Exhibit
10.12  AMENDED AND
RESTATED EMPLOYMENT AGREEMENT  THIS AMENDED AND
RESTATED EMPLOYMENT AGREEMENT dated as of January 3, 2008 (the Agreement)
is by and between Sirtris Pharmaceuticals, Inc. (the Company), a Delaware
corporation with its principal place of business at 200 Technology Square,
Cambridge, Massachusetts, and Peter Elliott (the Executive).  WHEREAS, the
Company and the Executive are parties to a certain Employment Agreement dated August 16,
2005 (the Previous Agreement) pursuant to which the Executive has been
serving the Company as its Senior Vice President, Head of Development; and  WHEREAS, the
Company and the Executive desire to make certain changes to the terms and
conditions of the Executives employment;  NOW, THEREFORE, in
consideration of the mutual covenants and promises contained herein and other
good and valuable consideration, the receipt and sufficiency of which are
hereby acknowledged, the Company offers and the Executive accepts employment
upon the following amended and restated terms and conditions:  1.Position and Duties.  (a)The Company.Upon the terms and subject to the
conditions set forth in this Agreement, the Company hereby offers and the
Executive hereby accepts employment with the Company to serve as its Senior
Vice President, Head of Development, subject to the direction and control of
the Chief Executive Officer of the Company. 
Subject to the discretion of the Chief Executive Officer, the Executives
duties will include oversight of the non-clinical and clinical development
activities of the Company.  The Executive
agrees to perform the duties of his position and such other duties as
reasonably may be assigned to him from time to time. The Executive also agrees
that while employed by the Company, he will devote one hundred percent (100%)
of his business time and his reasonable commercial efforts, business judgment,
skill and knowledge exclusively to the advancement of the business and
interests of the Company and to the discharge of his duties and responsibilities
for it.  The Executive may, however, (i) serve
as an officer, director, trustee or committee member of any religious,
professional, civic, charitable or educational organization, (ii) with the
prior approval of the Chief Executive Officer of the Company, serve as a
director of up to one corporation whose businesses are not competitive with the
Company, and (iii) engage in, and devote time and effort to, any and all
personal investments (which shall in no event include being an officer or
principal shareholder of any public or private company) unrelated to the
business or affairs of the Company, in each case so long as such activities do
not require more than ten (10) hours per week of the Executives time or
otherwise interfere with the Executives obligations to the Company hereunder
or compete or conflict in any way with the business of the Company. During the
Executives employment with the Company, the Executive may provide consulting
services to other Persons only with the prior approval of the Chief Executive
Officer and the Board.


2.              Compensation
and Benefits.  During the
Executives employment, as compensation for all services performed by the
Executive for the Company and subject to his performance of his duties and
responsibilities for the Company, pursuant to this Agreement or otherwise, the
Company will provide the Executive the following pay and benefits:  (a)Base Salary.From
the period of the date hereof until December 31, 2008, the Company will
pay the Executive a base salary at the rate of Three Hundred Twenty Two
Thousand Five Hundred Dollars ($322,500) per year.  Such amount shall be payable in accordance
with the regular payroll practices of the Company for its executives, as in
effect from time to time, and subject to increase from time to time by the
Board in its discretion.  (b)Bonus Compensation.  The
Executive shall be considered annually by the Board for a bonus with a target
of 35% of the Base Salary earned, which percentage shall be subject to
adjustment from time to time by the Board in its discretion.  The amount of the bonus shall be determined by
the Board, based on its assessment, in its discretion, of the Executives
performance and that of the Company against appropriate goals established
annually by the Company after consultation with the Executive.Any bonus due to the
Executive hereunder will be payable not later than two and one-half months
following the close of the Companys fiscal year or the close of the calendar
year, if later, in which occurs the later of the two following dates:  (i) the date on which the Executive
first has a legally binding right (whether or not vested) to the bonus; and (ii) if
the Executives right to the bonus is subject to one or more vesting
conditions, the first date on which the Executives right to the bonus is no
longer subject to any substantial risk of forfeiture.  The foregoing rules shall be construed
and applied to ensure that any bonus payable to the Executive qualifies as a short-term
deferral under Section 409A of the Internal Revenue Code, as amended
(including the regulations thereunder, Section 409A).  Without limiting the generality of the
foregoing, for purposes of these rules the terms legally binding right
and substantial risk of forfeiture shall have the meaning assigned to them
under Treas. Regs. § 1.409A-1(b)(1) and § 1.409A-1(d),
respectively.  (c)Stock Options.The Company previously granted to the Executive
on September 20, 2005 an option to purchase 1,250,000 shares of the common
stock of the Company at $0.08 per share (the Employment Option). The Employment
Option shall continue to vest on the schedule set forth in the Previous
Agreement, restated here as follows: twenty-five percent (25%) of the shares
subject to the Employment Option vested on September 20, 2006 and the
remainder of the shares subject to the Employment Option shall vest ratably, on
a quarterly basis, on the last date of each of the next twelve (12) quarters
thereafter, provided that the Executive remains in the Companys employ at each
such vesting date.  The Employment Option and all other options and
restricted stock granted the Executive by the Company shall be subject to any
applicable stock option plan, stock certificate and shareholder and/or option
holder and restricted stock agreements and other restrictions and limitations
generally applicable to equity held by Company executives or otherwise required
by law.  The Executive shall not be
eligible to receive any stock options, restricted stock or other equity of the
Company, however, whether under an equity incentive plan or otherwise, except   2


