Document:

<Page>

                                                                    Exhibit 10.6

                               ACTIVBIOTICS, INC.

                        2006 EMPLOYEE STOCK PURCHASE PLAN

     The following constitute the provisions of the 2006 Employee Stock Purchase
Plan of ActivBiotics, Inc.

1.   PURPOSE

     The purpose of the Plan is to provide employees of the Company and its
Designated Subsidiaries with an opportunity to purchase Common Stock of the
Company. It is the intention of the Company to have the Plan qualify as an
"Employee Stock Purchase Plan" under Section 423 of the Code. The provisions of
the Plan shall, accordingly, be construed so as to extend and limit
participation in a manner consistent with the requirements of that section of
the Code.

2.   DEFINITIONS

     2.1. BOARD means the Board of Directors of the Company.

     2.2. CODE means the Internal Revenue Code of 1986, as amended.

     2.3. COMMON STOCK means the common stock, par value $0.001 per share, of
the Company.

     2.4. COMPANY means ActivBiotics, Inc., a Delaware corporation.

     2.5. COMPENSATION means all regular straight time compensation including
commissions but shall not include payments for overtime, shift premium,
incentive compensation, incentive payments, bonuses and other irregular or
infrequent compensation or benefits.

     2.6. CONTINUOUS STATUS AS AN EMPLOYEE means the absence of any interruption
or termination of service as an Employee. Continuous Status as an Employee shall
not be considered interrupted in the case of (i) sick leave; (ii) military
leave; (iii) any other leave of absence approved by the Administrator, provided
that such leave is for a period of not more than 90 days, unless reemployment
upon the expiration of such leave is guaranteed by contract or statute, or
unless provided otherwise pursuant to Company policy adopted from time to time;
or (iv) in the case of transfers between locations of the Company or between the
Company and its Designated Subsidiaries.

     2.7. CONTRIBUTIONS means all amounts credited to the account of a
participant pursuant to the Plan.

     2.8. CORPORATE TRANSACTION means a merger or consolidation of the Company
with and into another person or the sale, transfer, or other disposition of all
or substantially all of the Company's assets to one or more persons (other than
any wholly-owned subsidiary of the Company) in a single transaction or series of
related transactions.

     2.9. DESIGNATED SUBSIDIARIES means the Subsidiaries which have been
designated by the Board from time to time in its sole discretion as eligible to
participate in the Plan.

<Page>

                                        2

     2.10. EMPLOYEE means any person, including an Officer, who is customarily
employed for at least twenty (20) hours per week and more than five (5) months
in a calendar year by the Company or one of its Designated Subsidiaries.

     2.11. EXCHANGE ACT means the Securities Exchange Act of 1934, as amended.

     2.12. OFFERING COMMENCEMENT DATE means the first business day of each
Offering Period of the Plan.

     2.13. OFFERING PERIOD means any of the periods, generally of six (6) months
duration, as set forth in Section 4.

     2.14. OFFICER means a person who is an officer of the Company within the
meaning of Section 16 of the Exchange Act and the rules and regulations
promulgated thereunder.

     2.15. OFFERING TERMINATION DATE means the last business day of each
Offering Period of the Plan.

     2.16. PLAN means this Employee Stock Purchase Plan.

     2.17. PURCHASE PRICE means with respect to an Offering Period an amount
equal to eighty five percent (85%) of the Fair Market Value (as defined in
Section 7.2 below) of a Share on the Offering Commencement Date or on the
Offering Termination Date, whichever is lower; provided, however, that (i) if
there is an increase in the number of Shares available for issuance under the
Plan as a result of a stockholder-approved amendment to the Plan, (ii) all or a
portion of such additional Shares are to be issued with respect to the Offering
Period underway at the time of such increase ("Additional Shares"), and (iii)
the Fair Market Value of a Share of Common Stock on the date of such increase
(the "Approval Date Fair Market Value") is higher than the Fair Market Value on
the Offering Commencement Date for such Offering Period, then in such instance
the Purchase Price with respect to Additional Shares shall be eighty five
percent (85%) of the Approval Date Fair Market Value or the Fair Market Value of
a Share of Common Stock on the Offering Termination Date, whichever is lower.

     2.18. SHARE means a share of Common Stock, as adjusted in accordance with
Section 18 of the Plan.

     2.19. SUBSIDIARY means a corporation, in an unbroken chain of corporations
beginning with the Company if, at the time of the granting of the option, each
of the corporations other than the last corporation in the unbroken chain owns
stock possessing fifty percent (50%) or more of the total combined voting power
of all classes of stock in one of the other corporations in such chain.

3.   ELIGIBILITY

     3.1. Any person who is an Employee as of the Offering Commencement Date of
a given Offering Period shall be eligible to participate in such Offering Period
under the Plan, subject to the requirements of Sections 5.1 and the limitations
imposed by Section 423(b) of the Code.

<Page>

                                        3

     3.2. Any provisions of the Plan to the contrary notwithstanding, no
Employee shall be granted an option under the Plan (i) if, immediately after the
grant, such Employee (taking into account stock which would be attributed to
such Employee pursuant to Section 424(d) of the Code) would own capital stock of
the Company and/or hold outstanding options to purchase stock possessing five
percent (5%) or more of the total combined voting power or value of all classes
of stock of the Company or of any Subsidiary of the Company, or (ii) if such
option would permit his or her rights to purchase stock under all employee stock
purchase plans (described in Section 423 of the Code) of the Company and its
Subsidiaries to accrue at a rate which exceeds Twenty-Five Thousand Dollars
($25,000) of the Fair Market Value (as defined in Section 7.2 below) of such
stock (determined at the time such option is granted) for each calendar year in
which such option is outstanding at any time.

4.   OFFERING PERIODS

     Each Offering Period will begin on January 1 or July 1 and end on the next
following June 30 or December 31, respectively, with the first Offering Period
commencing on January 1, 2007. At any time and from time to time, the Board may
change the duration and/or the frequency of Offering Periods with respect to
future Offering Periods or suspend operation of the Plan with respect to
Offering Periods not yet commenced.

5.   PARTICIPATION

     5.1. An eligible Employee may become a participant in the Plan by
completing a subscription agreement on the form provided by the Company and
filing it with the Company's payroll office prior to the applicable Offering
Commencement Date, unless a later time for filing the subscription agreement is
set by the Board for all eligible Employees with respect to a given Offering
Period. The subscription agreement shall set forth the percentage of the
participant's Compensation (subject to Section 6.1 below) to be paid as
Contributions pursuant to the Plan.

     5.2. Payroll deductions shall commence on the first payroll following the
Offering Commencement Date and shall end on the last payroll paid on or prior to
the Offering Termination Date of the Offering Period to which the subscription
agreement is applicable, unless sooner terminated by the participant as provided
in Section 10.

6.   METHOD OF PAYMENT of CONTRIBUTIONS

     6.1. A participant may elect to have payroll deductions made on each payday
during any Offering Period in an amount not less than one percent (1%) and not
more than fifteen percent (15%) (or such other percentage as the Board may
establish from time to time before an Offering Commencement Date) of such
participant's Compensation on each payday during the Offering Period. All
payroll deductions made by a participant shall be credited to his or her account
under the Plan. A participant may not make any additional payments into such
account.

     6.2. A participant may discontinue his or her participation in the Plan as
provided in Section 10. In addition, if the Board has so announced to Employees
at least five (5) days prior to the scheduled beginning of the next Offering
Period to be affected by the Board's determination, a participant may, on one
occasion only during each Offering Period, change the rate of his or her
Contributions with respect to the Offering Period by completing and filing with
the Company a new subscription agreement authorizing a change in the payroll
deduction rate. If otherwise permitted, no such change shall enable a
participant to resume Contributions other than as of an

<Page>

                                        4

Offering Commencement Date, following a withdrawal of Contributions during an
Offering Period pursuant to Section 10. Any such change in rate shall be
effective as of the first payroll period following the date of filing of the new
subscription agreement, if the agreement is filed at least ten (10) business
days prior to such period and, if not, as of the second following payroll
period.

     6.3. Notwithstanding the foregoing, to the extent necessary to comply with
Section 423(b)(8) of the Code and Section 3.2 herein, a participant's payroll
deductions may be decreased during any Offering Period scheduled to end during
the current calendar year to zero percent (0%). Payroll deductions reduced to
zero percent (0%) in compliance with this Section 6.3 shall re-commence
automatically at the rate provided in such participant's subscription agreement
at the beginning of the first Offering Period which is scheduled to end in the
following calendar year, unless terminated by the participant as provided in
Section 10.

7.   GRANT OF OPTION

     7.1. On the Offering Commencement Date of each Offering Period, each
eligible Employee participating in such Offering Period shall be granted an
option to purchase on the Offering Termination Date of that Offering Period a
number of Shares determined by dividing such Employee's Contributions
accumulated prior to such Offering Termination Date and retained in the
participant's account as of the Offering Termination Date by the applicable
Purchase Price. However, the maximum number of Shares an Employee may purchase
during each Offering Period shall be________Shares(1), and provided further that
such purchase shall be subject to the limitations set forth in Sections 3.2 and
12.

     7.2. The fair market value of the Company's Common Stock on a given date
(the "Fair 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 Fair Market
Value of the Common Stock as of any date (or, in the event that the Common Stock
is not traded on such date, on the immediately preceding trading date), is the
closing price for the Common Stock as reported by the National Association of
Securities Dealers Automated Quotation ("Nasdaq") System (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.

8.   EXERCISE OF OPTION

     Unless a participant withdraws from the Plan as provided in Section 10, his
or her option for the purchase of Shares will be exercised automatically on the
Offering Termination Date of an Offering Period, and the maximum number of full
Shares subject to the option will be purchased at the applicable Purchase Price
with the accumulated Contributions in his or her account. No fractional Shares
shall be issued. The Shares purchased upon exercise of an option hereunder shall
be deemed to be transferred to the participant on the Offering Termination Date.
During his or her lifetime, a participant's option to purchase Shares hereunder
is exercisable only by him or her.

----------
(1)  This number will represent [twenty-five] percent (|25|%) of the total
     allocable pool under the Plan.

<Page>

                                        5

9.   DELIVERY

     As promptly as practicable after each Offering Termination Date of each
Offering Period, the Company shall arrange the delivery to each participant, as
appropriate, of a certificate representing the Shares purchased upon exercise of
his or her option. Any payroll deductions accumulated in a participant's account
which are not sufficient to purchase a full Share shall be retained in the
participant's account for the subsequent Offering Period, subject to earlier
withdrawal by the participant as provided in Section 10 below. Any other amounts
left over in a participant's account after an Offering Termination Date shall be
returned to the participant.

10.  VOLUNTARY WITHDRAWAL; TERMINATION OF EMPLOYMENT

     10.1. A participant may withdraw all but not less than all of the
Contributions credited to his or her account under the Plan at any time prior to
each Offering Termination Date by giving written notice to the Company. All of
the participant's Contributions credited to his or her account will be paid to
him or her promptly after receipt of his or her notice of withdrawal and his or
her option for the current Offering Period will be automatically terminated, and
no further Contributions for the purchase of Shares will be made during the
Offering Period.

     10.2. Upon termination of the participant's Continuous Status as an
Employee prior to the Offering Termination Date of an Offering Period for any
reason, including retirement or death, the Contributions credited to his or her
account will be returned to him or her or, in the case of his or her death, to
the person or persons entitled thereto under Section 14, and his or her option
will be automatically terminated.

     10.3. In the event an Employee fails to remain in Continuous Status as an
Employee of the Company for at least twenty (20) hours per week during the
Offering Period in which the employee is a participant, he or she will be deemed
to have elected to withdraw from the Plan and the Contributions credited to his
or her account will be returned to him or her and his or her option terminated.

     10.4. A participant's withdrawal during an Offering Period will not have
any effect upon his or her eligibility to participate in a succeeding Offering
Period or in any similar plan which may hereafter be adopted by the Company.

11.  INTEREST

     No interest shall accrue on the Contributions of a participant in the Plan.

12.  STOCK

     12.1. Subject to adjustment as provided in Section 18, the maximum number
of Shares which shall be made available for sale under the Plan shall be________
(2)Shares. If the Board determines that, on a given Offering Termination Date,
the number of shares with respect

----------
(2). This number will represent [one and a half] percent (|1.5|%) of the Company
     on a fully diluted basis immediately after the closing of the IPO.

<Page>

                                        6

to which options are to be exercised may exceed (i) the number of shares of
Common Stock that were available for sale under the Plan on the Offering
Commencement Date, or (ii) the number of shares available for sale under the
Plan on such Offering Termination Date, the Board may in its sole discretion
provide that the Company shall make a pro rata allocation of the Shares
available for purchase on such Offering Commencement Date or Offering
Termination Date, as applicable, in as uniform a manner as shall be practicable
and as it shall determine in its sole discretion to be equitable among all
participants exercising options to purchase Common Stock on such Offering
Termination Date. The Company may make pro rata allocation of the Shares
available on the Offering Commencement Date of the applicable Offering Period
pursuant to the preceding sentence, notwithstanding any authorization of
additional Shares for issuance under the Plan by the Company's stockholders
subsequent to such Offering Commencement Date.

     12.2. The participant shall have no interest or voting right in Shares
covered by his or her option until such option has been exercised.

     12.3. Shares to be delivered to a participant under the Plan will be
registered in the name of the participant or in the name of the participant and
his or her spouse, as directed by the participant.

13.  ADMINISTRATION

     The Board, or a committee named by the Board, shall supervise and
administer the Plan and shall have full power to adopt, amend and rescind any
rules deemed desirable and appropriate for the administration of the Plan and
not inconsistent with the Plan, to construe and interpret the Plan, and to make
all other determinations necessary or advisable for the administration of the
Plan. The Board'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 this Plan.

14.  DESIGNATION OF BENEFICIARY

     14.1. A participant may file a written designation of a beneficiary who is
to receive any Shares and cash, if any, from the participant's account under the
Plan in the event of such participant's death subsequent to the end of an
Offering Period but prior to delivery to him or her of such Shares and cash. Any
such beneficiary shall also be entitled to receive any cash from the
participant's account under the Plan in the event of such participant's death
prior to the Offering Termination Date of an Offering Period.

     14.2. Such designation of beneficiary may be changed by the participant at
any time by written notice. In the event of the death of a participant and in
the absence of a beneficiary validly designated under the Plan who is living at
the time of such participant's death, the Company shall deliver such Shares
and/or cash to the executor or administrator of the estate of the participant,
or if no such executor or administrator has been appointed (to the knowledge of
the Company), the Company, in its discretion, may deliver such Shares and/or
cash to the spouse or to any one or more dependents or relatives of the
participant, or if no spouse, dependent or relative is known to the Company,
then to such other person as the Company may designate.

