of the research from which any such invention
arises.

*    CONFIDENTIAL TREATMENT REQUESTED

                                        4

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     2.6 LICENSEE shall have the right to enter into sublicensing agreements for
the rights, privileges and licenses granted hereunder. Upon any termination of
this Agreement, sublicensees' rights shall also terminate, subject to Paragraph
13.6 hereof.

     2.7 LICENSEE agrees that any sublicenses granted by it shall provide that
the obligations to M.I.T. of Articles 2, 5, 7, 8, 9, 10, 12, 13 and 15 of this
Agreement shall be binding upon the sublicensee as if it were a party to this
Agreement. LICENSEE further agrees to attach copies of these Articles to
sublicense agreements.

     2.8 LICENSEE agrees to forward to M.I.T. a copy of any and all sublicense
agreements promptly upon execution by the parties.

     2.9 The license granted hereunder shall not be construed to confer any
rights upon LICENSEE by implication, estoppel or otherwise as to any technology
not specifically set forth in Appendix A hereof.

                           ARTICLE 3 - DUE DILIGENCE

     3.1 LICENSEE shall use diligent efforts to bring LICENSED PRODUCTS to
market through a thorough, vigorous and diligent program for exploitation of the
PATENT RIGHTS and to continue active, diligent development and marketing efforts
for LICENSED PRODUCTS throughout the life of this Agreement.

     3.2 LICENSEE shall raise a cumulative total of investment capital and/or
research and development funds of at least:

          (a)  Five Hundred Thousand Dollars ($500,000) within twelve (12)
               months from the Effective Date,

          (b)  Two Million Dollars ($2,000,000) including funds under (a) hereof
               within twenty-seven (27) months from the Effective Date,

*    CONFIDENTIAL TREATMENT REQUESTED

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          (c)  Five Million Dollars ($5,000,000) including funds under (a) and
               (b) hereof within fifty-one (51) months from the Effective Date.

     Included in the cumulative investment capital and/or research and
development funds hereunder shall be such funds invested or expanded by a joint
venture in which LICENSEE owns at least a 33% interest provided that such finds
are used substantially for the development and marketing of LICENSED PRODUCTS.

     3.3 LICENSEE's failure to perform in accordance with Paragraphs 3.1 and 3.2
above shall be grounds for M.I.T. to terminate this Agreement pursuant to
Paragraph 13.3 hereof.

                              ARTICLE 4 - ROYALTIES

     4.1 For the rights, privileges and license granted hereunder, LICENSEE
shall pay royalties to M.I.T. in the manner hereinafter provided to the end of
the term of the PATENT RIGHTS or until this Agreement shall earlier be
terminated:

          (a)  A License Issue Fee of *, which said License Issue Fee shall be
               deemed earned and due in two parts:

               (i)  * due upon the signing of this Agreement; and

               (ii) * due upon the raising of Two Million Dollars ($2,000,000)
                    in investment capital by LICENSEE.

          (b)  License Maintenance Fees of Twenty-Five Thousand Dollars
               ($25,000) per year payable on the second anniversary of the
               Effective Date and on each subsequent anniversary during the term
               of this Agreement; provided, however, that Running Royalties
               subsequently due on NET SALES for each said year, if any, shall
               be creditable against the License Maintenance Fee for said year.
               License Maintenance Fees paid in excess of Running Royalties
               shall not be creditable to Running Royalties for future years.

          (c)  * of the NET SALES of LICENSED PRODUCTS and LICENSED PROCESSES by
               LICENSEE.

          (d)  A share of sublicensing revenue received by LICENSEE equal to:

*    CONFIDENTIAL TREATMENT REQUESTED

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               (i)  * if only the PATENT RIGHTS are sublicensed.

               (ii) Where the sublicensee revenue includes revenue received for
                    PATENT RIGHTS sublicensed in conjunction with products
                    and/or substantial technology developed by LICENSEE, * up to
                    the time LICENSEE has raised Five Hundred Thousand Dollars
                    ($500,000) as provided in Section 3.2(a) hereof, thereafter
                    * up to the time LICENSEE has raised Two Million Dollars
                    ($2,000,000) as provided in Section 3.2(b) hereof and
                    thereafter * for the remaining term of this Agreement.

               In no case shall the revenue paid to M.I.T. for each sublicense
               be less than * of the sales value of the LICENSED PRODUCTS made,
               used or sold by that sublicensee.

          (e)  Shares of common stock of LICENSEE equal to * of the outstanding
               common and preferred shares of LICENSEE at the completion of the
               first round of equity of investment.

