News Release

ZymoGenetics Licenses Non-Core Assets to Seattle Life Sciences

May 4, 2009

SEATTLE--(BUSINESS WIRE)--May. 4, 2009-- ZymoGenetics, Inc. (NASDAQ:ZGEN) today announced the licensing of rights to eight early stage product candidates to Seattle Life Sciences. ZymoGenetics received rights to potential milestones and royalties, in exchange for licensing Seattle Life Sciences (SLS) rights to develop the product candidates. In addition, ZymoGenetics is entitled to an equity interest in Seattle Life Sciences that will be issued in connection with SLS obtaining venture capital financing.

“The assets licensed to SLS are early stage preclinical candidates outside our areas of focus and, as a result, were not being developed internally,” said Douglas E. Williams, Ph.D., Chief Executive Officer of ZymoGenetics. “Through transactions like this, we have the potential to generate value from our patent portfolio without investing our own capital by finding committed licensees like SLS. This is consistent with our overall goal to effectively manage our internal research and development spending.”

Shane M. Kelly, Chairman of the Board of SLS said, “By acquiring the assets associated with a valuable collection of potent biological agents, we plan to rapidly build a pipeline of clinical candidates for advancement. Product opportunities include recombinant protein-based drug candidates and monoclonal antibody-based inhibitors of factors believed to affect disease pathology. The intellectual property acquired will provide opportunities for more than eight drug development programs which address clinical indications with significant unmet clinical need, and range from niche opportunities to those applicable to large markets with strong growth potential.”

About ZymoGenetics

ZymoGenetics creates novel protein drugs that help patients fight disease. The Company developed and markets RECOTHROM^® Thrombin, topical (Recombinant). Other product candidates are focused on cancer, autoimmune and viral diseases. ZymoGenetics intends to commercialize product candidates through internal development, collaborations with partners, and out-licensing of patents from its extensive patent portfolio. For further information, visit www.zymogenetics.com.

About SLS

Seattle Life Sciences (SLS) is a product-driven, preclinical stage biotechnology company that has been formed to focus on the development of a portfolio of novel protein therapeutic candidates licensed from the prolific discovery programs at ZymoGenetics, Inc. Our dynamic management team includes entrepreneurs, scientists, financiers, and corporate/business development experts with proven track records in the biotechnology industry. The team possesses unique knowledge of the project portfolio as well as strong networks in the financial and biotech/pharma communities.

This press release contains "forward-looking statements" within the meaning of the Private Securities Litigation Reform Act of 1995. These forward-looking statements are based on the current intent and expectations of the management of ZymoGenetics. These statements are not guarantees of future performance and involve risks and uncertainties that are difficult to predict. ZymoGenetics' actual results and the timing and outcome of events may differ materially from those expressed in or implied by the forward-looking statements because of risks associated with our unproven product sales and marketing abilities, discovery strategy, preclinical and clinical development, strategic partnering, regulatory oversight, intellectual property claims and litigation and other risks detailed in the company's public filings with the Securities and Exchange Commission, including the company's Annual Report on Form 10-K for the year ended December 31, 2008. Except as required by law, ZymoGenetics undertakes no obligation to update any forward-looking or other statements in this press release, whether as a result of new information, future events or otherwise.

Source: ZymoGenetics, Inc.

ZymoGenetics
Susan W. Specht, Director, Corporate Communications, 206-442-6592
or
Seattle Life Sciences
Stephen Jaspers, Ph.D., Chief Scientific Officer, 425-208-1500
sjaspers@seabiosci.com