Cytokinetics Announces Data from Heart Failure Drug Discovery Program Presented at the 2004 Scientific Sessions of the American Heart Association.

SOUTH SAN FRANCISCO, Calif. -- Results Support Novel Mechanism of Action for Potential Drug Candidates

Cytokinetics, Inc. (Nasdaq: CYTK) announced today the presentation of non-clinical research data relating to its congestive heart failure drug discovery program. The presentation, entitled "The Cardiac Myosin Activator, CK1122534, Increases Contractility in Adult Cardiac Myocytes but Does Not Affect the Calcium Transient or Depend on Second Messenger Signaling" was presented at the 2004 Scientific Sessions of the American Heart Association in New Orleans, LA.

The scientific results presented were the first data from this research program to be communicated in a public scientific forum and are specifically related to an experimental compound CK-1122534 that was discovered at the company. This compound has been shown to act by a novel mechanism to directly stimulate the activity of the cardiac myosin motor protein by accelerating the rate-limiting step of the myosin enzymatic cycle and thereby shifting the enzymatic cycle in favor of the force producing state. The data presented today show that this mechanism generated a dose-dependent increase in fractional shortening in ventricular myocytes, a measure of cardiac contractility.

Furthermore, Cytokinetics presented results that demonstrated that CK-1122534 does not increase the calcium transient and does not inhibit phosphodiesterase activity and that the attendant increase in fractional shortening is not attenuated by the addition of a beta-adrenergic blocker, altogether providing evidence that CK-1122534 increases myocyte contractility by directly activating cardiac myosin. These findings also support the hypothesis that drug candidates arising from this research program may address certain clinical liabilities of existing pharmaceuticals in the treatment of acute and chronic heart failure.

"We are pleased to share these important scientific data from this drug discovery program with the cardiology research community," stated Dr. David Morgans, Jr., Cytokinetics' Senior Vice President, Drug Discovery and Development. "Over the last several years, our scientists have pioneered an elegant and distinctive approach to the treatment of congestive heart failure by focusing multi-disciplinary research activities on the molecular actors that directly contribute to contractile force and cardiac pump function. For the first time, we have now demonstrated that a small molecule activator of cardiac myosin can enhance cardiac contractility and, through this novel approach, potentially improve compromised mechanical heart function without increasing intracellular calcium or inhibiting phosphodiesterase activity, each of which may be arrhythmogenic and has been associated with adverse effects."

"Cytokinetics has again demonstrated that our core focus to cytoskeletal pharmacology can produce a first-in-class pharmaceutical approach with relevance to an increasingly important medical need," stated Dr. James Sabry, Cytokinetics' President and Chief Executive Officer. "By leveraging our biological expertise and assay technologies, which were first validated by our novel approach to the treatment of cancer, we have verified that our research may be similarly fruitful in the treatment of congestive heart failure and potentially deliver an additional next-generation compound to our expanding portfolio of promising drug candidates. We look forward to sharing more advanced data from this program in other scientific and clinical venues as we plan to progress a development compound into IND-enabling studies and to initiate Phase I trials in 2005 to further assess the safety of a potential drug candidate emerging from ongoing preclinical optimization activities."

About Cytokinetics

Cytokinetics is a leading biopharmaceutical company focused on the discovery, development and commercialization of novel small molecule drugs that specifically target the cytoskeleton. The cytoskeleton is a complex biological infrastructure that plays a fundamental role within every human cell. Cytokinetics' focus on the cytoskeleton enables it to develop novel and potentially safer and more effective classes of drugs directed at treatments for cancer, cardiovascular disease, fungal diseases and other diseases. Cytokinetics has developed a cell biology driven approach and proprietary technologies to evaluate the function of many interacting proteins in the complex environment of the intact human cell. Cytokinetics employs the PUMA(TM) system and Cytometrix(TM) technologies to enable early identification and automated prioritization of compounds that are highly selective for their intended protein targets without other cellular effects, and are thereby less likely to give rise to clinical side effects. Cytokinetics and GlaxoSmithKline have entered into a strategic alliance to discover, develop and commercialize small molecule therapeutics targeting human mitotic kinesins for applications in the treatment of cancer and other diseases. GlaxoSmithKline is conducting Phase II and Phase Ib clinical trials for SB-715992 and a Phase I clinical trial for SB-743921, each a drug candidate that has emerged from the strategic alliance. Additional information about Cytokinetics can be obtained at www.cytokinetics.com.

This press release contains forward-looking statements for purposes of the Private Securities Litigation Reform Act of 1995 (the "Act"). Cytokinetics disclaims any intent or obligation to update these forward-looking statements, and claims the protection of the Safe Harbor for forward-looking statements contained in the Act. Examples of such statements include, but are not limited to, statements relating to the expected timing, scope and results of our clinical development and research programs and statements regarding the potential benefits of our drug candidates and potential drug candidates and the enabling capabilities of our proprietary technologies. Such statements are based on management's current expectations, but actual results may differ materially due to various factors. Such statements involve risks and uncertainties, including, but not limited to, those risks and uncertainties relating to difficulties or delays in development, testing, regulatory approval, production and marketing of Cytokinetics' drug candidates that could slow or prevent clinical development, product approval or market acceptance (including the risks related to uncertainty of patent protection for Cytokinetics' intellectual property or trade secrets, Cytokinetics' ability to obtain additional financing if necessary and unanticipated research and development and other costs). For further information regarding these and other risks related to Cytokinetics' business, investors should consult Cytokinetics' filings with the Securities and Exchange Commission.