Merck & Co. 10-K 2025-12-31

As filed with the Securities and Exchange Commission on February 24, 2026

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D. C. 20549

_________________________________

FORM 10-K

For the Fiscal Year Ended December 31, 2025

OR

For the transition period from to

Commission File No. 1-6571

Merck & Co., Inc.

(908) 740-4000

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 Exchange Act). Yes ☐ No ☒

Number of shares of Common Stock ($0.50 par value) outstanding as of January 31, 2026: 2,472,392,003.

Aggregate market value of Common Stock ($0.50 par value) held by non-affiliates on June 30, 2025 based on the closing price on June 30, 2025, the last business day of the registrant’s most recently completed second fiscal quarter: approximately $198,051,000,000.

Table of Contents

PART I

Merck & Co., Inc. (Merck or the Company) is a global health care company that delivers innovative health solutions through its prescription medicines, including biologic therapies, vaccines and animal health products. The Company’s operations are principally managed on a product basis and include two operating segments, Pharmaceutical and Animal Health, both of which are reportable segments.

The Pharmaceutical segment includes human health pharmaceutical and vaccine products. Human health pharmaceutical products consist of therapeutic and preventive agents, generally sold by prescription, for the treatment of human disorders. The Company sells these human health pharmaceutical products primarily to drug wholesalers and retailers, hospitals, government agencies, and managed health care providers such as health maintenance organizations, pharmacy benefit managers and other institutions. Human health vaccine products consist of preventive pediatric, adolescent and adult vaccines. The Company sells these human health vaccines primarily to physicians, wholesalers, distributors and government entities.

The Animal Health segment discovers, develops, manufactures and markets a wide range of veterinary pharmaceutical and vaccine products, as well as health management solutions and services, for the prevention, treatment and control of disease in all major livestock and companion animal species. The Company also offers an extensive suite of digitally connected identification, traceability and monitoring products. The Company sells its products to veterinarians, distributors, animal producers, farmers and pet owners.

All product or service marks appearing in type form different from that of the surrounding text are trademarks or service marks owned, licensed to, promoted or distributed by Merck, its subsidiaries or affiliates, except as noted. All other trademarks or service marks are those of their respective owners.

Product Sales

Total Company sales, including sales of the Company’s top pharmaceutical products, as well as sales of animal health products, were as follows:

*(1)*Alliance revenue represents Merck’s share of profits, which are product sales net of cost of sales and commercialization costs.

*(2)*Other revenues are primarily comprised of miscellaneous corporate revenues, including revenue hedging activities, as well as revenue from third-party manufacturing arrangements.

Pharmaceutical

The Pharmaceutical segment includes human health pharmaceutical and vaccine products. Human health pharmaceutical products consist of therapeutic and preventive agents, generally sold by prescription, for the treatment of human disorders. Human health vaccine products consist of preventive pediatric, adolescent and adult vaccines. Certain of the products within the Company’s franchises are as follows:

Oncology

Keytruda (pembrolizumab) is an anti-PD-1 (programmed death receptor-1) therapy available for intravenous administration that has been approved as monotherapy for the treatment of certain patients with cervical cancer, classical Hodgkin lymphoma (cHL), cutaneous squamous cell carcinoma, esophageal or gastroesophageal junction (GEJ) carcinoma, head and neck squamous cell carcinoma (HNSCC), hepatocellular carcinoma (HCC), melanoma, Merkel cell carcinoma, microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR) solid tumors (including MSI-H/dMMR colorectal cancer and endometrial carcinoma), non-small cell lung cancer (NSCLC), primary mediastinal large B-cell lymphoma (PMBCL), tumor mutational burden-high (TMB-H) solid tumors, and urothelial cancer including non-muscle invasive bladder cancer. Keytruda is also approved as monotherapy for the adjuvant treatment of certain patients with melanoma, and for certain patients with renal cell carcinoma (RCC) post-surgery. Keytruda is approved for adjuvant treatment following resection and platinum-based chemotherapy for certain patients with NSCLC.