          (f)  Antidilution: If, following the first round of equity funding,
               LICENSEE issues additional shares of stock such that
               M.I.T.'s total share of outstanding stock falls below *, then
               LICENSEE shall grant to M.I.T. additional shares such that
               M.I.T.'s fraction of total outstanding shares remains at * until
               a total of Four Million Dollars ($4,000,000) is invested in
               LICENSEE. Thereafter, no additional shares shall be due to
               M.I.T., provided that in subsequent rounds of financing, M.I.T.
               shall have the right to invest in additional shares, on a pro
               rata basis, at the same price as is granted to other
               investors holding common or preferred stock.

     4.2 All payments due hereunder shall be paid in full, without deduction of
taxes or other fees which may be imposed by any government and which shall be
paid by LICENSEE.

     4.3 No multiple royalties shall be payable because any LICENSED PRODUCT,
its manufacture, use, lease or sale are or shall be covered by more than one
PATENT RIGHTS patent application or PATENT RIGHTS patent licensed under this
Agreement.

     4.4 Royalty payments shall be paid in United States dollars in Cambridge,
Massachusetts, or at such other place as M.I.T. may reasonably designate
consistent with the laws and regulations controlling in any foreign country. If
any currency conversion shall be

*    CONFIDENTIAL TREATMENT REQUESTED

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required in connection with the payment of royalties hereunder, such conversion
shall be made by using the exchange rate prevailing at the Chase Manhattan Bank
(N.A.) on the last business day of the calendar quarterly reporting period to
which such royalty payments relate.

                        ARTICLE 5 - REPORTS AND RECORDS

     5.1 LICENSEE shall keep full, true and accurate books of account containing
all particulars that may be necessary for the purpose of showing the amounts
payable to M.I.T. hereunder. Said books of account shall be kept at LICENSEE's
principal place of business or the principal place of business of the
appropriate division of LICENSEE to which this Agreement relates. Said books and
the supporting data shall be open at all reasonable times for three (3) years
following the end of the calendar year to which they pertain, to the inspection
of M.I.T. or its agents for the purpose of verifying LICENSEE's royalty
statement or compliance in other respects with this Agreement. Should such
inspection lead to the discovery of a greater than Ten Percent (10%) discrepancy
in reporting, LICENSEE agrees to pay the full cost of such inspection.

     5.2 LICENSEE, within sixty (60) days after December 31 of each year prior
to the first commercial sale of a LICENSED PRODUCT and sixty days after March
31, June 30, September 30 and December 31, of each year after the first
commercial sales of a LICENSED PRODUCT, shall deliver to M.I.T. true and
accurate reports, giving such particulars of the business conducted by LICENSEE
during the preceding three-month period under this Agreement as shall be
pertinent to a royalty accounting hereunder. These shall include at least the
following:

*    CONFIDENTIAL TREATMENT REQUESTED

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          (a)  number of LICENSED PRODUCTS manufactured and sold by LICENSEE;

          (b)  total billings for LICENSED PRODUCTS manufactured and sold by
               LICENSEE;

          (c)  accounting for all LICENSED PROCESSES used or sold by LICENSEE;

          (d)  deductions applicable as provided in Paragraph 1.5;

          (e)  total royalties due; and

          (f)  names and addresses of all sublicensees of LICENSEE.

     LICENSEE shall endeavor to obtain similar information from its sublicensees
and will provide such information which is obtained to M.I.T.

     5.3 With each such report submitted, LICENSEE shall pay to M.I.T. the
royalties due and payable under this Agreement. If no royalties shall be due,
LICENSEE shall so report.

     5.4 On or before the ninetieth (90th) day following the close of LICENSEE's
fiscal year, LICENSEE shall provide M.I.T. with LICENSEE's certified financial
statements for the preceding fiscal year including, at a minimum, a Balance
Sheet and an Operating Statement.

     5.5 The royalty payments set forth in this Agreement and amounts due under
Article 6 shall, if overdue, bear interest until payment at a per annum rate Two
Percent (2%) above the prime rate in effect at the Chase Manhattan Bank (N.A.)
on the due date. The payment of such interest shall not foreclose M.I.T. from
exercising any other rights it may have as a consequence of the lateness of any
payment.

