Molnupiravir

· In a large-scale post-marketing clinical study conducted by Tokushukai Medical Group, the incidence of post-COVID-19 conditions (PCC) (commonly referred to as Long COVID) was approximately 26% among patients who did not receive oral antiviral treatment. · Oral antiviral treatment reduced the risk of developing PCC by a statistically significant 14% compared to no antivirals. · These findings suggest that oral antiviral treatment may help prevent the onset of PCC. OSAKA, Japan, November 5, 2025 - General Incorporated Association Tokushukai (Location: Chiyoda-ku, Tokyo; Chairperson of the Board: Shinichi Higashiue, M.D.; hereinafter “Tokushukai Medical Group”) and Shionogi & Co., Ltd. (Head Office: Osaka, Japan; Chief Executive Officer: Isao Teshirogi, Ph.D.; hereafter "Shionogi") announced new clinical data from the ANCHOR study, a large-scale post-marketing clinical study conducted by Tokushukai Medical Group in patients diagnosed with COVID-19. The primary endpoint results were presented at the 8th ISRV-AVG Meeting and 3rd IMRP held in Singapore (September 17–20, 2025), and secondary endpoint results were presented at APCCMI 2025 in Thailand (November 2–4, 2025). The World Health Organization (WHO) defines PCC as occurring in individuals with a history of probable or confirmed SARS-CoV-2 infection, typically around three months after the onset of COVID-19, with symptoms lasting for at least two months and not explainable by an alternative diagnosis1. Common symptoms include fatigue, shortness of breath, loss of taste or smell, cognitive dysfunction but also others which generally have an impact on everyday functioning2. PCC is a significant challenge not only in Japan but globally. However, evidence supporting the effectiveness of antiviral in preventing these symptoms has been limited. In response, the Tokushukai Medical Group conducted a large-scale clinical study (ANCHOR study) targeting outpatients diagnosed with COVID-19. This study evaluated the impact of antiviral use on the PCC. This multi-center, nationwide, prospective observational study enrolled outpatients aged ≥12 years diagnosed with COVID-19 at 51 Tokushukai Group hospitals across Japan. As a collaborative research partner, Shionogi contributed to the execution of this study. The clinical study presented this time included approximately 9,000 cases enrolled between February 1 and October 31, 2024. The primary endpoint of this study, “the incidence of PCC,” in the antiviral and non-antiviral group, defined as persistence of any of five pre-specified symptoms (fatigue, dyspnea or respiratory distress, cough, smell disorder, taste disorder) on both Days 28 and 84, excluding symptoms not attributed to COVID-19. The incidence of post-COVID-19 symptoms was then evaluated based on this definition. The incidence of PCC was approximately 26% in the non-antiviral group (N=5,518) and approximately 24% in the antiviral group (N=2,181, combined group of ensitrelvir, nirmatrelvir/ritonavir, and molnupiravir). Antiviral treatment significantly reduced the risk by about 14% (adjusted risk ratio: 0.86 [95% CI: 0.78–0.93]; P < 0.001). For ensitrelvir alone, the risk was also significantly reduced by about 14% compared to non-antiviral treatment (adjusted risk ratio: 0.86 [95% CI: 0.79–0.95]; P = 0.002). For the secondary endpoint, “Frequency of COVID-19–related re-consultations within 28 days,” no significant risk reduction was observed in the overall antiviral group compared to the non-antiviral group (adjusted risk ratio: 0.93 [95% CI: 0.83–1.04]; P = 0.266). However, ensitrelvir alone showed a significant 12% reduction in re-visit risk (adjusted risk ratio: 0.88 [95% CI: 0.78–0.99]; P = 0.030). These findings suggest that oral antiviral treatment may contribute to improving acute-phase symptoms, reducing the incidence of PCC, and potentially lowering re-visit frequency. “Managing PCC remains a major unmet medical need. We are pleased that the ANCHOR study results indicate that antiviral treatment during the acute phase may help prevent the onset of PCC. This study represents an important step toward new directions in COVID-19 treatment and is expected to inform clinical decision-making and long-term health management,” said Dr. Makoto Hibino, MD, principal investigator of this study, Deputy Director of Shonan Oiso Hospital, and Chair of the Tokushukai Respiratory Committee. In the “Guidelines for the Clinical Management of COVID-19 issued by five academic societies” published on October 17, 2025, it is stated that “the fundamental principle of clinical care for infectious diseases, particularly viral infections, is early diagnosis and early treatment. This approach may help prevent severe illness, alleviate symptoms, and enable early return to social activities for individuals, while also reducing the burden on society by preventing widespread transmission and decreasing the number of hospitalized patients.”3 Based on these principles outlined in the guidelines, Tokushukai Group and Shionogi will continue to collaborate in accumulating evidence related to COVID-19 and delivering it back to clinical practice. About ANCHOR Study The purpose of ANCHOR study is to collect information of the clinical course of patients with COVID-19 treated at Tokushukai hospitals with and without antiviral drugs and to explore the clinical course in the acute phase, the frequency of severe disease, and frequency of PCC by the treatment, after adjusting by patient background including risk factor(s) and symptoms at the time of registration. In this study, Shionogi is participating as a collaborative research partner. About Tokushukai Medical Group Tokushukai Medical Group philosophy is “All livin beings are created equal”. Under this philosophy, we continuously strive for realizing “Anybody in the society is to receive the best possible medical care in anywhere, at whenever necessary”. From Emergency Medical Care, an origin of medical care, to