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                                                                   Exhibit 10.5

                               ACTIVBIOTICS, INC.

                           2006 EQUITY INCENTIVE PLAN

1.   PURPOSE

     This Plan is intended to encourage ownership of Common Stock by employees,
consultants and directors of the Company and its Affiliates and to provide
additional incentive for them to promote the success of the Company's business.
The Plan is intended to be an incentive stock option plan within the meaning of
Section 422 of the Code but not all Awards granted hereunder are required to be
Incentive Options.

2.   DEFINITIONS

     As used in the Plan the following terms shall have the respective meanings
set out below, unless the context clearly requires otherwise:

     2.1. "Accelerate", "Accelerated", and "Acceleration", when used with
respect to an Option, means that as of the time of reference such Option will
become exercisable with respect to some or all of the shares of Common Stock for
which it was not then otherwise exercisable by its terms, and, when used with
respect to Restricted Stock or Restricted Stock Units, as the case may be, means
that the Risk of Forfeiture otherwise applicable to such Restricted Stock or
Restricted Stock Units, as the case may be, shall expire with respect to some or
all of the shares of Restricted Stock or some or all of the Restricted Stock
Units, as the case may be, then still otherwise subject to the Risk of
Forfeiture.

     2.2. "Acquiring Person" means, with respect to any Transaction or any
acquisition described in clause (ii) of the definition of Change of Control, the
surviving or acquiring person or entity in connection with such Transaction or
acquisition, as the case may be, provided that if such surviving or acquiring
person or entity is controlled, directly or indirectly, by any other person or
entity (an "Ultimate Parent Entity") that is not itself controlled by any entity
or person that is not a natural person, the term "Acquiring Person" shall mean
such Ultimate Parent Entity.

     2.3. "Affiliate" means, with respect to any person or entity, any other
person or entity controlling, controlled by or under common control with the
first person or entity.

     2.4. "Applicable Voting Control Percentage" means twenty percent (20%).

     2.5. "Award" means any grant or sale pursuant to the Plan of Options,
Restricted Stock, Restricted Stock Units or Stock Grants.

     2.6. "Award Agreement" means an agreement between the Company and the
recipient of an Award, setting forth the terms and conditions of the Award.

     2.7. "Beneficial Ownership" has the meaning ascribed to such term in Rule
13d-3, or any successor rule thereto, promulgated by the Securities and Exchange
Commission pursuant to the Exchange Act.


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     2.8. "Board" means the Company's board of directors.

     2.9. "Change of Control" means (i) the closing of any Sale of the Company
Transaction or (ii) the direct or indirect acquisition, in a single transaction
or a series of related transactions, by any person or Group (other than the
Company or a Controlled Affiliate of the Company) of Beneficial Ownership of
previously outstanding shares of capital stock of the Company if (A) immediately
after such acquisition, such person or Group, together with their respective
Affiliates, shall own or hold shares of capital stock of the Company possessing
at least the Applicable Voting Control Percentage of the total voting power of
the outstanding capital stock of the Company and (B) immediately prior to such
acquisition, such person or Group, together with their respective Affiliates,
did not own or hold shares of capital stock of the Company possessing at least
the Applicable Voting Control Percentage of the total voting power of the
outstanding capital stock of the Company. Notwithstanding anything expressed or
implied in the foregoing provisions of this definition to the contrary, any
direct or indirect acquisition referred to in clause (ii) above in this
definition shall not be treated as a Change of Control if, at any time prior to
or after such direct or indirect acquisition, a majority of the members of the
board of directors of the Company as constituted immediately prior to such
direct or indirect acquisition consent in writing to exclude such direct or
indirect acquisition from the scope of this definition.

     2.10. "Code" means the Internal Revenue Code of 1986, as amended from time
to time, or any successor statute thereto, and any regulations issued from time
to time thereunder.

     2.11. "Controlled Affiliate" means, with respect to any person or entity,
any other person or entity that is controlled by such person or entity.

     2.12. "Committee" means any committee of the Board delegated responsibility
by the Board for the administration of the Plan, as provided in Section 5 of the
Plan. For any period during which no such committee is in existence, "Committee"
shall mean the Board and all authority and responsibility assigned the Committee
under the Plan shall be exercised, if at all, by the Board.

     2.13. "Common Stock" means common stock, par value $0.01 per share, of the
Company.

     2.14. "Company" means ActivBiotics, Inc., a corporation organized under the
laws of the State of Delaware.

     2.15. "Exchange Act" means the Securities Exchange Act of 1934, as amended.

     2.16. "Grant Date" means the date as of which an Option is granted, as
determined under Section 7.1(a).

     2.17. "Group" has the meaning ascribed to such term in Section 13(d)(3) of
the Exchange Act or any successor section thereto.

     2.18. "Incentive Option" means an Option which by its terms is to be
treated as an "incentive stock option" within the meaning of Section 422 of the
Code.


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     2.19. "Market Value" means the value of a share of Common Stock on a
particular date determined by such methods or procedures as may be established
by the Committee. Unless otherwise determined by the Committee, the Market Value
of Common Stock as of any date is the closing price for the Common Stock as
reported on The NASDAQ Global Market (or on any other national securities
exchange on which the Common Stock is then listed) for that date or, if no
closing price is reported for that date, the closing price on the next preceding
date for which a closing price was reported.

     2.20. "Nonstatutory Option" means any Option that is not an Incentive
Option.

     2.21. "Option" means an option granted under the Plan to purchase shares of
Common Stock.

     2.22. "Optionee" means an employee, consultant or director of the Company
to whom an Option shall have been initially granted under the Plan.

     2.23. "Participant" means any holder of an outstanding Award under the
Plan.

     2.24. "Plan" means this 2006 Equity Incentive Plan of the Company, as
amended and in effect from time to time.

     2.25. "Restricted Stock" means a grant or sale pursuant to the Plan of
shares of Common Stock to an employee, consultant or director of the Company
subject to a Risk of Forfeiture.

     2.26. "Restricted Stock Units" means rights granted pursuant to the Plan to
receive shares of Common Stock at the close of a Restriction Period, subject to
a Risk of Forfeiture.

     2.27. "Restriction Period" means the period of time, established by the
Committee in connection with an Award of Restricted Stock or Restricted Stock
Units, during which the shares of Restricted Stock or the Restricted Stock Units
are subject to a Risk of Forfeiture described in the applicable Award Agreement.

     2.28. "Risk of Forfeiture" means a limitation on the right of a Participant
to retain an Award of Restricted Stock or Restricted Stock Units, including a
right in the Company to reacquire such Restricted Stock at less than its then
Market Value and/or the forfeiture of Restricted Stock Units held by a
Participant, arising because of the occurrence or non-occurrence of specified
events or conditions.

     2.29. "Sale of the Company Transaction" means any Transaction in which the
stockholders of the Company immediately prior to such Transaction, together with
any and all of such stockholders' Affiliates, do not own or hold, immediately
after consummation of such Transaction, shares of capital stock of the Acquiring
Person in connection with such Transaction possessing at least a majority of the
total voting power of the outstanding capital stock of such Acquiring Person.

