Pretreatment serum biomarkers and clinical outcome in the phase II trial of zibotentan (endothelin A receptor antagonist) in metastatic CRPC.

154 Background: Three angiogenesis-related serum biomarkers [TIMP-1 (tissue inhibitor of metalloproteinase-1), CA IX (carbonic anhydrase 9), and VEGF] and PSA were correlated with outcome in the phase II zibotentan [endothelin A (ETA) receptor inhibitor] trial in metastatic CRPC. Methods: Pretreatment serum samples were available from 206 of 312 patients enrolled in the multicenter phase II trial evaluating zibotentan in patients with metastatic CRPC and bone metastases who were pain free or mildly symptomatic for pain, with a 1:1:1 randomization to zibotentan 10mg, 15mg, or placebo. The CA IX, TIMP-1, and VEGF ELISAs were from WILEX Inc./Oncogene Science, Cambridge, MA. Progression-free survival (PFS) and overall survival (OS) were analyzed using the Kaplan-Meier method and Cox modeling. Results: In the final efficacy report, there were no statistical differences in PFS, but a trend for OS improvement was observed in the zibotentan arms compared with placebo: 15 mg (HR 0.76; 80% CI 0.61–0.94; p= 0.103) a...