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Merck & Co (MRK) Announces the Approval of ENFLONSIA
Merck & Co (MRK) Announces the Approval of ENFLONSIA

Yahoo

time06-07-2025

  • Business
  • Yahoo

Merck & Co (MRK) Announces the Approval of ENFLONSIA

Merck & Co., Inc. (NYSE:MRK) is one of the 11 Best 52-Week Low Stocks to Buy Right Now. On June 26, Merck & Co., Inc. (NYSE:MRK) announced that the Advisory Committee on Immunization Practices has approved ENFLONSIA for preventing respiratory syncytial virus in infants younger than 8 months. The recommendation is provisional and is pending the final approval of the CDC Director or the Health and Human Services Secretary. Merck & Co., Inc. (NYSE:MRK) noted that ENFLONSIA is the first and only RSV preventive option administered to infants using the same dose regardless of weight, simplifying dosing logistics. Moreover, earlier this month, the FDA approved ENFLONSIA based on the strong clinical trial data from the Phase 2b/3 CLEVER and Phase 3 SMART trials. The results showed a 60.5% reduction in medically attended RSV lower respiratory infections and an 84.3% reduction in RSV-associated hospitalizations. A close-up of a person's hand holding a bottle of pharmaceuticals. Merck & Co., Inc. (NYSE:MRK) is a global healthcare company that operates through two main business segments including the Pharmaceuticals and Animal Health Segments. It is known for Keytruda and Gardasil, which are the main sources of the company's revenue. While we acknowledge the potential of MRK as an investment, we believe certain AI stocks offer greater upside potential and carry less downside risk. If you're looking for an extremely undervalued AI stock that also stands to benefit significantly from Trump-era tariffs and the onshoring trend, see our free report on the best short-term AI stock. READ NEXT: The Best and Worst Dow Stocks for the Next 12 Months and 10 Unstoppable Stocks That Could Double Your Money. Disclosure: None. Error in retrieving data Sign in to access your portfolio Error in retrieving data Error in retrieving data Error in retrieving data Error in retrieving data

Merck & Co. (MRK) Announces that US FDA Approves ENFLONSIA™ For Preventing RSV Lower Respiratory Tract Disease
Merck & Co. (MRK) Announces that US FDA Approves ENFLONSIA™ For Preventing RSV Lower Respiratory Tract Disease

Yahoo

time03-07-2025

  • Business
  • Yahoo

Merck & Co. (MRK) Announces that US FDA Approves ENFLONSIA™ For Preventing RSV Lower Respiratory Tract Disease

