Genetic polymorphisms to predict progression-free survival in patients with metastatic castration-resistant prostate cancer (mCRPC) receiving abiraterone therapy: Results from the NCI 9012 trial

145 Background: Abiraterone is a CYP17 inhibitor approved for treatment of men with mCRPC. The NCI 9012 trial evaluated abiraterone alone with or without the PARP inhibitor veliparib in mCRPC patients. We hypothesized that germline genetic variation in the androgen axis and other metabolic enzymes would predict response to veliparib + abiraterone vs. abiraterone alone. Methods: A randomized trial cohort of (148) men with advanced mCRPC treated with abiraterone with or without veliparib was genotyped for 120 DNA polymorphisms in genes involved in androgen metabolism using Lifetech Open array chips. Blood for pharmacogenomic SNP analysis were collected at pre-treatment from each subject into 10-mL EDTA tube. Polymorphisms were tested using Cox models without treatment for prognostic testing and with treatment arm for predictive testing. Results: Genotyping was completed in 143 of 148 men; all were treated with abiraterone; 72 without veliparib (Median PFS: 10.3m) and 71 with veliparib (Median PFS: 11.3m). Polymorphisms in separate genes (SLCO2B1, KIF3C CYP19A, ESR1) were significantly (P ≤ .025) associated with progression-free survival (PFS) during abiraterone (q-value < 0.69). Polymorphisms in (CYP11A1, HSD17B4, ABHD13;LIG4, CYP19A1, HSD17B4, TRMT11) were predictive for PFS in patients treated with combination of abiraterone/veliparib compared to abiraterone alone (p-value < 0.025; q-value < 0.28). Conclusions: This analysis examines the influence of inherited variations on the efficacy of abiraterone, establishing the importance of pharmacogenomics on individual’s response to this therapy. Genotyping patients at these loci could be predictive of improved PFS to valiparib in combination with abiraterone. Further analysis of the association of more than one polymorphisms compared to zero or one with PFS associated with improved TTP demonstrated a better response to therapy than individuals carrying zero or one is ongoing. Clinical trial information: NCT01576172.