as expressly provided in
this Agreement or as otherwise expressly authorized for him individually by the
Board. Further, prior to issuing the Employment Option or Performance Option or
any other stock options to the Executive, the Company may require that the
Executive provide such representations regarding the Executives sophistication
and investment intent and other such matters as the Company may reasonably
request.  (d)Participation in Employee Benefit
Plans.  The Executive will be entitled to participate
in all Employee Benefit Plans from time to time in effect for employees of the
Company generally, except to the extent such plans are duplicative of benefits
otherwise provided the Executive under this Agreement (e.g.,
severance pay) or under any other agreement. 
The Executive participation will be subject to the terms of the
applicable plan documents and generally applicable Company policies.  The Company may alter, modify, add to or
delete its Employee Benefit Plans at any time as it, in its sole judgment,
determines to be appropriate, without recourse by the Executive. For purposes
of this Agreement, Employee Benefit Plan shall have the meaning ascribed to
such term in Section 3(3) of ERISA, as amended from time to time.  (e)Vacations.The
Executive will accrue three weeks paid vacation per year (or such greater
amount as is generally made available to the Companys executive officers) in
accordance with the Companys policies from time to time in effectand receive
paid holidays (currently 11 per year) in accordance with the Company holiday
schedule.  Vacation may be taken at such times and
intervals as the Executive shall determine, subject to the business needs of
the Company, and otherwise shall be subject to the policies of the Company, as
in effect from time to time.  (f)Business Expenses.The Company will pay or reimburse the Executive for all reasonable business
expenses incurred or paid by the Executive in the performance of his duties and
responsibilities for the Company, subject to any maximum annual limit and other
restrictions on such expenses set by the Company and to such reasonable
substantiation and documentation as it may specify from time to time.  Any such reimbursement that would constitute
nonqualified deferred compensation subject to Section 409A shall be
subject to the following additional rules: 
(i) no reimbursement of any such expense shall affect the Executives
right to reimbursement of any other such expense in any other taxable year; (ii) reimbursement
of the expense shall be made, if at all, not later than the end of the calendar
year following the calendar year in which the expense was incurred; and (iii) the
right to reimbursement shall not be subject to liquidation or exchange for any
other benefit.  3.Confidential Information, Non-Competition
and Proprietary Information.The
Executive previously executed the Companys Confidentiality, Non-Competition
and Proprietary Information Agreement.  
It is understood and agreed that breach by the Executive of the
Confidential Information, Non-Competition and Proprietary Information Agreement
shall constitute a material breach of this Agreement.  4.             Termination
of Employment.   The Executives
employment under this Agreement shall continue until terminated pursuant to
this Section 4.  3


