Exhibit 10.1

FIRST AMENDMENT

This is the first amendment to the Employment Agreement dated August 29, 2004
between ZymoGenetics, Inc. and Douglas E. Williams.

Effective July 1, 2007, the following terms are amended:

Section 1 “Employment”: “Executive Vice President, Research and Development” is
replaced with “President”;

Section 2 “Duties”: “President” is replaced with “Chief Executive Officer”;

Section 4.4 “Good Reason”, Parts e) and f): “Executive Vice President, Research
and Development” is replaced with “President”;

Section 13 “Notices”: For purposes of Notices, Executive’s title of “Executive
Vice President, Research and Development” is replaced with “President”, and
Bruce L.A. Carter’s title of “President and CEO” is replaced with “CEO and
Chairman.”

All other terms remain unchanged as of July 1, 2007.

 

ZYMOGENETICS, INC. By:   /s/ BRUCE L.A. CARTER Dr. Bruce L. A. Carter, Chief
Executive Officer & Chairman EXECUTIVE: /s/ DOUGLAS E. WILLIAMS Douglas E.
Williams, Ph.D. Date: August 21, 2007