Oncternal Therapeutics, Inc. announced that the U.S. Food and Drug Administration (FDA) has designated ONCT-534, its novel dual-acting androgen receptor inhibitor (DAARI), as a Fast Track development program for the investigation of the treatment of patients with relapsed or refractory metastatic castration-resistant prostate cancer (mCRPC) resistant to approved androgen receptor pathway inhibitors (ARPIs). ONCT-534 interacts with both the N-terminal domain and the ligand-binding domain (LBD) of the AR, inhibiting cell growth and inducing AR degradation. Preclinical studies have shown activity in prostate cancer models against bothmutated AR, and against multiple mutations, including AR amplification, mutations in the AR LBD, and splice variants with loss of the AR LBD.

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 daralutamide. After the safety and tolerability and preliminary antitumor activity of Oncternal Therapeutics have been assessed in Phase 1, Phase 2 will commence to further evaluate the safety and preliminary antitumor activities of ONCT-534 to allow for selecting an optimal dose.