Merck & Co., Inc. (NYSE:MRK) is one of the 10 Best Value Stocks to Buy According to Billionaires. The company announced that the US FDA approved ENFLONSIA™ (clesrovimab-cfor) for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in neonates (newborns) and infants who were born during or entering their first RSV season. To provide a brief context, ENFLONSIA happens to be a preventive, long-acting monoclonal antibody (mAb) which has been designed to offer direct, rapid, and durable protection through 5 months, a typical RSV season, with the same 105 mg dose irrespective of weight. Merck & Co., Inc. (NYSE:MRK) further mentioned that the typical RSV season generally spans autumn to spring of the next year. A close-up of a person's hand holding a bottle of pharmaceuticals. However, ENFLONSIA should not be administered to infants who have a history of serious hypersensitivity reactions, including anaphylaxis, to any of the components of ENFLONSIA. Merck & Co., Inc. (NYSE:MRK) added that the approval is basis the results from the pivotal Phase 2b/3 CLEVER trial (MK-1654-004) evaluating a single dose of ENFLONSIA administered to preterm and full-term infants. Furthermore, the focus is to ensure the availability of ENFLONSIA in the US before the upcoming RSV season begins. This is to help in reducing the significant burden of the widespread seasonal infection on families and health care systems. Artisan Partners, an investment management company, released its Q1 2025 investor letter. Here is what the fund said: 'Shares of Merck & Co., Inc. (NYSE:MRK), a health care solutions company, were down 9%. Operating results have been solid, with Q4 earnings beating expectations, but investors were more focused on the continued weak demand in China for Gardasil, a vaccine for human papillomavirus (HPV), and the company's decision to pause vaccine shipments through at least mid-2025 to pare inventories. Though recent Gardasil setbacks have weighed on sentiment, the overarching issue for shareholders remains the success of Merck's late-stage pipeline to replace sales that will be lost when blockbuster oncology drug Keytruda (50% of Q4sales) comes off patent in 2028. As shares sell cheaply at just 10X earnings, Merck seems to be getting little credit from investors for the 60+ programs it has in clinical development, despite having several solid and large new product opportunities. Additionally, the company's strong balance sheet and robust free cash flow provide it multiple options for future partnerships and acquisitions, besides return of capital to shareholders via dividends and share repurchases.' While we acknowledge the potential of MRK to grow, our conviction lies in the belief that some AI stocks hold greater promise for delivering higher returns and have limited downside risk. If you are looking for an AI stock that is more promising than MRK and that has 100x upside potential, check out our report about this cheapest AI stock. READ NEXT: 13 Cheap AI Stocks to Buy According to Analysts and 11 Unstoppable Growth Stocks to Invest in Now Disclosure: None. Insider Monkey focuses on uncovering the best investment ideas of hedge funds and insiders. Please subscribe to our free daily e-newsletter to get the latest investment ideas from hedge funds' investor letters by entering your email address below. Error in retrieving data Sign in to access your portfolio Error in retrieving data Error in retrieving data Error in retrieving data Error in retrieving data

ACIP Recommends Use of Merck's ENFLONSIA™ (clesrovimab-cfor) for Prevention of Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease in Infants Younger than 8 Months of Age Born During or Entering Their First RSV Season
ACIP Recommends Use of Merck's ENFLONSIA™ (clesrovimab-cfor) for Prevention of Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease in Infants Younger than 8 Months of Age Born During or Entering Their First RSV Season

Business Wire

time26-06-2025

  • Health
  • Business Wire

ACIP Recommends Use of Merck's ENFLONSIA™ (clesrovimab-cfor) for Prevention of Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease in Infants Younger than 8 Months of Age Born During or Entering Their First RSV Season

