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                                                                   EXHIBIT 10.27

                                   AGREEMENT
                                   ---------

     THIS AGREEMENT is dated as of June 15, 1998 between AUTOIMMUNE INC., a
Delaware corporation ("AutoImmune") and ANTIGENICS, LLC, a Delaware limited
liability company ("Antigenics").

                                  BACKGROUND
                                  ----------

     AutoImmune, as Sublandlord, and Antigenics, as Subtenant, entered into a
Sublease, effective as of November 1, 1997, for certain premises on the 400, 500
and 600 levels in the building known as Building B of One Ledgemont Center (the
"Subleased Premises") (the "Sublease"). Capitalized terms used herein shall have
the same meaning ascribed to them in the Sublease. AutoImmune and Antigenics
have consented to termination of the Sublease to ensure that Antigenics will
vacate the Subleased Premises by a date certain, subject to the terms and
provisions of this Agreement. Neither party acknowledges any default under the
terms of the Sublease.

     NOW, THEREFORE, AutoImmune and Antigenics hereby agree as follows:

          1. AutoImmune and Antigenics agree that the Sublease was terminated as
             of June 15, 1998. Subject to the terms and provisions of this
             Agreement, however, Antigenics may continue to occupy the Subleased
             Premises (except for the "Excluded 600 Level Space" [defined
             herein]) until
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             September 30, 1998 (the period commencing on June 16, 1998 and
             ending on September 30, 1998 shall be referred to herein as the
             "Contingent Occupancy Period"), subject to the provisions of
             Section 15. Antigenics' occupancy of the Subleased Premises (except
             for the Excluded 600 Level Space) during the Contingent Occupancy
             Period shall be subject to all of the terms and provisions of the
             Sublease, as modified by this Agreement; however, nothing in this
             Agreement shall be construed to create a new tenancy between
             AutoImmune and Antigenics.

          2. Except for one office located on the 600 level of the Subleased
             Premises, which office is shown on Exhibit A hereto as the
             "Occupied Office," Antigenics shall vacate all other portions of
             the 600 Level of the Subleased Premises effective as of the date
             hereof (such other portions of the 600 Level of the Subleased
             Premises shall be referred to herein as the "Excluded 600 Level
             Space") (As used hereinafter in this Agreement, the term "Subleased
             Premises" shall be deemed to mean the Subleased Premises prior to
             the date of this Agreement minus the Excluded 600 Level Space).
             Effective as of the date hereof, Antigenics shall have no right to
             use or access, nor allow other parties to use or access, any
             portion of the Excluded 600 Level Space. Antigenics shall have no
             right to deny AutoImmune, AutoImmune's tenants, Overlandlord or

                                      -2-
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             Overlandlord's tenants access to, nor shall Antigenics have the
             right to prevent any of such parties from using, all or any portion
             of the Excluded 600 Level Space.

          3. On the date hereof, Antigenics shall pay to AutoImmune the
             aggregate amount of Annual Rent, additional rent and other charges
             due under the Sublease (except for Level 600 for the period May 16,
             1998 through June 15, 1998) for the period beginning on April 1,
             1998 and ending on June 15, 1998, which the parties hereby
             stipulate is $119,153.10.

          4. Antigenics shall also pay to AutoImmune payments for use and
             occupancy (the "Occupancy Payments") for and on account of its
             occupancy of the Subleased Premises during the Contingent Occupancy
             Period. The Occupancy Payments for the Contingent Occupancy Period
             shall be payable at the rate of $33,413.85 per month. Antigenics
             shall pay the entire sum (i.e., $116,949.49) of all Occupancy
             Payments due for and during the Contingency Occupancy Period, in
             advance on the date hereof, subject to Sections 5 and 15 hereof.

          5. AutoImmune agrees to purchase from Antigenics the office furniture
             described in the Bill of Sale which is annexed as Exhibit B hereto,
             which furniture is currently located in the Subleased Premises, for
             the

                                      -3-
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             aggregate price of $27,942. Such amount shall be paid for by
             AutoImmune by providing Antigenics with a credit against the
             aggregate amount of Occupancy Payments due from Antigenics on the
             date hereof. The purchase of such furniture (the "Purchased
             Furniture") shall be effective as of the date hereof.
             Simultaneously with the execution of this Agreement by Antigenics,
             Antigenics shall execute and deliver to AutoImmune a Bill of Sale
             in the form of Exhibit B hereto. Antigenics shall permit AutoImmune
             to enter the Subleased Premises and remove certain of the Purchased
             Furniture within fifteen (15) days of receiving a prior written
             notice from AutoImmune, not to exceed five (5) items of any
             category in Exhibit B.

