Antigenics’ Oncophage Cancer Vaccine Receives European Orphan Drug Designation for Renal Cell Carcinoma

NEW YORK — June 7, 2005 — Antigenics Inc. (NASDAQ: AGEN) today announced that Oncophage^® (HSPPC-96), an investigational personalized cancer vaccine, has been granted orphan drug status for the treatment of renal cell carcinoma (RCC, the most common type of kidney cancer) by the European Medicines Agency (EMEA). This designation provides Antigenics with, among other benefits, 10 years of potential market exclusivity if the product is approved for marketing in the European Union (EU). The US Food and Drug Administration (FDA) previously granted orphan drug designation for Oncophage in RCC in May 2002.

“We are pleased with the EMEA’s decision to grant Oncophage orphan drug status for RCC,” stated Garo H. Armen, PhD, chairman and CEO of Antigenics. “In addition to the FDA’s earlier orphan drug designation and recent agreement to our proposed registration plan for Oncophage in RCC, the European designation reinforces our belief that Oncophage has the potential to become a worldwide treatment alternative for patients with this devastating disease.”

The EMEA regulation on orphan medicinal products is designed to encourage companies to develop and market treatments for rare, life threatening medical conditions that affect less than five people in every 10,000 in the EU. In addition to potential 10-year EU market exclusivity following marketing approval, orphan drug status provides regulatory assistance, reduced regulatory fees associated with applying for marketing approval, and protocol assistance.

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 only cancer cells bearing this fingerprint. Oncophage is intended to leave healthy tissue unaffected to virtually eliminate the serious side effects associated with traditional cancer treatments. Oncophage is currently in Phase 3 trials for RCC and metastatic melanoma, and has been granted FDA fast track and orphan drug designations in both indications.

About Renal Cell Carcinoma

Renal cell carcinoma is the most common type of kidney cancer, accounting for about 85 percent of all kidney tumors. The American Cancer Society estimates that there will be more than 36,100 new cases of kidney cancer in the United States this year, and that almost 13,000 people will die from the disease.

About Antigenics

Antigenics is working to develop personalized immunotherapeutics and revolutionary treatments for cancers and infectious diseases. The company’s lead product in development is Oncophage, a late-stage, personalized cancer vaccine being evaluated in several indications, including renal cell carcinoma and metastatic melanoma. Antigenics’ portfolio of investigational products also includes AG-858 (HSPPC-70), a personalized cancer vaccine in Phase 2 development; two Phase 2 liposomal cancer treatments, Aroplatin™ and ATRA-IV; and AG-702/AG-707, a Phase 1 genital herpes program.

This press release contains forward-looking statements, including statements regarding the impact of EMEA orphan drug designation, and the development, commercialization and commercial potential of Oncophage. 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 Oncophage may not be approved for sale in any market and, if approved, may not succeed commercially; that orphan drug status may not be maintained in the event of legislative changes or introduction of a more efficacious product in this disease category; 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 section of Antigenics’ Form 10-Q, filed May 10, 2005, for a more complete discussion of these and other risk factors. The grant of orphan designation by the EMEA does not assure rapid regulatory decision-making or approval. Antigenics cautions investors not to place considerable 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.