Cancer: SB-715992 has entered a Phase II clinical trial for the treatment of non-small cell lung cancer and is expected to enter multiple Phase II clinical trials in other solid cancers throughout 2004. SB-715992 is a novel small molecule drug candidate that inhibits cell proliferation and promotes cancer cell death by specifically disrupting the function of a cytoskeletal protein known as kinesin spindle protein, or KSP. KSP is essential for cell proliferation, a process that when unregulated results in tumor growth. KSP plays no role outside of cell proliferation. Current drugs that inhibit cell proliferation, such as Taxol (paclitaxel) and Taxotere (docetaxel), are standard treatments for many types of cancers, but these drugs target tubulin, a cytoskeletal protein that is essential not only to cell proliferation but also to many other important cellular functions. Because SB-715992 inhibits only cell proliferation, we believe it may exhibit a lower incidence of toxicities than many existing cancer drugs. In addition, SB-715992s novel mechanism of action may be effective against a broader range of tumor types

EX-4.1 2 f95504a3exv4w1.txt EXHIBIT 4.1 . . . EXHIBIT 4.1 COMMON STOCK COMMON STOCK NUMBER SHARES CYTK THIS CERTIFICATE IS TRANSFERABLE IN SEE REVERSE FOR CERTAIN DEFINITIONS AND NEW YORK, N.Y. AND RIDGEFIELD PARK, N.J. A STATEMENT AS TO THE RIGHTS, PREFERENCES, PRIVILEGES AND RESTRICTIONS ON TRANSFER CUSIP 23282W 10 0 (CYTOKENETICS LOGO) INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE THIS CERTIFIES THAT IS THE RECORD HOLDER OF FULLY PAID AND NONASSESSABLE SHARES OF COMMON STOCK, $.001 PAR VALUE, OF - ----------------------------------------------------- CYTOKINETICS, INCORPORATED --------------------------------------------------- transferable on the books of the Corporation by the holder hereof in person or by duly authorized attorney upon surrender of this certificate properly endorsed. This certificate is not valid until countersigned and registered by the Transfer Agent and Registrar. WITNESS the facsimile seal of the Corporation and the facsimile signatures of its duly authorized officers. Dated: /s/ Robert Blum /s/ James Sabry SECRETARY PRESIDENT (CYTOKINETICS CORPORATE SEAL) COUNTERSIGNED AND REGISTERED: MELLON INVESTOR SERVICES LLC TRANSFER AGENT AND REGISTRAR BY AUTHORIZED SIGNATURE

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