E7389, a novel anti-tubulin, in patients with refractory breast cancer

653 Background: E7389 is a synthetic analog of halichondrin B, with a broad anti- proliferative activity against tumor cells. Methods: E7389 was evaluated in an open-label, single-arm Phase II trial as monotherapy for patients with refractory breast cancer (≥2 prior chemotherapy regimens, which must have included an anthracycline and a taxane). E7389 was administered as an IV bolus of 1.4 mg/m2 on Days 1, 8, and 15 of a 28-day cycle (group 1), or on Days 1 and 8 of a 21-day cycle (group 2). The primary efficacy endpoint was ORR. Results: As of 9 December 2005, 88 patients had received treatment, 68 in group 1 and 20 in group 2. Median age was 55 yrs (range 36–84) and ECOG performance status 0–1. Sixty-six percent of the tumors were ductal carcinomas, 6% lobular, and 27% were unclassified. Sixty percent of the tumors were ER+, 47% PR+, and 17% Her2/neu 3+. The patients had received at least two previous regimens, with a median number of 5 (range 2–14). Forty-eight percent of the patients had also used horm...