     2.30. "Securities Act" means the Securities Act of 1933, as amended.

     2.31. "Stock Grant" means the grant pursuant to the Plan of shares of
Common Stock not subject to restrictions or other forfeiture conditions.


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     2.32. "Ten Percent Owner" means a person who owns, or is deemed within the
meaning of Section 422(b)(6) of the Code to own, stock possessing more than 10%
of the total combined voting power of all classes of stock of the Company (or
any parent or subsidiary corporations of the Company, as defined in Section
424(e) and (f), respectively, of the Code). Whether a person is a Ten Percent
Owner shall be determined with respect to each Option based on the facts
existing immediately prior to the Grant Date of such Option.

     2.33. "Transaction" means any merger or consolidation of the Company with
or into another person or entity or the sale or transfer of all or substantially
all of the assets of the Company, in each case in a single transaction or in a
series of related transactions.

3.   TERM OF THE PLAN

     Unless the Plan shall have been earlier terminated by the Board, Awards may
be granted under this Plan at any time in the period commencing upon the
effectiveness of the Plan in accordance with the provisions of Section 17 hereof
and ending immediately prior to the tenth anniversary of the adoption of the
Plan by the Board. Awards granted pursuant to the Plan within such period shall
not expire solely by reason of the termination of the Plan. Awards of Incentive
Options granted prior to stockholder approval of the Plan are hereby expressly
conditioned upon such approval, but in the event of the failure of the
stockholders to approve the Plan shall thereafter and for all purposes be deemed
to constitute Nonstatutory Options.

4.   STOCK SUBJECT TO THE PLAN

     Subject to the provisions of Section 8 of the Plan, at no time shall the
number of shares of Common Stock issued pursuant to or subject to outstanding
Awards granted under the Plan (including, without limitation, pursuant to
Incentive Options), nor the number of shares of Common Stock issued pursuant to
Incentive Options, exceed the sum of (a) 300,000 shares of Common Stock plus (b)
an additional 500,000 shares on each of January 1, 2007 and January 1, 2008, and
an additional number of shares on each January 1 thereafter (beginning with
January 1, 2009) equal to the lesser of (i) 2.5% of the fully-diluted
capitalization of the Company as of such date (including for this purpose all
outstanding options, warrants and other rights to acquire, whether directly or
indirectly, the Common Stock of the Company, whether vested or not), and (ii)
400,000 shares of Common Stock; PROVIDED, HOWEVER, that the Board may, at any
time and on any one or more occasions, take action to waive the annual increase
set forth in clause (b), in whole or in part. For purposes of applying the
foregoing limitation, (x) if any Option expires, terminates, or is cancelled for
any reason without having been exercised in full, or if any Award of Restricted
Stock or Restricted Stock Units is forfeited, the shares not purchased by the
Participant or forfeited by the Participant shall again be available for Awards
thereafter to be granted under the Plan, and (y) if any Option is exercised by
delivering previously owned shares in payment of the exercise price therefor,
only the net number of shares, that is, the number of shares issued minus the
number received by the Company in payment of the exercise price, shall be
considered to have been issued pursuant to an Award granted under the Plan.
Shares of Common Stock issued pursuant to the Plan may be either authorized but
unissued shares or shares held by the Company in its treasury.

5.   ADMINISTRATION

     The Plan shall be administered by the Committee; PROVIDED, HOWEVER, that at
any time and on any one or more occasions the Board may itself exercise any of
the powers and


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responsibilities assigned the Committee under the Plan and when so acting shall
have the benefit of all of the provisions of the Plan pertaining to the
Committee's exercise of its authorities hereunder; AND PROVIDED FURTHER that the
Committee may delegate to an executive officer or officers the authority to
grant Awards hereunder to employees who are not officers, and to consultants, in
accordance with such guidelines as the Committee shall set forth at any time or
from time to time. Subject to the provisions of the Plan, the Committee shall
have complete authority, in its discretion, to make or to select the manner of
making all determinations with respect to each Award to be granted by the
Company under the Plan in addition to any other determination allowed the
Committee under the Plan including, without limitation: (a) the employee,
consultant or director to receive the Award; (b) the form of Award; (c) whether
an Option (if granted to an employee) will be an Incentive Option or a
Nonstatutory Option; (d) the time of granting an Award; (e) the number of shares
subject to an Award; (f) the exercise price of an Option or purchase price, if
any, for shares of Restricted Stock or for a Stock Grant and the method of
payment of such exercise price or such purchase price; (g) the term of an
Option; (h) the vesting period of shares of Restricted Stock or of Restricted
Stock Units and any acceleration thereof; (i) the exercise date or dates of an
Option and any acceleration thereof; and (j) the effect of termination of any
employment, consulting or Board member relationship with the Company or any of
its Affiliates on the subsequent exercisability of an Option or on the Risk of
Forfeiture of Restricted Stock or Restricted Stock Units. In making such
determinations, the Committee may take into account the nature of the services
rendered by the respective employees, consultants and directors, their present
and potential contributions to the success of the Company and its Affiliates,
and such other factors as the Committee in its discretion shall deem relevant.
Subject to the provisions of the Plan, the Committee shall also have complete
authority to interpret the Plan, to prescribe, amend and rescind rules and
regulations relating to it, to determine the terms and provisions of the
respective Award Agreements (which need not be identical), and to make all other
determinations necessary or advisable for the administration of the Plan. The
Committee's determinations made in good faith on matters referred to in this
Plan shall be final, binding and conclusive on all persons having or claiming
any interest under the Plan or an Award made pursuant hereto.

6.   AUTHORIZATION AND ELIGIBILITY

     The Committee may grant from time to time and at any time prior to the
termination of the Plan one or more Awards, either alone or in combination with
any other Awards, to any employee of or consultant to one or more of the Company
and its Affiliates or to any non-employee member of the Board or of any board of
directors (or similar governing authority) of any Affiliate. However, only
employees of the Company, and of any parent or subsidiary corporations of the
Company, as defined in Sections 424(e) and (f), respectively, of the Code, shall
be eligible for the grant of an Incentive Option. Further, in no event shall the
number of shares of Common Stock covered by Options or other Awards granted to
any one person in any one calendar year (or portion of a year) exceed twenty
five percent (25%) of the aggregate number of shares of Common Stock subject to
the Plan.

     Each grant of an Award shall be subject to all applicable terms and
conditions of the Plan (including but not limited to any specific terms and
conditions applicable to that type of Award set out in the following Section),
and such other terms and conditions, not inconsistent with the terms of the
Plan, as the Committee may prescribe. No prospective Participant shall have any
rights with respect to an Award, unless and until such Participant has executed
an agreement evidencing the Award, delivered a fully executed copy thereof to
the Company, and otherwise complied with the applicable terms and conditions of
such Award.


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7.   SPECIFIC TERMS OF AWARDS

     7.1. Options.

          (a) Date of Grant. The granting of an Option shall take place at the
time specified in the Award Agreement. Only if expressly so provided in the
applicable Award Agreement shall the Grant Date be the date on which the Award
Agreement shall have been duly executed and delivered by the Company and the
Optionee.

