Oncternal Therapeutics, Inc. announced that the fourth patient has now been enrolled into its Phase 1/2 study of ONCT-534, its dual-action androgen receptor inhibitors, for the treatment of patients with advanced prostate cancer who are relapsed or refractory to approved androgen receptor pathway inhibitors (ARPI). The last two patients were enrolled into the third dosing cohort, to receive ONCT-534 at a dose of 160 mg taken orally each day. The study utilizes an adaptive Bayesian Optimal Interval (BOIN) design, under which the first two dosing cohorts treated one patient each at 40 mg ONCT-534 per day and 80 mg ONCT-534 Per day, respectively.

The decision to proceed to dose level 3 was confirmed by the study's Safety Review Committee (SRC). Study ONCT-534-101 is a Phase 1/2, single-arm, open-label, multi-center study to evaluate the safety and tolerability, pharmacokinetics, and preliminary anti-tumor activity of ONCT-534 in patients with mCRPC who have relapsed or are refractory to approved ARPIs including enzalutamide, abiraterone, apalutamide and darolutamide. After the safety and tolerability and preliminary antitumor activity of ONCT-534 have been assessed in the Phase 1 portion of this study, Phase 2 will commence to further evaluate the safety and preliminary antitumor activity of ONCT-534 to support selecting an optimal dose.