preventive health care, chronic medical care and advanced medical care, we provide the optimal medical care. For more information on Tokushukai Medical Group, please visit https://www.tokushukai.or.jp/en/ About Shionogi & Co., Ltd. For over 60 years, Shionogi has been engaged in the research and development of infectious disease treatments. Identifying " Protect people from the threat of infectious diseases" as a material issue (materiality) to be addressed, the company is working towards the realization of comprehensive infectious disease care. As a leading company in the field of infectious diseases, Shionogi is strengthening its initiatives, including collaborations with external partners, to provide healthcare solutions to a broader audience and continuously address a wide range of infectious diseases. For more information on Shionogi & Co., Ltd., please visit https://www.shionogi.com/global/en Forward-Looking Statements This announcement contains forward-looking statements. These statements are based on expectations in light of the information currently available, assumptions that are subject to risks and uncertainties which could cause actual results to differ materially from these statements. Risks and uncertainties include general domestic and international economic conditions such as general industry and market conditions, and changes of interest rate and currency exchange rate. These risks and uncertainties particularly apply with respect to product-related forward-looking statements. Product risks and uncertainties include, but are not limited to, completion and discontinuation of clinical trials; obtaining regulatory approvals; claims and concerns about product safety and efficacy; technological advances; adverse outcome of important litigation; domestic and foreign healthcare reforms and changes of laws and regulations. Also for existing products, there are manufacturing and marketing risks, which include, but are not limited to, inability to build production capacity to meet demand, lack of availability of raw materials and entry of competitive products. The company disclaims any intention or obligation to update or revise any forward-looking statements whether as a result of new information, future events or otherwise. For Further Information, Contact: SHIONOGI Website Inquiry Form: https://www.shionogi.com/global/en/contact.html Reference List: 1. WHO, Post COVID-19 conditions; https://www.who.int/teams/health-care-readiness/post-covid-19-condition 2. Ministry of Health, Labour and Welfare (Japan), Guidelines for COVID-19 Clinical Management – Supplement: Management of Post-COVID-19 Conditions, Version 3.1, 2025; https://www.mhlw.go.jp/content/10900000/001422904.pdf 3. Guidelines for the Clinical Management of COVID-19 issued by five academic societies 2025

Total Worldwide Sales Were $17.3 Billion, an Increase of 4% From Third Quarter 2024; Excluding the Impact of Foreign Exchange, Sales Grew 3% KEYTRUDA Sales Grew 10% to $8.1 Billion; Excluding the Impact of Foreign Exchange, Sales Grew 8% WINREVAIR Sales Were $360 Million; Growth of 141% Both Nominally and Excluding the Impact of Foreign Exchange CAPVAXIVE Sales Were $244 Million GARDASIL/GARDASIL 9 Sales Declined 24% to $1.7 Billion; Excluding the Impact of Foreign Exchange, Sales Declined 25% Animal Health Sales Grew 9% to $1.6 Billion; Excluding the Impact of Foreign Exchange, Sales Grew 7% KEYTRUDA Sales Grew 10% to $8.1 Billion; Excluding the Impact of Foreign Exchange, Sales Grew 8% WINREVAIR Sales Were $360 Million; Growth of 141% Both Nominally and Excluding the Impact of Foreign Exchange CAPVAXIVE Sales Were $244 Million GARDASIL/GARDASIL 9 Sales Declined 24% to $1.7 Billion; Excluding the Impact of Foreign Exchange, Sales Declined 25% Animal Health Sales Grew 9% to $1.6 Billion; Excluding the Impact of Foreign Exchange, Sales Grew 7% GAAP EPS Was $2.32; Non-GAAP EPS Was $2.58; GAAP and Non-GAAP EPS Include a Charge of $0.10 per Share for Milestone Payment to LaNova for Technology Transfer for MK-2010 Received FDA Approval of KEYTRUDA QLEX Injection for Subcutaneous Use Across All Solid Tumor Indications for KEYTRUDA Presented New Research Across More Than 20 Types of Cancer and Multiple Treatment Settings at ESMO Congress 2025, Including Positive Survival Data From KEYNOTE-905 and KEYNOTE-B96 Announced Positive Topline Results From Third Phase 3 CORALreef Lipids Trial of Enlicitide Decanoate for Treatment of Adults With Hypercholesterolemia Completed Acquisition of Verona Pharma and Its First-In-Class COPD Maintenance Treatment for Adults, OHTUVAYRE, in October Full-Year 2025 Financial Outlook Now Expects Worldwide Sales To Be Between $64.5 Billion and $65.0 Billion Raises and Narrows Expected Non-GAAP EPS Range To Be Between $8.93 and $8.98 Now Expects Worldwide Sales To Be Between $64.5 Billion and $65.0 Billion Raises and Narrows Expected Non-GAAP EPS Range To Be Between $8.93 and $8.98 RAHWAY, N.J.--(BUSINESS WIRE)--Merck & Co., Inc., Rahway, N.J., USA (NYSE: MRK), known as MSD outside the United States and Canada, today announced financial results for the third quarter of 2025. “In the third quarter, we continued to execute on our strategy with important pipeline advancements, significant approvals and successful new product launches,” said Robert M. Davis, chairman and chief executive officer. “We’re delivering value to patients and customers through our innovative portfolio of medicines and vaccines, and we’re securing our future by making important investments in our pipeline – including through compelling, strategic business development like our completed acquisition of Verona Pharma and expanded U.S. manufacturing and R&D spending. With each milestone we achieve, my conviction that we’re well-positioned to drive the next chapter of success for our Company increases.” Financial Summary Third Quarter $ in millions, except EPS amounts 2025 2024 Change Change Ex-Exchange Sales $17,276 $16,657 4% 3% GAAP net income1 