Document:

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                                                                   Exhibit 10.10

                       VENTURE LOAN AND SECURITY AGREEMENT

                                                       Dated as of June 16, 2006

                                 by and between

                     HORIZON TECHNOLOGY FUNDING COMPANY LLC,
                      a Delaware limited liability company
                             76 Batterson Park Road
                              Farmington, CT 06032
                                    as Lender

                                       and

                               ACTIVBIOTICS, INC.,
                             a Delaware corporation
                               110 Hartwell Avenue
                               Lexington, MA 02421
                                  as a Borrower

Commitment Amount:             $5,000,000

Commitment Termination Date:   June 16, 2006

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This Venture Loan and Security Agreement (this "Agreement") is made by and
between ActivBiotics, Inc., a Delaware corporation ("Borrower") and Horizon
Technology Funding Company LLC, a Delaware limited liability company ("Lender").
Lender and Borrower hereby agree as follows:

                                    AGREEMENT

     1. Definitions and Construction.

          1.1 Definitions. As used in this Agreement, the following capitalized
terms shall have the following meanings:

     "ABI Canada" means ActivBiotics (Canada) Inc., a Canadian corporation.

     "Account Control Agreement" means an agreement acceptable to Lender which
perfects via control Lender's security interest in Borrower's deposit accounts
and/or accounts holding securities.

     "Affiliate" means any Person that owns or controls directly or indirectly
ten percent (10%) or more of the stock of another entity, any Person that
controls or is controlled by or is under common control with such Persons or any
Affiliate of such Persons and each of such Person's officers, directors, joint
venturers or partners.

     "Agreement" means this certain Venture Loan and Security Agreement by and
between Borrower and Lender dated as of the date on the cover page hereto (as it
may from time to time be amended or supplemented in writing signed by the
Borrower and Lender).

     "Borrower" means ActivBiotics, Inc., a Delaware corporation.

     "Borrower's Home State" means Massachusetts.

     "Business Day" means any day that is not a Saturday, Sunday, or other day
on which banking institutions are authorized or required to close in Connecticut
or Borrower's Home State.

     "Claim" has the meaning given such term in Section 10.3 of this Agreement.

     "Co-Development Licenses" means (i) the Co-Development, License and
Distribution Agreement, dated as of March 22, 2005 by and between Borrower and
ABI Canada, as amended from time to time and (ii) the Co-Development, License
and Distribution Agreement, dated as of May 17, 2006 by and between Borrower and
ABI Canada, as amended from time to time.

     "Code" means the Uniform Commercial Code as adopted and in effect in the
State of Connecticut, as amended from time to time; provided that if by reason
of mandatory provisions of law, the creation and/or perfection or the effect of
perfection or non-perfection of the security interest in any Collateral is
governed by the Uniform Commercial Code as in effect in a

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jurisdiction other than Connecticut, the term "Code" shall also mean the Uniform
Commercial Code as in effect from time to time in such jurisdiction for purposes
of the provisions hereof relating to such creation, perfection or effect of
perfection or non-perfection.

     "Collateral" has the meaning given such term in Section 4.1 of this
Agreement.

     "Commitment Amount" has the meaning as set forth on the cover page of this
Agreement.

     "Commitment Fee" has the meaning given such term in Section 2.6(c) of this
Agreement.

     "Commitment Termination Date" has the meaning as set forth on the cover
page of this Agreement.

     "Default" means any event which with the passing of time or the giving of
notice or both would become an Event of Default hereunder.

     "Default Rate" means the per annum rate of interest equal to five percent
(5%) over the Loan Rate, but such rate shall in no event be more than the
highest rate permitted by applicable law to be charged on commercial loans in a
default situation.

     "Disclosure Schedule" means Exhibit A attached hereto.

     "Environmental Laws" means all foreign, federal, state or local laws,
statutes, common law duties, rules, regulations, ordinances and codes, together
with all administrative orders, directed duties, requests, licenses,
authorizations and permits of, and agreements with, any Governmental
Authorities, in each case relating to environmental, health, safety and land use
matters, including the Comprehensive Environmental Response, Compensation and
Liability Act of 1980, the Clean Air Act, the Federal Water Pollution Control
Act of 1972, the Solid Waste Disposal Act, the Federal Resource Conservation and
Recovery Act, the Toxic Substances Control Act and the Emergency Planning and
Community Right-to-Know Act.

     "Equity Securities" of any Person means (a) all common stock, preferred
stock, participations, shares, partnership interests, membership interests or
other equity interests in and of such Person (regardless of how designated and
whether or not voting or non-voting) and (b) all warrants, options and other
rights to acquire any of the foregoing.

     "ERISA" has the meaning given to such term in Section 7.12 of this
Agreement.

     "Event of Default" has the meaning given to such term in Section 8 of this
Agreement.

     "Excluded Taxes" means, with respect to Lender, or any other recipient of
any payment to be made by or on account of any Obligation hereunder, income, net
worth or franchise taxes imposed on (or measured by) its net income or net worth
by the United States of America, or by the jurisdiction under the laws of which
such recipient is organized or in which its principal office is located or, in
the case of Lender, in which its lending office is located or in which it is
taxable solely on account of some connection other than the execution, delivery
or performance of this Agreement or the receipt of income hereunder.

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     "Funding Certificate" means a certificate executed by a Responsible Officer
of Borrower substantially in the form of Exhibit B or such other form as Lender
may agree to accept.

     "Funding Date" means any date on which the Loan is made to or on account of
Borrower under this Agreement.

     "GAAP" means generally accepted accounting principles as in effect in the
United States of America from time to time, consistently applied.

     "Good Faith Deposit" has the meaning given such term in Section 2.6(a) of
this Agreement.

     "Governmental Authority" means (a) any federal, state, county, municipal or
foreign government, or political subdivision thereof, (b) any governmental or
quasi-governmental agency, authority, board, bureau, commission, department,
instrumentality or public body, (c) any court or administrative tribunal, or (d)
with respect to any Person, any arbitration tribunal or other non-governmental
authority to whose jurisdiction that Person has consented.

     "Guarantor" means any guarantor of the Obligations, including, without
limitation, ABI Canada and Metaphore Pharmaceuticals, Inc.

     "Hazardous Materials" means all those substances which are regulated by, or
which may form the basis of liability under, any Environmental Law, including
all substances identified under any Environmental Law as a pollutant,
contaminant, hazardous waste, hazardous constituent, special waste, hazardous
substance, hazardous material, or toxic substance, or petroleum or petroleum
derived substance or waste.

     "Indebtedness" means, with respect to Borrower or any Subsidiary, the
aggregate amount of, without duplication, (a) all obligations of such Person for
borrowed money, (b) all obligations of such Person evidenced by bonds,
debentures, notes or other similar instruments, (c) all obligations of such
Person to pay the deferred purchase price of property or services (excluding
trade payables aged less than one hundred eighty (180) days), (d) all capital
lease obligations of such Person, (e) all obligations or liabilities of others
secured by a Lien on any asset of such Person, whether or not such obligation or
liability is assumed, (f) all obligations or liabilities of others guaranteed by
such Person, and (g) any other obligations or liabilities which are required by
GAAP to be shown as debt on the balance sheet of such Person. Unless otherwise
indicated, the term "Indebtedness" shall include all Indebtedness of Borrower
and the Subsidiaries.

     "Indemnified Person" has the meaning given such term in Section 10.3 of
this Agreement.

     "Indemnified Taxes" means all Taxes other than (a) Excluded Taxes and Other
Taxes and (b) amounts constituting penalties or interest imposed with respect to
Excluded Taxes or Other Taxes.

     "Intellectual Property" means all of Borrower's and its Subsidiaries'
right, title and interest in and to (i) patents, patent rights (and applications
and registrations therefor), trademarks and service marks (and applications and
registrations therefor), inventions,

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copyrights, mask works (and applications and registrations therefor), trade
names, trade styles, software and computer programs, source code, object code,
trade secrets, methods, processes, know how, drawings, specifications,
descriptions, and all memoranda, notes, and records with respect to any research
and development and (ii) any licenses or contracts for the development, use,
sharing or commercializing of any of the foregoing (including, but not limited
to, the Co-Development Licenses, the Kaneka License and the Pfizer License) all
whether now owned or subsequently acquired or developed by Borrower and whether
in tangible or intangible form or contained on magnetic media readable by
machine together with all such magnetic media (but not including embedded
computer programs and supporting information included within the definition of
"goods" under the Code).

     "Investment" means the purchase or acquisition of any capital stock, equity
interest, or any obligations or other securities of, or any interest in, any
Person, or the extension of any advance, loan, extension of credit or capital
contribution to, or any other investment in, or deposit with, any Person.

     "Kaneka License" means the License Agreement dated as of September 27, 2001
by and between ABI and Kaneka Corporation, as amended from time to time.

     "knowledge" when used in this Agreement has the following meaning:

     (i) an individual will be deemed to have knowledge of a particular fact or
other matter if the individual is actually aware of such fact or other matter;
and

     (ii) in the case of a Person that is not an individual, such Person will be
deemed to have knowledge of a particular fact or other matter (a) if any
principal, senior manager, officer or director of such person is actually aware
of such fact or other matter, or (b) if a principal, senior manager, officer or
director of such Person could be expected to have discovered or otherwise become
aware of such fact or other matter in the ordinary course of not performing his
or her duties.

     "Landlord Agreement" means an agreement substantially in the form provided
by Lender to Borrower or such other form as Lender may agree to accept.

     "Lender" means the Lender as defined in the preamble to this Agreement.

     "Lender's Expenses" means all reasonable costs or expenses (including
reasonable attorneys' fees and expenses) incurred in connection with the
preparation, negotiation, documentation, administration and funding of the Loan
Documents; and Lender's reasonable attorneys' fees, costs and expenses incurred
in amending, modifying, enforcing or defending the Loan Documents (including
fees and expenses of appeal or review), including the exercise of any rights or
remedies afforded hereunder or under applicable law, whether or not suit is
brought, whether before or after bankruptcy or insolvency, including without
limitation all fees and costs incurred by Lender in connection with Lender's
enforcement of its rights in a bankruptcy or insolvency proceeding filed by or
against Borrower or its Property.

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     "Lien" means any voluntary or involuntary security interest, pledge,
bailment, lease, mortgage, hypothecation, conditional sales and title retention
agreement, encumbrance or other lien with respect to any Property in favor of
any Person.

     "Loan" means the advance of credit by Lender to Borrower under this
Agreement.

     "Loan Documents" means, collectively, this Agreement, the Note, the
Warrant, any Landlord Agreement, any Account Control Agreement and all other
documents, instruments and agreements entered into in connection with this
Agreement, all as amended or extended from time to time.

     "Loan Rate" means the per annum rate of interest (based on a year of twelve
30-day months) equal to the greater of (a) 11.9% or (b) 11.9% plus the positive
difference, if any, between (i) the one month LIBOR Rate (rounded to the nearest
one hundredth percent), as reported in the Wall Street Journal, on the date
which is five (5) Business Days before the Funding Date for such Loan (or, if
the Wall Street Journal is not published on such date, the next earlier date on
which it is published) and (ii) 4.41%.

     "Maturity Date" means January 1, 2010, or if earlier, the date of
acceleration of the Loan following an Event of Default or the date of
prepayment, whichever is applicable.

     "Note" means the promissory note executed in connection with the Loan in
substantially the form of Exhibit C attached hereto.

     "Obligations" means all debt, principal, interest, fees, charges, expenses
and attorneys' fees and costs and other amounts, obligations, covenants, and
duties owing by Borrower to Lender of any kind and description (whether pursuant
to or evidenced by the Loan Documents (other than the Warrant), or by any other
agreement between Lender and Borrower, and whether or not for the payment of
money), other than with respect to the Warrant or shares issued thereunder or
rights relating thereto, whether direct or indirect, absolute or contingent, due
or to become due, now existing or hereafter arising, including all Lender's
Expenses.

     "Officer's Certificate" means a certificate executed by a Responsible
Officer substantially in the form of Exhibit E or such other form as Lender may
agree to accept.

     "Other Taxes" means any and all present or future stamp or documentary
taxes or any other excise or property taxes, charges or similar levies arising
from any payment made hereunder or from the execution, delivery or enforcement
of, or otherwise with respect to, this Agreement and the other Loan Documents,
provided that there shall be excluded from "Other Taxes" all Excluded Taxes.

     "Payment Date" has the meaning given such term in Section 2.2(a) of this
Agreement.

     "Permitted Indebtedness" means and includes:

               (a) Indebtedness of Borrower to Lender;

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               (b) Indebtedness of Borrower secured by Liens permitted under
clause (e) of the definition of Permitted Liens; provided that such Indebtedness
is limited to an aggregate amount outstanding at one time of Five Million
Dollars ($5,000,000);

               (c) Indebtedness arising from the endorsement of instruments in
the ordinary course of business;

               (d) Indebtedness existing on the date hereof and set forth on the
Disclosure Schedule;

               (e) any intercompany Indebtedness between Borrower and any of its
Subsidiaries, provided, that at Lender's request such Subsidiary has guaranteed
the Obligations and provided a security interest in its assets to secure such
guaranty;

               (f) any Indebtedness between Borrower and ABI Canada;

               (g) Other Indebtedness aggregating not in excess of One Hundred
Thousand Dollars ($100,000) at any time; and

               (h) Any obligations of Borrower for payments made or owed by
Borrower under licenses or contracts executed in connection with Intellectual
Property, to the extent such licenses or contracts are permitted under this
Agreement.

     "Permitted Investments" means and includes any of the following Investments
as to which Lender, in the cases of clauses (a) through (e), have a perfected
security interest:

               (a) Deposits and deposit accounts with commercial banks organized
under the laws of the United States or a state thereof to the extent: (i) the
deposit accounts of each such institution are insured by the Federal Deposit
Insurance Corporation up to the legal limit; and (ii) each such institution has
an aggregate capital and surplus of not less than One Hundred Million Dollars
($100,000,000).

               (b) Investments in marketable obligations issued or fully
guaranteed by the United States and maturing not more than one (1) year from the
date of issuance.

               (c) Investments in open market commercial paper rated at least
"Al" or "PI" or higher by a national credit rating agency and maturing not more
than one (1) year from the creation thereof.

               (d) Investments pursuant to or arising under currency agreements
or interest rate agreements entered into in the ordinary course of business.

               (e) Other Investments aggregating not in excess of Two Hundred
Fifty Thousand Dollars ($250,000) at any time.

               (f) Licenses of Intellectual Property entered into in a
transaction negotiated at arms-length in the ordinary course of business;
provided, that the granting of a security interest or other Lien in such
licenses shall not be permitted.

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               (g) Any Investment pursuant to the Put and Support Agreement.

     "Permitted Liens" means and includes:

               (a) the Lien created by this Agreement;

               (b) Liens for fees, taxes, levies, imposts, duties or other
governmental charges of any kind which are not yet delinquent or which are being
contested in good faith by appropriate proceedings which suspend the collection
thereof (provided that such appropriate proceedings do not involve any
substantial danger of the sale, forfeiture or loss of any material item of
Collateral which in the aggregate is material to Borrower and/or its
Subsidiaries and that Borrower and/or its Subsidiaries has adequately bonded
such Lien or reserves sufficient to discharge such Lien have been provided on
the books of Borrower and/or its Subsidiaries);

               (c) Liens identified on the Disclosure Schedule or any other Loan
Documents in favor of Lender;

               (d) carriers', warehousemen's, mechanics', materialmen's,
repairmen's or other similar Liens arising in the ordinary course of business
and which are not delinquent or remain payable without penalty or which are
being contested in good faith and by appropriate proceedings (provided that such
appropriate proceedings do not involve any substantial danger of the sale,
forfeiture or loss of any material item of Collateral or Collateral which in the
aggregate is material to Borrower and/or its Subsidiaries and that Borrower
and/or its Subsidiaries has adequately bonded such Lien or reserves sufficient
to discharge such Lien have been provided on the books of Borrower and/or its
Subsidiaries);

               (e) Liens upon any equipment or other personal property acquired
by Borrower and/or its Subsidiaries after the date hereof to secure (i) the
purchase price of such equipment or other personal property, or (ii) lease
obligations or indebtedness incurred solely for the purpose of financing the
acquisition of such equipment or other personal property; provided that (A) such
Liens are confined solely to the equipment or other personal property so
acquired and the amount secured does not exceed the acquisition price thereof,
and (B) no such Lien shall be created, incurred, assumed or suffered to exist in
favor of any Borrower's and/or its Subsidiaries' officers, directors or
shareholders holding five percent (5%) or more of any Borrower's Equity
Securities;

               (f) in-licenses to Borrower or its Subsidiaries of Intellectual
Property;

               (g) pledges or deposits in the ordinary course of business in
connection with workers' compensation, unemployment insurance and other social
security legislation;

               (h) deposits to secure bids, trade contracts, leases, statutory
obligations, surety bonds or performance bonds entered into in the ordinary
course of business;

               (i) easements, rights of way and other similar restrictions, if
any, which are not material and do not materially interfere with the business;

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               (j) Liens securing judgments for payment of money not
constituting an Event of Default or securing appeal or other surety bonds
related to such judgments; provided such Liens are bonded off within sixty (60)
days;

               (k) Liens securing the Indebtedness permitted under clauses (e)
and (f) of the definition of Permitted Indebtedness;

               (l) licenses of Intellectual Property entered into pursuant to a
transaction negotiated at arms-length in the ordinary course of business,
including but not limited to, the Kaneka License, the Pfizer License, the
Research Agreements and the Co-Development Licenses, provided that the granting
of a security interest or other Lien in such licenses shall not be permitted;
and

               (j) other Liens consented to in writing by the Lender.

     "Person" means and includes any individual, any partnership, any
corporation, any business trust, any joint stock company, any limited liability
company, any unincorporated association or any other entity and any domestic or
foreign national, state or local government, any political subdivision thereof,
and any department, agency, authority or bureau of any of the foregoing.

     "Pfizer License" means that License Agreement, dated as of December 19,
2003, by and between Pfizer, Inc. and Metaphore Pharmaceuticals, Inc.

     "Property" means any interest in any kind of property or asset, whether
real, personal or mixed, whether tangible or intangible.

     "Put and Support Agreement" means that Put and Support Agreement, dated as
of March 22, 2005 by and among Borrower, ABI Canada and the Investors named
therein.

     "Requirements of Law" as to any Person, the certificate of incorporation
and by-laws or other organizational or governing documents of such Person, and
any law, treaty, rule or regulation or determination of an arbitrator or a court
or other Governmental Authority, in each case applicable to or binding upon such
Person or any of its property or to which such Person or any of its property is
subject.

     "Research Agreements" means (i) that Research and Development Cost-Sharing
Agreement dated as of March 22, 2005 between Borrower and ABI Canada, as amended
from time to time and (ii) that Research and Development Cost-Sharing Agreement
dated as of May 17, 2006 between Borrower and ABI Canada, as amended from time
to time.

     "Responsible Officer" has the meaning given such term in Section 6.3 of
this Agreement.

     "Scheduled Payments" has the meaning given such term in Section 2.2(a) of
this Agreement.

     "Solvent" has the meaning given such term in Section 5.11 of this
Agreement.

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     "Subsidiary" means any corporation or other entity of which a majority of
the outstanding Equity Securities entitled to vote for the election of directors
or other governing body (otherwise than as the result of a default) is owned by
Borrower or ABI Canada directly or indirectly through Subsidiaries.

     "Taxes" means any and all present or future taxes, levies, imposts, duties,
deductions, charges or withholdings imposed by any Governmental Authority.

     "Third Party Equipment" has the meaning given such term in Section 4.8 of
this Agreement.

     "Transfer" has the meaning given such term in Section 7.4 of this
Agreement.

     "Warrant" means the separate warrant or warrants dated on or about the date
hereof in favor of Horizon or its designees to purchase securities of Borrower,
and collectively, means all such "Warrants".

          1.2 Construction. References in this Agreement to "Articles,"
"Sections," "Exhibits," "Schedules" and "Annexes" are to recitals, articles,
sections, exhibits, schedules and annexes herein and hereto unless otherwise
indicated. References in this Agreement and each of the other Loan Documents to
any document, instrument or agreement shall include (a) all exhibits, schedules,
annexes and other attachments thereto, (b) all documents, instruments or
agreements issued or executed in replacement thereof, and (c) such document,
instrument or agreement, or replacement or predecessor thereto, as amended,
modified and supplemented from time to time and in effect at any given time. The
words "hereof," "herein" and "hereunder" and words of similar import when used
in this Agreement or any other Loan Document shall refer to this Agreement or
such other Loan Document, as the case may be, as a whole and not to any
particular provision of this Agreement or such other Loan Document, as the case
may be. The words "include" and "including" and words of similar import when
used in this Agreement or any other Loan Document shall not be construed to be
limiting or exclusive. Unless otherwise indicated in this Agreement or any other
Loan Document, all accounting terms used in this Agreement or any other Loan
Document shall be construed, and all accounting and financial computations
hereunder or thereunder shall be computed, in accordance with GAAP, and all
terms describing Collateral shall be construed in accordance with the Code. The
terms and information set forth on the cover page of this Agreement are
incorporated into this Agreement.

     2. Loans; Repayment.

          2.1 Commitment.

               (a) The Commitment Amount. Subject to the terms and conditions of
this Agreement and relying upon the representations and warranties herein set
forth as and when made or deemed to be made, Lender agrees to lend to Borrower
prior to the Commitment Termination Date, the Loan in the Commitment Amount.

               (b) The Loan and the Note. The obligation of Borrower to repay
the unpaid principal amount of and interest on the Loan made under this
Agreement shall be

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evidenced by a single promissory note in favor of Lender in the form of Exhibit
C attached hereto, duly completed, executed and delivered to Lender dated on or
about the Funding Date for the Loan and made payable to Lender. Borrower hereby
authorizes Lender to record on the Note or on its internal computerized records,
the principal amount of the Loan and of each payment of principal received by
Lender on account of the Loan, which recordance, in the absence of manifest
error, shall be conclusive as to the outstanding principal balance of the Loan;
provided that, the failure to make such recordation with respect to the Loan or
payment shall not limit or otherwise affect the obligations of the Borrower
under this Agreement, the Note or the other Loan Documents.

               (c) Use of Proceeds. The proceeds of the Loan shall be used
solely for working capital or general corporate purposes of Borrower consistent
with this Agreement.

               (d) Termination of Commitment to Lend. Notwithstanding anything
in the Loan Documents, Lender's obligation to lend the undisbursed portion of
its Commitment Amount to Borrower hereunder shall terminate on the earlier of
(i) at such Lender's sole election, the occurrence of any Default or Event of
Default hereunder, and (ii) the Commitment Termination Date. Notwithstanding the
foregoing, Lender's obligation to lend the undisbursed portion of its Commitment
Amount to Borrower shall terminate if, in Lender's sole judgment, acting
reasonably, there has been a material adverse change in the general affairs,
management, results of operations, condition (financial or otherwise) or
prospects of Borrower, whether or not arising from transactions in the ordinary
course of business, or there has been any material adverse deviation by Borrower
from the business plan of Borrower presented to Lender on or before the date of
this Agreement.