15.  TRANSFERABILITY OF OPTIONS AND SHARES

     Neither Contributions credited to a participant's account nor any rights
with regard to the exercise of an option or to receive Shares under the Plan may
be assigned, transferred, pledged or

<Page>

                                        7

otherwise disposed of in any way (other than by will, the laws of descent and
distribution, or as provided in Section 14) by the participant. Any such attempt
at assignment, transfer, pledge or other disposition shall be without effect,
except that the Company may treat such act as an election to withdraw funds in
accordance with Section 10. In addition, if the Board has so announced to
Employees at least five (5) days prior to the scheduled beginning of the next
Offering Period to be affected by the Board's determination, any Shares acquired
on the Offering Termination Date of such Offering Period may be subject to
restrictions specified by the Board on the transfer of such Shares. Any
participant selling or transferring any or all of his or her Shares purchased
pursuant to the Plan must provide written notice of such sale or transfer to the
Company within five business days after the date of sale or transfer. Such
notice to the Company shall include the gross sales price, if any, the Offering
Period during which the Shares being sold were purchased by the participant, the
number of Shares being sold or transferred and the date of sale or transfer.

16.  USE OF FUNDS

     All Contributions received or held by the Company under the Plan may be
used by the Company for any corporate purpose, and the Company shall not be
obligated to segregate such Contributions from its other assets.

17.  REPORTS

     Individual accounts will be maintained for each participant in the Plan.
Statements of account will be given to participating Employees at least
annually, which statements will set forth the amounts of Contributions, the per
Share Purchase Price, the number of Shares purchased and the remaining cash
balance, if any.

18.  ADJUSTMENTS UPON CHANGES IN CAPITALIZATION; CORPORATE TRANSACTIONS

     18.1. ADJUSTMENT. Subject to any required action by the stockholders of the
Company, the number of shares covered by each option under the Plan which has
not yet been exercised and the number of Shares which have been authorized for
issuance under the Plan but have not yet been placed under option (collectively,
the "Reserves"), as well as the maximum number of shares of Common Stock which
may be purchased by a participant in an Offering Period, the number of shares of
Common Stock set forth in Section 12.1 above, and the price per Share of Common
Stock covered by each option under the Plan which has not yet been exercised,
shall be proportionately adjusted for any increase or decrease in the number of
the Company's issued Shares resulting from a stock split, reverse stock split,
stock dividend, combination or reclassification of the Common Stock (including
any such change in the number of Shares of Common Stock effected in connection
with a change in domicile of the Company), or any other increase or decrease in
the number of Shares effected without receipt of consideration by the Company;
provided however that conversion of any convertible securities of the Company
shall not be deemed to have been "effected without receipt of consideration."
Such adjustment shall be made by the Board, whose determination in that respect
shall be final, binding and conclusive.

     18.2. CORPORATE TRANSACTIONS. In the event of a dissolution or liquidation
of the Company, the Offering Period then in progress will terminate immediately
prior to the consummation of such action, unless otherwise provided by the
Board. In the event of a Corporate Transaction, each option outstanding under
the Plan shall be assumed or an equivalent option shall be substituted by the
successor corporation or a parent or Subsidiary of such

<Page>

                                        8

successor corporation. In the event that the successor corporation refuses to
assume or substitute for outstanding options, the Offering Period then in
progress shall be shortened and a new Offering Termination Date shall be set
(the "New Offering Termination Date"), as of which date the Offering Period then
in progress will terminate. The New Offering Termination Date shall be on or
before the date of consummation of the transaction and the Board shall notify
each participant in writing, at least ten (10) days prior to the New Offering
Termination Date, that the Offering Termination Date for his or her option has
been changed to the New Offering Termination Date and that his or her option
will be exercised automatically on the New Offering Termination Date, unless
prior to such date he or she has withdrawn from the Offering Period as provided
in Section 10. For purposes of this Section 18, an option granted under the Plan
shall be deemed to be assumed, without limitation, if, at the time of issuance
of the stock or other consideration upon a Corporate Transaction, each holder of
an option under the Plan would be entitled to receive upon exercise of the
option the same number and kind of shares of stock or the same amount of
property, cash or securities as such holder would have been entitled to receive
upon the occurrence of the transaction if the holder had been, immediately prior
to the transaction, the holder of the number of Shares of Common Stock covered
by the option at such time (after giving effect to any adjustments in the number
of Shares covered by the option as provided for in this Section 18); provided
however that if the consideration received in the transaction is not solely
common stock of the successor corporation or its parent (as defined in Section
424(e) of the Code), the Board may, with the consent of the successor
corporation, provide for the consideration to be received upon exercise of the
option to be solely common stock of the successor corporation or its parent
equal in Fair Market Value to the per Share consideration received by holders of
Common Stock in the transaction.

     The Board may, if it so determines in the exercise of its sole discretion,
also make provision for adjusting the Reserves, as well as the price per Share
of Common Stock covered by each outstanding option, in the event that the
Company effects one or more reorganizations, recapitalizations, rights offerings
or other increases or reductions of Shares of its outstanding Common Stock, and
in the event of the Company's being consolidated with or merged into any other
corporation.

19.  AMENDMENT OR TERMINATION

     19.1. The Board may at any time and for any reason terminate or amend the
Plan. Except as provided in Section 18, no termination of the Plan may affect
options previously granted, provided that the Plan or an Offering Period may be
terminated by the Board on an Offering Termination Date or by the Board's
setting a new Offering Termination Date with respect to an Offering Period then
in progress if the Board determines that termination of the Plan and/or the
Offering Period is in the best interests of the Company and its stockholders or
if continuation of the Plan and/or the Offering Period would cause the Company
to incur adverse accounting charges as a result of the Plan. Except as provided
in Section 18 and in this Section 19, no amendment to the Plan shall make any
change in any option previously granted which adversely affects the rights of
any participant.

     19.2. In addition to the foregoing, without stockholder consent and without
regard to whether any participant rights may be considered to have been
adversely affected, the Board (or its committee) shall be entitled to change the
Offering Periods, limit the frequency and/or number of changes in the amount
withheld during an Offering Period, establish the exchange ratio applicable to
amounts withheld in a currency other than U.S. dollars, permit payroll
withholding in excess of the amount designated by a participant in order to
adjust for delays or mistakes in the

<Page>

                                        9

Company's processing of properly completed withholding elections, establish
reasonable waiting and adjustment periods and/or accounting and crediting
procedures to ensure that amounts applied toward the purchase of Common Stock
for each participant properly correspond with amounts withheld from the
participant's Compensation, and establish such other limitations or procedures
as the Board (or its committee) determines in its sole discretion advisable
which are consistent with the Plan.

20.  NOTICES

     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 ease 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 connection with the Plan shall be
deemed to have been duly given when received in the form specified by the
Company at the location, or by the person, designated by the Company for the
receipt thereof.

21.  CONDITIONS TO ISSUANCE OF SHARES

     Shares shall not be issued with respect to an option unless the exercise of
such option and the issuance and delivery of such Shares pursuant thereto shall
comply with all applicable provisions of law, domestic or foreign, including,
without limitation, the Securities Act of 1933, as amended, the Exchange Act,
the rules and regulations promulgated thereunder, applicable state securities
laws and the requirements of any stock exchange upon which the Shares may then
be listed, and shall be further subject to the approval of counsel for the
Company with respect to such compliance.

     As a condition to the exercise of an option, the Company may require the
person exercising such option to represent and warrant at the time of any such
exercise that the Shares are being purchased only for investment and without any
present intention to sell or distribute such Shares if, in the opinion of
counsel for the Company, such a representation is required by any of the
aforementioned applicable provisions of law.

22.  TERM OF PLAN; EFFECTIVE DATE

     The Plan shall become effective upon the IPO Date. It shall continue in
effect for a term of five (5) years unless sooner terminated under Section 19.

<Page>

                                                  FORM OF SUBSCRIPTION AGREEMENT

                               ACTIVBIOTICS, INC.

                        2006 EMPLOYEE STOCK PURCHASE PLAN

                             SUBSCRIPTION AGREEMENT

New Election: ___

Change of Election: ___

     1. I, ________________, hereby elect to participate in the ActivBiotics,
Inc. 2006 Employee Stock Purchase Plan (as amended, the "Plan") for the Offering
Period _____________ ___, _____ to ___________ _____, _____, and subscribe to
purchase shares of the Company's Common Stock in accordance with this
Subscription Agreement and the Plan.

     2. I elect to have Contributions in the amount of ___% of my Compensation,
as those terms are defined in the Plan, applied to this purchase. I understand
that this amount must not be less than 1% and not more than 15% of my
Compensation during the Offering Period. (Please note that no fractional
percentages are permitted).

     3. I hereby authorize payroll deductions from each paycheck during the
Offering Period at the rate stated in Item 2 of this Subscription Agreement. I
understand that all payroll deductions made by me shall be credited to my
account under the Plan and that I may not make any additional payments into such
account. I understand that all payments made by me shall be accumulated, without
interest or earnings, for the purchase of shares of Common Stock at the
applicable purchase price determined in accordance with the Plan. I further
understand that, except as otherwise set forth in the Plan, shares will be
purchased for me automatically on the Offering Termination Date of each Offering
Period unless I otherwise withdraw from the Plan by giving written notice to the
Company for such purpose.

     4. I understand that I may discontinue at any time prior to the Offering
Termination Date my participation in the Plan as provided in Section 10 of the
Plan. I acknowledge that, unless I discontinue my participation in the Plan as
provided in Section 10 of the Plan, my election will continue to be effective
for each successive Offering Period.

     5. I have received a copy of the complete ActivBiotics, Inc. 2006 Employee
Stock Purchase Plan. I understand that my participation in the Plan is in all
respects subject to the terms of the Plan.

     6. Shares purchased for me under the Plan should be issued in the name(s)
of (name of employee or employee and spouse only):

                     _____________________________________

                     _____________________________________

     7. In the event of my death, I hereby designate the following as my
beneficiary(ies) to receive all payments and shares due to me under the Plan:

<Page>

                                        2

NAME: (Please print)                    ________________________________________
                                        (First)         (Middle)          (Last)

_____________________________________   ________________________________________
(Relationship)                          (Address)

                                        ________________________________________

     8. I understand that if I dispose of any shares received by me pursuant to
the Plan within 2 years after the Offering Commencement Date (the first day of
the Offering Period during which I purchased such shares) or within 1 year after
the Offering Termination Date, I will be treated for federal income tax purposes
as having received ordinary compensation income at the time of such disposition
in an amount equal to the excess of the fair market value of the shares on the
Offering Termination Date over the price which I paid for the shares, regardless
of whether I disposed of the shares at a price less than their fair market value
at the Offering Termination Date. The remainder of the gain or loss, if any,
recognized on such disposition will be treated as capital gain or loss.

     I hereby agree to notify the Company in writing within 30 days after the
date of any such disposition, and I will make adequate provision for federal,
state or other tax withholding obligations, if any, which arise upon the
disposition of the Common Stock. The Company may, but will not be obligated to,
withhold from my compensation the amount necessary to meet any applicable
withholding obligation including any withholding necessary to make available to
the Company any tax deductions or benefits attributable to the sale or early
disposition of Common Stock by me.

     9. If I dispose of such shares at any time after expiration of the 2-year
and 1-year holding periods, I understand that I will be treated for federal
income tax purposes as having received compensation income only to the extent of
an amount equal to the lesser of (1) the excess of the fair market value of the
shares at the time of such disposition over the purchase price which I paid for
the shares under the option, or (2) 15% of the fair market value of the shares
on the Offering Commencement Date. The remainder of the gain or loss, if any,
recognized on such disposition will be treated as capital gain or loss.

     I understand that this tax summary is only a summary and is subject to
change. I further understand that I should consult a tax advisor concerning
certain tax implications of the purchase and sale of stock under the Plan.

     10. I hereby agree to be bound by the terms of the Plan. The effectiveness
of this Subscription Agreement is dependent upon my eligibility to participate
in the Plan.

                                        SIGNATURE:
                                                   -----------------------------

                                        SOCIAL SECURITY #:
                                                           ---------------------

                                        DATE:
                                              ----------------------------------

<Page>

                                                    FORM OF NOTICE OF WITHDRAWAL

                               ACTIVBIOTICS, INC.

                        2006 EMPLOYEE STOCK PURCHASE PLAN

                              NOTICE OF WITHDRAWAL

     I, ____________, hereby elect to withdraw my participation in the
ActivBiotics, Inc. 2006 Employee Stock Purchase Plan (the "Plan") for the
Offering Period that began on ________________, _________. This withdrawal
covers all Contributions credited to my account and is effective on the date
designated below.

     I understand that all Contributions credited to my account will be paid to
me within ten (10) business days of receipt by the Company of this Notice of
Withdrawal and that my option for the current period will automatically
terminate, and that no further Contributions for the purchase of shares can be
made by me during the Offering Period.

     The undersigned further understands and agrees that be or she shall be
eligible to participate in succeeding Offering Periods only by delivering to the
Company a new Subscription Agreement.

Dated:
       ------------------------------   ----------------------------------------
                                                  Signature of Employee

                                        ----------------------------------------
                                                 Social Security Number<Page>

                                                                    Exhibit 10.7

            "CONFIDENTIAL TREATMENT REQUESTED BY ACTIVBIOTICS, INC."

                                LICENSE AGREEMENT

                                     between

                            Merlin Technologies, Inc.

                                       and

                               Kaneka Corporation

                               September 27, 2001

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

                     AMENDED AND RESTATED LICENSE AGREEMENT

          THIS AMENDED AND RESTATED LICENSE AGREEMENT is dated and entered into
as of September 27, 2001, between Kaneka Corporation, a Japanese corporation
having its principal place of business at 2-4, Nakanoshima 3-Chome, Kita-Ku,
Osaka 530-8288, Japan ("Licensor"), and Merlin Technologies, Inc., a Delaware
corporation having its principal place of business at 2 Oliver Street, 3rd
Floor, Boston, MA 02109, U.S.A. ("Licensee"), and is effective as of July 24,
2001 ("the Effective Date").

