Cytokinetics Announces the Initiation of a Broad Phase II Clinical Trials Program in Oncology for SB-715992

Milestone Payment Triggered under Collaboration with GlaxoSmithKline

South San Francisco, CA - January 14, 2004

Cytokinetics, Inc. today announced that GlaxoSmithKline (GSK) has initiated a broad Phase II program to expand the clinical development of SB-715992, a novel small molecule oncology drug candidate directed against kinesin spindle protein (KSP), a cytoskeletal protein essential for DNA division, which is also known as mitosis. The multi-country clinical program, which is scheduled to be conducted by GSK throughout 2004, is expected to encompass multiple parallel Phase II monotherapy and Phase Ib/II combination therapy studies across a wide array of tumor types representing large commercial markets, including non-small cell lung, breast, ovarian and colorectal cancers, as well as selected other tumor types. In addition, The National Cancer Institute (NCI) has agreed to sponsor a series of additional clinical trials which will complement these clinical development activities by focusing on other specified tumor types.

The initiation of the expansive Phase II program triggers a milestone payment from GlaxoSmithKline to Cytokinetics under the terms of the companies’ collaboration established in June 2001. SB-715992 is the first drug candidate to emerge from this collaboration, which was designed to discover, develop and commercialize novel small molecule therapeutics directed against human mitotic kinesins for the treatment of cancer and other diseases.

"This continuing clinical trials program represents a broad effort in Phase II to evaluate the potential effectiveness of this novel, targeted anti-mitotic agent in cancer patients," stated James Sabry, M.D., Ph.D., Cytokinetics' President and Chief Executive Officer. "This next stage of human clinical testing builds upon the encouraging initial safety and pharmacokinetics profile that we have observed for SB-715992 in Phase I studies as well as the encouraging results that we have seen for the compound across a wide array of preclinical tumor models."

"We are encouraged by the data generated to date on this novel compound and are interested in the advancement of this drug candidate to examine its potential clinical utility across a wide range of human cancers," added Skip Burris, Director, Drug Development at the Sarah Cannon Cancer Center and a Phase I investigator of SB-715992. "This next-generation approach to inhibiting mitosis may address the liabilities of existing chemotherapeutics while also potentially having therapeutic activity in a larger array of tumors."

"Clinical impact in cancer often comes from the introduction of pharmaceuticals that act by a novel mechanism of action," commented Dr. Eric Rowinsky, Director of Clinical Research at the CTRC Institute for Drug Development and a Phase I investigator of SB-715992. "I am impressed by the commitment of Cytokinetics and GlaxoSmithKline to conduct a broad Phase II program to examine the potential of this new mechanistic approach to the treatment of cancer."

Background

KSP is required at the earliest stages of mitosis and is the mitotic kinesin for which biological function is best understood. Kinesins are a class of cytoskeletal proteins that translate chemical energy into mechanical force along intracellular filaments in order to carry out many important biological functions. The mitotic kinesins are a functional subgroup of kinesins that work in an ordered fashion to facilitate the mechanical processes required for mitosis and the division of DNA during cell division. Academic and biopharmaceutical research activities have demonstrated that these enzyme targets are amenable to small molecule perturbation thereby disrupting mitotic spindle function, interrupting DNA and cell division and inducing apoptosis or cell death.

Since the introduction of anti-mitotic drugs 30 years ago, these agents (taxanes and vinca alkaloids, which affect tubulin polymerization), have dramatically advanced cancer patient care and have served as a cornerstone of modern cancer chemotherapy. However, use of these agents is severely constrained by dose-limiting toxicities related to the broad role that tubulin plays in important cellular processes unrelated to cell division. In contrast, mitotic kinesins represent a family of newly identified enzymes. Each family member appears to perform a discrete and non-redundant role in mitotic spindle formation and function. Unlike tubulin, KSP and other mitotic kinesins are expressed only in proliferating cells and appear to play no role outside mitosis. Inhibitors of KSP and other mitotic kinesins may therefore represent next-generation anti-mitotics, by targeting the mitotic process specifically.

About Cytokinetics

Founded in 1998 and privately held, Cytokinetics is dedicated to the discovery, development and commercialization of a novel class of therapeutics resulting from its leadership position in the emerging field of cytoskeletal pharmacology. The cytoskeleton is a complex, dynamic framework that impacts all aspects of cell function including cell division, cell motility, intracellular transport, muscle contractility and regulation of cellular organization. Cytokinetics' R&D efforts aim to address pharmaceutical needs in cancer, cardiovascular and infectious diseases and feature proprietary Cytometrix™ cellular phenotyping technologies designed to industrialize cell biology for increased speed and productivity in drug discovery and development. Cytokinetics and GlaxoSmithKline have entered into a broad strategic collaboration to discover, develop and commercialize novel small molecule therapeutics targeting mitotic kinesins for applications in the treatment of cancer and other diseases. GlaxoSmithKline is conducting Phase II studies with SB-715992, a novel investigational drug candidate that has emerged from the collaboration. Additional information about Cytokinetics can be obtained at www.cytokinetics.com.