Antigenics Announces that Immunological Data from Phase II Melanoma and Colorectal Cancer Trials of Oncophage Cancer Vaccine Published in The Journal Of Immunology.

Business Editors/Health/Medical Writers

NEW YORK--(BUSINESS WIRE)--Oct. 1, 2003

Study Reveals Immune Response Mechanism in Clinical Setting

Antigenics Inc. (NASDAQ: AGEN), the world leader in heat shock protein technology, announced that immunological results from Phase II trials evaluating the company's personalized cancer vaccine Oncophage(R) (HSPPC-96) in the treatment of both advanced melanoma and colorectal cancer were published today in The Journal of Immunology. In the analysis, researchers observed a significant cancer-specific immune response among patients receiving Oncophage and determined that the immunological mechanism of action is the same for both melanoma and colorectal cancer.

"Earlier laboratory and clinical studies have shown that the heat shock protein found in Oncophage can present antigenic peptides to T cells and activate them," said Jonathan J. Lewis, MD, PhD, chief medical officer of Antigenics. "This study provides further support that this mechanism - considered to play a key function in immune responses to tumors and viruses - is occurring in the human body in response to Oncophage vaccination."

Researchers evaluated five patients from each trial for immune response to Oncophage vaccination. Approximately half of patients tested (three patients with melanoma, two patients with colorectal cancer) demonstrated cancer-specific immune responses, including an increased production of T cells that can specifically attack melanoma or colorectal cancer cells.

The study also included in vitro analysis to characterize the role of the heat shock protein used in Oncophage (gp96) in cancer-specific immunity. The immunological mechanism of action was observed to be identical in melanoma and colorectal cancer. These findings are consistent with earlier data from animal studies and provide additional evidence that the mechanism is conserved across species.

Derived from each individual's tumor, Oncophage contains the 'antigenic fingerprint' of the patient's particular cancer, and is designed to reprogram the body's immune system to target and destroy only cancer cells bearing this fingerprint. Oncophage is intended to leave healthy tissue unaffected and limit the debilitating side effects associated with traditional cancer treatments such as chemotherapy and radiation therapy. Oncophage has been granted fast track and orphan drug designations from the US Food and Drug Administration in both metastatic melanoma and renal cell carcinoma (the most common type of kidney cancer).

About Melanoma

According to the American Cancer Society, melanoma only accounts for about 4 percent of skin cancer cases, yet it causes about 79 percent of skin cancer deaths. It is estimated that in 2003, there will be 54,200 new cases of melanoma in the United States, and about 7,600 people will die of the disease. Current treatment options include surgical removal, radiation therapy, chemotherapy and immune therapy.

About Colorectal Cancer

Together, cancers of the colon and rectum are among the most common cancers in the United States. This year, it is estimated that there will be about 105,500 new cases of colon cancer and 42,000 new cases of rectal cancer, together causing more than 57,000 deaths. They occur in both men and women and are most often found among people who are over the age of 50. The three main types of treatment for colorectal cancer are surgery, radiation therapy and chemotherapy.

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-70X, a Phase I genital herpes immunotherapeutic. For more information about Antigenics, please visit www.antigenics.com.

This press release may be deemed to contain forward-looking statements, including statements about the potential of Oncophage as a therapy for melanoma and colorectal cancer. Such statements are subject to risks and uncertainties that could cause actual results to differ materially from those projected in the forward-looking statements. Risks and uncertainties associated with the product development and commercialization efforts of Antigenics include, among others, that clinical trials fail to demonstrate that products are both safe and more effective than current standards of care; failure to obtain the regulatory approvals necessary to conduct additional clinical trials or to market products; that budget constraints will limit or slow down development programs; failure to adequately protect intellectual property or infringement of the intellectual property of others; and the factors described in the company's periodic filings with the Securities and Exchange Commission. Please see Exhibit 99.1 of the Antigenics Quarterly Report on Form 10-Q for the quarter ending June 30, 2003, for a discussion of these and other risk factors. Antigenics cautions investors not to place undue reliance on any forward-looking information in this press release. Although the results from the Phase II trials indicate that, in some patients, Oncophage appears to stimulate a cancer-specific immune response, later trials may fail to duplicate these results. Phase II trials are not designed to establish efficacy of a product candidate. Significant additional trials and regulatory approvals would be required prior to commercializing Oncophage in patients with melanoma or colorectal cancer. The statements in this press release speak only as of the date of this document, and Antigenics undertakes no obligation to update or revise the statements.