Additionally, in perioperative settings, Keytruda is approved for patients with certain types of resectable NSCLC in combination with chemotherapy as neoadjuvant treatment, and then continued as a single agent as adjuvant treatment after surgery; for certain patients with high-risk early stage triple-negative breast cancer (TNBC) in combination with chemotherapy as neoadjuvant treatment, and then continued as a single agent as adjuvant treatment after surgery; for certain patients with resectable locally advanced HNSCC as a single agent as neoadjuvant treatment, continued as adjuvant treatment in combination with radiotherapy with or without cisplatin chemotherapy and then as a single agent; and for certain patients with muscle invasive bladder cancer (MIBC), in combination with enfortumab vedotin, as neoadjuvant treatment and then continued after cystectomy as adjuvant treatment.

In addition, Keytruda is approved in combination with chemotherapy for the treatment of certain patients with advanced NSCLC, advanced malignant pleural mesothelioma, HNSCC, advanced biliary tract cancer, advanced esophageal cancer, advanced TNBC, and advanced or recurrent endometrial carcinoma; in combination with chemotherapy with or without bevacizumab, and in combination with chemoradiotherapy, for the treatment of certain patients with advanced cervical cancer; in combination with trastuzumab and chemotherapy for the treatment of certain patients with advanced human epidermal growth factor receptor 2 (HER2)-positive gastric or GEJ adenocarcinoma, and in combination with chemotherapy for the treatment of certain patients with advanced HER2-negative gastric or GEJ adenocarcinoma; in combination with axitinib for the treatment of certain patients with advanced RCC; in combination with Lenvima (lenvatinib) for the treatment of certain patients with advanced RCC or advanced endometrial carcinoma; in combination with enfortumab vedotin for certain patients with locally advanced or metastatic urothelial cancer; and in combination with chemotherapy with or without bevacizumab for certain patients with platinum-r

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Summary Risk Factors

The Company is subject to a number of risks that if realized could materially adversely affect its business, results of operations, cash flows, financial condition or prospects. The following is a summary of the principal risk factors facing the Company:

• The Company is dependent on its patent rights, and if its patent rights are invalidated or circumvented, its business could be materially adversely affected.

• As the Company’s products lose market exclusivity, the Company generally experiences a significant and rapid loss of sales from those products.

• Key products generate a significant amount of the Company’s profits and cash flows, and any events that adversely affect the markets for its leading products could have a material adverse effect on the Company’s results of operations, cash flows, financial condition, and prospects.

• The Company’s research and development efforts may not succeed in developing commercially successful products and the Company may not be able to acquire commercially successful products in other ways; consequently, the Company may not be able to replace sales of successful products that lose patent protection.

• The Company’s success is dependent on the successful development and marketing of new products, which are subject to substantial risks.

• The Company faces continued pricing pressure with respect to its products in the public and private sectors.

• Unfavorable or uncertain economic conditions, together with cost-reduction measures being taken by the U.S. and other countries, could negatively affect the Company’s operating results.

• The Company faces intense competition from both lower cost generic and biosimilar products and competitors’ products.

• The Company has significant global operations, which expose it to additional risks, and any adverse event could have a material adverse effect on the Company’s results of operations, cash flows, financial condition, and prospects.

• Climate change or legal, regulatory or market measures to address climate change may negatively affect the Company’s business, results of operations, cash flows, financial condition, and prospects.

• Environmental, social and governance matters may impact the Company’s business and reputation.

• Failure to attract and retain highly qualified personnel could affect the Company’s ability to successfully develop and commercialize products.

• The Company may experience difficulties and delays in manufacturing certain of its products, including vaccines.

• The Company’s business in China experienced significantly lower sales of Gardasil/Gardasil 9 in 2025 and the Company expects that sales of Gardasil/Gardasil 9 in China will not materially increase in 2026. As a consequence of the reduced sales of Gardasil/Gardasil 9, the Company’s business in China declined significantly.

• The Company may not be able to realize the expected benefits of its investments in emerging markets.

• The Company is exposed to market risk from fluctuations in currency exchange rates and interest rates.

• Pharmaceutical products can develop unexpected safety or efficacy concerns.

• Reliance on third-party relationships and outsourcing arrangements could materially adversely affect the Company’s business.

• Negative events in the animal health industry could have a material adverse effect on future results of operations and financial condition of the Company or its Animal Health business.

• Biologics and vaccines carry unique risks and uncertainties, which could have a material adverse effect on the Company’s future results of operations, cash flows, financial condition, and prospects.

• The health care industry in the U.S. has been, and will continue to be, subject to increasing regulation and political action.

• The Company’s products, including products in development, cannot be marketed unless the Company obtains and maintains regulatory approval or authorization.

