Merck, known as MSD outside of the United States and Canada, today announced positive topline results from its Phase 2b/3 clinical trial (MK-1654-004) evaluating clesrovimab (MK-1654), the company’s investigational prophylactic monoclonal antibody designed to protect infants from respiratory syncytial virus (RSV) disease. The trial demonstrated that clesrovimab met its primary safety and efficacy endpoints, including a significant reduction in medically attended lower respiratory infections (MALRI) caused by RSV through Day 150. Detailed findings from this pivotal study will be presented at an upcoming scientific congress, and Merck plans to file these data with global regulatory authorities to facilitate the approval process.
RSV is a highly contagious virus that can cause severe inflammation in the airways of infants, often leading to difficulty in breathing. It is a widespread illness globally and stands as the leading cause of hospitalization for otherwise healthy infants.
“RSV is highly contagious and can cause inflammation in the airways of infants, leading to difficulty breathing. As a widespread illness globally, respiratory syncytial virus is the leading cause of hospitalization for healthy infants,” said Dr. Paula Annunziato, senior vice president of infectious diseases and vaccines, Global Clinical Development, Merck Research Laboratories. “We are encouraged by these findings and look forward to working with regulators to provide a new option to help address the impact of respiratory syncytial virus on infants and their families.”
Merck’s Clesrovimab Shows Promising Results in Phase 2b/3 Trial for Preventing Respiratory Syncytial Virus in Infants
The clinical trial MK-1654-004 (NCT04767373) is a Phase 2b/3 double-blind, randomized, placebo-controlled study designed to evaluate the safety and efficacy of clesrovimab in healthy preterm and full-term infants. Participants in the study were randomized to receive either a single dose of clesrovimab or a placebo. The primary endpoints of the trial included the incidence of participants with respiratory syncytial virus-associated medically attended lower respiratory infection (MALRI) from Day 1 (post-dose) to Day 150, as compared to placebo. Safety measures were rigorously assessed and included the percentage of participants experiencing any injection-related adverse events (AEs), adverse events of special interest (AESIs), solicited systemic AEs, or serious adverse events (SAEs).
Clesrovimab (MK-1654) is an investigational extended half-life monoclonal antibody (mAb) developed as a form of passive immunization to prevent respiratory syncytial virus-associated medically attended lower respiratory infection (MALRI). This innovative treatment is being studied in both preterm and full-term infants to provide rapid and durable protection throughout their first RSV season, requiring only a single, fixed-dose administration.
Respiratory syncytial virus (RSV) poses a significant health threat as a contagious virus responsible for widespread seasonal infections, particularly affecting infants and older adults. The burden of respiratory syncytial virus is substantial, with a high unmet need for effective preventative options for both healthy and high-risk infants. Globally, RSV remains the leading cause of hospitalization for healthy infants under a year old. The virus can lead to severe respiratory conditions such as bronchiolitis and pneumonia, resulting in an estimated 101,000 deaths annually worldwide in children under five years of age.
Merck’s Legacy of Innovation Continues with Promising Results from Clesrovimab Respiratory Syncytial Virus Trial
Merck, also known as MSD outside of the United States and Canada, has a longstanding commitment to using the power of leading-edge science to save and improve lives around the world. With a legacy spanning more than 130 years, Merck has consistently brought hope to humanity through the development of critical medicines and vaccines.
The company aspires to be the premier research-intensive biopharmaceutical entity globally, striving to be at the forefront of research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and animals. Merck fosters a diverse and inclusive global workforce and operates responsibly every day to ensure a safe, sustainable, and healthy future for all people and communities.
The promising results from the Phase 2b/3 trial of clesrovimab underscore Merck’s dedication to addressing significant public health challenges through innovative scientific approaches. By providing a potential new preventative treatment for respiratory syncytial virus, Merck aims to alleviate the substantial healthcare burden posed by this virus, improving outcomes for infants and their families globally. The company looks forward to further collaboration with regulatory authorities to bring this important therapeutic option to market, reinforcing its commitment to enhancing patient care and advancing global health.
Resource: Merck, July 23, 2024

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