Advances in PARP Inhibitors for Prostate Cancer

SIMPLE SUMMARY: Recent practice-changing trials have highlighted the importance of polyadenosine diphosphate-ribose polymerase inhibitors (PARPi) in metastatic castrate resistant prostate cancer (mCRPC). PARP plays a quintessential role in repairing deoxyribonucleic acid (DNA) single-strand breaks by signaling and recruiting the necessary repair machinery to damaged areas. In mCRPC, where mutations are more likely to impair important repair pathways such as the homologous recombinational repair (HRR), remaining PARP repair pathways become critical to cell survival and can be exploited with targeted therapies. The purpose of our review was to compare and contrast recent pivotal trials in this setting and explore future avenues of research. ABSTRACT: Poly-adenosine diphosphate-ribose polymerase plays an essential role in cell function by regulating apoptosis, genomic stability and DNA repair. PARPi is a promising drug class that has gained significant traction in the last decade with good outcomes in different cancers. Several trials have sought to test its effectiveness in metastatic castration resistant prostate cancer (mCRPC). We conducted a comprehensive literature review to evaluate the current role of PARPi in this setting. To this effect, we conducted queries in the PubMed, Embase and Cochrane databases. We reviewed and compared all major contemporary publications on the topic. In particular, recent phase II and III studies have also demonstrated the benefits of olaparib, rucaparib, niraparib, talazoparib in CRPC. Drug effectiveness has been assessed through radiological progression or overall response. Given the notion of synthetic lethality and potential synergy with other oncological therapies, several trials are looking to integrate PARPi in combined therapies. There remains ongoing controversy on the need for genetic screening prior to treatment initiation as well as the optimal patient population, which would benefit most from PARPi. PARPi is an important asset in the oncological arsenal for mCRPC. New combinations with PARPi may improve outcomes in earlier phases of prostate cancer.