Phase I Study of Seviteronel, a Selective CYP17 Lyase and Androgen Receptor Inhibitor, in Men with Castration-Resistant Prostate Cancer

Purpose: Seviteronel (INO-464) is a selective cytochrome P450c17a (CYP17) 17,20-lyase (lyase) and androgen receptor (AR) inhibitor with antitumor activity in vitro and in vivo. This open-label phase I clinical study evaluated the safety, tolerability, pharmacokinetics and activity of once-daily seviteronel in male chemotherapy-naive subjects with castration-resistant prostate cancer (CRPC). Patients and Methods: Seviteronel was administered at 600 mg once daily with dose titration (DT) and in modified 3 thorn 3 dose escalation once-daily cohorts at 600, 750, and 900 mg without DT. The primary objectives of this study were to establish safety, tolerability, and the MTD of seviteronel in chemotherapy-naive subjects with or without prior treatment with FDA-approved CRPC treatments, abiraterone acetate (AA), and enzalutamide. Secondary objectives were to assess pharmacokinetics, PSA, tumor response, and endocrine results. Results: Twenty-one subjects were enrolled. No dose-limiting toxicities (DLT) were observed through 750 mg once daily. Most treatment-emergent adverse events (AE) reported at grade 1-2. The most commonly reported AEs were fatigue (71%), dizziness (52%), blurred vision (38%), and dysgeusia (33%), with most AEs improving after dose reduction or dose interruption. Conclusions: Once-daily seviteronel was generally well tolerated in this phase I study of men with CRPC, a majority of which had progressed on prior AA or enzalutamide, or both. Of the doses evaluated, 600 mg once daily was chosen as the recommended phase II dose for future studies in subjects with CRPC. (C) 2018 AACR.