Antigenics Reports Update on Cancer Vaccine Clinical Trials at American Society of Hematology Meeting.

Business Editors/Health/Medical Writers

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SAN DIEGO--(BUSINESS WIRE)--Dec. 9, 2003

Clinical Responses Observed in Trials of Heat Shock Protein-Based

Cancer Vaccines in Chronic Myelogenous Leukemia and Non-Hodgkin's

Lymphoma

Antigenics Inc. (NASDAQ: AGEN) today announced updated results from clinical trials of HSPPC-70 (previously referred to as AG-858) and Oncophage(R) (HSPPC-96) personalized cancer vaccines, both of which are based on the company's proprietary heat shock protein (HSP) technology.

Preliminary data from a Phase I study of HSPPC-70 in chronic myelogenous leukemia and from a Phase II trial of Oncophage in non-Hodgkin's lymphoma indicate that treatment with the HSP-based vaccines is well tolerated and feasible, and may be associated with clinical response. Findings were presented in separate poster sessions at the 45th annual meeting of the American Society of Hematology (ASH).

"We are very pleased to report that the consistency of the clinical findings continue to point to the potential applicability of our HSP technology to a multitude of cancers," said Garo H. Armen, Ph.D, chairman and CEO of Antigenics. "Our CML and NHL experience extend the use of our technology to hematological cancers in addition to solid tumors. If successfully developed we hope our products will provide many cancer patients with improved therapies and quality of life."

Promising Data in Hematological Cancers

Among the presentations at the ASH meeting was an update from an ongoing Phase I, open-label, single-arm study being conducted at the University of Connecticut evaluating HSPPC-70 in combination with Gleevec(TM) (imatinib mesylate, Novartis) for treatment of chronic myelogenous leukemia (CML) in chronic phase (abstract #3392). Zihai Li, MD, Ph.D, principal investigator of the trial, reported that of the 17 evaluable patients, 11 experienced a reduction in levels of cytogenetic or molecular disease burden (as measured by cytogenetic tests or polymerase chain reaction, respectively). Thus far, immunological response to vaccination has been measured in 11 of the 17 evaluable patients; nine patients demonstrated an increased level of interferon gamma-producing T cells, a specialized type of immune cell crucial in fighting cancers and infections. HSPPC-70 vaccines were successfully prepared for all patients and were well tolerated in the clinical trial.

Based on earlier data from this Phase I, proof-of-principle study of HSPPC-70, Antigenics is conducting an exploratory Phase II trial with AG-858 to evaluate the safety and efficacy of combination treatment in patients with chronic phase CML who are cytogenetically positive after treatment with Gleevec.

Also presented at the ASH meeting were recent findings from a Phase II, open-label, single-arm study being conducted at M.D. Anderson Cancer Center evaluating the efficacy and safety of Oncophage vaccination in patients with newly diagnosed or relapsed low-grade, indolent (slow-growing) non-Hodgkin's lymphoma (abstract #3343). The study's lead investigator reported indications of clinical activity in eight out of 14 evaluable patients in the trial, including one partial response, two minor responses and five disease stabilizations. These eight patients were either previously untreated or had received only one prior treatment regimen. Oncophage was reported to be well tolerated, without significant adverse effects, and researchers concluded that Oncophage warranted further study to confirm clinical activity.

Both Oncophage and AG-858 are cancer vaccines based on Antigenics' founding heat shock protein technology. Derived from each patient's cancerous cells, the vaccines consist heat shock proteins (gp96 in Oncophage, HSP70 in AG-858) and their associated peptides. The vaccines are designed to capture the 'antigenic fingerprint' of the patient's particular cancer to reprogram the body's immune system to target and fight against only the cells bearing this fingerprint. Both Oncophage and AG-858 are intended to leave healthy tissue unaffected, minimizing the debilitating side effects associated with traditional cancer treatments such as chemotherapy and radiation therapy.

About Chronic Myelogenous Leukemia and Non-Hodgkin's Lymphoma

Chronic myelogenous leukemia is a cancer of the blood and bone marrow characterized by overproduction of white blood cells. Most people with CML have a genetic mutation called the Philadelphia chromosome, which produces an abnormal enzyme (Bcr-Abl tyrosine kinase) that causes the excess white blood cells typical of CML. The American Cancer Society estimates that there will be about 4,300 new cases of chronic myelogenous leukemia in the United States this year. CML mainly affects adults and is slightly more common in men than women.

Non-Hodgkin's lymphoma is a disease in which cancerous cells are found in the lymph system. It is estimated that in 2003, 53,400 Americans, including adults and children, will be diagnosed with non-Hodgkin's lymphoma, and that 23,400 will die from the disease. It is the sixth most common cancer in this country, excluding nonmelanoma skin cancers. Non-Hodgkin's lymphoma is more common in men than in women, and more than 95 percent of non-Hodgkin's lymphoma cases occur in adults, with the average age of diagnosis in the early 40s. Because the risk of developing non-Hodgkin's lymphoma rises with age, the aging of the American population is expected to increase the number of non-Hodgkin's lymphoma cases during the next several years.

About Antigenics

Antigenics is working to develop personalized immunotherapeutics and revolutionary treatments for cancers, infectious diseases and autoimmune disorders. The company's lead product candidate is Oncophage, a late-stage, personalized cancer vaccine being evaluated in several indications, including renal cell carcinoma and metastatic melanoma. Antigenics' portfolio also includes AG-858, a personalized cancer vaccine in Phase II development; Aroplatin(TM) and ATRA-IV, two Phase II liposomal chemotherapeutics; and AG-702/AG-707, a Phase I genital herpes immunotherapeutic. For more information about Antigenics, please visit www.antigenics.com.

This press release contains forward-looking statements, including the statements regarding the tolerability, feasibility and clinical efficacy of HSPPC-70 and Oncophage; the significance of the consistency of the clinical findings with regards to the potential applicability of HSP technology to a multitude of cancers; and the potential of the company's products to provide cancer patients with improved therapies and quality of life. These statements are subject to risks and uncertainties that could cause actual results to differ materially from those projected in these forward-looking statements. These risks and uncertainties include, among others, that Antigenics may not be able to enroll sufficient numbers of patients in clinical trials to demonstrate statistically significant results; that Antigenics may be unable to obtain the regulatory approvals necessary to conduct additional clinical trials or to market Oncophage and AG-858, alone or in combination treatments; that budget constraints will limit or slow down Antigenics' development programs; that Antigenics may fail to adequately protect its intellectual property or is determined to infringe on the intellectual property of others; and the factors described in the company's periodic filings with the Securities and Exchange Commission. Please see the disclosure under the heading "Factors That May Impact Future Results" in the Management's Discussion and Analysis of Financial Condition and Results of Operations section of the Antigenics Quarterly Report on Form 10-Q for the quarter ending September 30, 2003, for a more complete discussion of these and other risk factors. Antigenics cautions investors not to place undue reliance on the forward-looking statements contained in this press release. These statements speak only as of the date of this document, and Antigenics undertakes no obligation to update or revise the statements. All forward-looking statements are expressly qualified in their entirety by this cautionary statement. Antigenics' business is subject to substantial risks and uncertainties, including those identified above. When evaluating Antigenics' business and securities, investors should give careful consideration to these risks and uncertainties.