Co-Inhibition of Androgen Receptor and PARP as a Novel Treatment Paradigm in Prostate Cancer-Where Are We Now?

Metastatic prostate cancer remains lethal with a 5-year survival rate of about 30%, indicating the need for better treatment options. Novel antiandrogens (NAA)-enzalutamide and abiraterone-have been the mainstay of treatment for advanced disease since 2011. In patients who progress on the first NAA, responses to the second NAA are infrequent (25-30%) and short-lasting (median PFS ~3 months). With the growing adoption of NAA therapy in pre-metastatic castration-resistant settings, finding better treatment options for first-line mCRPC has become an urgent clinical need. The regulatory approval of two PARP inhibitors in 2020-rucaparib and olaparib-has provided the first targeted therapy option for patients harboring defects in selected DNA damage response and repair (DDR) pathway genes. However, a growing body of preclinical and clinical data shows that co-inhibition of AR and PARP induces synthetic lethality and could be a promising therapy for patients without any DDR alterations. In this review article, we will investigate the limitations of NAA monotherapy, the mechanistic rationale for synthetic lethality induced by co-inhibition of AR and PARP, the clinical data that have led to the global development of a number of these AR and PARP combination therapies, and how this may impact patient care in the next 2-10 years.

Optimal Sequencing and Predictive Biomarkers in Patients with Advanced Prostate Cancer

The treatment landscape of advanced prostate cancer has completely changed during the last decades. Chemotherapy (docetaxel, cabazitaxel), androgen-receptor signaling inhibitors (ARSi) (abiraterone acetate, enzalutamide), and radium-223 have revolutionized the management of metastatic castration-resistant prostate cancer (mCRPC). Lutetium-177-PSMA-617 is also going to become another treatment option for these patients. In addition, docetaxel, abiraterone acetate, apalutamide, enzalutamide, and radiotherapy to primary tumor have demonstrated the ability to significantly prolong the survival of patients with metastatic hormone-sensitive prostate cancer (mHSPC). Finally, apalutamide, enzalutamide, and darolutamide have recently provided impactful data in patients with nonmetastatic castration-resistant disease (nmCRPC). However, which is the best treatment sequence for patients with advanced prostate cancer? This comprehensive review aims at discussing the available literature data to identify the optimal sequencing approaches in patients with prostate cancer at different disease stages. Our work also highlights the potential impact of predictive biomarkers in treatment sequencing and exploring the role of specific agents (i.e., olaparib, rucaparib, talazoparib, niraparib, and ipatasertib) in biomarker-selected populations of patients with prostate cancer (i.e., those harboring alterations in DNA damage and response genes or PTEN).

A New Old Target: Androgen Receptor Signaling and Advanced Prostate Cancer

Owing to the development of multiple novel therapies, there has been major progress in the treatment of advanced prostate cancer over the last two decades; however, the disease remains invariably fatal. Androgens and the androgen receptor (AR) play a critical role in prostate carcinogenesis, and targeting the AR signaling axis with abiraterone, enzalutamide, darolutamide, and apalutamide has improved outcomes for men with this lethal disease. Targeting the AR and elucidating mechanisms of resistance to these agents remains central to drug development efforts. This review provides an overview of the evolution and current approaches for targeting the AR in advanced prostate cancer. It describes the biology of AR signaling, explores AR-targeting resistance mechanisms, and discusses future perspectives and promising novel therapeutic strategies. Expected final online publication date for the Annual Review of Pharmacology and Toxicology, Volume 62 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.