Oncternal Therapeutics, Inc. (NASDAQ:ONCT), a clinical-stage biopharmaceutical company focused on the development of novel oncology therapies, today announced that enrollment has been completed and dosing initiated for the fifth dose cohort of its Phase 1/2 study of ONCT-534 for the treatment of patients with metastatic castration-resistant prostate cancer who are relapsed or refractory to approved androgen receptor pathway inhibitors (ARPI). Patients in the fifth cohort are receiving ONCT-534, the company's dual-action androgen receptor inhibitor (DAARI), at a dose of 600 mg taken orally once each day. The decision to proceed to this higher dose level was made by the study's Safety Review Committee (SRC) after reviewing data from the fourth dose level of 300 mg ONCT-534 daily. An initial update on ONCT-534 safety and efficacy based on prostate-specific antigen (PSA) levels from this study is expected in the third quarter of 2024 and will include data from this 600 mg dose cohort.