Exhibit 10.4

Confidential Materials omitted and filed separately with the
Securities and Exchange Commission. Asterisks denote omissions.

AMENDMENT

This Amendment (the “ Amendment ”) to the License Agreement dated as of December 18, 2003 by and between

(1)            ASTRAZENECA AB, a company incorporated under the laws of Sweden with its registered office at SE-151 85 Södertälje, Sweden (“ASTRAZENECA”) (“ AstraZeneca ”); and

(2)            The MEDICINES COMPANY, a company incorporated under the laws of Delaware with its registered office at 8 Campus Drive, Parsippany, New Jersey 07054, United States (“TMC”).

(the “ Agreement ”) is made effective as of July 6, 2007 (the “ Amendment Effective Date ”).

Recitals

WHEREAS, the Parties desire to amend, modify and restate certain terms and conditions of the Agreement.

Agreement

NOW, THEREFORE, in consideration of the mutual covenants contained in this Amendment, and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the Parties, intending to be legally bound, agree as follows:

1               Definitions .

Any capitalized term not separately defined in this Amendme