FOR IMMEDIATE RELEASE/SEPTEMBER 22, 1999




                                                                    
Una S. Ryan, Ph.D.               Thomas R. Fuerst, Ph.D.                  FOR MEDIA:
President and CEO                Vice President, Corporate Development    Joan Kureczka/Jesse Fisher
AVANT Immunotherapeutics, Inc.   AVANT Immunotherapeutics, Inc.           J. Kureczka Associates
(781) 433-0771                   (781) 433-0771                           (415) 821-2413
                                 INFO@AVANTIMMUNE.COM                     JKURECZKA@AOL.COM






               AVANT ANNOUNCES $10.5 MILLION IN PRIVATE PLACEMENT

NEEDHAM, MA (SEPTEMBER 22, 1999): AVANT Immunotherapeutics, Inc. (Nasdaq: AVAN)
announced today the closing of a private placement of approximately 5.5 million
shares of AVANT common stock at $1.92 per share for a total amount of $10.5
million. Nomura was the placing agent for the offering that included several
leading European and U.S. institutional investors. Proceeds from the private
placement will be used to support clinical development of AVANT's lead
complement inhibitor, TP10, in infants undergoing cardiac surgery on
cardiopulmonary bypass (CPB) and other company activities. After completion of
the placement, AVANT will have 48,003,734 shares outstanding with approximately
40% of those shares owned by institutional investors.

"This financing provides the resources to drive the clinical development of TP10
in infants undergoing cardiac surgery for congenital heart defects," said Una S.
Ryan, Ph.D., President and Chief Executive Officer of AVANT Immunotherapeutics.
"We look forward to advancing TP10 through late-stage clinical development with
the hope of providing a much needed therapy that may have the potential to
improve the lives of these young patients."

During cardiac surgery on CPB, complement activation is triggered by both
reperfusion injury, when blood flow is restored to ischemic tissue, and by
exposure of blood to the heart-lung machine (CPB circuit). Complement activation
can damage heart and lung function and can contribute significantly to
postoperative complications that impair patient recovery resulting in prolonged
hospital stays and increased medical expenses.

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AVANT ANNOUNCES $10.5 MILLION IN PRIVATE PLACEMENT
September 22, 1999
Page 2


Complement is a family of proteins that circulate in the blood and provide a
defense against foreign materials and organisms. Excessive complement
activation, however, is involved in a wide range of diseases including
ischemia-reperfusion injury (heart attack, stroke), cardiac surgery,
transplantation, and chronic inflammatory diseases (arthritis, multiple
sclerosis). TP10 is a soluble form of complement receptor 1 (CR1), a naturally
occurring protein found on blood cells. When sCR1 binds to its targets, it works
uniquely at several points in the complement system to minimize
complement-mediated injury.


AVANT Immunotherapeutics, Inc. is engaged in the discovery, development and
commercialization of products that harness the human immune response to prevent
and treat disease. The Company's lead therapeutic program is focused on
compounds that inhibit the inappropriate activity of the complement cascade,
which is a vital part of the body's immune defense system. The Company is also
engaged in the development of Therapore(TM), a novel system for the delivery of
immunotherapeutics for chronic viral infections and certain cancers. The Company
and its collaborators are developing vaccines using its proprietary adjuvants,
Adjumer(R) and Micromer(TM). In a further collaboration, the Company is
developing an oral human rotavirus vaccine, and is developing its own
proprietary vaccine for the management of atherosclerosis.



Additional information on AVANT Immunotherapeutics, Inc. can be obtained through
the Company's site on the world wide web:  HTTP://WWW.AVANTIMMUNE.COM.

THIS IS NOT AN OFFER OF SECURITIES FOR SALE IN THE UNITED STATES. THE SECURITIES
DESCRIBED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933 OF
THE UNITED STATES, AS AMENDED AND MAY NOT BE OFFERED OR SOLD IN THE UNITED
STATES EXCEPT PURSUANT TO THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT OF
1933 OF THE UNITED STATES, AS AMENDED OR PURSUANT TO AN AVAILABLE EXEMPTION FROM
REGISTRATION. ANY PUBLIC OFFERING OF SECURITIES TO BE MADE IN THE UNITED STATES
WILL BE MADE BY MEANS OF A PROSPECTUS THAT MAY BE OBTAINED FROM THE COMPANY AND
THAT WILL CONTAIN DETAILED INFORMATION ABOUT THE COMPANY AND MANAGEMENT, AS WELL
AS FINANCIAL STATEMENTS.


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AVANT ANNOUNCES $10.5 MILLION IN PRIVATE PLACEMENT
September 22, 1999
Page 3


SAFE HARBOR STATEMENT UNDER THE PRIVATE SECURITIES LITIGATION REFORM ACT OF
1995: THIS RELEASE INCLUDES FORWARD-LOOKING STATEMENTS WHICH REFLECT AVANT'S
CURRENT VIEWS WITH RESPECT TO FUTURE EVENTS AND FINANCIAL PERFORMANCE. THE WORDS
"BELIEVE," "EXPECT," "ANTICIPATE," AND SIMILAR EXPRESSIONS IDENTIFY
FORWARD-LOOKING STATEMENTS. INVESTORS SHOULD NOT RELY ON FORWARD-LOOKING
STATEMENTS BECAUSE THEY ARE SUBJECT TO A VARIETY OF RISKS, UNCERTAINTIES, AND
OTHER FACTORS THAT COULD CAUSE ACTUAL RESULTS TO DIFFER MATERIALLY FROM THOSE
EXPRESSED IN ANY SUCH FORWARD-LOOKING STATEMENTS. THESE FACTORS INCLUDE, BUT ARE
NOT LIMITED TO: (1) THE ABILITY TO SUCCESSFULLY COMPLETE DEVELOPMENT AND
COMMERCIALIZATION OF PRODUCTS, INCLUDING THE COST, SCOPE AND RESULTS OF
PRECLINICAL AND CLINICAL TESTING; (2) THE ABILITY TO SUCCESSFULLY COMPLETE
PRODUCT RESEARCH AND FURTHER DEVELOPMENT, INCLUDING ANIMAL, PRE-CLINICAL AND
CLINICAL STUDIES; (3) CHANGES IN EXISTING AND POTENTIAL RELATIONSHIPS WITH
CORPORATE COLLABORATORS; (4) THE TIME, COST AND UNCERTAINTY OF OBTAINING
REGULATORY APPROVALS; (5) THE ABILITY TO OBTAIN SUBSTANTIAL ADDITIONAL FUNDING;
(6) THE ABILITY TO DEVELOP AND COMMERCIALIZE PRODUCTS BEFORE COMPETITORS; AND
(7) OTHER FACTORS DETAILED FROM TIME TO TIME IN FILINGS WITH THE SECURITIES AND
EXCHANGE COMMISSION.

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