Exhibit 99.1


 Antigenics Reports First Quarter 2004 Financial Results and Recent Highlights

    NEW YORK--(BUSINESS WIRE)--April 20, 2004--Antigenics Inc.
(NASDAQ: AGEN) reported results today for the quarter ended March 31,
2004. The company incurred a net loss attributable to common
stockholders of $17.4 million, or $0.41 per share, basic and diluted.
This is compared with a net loss attributable to common stockholders
in the first quarter of 2003 of $13.5 million, or $0.36 per share,
basic and diluted. Research and development costs were $11.1 million
in the first quarter of 2004, compared with $10.3 million for the same
period in 2003. The increased losses reflect the continued progress of
the company's clinical product candidates, including Oncophage(R)
(HSPPC-96), Antigenics' lead product candidate, and AG-858; costs
associated with the transition of the company's operations from its
Woburn facility to its Lexington facility; as well as the reduction in
revenue due to the anticipation of the sale of the company's
manufacturing rights for feline leukemia virus vaccine and due to
lower sales of QS-21 to our QS-21 licensees. Cash, cash equivalents
and short-term investments equaled $132 million on March 31, 2004.
    "With the sale of our feline leukemia vaccine manufacturing
business, the strengthening of our balance sheet and our move to the
new Lexington facility, we continue to focus our efforts toward making
Oncophage available to patients," said Garo H. Armen, PhD, chairman
and CEO of Antigenics.

    Recent Highlights

    --  In March 2004, Antigenics sold its manufacturing rights for
        feline leukemia virus vaccine to French veterinary
        pharmaceutical manufacturer Virbac S.A. (Paris: VIRB.PA) for
        $14.25 million in cash. The transaction is contingent upon
        United States Department of Agriculture (USDA) product
        licenses being transferred to Virbac S.A. within 90 days of
        closing.

    --  Antigenics initiated a Phase II trial of Oncophage in lung
        cancer, to be conducted at St. Thomas' Hospital in the United
        Kingdom.

    --  Two abstracts have been accepted for presentation at the
        upcoming American Society of Clinical Oncology annual meeting.

    --  Antigenics began a nationwide kidney cancer awareness campaign
        in conjunction with Olympic swimmer Mark Spitz and the Kidney
        Cancer Association.

    --  In February 2004, Antigenics raised approximately $54 million
        in a follow-on offering of common stock.

    --  Antigenics completed its move to a new manufacturing, research
        and development facility in Lexington, Massachusetts.

    Conference Call Information

    Antigenics executives, including Chairman and CEO Garo Armen,
Senior Vice President of Development Renu Gupta, MD, and Chief
Financial Officer Jeff Clark will host a conference call at 11:00 a.m.
ET today. To access the live call, dial 877.416.2362 (domestic) or
706.679.3850 (international); the access code is 6184241. The call
will also be webcast and will be accessible from the company's website
at www.antigenics.com/webcast/. A replay will be available
approximately two hours after the call through midnight ET on May 4,
2004. The replay number is 800.642.1687 (domestic) or 706.645.9291
(international), and the access code is 6184241. The replay will also
be available on the company's website approximately two hours after
the live call.

    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), a Phase II
liposomal chemotherapeutic; and AG-702/AG-707, a Phase I genital
herpes program. For more information about Antigenics, please visit
www.antigenics.com.

    This press release contains forward-looking statements, including
statements regarding the sale to Virbac and that Oncophage is a
later-stage product candidate. These statements are subject to risks
and uncertainties that could cause actual results to differ materially
from those projected in these forward-looking statements. The sale to
Virbac is subject to a condition relating to the successful transfer
of a USDA license and the proceeds from the sale are subject to
potential post-closing claims for indemnification. Risks and
uncertainties relating to commercialization of Oncophage and our other
product candidates include, among others, the results from ongoing
Phase III clinical trials; the need for and extent of additional
clinical trials; the need to resolve product characterization issues;
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 Annual Report on Form
10-K for the fiscal year ending December 31, 2003, for a more complete
discussion of these and other risk factors. 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.


              Summary Consolidated Financial Information

         Condensed Consolidated Statements of Operations Data
                 (in thousands, except per share data)
                              (unaudited)

                                                 Three months ended
                                                      March 31,
                                                 2004         2003
                                             ------------ ------------

Revenue                                             $447       $1,780

Operating expenses:
  Cost of sales                                      594          620
  Research and development                        11,139       10,316
  General and administrative                       6,294        4,887

                                             ------------ ------------
     Operating loss                              (17,580)     (14,043)

Other income, net                                    425          551

                                             ------------ ------------
     Net loss                                   $(17,155)    $(13,492)

Dividends on Series A Convertible Preferred
 Stock                                               198            -

                                             ------------ ------------
Net loss attributable to common stockholders    $(17,353)    $(13,492)
                                             ============ ============

Net loss per share, basic and diluted             $(0.41)      $(0.36)
Weighted average number of shares
 outstanding, basic and diluted                   42,778       37,575


               Condensed Consolidated Balance Sheet Data
                            (in thousands)
                              (unaudited)

                                               March 31,    Dec. 31,
                                                 2004         2003
                                             ------------ ------------

Cash, cash equivalents and short-term
 investments                                    $131,919      $89,478
Total assets                                     180,905      140,080
Total stockholders' equity                       142,015      105,246


    CONTACT: Antigenics Inc.
             Investor Relations:
             Jack Howarth, 212-994-8244
             jhowarth@antigenics.com
              or
             Corporate Communications:
             Sunny Uberoi, 212-994-8206
             suberoi@antigenics.com