Document:

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                                                                  EXHIBIT 10.72

                     LOAN DOCUMENT MODIFICATION AGREEMENT
                     ------------------------------------
                     Number 4; dated as of April 20, 2001
                     ------------------------------------

     LOAN DOCUMENT MODIFICATION AGREEMENT dated as of April 20, 2001 (this
"Agreement") by and among SILICON VALLEY BANK (the "Bank"), a California-
chartered bank with its principal place of business located at 3003 Tasman
Drive, Santa Clara, California 95054, INT'L.COM, INC. ("INTL"), a Delaware
corporation with its principal place of business located at 950 Winter Street,
Waltham, Massachusetts 02451, INTERNATIONAL LANGUAGE ENGINEERING CORPORATION
("ILEC"), a Colorado corporation with its principal place of business located at
950 Winter Street, Waltham, Massachusetts 02451, and ILE INTERNATIONAL
CORPORATION ("ILE"), a Colorado corporation with its principal place of business
located at 950 Winter Street, Waltham, Massachusetts 02451 (each a "Borrower"
and collectively, the "Borrowers").

     1.  Reference to Existing Loan Documents.
         ------------------------------------

     Reference is hereby made to that Loan Agreement and Security Agreement
dated January 19, 2000 among the Bank and the Borrowers, as amended by that
certain Amendment to Loan Documents dated January 19, 2000, that certain Limited
Waiver and Amendment to Loan Documents dated March 21, 2000 and that certain
Loan Document Modification Agreement Number 3 dated as of January 19, 2001 (with
the attached schedules and exhibits, and as the same may hereafter be further
amended, modified, supplemented, extended or restated from time to time, the
"Loan Agreement") and the related loan documents, including without limitation
that certain Cross-Corporate Continuing Guarantee of the Borrowers dated January
19, 2000, that certain Collateral Assignment, Patent Mortgage and Security
Agreement dated January 19, 2000 between INTL and the Bank and that certain
Collateral Assignment, Patent Mortgage and Security Agreement dated January 19,
2000 between ILEC and the Bank (collectively, the "Loan Documents").  Unless
otherwise defined herein, capitalized terms used in this Agreement shall have
the same respective meanings as set forth in the Loan Agreement.

     2.  Effective Date.
         --------------

     This Agreement shall become effective as of April 20, 2001 (the "Effective
Date"), provided that the Bank shall have received the following on or before
May 3, 2001 and provided further, however, in no event shall this Agreement
become effective until signed by an officer of the Bank in California:

         a.  two copies of this Agreement, duly executed by each Borrower; and

         b.  such other documents, and completion of such other matters, as the
Bank may reasonably request in connection with the amendment of the Loan
Agreement, as contemplated hereunder.

     By the signature of its authorized officer below, the Borrowers are hereby
representing that, except as modified in Schedule A attached hereto, the
                                         ----------
representations of the Borrowers set forth in the Loan Documents (including
those contained in the Loan Agreement, as amended by this Agreement) are true
and correct as of the Effective Date as if made on and as of such date.
<PAGE>

                                      -2-

Finally, the Borrowers agree that, as of the Effective Date, they have no
defenses against their obligations to pay any amounts under the Loan Agreement
and the other Loan Documents.

     3.  Description of Change in Terms.
         ------------------------------

         a.  As of the Effective Date, the Loan Agreement is modified by
setting the Maturity Date set forth in the Schedule to the Loan Agreement at May
31, 2001.

         b.  The Loan Agreement and the other Loan Documents are hereby amended
wherever necessary or appropriate to reflect the foregoing changes.

     4.  Continuing Validity.
         -------------------

     Upon the effectiveness hereof, each reference in each Loan Document to the
"Loan Agreement," "thereunder," "thereof," "therein" or words of like import
referring to the Loan Agreement, shall mean and be a reference to the Loan
Agreement, as amended hereby.  Except as specifically set forth above, the Loan
Agreement shall remain in full force and effect and is hereby ratified and
confirmed.

