EX-99 4 z4149165c.txt EXHIBIT 99.3 JOINT FILERS' SIGNATURES Warburg, Pincus Equity Partners, L.P. ZymoGenetics, Inc. (ZGEN) February 25, 2008 Exhibit 99.3 ------------ Joint Filers' Signatures WARBURG PINCUS & CO. By: /s/ Scott A. Arenare 02/27/08 --------------------------------------- -------- Name: Scott A. Arenare Date Title: Partner WARBURG PINCUS PARTNERS LLC By: Warburg Pincus & Co., its Managing Member By: /s/ Scott A. Arenare 02/27/08 ---------------------------------- -------- Name: Scott A. Arenare Date Title: Partner WARBURG PINCUS LLC By: /s/ Scott A. Arenare 02/27/08 --------------------------------------- -------- Name: Scott A. Arenare Date Title: Managing Director /s/ Scott A. Arenare 02/27/08 -------------------------------------------- -------- Name: Charles R. Kaye By: Scott A. Arenare, Attorney-in-Fact* /s/ Scott A. Arenare 02/27/08 -------------------------------------------- -------- Name: Joseph P. Landy By: Scott A. Arenare, Attorney-in-Fact** * The Power of Attorney given by Mr. Kaye was previously filed with the SEC on March 2, 2006 as an exhibit to a statement on Schedule 13D filed by Building Products, LLC with respect to Builders FirstSource, Inc. ** The Power of Attorney given by Mr. Landy was previously filed with the SEC on March 2, 2006 as an exhibit to a statement on Schedule 13D filed by Building Products, LLC with respect to Builders FirstSource, Inc.