5,785 3,157 83% 84% Non-GAAP net income that excludes certain items1,2* 6,448 3,985 62% 62% GAAP EPS 2.32 1.24 87% 88% Non-GAAP EPS that excludes certain items2* 2.58 1.57 64% 65% *Refer to table on page 7. For the third quarter of 2025, Generally Accepted Accounting Principles (GAAP) earnings per share (EPS) assuming dilution was $2.32 and non-GAAP EPS was $2.58. GAAP and non-GAAP EPS in the third quarter of 2025 include a charge of $0.10 per share for a milestone payment to LaNova Medicines Ltd. (LaNova, acquired by Sino Biopharmaceutical Limited) associated with the technology transfer for MK-2010. GAAP and non-GAAP EPS in the third quarter of 2024 include a net charge of $0.79 per share in the aggregate for the acquisition of Eyebiotech Limited (EyeBio) and a related development milestone, the acquisition of MK-1045 from Curon Biopharmaceutical (Curon), as well as a payment received from Daiichi Sankyo related to the expansion of the existing development and commercialization agreement to include gocatamig (MK-6070). Non-GAAP EPS in both periods excludes acquisition- and divestiture-related costs, costs related to restructuring programs, and income and losses from investments in equity securities. Non-GAAP EPS in the third quarter of 2025 also excludes tax expense relating to audit reserve adjustments. Year-to-date results can be found in the attached tables. Third-Quarter Sales Performance The following table reflects sales of the Company’s top products and significant performance drivers. Third Quarter $ in millions 2025 2024 Change Change Ex-Exchange Commentary Total Sales $17,276 $16,657 4% 3% Pharmaceutical 15,611 14,943 4% 3% Increase primarily driven by growth in oncology, cardiovascular and diabetes, partially offset by declines in vaccines, virology and immunology. KEYTRUDA 8,142 7,429 10% 8% Growth driven by continued strong global demand from metastatic indications, including urothelial, endometrial and gastric cancers, as well as robust global uptake in earlier-stage indications including triple-negative breast cancer, cervical cancer, renal cell carcinoma (RCC) and non-small cell lung cancer (NSCLC). Sales also benefitted from timing of wholesaler purchases in the U.S., partially offset by other channel movements. GARDASIL/GARDASIL 9 1,749 2,306 -24% -25% Decline primarily due to lower demand in China. Excluding China, sales declined 2%, or 3% excluding impact of foreign exchange, reflecting lower demand in Japan following a national catch-up immunization program, partially offset by higher sales in the U.S. due to higher net pricing and favorable public-sector purchasing patterns. PROQUAD, M-M-R II and VARIVAX 684 703 -3% -3% Decline primarily due to lower demand, partially offset by higher net pricing in the U.S. JANUVIA/JANUMET 624 482 29% 29% Growth driven by higher net pricing in the U.S., partially offset by lower demand in China as well as in most other international markets due to generic competition. BRIDION 439 420 5% 4% Growth primarily due to higher demand in the U.S., partially offset by lower demand in most international markets due to ongoing generic competition. Lynparza* 379 337 12% 12% Growth primarily due to higher demand in the U.S. and certain international markets. WINREVAIR 360 149 141% 141% Growth largely reflects continued uptake in the U.S., partially offset by timing of distributor purchases and lower net pricing in the U.S. largely due to Medicare Part D redesign. PREVYMIS 266 208 28% 25% Increase primarily due to higher demand in the U.S. and launch of new indications in certain international markets, partially offset by lower demand in China due to generic competition. Lenvima* 258 251 3% 2% Increase primarily due to higher sales in the U.S. reflecting higher demand, partially offset by lower net pricing. CAPVAXIVE 244 47 N/M N/M Represents continued uptake since third-quarter 2024 launch in the U.S., as well as expected seasonal inventory build. VAXNEUVANCE 226 239 -6% -7% Decline primarily due to lower demand in certain international markets, particularly in Japan due to competitive pressure, partially offset by higher demand in certain European markets. WELIREG 196 139 42% 41% Growth primarily driven by higher demand in the U.S. and continued launch uptake in certain European markets, partially offset by lower net pricing in the U.S. LAGEVRIO 138 383 -64% -65% Decline primarily due to lower demand in the Asia Pacific region, particularly in Japan, as well as in the U.S. SIMPONI - 189 -100% -100% Marketing rights in former territories of the Company reverted to Johnson & Johnson on Oct. 1, 2024. Animal Health 1,615 1,487 9% 7% Growth primarily due to performance of livestock products. Livestock 1,023 886 16% 14% Growth primarily driven by higher demand across all species, as well as timing of sales. Companion Animal 592 601 -2% -3% Decline primarily due to lower demand, reflecting a reduction in veterinary visits and competitive pressure for parasiticides, partially offset by higher pricing, improved supply and new product launches. Sales of BRAVECTO were $262 million and $266 million in current and prior-year quarters, respectively, which represents a decline of 1%, or 3% excluding impact of foreign exchange. Other Revenues** 50 227 -78% -27% Decline primarily due to unfavorable impact of revenue-hedging activities and lower revenue from third-party manufacturing arrangements. *Alliance revenue for this product represents the Company’s share of profits, which are product sales net of cost of sales and commercialization costs. **Other revenues are comprised primarily of revenues from third-party manufacturing arrangements and miscellaneous corporate revenues, including revenue-hedging activities. N/M- Not meaningful. In addition, Koselugo alliance revenue was $214 million in the third quarter of 2025 compared with $39 million in the third quarter of 2024. The increase was due to an amendment to the collaboration agreement with AstraZeneca, which