(a)The Company may terminate the Executives
employment for Cause upon written notice to the Executive setting forth in
reasonable detail the nature of the Cause. 
The following, as determined by the Board in its reasonable judgment,
shall constitute Cause for termination:  (i) the
Executives willful failure to perform, or gross negligence in the performance
of, his material duties and responsibilities to the Company and its Affiliates
which is not remedied within thirty (30) days of written notice thereof; (ii) material
breach by the Executive of any material provision of this Agreement or any
other agreement with the Company or any of its Affiliates which is not remedied
within thirty (30) days of written notice thereof; (iii) fraud,
embezzlement or other dishonesty with respect to the Company and any of its Affiliates,
taken as a whole, which, in the case of such other dishonesty, causes or could
reasonably be expected to cause material harm to the Company and any of its
Affiliates, taken as a whole; or (iv) the Executives conviction of a
felony.  (b)The Company may terminate the Executives
employment at any time other than for Cause upon written notice to the
Executive.  (c)The Executive may terminate his
employment hereunder for Good Reason by providing notice to the Company of the
condition giving rise to the Good Reason no later than thirty (30) days
following the occurrence of the condition, by giving the Company thirty (30)
days to remedy the condition and by terminating employment for Good Reason
within thirty (30) days thereafter if the Company fails to remedy the
condition.   For purposes of this
Agreement, Good Reason shall mean, without the Executives consent, the
occurrence of any one or more of the following events: (i) material
diminution in the nature or scope of the Executives responsibilities, duties
or authority, provided that in the absence of a Change of Control none of the
following shall constitute Good Reason: (x) the Companys failure to
continue the Executive appointment or election as a director or officer of any
of its Affiliates; (y) any diminution in the nature or scope of the
Executives responsibilities, duties or authority that is reasonably related to
a diminution of the business of the Company or any of its Affiliates shall
constitute Good Reason; or (z) the hiring of a head of Research and
Development for the Company other than the Executive and any resultant change
in his responsibilities, duties or authority reasonably related to such hire; (ii) a
reduction in the Executives base salary other than one temporary reduction of
not more than 120 days and not in excess of 20% of the Executives base salary
in connection with and in proportion to a general reduction of the base
salaries of the Companys executive officers; (iii) failure of the Company
to provide the Executive the salary or benefits in accordance with Section 2
hereof after thirty (30) days notice during which the Company does not cure
such failure or (iv) relocation of the Executives office more than
thirty-five (35) miles from the location of the Companys principal offices as
of January 1, 2008.  (d)The Executive may terminate his
employment with the Company other than for Good Reason at any time upon one
months notice to the Company.  (e)This Agreement shall automatically
terminate in the event of the Executives death during employment.  The Company may terminate the Executives
employment, upon notice to the Executive, in the event the Executive becomes
disabled during employment and, as a result, is unable to continue to perform
substantially all of his material   4


