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                                                                     EXHIBIT 4.1

                        RIGHT OF FIRST REFUSAL AGREEMENT

      This Right of First Refusal Agreement (this "Agreement"), dated as of May
21, 2004, is between Antigenics Inc. , a Delaware corporation (the "Company"),
and Brad M. Kelley (the "Purchaser").

                                    RECITALS

      WHEREAS, on September 24, 2003, the Purchaser purchased shares of the
Company's Series A Convertible Preferred Stock (the "Preferred Stock");

      WHEREAS, the Company and the Purchaser desire to establish in this
Agreement certain conditions of the relationship with the Company of the
Purchaser and their Affiliates and Associates; and

      WHEREAS, the Company and the Purchaser desire to limit the applicability
of this Agreement to the Preferred Stock and the securities issued upon
conversion of the Preferred Stock, including any securities issued in exchange
therefore, in substitution thereof, or with respect thereto (the "Conversion
Shares").

                                    AGREEMENT

      NOW, THEREFORE, in consideration of the mutual covenants and agreements
contained herein and other good and valuable considerations, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto agree as
follows:

      1.    DEFINITIONS.

      As used in this Agreement, the following terms shall have the meanings set
forth below:

      "Action" means any claim, action, cause of action or suit (whether in
contract or tort or otherwise), litigation (whether at law or in equity, whether
civil or criminal), controversy, assessment, arbitration, investigation,
hearing, charge, complaint, demand, notice or proceeding to, from, by or before
any United States federal, state or local or any foreign government, or
political subdivision thereof, or any multinational organization or authority or
any authority, agency or commission entitled to exercise any administrative,
executive, judicial, legislative, police, regulatory or taxing authority or
power, any court or tribunal (or any department, bureau or division thereof), or
any arbitrator or arbitral body.

      "Affiliate" shall have the meaning given it in Rule 12b-2 under the
Exchange Act.

      "Agreement" shall have the meaning set forth in the preamble.

      "Associate" shall have the meaning given it in Rule 12b-2 under the
Exchange Act.

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      "Beneficial Owner" shall have the meaning given it in Rule 13(d)(3) under
the Exchange Act; and "Beneficially Own" and "Beneficial Ownership" shall apply
to securities held by a Beneficial Owner of such securities.

      "Change of Control" shall mean (1) the acquisition by a Third Party of
more than 50% of the Company's then outstanding Voting Securities, excluding
however, the acquisition by an underwriter or group of underwriters pursuant to
an Underwriting Agreement (or similar agreement) in a registered public offering
to the public; (2) the consummation of a merger, acquisition, consolidation or
reorganization or series of such related transactions involving the Company,
unless both (x) immediately after such transaction or transactions, the
Beneficial Owners of the Company immediately prior to such transaction shall
Beneficially Own at least 50% of the outstanding Voting Securities of the
Company (or, if the Company shall not be the surviving company in such merger,
consolidation or reorganization, the Voting Securities of the surviving
corporation issued in such transaction in respect of Voting Securities of the
Company shall represent at least 50% of the Voting Securities of such surviving
company), and (y) the Company is not subject to an agreement that provides that
individuals who are directors of the Company immediately prior to such
transaction (or individuals designated by the Company at or before the closing
of such transaction) shall constitute less than a majority of the directors of
the Company (or such surviving company, as the case may be) after the closing of
such transaction; (3) a change or changes in the membership of the Company's
Board of Directors which represents a change of a majority or more of such
membership during any twelve month period (unless such change or changes in
membership are caused by the actions of the then-existing Board of Directors);
(4) an Insolvency Proceeding (as defined below); or (5) the consummation of a
sale of all or substantially all of the Company's assets unless, immediately
after such transaction, the Beneficial Owners of the Company immediately prior
to such transaction shall Beneficially Own at least 50% of the Voting Securities
of the acquiring company.

      "Company's Notice" shall have the meaning set forth in Section 3.1.

      "Conversion Shares" shall have the meaning set forth in the preamble.

      "Exchange Act" shall mean the Securities Exchange Act of 1934, as amended.

      "Group" shall mean two or more persons acting as a partnership, limited
partnership, limited liability company, syndicate or other group for the
purposes of acquiring, holding, or disposing of securities or material assets of
an issuer.

