Bipolar Androgen Therapy as a Potential Mechanistic Bridge to Enhance PARP Inhibitor Efficacy in Prostate Cancer.

Prostate cancer remains a leading cause of cancer-related mortality, largely driven by progression to metastatic castration-resistant prostate cancer (mCRPC). Although poly(ADP-ribose) polymerase inhibitors (PARPis) have improved outcomes in patients with homologous recombination repair (HRR) alterations, particularly in BRCA2-mutated disease, their clinical benefit is limited by restricted patient selection, modest efficacy in non-BRCA HRR alterations, and the frequent emergence of resistance. These limitations highlight an unmet need for strategies that can both expand the therapeutic population and overcome PARPi resistance. Bipolar androgen therapy (BAT), which alternates between supraphysiological and near-castrate androgen exposure, has emerged as a paradoxical yet clinically active approach in mCRPC. Unlike conventional androgen deprivation strategies, preclinical evidence suggests that BAT induces acute androgen receptor-mediated DNA damage while simultaneously suppressing HRR gene expression. This dual effect may generate a transcription-coupled homologous recombination-deficient state that is independent of canonical baseline genomic HRR alterations, thereby potentially sensitizing tumors to PARP inhibition. Current clinical trials of BAT combined with PARP inhibitors suggest activity in both HRR-deficient and HRR-proficient disease. Collectively, these findings suggest a preliminary, hypothesis-generating conceptual framework in which BAT may expand the therapeutic scope of PARPis beyond genomically defined HRR-mutated tumors and may help counteract mechanisms of PARPi resistance in mCRPC.