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    Merck Announces Late-Breaking Data from Three Phase 3 Trials Evaluating Doravirine/Islatravir (DOR/ISL), an Investigational, Once-Daily, Two-Drug Regimen for the Treatment of Adults Living with HIV-1 at CROI 2026

    2/25/26 12:37:00 PM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
    Health Care
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    DOR/ISL is the first non-INSTI, two-drug regimen to demonstrate non-inferiority and a similar safety profile at Week 48 to BIC/FTC/TAF in adults living with HIV-1 who had not previously received antiretroviral treatment

    DOR/ISL maintained virologic suppression at Week 96 in adults with virologically suppressed HIV-1 who switched from other oral antiretroviral therapies, including BIC/FTC/TAF

    Merck (NYSE:MRK), known as MSD outside of the United States and Canada, today announced the presentation of results from three pivotal Phase 3 trials evaluating the investigational, once-daily, oral, two-drug regimen of doravirine/islatravir [DOR/ISL (100 mg/0.25 mg), (MK-8591A)] in adults with HIV-1. The findings were shared in late-breaking presentations at the 33rd Conference on Retroviruses and Opportunistic Infections (CROI) being held in Denver.

    "We are proud to continue building on our 40-year history of HIV research with the presentation of compelling new data from our HIV pipeline at CROI this year," said Dr. Eliav Barr, senior vice president, head of global clinical development and chief medical officer, Merck Research Laboratories. "Islatravir blocks HIV-1 replication through multiple mechanisms, including reverse transcriptase translocation inhibition, and could serve as the anchor for a series of two-drug, non-INSTI, daily and weekly treatment regimens. If approved, DOR/ISL will be the first of these regimens in our portfolio and may provide an important new option to help meet the evolving treatment needs of people living with HIV."

    The Phase 3, double-blind, clinical trial MK-8591A-053 evaluating DOR/ISL versus bictegravir/emtricitabine/tenofovir alafenamidei [(50 mg/200 mg/25 mg),(BIC/FTC/TAF)] in adults living with HIV-1 who had not previously received antiretroviral treatment (treatment-naïve), met its primary efficacy endpoint of percentage of participants achieving viral suppression (HIV-1 RNA <50 copies/mL), demonstrating non-inferiority for DOR/ISL compared to BIC/FTC/TAF at Week 48, 91.8% and 90.6% respectively (treatment difference 1.2%, 95% CI: -3.7, 6.2, p<0.001). The safety profile was similar between both treatment groups and consistent with that observed in previous studies. Drug-related adverse events (AEs) and discontinuations due to drug-related AEs were similar between groups (14% for DOR/ISL and 18% for BIC/FTC/TAF; 1.1% for DOR/ISL and 2.2% for BIC/FTC/TAF, respectively). These data, which are being published simultaneously in The Lancet HIV, build on the previously reported Phase 3 data in adults with virologically suppressed HIV-1 and will form the basis of future regulatory applications.

    "These new Phase 3 results are meaningful, showing that an investigational two-drug regimen without an INSTI demonstrated non-inferior efficacy and a comparable safety profile versus BIC/FTC/TAF in previously untreated adults with HIV-1, including those with advanced disease," said Dr. Jürgen K. Rockstroh, professor of medicine, head of the HIV Outpatient Clinic at the University of Bonn. "This study evaluated a diverse, global population, and included a significant proportion of participants with high viral loads and low CD4 counts. These findings add to the growing evidence supporting the potential role of DOR/ISL in HIV care."

    New 96-week data from the Phase 3 MK-8591A-052 and MK-8591A-051 trials evaluating DOR/ISL vs. BIC/FTC/TAF or baseline antiretroviral therapy (bART), in participants with virologically suppressed HIV-1 and who were switched to DOR/ISL, were also presented. In both trials, DOR/ISL maintained high rates of viral suppression at Week 96 and had a similar safety profile to BIC/FTC/TAF and bART. The 48-week data from these trials supported the initial New Drug Application (NDA) for DOR/ISL for the treatment of HIV-1 infection in adults who are virologically-suppressed on a stable antiretroviral regimen; the U.S. FDA has set a target action date of April 28, 2026 for the application under the Prescription Drug User Fee Act (PDUFA). In the U.S., doravirine is approved for the treatment of adults with HIV-1 in combination with other antiretrovirals as a single agent (PIFELTRO) and a component of a single-tablet regimen [DELSTRIGO; doravirine, lamivudine, and tenofovir disoproxil fumarate (DOR/3TC/TDF)].

