Phase I clinical trial of bavituximab (Bavi) and paclitaxel (P) in patients (pts) with HER2-negative metastatic breast cancer (MBC).

567 Background: Bavituximab is a novel tumor vascular targeting agent. It is an unconjugated, chimeric immunoglobulin G1 monoclonal antibody directed against phosphatidylserine (PS). PS is externally expressed on endothelial cells when exposed to hypoxia and/or other physiological stressors frequently observed in tumor-associated vasculature. On attaching to PS, Bavi triggers antitumor effects by inducing antibody-dependent cellular cytotoxicity and promoting antitumor immunity. Methods: We conducted a phase I clinical trial of Bavi in combination with P in pts with HER-2 negative MBC. Pts were treated with weekly P (80mg/m2 for 3/ 4 weeks) and weekly Bavi (3mg/kg for 4/ 4 wks). Microparticle generation, activation and circulating endothelial cell apoptotic markers were measured by flow cytometry. Results: 14 pts with MBC were enrolled. Median age at MBC diagnosis was 50yrs. Seven pts had triple negative MBC; 4 pts presented with de-novo metastatic disease. Prior treatments included chemotherapy in the ad...