Androgen receptor pathway inhibitor (ARPI)

Abiraterone blocks CYP17 androgen synthesis (given with prednisone); enzalutamide, apalutamide and darolutamide are potent AR antagonists. Adding an ARPI to ADT extends survival in metastatic hormone-sensitive disease (LATITUDE, ARCHES, TITAN, ARASENS), in non-metastatic castration-resistant disease and in castration-resistant disease before or after docetaxel. Resistance arises via AR amplification, ligand-binding domain mutations, the AR-V7 splice variant and lineage plasticity to neuroendocrine disease; switching ARPIs after failure gives little benefit, so PSMA radioligands, PARP inhibitors and chemotherapy follow. Older antiandrogens (bicalutamide) are weaker first-generation drugs.