      "Insolvency Proceeding" shall mean (1) an assignment by the Company for
the benefit of creditors, (2) the filing by the Company of a petition to have
the Company adjudged insolvent, bankrupt or which seeks a reorganization or
liquidation under any law relating to bankruptcy, insolvency or receivership,
(3) an appointment of a receiver or trustee for all or substantially all of the
assets of the Company, unless appointed without the Company's consent, and such
appointment has not been vacated or stayed after 60 days or (4) a public
admission in writing of the Company's inability to pay its debts as they come
due.

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      "Majority In Interest" means the Purchaser (and his transferees pursuant
to Section 3.1.6(d) and Section 3.1.6(g)) holding more than 50% of the Voting
Power of the shares of Preferred Stock and the Conversion Shares that remain
subject to the restrictions in this Agreement, taken together.

      "Offer Price" shall have the meaning set forth in Section 3.1.

      "Offered Shares" shall have the meaning set forth in Section 3.1.

      "Person" shall mean an individual, corporation, partnership, association,
trust, unincorporated organization or other entity.

      "Purchaser's Notice" shall have the meaning set forth in Section 3.1.

      "Preferred Stock" shall have the meaning set forth in the preamble.

      "Purchaser" shall have the meaning set forth in the preamble.

      "Reduced Transfer Price" shall have the meaning set forth in Section 3.1.

      "Reduced Transfer Price Notice" shall have the meaning set forth in
Section 3.1.

      "Restricted Securities" shall have the meaning set forth in Section 3.4.1.

      "Securities Act" shall mean the Securities Act of 1933, as amended.

      "SEC" means the Securities and Exchange Commission.

      "Third Party" shall mean any Person (other than the Purchaser and his
Affiliates and Associates) or Group (other than any Group that includes the
Purchaser or his Affiliates or Associates).

      "Total Voting Power" at any date, with respect to any Person, shall mean
the total combined Voting Power of all the Voting Securities of such Person then
outstanding and entitled to vote.

      "Transfer" shall have the meaning set forth in Section 3.1.

      "Voting Power" with respect to any Voting Securities of any Person on any
date shall mean the voting power in the general election of directors of the
relevant Person to which such Voting Securities would be entitled on such date.

      "Voting Securities" of any Person shall mean any securities entitled to
vote generally in the election of directors of such Person, or any direct or
indirect rights or options or warrants to acquire any such securities or any
securities (including, without limitation, the Preferred Stock) convertible or
exercisable into or exchangeable for such securities, whether or not such
securities are so convertible, exercisable or exchangeable at the time of
determination.

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      2.    TERM AND SUSPENSION OF RESTRICTIONS.

            2.1.  Term. The term (the "Term") of this Agreement shall commence
      on the date hereof and shall continue until the earlier to occur of the
      following:

                  (a)   a Change of Control of the Company or

                  (b)   the date on which the Voting Power of the Voting
            Securities of the Company Beneficially Owned by the Purchaser and
            all Affiliates and Associates of the Purchaser represents less than
            five percent (5%) of the Total Voting Power of the Company,
            assuming, for purposes of this calculation, conversion of all
            outstanding Preferred Stock or

                  (c)   the date which is the four (4) year anniversary of the
            date of the purchase of the Preferred Stock.

            2.2.  Suspension of Restrictions. The limitations provided in
      Section 3 shall immediately be suspended upon the occurrence of any of the
      following events:

                  (a)   on the 10th business day (as such term is defined in
            Rule 14d-1 under the Exchange Act) following the commencement by any
            Third Party of a tender or exchange offer seeking to acquire
            Beneficial Ownership of 50% or more of the outstanding shares of
            Voting Securities of the Company, but only if the Company has, on or
            prior to such date, publicly recommended that such offer be
            accepted;

                  (b)   the execution of a definitive agreement which, if
            consummated, would result in a Change of Control of the Company;

                  (c)   the 15th day following the filing of a preliminary
            proxy statement by any Third Party with respect to the commencement
            of a bona fide proxy or consent solicitation subject to Section 14
            of the Exchange Act to elect or remove a majority of the directors
            of the Company that is not publicly opposed by the Company's Board
            of Directors and which, if successful, would result in a change in
            the composition of a majority of the Board of Directors of the
            Company; or

                  (d)   the adoption by the Board of Directors of a plan of
            liquidation or dissolution.

