On May 26, 2023 Zentalis Pharmaceuticals, Inc. (Nasdaq: ZNTL), a clinical-stage biopharmaceutical company discovering and developing clinically differentiated small molecule therapeutics targeting fundamental biological pathways of cancers, reported positive data from the Phase 1b trial of azenosertib, the Company’s potentially first-in-class WEE1 inhibitor, in combination with chemotherapy in patients with platinum-resistant ovarian cancer (Press release, Zentalis Pharmaceuticals, MAY 26, 2023, View Source [SID1234632151]). Azenosertib was well tolerated in combination with multiple types of chemotherapy and demonstrated encouraging clinical activity, with noteworthy improvements in objective response rates (ORRs) and median progression free survival (mPFS) in all patients, especially those with Cyclin E1+ tumors, a subgroup recognized to have a poor prognosis and be refractory to chemotherapy. Results will be presented in a poster discussion session at the 2023 ASCO (Free ASCO Whitepaper) Annual Meeting on June 5th (Abstract #5513).

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"Azenosertib is emerging as a very promising clinical candidate, with demonstrated anti-tumor activity in difficult-to-treat tumor types when used in combination with standard chemotherapy regimens," said Kimberly Blackwell, M.D., Chief Executive Officer of Zentalis. "The addition of azenosertib increased ORRs and mPFS over those observed historically with chemotherapy alone, or compared to adavosertib in combination with chemotherapy. We are very encouraged by our robust chemotherapy combination data, particularly the strong efficacy and tolerability results when dosing azenosertib intermittently. These data provide a compelling rationale to advance azenosertib into a registrational study in combination with either carboplatin or paclitaxel in Cyclin E1+ ovarian cancer. We look forward to providing additional insights into our azenosertib clinical programs and the franchise potential we see for this product candidate during our June 6 investor webcast."

Efficacy and Safety Results:

A total of 115 patients were enrolled in the study across all chemotherapy combination groups. At the data cut-off of April 10, 2023, 94 were efficacy evaluable. Across all dosing schedules, azenosertib plus paclitaxel demonstrated the highest ORR of 50.0% (mPFS of 7.4m), followed by an ORR of 38.5% (mPFS of 8.3m) for azenosertib plus gemcitabine. Azenosertib plus carboplatin demonstrated an ORR of 35.7% (mPFS of 10.4m), and azenosertib plus PLD demonstrated an ORR of 19.4% (mPFS of 6.3m).

A total of 82 response-evaluable patients had available Cyclin E1 expression data by immunohistochemistry (IHC). Cyclin E1+ status (H-score >50) was associated with a superior ORR and a longer mPFS across the total patient population (ORR of 40.0% vs 8.3%; mPFS of 9.86 vs 3.25 months, HR = 0.37; P = 0.0078), showcasing the potential synergy of WEE1 inhibition with chemotherapy in this patient population.

Overall, the tolerability of azenosertib dosed intermittently in combination with either paclitaxel or carboplatin compares favorably to historical data from standard of care chemotherapy doublets of either paclitaxel-carboplatin or PLD-carboplatin. Frequent Grade ≥3 treatment-related adverse events (%) across all azenosertib intermittent dosing groups were thrombocytopenia (27.5%), neutropenia (25.5%), anemia (15.7%), and fatigue (9.8%). A recommended Phase 2 dose was determined for each of the azenosertib combinations with paclitaxel, carboplatin, and PLD.
Based on these results, the Company is planning to initiate a Phase 3 study comparing azenosertib dosed intermittently in combination with either carboplatin or paclitaxel in patients with Cyclin E1+ platinum-sensitive ovarian cancer. The Company expects to initiate the Phase 3 study in the first quarter of 2024.
"The results thus far for azenosertib in combination with chemotherapy are very promising, as there remains high unmet need in this patient population, particularly patients with Cyclin E1+ tumors who historically have not responded well to chemotherapy," said Joyce Liu, M.D., M.P.H., Associate Chief and Director of Clinical Research for the Division of Gynecologic Oncology at the Dana-Farber Cancer Institute. "I look forward to continuing to work with the Zentalis team to advance azenosertib in the clinic and, if approved, ultimately into medical practice as an important and novel treatment option for platinum-sensitive ovarian cancer patients."
Premal H. Thaker, M.D., Professor of Obstetrics and Gynecology, Director of Gynecological Oncology Clinical Research, Division of Gynecologic Oncology, Washington University School of Medicine, and an investigator on the study added, "The data for azenosertib in combination with chemotherapy are increasingly robust and encouraging. Moreover, the enrichment of patients by Cyclin E1+ status provides a compelling strategy for future clinical trials. I look forward to the initiation of a study examining the role of azenosertib in combination with chemotherapy in earlier lines of therapy."

The Company will host a webcast on Tuesday, June 6, 2023 at 8:00 a.m. ET to provide a clinical update, including an overview of the ASCO (Free ASCO Whitepaper) data, as well as safety, pharmacology and efficacy results for azenosertib as a monotherapy, and plans for future development of azenosertib as a monotherapy and in combination with chemotherapy. The corporate webcast will be accessible via the Investors page of Zentalis’ website, www.zentalis.com. The archived webcast and presentation will be available on the Company’s website after the event.

ASCO Presentation Details:
Poster Title: Correlation of Cyclin E1 expression and clinical outcomes in a Phase 1b dose-escalation study of Azenosertib (ZN-c3), a WEE1 inhibitor, in combination with chemotherapy in patients with platinum-resistant or refractory (R/R) epithelial ovarian, peritoneal, or fallopian tube cancer
Presenter: Dr. Liu, M.D., M.P.H., Associate Chief and Director of Clinical Research for the Division of Gynecologic Oncology at the Dana-Farber Cancer Institute.
Session Title: Gynecologic Cancer

Session Date and Time: Monday, June 5, 2023, 1:15 – 4:15 p.m. CT
Location: Hall A
Poster Board Number: 208
Poster Discussion Session Date and Time: Monday, June 5, 2023, 4:30 – 6:00 p.m. CT
Location: S100bc
Abstract Presentation Number: 5513

A video summary of the poster by Dr. Liu will be available on the ASCO (Free ASCO Whitepaper) virtual platform.
Once presented, the poster can be found on the Company’s website using this link.

About Azenosertib
Azenosertib is a potentially first-in-class and best-in-class small molecule WEE1 inhibitor in development for the treatment of cancer. Inhibition of WEE1, a DNA damage response kinase, drives cancer cells into mitosis without being able to repair damaged DNA, resulting in cell death. Currently, there are no FDA-approved WEE1 inhibitors, and azenosertib has been designed for superior selectivity and pharmacokinetic properties. Azenosertib is being developed in therapeutic areas of high unmet need and is being evaluated as a monotherapy, in combination with chemotherapy, and in combination with molecularly targeted agents.