QuickLinks -- Click here to rapidly navigate through this document

Exhibit 10.1

SECURITIES PURCHASE AGREEMENT

        This Securities Purchase Agreement (this "Agreement") is dated as of
July 1, 2003, among AVANT Immunotherapeutics, Inc., a Delaware corporation (the
"Company"), and the purchasers identified on the signature pages hereto (each a
"Purchaser" and collectively the "Purchasers"); and

        WHEREAS, subject to the terms and conditions set forth in this Agreement
and pursuant to Section 4(2) of the Securities Act (as defined below), and
Rule 506 promulgated thereunder, the Company desires to issue and sell to the
Purchasers, and the Purchasers, severally and not jointly, desire to purchase
from the Company in the aggregate, 4,444,444 shares of Common Stock and Warrants
(each as defined below) to purchase up to 444,444 shares of Common Stock.

        NOW, THEREFORE, IN CONSIDERATION of the mutual covenants contained in
this Agreement, and for other good and valuable consideration the receipt and
adequacy of which are hereby acknowledged, the Company and each Purchaser agrees
as follows:

ARTICLE I.
DEFINITIONS

        1.1    Definitions.    In addition to the terms defined elsewhere in
this Agreement, for all purposes of this Agreement, the following terms have the
meanings indicated in this Section 1.1:

        "Action" shall have the meaning ascribed to such term in Section 3.1(j).

        "Affiliate" means any Person that, directly or indirectly through one or
more intermediaries, controls or is controlled by or is under common control
with a Person as such terms are used in and construed under Rule 144. With
respect to a Purchaser, any investment fund or managed account that is managed
on a discretionary basis by the same investment manager as such Purchaser will
be deemed to be an Affiliate of such Purchaser.

        "Business Day" means any day except Saturday, Sunday and any day which
shall be a federal legal holiday or a day on which banking institutions in the
State of New York are authorized or required by law or other governmental action
to close.

        "Closing" means the closing of the purchase and sale of the Common Stock
and Warrants pursuant to Section 2.1.

        "Closing Date" means July 1, 2003.

        "Closing Price" means on any particular date (a) the last reported
closing bid price per share of Common Stock on such date on the Trading Market
(as reported by Bloomberg L.P. at 4:15 PM (New York time) as the last reported
closing bid price for regular session trading on such day), or (b) if there is
no such price on such date, then the closing bid price on the Trading Market on
the date nearest preceding such date (as reported by Bloomberg L.P. at 4:15 PM
(New York time) as the closing bid price for regular session trading on such
day), or (c) if the Common Stock is not then listed or quoted on the Trading
Market and if prices for the Common Stock are then reported in the "pink sheets"
published by the National Quotation Bureau Incorporated (or a similar
organization or agency succeeding to its functions of reporting prices), the
most recent bid price per share of the Common Stock so reported, or (d) if the
shares of Common Stock are not then publicly traded the fair market value of a
share of Common Stock as determined by an appraiser selected in good faith by
the Purchasers of a majority in interest of the Shares then outstanding.

        "Commission" means the Securities and Exchange Commission.

        "Common Stock" means the common stock of the Company, $0.001 par value
per share, and any securities into which such common stock may hereafter be
reclassified.

--------------------------------------------------------------------------------

        "Common Stock Equivalents" means any securities of the Company or the
Subsidiary which would entitle the holder thereof to acquire at any time Common
Stock, including without limitation, any debt, preferred stock, rights, options,
warrants or other instrument that is at any time convertible into or
exchangeable for, or otherwise entitles the holder thereof to receive, Common
Stock.

        "Company Counsel" means Goodwin Procter LLP.

        "Disclosure Materials" shall have the meaning ascribed to such term in
Section 3.1(h).

        "Disclosure Schedules" means the Disclosure Schedules concurrently
delivered herewith.

        "Effective Date" means the date that the Registration Statement is first
declared effective by the Commission.

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

        "Evaluation Date" shall have the meaning ascribed to such term in
Section 3.1(r).

        "FW" shall mean Feldman Weinstein LLP with offices at 420 Lexington
Avenue, New York, New York 10170-0002.

        "GAAP" shall have the meaning ascribed to such term in Section 3.1(h).

        "Intellectual Property Rights" shall have the meaning ascribed to such
term in Section 3.1(o).

        "Liens" means a lien, charge, security interest, encumbrance, right of
first refusal or other restriction.

        "Material Adverse Effect" shall have the meaning ascribed to such term
in Section 3.1(b).

        "Material Permits" shall have the meaning ascribed to such term in
Section 3.1(m).

        "Over-Allotment Amount" shall have the meaning ascribed to such term in
Section 4.4.

        "Per Share Purchase Price" equals $2.25, subject to adjustment for
reverse and forward stock splits, stock dividends, stock combinations and other
similar transactions of the Common Stock that occur after the date of this
Agreement.

        "Person" means an individual or corporation, partnership, trust,
incorporated or unincorporated association, joint venture, limited liability
company, joint stock company, government (or an agency or subdivision thereof)
or other entity of any kind.

        "Pro Rata Portion" shall have the meaning ascribed to such term in
Section 4.4.

        "Purchaser Party" shall have the meaning ascribed to such term in
Section 4.9.

        "Registration Statement" means a registration statement meeting the
requirements set forth in the Registration Rights Agreement and covering the
resale by the Purchasers of the Shares and the Warrant Shares.

        "Registration Rights Agreement" means the Registration Rights Agreement,
dated as of the date of this Agreement, among the Company and each Purchaser, in
the form of Exhibit B hereto.

        "Rule 144" means Rule 144 promulgated by the Commission pursuant to the
Securities Act, as such Rule may be amended from time to time, or any similar
rule or regulation hereafter adopted by the Commission having substantially the
same effect as such Rule.

        "SEC Reports" shall have the meaning ascribed to such term in
Section 3.1(h).

        "Securities" means the Shares, the Warrants and the Warrant Shares.

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

2

--------------------------------------------------------------------------------

        "Shares" means the shares of Common Stock issued or issuable to each
Purchaser pursuant to this Agreement.

        "Subscription Amount" means, as to each Purchaser and the Closing, the
amounts set forth below such Purchaser's signature block on the signature page
hereto, in United States dollars and in immediately available funds.

        "Subsequent Financing" shall have the meaning ascribed to such term in
Section 4.4.

        "Subsequent Financing Notice" shall have the meaning ascribed to such
term in Section 4.4.

        "Subsidiary" shall mean Megan Health, Inc., a Delaware corporation and
wholly owned subsidiary of the Company.

        "Trading Day" means (i) a day on which the Common Stock is traded on a
Trading Market, or (ii) if the Common Stock is not listed on a Trading Market, a
day on which the Common Stock is traded on the over-the-counter market, as
reported by the OTC Bulletin Board, or (iii) if the Common Stock is not quoted
on the OTC Bulletin Board, a day on which the Common Stock is quoted in the
over-the-counter market as reported by the National Quotation Bureau
Incorporated (or any similar organization or agency succeeding to its functions
of reporting prices); provided, that in the event that the Common Stock is not
listed or quoted as set forth in (i), (ii) and (iii) hereof, then Trading Day
shall mean a Business Day.

        "Trading Market" means the following markets or exchanges on which the
Common Stock is listed or quoted for trading on the date in question: the
American Stock Exchange, the New York Stock Exchange, the Nasdaq National Market
or the Nasdaq SmallCap Market.

        "Transaction Documents" means this Agreement, the Registration Rights
Agreement, the Warrant and any other documents or agreements executed in
connection with the transactions contemplated hereunder.