          2.2 Payments.

               (a) Scheduled Payments. Borrower shall make payments of accrued
interest only on the outstanding principal amount of the Loan on the first
eighteen (18) Payment Dates specified in the Note applicable to the Loan and
twenty-four (24) level payments of principal plus accrued interest on the
outstanding principal amount of the Loan on each subsequent Payment Date as set
forth in the Note (collectively, the "Scheduled Payments"). Borrower shall make
such Scheduled Payments commencing on the date set forth in the Note and
continuing thereafter on the first Business Day of each calendar month (each a
"Payment Date") through the Maturity Date. In any event, all unpaid principal
and accrued interest shall be due and payable in full on the Maturity Date.

               (b) Interim Payment. Unless the Funding Date for the Loan is the
first day of a calendar month, Borrower shall pay the per diem interest
(accruing at the Loan Rate from the Funding Date through the last day of that
month) payable with respect to the Loan on the first Business Day of the next
calendar month.

               (c) Payment of Interest. Borrower shall pay interest on the Loan
at a per annum rate of interest equal to the Loan Rate, applicable to the
Lender. All computations of interest (including interest at the Default Rate, if
applicable) shall be based on a year of twelve 30-day months. Notwithstanding
any other provision hereof, the amount of interest payable

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hereunder shall not in any event exceed the maximum amount permitted by the law
applicable to interest charged on commercial loans.

               (d) Application of Payments. All payments received by Lender
prior to an Event of Default shall be applied as follows: (1) first, to Lender's
Expenses then due and owing; and (2) second to all Scheduled Payments then due
and owing (provided, however, if such payments are not sufficient to pay the
whole amount then due, such payments shall be applied first to unpaid interest
at the Loan Rate, then to the remaining amount then due). After an Event of
Default, all payments and application of proceeds shall be made as set forth in
Section 9.7.

               (e) Late Payment Fee. Borrower shall pay to Lender a late payment
fee equal to four percent (4%) of any Scheduled Payment not paid when due.

               (f) Default Rate. Borrower shall pay interest at a per annum rate
equal to the Default Rate on any amounts required to be paid by Borrower under
this Agreement or the other Loan Documents (including Scheduled Payments),
payable with respect to the Loan, accrued and unpaid interest, and any fees or
other amounts which remain unpaid after such amounts are due. If an Event of
Default has occurred and the Obligations have been accelerated (whether
automatically or by Lender's election), Borrower shall pay interest on the
aggregate, outstanding accelerated balance hereunder from the date of the Event
of Default until such Event of Default shall have been cured prior to
acceleration of the Loan or waived by Lender or all Obligations are paid in
full, at a per annum rate equal to the Default Rate.

          2.3 Prepayments.

               (a) Mandatory Prepayment Upon an Acceleration. If the Loan is
accelerated following the occurrence of an Event of Default pursuant to Section
9.1(a) hereof, then Borrower, in addition to any other amounts which may be due
and owing hereunder, shall immediately pay to Lender the amount set forth in
Section 2.3(b) below, as if the Borrower had opted to prepay on the date of such
acceleration.

               (b) Upon ten (10) Business Days' prior written notice to Lender,
Borrower may, at its option, at any time, prepay all of the Loan by paying to
Lender an amount equal to (i) any accrued and unpaid interest on the outstanding
principal balance of the Loan; (ii) an amount equal to (A) if the Loan is
prepaid within twelve (12) months from the Funding Date thereof, four (4%)
percent of the then outstanding principal balance of the Loan, (B) if the Loan
is prepaid more than twelve (12) months from the Funding Date thereof but less
than twenty-four (24) months from the Funding Date, three (3%) percent of the
then outstanding principal balance of the Loan, or (C) if the Loan is prepaid
more than twenty-four (24) months from the Funding Date thereof, one (1%)
percent of the then outstanding principal balance of the Loan; (iii) the
outstanding principal balance of the Loan and (iv) all other sums, if any, that
shall have become due and payable hereunder.

          2.4 Other Payment Terms.

               (a) Place and Manner. Borrower shall make all payments due to
Lender in lawful money of the United States. All payments of principal,
interest, fees and other amounts payable by Borrower hereunder shall be made, in
immediately available funds, not later than

                                       11

<Page>

10:00 a.m. Connecticut time, on the date on which such payment is due. Borrower
shall make such payments to Lender as follows:

     Payment to Horizon via Wire
     Transfer                        Horizon Technology Funding Company
                                     LLC
     Credit:
     Bank Name:                      ABN Amro/LaSalle Bank NA CDO Trust
                                     Services
     Bank Address:                   135 South LaSalle Street, Suite 1625
                                     Chicago, Illinois 60603
                                     Attn: Greg Meyers, 312-904-0283
     Account No.:                    2090067 - Trust GL
     FFCT-Reference Account Number   721771.1
     ABA Routing No.:                071000505
     Reference:                      ActivBiotics Invoice #

               (b) Date. Whenever any payment is due hereunder on a day other
than a Business Day, such payment shall be made on the next succeeding Business
Day, and such extension of time shall be included in the computation of interest
or fees, as the case may be.

          2.5 Procedure for Making the Loans.

               (a) Notice. Borrower shall notify Lender of the date on which
Borrower desires Lender to make the Loan at least five (5) Business Days in
advance of the desired Funding Date, unless Lender elect at its sole discretion
to allow the Funding Date to be within five (5) Business Days of Borrower's
notice. Borrower's execution and delivery to Lender of a Note shall be
Borrower's agreement to the terms and calculations thereunder with respect to
the Loan. Lender's obligation to make the Loan shall be expressly subject to the
satisfaction of the conditions set forth in Section 3.

               (b) Loan Rate Calculation. Prior to the Funding Date, Lender
shall establish the Loan Rate with respect to the Loan, which shall be set forth
in the Note and shall be conclusive in the absence of a manifest error. Once
established, the Loan Rate shall be fixed for the term of the Loan.

               (c) Disbursement. Lender shall disburse the proceeds of the Loan
by wire transfer to Borrower at the account specified in the Funding Certificate
for the Loan.

          2.6 Good Faith Deposit; Legal and Closing Expenses; and Commitment
Fee.

               (a) Good Faith Deposit. Borrower has delivered to Borrower a good
faith deposit in the amount of Twenty Five Thousand Dollars ($25,000) (the "Good
Faith Deposit"). The Good Faith Deposit will be utilized to pay a portion of the
amounts due to Lender under Section 2.6(b) below and the balance will be applied
to the Commitment Fee.

                                       12

<Page>

               (b) Legal, Due Diligence and Documentation Expenses. Borrower
shall pay to Lender concurrently with its execution and delivery of this
Agreement Lender's legal, due diligence and documentation expenses in connection
with the negotiation and documentation of this Agreement and the Loan Documents,
which amount shall not exceed Eight Thousand Dollars ($8,000) without the prior
consent of Borrower.

               (c) Commitment Fee. Borrower shall pay Lender concurrently with
its execution and delivery of this Agreement a commitment fee in the amount of
Twenty-Five Thousand Dollars ($25,000) to Horizon (the "Commitment Fee"). The
Commitment Fee shall be retained by Lender and be deemed fully earned upon
receipt.

          2.7 Taxes.

               (a) Any and all payments by or on account of any Obligations by
the Borrower hereunder (or by any Guarantor) shall be made free and clear of and
without deduction for any Indemnified Taxes or Other Taxes; PROVIDED that if
Borrower (or any Guarantor) shall be required to deduct any Indemnified Taxes or
Other Taxes from such payments, then (i) the sum payable shall be increased as
necessary so that after making all required deductions (including deductions
applicable to additional sums payable under this Section) the Lender receives an
amount equal to the sum it would have received had no such deductions been made,
(ii) the Borrower (or such Guarantor) shall make such deductions and (iii) the
Borrower (or such Guarantor) shall pay the full amount deducted to the relevant
Governmental Authority in accordance with applicable law.

          (b) In addition, the Borrower shall pay all Other Taxes to the
relevant Governmental Authority in accordance with applicable law.

          (c) The Borrower and each Guarantor shall indemnify Lender within
thirty (30) days after written demand therefor for the full amount of any
Indemnified Taxes or Other Taxes (including Indemnified Taxes or Other Taxes
imposed or asserted on or attributable to amounts payable under this Section 2.7
paid by Lender (and any penalties, interest and reasonable expenses arising
therefrom or with respect thereto during the period prior to the Borrower's
making the payment demanded under this paragraph (c)), whether or not such
Indemnified Taxes or Other Taxes were correctly or legally imposed or asserted
by the relevant Governmental Authority. A certificate as to the amount of such
payment or liability delivered to the Borrower by Lender shall be conclusive
absent manifest error.

          (d) As soon as practicable after any payment of Indemnified Taxes or
Other Taxes by the Borrower (or any Guarantor) to a Governmental Authority, the
Borrower (or such Guarantor) shall deliver to Lender the original or a certified
copy of a receipt issued by such Governmental Authority evidencing such payment,
a copy of the return reporting such payment or other evidence of such payment
reasonably satisfactory to Lender.

     3. Conditions of Loan.

          3.1 Conditions Precedent to Closing. At the time of the execution and
delivery of this Agreement, Lender shall have received, in form and substance
reasonably satisfactory to Lender, all of the following (unless Lender has
agreed to waive such condition or document, in

                                       13

<Page>

which case such condition or document shall be a condition precedent to the
making of the Loan and shall be deemed added to Section 3.2):

               (a) Loan Agreement. This Agreement duly executed by Borrower and
Lender.

               (b) Warrants. The Warrants duly executed by Borrower.

               (c) Secretary's Certificate. A certificate of the secretary or
assistant secretary of the Borrower with copies of the following documents
attached: (i) the certificate of incorporation and bylaws of Borrower certified
by Borrower as being complete and in full force and effect on the date thereof,
(ii) incumbency and representative signatures, and (iii) resolutions authorizing
the execution and delivery of this Agreement and each of the other Loan
Documents.

               (d) Good Standing Certificates. A good standing certificate from
Borrower's jurisdiction of organization and the state in which Borrower's
principal place of business is located, each dated as of a recent date.

               (e) Certificate of Insurance. Evidence of the insurance coverage
required by Section 6.8 of this Agreement.

               (f) Consents. All necessary consents of shareholders and other
third parties with respect to the execution, delivery and performance of this
Agreement, the Warrant and the other Loan Documents.

               (g) Legal Opinion. A legal opinion of from Borrower's counsel
addressed to Lender covering the matters set forth in Exhibit D hereto.

               (h) Account Control Agreements. Account Control Agreements for
all of Borrower's deposit accounts and accounts holding securities located in
the United States duly executed by all of the parties thereto, in the forms
provided by Lender.

               (i) Guaranty and General Security Agreement. An unlimited
Guarantee executed and delivered by ABI Canada in favor of Lender in
substantially the form of Exhibit F attached hereto and made a part hereof.

               (j) Guaranty and General Security Agreement. An unlimited
Guarantee executed and delivered by Metaphore Pharmaceuticals, Inc. in favor of
Lender in substantially the form of Exhibit G attached hereto and made a part
hereof.

               (k) Other Documents. Such other documents and completion of such
other matters, as Lender may reasonably deem necessary or appropriate.

          3.2 Conditions Precedent to Making a Loan. The obligation of Lender to
make the Loan is further subject to the following conditions:

               (a) No Default. No Default or Event of Default shall have
occurred and be continuing.

                                       14

<Page>

               (b) Landlord Agreements. Borrower shall have provided Lender with
a Landlord Agreement for each location where Borrower's books and records and
the Collateral is located (unless Borrower is the fee owner thereof).

               (c) Note. Borrower shall have duly executed and delivered to
Lender a Note in the amount of the Loan.

               (d) UCC Financing Statements. Lender shall have received such
documents, instruments and agreements, including UCC financing statements or
amendments to such financing statements, as Lender shall reasonably request to
evidence the perfection and priority of the security interests granted to Lender
pursuant to Section 4. Borrower authorizes Lender to file any UCC financing
statements, continuations of or amendments to such financing statements it deems
necessary to perfect their security interest in the Collateral.

               (e) Funding Certificate. Borrower shall have duly executed and
delivered to Lender a Funding Certificate for the Loan.

               (f) Other Documents. Such other documents and completion of such
other matters, as Lender may reasonably deem necessary or appropriate.

          3.3 Covenant to Deliver. Borrower agrees (not as a condition but as a
covenant) to deliver to Lender each item required to be delivered to Lender as a
condition to the Loan, if the Loan is advanced. Borrower expressly agrees that
the extension of the Loan prior to the receipt by Lender of any such item shall
not constitute a waiver by Lender of Borrower's obligation to deliver such item,
and any such extension in the absence of a required item shall be in Lender's
sole discretion.

     4. Creation of Security Interest.

          4.1 Grant of Security Interest. Borrower grants to Lender a valid,
continuing security interest in all presently existing and hereafter acquired or
arising Collateral in order to secure prompt, full and complete payment of any
and all Obligations now or hereafter owed to Lender and in order to secure
prompt, full and complete performance by Borrower of its covenants and duties
now or hereafter owed to Lender under each of the Loan Documents (other than the
Warrant). The "Collateral" shall mean and include all right, title, interest,
claims and demands of Borrower in and to all personal property of Borrower,
including without limitation, all of the following:

               (a) All goods (and embedded computer programs and supporting
information included within the definition of "goods" under the Code) and
equipment now owned or hereafter acquired, including, without limitation, all
laboratory equipment, computer equipment, office equipment, machinery, fixtures,
vehicles (including motor vehicles and trailers), and any interest in any of the
foregoing, and all attachments, accessories, accessions, replacements,
substitutions, additions, and improvements to any of the foregoing, wherever
located;

               (b) All inventory now owned or hereafter acquired, including,
without limitation, all merchandise, raw materials, parts, supplies, packing and
shipping materials, work

                                       15

<Page>

in process and finished products including such inventory as is temporarily out
of Borrower's custody or possession or in transit and including any returns upon
any accounts or other proceeds, including insurance proceeds, resulting from the
sale or disposition of any of the foregoing and any documents of title
representing any of the above, and Borrower's books relating to any of the
foregoing;

               (c) All contract rights and general intangibles (except to the
extent included within the definition of Intellectual Property), now owned or
hereafter acquired, including, without limitation, goodwill, license agreements,
franchise agreements, blueprints, drawings, purchase orders, customer lists,
route lists, infringements, claims, software, computer programs, computer disks,
computer tapes, literature, reports, catalogs, design rights, income tax
refunds, payment intangibles, commercial tort claims, payments of insurance and
rights to payment of any kind;

               (d) All now existing and hereafter arising accounts, contract
rights, royalties, license rights, license fees and all other forms of
obligations owing to Borrower arising out of the sale or lease of goods, the
licensing of technology or the rendering of services by Borrower (subject, in
each case, to the contractual rights of third parties to require funds received
by Borrower to be expended in a particular manner), whether or not earned by
performance, and any and all credit insurance, guaranties, and other security
therefor, as well as all merchandise returned to or reclaimed by Borrower and
Borrower's books relating to any of the foregoing;

               (e) All documents, cash, deposit accounts, letters of credit
(whether or not the letter of credit is evidenced by a writing), certificates of
deposit, instruments, promissory notes, chattel paper (whether tangible or
electronic) and investment property, including, without limitation, all
securities, whether certificated or uncertificated, security entitlements,
securities accounts, commodity contracts and commodity accounts, and all
financial assets held in any securities account or otherwise, wherever located,
now owned or hereafter acquired and Borrower's books relating to the foregoing;

               (f) Any and all claims, rights and interests in any of the above
and all substitutions for, additions and accessions to and proceeds thereof,
including, without limitation, insurance, condemnation, requisition or similar
payments and proceeds of the sale or licensing of Intellectual Property to the
extent such proceeds no longer constitute Intellectual Property; but

               (g) Notwithstanding the foregoing, the Collateral shall not
include any Intellectual Property; provided, however, that the Collateral shall
include all accounts receivable, accounts, and general intangibles that consist
of rights to payment and proceeds from the sale, licensing or disposition of all
or any part, or rights in, the foregoing (the "Rights to Payment").

          4.2 After-Acquired Property. If Borrower shall at any time acquire a
commercial tort claim, as defined in the Code, Borrower shall promptly notify
Lender in writing signed by the Borrower of the brief details thereof and, upon
Lender's request, grant to Lender in such writing a security interest therein
and in the proceeds thereof, all upon the terms of this Agreement, with such
writing to be in form and substance satisfactory to Lender.

                                       16

<Page>

          4.3 Duration of Security Interest. Lender's security interest in the
Collateral shall continue until the payment in full and the satisfaction of all
Obligations and termination of Lender's commitment to fund the Loan, whereupon
such security interest shall terminate. Lender shall, at Borrower's sole cost
and expense, promptly execute such further documents and take such further
actions as may be reasonably necessary to make effective the release
contemplated by this Section 4.3, including duly executing and delivering
termination statements for filing in all relevant jurisdictions under the Code.

          4.4 Location and Possession of Collateral. The Collateral is and shall
remain in the possession of Borrower at its location listed on the cover page
hereof or as set forth in the Disclosure Schedule. Borrower shall remain in full
possession, enjoyment and control of the Collateral (except only as may be
otherwise required by Lender for perfection of its security interest therein)
and so long as no Event of Default has occurred, shall be entitled to manage,
operate and use the same and each part thereof with the rights and franchises
appertaining thereto; provided that the possession, enjoyment, control and use
of the Collateral shall at all time be subject to the observance and performance
of the terms of this Agreement.

          4.5 Delivery of Additional Documentation Required. Borrower shall from
time to time execute and deliver to Lender, at the request of Lender, all
financing statements and other documents Lender may reasonably request, in form
satisfactory to Lender, to perfect and continue Lender's perfected security
interests in the Collateral and in order to consummate fully all of the
transactions contemplated under the Loan Documents.

          4.6 Right to Inspect. Lender (through any of its officers, employees,
or agents) shall have the right, upon reasonable prior notice, from time to time
during Borrower's usual business hours, to inspect Borrower's books and records
and to make copies thereof and to inspect, test, and appraise the Collateral in
order to verify Borrower's financial condition or the amount, condition of, or
any other matter relating to, the Collateral.

          4.7 Protection of Intellectual Property. Borrower shall (i) protect,
defend and maintain the validity and enforceability of its Intellectual Property
and promptly advise Lender in writing of material infringements, and (ii) not
abandon, forfeit or dedicate to the public any Intellectual Property material to
Borrower's business without Lender's prior written consent.

          4.8 Lien Subordination. Lender agrees that the Liens granted to it
hereunder in Third Party Equipment shall be subordinate to the Liens of future
lenders providing equipment financing and equipment lessors for equipment and
other personal property acquired by Borrower after the date hereof ("Third Party
Equipment"); provided that such Liens are confined solely to the equipment so
financed and the proceeds thereof and are Permitted Liens. Notwithstanding the
foregoing, the Obligations hereunder shall not be subordinate in right of
payment to any obligations to other equipment lenders or equipment lessors and
Lender's rights and remedies hereunder shall not in any way be subordinate to
the rights and remedies of any such lenders or equipment lessors. So long as no
Event of Default has occurred, Lender agrees to execute and deliver such
agreements and documents as may be reasonably requested by Borrower from time to
time which set forth the lien subordination described in this Section 4.8 and
are reasonably acceptable to Lender. Lender shall have no obligation to execute
any

                                       17

<Page>

agreement or document which would impose obligations, restrictions or lien
priority on Lender which are less favorable to Lender than those described in
this Section 4.8.

     5. Representations and Warranties. Except as set forth in the Disclosure
Schedule, Borrower represents and warrants as follows:

          5.1 Organization and Qualification. Borrower is a corporation duly
organized and validly existing under the laws of its state or country of
incorporation and qualified and licensed to do business in, and is in good
standing in, any state or country in which the conduct of its business or its
ownership of Property requires that it be so qualified or in which the
Collateral is located, except for such jurisdictions as to which any failure to
so qualify would not reasonably be expected to have a material adverse effect on
Borrower.

          5.2 Authority. Borrower has all necessary power and authority to
execute, deliver, and perform in accordance with the terms thereof, the Loan
Documents to which it is a party. Borrower has all requisite power and authority
to own and operate its Property and to carry on its businesses as now conducted.

          5.3 Conflict with Other Instruments, etc. Neither the execution and
delivery of any Loan Document to which Borrower is a party nor the consummation
of the transactions therein contemplated nor compliance with the terms,
conditions and provisions thereof will conflict with or result in a breach of
any of the terms, conditions or provisions of the certificate of incorporation,
the by-laws, or any other organizational documents of Borrower or any law or any
regulation, order, writ, injunction or decree of any court or governmental
instrumentality or any material agreement or instrument to which Borrower is a
party or by which it or any of its Property is bound or to which it or any of
its Property is subject, or constitute a default thereunder or result in the
creation or imposition of any Lien, other than Permitted Liens.

          5.4 Authorization; Enforceability. The execution and delivery of this
Agreement, the granting of the security interest in the Collateral, the
incurring of the Loan, the execution and delivery of the other Loan Documents to
which Borrower is a party and the consummation of the transactions herein and
therein contemplated have each been duly authorized by all necessary action on
the part of Borrower. No authorization, consent, approval, license or exemption
of, and no registration, qualification, designation, declaration or filing with,
or notice to, any Person is, was or will be necessary to (i) the valid execution
and delivery of any Loan Document to which Borrower is a party, (ii) the
performance of Borrower's obligations under any Loan Document, or (iii) the
granting of the security interest in the Collateral, except for filings in
connection with the perfection of the security interest in any of the Collateral
or the issuance of the Warrant. The Loan Documents have been duly executed and
delivered and constitute legal, valid and binding obligations of Borrower,
enforceable in accordance with their respective terms, except as the
enforceability thereof may be limited by bankruptcy, insolvency or other similar
laws of general application relating to or affecting the enforcement of
creditors' rights or by general principles of equity.

          5.5 No Prior Encumbrances. Borrower has good and marketable title to
its Collateral, free and clear of Liens except for Permitted Liens. Borrower has
good title and ownership of, or is licensed under, all of its current
Intellectual Property. Borrower has not

                                       18

<Page>

received any communications alleging that it has violated, or, by conducting its
business as proposed, would violate any proprietary rights of any other Person.
Borrower has no knowledge of any infringement or violation by it of the
intellectual property rights of any third party and has no knowledge of any
violation or infringement by a third party of any of its Intellectual Property.
The Collateral and the Intellectual Property constitute substantially all of the
assets and property of Borrower.

          5.6 Name; Location of Chief Executive Office, Principal Place of
Business and Collateral. Borrower has not done business under any name other
than that specified on the signature page hereof. Borrower's jurisdiction of
organization, chief executive office, principal place of business, and the place
where it maintains its records concerning the Collateral are presently located
in the jurisdiction and at the addresses set forth on the cover page of this
Agreement. The Collateral is presently located at the addresses set forth on the
cover page hereof or as set forth in the Disclosure Schedule.

          5.7 Litigation. There are no actions or proceedings pending by or
against Borrower before any court or administrative agency in which an adverse
decision is reasonably expected to have a material adverse effect on Borrower or
the aggregate value of the Collateral. Borrower has no knowledge of any such
pending or threatened actions or proceedings.

          5.8 Financial Statements. All financial statements relating to
Borrower or any Affiliate that have been delivered by Borrower to Lender present
fairly in all material respects Borrower's financial condition as of the date
thereof and Borrower's results of operations for the period then ended.