          (b) Exercise Price. The price at which shares of Common Stock may be
acquired under each Incentive Option shall be not less than 100% of the Market
Value of Common Stock on the Grant Date, or not less than 110% of the Market
Value of Common Stock on the Grant Date if the Optionee is a Ten Percent Owner.
The price at which shares may be acquired under each Nonstatutory Option shall
not be so limited solely by reason of this Section.

          (c) Option Period. No Incentive Option may be exercised on or after
the tenth anniversary of the Grant Date, or on or after the fifth anniversary of
the Grant Date if the Optionee is a Ten Percent Owner. The Option period under
each Nonstatutory Option shall not be so limited solely by reason of this
Section.

          (d) Exercisability. An Option may be immediately exercisable or become
exercisable in such installments, cumulative or non-cumulative, as the Committee
may determine. In the case of an Option not otherwise immediately exercisable in
full, the Committee may Accelerate such Option in whole or in part at any time;
PROVIDED, HOWEVER, that in the case of an Incentive Option, any such
Acceleration of such Incentive Option would not cause such Incentive Option to
fail to comply with the provisions of Section 422 of the Code or the Optionee
consents to such Acceleration.

          (e) Effect of Termination of Employment, Consulting or Board Member
Relationship. Unless the Committee shall provide otherwise with respect to any
Option, if the applicable original grantee's association with the Company or any
of its Affiliates as an employee, director or consultant ends for any reason or
no reason, regardless of whether the end of such association is effected by the
Company, any such Affiliate or such original grantee (whether voluntarily or
involuntarily, including because an entity with which such original grantee has
any such association ceases to be an Affiliate of the Company), and immediately
following the end of any such association, such original grantee is not
associated with the Company or any of its Affiliates as an employee, director or
consultant, or if such original grantee dies, then any outstanding Option
initially granted to such original grantee, whether then held by the Optionee or
any other Participant, shall cease to be exercisable in any respect not later
than ninety (90) days following the end of such association or such death and,
for the period it remains exercisable following the end of such association or
such death, shall be exercisable only to the extent exercisable on the date of
the end of such association or such death. Military or sick leave or other bona
fide leave shall not be deemed a termination of employment, PROVIDED that it
does not exceed the longer of ninety (90) days or the period during which the
absent Optionee's reemployment rights, if any, are guaranteed by statute or by
contract.

          (f) Transferability. Except as otherwise provided in this subsection
(f), Options shall not be transferable, and no Option or interest therein may be
sold, transferred, pledged, assigned, or otherwise alienated or hypothecated,
other than by will or by the laws of descent and distribution (subject always to
the provisions of subsection (e) above). Except as


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otherwise provided in this subsection (f), all of a Participant's rights in any
Option may be exercised during the life of such Participant only by such
Participant or such Participant's legal representative. However, the applicable
Award Agreement or the Committee (at or after the grant of a Nonstatutory
Option) may provide that a Nonstatutory Option may be transferred by the
applicable Participant to a family member; provided, however, that any such
transfer is without payment of any consideration whatsoever and that no transfer
of a Nonstatutory Option shall be valid unless first approved by the Committee,
acting in its sole discretion, unless such transfer is permitted under the
applicable Award Agreement. For this purpose, "family member" means any child,
stepchild, grandchild, parent, stepparent, spouse, former spouse, sibling,
niece, nephew, mother-in-law, father-in-law, son-in-law, daughter-in-law,
brother-in-law, or sister-in-law, including adoptive relationships, any person
sharing the Optionee's household (other than a tenant or employee), a trust in
which the foregoing persons and/or the Optionee have more than fifty percent
(50%) of the beneficial interests, a foundation in which the foregoing persons
and/or the Optionee control the management of assets, and any other entity in
which these persons and/or the Optionee own more than fifty percent (50%) of the
voting interests. The Committee may at any time or from time to time delegate to
one or more officers of the Company the authority to permit transfers of
Nonstatutory Options to third parties pursuant to this subsection (f), which
authorization shall be exercised by such officer or officers in accordance with
guidelines established by the Committee at any time and from time to time. The
restrictions on transferability set forth in this subsection (f) shall in no way
preclude any Participant from effecting "cashless" exercises of an Option
pursuant to the terms of the Plan.

          (g) Method of Exercise. An Option may be exercised by a Participant
giving written notice, in the manner provided in Section 15, specifying the
number of shares of Common Stock with respect to which the Option is then being
exercised. The notice shall be accompanied by payment in the form of cash or
check payable to the order of the Company in an amount equal to the exercise
price of the shares of Common Stock to be purchased or, subject in each instance
to the Committee's approval, acting in its sole discretion and subject to such
conditions, if any, as the Committee may deem necessary to comply with
applicable laws, rules and regulations or to avoid adverse accounting effects to
the Company, by delivery to the Company of (i) shares of Common Stock having a
Market Value equal to the exercise price of the shares to be purchased, or (ii)
the Participant's executed promissory note in the principal amount equal to the
exercise price of the shares to be purchased and otherwise in such form as the
Committee shall have approved. If the Common Stock is traded on an established
market, payment of any exercise price may also be made through and under the
terms and conditions of any formal cashless exercise program authorized by the
Company entailing the sale of the Common Stock subject to any Option in a
brokered transaction (other than to the Company). Receipt by the Company of such
notice and payment in any authorized or combination of authorized means shall
constitute the exercise of the Option. Within thirty (30) days thereafter but
subject to the remaining provisions of the Plan, the Company shall deliver or
cause to be delivered to the Participant or his agent a certificate or
certificates for the number of shares then being purchased. Such shares shall be
fully paid and nonassessable. Notwithstanding any of the foregoing provisions in
this subsection (g) to the contrary, (A) no Option shall be considered to have
been exercised unless and until all of the provisions governing such exercise
specified in the Plan and in the relevant Award Agreement shall have been duly
complied with; and (B) the obligation of the Company to issue any shares upon
exercise of an Option is subject to the provisions of Section 9.1 hereof and to
compliance by the Optionee and the Participant with all of the provisions of the
Plan and the relevant Award Agreement.


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          (h) Limit on Incentive Option Characterization. An Incentive Option
shall be considered to be an Incentive Option only to the extent that the number
of shares of Common Stock for which the Option first becomes exercisable in a
calendar year do not have an aggregate Market Value (as of the date of the grant
of the Option) in excess of the "current limit". The current limit for any
Optionee for any calendar year shall be $100,000 MINUS the aggregate Market
Value at the date of grant of the number of shares of Common Stock available for
purchase for the first time in the same year under each other Incentive Option
previously granted to the Optionee under the Plan, and under each other
incentive stock option previously granted to the Optionee under any other
incentive stock option plan of the Company and its Affiliates, after December
31, 1986. Any shares of Common Stock which would cause the foregoing limit to be
violated shall be deemed to have been granted under a separate Nonstatutory
Option, otherwise identical in its terms to those of the Incentive Option.

          (i) Notification of Disposition. Each person exercising any Incentive
Option granted under the Plan shall be deemed to have covenanted with the
Company to report to the Company any disposition of such shares prior to the
expiration of the holding periods specified by Section 422(a)(1) of the Code
and, if and to the extent that the realization of income in such a disposition
imposes upon the Company federal, state, local or other withholding tax
requirements, or any such withholding is required to secure for the Company an
otherwise available tax deduction, to remit to the Company an amount in cash
sufficient to satisfy those requirements.