        "Warrants" means the Common Stock Purchase Warrants, in the form of
Exhibit C, issuable to the Purchasers at Closing, which warrants shall be
exercisable immediately and have an exercise price equal to $3.00 and a term of
exercise of five (5) years.

        "Warrant Shares" means the shares of Common Stock issuable upon exercise
of the Warrants.

ARTICLE II.
PURCHASE AND SALE

        2.1    Closing.    At the Closing, the Purchasers shall purchase,
severally and not jointly, and the Company shall issue and sell, in the
aggregate, 4,444,444 shares of Common Stock and Warrants to purchase up to
444,444 shares of Common Stock on the Closing Date. Each Purchaser shall
purchase from the Company, and the Company shall issue and sell to each
Purchaser, a number of Shares equal to such Purchaser's Subscription Amount
divided by the Per Share Purchase Price. Upon satisfaction of the conditions set
forth in Section 2.2, the Closing shall occur at the offices of FW, or such
other location as the parties shall mutually agree.

        2.2    Closing Conditions.    

        (a)   At the Closing (unless otherwise specified below) the Company
shall deliver or cause to be delivered to each Purchaser the following:

        (i)    this Agreement duly executed by the Company;

        (ii)   within three (3) Business Days of the Closing Date, a certificate
evidencing a number of Shares equal to such Purchaser's Subscription Amount
divided by the Per Share Purchase Price, registered in the name of such
Purchaser;

3

--------------------------------------------------------------------------------

        (iii)  within three (3) Business Days of the Closing Date, a Warrant,
registered in the name of such Purchaser, pursuant to which such Purchaser shall
have the right to acquire up to the number of shares of Common Stock equal to
ten percent (10%) of the Shares to be issued to such Purchaser at such Closing;

        (iv)  the Registration Rights Agreement duly executed by the Company;
and

        (v)   a legal opinion of Company Counsel, in the form of Exhibit A
attached hereto.

        (b)   At the Closing, each Purchaser shall deliver or cause to be
delivered to the Company the following:

        (i)    this Agreement duly executed by such Purchaser;

        (ii)   such Purchaser's Subscription Amount as to such Closing by wire
transfer to the account of the Company as provided to the Purchasers in writing
prior to the Closing Date; and

        (iii)  the Registration Rights Agreement duly executed by such
Purchaser.

        (c)   All representations and warranties of the other party contained
herein shall remain true and correct as of the Closing Date.

        (d)   As of the Closing Date, there shall have been no Material Adverse
Effect with respect to the Company since the date hereof.

        (e)   From the date hereof to the Closing Date, trading in the Common
Stock shall not have been suspended by the Commission (except for any suspension
of trading of limited duration agreed to by the Company, which suspension shall
be terminated prior to the Closing), and, at any time prior to the Closing Date,
trading in securities generally as reported by Bloomberg Financial Markets shall
not have been suspended or limited, or minimum prices shall not have been
established on securities whose trades are reported by such service, or on any
Trading Market, nor shall a banking moratorium have been declared either by the
United States or New York State authorities.

ARTICLE III.
REPRESENTATIONS AND WARRANTIES

        3.1    Representations and Warranties of the Company.    Except as set
forth under the corresponding section of the Disclosure Schedules delivered
concurrently herewith, the Company hereby makes the following representations
and warranties as of the date hereof and as of the Closing Date to each
Purchaser:

        (a)    Subsidiary.    The Company owns, directly or indirectly, all of
the capital stock of its Subsidiary free and clear of any lien, charge, security
interest, encumbrance, right of first refusal or other restriction
(collectively, "Liens"), and all the issued and outstanding shares of capital
stock of the Subsidiary are validly issued and are fully paid, non-assessable
and free of preemptive and similar rights.

        (b)    Organization and Qualification.    Each of the Company and the
Subsidiary is an entity duly incorporated or otherwise organized, validly
existing and in good standing under the laws of the jurisdiction of its
incorporation or organization (as applicable), with the requisite corporate
power and authority to own and use its properties and assets and to carry on its
business as currently conducted. Neither the Company nor the Subsidiary is in
violation of any of the provisions of its respective certificate of
incorporation, bylaws or other organizational or charter documents. Each of the
Company and the Subsidiary is duly qualified to conduct business and is in good
standing as a foreign corporation or other entity in each jurisdiction in which
the nature of

4

--------------------------------------------------------------------------------

the business conducted or property owned by it makes such qualification
necessary, except where the failure to be so qualified or in good standing, as
the case may be, would not have or reasonably be expected to result in (i) a
material adverse effect on the legality, validity or enforceability of any
Transaction Document, (ii) a material adverse effect on the results of
operations, assets, business or financial condition of the Company and the
Subsidiary, taken as a whole, or (iii) a material adverse effect on the
Company's ability to perform in any material respect on a timely basis its
obligations under any Transaction Document (any of (i), (ii) or (iii), a
"Material Adverse Effect").

        (c)    Authorization; Enforcement.    The Company has the requisite
corporate power and authority to enter into and to consummate the transactions
contemplated by each of the Transaction Documents and otherwise to carry out its
obligations thereunder. The execution and delivery of each of the Transaction
Documents by the Company and the consummation by it of the transactions
contemplated thereby have been duly authorized by all necessary action on the
part of the Company and no further action is required by the Company in
connection therewith. Each Transaction Document has been (or upon delivery will
have been) duly executed by the Company and, when delivered in accordance with
the terms hereof, will constitute the valid and binding obligation of the
Company enforceable against the Company in accordance with its terms except
(i) as limited by applicable bankruptcy, insolvency, reorganization, moratorium
and other laws of general application affecting enforcement of creditors' rights
generally and (ii) as limited by laws relating to the availability of specific
performance, injunctive relief or other equitable remedies, and (iii) with
respect to the indemnification provisions set forth in the Registration Rights
Agreement, as limited by public policy.

        (d)    No Conflicts.    The execution, delivery and performance of the
Transaction Documents by the Company and the consummation by the Company of the
transactions contemplated thereby do not and will not (i) conflict with or
violate any provision of the Company's or the Subsidiary's certificate of
incorporation, bylaws or other organizational or charter documents, or
(ii) conflict with, or constitute a default (or an event that with notice or
lapse of time or both would become a default) under, or give to others any
rights of termination, amendment, acceleration or cancellation (with or without
notice, lapse of time or both) of, any agreement, credit facility, debt or other
instrument (evidencing a Company or Subsidiary debt or otherwise) or other
understanding to which the Company or the Subsidiary is a party or by which any
property or asset of the Company or the Subsidiary is bound or affected, or
(iii) result in a violation of any law, rule, regulation, order, judgment,
injunction, decree or other restriction of any court or governmental authority
to which the Company or the Subsidiary is subject (including federal and state
securities laws and regulations), or by which any property or asset of the
Company or the Subsidiary is bound or affected; except in the case of each of
clauses (ii) and (iii), such as would not have or reasonably be expected to
result in a Material Adverse Effect.

        (e)    Filings, Consents and Approvals.    The Company is not required
to obtain any consent, waiver, authorization or order of, give any notice to, or
make any filing or registration with, any court or other federal, state, local
or other governmental authority or other Person in connection with the
execution, delivery and performance by the Company of the Transaction Documents,
other than (i) the filing with the Commission of the Registration Statement, and
one or more Forms D with respect to the Shares as required under Regulation D of
the Securities Act, the application(s) to each Trading Market for the listing of
the Shares and Warrant Shares for trading thereon in the time and manner
required thereby, and applicable Blue Sky filings and (ii) such as have already
been obtained or such exemptive filings as are required to be made under
applicable securities laws.

