Final analysis of phase II study of EZN-2208 (PEG-SN38) in metastatic breast cancer (MBC).

1017 Background: EZN-2208 is a water-soluble PEGylated conjugate of SN38. EZN-2208 results in prolonged exposure of tumors to SN38 via preferential accumulation of EZN-2208 in the tumor and prolonged release of SN38. These data represent the final analysis of our study evaluating EZN-2208 in MBC. Methods: EZN-2208 9 mg/m2 (SN38 equivalents) was delivered as a 60-minute IV infusion, weekly for 3 wks in 4‑wk cycles. The primary objective was to determine the overall response rate (RR) in female patients with metastatic breast cancer (MBC) who had received prior adjuvant or metastatic therapy with either 1) anthracycline and taxane (AT) or 2) anthracycline, taxane, and capecitabine (ATX). Secondary objectives included evaluation of RR based on tumor receptor status, duration of response, progression-free survival (PFS), overall survival (OS), and safety. Results: Patients with MBC (n=164) were treated with a median (range) of 3.3 (0.3-22) cycles of EZN-2208. The objective response rate (RR) was 20% for AT an...