Potential Amplified Efficacy Signal Observed With Greater Dose-Density on New Schedule

SOUTH SAN FRANCISCO, CA -- (Marketwire) -- 05/30/09 -- Cytokinetics, Incorporated (NASDAQ: CYTK) announced today that a poster presentation summarizing interim data from the Phase I portion of a Phase I/II clinical trial data evaluating SB-743921, a novel inhibitor of kinesin spindle protein (KSP), in patients with non-Hodgkin and Hodgkin lymphoma was presented at the 2009 Annual Meeting of the American Society of Clinical Oncology (ASCO) held from May 29 - June 2, 2009 in Orlando, FL. The poster highlighted that greater dose-density has been achieved with a dosing schedule of days 1 and 15 of a 28-day cycle in this clinical trial, as compared to a previous Phase I trial evaluating SB-743921. In addition, a potential amplified efficacy signal was observed without any significant increase in side effects.

"In the Phase I portion of this Phase I/II clinical trial, we have observed objective partial response in 3 of 10 patients (30%) treated at the two highest dose levels of 8 mg/m2 and 9 mg/ m2," stated Owen A. O'Connor, MD, PhD, Columbia Medical Center, New York, NY. "This new dosing schedule with cytokine support appears to allow us to achieve higher doses, with potentially marked improvement in the activity of SB-743921. This clinical activity, along with the very favorable side effect profile and novel mechanism of action, may represent a new approach to treating lymphoma patients."

"We are encouraged by the amplified activity that we are observing in this Phase I/II clinical trial," stated Andrew A. Wolff, MD, FACC, Cytokinetics' Senior Vice President of Clinical Research and Development and Chief Medical Officer. "The favorable tolerability profile of SB-743921 combined with this signal of clinical activity in the on-going Phase I portion of this clinical trial is encouraging, as we continue to dose-escalate with this newer dosing schedule and with granulocyte colony-stimulating factor support. We look forward to identifying the maximum-tolerated dose that can be achieved when SB-743921 is given on this schedule with supportive care."

Poster Presentation at ASCO

The poster titled, "A Phase I/II Trial of Kinesin Spindle Protein (KSP) Inhibitor SB-743921 Dosed q14d Without and With Prophylactic G-CSF in Non-Hodgkin (NHL) or Hodgkin Lymphoma (HL)" was presented on Saturday, May 30, 2009. This poster summarized an ongoing, multi-center, international Phase I/II open-label, non-randomized dose-finding clinical trial evaluating, SB-743921 in patients with non-Hodgkin or Hodgkin lymphoma who have progressed or relapsed on standard therapy. The primary objective of this clinical trial is to determine the dose-limiting toxicities (DLTs) and the maximum-tolerated dose (MTD) of SB-743921 administered as a 1-hour infusion on days 1 and 15 of a 28-day cycle, first without and then with prophylactic granulopoietic factor support (i.e., granulocyte colony-stimulating factor or G-CSF) and to assess the safety and tolerability of SB-743921 on this schedule. The secondary objectives are to characterize the pharmacokinetics of SB-743921 administered on this schedule and to evaluate the effect of SB-743921 on biomarkers of cell proliferation in patients with accessible tumors. The authors concluded that the main DLT of SB-743921 on this schedule without G-CSF was neutropenia, leading to a DLT of 6 mg/m2.