Dose-Ranging Study of AVANT's CholeraGarde Presented at ICAAC; Study Results Confirm Immunogenicity, Dosing and Tolerability of Oral Cholera Vaccine.

Business Editors/Health/Medical Writers

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NEEDHAM, Mass.--(BUSINESS WIRE)--Sept. 16, 2003

AVANT Immunotherapeutics, Inc. (Nasdaq: AVAN) today presented the full study results of a dose-ranging, immunological study of the company's oral cholera vaccine candidate, CholeraGarde(TM), in healthy volunteers as a poster presentation at the 43rd annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in Chicago, IL. The study results demonstrate a dose-response relationship and showed the vaccine's ability to elicit vibriocidal antibodies without an increased incidence of adverse effects compared to placebo.

In a previous Phase IIb double-blind, placebo-controlled challenge study, a single, oral dose of CholeraGarde(TM) demonstrated 100% protection against moderate and severe diarrhea and 93% protection against any diarrhea. Phase II field trials of CholeraGarde(TM) in adults and children are currently being conducted by the International Vaccine Institute in Bangladesh.

AVANT Immunotherapeutics, Inc. is engaged in the discovery, development and commercialization of products that harness the human immune system to prevent and treat disease. The company is developing a broad portfolio of vaccines addressing a wide range of applications including bacterial and viral diseases, chronic human disease, biodefense and food safety. These include single-dose, oral vaccines that protect against important disease-causing agents and a novel, proprietary vaccine candidate for cholesterol management. AVANT's goal is to demonstrate proof-of-concept for its products before leveraging their value through partnerships. Current collaborations encompass the development of an oral human rotavirus vaccine, vaccines to combat threats of biological warfare, and vaccines addressed to human food safety and animal health.

Additional information on AVANT Immunotherapeutics, Inc. can be obtained through our site on the World Wide Web: http://www.avantimmune.com.

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. These forward-looking statements are based on management's beliefs and assumptions and information currently available. The words "believe", "expect", "anticipate", "intend", "estimate", "project" and similar expressions which do not relate solely to historical matters identify forward-looking statements. Investors should be cautious in relying 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 integration of multiple technologies and programs; (2) the ability to adapt AVANT's vectoring systems to develop new, safe and effective orally administered vaccines against anthrax and plague or other bioterrorism threats or emerging health care threats; (3) the ability to successfully complete development and commercialization of CETi-1, CholeraGarde(TM) (Peru-15), Ty800 and other products; (4) the cost, timing, scope and results of ongoing safety and efficacy trials of CETi-1, CholeraGarde(TM) (Peru-15), Ty800 and other preclinical and clinical testing; (5) the ability to successfully complete product research and further development, including animal, pre-clinical and clinical studies of CETi-1, CholeraGarde(TM) (Peru-15), Ty800 and other products; (6) the ability of the Company to manage multiple late stage clinical trials for a variety of product candidates; (7) the volume and profitability of product sales of Megan(R)Vac 1 and other future products; (8) changes in existing and potential relationships with corporate collaborators; (9) the availability, cost, delivery and quality of clinical and commercial grade materials supplied by contract manufacturers; (10) the timing, cost and uncertainty of obtaining regulatory approvals to use CETi-1, CholeraGarde(TM) (Peru-15) and Ty800, among other purposes, to raise serum HDL cholesterol levels and to protect travelers and people in endemic regions from diarrhea causing diseases, respectively; (11) the ability to obtain substantial additional funding; (12) the ability to develop and commercialize products before competitors; (13) the ability to retain certain members of management; and (14) other factors detailed from time to time in filings with the Securities and Exchange Commission. We expressly disclaim any responsibility to update forward-looking statements.