        (f)    Issuance of the Securities.    The Securities are duly authorized
and, when issued and paid for in accordance with the Transaction Documents, will
be duly and validly issued, fully paid and

5

--------------------------------------------------------------------------------

nonassessable, free and clear of all Liens. The Company has reserved from its
duly authorized capital stock the maximum number of shares of Common Stock
issuable pursuant to this Agreement and the Warrants.

        (g)    Capitalization.    The capitalization of the Company is as
described in the Company's most recent periodic report filed with the
Commission. The Company has not issued any capital stock since such filing other
than pursuant to the exercise of employee stock options under the Company's
stock option plans and pursuant to the conversion or exercise of Common Stock
Equivalents outstanding on the date hereof. No Person has any right of first
refusal, preemptive right, right of participation, or any similar right to
participate in the transactions contemplated by the Transaction Documents.
Except as a result of the purchase and sale of the Securities and except for
employee stock options under the Company's stock option plans, there are no
outstanding options, warrants, script rights to subscribe to, calls or
commitments of any character whatsoever relating to, or securities, rights or
obligations convertible into or exchangeable for, or giving any Person any right
to subscribe for or acquire, any shares of Common Stock, or contracts,
commitments, understandings or arrangements by which the Company or the
Subsidiary is or may become bound to issue additional shares of Common Stock, or
securities or rights convertible or exchangeable into shares of Common Stock.
The issue and sale of the Securities will not obligate the Company to issue
shares of Common Stock or other securities to any Person (other than the
Purchasers) and will not result in a right of any holder of Company securities
to adjust the exercise, conversion, exchange or reset price under such
securities.

        (h)    SEC Reports; Financial Statements.    Except as disclosed in the
SEC Reports, the Company has filed all reports required to be filed by it under
the Securities Act and the Exchange Act, including pursuant to Section 13(a) or
15(d) of the Exchange Act, for the two years preceding the date hereof (or such
shorter period as the Company was required by law to file such material) (the
foregoing materials, including the exhibits thereto, being collectively referred
to herein as the "SEC Reports" and, together with the Disclosure Schedules to
this Agreement, the "Disclosure Materials") on a timely basis or has received a
valid extension of such time of filing and has filed any such SEC Reports prior
to the expiration of any such extension. As of their respective dates, the SEC
Reports complied in all material respects with the requirements of the
Securities Act and the Exchange Act and the rules and regulations of the
Commission promulgated thereunder, as applicable, and none of the SEC Reports,
when filed, contained any untrue statement of a material fact or omitted to
state a material fact required to be stated therein or necessary in order to
make the statements therein, in light of the circumstances under which they were
made, not misleading. Except as disclosed in the SEC Reports, the financial
statements of the Company included in the SEC Reports comply in all material
respects with applicable accounting requirements and the rules and regulations
of the Commission with respect thereto as in effect at the time of filing.
Except as disclosed in the SEC Reports, such financial statements have been
prepared in accordance with generally accepted accounting principles applied on
a consistent basis during the periods involved ("GAAP"), except as may be
otherwise specified in such financial statements or the notes thereto and except
that unaudited financial statements may not contain all footnotes required by
GAAP, and fairly present in all material respects the financial position of the
Company and its consolidated Subsidiary as of and for the dates thereof and the
results of operations and cash flows for the periods then ended, subject, in the
case of unaudited statements, to normal, immaterial, year-end audit adjustments.

        (i)    Material Changes.    Since the date of the latest audited
financial statements included within the SEC Reports, except as disclosed in the
SEC Reports, (i) there has been no event, occurrence or development that has had
or that could reasonably be expected to result in a Material Adverse Effect,
(ii) the Company has not incurred any liabilities (contingent or otherwise)
other than (A) trade payables and accrued expenses incurred in the ordinary
course of business consistent with past practice and (B) liabilities not
required to be reflected in the Company's

6

--------------------------------------------------------------------------------

financial statements pursuant to GAAP or required to be disclosed in filings
made with the Commission, (iii) the Company has not altered its method of
accounting, (iv) the Company has not declared or made any dividend or
distribution of cash or other property to its stockholders or purchased,
redeemed or made any agreements to purchase or redeem any shares of its capital
stock and (v) the Company has not issued any equity securities to any officer,
director or Affiliate, except pursuant to existing Company stock option plans.
The Company does not have pending before the Commission any request for
confidential treatment of information.

        (j)    Litigation.    Except as disclosed in the SEC Reports, there is
no action, suit, inquiry, notice of violation, proceeding or investigation
pending or, to the knowledge of the Company, threatened against or affecting the
Company, the Subsidiary or any of their respective properties before or by any
court, arbitrator, governmental or administrative agency or regulatory authority
(federal, state, county, local or foreign) (collectively, an "Action") which
(i) adversely affects or challenges the legality, validity or enforceability of
any of the Transaction Documents or the Securities or (ii) could, if there were
an unfavorable decision, have or reasonably be expected to result in a Material
Adverse Effect. Neither the Company nor the Subsidiary, nor, to the knowledge of
the Company, any director or officer thereof, is or has been the subject of any
Action involving a claim of violation of or liability under federal or state
securities laws or a claim of breach of fiduciary duty. There has not been, and
to the knowledge of the Company, there is not pending or contemplated, any
investigation by the Commission involving the Company or any current or former
director or officer of the Company. The Commission has not issued any stop order
or other order suspending the effectiveness of any registration statement filed
by the Company or the Subsidiary under the Exchange Act or the Securities Act.

        (k)    Labor Relations.    Except as disclosed in the SEC Reports, no
material labor dispute exists or, to the knowledge of the Company, is imminent
with respect to any of the employees of the Company which could reasonably be
expected to result in a Material Adverse Effect.

        (l)    Compliance.    Except as disclosed in the SEC Reports, neither
the Company nor the Subsidiary (i) is in default under or in violation of (and
no event has occurred that has not been waived that, with notice or lapse of
time or both, would result in a default by the Company or the Subsidiary under),
nor has the Company or the Subsidiary received notice of a claim that it is in
default under or that it is in violation of, any indenture, loan or credit
agreement or any other agreement or instrument to which it is a party or by
which it or any of its properties is bound (whether or not such default or
violation has been waived), (ii) is in violation of any order of any court,
arbitrator or governmental body, or (iii) is or has been in violation of any
statute, rule or regulation of any governmental authority, including without
limitation all foreign, federal, state and local laws applicable to its
business, except in the case of clauses (i), (ii) and (iii) as would not have or
reasonably be expected to result in a Material Adverse Effect.

        (m)    Regulatory Permits.    Except as disclosed in the SEC Reports,
the Company and the Subsidiary possess all certificates, authorizations and
permits issued by the appropriate federal, state, local or foreign regulatory
authorities necessary to conduct their respective businesses as described in the
SEC Reports, except where the failure to possess such permits would not have or
reasonably be expected to result in a Material Adverse Effect ("Material
Permits"), and neither the Company nor the Subsidiary has received any notice of
proceedings relating to the revocation or modification of any Material Permit.

        (n)    Title to Assets.    Except as disclosed in the SEC Reports, the
Company and the Subsidiary have good and marketable title in fee simple to all
real property owned by them that is material to the business of the Company and
the Subsidiary, taken as a whole, and good and marketable title in all personal
property owned by them that is material to the business of the Company and the
Subsidiary, taken as a whole, in each case free and clear of all Liens, except
for Liens as do not materially affect the value of such property and do not
materially interfere with

7

--------------------------------------------------------------------------------

the use made and proposed to be made of such property by the Company and the
Subsidiary and Liens for the payment of federal, state or other taxes, the
payment of which is neither delinquent nor subject to penalties. Except as
disclosed in the SEC Reports, any real property and facilities held under lease
by the Company and the Subsidiary are held by them under valid, subsisting and
enforceable leases with which the Company and the Subsidiary are in material
compliance.