RAHWAY, N.J.--(BUSINESS WIRE)--Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced the U.S. Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) voted to recommend ENFLONSIA™ (clesrovimab-cfor) as an option for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in infants younger than 8 months of age who are born during or entering their first RSV season. The ACIP also voted to include ENFLONSIA in the Vaccines for Children Program—an important step in ensuring broad access to this preventive option for infants. ENFLONSIA is a preventive, long-acting monoclonal antibody (mAb) designed to provide direct, rapid and durable protection through 5 months, a typical RSV season, with the same dose regardless of weight. A typical RSV season usually spans autumn to spring of the next year. ENFLONSIA should not be administered to infants with a history of serious hypersensitivity reactions, including anaphylaxis, to any component of ENFLONSIA. See additional Selected Safety Information below. 'Ahead of the 2025-2026 RSV season, we are proud to offer ENFLONSIA as a new preventive option designed to protect healthy and at-risk infants from RSV disease across a spectrum of severity, including worsening disease requiring hospitalization,' said Dr. Richard M. Haupt, vice president, head of global medical & scientific affairs, vaccines and infectious diseases, Merck Research Laboratories. 'The Committee's recommendation is an important step forward in efforts to help reduce the significant burden RSV continues to place on infants, families and health care systems.' The U.S. Food and Drug Administration (FDA) approved ENFLONSIA earlier this month based on clinical data from the Phase 2b/3 CLEVER and Phase 3 SMART trials. Merck plans to make ENFLONSIA available for ordering by physicians and health care administrators in July 2025, with shipments to be delivered before the start of the 2025-2026 RSV season. The ACIP's recommendation for ENFLONSIA is provisional and will be official once reviewed and finalized by the CDC Director or the Health and Human Services Secretary (in the absence of a CDC Director). About ENFLONSIA™ (clesrovimab-cfor) ENFLONSIA is Merck's extended half-life monoclonal antibody (mAb) indicated for passive immunization for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in newborns and infants who are born during or entering their first RSV season. ENFLONSIA is administered using the same dose regardless of weight (105 mg/0.7 mL in a prefilled syringe) and is designed to provide direct, rapid and durable protection through 5 months, a typical RSV season. For infants born during the RSV season, ENFLONSIA is to be administered within the first week of life. For infants born outside of the RSV season, ENFLONSIA should be administered shortly before the RSV season begins. For infants undergoing cardiac surgery with cardiopulmonary bypass during or entering their first RSV season, an additional 105 mg dose is recommended as soon as the infant is stable after surgery. ENFLONSIA has a 30-month shelf life. Selected Safety Information for ENFLONSIA™ (clesrovimab-cfor) Do not administer ENFLONSIA to infants with a history of serious hypersensitivity reactions, including anaphylaxis, to any component of ENFLONSIA. Serious hypersensitivity reactions, including anaphylaxis, have been observed with other human immunoglobulin G1 (IgG1) monoclonal antibodies. If signs or symptoms of a clinically significant hypersensitivity reaction or anaphylaxis occur, initiate appropriate medications and/or supportive therapy. The most common adverse reactions were injection-site erythema (3.8%), injection-site swelling (2.7%) and rash (2.3%). About RSV Respiratory syncytial virus (RSV) is a contagious virus that causes widespread seasonal infections and can lead to serious respiratory conditions such as bronchiolitis and pneumonia. According to the CDC, two to three out of every 100 infants under 6 months of age are hospitalized with RSV annually. As the leading cause of hospitalization among infants in the U.S., there is persisting unmet need for RSV preventive options for both healthy and high-risk infants born during or entering their first RSV season. RSV season is the time of year when RSV infections are most common, usually occurring fall/autumn through spring of the next year. RSV typically peaks in the winter in most regions of the United States, but timing and severity in a given community or region can vary year to year. 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 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, 2024 and the company's other filings with the Securities and Exchange Commission (SEC) available at the SEC's Internet site ( Please see Prescribing Information for ENFLONSIA (clesrovimab-cfor) at and Patient Information/Medication Guide for ENFLONSIA at

U.S. FDA Approves Merck's ENFLONSIA™ (clesrovimab-cfor) for Prevention of Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease in Infants Born During or Entering Their First RSV Season
U.S. FDA Approves Merck's ENFLONSIA™ (clesrovimab-cfor) for Prevention of Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease in Infants Born During or Entering Their First RSV Season

Yahoo

time09-06-2025

  • Health
  • Yahoo

U.S. FDA Approves Merck's ENFLONSIA™ (clesrovimab-cfor) for Prevention of Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease in Infants Born During or Entering Their First RSV Season