• Developments following regulatory approval or authorization may adversely affect sales of the Company’s products.

• The Company is subject to a variety of U.S. and international laws and regulations.

• The Company is subject to evolving and complex tax laws, which may result in additional liabilities that may affect results of operations and financial condition.

• Adverse outcomes in current or future legal matters could negatively affect the Company’s business.

• Product liability insurance for products may be limited, cost prohibitive or unavailable.

• The Company is increasingly dependent on sophisticated software applications and computing infrastructure, including the use of cloud-based applications and environments. The Company continues to be a target of cyber-attacks that could lead to a disruption of its worldwide operations, including manufacturing, research and sales operations.

• The Company is increasing its use of artificial intelligence (AI) systems to automate processes, analyze data, and support decision-making, which poses inherent risks.

• Social media and mobile messaging platforms present risks and challenges.

The above list is not exhaustive, and the Company faces additional challenges and risks. Investors should carefully consider all of the information set forth in this Form 10-K, including the following risk factors, before deciding to invest in any of the Company’s securities.

Risk Factors

The risks below are not the only ones the Company faces. Additional risks not currently known to the Company or that the Company presently deems immaterial may also impair its business operations. The Company’s business, financial condition, results of operations, cash flows or prospects could be materially adversely affected by any of these risks. This Form 10-K also contains forward-looking statements that involve risks and uncertainties. The Company’s results could materially differ from those anticipated in these forward-looking statements as a result of certain factors, including the risks it faces described below and elsewhere. See “Cautionary Factors that May Affect Future Results” below.

Risks Related to the Company’s Business

The Company is dependent on its patent rights, and if its patent rights are invalidated or circumvented, its business could be materially adversely affected.

Patent protection is considered, in the aggregate, to be of material importance to the Company’s marketing of human health and animal health products in the U.S. and in most major foreign markets. Patents covering products that it has introduced normally provide market exclusivity, which is important for the successful marketing and sale of its products. The Company seeks patents covering each of its products in each of the markets where it intends to sell the products and where meaningful patent protection is available.

Even if the Company succeeds in obtaining patents covering its products, third parties or government authorities may challenge or seek to invalidate or circumvent its patents and patent applications. It is important for the Company’s business to successfully assert and defend the patent rights that provide market exclusivity for its products. The Company is often involved in patent disputes relating to challenges to its patents or claims by third parties of infringement against the Company. The Company asserts and defends its patents both within and outside the U.S., including by filing claims of infringement against other parties. See Item 8. “Financial Statements and Supplementary Data,” Note 10. “Contingencies and Environmental Liabilities” below. In particular, manufacturers of generic or biosimilar pharmaceutical products from time to time file abbreviated NDAs or BLAs with the FDA seeking to market generic/biosimilar forms of the Company’s products prior to the expiration of relevant patents owned or licensed by the Company. The Company normally responds by asserting one or more of its patents with a l

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None.

The Company’s cybersecurity measures are primarily focused on ensuring the security and protection of its IT systems and data. The Company’s information security program is managed by a dedicated Chief Information Security Officer (CISO), whose group is responsible for leading enterprise-wide cybersecurity risk management, strategy, policy, standards, architecture, and processes. The Company’s interim CISO has over 22 years of experience in cybersecurity and national security, including distinguished service in the U.S. Army and the National Security Agency. He holds a Master’s degree in Cyber Intelligence Studies and a Bachelor’s degree in Mathematical Physics, and maintains the Certified Information Systems Security Professional (CISSP) credential. Oversight of the information security program remains fully integrated into the Company’s overall enterprise risk management framework.

The CISO provides periodic reports to the Audit Committee (Audit Committee) of the Board of Directors (Board), the full Board, as well as to the Company’s Chief Executive Officer and other members of senior management, as appropriate. These reports include updates on the Company’s cybersecurity risks and threats, the status of projects intended to strengthen its information security systems, assessments of the information security program (including remediation, mitigation, and management of identified vulnerabilities), and the emerging threat landscape. The information security program is regularly evaluated by internal and external consultants and auditors with the results of those reviews reported to senior management and the Audit Committee, which is comprised entirely of independent directors and has oversight responsibility for these risks.