        (o)    Patents and Trademarks.    Except as disclosed in the SEC
Reports, to the knowledge of the Company and the Subsidiary, the Company and the
Subsidiary have rights to use all patents, patent applications, trademarks,
trademark applications, service marks, trade names, copyrights, licenses and
other similar rights used in connection with their current respective businesses
as described in the SEC Reports, unless the failure to so have could not
reasonably be expected to result in a Material Adverse Effect (collectively, the
"Intellectual Property Rights").

        (p)    Insurance.    Except as disclosed in the SEC Reports, the Company
and the Subsidiary are insured by insurers of recognized financial
responsibility against such losses and risks and in such amounts as are prudent
and customary in the businesses in which the Company and the Subsidiary are
engaged. Neither the Company nor the Subsidiary has any reason to believe that
it will not be able to renew its existing insurance coverage as and when such
coverage expires or to obtain similar coverage from similar insurers as may be
necessary to continue its business without a significant increase in cost.

        (q)    Transactions With Affiliates and Employees.    Except as set
forth in the SEC Reports, none of the officers or directors of the Company and,
to the knowledge of the Company, none of the employees of the Company is
presently a party to any transaction with the Company or the Subsidiary (other
than for services as employees, officers and directors), including any contract,
agreement or other arrangement providing for the furnishing of services to or
by, providing for rental of real or personal property to or from, or otherwise
requiring payments to or from any officer, director or such employee or, to the
knowledge of the Company, any entity in which any officer, director, or any such
employee has a substantial interest or is an officer, director, trustee or
partner, in each case in excess of $60,000 other than (i) for payment of salary
or consulting fees for services rendered, (ii) reimbursement for expenses
incurred on behalf of the Company and (ii) for other employee benefits,
including stock option agreements under any stock option plan of the Company.

        (r)    Internal Accounting Controls.    The Company and the Subsidiary
maintains a system of internal accounting controls sufficient to provide
reasonable assurance that (i) transactions are executed in accordance with
management's general or specific authorizations, (ii) transactions are recorded
as necessary to permit preparation of financial statements in conformity with
GAAP and to maintain asset accountability, (iii) access to assets is permitted
only in accordance with management's general or specific authorization, and
(iv) the recorded accountability for assets is compared with the existing assets
at reasonable intervals and appropriate action is taken with respect to any
differences. The Company has established disclosure controls and procedures (as
defined in Exchange Act Rules 13a-14 and 15d-14) for the Company and designed
such disclosure controls and procedures to ensure that material information
relating to the Company, including its Subsidiary, is made known to the
certifying officers by others within those entities, particularly during the
period in which the Company's Form 10-K or 10-Q, as the case may be, is being
prepared. The Company's certifying officers have evaluated the effectiveness of
the Company's controls and procedures as of a date within 90 days prior to the
filing date of the Form 10-Q for the quarter ended March 31, 2003 (such date,
the "Evaluation Date"). The Company presented in its Form 10-Q for the quarter
ended March 31, 2003 the conclusions of the certifying officers about the
effectiveness of the disclosure controls and procedures based on their
evaluations as of the Evaluation Date. Since the Evaluation Date, there have
been no significant changes in the Company's internal controls (as such term is
defined in Item 307(b) of Regulation S-K under the

8

--------------------------------------------------------------------------------

Exchange Act) or, to the Company's knowledge, in other factors that could
significantly affect the Company's internal controls.

        (s)    Certain Fees.    No brokerage or finder's fees or commissions are
or will be payable by the Company to any broker, financial advisor or
consultant, finder, placement agent, investment banker, bank or other Person
with respect to the transactions contemplated by this Agreement, other than such
fees payable to Rodman and Renshaw, Inc., whose fees will be paid solely by the
Company. The Purchasers shall have no obligation with respect to any fees or
with respect to any claims made by or on behalf of other Persons for fees of a
type contemplated in this Section that may be due in connection with the
transactions contemplated by this Agreement.

        (t)    Private Placement.    Assuming the accuracy of the Purchasers
representations and warranties set forth in Section 3.2, no registration under
the Securities Act is required for the offer and sale of the Securities by the
Company to the Purchasers as contemplated hereby. The issuance and sale of the
Securities hereunder does not contravene the rules and regulations of the
Trading Market.

        (u)    Investment Company.    The Company is not, and is not an
Affiliate of, an "investment company" within the meaning of the Investment
Company Act of 1940, as amended.

        (v)    Registration Rights.    No Person has any right to cause the
Company to effect the registration under the Securities Act of any securities of
the Company.

        (w)    Form S-3 Eligibility.    Subject to the Company's continued
listing on The Nasdaq Stock Market, the Company is eligible to register the
resale of its Common Stock by the Purchasers under Form S-3 promulgated under
the Securities Act.

        (x)    Listing and Maintenance Requirements.    The Company has not, in
the 12 months preceding the date hereof, received notice from any Trading Market
on which the Common Stock is or has been listed or quoted to the effect that the
Company is not in compliance with the listing or maintenance requirements of
such Trading Market. The Company is, and has no reason to believe that it will
not in the foreseeable future continue to be, in compliance with all such
listing and maintenance requirements.

        (y)    Application of Takeover Protections.    Assuming the Purchasers
beneficially own any shares of Common Stock prior to the date hereof, the
Company and its Board of Directors have taken all necessary action, if any, in
order to render inapplicable any control share acquisition, business
combination, poison pill (including any distribution under a rights agreement)
or other similar anti-takeover provision under the Company's Certificate of
Incorporation (or similar charter documents) or the laws of its state of
incorporation that is or could become applicable to the Purchasers as a result
of the Purchasers and the Company fulfilling their obligations or exercising
their rights under the Transaction Documents, including without limitation the
Company's issuance of the Securities and the Purchasers' ownership of the
Securities.

        (z)    Disclosure.    The Company confirms that, neither the Company nor
any other Person acting on its behalf has provided any of the Purchasers or
their agents or counsel with any information that constitutes or might
constitute material, non-public information. The Company understands and
confirms that the Purchasers will rely on the foregoing representations and
covenants in effecting transactions in securities of the Company.

        (aa)    No Integrated Offering.    Neither the Company, nor any of its
Affiliates, nor any Person acting on its or their behalf has, directly or
indirectly, made any offers or sales of any security or solicited any offers to
buy any security, under circumstances that would cause this offering of the
Securities to be integrated with prior offerings by the Company for purposes of
the Securities Act or any applicable stockholder approval provisions, including,
without limitation, under the rules and regulations of any exchange or automated
quotation system on which any of the securities of the Company are listed or
designated.

9

--------------------------------------------------------------------------------

        3.2    Representations and Warranties of the Purchasers.    Each
Purchaser hereby, for itself and for no other Purchaser, represents and warrants
as of the date hereof and as of the Closing Date to the Company as follows:

        (a)    Organization; Authority.    Such Purchaser is an entity duly
organized, validly existing and in good standing under the laws of the
jurisdiction of its organization with full right, corporate or partnership power
and authority to enter into and to consummate the transactions contemplated by
the Transaction Documents and otherwise to carry out its obligations thereunder.
The execution, delivery and performance by such Purchaser of the transactions
contemplated by this Agreement has been duly authorized by all necessary
corporate or similar action on the part of such Purchaser. Each Transaction
Document to which it is a party has been duly executed by such Purchaser, and
when delivered by such Purchaser in accordance with the terms hereof, will
constitute the valid and legally binding obligation of such Purchaser,
enforceable against it in accordance with its terms.