discontinued the provisions whereby the Company shared revenue and costs with AstraZeneca, and revised the payment structure, resulting in the Company’s recognition of a $150 million upfront payment and a $50 million regulatory milestone. Third-Quarter Expense, EPS and Related Information The table below presents selected expense information. $ in millions GAAP Acquisition- and Divestiture- Related Costs3 Restructuring Costs (Income) Loss From Investments in Equity Securities Non-GAAP2 Third Quarter 2025 Cost of sales $3,855 $621 $110 $- $3,124 Selling, general and administrative 2,633 34 - - 2,599 Research and development 4,234 4 233 - 3,997 Restructuring costs 47 - 47 - - Other (income) expense, net (238) - - (344) 106 Third Quarter 2024 Cost of sales $4,080 $639 $192 $- $3,249 Selling, general and administrative 2,731 43 31 - 2,657 Research and development 5,862 24 - - 5,838 Restructuring costs 56 - 56 - - Other (income) expense, net (162) (27) - 58 (193) GAAP Expense, EPS and Related Information Gross margin was 77.7% for the third quarter of 2025 compared with 75.5% for the third quarter of 2024. The increase was primarily due to the favorable impact of product mix and lower restructuring costs, partially offset by higher inventory write-offs and the unfavorable impact of foreign exchange. Selling, general and administrative (SG&A) expenses were $2.6 billion in the third quarter of 2025, a decrease of 4% compared with the third quarter of 2024. The decrease was primarily due to lower administrative, restructuring and selling costs, partially offset by the unfavorable impact of foreign exchange. Research and development (R&D) expenses were $4.2 billion in the third quarter of 2025, a decrease of 28% compared with the third quarter of 2024. The decrease was primarily due to lower charges for business development activity, including charges of $2.2 billion in the aggregate related to the acquisitions of EyeBio and MK-1045 in the third quarter of 2024, compared with a charge of $300 million in the third quarter of 2025 related to a milestone payment to LaNova for the completion of the technology transfer for MK-2010. Excluding these charges, R&D expenses increased primarily due to higher restructuring costs and clinical development spending. Other (income) expense, net, was $238 million of income in the third quarter of 2025 compared with $162 million of income in the third quarter of 2024. The favorability was primarily due to net income from investments in equity securities in 2025 compared with net losses from investments in equity securities in 2024, partially offset by $170 million of income recognized in 2024 related to a payment received from Daiichi Sankyo associated with the expansion of an existing development and commercialization agreement to include gocatamig (MK-6070). The effective tax rate was 14.2% for the third quarter of 2025. GAAP EPS was $2.32 for the third quarter of 2025 compared with $1.24 for the third quarter of 2024. The increase was primarily driven by a net charge of $0.79 per share in the aggregate in 2024 for the EyeBio, Curon and Daiichi Sankyo transactions, partially offset by a charge of $0.10 per share in 2025 related to the LaNova technology transfer milestone payment. Non-GAAP Expense, EPS and Related Information Non-GAAP gross margin was 81.9% for the third quarter of 2025 compared with 80.5% for the third quarter of 2024. The increase was primarily due to the favorable impact of product mix, partially offset by higher inventory write-offs and the unfavorable impact of foreign exchange. Non-GAAP SG&A expenses were $2.6 billion in the third quarter of 2025, a decrease of 2% compared with the third quarter of 2024. The decrease was primarily due to lower administrative and selling costs, partially offset by the unfavorable impact of foreign exchange. Non-GAAP R&D expenses were $4.0 billion in the third quarter of 2025, a decrease of 32% compared with the third quarter of 2024. The decrease was primarily due to lower charges for business development activity, including charges of $2.2 billion in the aggregate related to the acquisitions of EyeBio and MK-1045 in the third quarter of 2024, compared with a charge of $300 million in the third quarter of 2025 related to a milestone payment to LaNova for the completion of the technology transfer for MK-2010. Excluding these charges, R&D expenses increased primarily due to higher clinical development spending. Non-GAAP other (income) expense, net, was $106 million of expense in the third quarter of 2025 compared with $193 million of income in the third quarter of 2024. The unfavorability was primarily due to $170 million of income recognized in 2024 related to a payment received from Daiichi Sankyo associated with the expansion of an existing development and commercialization agreement to include gocatamig (MK-6070). The non-GAAP effective tax rate was 13.4% for the third quarter of 2025. Non-GAAP EPS was $2.58 for the third quarter of 2025 compared with $1.57 for the third quarter of 2024. The increase was primarily driven by a net charge of $0.79 per share in the aggregate in 2024 for the EyeBio, Curon and Daiichi Sankyo transactions, partially offset by a charge of $0.10 per share in 2025 related to the LaNova technology transfer milestone payment. A reconciliation of GAAP to non-GAAP net income and EPS is provided in the table that follows. Third Quarter $ in millions, except EPS amounts 2025 2024 EPS GAAP EPS $2.32 $1.24 Difference 0.26 0.33 Non-GAAP EPS that excludes items listed below2 $2.58 $1.57 Net Income GAAP net income1 $5,785 $3,157 Difference 663 828 Non-GAAP net income that excludes items listed below1,2 $6,448 $3,985 Excluded Items: Acquisition- and divestiture-related costs3 $659 $679 Restructuring costs 390 279 (Income) loss from investments in equity securities (344) 58 Decrease to net income before taxes 705 1,016 Estimated income tax (benefit) expense4 (42) (188) Decrease to net income $663 $828 Pipeline and Portfolio Highlights In the third quarter, the Company continued to demonstrate pipeline progress with the achievement of key regulatory and clinical milestones. In oncology, in September 2025, the U.S. Food and Drug Administration (FDA) approved KEYTRUDA QLEX injection for subcutaneous (SC) administration for use in adults across most solid tumor indications for KEYTRUDA, based on results from the Phase 3 MK-3475A-D77 trial. In October 2025, the FDA subsequently approved KEYTRUDA QLEX for the treatment of certain adult patients with resectable locally advanced head and neck squamous cell carcinoma (LA-HNSCC), based on results from the Phase 3 KEYNOTE-689 trial. KEYTRUDA QLEX is now approved for use in adults across all solid tumor indications approved for KEYTRUDA and is the first and only subcutaneously administered immune checkpoint inhibitor that can be given by a health care provider in as little as one minute. In addition, the European Medicines Agency’s Committee for Medicinal Products for Human Use (CHMP) adopted a positive opinion recommending approval for SC administration of KEYTRUDA for all adult indications; a final decision is expected in the fourth quarter of 2025. The European Commission (EC) also approved KEYTRUDA as part of a perioperative regimen for the treatment of PD-L1+ resectable LA-HNSCC. At the European Society for Medical Oncology (ESMO) Congress 2025, the Company announced new research from its broad and differentiated portfolio and pipeline, highlighting progress in new tumor types and earlier stages of disease. This included positive results from the Phase 3 KEYNOTE-905 trial (also known as EV-303) in cisplatin-ineligible patients with muscle-invasive bladder cancer (MIBC), the Phase 3 KEYNOTE-B96 trial in platinum-resistant recurrent ovarian cancer and the Phase 2/3 REJOICE-Ovarian01 trial in collaboration with Daiichi Sankyo in certain types of platinum-resistant ovarian cancer, long-term follow-up data from the Phase 3 KEYNOTE-775 trial in advanced endometrial cancer, as well as long-term data for KEYTRUDA in both earlier-stage and metastatic NSCLC. In vaccines and infectious diseases, in August 2025, the Company received two approvals in Japan: its nine-valent HPV vaccine for use in males ages 9 and older that will be marketed under the trademark SILGARD 9, and CAPVAXIVE for use in the elderly or adults who are at an increased risk of pneumococcal disease. At the European AIDS Clinical Society 2025 conference, the Company also presented new data from Phase 3 trials evaluating the once-daily, oral, two-drug regimen of doravirine/islatravir in adults with virologically suppressed HIV-1 infection, which showed minimal changes in weight and body composition and no clinically meaningful effect on fasting lipids and the homeostatic model assessment of insulin resistance across both clinical trials. In cardiovascular disease, the Company announced positive topline results from the Phase 3 CORALreef Lipids trial evaluating the safety and efficacy of enlicitide decanoate, an investigational, once-daily oral proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor being evaluated for the treatment of adults with hypercholesterolemia. The trial met all primary and key secondary endpoints. Enlicitide has the potential to be the first approved oral PCSK9 inhibitor. In addition, the FDA approved an update to the U.S. product label for WINREVAIR, based on results from the Phase 3 ZENITH trial, expanding the indication to include components of the clinical worsening events: hospitalization for pulmonary arterial hypertension (PAH), lung transplantation and death. Further, at the 2025 European Respiratory Society Congress, the Company presented positive results from the Phase 3 HYPERION trial evaluating WINREVAIR versus placebo (both in combination with background therapy) in adults recently diagnosed with PAH (Group 1 pulmonary hypertension) with World Health Organization (WHO) functional class II or III at intermediate or high risk of disease progression. Results showed that adding WINREVAIR within the first year after PAH diagnosis significantly reduced the risk of clinical worsening events compared to placebo. The Company also completed its acquisition of Verona Pharma plc (Verona Pharma) in October 2025, strengthening its cardio-pulmonary portfolio with the addition of OHTUVAYRE, an FDA-approved, first-in-class maintenance treatment for chronic obstructive pulmonary disease (COPD) in adult patients. Notable recent news releases on the Company’s pipeline and portfolio are provided in the table that follows. Visit the News Releases section of the Company’s website to read the releases.* Oncology FDA Approved KEYTRUDA QLEX Injection for SC Use in Adults Across Most Solid Tumor Indications for KEYTRUDA; Based on Results From Phase 3 MK-3475A-D77 Trial FDA Granted Breakthrough Therapy Designation for Raludotatug Deruxtecan (R-DXd) for Patients With CDH6 Expressing Platinum-Resistant Ovarian, Primary Peritoneal, or Fallopian Tube Cancers Previously Treated With Bevacizumab; Based on Results From Phase 1 Trial and REJOICE-Ovarian01 Phase 2/3 Trial FDA Granted Breakthrough Therapy Designation for Ifinatamab Deruxtecan (I-DXd) for Patients With Pretreated Extensive-Stage Small Cell Lung Cancer; Based on Results From Phase 2 IDeate-Lung01 Trial FDA Granted Priority Review for KEYTRUDA and KEYTRUDA QLEX, Each in Combination With Padcev, for Certain Patients With MIBC; FDA Set Prescription Drug User Fee Act (PDUFA) Date of April 7, 2026 EC Approved KEYTRUDA as Part of a Treatment Regimen for Adults With Resectable LA-HNSCC Expressing PD-L1 (CPS≥1); Based on Results From Phase 3 KEYNOTE-689 Trial EU CHMP Adopted Two Positive Opinions for KEYTRUDA, for SC Administration and for New Indication for Earlier-Stage Head and Neck Cancer; Latter Based on Results From Phase 3 KEYNOTE-689 Trial KEYTRUDA Plus Padcev Reduced Risk of Event-Free Survival Events by 60% and Risk