          5.9 No Material Adverse Effect. No event has occurred and no condition
exists which is reasonably expected to have a material adverse effect on the
financial condition, business or operations of Borrower since June 30, 2005.

          5.10 Full Disclosure. No representation, warranty or other statement
made by Borrower in any Loan Document (including the Disclosure Schedule),
certificate or written statement furnished to Lender contains any untrue
statement of a material fact or omits to state a material fact necessary in
order to make the statements contained in such certificates or statements not
misleading. There is no fact known to Borrower which materially adversely
affects its ability to perform its obligations under this Agreement.

          5.11 Solvency, Etc. Borrower is Solvent (as defined below) and, after
the execution and delivery of the Loan Documents and the consummation of the
transactions contemplated thereby, Borrower will be Solvent. "Solvent" means,
with respect to any Person on any date, that on such date (a) the fair value of
the property of such Person is greater than the fair value of the liabilities
(including, without limitation, contingent liabilities) of such Person, (b) the
present fair saleable value of the assets of such Person is not less than the
amount that will be required to pay the probable liability of such Person on its
debts as they become absolute and matured and (c) such Person does not intend
to, and does not believe that it will, incur debts or liabilities beyond such
Person's ability to pay as such debts and liabilities mature.

                                       19

<Page>

          5.12 Subsidiaries. Borrower has no Subsidiaries, except as listed on
the Disclosure Schedule.

          5.13 Catastrophic Events; Labor Disputes. Neither Borrower nor its
properties is or has been affected by any fire, explosion, accident, strike,
lockout or other labor dispute, drought, storm, hail, earthquake, embargo, act
of God or other casualty that is reasonably expected to have a material adverse
effect on the financial condition, business or operations of Borrower. There are
no disputes presently subject to grievance procedure, arbitration or litigation
under any of the collective bargaining agreements, employment contracts or
employee welfare or incentive plans to which Borrower is a party, and there are
no strikes, lockouts, work stoppages or slowdowns, or, to the knowledge of
Borrower, jurisdictional disputes or organizing activity occurring or threatened
which is reasonably expected to have a material adverse effect on the financial
condition, business or operations of Borrower.

          5.14 Certain Agreements of Officers, Employees and Consultants.

               (a) No Violation. To the Borrower's knowledge, no employee of the
Borrower, nor any consultant with whom the Borrower has contracted, is in
violation of any term of any employment contract, proprietary information
agreement or any other agreement relating to the right of any such individual to
be employed by, or to contract with, the Borrower; and to the Borrower'
knowledge the continued employment by the Borrower of its present employees, and
the performance of the Borrower's contracts with its independent contractors,
will not result in any such violation. The Borrower has not received any notice
alleging that any such violation has occurred.

               (b) No Present Intention to Terminate. Except for James Warren,
to the knowledge of Borrower, no officer of Borrower, and no employee or
consultant of Borrower whose termination, either individually or in the
aggregate, is reasonably expected to have a material adverse effect on the
financial condition, business or operations of Borrower, has any present
intention of terminating his or her employment or consulting relationship with
Borrower.

          5.15 Compliance with Laws. Borrower is in compliance with all
Requirements of Law, except to the extent that the failure to comply therewith
would not, in the aggregate, reasonably be expected to have a material adverse
effect on the Borrower and its Subsidiaries.

     6. Affirmative Covenants. Borrower, until the full and complete payment of
the Obligations covenants and agrees that:

          6.1 Good Standing. Borrower shall maintain its corporate existence and
its good standing in its jurisdiction of incorporation and maintain
qualification in each jurisdiction in which the failure to so qualify could
reasonably be expected to have a material adverse effect on the financial
condition, operations or business of Borrower. Borrower shall maintain in force
all licenses, approvals and agreements, the loss of which could reasonably be
expected to have a material adverse effect on their financial condition,
operations or business.

          6.2 Government Compliance. Borrower shall comply with all statutes,
laws, ordinances and government rules and regulations to which it is subject,
noncompliance with

                                       20

<Page>

which could reasonably be expected to materially adversely affect the financial
condition, operations or business of Borrower.

          6.3 Financial Statements, Reports, Certificates. Borrower shall
deliver to Lender: (a) as soon as available, but in any event within thirty (30)
days after the end of each month, a company prepared balance sheet, income
statement and cash flow statement covering Borrower's operations during such
period, certified by Borrower's president, treasurer or chief financial officer
(each, a "Responsible Officer"); (b) as soon as available, but in any event
within one hundred twenty (120) days after the end of Borrower's fiscal year,
audited financial statements of Borrower prepared in accordance with GAAP,
together with an unqualified opinion on such financial statements of a
nationally recognized or other independent public accounting firm reasonably
acceptable to Lender; and (c) as soon as available, but in any event within
ninety (90) days after the end of Borrower's fiscal year or the date of
Borrower's board of directors' adoption, Borrower's operating budget and plan
for the next fiscal year; and (d) such other financial information as Lender may
reasonably request from time to time. From and after such time as a Borrower
becomes a publicly reporting company, promptly as they are available and in any
event, it shall deliver to Lender: (x) at the time of filing its Form 10-K with
the Securities and Exchange Commission after the end of each fiscal year of such
Borrower, the financial statements of such Borrower filed with such 10-K and (y)
at the time of filing such Borrower's Form 10-Q with the Securities and Exchange
Commission after the end of each of the first three fiscal quarters of such
Borrower, the financial statements of Borrower filed with such Form 10-Q.
Borrower shall deliver to Lender (i) promptly upon becoming available, copies of
all material statements, reports and notices sent or made available generally by
Borrower to its security holders; (ii) promptly upon receipt of notice thereof,
a report of any material legal actions pending or threatened against Borrower or
the commencement of any action, proceeding or governmental investigation
involving the Borrower is commenced that is reasonably expected to result in
damages or costs to Borrower of Two Hundred Fifty Thousand Dollars ($250,000) or
more; and (iii) such other financial information as Lender may reasonably
request from time to time.

          6.4 Certificates of Compliance. Each time financial statements are
furnished pursuant to Section 6.3 above, Borrower shall deliver to Lender an
Officer's Certificate signed by a Responsible Officer in the form of, and
certifying to the matters set forth in Exhibit E hereto.

          6.5 Notice of Defaults. As soon as possible, and in any event within
five (5) days after the occurrence of a Default or an Event of Default, Borrower
shall provide Lender with an Officer's Certificate setting forth the facts
relating to or giving rise to such Default or Event of Default and the action
which Borrower proposes to take with respect thereto.

          6.6 Taxes. Borrower shall make due and timely payment or deposit of
all federal, state, and local taxes, assessments, or contributions required of
it by law or imposed upon any Property belonging to it, and will execute and
deliver to Lender, on demand, appropriate certificates attesting to the payment
or deposit thereof; and Borrower will make timely payment or deposit of all tax
payments and withholding taxes required of it by applicable laws, including
those laws concerning F.I.C.A., F.U.T.A., state disability, and local, state,
and federal income taxes applicable to Borrower, and will, upon request, furnish
Lender with proof

                                       21

<Page>

satisfactory to Lender indicating that Borrower has made such payments or
deposits; provided that Borrower need not make any payment if the amount or
validity of such payment is contested in good faith by appropriate proceedings
which suspend the collection thereof (provided that such proceedings do not
involve any substantial danger of the sale, forfeiture or loss of any material
item of Collateral or Collateral which in the aggregate is material to Borrower
and that Borrower has adequately bonded such amounts or reserves sufficient to
discharge such amounts have been provided on the books of Borrower).

          6.7 Use; Maintenance. Borrower shall keep and maintain all items of
equipment and other similar types of personal property that form any significant
portion or portions of the Collateral in good operating condition, reasonable
wear and tear excepted, and will comply in all material respects with all laws,
rules and regulations to which the use and operation of the Collateral may be or
become subject. Such obligation shall extend to repair and replacement of any
partial loss or damage to all items of equipment and other similar types of
personal property that form any significant portion or portions of collateral,
regardless of the cause. Borrower shall not permit any such material item of
Collateral to become a fixture to real estate or an accession to other personal
property, without the prior written consent of Lender, not to be unreasonably
withheld. With respect to items of leased equipment (to the extent Lender has
any security interest in any residual Borrower's interest in such equipment
under the lease), Borrower shall keep, maintain, repair, replace and operate
such leased equipment in accordance with the terms of the applicable lease.

          6.8 Insurance. Borrower shall keep its business and the Collateral
insured for risks and in amounts, as is customary for companies in Borrower's
industry and at Borrower's stage of development. Insurance policies shall be in
a form, with companies, and in amounts that are satisfactory to Lender. All
property policies shall have a lender's loss payable endorsement showing Lender
as an additional loss payee and all liability policies shall show Lender as an
additional insured and all policies shall provide that the insurer must give
Lender at least thirty (30) days notice before canceling its policy. At Lender's
request, Borrower shall deliver certified copies of policies and evidence of all
premium payments. Proceeds payable under any policy shall, at Lender's option,
be payable to Lender on account of the Obligations, but unless an Event of
Default shall have occurred, such payment to Lender shall not cause any
prepayment penalty to become due under Section 2.3. Notwithstanding the
foregoing, so long as no Event of Default has occurred and is continuing,
Borrower shall have the option of applying the proceeds of any casualty policy,
toward the replacement or repair of destroyed or damaged property; provided that
(i) any such replaced or repaired property (a) shall be of equal or like value
as the replaced or repaired Collateral and (b) shall be deemed Collateral in
which Lender has been granted a first priority security interest and (ii) after
the occurrence and during the continuation of an Event of Default all proceeds
payable under such casualty policy shall, at the option of Lender, be payable to
Lender, on account of the Obligations. If Borrower fails to obtain insurance as
required under Section 6.8 or to pay any amount or furnish any required proof of
payment to third persons and Lender, Lender may make all or part of such payment
or obtain such insurance policies required in Section 6.8, and take any action
under the policies Lender deems prudent. On or prior to the first Funding Date
and prior to each policy renewal, Borrower shall furnish to Lender certificates
of insurance or other evidence satisfactory to Lender that insurance complying
with all of the above requirements is in effect.

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          6.9 Security Interest. Assuming the proper filing of one or more
financing statement(s) identifying the Collateral with the proper state and/or
local authorities, the security interests in the Collateral granted to Lender
pursuant to this Agreement (i) constitute and will continue to constitute first
priority security interests (except to the extent any Permitted Liens may have a
superior priority to Lender's Lien under this Agreement) and (ii) are and will
continue to be superior and prior to the rights of all other creditors of
Borrower (except to the extent of such Permitted Liens).

          6.10 Further Assurances. At any time and from time to time Borrower
shall execute and deliver such further instruments and take such further action
as may reasonably be requested by Lender to make effective the purposes of this
Agreement, including without limitation, the continued perfection and priority
of Lender's security interest in the Collateral.

          6.11 Private Equity Investment. Borrower shall permit Lender or its
assignees, at Lender's option, to purchase up to Five Hundred Thousand
($500,000) of the securities sold in Borrower's next round of private equity
financing at the same price and on the same terms as paid and received by the
lead investor of the private equity financing. Borrower agrees that it shall
notify Lender promptly upon the execution by Borrower of a term sheet or letter
of intent setting forth the terms and conditions of such financing and in any
event within five (5) days of such execution. For the avoidance of doubt,
Section 6.11 hereof shall not apply in a public offering of securities by
Borrower nor shall it apply in the event the investors of ABI Canada (or either
of them) exercise their respective put rights pursuant to the Put and Support
Agreement.

     7. Negative Covenants. Borrower, until the full and complete payment of the
Obligations, covenants and agrees that, without the prior written consent of
Lender, it shall not:

          7.1 Chief Executive Office. Change its name, jurisdiction of
incorporation, chief executive office, principal place of business or any of the
items set forth in Section 1 of the Disclosure Schedule without thirty (30) days
prior written notice to Lender.

          7.2 Collateral Control. Subject to its rights under Sections 4.4 and
7.4. remove any items of Collateral from Borrower's facilities located at the
address set forth on the cover page hereof or as set forth on the Disclosure
Schedule.

          7.3 Liens. Create, incur, assume or suffer to exist any Lien or permit
any of its Subsidiaries to create, incur, assume or permit to exist any Lien of
any kind upon any of Borrower's Property, whether now owned or hereafter
acquired, except Permitted Liens.

          7.4 Other Dispositions of Collateral. Convey, sell, lease or otherwise
dispose of all or any part of the Collateral to any Person (collectively, a
"Transfer"), except for: (i) Transfers of inventory in the ordinary course of
business; (ii) Transfers of worn-out or obsolete equipment; (iii) Transfers
permitted under subclauses (f) and (1) of the definition of Permitted Liens with
respect to Collateral or (iv) Transfers of Collateral during the term of the
Loans equal in aggregate value to less than Two Hundred Thousand Dollars
($200,000).

          7.5 Distributions. (i) Pay any cash dividends or make any cash
distributions on its Equity Securities; (ii) purchase, redeem, retire, defease
or otherwise acquire for value any of

                                       23

<Page>

its Equity Securities (other than repurchases pursuant to the terms of employee
stock purchase plans, employee restricted stock agreements or similar
arrangements in an aggregate amount not to exceed One Hundred Thousand Dollars
($100,000)); (iii) return any capital to any holder of its Equity Securities as
such; (iv) make any distribution of assets, obligations or securities of any
other Persons to any holder of its Equity Securities as such; or (v) set apart
any sum for any such purpose; provided, however, Borrower may pay dividends
payable solely in common stock.

          7.6 Mergers or Acquisitions. Merge or consolidate with or into any
other Person or acquire all or substantially all of the capital stock or assets
of another Person.

          7.7 Change in Ownership. Engage in or permit any of its Subsidiaries
to engage in any business other than the businesses currently engaged in by
Borrower or reasonably related thereto or have a material change in its
ownership of greater than thirty-three percent (33%) (other than by the sale by
Borrower of Borrower's Equity Securities in a public offering or to venture
capital investors so long as Borrower identifies to Lender the venture capital
investors prior to the closing of the investment or pursuant to any transaction
contemplated in the Put and Support Agreement).

          7.8 Transactions With Affiliates. Enter into any contractual
obligation with any Affiliate or engage in any other transaction with any
Affiliate except upon prices, terms and requirements at least as favorable to
Borrower as an arms-length transaction with Persons who are not Affiliates of
Borrower, except for contractual obligations between Borrower and ABI Canada (or
shareholders of either of them, as applicable) pursuant to the Co-Development
License or Put and Support Agreement or the Research Agreements, or contractual
obligations entered into with an Affiliate in connection with the sales of
Equity Securities of the Borrower.

          7.9 Indebtedness Payments. (i) Prepay, redeem, purchase, defease or
otherwise satisfy in any manner prior to the scheduled repayment thereof any
Indebtedness for borrowed money (other than amounts due or permitted to be
prepaid under this Agreement) or lease obligations; provided, that the Borrower
may prepay its obligations to Silicon Valley Bank, N.A., (ii) amend, modify or
otherwise change the terms of any Indebtedness for borrowed money or lease
obligations so as to accelerate the scheduled repayment thereof or (iii) repay
any notes to officers, directors or shareholders.

          7.10 Indebtedness. Create, incur, assume or permit to exist any
Indebtedness except Permitted Indebtedness.

          7.11 Investments. Make any Investment except for Permitted
Investments.

          7.12 Compliance. Become an "investment company" or a company
controlled by an "investment company" under the Investment Company Act of 1940
or undertake as one of its important activities extending credit to purchase or
carry margin stock, or use the proceeds of any Loan for that purpose; fail to
meet the minimum funding requirements of the Employment Retirement Income
Security Act of 1974, and its regulations, as amended from time to time
("ERISA"), permit a Reportable Event or Prohibited Transaction, as defined in
ERISA, to occur; fail to comply with the Federal Fair Labor Standards Act or
violate any other

                                       24

<Page>

law or regulation, if the violation could reasonably be expected to have a
material adverse effect on Borrower's business or operations or could reasonably
be expected to cause a material adverse change, or permit any of its
Subsidiaries to do so.

          7.13 Maintenance of Accounts. (i) Maintain any deposit account or
account holding securities owned by Borrower except accounts with respect to
which Lender is able to take such actions as they deem necessary to obtain a
perfected security interest in such accounts through one or more Account Control
Agreements; or (ii) grant or allow any other Person (other than Lender) to
perfect a security interest in, or enter into any agreements with any Persons
(other than Lender) accomplishing perfection via control as to, any of its
deposit accounts or accounts holding securities.

          7.14 Negative Pledge Regarding Intellectual Property. Create, incur,
assume or suffer to exist any Lien of any kind upon any Intellectual Property or
Transfer any Intellectual Property, whether now owned or hereafter acquired,
other than licenses or contracts to or from Borrower and its Subsidiaries for
the development, use, sharing or commercializing of Intellectual Property,
including the Kaneka License, the Pfizer License and the Co-Development Licenses
or licenses entered into in connection with a transaction negotiated at
arms-length and for adequate consideration in the ordinary course of business;
provided, that notwithstanding anything contained herein to the contrary,
Borrower shall not grant a security interest in any of its Intellectual Property
(including, without limitation, any such licenses or contracts) to any Person.

     8. Events of Default. Any one or more of the following events shall
constitute an "Event of Default" by Borrower under this Agreement:

          8.1 Failure to Pay. If Borrower fails to pay when due and payable or
when declared due and payable in accordance with the Loan Documents: (i) any
Scheduled Payment on the relevant Payment Date or on the relevant Maturity Date,
or (ii) any other portion of the Obligations within five (5) Business Days after
receipt of written notice from the applicable Lender that such payment is due.

          8.2 Certain Covenant Defaults. If Borrower fails to perform any
obligation under Section 4.6, Section 6.8 or violates any of the covenants
contained in Section 7 of this Agreement.

          8.3 Other Covenant Defaults. If Borrower fails or neglect to perform,
keep, or observe any other material term, provision, condition, covenant, or
agreement contained in this Agreement (other than as set forth in Sections 8.1,
8.2 or 8.4 through 8.13), in any of the other Loan Documents and Borrower has
failed to cure such default within thirty (30) days of the occurrence of such
default. During this thirty (30) day period, the failure to cure the default is
not an Event of Default.

          8.4 Intentionally Omitted.

          8.5 Seizure of Assets, Etc. If any material portion of Borrower's
assets are attached, seized, subjected to a writ or distress warrant, or are
levied upon, or come into the possession of any trustee, receiver or Person
acting in a similar capacity and such attachment

                                       25

<Page>

seizure, writ or distress warrant or levy has not been removed, discharged or
rescinded within twenty (20) days, or if Borrower is enjoined, restrained, or in
any way prevented by court order from continuing to conduct all or any material
part of its business affairs, or if a judgment or other claim becomes a lien or
encumbrance upon any material portion of Borrower's assets, or if a notice of
lien, levy, or assessment is filed of record with respect to any of Borrower's
assets by the United States Government, or any department, agency, or
instrumentality thereof, or by any state, county, municipal, or governmental
agency, and the same is not paid within twenty (20) days after Borrower receives
notice thereof: provided that none of the foregoing shall constitute an Event of
Default where such action or event is stayed or an adequate bond has been posted
pending a good faith contest by Borrower.

          8.6 Service of Process. The service of process upon any Lender seeking
to attach by a trustee or other process any funds of Borrower on deposit or
otherwise held by Lender, or the delivery upon Lender of a notice of foreclosure
by any Person seeking to attach or foreclose on any funds of Borrower on deposit
or otherwise held by Lender, or the delivery of a notice of foreclosure or
exclusive control to any entity holding or maintaining Borrower's deposit
accounts or accounts holding securities by any Person seeking to foreclose or
attach any such accounts or securities.

          8.7 Default on Indebtedness. One or more defaults shall exist, which
defaults have not been cured within the applicable cure period, if any, under
any agreement of Borrower with any third party or parties which consists of the
failure to pay any Indebtedness at maturity or which results in a right by such
third party or parties, whether or not exercised, to accelerate the maturity of
Indebtedness in an aggregate amount in excess of Two Hundred Thousand Dollars
($200,000) or a default shall exist under any financing agreement with Lender or
any of Lender's Affiliates.

          8.8 Judgments. If a judgment or judgments for the payment of money in
an amount, individually or in the aggregate, of at least Two Hundred Thousand
Dollars ($200,000) shall be rendered against Borrower and shall remain
unsatisfied and unstayed for a period of twenty (20) days or more.

          8.9 Misrepresentations. If any material misrepresentation or material
misstatement exists now or hereafter in any warranty, representation, statement,
certification, or report made to Lender by Borrower or any officer, employee,
agent, or director of Borrower.

          8.10 Breach of Warrant. If Borrower shall breach any material term of
the Warrant.

          8.11 Unenforceable Loan Document. If any Loan Document shall in any
material respect cease to be, or Borrower shall assert that any Loan Document is
not, a legal, valid and binding obligation of Borrower enforceable in accordance
with its terms.

          8.12 Involuntary Insolvency Proceeding. If a proceeding shall have
been instituted in a court having jurisdiction in the premises seeking a decree
or order for relief in respect of Borrower in an involuntary case under any
applicable bankruptcy, insolvency or other similar law now or hereafter in
effect, or for the appointment of a receiver, liquidator, assignee,

                                       26

<Page>

custodian, trustee (or similar official) of Borrower or for any substantial part
of its Property, or for the winding-up or liquidation of its affairs, and such
proceeding shall remain undismissed or unstayed and in effect for a period of
sixty (60) consecutive days or such court shall enter a decree or order granting
the relief sought in such proceeding.

          8.13 Voluntary Insolvency Proceeding. If Borrower shall commence a
voluntary case under any applicable bankruptcy, insolvency or other similar law
now or hereafter in effect, shall consent to the entry of an order for relief in
an involuntary case under any such law, or shall consent to the appointment of
or taking possession by a receiver, liquidator, assignee, trustee, custodian (or
other similar official) of Borrower or for any substantial part of its Property,
or shall make a general assignment for the benefit of creditors, or shall fail
generally to pay its debts as they become due, or shall take any corporate
action in furtherance of any of the foregoing.

