<PAGE>

                                                                   EXHIBIT 10.57

                       AMENDMENT NO. 1 TO CREDIT AGREEMENT

         THIS AMENDMENT NO. 1 (this "AMENDMENT") dated as of December 31, 2003
to the CREDIT AGREEMENT (the "CREDIT AGREEMENT") dated March 12, 2003, is by and
among ARIAD Pharmaceuticals, Inc., a Delaware corporation, ARIAD Corporation, a
Delaware corporation, and ARIAD Gene Therapeutics, Inc., a Delaware corporation
(hereinafter sometimes referred to collectively as the "BORROWERS") and Citizens
Bank of Massachusetts, a Massachusetts bank (the "LENDER"). All capitalized
terms not defined herein but defined in the Credit Agreement shall have the
meanings given to such terms in the Credit Agreement.

         WHEREAS, the Borrowers have applied to the Lender for an extension of
and increase to the Loan made pursuant to the Credit Agreement; and

         WHEREAS, the Borrowers and the Lender have agreed to certain other
modifications to the Credit Agreement as set forth herein.

         NOW, THEREFORE, in consideration of the mutual promises and covenants
set forth herein, the Borrowers and the Lender hereby agree that the Credit
Agreement is amended as follows:

         1. AMENDMENT TO SUBSECTION 2.1(A). Subsection 2.1(a) of the Credit
Agreement is hereby deleted in its entirety and replaced with the following:

                  2.1 General.

                           (a) Subject to the terms and conditions hereof, the
                  Lender agrees to make a loan (the "LOAN") to the Borrowers on
                  the Closing Date in the principal amount of Eight Million
                  Three Hundred Seventy-Five Thousand and 00/100 Dollars
                  ($8,375,000.00). The principal amount of the Loan may from
                  time to time be advanced as or converted to (i) LIBOR Loans,
                  (ii) Prime Rate Loans or (iii) a combination thereof, as
                  determined by the Borrowers and notified to the Lender in
                  accordance with subsections 2.2 and 2.8.

         2. AMENDMENT TO SUBSECTION 2.5. Subsection 2.5 of the Credit Agreement
is hereby deleted in its entirety and replaced with the following:

                  2.5 Payment of Term Loan. The Borrowers hereby unconditionally
         promise to pay to the order of the Lender the principal amount of the
         Loan in thirty-eight monthly installments of One Hundred Fifty Thousand
         and 00/100 Dollars ($150,000.00) commencing on January 31, 2004, and
         continuing on the last day of each consecutive month thereafter until
         the Maturity Date. The Borrowers hereby further agree to pay interest
         on the unpaid principal balance of the Loan, in arrears, on each
         Interest Payment Date; provided, however, any such interest accruing at
         the Late Rate shall be due and payable on demand. On the Maturity Date
         (or such earlier date on which the Loan becomes due and payable
         pursuant to subsection 7.1), the entire remaining outstanding



<PAGE>



         balance of the Loan (including, without limitation, all unpaid
         principal, all accrued but unpaid interest and all unpaid fees,
         charges, costs and expenses) shall be immediately due and payable in
         full.

         3. AMENDMENT TO SUBSECTION 5.13. Subsection 5.13 of the Credit
Agreement is hereby deleted in its entirety and replaced with the following:

                  5.13 Cash, Cash Equivalents, Marketable Securities and
         Investments.

                  (a) During the term of this Agreement, the Borrowers shall
         maintain, as evidenced on their consolidated balance sheet, not less
         than Twelve Million and 00/100 Dollars ($12,000,000.00) in Unrestricted
         Cash, unrestricted Cash Equivalents, and unrestricted marketable
         securities (the "LIQUID ASSETS").

                  (b) Not less than Eighty-Five Percent (85%) of the Borrowers'
         total Liquid Assets shall be invested through and held by the Treasury
         Desk in Cash Equivalents or such other debt investments as are offered
         through the Treasury Desk and which are consistent with the Borrowers'
         current investment policy, a copy of which is attached hereto as
         EXHIBIT D, all of such investments to be in book entry form with
         maturity dates of not less than thirty (30) days (each singly, a
         "TREASURY DESK INVESTMENT" and collectively, the "TREASURY DESK
         INVESTMENTS"). Notwithstanding the foregoing, in no event shall the
         Borrowers be required to invest more than Seventeen Million and 00/100
         Dollars ($17,000,000.00) with the Treasury Desk during the Term of this
         Agreement.

