Biomarkers as potential predictors of response to treatment with motesanib or bevacizumab in combination with paclitaxel (P) in patients (pts) with locally recurrent or advanced metastatic breast cancer (MBC).

1048^ Background: Motesanib is an orally administered small-molecule antagonist of VEGF receptors (VEGFRs) 1, 2, and 3; PDGFR; and Kit. In a phase II study, objective response rates (per RECIST) of 35%, 48%, and 45% were observed in pts with HER2-negative MBC who received first-line P plus placebo (arm A), motesanib 125 mg once daily (arm B), or bevacizumab 10 mg/kg every 2 weeks (arm C; Eur J Cancer Suppl. 2009; 7[2]:259). We evaluated whether pharmacodynamic changes in angiogenic biomarkers are associated with tumor response. Methods: Blood samples were collected from baseline (pretreatment) until 30 days after study completion. Serum samples from 224 of 277 treated pts were available for analysis. A panel of 5 biomarkers was measured by electrochemiluminescent multiplexed sandwich immunoassays. Analyses were performed using the Fisher exact test on log-transformed values. Results: In both arms B and C placental growth factor (PlGF) showed the greatest change from baseline (arm B, 3.69-fold increase aft...