     9. Lender's Rights and Remedies.

          9.1 Rights and Remedies. Upon the occurrence of any Default or Event
of Default, Lender shall not have any further obligation to advance money or
extend credit to or for the benefit of Borrower. In addition, upon the
occurrence of an Event of Default, Lender shall have the rights, options, duties
and remedies of a secured party as permitted by law and, in addition to and
without limitation of the foregoing, Lender may, at its election, without notice
of election and without demand, do any one or more of the following, all of
which are authorized by Borrower:

               (a) Acceleration of Obligations. Declare all Obligations whether
evidenced by this Agreement, by any of the other Loan Documents, or otherwise,
including (i) any accrued and unpaid interest, (ii) the amounts which would have
otherwise come due under Section 2.3(b)(ii) if the Loan had been voluntarily
prepaid, (iii) the unpaid principal balance of the Loan and (iv) all other sums,
if any, that shall have become due and payable hereunder, immediately due and
payable (provided that upon the occurrence of an Event of Default described in
Section 8.12 or 8.13 all Obligations shall become immediately due and payable
without any action by Lender);

               (b) Protection of Collateral. Make such payments and do such acts
as Lender considers necessary or reasonable to protect Lender's security
interest in the Collateral. Borrower agrees to assemble the Collateral if Lender
so requires and to make the Collateral available to Lender or as Lender may
otherwise designate. Borrower authorizes Lender and its designees and agents to
enter the premises where the Collateral is located, to take and maintain
possession of the Collateral, or any part of it, and to pay, purchase, contest,
or compromise any Lien which in Lender's determination appears or is claimed to
be prior or superior to its security interest and to pay all expenses incurred
in connection therewith. With respect to any of Borrower's owned premises,
Borrower hereby grants Lender a license to enter into possession of such
premises and to occupy the same, without charge, for up to one hundred twenty
(120) days in order to exercise any of Lender's rights or remedies provided
herein, at law, in equity, or otherwise;

                                       27

<Page>

               (c) Preparation of Collateral for Sale. Ship, reclaim, recover,
store, finish, maintain, repair, prepare for sale, advertise for sale, and sell
(in the manner provided for herein) the Collateral. Lender and its agents and
any purchasers at or after foreclosure are hereby granted a non-exclusive,
irrevocable, perpetual, fully paid, royalty-free license or other right, solely
pursuant to the provisions of this Section 9.1, to use, without charge,
Borrower's Intellectual Property, including without limitation, labels, patents,
copyrights, rights of use of any name, trade secrets, trade names, trademarks,
service marks, and advertising matter, or any Property of a similar nature, now
or at any time hereafter owned or acquired by Borrower or in which Borrower now
or at any time hereafter has any rights; provided that such license shall only
be exercisable in connection with the disposition of Collateral upon Lender's
exercise of its remedies hereunder and such license shall immediately terminate
upon the disposition of the Collateral;

               (d) Sale of Collateral. Sell the Collateral at either a public or
private sale, or both, by way of one or more contracts or transactions, for cash
or on terms, in such manner and at such places (including Borrower's premises)
as Lender determines is commercially reasonable; and

               (e) Purchase of Collateral. Credit bid and purchase all or any
portion of the Collateral at any public sale.

Any deficiency that exists after disposition of the Collateral as provided above
will be paid immediately by Borrower.

          9.2 Set Off Right. Any time after the occurrence of an Event of
Default, Lender may set off and apply to the Obligations any and all
indebtedness at any time owing to or for the credit or the account of Borrower
or any other assets of Borrower in Lender's possession or control, whether or
not the Obligations have matured and whether or not the Lender is otherwise
fully secured.

          9.3 Effect of Sale. Upon the occurrence of an Event of Default, to the
extent permitted by law, Borrower covenants that it will not at any time insist
upon or plead, or in any manner whatsoever claim or take any benefit or
advantage of, any stay or extension law now or at any time hereafter in force,
nor claim, take nor insist upon any benefit or advantage of or from any law now
or hereafter in force providing for the valuation or appraisement of the
Collateral or any part thereof prior to any sale or sales thereof to be made
pursuant to any provision herein contained, or to the decree, judgment or order
of any court of competent jurisdiction; nor, after such sale or sales, claim or
exercise any right under any statute now or hereafter made or enacted by any
state or otherwise to redeem the property so sold or any part thereof, and, to
the full extent legally permitted, except as to rights expressly provided
herein, hereby expressly waives for itself and on behalf of each and every
Person, except decree or judgment creditors of Borrower, acquiring any interest
in or title to the Collateral or any part thereof subsequent to the date of this
Agreement, all benefit and advantage of any such law or laws, and covenants that
it will not invoke or utilize any such law or laws or otherwise hinder, delay or
impede the execution of any power herein granted and delegated to Lender, but
will suffer and permit the execution of every such power as though no such
power, law or laws had been made or enacted. Any sale, whether under any power
of sale hereby given or by virtue of

                                       28

<Page>

judicial proceedings, shall operate to divest all right, title, interest, claim
and demand whatsoever, either at law or in equity, of Borrower in and to the
Property sold, and shall be a perpetual bar, both at law and in equity, against
Borrower, its successors and assigns, and against any and all Persons claiming
the Property sold or any part thereof under, by or through Borrower, its
successors or assigns.

          9.4 Power of Attorney in Respect of the Collateral. Borrower does
hereby irrevocably appoint Lender (which appointment is coupled with an
interest), the true and lawful attorney in fact of Borrower with full power of
substitution, for it and in its name to file any notices of security interests,
financing statements and continuations and amendments thereof pursuant to the
Code or federal law, as may be necessary to perfect, or to continue the
perfection of Lender's security interests in the Collateral. Borrower does
hereby irrevocably appoint Lender (which appointment is coupled with an
interest) on the occurrence of an Event of Default, the true and lawful attorney
in fact of Borrower with full power of substitution, for it and in its name: (a)
to ask, demand, collect, receive, receipt for, sue for, compound and give
acquittance for any and all rents, issues, profits, avails, distributions,
income, payment draws and other sums in which a security interest is granted
under Section 4 with full power to settle, adjust or compromise any claim
thereunder as fully as if Lender were Borrower itself; (b) to receive payment of
and to endorse the name of Borrower to any items of Collateral (including
checks, drafts and other orders for the payment of money) that come into
Lender's possession or under Lender's control; (c) to make all demands, consents
and waivers, or take any other action with respect to, the Collateral; (d) in
Lender's discretion to file any claim or take any other action or proceedings,
either in its own name or in the name of Borrower or otherwise, which Lender may
reasonably deem necessary or appropriate to protect and preserve the right,
title and interest of Lender in and to the Collateral; (e) endorse Borrower's
name on any checks or other forms of payment or security; (f) sign Borrower's
name on any invoice or bill of lading for any account or drafts against account
debtors; (g) make, settle, and adjust all claims under Borrower's insurance
policies; (h) settle and adjust disputes and claims about the accounts directly
with account debtors, for amounts and on terms Lender determines reasonable; (i)
transfer the Collateral into the name of Lender or a third party as the Code
permits; and (j) to otherwise act with respect thereto as though Lender was the
outright owner of the Collateral to the extent not prohibited under the Code or
other applicable law.

          9.5 Lender's Expenses. If Borrower fails to pay any amounts or furnish
any required proof of payment due to third persons or entities, as required
under the terms of this Agreement, then Lender may do any or all of the
following: (a) make payment of the same or any part thereof; or (b) obtain and
maintain insurance policies of the type discussed in Section 6.8 of this
Agreement, and take any action with respect to such policies as Lender deems
prudent. Any amounts paid or deposited by Lender shall constitute Lender's
Expenses, shall be immediately due and payable, shall bear interest at the
Default Rate and shall be secured by the Collateral. Any payments made by Lender
shall not constitute an agreement by Lender to make similar payments in the
future or a waiver by Lender of any Event of Default under this Agreement.
Borrower shall pay all reasonable fees and expenses, including without
limitation, Lender's Expenses, incurred by Lender in the enforcement or attempt
to enforce any of the Obligations hereunder not performed when due.

                                       29

<Page>

          9.6 Remedies Cumulative. Lender's rights and remedies under this
Agreement, the Loan Documents, and all other agreements shall be cumulative.
Lender shall have all other rights and remedies not inconsistent herewith as
provided under the Code, by law, or in equity. No exercise by Lender of one
right or remedy shall be deemed an election, and no waiver by Lender of any
Event of Default on Borrower's part shall be deemed a continuing waiver. No
delay by Lender shall constitute a waiver, election, or acquiescence by it.

          9.7 Application of Collateral Proceeds. The proceeds and/or avails of
the Collateral, or any part thereof, and the proceeds and the avails of any
remedy hereunder (as well as any other amounts of any kind held by Lender, at
the time of or received by Lender after the occurrence of an Event of Default
hereunder) shall be paid to and applied as follows:

               (a) First, to the payment of out-of-pocket costs and expenses,
including all amounts expended to preserve the value of the Collateral, of
foreclosure or suit, if any, and of such sale and the exercise of any other
rights or remedies, and of all proper fees, expenses, liability and advances,
including reasonable legal expenses and attorneys' fees, incurred or made
hereunder by Lender, including, without limitation, Lender's Expenses;

               (b) Second, to the payment to Lender of the amount then owing or
unpaid on the Loan for any accrued and unpaid interest, the amounts which would
have otherwise come due under Section 2.3(b)(ii), if the Loan had been
voluntarily prepaid, the principal balance of the Loan, and all other
Obligations with respect to the Loan (provided, however, if such proceeds shall
be insufficient to pay in full the whole amount so due, owing or unpaid upon the
Loan, then to the unpaid interest thereon, then to the amounts which would have
otherwise come due under Section 2.3(b)(ii), if the Loan had been voluntarily
prepaid, then to the principal balance of the Loan, and then to the payment of
other amounts then payable to Lender under any of the Loan Documents); and

               (c) Third, to the payment of the surplus, if any, to Borrower,
its successors and assigns, or to the Person lawfully entitled to receive the
same.

          9.8 Reinstatement of Rights. If Lender shall have proceeded to enforce
any right under this Agreement or any other Loan Document by foreclosure, sale,
entry or otherwise, and such proceedings shall have been discontinued or
abandoned for any reason or shall have been determined adversely, then and in
every such case (unless otherwise ordered by a court of competent jurisdiction),
Lender shall be restored to its former position and rights hereunder with
respect to the Property subject to the security interest created under this
Agreement.

     10. Waivers; Indemnification.

          10.1 Demand; Protest. Borrower waives demand, protest, notice of
protest, notice of default or dishonor, notice of payment and nonpayment, notice
of any default, nonpayment at maturity, release, compromise, settlement,
extension, or renewal of accounts, documents, instruments, chattel paper, and
guarantees at any time held by Lender on which Borrower may in any way be
liable.

          10.2 Lender's Liability for Collateral. So long as Lender complies
with its obligations, if any, under the Code, Lender shall not in any way or
manner be liable or

                                       30

<Page>

responsible for: (a) the safekeeping of the Collateral; (b) any loss or damage
thereto occurring or arising in any manner or fashion from any cause other than
Lender's gross negligence or willful misconduct; (c) any diminution in the value
thereof; or (d) any act or default of any carrier, warehouseman, bailee,
forwarding agency, or other Person whomsoever. All risk of loss, damage or
destruction of the Collateral shall be borne by Borrower.

          10.3 Indemnification and Waiver. Whether or not the transactions
contemplated hereby shall be consummated:

               (a) General Indemnity. Borrower agrees upon demand to pay or
reimburse Lender for all liabilities, obligations and out-of-pocket expenses,
including Lender's Expenses and reasonable fees and expenses of counsel for
Lender from time to time arising in connection with the enforcement or
collection of sums due under the Loan Documents, and in connection with any
amendment or modification of the Loan Documents or any "work-out" in connection
with the Loan Documents. Borrower shall indemnify, reimburse and hold the
Lender, and its respective successors, assigns, agents, attorneys, officers,
directors, shareholders, servants, agents and employees (each an "Indemnified
Person") harmless from and against all liabilities, losses, damages, actions,
suits, demands, claims of any kind and nature (including claims relating to
environmental discharge, cleanup or compliance), all costs and expenses
whatsoever to the extent they may be incurred or suffered by such Indemnified
Person in connection therewith (including reasonable attorneys' fees and
expenses), fines, penalties (and other charges of any applicable Governmental
Authority), licensing fees relating to any item of Collateral, damage to or loss
of use of property (including consequential or special damages to third parties
or damages to Borrower's property), or bodily injury to or death of any person
(including any agent or employee of Borrower) (each, a "Claim"), directly or
indirectly relating to or arising out of the use of the proceeds of the Loan or
otherwise, the falsity of any representation or warranty of Borrower or
Borrower's failure to comply with the terms of this Agreement or any other Loan
Document. The foregoing indemnity shall cover, without limitation, (i) any Claim
in connection with a design or other defect (latent or patent) in any item of
equipment or product included in the Collateral, (ii) any Claim for infringement
of any patent, copyright, trademark or other intellectual property right, (iii)
any Claim resulting from the presence on or under or the escape, seepage,
leakage, spillage, discharge, emission or release of any Hazardous Materials on
the premises owned, occupied or leased by Borrower, including any Claims
asserted or arising under any Environmental Law, (iv) any Claim for negligence
or strict or absolute liability in tort, or (v) any Claim asserted as to or
arising under any Account Control Agreement or any Landlord Agreement; provided,
however, Borrower shall not indemnify Lender for any liability incurred by such
Lender as a direct and sole result of Lender's gross negligence or willful
misconduct, as applicable. Such indemnities shall continue in full force and
effect, notwithstanding the expiration or termination of this Agreement. Upon
Lender's written demand, Borrower shall assume and diligently conduct, at its
sole cost and expense, the entire defense of Lender, its partners, and its
respective, agents, employees, directors, officers, shareholders, successors and
assigns against any indemnified Claim described in this Section 10.3(a).
Borrower shall not settle or compromise any Claim against or involving Lender
without first obtaining Lender's written consent thereto, which consent shall
not be unreasonably withheld.

               (b) Waiver. NOTWITHSTANDING ANYTHING TO THE CONTRARY CONTAINED IN
THIS AGREEMENT OR ANYWHERE ELSE, BORROWER AGREES

                                       31

<Page>

THAT IT SHALL NOT SEEK FROM LENDER UNDER ANY THEORY OF LIABILITY (INCLUDING ANY
THEORY IN TORTS), ANY SPECIAL, INDIRECT, CONSEQUENTIAL OR PUNITIVE DAMAGES.

               (c) Survival; Defense. The obligations in this Section 10.3 shall
survive payment of all other Obligations pursuant to Section 12.8. At the
election of any Indemnified Person, Borrower shall defend such Indemnified
Person using legal counsel satisfactory to such Indemnified Person in such
Person's reasonable discretion, at the sole cost and expense of Borrower. All
amounts owing under this Section 10.3 shall be paid within thirty (30) days
after written demand.

     11. Notices. Unless otherwise provided in this Agreement, all notices or
demands by any party relating to this Agreement or any other agreement entered
into in connection herewith shall be in writing and (except for financial
statements and other informational documents which may be sent by first-class
mail, postage prepaid) shall be personally delivered or sent by certified mail,
postage prepaid, return receipt requested, by prepaid nationally recognized
overnight courier, or by facsimile to Borrower or to Lender, as the case may be,
at their respective addresses set forth below:

     If to Borrower:   ActivBiotics, Inc.
                       110 Hartwell Avenue
                       Lexington, MA 02421
                       Attention: Steve Gilman
                       Fax:(781)274-8638
                       Ph:(781)372-4855

     If to Lender:     Horizon Technology Funding Company LLC
                       76 Batterson Park Road
                       Farmington, CT 06032
                       Attention: Legal Department
                       Fax:(860) 676-8655
                       Ph:(860) 676-8654

     The parties hereto may change the address at which they are to receive
notices hereunder, by notice in writing in the foregoing manner given to the
other.

     12. General Provisions.

          12.1 Successors and Assigns. This Agreement and the Loan Documents
shall bind and inure to the benefit of the respective successors and permitted
assigns of each of the parties; provided, however, neither this Agreement nor
any rights hereunder may be assigned by Borrower without Lender's prior written
consent, which consent may be granted or withheld in Lender's sole discretion.
Lender shall have the right without the consent of or notice to Borrower to
sell, transfer, assign, negotiate, or grant participations in all or any part
of, or any interest in Lender's rights and benefits hereunder. Lender may
disclose the Loan Documents and any other financial or other information
relating to Borrower or any Subsidiary to any potential participant or assignee
of any of the Loan, provided that such participant or assignee

                                       32

<Page>

agrees to protect the confidentiality of such documents and information using
the same measures that it uses to protect its own confidential information.

          12.2 Time of Essence. Time is of the essence for the performance of
all obligations set forth in this Agreement.

          12.3 Severability of Provisions. Each provision of this Agreement
shall be several from every other provision of this Agreement for the purpose of
determining the legal enforceability of any specific provision.

          12.4 Entire Agreement; Construction; Amendments and Waivers.

               (a) Entire Agreement. This Agreement and each of the other Loan
Documents dated as of the date hereof, taken together, constitute and contain
the entire agreement between Borrower and Lender and supersede any and all prior
agreements, negotiations, correspondence, understandings and communications
between the parties, whether written or oral, respecting the subject matter
hereof. Borrower acknowledges that it is not relying on any representation or
agreement made by Lender or any employee, attorney or agent thereof, other than
the specific agreements set forth in this Agreement and the Loan Documents.

               (b) Construction. This Agreement is the result of negotiations
between and has been reviewed by Borrower and Lender executing this Agreement as
of the date hereof and their respective counsel; accordingly, this Agreement
shall be deemed to be the product of the parties hereto, and no ambiguity shall
be construed in favor of or against Borrower or Lender. Borrower and Lender
agree that they intend the literal words of this Agreement and the other Loan
Documents and that no parol evidence shall be necessary or appropriate to
establish Borrower's or Lender's actual intentions.

               (c) Amendments and Waivers. Any and all discharges or waivers of,
or consents to any departures from any provision of this Agreement or of any of
the other Loan Documents shall not be effective without the written consent of
Lender. Any and all amendments and modifications of this Agreement or of any of
the other Loan Documents shall not be effective without the written consent of
Lender and Borrower. Any waiver or consent with respect to any provision of the
Loan Documents shall be effective only in the specific instance and for the
specific purpose for which it was given. No notice to or demand on Borrower in
any case shall entitle Borrower to any other or further notice or demand in
similar or other circumstances. Any amendment, modification, waiver or consent
affected in accordance with this Section 12.4 shall be binding upon Lender and
Borrower.

          12.5 Reliance by Lender. All covenants, agreements, representations
and warranties made herein by Borrower shall be deemed to be material to and to
have been relied upon by Lender, notwithstanding any investigation by Lender.

          12.6 No Set-Offs by Borrower. All sums payable by Borrower pursuant to
this Agreement or any of the other Loan Documents shall be payable without
notice or demand and shall be payable in United States Dollars without set-off
or reduction of any manner whatsoever.

                                       33

<Page>

          12.7 Counterparts. This Agreement may be executed in any number of
counterparts and by different parties on separate counterparts, each of which,
when executed and delivered, shall be deemed to be an original, and all of
which, when taken together, shall constitute but one and the same Agreement.

          12.8 Survival. All covenants, representations and warranties made in
this Agreement shall continue in full force and effect so long as any
Obligations or commitment to fund remain outstanding. The obligations of
Borrower to indemnify Lender with respect to the expenses, damages, losses,
costs and liabilities described in Section 10.3 shall survive until all
applicable statute of limitations periods with respect to actions that may be
brought against Lender have run.

     13. Relationship of Parties. Borrower and Lender acknowledge, understand
and agree that the relationship between Borrower, on the one hand, and Lender on
the other, is, and at all time shall remain solely that of a borrower and
lender. Lender shall not under any circumstances be construed to be a partner or
a joint venturer of Borrower or any of its Affiliates; nor shall Lender under
any circumstances be deemed to be in a relationship of confidence or trust or a
fiduciary relationship with Borrower or any of its Affiliates, or to owe any
fiduciary duty to Borrower or any of its Affiliates. Lender does not undertake
or assume any responsibility or duty to Borrower or any of its Affiliates to
select, review, inspect, supervise, pass judgment upon or otherwise inform
Borrower or any of its Affiliates of any matter in connection with its or their
Property, any Collateral held by Lender or the operations of Borrower or any of
its Affiliates. Borrower and each of its Affiliates shall rely entirely on their
own judgment with respect to such matters, and any review, inspection,
supervision, exercise of judgment or supply of information undertaken or assumed
by Lender in connection with such matters is solely for the protection of Lender
and neither Borrower nor any Affiliate is entitled to rely thereon.

     14. Confidentiality. All information (other than periodic reports filed by
Borrower with the Securities and Exchange Commission) disclosed by Borrower to
Lender in writing or through inspection pursuant to this Agreement that is
marked confidential shall be considered confidential. Lender agrees to use the
same degree of care to safeguard and prevent disclosure of such confidential
information as Lender uses with its own confidential information, but in any
event no less than a reasonable degree of care. Lender shall not disclose such
information to any third party (other than to Lender's partners, attorneys,
governmental regulators, or auditors, or to Lender's subsidiaries and affiliates
and prospective transferees and purchasers of the Loan, all subject to the same
confidentiality obligation set forth herein or as required by law, regulation,
subpoena or other order to be disclosed) and shall use such information only for
purposes of evaluation of its investment in Borrower and the exercise of
Lender's rights and the enforcement of its remedies under this Agreement and the
other Loan Documents. The obligations of confidentiality shall not apply to any
information that (a) was known to the public prior to disclosure by Borrower
under this Agreement, (b) becomes known to the public through no fault of
Lender, (c) is disclosed to Lender by a third party having a legal right to make
such disclosure, or (d) is independently developed by Lender. Notwithstanding
the foregoing, Lender's agreement of confidentiality shall not apply if Lender
has acquired indefeasible title to any Collateral or in connection with any
enforcement or exercise of Lender's rights and remedies under this Agreement
following an Event of Default, including the enforcement of Lender's security
interest in the Collateral.

                                       34

<Page>

     15. CHOICE OF LAW AND VENUE; JURY TRIAL WAIVER. THIS AGREEMENT SHALL BE
GOVERNED BY, AND CONSTRUED IN ACCORDANCE WITH, THE INTERNAL LAWS OF THE STATE OF
CONNECTICUT, WITHOUT REGARD TO PRINCIPLES OF CONFLICTS OF LAW. BORROWER AND
LENDER HEREBY SUBMIT TO THE NON-EXCLUSIVE JURISDICTION OF THE STATE AND FEDERAL
COURTS LOCATED IN THE STATE OF CONNECTICUT. BORROWER AND LENDER HEREBY WAIVE
THEIR RESPECTIVE RIGHTS TO A JURY TRIAL OF ANY CLAIM OR CAUSE OF ACTION BASED
UPON OR ARISING OUT OF ANY OF THE LOAN DOCUMENTS OR ANY OF THE TRANSACTIONS
CONTEMPLATED THEREIN, INCLUDING CONTRACT CLAIMS, TORT CLAIMS, BREACH OF DUTY
CLAIMS, AND ALL OTHER COMMON LAW OR STATUTORY CLAIMS.

                  [Remainder of page intentionally left blank.]

                                       35

<Page>

     IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
executed as of the date first above written.

                                       BORROWER:
                                       ACTIVBIOTICS, INC.

                                       By: /s/ Steven C Glman
                                           -------------------------------------
                                       Name: Steven C Glman
                                       Title: President & CEO

                                       LENDER:

                                       HORIZON TECHNOLOGY FUNDING
                                       COMPANY LLC
                                       By: Horizon Technology Finance, LLC, its
                                       sole member

                                       By: /s/ Robert D. Pomeroy, Jr.
                                           -------------------------------------
                                       Name: Robert D. Pomeroy, Jr.
                                       Title: Managing Member

                                       36<Page>

                                                                   Exhibit 10.11

                               ACTIVBIOTICS, INC.

                                RIGHTS AGREEMENT

          This Registration Rights Agreement (this "Agreement") is made and
entered into as of the _____th day of November, 2003 by and between
ActivBiotics, Inc., a Delaware corporation (the "Corporation") and Silicon
Valley Bank, a California chartered bank ("SVB").