The Company’s information security group monitors the Company’s information systems to prevent, detect, mitigate, and remediate cybersecurity incidents. The Company uses tools and techniques to continually assess and monitor, manage and mitigate cybersecurity threats to its IT systems in a manner consistent with industry practice. The Company engages with key vendors, industry participants, and intelligence and law enforcement communities as part of its continuing efforts to obtain current threat intelligence, collaborate on security enhancements, and evaluate and improve the effectiveness of its information security program. As part of this program, the Company conducts periodic tabletop and red-teaming exercises to assess its cybersecurity incident response processes and defenses. The Company also maintains vendor management diligence and oversight processes to identify and monitor potential risks from cybersecurity threats attendant to its use of third-party service providers. Additionally, the Company monitors cybersecurity threat intelligence received from key third-party service providers associated with the Company.

In the event of a cybersecurity incident, the Company has a process in place whereby members of the information security group will alert the CISO and the CISO will alert the appropriate levels of management, including an incident assessment team, as well as the legal and finance departments so that the materiality of any such event can be assessed in furtherance of fulfilling any reporting requirements. If warranted, senior management will notify the Audit Committee or the full Board, as appropriate.

The Company has been and continues to be the target of cyber-attacks and network disruptions. To date, the risks posed by such cybersecurity threats have not materially affected the Company and its business strategy, results of operations and financial condition, and as of the date of this report, the Company is not aware of any material risks from cybersecurity threats that are reasonably likely to do so, but there can be no assurance that the Company will not be materially affected by such risks in the future. For further information, see Item 1A. “Risk Factors — The Company is increasingly dependent on sophisticated software applications and computing infrastructure. The Company continues to be a target of cyber-attacks that could lead to a disruption of its worldwide operations, including manufacturing, research and sales operations.”

The Company’s corporate headquarters are located in Rahway, New Jersey. The Company also maintains divisional headquarters in Upper Gwynedd, Pennsylvania. Principal U.S. research facilities are located in Rahway, New Jersey; West Point, Pennsylvania; Boston and Cambridge, Massachusetts; South San Francisco, California; and Elkhorn, Nebraska (Animal Health). Principal research facilities outside the U.S. are located in the United Kingdom,

Switzerland and China. The Company’s manufacturing operations are currently headquartered in Rahway, New Jersey. The Company also has production facilities for human health products at five locations in the U.S. and Puerto Rico. Outside the U.S., through subsidiaries, the Company owns or has an interest in manufacturing plants or other properties in Western Europe, Africa and Asia.

The Company and its subsidiaries own their principal facilities and manufacturing plants under titles that they consider to be satisfactory. The Company believes that its properties are in good operating condition and that its machinery and equipment have been well maintained. The Company believes that its plants for the manufacture of products are suitable for their intended purposes and have capacities and projected capacities, including previously disclosed capital expansion projects, that will be adequate for current and projected needs for existing Company products. Some capacity of the plants is being converted, with any needed modification, to the requirements of newly introduced and future products.

The information called for by this Item is incorporated herein by reference to Item 8. “Financial Statements and Supplementary Data,” Note 10. “Contingencies and Environmental Liabilities.”

Not Applicable.

Executive Officers of the Registrant (ages as of February 1, 2026)

All officers listed below serve at the pleasure of the Board of Directors. None of these officers was elected pursuant to any arrangement or understanding between the officer and any other person(s).

On February 2, 2026, the Company announced that Sanat Chattopadhyay, Executive Vice President and President, Merck Manufacturing Division, will retire from the Company, effective July 1, 2026. The Company announced that Mr. David R. Maraldo will assume the role as Executive Vice President and President, Merck Manufacturing Division, effective May 1, 2026, at which time Mr. Maraldo will become, and Mr. Chattopadhyay will cease to be, an Executive Officer of the Company. Mr. Chattopadhyay will remain in a strategic advisory role at the Company until his retirement.

On February 12, 2026, the Company announced that Joseph Romanelli has decided to retire from the Company in the second quarter of 2026.

On February 23, 2026, the Company announced that Brian Foard will join the Company as Executive Vice President, and President Specialty, Pharma & Infectious Diseases, effective March 2, 2026. Mr. Foard most recently served as Executive Vice President and Head of Specialty Care at Sanofi.

PART II

The principal market for trading of the Company’s Common Stock is the New York Stock Exchange (NYSE) under the symbol MRK.

As of January 31, 2026, there were approximately 80,500 shareholders of record of the Company’s Common Stock.