                                   WITNESSETH:

     WHEREAS, Licensor has developed a certain Compound as hereinafter defined
and possesses certain patents, know-how and confidential technical information
relating thereto, and

     WHEREAS, Licensee desires to acquire from Licensor an exclusive license, on
the terms set forth herein, to make, use and sell Compound and Products, as
hereinafter defined, and

     WHEREAS, subject to all the terms and conditions of this Agreement,
Licensor is willing to grant to Licensee such exclusive license, and

     WHEREAS, the parties entered into a License Agreement as of July 24, 2001
and desire to amend and restate such Agreement to read in full and as set forth
in this amended and restated License Agreement (as amended and restated, "this
Agreement").

     NOW, THEREFORE, IT IS AGREED AS FOLLOWS:

ARTICLE 1. DEFINITIONS

          As used herein, the following terms shall have the following meanings:

     1.1 "Analog Product" or "the Analog Product" shall mean any pharmaceutical
product manufactured from a Compound Analog.

     1.2 "Commercial Production" shall mean production of a Product for the
purpose of commercial sales.

     1.3 "Compound" shall mean KRM-1648, which is described in Appendix 1
attached hereto.

     1.4 "Compound Analog" shall mean any analogs of Compounds developed by
Licensor or covered by Licensor's Patents listed in Appendix 3.

     1.5 "Trademark" shall mean any trademarks or names or registered names or
generic names with respect to Compound and Compound Analogs that is owned by
Licensor or as to which Licensor otherwise has a transferable interest.

     1.6 "FDA" shall mean the United States Food and Drug Administration or any
successor to that agency.

     1.7 "Field" shall mean any and all possible indications and uses of the
Compound for

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                        2

<Page>

prevention, treatment or diagnosis of disease in humans or animals, subject to
the terms of Section 2.1(b) hereof with respect to veterinary applications.

     1.8 "IND" shall mean designations by the FDA of a product as an
Investigational New Drug.

     1.9 "Intellectual Property" means:

          (a) the Patents; and

          (b) the Technical Information

     1.10 "NDA" shall mean a New Drug Application to the FDA or a relevant
procedure in a Country in the Territory in respect of a Product.

     1.11 "Net Sales" shall mean the amounts received by Licensee and/or its
sub-icensee(s), or Licensor and/or its sub-licensee(s), as the case may be,
from independent customers who are not affiliates of Licensee, Licensor or their
respective Sub-licensees, for the sale of a Product or Analog Product, less(a)
trade, cash and/or quantity discounts actually allowed and taken; (b) excises,
sales taxes, value added taxes, duties and the like paid by the buyer in
addition to the sales price of the goods; (c) amounts repaid or credited by
reason of purchase charge backs, recalls, rebates (including government mandated
rebates), rejections defects or returns; and (d) freight, postage and
transportation insurance paid for and separately identified on the invoice or
other documentation maintained in the ordinary course of business.

     1.12 "Option Country" shall mean any of Japan, Korea, People's Republic of
China (including Hong Kong SAR), India, Taiwan and the Philippines.

     1.13 "Patents" shall mean Licensor's United States, European and other
countries issued patents and applications for patents relating to the Compound,
now or hereafter issued or applied for, the inventions which are described and
claimed therein, any reissues, divisions, substitutions, continuations,
continuations-in-part, re-examinations and improvements thereon and extensions
thereof, and any corresponding patent rights in any other country. All Patents
heretofore issued and any pending applications are set forth in Appendix 2
attached hereto.

     1.14 "Products" or "the Product" shall mean any pharmaceutical product
manufactured from the Compound.

     1.15 "Technical Information" shall mean any know-how, technical, scientific
and medical facts, data, advice or other information, written (in the form of
reports, drawings, specifications and the like) or oral, tangible or intangible,
which is now or hereafter controlled or possessed by Licensor and which Licensor
has the right to license (a) relating to a Product or for conversion of the
Compound to a Product, (b) relating to the manufacture of the Compound, provided
such information is required for application of IND or NDA for the Product, (c)
relating to marketing of a Product, or (d) required to comply with applicable
laws or regulations. Technical information shall include, but not be limited to,
patent files, manufacturing know-how, clinical tests and test results,
regulatory submissions and correspondence files, and any other proprietary or
trade secret information concerning the Compound and Intellectual Property
subject to the confidentiality provisions hereof.

     1.16 "Territory" shall mean all the countries of the world, subject to
certain rights retained by Licensor to Option Countries pursuant to Section 2.1
(a) hereof.

     1.17 "Follow On License" shall mean license agreements for Products based
on Compound analogs described in Patents listed in Appendix 3 of this Agreement.

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                        3

<Page>

ARTICLE 2. GRANT OF LICENSE

     2.1 Grant. (i) Licensor hereby grants to Licensee a license to the Compound
and Intellectual Property (a) to research, develop, make, have made, use and
sell Compound and (b) to develop, make, have made, import, export, use,
distribute for sale, promote, market, offer for sale, import, export and sell
(on a royalty basis only, except in the case of compassionate use or in the case
of clinical trials prior to the issuance of a United States NDA approval)
Products in the Field in the Territory in accordance with the terms of this
Agreement. This License shall be an exclusive license, with the right to
sublicense, except to the extent Licensor has retained certain rights to the
Option Countries as set forth below and, further, to the extent Licensor has
retained the right to manufacture the Compound pursuant to Article6 hereof.

          (ii) Licensor hereby grants to Licensee a license to the Compound
Analogs and Intellectual Property (a) to research, develop, make, have made, use
and sell Compound Analog and (b) to develop, make, have made, import, export,
use, distribute for sale, promote, market, offer for sale, import, export and
sell (on a royalty basis only, except in the case of compassionate use or in the
case of clinical trials prior to the issuance of a United States NDA approval)
Analog Products in the Field in the Territory in accordance with the terms of
this Agreement. This License shall be an exclusive license, with the right to
sublicense, except to the extent Licensor has retained certain rights to the
Option Countries as set forth below and, further, to the extent Licensor has
retained the right to manufacture the Compound Analogs.

          (iii) Licensor agrees to assign and hereby assigns to Licensee all
right, title and interest in and to the Trademarks, subject to the condition
that in the event that Licensor executes the option to sell Product or Analog
Product in any Option Country in accordance with this Agreement, Licensee shall
grant to Licensor a license to use such trademark(s) in such Option Country.

          (a) When Licensee applies for an NDA for a Product or Analog Product
in any country in the Territory, Licensee shall notify Licensor thereof in
writing as soon as practically possible. For a period of three (3) months from
Licensor's receipt of the notice from Licensee, Licensor may execute an option
to an exclusive license, to develop, make, have made, use and sell such Product
or Analog Product in any or all of the Option Countries, by a written notice to
Licensee. If Licensor properly exercises the option, Licensee shall grant to
Licensor such license upon the same terms applied to the Licensee from the
Licensor in this agreement, and Licensor shall use its best efforts to develop,
make, have made and sell the Product or Analog Product in the selected Option
Countries and Licensor shall pay to Licensee a counter-royalty equivalent to the
royalty owing from Licensee to Licensor pursuant to Section 3.1 (d) of this
Agreement. If Licensor properly exercises the option, it may be terminated upon
written notice from Licensee to Licensor upon same terms as described from
Licensee to Licensor in Section 7.4 of this Agreement. If Licensor declines or
fails to exercise the option with respect to an Option Country in such
three-month period, Licensor shall have no further rights to develop, use, make,
have made or sell the Product or Analog Product in such Option Country.

          (b) Should Licensor or Licensee receive from a third party a formal
inquiry for sublicense in one or more countries of the Option Countries,
Licensor or Licensee shall notify Licensee or Licensor thereof in writing, and
Licensor and Licensee shall negotiate in good faith in order to decide how to
treat such inquiry within three (3) months from such notice by Licensor or
Licensee.

          (c) Licensee shall use reasonable good faith efforts to develop
Product or Analog Product for veterinary uses during the term of this Agreement.
Licensee shall inform Licensor (not less than annually) of the status of such
development. In the event Licensor reasonably determines that Licensee has not
made significant progress toward market introduction of Product or Analog
Product for veterinary uses, Licensor shall inform Licensee in writing of such
fact and the basis for Licensor's determination. Licensee shall then have three
months in which to cure or to initiate a cure of the default. In the event
Licensee has not affected a cure or not made significant progress in good faith
to effect a cure

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                        4

<Page>

within three months from Licensor's written notice, at Licensor's election, the
"Field" as used in this Agreement shall be limited to non-veterinary uses.

          (d) Licensee shall periodically report, semiannually, to the Licensor
the progress of projects using the Product or Analog Product for non-veterinary
use.

     2.2 Technical Information and Support. Within three (3) months after the
execution of this Agreement, Licensor shall disclose and furnish to Licensee all
Patent actions and prosecutions as well as Technical Information in the
possession of Licensor at the date hereof. In addition, to the extent deemed
necessary by Licensee and subject to the agreement of Licensor, Licensor shall
provide such technical support necessary or desirable to enable Licensee to
develop, market and sell Product and Analog Product. Immediately upon execution
of this Agreement, Licensor shall undertake all necessary and appropriate
actions to assign all IND's and related files at any regulatory agency within
the Territory to Licensee. Licensor shall provide all Technical Information
obtained from any prior licensee(s), to the extent that Licensor has the right
to do so, with particular emphasis on information related to regulatory and
clinical matters. Licensor shall provide a list of all third parties who were
provided with Compound for research purposes and shall provide introductions to
those parties if so requested by Licensee.

     2.3 Sub-licenses. Licensee may grant sublicenses hereunder to third parties
("Sub-licenses"), provided however that (i) for Sub-licenses to manufacture
Compound and Compound Analog in the Territory, and (ii) for Sublicense to market
Product and Analog Product within the Option Countries, Licensee shall inform
the outline of such Sub-license Agreement to Licensor for its consent, who's
consent shall not be unreasonably withheld, and (iii) for Sub-license to market
Product and Analog Product in the Territory excluding Option Countries, Licensee
does not need to inform Licensor for its consent. Promptly following execution
of a Sub-license, Licensee shall give Licensor a copy of the Sub-license.
Licensee shall not grant a Sub-license unless Licensee's rights thereunder are
no less favorable to Licensee than Licensor's rights under Section 3.1 (d) of
this Agreement are to Licensor. Licensee shall require each Sub-licensee
hereunder to comply with its Sub-license, and shall take such action as may be
reasonably necessary to obtain such compliance, including, without limitation,
the institution of legal proceedings.

     2.4 Termination of Sub-license. Any Sub-license granted by Licensee under
Section 2.3 shall provide that either (a) such sub-license will terminate no
later than the date of termination of this Agreement; or (b) upon any
termination of this Agreement, such sub-license shall automatically be assigned
to Licensor provided that (i) the sub-licensee agrees in writing that Licensor
may enforce the terms of such sub-license directly against the sub-licensee,
(ii) the sub-license is subordinate to this Agreement, and (iii) the Licensor
shall have no obligation as a result of such assignment except to keep the
sub-license in effect.

     2.5 Territorial Limitation on Sub-licenses, Sub-licensee shall not directly
or indirectly sell the Product or Analog Product to a person where Sub-licensee
is aware, or ought reasonably to be aware, that the person is proposing to use,
make or sell the Product or Analog Product outside the sub-licensed territory.

     2.6 Extension of Patent Term. Upon the request of Licensee, Licensor will
execute and file any appropriate application to extend the term of any Patent
and any other document related to such application for extension.

     2.7 Use of Compound Limited to Product. Licensee will use the Compound only
in connection with the development, manufacture and sale of the Product.

     2.8 Right to Compound Analogs. In consideration of the license granted
under Section 2.1(ii), Licensee shall pay Licensor [***] dollars
($[***] USD), which payment shall be made by

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                        5

<Page>

October 24, 2001.

     2.9 Improvement. In the event that either of the party develops new
technology, patentable or not, which may significantly improve the production
efficiency or quality of Compound or Product or Compound Analog or Analog
Product, the party shall notify thereof to the other party in writing, and if
the notified party be interested in the licensing of such technology, the
parties hereto shall have a first refusal right to negotiate such licensing in
good faith.

ARTICLE 3. CONSIDERATION, METHOD OF PAYMENT AND RECORD KEEPING

     3.1 Consideration and Method of Payment. In consideration for the license
granted by Licensor hereunder and as the fee for furnishing Technical
Information, Licensee shall pay to Licensor, the payments set forth in this
Section 3.1, less all applicable withholding taxes or other taxes equivalent
thereto which Licensee shall remit directly to the appropriate taxing
authorities. Licensor acknowledges that Licensor has been paid ninety thousand
dollars as of the signing of this Amended and Restated License Agreement.

          (a) Initial Payment. Upon execution hereof, Licensee shall pay [***]
dollars ($[***]) to Licensor, which shall include (i) [***] dollars ($[***])
in cash and (ii) either [***] dollars ($[***]) in cash or [***] dollars
($[***]) in the form of common stock of the Licensee (such stock to be valued at
a price per share equal to that paid by Licensee's then most recent equity
investor) at the sole option of the licensee. Within three months of the
Effective Date of this Agreement, Licensee shall pay an additional [***] dollars
($[***]) in cash to Licensor.

          (b) First Milestone Payment. Licensee shall pay Licensor [***] dollars
($[***]) which shall include (i) ([***]) dollars [$***] in cash and (ii) [***]
dollars ($[***]) in cash or [***] dollars ($[***]) in the form of common stock
of the Licensee (such stock to be valued at a price per share equal to that paid
by Licensee's then most recent equity investor), such form of payment to be
determined by the Licensee and the Licensor through discussions and upon
reaching a reasonable agreement, upon demonstration of human clinical efficacy
of a Product by Licensee or its Sub-licensee (i.e,. transition from Phase II to
Phase III trials, which shall be indicated by enrollment of the first five
patients in a pivotal Phase III trial) in at least one indication of the
following indications: MAC in AIDS patients, M. tuberculosis, H. Pylori in
Peptic ulcer patients, Chlamydia pneumoniae in Multiple Sclerosis or
Atherosclerosis, Chlamydia trachomatis in Sexually Transmitted Disease or
Community acquired pneumonia patients or Staphylococcus aureus infection.

          (c) Final Milestone Payment. Upon NDA approval obtained by Licensee or
its Sub-licensee in the United States, Europe or Japan, Licensee shall pay
Licensor [***] ($[***]) which shall include (i) [***] dollars ($[***]) in cash
and (ii) [***] dollars ($[***]) in cash or [***] dollars ($[***]) in the form of
common stock of the Licensee (such stock to be valued at a price per share equal
to that paid by Licensee's then most recent equity investor) at the sole option
of the Licensee.

