Clesrovimab

Clesrovimab
Monoclonal antibody
Type	Whole antibody
Source	Human
Target	Respiratory syncytial virus F protein
Clinical data
Trade names	Enflonsia
Other names	MK-1654, clesrovimab-cfor
License data	US DailyMed: Clesrovimab;
Routes of; administration	Intramuscular
Drug class	Antiviral
ATC code	None;
Legal status
Legal status	US: ℞-only;
Identifiers
CAS Number	2429913-18-6;
DrugBank	DB18877;
UNII	VJO29R4CP9;
KEGG	D12153;
Chemical and physical data
Formula	C6526H10118N1732O2039S40
Molar mass	146747.22 g·mol−1

Clesrovimab, sold under the brand name Enflonsia, is a fully human immunoglobulin G1 kappa monoclonal antibody designed to prevent respiratory syncytial virus (RSV) infection.^[1] It is a respiratory syncytial virus (RSV) F protein-directed fusion inhibitor.^[1] It was developed by Merck,^[2] and was approved for medical use in the United States in June 2025.^[3]

Medical uses

Clesrovimab is indicated for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in neonates and infants who are born during or entering their first RSV season.^[1]

Society and culture

Legal status

Clesrovimab was approved for medical use in the United States in June 2025.^[2]^[4]

Names

Clesrovimab is the international nonproprietary name.^[5]

Clesrovimab is sold under the brand name Enflonsia.^[1]

References

^ ^a ^b ^c ^d ^e https://www.accessdata.fda.gov/drugsatfda_docs/label/2025/761432s000lbl.pdf
^ ^a ^b "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" (Press release). Merck. 9 June 2025. Retrieved 14 June 2025 – via Business Wire.
^ "Novel Drug Approvals for 2025". U.S. Food and Drug Administration. 9 June 2025. Retrieved 14 June 2025.
^ "Clesrovimab Receives FDA Approval for RSV Lower Respiratory Tract Prevention in Infants".
^ World Health Organization (2022). "International nonproprietary names for pharmaceutical substances (INN): recommended INN: list 88". WHO Drug Information. 36 (3). hdl:10665/363551.

Cunningham, Steve; Zar, Heather J. (June 2023). "New Interventions to Prevent Respiratory Syncytial Virus Disease in Infants—Time for Equitable Global Access". American Journal of Respiratory and Critical Care Medicine. 207 (12): 1556–1557. doi:10.1164/rccm.202303-0568VP. PMC 10273123. PMID 37104655.
Dolgin, Elie (September 2023). "Antibody therapies set to transform respiratory syncytial virus prevention for babies". Nature. 621 (7980): S55 – S57. Bibcode:2023Natur.621S..55D. doi:10.1038/d41586-023-02957-z. PMID 37758887. S2CID 262894944.
Liszewski, Kathy (May 2023). "Multiple Vaccine Technologies Converge on Respiratory Syncytial Virus: Advances include a bivalent subunit vaccine, a liposome-based adjuvant, an mRNA vaccine, and a passive vaccination approach". Genetic Engineering & Biotechnology News. 43 (5): 16–18, 20. doi:10.1089/gen.43.05.05. S2CID 258583326.
Messina, Alessandro; Germano, Chiara; Avellis, Vincenzo; Tavella, Elena; Dodaro, Valentina; Massaro, Alessio; et al. (November 2022). "New strategies for the prevention of respiratory syncytial virus (RSV)". Early Human Development. 174: 105666. doi:10.1016/j.earlhumdev.2022.105666. PMID 36174288.</ref>
Odumade, Oludare A; van Haren, Simon D; Angelidou, Asimenia (August 2022). "Implications of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Pandemic on the Epidemiology of Pediatric Respiratory Syncytial Virus Infection". Clinical Infectious Diseases. 75 (Supplement_1): S130 – S135. doi:10.1093/cid/ciac373. PMC 9129219. PMID 35579506.
Phuah, Jia Yao; Maas, Brian M.; Tang, Aimin; Zhang, Ying; Caro, Luzelena; Railkar, Radha A.; et al. (December 2023). "Quantification of clesrovimab, an investigational, half-life extended, anti-respiratory syncytial virus protein F human monoclonal antibody in the nasal epithelial lining fluid of healthy adults". Biomedicine & Pharmacotherapy. 169: 115851. doi:10.1016/j.biopha.2023.115851. PMID 37976891. S2CID 265251138.
Qiu, Xirui; Xu, Siyan; Lu, Yang; Luo, Zichen; Yan, Yangtian; Wang, Chuyue; et al. (December 2022). "Development of mRNA vaccines against respiratory syncytial virus (RSV)". Cytokine & Growth Factor Reviews. 68: 37–53. doi:10.1016/j.cytogfr.2022.10.001. PMID 36280532. S2CID 252877115.
Verwey, Charl; Madhi, Shabir A. (May 2023). "Review and Update of Active and Passive Immunization Against Respiratory Syncytial Virus". BioDrugs. 37 (3): 295–309. doi:10.1007/s40259-023-00596-4. PMC 10127166. PMID 37097594.

External links

Clinical trial number NCT04767373 for "Efficacy and Safety of Clesrovimab (MK-1654) in Infants (MK-1654-004) (CLEVER)" at ClinicalTrials.gov
Clinical trial number NCT04938830 for "Clesrovimab (MK-1654) in Infants and Children at Increased Risk for Severe Respiratory Syncytial Virus (RSV) Disease (MK-1654-007) (SMART)" at ClinicalTrials.gov

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[Enflonsia_FDA_label-1] ttps://www.accessdata.fda.gov/drugsatfda_docs/label/2025/761432s000lbl.pdf

[Merck_PR_20250609-2] "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" (Press release). Merck. 9 June 2025. Retrieved 14 June 2025 – via Business Wire.

[3] "Novel Drug Approvals for 2025". U.S. Food and Drug Administration. 9 June 2025. Retrieved 14 June 2025.

[4] "Clesrovimab Receives FDA Approval for RSV Lower Respiratory Tract Prevention in Infants".

[5] World Health Organization (2022). "International nonproprietary names for pharmaceutical substances (INN): recommended INN: list 88". WHO Drug Information. 36 (3). hdl:10665/363551.

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