Issuer purchases of equity securities for the three months ended December 31, 2025 were as follows:

Issuer Purchases of Equity Securities

(1) All shares purchased during the period were made as part of a plan approved by the Board of Directors in January 2025 to purchase up to $10 billion in Merck shares for its treasury.

Performance Graph

The following graph assumes a $100 investment on December 31, 2020, and reinvestment of all dividends, in each of the Company’s Common Stock, the S&P 500 Index, and a composite peer group of major U.S. and European-based pharmaceutical companies, which are: AbbVie Inc., Amgen Inc., AstraZeneca plc, Bristol-Myers Squibb Company, Johnson & Johnson, Eli Lilly and Company, Gilead Sciences Inc., GlaxoSmithKline plc, Novartis AG, Pfizer Inc., Roche Holding AG, and Sanofi SA.

Comparison of Five-Year Cumulative Total Return

Merck & Co., Inc., Composite Peer Group and S&P 500 Index

** Compound Annual Growth Rate*

*** Peer group average was calculated on a market cap weighted basis as of December 31, 2020.*

This Performance Graph will not be deemed to be incorporated by reference into any filing under the Securities Act of 1933 or the Securities Exchange Act of 1934, except to the extent that the Company specifically incorporates it by reference. In addition, the Performance Graph will not be deemed to be “soliciting material” or to be “filed” with the SEC or subject to Regulation 14A or 14C, other than as provided in Regulation S-K, or to the liabilities of section 18 of the Securities Exchange Act of 1934, except to the extent that the Company specifically requests that such information be treated as soliciting material or specifically incorporates it by reference into a filing under the Securities Act or the Exchange Act.

The following section of this Form 10-K generally discusses 2025 and 2024 results and year-to-year comparisons between 2025 and 2024. Discussion of 2023 results and year-to-year comparisons between 2024 and 2023 that are not included in this Form 10-K can be found in Part II, Item 7. “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2024 filed on February 25, 2025**.**

Description of Merck’s Business

Merck & Co., Inc. (Merck or the Company) is a global health care company that delivers innovative health solutions through its prescription medicines, including biologic therapies, vaccines and animal health products. The Company’s operations are principally managed on a product basis and include two operating segments, Pharmaceutical and Animal Health, both of which are reportable segments.

The Pharmaceutical segment includes human health pharmaceutical and vaccine products. Human health pharmaceutical products consist of therapeutic and preventive agents, generally sold by prescription, for the treatment of human disorders. The Company sells these human health pharmaceutical products primarily to drug wholesalers and retailers, hospitals, government agencies, and managed health care providers such as health maintenance organizations, pharmacy benefit managers and other institutions. Human health vaccine products consist of preventive pediatric, adolescent and adult vaccines. The Company sells these human health vaccines primarily to physicians, wholesalers, distributors and government entities.

The Animal Health segment discovers, develops, manufactures and markets a wide range of veterinary pharmaceutical and vaccine products, as well as health management solutions and services, for the prevention, treatment and control of disease in all major livestock and companion animal species. The Company also offers an extensive suite of digitally connected identification, traceability and monitoring products. The Company sells its products to veterinarians, distributors, animal producers, farmers and pet owners.

Overview

Financial Highlights

** > 100%*

(1) Non-GAAP net income and non-GAAP earnings per share (EPS) exclude acquisition- and divestiture-related costs, restructuring costs, income and losses from investments in equity securities, and certain other items from Merck’s results prepared in accordance with generally accepted accounting principles in the U.S. (GAAP). For further discussion and a reconciliation of GAAP to non-GAAP net income and EPS, see “Non-GAAP Income and Non-GAAP EPS” below.

Executive Summary

In 2025, Merck successfully advanced its science-led strategy through new product approvals and launches, strong clinical execution, important data readouts, and the addition of novel innovation through business development efforts. The Company also continued to return capital to shareholders, primarily through dividends.

Worldwide sales were $65.0 billion in 2025, an increase of 1% compared with 2024, or 2% excluding the unfavorable effect of foreign exchange. The sales increase was primarily due to growth in oncology, cardiometabolic and respiratory, diabetes, and animal health, largely offset by declines in vaccines, immunology (as Merck’s marketing rights to these products ended in 2024), and virology (driven largely by lower sales of COVID-19 medication Lagevrio).