          (d) Royalties. Licensee shall pay to Licensor royalties payment based
on the Net Sales of the Product. The royalty shall be paid quarterly within
sixty (60) days of the close of Licensee's fiscal quarter and shall be equal to
[***] percent ([***]%) of the Net Sales of Product, [***] percent ([***]%) in
the case of combination product(s) containing Compound as an active component
wherein Licensee must pay a royalty to a third party or already acquired it from
a third party with no royalty payments or developed it internally de novo, and
[***] percent ([***]%) for a combination product containing Compound as one of
the

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                        6

<Page>

active components where Licensee does not pay a royalty to a third party. In the
case of a Product for veterinary use, where Compound is the only active
ingredient for which the royalty is paid, the royalty shall be equal to [***]
percent ([***]%) of the Net Sales, and [***] percent (***%) in the case of
combination Product(s) wherein Licensee must pay a royalty to a third party.

          (e) Due Diligence. Licensor may elect to convert this Agreement to a
non-exclusive license agreement with the same terms and conditions upon thirty
(30) days prior written notice to Licensee if (a) an NDA has not been approved
in the United States as of a date seven (7) years from the Effective Date of
this Agreement, or (b) Licensee has not marketed a Product or Analog Product
within twenty-four (24) months following NDA approval. Notwithstanding the
foregoing, this Agreement shall remain as an exclusive license for two years
following the date set forth in clause (a) or clause (b) above, as applicable,
if Licensee pays Licensor during such two-year period a minimum annual royalty
of [***] the difference between the actual royalties paid during each year of
such minimum royalty period and such [***] minimum to be payable within 90
days of the end of Licensee's fiscal year during each year of such minimum
period (and such [***] minimum to be prorated to account for any portion of
Licensee's fiscal year during which such minimum royalty obligation is not
applicable)

          (f) Analog Royalties. Licensee shall pay to Licensor royalties payment
based on the Net Sales of the Analog Product. The royalty shall be paid
quarterly within sixty (60) days of the close of Licensee's fiscal quarter and
shall be equal to [***] percent ([***]%) of the Net Sales of Analog Product,
[***] percent ([***]%) in the case of combination product(s) containing [***]
Compound Analog as an active component wherein Licensee must pay a royalty to a
third party or already acquired it from a third party with no royalty payments
or developed it internally de novo, and [***]% for a combination product
containing Compound Analog as one of the active components where Licensee does
not pay a royalty to a third party. In the case of a Analog Product for
veterinary use, where Compound Analog is the only active ingredient for which
the royalty is paid, the royalty shall be equal to [***] percent ([***]%) of the
Net Sales, and [***] percent [***] in the case of combination Analog Product(s)
wherein Licensee must pay a royalty to a third party.

          (g) With respect to Analog Product, upon approval of a New Drug
Application therefor in the United States or the equivalent thereof in Europe or
Japan, Licensee shall pay Licensor [***] dollars ($[***]), and no other
milestone payments.

     3.2 Officer's Certificate. With each payment made pursuant to Section
3.1(d) hereof, Licensee shall provide Licensor with a certificate signed by an
officer of Licensee which states the total amount due and payable and the manner
in which that amount was calculated and which certifies that the information so
provided is true and correct.

     3.3 Books and Records. Licensee shall, and shall use its reasonable
endeavors to require that its sub-licensees shall, keep full, true and accurate
books of accounts and records which truly and accurately disclose the number of
the Product and Analog Product sold by it or its sub-licensees in the Territory
and all matters relating to those sales which are relevant for the purposes of
determining the royalty to be paid by Licensee to Licensor. Such books and
records shall be retained for three (3) years following the occurrence of such
sales and shall be in the form which enables speedy and accurate checks to be
made thereof and shall be supported by all relevant vouchers, invoices, work
orders, delivery notes, receipts and the like, all of which shall be
cross-referenced.

     3.4 Inspection. Licensee shall, and shall require that its sub-licensees
shall, not more frequently than once per calendar year, make the aforesaid books
of accounts and records available for inspection by Licensor or its authorized
representative at any reasonable time during business hours upon reasonable
request at no charge by Licensee to Licensor. Licensor or its duly authorized
representative shall be entitled to take copies of or extracts from any such
account or record. Licensor and its authorized

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                        7

<Page>

representative shall hold any such information in strict confidence except to
the extent necessary to enforce Licensor's rights under this Agreement.

ARTICLE 4. REPRESENTATIONS AND WARRANTIES

     4.1 Representations of Licensor. Licensor represents and warrants that it
owns the Compound and the Intellectual Property exclusive of any and all rights
of any other person or entity. Licensor agrees that it shall not enter into any
agreement or arrangement that would limit Licensor's right to license the
Patents to Licensee pursuant to this Agreement.

     4.2 Patent Defense. Each party hereto shall be responsible for maintenance
and defense of its patent portfolios relating to the Compound or Compound Analog
or Product or Analog Product. However, if Licensor elects not to defend in a
given country, then Licensee shall have the right to defend at its expense. If
Licensee desires to maintain a certain patent or prosecute a certain application
in a Country in the Territory, which Licensor will not maintain or prosecute, by
written request by Licensee, Licensor will, on behalf of Licensee, pay
maintenance or prosecution fees therefore. Licensee shall reimburse Licensor for
such maintenance or prosecution fees plus administrative charge (five percent -
5 % - of such maintenance or prosecution fees incurred by Licensor for each
patent or patent application in each country in the Territory. If this Agreement
terminates, each party has no responsibility for maintenance of the patents
listed in Appendix 2, Appendix 3 and Appendix 4. Licensor and Licensee agree
that the patents and designated countries, described in Appendix 4, are really
required and valuable for maintenance, as part of this Agreement. Licensor will
keep Licensee informed of all patent ongoing actions and prosecutions listed as
Patents and Countries requiring maintenance listed in Appendix 4. In addition,
to the extent Licensor refuses to maintain or abandons a Patent that Licensee
desires to maintain, Licensor shall assign such Patent to Licensee at Licensee's
expense. As to the pending European Patent Application(s) at the European Patent
Office on the execution of this Agreement, Licensor shall be responsible for the
prosecution of such application(s). After such application(s) will be patented,
if Licensee desires to maintain such patent(s) in certain countries of EC and
Licensor will not maintain such patent(s) in such countries, Licensor shall
assign such patent(s) to Licensee at Licensee's expenses incurred by Licensor
after the execution of this Agreement.

     4.3 Right to Grant License. Licensor represents and warrants that it has
the right to grant the license as set forth in Section 2.1.

     4.4 Patents. Licensor represents and warrants that it is unaware of any
information that would adversely affect the validity or enforceability of the
Patents. To the best of Licensor's knowledge, actual and constructive, there are
no pending or threatened claims of litigation brought by a third party under any
third party patent, trade secret or other third party right regarding the
Intellectual Property. Except as set forth in the preceding sentences, Licensor
does not give any warranty that the manufacture, sale or use of the Product or
Analog Product will not infringe the intellectual property rights of any third
party.

     4.5 Name of Licensor. Licensor represents and warrants that Kaneka
Corporation is the English language name of Kanegafuchi Kagaku Kogyo
Kabushiki Kaisha and both names refer to the same corporation.

     4.6 Licensor represents and warrants that it is unaware of any
regulatory information that would adversely affect the development and
registration of the Product or any Analog Product other than as contained in
Technical Information to be provided to Licensee in accordance with Section
2.2.

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                        8

<Page>

ARTICLE 5. INFRINGEMENT

     5.1 Notification. If any Patent is infringed by a third party, either party
hereto learning of such infringement shall promptly inform the other party
hereto. In the event that Licensor shall not promptly take and diligently pursue
action to enjoin the infringement, Licensee shall have the right to take legal
action to enjoin the infringement in its own name or jointly with Licensor.

     5.2 Action by Both Parties. If either of the parties hereto files an
infringement action, then the other party may join in the lawsuit, in which case
each party hereto shall pay fifty percent (50%) of the expenses of the
litigation. Except as provided in Section 5.3 below, the net amount of any
recovery from a third party by judgment or settlement with respect to a claim of
infringement of any Patent shall be paid to the parties in the same proportion
as they have shared the expenses of conducting the suit.

     5.3 Action by One Party. If the other party hereto does not join such suit,
other than as a nominal plaintiff, then the party filing such suit shall pay all
expenses related to such suit and shall retain the entire net amount of any
settlement or judgment award as an extraordinary gain outside of this Agreement.
If it is the Licensee who successfully defend the Patent in a country in the
Territory, then Licensor shall assign the Patent in that country to Licensee.

     5.4 Cooperation. Licensor and Licensee will cooperate with each other in
connection with any claim or litigation involving a third party involving
alleged infringement by or with respect to any Patent.

     5.5 Abandonment. In the event that Licensor elects not to file a patent
application or decides to abandon any pending application or granted patent in
any country, Licensor shall provide adequate notice to Licensee and give
Licensee the opportunity to file or maintain such application or patent at its
own expense; provided, however, that except for the right to file and maintain
such patent rights, the ownership rights of Licensor to such patent rights shall
not be affected by reason of this paragraph.

     5.6 Maintenance upon Termination. If this Agreement terminates in
accordance with Article 7, neither party shall be obligated to maintain the
Patents listed in Appendix 2 attached hereto.

ARTICLE 6. SUPPLY OF COMPOUND

     6.1 Product Development. Licensor shall supply, from its current stock bulk
batch on hand, quantities of Compound required for Product development and for
use during the development of registration dossiers within the Territory at no
charge to Licensee. The precise amount and timing of supply shall be defined
within twelve (12) months from the Effective Date of this Agreement and agreed
by both parties. Licensee shall be responsible for the costs of shipping,
insurance and duties directly incurred from this supply obligation. Licensor
shall supply Licensee Compound Analog, which Licensor reserves.

     6.2 Commercial Supply. Notwithstanding the terms of Section 6.1, Licensor
has elected to terminate the production of new batches of commercial material of
Compound. Licensor will facilitate and expedite the transfer of technology and
know-how required to produce Compound through two independent companies (leading
and secondary manufacturers) designated by Licensee. The transfer of technology
and know-how means:

               (a) Licensor will furnish Licensee with the documents on
technology and know-how required to produce Compound, which Licensor possesses.

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                        9

<Page>

               (b) The technology and know-how is based on the pilot scale
Compound manufacturing (7-15kg production per batch).

               (c) Licensee will dispatch the chemists to Japan to receive the
lectures of the technology and know-how for the production of Compound at the
expense of Licensee.

               (d) Licensor has no responsibility if the Compound which Licensee
or such two independent companies produce meets registration requirements within
the Territory.

Licensor and Licensee will bear respective costs for such technology transfer
based on the discussion of the cost-sharing between the parties. Notwithstanding
any technology transfer, Licensor shall retain the right to manufacture Compound
pursuant to this Section 6.2 in the future. Licensor authorizes Licensee to
maintain Licensor as producer of record for Compound supply in the current FDA
clinical trials dossier and subsequent registration dossiers to be filed
elsewhere (referring to the current stock bulk batch and releasing test records
of Compound GMP supply, which will be used for Licensee's clinical trials and
registration dossiers with the FDA). Licensee will not maintain Licensor as an
alternate source of commercial material.

     6.3 Liability. Licensor shall have no obligation or liability for any
claim, loss or damage arising out of or in relation to the supply of Compound to
Licensee, and/or any use of Compound or any Product containing Compound made by
Licensee or Licensee's sub-licensee, or designated companies referred to in
Section 6.2.

ARTICLE 7. TERM AND TERMINATION

     7.1 Term. Unless otherwise terminated earlier pursuant to this Article 7,
this Agreement shall continue in full force and effect until the fifteenth
(15th) anniversary of first sale of a Product or Analog Product by Licensee.

     7.2 Termination for Breach. Either party may terminate this Agreement in
the event the other party shall have materially breached or defaulted in the
performance of any of its material obligations hereunder, and such default shall
have continued for one hundred twenty (120) days after written notice thereof
was provided to the breaching party by the non-breaching party. Any termination
shall become effective at the end of such one hundred twenty (120) day period
unless the breaching party (or any other party acting on its behalf) has cured
any such breach or default prior to the expiration of the one hundred twenty
(120) day period.

     7.3 Termination for Insolvency. If voluntary or involuntary proceedings by
or against a party are instituted in bankruptcy under any insolvency law, or a
receiver or custodian is appointed for such party, or proceedings are instituted
by or against such party for corporate reorganization or the dissolution of such
party, which proceedings, if voluntary, shall not have been dismissed within
sixty (60) days after the date of filing, or if such party makes an assignment
for the benefit of creditors, or substantially all of the assets of such party
are seized or attached and not released within sixty (60) days thereafter, the
other party may immediately terminate this Agreement effective upon notice of
such termination.

     7.4 Clinical Studies, Product Development and Abandonment. This Agreement
may be terminated upon written notice from Licensor to Licensee if:

          (a) Licensee fails to begin a clinical study with respect to a Product
or Analog Product

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                       10

<Page>

within one year after FDA approval of the Licensee's IND for the first Product
or Analog Product; or

          (b) Licensee fails to engage in and continue further stages of a
clinical study of a Product or Analog Product within one year after FDA approval
of the first Licensee protocol for a clinical study; or

          (c) Licensee does not develop, or has no intention to develop the
Compound or a Compound Analog, as determined at the discretion of Licensor, or
Licensee does not initiate the development of the Compound or any Compound
Analog as a human drug within one (1) year after the execution of this
Agreement, or as an animal drug within two (2) years after the Effective Date of
this Agreement.

     7.5 Effect of Breach or Termination.

          7.5.1. Paid Up License. Upon expiration of this Agreement as provided
in Section 7.1, the license hereunder shall revert to a fully paid, royalty free
license with the terms and conditions effective then, other than royalty payment
obligation.

          7.5.2 Accrued Obligations. Termination of this Agreement for any
reason shall not release any party hereto from any liability which, at the time
of such termination, has already accrued to the other party or which is
attributable to such termination, nor shall it preclude either party from
pursuing all rights and remedies it may have hereunder or at law or in equity
with respect to any breach of this Agreement.

          7.5.3 Stock on Hand. In the event this Agreement is terminated for any
reason, Licensee shall have the right to sell or otherwise dispose of the stock
of any Product or Analog Product subject to this Agreement then on hand or in
the process of manufacture at the time of termination, subject to the right of
Licensor to receive royalties thereon.