    "As people living with HIV age, managing other health conditions becomes a reality for many, making it especially important to have treatment options that can help meet each person's unique health needs," said Dr. Amy Colson, director of research at Community Resource Initiative, Cambridge, Massachusetts. "Over time, people may need to adjust their HIV treatment regimens because of comorbidities, concerns about toxicities, tolerability challenges, or a desire for regimens with fewer medications. These 96-week data are encouraging, showing a non-INSTI option like investigational DOR/ISL could offer an important alternative."

    About the Phase 3 data from MK-8591A-053

    MK-8591A-053 is an ongoing Phase 3 randomized, active-controlled, double-blind, clinical trial evaluating the efficacy and safety of investigational, once-daily DOR/ISL (100 mg/0.25 mg) versus BIC/FTC/TAF in adults living with HIV-1 infection who had not previously received antiretroviral treatment. Participants were randomized 1:1 to DOR/ISL (n=269) or BIC/FTC/TAF (with matching placebos) (n=267), stratified by screening CD4+ T-cell count (<200 cells/mm³) and HIV-1 RNA (>100,000 copies/mL). The primary efficacy endpoint was the percentage of participants with HIV-1 RNA <50 copies/mL at Week 48 (non-inferiority margin 10%). Of the total participants enrolled in the trial, 36.8% had baseline HIV-1 RNA >100,000 copies/mL, 10.3% had HIV-1 RNA >500,000 copies/mL and 17.2% had baseline CD4+ T-cell count <200 cells/mm3.

    At Week 48, virological efficacy as measured by the percentage of participants with HIV-1 RNA levels < 50 copies/mL, was comparable in participants on DOR/ISL versus BIC/FTC/TAF with screening HIV-1 RNA >100,000 copies/mL (94.0% vs 87.6%, respectively) and >500,000 copies/mL (90.3% vs 84.4%, respectively).

    Drug-related AEs were reported in 14.1% of participants on DOR/ISL and 18.0% on BIC/FTC/TAF and discontinuations due to AEs (1.1% vs. 2.2%) were similar in both groups. Immune reconstitution was similar in DOR/ISL vs. comparator with no between-group differences in mean increases in CD4+ T-cell counts or total lymphocyte counts (TLC).

    About the Phase 3 data from MK-8591A-052

    MK-8591A-052 is a Phase 3, randomized, active-controlled, double-blind, clinical trial to evaluate the efficacy and safety of a switch to investigational, once-daily DOR/ISL (100 mg/0.25 mg) in adults with HIV-1 infection that has been virologically suppressed on BIC/FTC/TAF (50 mg/200 mg/25 mg). In this trial, 513 adults with HIV-1 who had virologic suppression for three months or more on BIC/FTC/TAF, no history of treatment failure and no known resistance to DOR were randomized (2:1) and switched to DOR/ISL (n= 342) or continued treatment with BIC/FTC/TAF (n=171). The primary efficacy endpoint, the percentage of participants with HIV-1 RNA ≥50 copies/mL at Week 48 (non-inferiority margin 4%), was met, demonstrating non-inferiority to BIC/FTC/TAF; 1.5% of participants who switched to DOR/ISL had a viral load of ≥50 copies/mL at Week 48, compared to 0.6% on BIC/FTC/TAF (treatment difference 0.9%, 95% CI -1.9, 2.9). Results at Week 48 were recently published in The Lancet.

    At Week 96, DOR/ISL continued to demonstrate similar efficacy compared to BIC/FTC/TAF; 1.5% of participants on DOR/ISL had a viral load of ≥50 copies/mL compared to 1.2% of participants on BIC/FTC/TAF (treatment difference 0.3%, 95% CI -2.8, 2.4); 88.9% of participants on DOR/ISL maintained virologic suppression (HIV-1 RNA <50 copies/mL) compared to 90.1% of participants continuing BIC/FTC/TAF (treatment difference -1.2%, 95% CI -6.5, 5.0). No hypothesis testing was performed for these secondary endpoints.