Merck continues to execute science-led business development transactions to augment its robust internal pipeline and portfolio with compelling external science focused on delivering innovation to patients, long-term growth, and value creation to shareholders. Highlights of 2025 activity include the following:

• Entered into an agreement to acquire Cidara Therapeutics, Inc. (Cidara), a biotechnology company developing drug-Fc conjugate therapeutics, including a long-acting antiviral designed to prevent seasonal and pandemic influenza; this transaction closed in January 2026.

• Acquired Verona Pharma plc (Verona Pharma), a biopharmaceutical company focused on respiratory diseases, through which Merck obtained Ohtuvayre, a product approved for the maintenance treatment of chronic obstructive pulmonary disease (COPD).

• Closed an exclusive license agreement for MK-7262 (HRS-5346), an investigational oral small molecule Lipoprotein(a) inhibitor from Jiangsu Hengrui Pharmaceuticals Co., Ltd. (Hengrui Pharma).

• Closed an agreement with Dr. Falk Pharma GmbH (Falk) to acquire sole global rights to MK-8690, an investigational anti-CD30 ligand monoclonal antibody.

During 2025, Merck continued its efforts to address unmet medical needs by launching Enflonsia in the U.S. for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in neonates (newborns) and infants born during or entering their first RSV season. Also in 2025, the Company launched Keytruda Qlex, which was approved by the U.S. Food and Drug Administration (FDA) for subcutaneous administration across all solid tumor indications for Keytruda in the U.S., and the European Commission (EC) approved a new subcutaneous (SC) route of administration and a new pharmaceutical form (solution for injection) of Keytruda (to be marketed as Keytruda SC) for use across all Keytruda indications for adult patients in Europe. Additionally, in pulmonary arterial hypertension (PAH), the Company launched an expanded indication for Winrevair in the U.S. based on the results of the ZENITH trial.

The Company also received num

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The information required by this Item is incorporated by reference to the discussion under “Financial Instruments Market Risk Disclosures” in Item 7. “Management’s Discussion and Analysis of Financial Condition and Results of Operations.”

**(a)**Financial Statements

The consolidated balance sheet of Merck & Co., Inc. and subsidiaries as of December 31, 2025 and 2024, and the related consolidated statements of income, of comprehensive income (loss), of equity and of cash flows for each of the three years in the period ended December 31, 2025, the notes to consolidated financial statements, and the report dated February 24, 2026 of PricewaterhouseCoopers LLP, independent registered public accounting firm, are as follows:

Consolidated Statement of Income

Merck & Co., Inc. and Subsidiaries

Years Ended December 31

($ in millions except per share amounts)

Consolidated Statement of Comprehensive Income (Loss)

Merck & Co., Inc. and Subsidiaries

Years Ended December 31

($ in millions)

The accompanying notes are an integral part of these consolidated financial statements.

Consolidated Balance Sheet

Merck & Co., Inc. and Subsidiaries

December 31

($ in millions except per share amounts)

The accompanying notes are an integral part of this consolidated financial statement.

Consolidated Statement of Equity

Merck & Co., Inc. and Subsidiaries

Years Ended December 31

($ in millions except per share amounts)

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Not applicable.

Management of the Company, with the participation of its Chief Executive Officer and Chief Financial Officer, has evaluated the effectiveness of the Company’s disclosure controls and procedures. Based on their evaluation, as of the end of the period covered by this Form 10-K, the Company’s Chief Executive Officer and Chief Financial Officer have concluded that the Company’s disclosure controls and procedures (as defined in Rules 13a-15(e) or 15d-15(e) under the Securities Exchange Act of 1934, as amended (the Act)) are effective. For the fourth quarter of 2025, there have been no changes in internal control over financial reporting that materially affected, or are reasonably likely to materially affect, the Company’s internal control over financial reporting.

Management is responsible for establishing and maintaining adequate internal control over financial reporting, as such term is defined in Rule 13a-15(f) of the Act. Management conducted an evaluation of the effectiveness of internal control over financial reporting based on the framework in Internal Control — Integrated Framework issued in 2013 by the Committee of Sponsoring Organizations of the Treadway Commission. Based on this evaluation, management concluded that internal control over financial reporting was effective as of December 31, 2025. PricewaterhouseCoopers LLP, an independent registered public accounting firm, has performed its own assessment of the effectiveness of the Company’s internal control over financial reporting and its attestation report is included in this Form 10-K filing.

