News Release

ZymoGenetics Reports Encouraging Preliminary Results from Phase 2 Study of IL-21 in Metastatic Melanoma Conducted by NCIC

May 13, 2009

SEATTLE--(BUSINESS WIRE)--May. 13, 2009-- ZymoGenetics, Inc. (NASDAQ:ZGEN) today announced that Interleukin 21 (IL-21) demonstrated an impressive overall response rate in the treatment of metastatic melanoma. In interim Phase 2 results from 24 patients, 29 percent showed a partial response, with an additional 33 percent of patients showing stable disease in this difficult to treat disease.

“We are seeing promising anti-tumor response with IL-21 in patients with metastatic melanoma in this Phase 2 study,” said Nicole Onetto, M.D., Senior Vice President and Chief Medical Officer of ZymoGenetics. “The response rate is favorable, particularly when compared to those of approved agents. Patients with advanced melanoma have few effective treatment options, so a clear need exists for new agents to manage this disease.”

Results from the Phase 2 clinical trial in patients with metastatic melanoma were presented at the World Congress on Melanoma meeting in Vienna, Austria. The single-agent multi-center clinical trial is being conducted by the NCIC Clinical Trials Group in Canada and is evaluating three dosing regimens of IL-21 in patients with no prior systemic therapy for metastatic melanoma. The primary endpoint is efficacy, as measured by objective response or lack of early disease progression.

To date 7 of the 24 patients (29%) had a partial response (5 confirmed by RECIST criteria). Eight patients (33%) had stable disease. The most common adverse events were mild or moderate fatigue and rash.

Two schedules testing 50 mcg/kg were evaluated in a total of 10 patients but were poorly tolerated due to adverse events including neutropenia and skin rash. The trial will be completed with a full cohort of 30 patients to be treated at the 30 mcg/kg dose, which is tolerable for outpatient dosing and active as assessed by tumor response.

About Interleukin 21 (IL-21)

IL-21, a cytokine that enhances CD8+ T cell and NK cell activity, has single-agent anti-tumor activity (J Clin Oncol 26:2034, 2008). ZymoGenetics has worldwide rights to IL-21 and is developing IL-21 for the treatment of renal cell carcinoma and metastatic melanoma.

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.

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 preclinical and clinical development, product sales and marketing abilities, discovery strategy, 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 and subsequent Quarterly Report on Form 10-Q. 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, Inc.
Susan W. Specht
Director, Corporate Communications
206-442-6592