Final efficacy results of a phase I/II trial of ixabepilone in combination with capecitabine in patients with metastatic breast cancer (MBC) previously treated with a taxane and an anthracycline
10511 Background: Ixabepilone is an epothilone B analog that has demonstrated efficacy in taxane-sensitive and taxane-resistant MBC. Differing mechanisms of action and minimally overlapping toxicities provide the potential for synergy between ixabepilone and other cytotoxics. Methods: This open-label Phase I/II study was conducted to determine the recommended Phase II (and III) doses of ixabepilone and capecitabine using a 3-hour infusion of ixabepilone given on Day 1 (Schedule A) or a 1-hour infusion of ixabepilone given for 3 consecutive days (Schedule B) in combination with capecitabine given orally on Days 1–14 every 21 days in patients (pts) with MBC previously treated with a taxane and an anthracycline in the adjuvant or metastatic setting. Pts were excluded if they had received >3 prior chemotherapy regimens in the metastatic setting. Tumor response was determined after every 2 cycles. Results from the 62 patients treated with ixabepilone 40 mg/m2 as a 3 hr-infusion and capecitabine 2000 mg/m2 are shown here. Results: 56/62 patients (90%) were aged <65 yrs. 80% of pts had visceral disease and 44% were ER/PR/HER-2 negative. 44% of pts had received ≥2 prior chemotherapies in the metastatic setting. Pts received a median of 4 cycles (range 1–20). The overall response rate was 30% (15/50; 95% CI = 17.9–44.6%) comprised of one (2%) complete response and 14 (28%) partial responses. All 15 of the responders had extensive tumor metastases at baseline. Four of the 15 responders were triple negative for ER/PR/HER-2. The median time to response was 6 weeks (range 5–14 weeks), with most responders achieving an objective response by the end of Cycle 2. The median duration of response was 6.9 months (95% CI = 4.3–9.7 months). Conclusions: The recommended Phase II (and III) doses were 40 mg/m2 ixabepilone (3-hour infusion on Day 1 every 21 days) and 2000 mg/m2 capecitabine (2 doses on Days 1–14 every 21 days). This ixabepilone/capecitabine combination demonstrated promising synergistic antitumor activity and a manageable safety profile in pts with MBC previously treated with a taxane and an anthracycline. [Table: see text]