duties and
responsibilities under this Agreement for one-hundred and twenty (120) days
during any period of three hundred and sixty-five (365) consecutive calendar
days.  If any question shall arise as to
whether the Executive is disabled to the extent that the Executive is unable to
perform substantially all of his material duties and responsibilities for the
Company and its Affiliates, the Executive shall, at the Companys request and
expense, submit to a medical examination by a physician selected by the Company
to whom the Executive or the Executives guardian, if any, has no reasonable
objection to determine whether the Executive is so disabled and such
determination shall for the purposes of this Agreement be conclusive of the
issue.  If such a question arises and the
Executive fails to submit to the requested medical examination, the Companys
determination of the issue shall be binding on the Executive.  5.             Severance Payments and Other Matters Related to
Termination.  (a)Termination pursuant to Section 4(b),
4(c) or 4(e).Except as provided in Section 5(c) below,  (i) in
the event of termination of the Executives employment by the Company other
than for Cause pursuant to Section 4(a) of this Agreement or in the
event of termination of the Executives employment by the Executive for Good
Reason pursuant to Section 4(c) of this Agreement, (a) all
unvested options and restricted stock which, by their terms, vest only based on
the passage of time (disregarding any acceleration of the vesting of such
options based on individual or Company performance) shall vest as of the date
of termination (notwithstanding anything to the contrary in Section 2(c) of
this Agreement) with respect to an additional one year of vesting (except that
with respect to restricted stock, a minimum of 25% of such unvested shares
shall vest); and (b) the Company will continue to pay the Executives base
salary, at the rate in effect on the date of termination, for a period of
twelve (12) months from the date of termination and pay a pro-rata portion (for
the period from January 1 of the year of termination through the date of
termination) of the target cash bonus for the year in which the Executive is
terminated; or  (ii) in the event of the Executives termination
of employment as a result of the Executives death or disability at any time
pursuant to Section 4(e) of the Agreement, (a) all unvested
options and restricted stock which, by their terms, vest only based on the
passage of time (disregarding any acceleration of the vesting of such options
based on individual or Company performance) shall vest as of the date of
termination (notwithstanding anything to the contrary in Section 2(c) of
this Agreement) with respect to an additional one year of vesting (except that
with respect to restricted stock, a minimum of 25% of such unvested shares
shall vest); (b) to the extent the Companys benefits do not include
disability insurance benefits that will continue the Executives base salary at
100% of the amount of such base salary for the period of twelve (12) months
from the date of termination, the Company shall pay such amount at the time
that the Executives base salary would be otherwise paid as shall equal the
amount by which 100% of the Executives base salary exceeds the disability
insurance benefits, if any, actually paid to him; and (c) the Company
shall pay him a pro-rata portion (for the period from January 1 of the
year of termination through the date of termination) of the target cash bonus
for the year in which the Executive is terminated.   5


If the Executive is
participating in the Companys group health plan and/or dental plan at the time
the Executives employment terminates (whether such termination is as described
in (i) or (ii) above), and the Executive exercises his right to
continue participation in those plans under the federal law known as COBRA, or
any successor law, the Company will pay or, at its option, reimburse the
Executive, for the full premium cost of that participation for twelve (12) months
following the date on which the Executives employment with the Company
terminates or, if earlier, until the date the Executive becomes eligible to
enroll in the health (or, if applicable, dental) plan of a new employer.  The Company will also pay the Executive on
the date of termination any base salary earned but not paid through the date of
termination and pay for any vacation time accrued but not used to that
date.  In addition, the Company will pay
the Executive any bonus which has been awarded to the Executive, but not yet
paid on the date of termination of his employment.  Subject to the Companys discretion, the
portion of any of the Executives base salary to be paid pursuant to i(b) and
ii(b) above that does not constitute nonqualified deferred compensation
within the meaning of Section 409A, will either be paid in a lump sum or
in accordance with normal payroll practices. Any portion of any of the Executives
base salary to be paid pursuant to i(b) and ii(b) above that
constitutes nonqualified deferred compensation within the meaning of Section 409A
shall be paid in a lump sum.  Any obligation of
the Company to provide the Executive severance payments or other benefits under
this Section 5(a) is conditioned on the Executive signing an
effective release of claims in the form provided by the Company (the Employee
Release) following the termination of the Executives employment, which
release shall not apply to (i) claims for indemnification in the Executives
capacity as an officer or director of the Company under the Companys
Certificate of Incorporation, By-laws or agreement, if any, providing for
director or officer indemnification, (ii) rights to receive insurance
payments under any policy maintained by the Company and (iii) rights to
receive retirement benefits that are accrued and fully vested at the time of the
Executives termination.  Any severance
payments to be made in the form of salary continuation pursuant to the terms of
this Agreement shall be payable in accordance with the normal payroll practices
of the Company, and will begin at the Companys next regular payroll period
following the effective date of the Employee Release, but shall be retroactive
to the date of termination. The Executive agrees to provide the Company prompt
notice of the Executives eligibility to participate in the health plan and, if
applicable, dental plan of any employer. 
The Executive further agrees to repay any overpayment of health benefit
premiums made by the Company hereunder.  (b)Termination other than pursuant to Section 4(b),
4(c) or 4(e).In the event of any termination of the
Executives employment, other than a termination by the Company pursuant to Section 4(b) of
this Agreement, a termination by the Executive for Good Reason pursuant to Section 4(c) of
this Agreement or a termination as a result of the Executives death or
disability pursuant to Section 4(e) of this Agreement, the Company
will pay the Executive any base salary earned but not paid through the date of
termination and pay for any vacation time accrued but not used to that
date.  In addition, the Company will pay the
Executive any bonus which has been awarded to the Executive, but not yet paid
on the date of termination of the  6