          (j) Rights Pending Exercise. No person holding an Option shall be
deemed for any purpose to be a stockholder of the Company with respect to any of
the shares of Common Stock issuable pursuant to such Option, except to the
extent that such Option shall have been exercised with respect thereto and, in
addition, a certificate shall have been issued therefor and delivered to such
person or his agent.

     7.2. Restricted Stock.

          (a) Purchase Price. Shares of Restricted Stock shall be issued under
the Plan for such consideration, in cash, other property or services, or any
combination thereof, as is determined by the Committee.

          (b) Issuance of Certificates. Subject to subsection (c) below, each
Participant receiving an Award of Restricted Stock shall be issued a stock
certificate in respect of such shares of Restricted Stock. Such certificate
shall be registered in the name of such Participant, and, if applicable, shall
bear an appropriate legend referring to the terms, conditions, and restrictions
applicable to such Award substantially in the following form:

          The transferability of this certificate and the shares represented by
          this certificate are subject to the terms and conditions of the
          ActivBiotics, Inc. 2006 Equity Incentive Plan and an Award Agreement
          entered into by the registered owner and ActivBiotics, Inc. Copies of
          such Plan and Agreement are on file in the offices of ActivBiotics,
          Inc.

          (c) Escrow of Shares. The Committee may require that the stock
certificates evidencing shares of Restricted Stock be held in custody by a
designated escrow agent (which may but need not be the Company) until the
restrictions thereon shall have lapsed, and that the


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Participant deliver a stock power, endorsed in blank, relating to the Common
Stock covered by such Award.

          (d) Restrictions and Restriction Period. During the Restriction Period
applicable to shares of Restricted Stock, such shares shall be subject to
limitations on transferability and a Risk of Forfeiture arising on the basis of
such conditions related to the performance of services, Company or Affiliate
performance or otherwise as the Committee may determine and provide for in the
applicable Award Agreement. Any such Risk of Forfeiture may be waived or
terminated, or the Restriction Period shortened, at any time by the Committee on
such basis as it deems appropriate.

          (e) Rights Pending Lapse of Risk of Forfeiture or Forfeiture of Award.
Except as otherwise provided in the Plan or the applicable Award Agreement, at
all times prior to lapse of any Risk of Forfeiture applicable to, or forfeiture
of, an Award of Restricted Stock, the Participant shall have all of the rights
of a stockholder of the Company, including the right to vote the shares of
Restricted Stock.

          (f) Effect of Termination of Employment, Consulting or Board Member
Relationship. Unless otherwise determined by the Committee at or after grant and
subject to the applicable provisions of the Award Agreement, if the applicable
original grantee's association with the Company or any of its Affiliates as an
employee, director or consultant ends for any reason or no reason during the
Restriction Period, regardless of whether the end of such association is
effected by the Company, any such Affiliate or such original grantee (whether
voluntarily or involuntarily, including because an entity with which such
original grantee has any such association ceases to be an Affiliate of the
Company), and immediately following the end of any such association, such
original grantee is not associated with the Company or any of its Affiliates as
an employee, director or consultant, or if such original grantee dies, then all
outstanding shares of Restricted Stock initially granted to such original
grantee that are still subject to Risk of Forfeiture, whether then held by such
original grantee or any other Participant, shall be forfeited or otherwise
subject to return to or repurchase by the Company if and to the extent so
provided by, and subject to and in accordance with, the terms of the applicable
Award Agreement; provided, however, that military or sick leave or other bona
fide leave shall not be deemed a termination of employment, if it does not
exceed the longer of ninety (90) days or the period during which the absent
original grantee's reemployment rights, if any, are guaranteed by statute or by
contract.

          (g) Lapse of Restrictions. If and when the Restriction Period expires
without a prior forfeiture of the Restricted Stock, the certificates for such
shares shall be delivered to the Participant promptly if not theretofore so
delivered.

          (h) Transferability. Except as otherwise provided in this subsection
(h), shares of Restricted Stock shall not be transferable, and no share of
Restricted Stock or interest therein may be sold, transferred, pledged,
assigned, or otherwise alienated or hypothecated, other than by will or by the
laws of descent and distribution (subject always to the provisions of subsection
(f) above). The applicable Award Agreement or the Committee (at or after the
grant of a share of Restricted Stock) may provide that such share of Restricted
Stock may be transferred by the applicable Participant to a family member;
provided, however, that any such transfer is without payment of any
consideration whatsoever and that no transfer of a share of Restricted Stock
shall be valid unless first approved by the Committee, acting in its sole
discretion, unless such transfer is permitted under the applicable Award
Agreement. For this purpose, "family member" means


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any child, stepchild, grandchild, parent, stepparent, spouse, former spouse,
sibling, niece, nephew, mother-in-law, father-in-law, son-in-law,
daughter-in-law, brother-in-law, or sister-in-law, including adoptive
relationships, any person sharing the original grantee's household (other than a
tenant or employee), a trust in which the foregoing persons and/or the original
grantee have more than fifty percent (50%) of the beneficial interests, a
foundation in which the foregoing persons and/or the original grantee control
the management of assets, and any other entity in which these persons and/or the
original grantee own more than fifty percent (50%) of the voting interests. The
Committee may at any time or from time to time delegate to one or more officers
of the Company the authority to permit transfers of shares of Restricted Stock
to third parties pursuant to this subsection (h), which authorization shall be
exercised by such officer or officers in accordance with guidelines established
by the Committee at any time and from time to time.

     7.3. Restricted Stock Units.

          (a) Character. Each Restricted Stock Unit shall entitle the recipient
to a share of Common Stock at a close of such Restriction Period as the
Committee may establish and subject to a Risk of Forfeiture arising on the basis
of such conditions relating to the performance of services, Company or Affiliate
performance or otherwise as the Committee may determine and provide for in the
applicable Award Agreement. Any such Risk of Forfeiture may be waived or
terminated, or the Restriction Period shortened, at any time by the Committee on
such basis as it deems appropriate.

          (b) Issuance of Certificates. Unless otherwise determined by the
Committee at or after grant and subject to the applicable provisions of the
Award Agreement, at the close of the Restriction Period applicable to any
Restricted Stock Units (including, without limitation, the close of the
applicable Restriction Period as a result of (i) any Acceleration of Restricted
Stock Units in accordance with the terms of this Plan or any applicable Award
Agreement, (ii) any waiver, lapse or termination of the Risk of Forfeiture
applicable to Restricted Stock Units in accordance with the terms of this Plan
or any applicable Award Agreement or (iii) any shortening of the Restriction
Period applicable to any Restricted Stock Units in accordance with the terms of
this Plan or any applicable Award Agreement), the Company shall deliver or cause
to be delivered to the Participant that is the holder of such Restricted Stock
Units a stock certificate in respect of the shares of Common Stock subject to
such Restricted Stock Units. Such certificate shall be registered in the name of
such Participant, and, if applicable, shall bear an appropriate legend referring
to the terms, conditions, and restrictions applicable to such shares of Common
Stock substantially in the following form:

          The transferability of this certificate and the shares represented by
          this certificate are subject to the terms and conditions of the
          ActivBiotics, Inc. 2006 Equity Incentive Plan and an Award Agreement
          entered into by the registered owner and ActivBiotics, Inc. Copies of
          such Plan and Agreement are on file in the offices of ActivBiotics,
          Inc.