     Each of the other Loan Documents is in full force and effect and is hereby
ratified and confirmed.  The amendments set forth above shall not prejudice any
rights which the Bank may now or hereafter have under or in connection with the
Loan Agreement, as modified hereby, or the other Loan Documents, and shall not
obligate the Bank to assent to any further modifications.

     5.  Miscellaneous.
         -------------

         a.  This Agreement may be signed in one or more counterparts each of
which taken together shall constitute one and the same document.

         b.  THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE
WITH THE LAWS OF THE STATE OF CALIFORNIA.

         c.  THE BORROWERS ACCEPT FOR THEMSELVES AND IN CONNECTION WITH THEIR
PROPERTIES, UNCONDITIONALLY, THE NON-EXCLUSIVE JURISDICTION OF ANY STATE OR
FEDERAL COURT OF COMPETENT JURISDICTION IN THE STATE OF CALIFORNIA, COUNTY OF
SANTA CLARA, IN ANY ACTION, SUIT, OR PROCEEDING OF ANY KIND AGAINST THEM WHICH
ARISES OUT OF OR BY REASON OF THIS AGREEMENT.

         d.  The Borrowers agree to promptly pay on demand all costs and
expenses of the Bank in connection with the preparation, reproduction, execution
and delivery of this Agreement and the other instruments and documents to be
delivered hereunder, including the reasonable fees and out-of-pocket expenses of
Sullivan & Worcester LLP, special counsel for the Bank with respect thereto.
<PAGE>

                                      -3-

     IN WITNESS WHEREOF, the Bank and the Borrowers have caused this Agreement
to be signed under seal by their respective duly authorized officers as of the
date set forth above.

                                    Sincerely,

                                    SILICON VALLEY BANK

                                    By: /s/ Peter Bendoris
                                        ------------------------
                                        Name:  Peter Bendoris
                                        Title: Vice President

                                    BORROWERS:

                                    INT'L.COM, INC.

                                    By: /s/ LeeAnn Horner
                                        ------------------------
                                        Name:  LeeAnn Horner
                                        Title: Assistant Treasurer

                                    INTERNATIONAL LANGUAGE   ENGINEERING
                                    CORPORATION

                                    By: /s/ LeeAnn Horner
                                        ------------------------
                                        Name:  Lee Ann Horner
                                        Title: Assistant Treasurer

                                    ILE INTERNATIONAL CORPORATION

                                    By: /s/ LeeAnn Horner
                                        ------------------------
                                        Name: LeeAnn Horner
                                        Title:   Assistant Treasurer
<PAGE>

                                  SCHEDULE A
                                  ----------

             Borrowers' Exceptions to Loan Document Representations

                                     None.<PAGE>

                                                                   Exhibit 10.01

                                  CURIS, INC.

                              Severance Agreement
                              -------------------

     THIS SEVERANCE AGREEMENT by and between Curis, Inc., a Delaware corporation
(the "Company"), and Andrew C.G. Uprichard (the "Executive") is made as of
November 20, 2000 (the "Effective Date").

     WHEREAS, the Board of Directors of the Company (the "Board") has determined
that appropriate steps should be taken to reinforce and encourage the continued
employment and dedication of certain of the Company's key personnel; and

     WHEREAS, the Company wishes to provide the Executive with severance pay in
the event of the Executive's separation from the Company under the circumstances
provided for herein;

     NOW, THEREFORE, in consideration of the Executive's continued employment by
the Company and other good and valuable consideration, the sufficiency of which
is hereby acknowledged, the parties agree as follows:

     1.   Term of Agreement.  This Agreement, and all rights and obligations of
          -----------------
the parties hereunder, shall take effect upon the Effective Date and shall
expire at midnight on November 20, 2001 (the "Expiration Date").

     2.   Not an Employment Contract.  The Executive acknowledges that this
          --------------------------
Agreement does not constitute a contract of employment or impose on the Company
any obligation to retain the Executive as an executive or employee of the
Company and that this Agreement does not prevent the Executive from terminating
his employment with the Company at any time.