     7.6 Assignment. Neither party shall assign its rights or obligations under
this Agreement, in whole or in part, by operation of law or otherwise, without
the prior written consent of the other party; provided however, that either
party may, without such consent, assign this Agreement and its rights and
obligations thereunder in connection with the transfer or sale of all or
substantially all of its business, or in the event of its merger, consolidation,
change in control or similar transaction; provided further that, in the event of
any such transaction, intellectual property rights of any person or entity,
other than Licensor or Licensee or their affiliates, that is an acquiring party
in such transaction shall not be included in the intellectual property licensed
hereunder. Any purported assignment in violation of this Section 7.6 shall be
void. This Agreement shall inure to the benefit of and be binding upon the
parties hereto and their respective successors and permitted assigns.

     7.7 Survival. Section 6.3 and Articles 7, 8 and 9 shall survive any
termination of this Agreement for any reason.

ARTICLE 8. CONFIDENTIALITY

     8.1 Confidential Information. Except as expressly provided herein, the
parties agree that, for the term of this Agreement and for seven (7) years
thereafter, the receiving party shall keep confidential and shall not publish or
otherwise disclose and shall not use for any purpose other than the purposes
contemplated by this Agreement any information and data furnished to it by the
disclosing party hereto pursuant to this Agreement (hereinafter referred to as
"Confidential Information"), except that to the extent that it can be
established by competent proof by the receiving party that such Confidential
Information:

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                       11

<Page>

     (a) was already known to the receiving party, other than under an
obligation of confidentiality, at the time of disclosure, as evidenced by its
written records; or

     (b) was generally available to the public or otherwise part of the public
domain at the time of its disclosure to the receiving party; or

     (c) became generally available to the public or otherwise became part of
the public domain after its disclosure, other than through any act or omission
of the receiving party in breach of this Agreement; or

     (d) was independently developed by the receiving party, as demonstrated by
documented evidence prepared contemporaneously with such independent
development; or

     (e) was subsequently lawfully disclosed to the receiving party by a person
other than a party hereto.

     8.2 Oral Disclosure. Information or data which is orally disclosed shall
constitute Confidential Information if disclosing party, within thirty (30) days
after such disclosure, delivers to the receiving party a written notice
describing such Confidential Information and referring the place and date of
such oral disclosure and the names of the employees or officers of the receiving
party to whom such disclosure was made.

     8.3 Permitted Use and Disclosure. Each party hereto may use or disclose
information disclosed to it by the other party to the extent such use or
disclosure is reasonably necessary in filing or prosecuting patent
applications contemplated hereby, prosecuting or defending litigation, complying
with applicable governmental regulations or otherwise submitting information to
tax or other governmental authorities, conducting clinical trials contemplated
hereby, or making a permitted sublicense or otherwise exercising its rights
hereunder, provided that if a party is required to make any such disclosure of
another party's Confidential Information, other than pursuant to a
confidentiality agreement, it will give reasonable advance notice to the latter
party of such disclosure and, save to the extent inappropriate in the case of
patent applications, will use its best efforts to secure confidential treatment
of such information prior to its disclosure (whether through protective orders
or otherwise).

     8.4 Public Disclosure. Except as otherwise required by law, neither party
shall issue a press release or make any other public oral or written disclosure
of the terms of this Agreement without the prior approval of such press release
or other public disclosure by the other party. Each party shall submit any such
press release or public disclosure to the other party, and the receiving party
shall have reasonable time and up to two (2) weeks to review and approve or
disapprove any such press release or public disclosure. If the receiving party
does not respond within such two (2) weeks period, the press release or public
disclosure shall be deemed approved. In addition, if a public disclosure is
required by law, including without limitation in a filing with the Securities
and Exchange Commission, the disclosing party shall provide copies of the
disclosure reasonably in advance of such filing or other disclosure for the
non-disclosing party's prior review and comment.

     8.5 Return of Confidential Information. Upon any termination, but not
expiration, of this Agreement, all licenses and rights under such licenses shall
terminate, and Licensor and Licensee shall promptly return to the other party
all Confidential Information received from the other party (except one copy of
which may be retained for archival purposes), and neither party shall be
entitled to use any such Confidential Information of the other party for any
purpose following such termination.

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                       12

<Page>

Article 9. Miscellaneous

     9.1 Governing Law. This Agreement and any disputes arising from the
performance or breach hereof shall be governed by and construed and enforced in
accordance with the laws of the Commonwealth of Massachusetts, without reference
to conflict of law principles.

     9.2 Entire Agreement. This Agreement, which includes the Appendices hereto,
contains the entire agreement between Licensor and Licensee with respect to the
transactions contemplated by this Agreement and supersedes all prior
arrangements or understandings with respect thereto including the License
Agreement between the parties dated and entered into as of July 24, 2001.

     9.3 Notices. All notices or other communications, which are required or
permitted hereunder, must be in writing and must be mailed (registered postage
prepaid), or sent by confirmed facsimile, to the appropriate party addressed
as follows:

          If to Licensor: Kaneka Corporation

               2-4, Nakanoshima 3-chome, Kita-Ku
               Osaka 530-8288, Japan

                    Attention: General Manager
                    Life Science RD Center
                    Fax: +81(794)45-2459

          If to Licensee: Merlin Technologies, Inc.
               2 Oliver Street, 3rd Floor
               Boston, Massachusetts 02109, USA

                    Attention: Chief Executive Officer
                    Fax: +1(617) 423-9997

If any notice or other communication, which is required or permitted hereunder,
is given by airmail, it will be effective on seventh (7th) day after it is
deposited in the mails; if given by confirmed facsimile, when delivered. Any
party may by such notice change the address to which notice of other
communications to it is to be delivered or mailed.

     9.4 Waivers and Amendments. Any waivers of any term or condition of this
Agreement, or any amendment or supplementation of this Agreement, shall be
effective only if in writing signed by the parties. A waiver of any breach or
failure to enforce any of the terms or conditions of this Agreement shall not in
any way affect, limit or waive a party's rights hereunder at any time to enforce
strict compliance thereafter with every term or condition of this Agreement.

     9.5 Severability. In the event that any provision contained in this
Agreement shall be determined to be invalid, illegal or unenforceable in any
respect for any reason, the validity, legality, and enforceability of any such
provision in every other respect and the remaining provision of this Agreement
shall not, at the election of the party for whose benefit the provision exists,
be in any way impaired.

     9.6 Section Headings. The section headings contained herein are for the
purpose of convenience and are not intended to define or limit the contents of
such sections.

     9.7 Arbitration. Any controversy arising out of or in relation to this
Agreement, or the breach

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                       13

<Page>

thereof shall be settled mutual consultation and negotiation between the parties
hereto, but if failed, the claim brought against Licensor shall be settled
exclusively by arbitration to be held in Osaka, Japan, in accordance with the
rules of the Japan Commercial Arbitration Association, and the claim brought
against Licensee shall be settled exclusively by arbitration to be held in
Boston, Massachusetts, USA, in accordance with the Commercial Arbitration Rules
of the American Arbitration Association. Any judgment upon, the award rendered
by the arbitrators may be entered in any court having jurisdiction.

     9.8 Counterparts. This Agreement may be signed in one or more counterparts,
each of which shall be deemed an original, but all of which together shall
constitute one and the same instrument.

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                       14

<Page>

IN WITNESS WHEREOF, the parties hereby have executed this Agreement by their
duly authorized representatives as of the Effective Date.

                                        KANEKA CORPORATION

                                        By: /s/ Takehisa Ohashi
                                            ------------------------------------
                                            Name: Takehisa Ohashi, PhD
                                            Title: General Manager
                                                   Life Science RD Center

                                        MERLIN TECHNOLOGIES, INC

                                        By: /s/ Chalom Sayada
                                            ------------------------------------
                                            Name: Chalom Sayada, PhD, MD
                                            Title: President and Chief
                                                   Executive Officer

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                       15

<Page>

APPENDIX 1

CHEMICAL STRUCTURE

                                    [GRAPHIC]

CODE NO.: KRM-1648

GENERAL NAME: Rifalazil

CAS NO.: 129791-92-0

CHEMICAL NAME: 5,12-Dihydroxy-2,4-dimethyl-10-[4-(2-methyl- propyl)-l-
piperazinyl]-2,7-[oxy(5-acetoxy-7, 9-dihydroxy-3-methoxy-4,6,8,10,14-
pentamethyl-15-oxo-l,ll,13-pentadecatriene-l,15-diyl)imino]-6H-benzofuro
[4,5-a]phenoxazine-l(2H),6-dione
or
3'-Hydroxy-5'-(4-isobutyl-l-piperazinyl)benzoxazinorifamycin

MOLECULAR FORMULA: C(51)H(64)N(4)O(13)

MOLECULAR WEIGHT:

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                       16

<Page>

APPENDIX 2

             LIST OF THE PATENTS RELATED TO THE RIFAMYCIN DERIVATIVE

1.   "3'- Hydroxybenzoxazinorifamycin derivative, process for preparing the same
     and antibacterial agent containing the same"
     U.S.: Patent No. 4,983,602           Expiration Date: February 5, 2006
     Canada: Patent No. 1,304,363         Expiration Date: June 30, 2009
     EPC (BE, CH, DE, ES, FR, GB, IT, LI):
          Patent No. 0366914              Expiration Date: September 14, 2009
          Patent No. (DE) 68919650.4
     China: Patent No. 24,993             Expiration Date: September 16, 2004
     Singapore: Patent No. 9,790,350-4    Expiration Date: September 14, 2009
     Japan Patent No. 2544488             Expiration Date: November 1, 2008

2.   "3'-alkyl, -arylsiryloxybenzoxazinorifamycin derivatives"
     China: Patent No. 39,298             Expiration Date: August 16, 2006
     Taiwan: Patent No. 60,726            Expiration Date: January 20, 2008
     Korea: Patent No. 203615             Expiration Date: August 3, 2011
             Patent No. 203729            Expiration Date: August 3, 2011
     Japan Patent No. 2620399             Expiration Date: August 10, 2010

3.   "Production method for fine granules"
     U.S.: Patent No. 5,547,683           Expiration Date: October 6, 2013
     EPC (BE, CH, DE, ES, FR, GB, IT, LI):
          Patent No. 0616841              Expiration Date: October 6, 2013
          Patent No. (DE) 69322764.8
     Canada: Appl. No. 2,124,568          Filed: October 6, 1993
                                                             (under examination)
     China: Appl. No. 93,118,594.7        Filed: October 6, 1993
                                          Expiration Date:  October 6, 2013
     Korea: Appl. No. 701,971-94          Filed: October 6, 1993
                                                             (under examination)
     Japan: Appl. No. P04-297905          Filed: October 9, 1992
                                                             (under examination)

4.   "Treatment of chlamydia infectious diseases by rifamycin derivative"
     US: Patent No. 5,786,349             Expiration Date: December 9, 2016
     Canada: Appl. No. 2,192,255          Filed : December 6, 1996
     EPC (BE, CH, DE, ES, FR, GB, IT, LI):
          Patent No. 0778022              Expiration Date: December 6, 2016
          Patent No. (DE) 69612465.3
     Japan: Appl. No. P08-002634          Filed: January 10, 1995

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                       17

<Page>

5.   "Treatment of disease caused by infection of Helicobacter"
     US: Patent No. 5,981,522             Expiration Date : August 29, 2016
     Canada: Appl. No. 2,204,007          Filed: August 29, 1996
          Appl. No. 2,230,649             Filed: February 27, 1998
     EPC (BE, CH, DE, ES, FR, GB, IT, LI):
          Appl. No. 96928723.4            Filed: August 29, 1996
          Appl. No. 98103481              Filed: February 27, 1998
     Taiwan: Patent No. 113445            Expiration Date : September 5, 2016
          Appl. No. 85110867.1            Filed: February 27, 1998
     Korea: Appl. No. 702,879-97          Filed: August 29, 1996
          Appl. No. 6,462-98              Filed: February 27, 1998
     Japan: Appl. No. P10-038590          Filed: February 20, 1998

6.   "Method for treating mastitis in a domestic animal"
     US: Appl. No. 463580                 Filed: July 29, 1997
     CA: Appl. No. 2297012                Filed: July 29, 1998
     EPC (DE, GB, FR, IT, CH, NL, SE) :
          Appl. No. 98,937,047.3          Filed: July 29, 1998
     Taiwan: Appl. No. 88,100,078         Filed: January 5, 1999
     Korea: Appl. No. 00-7,000,601        Filed: July 29, 1998
     Australia: Appl. No. 85844-98        Filed: July 29, 1998
     New Zealand: Appl. No. 503,027       Filed: July 29, 1998
     China: Appl. No. 98,807,682.9        Filed: July 29, 1998
     Japan: Appl. No. P2000-504.861       Filed: July 29, 1998

7.   "Antimicrobial compositions with synergistic effect, drugs and remedies for
     digestive diseases containing the same, process for the production thereof
     and preparations associated therewith"
     PCT (US, CA, DE, GB, FR, IT, CH, BE, ES, JP, KR):
          Appl. No. PTC/WO99-43327        Filed: February 17, 1999
     Taiwan: Appl. No. 88,102,542        Filed: February 22, 1999

8.   "Method for treatment of bacterial infections with once or twice-weekly
     administered rifalazil"(PathoGenesis assigned to Kaneka, 2000)
     US: Appl. No. 112,921                Filed: December 18, 1998
     PCT ( CA, DE, ES, FR, GB, IT, AT, BE, CH, DK, GR, FI, LU, NL, PT, SE, KR,
     CN, JP):
     Appl. No. PTC/WO00/35408,            Filed: December 18, 1998

9.   "Benzoxazinorifamycin derivative, process for preparing the same and
     antibacterial agent containing the same"
     US Patent No. 4,690,919              Expiration Date February 5, 2006
     Canada Patent No. 1,256,430          Expiration Date June 27, 2006
     EPC (BE, CH, FR, GB, IT, LI, NL, SE, DE)
          Patent No. 0,190,709            Expiration Date February 4, 2006
     China Patent No. 24,976              Expiration Date May 31, 2001
     Japan Patent No. 1,854,546           Expiration Date January 20, 2006

          [***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH
          CONFIDENTIAL TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL
          HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO
          RULE 24b-2 PROMULGATED UNDER THE SECURITIES EXCHANGE ACT OF 1934, AS
          AMENDED

                                       18

<Page>

10.  "Alkyl-substituted benzoxazinorifamycin derivative, process for preparing
     the same and antibacterial agent containing the same"
     US: Patent No. 4,859,661             Expiration Date: July 13, 2007