          (c) Dividends. At the discretion of the Committee, Participants may be
entitled to receive payments equivalent to any dividends declared with respect
to Common Stock referenced in grants of Restricted Stock Units but only
following the close of the applicable Restriction Period and then only if the
underlying Common Stock shall have been earned. Unless the Committee shall
provide otherwise, any such dividend equivalents shall be paid, if at all,
without interest or other earnings.


                                       10
<Page>

          (d) Effect of Termination of Employment, Consulting or Board Member
Relationship. Unless otherwise determined by the Committee at or after grant and
subject to the applicable provisions of the Award Agreement, if the applicable
original grantee's association with the Company or any of its Affiliates as an
employee, director or consultant ends for any reason or no reason during the
Restriction Period, regardless of whether the end of such association is
effected by the Company, any such Affiliate or such original grantee (whether
voluntarily or involuntarily, including because an entity with which such
original grantee has any such association ceases to be an Affiliate of the
Company), and immediately following the end of any such association, such
original grantee is not associated with the Company or any of its Affiliates as
an employee, director or consultant, or if such original grantee dies, then all
outstanding Restricted Stock Units initially granted to such original grantee
that are still subject to Risk of Forfeiture, whether then held by such original
grantee or any other Participant, shall be forfeited or otherwise subject to
return to the Company in accordance with the terms of the applicable Award
Agreement; PROVIDED, HOWEVER, that military or sick leave or other bona fide
leave shall not be deemed a termination of employment, if it does not exceed the
longer of ninety (90) days or the period during which the absent original
grantee's reemployment rights, if any, are guaranteed by statute or by contract.

          (e) Transferability. Except as otherwise provided in this subsection
(e), Restricted Stock Units shall not be transferable, and no Restricted Stock
Unit or interest therein may be sold, transferred, pledged, assigned, or
otherwise alienated or hypothecated. The applicable Award Agreement or the
Committee (at or after the grant of a Restricted Stock Unit) may provide that
such Restricted Stock Unit may be transferred by the original grantee to a
family member; PROVIDED, HOWEVER, that any such transfer is without payment of
any consideration whatsoever and that no transfer of a Restricted Stock Unit
shall be valid unless first approved by the Committee, acting in its sole
discretion, unless such transfer is permitted under the applicable Award
Agreement. For this purpose, "family member" means any child, stepchild,
grandchild, parent, stepparent, spouse, former spouse, sibling, niece, nephew,
mother-in-law, father-in-law, son-in-law, daughter-in-law, brother-in-law, or
sister-in-law, including adoptive relationships, any person sharing the original
grantee's household (other than a tenant or employee), a trust in which the
foregoing persons and/or the original grantee have more than fifty percent (50%)
of the beneficial interests, a foundation in which the foregoing persons and/or
the original grantee control the management of assets, and any other entity in
which these persons and/or the original grantee own more than fifty percent
(50%) of the voting interests. The Committee may at any time or from time to
time delegate to one or more officers of the Company the authority to permit
transfers of Restricted Stock Units to third parties pursuant to this subsection
(e), which authorization shall be exercised by such officer or officers in
accordance with guidelines established by the Committee at any time and from
time to time.

          (f) Rights Pending Close of Applicable Restriction Period. No person
holding Restricted Stock Units shall be deemed for any purpose to be a
stockholder of the Company with respect to any of the shares of Common Stock
subject to such Restricted Stock Units, except to the extent that the Restricted
Period with respect to such Restricted Stock Units shall have closed and, in
addition, a certificate shall have been issued for such shares of Common Stock
and delivered to such person or his agent. Shares of Common Stock subject to
Restricted Stock Units shall be issued and outstanding only if and to the extent
that a stock certificate representing such shares has been issued and delivered
in accordance with the provisions of this Section 7.3.


                                       11
<Page>

     7.4. Stock Grants.

          (a) In General. Stock Grants shall be issued for such consideration,
in cash, other property or services, or any combination thereof, as is
determined by the Committee. Without limiting the generality of the foregoing,
Stock Grants may be awarded in such circumstances as the Committee deems
appropriate, including without limitation in recognition of significant
contributions to the success of the Company or its Affiliates or in lieu of
compensation otherwise already due. Stock Grants shall be made without
forfeiture conditions of any kind.

          (b) Issuance of Certificates. Each Participant receiving a Stock Grant
shall be issued a stock certificate in respect of such Stock Grant. Such
certificate shall be registered in the name of such Participant, and, if
applicable, shall bear an appropriate legend referring to the terms, conditions,
and restrictions applicable to such Award substantially in the following form:

          The transferability of this certificate and the shares represented by
          this certificate are subject to the terms and conditions of the
          ActivBiotics, Inc. 2006 Equity Incentive Plan. A copy of such Plan is
          on file in the offices of ActivBiotics, Inc.

     7.5. Awards to Participants Outside the United States. The Committee may
modify the terms of any Award under the Plan granted to a Participant who is, at
the time of grant or during the term of the Award, resident or primarily
employed outside of the United States in any manner deemed by the Committee to
be necessary or appropriate in order that such Award shall conform to laws,
regulations, and customs of the country in which the Participant is then
resident or primarily employed, or so that the value and other benefits of the
Award to the Participant, as affected by foreign tax laws and other restrictions
applicable as a result of the Participant's residence or employment abroad,
shall be comparable to the value of such an Award to a Participant who is
resident or primarily employed in the United States. An Award may be modified
under this Section 7.5 in a manner that is inconsistent with the express terms
of the Plan, so long as such modifications will not contravene any applicable
law or regulation. The Committee may establish supplements to, or amendments,
restatements, or alternative versions of the Plan for the purpose of granting
and administrating any such modified Award. No such modification, supplement,
amendment, restatement or alternative version may increase the share limit of
Section 4.

8.   ADJUSTMENT PROVISIONS

     8.1. Adjustment for Corporate Actions. All of the share numbers set forth
in the Plan reflect the capital structure of the Company immediately after the
closing of the initial public offering of the Company's Common Stock. Subject to
the provisions of Section 8.2, if subsequent to such date the outstanding shares
of Common Stock (or any other securities covered by the Plan by reason of the
prior application of this Section) are increased, decreased, or exchanged for a
different number or kind of shares or other securities, or if additional shares
or new or different shares or other securities are distributed with respect to
such shares of Common Stock or other securities, through merger, consolidation,
sale of all or substantially all the property of the Company, reorganization,
recapitalization, reclassification, stock dividend, stock split, reverse stock
split, or other distribution with respect to such shares of Common Stock, or
other securities, an appropriate and proportionate adjustment will be made in
(i) the maximum numbers and kinds of shares provided in Section 4, (ii) the
numbers and kinds of shares or other securities subject to the then outstanding
Awards, (iii) the exercise price for each share or other


                                       12
<Page>

unit of any other securities subject to then outstanding Options (without change
in the aggregate purchase price as to which such Options remain exercisable),
and (iv) the repurchase price of each share of Restricted Stock then subject to
a Risk of Forfeiture in the form of a Company repurchase right.