of Death by 50% for Certain Patients With MIBC When Given Before and After Surgery; Based on Results From Phase 3 KEYNOTE-905 Trial KEYTRUDA Plus Chemotherapy, With or Without Bevacizumab, Reduced Risk of Disease Progression or Death Versus Chemotherapy, With or Without Bevacizumab, in Certain Patients With Platinum-Resistant Recurrent Ovarian Cancer; Based on Results From Phase 3 KEYNOTE-B96 Trial; FDA Set PDUFA Date of Feb. 20, 2026 Phase 3 KEYNOTE-B96 Trial Met Secondary Endpoint of Overall Survival in All Comers Population of Patients With Platinum-Resistant Recurrent Ovarian Cancer R-DXd Demonstrated Clinically Meaningful Response Rates in Patients With Recurrent Platinum-Resistant Ovarian, Primary Peritoneal or Fallopian Tube Cancer in Phase 2 Part of REJOICE-Ovarian01 Phase 2/3 Trial KEYTRUDA Demonstrated Long-Term Survival Benefit in Certain Patients With Earlier or Advanced Stages of NSCLC; Based on Exploratory Five-Year Analyses of Phase 3 KEYNOTE-671 Trial, Eight-Year Analyses of Phase 3 KEYNOTE-024 and KEYNOTE-042 Trials, and 10-Year Analyses of Phase 1b KEYNOTE-001 and Phase 2/3 KEYNOTE-010 Trials KEYTRUDA Plus Lenvima Demonstrated Durable Five-Year Survival Benefit Versus Chemotherapy for Patients With Advanced Endometrial Carcinoma Following One Prior Platinum-Based Regimen; Based on Results From Phase 3 KEYNOTE-775 Trial WELIREG Plus Lenvima Met Primary Endpoint of Progression-Free Survival in Certain Previously Treated Patients With Advanced RCC; Based on Results From Phase 3 LITESPARK-011 Trial KEYTRUDA Plus WELIREG Met Primary Endpoint of Disease-Free Survival in Certain Patients With Clear Cell RCC Following Nephrectomy; Based on Results From Phase 3 LITESPARK-022 Trial I-DXd Demonstrated Clinically Meaningful Response Rates in Patients With Extensive-Stage Small Cell Lung Cancer in IDeate-Lung01 Phase 2 Trial HERTHENA-Breast04 Phase 3 Trial of Patritumab Deruxtecan (HER3-DXd) Initiated in Patients With Metastatic Hormone Receptor-Positive, HER2-Negative Breast Cancer Previously Treated With Endocrine Therapy Vaccines and Infectious Diseases CAPVAXIVE Demonstrated Positive Immune Responses in Children and Adolescents at Increased Risk of Pneumococcal Disease; Based on Results From Phase 3 STRIDE-13 Trial The Company Announced New Data From Phase 3 Trials Evaluating the Investigational, Once-Daily, Oral, Two-Drug Regimen of Doravirine/Islatravir in Adults With Suppressed HIV-1 Infection; Based on Results From Phase 3 MK-8591A-051 and MK-8591A-052 Trials Systematic Review of 15 Studies Focused on Epidemiology and Antimicrobial Resistance of Pneumococcal Serotypes Covered by CAPVAXIVE in U.S. Adults Cardiovascular FDA Approved Updated Indication for WINREVAIR in Adults With PAH Based on Phase 3 ZENITH Study WINREVAIR Reduced the Risk of Clinical Worsening Events by 76% Compared to Placebo in Patients Recently Diagnosed With PAH on Background Therapy in Phase 3 HYPERION Trial Oral PCSK9 Inhibitor Enlicitide Decanoate Met All Primary and Key Secondary Endpoints in Adults With Hypercholesterolemia in Pivotal Phase 3 CORALreef Lipids Study Immunology The Company Expanded Tulisokibart Clinical Development Program With Initiation of Phase 2b Trials in Three Additional Immune-Mediated Inflammatory Diseases *References to the Company’s name in the above news release titles have been modified for the purpose of this announcement. Manufacturing and R&D Investment The Company continued to make long-term investments in its U.S. manufacturing and R&D capabilities and broke ground on a new $3 billion Center of Excellence for Pharmaceutical Manufacturing at its Elkton, Virginia site. The 400,000-square-foot facility will include both active pharmaceutical ingredient and drug product investment to support small molecule manufacturing and testing, creating more than 500 full-time jobs. This investment is part of the Company’s commitment to dedicate more than $70 billion beginning in 2025 to expand domestic manufacturing and R&D — not including any future business development in R&D — to drive its long-term growth and strengthen the U.S. as a global leader in biopharmaceutical innovation. Upcoming Investor Event The Company also plans to present new data from its innovative cardiovascular pipeline and portfolio at the American Heart Association (AHA) Scientific Sessions 2025 from Nov. 7-10. The Company will host an Investor Event to coincide with the AHA Scientific Sessions 2025 on Sunday, Nov. 9 at 6 p.m. CT. The event will take place in New Orleans and will be accessible via live audio webcast at this weblink. Sustainability Highlights The Company’s 2024/2025 Purpose for Progress Impact Report provided a comprehensive view of how it is pursuing innovative science for the health of people and animals and ensuring its efforts drive significant and sustainable value. The report noted that the Company’s medicines and vaccines reached more than 450 million people around the world in 2024. Full-Year 2025 Financial Outlook The following table summarizes the Company’s full-year financial outlook. Full Year 2025 Updated Prior Sales* $64.5 billion to $65.0 billion $64.3 billion to $65.3 billion Non-GAAP Gross margin2 Approximately 82% Approximately 82% Non-GAAP Operating expenses2(a) $25.9 billion to $26.4 billion $25.6 billion to $26.4 billion Non-GAAP Other (income) expenses, net2 $400 million to $500 million expense $300 million to $400 million expense Non-GAAP Effective tax rate2 14.0% to 15.0% 15.0% to 16.0% Non-GAAP EPS2(b)(c) $8.93 to $8.98 $8.87 to $8.97 Share count (assuming dilution) Approximately 2.51 billion Approximately 2.51 billion *The Company does not have any non-GAAP adjustments to sales. (a)Includes one-time R&D charges of $300 million for a milestone payment to LaNova associated with the technology transfer for MK-2010 and $200 million for an upfront payment for a license agreement with Jiangsu Hengrui Pharmaceuticals Co., Ltd. (Hengrui Pharma). Outlook does not assume any additional