        (b)    General Solicitation.    Such Purchaser is not purchasing the
Securities as a result of any advertisement, article, notice or other
communication regarding the Securities published in any newspaper, magazine or
similar media or broadcast over television or radio or presented at any seminar
or any other general solicitation or general advertisement.

        (c)    No Public Sale or Distribution.    Such Purchaser is
(i) acquiring the Shares and (ii) upon exercise of the Warrants will acquire the
Warrant Shares, for its own account and not with a view towards, or for resale
in connection with, the public sale or distribution thereof, except pursuant to
sales registered or exempted under the Securities Act; provided, however, that
by making the representations herein, such Purchaser does not agree to hold any
of the Securities for any minimum or other specific term and reserves the right
to dispose of the Securities at any time in accordance with or pursuant to a
registration statement or an exemption under the Securities Act. Such Purchaser
is acquiring the Securities hereunder in the ordinary course of its business.
Such Purchaser does not have any agreement or understanding, directly or
indirectly, with any Person to distribute any of the Securities.

        (d)    Accredited Investor Status.    Such Purchaser is an "accredited
investor" as that term is defined in Rule 501(a) of Regulation D. Such Purchaser
is not required to be registered as a broker-dealer under Section 15 of the
Exchange Act.

        (e)    Reliance on Exemptions.    Such Purchaser understands that the
Shares and Warrants are being offered and sold to it in reliance on specific
exemptions from the registration requirements of United States federal and state
securities laws and that the Company is relying in part upon the truth and
accuracy of, and such Purchaser's compliance with, the representations,
warranties, agreements, acknowledgments and understandings of such Purchaser set
forth herein in order to determine the availability of such exemptions and the
eligibility of such Purchaser to acquire the Common Stock and Warrants.

        (f)    Information.    Such Purchaser and its advisors, if any, have
been furnished with all publicly available materials relating to the business,
finances and operations of the Company and such other publicly available
materials relating to the offer and sale of the Shares and Warrants as have been
requested by such Purchaser. Such Purchaser and its advisors, if any, have been
afforded the opportunity to ask questions of the Company. Neither such inquiries
nor any other due diligence investigations conducted by such Purchaser or its
advisors, if any, or its representatives shall modify, amend or affect such
Purchaser's right to rely on the Company's representations and warranties
contained herein. Such Purchaser understands that its investment in the Shares
and Warrants involves a high degree of risk. Such Purchaser has sought such
accounting, legal and tax advice as it has considered necessary to make an
informed investment decision with respect to its acquisition of the Shares and
Warrants.

10

--------------------------------------------------------------------------------

        (g)    No Governmental Review.    Such Purchaser understands that no
United States federal or state agency or any other government or governmental
agency has passed on or made any recommendation or endorsement of the Shares and
Warrants or the fairness or suitability of the investment in the Shares and
Warrants nor have such authorities passed upon or endorsed the merits of the
offering of the Shares and Warrants.

        (h)    Experience of Such Purchaser.    Such Purchaser, either alone or
together with its representatives, has such knowledge, sophistication and
experience in business and financial matters, including investing in
biotechnology companies, so as to be capable of evaluating the merits and risks
of the prospective investment in the Shares and Warrants, and has so evaluated
the merits and risks of such investment. Such Purchaser is able to bear the
economic risk of an investment in the Shares and Warrants and, at the present
time, is able to afford a complete loss of such investment.

        The Company acknowledges and agrees that each Purchaser does not make or
has not made any representations or warranties with respect to the transactions
contemplated hereby other than those specifically set forth in this Section 3.2.

ARTICLE IV.
OTHER AGREEMENTS OF THE PARTIES

        4.1    Transfer Restrictions.    

        (a)   The Securities may only be disposed of in compliance with state
and federal securities laws. In connection with any transfer of Securities other
than pursuant to an effective registration statement, to the Company, to an
Affiliate of a Purchaser or in connection with a pledge as contemplated in
Section 4.1(b), the Company may require the transferor thereof to provide to the
Company an opinion of counsel selected by the transferor, the form and substance
of which opinion shall be reasonably satisfactory to the Company, to the effect
that such transfer does not require registration of such transferred Securities
under the Securities Act. As a condition of transfer, any such transferee shall
agree in writing to be bound by the terms of this Agreement and shall have the
rights of a Purchaser under this Agreement and the Registration Rights
Agreement.

        (b)   The Purchasers agree to the imprinting, so long as is required by
this Section 4.1(b), of a legend on any of the Securities in the following form:

THESE SECURITIES HAVE NOT BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE
COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN
EXEMPTION FROM REGISTRATION UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE
"SECURITIES ACT"), AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT
TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT OR PURSUANT TO
AN AVAILABLE EXEMPTION FROM, OR IN A TRANSACTION NOT SUBJECT TO, THE
REGISTRATION REQUIREMENTS OF THE SECURITIES ACT AND IN ACCORDANCE WITH
APPLICABLE STATE SECURITIES LAWS AS EVIDENCED BY A LEGAL OPINION OF COUNSEL TO
THE TRANSFEROR TO SUCH EFFECT, THE SUBSTANCE OF WHICH SHALL BE REASONABLY
ACCEPTABLE TO THE COMPANY. THESE SECURITIES MAY BE PLEDGED IN CONNECTION WITH A
BONA FIDE MARGIN ACCOUNT WITH A REGISTERED BROKER-DEALER OR OTHER LOAN WITH A
FINANCIAL INSTITUTION THAT IS AN "ACCREDITED INVESTOR" AS DEFINED IN RULE 501(a)
UNDER THE SECURITIES ACT.

11

--------------------------------------------------------------------------------

The Company acknowledges and agrees that a Purchaser may from time to time
pledge pursuant to a bona fide margin agreement with a registered broker-dealer
or grant a security interest in some or all of the Securities to a financial
institution that is an "accredited investor" as defined in Rule 501(a) under the
Securities Act and, if required under the terms of such arrangement, such
Purchaser may transfer pledged or secured Securities to the pledgees or secured
parties. Such a pledge or transfer would not be subject to approval of the
Company and no legal opinion of legal counsel of the pledgee, secured party or
pledgor shall be required in connection therewith. Further, no notice shall be
required of such pledge. At the appropriate Purchaser's expense, the Company
will execute and deliver such reasonable documentation as a pledgee or secured
party of Securities may reasonably request in connection with a pledge or
transfer of the Securities, including the preparation and filing of any required
prospectus supplement under Rule 424(b)(3) under the Securities Act or other
applicable provision of the Securities Act to appropriately amend the list of
Selling Stockholders thereunder.

        (c)   Certificates evidencing the Shares and Warrant Shares shall not
contain any legend (including the legend set forth in Section 4.1(b)), (i) while
a registration statement (including the Registration Statement) covering the
resale of such security is effective under the Securities Act, or (ii) following
any sale of such Shares or Warrant Shares pursuant to Rule 144, or (iii) if such
Shares or Warrant Shares are eligible for sale under Rule 144(k), or (iv) if
such legend is not required under applicable requirements of the Securities Act
(including judicial interpretations and pronouncements issued by the Staff of
the Commission). The Company shall cause its counsel to issue a legal opinion to
the Company's transfer agent promptly after the Effective Date if required by
the Company's transfer agent to effect the removal of the legend hereunder. If
all or any portion of a Warrant is exercised at a time when there is an
effective registration statement to cover the resale of the Warrant Shares, such
Warrant Shares shall be issued free of all legends. The Company agrees that
following the Effective Date or at such time as such legend is no longer
required under this Section 4.1(c), it will, no later than five (5) Trading Days
following the delivery by a Purchaser to the Company or the Company's transfer
agent of a certificate representing Shares or Warrant Shares, as the case may
be, issued with a restrictive legend, deliver or cause to be delivered to such
Purchaser a certificate representing such Securities that is free from all
restrictive and other legends. The Company may not make any notation on its
records or give instructions to any transfer agent of the Company that enlarge
the restrictions on transfer set forth in this Section.