    The safety profile for DOR/ISL at Week 96 continued to be similar to BIC/FTC/TAF with no new safety findings. No additional drug-related serious adverse events were reported in any group between Week 48 and Week 96. At Week 96, rates of discontinuation due to AEs were similar for both groups (3.2% vs. 2.9%). There were no differences between trial arms in CD4+ T-cell count or TLC changes through Week 96.

    About the Phase 3 data from MK-8591A-051

    MK-8591A-051 is a Phase 3, open-label randomized, active-controlled, clinical trial to evaluate the efficacy and safety of a switch to investigational, once-daily DOR/ISL (100 mg/0.25 mg) in adults with HIV-1 infection that has been virologically suppressed using bART. In this trial, 551 adults with HIV-1 RNA <50 copies/mL for three months or more on oral 2- or 3-drug ART, with no history of treatment failure and no known virologic resistance to DOR, were randomized 2:1 and switched to DOR/ISL (n= 366) or continued bART (n=185), stratified by bART regimen. The primary efficacy endpoint, percentage of participants with HIV-1 RNA ≥50 copies/mL at Week 48 (non-inferiority margin 4%), was met, demonstrating DOR/ISL to be non-inferior to bART; 1.4% of participants who received DOR/ISL had a viral load of ≥50 copies/mL at Week 48, compared to 4.9% on bART (treatment difference -3.6%, 95% CI -7.8, -0.8). After Week 48 of the comparative portion of the study, all participants received open-label DOR/ISL through Week 144. Results at Week 48 were recently published in The Lancet.

    At Week 96, 1.9% of participants who continued on DOR/ISL for 96 weeks had HIV-1 RNA ≥50 copies/mL and 1.1% of participants who switched from bART to DOR/ISL at Week 48. Additionally, 92.6% of participants who were on DOR/ISL through 96 weeks and 96.6% of participants who switched to DOR/ISL at Week 48 maintained virologic suppression (HIV-1 RNA <50 copies/mL) at Week 96.

    At Week 96, there were similar rates of drug-related AEs between those who continued on DOR/ISL (13.7%) for 96 weeks and for those who switched from bART to DOR/ISL at Week 48 (11.3%) and rates of discontinuations due to AEs for those on DOR/ISL for 96 weeks (1.1%) and for those who switched from bART to DOR/ISL at Week 48 (0.6%) were similar. The mean percent change in total lymphocyte and CD4 counts were similar for participants who continued on DOR/ISL and switched from bART to DOR/ISL. No participants discontinued treatment due to decreased CD4+ T-cell count or TLC.

    About Islatravir (MK-8591) and Merck's HIV Research

    Islatravir (MK-8591) is Merck's investigational nucleoside analog that blocks HIV-1 replication by multiple mechanisms including inhibition of reverse transcriptase translocation, resulting in immediate chain termination and induction of structural changes in the viral DNA.

    Islatravir is under evaluation in multiple ongoing early and late-stage clinical trials in combination with other antiretrovirals for potential daily and once-weekly treatments for HIV-1, with islatravir serving as the anchor medicine in these two-drug regimens.

    Islatravir in combination with Gilead's lenacapavir is in Phase 3 development as a novel oral once-weekly treatment for HIV-1 [ISLEND-1 (NCT06630286) and ISLEND-2 (NCT06630299)], and islatravir in combination with our company's investigational non-nucleoside reverse transcriptase inhibitor (NNRTI) ulonivirine (MK-8507) is in Phase 2b development (MK-8591B-060, NCT06891066 and MK-8591B-062, NCT07266831) as an oral once-weekly treatment.