significant potential business development transactions. (b)Includes one-time charges totaling $0.16 per share associated with the payment for the LaNova technology transfer for MK-2010 and the upfront payment to Hengrui Pharma. (c)Updated full-year 2025 outlook reflects a benefit of approximately $0.09 per share resulting from an amendment to the collaboration agreement with AstraZeneca related to Koselugo, and an estimated negative impact of $0.04 per share related to the acquisition of Verona Pharma. The Company has not provided a reconciliation of forward-looking non-GAAP gross margin, non-GAAP operating expenses, non-GAAP other (income) expense, net, non-GAAP effective tax rate and non-GAAP EPS to the most directly comparable GAAP measures, given it cannot predict with reasonable certainty the amounts necessary for such a reconciliation, including intangible asset impairment charges, legal settlements, and income and losses from investments in equity securities either owned directly or through ownership interests in investment funds, without unreasonable effort. These items are inherently difficult to forecast and could have a significant impact on the Company’s future GAAP results. The Company now expects full-year 2025 sales to be between $64.5 billion and $65.0 billion, including a negative impact of foreign exchange of approximately 0.5% at mid-October 2025 exchange rates. The Company now expects its full-year non-GAAP effective income tax rate to be between 14.0% and 15.0%. The Company now expects its full-year non-GAAP EPS to be between $8.93 and $8.98, including a negative impact of foreign exchange of approximately $0.15 per share. This revised non-GAAP EPS outlook reflects several items not previously included, such as a benefit from an amended collaboration agreement with AstraZeneca related to Koselugo, and operational improvements, including a more favorable estimated tax rate and lower estimated costs related to the impact of tariffs, partially offset by an estimated negative impact related to the acquisition of Verona Pharma and an incremental negative impact from foreign exchange. The midpoint of this revised non-GAAP EPS range reflects a net improvement of $0.04 per share compared to the midpoint of the Company’s prior outlook. As previously communicated, the revised estimated full-year 2025 non-GAAP EPS range reflects the impacts of the one-time charges in connection with a license agreement with Hengrui Pharma and the completion of the technology transfer with LaNova for MK-2010, which impact EPS by approximately $0.16 in the aggregate. In 2024, non-GAAP EPS of $7.65 was negatively impacted by a net charge of $1.28 per share related to certain asset acquisitions, licensing agreements and collaborations. Consistent with past practice, the financial outlook does not assume additional significant potential business development transactions. Earnings Conference Call Investors, journalists and the general public may access a live audio webcast of the call on Thursday, Oct. 30, at 9 a.m. ET via this weblink. A replay of the webcast, along with the sales and earnings news release, supplemental financial disclosures and slides highlighting the results, will be available on the Company’s website. All participants may join the call by dialing (800) 369-3351 (U.S. and Canada Toll-Free) or (517) 308-9448 and using the access code 9818590. About Our Company At Merck & Co., Inc., Rahway, N.J., USA, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than 130 years, we have brought hope to humanity through the development of important medicines and vaccines. We aspire to be the premier research-intensive biopharmaceutical company in the world – and today, we are at the forefront of research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and animals. We foster a diverse and inclusive global workforce and operate responsibly every day to enable a safe, sustainable and healthy future for all people and communities. Forward-Looking Statement of Merck & Co., Inc., Rahway, N.J., USA This news release of Merck & Co., Inc., Rahway, N.J., USA (the “Company”) includes “forward-looking statements” within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. These statements are based upon the current beliefs and expectations of the Company’s management and are subject to significant risks and uncertainties. There can be no guarantees with respect to pipeline candidates that the candidates will receive the necessary regulatory approvals or that they will prove to be commercially successful. If underlying assumptions prove inaccurate or risks or uncertainties materialize, actual results may differ materially from those set forth in the forward-looking statements. Risks and uncertainties include but are not limited to, general industry conditions and competition; general economic factors, including interest rate and currency exchange rate fluctuations; the impact of pharmaceutical industry regulation and health care legislation in the United States and internationally; global trends toward health care cost containment; technological advances, new products and patents attained by competitors; challenges inherent in new product development, including obtaining regulatory approval; the Company’s ability to accurately predict future market conditions; manufacturing difficulties or delays; financial instability of international economies and sovereign risk; dependence on the effectiveness of the Company’s patents and other protections for innovative products; and the exposure to litigation, including patent litigation, and/or regulatory actions. The Company undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Additional factors that could cause results to differ materially from those described in the forward-looking statements can be found in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024 and the Company’s other filings with the Securities and Exchange Commission (SEC) available at the