New Cholera Vaccine is Safe and Immunogenic in Infants and Children; AVANT Reports Positive Phase II Study Results of Single Dose Oral CholeraGarde(R).

NEEDHAM, Mass. -- AVANT Immunotherapeutics, Inc. (Nasdaq: AVAN) announced today a breakthrough in the control of cholera with positive preliminary results from a Phase II clinical trial of CholeraGarde(R) in infants and children. The researchers found the single dose, oral vaccine to be well tolerated and highly immunogenic, with 77% of children aged 9 months to 5 years generating protective immune responses. The ability to induce protective immune responses in children under age two would allow the introduction of the vaccine into the routine pediatric immunization calendar in endemic regions. There are currently no licensed cholera vaccines indicated for use in children under age two. Cholera remains a global threat according to the World Health Organization, especially in developing countries and to travelers. Infants, children and the elderly are at the highest risk of dying from the disease.

The double-blind, randomized, placebo-controlled study was conducted at the Centre for Health and Population Research of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) in collaboration with the International Vaccine Institute (IVI), Korea. The trial was sponsored by the Diseases of the Most Impoverished (DOMI) Program of the IVI which is funded by the Bill and Melinda Gates Foundation.

"Cholera remains endemic in many developing areas of the world, as well as being an important potential health threat for refugees and for persons in areas affected by natural disasters such as severe flooding in areas that result in contaminated water supplies," said Dr. David A. Sack, Director of ICDDR,B. "In cholera-endemic areas the highest attack rates are in children aged 2-4 years, so it is important to administer an effective vaccine prior to age 2 to protect this high risk group. In addition, the development of an effective and practical vaccine for all ages will provide an important tool for controlling this disease."

"A safe cholera vaccine that can be easily administered to all age groups could significantly reduce the mortality of the higher risk populations, children and elderly," stated John D. Clemens, M.D., Director of the International Vaccine Institute. "Our partnership with AVANT underscores IVI's mission of accelerating vaccine development to relieve the burden of disease in developing countries. IVI works with vaccine partners like AVANT to pursue vaccine development that otherwise may not occur."

About CholeraGarde(R)

AVANT's CholeraGarde(R) vaccine candidate is the most advanced in a portfolio of single-dose, oral vaccines in development at AVANT, aimed at protecting against serious bacterial diseases. CholeraGarde(R) is based on the Peru-15 attenuated strain of cholera and is under investigation to evaluate its use against the common O1 strain of V. cholerae. Over 400 people have been vaccinated with CholeraGarde(R) in the United States and Bangladesh. The vaccine has shown to be well tolerated and highly immunogenic both in in-patient and clinical field studies. AVANT previously reported that 75% of adults vaccinated with CholeraGarde(R) as part of this Phase II trial achieved protective immune responses within seven days following vaccination. The detailed results from the adult portion of the study have been recently published electronically and will appear in the August 15, 2005 print issue of the Journal of Infectious Diseases.

"The trial results further confirm the value of AVANT's bacterial vaccines technology for the development of safe, effective, and rapidly-acting vaccines against important global health threats to residents, travelers and military personnel," said Una S. Ryan, Ph.D., President and Chief Executive Officer of AVANT Immunotherapeutics. "Combined with our VitriLife(R) technology, which will enable such vaccines to be stored without refrigeration, CholeraGarde(R), if successfully developed, has the potential to become the ideal vaccine for use worldwide: effective, safe, rapid-acting with a single oral dose, and able to be transported without the need for a cold chain." AVANT recently announced that the company and Harvard University had received a grant of approximately $500,000 to apply AVANT's VitriLife(R) technology to CholeraGarde(R). AVANT expects to begin manufacturing CholeraGarde(R) in its Fall River facility later this year for further clinical trials to be initiated in 2006. There is currently no licensed cholera vaccine in the United States.

The Study

A total of 120 infants (9-23 months of age) and 120 children (2-5 years of age) participated in the CholeraGarde(R) study, which was carried out in two phases: the first phase at an in-patient facility at ICDDR,B which investigated two different dose levels of the vaccine versus placebo, followed by an outpatient phase at a Mirpur field site in Dhaka, Bangladesh which studied only the higher dose versus placebo. A total of 60 participants in each age group were included in the in-patient portion of the study: 20 children received the reduced dose (2x107 CFU), 20 received the full dose (2x108 CFU), and 20 received placebo consisting of buffer only. The outpatient portion of the study was carried out in 60 participants from each age group, half of whom received the full dose of vaccine and half the placebo. In those participants vaccinated with the full dose, 70% of infants and 84% of children showed levels of immune responses that correlate well with protection from cholera disease. When the results in the children are grouped together, the responder frequency was 77%. Detailed results of the study will be presented at an appropriate scientific meeting to be determined, as well as published in a scientific journal. The Principal Investigator of the study was Dr. Firdausi Qadri of the ICDDR,B.

About ICDDR,B

The ICDDR,B: Centre for Health and Population Research is an international health research institution located in Dhaka, the capital of Bangladesh. The Centre, the developer of oral rehydration solution, conducts research on a wide variety of health, nutrition and population issues facing poor countries and is the recipient of the first Gates Award for Global Health in 2001. It has previously carried out studies on a variety of enteric vaccines. For more information, please visit the ICDDR,B website at www.icddrb.org.

About IVI

The IVI is the world's only international organization devoted exclusively to research and development of new vaccines for the poor in developing countries. It conducts field research to accelerate the introduction of vaccines in 21 developing countries of Asia, Africa and Latin America, and laboratory research to develop new vaccines at its headquarters on the campus of Seoul National University. For more information, visit the IVI website at www.ivi.int. IVI, through its Diseases of the Most Impoverished ("DOMI") Program, seeks to accelerate the development and introduction of vaccines against cholera, typhoid fever and shigellosis. The DOMI Program has been funded by the Bill and Melinda Gates Foundation.

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 pre-clinical 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), 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, 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) changes in existing and potential relationships with corporate collaborators; (10) the availability, cost, delivery and quality of clinical and commercial grade materials supplied by contract manufacturers; (11) 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; (12) the ability to obtain substantial additional funding; (13) the ability to develop and commercialize products before competitors; (14) the ability to retain certain members of management; and (15) 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.