EXHIBIT 10.6

CONSULTING AGREEMENT

FIRST AMENDMENT

This First Amendment, to the Consulting Agreement (the “First Amendment”), is made effective as of the latter date of execution by both parties (the “Amendment Effective Date”) and is entered into by and between Vical Incorporated (“Vical”), a Delaware Corporation, having a place of business at 10390 Pacific Center Court, San Diego, CA 92121-4340 and Gary A. Lyons (the “Consultant”), an individual having a principal address of 1344 Stratford Court, Del Mar, CA 92014.

Whereas, Vical and Consultant entered into a Consulting Agreement (the “Agreement”), effective August 1, 2010;

Whereas, the Vical and Consultant wish to amend the Agreement to extend the term for six (6) months, that is until June 30, 2011.

Now, therefore, in consideration of the covenants and promises contained herein, the parties agree as follows:

Exhibit A of the Agreement is hereby amended to be replaced in its entirety as follows:

Except as amended hereby, all other terms and conditions of the Agreement shall remain unchanged and shall continue in full force and effect.

In witness whereof, the parties have executed this First Amendment to the Consulting Agreement as of the last day indicated below.