EXHIBIT 10.1

[ * ] = Certain confidential information contained in this document, marked by brackets, has been omitted and filed separately with the Securities and Exchange Commission pursuant to Rule 24b-2 of the Securities Exchange Act of 1934, as amended.

SECOND AMENDMENT TO DRUG DISCOVERY COLLABORATION AGREEMENT

THIS AMENDMENT NO. 2 (“Second Amendment”), effective as of October 1, 2005 (Amendment Date”), is entered into by and between Genentech, Inc., a Delaware corporation, having a principal place of business at 1 DNA Way, South San Francisco, California 94080 (“Genentech”) and Array BioPharma Inc., a Delaware corporation, having a principal place of business at 3200 Walnut Street, Boulder, Colorado 80301 (“Array”) (collectively, the “Parties” or individually, a “Party”).

WHEREAS, Genentech and Array entered into a Drug Discovery Collaboration Agreement, effective as of December 22, 2003, which was subsequently modified by a Letter Agreement, dated October 11, 2004, and amended by a First Amendment, dated May 20, 2005 (collectively, the “Agreement”).

WHEREAS, the Parties desire to amend the Agreement as set forth below.

NOW, THEREFORE, the Parties agree as follows:

1.               This Second Amendment hereby amends and revises the Agreement to incorporate the terms and conditions set forth in this Second Amendment.  The relationship of the Parties shall continue to be governed by the terms of the Agreement, as amended.

2.               All capitalized terms used in this Second Amendment shall have the meanings defined in the Agreement unless otherwise defined herein.

3.               Section 1.55 of the Agreement is hereby amended and replaced in its entirety as follows:

“              1.55        “Research Term” means the period commencing on January 30, 2004 (the date that the Research Plan was Approved by the JRC) and ending on the first to occur of (a) termination of this Agreement by either Party under Article 10; or (b) [*].  Genentech has the right to extend the foregoing Research Term, in its sole discretion, for [*], upon written notice to Array at least six (6) months prior to the expiration of the Research Term.  Any such notice shall specify the number of [*] for which Genentech is extending the Research Term.”

4.               As of the Amendment Date, there are three (3) Collaboration Targets ([*], [*] and [*]) and Array is currently devoting, and Genentech is paying for, [*] to perform activities under the Research Plan ([*] for each Collaboration Target, pursuant to Section 2.7 of the Agreement, and an additional [*] that are [*] pursuant to the Letter Agreement, dated October 11, 2004).  As of the