AVANT Completes Enrollment of TP10 Phase IIb Study in Women Undergoing Cardiac Bypass Surgery.

NEEDHAM, Mass. -- AVANT Immunotherapeutics, Inc. (Nasdaq: AVAN) today announced that it has completed enrollment of the Phase IIb trial of its complement inhibitor, TP10, in female subjects undergoing high risk cardiac surgery utilizing cardiopulmonary bypass (CPB). The objective of this double-blind, placebo-controlled study is to assess the safety and treatment effect of TP10 as compared to placebo in reducing the incidence of death or heart attack that occurs in cardiac surgery patients on CPB, thus potentially improving post-operative outcomes.

"We are pleased to have achieved our enrollment objective of 300 subjects in this important study of TP10 in females," said Una S. Ryan, AVANT's President and Chief Executive Officer. "We appreciate the enthusiasm and support of the clinical investigators, their research staffs and the patients who have participated in this study." AVANT expects to report results of this study in the first quarter of 2006. AVANT then plans to seek a corporate partner to complete development and to commercialize TP10.

TP10 is a human recombinant protein that blocks complement activation, an acute inflammatory process that can lead to tissue damage and increased surgical complications that can impact patient survival. Results of a previous Phase II study demonstrated the ability of TP10 to significantly decrease postsurgical heart attacks and deaths in male CPB patients, although not in women. Results were published in Circulation on September 14, 2004.

About AVANT Immunotherapeutics, Inc.

AVANT Immunotherapeutics, Inc. discovers and develops innovative vaccines and therapeutics that harness the human immune system to prevent and treat disease. Six of AVANT's products are in clinical development, including a treatment to reduce complement-mediated tissue damage associated with cardiac bypass surgery and a novel vaccine for cholesterol management. AVANT is also developing a pipeline of bacteria-fighting products for biodefense, travelers' vaccines, and global health needs based on AVANT'S rapid-protecting, single-dose, oral and temperature stable vaccine technology.

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 TP10, CETi-1, CholeraGarde(R) (Peru-15), Ty800 and other products; (4) the cost, timing, scope and results of ongoing safety and efficacy trials of TP10, CETi-1, CholeraGarde(R) (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 TP10, CETi-1, CholeraGarde(R) (Peru-15), Ty800and 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, Megan(R)Egg and other future products; (8) the process of obtaining regulatory approval for the sale of Rotarix (R) in major commercial markets, as well as the timing and success of worldwide commercialization of Rotarix (R) by our partner, GlaxoSmithKline; (9)GSK's strategy and business plans to launch and supply Rotarix (R) worldwide, including in the US and other major markets;(10) changes in existing and potential relationships with corporate collaborators; (11) the availability, cost, delivery and quality of clinical and commercial grade materials supplied by contract manufacturers; (12) the timing, cost and uncertainty of obtaining regulatory approvals to use TP10, CETi-1, CholeraGarde(R) (Peru-15) and Ty800, among other purposes, for adults undergoing cardiac surgery, to raise serum HDL cholesterol levels and to protect travelers and people in endemic regions from diarrhea causing diseases, respectively; (13) the ability to obtain substantial additional funding; (14) the ability to develop and commercialize products before competitors and that are superior to the alternatives developed by competitors; (15) the ability to retain certain members of management; and (16) 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.