AVANT Immunotherapeutics Announces that Rotarix(R) Rotavirus Vaccine Has Received a Positive Opinion from the European Regulatory Authorities; Partner GlaxoSmithKline Biologicals Seeking to Commercialize Rotarix(R) in Europe in First Half of 2006.

NEEDHAM, Mass. -- AVANT Immunotherapeutics (Nasdaq: AVAN) today announced that its partner GlaxoSmithKline (GSK) Biologicals has received a positive opinion from the Committee for Medicinal Products for Human Use (CHMP) for Rotarix(R) rotavirus vaccine. The CHMP is the Scientific Committee that evaluates the quality, safety and efficacy of medicinal products in the European Union.

According to the new legislation, a European Marketing Authorization from the European Commission could be expected from late February 2006 onwards, which will make Rotarix(R) the first rotavirus vaccine available to children in Europe. GSK submitted a registration file for Rotarix(R) to the European Medicines Agency (EMEA) in December 2004. GSK intends to introduce this vaccine throughout Europe immediately after the marketing authorization has been granted.

"We are delighted that our partner GSK has received a positive recommendation for the approval of Rotarix(R) in Europe," said Una S. Ryan, Ph.D., President and Chief Executive Officer of AVANT Immunotherapeutics. "European approval would mark a significant milestone, not only for the global commercialization of Rotarix(R), which has already been approved for commercial use in over 24 countries. It will also bring a substantial payment of $40 million to AVANT through its transaction with the Paul Royalty Fund regarding Rotarix(R) royalties."

Virtually every child worldwide will experience an episode of rotavirus disease by the time they reach 5 years of age, irrespective of where they live or how rich or poor they are(1). Globally, rotavirus infections are responsible for over 600 000 deaths per year globally - one child every minute(1,2). Approximately 4.5 million cases of rotavirus gastroenteritis occur yearly among children under 5 years in the EU, which makes rotavirus the most frequent vaccine preventable illness among young children in the EU(3). This translates into one child out of five visiting a physician and one out of fifty being hospitalized annually.

The rotavirus market potential by 2010 is estimated between U.S. $1.75 - $2.3 billion. Europe accounts for 20% of the total market.

ABOUT ROTARIX

Rotarix(R) has been developed by GSK Biologicals since 1997 when it was in-licensed from AVANT Immunotherapeutics. Dr Richard Ward originally developed the vaccine at the Children's Hospital of Cincinnati.

Rotarix(R) is the first human rotavirus vaccine derived from a human virus strain available in the market. The vaccine, which is given orally, confers significant protection against rotavirus diarrhea. Clinical trials have shown high efficacy against the most prevalent rotavirus strains. The vaccine can be co-administered with all major infant vaccines including oral polio vaccine(4). It is given in a two-dose schedule as of six weeks of age, allowing for an early protection.

Since Rotarix(R) launch in Mexico in 2004, an additional 24 licenses have been granted worldwide (12 Latin American countries including Brazil; Philippines and Singapore being the first Asian countries). Furthermore, Rotarix(R) has been filed in 75 countries. There are plans to file in the US where discussions are ongoing with the FDA.

Recently, Brazil and Panama included for the first time the rotavirus vaccine in their national official vaccination calendars. As part of the government's pediatric immunization program, vaccination with Rotarix(R) will be available free at public health clinics in Brazil and Panama.

About GlaxoSmithKline Biologicals

GSK Biologicals, one of the world's leading vaccine manufacturers, is located in Rixensart, Belgium, which is the centre of all GlaxoSmithKline's activities in the field of vaccine research, development and production. GSK Bio employs more than 1 000 research scientists, who are devoted to discovering new vaccines and developing more cost-effective and convenient combination products to prevent infections that cause serious medical problems worldwide. GSK Bio future vaccine pipeline contains more than 20 new vaccines in clinical development.

In 2004, GSK Bio distributed more than 1.5 billion doses of vaccines to 168 countries in both the developed and the developing world - an average of 45 doses per second. Of those vaccine doses, approximately 140 million were doses of combination paediatric vaccines, which protect the world's children against a minimum of three - and as many as six - diseases in one vaccine. For more information, visit GlaxoSmithKline's vaccine websites at www.gsk-bio.com.

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), 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.

References

(1) Parashar UD et al. Global illness and deaths caused by rotavirus disease in children. Emerg Infect Dis 2003;9(5):565-72

(2) Parashar UD. Rotavirus and Rotavirus Vaccines Proc 6th Int Rotavirus Symp, July 7-9, 2004, Mexico City

(3) Verstraeten T, et al. Burden of Rotavirus in the new European Union. Poster presented at ESPID annual meeting, May 18-20, 2005, Valencia.

(4) Steele AD. et al. Concomitant administration of live attenuated oral rotavirus vaccine (RIX4414) with poliovirus vaccines in African infants. Poster presented at ESPID annual meting, May 2005.