    MK-8527 is the company's investigational, novel, once-monthly, oral candidate for pre-exposure prophylaxis (PrEP) for HIV-1. The Phase 3 EXPrESSIVE-11 (MK-8527-011, NCT07044297) trial is evaluating the safety and efficacy of MK-8527 as PrEP to reduce the risk of sexually acquired HIV-1 infection among people likely to be exposed to HIV-1 in 16 countries. The Phase 3 EXPrESSIVE-10 (MK-8527-010, NCT07071623) trial is evaluating the safety and efficacy of MK-8527 as PrEP to reduce the risk of sexually acquired HIV-1 infection among women and adolescent girls in sub-Saharan Africa. Both trials are now enrolling.

    For an overview of Merck's HIV treatment and prevention clinical development program, please click here.

    Indications and usage for PIFELTRO® (doravirine) and DELSTRIGO® (doravirine, lamivudine, and tenofovir disoproxil fumarate) in the U.S.

    PIFELTRO is indicated in combination with other antiretroviral (ARV) agents for the treatment of HIV-1 infection in adult patients with no prior ARV treatment history or to replace the current ARV regimen in those who are virologically suppressed (HIV-1 RNA less than 50 copies per mL) on a stable ARV regimen with no history of treatment failure and no known substitutions associated with resistance to doravirine.

    DELSTRIGO is indicated as a complete regimen for the treatment of HIV-1 infection in adult patients with no prior ARV treatment history or to replace the current ARV regimen in those who are virologically suppressed (HIV-1 RNA less than 50 copies per mL) on a stable ARV regimen with no history of treatment failure and no known substitutions associated with resistance to the individual components of DELSTRIGO.

    Selected Safety Information

    Warning: Posttreatment Acute Exacerbation of Hepatitis B Virus (HBV) for DELSTRIGO

    All patients with HIV-1 should be tested for the presence of HBV before initiating ARV therapy. Severe acute exacerbations of HBV have been reported in people with concomitant HIV-1 and HBV who have discontinued products containing lamivudine or tenofovir disoproxil fumarate (TDF), which are components of DELSTRIGO. Patients coinfected with HIV-1 and HBV who discontinue DELSTRIGO should be monitored with both clinical and laboratory follow-up for at least several months after stopping DELSTRIGO. If appropriate, initiation of anti-HBV therapy may be warranted.

    Contraindications

    PIFELTRO and DELSTRIGO are contraindicated when coadministered with drugs that are strong cytochrome P450 (CYP)3A enzyme inducers (including the anticonvulsants carbamazepine, oxcarbazepine, phenobarbital, and phenytoin; the androgen receptor inhibitor enzalutamide; the antimycobacterials rifampin and rifapentine; the cytotoxic agent mitotane; and the herbal product St. John's wort (Hypericum perforatum)), as significant decreases in doravirine plasma concentrations may occur, which may decrease the effectiveness of DELSTRIGO and PIFELTRO.

    DELSTRIGO is contraindicated in patients with a previous hypersensitivity reaction to lamivudine.

    Warnings and Precautions

    Severe Skin Reactions

    Severe skin reactions, including Stevens-Johnson syndrome (SJS)/toxic epidermal necrolysis (TEN), have been reported during the postmarketing experience with doravirine-containing regimens. Discontinue PIFELTRO or DELSTRIGO, and other medications known to be associated with severe skin reactions, immediately if a painful rash with mucosal involvement or a progressive severe rash develops. Clinical status should be closely monitored, and appropriate therapy should be initiated.

    New or Worsening Renal Impairment

    Renal impairment, including cases of acute renal failure and Fanconi syndrome, have been reported with the use of TDF. DELSTRIGO should be avoided with concurrent or recent use of a nephrotoxic agent (e.g., high-dose or multiple NSAIDs). Cases of acute renal failure after initiation of high-dose or multiple NSAIDs have been reported in people living with HIV with risk factors for renal dysfunction who appeared stable on TDF.

    Prior to or when initiating DELSTRIGO, and during treatment, assess serum creatinine, estimated creatinine clearance, urine glucose, and urine protein in all patients. In patients with chronic kidney disease, also assess serum phosphorus. Discontinue DELSTRIGO in patients who develop clinically significant decreases in renal function or evidence of Fanconi syndrome. Discontinue DELSTRIGO if estimated creatinine clearance declines below 50 mL/min.