SEC’s Internet site (www.sec.gov). Appendix Generic product names are provided below. Pharmaceutical BRIDION (sugammadex) CAPVAXIVE (Pneumococcal 21-valent Conjugate Vaccine) GARDASIL (Human Papillomavirus Quadrivalent [Types 6, 11, 16 and 18] Vaccine, Recombinant) GARDASIL 9 (Human Papillomavirus 9-valent Vaccine, Recombinant) JANUMET (sitagliptin and metformin HCl) JANUVIA (sitagliptin) KEYTRUDA (pembrolizumab) KEYTRUDA QLEX (pembrolizumab and berahyaluronidase alfa-pmph) Koselugo (selumetinib) LAGEVRIO (molnupiravir) Lenvima (lenvatinib) Lynparza (olaparib) M-M-R II (Measles, Mumps and Rubella Virus Vaccine Live) OHTUVAYRE (ensifentrine) PREVYMIS (letermovir) PROQUAD (Measles, Mumps, Rubella and Varicella Virus Vaccine Live) SIMPONI (golimumab) VARIVAX (Varicella Virus Vaccine Live) VAXNEUVANCE (Pneumococcal 15-valent Conjugate Vaccine) WELIREG (belzutifan) WINREVAIR (sotatercept-csrk) Animal Health BRAVECTO (fluralaner) 1 Net income attributable to the Company. 2 The Company is providing certain 2025 and 2024 non-GAAP information that excludes certain items because of the nature of these items and the impact they have on the analysis of underlying business performance and trends. Management believes that providing this information enhances investors’ understanding of the Company’s results because management uses non-GAAP results to assess performance. Management uses non-GAAP measures internally for planning and forecasting purposes and to measure the performance of the Company along with other metrics. In addition, annual employee compensation, including senior management’s compensation, is derived in part using a non-GAAP pretax income metric. This information should be considered in addition to, but not as a substitute for or superior to, information prepared in accordance with GAAP. For a description of the non-GAAP adjustments, see Table 2a attached to this release. 3 Reflects expenses related to business combinations, including the amortization of intangible assets, intangible asset impairment charges, and expense or income related to changes in the estimated fair value measurement of liabilities for contingent consideration. Also includes integration, transaction and certain other costs associated with acquisitions and divestitures, as well as amortization of intangible assets related to collaborations and licensing arrangements. 4 Includes the estimated tax impacts on the reconciling items based on applying the statutory rate of the originating territory of the non-GAAP adjustments for both periods presented. Amount in the third quarter of 2025 also includes $86 million of tax expense relating to audit reserve adjustments. GAAP % Change GAAP % Change 3Q25 3Q24 Sep YTD 2025 Sep YTD 2024 $ 17,276 $ 16,657 4% $ 48,611 $ 48,544 0% 3,855 4,080 -6% 10,831 11,365 -5% 2,633 2,731 -4% 7,835 7,952 -1% 4,234 5,862 -28% 11,903 13,354 -11% 47 56 -16% 676 258 * (238 ) (162 ) 47% (281 ) (151 ) 86% 6,745 4,090 65% 17,647 15,766 12% 958 929 2,346 2,377 5,787 3,161 83% 15,301 13,389 14% 2 4 10 15 $ 5,785 $ 3,157 83% $ 15,291 $ 13,374 14% $ 2.32 $ 1.24 87% $ 6.08 $ 5.26 16% 2,498 2,541 2,514 2,543 14.2 % 22.7 % 13.3 % 15.1 % GAAP Acquisition- and Divestiture-Related Costs (1) Restructuring Costs (2) (Income) Loss from Investments in Equity Securities Certain Other Items Adjustment Subtotal Non-GAAP $ 3,855 621 110 731 $ 3,124 2,633 34 34 2,599 4,234 4 233 237 3,997 47 47 47 – (238 ) (344 ) (344 ) 106 6,745 (659 ) (390 ) 344 (705 ) 7,450 958 (119 ) (3) (82 ) (3) 73 (3) 86 (4) (42 ) 1,000 5,787 (540 ) (308 ) 271 (86 ) (663 ) 6,450 5,785 (540 ) (308 ) 271 (86 ) (663 ) 6,448 $ 2.32 (0.22 ) (0.12 ) 0.11 (0.03 ) (0.26 ) $ 2.58 14.2 % 13.4 % $ 10,831 1,817 311 2,128 $ 8,703 7,835 72 1 73 7,762 11,903 14 286 300 11,603 676 676 676 – (281 ) (3 ) (512 ) (515 ) 234 17,647 (1,900 ) (1,274 ) 512 (2,662 ) 20,309 2,346 (338 ) (3) (239 ) (3) 109 (3) (60 ) (4) (528 ) 2,874 15,301 (1,562 ) (1,035 ) 403 60 (2,134 ) 17,435 15,291 (1,562 ) (1,035 ) 403 60 (2,134 ) 17,425 $ 6.08 (0.62 ) (0.41 ) 0.16 0.02 (0.85 ) $ 6.93 13.3 % 14.2 % 2025 2024 3Q Sep YTD 1Q 2Q 3Q Sep YTD 1Q 2Q 3Q Sep YTD 4Q Full Year Nom % Ex-Exch % Nom % Ex-Exch % $15,529 $15,806 $17,276 $48,611 $15,775 $16,112 $16,657 $48,544 $15,624 $64,168 4 3 0 1 13,638 14,050 15,611 43,299 14,006 14,408 14,943 43,358 14,042 57,400 4 3 0 0 7,205 7,956 8,142 23,303 6,947 7,270 7,429 21,646 7,836 29,482 10 8 8 8 312 370 379 1,061 292 317 337 947 365 1,311 12 12 12 12 258 265 258 781 255 249 251 755 255 1,010 3 2 3 3 137 162 196 496 85 126 139 349 160 509 42 41 42 42 119 107 136 361 71 90 100 261 110 371 36 36 39 39 1,327 1,126 1,749 4,202 2,249 2,478 2,306 7,032 1,550 8,583 -24 -25 -40 -40 539 609 684 1,832 570 617 703 1,891 594 2,485 -3 -3 -3 -3 230 229 226 685 219 189 239 647 161 808 -6 -7 6 6 228 121 204 554 216 163 193 572 139 711 6 5 -3 -3 107 129 244 480 47 47 50 97 * * * * 41 38 45 124 61 59 68 188 74 263 -34 -35 -34 -34 441 461 439 1,341 440 455 420 1,315 449 1,764 5 4 2 2 208 228 266 702 174 188 208 570 215 785 28 25 23 23 70 74 81 225 56 62 64 182 70 252 25 24 24 24 83 96 43 222 73 92 96 261 79 340 -55 -55 -15 -15 280 336 360 976 70 149 219 200 419 141 141 * * 106 123 112 340 98 106 102 306 109 415 9 9 11 11 68 80 82 229 70 72 72 214 73 287 14 7 7 5 102 83 138 323 350 110 383 843 121 964 -64 -65 -62 -62 90 86 82 258 111 89 102 302 92 394 -20 -21 -15 -14 67 83 77 228 56 60 65 180 69 249 19 13 26 24 45 41 43 128 42 39 42 123 40 163 1 -1 4 4 50 40 47 137 46 53 78 177 45 222 -40 -40 -23 -22 184 172 189 545 543 -100 -100 -100 -100 39 35 41 115 114 -100 -100 -100 -100 549 372 382 1,302 419 405 278 1,102 232 1,334 37 37 18 19 247 251 243 741 251 224 204 679 255 935 19 20 9 11 729 584 953 2,268 632 618 638 1,890 699 2,590 50 49 20 21 1,588 1,646 1,615 4,849 1,511 1,482 1,487 4,480 1,397 5,877 9 7 8 10 924 961 1,023 2,909 850 837 886 2,573 889 3,462 16 14 13 15 664 685 592 1,940 661 645 601 1,907 508 2,415 -2 -3 2 2 303 110 50 463 258 222 227 706 185 891 -78 -27 -34 -4