Onconova Therapeutics, Inc. announced that the first patient has been dosed in the Company's Phase 1/2a trial evaluating narazaciclib combined with letrozole in recurrent metastatic low-grade endometrioid endometrial cancer (LGEEC). Narazaciclib is a multi-kinase inhibitor targeting CDK 4, CDK 6, and other kinases important for cell proliferation and motility. Preliminary data from the trial's Phase 1 portion are expected in Fourth Quarter 2023.

Endometrial cancer arises in the uterine lining and is the most common cancer of the female reproductive organs. Endometrioid endometrial cancer is the most common subtype of endometrial cancer, accounting for approximately 75% of cases. Data from prior randomized and single-arm trials have demonstrated the anti-cancer activity of letrozole combined with CDK 4/6 inhibition in recurrent endometrial cancer1-3. Currently, there is no health authority-approved CDK 4/6 inhibitor for the treatment of endometrial cancer.

The Phase 1/2a trial is an open-label, multicenter study evaluating narazaciclib in combination with letrozole as a second or third-line treatment for patients with recurrent metastatic LGEEC. Both narazaciclib and letrozole are administered orally with a continuous daily dosing schedule. The trial begins with a Phase 1 dose escalation phase before moving to a Phase 2 expansion cohort designed to enroll approximately 30 patients.

The primary objective of the Phase 1 portion of the trial is to evaluate safety, tolerability, pharmacokinetics, and pharmacodynamics in order to determine a recommended Phase 2 dose (RP2D) of the combination. The primary objective of the Phase 2 portion will be to evaluate the efficacy of the combination at the RP2D, as measured by progression-free survival at 24 weeks. The estrogen/progesterone receptor status of participants will be recorded as part of an exploratory objective.

The trial will be conducted at sites including NYU Langone Health, the site of the Principal Investigator of the study, sites affiliated with MD Anderson Cancer Center, and U.S. Oncology Research sites.