            The Company shall provide the Purchaser with prompt written notice
            of the occurrence of any of the events set forth in this Section
            2.2. Upon any (i) withdrawal or lapsing of any such tender or
            exchange offer referred to in Section 2.2(a) in which such Third
            Party does not acquire more than 50% of the outstanding Voting
            Securities of the Company, (ii) the termination of the agreement
            referred in Section 2.2(b) without consummation thereof, (iii) the
            withdrawal or termination or failure of the solicitation referred to
            in Section 2.2(c) or (iv) the termination of the plan of liquidation
            referenced in Section 2.2(d), as

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            the case may be, the limitations provided in Section 3 (except to
            the extent then suspended as a result of any other event specified
            in this Section 2.2) shall again be applicable for so long as and
            only to the extent provided in this Agreement.

            2.3.  Applicability. The restrictions in Section 3 of this Agreement
      apply only to the Conversion Shares and do not apply to any of Purchaser's
      other holdings of Common Stock of the Company.

            2.4.  Ownership of Company Voting Securities. On the date hereof,
      the Purchaser represents that, to the best of his knowledge, neither the
      Purchaser nor any of his Affiliates or Associates Beneficially Owns any
      Voting Securities of the Company, except as set forth on Schedule 2.4.

      3.    TRANSFER RESTRICTIONS.

            3.1.  Right of First Refusal.

                  3.1.1 If the Purchaser desires to, directly or indirectly,
            sell, assign, grant, loan, gift, put, call, make any short sale of,
            pledge or hypothecate, or grant other similar rights with respect to
            or otherwise transfer or dispose of (each a "Transfer") any
            Conversion Shares other than pursuant to an Exempted Transfer, he
            shall provide written notice (a "Purchaser's Notice") to the Company
            (a) stating that he desires to make such Transfer, and (b) setting
            forth the number of Conversion Shares proposed to be transferred
            (the "Offered Shares"), the cash price per share that he proposes to
            be paid for such Offered Shares (the "Offer Price"), and the other
            material terms and conditions of such Transfer. A Purchaser's Notice
            shall constitute an irrevocable offer by the Purchaser to sell to
            the Company the Offered Shares at the Offer Price in cash.

                  3.1.2 Within ten days after receipt of a Purchaser's Notice
            from the Purchaser, the Company may elect to purchase all (but not
            less than all) of the Offered Shares at the Offer Price in cash by
            delivery of a notice ("Company's Notice") to the Purchaser stating
            the Company's irrevocable acceptance of the Offer.

                  3.1.3 If the Company fails to elect to purchase all of the
            Offered Shares within the time period specified in Section 3.1.2,
            the Purchaser may, within a period of 90 days following the
            expiration of the time period specified in Section 3.1.2, Transfer
            all or any Offered Shares for cash; provided, that if the purchase
            price per share to be paid by any purchaser of the Offered Shares is
            less than 95% of the Offer Price (the "Reduced Transfer Price"), the
            Purchaser shall promptly provide written notice (the "Reduced
            Transfer Price Notice") to the Company of such intended Transfer
            (including the material terms and conditions thereof) and the
            Company shall have the right, exercisable by delivery of a written
            election notice to the Purchaser within ten days of receipt of such
            notice, to purchase such Offered Shares at the Reduced Transfer
            Price.

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                  3.1.4 If the Company fails to elect to purchase the Offered
            Shares at the Offer Price (or, if applicable, the Reduced Transfer
            Price) within the relevant time period specified in Section 3.1.2
            (or, if applicable, Section 3.1.3) and the Purchaser shall not have
            transferred or entered into an agreement to transfer the Offered
            Shares prior to the expiration of the 90 day period specified in
            Section 3.1.3, the right of the first refusal under this Section 3.1
            shall again apply in connection with any subsequent Transfer of such
            Offered Shares.

                  3.1.5 Any purchase of Offered Shares by the Company pursuant
            to this Section 3.1 shall be on a mutually determined closing date
            that shall be not less than 30 days nor more than 60 days after the
            last Purchaser's Notice or Reduced Transfer Price Notice is given
            with respect to such purchase. The closing shall be held at 10:00
            A.M., local time, at the principal executive office of the Company,
            or at such other time or place as the parties mutually agree. On the
            closing date, the Purchaser shall deliver (a) certificates
            representing the Offered Shares being sold, free and clear of any
            lien and (b) such other documents, including evidence of ownership
            and authority, as the Company may reasonably request. The purchase
            price shall be paid by wire transfer of immediately available funds
            no later than 2:00 P.M. on the closing date.

