FOURTH AMENDMENT TO EXCLUSIVE LICENSE AGREEMENT

Exhibit 10.7

FOURTH AMENDMENT TO EXCLUSIVE LICENSE AGREEMENT

This Fourth Amendment is made and entered into as of August 22, 2007 (the “Fourth Amendment Effective Date”) by and between THE REGENTS OF THE UNIVERSITY OF COLORADO, a body corporate, having its principal office at 1800 Grant Street, 8^th Floor, Denver, CO 80203 (hereinafter “University”) and ARCA Discovery, Inc., a Delaware corporation having its principal office at 1200 17^th Street, Suite 620, Denver, CO 80202 (hereinafter “Licensee”).

WITNESSETH

WHEREAS, the parties entered into an Exclusive License Agreement on October 14, 2005 (as previously amended, the “License Agreement”); and

WHEREAS, the License Agreement was subsequently amended on June 23, 2006, July 20, 2006 and July 19, 2007; and

WHEREAS, the July 20, 2006 amendment granted Licensee a one year option for an exclusive license to, among others, the ERK1/2 patent rights owned by University, and provided for an [ * ] for patent rights licensed after 60 days from July 20, 2006; and

WHEREAS, the parties further amended the License Agreement to extend the option period for the ERK1/2 patent rights to [ * ]; and

WHEREAS, Licensee has indicated its desire to exercise its option with respect to the ERK1/2 patent rights and desires that such ERK1/2 patent rights be included in the Patent Rights and University desires to have the ERK1/2 patent rights developed and commercialized to benefit the public and is willing to grant such exercise of the option rights; and

WHEREAS, the parties agree that the economic terms set forth in Appendix C of the License Agreement constitute commercially reasonable terms for the ERK1/2 patent rights;

NOW, THEREFORE, the parties agree as follows:

ARTICLE 1. DEFINITIONS

1 of 3

ARTICLE 2. GRANT OF LICENSE

ARTICLE 3. ACQUISITION FEES

ARTICLE 4. PERFORMANCE MILESTONES

a. On or before July 1, 2008, Licensee shall deliver to University a business plan that communicates the Licensee’s product development and marketing (strategic, tactical and financial) plans for the CU1403H Disclosure Invention. This document shall include forecasts showing the funds, personnel and time budgeted and planned for development of any Licensed Product(s) and Licensed Process(es) incorporating the CU1403H Disclosure Invention. Licensee shall provide similar reports or updates, as the case may be, to University on [ * ].

b. Licensee agrees that if any particular patent application or issued patent that is a part of the CU1403H Disclosure Patent Rights is not developed, sublicensed, being diligently used in research and development, or being diligently pursued for commercialization, within eighteen (18) months of the Fourth Amendment Effective Date, Licensee shall relinquish all rights to that portion of the Patent Rights to University without additional compensation, credit or refund of any amounts paid.

ARTICLE 5. MISCELLANEOUS

2 of 3

IN WITNESS WHEREOF the parties hereto have caused this Fourth Amendment, which is effective on the Fourth Amendment Effective Date, to be executed in duplicate by their respective duly authorized officers.

3 of 3