Executives
employment. The Company shall have no other obligation to the Executive under
this Agreement.  (c)Upon a Change of Control.  (i)If a Change of Control (as defined in Section 6
hereof) occurs, twenty-five percent (25%) of the Executives stock options and
restricted stock which, by their terms, vest only based on the passage of time (disregarding
any acceleration of the vesting of such options based on individual or Company
performance) shall vest as of the date of such Change of Control, provided that
no more than one hundred-percent (100%) of the total shares may vest at any
time. If, within one year following such Change of Control or otherwise in
connection with such Change of Control, the Company or any successor thereto
terminates the Executives employment other than for Cause, or the Executive
terminates his employment for Good Reason, then, in lieu of any payments to the
Executive or on the Executives behalf under Section 5(a) hereof, (i) all
of the Executives then remaining unvested options and restricted stock which,
by their terms, vest only based on the passage of time (disregarding any
acceleration of the vesting of such options based on individual or Company
performance) shall automatically vest as of the date of termination
(notwithstanding anything to the contrary in Section 2(c) of this
Agreement) and (ii) the Company shall pay, within thirty (30) days of such
termination, (x) a lump sum payment equal to the Executives then-current
annual base salary for a period of twelve (12) months; and (y) pay a
pro-rata portion (for the period from January 1 of the year of termination
through the date of termination) of the target cash bonus for the year in which
the Executive is terminated; and,  (ii)The Company and the Executive agree that
in the event it shall be determined that any of the payments or benefits
received or to be received by the Executive in connection with a Change of
Control or the Executives termination from employment would be subject to the
excise tax imposed by Section 4999 of the Code, together with any interest
or penalties imposed with respect to such excise tax (the Excise Tax), then the
Executive shall be entitled to promptly receive from the Company an additional
lump sum cash payment (the Gross-Up Payment) in an amount such that, after
payment by the Executive of all taxes related to such payments and benefits,
including any income taxes and the Excise Tax imposed upon the Gross-Up
Payment, the Executive retains an amount of the Gross-Up Payment equal to the
Excise Tax imposed upon such payments and benefits.  (d)Except for any right the Executive may
have under applicable law to continue participation in the Companys group
health and dental plans under COBRA, or any successor law, benefits shall
terminate in accordance with the terms of the applicable benefit plans based on
the date of termination of the Executives employment, without regard to any
continuation of base salary or other payment to the Executive following
termination.  (e)Provisions of this Agreement shall
survive any termination if so provided in this Agreement or if necessary or
desirable to accomplish the purposes of other surviving   7