ENFLONSIA is a preventive monoclonal antibody designed to protect infants against a spectrum of RSV disease severity, including worsening disease requiring hospitalization ENFLONSIA is the first and only RSV preventive option administered to infants using the same dose regardless of weight RAHWAY, N.J., June 09, 2025--(BUSINESS WIRE)--Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced the U.S. Food and Drug Administration (FDA) has approved ENFLONSIA™ (clesrovimab-cfor) for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in neonates (newborns) and infants who are born during or entering their first RSV season. ENFLONSIA is a preventive, long-acting monoclonal antibody (mAb) designed to provide direct, rapid and durable protection through 5 months, a typical RSV season, with the same 105 mg dose regardless of weight. A typical RSV season usually spans autumn to spring of the next year. "RSV disease is the leading cause of infant hospitalization in the U.S. and can lead to serious respiratory conditions like bronchiolitis and pneumonia," said Dr. Octavio Ramilo, chair of the Department of Infectious Diseases at St. Jude Children's Research Hospital and investigator for the CLEVER (MK-1654-004) and SMART (MK-1654-007) trials. "ENFLONSIA combines dosing convenience with strong clinical data showing significant reductions in RSV disease incidence and hospitalizations, making it a promising new intervention to help protect infants from RSV." ENFLONSIA should not be administered to infants with a history of serious hypersensitivity reactions, including anaphylaxis, to any component of ENFLONSIA. See additional Selected Safety Information below. The approval is based on results from the pivotal Phase 2b/3 CLEVER trial (MK-1654-004) evaluating a single dose of ENFLONSIA administered to preterm and full-term infants (birth to 1 year of age). The trial met its primary and key secondary endpoints, as outlined below. ENFLONSIA demonstrated a reduction in incidence of RSV-associated medically attended lower respiratory infections (MALRI) requiring ≥1 indicator of lower respiratory infection (LRI) or severity compared to placebo through 5 months (primary endpoint) by 60.5% (95% CI: 44.2, 72.0, p<0.001) (incidence rates: ENFLONSIA, 0.026; placebo, 0.065). ENFLONSIA demonstrated a reduction in RSV-associated hospitalizations through 5 months (key secondary endpoint) by 84.3% (95% CI: 66.7, 92.6, p<0.001) (incidence rates: ENFLONSIA, 0.004; placebo, 0.024), showing increasing efficacy with increasing disease severity. The approval is also supported by results from the Phase 3 SMART trial (MK-1654-007) evaluating the safety and efficacy of ENFLONSIA versus palivizumab in infants at increased risk for severe RSV disease. "ENFLONSIA provides an important new preventive option to help protect healthy and at-risk infants born during or entering their first RSV season with the same dose regardless of weight," said Dr. Dean Y. Li, president, Merck Research Laboratories. "We are committed to ensuring availability of ENFLONSIA in the U.S. before the start of the upcoming RSV season to help reduce the significant burden of this widespread seasonal infection on families and health care systems." The U.S. Centers for Disease Control and Prevention's (CDC's) Advisory Committee on Immunization Practices is expected to meet later this month to discuss and make recommendations for the use of ENFLONSIA in infants. Ordering is anticipated to begin in July, with shipments delivered before the start of the 2025-2026 RSV season. About ENFLONSIA™ (clesrovimab-cfor) ENFLONSIA (clesrovimab-cfor) is Merck's extended half-life monoclonal antibody (mAb) indicated for passive immunization for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in newborns and infants who are born during or entering their first RSV season. ENFLONSIA is administered using non-weight-based dosing and is designed to provide direct, rapid and durable protection through 5 months, a typical RSV season. For infants born during the RSV season, ENFLONSIA is to be administered starting from birth. For infants born outside of the RSV season, ENFLONSIA should be administered prior to the start of their first RSV season. For infants undergoing cardiac surgery with cardiopulmonary bypass during or entering their first RSV season, an additional 105 mg dose is recommended as soon as the infant is stable after surgery. Selected Safety Information for ENFLONSIA (clesrovimab-cfor) Do not administer ENFLONSIA to infants with