Phase II study of ixabepilone in patients (pts) with taxane-resistant metastatic breast cancer (MBC): Final report

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Abstract
10505 Background: Ixabepilone is the first epothilone analog in a new class of antineoplastic agents, which optimizes the properties of the naturally occurring epothilone B. The epothilones promote tumor cell death by uniquely binding to tubulin and stabilizing microtubules. Methods: This international, multicenter, open-label Phase II trial was designed to assess the activity of ixabepilone in pts with highly resistant MBC who had progressed following taxane treatment. Eligible pts were aged ≥18 years with MBC (progressed on or within 4 months of taxane therapy [or within 6 months if adjuvant taxane only]). Pts must have received a taxane as their last regimen. Pts were excluded if they had received ≥3 prior chemotherapy regimens for MBC or had ≥Grade 2 neuropathy. Ixabepilone was administered intravenously as a 3-hour infusion at a dose of 40 mg/m2 every 3 weeks. Results: Of 49 pts (median age 54 years, range 30–81), 86% of pts had received at least two prior chemotherapy regimens. 98% had received prior anthracycline treatment. 73% of pts had progressed within 1 month of their last taxane dose. 84% had visceral metastases. Pts received a median of three cycles (range 1–5) and median cumulative dose of 120 mg/m2 (range 40–498 mg/m2). The tumor response rate (number of responders [complete and partial response]/number of response-evaluable pts) was 12% (95% CI = 4.7–26.5%). All the responders (n = 6) had partial responses; five of the six had not responded to prior taxane therapy. The responders received a median of 10.5 cycles (range 5–15) and had a median duration of response of 10.4 months (95% CI = 6.3–22.0 months). In 20 pts (41%) stable disease was reported as the best overall outcome. The majority of these pts (16 of 20, 80%) received ≥4 cycles of ixabepilone therapy. The median time to progression was 2.2 months (95% CI = 1.4–3.2 months); the median survival was 7.9 months (95% CI = 6.1–14.5 months). Conclusions: Ixabepilone (40 mg/m2 as a 3-hour infusion every 3 weeks) demonstrates promising antitumor activity, along with an acceptable safety profile in pts with clearly defined taxane-resistant MBC. [Table: see text]

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