     8.2. Change of Control. Subject to the applicable provisions of the Award
Agreement, in the event of a Change of Control, the Committee shall have the
discretion, exercisable in advance of, at the time of, or (except to the extent
otherwise provided below) at any time after, the Change of Control, to provide
for any or all of the following (subject to and upon such terms as the Committee
may deem appropriate): (A) the Acceleration, in whole or in part, of any or all
outstanding Options (including Options that are assumed or replaced pursuant to
clause (D) below) that are not exercisable in full at the time the Change of
Control, such Acceleration to become effective at the time of the Change of
Control, or at such time following the Change of Control that the employment,
consulting or Board member relationship of the applicable Optionee or Optionees
with the Company and its Affiliates terminates, or at such other time or times
as the Committee shall determine; (B) the lapse or termination of the Risk of
Forfeiture (including, without limitation, any or all of the Company's
repurchase rights) with respect to outstanding Awards of Restricted Stock, such
lapse or termination to become effective at the time of the Change of Control,
or at such time following the Change of Control that the employment, consulting
or Board member relationship with the Company and its Affiliates of the
Participant or Participants that hold such Awards of Restricted Stock (or the
person to whom such Awards of Restricted Stock were initially granted)
terminates, or at such other time or times as the Committee shall determine; (C)
the lapse or termination of the Risk of Forfeiture with respect to any or all
outstanding Awards of Restricted Stock Units (including Restricted Stock Units
that are assumed or replaced pursuant to clause (D) below), such lapse or
termination to become effective at the time of the Change of Control, or at such
time following the Change of Control that the employment, consulting or Board
member relationship with the Company and its Affiliates of the Participant or
Participants that hold such Awards of Restricted Stock Units (or the person to
whom such Awards of Restricted Stock Units were initially granted) terminates,
or at such other time or times as the Committee shall determine; (D) the
assumption of outstanding Options or Restricted Stock Units, or the substitution
of outstanding Options or Restricted Stock Units with equivalent options or
equivalent restricted stock units, as the case may be, by the acquiring or
succeeding corporation or entity (or an affiliate thereof); (E) the termination
of all Options (other than Options that are assumed or substituted pursuant to
clause (D) above) that remain outstanding at the time of the consummation of the
Change of Control, provided that, the Committee shall have made the
determination to effect such termination prior to the consummation of the Change
of Control and the Committee shall have given, or caused to be given, to all
Participants written notice of such potential termination at least five business
days prior to the consummation of the Change of Control, and provided, further,
that, if the Committee shall have determined in its sole and absolute discretion
that the Corporation make payment or provide consideration to the holders of
such terminated Options on account of such termination, which payment or
consideration shall be on such terms and conditions as the Committee shall have
determined (and which could consist of, in the Committee's sole and absolute
discretion, payment to the applicable Optionee or Optionees of an amount of cash
equal to the difference between the Market Value of the shares of Common Stock
for which the Option is then exercisable and the aggregate exercise price for
such shares under the Option), then the Corporation shall be required to make
such payment or provide such consideration in accordance with the terms and
conditions so determined by the Committee, otherwise the Corporation shall not
be required to make any payment or provide any consideration in connection with,
or as a result of, the termination of Options pursuant to the foregoing
provisions of this clause (E); or (F)


                                       13
<Page>

the termination of all Restricted Stock Units (other than Restricted Stock Units
that are assumed or substituted pursuant to clause (D) above) that remain
outstanding at the time of the consummation of the Change of Control, provided
that, if the Committee shall have determined in its sole and absolute discretion
that the Corporation make payment or provide consideration to the holders of
such terminated Restricted Stock Units on account of such termination, which
payment or consideration shall be on such terms and conditions as the Committee
shall have determined (and which could consist of, in the Committee's sole and
absolute discretion, payment to the applicable Participant or Participants of an
amount of cash equal to the Market Value of the shares of Common Stock subject
to the terminated Restricted Stock Units), then the Corporation shall be
required to make such payment or provide such consideration in accordance with
the terms and conditions so determined by the Committee, otherwise the
Corporation shall not be required to make any payment or provide any
consideration in connection with, or as a result of, the termination of
Restricted Stock Units pursuant to the foregoing provisions of this clause (F).
The provisions of this Section 8.2 shall not be construed as to limit or
restrict in any way the Committee's general authority under Sections 7.1(d) or
7.2(d) hereof to Accelerate Options in whole or in part at any time or to waive
or terminate at any time any Risk of Forfeiture applicable to shares of
Restricted Stock or Restricted Stock Units. Each outstanding Option or
Restricted Stock Unit that is assumed in connection with a Change of Control, or
is otherwise to continue in effect subsequent to a Change of Control, will be
appropriately adjusted, immediately after the Change of Control, as to the
number and class of securities and the price at which it may be exercised in
accordance with Section 8.1.

     8.3. Dissolution or Liquidation. Upon dissolution or liquidation of the
Company, each outstanding Option shall terminate, but the Optionee (if at the
time he or she has an employment, consulting or Board member relationship with
the Company or any of its Affiliates) shall have the right, immediately prior to
such dissolution or liquidation, to exercise the Option to the extent
exercisable on the date of such dissolution or liquidation.

     8.4. Related Matters. Any adjustment in Awards made pursuant to this
Section 8 shall be determined and made, if at all, by the Committee and shall
include any correlative modification of terms, including exercise prices, rates
of vesting or exercisability, Risks of Forfeiture and applicable repurchase
prices, which the Committee may deem necessary or appropriate so as to ensure
that the rights of the Participants in their respective Awards are not
substantially diminished nor enlarged as a result of the adjustment and
corporate action other than as expressly contemplated in this Section 8. No
fraction of a share shall be purchasable or deliverable upon exercise, but in
the event any adjustment hereunder of the number of shares covered by an Award
shall cause such number to include a fraction of a share, such number of shares
shall be adjusted to the nearest smaller whole number of shares. No adjustment
of an Option exercise price per share pursuant to this Section 8 shall result in
an exercise price which is less than the par value of the Common Stock.

9.   SETTLEMENT OF AWARDS

     9.1. Violation of Law. Notwithstanding any other provision of the Plan or
the relevant Award Agreement, if, at any time, in the reasonable opinion of the
Company, the issuance of shares of Common Stock covered by an Award may
constitute a violation of law, then the Company may delay such issuance and the
delivery of a certificate for such shares until (i) approval shall have been
obtained from such governmental agencies, other than the Securities and Exchange
Commission, as may be required under any applicable law, rule, or regulation and
(ii) in the case where such issuance would constitute a violation of a law
administered by or a


                                       14
<Page>

regulation of the Securities and Exchange Commission, one of the following
conditions shall have been satisfied:

          (a) the shares are at the time of the issue of such shares effectively
registered under the Securities Act; or

          (b) the Company shall have determined, on such basis as it deems
appropriate (including an opinion of counsel in form and substance satisfactory
to the Company) that the sale, transfer, assignment, pledge, encumbrance or
other disposition of such shares or such beneficial interest, as the case may
be, does not require registration under the Securities Act or any applicable
state securities laws.

