1 EXHIBIT 10.10 CONFIRMATORY SECOND AMENDMENT TO LEASE Reference is hereby made to a Lease dated June 21, 1988, as amended (the "Lease") by and between James H. Mitchell, Trustee of New Providence Realty Trust, as Lessor ("Lessor"), and ImmunoGen,...

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                                                                   EXHIBIT 10.10


                     CONFIRMATORY SECOND AMENDMENT TO LEASE

         Reference is hereby made to a Lease dated June 21, 1988, as amended
(the "Lease") by and between Xxxxx X. Xxxxxxxx, Trustee of New Providence Realty
Trust, as Lessor ("Lessor"), and ImmunoGen, Inc. as Lessee ("Lessee").

         Whereas Lessor and Lessee intend to make certain changes in the Lease,

         Now, therefore, in consideration of the mutual conditions and covenants
set forth herein, and for other good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties agree as follows:

         1.       The size of the Premises now consists of 27,650 square feet,
                  and all references thereto in the Lease shall be so amended.

         2.       The term of the Lease is hereby extended for the period
                  beginning July 1, 1997 and ending on June 30, 2000.

         3.       Lessee shall have the right to extend this Lease for one
                  3-year period by notifying Lessor in writing at least 120 days
                  before the Expiration Date of Lessee's election to extend the
                  Lease Term. The Extension Term shall commence immediately
                  after the original Expiration Date set forth in paragraph 2
                  herein. All other terms and conditions of the Lease shall
                  remain in full force and effect, except as provided herein.

         4.       The Yearly Fixed Base Rent during the term set forth in
                  paragraph 2 herein shall be $214,287.50, payable in monthly
                  installments of $17,857.29. The Yearly Fixed Base Rent during
                  the Extension Term shall be $248,850, payable in monthly
                  installments of $20,737.50.

         5.       Tenant's Pro-Rata share of Operating Costs and Real Estate
                  Taxes, subject to adjustment as provided in the Lease, shall
                  be paid monthly in advance together with Fixed Base Rent, as
                  follows:


                                                                  
                   Real Estate Taxes         $23,382.70/year            $2,115.22/month
                   Operating Costs           $21,152.25/year            $1,762.68/month


Executed as a sealed instrument this 17th day of September 1997.

LESSOR:  New Providence Realty Trust  LESSEE:  ImmunoGen, Inc.

By:  /s/Xxxxx X. Xxxxxxxx              By:  /s/Xxxxxxxx X.Xxxxxxx
   -------------------------------          ------------------------------------
     Xxxxx X. Xxxxxxxx, Trustee             Xxxxxxxx X. Xxxxxxx, Vice President
     and not individually                   Finance and Administration,
                                            duly authorized