{"url_path":"/sec/zntl/8-k/2026-05-21/item-8-01","section_key":"item-8-01","section_title":"Item 8.01 Other Events.","topic":"sec","document":{"doc_type":"8-K","doc_date":"2026-05-21","source_url":"https://www.sec.gov/Archives/edgar/data/1725160/0001725160-26-000045-index.html","accession_number":"0001725160-26-000045","cik":"0001725160","ticker":"ZNTL","issuer_name":"Zentalis Pharmaceuticals, Inc.","edgar_url":"https://www.sec.gov/Archives/edgar/data/1725160/0001725160-26-000045-index.html","primary_entity_key":"0001725160","primary_entity_name":"Zentalis Pharmaceuticals, Inc."},"word_count":1027,"has_tables":true,"body_markdown":"Item 8.01 Other Events.\n\nOn May 21, 2026, Zentalis Pharmaceuticals, Inc. (the “Company”) announced that data from Part 1 of the Phase 1b MUIR trial will be presented at the 2026 American Society of Clinical Oncology (\"ASCO\") Annual Meeting, being held May 29 – June 2, 2026, in Chicago, Illinois.\n\nMUIR is a multi-part, open-label Phase 1b clinical trial evaluating azenosertib in combination with chemotherapy in patients with ovarian cancer. Part 1 evaluated azenosertib in combination with four chemotherapy regimens in patients with platinum-resistant ovarian cancer (\"PROC\"), with data from the paclitaxel arm presented at ASCO as paclitaxel is commonly used across multiple tumor types, including ovarian cancer. Data from the other combination arms will be presented separately at a later date. The findings reflect a December 1, 2025 data cutoff and include 46 patients who received azenosertib across four dose cohorts — 200 mg QD continuously or 200 mg, 250 mg, or 300 mg QD intermittently (5 days on, 2 days off) — in combination with paclitaxel 80 mg/m². All patients had received prior paclitaxel.\n\nIn an all-comer PROC population across all four dose cohorts (n=46), the following clinical activity was observed:\n\n•Overall Response Rate (ORR): 39.1% (95% CI: 25.1–54.6)\n\n•Clinical Benefit Rate (CBR): 58.7% (95% CI: 42.2–73.0)\n\n•Median Duration of Response (DOR): 5.6 months (95% CI: 5.6–9.2)\n\n•Median Progression-Free Survival (PFS): 7.3 months (95% CI: 3.7–7.5)\n\nClinical activity was broadly comparable in Cyclin E1-positive patients (ORR: 41.4% [95% CI: 23.5-61.1]; median PFS: 7.3 months [95% CI: 3.7-9.1]) and Cyclin E1-negative patients (ORR: 35.7% [95% CI: 12.8-64.9]; median PFS: 5.4 months [95% CI: 1.7-NE]), suggesting that Cyclin E1-positive biomarker status may not be required to derive benefit when azenosertib is combined with a cytotoxic agent.\n\nAt the 250 mg intermittent (5:2) dose cohort (n=12), which demonstrated the potential optimal therapeutic index, the following clinical activity was observed:\n\n•ORR: 50.0% (95% CI: 21.1–78.9), including one complete response\n\n•CBR: 66.7% (95% CI: 34.9-90.1)\n\n•Median DOR: 9.2 months (95% CI: 3.8–NE)\n\n•Median PFS: 5.5 months (95% CI: 1.7–12.9)\n\nAs of the December 1, 2025 data cutoff, a manageable safety profile with a low rate of high-grade events across all four dose cohorts (n=46) was observed:\n\n•The most common all-grade treatment-related adverse events (TRAEs): fatigue (60.9%), anemia (58.7%), nausea (52.2%), and neutropenia (50.0%).\n\n•The most frequent Grade ≥3 TRAEs: neutropenia (30.4%) and anemia (19.6%); rates of high-grade fatigue and nausea were less than 10%.\n\n•Serious TRAEs occurred in approximately 20% of patients; the most frequent were fatigue, diarrhea, and neutropenia, each of which occurred in 2 patients.\n\n•Of 15 patients (32.6%) who discontinued due to adverse events, approximately half discontinued paclitaxel only and were able to continue on azenosertib monotherapy until disease progression.\n\n•One Grade 5 event due to sepsis was assessed as related to azenosertib by the investigator (previously reported in June 2024). While the role of azenosertib cannot be excluded, the event may have been attributable to the patient's advanced disease, given the absence of neutropenia and negative blood cultures at the time of the event.\n\nCautionary Note Regarding Forward-Looking Statements\n\nThis Current Report contains forward-looking statements within the meaning of the U.S. Private Securities Litigation Reform Act of 1995, as amended. All statements contained in this Current Report that do not relate to matters of historical fact should be considered forward-looking statements, including, but not limited to, statements regarding: the continued development of azenosertib; the clinical and therapeutic potential of azenosertib as a monotherapy and as a combination agent; the potential benefits of azenosertib across multiple lines of ovarian cancer and other tumor types; the presentation of data from other combination arms; the significance of the referenced results; and the Company’s presentation at ASCO. The terms \"evaluate,\" “develop,” “expect,” “intend,” “plan,” “potential,” “may,” “strategy,” \"suggest,\" and “will” and similar references are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause the Company's actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including, but not limited to, the following: the Company’s limited operating history, which may make it difficult to evaluate the Company’s current business and predict the Company’s future success and viability; the Company has incurred and expects to continue to incur significant losses; the Company’s need for additional funding, which may not be available; the Company’s substantial dependence on the success of azenosertib; the Company’s plans, including the costs thereof, of development of companion diagnostics; the outcome of early clinical trials may not be predictive of the success of later clinical trials; potential unforeseen events during clinical trials could cause delays or other adverse consequences; risks relating to the regulatory approval process or ongoing regulatory obligations; the Company’s product candidates may cause serious adverse side effects; the Company's ability to establish effective sales or marketing capabilities; the interim and preliminary data from the Company's clinical trials may change as more patient data becomes available, and are subject to audit and verification procedures that could result in material changes in the final data; if the Company's confirmatory trials do not verify clinical benefit, the FDA may seek to withdraw accelerated approval; the Company's ability to establish effective sales or marketing capabilities; the Company’s reliance on third parties; effects of significant competition; the possibility of system failures or security breaches; risks relating to intellectual property; the Company’s ability to attract, retain and motivate qualified personnel; significant costs as a result of operating as a public company; and the other important factors discussed under the caption “Risk Factors” in the Company’s most recently filed periodic report on Form 10-K or 10-Q and subsequent filings with the U.S. Securities and Exchange Commission (SEC) and the Company’s other filings with the SEC. Any such forward-looking statements represent management’s estimates as of the date of this Current Report. While the Company may elect to update such forward-looking statements at some point in the future, the Company disclaims any obligation to do so, even if subsequent events cause the Company’s views to change."}