                         ARTICLE 6 - PATENT PROSECUTION

     6.1 Throughout the term of this Agreement, LICENSEE, at its own expense,
shall have the right, but shall not be obligated, to file such United States
and/or foreign patent

*    CONFIDENTIAL TREATMENT REQUESTED

                                       9

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applications covering any patentable invention included within the Patent
Rights; to prosecute and defend such applications against third party
oppositions; and upon grant of any Letters Patent covering inventions included
within the Patent Rights, to maintain such Letters Patent in force. LICENSEE
agrees to seek strong, broad claims in the best interest of M.I.T. and shall not
abandon the subject matter of any substantive claim without the permission of
M.I.T., such permission not to be unreasonably withheld. If LICENSEE elects not
to file or prosecute such applications or maintain such Letters Patent, LICENSEE
shall so notify M.I.T., in which event M.I.T. shall have the right to file or
prosecute such applications and to maintain such Letters Patent.

     6.2 Payment of all out-of-pocket fees and costs relating to the filing,
prosecution, and maintenance of the PATENT RIGHTS shall be the responsibility of
LICENSEE, whether such fees and costs were incurred before or after the date of
this Agreement. Payment for out-of-pocket costs incurred by M.I.T. prior to the
Effective Date shall be made in three parts:

          (a)  Twenty-Five Percent (25%) on or before a date three (3) months
               from the Effective Date of this Agreement;

          (b)  Twenty-Five Percent (25%) on or before a date nine (9) months
               from the Effective Date of this Agreement;

          (c)  The remaining Fifty Percent (50%) on or before a date fifteen
               (15) months from the Effective Date of this Agreement,

     Patenting costs incurred by M.I.T. after the Effective Date of this
Agreement shall be paid within sixty (60) days of invoicing by M.I.T.

                            ARTICLE 7 - INFRINGEMENT

     7.1 LICENSEE shall inform M.I.T. promptly in writing of any alleged
infringement of the PATENT RIGHTS by a third party and of any available evidence
thereof.

*    CONFIDENTIAL TREATMENT REQUESTED

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     7.2 During the term of this Agreement, LICENSEE shall have the right, but
shall not be obligated, to prosecute at its own expense any such infringements
of the PATENT RIGHTS and, in furtherance of such right, M.I.T. hereby agrees
that LICENSEE may join M.I.T. as a party plaintiff in any such suit, without
expense to M.I.T. The total cost of any such infringement action commenced or
defended solely by LICENSEE shall be borne by LICENSEE, LICENSEE may, for such
purposes, use the name of M.I.T. as party plaintiff; provided, however, that
such right to bring an infringement action shall remain in effect only for so
long as the license granted herein remains exclusive. No settlement, consent
judgement or other voluntary final disposition of the suit may be entered into
without the consent of M.I.T. which consent shall not unreasonably be withheld.
LICENSEE shall indemnify M.I.T. against any order for costs that may be made
against M.I.T. in proceedings commenced and defended solely by LICENSEE.

     7.3 In the event that LICENSEE shall undertake the enforcement and/or
defense of the PATENT RIGHTS by litigation, LICENSEE may withhold up to * of the
royalties otherwise thereafter due M.I.T. hereunder and apply the same toward
reimbursement of up to * of LICENSEE's expenses, including reasonable attorneys'
fees, in connection therewith. Any recovery of damages by LICENSEE for any such
suit shall be applied first in satisfaction of any unreimbursed expenses and
legal fees of LICENSEE relating to the suit, and next toward reimbursement of
M.I.T. for any royalties past due or withheld and applied pursuant to this
Article VII. The balance remaining from any such recovery attributable to
damages for lost sales shall be divided according to the royalty percentages set
forth in Section 4.1; any remaining balance shall be paid to LICENSEE.

*    CONFIDENTIAL TREATMENT REQUESTED

                                       11

<Page>

     7.4 If within six (6) months after having been notified of any alleged
infringement, LICENSEE shall have been unsuccessful in persuading the alleged
infringer to desist and shall not have brought and shall not be diligently
prosecuting an infringement action, or if LICENSEE shall notify M.I.T. at any
time prior thereto of its intention not to bring suit against any alleged
infringer, then, and in those events only, M.I.T. shall have the right, but
shall not be obligated, to prosecute at its own expense any infringement of the
PATENT RIGHTS, and, in furtherance of such right, LICENSEE hereby agrees that
M.I.T. may include LICENSEE as a party plaintiff in any such suit, without
expense to LICENSEE. The total cost of any such infringement action commenced or
defended solely by M.I.T. shall be borne by M.I.T., and M.I.T. shall keep any
recovery or damages for past infringement derived therefrom.

     7.5 In the event that a declaratory judgment action alleging invalidity or
noninfringement of any of the PATENT RIGHTS shall be brought against LICENSEE,
M.I.T., at its option, shall have the right, within sixty (60) days after
commencement of such action, to join in the defense of the action at its own
expense.