11.  "Substituted benzoxazinorifamycin derivative and antibacterial agent
     containing the same"
     US Patent No. 4,965,261              Expiration Date: March 16, 2009
     Canada Patent No. 1,293,503          Expiration Date: December 23, 2008
     EPC (BE, CH, ES, FR, GB, IT, LI, DE):
          Patent No. 0,333,176            Expiration Date: March 15, 2009
          Patent No. (DE) 68924722.2
     China Patent No. 20,729              Expiration Date: March 17, 2004
     Japan Patent No. 2544488             Expiration Date: September 14, 2009

Note: Request the Patent Office to proceed the validity of patent 10 and 11 to
be recovered

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                       19

<Page>

APPENDIX 3

1*.  "3'- Hydroxybenzoxazinorifamycin derivative, process for preparing the same
     and antibacterial agent containing the same"

2.   "3'-alkyl, -arylsiryloxybenzoxazinorifamycin derivatives"

4.   "Treatment of chlamydia infectious diseases by rifamycin derivative"

5.   "Treatment of disease caused by infection of Helicobacter"

6.   "Method for treating mastitis in a domestic animal"

8.   "Method for treatment of bacterial infections with once or twice-weekly
     administered rifalazil" (PathoGenesis assigned to Kaneka, 2000)

9.   "Benzoxazinorifamycin derivative, process for preparing the same and
     antibacterial agent containing the same"

10.  "Alkyl-substituted benzoxazinorifamycin derivative, process for preparing
     the same and antibacterial agent containing the same"

11.  "Substituted benzoxazinorifamycin derivative and antibacterial agent
     containing the same"

* Serial numbers are the same as shown in Appendix 2

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                       20

<Page>

APPENDIX 4

                   PATENTS AND COUNTRIES REQUIRING MAINTENANCE

1*.  "3'- Hydroxybenzoxazinorifamycin derivative, process for preparing the same
     and antibacterial agent containing the same"
     US, CA, DE, ES, FR, GB, IT, Singapore, Japan

2.   "3'-alkyl, -arylsiryloxybenzoxazinorifamycin derivatives"
     China, Taiwan, Korea, Japan

3.   "Production method for fine granules"
     US, CA, DE, ES, FR, GB, IT, CN, Japan, KR

4.   "Treatment of chlamydia infectious diseases by rifamycin derivative"
     US, CA, DE, ES, FR, GB, IT, Japan

5.   "Treatment of disease caused by infection of Hehcobacter"
     US, CA, DE, ES, FR, GB, IT, Taiwan, Korea, Japan

6.   "Method for treating mastitis in a domestic animal"
     US, CA, DE, GB, FR, IT, NL, Taiwan, Australia, New Zealand, China, Japan

8.   "Method for treatment of bacterial infections with once or twice-weekly
     administered rifalazil"
     US, CA, DE, ES, FR, GB, IT, Korea, China, Japan

9.   "Benzoxazinorifamycin derivative, process for preparing the same and
     antibacterial agent containing the same"
     US, CA, FR, GB, IT, DE, Japan

* Serial numbers are the same as shown in Appendix 2

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

                                       21

<Page>

                           SECOND AMENDMENT AGREEMENT

This AMENDMENT is made on this day of September 18th, 2002, by and between
Kaneka Corporation, a Japanese corporation, having its principal place of
business at 2-4, Nakanoshima 3-Chome, Kita-Ku, Osaka 530-8288, Japan
("Licensor") and ActivBiotics, Inc. (formerly known as Merlin Technologies,
Inc.), a Delaware corporation, having its principal place of business at 198
Broadway Street, Cambridge, MA 02139, U.S.A. ("Licensee").

WHEREAS, the Licensor and the Licensee have entered into the License Agreement,
as of July 24th, 2001;

WHEREAS, the Licensor and the Licensee have entered into the Amended and
Restated License Agreement, as of September 27th, 2001 (the "Agreement"); and

WHEREAS, in response to the Licensee's request and inquiry, the Licensor has
decided to definitively not to keep any rights to execute at any time its option
to an exclusive license in the Option Country, as provided in Section 2.1 (a) of
the Agreement.

NOW, THEREFORE, the parties hereto have agreed as follows:

Article 1. Defined Terms

     The terms defined in the Agreement and not otherwise defined herein shall
     have the respective meanings set forth in the Agreement.

Article 2. Amendments to the Agreement

2.1  The Licensor and the Licensee agree to add the followings to Section 3.1 of
     the Agreement:

     (h)  Initial Payment. The Licensee shall pay [***] dollars ($[***]) in cash
          to the Licensor, within sixty (60) days from the date of the execution
          hereof.

     (i)  First Milestone Payment. The Licensee shall pay the Licensor [***]
          dollars ($[***]) in the form of shares of a new series of preferred
          stock of the Licensee (such shares of such new series of preferred
          stock to be specific for this milestone payment and equivalent to the
          Common Stock in all respects except that such series of preferred
          stock will rank senior to the common stock and that the per share
          price of each share of such new series of preferred stock shall
          be equal to that paid by the licensee's then most recent equity
          investor), such form of payment to be determined by the Licensee
          and the Licensor

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

                                        2

          through discussions and upon reaching a reasonable agreement, upon
          demonstration of human clinical efficacy of a Product by the Licensee
          or its Sub-licensee (i.e., transition from Phase II to Phase III
          trials in the Option Country, which shall be indicated by enrollment
          of the first five patients in a pivotal Phase III trial) in at least
          one indication of the following indications: MAC in AIDS patients, M.
          tuberculosis, H. Pylori in Peptic ulcer patients, Chlamydia pneumoniae
          in Multiple Sclerosis or Atherosclerosis, Chlamydia trachomatis in
          Sexually Transmitted Disease or Community acquired pneumonia patients
          or Staphylococcus aureus infection.

          (j)  Final Milestone Payment. Upon NDA approval in the Option Country
               (except [***]; [***] shall still be subjected to the terms and
               conditions of Section 3.1(c) in the Agreement) obtained by the
               Licensee or its Sub-licensee, the Licensee shall pay the Licensor
               [***] dollars ($[***]) in the form of shares of a new series of
               preferred stock of the Licensee (such shares of such new series
               of preferred stock to be specific for this milestone payment and
               equivalent to the Common Stock in all respects except that such
               series of preferred stock will rank senior to the Common Stock
               and that the per share price of each share of such new series of
               preferred stock shall be equal to that paid by the Licensee's
               then most recent equity investor) or in cash, at the sole option
               of the Licensee.

2.2  The Licensor and the Licensee agree to amend Section 2.9 of the Agreement
     as follows:

     2.9  Improvement. In the event that either of the party develops new
          production or manufacturing technology, patentable or not, which may
          significantly improve the production efficiency or the production
          quality of Compound or Product or Compound Analog or Analog Product,
          the party shall notify thereof to the other party in writing, and if
          the notified party be interested in the licensing of such production
          or manufacturing technology, the parties hereto shall have a first
          refusal right to negotiate such licensing in good faith.

2.3  The Licensor and the Licensee agree to amend Sections 3.1(b), 3.1(c),
     3.1(d) and 3.1(f) of the Agreement as follows:

          (b) First Milestone Payment. Licensee shall pay Licensor [***] dollars
          ($[***]) which shall include (i) [***] dollars ($[***]) in cash and
          (ii) [***] dollars ($[***]) in cash or [***] dollars ($[***]) in the
          form shares of a new series of preferred stock of the Licensee (such
          shares of such new series of

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

                                        3

          preferred stock to be specific for this milestone payment and
          equivalent to the Common Stock in all respects except that such series
          of preferred stock will rank senior to the Common Stock and that the
          per share price of each share of such new series of preferred stock
          shall be equal to that paid by the Licensee's then most recent equity
          investor), such form of payment to be determined by the Licensee and
          the Licensor through discussions and upon reaching a reasonable
          agreement, upon demonstration of human clinical efficacy of a Product
          by Licensee or its Sub - licensee (i.e., transition from Phase II to
          Phase III trials, which shall be indicated by enrollment of the first
          five patients in a pivotal Phase III trial) in at least one indication
          of the following indications: MAC in AIDS patients, M. tuberculosis,
          H. Pylori in Peptic ulcer patients, Chlamydia pneumoniae in Multiple
          Sclerosis or Atherosclerosis, Chlamydia trachomatis in Sexually
          Transmitted Disease or Community acquired pneumonia patients or
          Staphylococcus aureus infection.

          (c) Final Milestone Payment. Upon NDA approval obtained by Licensee or
          its Sub - licensee in the United States, Europe or Japan, Licensee
          shall pay Licensor [***] dollars ($[***]) which shall include (i)
          [***] dollars ($[***]) in cash and (ii) [***] dollars ($[***]) in cash
          or [***] dollars ($[***]) in the form of shares of a new series of
          preferred stock of the Licensee (such shares of such new series of
          preferred stock to be specific for this milestone payment and
          equivalent to the Common Stock in all respects except that such series
          of preferred stock will rank senior to the Common Stock and that the
          per share price of each share of such new series of preferred stock
          shall be equal to that paid by the Licensee's then most recent equity
          investor) at the sole option of the Licensee.

     3.1(d) Royalties. The Licensee shall pay to the Licensor royalties based on
          the Net Sales of the Product. The royalty shall be paid quarterly
          within sixty (60) days of the close of the Licensee's fiscal quarter.
          In the case of a product for Human use, where Compound is the only
          active ingredient for which the royalty is paid, the royalty shall be
          equal to [***] percent ([***]%) of the Net Sales of Product for a
          combination product containing Compound as one of the active component
          where the Licensee does not pay a royalty to third party, or [***]
          percent ([***]%) in the case of combination product(s) containing
          Compound as an active component wherein the Licensee must pay a
          royalty to a third party, or already acquired the additional patented
          combined technology from a third party even with no royalty payments,
          or developed the new patented combined technology internally de novo.
          In the case of a Product for veterinary use, where Compound is the
          only active ingredient for which the royalty is paid, the royalty
          shall be equal to [***] percent

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

                                        4

          ([***]) of the Net Sales, or [***] percent ([***]) in the case of
          combination Product(s) wherein the Licensee must pay a royalty to a
          third party.

     3.1  (f) Analog Royalties. The Licensee shall pay to the Licensor
          royalties based on the Net Sales of the Analog Product. The royalty
          shall be paid quarterly within sixty (60) days of the close of the
          Licensee's fiscal quarter. In the case of a product for Human use,
          where Compound Analog is the only active ingredient for which the
          royalty is paid, the royalty shall be equal to [***] percent ([***]%)
          of the Net Sales of Analog Product for a combination product
          containing Compound Analog as one of the active components where the
          Licensee does not pay a royalty to third party, or [***] percent
          ([***]%) in the case of combination product(s) containing Compound
          Analog as an active component wherein the Licensee must pay a royalty
          to a third party, or already acquired the additional patented combined
          technology from a third party even with no royalty payments, or
          developed the new patented combined technology internally de novo. In
          the case of a Analog Product for veterinary use, where Compound Analog
          is the only active ingredient for which the royalty is paid, the
          royalty shall be equal to [***] percent ([***]%) of the Net Sales, or
          [***] percent ([***]%) in the case of combination Analog Product(s)
          wherein the Licensee must pay a royalty to a third party.

Article 3. Exchange of Stock

     Licensor and Licensee hereby agree to convert the one hundred twenty
     thousand common stocks issued to Licensor by Licensee on October 15th,
     2001, pursuant to the provision in the Agreement, to one hundred twenty
     thousand Preferred A Shares, equivalent in all respects to the Series A
     round Preferred A Shares issued in October 2001 as part of the Series A
     round of financing.

Article 4. No Other Amendments or Waivers

     Except as expressly provided in this Amendment, all the terms and
     conditions of the Agreement are hereby ratified and confirmed and remain in
     full force and effect.

Article 5. Execution in Counterparts

     This Amendment may be executed in any number of counterparts, each of which
     shall be deemed an original, but which together shall constitute one
     instrument.

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

                                        5

     This Amendment shall be effective upon execution and delivery of this
     Amendment by the parties hereto, and shall be governed by the applicable
     law specified in Section 9.1 of the Agreement.

Signed and delivered by a duly authorized representative of each party.

                                        KANEKA CORPORATION

                                        /s/ Takehisa Ohashi
                                        ----------------------------------------
                                        Takehisa Ohashi, PhD
                                        General Manager, Life Science RD Center

                                        ACTIVBIOTICS, INC.

                                        /s/ Chalom Sayada
                                        ----------------------------------------
                                        Chalom Sayada, PhD, MD
                                        President and Chief Executive Officer

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

                            THIRD AMENDMENT AGREEMENT

     This THIRD AMENDMENT AGREEMENT ("Amendment") is made on this 29th day of
August, 2004, by and between Kaneka Corporation, a Japanese corporation, having
its principal place of business at 2-4, Nakanoshima 3-Chome, Kita-Ku, Osaka
530-8288, Japan ("Licensor") and ActivBiotics, Inc. (formerly known as Merlin
Technologies, Inc.), a Delaware corporation, having its principal place of
business at 128 Spring Street, Lexington, MA, 02421, U.S.A. ("Licensee").

     WHEREAS, the Licensor and the Licensee have entered into the License
Agreement, as of July 24, 2001;

     WHEREAS, the Licensor and the Licensee have entered into the Amended and
Restated License Agreement, as of September 27, 2001 (the "Amended and Restated
Agreement");

     WHEREAS, the Licensor and the Licensee have entered into the Second
Amendment Agreement, as of September 18, 2002 (the "Second Amendment
Agreement"), pursuant to which Licensor and Licensee have agreed to amend the
Amended and Restated Agreement to, among other things, terminate any and all
rights that Licensor retained under the Amended and Restated Agreement with
respect to the Option Countries;

     WHEREAS, Licensor and Licensee acknowledge that there is no First Amendment
Agreement to the Amended and Restated Agreement and that, upon execution and
delivery by the parties of this Amendment, the Second Amended Agreement and this
Amendment shall be the only amendments in effect to the Amended and Restated
Agreement; and

     WHEREAS, in response to the Licensee's request and inquiry, the Licensor
has decided to assign to the Licensee certain patents or patent applications of
the Licensor as further provided in this Amendment.

     NOW, THEREFORE, the parties hereto have agreed as follows:

ARTICLE 1. DEFINED TERMS

          The term "Current Agreement" as used in this Amendment shall mean the
          Amended and Restated Agreement as amended and modified by the Second
          Amendment Agreement Capitalized terms used in this Amendment without
          definition and that are defined in the Amended and Restated Agreement
          shall have the meaning ascribed to such terms in the Amended and
          Restated Agreement. From and after the date of this Amendment, the
          term "Agreement" as used throughout the Amended and Restated Agreement
          and/or this Amendment shall mean the Amended and Restated Agreement as
          amended and modified by the Second Amendment Agreement and this
          Amendment.