          6. Simultaneously herewith, AutoImmune and Antigenics shall execute an
             Agreement For Judgement in the form attached hereto as Exhibit C.
             Antigenics hereby authorizes AutoImmune to file such Agreement For
             Judgement in a Summary Process Action which AutoImmune shall
             promptly commence in the Commonwealth of Massachusetts, District
             Court Department of the Trial Court, Concord Division (the "Summary
             Process Action"). Antigenics hereby waives all notice and
             termination requirements under the Sublease. Antigenics agrees to
             accept service of the Summary Process Complaint at the Subleased
             Premises and hereby waives all claims for insufficient or
             inadequate service of process in such

                                      -4-
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             Summary Process Action. Antigenics waives all of its rights to
             appeal from the Judgement which shall be entered in the Summary
             Process Action in accordance with such Agreement for Judgement, and
             Antigenics will not object to the issuance of a Writ of Execution
             on such Judgement (the "Execution").

          7. As long as no "Eviction Default" (as defined in Section 9 of this
             Agreement) has occurred, AutoImmune agrees to forbear from
             enforcing the Execution. Subject to the prior sentence, AutoImmune
             will hold the Execution in escrow during the Contingent Occupancy
             Period.

          8. Antigenics shall vacate the Subleased Premises on or before the
             last day of the Contingent Occupancy Period and shall leave the
             same in the "yield up condition" (as defined in Section 5.1.9 of
             the Overlease and incorporated by reference into the Sublease)
             required of the Subtenant by the Sublease as of the expiration or
             sooner termination of the Sublease term. Without limiting the
             generality of the foregoing, Antigenics agrees to remove, or to
             arrange for the removal of, all of its personal property from the
             Subleased Premises on or before the last day of the Contingent
             Occupancy Period. Antigenics also agrees to remove, at Antigenics'
             sole cost and expense, on or before the last day of the Contingent
             Occupancy Period, that certain Lab Irradiator currently located on
             Level

                                      -5-
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             400 of the Subleased Premises (the "Irradiator") from the Subleased
             Premises. Antigenics shall repair any damage to the Subleased
             Premises caused by the removal of the Irradiator and any of its
             personal property. Antigenics specifically acknowledges and agrees
             that AutoImmune shall have no responsibility to remove the
             Irradiator from the Subleased Premises.

          9. Upon the occurrence of an Eviction Default as defined herein,
             AutoImmune shall have the right to enforce the Execution
             immediately and without further notice. The occurrence of any one
             or more of the following events shall constitute an "Eviction
             Default": (i) Antigenics fails to vacate the Subleased Premises on
             or before September 30, 1998 in accordance with the provisions of
             the Sublease and this Agreement; (ii) Antigenics fails to maintain
             the Subleased Premises in the condition required of the Subtenant
             under the Sublease; (iii) Antigenics fails to maintain the
             insurance required of the Subtenant under the Sublease; or (iv)
             Antigenics fails to abide by any of the provisions of this
             Agreement.

         10. In the event of a breach of this Agreement by a party, the
             breaching party shall pay all of the non-breaching party's legal
             fees and expenses incurred in enforcing the non-breaching party's
             rights under this Agreement.

                                      -6-
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         11. Any notice or other communication given pursuant to the provisions
             of this Agreement shall be deemed to have been given only if in
             writing and, only if hand-delivered or mailed by overnight mail via
             a nationally recognized overnight carrier that maintains receipts,
             if to AutoImmune in care of AutoImmune Inc., 128 Spring Street,
             Lexington, Massachusetts 02173, Attention: Heather Ellerkamp, and
             if to Antigenics at 630 Fifth Avenue, Suite 2170, New York, New
             York 10011, Attention: Garo Armen, with a copy to the Subleased
             Premises, except that service of process of Antigenics in
             connection with the Summary Process Action shall be only required
             to be made at the Subleased Premises, and Antigenics agrees to
             accept such service of process at the Subleased Premises.

         12. Antigenics agrees that the $25,231.50 Security Deposit under the
             Sublease shall be held by AutoImmune as a security deposit under
             this Agreement (the "Security Deposit"). The Security Deposit shall
             be held by AutoImmune in a non-interest bearing account, and shall
             serve to partially secure Antigenics' obligations under this
             Agreement. The Security Deposit may be applied, at AutoImmune's
             sole discretion, to fulfill any of Antigenics' obligations under
             this Agreement. In no event shall Antigenics have any right to
             direct AutoImmune how to apply the

                                      -7-
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             Security Deposit. Provided there is not then any breach of any
             undertaking of this Agreement by Antigenics, the Security Deposit
             (to the extent the same has not been previously utilized by
             AutoImmune as described herein) shall be returned to Antigenics
             within fifteen (15) days of the last day of the occupancy of the
             Subleased Premises by Antigenics.

         13. The parties to this Agreement hereby release, remise and forever
             discharge one another of and from all debts, demands, actions,
             causes of action, suits, accounts, covenants, contracts,
             agreements, damages and any and all claims, demands and liabilities
             whatsoever of every name and nature, both at law and in equity,
             arising out of or connected with or incidental to the Sublease and
             the Subleased Premises, whether known or unknown, contingent or
             uncontingent, from the beginning of the world to the date of this
             Agreement. Antigenics also releases, remises and forever discharges
             AutoImmune from all debts, demands, causes of action, suits,
             accounts, covenants, contracts, agreements, damages and any and all
             claims, demands and liabilities arising out of the institution by
             AutoImmune of the Summary Process Action and any actions taken by
             AutoImmune in connection therewith to the extent the same are
             authorized by this Agreement. Notwithstanding the generality of the

                                      -8-
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             foregoing, AutoImmune does not release Antigenics from its
             obligations pursuant to the Summary Process Action.

