Oncternal Therapeutics announces updated data from Phase 1/2 study of ONCT-534

Oncternal Therapeutics (ONCT) announced updated data from its Phase 1/2 Study of ONCT-534 for the treatment of patients with relapsed or refractory metastatic Castration-Resistant Prostate Cancer, mCRPC. Based on initial pharmacokinetic results, two additional dosing cohorts with twice daily, BID, oral dosing of ONCT-534 had been incorporated in the Phase 1/2 study ONCT-534-101. Overall, fifteen patients received ONCT-534 once daily in six dosing cohorts and six patients received ONCT-534 BID in two dosing cohorts. Based on a data cut off of September 30, 2024, the BID dosing schedule was well tolerated, with no related Grade 3 or higher toxicities. One patient, who experienced a rising PSA on ONCT-534 at 160 mg BID, had a subsequent 50% reduction in PSA after four weeks of ONCT-534 at 300 mg BID, and at the same time the CAT Scan showed a 16% reduction in target lesions compared to baseline. Enumeration and biomarker analysis of circulating tumor cells showed promising effects on expression of androgen receptor-regulated genes, and AR nuclear translocation in six additional patients. CTC analysis also showed that some patients who did not respond to ONCT-534 had prostate cancer that had developed neuroendocrine features, which are associated with AR independent disease.