     7.6 In any infringement suit as either party may institute to enforce the
PATENT RIGHTS pursuant to this Agreement, the other party hereto shall, at the
request and expense of the party initiating such suit, cooperate in all respects
and, to the extent possible, have its employees testify when requested and make
available relevant records, papers, information, samples, specimens and the
like.

     7.7 LICENSEE, during the period of this Agreement, shall have the sole
right in accordance with the terms and conditions herein to sublicense any
alleged infringer for future use of the PATENT RIGHTS.

*    CONFIDENTIAL TREATMENT REQUESTED

                                       12

<Page>

                         ARTICLE 8 - PRODUCT LIABILITY

     8.1 LICENSEE shall at all times during the term of this Agreement and
thereafter, indemnify, defend and hold M.I.T., its trustees, officers, employees
and affiliates, harmless against all claims and expenses, including legal
expenses and reasonable attorneys' fees, arising out of the death of or injury
to any person or persons or out of any damage to property and against any other
claim, proceeding, demand, expense and liability of any kind whatsoever
resulting from the production, manufacture, sale, use, lease, consumption or
advertisement of the LICENSED PRODUCT(s) and/or LICENSED PROCESS(es) or arising
from any obligation of LICENSEE hereunder.

     8.2 Prior to the first use of a LICENSED PRODUCT on humans, LICENSEE shall
obtain and carry in full force and effect liability insurance which shall
protect LICENSEE and M.I.T. in regard to events covered by Paragraph 8.1 above.

     8.3 EXCEPT AS OTHERWISE EXPRESSLY SET FORTH IN THIS AGREEMENT, M.I.T. MAKES
NO REPRESENTATIONS AND EXTENDS NO WARRANTIES OF ANY KIND, EITHER EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO WARRANTIES OF MERCHANTABILITY, FITNESS FOR
A PARTICULAR PURPOSE, AND VALIDITY OF PATENT RIGHTS CLAIMS, ISSUED OR PENDING.
NOTHING IN THIS AGREEMENT SHALL BE CONSTRUED AS A REPRESENTATION MADE OR
WARRANTY GIVEN BY M.I.T. THAT THE PRACTICE BY LICENSEE OF THE LICENSE GRANTED
HEREUNDER SHALL NOT INFRINGE THE PATENT RIGHTS OF ANY THIRD PARTY.

*    CONFIDENTIAL TREATMENT REQUESTED

                                       13

<Page>

                          ARTICLE 9 - EXPORT CONTROLS

     It is understood that M.I.T. is subject to United States laws and
regulations controlling the export of technical data, computer software,
laboratory prototypes and other commodities (including the Arms Export Control
Act, as amended and the Export Administration Act of 1979), and that its
obligations hereunder are contingent on compliance with applicable United States
export laws and regulations. The transfer of certain technical data and
commodities may require a license from the cognizant agency of the United States
Government and/or written assurances by LICENSEE that LICENSEE shall not export
data or commodities to certain foreign countries without prior approval of such
agency. M.I.T. neither represents that a license shall not be required not that,
if required, it shall be issued.

                         ARTICLE 10 - NON-USE OF NAMES

     Except as required by law, LICENSEE shall not use the names or trademarks
of the Massachusetts Institute of Technology, nor any adaptation thereof, nor
the names of any of its employees, in any advertising, promotional or sales
literature without prior written consent obtained from M.I.T., or said employee,
in each case, except that LICENSEE may state that it is licensed by M.I.T. under
one or more of the patents and/or applications comprising the PATENT RIGHTS.
LICENSEE may, however, use the name of Oliver P. Peoples, Anthony J. Sinskey,
and/or any other employee of M.I.T. who is a consultant or member of an advisory
board of LICENSEE, with their permission, and provided, also, that their
affiliation with LICENSEE is identified.

*    CONFIDENTIAL TREATMENT REQUESTED

                                       14

<Page>

                            ARTICLE 11 - ASSIGNMENT

     This Agreement is not assignable, except in the case where LICENSEE
transfers its business relating to the subject matter hereof or transfers a
subsidiary of LICENSEE, or a joint venture in which LICENSEE is a participant,
or all of any other entity in which LICENSEE has a controlling interest,
whereupon transferee shall acquire all of LICENSEE's benefits and obligations
hereunder. Any other assignment shall be void.

