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                                                                 EXHIBIT 10.28


                            FIRST AMENDMENT TO LEASE

         THE FIRST AMENDMENT TO LEASE (this "FIRST AMENDMENT") is made as of the
17th day of November, 1998, by and between BIOLEASE, INC., a Massachusetts
corporation ("Landlord") and BIOTRANSPLANT INCORPORATED, a Delaware corporation
"TENANT").

         WHEREAS, Landlord and Tenant have entered into that certain Lease dated
March 17, 1994 (the "LEASE"), with respect to that building in the so-called
Charlestown Navy Yard section of the City of Boston known as Building 75 (the
"BUILDING") located at Third Avenue; and

         WHEREAS, Landlord and Tenant now desire to amend the Lease as
hereinafter provided;

         NOW, THEREFORE, in consideration of the foregoing and the mutual
covenants contained herein and other good and valuable consideration, the
receipt and sufficiency of which is hereby acknowledged, Landlord and Tenant
hereby agree as follows:

         1.  SECTION 1.1 of the Lease is hereby amended as follows:

         (a) The definition of "Original Term" is hereby deleted in its entirety
and the following inserted in its place:

             Original
             Term: Commencing on October 5, 1994 (the "COMMENCEMENT DATE") and
                   expiring as of October 31, 2009.

         (b) The definition of "Annual Fixed Rent" is hereby deleted in its
entirety and the following inserted in its place:

                  Annual
                  Fixed
                  Rent:    (i) For the period commencing on the Commencement
                           Date and ending on the day preceding the date hereof,
                           One Million Thirteen Thousand Four Hundred
                           Sixty-Three and 96/100 Dollars ($1,013,463.96) per
                           annum, Eighty Four Thousand Four Hundred Fifty-Five
                           and 33/100 Dollars ($84,455.33) per month;

                           (ii) For the period commencing on the date hereof and
                           ending on the date preceding the fifth anniversary of
                           the Commencement Date, One Million Twenty Thousand
                           and 00/100 Dollars ($1,020,000.00) per annum, Eighty
                           Five Thousand and 00/100 Dollars ($85,000.00) per
                           month.

                           (iii) For the period commencing on the fifth
                           anniversary of the Commencement Date and ending on
                           October 31, 2009, One Million Twenty-Five Thousand
                           and 00/100 Dollars ($1,025,000.00) per annum,


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                           Eighty Five Thousand Four Hundred Sixteen and 67/100
                           Dollars ($85,416.67) per month.

         2. SECTION 2.1 of the Lease is hereby amended by adding the following
sentence at the end of the first paragraph thereof:

                           Landlord and Tenant agree that the Building shall be
                           deemed to contain 29,000 square feet of rentable area
                           from and after [_______ __, 1998 [the date hereof]].

         3. SECTION 2.3 of the Lease is hereby amended by deleting the first
paragraph therein and replacing it with the following paragraph:

                           2.3 EXTENSION OPTION. So long as there exists no
                           Default of Tenant, this Lease is still in full force
                           and effect, and Tenant shall not have sublet,
                           assigned or otherwise transferred all or any portion
                           of its interest under this Lease (other than to
                           Affiliates), Tenant shall have the right to extend
                           the term of this Lease for one (1) additional period
                           (the "EXTENDED TERM") of five (5) years. The Extended
                           Term shall commence on the day succeeding the
                           expiration of the Original Term and shall end on the
                           day immediately preceding the fifth anniversary of
                           the commencement of the Extended Term. All of our
                           terms, covenants and provisions of this Lease shall
                           apply to each such Extended Term except that (i) the
                           Annual Fixed Rent for the Extended Term shall be the
                           Market Rate (as hereinafter defined) for the Property
                           determined as of the commencement of the Extended
                           Term, as designated by Landlord by notice to Tenant
                           ("LANDLORD'S NOTICE"), but subject to Tenant's right
                           to dispute as hereinafter provided; and (ii) Tenant
                           shall have no further right to extend the term of
                           this Lease beyond the Extended Term hereinabove
                           provided. If Tenant fails to give any such notice to
                           Landlord, this Lease shall automatically terminate at
                           the end of the Original Term then in effect, and
                           Tenant shall have no further option to extend the
                           term of this Lease, it being agreed that time is of
                           the essence with respect to the giving of any such
                           notice. If Tenant gives such notice, the extension of
                           this Lease shall be automatically effected without
                           the execution of any additional documents, subject to
                           Tenant's right to cancel such election as hereinafter
                           provided.

  SECTION 2.3 of the Lease is further amended by (i) deleting "applicable" from
  the second line of the second paragraph therein, (ii) deleting "applicable"
  from the third and fourth lines of the sixth paragraph therein, (iii) deleting
  "or the Extended Term (as applicable)" from the eighth and ninth lines of the
  sixth paragraph therein, (iv) deleting "either of its options" from the second
  line of the seventh paragraph therein and replacing it with "the option", (v)
  deleting "or the preceding Extended Term (as applicable") from the fourth and
  fifth lines of the first sub-paragraph on page 8 of the Lease, (vi) deleting
  "applicable" from the sixth line of the first sub-paragraph on page 8 of the
  Lease, (vii) deleting "or the Extended Term" from the fourth line of



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  the second sub-paragraph on Page 8 of the Lease, and (viii) deleting
  "applicable" from the eight line of the eighth paragraph therein.

         4. ARTICLE 4 is hereby amended by adding the following Section 4.2.7
thereto:

                           4.2.7 GROUND LESSOR PAYMENTS. Landlord and Tenant
                           agree that Tenant shall pay, as Additional Rent, any
                           and all additional rent due and payable by Tenant to
                           Ground Lessor pursuant to Sections 3.1 [(C)(1)] and
                           (3) of the Ground Lease.

         5. Landlord, by the execution hereof, consents to Tenant's performance
  of the alterations to the Mezzanine (as defined in the Lease) described in
  EXHIBIT __ subject, in all events however, to Tenant's compliance with the
  requirements of SECTION 6.2.4 of the Lease and Article 7 of the Ground Lease.

         6. Tenant hereby acknowledges that Landlord has satisfactorily
performed all of Landlord's Work (as defined in SECTION 3.2 of the Lease).

         7. Tenant warrants and represents that it has dealt with no broker in
  connection with the consummation of this First Amendment, and in the event of
  any brokerage claims from a broker dealing or claiming to have dealt with
  Tenant, against Landlord, Tenant agrees to defend same and indemnify and hold
  Landlord harmless against any such claim. Landlord warrants and represents
  that it has dealt with no broker in connection with the consummation of this
  First Amendment, and in the event of any brokerage claims from a broker
  dealing or claiming to have dealt with Landlord, including, but not limited
  to, Lynch, Murphy, Walsh and Partners against Tenant, Landlord agrees to
  defend same and indemnify and hold Tenant harmless against any such claim.

         8. As amended hereby, the Lease is hereby ratified and confirmed.


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         IN WITHNESS WHEREOF, Landlord and Tenant have executed this First
Amendment as a sealed instrument as of the date first above written.

                                       LANDLORD:

                                       BIOLEASE, INC.

                                       By: /s/ Neil St. John Raymond
                                           -----------------------------
                                          Name: Neil St. John Raymond
                                                ------------------------
                                          Title:
                                                ------------------------

                                       TENANT:

                                       BIOTRANSPLANT INCORPORATED

                                       By: /s/ Richard Capasso
                                           -----------------------------
                                          Name: Richard Capasso
                                                ------------------------
                                          Title: VP Finance and Treasurer
                                                ------------------------