                  3.1.6 An "Exempted Transfer" means

                  (a)   A Transfer to the Company;

                  (b)   A Transfer pursuant to a merger, consolidation or other
            business combination involving the Company that has been approved by
            the Board of Directors of the Company;

                  (c)   A Transfer to any Person or Group, if such Transfer is
            approved by the Board of Directors of the Company in writing in
            advance;

                  (d)   A Transfer to an Affiliate of such Purchaser, provided
            that such Affiliate (i) agrees to be bound by the terms and
            conditions of this Agreement applicable to the Purchaser in a
            written instrument acceptable to the Company (it being understood
            that any transferee of Conversion Shares pursuant to this clause (d)
            or clause (g) below shall not be permitted to transfer such
            Conversion Shares pursuant to the terms of this clause (d) other
            than to the Purchaser or an Affiliate of the Purchaser) and (ii)
            agrees to transfer promptly to the Purchaser any Conversion Shares
            so Transferred to such Affiliate if the Affiliate ceases to be an
            Affiliate of the Purchaser;

                  (e)   A sale pursuant to a firm commitment, underwritten
            public offering of securities registered under the Securities Act;

                  (f)   An open market sale to the public pursuant to Rule 144
            under the Securities Act that complies with the manner of sale
            provisions under paragraph (f) of Rule 144; or

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                  (g)   A private Transfer exempt from the registration
            requirements under the Securities Act; provided, however, that (i)
            such transferee shall agree to be bound by the terms and conditions
            of this Agreement applicable to the Purchaser in a written
            instrument acceptable to the Company and (ii) such Transfer is not
            made to: (A) any Person or Group which has theretofore filed a
            Schedule 13D with the SEC with respect to any class of "equity
            security" (as defined in Rule 3a11-1 under the Exchange Act) of the
            Company and which, at the time of such sale, continues to reflect
            Beneficial Ownership in excess of five percent (5%) of the Total
            Voting Power of the Company; (B) any Person or Group which, after
            giving effect to the sale and to the knowledge of such Purchaser
            (after reasonable investigation), will Beneficially Own Voting
            Securities that reflect in excess of five percent (5%) of the Total
            Voting Power of the Company or to the knowledge of such Purchaser
            (after reasonable investigation) be accumulating stock on behalf of
            or acting in concert with any such Person or Group or a Person or
            Group contemplated by clause (A) above, or (C) any Person or Group
            that has announced or commenced an unsolicited offer for any Voting
            Securities of the Company or publicly initiated, proposed or
            otherwise solicited Company stockholders for the approval of one or
            more stockholder proposals with respect to the Company or publicly
            made, or in any way participated in, any "solicitation" of "proxies"
            (as such terms are defined in Rule 14a-1 under the Exchange Act)
            with respect to any Voting Securities of the Company.

            3.2.  Procedures for Certain Transfers. Prior to any proposed
      transfer of any Conversion Shares pursuant to Section.3.1.6, the Purchaser
      shall provide written notice to the Company of the Purchaser's intention
      to effect such transfer. Each such notice shall describe the manner and
      circumstances of the proposed transfer in sufficient detail, and, an
      explanation of how the transfer complies with any restrictive legends on
      the certificates evidencing such Conversion Shares.

            3.3.  Impermissible Transfers. Any Transfer in contravention of the
      provisions of Section 3.1 shall be null and void, and the Company shall
      have no obligation in any way to give effect to any such impermissible
      Transfer.

            3.4.  Legends.

                  3.4.1 Required Legends. The certificate or certificates
            representing (a) any Preferred Stock, (b) any Conversion Shares and
            (c) any securities issued in respect of the foregoing as a result of
            any stock split, stock dividend, recapitalization, or similar
            transaction (such securities identified in clauses (a), (b) and (c),
            collectively, the "Restricted Securities"), shall be stamped or
            otherwise imprinted with a legend substantially in the following
            form (in addition to any legends required pursuant to the
            Certificate of Designations of the Preferred Stock, any other
            agreement between the parties hereto or the laws of any applicable
            jurisdiction):

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                  THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO
                  CERTAIN OBLIGATIONS CONTAINED IN A RIGHT OF FIRST REFUSAL
                  AGREEMENT DATED AS OF MAY 21, 2004, A COPY OF WHICH IS
                  AVAILABLE FOR INSPECTION AT THE PRINCIPAL EXECUTIVE OFFICES OF
                  THE ISSUER HEREOF.

