Poster summarizing clinical trial data regarding SB-743921 presented by Cytokinetics

Cytokinetics, Incorporated (NASDAQ: CYTK) announced today that a poster summarizing clinical trial data regarding SB-743921 was presented at the 2009 American Society of Hematology (ASH) Annual Meeting and Exposition held December 5-8, 2009 at the Ernest N. Morial Convention Center in New Orleans, Louisiana. SB-743921 is a novel, small molecule inhibitor of kinesin spindle protein (KSP), a mitotic kinesin essential for proper cell division.

"We are pleased by the results emerging from this Phase I/II clinical trial, especially in patients with Hodgkin Lymphoma," stated Andrew A. Wolff, MD, FACC, Cytokinetics' Senior Vice President of Clinical Research and Development and Chief Medical Officer. "The clinical activity as well as the favorable tolerability profile of SB-743921 that have been observed in the Phase I portion of this clinical trial strengthen our belief that this novel drug candidate warrants further development in patients with lymphomas and we look forward to advancing this program under a potential partnership."

Poster Presentation at the 2009 American Society of Hematology (ASH) Annual Meeting and Exposition:

The poster titled, "A Phase I/II Trial of the 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, December 5, 2009 by Owen A. O'Connor, M.D., Ph.D., Deputy Director of Clinical Research and Cancer Treatment at The Cancer Institute and Chief of the new Division of Hematologic Malignancies and Medical Oncology in the department of Medicine, New York University Langone Medical Center, New York, NY. This poster summarized the Phase I portion of a 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 objectives of this clinical trial were 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 were 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 MTD of SB-743921 given on this schedule with G-CSF support was 9 mg/m2. The main DLT of SB-743921 on this schedule with G-CSF support was thrombocytopenia and neutropenia. The authors noted that a greater dose-density was achieved with SB-743921 given on a once every two week schedule without prophylactic G-CSF (i.e., 6 mg/m2 = 0.43 mg/m2/day) than a once every 21 days schedule (i.e., 4 mg/m2 = 0.19 mg/m2/day). Dose-density with G-CSF on the once every two week schedule was equal to 0.64 mg/m2. Grade 3 or 4 toxicities other than myelosuppression were infrequent; in particular, there was no evidence of neuropathy or alopecia greater than Grade 1. An efficacy signal was observed at doses at or above 6 mg/m2 in Hodgkin Lymphoma patients. Of the 55 patients evaluable for efficacy, four partial responses (three patients with Hodgkin Lymphoma and one with indolent non-Hodgkin Lymphoma) were observed. The duration of the response in the patients with a partial response was between 8 weeks and 28 weeks. Best response as a percentage reduction in the sum of the product of diameters for the dominant lesion ranged from 53% to 71%. The small numbers of patients in each of the non-Hodgkin Lymphoma subtypes limited the assessment of activity in those populations. The authors concluded that further evaluation of SB-743921 in selected Hodgkin Lymphoma populations as a single agent, and in combination with other promising drug candidates, is warranted.