                                    RECITALS

          WHEREAS, the Corporation and SVB have entered into a Loan and Security
Agreement of even date herewith (the "Loan Agreement"), pursuant to which the
Bank has agreed to loan to the Corporation up to $1,000,000 (the "Loan"); and

          WHEREAS, in connection with the Loan, the Corporation has delivered to
SVB a Warrant to Purchase Stock of even date herewith (the "Warrant Agreement"),
pursuant to which SVB has the right to purchase up to 30,000 shares of the
Corporation's Series B Convertible Preferred Stock (the "Series B Shares"); and

          WHEREAS, the Corporation and certain investors have entered into a
First Amended and Restated Stockholders' Agreement (the "Stockholders'
Agreement"), a copy of which is attached hereto as Exhibit A; and

          WHEREAS, it is a condition to the consummation of the transactions
contemplated by the Loan Agreement that the Corporation deliver this Agreement
to provide for the registration of the Series B Shares in the event that the
Bank exercises its right to purchase the Series B Shares pursuant to the terms
of the Warrant Agreement.

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

1.   DEFINITIONS.

     Capitalized terms used and not otherwise defined herein shall have the
meanings given them in the Stockholders Agreement.

2.   REGISTRATION RIGHTS.

     2.1. Piggyback Registration. The Series B Shares and any other securities
of the Corporation acquired pursuant to the Warrant Agreement shall be deemed
Restricted Securities, and SVB shall have the same rights as those granted to
the holders of Restricted Securities in Sections 3.5, 3.7, 3.8, 3.9, 3.10 and
3.11 of the Stockholders' Agreement.

     2.2. Other Provisions. SVB agrees to be bound by and shall be entitled to
the rights granted under the provisions of Section 2.5, Section 4 and Section 12
of the Stockholders' Agreement as of SVB were an "Investor" and as if the Series
B Shares held by SVB were Restricted Shares under the Stockholders Agreement,
provided however, that SVB shall not be

<Page>

entitled to the rights granted to holders of Restricted Shares under Section 3.6
of the Stockholders' Agreement.

3.   BRING-ALONG RIGHTS.

     After the exercise of the warrant pursuant to the Warrant Agreement, SVB
agrees that it shall be bound by the provisions of Section 2.14 of the
Stockholders' Agreement with respect to any Series B Shares and any other
securities acquired by SVB pursuant to the Warrant Agreement.

4.   MISCELLANEOUS.

     4.1. Governing Law. This Agreement shall be governed in all respects by the
laws of the Commonwealth of Massachusetts, without giving effect to principles
of conflicts of law.

     4.2. Successors and Assigns. Except as otherwise expressly provided herein,
the terms and conditions of this Agreement shall inure to the benefit of and be
binding upon the respective successors and assignees of the parties; provided,
that written notice of such assignment is provided to the Corporation. Nothing
in this Agreement, express or implied, is intended to confer upon any party
other than the parties hereto or their respective successors and assignees any
rights, remedies, obligations, or liabilities under or by reason of this
Agreement, except as expressly provided in this Agreement.

     4.3. Entire Agreement; Amendment; Waiver. This Agreement constitutes the
full and entire understanding and agreement between the parties with regard to
the subjects hereof Neither this Agreement nor any term hereof may be amended,
waived, discharged or terminated, except by a written instrument signed by the
Corporation and SVB, provided however, that SVB shall be bound by any amendment
to or restatement of the Stockholders' Agreement to the extent that such
amendment is applicable to SVB under the terms of Sections 2 and 3 of this
Agreement and Section 12 of the Stockholders' Agreement.

     4.4. Notices, etc. All notices, demands or other communications to be given
or delivered under or by reason of the provisions of this Agreement shall be in
writing and shall be deemed to have been given when delivered personally to the
recipient, sent to the recipient by reputable overnight courier service (charges
prepaid), or transmitted by facsimile or electronic mail (with request for
immediate confirmation of receipt in a manner customary for communications of
such type and with physical delivery of the communication being made by one of
the other means specified in this Section as promptly as practicable
thereafter). Such notices, demands and other communications shall be addressed
as follows:

          If to the Corporation: ActivBiotics, Inc.
                                 128 Spring Street
                                 Lexington, Massachusetts
                                 Attn: James Warren, Chief Financial Officer
                                 FAX:(781)274-9129

                                        2

<Page>

          with a copy to:        Bingham McCutchen LLP
                                 150 Federal Street
                                 Boston, Massachusetts 02110
                                 Attn: Julio Vegas, Esquire
                                 FAX:(617)951-8536

          If to SVB:             Silicon Valley Bank
                                 One Newton Executive Park, Suite 200
                                 2221 Washington Street
                                 Newton, Massachusetts 02462
                                 Attn: R Bryan Jadot
                                 Fax:(617)969-5973

          with a copy to:        Riemer & Braunstein LLP
                                 Three Center Plaza
                                 Boston, Massachusetts 02108
                                 Attn: David A. Ephraim, Esquire
                                 FAX:(617)880-3456

     4.5. Titles and Subtitles. The titles of the paragraphs and subparagraphs
of this Agreement are for convenience of reference only and are not to be
considered in construing or interpreting this Agreement.

     4.6. Severability. If one or more provisions of this Agreement are held to
be unenforceable under applicable law, such provision shall be limited or
excluded from this Agreement to the minimum extent necessary and the balance of
the Agreement shall be interpreted as if such provision were so limited or
excluded and shall be enforceable in accordance with its terms.

     4.7. Counterparts. This Agreement may be executed in any number of
counterparts, each of which shall be an original, but all of which together
shall constitute one instrument.

          [ADDITIONAL TEXT AND SIGNATURES APPEAR ON THE FOLLOWING PAGE]

                                        3

<Page>

     IN WITNESS WHEREOF, the parties hereto have executed this Rights Agreement
effective as of the day and year first above written.

ACTIVBIOTICS, INC.

By /s/ J. L. Warren
   ----------------------------------
Name: J. L. WARREN
Title: C.E.O.

SILICON VALLEY BANK

By /s/ R. Bryan Jadot
   ----------------------------------
Name: R. BRYAN JADOT
Title: VICE PRESIDENT

                                        4

<Page>

                                    EXHIBIT A

               FIRST AMENDED AND RESTATED STOCKHOLDERS' AGREEMENT

     This FIRST AMENDED AND RESTATED STOCKHOLDERS' AGREEMENT (the "Agreement"),
dated this 30th day of April 2003, is entered into by and among ACTIVBIOTICS,
INC., a Delaware corporation (the "Corporation"), those holders of common stock
of the Corporation listed on SCHEDULE 1 hereto (hereinafter referred to
collectively as the "Original Stockholders"), those holders of Series A
Preferred Stock of the Corporation listed on SCHEDULE 2 hereto (hereinafter
referred to collectively as the "Series A Stockholders") and those purchasers of
the Series B Preferred Stock of the Corporation listed on SCHEDULE 3 hereto
(hereinafter referred to collectively as the "Series B Purchasers" and together
with the Series A Stockholders as the "Investors"). This Agreement amends and
restates and replaces in its entirety that certain Stockholders' Agreement by
and among the Corporation, the Original Stockholders and the Series A
Stockholders dated September 28, 2001.

                                   WITNESSETH:

     WHEREAS, the Corporation and the Series B Purchasers are entering into a
Convertible Preferred Stock Purchase Agreement dated the date hereof (the "Stock
Purchase Agreement") in connection with which the Corporation has agreed to sell
shares of its Series B Convertible Preferred Stock, par value $0.01 per share,
and the Corporation desires to grant to the Series B Purchasers certain
registration and other rights with respect to such shares; and

     WHEREAS, as a condition to the Series B Purchasers entering into the Stock
Purchase Agreement, the Original Stockholders have agreed to certain
restrictions on their rights to dispose of their shares of Common Stock, par
value $.01 per share, of the Corporation contained in this Agreement;

     NOW, THEREFORE, in consideration of the foregoing and of the respective
covenants and undertakings of the Corporation and the Series B Purchasers
hereunder and under the Stock Purchase Agreement, the parties hereto do hereby
agree as follows:

     SECTION 1. Definitions. As used herein, the following terms shall have the
following respective meanings:

     Board or Board of Directors shall mean the Board of Directors of the
Corporation.

     Budget shall have the meaning set forth in Section 2.8 hereof.

     Certificate shall mean the Third Amended and Restated Certificate of
Incorporation of the Corporation.

     Commission shall mean the U.S. Securities and Exchange Commission.

     Common Stock shall mean the Common Stock, par value $0.01 per share, of the
Corporation.

<Page>

     Environmental Laws shall mean all applicable federal, state and local laws,
ordinances, rules and regulations that regulate, fix liability for, or otherwise
relate to, the handling, use (including use in industrial processes, in
construction, as building materials, or otherwise), storage and disposal of
hazardous and toxic wastes and substances, and to the discharge, leakage,
presence, migration, threatened release or release (whether by disposal, a
discharge into any water source or system or into the air, or otherwise) of any
pollutant or effluent. Without limiting the preceding sentence, the term
"Environmental Laws" shall specifically include the following federal and state
laws, as amended:

                                     FEDERAL

          Comprehensive Environmental Response, Compensation and Liability Act
          of 1980, 42 U.S.C. 9601 et. seq.;

          Resource Conservation and Recovery Act of 1976, 42 U.S.C, 6901 et.
          seq.;

          Federal Water Pollution Control Act, 33 U.S.C. 1251 et. seq.; and

          Clean Air Act, 42 U.S.C. 7401 et. seq.

                                      STATE
                      MASSACHUSETTS ENVIRONMENTAL STATUTES

          Massachusetts Clean Waters Act, MassGen. L. Ch. 21, Section 26, et.
          seq., and regulations thereto;

          Massachusetts Solid Waste Disposal Laws, Mass. Gen. L, Ch. 16, Section
          18, et. seq., and Ch. 111, Section 105A, and regulations thereto;

          Massachusetts Oil and Hazardous Materials Release Prevention and
          Response Act, Mass. Gen. L., Ch. 21E, Section 1, et. seq., and
          regulations thereto;

          Massachusetts Solid Waste Facilities Law, Mass. Gen. L. Ch. 21H,
          Section 1, et. seq., and regulations thereto;

          Massachusetts Toxic Use Reduction Act, Mass. Gen. L, Ch. 21I, Section
          1, et. seq., and regulations thereto;

          Massachusetts Litter Control Laws, Mass. Gen. L. Ch. 111, Section
          150A, et. seq., and regulations thereto;

          Massachusetts Wetlands Protection Laws, Mass, Gen. L. Ch. 130,
          Section 105, et. seq., and regulations thereto;

          Massachusetts Environmental Air Pollution Control Law, Mass Gen, L.
          Ch. 101, Section 2B, et. seq., and regulations thereto;

                                        2

<Page>

          Massachusetts Environmental Policy Act, Mass Gen. L 30, Section 61,
          et. seq., and regulations thereto; and

          Massachusetts Hazardous Waste Laws, Mass Gen L. Ch. 21C, Section 1,
          et. seq., and regulations thereto

     Equity Percentage shall mean, as to any Investor, that percentage figure
which expresses the ratio that (a) the number of shares of issued and
outstanding Common Stock then owned by such Investor bears to (b) the aggregate
number of shares of issued and outstanding Common Stock then owned by all
Investors. For purposes solely of the computation set forth in clauses (a) and
(b) above and the right of oversubscription, all issued and outstanding
securities held by the Investors that are convertible into or exercisable or
exchangeable for shares of Common Stock (including any issued and outstanding
shares of Preferred Stock) or for any such convertible, exercisable or
exchangeable securities, shall be treated as having been so converted, exercised
or exchanged for such Common Stock or for such convertible, exercisable or
exchangeable securities (which shall be treated as having been further
converted, exercised or exchanged for such Common Stock) all at the rate(s) or
price(s) at which such securities are convertible, exercisable or exchangeable
(and, as applicable, further convertible, exercisable or exchangeable) for
shares of Common Stock in effect at the time in question (which, for purposes of
Section 2.3 of this Agreement, shall be at the time of delivery by the
Corporation of the Offer Notice contemplated by Section 2.3(b)), whether or not
such securities are at such time immediately convertible, exercisable or
exchangeable or, as applicable, further convertible, exercisable or
exchangeable.

     Exchange Act shall mean the Securities Exchange Act of 1934, as amended.

     Exchange Act Registration Statement shall have the meaning set forth in
Section 2.5 hereof.

     Excess Securities shall have the meaning set forth in Section 2.3(d)
hereof.

     Excess Securities Notice shall have the meaning set forth in Section 2.3(d)
hereof.

     Excess Securities Period shall have the meaning set forth in Section 2.3(d)
hereof.

     Excluded Forms shall have the meaning given such term in Section 3.5
hereof.

     Excluded Securities shall have the meaning herein as the term "Excluded
Stock" is defined to have in Article III, Section A.7(d)(ii) of the Certificate.

     Group shall mean: (i) as to an Investor that is a corporation: any and all
of the venture capital limited partnerships or corporations now existing or
hereafter formed that are affiliated with or under common control with one or
more of the controlling stockholders of such Investor and any predecessor or
successor thereto, (ii) in the case of HCV VI, the HCV Group, (iii) in the case
of MDS, the MDS Group and (iii) as to any Investor, any other Investor.

     Hazardous Materials shall include without limitation, any flammable
explosives, petroleum products, petroleum byproducts, radioactive materials,
hazardous wastes, hazardous substances, toxic substances or other similar
materials regulated by Environmental Laws.

                                        3

<Page>

     HCV Director shall have the meaning set forth in Section 5.1 (b) hereof.

     HCV Group shall mean, (i) HCV VI, (ii) any venture capital limited
partnership now existing or hereafter formed which is affiliated with or under
common control with one or more general partners of any general partner of HCV
VI (an "HCV Fund"); (iii) any limited partners or affiliates of HCV VI or any
other HCV Fund; and (iv) any successors or assigns of any of the foregoing.

     HCV VI shall mean HealthCare Ventures VI, L.P., a Delaware limited
partnership, including any successor thereto or any assignee of the interest, in
whole or in part, of HCV IV under this Agreement.

     Investors shall have the meaning (severally, but not jointly) set forth in
the preamble hereto.

     MDS shall mean MDS Capital Corp.

     MDS Group shall mean (i) MDS, (ii) any corporation, trust, partnership,
limited liability corporation, partnership or other form of business entity
which is an investment fund to which MDS or any of its affiliates provides
investment management and/or advisory services (which for greater certainty
currently includes, among others, MDS Life Sciences Technology Fund II NC
Limited Partnership, MDS Life Sciences Technology Fund II Quebec Limited
Partnership, MLII Co-Investment Fund NC Limited Partnership and SC Biotechnology
Development Fund LP (an "MDS Fund"); (iii) any limited partners or affiliates of
MDS or any MDS Fund; (iv) any venture capital limited partnership now existing
or hereafter formed which is affiliated with or under common control with one or
more general partners of any general partner of MDS and (iv) any successors or
assigns of any of the foregoing.

     Notice of Acceptance shall have the meaning set forth in Section 2.3(c)
hereof.

     Offer shall have the meaning set forth in Section 2.3(b) hereof.

     Offered Securities shall mean (i) any shares of Common Stock, Preferred
Stock or any other equity security of the Corporation, (ii) any debt security or
capitalized lease with any equity feature with respect to the Corporation, or
(iii) any option, warrant or other right to subscribe for, purchase or otherwise
acquire any such equity security, debt security or capitalized lease but shall
not include the Excluded Securities, securities issued and outstanding as of the
date of this Agreement and the Series B Preferred Stock to be issued pursuant to
the Stock Purchase Agreement.

     Option Shares shall have the meaning set forth in Section 5.2(a)(iii) of
the Stock Purchase Agreement.

     Other Shares shall have the meaning set forth in Section 3.5(e) hereof.

     Preferred Shares shall mean the Series A Preferred Shares and the Series B
Preferred Shares.

                                        4

<Page>

     Preferred Stock shall mean, collectively, the Series A Preferred Stock, par
value $0.01 per share, of the Corporation, and the Series B Preferred Stock, par
value $0.01 per share, of the Corporation.

     Preferred Stockholders shall mean, collectively, all holders of shares of
Preferred Stock of the Corporation.

     Property shall include, without limitation, land, buildings and laboratory
facilities owned or leased by the Corporation or as to which the Corporation now
has any duties, responsibilities (for clean-up, remedy or otherwise) or
liabilities under any Environmental Laws, or as to which the Corporation or any
subsidiary of the Corporation may have such duties, responsibilities or
liabilities because of past acts or omissions of the Corporation or any such
subsidiary or their predecessors, or because the Corporation or any such
subsidiary or their predecessors in the past was such an owner or operator of,
or bore some other relationship with, such land, buildings and/or laboratory
facilities.

     Qualified Public Offering shall have the meaning set forth in Section 2.17
hereof.

     Refused Securities shall have the meaning set forth in Section 2.3(f)
hereof.

     Restricted Securities shall mean any of the Preferred Shares and the Common
Stock issued or issuable upon the conversion of the Preferred Shares, all shares
of Common Stock issued or issuable in respect thereof by way of stock splits,
stock dividends, stock combinations, recapitalizations or like occurrences, and
any other shares of Common Stock or other securities of the Corporation which
may be issued hereafter to any of the Investors or any member of their Group
which are convertible into or exercisable for shares of Common Stock (including,
without limitation, other classes or series of Convertible Preferred Stock,
warrants, options or other rights to purchase Common Stock or convertible
debentures or other convertible debt securities) and the Common Stock issued or
issuable upon such conversion or exercise of such other securities, which have
not been sold (a) pursuant to an effective registration statement filed pursuant
to the Securities Act, or (b) pursuant to Rule 144 or Rule 144A promulgated by
the Commission under the Securities Act.

     Restricted Shares shall mean the shares of Common Stock issued or issuable
upon the conversion or exchange of the Restricted Securities or otherwise
constituting a portion of the Restricted Securities.

     Securities Act shall mean the Securities Act of 1933, as amended.

     Series A Directors shall mean the two members of the Board of Directors
designated by HCV VI pursuant to Section 5 hereof.

     Series A Preferred Shares shall mean issued and outstanding shares of the
Series A Preferred Stock.

     Series A Preferred Stock shall mean Series A Convertible Preferred Stock,
par value $01 per share, of the Corporation.

                                        5

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     Series B Director shall mean the member of the Board of Directors
designated by the members of the MDS Group then holding capital stock of the
Corporation pursuant to Section 5 hereof.

     Series B Preferred Shares shall mean shares of Series B Preferred Stock
issued or issuable pursuant to the Stock Purchase Agreement.

     Series B Preferred Stock shall mean Series B Convertible Preferred Stock,
par value $01 per share, of the Corporation.

     Stock Purchase Agreement shall mean the Convertible Preferred Stock
Purchase Agreement, dated as of the date hereof, by and among the Corporation
and the Series B Purchasers.

     Stockholders shall mean all holders of capital stock of the Corporation.

     Target Month shall have the meaning set forth in Section 2.7(a) hereof.

     20-Day Period shall have the meaning set forth in Section 2.3(b) hereof.

     Transfer shall mean any disposition of any Restricted Securities or of any
interest therein which would constitute a sale thereof within the meaning of the
Securities Act.

     SECTION 2. Certain Covenants of the Corporation.

     2.1. Meetings of the Board of Directors. The Corporation shall call, and
use its best efforts to have, regular meetings of the Board not less often than
quarterly. The Corporation shall pay all reasonable and appropriately documented
travel expenses and other out-of-pocket expenses incurred by directors who are
not employed by the Corporation in connection with attendance at meetings to
transact the business of the Corporation or attendance at meetings of the Board
or any committee thereof.

     2.2. Reservation of Shares of Common Stock and Preferred Stock, Etc. The
Corporation shall at all times have authorized and reserved out of its
authorized but unissued shares of Common Stock, a sufficient number of shares of
Common Stock to provide for the conversion of the Preferred Shares. Neither the
issuance of the Series B Preferred Shares nor the shares of Common Stock
issuable upon the conversion of the Preferred Shares shall be subject to a
preemptive right of any other Stockholder,

     2 3. Right of First Refusal

          (a) The Corporation shall not issue, sell or exchange, agree to issue,
sell or exchange, or reserve or set aside for issuance, sale or exchange, any
Offered Securities unless in each case the Corporation shall have first offered
to sell to the Investors all of such Offered Securities on the terms set forth
herein (the "Offer"). Each Investor shall be entitled to purchase up to its
Equity Percentage of the Offered Securities. In addition, each Investor shall
have a right of oversubscription ("Right of Oversubscription") such that if any
Investor fails to accept the Offer as to its Equity Percentage of the Offered
Securities, the remaining Investors shall, among

                                        6

<Page>

them, have the right to purchase up to the balance of the Offered Securities not
so purchased. Such Right of Oversubscription may be exercised by an Investor (an
"Oversubscribing Investor") by accepting the Offer as to more than its Equity
Percentage of the Offered Securities. If as a result thereof, such
oversubscriptions exceed the total number of the Offered Securities available in
respect of such oversubscription privilege, the Oversubscribing Investors shall
be cut back with respect to their oversubscriptions on a pro rata basis. Each
Investor may delegate or assign its rights and obligations with respect to such
Offer to one or more members of its Group, which members shall thereafter be
deemed to be "Investors" for the purpose of applying this Section 2.3 to such
Offer.

          (b) The Corporation shall deliver to each Investor written notice of
the Offer, specifying the price and terms and conditions of the Offer (the
"Offer Notice"). The Offer by its terms shall remain open and irrevocable for a
period of 20 days from the date of delivery of the Offer Notice to each Investor
(the "20-Day Period"), subject to extension to include the Excess Securities
Period (as such term is hereinafter defined).

          (c) Each Investor shall evidence its intention to accept the Offer by
delivering a written notice signed by the Investor setting forth the number of
shares that the Investor elects to purchase (the "Notice of Acceptance"). The
Notice of Acceptance must be delivered to the Corporation not later than the
last day of the 20-Day Period.

          (d) If any Investor fails to exercise its rights hereunder to purchase
all or any portion of its Equity Percentage of the Offered Securities, the
Corporation shall so notify the other Investors in a written notice (the "Excess
Securities Notice"). The Excess Securities Notice shall be given by the
Corporation promptly after it learns of any Investor's intention not to purchase
all or any portion of its Equity Percentage of the Offered Securities, but in no
event later than ten (10) days after the expiration of the 20 Day Period. The
Investors who or which have agreed to purchase their Equity Percentage of the
Offered Securities shall have the right to purchase the portion not purchased by
such other Investor(s) (the "Excess Securities"), on a pro rata basis, by giving
notice within ten (10) days after receipt of the Excess Securities Notice from
the Corporation. The twenty (20) day period during which (i) the Corporation
must give the Excess Securities Notice to the other Investors, and (ii) each of
the other Investors must give the Corporation notice of its intention to
purchase all or any portion of its pro rata share of its Excess Securities is
hereinafter referred to as the "Excess Securities Period."

