Onconova Therapeutics Doses First Patient in Phase 1/2a Trial of Narazaciclib Combined with Letrozole in Endometrial Cancer

Onconova Therapeutics

NEWTOWN, PA — Onconova Therapeutics, Inc. (NASDAQ: ONTX), a clinical-stage biopharmaceutical company, recently 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 4Q 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.

“Improved treatment options for recurrent LGEEC are urgently needed, as the CDK 4/6 inhibitors currently used off-label for this indication are marked by limitations related to safety, tolerability, and treatment resistance,” said Bhavana Pothuri, M.D., Professor, Department of Obstetrics and Gynecology at NYU Grossman School of Medicine and Director, Gynecologic Oncology Research; Perlmutter Cancer Center and Principal Investigator of the trial. “Narazaciclib’s kinase inhibitory profile suggests it can overcome each of these limitations thanks to reduced activity against kinases whose inhibition is associated with bone marrow toxicity and diarrhea, and increased activity against those implicated in pro-tumor immune suppression and cancer cell survival. This hypothesis is supported by data from in vitro and murine cancer models, and I look forward to its continued evaluation in the ongoing Phase 1/2a trial.”

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Steven M. Fruchtman, M.D., President and Chief Executive Officer of Onconova, commented, “Our recurrent LGEEC program provides an opportunity to establish narazaciclib as a best-in-class therapy in an indication where clinical proof-of-concept for its mechanism of action has been demonstrated. We, therefore, view the program as a key avenue for value creation and look forward to our Phase 1/2a trial’s preliminary data readout expected later this year.”


  1. Mirza MR. ESMO Virtual Congress 2020. Abstr. LBA28.
  2. Konstantinopoulos PA, et al.; 2022 SGO Annual Meeting on Women’s Cancer; March 18-21, 2022. Phoenix, AZ
  3. Colon-Otero G, Zanfagnin V, Hou X, et al. ESMO Open. 2020 Oct;5(5):e000926. doi: 10.1136/esmoopen-2020-000926.

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