provisions, including
without limitation the Executives obligations under Section 3 of this
Agreement and under the Confidentiality, Non-Competition and Proprietary
Information Agreement.  The obligation of
the Company to make payments to the Executive or on the Executives behalf
under Section 5 of this Agreement is expressly conditioned upon the
Executives continued full performance of the Executives obligations under Section 3
hereof, under the Confidentiality, Non-Competition and Proprietary Information
Agreement, and under any subsequent agreement between the Executive and the
Company or any of its Affiliates relating to confidentiality, non-competition,
proprietary information or the like.  6.             Definitions.For purposes of this Agreement,
the following definitions apply:  Affiliates means all
persons and entities directly or indirectly controlling, controlled by or under
common control with the Company, where control may be by management authority,
equity interest or otherwise.  Change of Control shall
mean (i) the acquisition of beneficial ownership (as defined in Rule 13d-3
under the Exchange Act) directly or indirectly by any person (as such term is
used in Sections 13(d) and 14(d) of the Exchange Act), of securities
of the Company representing a majority or more of the combined voting power of
the Companys then outstanding securities, other than an acquisition of
securities for investment purposes pursuant to a bona fide financing of the
Company; (ii) a merger or consolidation of the Company with any other
corporation in which the holders of the voting securities of the Company prior
to the merger or consolidation do not own more than 50% of the total voting
securities of the surviving corporation; or (iii) the sale or disposition
by the Company of all or substantially all of the Companys assets other than a
sale or disposition of assets to an Affiliate of the Company or a holder of
securities of the Company.  Person means an
individual, a corporation, an association, a partnership, an estate, a trust
and any other entity or organization, other than the Company or any of its
Affiliates.  7.             Conflicting Agreements.
The Executive hereby represents and warrants that his signing of this Agreement
and the performance of his obligations under it will not breach or be in
conflict with any other agreement to which the Executive is a party or is bound
and that the Executive is not now subject to any covenants against competition
or similar covenants or any court order that could affect the performance of the
Executives obligations under this Agreement. 
The Executive agrees that he will not disclose to or use on behalf of
the Company any proprietary information of a third party without that partys
consent.  8.             Withholding; Other Tax
Matters.  Anything to the
contrary notwithstanding, (a) all payments required to be made by the
Company hereunder to Executive shall be subject to the withholding of such
amounts, if any, relating to tax and other payroll deductions as the Company
may reasonably determine it should withhold pursuant to any applicable law or
regulation, and (b) to the extent any payment hereunder shall be required
to be delayed until six months   8


following separation from
service to comply with the specified employee rules of Section 409A
it shall be so delayed (but not more than is required to comply with such
rules).  9.             Assignment.  Neither the Executive nor the Company may
make any assignment of this Agreement or any interest in it, by operation of
law or otherwise, without the prior written consent of the other; provided,
however, that the Company may assign its rights and obligations under this
Agreement without the Executives consent to one of its Affiliates or to any
Person with whom the Company shall hereafter affect a reorganization,
consolidate with, or merge into or to whom it transfers all or substantially
all of its properties or assets.  This
Agreement shall inure to the benefit of and be binding upon the Executive and
the Company, and each of our respective successors, executors, administrators,
heirs and permitted assigns.  10.           Severability.  If any portion or provision of this Agreement
shall to any extent be declared illegal or unenforceable by a court of
competent jurisdiction, then the remainder of this Agreement, or the
application of such portion or provision in circumstances other than those as
to which it is so declared illegal or unenforceable, shall not be affected
thereby, and each portion and provision of this Agreement shall be valid and
enforceable to the fullest extent permitted by law.  11.Miscellaneous.  This Agreement, together with the
Confidentiality, Non-Competition and Proprietary Information Agreement, sets
forth the entire agreement between the Executive and the Company and replaces
all prior communications, agreements and understandings, written or oral, with
respect to the terms and conditions of the Executives employment.  This Agreement may not be modified or amended,
and no breach shall be deemed to be waived, unless agreed to in writing by the
Executive and an expressly authorized representative of the Board.  The headings and captions in this Agreement
are for convenience only and in no way define or describe the scope or content
of any provision of this Agreement.  This
Agreement may be executed in two or more counterparts, each of which shall be
an original and all of which together shall constitute one and the same instrument.
This is a Massachusetts contract and shall be governed and construed in
accordance with the laws of the Commonwealth of Massachusetts, without regard
to the conflict-of-laws principles thereof.  12.           Notices.  Any notices provided for in this Agreement
shall be in writing and shall be effective when delivered in person, consigned
to a reputable national courier service for overnight delivery or deposited in
the United States mail, postage prepaid, and addressed to the Executive at the
Executives last known address on the books of the Company or, in the case of
the Company, to it by notice to the Chairman of the Board of Directors, c/o
Sirtris Pharmaceuticals, Inc. at its principal place of business, or to
such other address(es) as either party may specify by notice to the other
actually received.  [Remainder of page intentionally
left blank.]   9


IN WITNESS WHEREOF, this Agreement has been executed as a
sealed instrument by the Company, by its duly authorized representative, and by
the Executive, as of the date first above written.  THE EXECUTIVE
  
  THE COMPANY/s/ Peter Elliott
  
  By:
  /s/ Christoph
  WestphalPeter ElliottTitle:
      Chief Executive Officer
   10