a history of serious hypersensitivity reactions, including anaphylaxis, to any component of ENFLONSIA. Serious hypersensitivity reactions, including anaphylaxis, have been observed with other human immunoglobulin G1 (IgG1) monoclonal antibodies. If signs or symptoms of a clinically significant hypersensitivity reaction or anaphylaxis occur, initiate appropriate medications and/or supportive therapy. The most common adverse reactions were injection-site erythema (3.8%), injection-site swelling (2.7%) and rash (2.3%). About Clinical Trials and Data Supporting U.S. FDA Approval The CLEVER trial (MK-1654-004) (NCT04767373) was a Phase 2b/3, randomized, double-blind, placebo-controlled trial to evaluate the safety and efficacy of ENFLONSIA in early and moderate preterm infants (≥29 to <35 weeks gestational age [GA]) and late preterm and full-term infants (≥35 weeks GA) entering their first RSV season. Participants were randomized 2:1 to receive a single 105 mg dose of ENFLONSIA (N=2,411) or saline placebo (N=1,203) by intramuscular (IM) injection. The primary endpoint was the incidence of participants with RSV-associated medically attended lower respiratory infection (MALRI) characterized as cough or difficulty breathing and requiring ≥1 indicator of LRI (wheezing, rales/crackles) or severity (chest wall in-drawing/retractions, hypoxemia, tachypnea, dehydration due to respiratory symptoms) from Day 1 through Day 150 (5 months) after dosing. Medically attended includes all health care provider visits in settings such as outpatient clinic, clinical study site, emergency department, urgent care center and/or hospital. The key secondary endpoint was RSV-associated hospitalization through Day 150 (5 months). The trial demonstrated that the safety profile of ENFLONSIA in infants entering their first RSV season was generally comparable to placebo. The most common adverse reactions were injection-site erythema occurring within 5 days post-dose (ENFLONSIA: 3.8%; placebo: 3.3%), injection-site swelling occurring within 5 days post-dose (ENFLONSIA: 2.7%; placebo: 2.6%) and rash occurring within 14 days post-dose (ENFLONSIA: 2.3%; placebo: 1.9%). Participants were monitored for serious adverse events (SAEs) through the duration of their participation for up to 365 days post-dose. Most (≥97%) of the adverse reactions were toxicity grade 1 (mild) or grade 2 (moderate). The SMART trial (MK-1654-007) (NCT04938830) was a Phase 3, randomized, partially-blind, palivizumab-controlled, multi-site trial to evaluate the safety and efficacy of ENFLONSIA in infants at increased risk of severe RSV disease, including early (<29 weeks GA) or moderate preterm infants (≥29 to ≤35 weeks GA) and infants with chronic lung disease of prematurity or congenital heart disease of any GA. Participants were randomized 1:1 to receive ENFLONSIA (N=446) or palivizumab (N=450) by IM injection. Among infants at increased risk of severe RSV disease and entering their first RSV season, the trial demonstrated that the safety profile of ENFLONSIA was generally comparable to palivizumab and consistent with the safety profile of ENFLONSIA in infants in the CLEVER trial. The efficacy of ENFLONSIA in infants at increased risk for severe RSV disease was established by extrapolation of efficacy of ENFLONSIA from the CLEVER trial to the SMART trial based on similar pharmacokinetic exposure. The incidence rates of RSV-associated MALRI requiring ≥1 indicator of LRI or severity and RSV-associated hospitalization were generally comparable between ENFLONSIA (3.6%, 95% CI: 2.0, 6.0 and 1.3%, 95% CI: 0.4, 2.9, respectively) and palivizumab (2.9%, 95% CI: 1.5, 5.2 and 1.5%, 95% CI: 0.5, 3.2, respectively) through Day 150 (5 months). In clinical trials, when ENFLONSIA was given concomitantly with routine childhood vaccines, the safety profile of the co-administered regimen was generally comparable to the safety profile when ENFLONSIA and childhood vaccines were administered alone. 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 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, 2024 and the company's other filings with the Securities and Exchange Commission (SEC) available at the SEC's Internet site ( Please see Prescribing Information for ENFLONSIA (clesrovimab-cfor) at and Patient Information/Medication Guide for ENFLONSIA at View source version on Contacts Media Contacts:Julie Cunningham(617) 519-6264Brittany Redmer(215) 527-6922 Investor Contacts:Damini Chokshi(732) 594-1577Peter Dannenbaum(732) 594-1579