                        ARTICLE 12 - DISPUTE RESOLUTION

     12.1 Except for the right of either party to apply to a court of competent
jurisdiction for a temporary restraining order, a preliminary injunction or
other equitable relief to preserve the status quo or prevent irreparable harm,
any and all claims, disputes or controversies arising under, out of or in
connection with the Agreement, including any dispute relating to patent validity
or infringement, which the parties shall be unable to resolve within one hundred
and twenty (120) days shall be mediated in good faith. The party raising such
dispute shall promptly advise the other party of such claim, dispute or
controversy in a writing which describes in reasonable detail the nature of such
dispute. By not later than ten (10) business days after the recipient has
received such notice of dispute, each party shall have selected for itself a
representative who shall have the authority to bind such party, and shall
additionally have advised the other party in writing of the name and title of
such representative. By not later than twenty (20) business days after the date
of such notice of dispute, such representatives shall schedule a date for a
mediation hearing with the Cambridge Dispute Settlement Center or Endispute Inc.
in Cambridge, Massachusetts. The parties shall enter into good faith mediation
and shall share the costs equally. If the representatives of the parties have
not been able to

*    CONFIDENTIAL TREATMENT REQUESTED

                                       15

<Page>

resolve the dispute within thirty (30) business days after such mediation
hearing, the parties shall have the right to pursue any other remedies legally
available to resolve such dispute in either the Courts of the Commonwealth of
Massachusetts or in the United States District Court for the District of
Massachusetts, to whose jurisdiction for such purposes M.I.T. and LICENSEE each
hereby irrevocably consents and submits.

     12.2 Notwithstanding the foregoing, nothing in this Article shall be
construed to waive any rights or timely performance of any obligations existing
under this Agreement.

                            ARTICLE 13 - TERMINATION

     13.1 If LICENSEE shall cease to carry on its business, this Agreement shall
terminate upon notice by M.I.T., except as provided in Article 11.

     13.2 Should LICENSEE fail to make any payment whatsoever due and payable to
M.I.T. hereunder, M.I.T. shall have the right to terminate this Agreement
effective on sixty (60) days' notice, unless LICENSEE shall make all such
payments to M.I.T. within said sixty (60) day period. Upon the expiration of the
sixty (60) day period, if LICENSEE shall not have made all such payments to
M.I.T., the rights, privileges and license granted hereunder shall automatically
terminate.

     13.3 Upon any material breach or default of this Agreement by LICENSEE,
other than those occurrences set out in Paragraphs 13.1 and 13.2 hereinabove,
which shall always take precedence in that order over any material breach or
default referred to in this Paragraph 13.3, M.I.T. shall have the right to
terminate this Agreement and the rights, privileges and license granted
hereunder effective on one hundred and twenty (120) days' notice to LICENSEE.
Such termination shall become automatically effective unless LICENSEE shall have
cured any such

*    CONFIDENTIAL TREATMENT REQUESTED

                                       16

<Page>

material breach or default prior to the expiration of the one hundred and twenty
(120) day period.

     13.4 LICENSEE shall have the right to terminate this Agreement at any time
on six (6) months' notice to M.I.T., and upon payment of all amounts due M.I.T.
through the effective date of the termination.

     13.5 Upon termination of this Agreement for any reason, nothing herein
shall be construed to release either party from any obligation that matured
prior to the effective date of such termination. LICENSEE and any sublicensee
thereof may, however, after the effective date of such termination, sell all
LICENSED PRODUCTS, and complete LICENSED PRODUCTS in the process of manufacture
at the time of such termination and sell the same, provided that LICENSEE shall
pay to M.I.T. the Running Royalties thereon as required by Article 4 of this
Agreement and shall submit the reports required by Article 5 hereof on the sales
of LICENSED PRODUCTS.

     13.6 Upon termination of this Agreement for any reason, any sublicensee not
then in default shall have the right to seek a license from M.I.T. M.I.T. agrees
to negotiate such licenses in good faith under reasonable terms and conditions.

            ARTICLE 14 - PAYMENTS, NOTICES AND OTHER COMMUNICATIONS

     Any payment, notice or other communication pursuant to this Agreement shall
be sufficiently made or given on the date of mailing if sent to such party by
certified first class mail, postage prepaid, addressed to it at its address
below or as it shall designate by written notice given to the other party:

     In the case of M.I.T.:

*    CONFIDENTIAL TREATMENT REQUESTED

                                       17

<Page>

                    Director
                    Technology Licensing Office
                    Massachusetts Institute of Technology
                    Room E32-300
                    Cambridge, Massachusetts 02139

In the case of LICENSEE:

                    President
                    Metabolix, Inc.
                    285 Commonwealth Ave.
                    Boston, MA 02115

                      ARTICLE 15 - MISCELLANEOUS PROVISIONS

     15.1 This Agreement shall be construed, governed, interpreted and applied
in accordance with the laws of the Commonwealth of Massachusetts, U.S.A., except
that questions affecting the construction and effect of any patent shall be
determined by the law of the country in which the patent was granted.

