AVANT's Typhoid Fever Vaccine Demonstrates Excellent Clinical Potential.

Single-Dose Oral Ty800 Vaccine Immunogenic & Well-Tolerated in NIH-Sponsored Phase 1/2 Study

NEEDHAM, Mass. -- AVANT Immunotherapeutics, Inc. (Nasdaq: AVAN) announced today positive preliminary results from an investigational double-blind, placebo-controlled Phase 1/2 dose-escalating clinical trial of its typhoid fever vaccine candidate, Ty800, in healthy volunteers. The researchers found the single-dose, oral vaccine to be well tolerated and immunogenic, with over 90% of vaccinated subjects generating immune responses. Based on these excellent results, AVANT plans to further develop Ty800 to compete in the expanding typhoid fever vaccine market, which currently has over $200 million in annual sales. AVANT plans to initiate its own sponsored Phase 2 dose-ranging trial of Ty800 in mid-2007.

"Typhoid fever remains endemic in many developing areas of the world, as well as being an important potential health threat for travelers and military personnel in areas affected by the disease," said Dr. Mitchell B. Cohen, Principal Investigator in the study and Director of Gastroenterology, Hepatology and Nutrition at Cincinnati Children's Hospital Medical Center. "The development of an effective and practical vaccine for all ages will provide an important tool for controlling this disease. A safe typhoid fever vaccine that can be easily administered could significantly reduce the morbidity and mortality associated with typhoid fever."

"We are delighted with these results for our single-dose, oral Ty800 vaccine candidate," said Una S. Ryan, Ph.D., President and Chief Executive Officer of AVANT Immunotherapeutics, Inc. "These results indicate that AVANT's vaccine may have significant potential advantages over the currently licensed vaccines, which offer limited protection rates of 50-80% and require either a single needle injection or three to four oral doses over the course of a week. We believe a more efficacious, easier-to-use typhoid fever vaccine could greatly expand the current markets for both travelers in developed countries and mass immunization programs in developing countries."

The Phase 1/2 study was an in-patient dose-escalating clinical trial aimed at determining the safety and immunogenicity of the single-dose, oral Ty800 vaccine. The trial evaluated three escalating dose levels of the vaccine in 47 healthy adult volunteers and followed each volunteer for six months post-vaccination. The clinical trial was sponsored by the National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health (NIH), and was conducted at the Cincinnati Children's Hospital Medical Center. This clinical trial has been funded in whole or in part with Federal funds from the NIAID of the NIH, Department of Health and Human Services, under contract No. NO AI 25459.

About the Ty800 Vaccine

AVANT has designed the Ty800 vaccine to offer rapid, oral, single-dose protection against Salmonella typhi, the cause of typhoid fever. The Ty800 vaccine was developed using genetic techniques to delete specific genes known to be essential to the virulence of S. typhi. The clinical trial was designed to show whether Ty800 would be well tolerated in humans and rapidly elicit strong immune responses.

The Study

A total of 47 healthy volunteers participated in the Ty800 study. Thirty-three subjects were randomly sorted into three different dose groups having mean doses administered of 8x107, 6x108 and 1x1010 colony-forming units (CFUs) and 14 received a placebo consisting of buffer only. The dose of 6x108 CFU in this study appeared to be immunogenic with similar reactogenicity as placebo. In addition, over 90% of vaccinees showed positive immune responses for both systemic (IgG) and mucosal (IgA) antibodies to typhoid based on an ELISPOT assay. Results of the study are being presented today at a vaccines meeting in Baltimore, MD entitled "Progress and Opportunities in the Prevention of Enteric Disease" by the Principal Investigator, Dr. Cohen. It is expected that detailed results of the study will be published in a scientific journal.

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. AVANT has three products on the market and four of AVANT's products are in clinical development. AVANT's pipeline includes products for travelers' vaccines and global health needs based on AVANT's oral, rapid-protecting, single-dose and temperature-stable vaccine technology.

Additional information on AVANT Immunotherapeutics, Inc. can be obtained through its 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 that are subject to a variety of risks and uncertainties and reflect AVANT's current views with respect to future events and financial performance. There are a number of important factors that could cause the actual results to differ materially from those expressed in any forward-looking statement made by AVANT. 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 any other microbes used as bioweapons and other disease causing agents; (3) the ability to successfully complete product research and further development, including animal, pre-clinical and clinical studies, and commercialization of CholeraGarde[R] (Peru-15), Ty800, ETEC E. coli vaccine, VLPs and other products and AVANT's expectations regarding market growth; (4) the cost, timing, scope and results of ongoing safety and efficacy trials of CholeraGarde[R] (Peru-15), Ty800, ETEC E. coli vaccine and other preclinical and clinical testing; (5) the ability to negotiate strategic partnerships or other disposition transactions for AVANT's cardiovascular programs, including TP10 and CETi; (6) the ability of AVANT to manage multiple clinical trials for a variety of product candidates; (7) AVANT's expectations regarding its technological capabilities and expanding its focus to broader markets for vaccines; (8) the Company's expectations regarding the cost of funding its development partnership with Select Vaccines Limited for the influenza vaccine, the opportunity to extend to other disease targets, and AVANT's ability to develop products through this collaboration; (9) changes in existing and potential relationships with corporate collaborators; (10) the availability, cost, delivery and quality of clinical and commercial grade materials produced at AVANT's own Manufacturing facility or supplied by contract manufacturers and partners; (11) the timing, cost and uncertainty of obtaining regulatory approvals; (12) the ability to develop and commercialize products before competitors that are superior to the alternatives developed by competitors; (13) the ability to retain certain members of management;(14) AVANT's expectations regarding research and development expenses and general and administrative expenses; (15) AVANT's expectations regarding cash balances, capital requirements, anticipated royalty payments (including those from Paul Royalty Fund), revenues and expenses, including infrastructure expenses; (16) our belief regarding the validity of our patents and potential litigation; and (17) certain other factors that might cause AVANT's actual results to differ materially from those in the forward-looking statements including those set forth under the headings "Business," "Risk Factors" and Management's Discussion and Analysis of Financial Condition and Results of Operations" in each of AVANT's Annual Report on Form 10-K, its Quarterly Reports on Form 8-K, as well as those described in AVANT's other press releases and filings with the Securities and Exchange Commission, from time to time. You should carefully review all of these factors, and you should be aware that there may be other factors that could cause these differences. These forward-looking statements were based on information, plans and estimates at the date of this press release, and AVANT does not promise to update any forward-looking statements to reflect changes in underlying assumptions or factors, new information, future events or other changes.