Clesrovimab offers single-dose RSV protection for infants in first season

Clesrovimab (ENFLONSIA; clesrovimab-cfor), a long-acting monoclonal antibody that targets the respiratory syncytial virus (RSV) fusion protein, has been profiled in Drugs & Therapy Perspectives as a useful addition to the prophylactic options for RSV-associated lower respiratory tract disease in neonates and infants born during or entering their first RSV season. The antibody has recently been approved in both the USA and the European Union for this indication, positioning it alongside existing preventive approaches for a virus that is a significant cause of infant hospitalizations and deaths.

The drug’s clinical evidence rests principally on the phase 2b/3 CLEVER trial. In that study, a single 105 mg dose of clesrovimab, administered irrespective of body weight, provided durable protection against RSV-associated medically-attended lower respiratory infection (RSV-MALRI) and reduced RSV-associated hospitalizations in neonates and infants born during or entering their first RSV season. The fixed 105 mg dose is administered irrespective of body weight, so no weight-based dosing calculation is required.

Supporting pharmacokinetic data come from the phase 3 SMART trial, which enrolled infants and children at increased risk of severe RSV disease, including those aged under 2 years. According to the profile, these pharmacokinetic findings support the efficacy of clesrovimab in this higher-risk population, extending the evidence base beyond healthy infants entering their first season.

On safety, clesrovimab was generally well tolerated, with low reactogenicity. Clesrovimab had a similar adverse event profile to placebo in the CLEVER trial and to palivizumab in the SMART trial.

Clesrovimab is described as the second long-acting monoclonal antibody approved for prevention of RSV disease, a class expansion that the profile frames as a meaningful addition to the options available to clinicians protecting neonates and infants during their first exposure season.

Subject of Research: Use of the long-acting monoclonal antibody clesrovimab for prevention of RSV lower respiratory tract disease in infants

Article Title: Clesrovimab in prevention of RSV lower respiratory tract disease: a profile of its use in infants

Article References: Brown, M. B., & Syed, Y. Y. (2026). Clesrovimab in prevention of RSV lower respiratory tract disease: a profile of its use in infants. Drugs & Therapy Perspectives. https://doi.org/10.1007/s40267-026-01270-9

Image Credits: AI Generated

DOI: 10.1007/s40267-026-01270-9

Keywords: clesrovimab, RSV, monoclonal antibody, infants, prophylaxis, lower respiratory tract disease, CLEVER trial, SMART trial, palivizumab, drug approval, prevention, lower