EX-10.52 FIRST AMENDMENT TO LICENSE AGREEMENT BETWEEN AMGEN INC. AND EPIX PHARMACEUTICALS, INC.

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                                                                   EXHIBIT 10.52

                                                                  EXECUTION COPY

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                                FIRST AMENDMENT TO
                                LICENSE AGREEMENT

                                     BETWEEN

                                   AMGEN INC.

                                       AND

                            EPIX PHARMACEUTICALS, INC.
       (AS SUCCESSOR-IN-INTEREST TO PREDIX PHARMACEUTICALS HOLDINGS, INC.)

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                      FIRST AMENDMENT TO LICENSE AGREEMENT

     THIS FIRST AMENDMENT TO LICENSE AGREEMENT (this "Amendment") is made and
entered into as of March 20, 2007, by and between EPIX Pharmaceuticals, Inc., a
Delaware corporation headquartered at 4 Maguire Road, Lexington, MA 02421
("EPIX"), and Amgen Inc., a Delaware corporation having its principal place of
business at One Amgen Center Drive, Thousand Oaks, CA 91320-1799 ("Amgen").
Predix and Amgen are sometimes referred to herein individually as a "Party" and
collectively as the "Parties."

                                     RECITALS

     WHEREAS, Predix Pharmaceuticals Holdings, Inc. ("Predix") and Amgen entered
into that certain License Agreement dated as of July 31, 2006 (the "Agreement");
and

     WHEREAS, EPIX (as successor-in-interest to Predix) and Amgen now desire to
amend the Agreement as set forth herein.

     NOW, THEREFORE in consideration of the foregoing and the mutual agreements
set forth below, the Parties agree as follows:

                                    ARTICLE 1

                                    DEFINITIONS

     1. Definitions. Unless otherwise defined herein, the terms in this
Amendment with initial let