     9.2. Corporate Restrictions on Rights in Stock. Any Common Stock to be
issued pursuant to Awards granted under the Plan shall be subject to all
restrictions upon the transfer thereof which may be now or hereafter imposed by
the Certificate of Incorporation and the By-laws of the Company, each as amended
and in effect from time to time. Whenever Common Stock is to be issued pursuant
to an Award, if the Committee so directs at the time of grant (or, if such Award
is an Option, at any time prior to the exercise thereof), the Company shall be
under no obligation, notwithstanding any other provision of the Plan or the
relevant Award Agreement to the contrary, to issue such shares until such time,
if ever, as the recipient of the Award (and any person who exercises any Option,
in whole or in part), shall have become a party to and bound by any agreement
that the Committee shall require in its sole discretion. In addition, any Common
Stock to be issued pursuant to Awards granted under the Plan shall be subject to
all stop-transfer orders and other restrictions as the Committee may deem
advisable under the rules, regulations and other requirements of any stock
exchange upon which the Common Stock is then listed, and any applicable federal
or state securities laws, and the Committee may cause a legend or legends to be
put on any such certificates to make appropriate reference to such restrictions.

     9.3. Investment Representations. The Company shall be under no obligation
to issue any shares covered by an Award unless the shares to be issued pursuant
to Awards granted under the Plan have been effectively registered under the
Securities Act or the Participant shall have made such written representations
to the Company (upon which the Company believes it may reasonably rely) as the
Company may deem necessary or appropriate for purposes of confirming that the
issuance of such shares will be exempt from the registration requirements of
that Act and any applicable state securities laws and otherwise in compliance
with all applicable laws, rules and regulations, including but not limited to
that the Participant is acquiring shares for his or her own account for the
purpose of investment and not with a view to, or for sale in connection with,
the distribution of any such shares.

     9.4. Registration. If the Company shall deem it necessary or desirable to
register under the Securities Act or other applicable statutes any shares of
Common Stock issued or to be issued pursuant to Awards granted under the Plan,
or to qualify any such shares of Common Stock for exemption from the Securities
Act or other applicable statutes, then the Company shall take such action at its
own expense. The Company may require from each recipient of an Award, or each
holder of shares of Common Stock acquired pursuant to the Plan, such information
in writing for use in any registration statement, prospectus, preliminary
prospectus or offering circular as is reasonably necessary for such purpose and
may require reasonable indemnity to the Company and its officers and directors
from such holder against all losses, claims, damage and liabilities arising from
such use of the information so furnished and caused by any untrue statement of
any material fact therein or caused by the omission to state a material fact
required to


                                       15
<Page>

be stated therein or necessary to make the statements therein not misleading in
the light of the circumstances under which they were made.

     9.5. Lock-Up. Without the prior written consent of the Company or the
managing underwriter in any public offering of shares of Common Stock, no
Participant shall sell, make any short sale of, loan, grant any option for the
purchase of, pledge or otherwise encumber, or otherwise dispose of, any shares
of Common Stock during the one hundred-eighty (180) day period commencing on the
effective date of the registration statement relating to any underwritten public
offering of securities of the Company. The foregoing restrictions are intended
and shall be construed so as to preclude any Participant from engaging in any
hedging or other transaction that is designed to or reasonably could be expected
to lead to or result in, a sale or disposition of any shares of Common Stock
during such period even if such shares of Common Stock are or would be disposed
of by someone other than such Participant. Such prohibited hedging or other
transactions would include, without limitation, any short sale (whether or not
against the box) or any purchase, sale or grant of any right (including without
limitation any put or call option) with respect to any shares of Common Stock or
with respect to any security that includes, relates to, or derives any
significant part of its value from any shares of Common Stock. Without limiting
the generality and applicability of the foregoing provisions of this Section
9.5, if, in connection with any underwritten public offering of securities of
the Company, the managing underwriter of such offering requires that the
Company's directors and officers enter into a lock-up agreement, then (a) each
Participant (regardless of whether or not such Participant has complied or
complies with the provisions of clause (b) below) shall be bound by, and shall
be deemed to have agreed to, the same lock-up terms as those to which the
Company's directors and officers are required to adhere; and (b) at the request
of the Company or such managing underwriter, each Participant shall execute and
deliver a lock-up agreement in form and substance equivalent to that which is
required to be executed by the Company's directors and officers.

     9.6. Placement of Legends; Stop Orders; Etc. Each share of Common Stock to
be issued pursuant to Awards granted under the Plan may bear a reference to the
investment representations made in accordance with Section 9.3 in addition to
any other applicable restrictions under the Plan, the terms of the Award and, if
applicable, under any agreement between the Company and any Optionee and/or
Participant, and to the fact that no registration statement has been filed with
the Securities and Exchange Commission in respect to such shares of Common
Stock. All certificates for shares of Common Stock or other securities delivered
under the Plan shall be subject to such stock transfer orders and other
restrictions as the Committee may deem advisable under the rules, regulations,
and other requirements of any stock exchange upon which the Common Stock is then
listed, and any applicable federal or state securities law, and the Committee
may cause a legend or legends to be placed on any such certificates to make
appropriate reference to such restrictions.

     9.7. Tax Withholding. Whenever shares of Common Stock are issued or to be
issued pursuant to Awards granted under the Plan, the Company shall have the
right to require the recipient to remit to the Company an amount sufficient to
satisfy federal, state, local or other withholding tax requirements if, when,
and to the extent required by law (whether so required to secure for the Company
an otherwise available tax deduction or otherwise) prior to the delivery of any
certificate or certificates for such shares. The obligations of the Company
under the Plan shall be conditional on satisfaction of all such withholding
obligations and the Company shall, to the extent permitted by law, have the
right to deduct any such taxes from any payment of any kind otherwise due to the
recipient of an Award. However, in such cases Participants may elect, subject to
the approval of the Committee, acting in its sole discretion, to satisfy an
applicable


                                       16
<Page>

withholding requirement, in whole or in part, by having the Company withhold
shares to satisfy their tax obligations. Participants may only elect to have
shares of Common Stock withheld having a Market Value on the date the tax is to
be determined equal to the minimum statutory total tax which could be imposed on
the transaction. All elections shall be irrevocable, made in writing, signed by
the Participant, and shall be subject to any restrictions or limitations that
the Committee deems appropriate.

10.  RESERVATION OF STOCK

     The Company shall at all times during the term of the Plan and any
outstanding Options granted hereunder reserve or otherwise keep available such
number of shares of Common Stock as will be sufficient to satisfy the
requirements of the Plan (if then in effect) and such Options and shall pay all
fees and expenses necessarily incurred by the Company in connection therewith.

