Zentalis Pharmaceuticals, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2025

OR

Commission File Number:001-39263

(Exact name of Registrant as specified in its Charter)

Registrant's telephone number, including area code (858)263-4333

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

(Title of class)

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes☐ No ☒

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. Yes☐ No ☒

Indicate by check mark whether the registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12-months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No☐

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and "emerging growth company" in Rule 12b-2 of the Exchange Act.

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report.☐

If securities are registered pursuant to Section 12(b)of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements.☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to § 240.10D-1(b).☐

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes ☐ No☒

The aggregate market value of the voting and non-voting stock held by non-affiliates of the registrant, as of June 30, 2025, the last business day of the registrant's most recently completed second fiscal quarter, was approximately $66.9 million based on the closing price of $1.16 as reported on The Nasdaq Global Market on such date. Solely for the purposes of this disclosure, shares of common stock held by executive officers, directors and certain stockholders of the registrant as of such date have been excluded because such holders may be deemed to be affiliates.

The number of shares of registrant's common stock outstanding as of March 20, 2026 was 70,931,016.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant's definitive Proxy Statement relating to its 2026 Annual Meeting of Stockholders to be filed with the SEC within 120 days after the end of the fiscal year ended December 31, 2025 are incorporated herein by reference in Part III of this Annual Report on Form 10-K.

TABLE OF CONTENTS

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K contains forward-looking statements within the meaning of the safe harbor provisions for forward-looking statements contained in Section 27A of the Securities Act of 1933, as amended, or the Securities Act, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act. All statements other than statements of historical facts contained in this Annual Report on Form 10-K are forward-looking statements. In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential,” “design,” “aim,” “support,” “advance,” “on track,” “strive,” "opportunity," "upcoming," or “continue” or the negative of these terms or other similar expressions, although not all forward-looking statements contain these words. Forward-looking statements contained in this Annual Report on Form 10-K include, but are not limited to, statements about:

•our competitive position, including information relating to our competitors and their products and product candidates in our industry;

•our expectations, projections and estimates regarding our capital requirements, need for additional capital, financing our future cash needs, costs, expenses, revenues, capital resources, cash flows, financial performance, profitability, tax obligations, liquidity, growth, contractual obligations, the period of time our cash resources will fund our current operating plan, our internal control over financial reporting and disclosure controls and procedures;

•our expectations regarding the impact of our January 2025 strategic restructuring, including anticipated cost savings, workforce reductions, and our ability to execute our business strategy with reduced personnel;

•our prioritization of azenosertib (ZN-c3) and the potential for azenosertib to be first-in-class and best-in-class;

•the ability of our clinical trials to demonstrate safety and efficacy of azenosertib and other positive results;

•the global macroeconomic environment and increased inflation;

•our plans for, including the timing and focus of, our ongoing and future clinical trials of azenosertib, including the reporting of data from those studies and trials and the timing thereof and the timing of initiation of enrollment in our clinical trials, including our Phase 3 ASPENOVA confirmatory study of monotherapy azenosertib in Cyclin E1-positive platinum-resistant ovarian cancer ("PROC") patients and our plans to enroll concurrently with DENALI Part 2b;

•the design of our clinical trials, such as for DENALI Part 2 and ASPENOVA, including our estimates of the number of patients that we will enroll in our clinical trials;

•the potential benefits of the measures in the DENALI Part 2 and ASPENOVA protocols for enhanced patient monitoring, guidance and supportive care;

•the beneficial characteristics, safety, efficacy and therapeutic effects of azenosertib;

•our and our collaborators' strategy, plans and expectations with respect to the development, manufacturing, supply, approval and commercialization of azenosertib and the timing thereof;

•the designs of our studies and the type of information and data expected from our studies and the expected benefits thereof;

•our ability to obtain and maintain any marketing authorizations and our ability to complete post-marketing requirements with respect thereto;

•the timing and amounts of payments from or to our collaborators, licensors and purchasers of assets, and the anticipated arrangements and benefits under our collaboration and license agreements, including with respect to milestones and royalties;

•our plans and ability to raise additional capital, including under our at-the-market offering program, and the terms and timing thereof;