Management’s Report

Management’s Responsibility for Financial Statements

Responsibility for the integrity and objectivity of the Company’s financial statements rests with management. The financial statements report on management’s stewardship of Company assets. These statements are prepared in conformity with generally accepted accounting principles and, accordingly, include amounts that are based on management’s best estimates and judgments. Nonfinancial information included in the Annual Report on Form 10-K has also been prepared by management and is consistent with the financial statements.

To assure that financial information is reliable and assets are safeguarded, management maintains an effective system of internal controls and procedures, important elements of which include: careful selection, training and development of operating and financial managers; an organization that provides appropriate division of responsibility; and communications aimed at assuring that Company policies and procedures are understood throughout the organization. A staff of internal auditors regularly monitors the adequacy and application of internal controls on a worldwide basis.

To ensure that personnel continue to understand the system of internal controls and procedures, and policies concerning good and prudent business practices, annually all employees of the Company are required to complete Code of Conduct training. This training reinforces the importance and understanding of internal controls by reviewing key corporate policies, procedures and systems. In addition, the Company has compliance programs, including an ethical business practices program to reinforce the Company’s long-standing commitment to high ethical standards in the conduct of its business.

The financial statements and other financial information included in the Annual Report on Form 10-K fairly present, in all material respects, the Company’s financial condition, results of operations and cash flows. Our formal certification to the Securities and Exchange Commission is included in this Form 10-K filing.

Management’s Report on Internal Control Over Financial Reporting

Management is responsible for establishing and maintaining adequate internal control over financial reporting, as such term is defined in Rule 13a-15(f) under the Securities Exchange Act of 1934. The Company’s internal control over financial reporting is designed to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles in the United States of America. Management conducted an evaluation of the effectiveness of internal control over financial reporting based on the framework in Internal Control — Integrated Framework issued in 2013 by the Committee of Sponsoring Organizations of the Treadway Commission. Based on this evaluation, management concluded that internal control over financial reporting was effective as of December 31, 2025.

Because of its inherent limitations, internal control over financial reporting may not prevent or detect misstatements. Projections of any evaluation of effectiveness to future periods are subject to the risk that controls

may become inadequate because of changes in conditions, or that the degree of compliance with the policies or procedures may deteriorate.

The effectiveness of the Company’s internal control over financial reporting as of December 31, 2025, has been audited by PricewaterhouseCoopers LLP, an independent registered public accounting firm, as stated in their report which appears herein.

Insider Trading Arrangements

During the three months ended December 31, 2025, none of the Company’s directors or executive officers adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement,” as each term is defined in Item 408 of Regulation S-K.

Not Applicable.

PART III

The required information on directors and nominees is incorporated by reference from the discussion under Proposal 1. Election of Directors of the Company’s Proxy Statement for the Annual Meeting of Shareholders to be held on May 26, 2026. Information on executive officers is set forth in Part I of this document on page 44.

The required information on compliance with Section 16(a) of the Securities Exchange Act of 1934, if applicable, is incorporated by reference from the discussion under the heading “Stock Ownership Information” of the Company’s Proxy Statement for the Annual Meeting of Shareholders to be held on May 26, 2026.

The Company has a Code of Conduct — Our Values and Standards applicable to all employees, including the principal executive officer, principal financial officer, and principal accounting officer. The Code of Conduct is available on the Company’s website at www.merck.com/company-overview/culture-and-values/code-of-conduct/values-and-standards/. The Company intends to disclose future amendments to certain provisions of the Code of Conduct, and waivers of the Code of Conduct granted to executive officers and directors, if any, on the website within four business days following the date of any amendment or waiver. Every Company employee is responsible for adhering to business practices that are in accordance with the law and with ethical principles that reflect the highest standards of corporate and individual behavior.

The required information on the identification of the audit committee and the audit committee financial expert is incorporated by reference from the discussion under the heading “Board Meetings and Committees” of the Company’s Proxy Statement for the Annual Meeting of Shareholders to be held on May 26, 2026.

The required information about the Company’s insider trading policy is incorporated by reference from the discussion under the heading “Insider Trading Policy” of the Company's Proxy Statement for the Annual Meeting of Shareholders to be held on May 26, 2026.