U.S. FDA Approves Merck's ENFLONSIA™ (clesrovimab-cfor) for Prevention of Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease in Infants Born During or Entering Their First RSV Season
U.S. FDA Approves Merck's ENFLONSIA™ (clesrovimab-cfor) for Prevention of Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease in Infants Born During or Entering Their First RSV Season

Business Wire

time09-06-2025

  • Health
  • Business Wire

U.S. FDA Approves Merck's ENFLONSIA™ (clesrovimab-cfor) for Prevention of Respiratory Syncytial Virus (RSV) Lower Respiratory Tract Disease in Infants Born During or Entering Their First RSV Season

BUSINESS WIRE)--Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced the U.S. Food and Drug Administration (FDA) has approved ENFLONSIA™ (clesrovimab-cfor) for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in neonates (newborns) and infants who are born during or entering their first RSV season. ENFLONSIA is a preventive, long-acting monoclonal antibody (mAb) designed to provide direct, rapid and durable protection through 5 months, a typical RSV season, with the same 105 mg dose regardless of weight. A typical RSV season usually spans autumn to spring of the next year. 'RSV disease is the leading cause of infant hospitalization in the U.S. and can lead to serious respiratory conditions like bronchiolitis and pneumonia,' said Dr. Octavio Ramilo, chair of the Department of Infectious Diseases at St. Jude Children's Research Hospital and investigator for the CLEVER (MK-1654-004) and SMART (MK-1654-007) trials. 'ENFLONSIA combines dosing convenience with strong clinical data showing significant reductions in RSV disease incidence and hospitalizations, making it a promising new intervention to help protect infants from RSV.' ENFLONSIA should not be administered to infants with a history of serious hypersensitivity reactions, including anaphylaxis, to any component of ENFLONSIA. See additional Selected Safety Information below. The approval is based on results from the pivotal Phase 2b/3 CLEVER trial (MK-1654-004) evaluating a single dose of ENFLONSIA administered to preterm and full-term infants (birth to 1 year of age). The trial met its primary and key secondary endpoints, as outlined below. ENFLONSIA demonstrated a reduction in incidence of RSV-associated medically attended lower respiratory infections (MALRI) requiring ≥1 indicator of lower respiratory infection (LRI) or severity compared to placebo through 5 months (primary endpoint) by 60.5% (95% CI: 44.2, 72.0, p<0.001) (incidence rates: ENFLONSIA, 0.026; placebo, 0.065). ENFLONSIA demonstrated a reduction in RSV-associated hospitalizations through 5 months (key secondary endpoint) by 84.3% (95% CI: 66.7, 92.6, p<0.001) (incidence rates: ENFLONSIA, 0.004; placebo, 0.024), showing increasing efficacy with increasing disease severity. The approval is also supported by results from the Phase 3 SMART trial (MK-1654-007) evaluating the safety and efficacy of ENFLONSIA versus palivizumab in infants at increased risk for severe RSV disease. 'ENFLONSIA provides an important new preventive option to help protect healthy and at-risk infants born during or entering their first RSV season with the same dose regardless of weight,' said Dr. Dean Y. Li, president, Merck Research Laboratories. 'We are committed to ensuring availability of ENFLONSIA in the U.S. before the start of the upcoming RSV season to help reduce the significant burden of this widespread seasonal infection on families and health care systems.' The U.S. Centers for Disease Control and Prevention's (CDC's) Advisory Committee on Immunization Practices is expected to meet later this month to discuss and make recommendations for the use of ENFLONSIA in infants. Ordering is anticipated to begin in July, with shipments delivered before the start of the 2025-2026 RSV season. About ENFLONSIA™ (clesrovimab-cfor) ENFLONSIA (clesrovimab-cfor) is Merck's extended half-life monoclonal antibody (mAb) indicated for passive immunization for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in newborns and infants who are born during or entering their first RSV season. ENFLONSIA is administered using non-weight-based dosing and is designed to provide direct, rapid and durable protection through 5 months, a typical RSV season. For infants born during the RSV season, ENFLONSIA is to be administered starting from birth. For infants born outside of the RSV season, ENFLONSIA should be administered prior to the start of their first RSV season. For infants undergoing cardiac surgery with cardiopulmonary bypass during or entering their first