          (e) If the Investors tender their Notices of Acceptance prior to the
end of the 20-Day Period indicating their intention to purchase all of the
Offered Securities, or if prior to the termination of the Excess Securities
Period, the Investors tender Excess Securities Notices to purchase all of the
Excess Securities, the Corporation shall proceed to promptly schedule a closing
of the sale of all such Offered Securities at which closing each Investor shall
(i) purchase from the Corporation that portion of the Offered Securities
(including the Excess Securities) for which it tendered a Notice of Acceptance
and an Excess Securities Notice, if applicable, upon the terms specified in the
Offer Notice, and (ii) execute and deliver an agreement further restricting
transfer of such Offered Securities substantially as set forth in Section 3.1,
3.2 and 3.3 of this Agreement. In addition, with respect to the Offered
Securities being purchased by the Investors at such closing, the Corporation
shall provide each such Investor with the rights and benefits set forth in this
Agreement. The obligation of the Investors to purchase such Offered

                                        7

<Page>

Securities at such closing is further conditioned upon the preparation of a
purchase agreement embodying the terms of the Offer, which shall be reasonably
satisfactory in form and substance to such Investor and the Investor's counsel

          (f) In the event the Corporation does not sell all of the Offered
Securities pursuant to Section 2.3(e), the Corporation shall have ninety (90)
days from the expiration of 20 Day Period or, if applicable, the Excess
Securities Period to sell the portion of the Offered Securities (including the
Excess Securities) refused by the Investors (the "Refused Securities") to any
other person or persons, but only upon terms and conditions which are in all
material respects (including, without limitation, price and interest rate) no
more favorable to such other person or persons, and no less favorable to the
Corporation, than those set forth in the Offer Notice Upon and subject to the
closing of the sale of all of the Refused Securities (which shall include full
payment to the Corporation), each Investor shall (i) purchase from the
Corporation those Offered Securities (including the Excess Securities) for which
it tendered a Notice of Acceptance or an Excess Securities Notice, as
applicable, upon the terms specified in the Offer Notice, and (ii) execute and
deliver an agreement restricting transfer of such Offered Securities (including
the Excess Securities) substantially as set forth in Sections 3.1, 3.2 and 3.3
of this Agreement. In addition, with respect to the Offered Securities being
purchased by the Investors, the Corporation shall provide each such Investor
with the rights and benefits set forth in this Agreement. The Corporation
agrees, as a condition precedent to accepting payment for and making delivery of
any Refused Securities to any person other than an Investor, to have each and
every such person execute and deliver a Stock Restriction Agreement in the
capacity of a "Principal Stockholder" as defined therein, substantially in the
form attached hereto as Exhibit A, or as may be modified or amended from time to
time with the prior approval of the holders of a majority of the combined voting
power of the Preferred Shares then outstanding, calculated in accordance with
Section A.6(a) of Article III of the Certificate (but including in such
calculation, any outstanding Restricted Shares held by such holders), to the
extent such purchaser has not already executed such Agreement. The obligation of
the Investor to purchase such Offered Securities (including the Excess
Securities) is further conditioned upon the preparation of a purchase agreement
embodying the terms of the Offer; which shall be reasonably satisfactory in form
and substance to such Investor and the Investor's counsel.

          (g) In each case, any Offered Securities not purchased either by the
Investors or by any other person in accordance with this Section 2.3 may not be
sold or otherwise disposed of until they are again offered to the Investors
under the procedures specified in Paragraphs (a), (b), (c), (d) (e) and (f)
hereof.

          (h) Each Investor may, by prior written consent, waive its rights
under this Section 2.3. Such a waiver shall be deemed a limited waiver and shall
only apply to the extent specifically set forth in the written consent of such
Investor.

     2.4. Negative Covenants.

          (a) Supermajority Approvals. The Corporation shall not, directly or
indirectly, take any of the actions specified in Article III, Section
A.6(c)(iii) of the Certificate without (x) the prior written consent or vote of
the holders of at least a majority of the then outstanding shares of the Series
A Preferred Stock, voting or consenting as a separate class, and (y) the prior

                                        8

<Page>

written consent or vote of the holders of at least two-thirds of the then
outstanding shares of the Series B Preferred Stock, voting or consenting as a
separate class.

          (b) Majority Approvals. The Corporation shall not, directly or
indirectly, take any of the actions specified in Article III, Section A.6(c)(iv)
of the Certificate without the prior written consent or vote of the holders of
at least a majority of the then outstanding shares of the Series A Preferred
Stock and the then outstanding shares of the Series B Preferred Stock, voting or
consenting together as a single class.

          (c) Registration Rights. The Corporation shall not hereafter grant to
any persons any rights to register or qualify stock of the Corporation under
federal or state securities laws, without the prior written consent or vote of
the holders of at least a majority of the then outstanding Restricted
Securities.

          (d) Board Approvals. In addition to and not in limitation of the
provisions of Section 2.4(a) and (b) above, the Corporation shall not, directly
or indirectly, take any of the actions specified in Article V, Section A.2 of
the Certificate without the prior written consent or vote of the Board of
Directors.

     2.5. Filing of Reports Under the Exchange Act

          (a) The Corporation shall give prompt notice to the holders of
Preferred Stock of (i) the filing of any registration statement (an "Exchange
Act Registration Statement") pursuant to the Exchange Act, relating to any class
of equity securities of the Corporation, (ii) the effectiveness of such Exchange
Act Registration Statement, and (iii) the number of shares of such class of
equity securities outstanding, as reported in such Exchange Act Registration
Statement, in older to enable the Investors to comply with any reporting
requirements under the Exchange Act or the Securities Act. Upon the written
request of a majority in interest of the holders of the Series A Preferred
Shares or a majority in interest of the Series B Preferred Shares, the
Corporation shall, at any time after the Corporation has registered any shares
of Common Stock under the Exchange Act, file an Exchange Act Registration
Statement relating to any class of equity securities of the Corporation then
held by the holders of the Series A Preferred Shares or the Series B Preferred
Shares, as applicable, or issuable upon conversion or exercise of any class of
debt or equity securities or warrants or options of the Corporation then held by
the applicable Investors, whether or not the class of equity securities with
respect to which such request is made shall be held by the number of persons
which would requite the filing of a registration statement under Section
12(g)(l) of the Exchange Act.

          (b) If the Corporation shall have filed an Exchange Act Registration
Statement or a registration statement (including an offering circular under
Regulation A promulgated under the Securities Act) pursuant to the requirements
of the Securities Act, which shall have become effective (and in any event, at
all times following the initial public offering of any of the securities of the
Corporation), then the Corporation shall comply with all of the reporting
requirements of the Exchange Act (whether or not it shall be required to do so)
and shall comply with all other public information reporting requirements of the
Commission as a condition to the availability of an exemption from the
Securities Act for the sale of any of the Restricted Shares by any holder of
Restricted Securities (including any such exemption pursuant to Rule 144 or

                                        9

<Page>

Rule 144A thereof, as amended from time to time, or any successor rule thereto
or otherwise) The Corporation shall cooperate with each holder of Restricted
Securities in supplying such information as may be necessary for such holder of
Restricted Securities to complete and file any information reporting forms
presently or hereafter required by the Commission as a condition to the
availability of an exemption from the Securities Act (under Rule 144 or Rule
144A thereunder or otherwise) for the sale of any of the Restricted Shares by
any holder of Restricted Securities.

     2.6 Access to Records. The Corporation shall afford to each of the
Investors and such Investor's employees, counsel and other authorized
representatives, free and full access, at all reasonable times and for
reasonable periods of time, to all of the books, records and properties of the
Corporation and to all officers and employees of the Corporation.

     2.7 Financial Reports. Until such time that the Corporation has a class of
its equity securities registered under the Exchange Act and is required to file
reports thereunder pursuant to Sections 13 or 15(d) of the Exchange Act, except
with respect to the obligation set forth in Section 2.7(e)(i) hereunder which
shall survive such time, the Corporation shall furnish each of the Investors
with the financial information described below:

          (a) Within 20 days after the last day of each calendar month (or such
other calendar period as is approved by the Board), financial statements,
including a balance sheet as of the last date of such month, a statement of
income (or monthly operating expenses) for such month, together with a
cumulative statement of income from the first day of the fiscal year to the last
day of such month, which statements shall be prepared from the books and records
of the Corporation, a cash flow analysis, together with cumulative cash flow
analyses from the first day of the fiscal year to the last day of such month,
and a comparison between the actual monthly operating expenses and the projected
figures for such month and the comparable figures for the prior year, subject to
the provisions of Section 2.9 hereof.

          (b) The Corporation shall deliver to each of the Investors, within 45
days after the end of each fiscal quarter, unaudited financial statements for
such fiscal quarter, certified by the Chief Financial Office or the Treasurer of
the Corporation as presenting fairly the financial condition and results of
operations of the Corporation and as having been prepared on a basis consistent
with the accounting principles reflected in the Corporation's annual audited
financial statements (subject to the absence of footnotes), accompanied by a
report, signed by the Chief Financial Officer or the Treasurer of the
Corporation, summarizing the operating and financial highlights of the
Corporation for such quarter, which report shall include (a) a comparison
between the actual quarterly operating and financial results, the Budget (as
defined in Section 2.8 hereof) and the results of that quarter for the prior
fiscal year of the Corporation, together with an explanation of material
variances from the Budget and such prior year quarter, as the case may be, and
(b) a narrative analysis of operations and trends in the business of the
Corporation during such quarter.

          (c) Within 90 days after the end of each fiscal year of the
Corporation, audited financial statements of the Corporation, which shall
include an income statement and a statement of cash flow for such fiscal year
and a balance sheet as of the last day thereof, each prepared in accordance with
generally accepted accounting principles consistently applied, and accompanied

                                       10

<Page>

by the report of an independent accounting firm of national reputation as shall
have been approved by the Board.

          (d) If for any period the Corporation shall have any subsidiary or
subsidiaries whose accounts are consolidated with those of the Corporation, then
the financial statements delivered for such period pursuant to paragraphs (a),
(b) and (c) of this Section 2.7 shall be the consolidated and consolidating
financial statements of the Corporation for all such consolidated subsidiaries.

          (e) Promptly upon becoming available:

               (i) copies of all financial statements, reports, press releases,
notices, proxy statements and other documents sent by the Corporation to its
Stockholders or released to the public and copies of all regular and periodic
reports, if any, filed by the Corporation with the Commission or any securities
exchange or self-regulatory organization; and

               (ii) any other financial or other information available to
management of the Corporation that any of the Investors shall have reasonably
requested on a timely basis.

     2.8. Budget and Operating Forecast. The Corporation shall prepare and
submit to the Board and each of the Investors an operating plan with monthly and
quarterly breakdowns (the "Budget") for each fiscal year at least 45 days prior
to the beginning of each fiscal year of the Corporation. The Budget shall be
deemed accepted as the Budget for such fiscal year only when it has been
approved by the Board. The Budget shall be reviewed by the Corporation
periodically and all changes therein, and all material deviations therefrom,
shall be reviewed by the Board on at least a quarterly basis.

     2.9. System of Accounting. The Corporation shall maintain, and cause each
of its subsidiaries, when and if any shall exist, to maintain, its books of
accounts, related records and system of accounting in accordance with good
business practices and generally accepted accounting principles, and shall cause
the matters contained therein to be appropriately and accurately reflected in
the financial reports (which shall be prepared in accordance with generally
accepted accounting principles) furnished pursuant to this Agreement.

     2.10. Restriction on Transfer Rights; Confidentiality. The rights granted
to each of the Investors pursuant to Sections 2.6 through 2.8 hereof shall not
be transferred or assigned by any Investor to, and shall not inure to the
benefit of, any successor, transferee or assignee of any Investor, while it is
engaged in any business directly competitive with the Corporation.

     2.11. Confidentiality and Non-Competition Agreements for Key Employees. The
Corporation shall cause each person who is presently an employee of or a
consultant or independent contractor to the Corporation or who becomes an
employee of or a consultant to the Corporation subsequent to the date hereof and
who shall have or be proposed to have access to confidential or proprietary
information of the Corporation to execute a confidentiality and non-competition
agreement in form and substance attached hereto or otherwise approved by the
Board prior to the commencement of such person's employment by the Corporation
in such capacity.

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     2.12. Stock Restriction Agreement for Chief Officers. The Corporation shall
cause Chalom B. Sayada, James L. Warren, and Art Michaelis to execute a First
Amended and Restated Stock Restriction Agreement substantially in the form
attached hereto as Exhibit A and maintain such agreement in full force and
effect.

     2.13. Marketing and Promotional Material. Each of the Investors will have
the right to review and approve, in advance of publication, distribution or
dissemination, any reference to such Investor or any entity affiliated with such
Investor (other than the Corporation), contained in any document, instrument,
report or filing or in any advertising, marketing, promotional and similar
materials.

     2.14. Bring-Along Rights.

          (a) If, by vote or written consent, (i) the Board of Directors and
(ii) the holders of at least a majority of the then outstanding shares of the
Series A Preferred Stock and the then outstanding shares of the Series B
Preferred Stock, voting or consenting together as a single class (the "Approving
Investors"), approve a change of control of the Corporation pursuant to which
any bona fide unaffiliated third party proposes to acquire all or substantially
all of the assets or all or substantially all of the capital stock of the
Corporation, whether by purchase, merger, consolidation, share exchange, sale of
assets, exclusive license or otherwise (an "Approved Sale"), the Approving
Investors shall provide all other Investors who are not Approving Investors and
each Original Stockholder (collectively, the "Remaining Stockholders") at least
ten (10) days advance notice of such Approved Sale, which notice shall include a
reasonably detailed description of the Approved Sale, including the proposed
time and place of closing, the consideration to be received by the Remaining
Stockholders, and any other material terms. The Remaining Stockholders shall
consent to, vote for and raise no objections to the Approved Sale, and (i) the
Remaining Stockholders shall waive any dissenters rights, appraisal rights or
similar rights, if any, in connection with such merger, consolidation or asset
sale, or (ii) if the Approved Sale is structured as a sale of the stock of the
Corporation, the Remaining Stockholders shall agree to sell all of their shares
of Capital Stock on the terms and conditions approved by the Approving
Investors, provided such terms do not provide that the Remaining Stockholders
would receive less than the amount that would be distributed to such Remaining
Stockholders in the event the proceeds of the Approved Sale were distributed in
accordance with the Restated Certificate. The Remaining Stockholders shall take
all reasonably necessary and desirable actions requested by the Approving
Investors in connection with the consummation of the Approved Sale, including
the execution of such agreements and such instruments (collectively, the "Sale
Documents") and other actions reasonably necessary to (i) effectuate the
Approved Sale, including (only in the case that a third party requires both the
Corporation and all of the Approving Investors and the Remaining Stockholders to
individually sign such Sale Documents) making such customary representations,
warranties, indemnities, covenants, conditions, escrow agreements and other
customary agreements relating to such Approved Sale (provided that each
Remaining Stockholder's aggregate liability pursuant to the Sale Documents or
otherwise in connection with the Approved Sale shall be limited to the value of
the consideration received by each such Remaining Stockholder on account of the
Approved Sale) and (ii) effectuate the agreed-upon allocation and distribution
of the aggregate consideration upon the Approved Sale.

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<Page>

          (b) Each of the Remaining Stockholders hereby appoints the Approving
Investor holding the largest number of shares of the Preferred Stock for so long
as the provisions of Section 2.14(a) remain in effect, as such Remaining
Stockholder's attorney and proxy with full power of substitution, to vote, and
otherwise act (by written consent or otherwise) with respect to the capital
stock of the Corporation owned by such Remaining Stockholder, solely on the
matters and in the manner specified in Section 2.14(a).

          (c) THE PROXIES AND POWER OF ATTORNEY GRANTED PURSUANT TO THE ABOVE
PARAGRAPH ARE IRREVOCABLE AND COUPLED WITH AN INTEREST. Each Remaining
Stockholder hereby revokes all other proxies and powers of attorney on the
matters specified in Section 2.14(a) with respect to the shares of capital stock
of the Corporation which such Remaining Stockholder may have heretofore
appointed or granted, and no subsequent proxy or power of attorney shall be
given or written consent executed (and if given or executed, shall not be
effective) by such Remaining Stockholder with respect thereto. All authority
herein conferred or agreed to be conferred shall survive the death or incapacity
of each Remaining Stockholder and any obligation of a Remaining Stockholder
under this Agreement shall be binding upon the heirs, personal representatives
and successors of such Remaining Stockholder.

     2.15. Vesting of Stock. Unless otherwise approved by the Board of Directors
by vote or written consent in which the Series A Directors and the Series B
Director concur, all stock, stock options and other stock equivalents issued
after the date of this Agreement to employees, directors, consultants and other
service providers pursuant to a stock purchase or option plan or other employee
stock incentive program or otherwise ("Stock Awards") (i) shall be subject to a
minimum vesting schedule of at least four years, pursuant to which 25% of the
shares subject to any such Stock Award will vest no sooner than one year after
the date of the issuance or grant of such Stock Award, and 75% of the shares
subject to such Stock Award will vest no more frequently and no sooner than
monthly on a pro rata basis beginning on the first anniversary of the date of
issuance or grant of such Stock Award, (ii) shall provide for termination of
vesting and forfeiture of any unvested portion of such Stock Award upon
cessation of employment and (ii) shall provide that as a condition to issuance
of any shares, the recipient of such shares shall sign a written agreement in a
form approved by the Board providing the Corporation with a right of first
refusal on any transfer of such shares with certain exceptions for transfers to
immediate family members and to trusts of which the holder is the trustee.

     2.16. Environmental Matters. All development, construction and operation of
property purchased, leased or otherwise acquired by the Corporation shall, in
all material respects, comply with, and shall be lawful, permitted and
conforming uses in all material respects under, all applicable building, fire,
safety, subdivision, zoning, sewer, environmental, securities, health, insurance
and other laws, ordinances, rules, regulations and plan approval conditions of
any governmental or public body or authority. The Corporation shall promptly
advise the Investors in writing of any pending or threatened claim, demand or
action by any governmental authority or third party relating to any Hazardous
Materials affecting the Property of which it has knowledge. The Corporation
shall not discharge, place, release, spill or dispose of any Hazardous Materials
or any other pollutants or effluents upon the Property or elsewhere (including,
but not limited to, underground injection of such substances), and the
Corporation shall not discharge into the air any emission which would require a
permit under the Clean Air

                                       13

<Page>

Act or its state counterparts or any other Environmental Laws, except in
compliance with the Environmental Laws. The Stockholders of the Corporation
shall have no control over, or authority with respect to, the waste disposal
operations of the Corporation. The Corporation hereby indemnifies, defends and
holds harmless the Investors from and against any and all manner of actions,
causes of action, suits, debts, accounts, controversies, judgments, claims,
demands, losses or liabilities of any nature (including reasonable attorneys'
fees) directly or indirectly arising out of or attributable to (a) any
misrepresentation or breach of the representations and covenants set forth in
Section 5.18 of the Stock Purchase Agreement, or (b) the use, generation,
storage, release, threatened release, discharge, disposal or presence of
Hazardous Materials on, under or about the Property by any person during the
period that the Corporation was the legal or equitable owner of the Property or
which occurred prior to such time and was otherwise actually known by, or should
have been known by, the Corporation. The obligation of the Corporation to
indemnify the Investors shall specifically cover and include, without
limitation, all fines and penalties imposed by federal, state or local
authorities, costs of removing or neutralizing the Hazardous Materials, injury
to the property adjoining the Property, injury to persons living or working on
or about the Property or adjoining or otherwise affecting property, and all
other indirect or consequential damages incurred by the Investors.

     2.17. Duration of Section. Section 2.3 and Sections 2.6-2.14 and the rights
and obligations of the parties thereunder shall automatically terminate on the
consummation of a firm commitment underwritten public offering of Common Stock
registered under the Securities Act pursuant to which (X) Common Stock is
offered to the public at a price of at least $5.00 per share of Common Stock
(subject to adjustment for stock splits, stock dividends, stock combinations,
recapitalizations and like occurrences) and (Y) the net proceeds to the
Corporation are at least $40 million (a "Qualified Public Offering").

     SECTION 3. Transfer of Securities.

     3.1. Restriction on Transfer. The Restricted Securities shall not be
transferable, except upon the conditions specified in this Section 3, which
conditions are intended solely to ensure compliance with the provisions of the
Securities Act in respect of the Transfer thereof.

     3.2. Restrictive Legend. Each certificate evidencing any Restricted
Securities and each certificate evidencing any such securities issued to
subsequent transferees of any Restricted Securities shall (unless otherwise
permitted by the provisions of Section 3.3 or 3.10 hereof) be stamped or
otherwise imprinted with a legend in substantially the following form;

          THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE BEEN ACQUIRED FOR
          INVESTMENT AND HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
          1933, AS AMENDED, OR ANY STATE SECURITIES LAW. THE SECURITIES MAY
          NOT BE PLEDGED, HYPOTHECATED, SOLD OR TRANSFERRED IN THE ABSENCE OF AN
          EFFECTIVE REGISTRATION STATEMENT FOR THE SECURITIES UNDER THE
          SECURITIES ACT OF 1933 OR ANY APPLICABLE STATE SECURITIES LAW OR AN
          EXEMPTION THEREFROM

                                       14

<Page>

          UNDER SUCH ACT OR LAW. ADDITIONALLY, THE TRANSFER OF THESE SECURITIES
          IS SUBJECT TO THE CONDITIONS SPECIFIED IN THE FIRST AMENDED AND
          RESTATED STOCKHOLDERS' AGREEMENT DATED APRIL 30, 2003 AMONG
          ACTIVBIOTICS, INC. AND CERTAIN OTHER SIGNATORIES THERETO, AND NO
          TRANSFER OF SUCH SECURITIES SHALL BE VALID OR EFFECTIVE UNTIL SUCH
          CONDITIONS HAVE BEEN FULFILLED. COPIES OF SUCH AGREEMENT MAY BE
          OBTAINED AT NO COST BY WRITTEN REQUEST MADE BY THE HOLDER OF RECORD OF
          THIS CERTIFICATE TO THE SECRETARY OF ACTIVBIOTICS, INC.