    Bone Loss and Mineralization Defects

    In clinical trials in adults living with HIV, TDF was associated with slightly greater decreases in bone mineral density (BMD) and increases in biochemical markers of bone metabolism. Serum parathyroid hormone levels and 1,25 Vitamin D levels were also higher. Cases of osteomalacia associated with proximal renal tubulopathy have been reported with the use of TDF. The effects of TDF-associated changes in BMD and biochemical markers on long-term bone health and future fracture risk in adults are unknown.

    Immune Reconstitution Syndrome

    Immune reconstitution syndrome can occur, including the occurrence of autoimmune disorders with variable time to onset, which may necessitate further evaluation and treatment.

    Drug Interactions

    Because DELSTRIGO is a complete regimen, coadministration with other antiretroviral medications for the treatment of HIV-1 infection is not recommended.

    Coadministration of PIFELTRO with efavirenz, etravirine, or nevirapine is not recommended.

    If DELSTRIGO is coadministered with rifabutin, take one tablet of DELSTRIGO once daily, followed by one tablet of doravirine (PIFELTRO) approximately 12 hours after the dose of DELSTRIGO.

    If PIFELTRO is coadministered with rifabutin, increase PIFELTRO dosage to one tablet twice daily (approximately 12 hours apart).

    Consult the full Prescribing Information prior to and during treatment for more information on potential drug-drug interactions.

    Dosage and Administration/Specific Populations

    Renal Impairment

    Because DELSTRIGO is a fixed-dose combination tablet and the dosage of lamivudine and TDF cannot be adjusted, DELSTRIGO is not recommended in patients with estimated creatinine clearance less than 50 mL/min.

    Adverse Reactions

    The most common adverse reactions with DELSTRIGO (incidence ≥5%, all intensities) were dizziness (7%), nausea (5%), and abnormal dreams (5%). The most common adverse reactions with PIFELTRO (incidence ≥5%, all intensities) were nausea (7%), dizziness (7%), headache (6%), fatigue (6%), diarrhea (6%), abdominal pain (5%), and abnormal dreams (5%).

    By week 96 in DRIVE-FORWARD, 2% of adult participants in the PIFELTRO group and 3% in the darunavir+ritonavir (DRV+r) group had adverse events leading to discontinuation of study medication.

    By week 96 in DRIVE-AHEAD, 3% of adult participants in the DELSTRIGO group and 7% in the efavirenz (EFV)/emtricitabine (FTC)/TDF group had adverse events leading to discontinuation of study medication.

    In DRIVE-FORWARD, mean changes from baseline at week 48 in LDL-cholesterol (LDL-C) and non-HDL-cholesterol (non-HDL-C) were pre-specified. LDL-C: -4.6 mg/dL in the PIFELTRO group vs 9.5 mg/dL in the DRV+r group. Non-HDL-C: -5.4 mg/dL in the PIFELTRO group vs 13.7 mg/dL in the DRV+r group. The clinical benefits of these findings have not been demonstrated.

    In DRIVE-AHEAD, mean changes from baseline at week 48 in LDL-C and non-HDL-C were pre-specified. LDL-C: -2.1 mg/dL in the DELSTRIGO group vs 8.3 mg/dL in the EFV/FTC/TDF group. Non-HDL-C: -4.1 mg/dL in the DELSTRIGO group vs 12.7 mg/dL in the EFV/FTC/TDF group. The clinical benefits of these findings have not been demonstrated.

    In DRIVE-SHIFT, mean changes from baseline at week 24 in LDL-C and non-HDL-C were pre-specified. LDL-C: -16.3 mg/dL in the DELSTRIGO group vs -2.6 mg/dL in the PI + ritonavir group. Non-HDL-C: -24.8 mg/dL in the DELSTRIGO group vs -2.1 mg/dL in the PI + ritonavir group. The clinical benefits of these findings have not been demonstrated.

    In DRIVE-AHEAD, neuropsychiatric adverse events were reported in the three pre-specified categories of sleep disorders and disturbances, dizziness, and altered sensorium. Twelve percent of adult participants in the DELSTRIGO group and 26% in the EFV/FTC/TDF group reported neuropsychiatric adverse events of sleep disorders and disturbances; 9% in the DELSTRIGO group and 37% in the EFV/FTC/TDF group reported dizziness; and 4% in the DELSTRIGO group and 8% in the EFV/FTC/TDF group reported altered sensorium.

