AVANT Announces Start of HIV Vaccine Trial by U.S. Army Based on AVANT's Therapore Technology.

Business Editors/Health/Medical Writers

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NEEDHAM, Mass.--(BUSINESS WIRE)--May 13, 2004

AVANT Immunotherapeutics, Inc. (Nasdaq: AVAN) today announced that the Walter Reed Army Institute of Research (WRAIR) has initiated a Phase I clinical trial to assess the safety and immunogenicity of an HIV vaccine based on AVANT's Therapore(R) technology. The placebo-controlled trial is evaluating the vaccine at three escalating dose levels in 18 healthy adult volunteers. The trial, in conjunction with the Division of AIDS (DAIDS), National Institute of Allergy and Infectious Diseases, National Institutes of Health (NIAID), U.S. Department of Health and Human Resources, is being conducted at the WRAIR Vaccine Clinical Research Center in Rockville, MD under the direction of principal investigator CDR Shirley Lee-Lecher. WRAIR and NIAID are working together through an established interagency agreement.

"We are very pleased that WRAIR/DAIDS has initiated human clinical trials of this experimental HIV vaccine, which is based upon AVANT's Therapore(R) technology," said Una Ryan, Ph.D., President and Chief Executive Officer of AVANT. "The company believes this technology offers significant advantages over other immunotherapeutic methods." Therapore(R) will be used to generate cell-mediated immune responses against the HIV gag p24 protein. Experts believe that cell-mediated immune responses may be a necessary attribute of a vaccine to prevent infection by the virus and subsequently to protect individuals from developing Acquired Immunodeficiency Syndrome (AIDS).

The clinical trial is being conducted under a Cooperative Research and Development Agreement (CRADA) between AVANT and WRAIR. Under the CRADA, AVANT is providing its proprietary Therapore(R) technology. Volunteers in each of the three dose groups in the study will receive three intramuscular vaccine immunizations or placebo injections at weeks 0, 4 and 16 and will be followed for at least 36 weeks following their final dose.

The WRAIR HIV vaccine, designated LFn-p24, consists of an anthrax-derived polypeptide called Lethal factor (LFn), from which the toxin domain has been removed, and which is fused to the HIV-1 gag p24 protein. The vaccine is aimed at inducing strong and persistent HIV-1 gag specific CD8 T Cell responses.

Therapore(R) utilizes bacterial toxin proteins to deliver target antigens into human cells to induce significant cell-mediated immune ("CMI") responses. Preclinical research with Therapore(R) has shown its ability to safely induce long-lived CMI responses with great efficiency. In addition, Therapore(R) has demonstrated an ability to deliver large peptides and protein antigens to the immune system, potentially enabling broader vaccine protective coverage in humans. AVANT plans to use its Therapore(R) technology to develop novel immunotherapeutics for the prevention and treatment of chronic viral infections including Hepatitis B, Hepatitis C, and HIV, as well as for the treatment of certain cancers.

HIV, the virus that causes AIDS, was discovered in 1983, following the first recognized cases of AIDS in 1981 and 1982. Since then, the World Health Organization (WHO) estimates that well over 20 million people have died throughout the world as a consequence of this disease. It's currently estimated that 40 million people around the world are currently living with HIV and/or AIDS, with 5 million of those having become newly infected in 2003. In the United States, over 886,000 cases of AIDS have been reported through 2002, resulting in more than 500,000 deaths. To date there is no approved HIV vaccine.

AVANT Immunotherapeutics, Inc. discovers, develops and sells innovative vaccines and therapeutics that harness the human immune system to prevent and treat disease. The company has developed a broad, well-staged pipeline of vaccines and therapeutics for large, high-value, under-served markets. Six of AVANT's products are in clinical development. These include an oral human rotavirus vaccine, a treatment to reduce complement-mediated tissue damage associated with cardiac by-pass surgery, and a novel vaccine for cholesterol management. AVANT has also assembled a technology platform that enables the creation of rapidly-protecting, single-dose, oral vaccines that remain stable without refrigeration. The company is developing applications of this vaccine technology in four areas: biodefense, travelers' vaccines, global health needs, and human food safety. AVANT's goal is to demonstrate proof-of-concept for its products before leveraging further development through both traditional pharmaceutical partnerships and collaborations with governmental and other organizations.

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(TM) (Peru-15), Ty800 and other products; (4) the cost, timing, scope and results of ongoing safety and efficacy trials of TP10, 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 TP10, 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 TP10, CETi-1, CholeraGarde(TM) (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; (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.