Biomarker analysis from a randomized phase II study of olaparib with or without cediranib in men with metastatic castration-resistant prostate cancer (mCRPC).

Abstract

7 Background: We previously reported that cediranib, a vascular endothelial growth factor receptor tyrosine kinase inhibitor, combined with olaparib, a poly (ADP-ribose) polymerase inhibitor, prolonged radiographic progression-free survival (rPFS) compared with olaparib alone in patients with mCRPC. Herein, we present updated clinical data in the overall population and in subgroups by homologous recombination (HR) gene status. Methods: Men with a minimum of one prior line of systemic therapy for mCRPC were randomized 1:1 to receive olaparib 200 mg by mouth twice daily with cediranib 30 mg by mouth daily (C+O) or olaparib 300 mg by mouth twice daily (O). Patients were required to undergo a baseline metastasis biopsy. Next generation sequencing of HR genes was performed on available samples using BROCA-HR assay. HR deficiency (HRD) was defined by presence of homozygous deletions or deleterious mutations in HR genes including BRCA1, BRCA2, ATM, and others. The primary endpoint was rPFS and secondary endpoint was overall survival (OS). Results: Eighty-four patients were included in the analysis of whom 26 patients (31.0%) had HRD mCRPC. The most common HR gene alterations included BRCA2 (n=17, 20%), CDK12 (n=9, 11%), and ATM (n=7, 8%). Consistent with our prior report, in the overall cohort, C+O compared to O resulted in a significant improvement in rPFS (Table). The benefit in rPFS was most pronounced in patients with HRD mCRPC; however, there was no difference between arms in HR proficient (HRP) cancers. Independent of arm allocation, rPFS and OS were numerically longer in patients with HRD mCRPC compared to HRP mCRPC (rPFS: 8.8 versus 4.3 months, p=0.14; OS: 18.6 vs. 12.3 months, p=0.24). Conclusions: C+O improved rPFS in patients with mCPRC compared with O alone. The biomarker analyses revealed that the rPFS benefit of C+O over O is likely driven by patients with HRD mCRPC. Our data warrant validation and support further investigation of the combination of C+O in patients with HRD mCRPC. Clinical trial information: NCT02893917. [Table: see text]