ARTICLE 2. OPTION COUNTRY

          The Licensor and Licensee hereby acknowledge, ratify, confirm and
          agree that, pursuant to the Second Amendment Agreement, Licensor and
          Licensee agreed to amend the Amended and Restated Agreement to, among
          other things, terminate any and all rights that Licensor had
          previously retained under the Amended and Restated Agreement with
          respect to the Option Countries. Accordingly, consistent with such
          agreement, Licensor and Licensee hereby agree that the obligations of
          Licensee under clause (ii) of Section 2.3 of the Current Agreement
          have been terminated effective as of the date of the Second Amendment
          Agreement.

Signature Page to Third Amendment

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

ARTICLE 3. PATENTS ASSIGNMENT

3.1  The Licensor hereby assigns to Licensee all of the Licensor's right, title
     and interest in and to those patents and patent applications that are
     listed as items number 3, 6, 7, 10 and 11 of the new Appendix 2 attached
     hereto, and to all rights and claims relating to or arising from such
     patents and patent applications. Licensor shall execute and deliver such
     additional documents and instruments of assignment as may be reasonably
     requested by Licensee from time to time to perfect or evidence the
     foregoing assignment.

3.2  Any procedures, including but not limited to the applications to or
     registrations at the relevant authorities in the Territory, necessary to
     complete the foregoing assignment shall be performed by Licensee.

3.3  The reasonable costs and expenses incurred by Licensor arising out of, or
     in connection with, the assignment of patents and patent applications
     contemplated under Section 3.1 of this Amendment shall be borne by
     Licensee.

ARTICLE 4. CONSIDERATION, ETC.

4.1  In consideration for the assignment of patents and patent applications
     pursuant to Section 3.1 of this Amendment, Licensee shall pay to Licensor
     [***] United States Dollars (US$[***]) in cash within thirty (30) days from
     the date Licensor executed and delivered such additional documents and
     instruments of assignment as may be reasonably requested by Licensee to
     perfect or evidence the assignment of patents and patent applications
     pursuant to Section 3.1 of this Amendment.

4.2  For the avoidance of doubt, the amount payable by Licensee pursuant to
     Section 4.1 of this Amendment is consideration only for the assignment of
     patents and patent applications pursuant to Section 3.1 of this Amendment,
     and no milestone payment or royalty to be paid to Licensor by Licensee
     under the Current Agreement shall be affected in any way notwithstanding
     the assignment of patents and patent applications pursuant to Section 3.1
     of this Amendment.

4.3  In the event that Licensee sells, transfers or assigns any part or all the
     right, title and/or interest in and to the patents and patent applications
     assigned to Licensee by Licensor hereunder to any third party, Licensee
     shall cause such third party to agree in writing to become bound by all of
     the terms and provisions of this Agreement applicable to such patents and
     patent applications to the same extent that Licensee is then bound under
     the Agreement, and Licensee shall provide Licensor with a copy of the
     documents and agreements signed by such third party for purposes of
     enabling Licensor to confirm that such third party is bound by all of the
     terms and provisions of this Agreement applicable to such patents and
     patent applications to the same extent that Licensee is then bound. This
     Section 4.3 shall survive the termination of the Agreement pursuant to
     Section 7.2, 7.3 and/or 7.4.

ARTICLE 5. AMENDMENTS TO THE CURRENT AGREEMENT

5.1  The terms of the Current Agreement will remain unchanged except to the
     extent that the Current Agreement is amended and modified pursuant to the
     provisions set forth in this Amendment.

5.2  Appendix 2 to the Current Agreement shall be replaced by the new Appendix 2
     attached hereto.

5.3  The definitions set forth in the Current Agreement are hereby amended as
     follows:

Signature Page to Third Amendment

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

     Sections 1.1, 1.4, 1.7, 1.8, 1.11, 1.12, 1.13, 1.14, 1.15 and 1.16 of the
     Current Agreement are hereby amended to read in their entirety as set forth
     below; and seven new definitions numbered as Sections 1.18, 1.19, 1.20,
     1.21, 1.22, 1.23 and 1.24 are hereby added as set forth below:

     1.1  "Analog Product" or "the Analog Product" shall mean any pharmaceutical
          product containing a Compound Analog as the active
          pharmaceutical ingredient of such pharmaceutical product.

     1.4  "Compound Analog" shall mean those analogs of Compound whose chemical
          structures are covered by composition of matter claims under any of
          the patents or patent applications listed in Appendix 2 attached
          hereto.

     1.7  "Field" shall mean any and all possible indications and uses of the
          Compound, any Compound Analog, any Derivative, any Product, any Analog
          Product and any Derivative Product, for prevention, treatment or
          diagnosis of disease in humans or animals, subject to the terms of
          Section 2.1(c) of this Agreement with respect to veterinary
          applications.

     1.8  "IND" shall mean designation by FDA of a Product as an Investigational
          New Drug.

     1.11 "Net Sales" shall mean the amounts received by the Licensee and/or its
          sub-licensee(s) from independent customers who are not affiliates of
          the Licensee or its sub-licensee, for the sale of Product, Analog
          Product or Royalty Bearing Derivative Product, as the case may be,
          less: (a) trade, cash and/or quantity discounts actually allowed and
          taken; (b) excises, sales taxes, value added taxes, duties and like
          received from the buyer in addition to the sales price of the goods;
          (c) amounts repaid or credited by reason of purchase charge backs,
          recalls, rebates (including government mandate rebates), rejections
          due to defects or returns; and (d) freight, postage and transportation
          insurance paid for and separately identified on the invoice or other
          documentation maintained in the ordinary course of business.

     1.12 "[INTENTIONALLY OMITTED]"

     1.13 "Patents" shall mean all of the Original Patents other than those of
          the Original Patents that are assigned by Licensor to Licensee
          pursuant to Section 3.1 of the Third Amendment

     1.14 "Products" or "the Product" shall mean any pharmaceutical product
          containing the Compound as the active pharmaceutical ingredient of
          such pharmaceutical product.

     1.15 "Technical Information" shall mean any know-how, technical, scientific
          and medical facts, data, advice or other information, written (in the
          form of reports, drawings, specifications and the like) or oral,
          tangible or intangible, which is now or hereafter controlled or
          possessed by Licensor and which Licensor has the right to license (a)
          relating to a Product or for conversion of the Compound to a Product,
          (b) relating to any Compound Analog or for the conversion of any
          Compound Analog into any Analog Product, (c) relating to the
          conversion of any Compound, Compound Analog, Product or Analog Product
          into any Derivative or any Derivative Product, (d) relating to any
          Derivative or any Derivative Product, or the conversion of any
          Derivative into any other Derivative or any Derivative Product, (e)
          relating to the manufacture of the Compound or any Compound Analog;

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

Signature Page to Third Amendment

<Page>

          Derivative, Product, Analog Product or Derivative Product, (f)
          relating to marketing of any Product, Analog Product or Derivative
          Product, or (g) required to comply with applicable laws or
          regulations. Technical Information shall include, but not be limited
          to, patent files, manufacturing know-how, clinical tests and test
          results, regulatory submissions and correspondence files, and any
          other proprietary or trade secret information concerning the Compound
          or any Compound Analog, Derivative, Product, Analog Product or
          Derivative Product subject to the confidentiality provisions hereof.

     1.16 "Territory" shall mean all countries of the world.

     1.18 "Derivatives" shall mean (i) new compounds or chemical entities that
          are discovered, invented, developed, synthesized, made or manufactured
          using Compound or any Compound Analog, Analog Product or Product,
          whether as a raw material, intermediate or otherwise, and (ii) new
          compounds or chemical entities that are discovered, invented,
          developed, synthesized, made or manufactured using any composition of
          matter structures, compounds, processes, technology or other items of
          any kind covered by any of the Original Patents or any of the
          Technical Information. For the avoidance of doubt, and notwithstanding
          anything express or implied in the foregoing definition to the
          contrary, the term "Derivatives" shall not include Compound or any
          Compound Analog, Analog Product or Product.

     1.19 "Derivative Product" shall mean any pharmaceutical product containing
          a Derivative as the active pharmaceutical ingredient of such
          pharmaceutical product.

     1.20 "Original Patents" shall mean (i) Licensor's United States, European
          and other countries issued patents and applications for patents
          relating to the Compound or any of the Compound Analogs, whether
          previously, currently or hereafter issued to, or applied for, by
          Licensor, (ii) the inventions which are described and claimed therein,
          (iii) any reissues, divisions, substitutions, continuations,
          continuations-in-part, re-examinations and improvements thereon and
          extensions thereof, and (iv) any corresponding patent rights in any
          other country. Licensor represents and warrants to Licensee that all
          of the patents and patent applications set forth in Appendix 2
          attached hereto are included within the Original Patents and that
          there are no other patents or patent applications within the Original
          Patents that are not set forth in Appendix 2 attached hereto.

     1.21 "Royalty Bearing Derivatives" shall mean (i) new compounds or chemical
          entities that are synthesized or manufactured in [***]or [***] using
          Compound or the compound designated KRM-1158, whether as a raw
          material, intermediate or otherwise, and (ii) new compounds or
          chemical entities that are synthesized or manufactured in [***] or
          [***] using processes covered by any valid claim of the Second Listed
          Patents.

     1.22 "Royalty Bearing Derivative Product" shall mean any pharmaceutical
          product or composition containing or manufactured from any Royalty
          Bearing Derivative.

     1.23 "Second Listed Patents" shall mean the patents listed as item 2 on
          Appendix 2 hereto.

     1.24 "Third Amendment" shall mean that certain Third Amendment Agreement,
          dated as of August [27], 2004 by and between Licensor and Licensee for
          purposes of amending this Agreement.

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

Signature Page to Third Amendment

<Page>

5.4  The last sentence of Section 2.l(i) of the Current Agreement is hereby
     deleted and the following two sentences are hereby inserted therein in lieu
     thereof:

          "This license shall be an exclusive license, with the right to
          sub-license. Nothing in this Section 2.l(i) shall limit Licensor's
          rights under Section 2.10 of this Agreement."

5.5  The last sentence of Section 2.l(ii) of the Current Agreement is hereby
     deleted and the following two sentences are hereby inserted therein in lieu
     thereof:

          "This license shall be an exclusive license, with the right to
          sub-license. Nothing in this Section 2.1(ii) shall limit Licensor's
          rights under Section 2.10 of this Agreement."

5.6  Section 2.l(iii) of the Current Agreement is hereby renumbered as Section
     2.l(iv) and the text thereof is hereby amended to read in its entirety as
     follows:

          "(iv) Licensor agrees to assign and hereby assigns to Licensee all
                right, title and interest in and to the Trademarks."

5.7  A new Section 2.1 (iii) is hereby added as follows:

          "(iii) Licensor hereby grants to Licensee a license to the Compound,
               the Compound Analogs and the Intellectual Property to research,
               develop, make, have made, import, export, use, distribute for
               sale, promote, market, offer for sale and sell (on a royalty
               basis only, except in the case of compassionate use or in the
               case of clinical trials prior to the issuance of a United States
               new drug application approval) Derivatives and Derivative
               Products in the Field in the Territory in accordance with the
               terms of this Agreement. This license shall be an exclusive
               license with the right to sublicense. The license granted by
               Licensor pursuant to this Section 2.1(iii) shall have retroactive
               effect to the date on which Licensor first granted to Licensee a
               license pursuant to Section 2.l(i) of this Agreement"

5.8  The text of each of Section 2.l(a) and Section 2.l(b) of the Current
     Agreement is hereby deleted and replaced with the following text:

               "[Intentionally Omitted]"

5.9  The first sentence of Section 2.3 of the Current Agreement shall be amended
     to read as follows:

               "Licensee may grant sublicenses hereunder to third parties (the
               "Sublicensees"), provided however that, if any of such
               sublicenses includes the right to manufacture Compound and/or
               Compound Analog-in the Territory, then (A) Licensee shall inform
               the outline of such Sub-license agreement to Licensor and (B) the
               terms of any such sublicense shall require that the sublicensee
               thereunder shall be subject to all of Licensee's obligations
               under Section 2.10 of this Agreement. In the event that Licensee
               intends to grant a sublicense hereunder to a third party that
               includes the right to manufacture Compound and/or Compound Analog
               in the Territory and such third party is not a

Signature Page to Third Amendment

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

          Competitor, then no consent of Licensor shall be required in order for
          Licensee to grant such sublicense. In the event that Licensee intends
          to grant a sublicense hereunder to a third party that includes the
          right to manufacture Compound and/or Compound Analog in the Territory
          and such third party is a Competitor, then, prior to Licensee granting
          such sublicense to such Competitor, Licensee shall have obtained
          Licensor's written consent to such sublicense, which consent shall not
          be unreasonably withheld or delayed by Licensor. For purposes of this
          Section 2.3, the term "Competitor" shall mean any third party that
          derives substantially all of its revenues from the business of
          contract manufacturing of bulk pharmaceutical products."

5.10 Section 2.7 of the Agreement shall be amended to read in its entirety as
     follows:

          "2.7 Permitted Uses of Compound, Compound Analogs and Derivatives.
          Notwithstanding anything expressed or implied in this Agreement to the
          contrary and without limiting the rights granted to Licensee pursuant
          to Section 2.1 above, (i) Licensee may use the Compound, any of the
          Compound Analogs or any Intellectual Property to research, develop,
          make, have made, manufacture, have manufactured, use, import, export,
          distribute, promote, market, offer for sale, sell or otherwise
          commercialize any Derivative or any Derivative Product anywhere in the
          Territory, and (ii) Licensee may use any Derivative to research,
          develop, make, have made, manufacture, have manufactured, use, import,
          export, distribute, promote, market, offer for sale, sell or otherwise
          commercialize any other Derivative or any Derivative Product anywhere
          in the Territory. For the avoidance of doubt, the parties hereby
          acknowledge and agree that the rights of Licensee under this Section
          2.7 shall be deemed to be within the scope of the rights licensed by
          Licensor to Licensee pursuant to Section 2.1 hereof and, accordingly,
          the lights of Licensee under this Section 2.7 are exclusive license
          rights with the light to sublicense."