                  3.4.2 Removal of Legends. Upon the expiration of the Term, or
            such earlier time as the restrictions imposed by this Agreement
            cease to apply to any Restricted Securities as result of a Transfer
            permitted by Section 3.1, which does not require the transferee to
            be bound by the terms hereof, the holder of such Restricted
            Securities shall be entitled to receive from the Company, without
            expense, a replacement certificate evidencing such Restricted
            Securities which does not bear the legend set forth above.

      4.    MISCELLANEOUS.

            4.1.  Notices. All notices, requests, demands, claims and other
      communications required or permitted to be delivered, given or otherwise
      provided under this Agreement must be in writing and must be delivered,
      given or otherwise provided:

                  (a)   by hand (in which case, it will be effective upon
            delivery);

                  (b)   by facsimile (in which case, it will be effective upon
            receipt of confirmation of good transmission); or

                  (c)   by overnight delivery by a nationally recognized courier
            service (in which case, it will be effective on the next weekday,
            not including any weekday on which banks in New York, New York are
            authorized or required to be closed, after being deposited with such
            courier service);

      in each case, to the address (or facsimile number) listed below:

                  If to the Company, to it at:

                  630 5th Avenue
                  Suite 2100

                  New York, NY  10111

                  Telephone number: (212) 994-8200
                  Facsimile number: (212) 332-4778
                  Attention:        Chief Executive Officer

                  If to the Purchaser, to him at:

                  P.O. Box 1355
                  Boca Grande, FL 33921
                  Telephone number: 941-964-0790

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                  Facsimile number: 941-964-0951
                  Attention:        Brad Kelley

                  With a copy to:

                  Greg A. Betterton, Esq.
                  981 Ridgewood Avenue, #101
                  Venice, FL 34285
                  Telephone number: 941-488-4422
                  Facsimile number: 941-483-4992

            Each of the parties to this Agreement may specify a different
            address or telecopy number by giving notice in accordance with this
            Section 4.1 to each of the other parties hereto.

            4.2.  Succession and Assignment; No Third-Party Beneficiary. Subject
      to Section 4.2.1 and 4.2.2, this Agreement shall be binding upon and inure
      to the benefit of the parties hereto and their respective successors and
      permitted assigns, each of which such successors and permitted assigns
      shall be deemed to be a party hereto for all purposes hereof. Except as
      expressly provided herein, this Agreement is for the sole benefit of the
      parties and their permitted successors and assignees and nothing herein
      expressed or implied shall give or be construed to give any Person, other
      than the parties and such successors and assignees, any legal or equitable
      rights hereunder.

                  4.2.1 The Purchaser may not assign, delegate or otherwise
            transfer either this Agreement or any of its rights, interests, or
            obligations hereunder without the prior written approval of the
            Company; provided, however, that this Section 4.2.1 shall not limit
            the Purchaser's ability to Transfer Voting Securities in accordance
            with Section 3.1 (provided that, notwithstanding any such Transfer,
            the Purchaser shall continue to be bound by its obligations under
            this Agreement). The terms and provisions of this Agreement shall
            not be binding upon any transferee of the Purchaser that purchases
            any securities subject to this Agreement without violation of any
            provision of this Agreement, except for an Affiliate of the
            Purchaser that acquires any such securities pursuant to Section
            3.1.6(d) and any Person that acquires any such securities pursuant
            to Section 3.1.6(g).

                  4.2.2 The Company may not assign, delegate or otherwise
            transfer either this Agreement or any of its rights, interests, or
            obligations hereunder without the prior written approval of a
            Majority in Interest, except that the Company may assign all or part
            of this Agreement and its rights, interests and obligations
            hereunder to the successor or an assignee of substantially all of
            the Company's business without such prior written approval.

            4.3.  Amendments and Waivers. No amendment or waiver of any
      provision of this Agreement shall be valid and binding unless the same
      shall be in writing and signed, (a) in the case of an amendment, by the
      Company and a Majority in Interest, (b) in the case of a waiver that is to
      be effective against the Company, by the

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      Company or (c) in the case of a waiver that is to be effective against the
      Purchasers, by a Majority in Interest. No waiver by any party of any
      breach of any provision hereunder, whether intentional or not, shall be
      deemed to extend to any prior or subsequent breach of any such provision
      hereunder or affect in any way any rights arising by virtue of any prior
      or subsequent such occurrence. No delay or omission on the part of any
      party in exercising any right, power or remedy under this Agreement shall
      operate as a waiver thereof.