•our pipeline, including its potential, and our related research and development activities;

•our plans relating to a companion diagnostic to identify patients with Cyclin E1-positive PROC and other potential biomarkers to identify patients, and the costs thereof;

•our plans relating to the further development of azenosertib, including program timelines, potential paths to registration, and additional indications we may pursue;

•our ability to negotiate, secure and maintain adequate pricing, coverage and reimbursement terms and processes on a timely basis, or at all, with third-party payors for azenosertib and any future product candidates, if approved;

•our plans to evaluate additional strategic opportunities to maximize the value of our pipeline;

•our plans to develop azenosertib in combination with other therapies, resources allowing;

•our ability to obtain, and negotiate favorable terms of any collaboration, licensing or other arrangements that may be necessary or desirable to develop, manufacture or commercialize azenosertib;

•timing and likelihood of success of our development and commercialization efforts;

•timing of expected milestones and results, and the announcement thereof;

•the broad franchise potential of azenosertib;

•the estimated size of the market opportunity for azenosertib, including the market opportunity for azenosertib in Cyclin E1-positive PROC, and our underlying assumptions thereof, including our estimate of the limited overlap between FRα-high PROC patients and those that have Cyclin E1 overexpression, and our belief that there is additional market opportunity for azenosertib outside of ovarian cancer across other solid tumors;

•our expectations regarding the approval and use of azenosertib;

•the timing or likelihood of regulatory filings and approvals;

•our ability to obtain and maintain regulatory approval of azenosertib and any future product candidates;

•our regulatory strategy, including the potential for DENALI Part 2, if successful, to support an accelerated approval for azenosertib;

•existing laws, regulations and regulatory developments in the United States, the European Union, or the EU, and other jurisdictions;

•our intellectual property position, including obtaining and maintaining patents, and the timing, outcome and impact of administrative, regulatory, legal and other proceedings relating to our patents and other proprietary and intellectual property rights, and the timing and resolution thereof;

•our facilities and lease commitments;

•accounting standards and estimates, their impact, and their expected timing of completion;

•cybersecurity and information security;

•expected ongoing reliance on third parties, including with respect to the development, manufacturing, supply and commercialization of azenosertib and any future product candidates;

•insurance coverage;

•estimated periods of performance of key contracts; and

•the potential need to hire personnel and our ability to attract and retain personnel, and our ability to provide competitive compensation and benefits.

The forward-looking statements in this Annual Report on Form 10-K are only predictions and are based largely on our current expectations and projections about future events and financial trends that we believe may affect our business, financial condition and results of operations. These forward-looking statements speak only as of the date of this Annual Report on Form 10-K and are subject to a number of known and unknown risks, uncertainties, assumptions and other important factors, including those described under "Summary Risk Factors" below and in the sections in this Annual Report on Form 10-K entitled “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and elsewhere in this Annual Report on Form 10-K.

Because forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified and some of which are beyond our control, they may turn out to be inaccurate and you should not rely on these forward-looking statements as predictions of future events. The events and circumstances reflected in our forward-looking statements may not be achieved or occur and actual results, financial condition, performance or achievements could differ materially from those projected in the forward-looking statements. Moreover, we operate in an evolving environment. New risk factors and uncertainties may emerge from time to time, and it is not possible for management to predict all risk factors and uncertainties. Except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances or otherwise.

ZENTALIS® and its associated logo are registered trademarks of Zentalis. All other trademarks, trade names and service marks appearing in this Annual Report on Form 10-K are the property of their respective owners. All website addresses given in this Annual Report on Form 10-K are for information only and are not intended to be an active link or to incorporate any website information into this document.

INDUSTRY AND OTHER DATA

This Annual Report on Form 10-K contains industry, market and competitive position data from our own internal estimates and research as well as industry and general publications and research surveys and studies conducted by third parties. Industry publications, studies and surveys generally state that they have been obtained from sources believed to be reliable, although they do not guarantee the accuracy or completeness of such information. Our internal data and estimates are based upon information obtained from trade and business organizations and other contacts in the markets in which we operate and our management’s understanding of industry conditions. While we believe that each of these studies and publications is reliable, we have not independently verified market and industry data from third-party sources. While we believe our internal company research is reliable and the market definitions are appropriate, neither such research nor definitions have been verified by an independent source.

