Cytokinetics breast cancer drug meets trial objectives

The trial was designed to evaluate the safety and efficacy of ispinesib in the second- or third-line treatment of patients with locally advanced or metastatic breast cancer whose disease had recurred or progressed despite treatment with anthracyclines and taxanes. In this trial, patients received ispinesib monotherapy at 18mg/m2 as a 1-hour intravenous infusion every 21 days.

The primary endpoint of the clinical trial was objective response as determined using the response evaluation criteria in solid tumors (RECIST) criteria. The best overall responses observed with ispinesib were partial responses in four of 45 evaluable patients as measured by the RECIST criteria. Responses were confirmed by independent radiology review and were seen in liver, lung and lymph node metastases.

The duration of response, independently reviewed, ranged from 7.1 weeks to 30 weeks. The median time to progression in the treated population was 5.9 weeks. The adverse events were manageable, predictable and consistent with those seen in the phase I trials of ispinesib.

Based on these data, and consistent with a focused approach to the further development of ispinesib, Cytokinetics anticipates initiating a phase I/II clinical trial in the first-line treatment of patients with locally advanced or metastatic breast cancer during the second half of 2007. The results from this trial are expected to provide data that may inform a decision on further development of ispinesib in advanced breast cancer.