EXHIBIT 99.2

undersigned Chief Executive Officer of Antigenics Inc. (the "Company"), hereby
certify that the Quarterly Report on Form 10-Q of the Company for the quarter
ended March 31, 2003 (the "Form 10-Q") fully complies with the requirements of
Section 13(a) or 15(d) of the Securities Exchange Act of 1934 and that
information contained in the Form 10-Q fairly presents, in all material
respects, the financial condition and results of operations of the Company.

                                        /s/ Garo H. Armen, Ph.D.
                                        ------------------------
                                        Garo H. Armen, Ph.D.
                                        Chairman and Chief Executive Officer

Date: May 15, 2003

A signed original of this written statement required by Section 906 has been
provided to Antigenics Inc. and will be retained by Antigenics Inc. and
furnished to the Securities and Exchange Commission or its staff upon request.