RSV season, an additional 105 mg dose is recommended as soon as the infant is stable after surgery. Selected Safety Information for ENFLONSIA (clesrovimab-cfor) Do not administer ENFLONSIA to infants with a history of serious hypersensitivity reactions, including anaphylaxis, to any component of ENFLONSIA. Serious hypersensitivity reactions, including anaphylaxis, have been observed with other human immunoglobulin G1 (IgG1) monoclonal antibodies. If signs or symptoms of a clinically significant hypersensitivity reaction or anaphylaxis occur, initiate appropriate medications and/or supportive therapy. The most common adverse reactions were injection-site erythema (3.8%), injection-site swelling (2.7%) and rash (2.3%). About Clinical Trials and Data Supporting U.S. FDA Approval The CLEVER trial (MK-1654-004) (NCT04767373) was a Phase 2b/3, randomized, double-blind, placebo-controlled trial to evaluate the safety and efficacy of ENFLONSIA in early and moderate preterm infants (≥29 to <35 weeks gestational age [GA]) and late preterm and full-term infants (≥35 weeks GA) entering their first RSV season. Participants were randomized 2:1 to receive a single 105 mg dose of ENFLONSIA (N=2,411) or saline placebo (N=1,203) by intramuscular (IM) injection. The primary endpoint was the incidence of participants with RSV-associated medically attended lower respiratory infection (MALRI) characterized as cough or difficulty breathing and requiring ≥1 indicator of LRI (wheezing, rales/crackles) or severity (chest wall in-drawing/retractions, hypoxemia, tachypnea, dehydration due to respiratory symptoms) from Day 1 through Day 150 (5 months) after dosing. Medically attended includes all health care provider visits in settings such as outpatient clinic, clinical study site, emergency department, urgent care center and/or hospital. The key secondary endpoint was RSV-associated hospitalization through Day 150 (5 months). The trial demonstrated that the safety profile of ENFLONSIA in infants entering their first RSV season was generally comparable to placebo. The most common adverse reactions were injection-site erythema occurring within 5 days post-dose (ENFLONSIA: 3.8%; placebo: 3.3%), injection-site swelling occurring within 5 days post-dose (ENFLONSIA: 2.7%; placebo: 2.6%) and rash occurring within 14 days post-dose (ENFLONSIA: 2.3%; placebo: 1.9%). Participants were monitored for serious adverse events (SAEs) through the duration of their participation for up to 365 days post-dose. Most (≥97%) of the adverse reactions were toxicity grade 1 (mild) or grade 2 (moderate). The SMART trial (MK-1654-007) (NCT04938830) was a Phase 3, randomized, partially-blind, palivizumab-controlled, multi-site trial to evaluate the safety and efficacy of ENFLONSIA in infants at increased risk of severe RSV disease, including early (<29 weeks GA) or moderate preterm infants (≥29 to ≤35 weeks GA) and infants with chronic lung disease of prematurity or congenital heart disease of any GA. Participants were randomized 1:1 to receive ENFLONSIA (N=446) or palivizumab (N=450) by IM injection. Among infants at increased risk of severe RSV disease and entering their first RSV season, the trial demonstrated that the safety profile of ENFLONSIA was generally comparable to palivizumab and consistent with the safety profile of ENFLONSIA in infants in the CLEVER trial. The efficacy of ENFLONSIA in infants at increased risk for severe RSV disease was established by extrapolation of efficacy of ENFLONSIA from the CLEVER trial to the SMART trial based on similar pharmacokinetic exposure. The incidence rates of RSV-associated MALRI requiring ≥1 indicator of LRI or severity and RSV-associated hospitalization were generally comparable between ENFLONSIA (3.6%, 95% CI: 2.0, 6.0 and 1.3%, 95% CI: 0.4, 2.9, respectively) and palivizumab (2.9%, 95% CI: 1.5, 5.2 and 1.5%, 95% CI: 0.5, 3.2, respectively) through Day 150 (5 months). In clinical trials, when ENFLONSIA was given concomitantly with routine childhood vaccines, the safety profile of the co-administered regimen was generally comparable to the safety profile when ENFLONSIA and childhood vaccines were administered alone. 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 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, 2024 and the company's other filings with the Securities and Exchange Commission (SEC) available at the SEC's Internet site ( Please see Prescribing Information for ENFLONSIA (clesrovimab-cfor) at / enflonsia_pi.pdf and Patient Information/Medication Guide for ENFLONSIA at / enflonsia_ppi.pdf.

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