    The safety of DELSTRIGO in virologically suppressed adults was based on week 48 data from participants in the DRIVE-SHIFT trial. Overall, the safety profile in virologically suppressed adult participants was similar to that in participants with no ARV treatment history.

    Serum ALT and AST Elevations: In the DRIVE-SHIFT trial, 22% and 16% of participants in the immediate switch group experienced ALT and AST elevations greater than 1.25 X ULN, respectively, through 48 weeks on DELSTRIGO. For these ALT and AST elevations, no apparent patterns with regard to time to onset relative to switch were observed. One percent of participants had ALT or AST elevations greater than 5 X ULN through 48 weeks on DELSTRIGO. The ALT and AST elevations were generally asymptomatic, and not associated with bilirubin elevations. In comparison, 4% and 4% of participants in the delayed switch group experienced ALT and AST elevations of greater than 1.25 X ULN through 24 weeks on their baseline regimen.

    Pregnancy/Breastfeeding

    There is a pregnancy exposure registry that monitors pregnancy outcomes in individuals exposed to PIFELTRO or DELSTRIGO during pregnancy. Healthcare providers are encouraged to register patients by calling the Antiretroviral Pregnancy Registry (APR) at 1-800-258-4263.

    Inform individuals with HIV-1 infection of the potential risks of breastfeeding, including: (1) HIV-1 transmission (in HIV-1–negative infants), (2) developing viral resistance (in HIV-1–positive infants), and (3) serious adverse reactions in a breastfed infant similar to those seen in adults.

    Merck's Commitment to HIV

    For 40 years, Merck has been committed to scientific research and discovery in HIV leading to scientific breakthroughs that have helped change HIV treatment. Our work has been pioneering in the development of new options across multiple drug classes to help those impacted by HIV. Today, we are developing a series of antiviral options designed to help people manage HIV and protect people from HIV. We are researching for real life and want to ensure people are not defined by HIV. Our work focuses on transformational innovations, collaborations with others in the global HIV community, and access initiatives aimed at the goal of helping to end the HIV epidemic for everyone.

    About Merck

    At Merck, 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. For more information, visit www.merck.com and connect with us on X (formerly Twitter), Facebook, Instagram, YouTube and LinkedIn.

    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, 2025 and the company's other filings with the Securities and Exchange Commission (SEC) available at the SEC's Internet site (www.sec.gov).

    Please see Prescribing Information for PIFELTRO (doravirine) at:

    https://www.merck.com/product/usa/pi_circulars/p/pifeltro/pifeltro_pi.pdf and

    Patient Information for PIFELTRO at:

    https://www.merck.com/product/usa/pi_circulars/p/pifeltro/pifeltro_ppi.pdf

    Please see Prescribing Information for DELSTRIGO (doravirine, lamivudine, and tenofovir disoproxil fumarate) at:

    https://www.merck.com/product/usa/pi_circulars/d/delstrigo/delstrigo_pi.pdf and

    Patient Information for DELSTRIGO at:

    https://www.merck.com/product/usa/pi_circulars/d/delstrigo/delstrigo_ppi.pdf

    _______________________

    i
    bictegravir/emtricitabine/tenofovir alafenamide (BIKTARVY) is a registered trademark of Gilead Sciences, Inc.

    View source version on businesswire.com: https://www.businesswire.com/news/home/20260225541915/en/

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    (215) 779-2234

    Investor Contacts:

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    (732) 594-1579

    Damini Chokshi

    (732) 594-1577

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    Merck to Participate in the TD Cowen 46th Annual Health Care Conference

    Merck (NYSE:MRK), known as MSD outside of the United States and Canada, announced today that Caroline Litchfield, executive vice president and chief financial officer, and Dr. Dean Y. Li, executive vice president and president, Merck Research Laboratories, are scheduled to participate in a fireside chat at the TD Cowen 46th Annual Health Care Conference on Tuesday, Mar. 3, 2026, at 1:50 p.m. EST. Investors, analysts, members of the media and the general public are invited to listen to a live audio webcast of the presentation at this weblink. About Merck At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge sci