        (d)   In addition to such Purchaser's other available remedies, the
Company shall pay to a Purchaser, in cash, as liquidated damages and not as a
penalty, for each $1,000 of Shares or Warrant Shares (based on the Closing Price
of the Common Stock on the date such Securities are submitted to the Company's
transfer agent) subject to Section 4.1(c), $10 per Trading Day (increasing to
$20 per Trading Day five (5) Trading Days after such damages have begun to
accrue) for each Trading Day after such fifth Trading Day until such certificate
is delivered. Nothing herein shall limit such Purchaser's right to pursue actual
damages for the Company's failure to deliver certificates representing any
Securities as required by the Transaction Documents, and such Purchaser shall
have the right to pursue all remedies available to it at law or in equity
including, without limitation, a decree of specific performance and/or
injunctive relief.

        (e)   Each Purchaser, severally and not jointly, agrees that the removal
of the restrictive legend from certificates representing Securities as set forth
in this Section 4.1 is predicated upon the Company's reliance that the Purchaser
will sell any Securities pursuant to either the registration requirements of the
Securities Act, including any applicable prospectus delivery requirements, or an
exemption therefrom.

12

--------------------------------------------------------------------------------

        4.2    Furnishing of Information.    As long as any Purchaser owns
Securities, the Company covenants to timely file (or obtain extensions in
respect thereof and file within the applicable grace period) all reports
required to be filed by the Company after the date hereof pursuant to the
Exchange Act. Upon the request of any such Purchaser, the Company shall deliver
to such Purchaser a written certification of a duly authorized officer as to
whether it has complied with the preceding sentence. As long as any Purchaser
owns Securities, if the Company is not required to file reports pursuant to the
Exchange Act, it will prepare and furnish to the Purchasers and make publicly
available in accordance with Rule 144(c) such information as is required for the
Purchasers to sell the Securities under Rule 144. The Company further covenants
that it will take such further action as any Purchaser may reasonably request,
all to the extent required from time to time to enable such Person to sell such
Securities without registration under the Securities Act within the limitation
of the exemptions provided by Rule 144.

        4.3    Integration.    The Company shall not sell, offer for sale or
solicit offers to buy or otherwise negotiate in respect of any security (as
defined in Section 2 of the Securities Act) that would be integrated with the
offer or sale of the Securities in a manner that would require the registration
under the Securities Act of the sale of the Securities to the Purchasers or that
would be integrated with the offer or sale of the Securities for purposes of the
rules and regulations of any Trading Market.

        4.4    Participation in Future Financing.    From the date hereof until
December 31, 2003, the Company shall not effect a financing of its Common Stock
or Common Stock Equivalents (a "Subsequent Financing") unless (i) the Company
delivers to each of such Purchasers a written notice at least five (5) Trading
Days prior to the closing of such Subsequent Financing (the "Subsequent
Financing Notice'') of its intention to effect such Subsequent Financing, which
Subsequent Financing Notice shall describe in reasonable detail the proposed
terms of such Subsequent Financing, the amount of proceeds intended to be raised
thereunder, the Person with whom such Subsequent Financing is proposed to be
effected, and attached to which shall be a term sheet or similar document
relating thereto and (ii) such Purchaser shall not have notified the Company by
6:30 p.m. (New York City time) on the fifth (5th) Trading Day after its receipt
of the Subsequent Financing Notice of its willingness to provide (or to cause
its designee to provide), subject to completion of mutually acceptable
documentation, up to 35% of Subsequent Financing gross proceeds to the Company
("Over-Allotment Amount") on the same terms set forth in the Subsequent
Financing Notice. Notwithstanding anything herein to the contrary, if one or
more Purchasers elects to exercise the right to participate hereunder, the
Company shall have the right to increase the size of the Subsequent Financing by
an amount equal to the amount to be purchased by such exercising Purchasers and
effect such increase in the Subsequent Financing with the Persons set forth in
the Subsequent Financing Notice. If one or more Purchasers shall fail to so
notify the Company of their willingness to participate in the Subsequent
Financing, the Company may effect the remaining portion of such Subsequent
Financing on the terms and to the Persons set forth in the Subsequent Financing
Notice; provided that the Company must provide the Purchasers with a second
Subsequent Financing Notice, and the Purchasers will again have the right of
first refusal set forth above in this Section 4.4, if the Subsequent Financing
subject to the initial Subsequent Financing Notice is not consummated for any
reason on the terms set forth in such Subsequent Financing Notice within 60
Trading Days after the date of the initial Subsequent Financing Notice with the
Person identified in the Subsequent Financing Notice. In the event the Company
receives responses to Subsequent Financing Notices from Purchasers seeking to
purchase more than the financing sought by the Company in the Subsequent
Financing such Purchasers shall have the right to purchase their Pro Rata
Portion (as defined below) of the Over-Allotment Amount. "Pro Rata Portion" is
the ratio of (x) such Purchaser's Subscription Amount and (y) the aggregate sum
of all of the Subscription Amounts. If any Purchaser no longer holds any Shares,
then the Pro Rata Portions shall be re-allocated among the remaining Purchasers.
Notwithstanding anything to the contrary herein, this Section 4.4 shall not
apply to the following (a) the granting of options to employees, officers and
directors of the Company pursuant to any stock option plan duly adopted by a

13

--------------------------------------------------------------------------------

majority of the non-employee members of the Board of Directors of the Company or
a majority of the members of a committee of non-employee directors established
for such purpose, or (b) the exercise of any security issued by the Company in
connection with the offer and sale of this Company's securities pursuant to this
Agreement, or (c) the exercise of or conversion of any convertible securities,
options or warrants issued and outstanding on the date hereof, provided such
securities have not been amended since the date hereof, or (d) acquisitions or
strategic investments, the primary purpose of which is not to raise capital.

        4.5    Securities Laws Disclosure; Publicity.    The Company shall, by
8:30 a.m. Eastern time on the second Business Day following the date of this
Agreement, issue a press release or file a Current Report on Form 8-K, in each
case reasonably acceptable to each Purchaser disclosing the transactions
contemplated hereby and make such other filings and notices in the manner and
time required by the Commission. The Company and each Purchaser shall consult
with each other in issuing any press releases with respect to the transactions
contemplated hereby, and neither the Company nor any Purchaser shall issue any
such press release or otherwise make any such public statement without the prior
consent of the Company, with respect to any press release of any Purchaser, or
without the prior consent of each Purchaser, with respect to any press release
of the Company, which consent shall not unreasonably be withheld, except if such
disclosure is required by law, in which case the disclosing party shall promptly
provide the other party with prior notice of such public statement or
communication. Notwithstanding the foregoing, the Company shall not publicly
disclose the name of any Purchaser, or include the name of any Purchaser in any
filing with the Commission or any regulatory agency or Trading Market, without
the prior written consent of such Purchaser, except (i) as required by federal
securities law in connection with the registration statement contemplated by the
Registration Rights Agreement and (ii) to the extent such disclosure is required
by law or Trading Market regulations, in which case the Company shall provide
the Purchasers with prior notice of such disclosure permitted under subclause
(i) or (ii).

        4.6    Shareholders Rights Plan.    No claim will be made or enforced by
the Company or any other Person that any Purchaser is an "Acquiring Person"
under any shareholders rights plan or similar plan or arrangement in effect or
hereafter adopted by the Company, or that any Purchaser could be deemed to
trigger the provisions of any such plan or arrangement, by virtue of receiving
Securities under the Transaction Documents or under any other agreement between
the Company and the Purchasers.