The information required on executive compensation is incorporated by reference from the discussion under the headings “Compensation Discussion and Analysis,” “Summary Compensation Table,” “All Other Compensation”, “CEO Pay Ratio,” “Pay Versus Performance”, “Grants of Plan-Based Awards”, “Outstanding Equity Awards”, “Option Exercises and Stock Vested”, “Pension Benefits”, “Nonqualified Deferred Compensation” table, and “Potential Payments Upon Termination or a Change in Control”, as well as all footnote information to the applicable tables, of the Company’s Proxy Statement for the Annual Meeting of Shareholders to be held on May 26, 2026.

The required information on director compensation is incorporated by reference from the discussion under the heading “Director Compensation” and related “Schedule of Director Fees” table and “2025 Director Compensation” table of the Company’s Proxy Statement for the Annual Meeting of Shareholders to be held on May 26, 2026.

The required information under the headings “Compensation and Management Development Committee Interlocks and Insider Participation” and “Compensation and Management Development Committee Report” is incorporated by reference from the Company’s Proxy Statement for the Annual Meeting of Shareholders to be held on May 26, 2026.

Information with respect to security ownership of certain beneficial owners and management is incorporated by reference from the discussion under the heading “Stock Ownership Information” of the Company’s Proxy Statement for the Annual Meeting of Shareholders to be held on May 26, 2026.

Equity Compensation Plan Information

The following table summarizes information about the options, warrants and rights and other equity compensation under the Company’s equity compensation plans as of the close of business on December 31, 2025. The table does not include information about tax qualified plans such as the Merck U.S. Savings Plan.

*(1)*Includes options to purchase shares of Company Common Stock and other rights under the following shareholder-approved plans: the Merck & Co., Inc. 2010 and 2019 Incentive Stock Plans, and the Merck & Co., Inc. 2010 Non-Employee Directors Stock Option Plan.

*(2)*Excludes approximately 15,722,346 shares of restricted stock units and 3,667,688 performance share units (assuming maximum payouts) under the Merck Sharp & Dohme 2010 and 2019 Incentive Stock Plans. Also excludes 140,237 shares of phantom stock deferred under the MSD Employee Deferral Program and 439,767 shares of phantom stock deferred under the Merck & Co., Inc. Plan for Deferred Payment of Directors’ Compensation.

The required information on transactions with related persons is incorporated by reference from the discussion under the heading “Related Person Transactions” of the Company’s Proxy Statement for the Annual Meeting of Shareholders to be held on May 26, 2026.

The required information on director independence is incorporated by reference from the discussion under the heading “Independence of Directors” of the Company’s Proxy Statement for the Annual Meeting of Shareholders to be held on May 26, 2026.

The information required for this item is incorporated by reference from the discussion under Proposal 3. Ratification of Appointment of Independent Registered Public Accounting Firm for 2026 beginning with the caption “Pre-Approval Policy for Services of Independent Registered Public Accounting Firm” through “Fees for Services Provided by the Independent Registered Public Accounting Firm” of the Company’s Proxy Statement for the Annual Meeting of Shareholders to be held on May 26, 2026.

PART IV

(a) The following documents are filed as part of this Form 10-K

1. Financial Statements

Consolidated statement of income for the years ended December 31, 2025, 2024 and 2023

Consolidated statement of comprehensive income (loss) for the years ended December 31, 2025, 2024 and 2023

Consolidated balance sheet as of December 31, 2025 and 2024

Consolidated statement of equity for the years ended December 31, 2025, 2024 and 2023

Consolidated statement of cash flows for the years ended December 31, 2025, 2024 and 2023

Notes to consolidated financial statements

Report of PricewaterhouseCoopers LLP, independent registered public accounting firm (PCAOB ID 238)

2. Financial Statement Schedules

Schedules are omitted because they are either not required or not applicable.

Financial statements of affiliates carried on the equity basis have been omitted because, considered individually or in the aggregate, such affiliates do not constitute a significant subsidiary.

3. Exhibits

Not applicable.

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

Dated: February 24, 2026

Pursuant to the requirements of the Securities Exchange Act of 1934, this report has been signed below by the following persons on behalf of the Registrant and in the capacities and on the dates indicated.

Jennifer Zachary, by signing her name hereto, does hereby sign this document pursuant to powers of attorney duly executed by the persons named, filed with the Securities and Exchange Commission as an exhibit to this document, on behalf of such persons, all in the capacities and on the date stated, such persons including a majority of the directors of the Company.