The NCI working group concluded that neither metastasis-directed therapy (MDT) nor systemic hormonal therapy should be required as a control arm in trials for biochemically recurrent (BCR) prostate cancer. This facilitates testing novel non-hormonal agents and reflects that surveillance is often a reasonable standard of care.

The next innovation for PARP inhibitors will likely involve combinations with other DNA-damaging agents beyond just ARPIs. Promising partners include radioligands like radium (an alpha emitter) and lutetium, or even therapies like superphysiologic testosterone (BAT) that are theorized to work by inducing DNA breaks.

Unlike bladder cancer, prostate cancer has highly effective androgen-pathway inhibitors (ARPIs) that extend survival. This success has pushed chemotherapy and, by extension, ADC development to later treatment lines as clinicians prioritize other novel mechanisms of action first.

The PRESTO trial evaluated adding apalutamide (APA) and abiraterone (Abby) to a standard LHRH analog. The triplet combination arm demonstrated increased toxicity without any additional efficacy gains compared to the doublet arm (LHRH + APA). This finding reinforces that more intensive combination therapy is not always better and can be detrimental in this setting.

The EMBARK trial showed that enzalutamide monotherapy was superior to standard ADT monotherapy for metastasis-free survival. This suggests potent AR antagonism may be a more effective strategy than simply depleting the testosterone ligand, challenging the long-held dogma of ADT being the fundamental building block for systemic prostate cancer therapy.

The rapid advancement of ARPIs wasn't just a scientific breakthrough. It was a rare convergence of FDA interest in new endpoints, a deeper biological understanding of castration resistance, and intense industry and academic collaboration that created a uniquely fertile ground for innovation.

Even when an ARPI is no longer effective as a standalone therapy, continuing it may be beneficial. By maintaining pressure on the androgen receptor pathway, the drug can upregulate downstream targets like PSMA, potentially enhancing the efficacy of subsequent PSMA-targeted therapies like radioligands or ADCs.

In oncology R&D, a successful two-drug combination isn't the final goal but the new standard of care to build upon. Researchers immediately begin planning for "triplets"—adding a third agent to the successful doublet—demonstrating a relentless, forward-looking strategy to incrementally improve patient outcomes.

Clinical trials combining potent ARPIs like abiraterone and enzalutamide have consistently failed. Once the androgen receptor pathway is maximally suppressed by one agent, adding another with a similar mechanism provides no further clinical advantage, much like hammering a nail that is already flush with the wood.