     15.2 The parties hereto acknowledge that this Agreement sets forth the
entire Agreement and understanding of the parties hereto as to the subject
matter hereof, and shall not be subject to any change or modification except by
the execution of a written instrument subscribed to by the parties hereto.

     15.3 The provisions of this Agreement are severable, and in the event that
any provisions of this Agreement shall be determined to be invalid or
unenforceable under any controlling body of the law, such invalidity or
unenforceability shall not in any way affect the validity or enforceability of
the remaining provisions hereof.

*    CONFIDENTIAL TREATMENT REQUESTED

                                       18

<Page>

     15.4 The failure of either party to assert a right hereunder or to insist
upon compliance with any term or condition of this Agreement shall not
constitute a waiver of that right or excuse a similar subsequent failure to
perform any such term or condition by the other party.

     IN WITNESS WHEREOF, the parties have duly executed this Agreement the day
and year set forth below.

                                        MASSACHUSETTS INSTITUTE OF TECHNOLOGY

                                        By  /s/ J.D. Litster
                                            ------------------------------------
                                        Name J.D. Litster
                                        Title Vice President for Research
                                        Date July 15, 1993

                                        METABOLIX, INC.

                                        By  /s/ Edward M. Muller
                                            ------------------------------------
                                        Name Edward M. Muller
                                        Title Chief Executive Officer
                                        Date 7/15/93

*    CONFIDENTIAL TREATMENT REQUESTED

                                       19

<Page>

                           APPENDIX A - PATENT RIGHTS

UNITED STATES PATENT RIGHTS

     M.I.T. Case No. 4403

     "Method for Producing Novel Polyester Biopolymers"
     By Oliver P. Peoples and Anthony J. Sinskey

     USSN 566,535        08/13/90
     USSN 700,109        05/08/91
     USSN 944,488        09/14/92
     USSN 944,839        09/14/92
     USSN 944,881        09/14/92
     Application Filed   06/03/93

FOREIGN PATENT RIGHTS

     Japan application filed 07/10/90
     EPC SN 88908449.7 filed 07/10/90
     CANADA filed 07/10/90

INVENTION DISCLOSURES

     M.I.T. Case No. 6113
     "Polymerase Technology for the Production of Long Chain and Short Chain
     Polymers"
     By: Tillman Gerngross, Oliver P. Peoples, Anthony J. Sinskey and Simon F.
     Williams

     M.I.T. Case No. 5977
     "Antibodies to A. eutrophus H16 PHB Synthase"
     By: Anthony J. Sinskey and Oliver P. Peoples

     M.I.T. Case No. 6010
     "Use of PHA Polymerases to Detect, Modify or Control Formation PHA's in
     Plants, Animals or Other Biological Systems"
     By: Oliver P. Peoples and Anthony J. Sinskey

     M.I.T. Case No. 6086
     "Anti-Short-Chain Polyhydroxyalkanoate Monoclonal Antibodies"
     By: Oliver P. Peoples, Anthony J. Sinskey and Simon F. Williams

*    CONFIDENTIAL TREATMENT REQUESTED

                                       20

<Page>

                      MASSACHUSETTS INSTITUTE OF TECHNOLOGY
                         28 CARLTON STREET, ROOM E32-300
                            CAMBRIDGE, MA 02142-1324

TECHNOLOGY LICENSING OFFICE                            TELEPHONE: (617) 253-8088
                                                       FACSIMILE: (617) 258-8790
                                                       TELEX: 921473 MIT CAM

                                 August 10, 1993

Mr. Edward M. Muller
Metabolix Inc.
P.O. Box 695
Cambridge, MA 02142

                      LETTER OF AMENDMENT (FIRST AMENDMENT)

Dear Ed;

     This is in response to your letter of July 21 concerning the
M.I.T./Metabolix License Agreement dated July 15, 1993.

     We hereby recognize that the following M.I.T. Cases

     No. 5977
     "Antibodies to A. eutrophus H16 PHB Synthase"
     By Anthony J. Sinskey and Oliver P. Peoples

     No. 6010
     "Use of PHA Polymerases to Detect, Modify or Control Formation PHA's in
     Plants, Animals or Other Biological Systems"
     By Oliver P. Peoples and Anthony J. Sinskey

     No. 6086
     "Anti-Short-Chain Polyhydroxyalkanoate Monoclonal Antibodies"
     By Oliver P. Peoples, Anthony J. Sinskey, and Simon F. Williams

were waived by M.I.T. to the inventors and are therefore no longer the property
of M.I.T.