            4.4.  Entire Agreement. This Agreement constitutes the entire
      agreement among the parties hereto with respect to the subject matter
      hereof and supersedes any and all prior discussions, negotiations,
      proposals, undertakings, understandings and agreements, whether written or
      oral, with respect thereto.

            4.5.  Counterparts. This Agreement may be executed in any number of
      counterparts, each of which shall be deemed an original, but all of which
      together shall constitute but one and the same instrument. This Agreement
      shall become effective when each party hereto shall have received
      counterparts hereof signed by the other parties hereto.

            4.6.  Severability. Any term or provision of this Agreement that is
      invalid or unenforceable in any situation in any jurisdiction shall not
      affect the validity or enforceability of the remaining terms and
      provisions hereof or the validity or enforceability of the offending term
      or provision in any other situation or in any other jurisdiction. In the
      event that any provision hereof would, under applicable law, be invalid or
      unenforceable in any respect, each party hereto intends that such
      provision shall be construed by modifying or limiting it so as to be valid
      and enforceable to the maximum extent compatible with, and possible under,
      applicable law.

            4.7.  Headings. The headings contained in this Agreement are for
      convenience purposes only and shall not in any way affect the meaning or
      interpretation hereof.

            4.8.  Construction.

                  4.8.1 The parties have participated jointly in the negotiation
            and drafting of this Agreement. In the event an ambiguity or
            question of intent or interpretation arises, this Agreement shall be
            construed as if drafted jointly by the parties and no presumption or
            burden of proof shall arise favoring or disfavoring any party by
            virtue of the authorship of any of the provisions of this Agreement.
            The parties intend that each provision contained herein shall have
            independent significance. If any party has breached any provision
            contained herein in any respect, the fact that there exists another
            provision relating to the same subject matter (regardless of the
            relative levels of specificity) which the party has not breached
            shall not detract from or mitigate the fact that the party is in
            breach of the first provision.

                  4.8.2 Each reference in this Agreement to the Securities Act,
            the Exchange Act, provisions thereof and rules promulgated
            thereunder shall be

                                      -10-

<PAGE>

            construed as a reference to such act, provision or rule as such may
            be amended or modified from time to time; provided, however, that in
            the event that any provision of or rule promulgated under the
            Securities Act or the Exchange Act is replaced with a new provision
            or rule, the reference in this Agreement shall be deemed to be a
            reference to such successor provision or rule.

            4.9.  Governing Law. This Agreement, the rights of the parties and
      all Actions arising in whole or in part under or in connection herewith
      shall be governed by and construed in accordance with the domestic
      substantive laws of the State of Delaware, without giving effect to any
      choice or conflict of law provision or rule that would cause the
      application of the laws of any other jurisdiction.

            4.10. Specific Performance. Each of the parties acknowledges and
      agrees that the other parties would be damaged irreparably in the event
      any of the provisions of this Agreement are not performed in accordance
      with their specific terms or otherwise are breached. Accordingly, each of
      the parties agrees that, without posting bond or other undertaking, the
      other parties shall be entitled to an injunction or injunctions to prevent
      breaches of the provisions of this Agreement and to enforce specifically
      this Agreement and the terms and provisions hereof in any Action
      instituted in any court of the United States or any state thereof having
      jurisdiction over the parties and the matter in addition to any other
      remedy to which it may be entitled, at law or in equity. Each party
      further agrees that, in the event of any action for specific performance
      in respect of such breach, it shall not assert the defense that a remedy
      at law would be adequate.

            4.11. Confidentiality. The Purchaser agrees to maintain the
      confidentiality of any nonpublic information provided to it by the Company
      pursuant to Section 2.2 of this Agreement until such time such information
      is publicly disclosed.

                     [REMAINDER OF PAGE INTENTIONALLY BLANK]

                                      -11-

<PAGE>

                                                Right of First Refusal Agreement


      IN WITNESS WHEREOF, each of the undersigned has executed this Agreement as
an agreement under seal as of the date first above written.

The Company:                     ANTIGENICS INC.

                                 By: /s/ Garo H. Armen
                                     ______________________________________
                                     Name:  Garo H. Armen
                                     Title: Chief Executive Officer

The Purchaser:                   BRAD M. KELLEY

                                 By: /s/ Brad M. Kelley
                                     ______________________________________

                                     Name: Brad M. Kelley