                  (c) Each maturing Treasury Desk Investment shall automatically
         be renewed for a like period and on market terms unless the Borrowers
         have notified the Lender of their intent to change the Treasury Desk
         Investment. To institute such a change, the Borrowers shall, not less
         than two (2) Business Days prior to the maturity of such Treasury Desk
         Investment, provide special instructions to the Treasury Desk regarding
         the maturing Treasury Desk Investment. The Borrowers shall confirm such
         instructions to the Treasury Desk and the Lender the same day by e-mail
         notification in the form attached hereto as EXHIBIT E (the
         "CONFIRMATION NOTIFICATION"). The Confirmation Notification shall
         contain, in addition to standard instructions, a representation and
         warranty that the execution of the requested instructions shall not
         cause a breach of any of the covenants contained in this Agreement.

         4. AMENDMENT TO APPENDIX A TO THE CREDIT AGREEMENT. The text of the
definition of "Maturity Date" contained in Appendix A of the Credit Agreement is
hereby deleted in its entirety and replaced with the following:

                  "MATURITY DATE": March 31, 2007

                                       2


<PAGE>


         5. AMENDMENT TO APPENDIX A TO EXHIBIT B TO THE CREDIT AGREEMENT.
Appendix A to Exhibit B of the Credit Agreement is hereby deleted in its
entirety and replaced with the attached Appendix A.

         6. NO FURTHER AMENDMENTS. Except as amended hereby, all other
provisions of the Credit Agreement shall remain in full force and effect. After
the effective date hereof, all references in the Credit Agreement and other
Financing Documents shall be deemed to refer to the Credit Agreement as amended
hereby, representing the entire expression of the parties with respect to the
subject matter hereof on the date this Amendment is executed.

         7. RATIFICATION OF FINANCING DOCUMENTS. By signing below, the Borrowers
ratify and affirm the terms of the Credit Agreement (as amended hereby), the
Note, the Security Agreements and all other Financing Documents executed in
connection with any of the foregoing, and confirm and represent that each
remains in full force and effect and that no default or event of default has
occurred thereunder (except such defaults or events of default as have been
waived in writing by the Lender on or before the date hereof or such defaults or
events of default as the Borrowers have requested, in writing prior to the date
hereof, the Lender to waive).

         8. GOVERNING LAW. This Amendment shall be governed in all respects by
the laws of the Commonwealth of Massachusetts without regard to any conflicts of
laws principles.

         9. DESCRIPTIVE HEADINGS. Descriptive headings are for convenience only
and will not control or affect the meaning or construction of any provisions of
this Amendment.

         10. COUNTERPARTS. This Amendment may be executed in any number of
identical counterparts, each of which will constitute an original but all of
which when taken together will constitute but one instrument.

         11. SEVERABILITY. In the event one or more of the provisions of this
Amendment should, for any reason, be held to be invalid, illegal or
unenforceable in any respect, such invalidity, illegality, or unenforceability
shall not affect any other provisions of this Amendment, and this Amendment
shall be construed as if such invalid, illegal or unenforceable provision had
never been contained herein.

                    [signatures contained on following page]

                                       3



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         WITNESS our hands and seals as of the date set forth above.

WITNESS AS TO ALL:                     ARIAD PHARMACEUTICALS, INC.


                                       By:  /s/ Edward M. Fitzgerald
                                            ------------------------------------
       /s/ Kerrie Kneeland                  Name:   Edward M. Fitzgerald
--------------------------                  Title:  Senior Vice President and
Name:  Kerrie Kneeland                              Chief Financial Officer


                                       ARIAD CORPORATION

                                       By:  /s/ Edward M. Fitzgerald
                                            ------------------------------------
                                            Name:   Edward M. Fitzgerald
                                            Title:  Vice President and
                                                    Chief Financial Officer

                                       ARIAD GENE THERAPEUTICS, INC.