*    CONFIDENTIAL TREATMENT REQUESTED

                                       21

<Page>

     This letter therefore amends the License Agreement to remove these cases
from the PATENT RIGHTS of Appendix A.

     Please sign and return one copy of this letter acknowledging this Amendment
for Metabolix.

                                        Sincerely,

                                        /s/ Lita L. Nelson
                                        ----------------------------------------
                                        Lita L. Nelsen
                                        Director

LLN/ak

5977.6010.6086.Metabolix.agt.810

ACKNOWLEDGED by:

METABOLIX, INC.

By: /s/Edward M. Muller
    ---------------------------------
Name: Edward M. Muller
Title: Chief Executive Officer
Date: August 23, 1993

*    CONFIDENTIAL TREATMENT REQUESTED

                                       22

<Page>

                                SECOND AMENDMENT

This Second Amendment with the effective date of March 6, 1995 is to the License
Agreement dated July 15, 1993, between MASSACHUSETTS INSTITUTE OF TECHNOLOGY and
METABOLIX, INC.

The parties thereto now further agree as follows:

1. The PATENT RIGHTS of M.I.T. Case 6726 "Overproduction of Soluble PHA
Synthase" by Oliver P. Peoples, et al., shall be jointly owned by the parties.
Inventor Oliver P. Peoples, an employee of Metabolix, shall assign his rights in
the invention jointly to M.I.T. and Metabolix, recognizing that his work on this
invention was performed at both institutions. As of the date of this amendment,
these PATENT RIGHTS consist of:

          U.S.S.N. 290131, Filed 08/12/94

2. M.I.T.'s rights in the PATENT RIGHTS of this case shall be added to the
PATENT RIGHTS of the License Agreement, thereby granting Metabolix an exclusive
license to these PATENT RIGHTS.

3. Metabolix shall reimburse M.I.T. for all of its out-of-pocket costs incurred
for filing and prosecution of these PATENT RIGHTS.

4. After execution of this Amendment, Metabolix shall assume responsibility for
prosecution of M.I.T. Case 6726, at its own expense, keeping M.I.T. informed of
its actions. M.I.T. agrees that Metabolix may abandon all or a portion of the
PATENT RIGHTS at Metabolix's own discretion.

Agreed to for:

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

By: /s/Lita L. Nelson
    ----------------------------------------
Name: Lita L. Nelson
Title: Director, Technology Licensing Office
Date: March 31, 1995

METABOLIX, INC.

By: /s/ Edward M. Muller
    ----------------------------------------
Name: Edward M. Muller
Title: President
Date: March 14, 1993

*    CONFIDENTIAL TREATMENT REQUESTED

                                       23

<Page>

                                 THIRD AMENDMENT

This Amendment with the effective date of March 6, 1995 is to the License
Agreement dated July 15, 1993 between MASSACHUSETTS INSTITUTE OF TECHNOLOGY and
METABOLIX, INC.

The parties thereto now further agree as follows:

1. The PATENT RIGHTS of M.I.T. Case 6867 Polyhydroxyalkanoates of Higher
Molecular Weight and Control of the Molecular Weight of Polyhydroxyalkanoates by
Modulation of Polyhydroxyalkanoate Synthase by Chokyun Rha, Anthony J. Sinskey,
and K.D. Snell shall be added to the PATENT RIGHTS of the License Agreement
under all the terms and conditions of the License Agreement.

2. Metabolix shall reimburse M.I.T. for all costs incurred in the filing,
prosecution and maintenance of the PATENT RIGHTS of this case. M.I.T. shall
consult with Metabolix on foreign filing of the PATENT RIGHTS of this case and
shall file and prosecute foreign patents only upon Matabolix's request.

4. Metabolix shall pay to M.I.T. a license issue fee of * for Case 6867. No
additional license maintenance fees or royalties shall be due other than those
specified in the License Agreement.

Agreed to for:

MASSACHUSETTS INSTITUTE OF TECHNOLOGY

By: /s/Lita L. Nelson
    ----------------------------------------
Name: Lita L. Nelson
Title: Director, Technology Licensing Office
Date: March 31, 1995

METABOLIX, INC.

By: /s/ Edward M. Muller
    ----------------------------------------
Name: Edward M. Muller
Title: President
Date: March 14, 1993

*    CONFIDENTIAL TREATMENT REQUESTED

                                       24

<Page>

                                FOURTH AMENDMENT

     This Fourth Amendment, effective as of the date set forth above the
signatures of the patties below, amends the License Agreement dated July 15,
1993, as amended ("7/15/93 LICENSE AGREEMENT") between the Massachusetts
Institute of Technology ("M.I.T.") and Metabolix, Inc. ("LICENSEE").