     3.   Termination For Cause or Voluntary Departure Prior to the Expiration
          --------------------------------------------------------------------
Date. In the event that prior to the Expiration Date (a) the employment of the
----
Executive is terminated by the Company for Cause (defined below) or (b) the
Executive voluntarily terminates his employment with the Company, the Company
shall pay to the Executive the compensation and benefits otherwise payable to
him through the last day of his or her actual employment by the Company.  For
the purposes of Sections 3 and 4, the term "Cause" shall mean (a) a good faith
finding by the Company that the Executive has engaged in dishonesty, gross
negligence or misconduct, (b) the conviction of the Executive of, or the entry
of a pleading of guilty or nolo contendere by the Executive to, any crime
involving moral turpitude or any felony or (c) any breach or threatened breach
by the Executive of any confidentiality or inventions agreement with the
Company.

     4.   Termination Without Cause Prior to the Expiration Date.  In the event
          ------------------------------------------------------
that the employment of the Executive is terminated by the Company without Cause
prior to the Expiration Date, the Company shall continue to pay to the Executive
as severance benefits his base salary as in effect on the date of termination
(payable in
<PAGE>

annualized biweekly installments in accordance with the Company's regular
payroll practices) and continue to provide to the Executive any other benefits
owed to him by virtue of his employment with the Company (to the extent such
benefits can be provided to non-employees, or to the extent such benefits cannot
be provided to non-employees, then the cash equivalent thereof) until the date
six months after the date of termination.

     5.   Termination After the Expiration Date.  This Agreement shall be of no
          -------------------------------------
force or effect with respect to any termination of the Executive's employment
with the Company which should occur after the Expiration Date.

     6.   Notices.  Any notices delivered under this Agreement shall be deemed
          -------
duly delivered four business days after it is sent by registered or certified
mail, return receipt requested, postage prepaid, or one business day after it is
sent for next-business day delivery via a reputable nationwide overnight courier
service, in each case to the address of the recipient set forth on the signature
page hereto. Either party may change the address to which notices are to be
delivered by giving written notice of such change to the other party.

     7.   Entire Agreement.  This Agreement constitutes the entire agreement
          ----------------
between the parties and supersedes all prior agreements and understandings,
whether written or oral, relating to the termination, resignation or other
discontinuation of employment with the Company.

     8.   Amendment.  This Agreement may be amended or modified only by a
          ---------
written instrument executed by both the Company and the Executive.

     9.   Governing Law.  This Agreement shall be governed by and construed in
          -------------
accordance with the laws of the Commonwealth of Massachusetts (without reference
to the conflicts of laws provisions thereof).  Any action, suit or other legal
proceeding arising under or relating to any provision of this Agreement shall be
commenced only in a court of the Commonwealth of Massachusetts (or, if
appropriate, a federal court located within Massachusetts), and the Company and
the Executive each consents to the jurisdiction of such a court.

     10.  Counterparts.  This Agreement may be executed in two signature
          ------------
counterparts, each of which shall constitute an original, but all of which taken
together shall constitute but one and the same instrument.

     THE EXECUTIVE ACKNOWLEDGES THAT HE HAS CAREFULLY READ THIS AGREEMENT AND
UNDERSTANDS AND AGREES TO ALL OF THE PROVISIONS IN THIS AGREEMENT.

                                      -2-
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have executed this Agreement as of
the day and year set forth above.

                              CURIS, INC.

                              /s/ George A. Eldridge
                              ----------------------------
                              George A. Eldridge
                              Vice President, Finance and Secretary

                              Address:  61 Moulton Street
                                        Cambridge, MA 02138

                              EXECUTIVE

                              /s/ Andrew C G. Uprichard
                              ----------------------------
                              Andrew C.G. Uprichard

                              Address:  61 Moulton Street
                                        Cambridge, MA 02138

                                      -3-

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