The industry in which we operate is subject to risks and uncertainties due to a variety of factors, including those described in Part I, Item 1A., “Risk Factors” in this Annual Report on Form 10-K. These and other factors could cause results to differ materially from those expressed in the estimates made by the independent parties and by us.

SUMMARY RISK FACTORS

Our business is subject to numerous risks and uncertainties, including those described in Part I, Item 1A., “Risk Factors” in this Annual Report on Form 10-K. You should carefully consider these risks and uncertainties when investing in our common stock. The principal risks and uncertainties affecting our business include the following:

•We have a limited operating history and have no products approved for commercial sale, which may make it difficult for you to evaluate our current business and predict our future success and viability.

•We have incurred significant net losses since inception, and we expect to continue to incur significant net losses for the foreseeable future.

•We will require substantial additional capital to finance our operations. If we are unable to raise such capital when needed, or on acceptable terms, we may be forced to delay, reduce and/or eliminate one or more of our research and drug development programs or future commercialization efforts.

•We are substantially dependent on the success of azenosertib, which is currently our only product candidate in clinical development. If we are unable to complete development of, obtain approval for and commercialize azenosertib in a timely manner, our business will be harmed.

•The clinical trials of azenosertib or any future product candidates may not demonstrate safety and efficacy to the satisfaction of the U.S. Food and Drug Administration, or FDA, or ex-U.S. regulatory authorities or otherwise produce positive results.

•We expect to be required by the FDA and ex-U.S. regulatory authorities to obtain approval of a companion diagnostic in connection with approval of our lead indication for azenosertib, and additional biomarkers may be required for the development and commercialization of azenosertib outside of our lead indication and for future product candidates. If regulatory approval is not obtained or there are delays in obtaining regulatory approval of any such companion diagnostic, we will not be able to commercialize azenosertib and, potentially, future product candidates, and our ability to generate product revenue will be materially impaired.

•The regulatory approval processes of the FDA and ex-U.S. regulatory authorities are lengthy, time consuming and inherently unpredictable. If we are ultimately unable to obtain regulatory approval for azenosertib or any future product candidates, we will be unable to generate product revenue and our business will be substantially harmed.

•We face significant competition, and if our competitors develop and market technologies or products more rapidly than we do or that are more effective, safer or less expensive than the product candidates we develop, our commercial opportunities will be negatively impacted.

•Our success depends on our ability to protect our intellectual property and our proprietary platform. If we are unable to adequately protect our intellectual property and our proprietary platform, or to obtain and maintain issued patents which are sufficient to protect azenosertib or any future product candidates, then others could compete against us more directly, which would negatively impact our business.

•Our existing collaborations are important to our business and future licenses may also be important to us and, if we are unable to maintain any of these collaborations, or if these arrangements are not successful, our business could be adversely affected.

•We rely, and expect to continue to rely, on third parties, including independent clinical investigators and contract research organizations, or CROs, to conduct certain aspects of our preclinical studies and clinical trials. If these third parties do not successfully carry out their contractual duties, comply with applicable regulatory requirements or meet expected deadlines, we may not be able to obtain regulatory approval for or commercialize azenosertib or any future product candidates and our business could be substantially harmed.

•We contract with third parties for the manufacture of azenosertib for preclinical studies and ongoing clinical trials, and expect to continue to do so for additional clinical trials and ultimately for commercialization. This reliance on third parties increases the risk that we will not have sufficient quantities of azenosertib or such quantities at an acceptable cost, which could delay, prevent or impair our development or commercialization efforts.

•Our commercial success depends significantly on our ability to operate without infringing the patents and other proprietary rights of third parties. Claims by third parties that we infringe their proprietary rights may result in liability for damages or prevent or delay our developmental and commercialization efforts.

•The competition for qualified personnel is particularly intense in our industry. If we are unable to retain or hire key personnel, then we may not be able to sustain or grow our business when needed.

•Unfavorable U.S., global, political or economic conditions could adversely affect our business, financial condition or results of operations.

•Business interruptions could adversely affect our operations.