        4.7    Non-Public Information.    The Company covenants and agrees that
neither it nor any other Person acting on its behalf will provide any Purchaser
or its agents or counsel with any information that the Company believes
constitutes material non-public information, unless prior thereto such Purchaser
shall have executed a written agreement regarding the confidentiality and use of
such information. The Company understands and confirms that each Purchaser shall
be relying on the foregoing representations in effecting transactions in
securities of the Company.

        4.8    Use of Proceeds.    Except as set forth on Schedule 4.8 attached
hereto, the Company shall use the net proceeds from the sale of the Securities
hereunder for working capital purposes and not for the satisfaction of any
portion of the Company's debt (other than payment of trade payables in the
ordinary course of the Company's business and prior practices), to redeem any
Company equity or equity-equivalent securities or to settle any outstanding
litigation.

        4.9    Indemnification of Purchasers.    The Company will indemnify and
hold the Purchasers and their directors, officers, shareholders, partners,
employees and agents (each, a "Purchaser Party") harmless from any and all
losses, liabilities, obligations, claims, contingencies, damages, costs and
expenses, including all judgments, amounts paid in settlements, court costs and
reasonable attorneys' fees and costs of investigation that any such Purchaser
Party may suffer or incur as a result of or relating to: (a) any
misrepresentation, breach or inaccuracy of any of the representations,
warranties, covenants or agreements made by the Company in this Agreement or in
the other Transaction

14

--------------------------------------------------------------------------------

Documents; or (b) any cause of action, suit or claim brought or made against
such Purchaser Party and arising solely out of or solely resulting from the
execution, delivery, performance or enforcement of this Agreement or any of the
other Transaction Documents and without causation by any other activity,
obligation, condition or liability pertaining to such Purchaser. The Company
will reimburse such Purchaser for its reasonable legal and other expenses
(including the cost of any investigation, preparation and travel in connection
therewith) incurred in connection therewith, as such expenses are incurred.

        4.10    Reservation of Common Stock.    As of the date hereof, the
Company has reserved and the Company shall continue to reserve and keep
available at all times, free of preemptive rights, a sufficient number of shares
of Common Stock for the purpose of enabling the Company to issue Shares pursuant
to this Agreement and Warrant Shares pursuant to the Warrants.

        4.11    Listing of Common Stock.    The Company hereby agrees to use
commercially reasonable efforts to maintain the listing of the Common Stock on
the Trading Market, and as soon as reasonably practicable following the Closing
(but not later than the earlier of the Effective Date and the first anniversary
of the Closing Date) to list the applicable Shares and Warrant Shares on the
Trading Market. The Company further agrees, if the Company applies to have the
Common Stock traded on any other Trading Market, it will include in such
application the Shares and the Warrant Shares, and will take such other action
as is necessary or desirable in the opinion of the Purchasers to cause the
Shares and Warrant Shares to be listed on such other Trading Market as promptly
as possible. The Company will take all action reasonably necessary to continue
the listing and trading of its Common Stock on a Trading Market and will comply
in all respects with the Company's reporting, filing and other obligations under
the bylaws or rules of the Trading Market.

        4.13    Subsequent Equity Sales.    From the date hereof until 10
Trading Days following the Effective Date, neither the Company nor the
Subsidiary shall issue additional shares of Common Stock or Common Stock
Equivalents. Notwithstanding anything to the contrary herein, this Section 4.13
shall not apply to the following (a) the granting of options to employees,
officers and directors of the Company pursuant to any stock option plan duly
adopted by a majority of the non-employee members of the Board of Directors of
the Company or a majority of the members of a committee of non-employee
directors established for such purpose, or (b) the exercise of any security
issued by the Company in connection with the offer and sale of the Company's
securities pursuant to this Agreement, or (c) the exercise of or conversion of
any convertible securities, options or warrants issued and outstanding on the
date hereof, provided such securities have not been amended since the date
hereof, or (d) acquisitions or strategic investments, the primary purpose of
which is not to raise capital.

ARTICLE V.
MISCELLANEOUS

        5.1    Fees and Expenses.    Each party shall pay the fees and expenses
of its advisers, counsel, accountants and other experts, if any, and all other
expenses incurred by such party incident to the negotiation, preparation,
execution, delivery and performance of this Agreement. The Company shall pay all
stamp and other taxes and duties levied in connection with the sale of the
Securities.

        5.2    Entire Agreement.    The Transaction Documents, together with the
exhibits and schedules thereto, contain the entire understanding of the parties
with respect to the subject matter hereof and supersede all prior agreements and
understandings, oral or written, with respect to such matters, which the parties
acknowledge have been merged into such documents, exhibits and schedules.

        5.4    Notices.    Any and all notices or other communications or
deliveries required or permitted to be provided hereunder shall be in writing
and shall be deemed given and effective on the earliest of (a) the date of
transmission, if such notice or communication is delivered via facsimile at the
facsimile number specified on the signature pages attached hereto prior to
6:30 p.m. (New York City time) on a

15

--------------------------------------------------------------------------------

Trading Day, (b) the next Trading Day after the date of transmission, if such
notice or communication is delivered via facsimile at the facsimile number on
the signature pages attached hereto on a day that is not a Trading Day or later
than 6:30 p.m. (New York City time) on any Trading Day, (c) the Trading Day
following the date of mailing, if sent by U.S. nationally recognized overnight
courier service, or (d) upon actual receipt by the party to whom such notice is
required to be given. The address for such notices and communications shall be
as set forth on the signature pages attached hereto.

        5.5    Amendments; Waivers.    No provision of this Agreement may be
waived or amended except in a written instrument signed, in the case of an
amendment, by the Company and each Purchaser or, in the case of a waiver, by the
party against whom enforcement of any such waiver is sought. No waiver of any
default with respect to any provision, condition or requirement of this
Agreement shall be deemed to be a continuing waiver in the future or a waiver of
any subsequent default or a waiver of any other provision, condition or
requirement hereof, nor shall any delay or omission of either party to exercise
any right hereunder in any manner impair the exercise of any such right.

        5.6    Construction.    The headings herein are for convenience only, do
not constitute a part of this Agreement and shall not be deemed to limit or
affect any of the provisions hereof. The language used in this Agreement will be
deemed to be the language chosen by the parties to express their mutual intent,
and no rules of strict construction will be applied against any party.

        5.7    Successors and Assigns.    This Agreement shall be binding upon
and inure to the benefit of the parties and their successors and permitted
assigns. The Company may not assign this Agreement or any rights or obligations
hereunder without the prior written consent of each Purchaser. Any Purchaser may
assign any or all of its rights under this Agreement to any Person, provided
such transferee agrees in writing to be bound, with respect to the transferred
Securities, by the provisions hereof that apply to the "Purchasers."

        5.8    No Third-Party Beneficiaries.    This Agreement is intended for
the benefit of the parties hereto and their respective successors and permitted
assigns and is not for the benefit of, nor may any provision hereof be enforced
by, any other Person, except as otherwise set forth in Sections 4.9.

