Exhibit 10.11.1    December 17,
2008  Dr. Oliver
Peoples c/o Metabolix, Inc. 21 Erie Street Cambridge,
MA 02139  Re:  First Amendment to Employment Agreement  Dear
Oliver:  This letter amends the terms of the Employment Letter
Agreement (the Agreement) dated as of July 20, 2006 by and between
Metabolix, Inc. (the Company) and you as set forth below.  Capitalized terms not defined herein shall
have the meaning specified in the Agreement.  1.Section 3(a) of
the Agreement is hereby amended by inserting the following immediately prior to
the period at the end of the first sentence thereof:  payable on a
semi-monthly basis in accordance with the Companys normal payroll practices  2.Section 4(a) of
the Agreement is hereby amended by inserting the following immediately before
the period at the end of the last sentence thereof:  but in no event more
than 45 days after the date on which your employment terminates  3.Section 4(b) of
the Agreement is hereby amended by adding the following immediately prior to
the comma after the phrase release of claims against the Company within the
first sentence thereof:  that is fully effective,
within thirty (30) days after the date of termination  4.Section 4(b) of
the Agreement is hereby amended by deleting subsections (A) and (B) thereof
and substituting the following therefor:  on the 37th day after the date on which your employment
terminates (provided the release referred to above is effective prior to such
date)  5.Section 4(c)(i) of
the Agreement is hereby amended by adding the following immediately prior to
the comma after the phrase release of claims against the Company within the
first sentence thereof:  Metabolix |21
Erie Street | Cambridge | MA | 02139 | USA tel: 617 583 1700 | fax: 617 583
1767 | www.metabolix.com


that is fully effective
within thirty (30) days after the date of termination  6.Section 4(c)(i)(A) of
the Agreement is hereby amended by deleting subsections (x) and (y) thereof
and substituting the following therefor:  in accordance with Section 4(b),
above.  7.Section 4(c)(ii) of
the Agreement is hereby amended by adding the following sentence at the end
thereof:  In the event that such
payments are required to be reduced hereunder, such payments shall be reduced
in the following order:  (1) cash
payments not subject to Section 409A of the Code; (2) cash payments
subject to Section 409A of the Code; (3) equity-based payments and
acceleration; and (4) non-cash forms of benefits, and to the extent any
payment is to be made over time (e.g., in installments, etc.), then the
payments shall be reduced in reverse chronological order.  8.Section 4(f) of
the Agreement is hereby amended by deleting said section in its entirety and
substituting the following therefor:  (f)Good
Reason shall mean that you have complied with the Good Reason Process
(hereinafter defined) following the occurrence of any of the following
events:  (i) a material diminution
in your responsibilities, authority or duties; (ii) a material diminution
in your Base Salary; (iii) a material change in the geographic location at
which you provide services to the Company; or (iv) the material breach of
this Agreement by the Company.  Good
Reason Process shall mean that (i) you reasonably determine in good faith
that a Good Reason condition has occurred; (ii) you notify the Company
in writing of the occurrence of the Good Reason condition within 60 days of the
occurrence of such condition; (iii) you cooperate in good faith with the
Companys efforts, for a period not less than 30 days following such notice
(the Cure Period), to remedy the condition; (iv) notwithstanding such
efforts, the Good Reason condition continues to exist; and (v) you
terminate your employment within 60 days after the end of the Cure Period.  If the Company cures the Good Reason condition
during the Cure Period, Good Reason shall be deemed not to have occurred.  9.Section 8(e) of
the Agreement is hereby amended by deleting the first sentence thereof and
substituting the following therefore:  2


The Company shall cause
its rights and obligations hereunder to be assumed by any person or entity that
succeeds to all or substantially all of the Companys business or that aspect
of the Companys business in which you are principally involved and may assign
its rights and obligations hereunder to any Company Affiliate.  10.Section 8(k) of
the Agreement is hereby amended by inserting the following after the word Agreement
and prior to the word comply within the second sentence thereof:  be exempt from, or  11.The
Agreement is hereby amended by inserting the following as a new section 8(l) and
renumbering the remaining sections of the Agreement accordingly:  (l)Section 409A.  (i)Notwithstanding
anything in this Agreement to the contrary:  (1)to
the extent that any payment or benefit described in this Agreement constitutes non-qualified
deferred compensation under Section 409A of the Code, and to the extent
that such payment or benefit is payable upon the termination of your
employment, then such payments or benefits shall only be payable upon your Separation
from Service.  The term Separation from
Service shall mean your separation from service from the Company, an
affiliate of the Company or a successor entity within the meaning set forth in Section 409A(a)(2)(A)(i) of
the Code, determined in accordance with the presumptions set forth in Treasury
Regulation Section 1.409A-1(h); and  (2)if
at the time of your separation from service, the Company determines that the
you are a specified employee within the meaning of Section 409A(a)(2)(B)(i) of
the Code, then to the extent any payment or benefit that you become entitled to
under this Agreement on account of your separation from service would be
considered deferred compensation subject to the 20 percent additional tax
imposed pursuant to Section 409A(a) of the Code as a result of the
application of Section 409A(a)(2)(B)(i) of the Code, such payment
shall not be payable and such benefit shall not be provided until the date that
is the earlier of (A) six months and one day after your separation from
service, or (B) your death.  If any
such delayed cash payment is otherwise payable on an installment basis, the
first payment shall  3


include a catch-up
payment covering amounts that would otherwise have been paid during the
six-month period but for the application of this provision, and the balance of
the installments shall be payable in accordance with their original schedule.  (ii)Solely
for purposes of Section 409A of the Code, any installment payments made
hereunder shall be considered separate payments.  12.Except
as amended herein, the Agreement is hereby confirmed in all other respects and
nothing contained herein shall be deemed a waiver of any right or abrogation of
any obligation otherwise existing under the Agreement except to the extent
specifically provided for herein.   Please indicate your acceptance of this amendment to
the Agreement by signing the enclosed copy of this letter and returning it to
me.   METABOLIX, INC.By:
  /s/ Richard P. EnoRichard P. EnoPresident & CEO   Accepted and agreed:/s/ Oliver P. PeoplesOliver P. PeoplesDate:
  12/19/2008  4