         14. This Agreement shall be binding upon and inure to the benefit of
             the parties hereto and their respective heirs, executors,
             administrators, successors and assigns.

         15. Notwithstanding the other terms and provisions of this Agreement,
             Antigenics, by written notice given to AutoImmune prior to August
             1, 1998, shall have the right to vacate the Subleased Premises in
             its entirety on or before August 31, 1998 (the "Pre-September 1,
             1998 Vacation"). In the event of a Pre-September 1, 1998 Vacation
             by Antigenics, AutoImmune shall pay to Antigenics $33,414.85 (i.e.,
             the Occupancy Payment for September of 1998) by September 20, 1998
             so long as each of the following events have occurred: (i)
             Antigenics is in full compliance with all its obligations under
             this Agreement as of September 1, 1998, including, without
             limitation, Antigenics' obligations to remove the Irradiator and
             all of its personal property from the Subleased Premises and to
             leave the Subleased Premises in the condition required by the
             Sublease upon the expiration or sooner termination of the Sublease
             term; and (ii) Antigenics provides notice to AutoImmune of the Pre-
             September 1, 1998 Vacation on or before August 1, 1998.

                                      -9-
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     WITNESS the execution hereof as an instrument under seal as of the day and
year first above written.



                              AUTOIMMUNE INC.


                              By: /s/ Robert C. Bishop
                                  ----------------------
                              Robert C. Bishop, CEO



                              ANTIGENICS, LLC


                              By: /s/ Garo Armen
                                  ----------------------
                              Garo Armen, President
 

                                      -10-
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                                   EXHIBIT A
                                   ---------

                   Plan Showing Occupied Office on 600 Level

                 [Map Depicting Occupied Office on 600 Level]
<PAGE>
 
                                   EXHIBIT B
                                   ---------

        Bill of Sale for Office Furniture Purchased by AutoImmune Inc.
<PAGE>
 
                                   EXHIBIT B
                                   ---------

                                 BILL OF SALE
                                 ------------

     ANTIGENICS, LLC, in consideration of the total sum of $27,942.00 to it paid
by AUTOIMMUNE INC., the receipt whereof is hereby acknowledged, does hereby
grant, bargain and sell to AUTOIMMUNE INC., its successors and assigns, the
items of personal property listed on Schedule B-1 attached hereto.

     To have and to hold all and singular the personal property to the said
AUTOIMMUNE INC., its successors and assigns, to their own use, forever.

     And ANTIGENICS, LLC, hereby covenants that it is the lawful owner of such
personal property; that such personal property is free from all encumbrances;
that it has the right to sell the same as aforesaid; and that it will warrant
and defend the same against the lawful claims and demands of all persons.

     IN WITNESS WHEREOF, ANTIGENICS, LLC has executed this Bill of Sale on this
____ day of July, 1998.


                                        ANTIGENICS, LLC

                                        By: __________________________
                                           Its

STATE OF ____________________         )
                                      ) SS
COUNTY OF _____________               )

 
     On this ____ day of July 1998, before me appeared _______________________
me known, who being duly sworn, did depose and say that they are the___________
_________________________________ of ANTIGENICS, LLC, the limited liability
company named in and which executed the foregoing instrument, that said
instrument was signed by them on behalf of said limited liability company and
they acknowledged said instrument to be the free act and deed of said limited
liability company.

                                     ____________________________
                                       Notary Public

                                     Commission Expires: _________________
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                            [Office Equipment List]
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                                   EXHIBIT C
                                   ---------

                            Agreement for Judgment

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                                   EXHIBIT C
                                   ---------

                         COMMONWEALTH OF MASSACHUSETTS

MIDDLESEX, ss.                                      CONCORD DISTRICT COURT
                                                           SUMMARY PROCESS

                                        CIVIL ACTION NO.______

AUTOIMMUNE INC.               )
                              )
                              )
        Plaintiff,            )
                              )
v.                            )                     AGREEMENT FOR JUDGMENT
                              )                     ----------------------
ANTIGENICS, LLC               )
                              )
        Defendant.            )
                              )

        Plaintiff AutoImmune Inc., and defendant Antigenics, LLC hereby
stipulate and agree that: (a) Judgment for the plaintiff AutoImmune Inc. for
possession shall enter this day; (b) because neither party admits any fault, no
award of damages or costs shall be entered for either party; and (c) the parties
having waived all rights of appeal, execution shall issue forthwith.

AUTOIMMUNE INC.                               ANTIGENICS, LLC

By its Attorneys:                             By:


_____________________________                 __________________________
Timothy M. Smith, Esq. (BBO#550397)
David L. Ferrera, Esq. (BBO#631183)
NUTTER, McCLENNEN & FISH, LLP
One International Place
Boston, MA 02110-2699
(617) 439-2000

Dated:  ________, 1998                                Dated:  _________, 1998