     3.3. Notice of Transfer. By acceptance of any Restricted Securities, the
holder thereof agrees to give prior written notice to the Corporation of such
holder's intention to effect any Transfer and to comply in all other respects
with the provisions of this Section 3.3. Each such notice shall describe the
manner and circumstances of the proposed Transfer and shall be accompanied by:
(a) the written opinion of counsel for the holder of such Restricted Securities,
or, at such holder's option, a representation letter of such holder, addressed
to the Corporation (which opinion and counsel, or representation letter, as the
case may be, shall be reasonably acceptable to the Corporation), as to whether,
in the case of a written opinion, in the opinion of such counsel, such proposed
Transfer involves a transaction requiring registration of such Restricted
Securities under the Securities Act and applicable state securities laws or an
exemption thereunder is available, or, in the case of a representation letter,
such letter sets forth a factual basis for concluding that such proposed
transfer involves a transaction requiring registration of such Restricted
Securities under the Securities Act and applicable State Securities laws or an
exemption thereunder is available, or (b) if such registration is required and
if the provisions of Section 3.4 hereof are applicable, a written request
addressed to the Corporation by the holder of such Restricted Securities,
describing in detail the proposed method of disposition and requesting the
Corporation to effect the registration of such Restricted Securities pursuant to
the terms and provisions of Section 3.4 hereof; provided, however, that (y) in
the case of a Transfer by a holder to a member of such holder's Group, no such
opinion of counsel or representation letter of the holder shall be necessary,
provided that the transferee agrees in writing to be subject to Sections 3.1,
3.2, 3.3 and 3.10 hereof to the same extent as if such transferee were
originally a signatory to this Agreement, and (z) in the case of any holder of
Restricted Securities that is a partnership, no such opinion of counsel or
representation letter of the holder shall be necessary for a Transfer by such
holder to a partner of such holder, or a retired partner of such holder who
retires after the date hereof, or the estate of any such partner or retired
partner if, with respect to such Transfer by a partnership, (i) such Transfer is
made in accordance with the partnership agreement of such partnership, and (ii)
the transferee agrees in writing to be subject to the terms of Sections 3.1,
3.2, 3.3 and 3.10 hereof to the same extent as if such transferee were
originally a signatory to this Agreement. If in such opinion of counsel or as
reasonably concluded from the facts set forth in the representation letter of
the holder (which opinion and counsel, or representation letter, as the case may
be, shall be reasonably acceptable to the Corporation), the proposed Transfer
may be effected without registration under the Securities Act and any applicable
state securities laws or "blue sky" laws, then the holder of Restricted
Securities shall thereupon be entitled to effect such Transfer in accordance
with the

                                       15

<Page>

terms of the notice delivered by it to the Corporation. Each certificate or
other instrument evidencing the securities issued upon such Transfer (and each
certificate or other) instrument evidencing any such securities not
Transferred) shall bear the legend set forth in Section 3.2 hereof unless: (a)
in such opinion of such counsel or as can be concluded from the representation
letter of such holder (which opinion and counsel or representation letter shall
be reasonably acceptable to the Corporation) the registration of future
Transfers is not required by the applicable provisions of the Securities Act and
state securities laws, or (b) the Corporation shall have waived the requirement
of such legend; provided, however, that such legend shall not be required on any
certificate or other instrument evidencing the securities issued upon such
Transfer in the event such Transfer shall be made in compliance with the
requirements of Rule 144 (as amended from time to time or any similar or
successor rule) promulgated under the Securities Act. The holder of Restricted
Securities shall not effect any Transfer until such opinion of counsel or
representation letter of such holder has been given to and accepted by the
Corporation (unless waived by the Corporation) or until registration of the
Restricted Securities involved in the above-mentioned request has become
effective under the Securities Act. In the event that an opinion of counsel is
required by the registrar or transfer agent of the Corporation to effect a
transfer of Restricted Securities in the future, the Corporation shall seek and
obtain such opinion from its counsel, and the holder of such Restricted
Securities shall provide such reasonable assistance as is requested by the
Corporation (other than the furnishing of an opinion of counsel) to satisfy the
requirements of the registrar or transfer agent to effectuate such transfer.

     3.4. Required Registration. At any time following the date that is the
earlier of (i) the fifth anniversary of the Stage IA Closing Date (as defined
under the Stock Purchase Agreement) and (ii) six months following the closing
of an initial public offering, if the Corporation shall be requested (i) by
holders of 15% or more of the outstanding Restricted Securities (on an
as-converted basis) to effect the registration under the Securities Act of
Restricted Shares, or (ii) after the first registration pursuant to this Section
3.4, by one or more of the holders of Restricted Securities, to effect the
registration under the Securities Act of Restricted Shares, then the Corporation
shall promptly give written notice of such proposed registration to all holders
of Restricted Securities, and thereupon the Corporation shall promptly use its
best efforts to effect the registration under the Securities Act of the
Restricted Shares that the Corporation has been requested to register for
disposition as described in the request of such holders of Restricted Securities
and in any response received from any of the holders of Restricted Securities
within 30 days after the giving of the written notice by the Corporation;
provided, however, that the Corporation shall not be obligated to effect any
registration under the Securities Act except in accordance with the following
provisions and Section 3.6:

          (a) Subject to Section 3.6, the Corporation shall not be obligated to
file and cause to become effective more than an aggregate of four (4)
registration statements (a maximum of two (2) of which may be initiated by the
Series B Stockholders and two (2) of which may be initiated by the Series A
Stockholders) in which Restricted Shares are registered under the Securities Act
pursuant to this Section 3.4, if all of the Restricted Shares offered pursuant
to such registration statements are sold thereunder upon the price and terms
offered

          (b) Notwithstanding the foregoing, the Corporation may include in each
such registration requested pursuant to this Section 3.4 any authorized but
unissued shares of

                                       16

<Page>

Common Stock (or authorized treasury shares) for sale by the Corporation or
any issued and outstanding shares of Common Stock for sale by others; provided,
however, that, if the number of shares of Common Stock so included pursuant to
this clause (b) exceeds the number of Restricted Shares requested by the holders
of Restricted Securities requesting such registration, then such registration
shall be deemed to be a registration in accordance with and pursuant to Section
3.5; and provided further, however, that in the event such registration is
pursuant to this Section 3.4, the inclusion of such previously authorized but
unissued shares by the Corporation or issued and outstanding shares of Common
Stock by others in such registration does not adversely affect, in the sole
opinion of the holders of Restricted Securities requesting such registration,
the ability of the holders of Restricted Securities requesting such registration
to market the entire number of Restricted Shares requested by them.

     3.5 Piggyback Registration.

          (a) Each time that the Corporation proposes for any reason to register
any of its securities under the Securities Act, other than the Corporation's
initial public offering or pursuant to a registration statement on Form S-4 or
Form S-8 or similar or successor forms (collectively, "Excluded Forms"), the
Corporation shall promptly give written notice of such proposed registration to
all holders of Restricted Securities, which shall offer such holders the
right to request inclusion of any Restricted Shares in the proposed
registration.

          (b) Each holder of Restricted Securities shall have 30 days from the
receipt of such notice to deliver to the Corporation a written request
specifying the number of Restricted Shares such holder intends to sell and the
holder's intended method of disposition.

          (c) In the event that the proposed registration by the Corporation is,
in whole or in part, an underwritten public offering of securities of the
Corporation, any request under Section 3.5(b) may specify that the Restricted
Shares be included in the underwriting (i) on the same terms and conditions as
the shares of Common Stock, if any, otherwise being sold through underwriters
under such registration, or (ii) on terms and conditions comparable to those
normally applicable to offerings of common stock in reasonably similar
circumstances in the event that no shares of Common Stock other than Restricted
Shares are being sold through underwriters under such registration.

          (d) Upon receipt of a written request pursuant to Section 3 5(b), the
Corporation shall promptly use its best efforts to cause all such Restricted
Shares to be registered under the Securities Act, to the extent required to
permit sale or disposition as set forth in the written request,

          (e) Notwithstanding the foregoing, if the managing underwriter of any
such proposed registration determines and advises in writing that the inclusion
of all Restricted Shares proposed to be included in the underwritten public
offering, together with any other issued and outstanding shares of Common
Stock proposed to be included therein by holders other than the holders of
Restricted Securities (such other shares hereinafter collectively referred to as
the "Other Shares"), would interfere with the successful marketing of the
Corporation's securities, then the total number of such securities proposed to
be included in such underwritten public offering shall be reduced. If such
proposed registration is in connection with an offering other

                                       17

<Page>

than a Qualified Public Offering, such reduction shall occur (i) first, by the
shares requested to be included in such registration by the holders of Other
Shares, and (ii) second, if necessary, (A) one-half by the securities proposed
to be issued by the Corporation, and (B) one-half by the Restricted Shares
proposed to be included in such registration by the holders thereof, on a pro
rata basis, based upon the number of Restricted Shares sought to be registered
by each such holder, provided however, that in no event shall the number of
Restricted Shares to be included in such offering be reduced to less than 15% of
the total shares to be included therein. The shares of Common Stock that are
excluded from the underwritten public offering pursuant to the preceding
sentence shall be withheld from the market by the holders thereof for a
period, not to exceed 180 days from the closing of such underwritten public
offering, that the managing underwriter reasonably determines as necessary in
order to effect such underwritten public offering.

     3.6 Registrations on Form S-3 At such time as the Corporation shall have
qualified for the use of Form S-3 (or any successor form promulgated under
the Securities Act), each holder of Restricted Securities shall have the right
to request in writing an unlimited number of registrations on Form S-3; provided
that the Corporation shall not be required to file more than two such
Registration Statements on Form S-3 pursuant to this Section 3.6 in any twelve
month period. Each such request by a holder shall: (a) specify the number of
Restricted Shares which the holder intends to sell or dispose of, (b) state the
intended method by which the holder intends to sell or dispose of such
Restricted Shares, and (c) request registration of Restricted Shares (including
those Restricted Shares proposed to be registered by persons other than the
initiating holder) having a proposed aggregate offering price of at least
$1,000,000. Upon receipt of a request pursuant to this Section 3.6, the
Corporation shall use its best efforts to effect such registration or
registrations on Form S-3.

     3.7. Preparation and Filing. If and whenever the Corporation is under an
obligation pursuant to the provisions of this Section 3 to use its best efforts
to effect the registration of any Restricted Shares, the Corporation shall, as
expeditiously as practicable:

          (a) prepare and file with the Commission a registration statement with
respect to such securities and use its best efforts to cause such registration
statement to become and remain effective in accordance with Section 3.7(b)
hereof;

          (b) prepare and file with the Commission such amendments and
supplements to such registration statement and the prospectus used in connection
therewith as may be necessary to keep such registration statement effective
until the earlier of(i) the sale of all Restricted Shares covered thereby
or (ii) nine months, and to comply with the provisions of the Securities Act
with respect to the sale or other disposition of all Restricted Shares
covered by such registration statement;

          (c) furnish to each holder whose Restricted Shares are being
registered pursuant to this Section 3 such number of copies of any summary
prospectus or other prospectus, including a preliminary prospectus, in
conformity with the requirements of the Securities Act and such other documents
as such holder may reasonably request in order to facilitate the public sale or
other disposition of such Restricted Shares;

                                       18

<Page>

          (d) use its best efforts to register or qualify the Restricted Shares
covered by such registration statement under the securities or blue sky laws of
such jurisdictions as each holder whose Restricted Shares are being registered
pursuant to this Section 3 shall reasonably request and do any and all other
acts or things which may be necessary or advisable to enable such holder to
consummate the public sale or other disposition in such jurisdictions of such
Restricted Shares; provided, however, that the Corporation shall not be required
to consent to general service of process for all purposes in any jurisdiction
where it is not then subject to process, qualify to do business as a foreign
corporation where it would not be otherwise required to qualify or submit to
liability for state or local taxes where it is not otherwise liable for such
taxes;

          (e) at any time when a prospectus covered by such registration
statement and relating thereto is required to be delivered under the Securities
Act within the appropriate period mentioned in Section 3.7(b) hereof, notify
each holder whose Restricted Shares are being registered pursuant to this
Section 3 of the happening of any event as a result of which the prospectus
included in such registration, as then in effect, includes an untrue statement
of a material fact or omits to state a material fact required to be stated
therein or necessary to make the statements therein not misleading in the light
of the circumstances then existing and, at the request of such holder, prepare,
file and furnish to such holder a reasonable number of copies of a supplement to
or an amendment of such prospectus as may be necessary so that, as thereafter
delivered to the purchasers of such shares, such prospectus shall not include an
untrue statement of a material fact or omit to state a material fact required to
be stated therein or necessary to make the statements therein not misleading in
the light of the circumstances then existing;

          (f) if the Corporation has delivered preliminary or final prospectuses
to the holders of Restricted Shares that are being registered pursuant to this
Section 3 and after having done so the prospectus is amended to comply with the
requirements of the Securities Act, the Corporation shall promptly notify such
holders and, if requested, such holders shall immediately cease making offers of
Restricted Shares and return all prospectuses to the Corporation. The
Corporation shall promptly provide such holders with revised prospectuses and,
following receipt of the revised prospectuses, such holders shall be free to
resume making offers of the Restricted Shares; and

          (g) furnish, at the request of any holder whose Restricted Shares are
being registered pursuant to this Section 3, on the date that such Restricted
Shares are delivered to the underwriters for sale in connection with a
registration pursuant to this Section 3, if such securities are being sold
through underwriters, or, on the date that the registration statement with
respect to such securities becomes effective, if such securities are not being
sold through underwriters, (i) an opinion, dated such date, of the counsel
representing the Corporation for the purposes of such registration, in form and
substance as is customarily given to underwriters in an underwritten public
offering, addressed to the underwriters, if any, and to the holder or holders
making such request, and (ii) a letter dated such date, from the independent
certified public accountants of the Corporation, in form and substance as is
customarily given by independent certified public accountants to underwriters in
an underwritten public offering, addressed to the underwriters, if any, and to
the holder or holders making such request.

     Notwithstanding the foregoing, if, after a registration statement becomes
effective, the Corporation becomes engaged in any activity which, in the good
faith determination of the

                                       19

<Page>

Board, involves information that would have to be disclosed in the registration
statement but which the Corporation desires to keep confidential for valid
business reasons, then the Corporation may at its option by notice to such
holders of Restricted Shares that have included shares in such registration
statement, require that such holders cease sales of such shares under such
registration statement for a period not in excess of ninety days from the date
of such notice, such right to be exercised by the Corporation not more than once
in any 12-month period. If in connection therewith, the Corporation considers it
appropriate for such registration statement to be amended, the Corporation shall
so amend such registration statement as promptly as practicable and such holders
shall suspend any further sales of their shares until the Corporation advises
them that such registration statement has been amended. The time periods
referred to herein during which such registration statement must be kept
effective shall be extended for an additional number of days equal to the number
of days during which the right to sell shares was suspended pursuant to this
paragraph.

     3.8. Expenses. The Corporation shall pay all expenses incurred by the
Corporation in complying with this Section 3, including, without limitation, all
registration and filing fees (including all expenses incident to filing with the
National Association of Securities Dealers, Inc.), fees and expenses of
complying with the securities and blue sky laws of all such jurisdictions in
which the Restricted Shares are proposed to be offered and sold, printing
expenses and fees and disbursements of counsel (including with respect to each
registration effected pursuant to Sections 3.4, 3.5 and 3.6, the reasonable fees
and disbursements of one counsel for the holders of Restricted Securities who
may be chosen by a majority in interest of the Restricted Shares being
registered in such offering); provided, however, that all underwriting discounts
and selling commissions applicable to the Restricted Shares covered by
registrations effected pursuant to Section 3.4, 3.5 or 3.6 hereof shall be borne
by the seller or sellers thereof, in proportion to the number of Restricted
Shares sold by each such seller or sellers

     3.9. Indemnification.

          (a) (i) In the event of any registration of any Restricted Shares
under the Securities Act pursuant to this Section 3 or registration or
qualification of any Restricted Shares pursuant to Section 3.7(d) hereof, the
Corporation shall indemnify and hold harmless the seller of such shares, each
underwriter of such shares, if any, each broker or any other person acting on
behalf of such seller and each other person, if any, who controls any of the
foregoing persons, within the meaning of the Securities Act, against any losses,
claims, damages or liabilities, joint or several, to which any of the foregoing
persons may become subject under the Securities Act or otherwise, insofar as
such losses, claims, damages or liabilities (or actions in respect thereof)
arise out of or are based upon an untrue statement or alleged untrue statement
of a material fact contained in any registration statement under which such
Restricted Shares were registered under the Securities Act, any preliminary
prospectus or final prospectus contained therein, or any amendment or supplement
thereto, or any document incident to registration or qualification of any
Restricted Shares pursuant to Section 3.7(d) hereof, or arise out of or are
based upon the omission or alleged omission to state therein a material fact
required to be stated therein or necessary to make the statements therein not
misleading or, with respect to any prospectus, necessary to make the statements
therein, in light of the circumstances under which they were made, not
misleading, or any violation by the Corporation of the Securities Act or any
state securities or blue sky laws applicable to the Corporation and relating to
action or inaction

                                       20

<Page>

required of the Corporation in connection with such registration or
qualification under the Securities Act or such state securities or blue sky
laws. The Corporation shall reimburse on demand such seller, underwriter, broker
or other person acting on behalf of such seller and each such controlling person
for any legal or any other expenses reasonably incurred by any of them in
connection with investigating or defending any such loss, claim, damage,
liability or action; provided, however, that the Corporation shall not be liable
in any such case to the extent that any such loss, claim, damage or liability
arises out of or is based upon (1) an untrue statement or alleged untrue
statement or omission or alleged omission made in said registration statement,
preliminary or final prospectus or amendment or supplement thereto or any
document incident to registration or qualification of any Restricted Shares
pursuant to Section 3.7(d) hereof, in reliance upon and in conformity with
written information furnished to the Corporation by such seller, underwriter,
broker, other person or controlling person specifically for use in the
preparation thereof, or (2) if the Corporation provides an amended prospectus
which corrects any misstatement or omission, any use of a prospectus which does
not contain such correction after such correction is made and the prospectus is
provided to such seller.

               (ii) In the event of any registration of any Restricted Shares
under the Securities Act pursuant to this Section 3 or registration or
qualification of any Restricted Shares pursuant to Section 3.7(d) hereof, the
Investors severally, but not jointly, shall indemnify and hold harmless the
Corporation and its directors, officers, employees, agents and affiliates and
any other person, if any, who controls any of the foregoing persons, within the
meaning of the Securities Act, against any losses, claims, damages or
liabilities (or actions in respect thereof) which arise out of or are based upon
an untrue statement or alleged untrue statement of a material fact contained in
any registration statement under which such Restricted Shares were registered
under the Securities Act, any preliminary prospectus or final prospectus
contained therein, or any amendment or supplement thereto, or any document
incident to registration or qualification of any Restricted Shares pursuant to
Section 3.7(d) hereof, or arise out of or based upon the omission or alleged
omission to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading or, with respect to any
prospectus, necessary to make statements therein, in light of the circumstances
under which they were made, not misleading, or any violation of the Securities
Act or any state securities or applicable blue sky laws relating to action or
inaction required of the Corporation in connection with such registration or
qualification under the Securities Act or such state securities or blue sky laws
arising out of or based upon written information furnished to the Corporation by
any such Investor specifically for use in the preparation thereof
Notwithstanding anything herein to the contrary, no Investor shall have any
obligation hereunder to pay any amount in excess of the net proceeds received by
any such Investor in connection with the registration of Restricted Shares.

          (b) Before Restricted Shares held by any prospective seller shall be
included in any registration pursuant to this Section 3, such prospective seller
and any underwriter acting on its behalf shall have agreed to indemnify and hold
harmless (in the same manner and to the same extent as set forth in paragraph
(a)) the Corporation, each director of the Corporation, each officer of the
Corporation who signs such registration statement and any person who controls
the Corporation within the meaning of the Securities Act, with respect to any
untrue statement or omission from such registration statement, any preliminary
prospectus or final prospectus contained therein, or any amendment or supplement
thereto, if such untrue statement or omission was made in reliance upon and in
conformity with written information furnished to the

                                       21

<Page>

Corporation through an instrument duly executed by such seller or such
underwriter specifically for use in the preparation of such registration
statement, preliminary prospectus, final prospectus or amendment or supplement;
provided, however, that the maximum amount of liability in respect of such
indemnification shall be limited, in the case of each prospective seller, to an
amount equal to the net proceeds actually received by such prospective seller
from the sale of Restricted Shares effected pursuant to such registration

          (c) Promptly after receipt by an indemnified party of notice of the
commencement of any action involving a claim referred to in Section 3.9(a) or
(b) hereof, such indemnified party will, if a claim in respect thereof is to be
made against the indemnifying party under this Section 3.9, give written notice
to the latter of the commencement of such action. In case any such action is
brought against an indemnified party, the indemnifying party will be entitled to
participate in and to assume the defense thereof, jointly with any other
indemnifying party similarly notified to the extent that it may wish, with
counsel reasonably satisfactory to such indemnified party, and, after notice to
such indemnified party from the indemnifying party of its election to assume the
defense thereof, the indemnifying party shall be responsible for any legal or
other expenses subsequently incurred by the latter in connection with the
defense thereof; provided, however, that, if any indemnified party shall have
reasonably concluded that there may be one or more legal defenses available to
such indemnified party which are different from, or additional to those
available to the indemnifying party, or that such claim or litigation involves
or could have an effect upon matters beyond the scope of the indemnity agreement
provided in this Section 3.9, the indemnifying party shall not have the right to
assume the defense of such action on behalf of such indemnified party, and such
indemnifying party shall reimburse such indemnified party and any person
controlling such indemnified party for the fees and expenses of counsel retained
by the indemnified party which are reasonably related to the matters covered by
the indemnity agreement provided in this Section 3.9. The indemnifying party
shall not make any settlement of any claims indemnified against hereunder
without the written consent of the indemnified party or parties, which consent
shall not be unreasonably withheld.

          (d) In order to provide for just and equitable contribution to joint
liability under the Securities Act in any case in which either (i) any holder of
Restricted Securities exercising rights under this Agreement, or any controlling
person of any such holder, makes a claim for indemnification pursuant to this
Section 3.9, but it is judicially determined (by the entry of a final judgment
or decree by a court of competent jurisdiction and the expiration of time to
appeal or the denial of the last right of appeal) that such indemnification may
not be enforced in such case notwithstanding the fact that this Section 3.9
provides for indemnification in such case, or (ii) contribution under the
Securities Act may be required on the part of any such holder or any such
controlling person in circumstances for which indemnification is provided under
this Section 3.9; then, in each such case, the Corporation and such holder will
contribute to the aggregate losses, claims, damages or liabilities to which they
may be subject as is appropriate to reflect the relative fault of the
Corporation and such holder in connection with the statements or omissions which
resulted in such losses, claims, damages or liabilities, it being understood
that the parties acknowledge that the overriding equitable consideration to be
given effect in connection with this provision is the ability of one party or
the other to correct the statement or omission which resulted in such losses,
claims, damages or liabilities, and that it would not be just and equitable if
contribution pursuant hereto were to be determined by pro rata allocation or by
any other

                                       22

<Page>

method of allocation which does not take into consideration the foregoing
equitable considerations. Notwithstanding the foregoing, (i) no such holder will
be required to contribute any amount in excess of the proceeds to it of all
Restricted Shares sold by it pursuant to such registration statement, and (ii)
no person or entity guilty of fraudulent misrepresentation, within the meaning
of Section 11(f) of the Securities Act, shall be entitled to contribution from
any person or entity who is not guilty of such fraudulent misrepresentation.

          (e) Notwithstanding any of the foregoing, if, in connection with an
underwritten public offering of any Restricted Shares, the Corporation, the
holders of such Restricted Shares and the underwriters enter into an
underwriting or purchase agreement relating to such offering which contains
provisions covering indemnification among the parties, then the indemnification
provision of this Section 3.9 shall be deemed inoperative for purposes of such
offering.

     3.10. Removal of Legends, Etc. Notwithstanding the foregoing provisions of
this Section 3, the restrictions imposed by this Section 3 upon the
transferability of any Restricted Securities shall cease and terminate when (a)
any such Restricted Shares are sold or otherwise disposed of in accordance with
the intended method of disposition by the seller or sellers thereof set forth in
a registration statement or such other method contemplated by Section 3.3 hereof
that does not require that the securities transferred bear the legend set forth
in Section 3.2 hereof, including a Transfer pursuant to Rule 144 or a successor
rule thereof (as amended from time to time), or (b) the holder of Restricted
Securities has met the requirements for transfer of such Restricted Securities
pursuant to subparagraph (k) of Rule 144 or a successor rule thereof (as amended
from time to time) promulgated by the Commission under the Securities Act.
Whenever the restrictions imposed by this Section 3 have terminated, a holder of
a certificate for Restricted Securities as to which such restrictions have
terminated shall be entitled to receive from the Corporation, without expense, a
new certificate not bearing the restrictive legend set forth in Section 3.2
hereof and not containing any other reference to the restrictions imposed by
this Section 3.