        5.9    Governing Law.    All questions concerning the construction,
validity, enforcement and interpretation of the Transaction Documents shall be
governed by and construed and enforced in accordance with the internal laws of
the State of New York, without regard to the principles of conflicts of law
thereof. Each party agrees that all legal proceedings concerning the
interpretations, enforcement and defense of the transactions contemplated by
this Agreement and any other Transaction Documents (whether brought against a
party hereto or its respective affiliates, directors, officers, shareholders,
employees or agents) shall be commenced exclusively in the state and federal
courts sitting in the City of New York. Each party hereto hereby irrevocably
submits to the exclusive jurisdiction of the state and federal courts sitting in
the City of New York, New York for the adjudication of any dispute hereunder or
in connection herewith or with any transaction contemplated hereby or discussed
herein (including with respect to the enforcement of any of the Transaction
Documents), and hereby irrevocably waives, and agrees not to assert in any suit,
action or proceeding, any claim that it is not personally subject to the
jurisdiction of any such court, that such suit, action or proceeding is
improper. Each party hereto hereby irrevocably waives personal service of
process and consents to process being served in any such suit, action or
proceeding by delivering a copy thereof via overnight delivery (with evidence of
delivery) to such party at the address in effect for notices to it under this
Agreement and agrees that such service shall constitute good and sufficient
service of process and notice thereof. Nothing contained herein shall be deemed
to limit in any way any right to serve process in any manner permitted by law.
Each party hereto (including its affiliates, agents, officers, directors and
employees) hereby irrevocably waives, to the fullest extent permitted by
applicable law, any and all right to trial by jury in any legal proceeding
arising out of or relating to this Agreement or the transactions contemplated
hereby. If either party shall commence an action or proceeding to enforce any
provisions of a Transaction

16

--------------------------------------------------------------------------------

Document, then the prevailing party in such action or proceeding shall be
reimbursed by the other party for its attorneys fees and other costs and
expenses incurred with the investigation, preparation and prosecution of such
action or proceeding.

        5.10    Survival.    The representations, warranties, agreements and
covenants contained herein shall survive the Closing and delivery of the Shares.

        5.11    Execution.    This Agreement may be executed in two or more
counterparts, all of which when taken together shall be considered one and the
same agreement and shall become effective when counterparts have been signed by
each party and delivered to the other party, it being understood that both
parties need not sign the same counterpart. In the event that any signature is
delivered by facsimile transmission, such signature shall create a valid and
binding obligation of the party executing (or on whose behalf such signature is
executed) with the same force and effect as if such facsimile signature page
were an original thereof.

        5.12    Severability.    If any provision of this Agreement is held to
be invalid or unenforceable in any respect, the validity and enforceability of
the remaining terms and provisions of this Agreement shall not in any way be
affected or impaired thereby and the parties will attempt to agree upon a valid
and enforceable provision that is a reasonable substitute therefor, and upon so
agreeing, shall incorporate such substitute provision in this Agreement.

        5.13    Replacement of Securities.    If any certificate or instrument
evidencing any Securities is mutilated, lost, stolen or destroyed, the Company
shall issue or cause to be issued in exchange and substitution for and upon
cancellation thereof, or in lieu of and substitution therefor, a new certificate
or instrument, but only upon receipt of evidence reasonably satisfactory to the
Company of such loss, theft or destruction and customary and reasonable
indemnity, if requested. The applicants for a new certificate or instrument
under such circumstances shall also pay any reasonable third-party costs
associated with the issuance of such replacement Securities.

        5.14    Remedies.    In addition to being entitled to exercise all
rights provided herein or granted by law, including recovery of damages, each of
the Purchasers and the Company will be entitled to specific performance under
the Transaction Documents. The parties agree that monetary damages may not be
adequate compensation for any loss incurred by reason of any breach of
obligations described in the foregoing sentence and hereby agrees to waive in
any action for specific performance of any such obligation the defense that a
remedy at law would be adequate.

        5.15    Payment Set Aside.    To the extent that the Company makes a
payment or payments to any Purchaser pursuant to any Transaction Document or a
Purchaser enforces or exercises its rights thereunder, and such payment or
payments or the proceeds of such enforcement or exercise or any part thereof are
subsequently invalidated, declared to be fraudulent or preferential, set aside,
recovered from, disgorged by or are required to be refunded, repaid or otherwise
restored to the Company, a trustee, receiver or any other person under any law
(including, without limitation, any bankruptcy law, state or federal law, common
law or equitable cause of action), then to the extent of any such restoration
the obligation or part thereof originally intended to be satisfied shall, to the
extent permissible under applicable law, be revived and continued in full force
and effect as if such payment had not been made or such enforcement or setoff
had not occurred.

        5.16    Independent Nature of Purchasers' Obligations and Rights.    The
obligations of each Purchaser under any Transaction Document are several and not
joint with the obligations of any other Purchaser, and no Purchaser shall be
responsible in any way for the performance of the obligations of any other
Purchaser under any Transaction Document. Nothing contained herein or in any
Transaction Document, and no action taken by any Purchaser pursuant thereto,
shall be deemed to constitute the Purchasers as a partnership, an association, a
joint venture or any other kind of entity, or create a presumption that the
Purchasers are in any way acting in concert or as a group with respect to such

17

--------------------------------------------------------------------------------

obligations or the transactions contemplated by the Transaction Document. Each
Purchaser shall be entitled to independently protect and enforce its rights,
including without limitation, the rights arising out of this Agreement or out of
the other Transaction Documents, and it shall not be necessary for any other
Purchaser to be joined as an additional party in any proceeding for such
purpose. Each Purchaser has been represented by its own separate legal counsel
in their review and negotiation of the Transaction Documents. For reasons of
administrative convenience only, Purchasers and their respective counsel have
chosen to communicate with the Company through FW. FW does not represent all of
the Purchasers in this transaction but only The Riverview Group, LLC. The
Company has elected to provide all Purchasers with the same terms and
Transaction Documents for the convenience of the Company and not because it was
required or requested to do so by the Purchasers.

(Signature Page Follows)

18

--------------------------------------------------------------------------------

        IN WITNESS WHEREOF, the parties hereto have caused this Securities
Purchase Agreement to be duly executed by their respective authorized
signatories as of the date first indicated above.

AVANT IMMUNOTHERAPEUTICS, INC. Address for Notice:
119 Fourth Avenue
Needham, Massachusetts 02494
Attn: Una S. Ryan, Ph.D.
Tel: (781) 433-0771
Fax:
By:
 
/s/  UNA S. RYAN      

--------------------------------------------------------------------------------

Name:  Una S. Ryan, Ph.D.
Title:    President and Chief Executive Officer
 
With copy to (which shall not constitute notice):
 
Goodwin Procter LLP
Exchange Place
Boston, Massachusetts 02109-2881
Attn: Stuart M. Cable, P.C.
Tel: (617) 570-1000
Fax: (617) 523-1231
 

[SIGNATURE PAGE CONTINUES]

19

--------------------------------------------------------------------------------

[PURCHASER SIGNATURE PAGES TO SECURITIES PURCHASE AGREEMENT]

THE RIVERVIEW GROUP, LLC Address for Notice:
c/o Millennium Partners, L.P.
666 5th Avenue
8th Floor
New York, New York 10103
Fax: (212) 841-6302
By:
 
/s/  TERRY FEENEY      

--------------------------------------------------------------------------------

Name:  Terry Feeney
Title:    Chief Operating Officer
 
Subscription Amount: $10,000,000
 
With a copy to:
 
Feldman Weinstein LLP
420 Lexington Avenue
New York, New York 10170-0002
Tel: (212) 931-8704
Fax: (212) 410-4741
Attn: Joseph A. Smith
 

        Notwithstanding the foregoing, any references throughout this Agreement
to more than one Purchaser shall be disregarded, and the above signatory shall
be recognized as the sole Purchaser hereto.

20

--------------------------------------------------------------------------------

QuickLinks

SECURITIES PURCHASE AGREEMENT
ARTICLE I. DEFINITIONS
ARTICLE II. PURCHASE AND SALE
ARTICLE III. REPRESENTATIONS AND WARRANTIES
ARTICLE IV. OTHER AGREEMENTS OF THE PARTIES
ARTICLE V. MISCELLANEOUS