    2/24/26 6:45:00 AM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
    Health Care

    Merck Evolves Human Health Operating Structure to Support Portfolio Execution

    Merck (NYSE:MRK), known as MSD outside of the United States and Canada, today highlighted steps to evolve the structure of its Human Health organization to ensure strong commercial execution of launches across diverse therapeutic areas, positioning the company for continued commercial success. As part of this evolution, Merck is organizing its Human Health business into an Oncology Business Unit and a Specialty, Pharma & Infectious Diseases Business Unit. This structure will enable Merck to sustain long-term leadership in oncology, while maintaining a sharp focus in support of a growing number of launches across an increasingly broad and diverse portfolio. In support of the new Human He

    2/23/26 6:45:00 AM ET
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    Biotechnology: Pharmaceutical Preparations
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    SEC Form 10-K filed by Merck & Company Inc.

    10-K - Merck & Co., Inc. (0000310158) (Filer)

    2/24/26 4:15:30 PM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
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    SEC Form 13F-HR filed by Merck & Company Inc.

    13F-HR - Merck & Co., Inc. (0000310158) (Filer)

    2/17/26 4:01:41 PM ET
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    Biotechnology: Pharmaceutical Preparations
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    SEC Form 144 filed by Merck & Company Inc.

    144 - Merck & Co., Inc. (0000310158) (Subject)

    2/4/26 4:38:27 PM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
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    RBC Capital Mkts initiated coverage on Merck with a new price target

    RBC Capital Mkts initiated coverage of Merck with a rating of Outperform and set a new price target of $142.00

    2/25/26 7:52:46 AM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
    Health Care

    Barclays initiated coverage on Merck with a new price target

    Barclays initiated coverage of Merck with a rating of Overweight and set a new price target of $140.00

    2/20/26 8:25:04 AM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
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    Merck upgraded by Deutsche Bank with a new price target

    Deutsche Bank upgraded Merck from Hold to Buy and set a new price target of $150.00

    2/13/26 8:35:09 AM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
    Health Care

    Director Thulin Inge G bought $250,000 worth of shares (2,833 units at $88.25), increasing direct ownership by 2,833% to 2,933 units (SEC Form 4)

    4 - Merck & Co., Inc. (0000310158) (Issuer)

    2/7/25 4:09:51 PM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
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    Director Baker Douglas M Jr bought $1,327,500 worth of shares (15,000 units at $88.50), increasing direct ownership by 1,500% to 16,000 units (SEC Form 4)

    4 - Merck & Co., Inc. (0000310158) (Issuer)

    2/7/25 4:04:52 PM ET
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    Biotechnology: Pharmaceutical Preparations
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    Merck & Co., Inc., Rahway, N.J., USA Announces Fourth-Quarter and Full-Year 2025 Financial Results; Highlights Progress Advancing Broad, Diverse Pipeline

    Reports Strength in Oncology and Animal Health, Plus Increasing Contributions From WINREVAIR and CAPVAXIVE Fourth-Quarter Worldwide Sales Were $16.4 Billion (5% Growth; 4% Growth ex-FX) Fourth-Quarter GAAP EPS Was $1.19; Non-GAAP EPS Was $2.04; GAAP and Non-GAAP EPS Include a Charge of $0.05 per Share for the Acquisition of MK-8690 Sole Global Rights Full-Year Worldwide Sales Were $65.0 Billion (1% Growth; 2% Growth ex-FX) KEYTRUDA/KEYTRUDA QLEX Sales Were $31.7 Billion (7% Growth Both Nominally and ex-FX); Includes KEYTRUDA QLEX Sales of $40 Million WINREVAIR Sales Were $1.4 Billion CAPVAXIVE Sales Were $759 Million GARDASIL/GARDASIL 9 Sales Were $5.2 Billion (39% Decli

    2/3/26 6:30:00 AM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
    Health Care

