The investigator-led PLUTO trial found docetaxel chemotherapy provided a better overall survival benefit than lutetium in first-line mCRPC. This result directly confronts the common clinical bias against chemotherapy ("chemophobia"), proving that older treatments can still outperform newer targeted agents and should not be prematurely abandoned.

A key hypothesis for why docetaxel showed better overall survival than lutetium in the PLUTO trial is that patients treated with lutetium upfront may become unfit for subsequent chemotherapy. This highlights a critical factor in trial design: the planned therapeutic sequence and a patient's ability to receive later-line treatments significantly impact survival outcomes.

Lutetium faces criticism for its fixed 6-cycle regimen, which may be suboptimal as the PSMA target diminishes with ADT. However, this critique is rarely applied to other drugs like PARP inhibitors, which are given until progression. This highlights a double standard and the tension between using a fixed regimen for regulatory approval versus finding the optimal dose in practice.

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.

Actuate employed a master protocol that tested their drug alongside eight different standard-of-care chemotherapies in patients who had already failed them. This design efficiently demonstrated the drug's ability to reverse chemo-resistance across multiple histologies, informing their Phase 2 strategy.

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.

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.

A significant criticism of the pivotal KEYNOTE-564 trial is that only half the patients in the control arm received standard-of-care immunotherapy upon relapse. This lack of subsequent optimal treatment complicates the interpretation of the overall survival benefit, raising questions about its true magnitude.

The FDA's current leadership appears to be raising the bar for approvals based on single-arm studies. Especially in slowly progressing diseases with variable endpoints, the agency now requires an effect so dramatic it's akin to a parachute's benefit—unmistakable and not subject to interpretation against historical data.