     3.11. Initial Public Offering.

          (a) In the event the Corporation undertakes an initial public
offering, the registration statement for which is first filed with the
Commission one year or more after the Stage IA Closing Date, and to the extent
permitted by applicable law, rules and regulations, the Corporation shall grant,
or cause the managing underwriter of such offering to grant, to each Series B
Stockholder a right to purchase all or part of its pro rata portion of an
aggregate of 10% of the shares of Common Stock offered by the Corporation in the
initial public offering. A Series B Stockholder's pro rata portion, for purposes
of this Section 3.11, shall equal a fraction, the numerator of which is the
number of shares of Common Stock then held by such Series B Stockholder (giving
effect to the conversion of all shares of Series B Stock then held by such
Series B Stockholder, but not giving effect to the conversion of any options,
warrants or other derivative securities then outstanding), and the denominator
of which is the total number of shares of Common Stock then held by all of the
Series B Stockholders (giving effect to the conversion of all shares of Series B
Stock then held by all of the Series B Stockholders, but not giving effect to
the conversion of any options, warrants or other derivative securities then
outstanding).

                                       23

<Page>

          (b) In the event the Corporation undertakes an initial public
offering, the registration statement for which is first filed with the
Commission prior to one year after the Stage IA Closing Date, or if the
Corporation is prohibited by applicable laws, rules or regulations from offering
initial public offering shares to the Series B Stockholders pursuant to Section
3.11(a), then in lieu thereof, the Corporation shall issue to each Series B
Stockholder a warrant to purchase the number of shares of Common Stock that is
equal to the number of shares of Common Stock that such Series B Stockholder
otherwise would have been entitled to purchase under Section 3.11(a). Each
warrant issued pursuant to this Section 3.11(b) shall have an exercise price
equal to the price at which shares of Common Stock are offered to the public in
the initial public offering and shall be exercisable in full for a period of
five years commencing six months after the closing of the initial public
offering. All such warrants shall be issued to the Series B Stockholders as soon
as practicable after the closing of the initial public offering and shall carry
equivalent registration rights to those rights provided in Section 3 hereof with
respect to Restricted Shares.

          (c) Each Investor, if requested by the Corporation and the managing
underwriter of initial public offering, shall enter into an agreement not to
sell or otherwise transfer or dispose of any Restricted Securities or other
securities of the Corporation (excluding securities acquired in the initial
public offering or in the public market after such offering) held by such
Investor for a period not to exceed 180 days following the effective date of the
initial public offering registration statement; provided that:

               (i) all officers, directors and holders of 1% or more of the
outstanding shares of Common Stock (on an as-converted basis) of the Corporation
enter into similar agreements;

               (ii) the Corporation use its best efforts to ensure that such
agreements provide for periodic early releases of the securities subject thereto
based upon specified events; and

               (iii) the Corporation use its best efforts to ensure that such
agreements provide that any discretionary waiver or termination of the
restrictions of such agreements by the Corporation or the managing underwriter
and any early release of shares from the restrictions of such agreements shall
apply to all persons subject to such agreements on a pro rata basis, based upon
the number of Common Shares (on an as-converted basis) held by such persons.

     SECTION 4. Securities Act Registration Statements. Except for securities of
the Corporation registered on Excluded Forms, the Corporation shall not file any
registration statement under the Securities Act covering any securities unless
it shall first have given each holder of Restricted Securities written notice
thereof. The Corporation further covenants that each holder of Restricted
Securities shall have the right, at any time when it may be deemed to be a
controlling person of the Corporation, within the meaning of the Securities Act,
to participate in the preparation of such registration statement and to request
the insertion therein of material furnished to the Corporation in writing which
in such holder's judgment should be included. In connection with any
registration statement referred to in this Section 4, the Corporation shall
indemnify, to the extent permitted by law, each holder of Restricted Securities,
its officers, partners and directors and each person, if any, who controls any
such holder within

                                       24

<Page>

the meaning of the Securities Act in the same manner and to the same extent as
the Corporation is required to indemnify a seller of Restricted Shares in
Section 3.9 hereof. If, in connection with any such registration statement, any
holder of Restricted Securities shall furnish written information to the
Corporation expressly for use in the registration statement, then such holder
shall indemnify the Corporation, each director of the Corporation, each officer
of the Corporation who signs such registration statement and each person, if
any, who controls the Corporation within the meaning of the Securities Act to
the same extent as a seller of Restricted Shares is required to indemnify such
persons in Section 3.9 hereof.

     SECTION 5. Election of Directors.

     5.1 Voting for Directors. At each annual meeting of the stockholders of the
Corporation and at each special meeting of the stockholders of the Corporation
called for the purposes of electing directors of the Corporation, and at any
time at which stockholders of the Corporation shall have the right to, or shall,
vote for or consent to the election of directors, then, in each such event,
each Original Stockholder and each Investor shall vote all shares of Preferred
Stock and any other shares of voting stock of the Corporation then owned (or
controlled as to voting rights) by it or him, whether by purchase, exercise of
rights, warrants or options, stock dividends or otherwise as follows:

          (a) to fix and maintain the number of directors on the Board of
Directors of the Corporation at nine (9);

          (b) as to Series A Stockholders, pursuant to Paragraph A.6(b)(iii) of
Article III of the Certificate, to elect to the Board two (2) directors
designated by HCV VI (each, an "HCV Director"), one of whom must be a
biotechnology industry expert not affiliated with HCV or any member of the HCV
Group (the "Unaffiliated HCV Director"); the HCV Director who is not the
Unaffiliated HCV Director shall also serve on each committee of the Board of
Directors;

          (c) as to Series B Stockholders, pursuant to Paragraph A.6(b)(i) of
Article III of the Certificate, to elect to the Board one (1) director
designated by the members of the MDS Group then holding capital stock of the
Corporation (the "MDS Director"), who shall also serve on the Compensation
Committee of the Board of Directors; and

          (d) to elect to the Board one (1) director (the "Bio Ventures
Director") designated by Bio Ventures Investors Limited Partnership II
("Bio Ventures Investors") so long as Bio Ventures Investors shall own at least
50% of the Series B Preferred Shares that it owns on the date of this
Agreement.

     5.2 Post-Closing Board State. Following the Stage IA Closing (as defined in
the Stock Purchase Agreement) of the issue and sale of the Series B Preferred
Stock, the Board of Directors shall be constituted as follows:

          (a) Ray Baddour, Chairman of the Board;

          (b) Chalom Sayada, President and Chief Executive Officer;

          (c) John Littlechild, as an HCV Director;

                                       25

<Page>

          (d) Walter Gilbert, as the BioVentures Director;

          (e) Paul Auerbach;

          (f) Mick Stadler;

          (g) Gerry Brunk, as the MDS Director; and

          (h) on or before July 30, 2003, two independent directors with
significant pharmaceutical industry experience, one of which shall be the
Unaffiliated HCV Director.

     5.3. Cooperation of the Corporation. The Corporation shall use its best
efforts to effectuate the purposes of this Section 5, including promoting the
adoption of any necessary amendment of the By-laws of the Corporation and the
Certificate.

     5.4. Notices. The Corporation shall provide the Investors with at least
twenty (20) days' prior notice in writing of any intended mailing of notice to
the Investors of the Corporation for a meeting at which directors are to be
elected, and such notice shall include the names of the persons designated by
the Corporation pursuant to this Section 5. HCV VI and the relevant members of
the MDS Group shall each notify the Corporation in writing at least three (3)
days prior to such mailing of the person(s) respectively designated by it
pursuant to Paragraphs A.6(b)(iii) and A.6(b)(i) of Article III of the
Certificate, as applicable, and Section 5.1 above as nominees for election to
the Board. In the absence of any notice from HCV VI or those members of the MDS
Group, the director(s) then serving and previously designated by HCV VI or
members of the MDS Group, as applicable, shall be renominated.

     5.5. Removal. Except as otherwise provided in this Section 5, no Investor
or Original Stockholder shall vote to remove any member of the Board designated
in accordance with the foregoing provisions of this Section 5 unless the party
who designated such director (the "Designating Party") shall so vote or
otherwise consent, and, if the Designating Party shall so vote or otherwise
consent, then the non-designating stockholders shall likewise so vote. Any
vacancy on the Board created by the resignation, removal, incapacity or death of
any person designated under the foregoing provisions of this Section 5 shall be
filled by another person designated by the original Designating Party. Each
Series A Stockholder shall vote all voting shares of Series A Stock and all
other shares of voting stock of the Corporation owned or controlled by such
Series A Stockholder for such subsequent designee where the original Designating
Party was the Series A Stockholders and each Series B Stockholder shall vote all
voting shares of Series B Stock and all other shares of voting stock of the
Corporation owned or controlled by such Series B Stockholder for such subsequent
designee where the original Designating Party was the Series B Stockholders,
each in accordance with each such new designation, and no such vacancy shall be
filled in the absence of a new designation by the original Designating Party.

     5.6 Duration of Section. This Section 5 and the rights and obligations of
the parties hereunder shall automatically terminate on the consummation of a
Qualified Public Offering. Prior to such termination the rights and
obligations of any Investor under this Section 5 shall terminate upon the date
on which such Investor no longer owns any Preferred Stock, whereupon

                                       26

<Page>

the obligations of the remaining Investors to vote in favor of the designee of
such Investor shall also terminate.

     SECTION 6. Indemnification and Insurance.

     6.1. Indemnification of Investors. In the event that any Investor or any
director, officer, employee, affiliate or agent thereof (the "Indemnitees")
become involved in any capacity in any action, proceeding, investigation or
inquiry other than a claim by the Corporation against such Indemnitee in
connection with or arising out of any matter related to the Corporation or any
Indemnitee's role or position with the Corporation, the Corporation shall
reimburse each Indemnitee for its legal and other expenses (including the cost
of any investigation and preparation) as they are incurred by such Indemnitee in
connection therewith. The Corporation also agrees to indemnify each Indemnitee,
pay on demand and protect, defend, save and hold harmless from and against any
and all liabilities, damages, losses, settlements, claims, actions, suits,
penalties, fines, costs or expenses (including, without limitation, attorneys'
fees) (any of the foregoing, a "Claim") incurred by or asserted against any
Indemnitee of whatever kind or nature, arising from, in connection with or
occurring as a result of this Agreement or the matters contemplated by this
Agreement. The foregoing agreement shall be in addition to any rights that any
Indemnitee may have at common law or otherwise. Notwithstanding the foregoing,
the Corporation shall not be required to indemnify any Indemnitee who is found
to have acted in a manner demonstrating willful misconduct or in connection with
any claim that such Indemnitee breached this Agreement unless it is determined
that the Indemnitee did not breach this Agreement.

     6.2. Advancement of Expenses. The Corporation shall advance all expenses
reasonably incurred by or on behalf of the Indemnitees in connection with any
Claim or potential Claim within twenty (20) days after the receipt by the
Corporation of a statement or statements from the Indemnitee requesting such
advance payment or payments from time to time.

     6.3. Life Insurance. The Corporation shall procure and maintain a key man
life insurance policy on the life of Chalom B. Sayada in the face amount of
$1,000,000 00, with the Corporation as the named insured on such policy,
effective as of the date hereof and continuing until such time as such person no
longer serves as a director, officer, employee or consultant of the Corporation.

     SECTION 7. Remedies. In case any one or more of the covenants and/or
agreements set forth in this Agreement shall have been breached by any party
hereto, the party or parties entitled to the benefit of such covenants or
agreements may proceed to protect and enforce its or their rights, either by
suit in equity and/or action at law, including, but not limited to, an action
for damages as a result of any such breach and/or an action for specific
performance of any such covenant or agreement contained in this Agreement.
Notwithstanding the generality of the foregoing, in the event that the
Corporation breaches any of its covenants and/or agreements set forth herein,
the Investors shall have the additional remedy, in their sole discretion,
provided that such breach has not been cured by the later to occur of 15 days
after receipt of notice of such breach by the Corporation or 30 days after
the occurrence of such breach, of electing to immediately exercise their right
of redemption set forth in Article III, Section A.5 of the Certificate, as
provided therein, irrespective of whether such light of redemption otherwise is

                                       27

<Page>

mature. The rights, powers and remedies of the parties under this Agreement are
cumulative and not exclusive of any other right, power or remedy which such
parties may have under any other agreement or law. No single or partial
assertion or exercise of any light, power or remedy of a party hereunder shall
preclude any other or further assertion or exercise thereof.

     SECTION 8. Successors and Assigns. Except as otherwise expressly provided
herein, this Agreement shall bind and inure to the benefit of the Corporation
and each of the Investors and the respective successors and assigns of the
Corporation and each of the Investors, Subject to the requirements of Section 3
hereof, this Agreement and the rights and duties of the Investors set forth
herein may be freely assigned, in whole or in part (i) by each Investor to any
member of such Investor's Group and (ii) to any other person or entity acquiring
Restricted Securities including any Restricted Securities that are convertible
into Common Stock, equal to no less than 100,000 shares of Common Stock. Any
transferee (other than an Investor) to whom rights under Section 3 are
transferred shall, as a condition to such transfer, deliver to the Corporation a
written instrument by which such transferee identifies itself, gives the
Corporation notice of the transfer of such rights, identifies the securities of
the Corporation owned or acquired by it and agrees to be bound by the
obligations imposed hereunder to the same extent as if such transferee were an
Investor hereunder. A transferee to whom rights are transferred pursuant to this
Section 8 will be thereafter deemed to be an Investor for the purpose of the
execution of such transferred rights and may not again transfer such rights to
any other person or entity, other than as provided in this Section 8. Neither
this Agreement nor any of the rights or duties of the Corporation set forth
herein shall be assigned by the Corporation, in whole or in part, without having
first received the written consent or vote of a majority of the then outstanding
shares of the Preferred Stock, voting together as a single class, on an
as-converted basis.

     SECTION 9. Duration of Agreement. Except as otherwise set forth herein, the
rights and obligations of the Corporation and each Investor set forth herein
shall survive indefinitely, unless and until, by their respective terms, they
are no longer applicable or except as specifically set forth herein.

     SECTION 10. Entire Agreement. This Agreement, together with the other
writings referred to herein or delivered pursuant hereto which form a part
hereof, contains the entire agreement among the parties with respect to the
subject matter hereof and amends, restates and supersedes all prior and
contemporaneous arrangements or understandings with respect thereto.

     SECTION 11. Notices. All notices, requests, consents and other
communications 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 mail, addressed or telecopied, as the case
may be, to such party at the address or telecopier number, as the case may be,
set forth below or such other address or telecopier number, as the case may be,
as may hereafter be designated in writing by the addressee to the addressor
listing all parties:

          (i) If to the Corporation, to: ActivBiotics, Inc.
                                         128 Spring Street
                                         Lexington, Massachusetts 02421
                                         Attention: Chief Executive Officer

                                       28

<Page>

                                         Telecopier: (781)274-9129
               with a copy to:           Bingham McCutchen LLP
                                         150 Federal Street
                                         Boston, Massachusetts 02110
                                         Attention: Julio E. Vega, Esq.
                                         Telecopier: (617)951-8736

          (ii) If to the Original Stockholders, as set forth on Schedule 1;

          (iii) If to the Series A Stockholders, as set forth on Schedule 2,

               with a copy to:           McCarter & English, LLP
                                         Four Gateway Center
                                         100 Mulberry Street
                                         Newark, New Jersey 07102
                                         Attention: Jeffrey A. Baumel, Esq.
                                         Telecopier: (973)624-7070

          (iv) If to the Series B Purchasers, as set forth on Schedule 3,

               with a copy to:           Palmer & Dodge LLP
                                         111 Huntington Avenue
                                         Boston, MA 02199-7613
                                         Attention: James T Barrett, Esq.
                                         Telecopier: (617)227-4420

     All such notices, requests, consents and communications shall be deemed to
have been received (a) in the case of personal delivery, on the date of such
delivery, (b) in the case of mailing, on the third business day following the
date of such mailing, (c) in the case of overnight mail, on the first business
day following the date of such mailing, and (d) in the case of facsimile
transmission, when confirmed by facsimile machine report.

     SECTION 12. Changes. The terms and provisions of this Agreement may not be
modified or amended, or any of the provisions hereof waived, temporarily or
permanently, except pursuant to the written consent of the Corporation and the
holders of a majority of the then outstanding shares of the Preferred Stock,
voting together as a single class, on an as-converted basis, provided, however,
that any such modification, amendment or waiver which materially and adversely
affects one or more holders of any class or series of the capital stock of the
Corporation (the "Affected Holders") in a manner different than other holders of
that class or series of the capital stock of the Corporation shall require the
written consent of each such Affected Holder, and provided further, that any
such modification, amendment or waiver of any provision of Section 2.14 shall
require the written consent of each holder of then outstanding shares of
Preferred Stock. Notwithstanding the foregoing, and without any action by any of
the parties hereto, any person who purchases shares of the Series B Preferred
Stock at the Stage IB Closing (as defined in the Stock Purchase Agreement) shall
be added as a party to this Agreement by signing a counterpart signature page
hereto, upon the execution of which such

                                       29

<Page>

person shall become a "Series B Purchaser" hereunder, entitled to all the
benefits and subject to all of the obligations of a "Series B Purchaser"
hereunder.

     SECTION 13. Counterparts. This Agreement may be executed in any number of
counterparts, and each such counterpart shall be deemed to be an original
instrument, but all such counterparts together shall constitute but one
agreement.

     SECTION 14. Headings. The headings of the various sections of this
Agreement have been inserted for convenience of reference only and shall not be
deemed to be a part of this Agreement.

     SECTION 15. Nouns and Pronouns. Whenever the context may require, any
pronouns used herein shall include the corresponding masculine, feminine or
neuter forms, and the singular form of names and pronouns shall include the
plural and vice-versa.

     SECTION 16. Severability. Any provision of this Agreement that is
prohibited or unenforceable in any jurisdiction shall, as to such jurisdiction,
be ineffective to the extent of such prohibition or unenforceability without
invalidating the remaining provisions hereof, and any such prohibition or
unenforceability in any jurisdiction shall not invalidate or render
unenforceable such provision in any other jurisdiction.

     SECTION 17. Governing Law. Except to the extent that any provision of this
Agreement is contrary to any mandatory provision of the Delaware General
Corporation Law (in which case such mandatory statutory provision shall apply),
this Agreement shall be governed by and construed in accordance with the laws of
the Commonwealth of Massachusetts and the laws of the United States applicable
therein (without giving effect to any choice or conflict of laws provision or
rule that would cause the application of the laws of any other jurisdiction) and
shall be treated in all respects as a Massachusetts contract.

     SECTION 18. Effectiveness. Notwithstanding any other provision of this
Agreement, this Agreement shall not be effective until the Stage IA Closing (as
such term is defined in the Stock Purchase Agreement).

                                       30

<Page>

     IN WITNESS WHEREOF the parties hereto have executed this First Amended and
Restated Stockholders' Agreement on the date first above written,

                                        THE CORPORATION:
                                        ACTIVBIOTICS, INC.

                                        By:
                                            ------------------------------------
                                            Chalom B. Sayada M.D., Ph.D.
                                            Title: Chief Executive Officer

                                        THE INVESTORS:
                                        MDS LIFE SCIENCES TECHNOLOGY FUND II
                                        NC LIMITED PARTNERSHIP

                                        By: MDS LSTF II (NCGP) Inc., its General
                                            Partner

                                        By:
                                            ------------------------------------
                                            Name:
                                            Title:

                                        MDS LIFE SCIENCES TECHNOLOGY FUND II
                                        QUEBEC LIMITED PARTNERSHIP

                                        By: MDS LSTF II (QGP) Inc., its General
                                            Partner

                                        By:
                                            ------------------------------------
                                            Name:
                                            Title:

                                        MLII CO-INVESTMENT FUND NC LIMITED
                                        PARTNERSHIP

                                        By: MLII (NCGP) Inc., its General
                                            Partner

                                        By:
                                            ------------------------------------
                                            Name:
                                            Title:

                                       31

<Page>

                                        SC BIOTECHNOLOGY DEVELOPMENT FUND LP

                                        By: SC (GP) Inc, its General Partner

                                        By:
                                            ------------------------------------
                                            Name:
                                            Title:

                                        HEALTHCARE VENTURES VI, L.P.

                                        By: HealthCare Partners VI, L.P.
                                            its General Partner

                                        By:
                                            ------------------------------------
                                            Jeffrey B. Steinberg
                                            Title: Administrative Partner

                                        DELPHI VENTURES V, L.P.
                                        By: Delphi Management Partners V, L.L.C.
                                            General Partner

                                        By:
                                            ------------------------------------
                                            Name:
                                            Title: Managing Member

                                        DELPHI BIOINVESTMENTS V, L.P.

                                        By: Delphi Management Partners V, L.L.C.
                                            General Partner

                                        By:
                                            ------------------------------------
                                            Name:
                                            Title: Managing Member

                                       32

<Page>

                                        JOHNSON & JOHNSON DEVELOPMENT
                                        CORPORATION

                                        By:
                                            ------------------------------------
                                            Ting Pau Oei
                                            Title: Vice President

                                        VANDERBILT UNIVERSITY

                                        By:
                                            ------------------------------------
                                             Name:
                                             Title:

                                        CHINA DEVELOPMENT INDUSTRIAL BANK INC

                                        By:
                                            ------------------------------------
                                            Name: Tze-Kaing Yang
                                            Title: President

                                        CDIB BIOTECH USA INVESTMENT CO., LTD.

                                        By:
                                            ------------------------------------
                                            Name: Bing Shen
                                            Title: Chairman

                                        DC 1998 NFA TRUST

                                        By:
                                            ------------------------------------
                                        Lee Casty, as Trustee

                                       33

<Page>

                                        BIOVENTURES INVESTORS LIMITED
                                        PARTNERSHIP II

                                        By: BioVentures Investors II, LLC,
                                            its General Partner

                                        By:
                                            ------------------------------------
                                            Name: Marc E. Goldberg
                                            Title: Managing Director

                                        NEW ENGLAND PARTNERS CAPITAL, L.P.

                                        By: NEP Capital, LLC, its General
                                            Partner

                                        By:
                                            ------------------------------------
                                            Name:
                                            Title:

                                        ----------------------------------------
                                        Justin P. Morreale

                                        ----------------------------------------
                                        David L. Engel

                                        ----------------------------------------
                                        Lawrence L. Silverstein

                                        ----------------------------------------
                                        Mitchell P. Cybulski

                                        ----------------------------------------
                                        Yuriko Dai-Cybulski

                                        ----------------------------------------
                                        William Koch

                                        ----------------------------------------
                                        John Finney

                                       34

<Page>

                                        ROCHE FINANCE LTD

                                        Grenzacherstrasse 124
                                        CH-4070 Basel
                                        Switzerland

                                        By:
                                            ------------------------------------
                                        Name:
                                        Title:

                                       35

<Page>

                                        THE ORIGINAL STOCKHOLDERS:

                                        ----------------------------------------
                                        Raymond Baddour

                                        ----------------------------------------
                                        Barry Eisenstein

                                        ----------------------------------------
                                        John Finney

                                        ----------------------------------------
                                        Walter Gilbert

                                        ----------------------------------------
                                        G. Mick Stadler

                                        ----------------------------------------
                                        Chalom B. Sayada

                                        ----------------------------------------
                                        Gary Magnant

                                        ----------------------------------------
                                        Richard Nicholson

                                        ----------------------------------------
                                        Art Michaelis

                                        ----------------------------------------
                                        Cathy Carew

                                       36

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