    Merck Announces Second-Quarter 2026 Dividend

    Merck (NYSE:MRK), known as MSD outside of the United States and Canada, announced today that the Board of Directors has declared a quarterly dividend of $0.85 per share of the company's common stock for the second quarter of 2026. Payment will be made on April 7, 2026, to shareholders of record at the close of business on March 16, 2026. About Merck At Merck, 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-inten

    1/27/26 3:07:00 PM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
    Health Care

    Merck to Hold Fourth-Quarter and Full-Year 2025 Sales and Earnings Conference Call Feb. 3

    Merck (NYSE:MRK), known as MSD outside of the United States and Canada, will hold its fourth-quarter and full-year 2025 sales and earnings conference call with institutional investors and analysts at 9:00 a.m. ET on Tuesday, Feb. 3. During the call, company executives will provide an overview of Merck's performance for the quarter. Investors, journalists and the general public may access a live audio webcast of the call 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 at www.merck.com. All participants may join the call by dialing (800) 369-3351 (U.S. and C

    1/7/26 6:30:00 AM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
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    Leadership Updates

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    Merck Evolves Human Health Operating Structure to Support Portfolio Execution

    Merck (NYSE:MRK), known as MSD outside of the United States and Canada, today highlighted steps to evolve the structure of its Human Health organization to ensure strong commercial execution of launches across diverse therapeutic areas, positioning the company for continued commercial success. As part of this evolution, Merck is organizing its Human Health business into an Oncology Business Unit and a Specialty, Pharma & Infectious Diseases Business Unit. This structure will enable Merck to sustain long-term leadership in oncology, while maintaining a sharp focus in support of a growing number of launches across an increasingly broad and diverse portfolio. In support of the new Human He

    2/23/26 6:45:00 AM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
    Health Care

    Merck to Acquire Cidara Therapeutics, Inc., Diversifying Its Portfolio to Include Late-Phase Antiviral Agent

    CD388 is an investigational long-acting, strain-agnostic antiviral agent currently in Phase 3, designed to prevent influenza infection in individuals at higher risk of influenza complications Acquisition aligns with Merck's science-led business development strategy, diversifying and expanding the company's pipeline Merck (NYSE:MRK), known as MSD outside of the United States and Canada, and Cidara Therapeutics, Inc. (NASDAQ:CDTX) ("Cidara"), a biotechnology company developing drug-Fc conjugate (DFC) therapeutics, today announced that the companies have entered into a definitive agreement under which Merck, through a subsidiary, will acquire Cidara for $221.50 per share in cash, for a tot

    11/14/25 6:45:00 AM ET
    $CDTX
    $MRK
    Biotechnology: Biological Products (No Diagnostic Substances)
    Health Care
    Biotechnology: Pharmaceutical Preparations

    REPAY Appoints New Chief Financial Officer

    Repay Holdings Corporation (NASDAQ:RPAY) ("REPAY" or the "Company"), a leading provider of integrated payment processing solutions, today announced the appointment of Robert Houser as Chief Financial Officer of the Company, effective September 8, 2025. "We are extremely excited to welcome Rob to REPAY. Rob brings over a decade of divisional CFO and operational experience within the payment industry to help him contribute immediately. Rob has held key strategic roles across his career and will be a great partner in running our company," said John Morris, Co-Founder and CEO. Most recently, Rob served as the Group CFO of the Public Sector and Advisor at Conduent Incorporated (NASDAQ:CNDT)

    8/11/25 4:06:00 PM ET
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    Large Ownership Changes

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    SEC Form SC 13G/A filed by Merck & Company Inc. (Amendment)

    SC 13G/A - Merck & Co., Inc. (0000310158) (Subject)

    2/13/24 4:55:49 PM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
    Health Care

    SEC Form SC 13G/A filed by Merck & Company Inc. (Amendment)

    SC 13G/A - Merck & Co., Inc. (0000310158) (Subject)

    2/9/23 10:54:48 AM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
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    SEC Form SC 13G/A filed by Merck & Company Inc. (Amendment)

    SC 13G/A - Merck & Co., Inc. (0000310158) (Subject)

    2/9/22 3:15:54 PM ET
    $MRK
    Biotechnology: Pharmaceutical Preparations
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