Oncternal Completes Enrollment and Starts Dosing in Phase 1/2 Study of ONCT-534 for Resistant Prostate Cancer

7 June 2024

SAN DIEGO, May 30, 2024 - Oncternal Therapeutics (Nasdaq: ONCT), a clinical-stage biopharmaceutical company, has successfully completed enrollment and commenced dosing for the fifth dose cohort in its Phase 1/2 trial of ONCT-534. This study focuses on patients with metastatic castration-resistant prostate cancer (mCRPC) who have not responded to approved androgen receptor pathway inhibitors (ARPIs). The current cohort involves administering 600 mg of ONCT-534 orally once daily. 

The decision to escalate to this higher dose was made by the Safety Review Committee (SRC) after evaluating the safety data from the previous 300 mg dose level. Preliminary safety and efficacy data, particularly regarding prostate-specific antigen (PSA) levels, will be shared in the third quarter of 2024 and will include findings from this 600 mg cohort.

Dr. Salim Yazji, Chief Medical Officer at Oncternal Therapeutics, expressed optimism about the rapid progress of the trial. He noted that the drug has been well tolerated with no significant toxicities. The company is also expanding the number of trial sites to meet the strong patient demand. Dr. Yazji anticipates that the upcoming data release will provide a comprehensive view of the drug's safety and efficacy, incorporating a broader set of clinical and biomarker results, as well as extended follow-up data from earlier cohorts.

Study ONCT-534-101 Overview

The ONCT-534-101 study is a Phase 1/2, single-arm, open-label, multi-center trial. It aims to assess the safety, tolerability, pharmacokinetics, and preliminary anti-tumor efficacy of ONCT-534 in mCRPC patients unresponsive to existing ARPIs like enzalutamide, abiraterone, apalutamide, and darolutamide. Phase 1 focuses on safety and preliminary efficacy, while Phase 2 will delve deeper into these aspects to identify the optimal dosing regimen.

About Oncternal Therapeutics

Oncternal Therapeutics is dedicated to developing innovative cancer treatments, particularly for conditions with significant unmet medical needs. The company specializes in therapies targeting previously unexplored biological pathways involved in cancer progression, focusing on hematological malignancies and prostate cancer.

ONCT-534, a dual-action androgen receptor inhibitor (DAARI), has shown preclinical effectiveness in prostate cancer models against both normal and aberrant androgen receptors. It holds promise for patients with mCRPC who are resistant to current ARPIs, including those with AR amplifications, mutations, or splice variants lacking the ligand-binding domain.

Other Key Programs at Oncternal

Besides ONCT-534, Oncternal is also developing ONCT-808, an investigational CAR T-cell therapy targeting ROR1. This treatment has demonstrated preclinical efficacy against various hematological cancers and solid tumors and offers a potentially faster manufacturing process compared to existing CAR T products. ONCT-808 is currently being tested in patients with aggressive B-cell lymphoma who have relapsed after previous CAR T treatments.

Zilovertamab, another investigational candidate, is a monoclonal antibody designed to inhibit ROR1. It has shown promising results in combination with ibrutinib in Phase 1/2 studies for mantle cell lymphoma, chronic lymphocytic leukemia, and marginal zone lymphoma, achieving 100% progression-free survival at 42 months in certain patient groups. Zilovertamab is also being tested in combination with docetaxel for mCRPC.

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