                                       By:  /s/ Harvey J. Berger, M.D.
                                            ------------------------------------
                                          Name:   Harvey J. Berger, M.D.
                                          Title:  Chief Executive Officer


                                       CITIZENS BANK OF MASSACHUSETTS

                                       By:             /s/ R. Scott Haskell
                                            ------------------------------------
                                            Name:   R. Scott Haskell
                                            Title:  Vice President

                                       4


<PAGE>


                          COMMONWEALTH OF MASSACHUSETTS

Middlesex County, ss.                                          December 23, 2003

         Then personally appeared the above-named Edward M. Fitzgerald, of ARIAD
Pharmaceuticals, Inc., and acknowledged the foregoing instrument to be his free
act and deed and the free act and deed of ARIAD Pharmaceuticals, Inc., before
me.


                                         /s/ Barbara D. Matyskiel
                                         ---------------------------------------
                                         Notary Public
                                         My commission expires: 3/15/07
                                         [AFFIX NOTARIAL SEAL]

                          COMMONWEALTH OF MASSACHUSETTS

Middlesex County, ss.                                          December 23, 2003

         Then personally appeared the above-named Edward M. Fitzgerald, of ARIAD
Corporation, and acknowledged the foregoing instrument to be his free act and
deed and the free act and deed of ARIAD Corporation, before me.

                                         /s/ Barbara D. Matyskiel
                                         ---------------------------------------
                                         Notary Public
                                         My commission expires: 3/15/07
                                         [AFFIX NOTARIAL SEAL]

                          COMMONWEALTH OF MASSACHUSETTS

Middlesex County, ss.                                          December 23, 2003

         Then personally appeared the above-named Harvey J. Berger, M.D., of
ARIAD Gene Therapeutics, Inc., and acknowledged the foregoing instrument to be
his free act and deed and the free act and deed of ARIAD Gene Therapeutics,
Inc., before me.


                                         /s/ Barbara D. Matyskiel
                                         ---------------------------------------
                                         Notary Public
                                         My commission expires: 3/15/07
                                         [AFFIX NOTARIAL SEAL]

                                       5



<PAGE>




                          COMMONWEALTH OF MASSACHUSETTS

Suffolk County, ss.                                            December 24, 2003

         Then personally appeared the above-named Scott Haskell, Vice President
of Citizens Bank of Massachusetts, and acknowledged the foregoing instrument to
be his free act and deed and the free act and deed of Citizens Bank of
Massachusetts, before me.

                                         /s/ Denise D. Finigan
                                         ---------------------------------------
                                         Notary Public
                                         My commission expires: 9/23/05
                                         [AFFIX NOTARIAL SEAL]

                                       6



<PAGE>


                      APPENDIX A TO COMPLIANCE CERTIFICATE
                           ARIAD PHARMACEUTICALS, INC.
                                ARIAD CORPORATION
                          ARIAD GENE THERAPEUTICS, INC.

<TABLE>
<S>                                                                                          <C>
I. TOTAL BALANCE SHEET CASH & INVESTMENTS:
   ---------------------------------------
       1. Total Cash & Investments:
                                                                                             -----------
       2. Required Total Cash & Investments Per Covenant:                                    $12,000,000
                                                                                             -----------
       3.Excess / (Deficit) (#1-#2)
                                                                                             -----------

II. CITIZENS TREASURY DESK INVESTMENTS:

       3. Borrowers' Investments at Citizens' Treasury Desk:
                                                                                             -----------
       4. Required Treasury Desk Investments*:
                                                                                             -----------
       5.Excess / (Deficit) Treasury Desk Investments (#3-#4):
                                                                                             -----------

III. TREASURY DESK INVESTMENT SUMMARY:
    ----------------------------------
       Government Securities:
                                                                                             -----------
       Commercial Paper:
                                                                                             -----------
       Citizens Certificate of Deposits:
                                                                                             -----------
       Treasury Bills:
                                                                                             -----------
       Total (Equals #3):
                                                                                             -----------
</TABLE>

* Equals the lesser of $17.0 million or 85% times Total Cash & Investments (Item
#1)

                                       7