Exhibit 4.1

                                 ANTIGENICS INC.

                               AMENDMENT NO. 1 TO
                           1999 EQUITY INCENTIVE PLAN


     Pursuant to Section 10(d) of the Antigenics Inc. 1999 Equity Incentive Plan
(the "Plan"), the Plan is hereby amended as follows:

     1.   Section 5(a) of the Plan is hereby amended and restated in its
entirety to read as follows:

          "(a) Subject to adjustment under subsection (b), Awards may be made
     under the Plan for up to 6,000,000 shares of Common Stock. If any Award in
     respect of shares of Common Stock expires or is terminated unexercised or
     is forfeited without the Participant having had the benefits of ownership
     (other than voting rights), the shares subject to such Award, to the extent
     of such expiration, termination or forfeiture, shall again be available for
     award under the Plan. Common Stock issued through the assumption or
     substitution of outstanding grants from an acquired company shall not
     reduce the shares available for Awards under the Plan. Shares issued under
     the Plan may consist in whole or in part of authorized but unissued shares
     or treasury shares."

     IN WITNESS WHEREOF, Antigenics Inc. has caused this instrument of amendment
to be executed by its duly authorized officer as of the 11th day of June, 2003.


                                        ANTIGENICS INC.


                                            /s/ Garo H. Armen, Ph.D.
                                        By:________________________________
                                           Name:  Garo H. Armen, Ph.D.
                                           Title: Chief Executive Officer