11.  NO SPECIAL SERVICE RIGHTS

     Nothing contained in the Plan or in any Award Agreement shall confer upon
any recipient of an Award any right with respect to the continuation of his or
her employment, consulting or Board member relationship or other association
with the Company (or any Affiliate), or interfere in any way with the right of
the Company (or any Affiliate), subject to the terms of any separate employment,
consulting or Board member agreement or provision of law or corporate articles
or by-laws to the contrary, at any time to terminate such employment, consulting
or Board member agreement or to increase or decrease, or otherwise adjust, the
other terms and conditions of the recipient's employment, consulting or Board
member relationship or other association with the Company and its Affiliates.

12.  NONEXCLUSIVITY OF THE PLAN

     Neither the adoption of the Plan by the Board nor the submission of the
Plan to the stockholders of the Company shall be construed as creating any
limitations on the power of the Board to adopt such other incentive arrangements
as it may deem desirable, including without limitation, the granting of stock
options, restricted stock and restricted stock units other than under the Plan,
and such arrangements may be either applicable generally or only in specific
cases.

13.  TERMINATION AND AMENDMENT OF THE PLAN

     The Board may at any time terminate the Plan or make such amendments or
modifications of the Plan as it shall deem advisable. In the event of the
termination of the Plan, the terms of the Plan shall survive any such
termination with respect to any Award that is outstanding on the date of such
termination, unless the holder of such Award agrees in writing to terminate such
Award or to terminate all or any of the provisions of the Plan that apply to
such Award. Unless the Board otherwise expressly provides, any amendment or
modification of the Plan shall affect the terms of any Award outstanding on the
date of such amendment or modification as well as the terms of any Award made
from and after the date of such amendment or modification; PROVIDED, HOWEVER,
that, except to the extent otherwise provided in the last sentence of this
paragraph, (i) no amendment or modification of the Plan shall apply to any Award
that is outstanding on the date of such amendment or modification if such
amendment or modification would reduce the number of shares subject to such
Award, increase the purchase price applicable to shares subject to such Award or
materially adversely affect the provisions


                                       17
<Page>

applicable to such Award that relate to the vesting or exercisability of such
Award or of the shares subject to such Award, (ii) no amendment or modification
of the Plan shall apply to any Incentive Option that is outstanding on the date
of such amendment or modification if such amendment or modification would result
in such Incentive Option no longer being treated as an "incentive stock option"
within the meaning of Section 422 of the Code and (iii) no amendment or
modification of the Plan shall apply to any Award that is outstanding on the
date of such amendment or modification unless such amendment or modification of
the Plan shall also apply to all other Awards outstanding on the date of such
amendment or modification. In the event of any amendment or modification of the
Plan that is described in clause (i), (ii) or (iii) of the foregoing proviso,
such amendment or modification of the Plan shall apply to any Award outstanding
on the date of such amendment or modification only if the recipient of such
Award consents in writing thereto.

     The Committee may amend or modify, prospectively or retroactively, the
terms of any outstanding Award without amending or modifying the terms of the
Plan itself, PROVIDED THAT as amended or modified such Award is consistent with
the terms of the Plan as in effect at the time of the amendment or modification
of such Award, but no such amendment or modification of such Award shall,
without the written consent of the recipient of such Award, reduce the number of
shares subject to such Award, increase the purchase price applicable to shares
subject to such Award, adversely affect the provisions applicable to such Award
that relate to the vesting or exercisability of such Award or of the shares
subject to such Award, or otherwise materially adversely affect the terms of
such Award (except for amendments or modifications to the terms of such Award or
of the stock subject to such Award that are expressly permitted by the terms of
the Plan or that result from any amendment or modification of the Plan in
accordance with the provisions of the first paragraph of this Section 13), or,
if such Award is an Incentive Option, result in such Incentive Option no longer
being treated as an "incentive stock option" within the meaning of Section 422
of the Code. Notwithstanding any of the foregoing provisions of this paragraph
to the contrary, the Committee is expressly authorized to amend any or all
outstanding Options to effect a repricing thereof by lowering the purchase price
applicable to the shares of Common Stock subject to such Option or Options
without the approval of the stockholders of the Company or the holder or holders
of such Option or Options, and, in connection with such repricing, to amend or
modify any of the other terms of the Option or Options so repriced, including,
without limitation, for purposes of reducing the number of shares subject to
such Option or Options or for purposes of adversely affecting the provisions
applicable to such Option or Options that relate to the vesting or
exercisability thereof, in each case without the approval of stockholders of the
Company or the holder or holders of such Option or Options.

     In addition, notwithstanding anything express or implied in any of the
foregoing provisions of this Section 13 to the contrary, the Committee may amend
or modify, prospectively or retroactively, the terms of any outstanding Award to
the extent the Committee reasonably determines necessary or appropriate to
conform such Award to the requirements of Section 409A of the Code (concerning
non-qualified deferred compensation), if applicable.

14.  INTERPRETATION OF THE PLAN

     In the event of any conflict between the provisions of this Plan and the
provisions of any applicable Award Agreement, the provisions of this Plan shall
control, except if and to the extent that the conflicting provision in such
Award Agreement was authorized and approved by the Committee at the time of the
grant of the Award evidenced by such Award Agreement or is ratified by the
Committee at any time subsequent to the grant of such Award, in which case the


                                       18
<Page>

conflicting provision in such Award Agreement shall control. Without limiting
the generality of the foregoing provisions of this Section 14, insofar as
possible the provisions of the Plan and such Award Agreement shall be construed
so as to give full force and effect to all such provisions. In the event of any
conflict between the provisions of this Plan and the provisions of any other
agreement between the Company and the Optionee and/or Participant, the
provisions of such agreement shall control except as required to fulfill the
intention that this Plan constitute an incentive stock option plan within the
meaning of Section 422 of the Code, but insofar as possible the provisions of
the Plan and any such agreement shall be construed so as to give full force and
effect to all such provisions.

15.  NOTICES AND OTHER COMMUNICATIONS

     Any notice, demand, request or other communication hereunder to any party
shall be deemed to be sufficient if contained in a written instrument delivered
in person or duly sent by first class registered, certified or overnight mail,
postage prepaid, or telecopied with a confirmation copy by regular, certified or
overnight mail, addressed or telecopied, as the case may be, (i) if to the
recipient of an Award, at his or her residence address last filed with the
Company and (ii) if to the Company, at its principal place of business,
addressed to the attention of its Chief Executive Officer, or to such other
address or telecopier number, as the case may be, as the addressee may have
designated by notice to the addressor. All such notices, requests, demands and
other communications shall be deemed to have been received: (i) in the case of
personal delivery, on the date of such delivery; (ii) in the case of mailing,
when received by the addressee; and (iii) in the case of facsimile transmission,
when confirmed by facsimile machine report.

16.  GOVERNING LAW

     The Plan and all Award Agreements and actions taken thereunder shall be
governed, interpreted and enforced in accordance with the laws of the
Commonwealth of Massachusetts, without regard to the conflict of laws principles
thereof.


17.  EFFECTIVENESS OF PLAN

     This 2006 Equity Incentive Plan was approved in July 2006 by the Board and
in October 2006 by the stockholders of the Company, and shall take effect only
upon the consummation of the Company's initial public offering of its Common
Stock.

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