AVANT Immunotherapeutics Announces Positive Phase II Trial Results of Its Experimental Cholesterol Management Vaccine.

Business Editors/Health/Medical Writers

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NEEDHAM, Mass.--(BUSINESS WIRE)--Oct. 22, 2003

AVANT Immunotherapeutics, Inc. (Nasdaq: AVAN) today announced positive preliminary results from a placebo-controlled Phase II clinical study of its experimental cholesterol management vaccine, CETi-1. Results showed that the vaccine was well-tolerated, immunogenic and produced an increase in HDL-cholesterol from baseline in all groups. For the high dose group, the increase in HDL-cholesterol from baseline was statistically significant. This increase was greater than the increase in HDL-cholesterol for the placebo population, but the difference was not statistically significant.

The study was designed to investigate the ability of CETi-1 to increase HDL-cholesterol in two groups of patients, those who were taking statin therapy and those who were not. In the population who were not receiving statin therapy (approximately two-thirds of the patients in the clinical trial) the high dose group of patients demonstrated an 8.4% increase in HDL-cholesterol, which met the primary endpoint for this study as the increase was statistically significant from both baseline and placebo. For the population who were concurrently using statins, however, the study did not show significant changes in HDL-cholesterol.

"We are very pleased that the vaccine worked as designed to elicit anti-CETP antibodies in an extremely high percentage of patients treated, approximately 90%," said Una S. Ryan, Ph.D., AVANT President and Chief Executive Officer. "We are analyzing the complex data from this clinical trial and will evaluate all possibilities for the continued development of this vaccine, including the possibility of initiating an additional Phase II study at different doses, with different frequency of treatment or in a different patient population. We may also explore changes in the vaccine's formulation to elicit a more robust antibody response.

The 203 patients participating in the trial received either placebo or vaccine at one of three doses, followed by additional vaccinations at four weeks and eight weeks, and a final booster at six months. The investigators then followed the patients for an additional six months, until one year after their initial injection. The primary endpoint was the change in HDL cholesterol from baseline measured after the six-month booster.

"The results from the study validate the scientific rationale behind this vaccine - that antibodies against CETP can produce an effect on HDL-cholesterol levels in humans. The treatment benefit seen in the population not taking statin therapy is an important one. There are 21 million patients in the United States alone who require treatment for low HDL. The 8% increase in HDL seen translates to a 22% reduction in the risk of death and non-fatal myocardial infarction for patients with coronary heart disease," said Alistair Wheeler, MD, AVANT Vice President, Medical Affairs. "The vaccine was well tolerated, the most frequent adverse events reported being injection site pain, nasopharyngitis and headache."

CETi-1 is designed to raise serum HDL cholesterol levels by blocking the transfer of cholesterol from HDL to LDL (low-density lipoprotein). HDL (often referred to as 'good' cholesterol) acts to protect against atherosclerosis while LDL (often referred to as 'bad' cholesterol) acts to promote atherosclerosis. CETi-1 induces antibodies against a portion of the serum protein responsible for this transfer, cholesteryl ester transfer protein (CETP). Atherosclerosis is an underlying cause of heart attacks, strokes, and peripheral vascular disease, and the cause of over 50% of the deaths in the Western World.

"The biggest limitation today to the successful management of patients with lipid disorders is their lack of long-term compliance with oral therapies," said Dr. Ryan. "A vaccine approach involving an annual or bi-annual treatment could overcome compliance issues, leading to better clinical outcomes and potentially lower cost of therapy."

AVANT Immunotherapeutics is engaged in the discovery, development and commercialization of products that harness the human immune system to prevent and treat disease. The company is developing a broad portfolio of vaccines addressing a wide range of applications including bacterial and viral diseases, chronic human disease, biodefense and food safety. These include single-dose, oral vaccines that protect against important disease-causing agents and a novel, proprietary vaccine candidate for cholesterol management. AVANT's goal is to demonstrate proof-of-concept for its products before leveraging their value through partnerships. Current collaborations encompass the development of an oral human rotavirus vaccine, vaccines to combat threats of biological warfare and vaccines addressed to human food safety and animal health.

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. 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 ability to successfully complete development and commercialization of CETi-1; (2) the cost, timing, scope and results of additional clinical trials; (3) the ability of the Company to manage multiple late stage clinical trials for a variety of product candidates; (4) the volume and profitability of future product sales; (5) changes in existing and potential relationships with corporate collaborators; (6) the cost, delivery and quality of clinical and commercial grade materials supplied by contract manufacturers; (7) the timing, cost and uncertainty of obtaining regulatory approvals to use CETi-1, among other purposes, to raise serum HDL cholesterol levels; (8) the ability to obtain substantial additional funding; (9) the ability to develop and commercialize products before competitors; (10) the ability to retain certain members of management; and (11) 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.