Catalytic partitioning and divergent steroidogenic effects of CYP17A1 inhibition by seviteronel and abiraterone

CYP17A1 inhibition suppresses adrenal androgen precursor production in advanced prostate cancer, but steroidal and non-steroidal inhibitors may differ in their selectivity towards 17α-hydroxylase and 17,20-lyase activities. Here we compare abiraterone and seviteronel using enzyme assays, adrenal steroidomics, structural analysis, molecular-dynamics simulations and prostate cancer cell models. Abiraterone was the more potent inhibitor of both CYP17A1 activities, whereas seviteronel showed weaker absolute potency but a higher lyase/hydroxylase selectivity index. In NCI-H295R cells, abiraterone caused marked pregnenolone and progesterone accumulation with broad depletion of downstream steroids. Seviteronel produced a more restricted shift, preserving partial 17α-hydroxylated flux while suppressing androgen output. Structural analysis showed that abiraterone combines heme coordination with a steroidal Asn202 anchor, whereas seviteronel uses Val482-backbone anchoring and a distinct non-steroidal contact distribution. Replicate simulations identified greater conformational heterogeneity of the central I-helix region in the seviteronel-bound system, although these dynamics do not establish the mechanism of catalytic selectivity. In prostate cancer models, both compounds preferentially reduced viability in androgen-responsive cells and increased sensitivity to ferroptosis-inducing lipid-peroxidation stress. These findings distinguish the endocrine, structural and redox pharmacology of two CYP17A1-targeted agents.