Oncternal Therapeutics Inc. has received a study may proceed letter from the FDA for a phase I/II dose-escalation study of ONCT-534, a novel dual-action androgen receptor inhibitor (DAARI), in patients with metastatic castration-resistant prostate cancer (mCRPC) who have relapsed or are refractory to approved androgen receptor signaling inhibitors (ARSIs). The letter was received prior to the 30-day review date.