     WHEREAS, LICENSEE and M.I.T. wish to modify the provisions of the 7/15/93
LICENSE AGREEMENT.

     NOW, THEREFORE, in consideration of the premises and mutual covenants
contained herein, the parties hereby agree to modify the 7/15/93 LICENSE
AGREEMENT as follows:

     1. Section 2.6 shall be deleted and replaced with the following:

     LICENSEE shall have the right to enter into sublicensing agreements for the
rights, privileges and licenses granted hereunder. In addition, LICENSEE may
grant any sublicensee the right to sublicense to third parties any or all of the
rights, privileges and licenses granted to such sublicensee and such third party
sublicenses may also include the right to sublicense.

     Upon any termination of this Agreement, the rights of all sublicensees
shall also terminate, subject to Paragraph 13.6 hereof.

     2. Section 13.6 shall be deleted and replaced with the following:

     Upon termination of this Agreement for any reason, any of LICENSEE's direct
sublicensees that are not then in default shall have the right to seek a license
from M.I.T. M.I.T. agrees to negotiate such licenses in good faith under
reasonable terms and conditions. Notwithstanding the foregoing, should Tepha,
Inc. request a license, M.I.T. hereby agrees to grant such a license under terms
and conditions no less favorable as a whole than those granted to Tepha, Inc. by
LICENSEE.

     3. The final paragraph of Section 4.1(d) shall be deleted and replaced with
the following:

     The royalties due under this Section 4.1(d) shall apply to revenue received
by LICENSEE from any and all sublicenses, regardless of whether the sublicense
is granted by LICENSEE, or by any sublicensee or any of their sublicensees. In
no case shall the revenue paid to M.I.T. for each sublicense be less than * of
the sales value of the LICENSED PRODUCTS made, used or sold by that sublicensee.

*    CONFIDENTIAL TREATMENT REQUESTED

                                       25

<Page>

     IN WITNESS WHEREOF, the parties have caused this Agreement to be executed
under seal by their duly authorized representatives.

THE EFFECTIVE DATE OF THIS FOURTH AMENDMENT IS SEPTEMBER 29, 2002.

MASSACHUSETTS INSTITUTE OF TECHNOLOGY   METABOLIX, INC.

By: /s/Lita L. Nelson                   By: /s/James J. Barber
    ---------------------------------       ------------------------------------
Name: Lita L. Nelson                    Name: James J. Barber
Title: Director, Technology Licensing   Title: President
       Office

*    CONFIDENTIAL TREATMENT REQUESTED

                                       26

<Page>

                                 FIFTH AMENDMENT

     This Fifth Amendment, effective as of July 6, 2005, pertains to the
Exclusive Patent License Agreement, effective on July 15, 1993, by and between
the Massachusetts Institute of Technology ("M.I.T.") and Metabolix, Inc.
("COMPANY").

     WHEREAS, COMPANY now wishes the License Agreement to include only M.I.T.
case numbers 4403 ("Genes Encoding B-Ketothiolase And Acetoacetyl-Coa
Reductase,") and 6867 ("Polyhydroxyalkanoates Of Higher Molecular Weight And
Control Of The Molecular Weight Of Polyhydroxyalkanoates By Modulation Of
Polyhydroxyalkanoate Synthase Activity");

     WHEREAS, COMPANY therefore wishes to remove from the License Agreement
M.I.T case numbers 6113, "Polymerase Technology For The Production Of Long Chain
And Short Chain Polyesters" and 6726, "Overexpression And Purification Of The
Soluble Polyhydroxyalkanoate Synthase From Alcaligenes Eutrophus Evidence For A
Required Post-Translational Modification For Catalytic Activity";

     NOW, THEREFORE, M.I.T. and COMPANY hereby agree to modify the Exclusive
Patent License Agreement as follows:

     M.I.T. case numbers 6113 and 6726 are removed from the Agreement, and
     COMPANY is not responsible for costs incurred on these cases after July 6,
     2005.

All other terms and conditions of the Exclusive Patent License Agreement shall
remain unchanged.

THE AMENDMENT EFFECTIVE DATE IS JULY 6, 2005.

Agreed to for:

MASSACHUSETTS INSTITUTE OF TECHNOLOGY   METABOLIX, INC.

By: /s/Lita L. Nelson                   By: /s/James J. Barber
    ---------------------------------       ------------------------------------
Name: Lita L. Nelson                    Name: James J. Barber
Title: Director, Technology Licensing   Title: President
       Office

*    CONFIDENTIAL TREATMENT REQUESTED

                                       27

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