5.12 A new Section 2.10 shall be added to the Current Agreement as follows:

          "2.10 The Licensor and Licensee hereby acknowledge, ratify, confirm
          and agree that, effective as of the date of the License Agreement,
          Licensor and Licensee have agreed to terminate any and all rights that
          Licensor had under the Amended and Restated Agreement to manufacture
          the Compound or any of the Compound Analogs, Products or Product
          Analogs. Accordingly, consistent with such agreement, Licensor and
          Licensee hereby agree that Licensee has exclusive worldwide rights to
          manufacture Compound, Compound Analogs, Derivatives, Products, Analog
          Products and Derivative Products. Licensor retains the right to
          negotiate with Licensee, for the manufacture and supply of Compound on
          terms that are competitive with Licensee's requirements, including,
          without limitation, competitive with Licensee's requirements on price
          and quality. Licensee shall be free to accept or reject Licensor's
          proposals."

Signature Page to Third Amendment

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

5.13 A new Section 3.1(k) will be added to the Current Agreement as
     follows:

          "(k) Royalties on Certain Derivative Products Subject to Section
               3.1(1) hereof, the Licensee shall pay to Licensor royalties based
               on the Net Sales of any Royalty Bearing Derivative Product. The
               royalty shall be paid quarterly within sixty (60) days of the
               close of the Licensee's fiscal quarter. In the case of a Royalty
               Bearing Derivative Product for human use where a Royalty Bearing
               Derivative is the only active pharmaceutical ingredient, the
               royalty shall be equal to [***] percent ([***]%) of the Net Sales
               with respect to such Royalty Bearing Derivative Product In the
               case of a combination product for human use where such
               combination product consists of any Royalty Bearing Derivative
               Product or any Royalty Bearing Derivative as one of the active
               pharmaceutical ingredients of such combination product, the
               royalty shall be equal to (i) [***] percent ([***]%) of the Net
               Sales for such combination product if Licensee is not required to
               pay a royalty to a third party in connection with such
               combination product and (ii)[***] percent ([***]%) of the Net
               Sales for such combination product if Licensee is required to pay
               a royalty to a third party in connection with such combination
               product, or if Licensee previously acquired such combination
               product or any active pharmaceutical ingredient of such
               combination product from a third party with or without royalty
               payment obligations to such third party, or if Licensee developed
               such combination product or any active pharmaceutical ingredient
               of such combination product internally de novo. In the case of a
               Royalty Bearing Derivative Product for veterinary use where a
               Royalty Bearing Derivative is the only active pharmaceutical
               ingredient, the royalty shall be equal to [***] percent ([***]%)
               of the Net Sales with respect to such Royalty Bearing Derivative
               Product. In the case of a combination product for veterinary use
               where such combination product consists of any Royalty Bearing
               Derivative Product or any Royalty Bearing Derivative as one of
               the active pharmaceutical ingredients of such combination
               product, the royalty shall be equal to (i) [***] percent ([***]%)
               of the Net Sales for such combination product if Licensee is not
               required to pay a royalty to a third party in connection with
               such combination product and (ii) [***] percent ([***]%) of the
               Net Sales for such combination product if Licensee is required to
               pay a royalty to a third party in connection with such
               combination product, or if Licensee previously acquired such
               combination product or any active pharmaceutical ingredient of
               such combination product from a third party with or without
               royalty payment obligations to such third party, or if Licensee
               developed such combination product or any active pharmaceutical
               ingredient of such combination product internally de novo."

5.14 Anew Sections 3.1(1) will be added to the Current Agreement as follows:

          "(l) Royalty Payment Obligation Notwithstanding anything expressed or
               implied in this Agreement to the contrary, the obligation of
               Licensee and its sublicensees to make payment of royalties to
               Licensor under this Agreement in connection with sales by
               Licensee or its sublicensees of any Royalty Bearing Derivative
               Product shall apply only if and for so long as the synthesis or
               manufacture of such Royalty Bearing Derivative Product by
               Licensee or any of its sublicensees would, absent an assignment
               of, or a license to, the Second Listed Patents, infringe an

Signature Page to Third Amendment

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

               unexpired valid claim of the Second Listed Patents."

5.15 Section 3.2 of the Current Agreement shall be amended to read in its
     entirety as follows:

          "3.2 Officer's Certificates. With each payment made pursuant to
               Section 3.1(d), (f) and (k) hereof, Licensee shall provide
               Licensor with a certificate signed by an officer of Licensee
               which states the total amount due and payable and the manner in
               which that amount was calculated and which certifies that the
               information so provided is true and correct."

5.16 Section 7.1 of the Current Agreement shall be amended to read in its
     entirety as follows:

          "7.1 Term. Unless otherwise terminated earlier pursuant to this
               Article 7, this Agreement shall continue in full force and effect
               until the fifteenth (15th) anniversary of first sale of a
               Product, an Analog Product or a Derivative Product, whichever is
               earlier, by Licensee or its sublicensees, notwithstanding any
               patent assignment to Licensee by Licensor hereunder or in the
               future nor any expiration or termination of Patents"

5.17 The addressees set forth in Section 9.3 of the Current Agreement shall be
     amended to read as follows:

     "If to Licensor:   Kaneka Corporation
                        Life Science RD Center
                        1-8, Miyamae-machi, Takasago-cho
                        Takasago-shi, Hyogo 676-8688, Japan

                        Attention: General Manager
                        Life Science RD Center
                        Fax: +81(794) 45-2459

     If to Licensee:    ActivBiotics, Inc.
                        128 Spring Street
                        Lexington, MA 02421
                        USA

                        Attention: Chief Executive Officer
                        Fax: +1 (781) 274-9129"

ARTICLE 6. NO OTHER AMENDMENTS OR WAIVERS

     Except as expressly provided in this Amendment, all the terms and
     conditions of the Current Agreement are hereby ratified and confirmed and
     remain in full force and effect.

ARTICLE 7. EXECUTION IN COUNTERPARTS, ETC.

7.1  This Amendment may be executed in any number of counterparts, each of which
     shall be deemed an original, but which together shall constitute one
     instrument.

7.2  This Amendment shall be effective upon execution of this Amendment by the
     parties hereto, and shall be governed by the applicable law specified in
     Section 9.1 of the Agreement.

Signature Page to Third Amendment

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

     This Amendment has been executed by a duly authorized representative of
each party as of the date first above written.

                                        KANEKA CORPORATION

                                        /s/ Nobutaka Tani
                                        ----------------------------------------
                                        Name: Nobutaka Tani, MS
                                        Title: General Manager, Life Science RD
                                               Center

                                        ACTIVBIOTICS, INC.

                                        /s/ Steven C. Gilman
                                        ----------------------------------------
                                        Name: Steven C. Gilman, Ph D.
                                        Title: President and Chief Executive
                                               Officer

Signature Page to Third Amendment

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

                                   APPENDIX 2

List of the patents related to the Rifamycin derivative:

1.   "'3'- Hydroxybenzoxazinorifamycin derivative, process for preparing the
     same and antibacterial agent containing the same"

     US: Patent No. 4,983,602                Expiration Date: February 5, 2006
     Canada: Patent No. 1,304,363            Expiration Date: June 30, 2009
     EPC (BE, CH, DE, ES, FR, GB, IT, LI):
             Patent No. 0366914              Expiration Date: September 14, 2009
             Patent No. (DE) 68919650.4
     China: Patent No. 24,993                Expiration Date: September 16, 2004
     Singapore: Patent No. 38437             Expiration Date: September 14, 2009
     Japan: Patent No. 2544488               Expiration Date: November 1, 2008

     THIS PATENT WILL BE RETAINED BY KANEKA.

2.   "'3'-alkyl, -arylsiryloxybenzoxazinorifamycin derivatives"

     China: Patent No. 39,298                Expiration Date: August 16, 2006
     Taiwan: Patent No. 60,726               Expiration Date: January 20, 2008
     Korea: Patent No. 203615                Expiration Date: August 3, 2011
            Patent No. 203729                Expiration Date: August 3, 2011
     Japan: Patent No. 2620399               Expiration Date: August 10, 2010

     THIS PATENT WILL BE RETAINED BY KANEKA.

3.   "Production method for fine granules"

     U.S.: Patent No. 5,547,683              Expiration Date: October 6, 2013
     EPC (BE, CH, DE, ES, FR, GB, IT, LI):
             Patent No. 0616841              Expiration Date: October 6, 2013
             Patent No (DE) 69322764 8
     Canada: Patent No. 2,124,568            Expiration Date: October 6, 2013
     China: Patent No. 1091628               Expiration Date: October 6, 2013
     Korea: Patent No. 294525                Expiration Date: October 6, 2013
     Japan: Patent No. 03492688              Expiration Date: October 9, 2012

     THIS PATENT HAS BEEN ASSIGNED TO ACTIVBIOTICS.

4.   "Treatment of chlamydia infectious diseases by rifamycin derivative"

     US: Patent No. 5,786,349                Expiration Date: December 9, 2016
     Canada: Appl. No. 2,192,255             Filed: December 6, 1996
             (decision of patent)
     EPC (BE, CH, DE, ES, FR, GB, IT, LI):
             Patent No. 0778022              Expiration Date: December- 6, 2016
             Patent No. (DE) 69612465.3
     Japan: Appl. No. 08-002634              Filed January 10, 1995

     THIS PATENT WILL BE RETAINED BY KANEKA.

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

5.   "Treatment of disease caused by infection of Helicobacter"

     U.S.: Patent No. 5,981,522              Expiration Date: August 29, 2016
     Canada:
          Appl. No. 2,230,649                Filed: February 27, 1998
          (decision of patent)
     EPC (BE, CH, DE, ES, FR, GB, IT, LI):
          Appl. No. 969287234                Filed: August 29, 1996
          (decision of patent)
          Appl. No. 98103481                 Filed: February 27, 1998
     Taiwan: Patent No. 113445               Expiration Date: February 26, 2018

     Korea: Patent No. 407849                Expiration Date: August 29, 2016
          Patent No. 407851                  Expiration Date: February 27, 2018
     Japan: Appl. No. 10-038590              Filed: February 20, 1998

     THIS PATENT WILL BE RETAINED BY KANEKA.

6.  "Method for treating mastitis in a domestic animal"

     U.S.: Patent No. 6486161                Expiration Date: July 28, 2017
     CA: Appl. No. 2297012                   Filed: July 29, 1998
          (on abandonment)
     EPC (DE, GB, FR, H, CH, NL, SE):
          Patent No. 1001778                 Expiration Date: July 28,
          (on abandonment)

     Taiwan: Appl. No. 88,100,078            Filed: January 5, 1999
          (on abandonment)
     Korea: Appl. No. 00-7,000,601           Filed: July 29, 1998
          (on abandonment)
     Australia: Patent. No. 756367           Expiration Date: July 28,2018
          (on abandonment)

     New Zealand: Patent No. 503027           Expiration Date: July 28, 2018
          (on abandonment)
     China: Appl. No. 98,807,682.9           Filed: July 29, 1998
          (on abandonment)
     Japan: Appl. No. 2000-504,861           Filed: July 29, 1998

     THIS PATENT HAS BEEN ASSIGNED TO ACTIVBIOTICS

7.   "Antimicrobial compositions with synergistic effect, drugs and remedies for
     digestive diseases containing the same, process for the production thereof
     and preparations associated therewith"

     U.S.: Patent. No. 6362169               Expiration Date: February 16, 2019
     EP: Appl. No. 99905227.7                Filed; February 17, 1999
     CA: Appl. No. 2321265                   Filed; February 17, 1999
     KR: Appl. No 00-7008855                 Filed; February 17, 1999

     Taiwan: Appl. No. 88,102,542            Filed; February 22, 1999
     JP: Appl. No. 2000-533123               Filed; February 17, 1999

THIS PATENT HAS BEEN ASSIGNED TO ACTIVBIOTICS

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

<Page>

8.   "Method for treatment of bacterial infections with once or twice-weekly
     administered rifalazil" (PathoGenesis assigned to Kaneka, 2000).

     U.S.: Patent No. 6316433                Expiration Date: December 15, 2019
          Patent No. 6566354                 Expiration Date: February 28, 2020
          Appl. No. 10/243141                Filed: November 14, 2002
     CA: Appl. No. 2355283                   Filed: December 16, 1998
     EPC: Appl. No. 99968906.0               Filed: December 16, 1998
          (under examination)
     KR: Appl. No. 01-7007717                Filed: December 16, 1998
          (under examination)
     CN: Appl. No. 99815782.1                Filed: December 16, 1998
     JP: Appl. No. 2000-587729               Filed: December 16, 1998

     THIS PATENT WILL BE RETAINED BY KANEKA.

9.   "Benzoxazinorifamycin derivative, process for preparing the same and
     antibacterial agent containing the same"

     U.S.: Patent No. 4,690,919              Expiration Date: February 5, 2006
     Canada: Patent No. 1,256,430            Expiration Date: June 27, 2006
     EPC (BE, CH, FR, GB, IT, LI, NL, SE, DE)
          Patent No. 0,190,709               Expiration Date: February 4, 2006
     China: Patent No. 24,976                Expiration Date: May 31, 2001
     Japan: Patent No. 1,854,546             Expiration Date: January 20, 2006

     THIS PATENT WILL BE RETAINED BY KANEKA.

10.  "Alkyl-substituted benzoxazinorifamycin derivative, process for preparing
     the same and antibacterial agent containing the same"

     U.S.: Patent No. 4,859,661              Expiration Date: July 13, 2007

     THIS PATENT HAS BEEN ASSIGNED TO ACTIVBIOTICS.

11.  "Substituted benzoxazinorifamycin derivative and antibacterial agent
     containing the same"

     U.S.: Patent No. 4,965,261              Expiration Date: March 16, 2009
     Canada: Patent No. 1,293,503            Expiration Date: December 23, 2008
     EPC (BE, CH, ES, FR, GB, IT, LI, DE):
          Patent No. 0,333,176               Expiration Date: March 15, 2009
          Patent No. (DE) 68924722 2
     China: Patent No. 20,729                Expiration Date: March 17, 2004
     Japan: Patent No. 2780807               Expiration Date: March 17, 2009
          (on abandonment)

     THIS PATENT HAS BEEN ASSIGNED TO ACTIVBIOTICS.

[***] INDICATES MATERIAL THAT HAS BEEN OMITTED AND FOR WHICH CONFIDENTIAL
TREATMENT HAS BEEN REQUESTED. ALL SUCH OMITTED MATERIAL HAS BEEN FILED WITH THE
SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 24b-2 PROMULGATED UNDER THE
SECURITIES EXCHANGE ACT OF 1934, AS AMENDED

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00108-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00108-of-00352.parquet"}]]