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Drug

Clesrovimab

Approved · EMA
Emerging researchLate-stage development

Also known as Enflonsia, clesrovimab (cvx 332).

RxNorm2716802UNIIVJO29R4CP9
2
Research papers
1
Regulatory events
Latest activity
beta

Recent clinical, regulatory, research and industry developments relating to this drug.

A Phase 3, Multicenter, Randomized, Partially Blinded, Palivizumab- Controlled Study to Evaluate the Safety, Efficacy, and Pharmacokinetics of MK-1654 in Infants and Children at Increased Risk for Severe RSV Disease

Clinical trial2026-05-08Results posted · ClinicalTrials.gov

Approval: Enflonsia (EMA)

Regulatory2026-04-15EMA

A Phase 2b/3 Double-Blind, Randomized, Placebo-Controlled Study to Evaluate the Efficacy and Safety of MK-1654 in Healthy Pre-Term and Full-Term Infants

Clinical trial2026-02-11Results posted · ClinicalTrials.gov

A Phase 1b/2a Trial of a Half-life Extended Respiratory Syncytial Virus Neutralizing Antibody, Clesrovimab, in Healthy Preterm and Full-term Infants.

Research2025-03-01The Journal of infectious diseases

Development of High-Titer Antidrug Antibodies in a Phase 1b/2a Infant Clesrovimab Trial Are Associated With RSV Exposure Beyond Day 150.

Research2025-03-01The Journal of infectious diseases

A Double-blind, Randomized, Placebo-controlled, Single Ascending Dose Study to Evaluate the Safety, Tolerability, and Pharmacokinetics of MK-1654 in Pre-Term and Full-Term Infants

Clinical trial2025-01-14Results posted · ClinicalTrials.gov

A Phase 2a Double-Blind, Randomized, Placebo-Controlled Study to Evaluate the Efficacy and Safety of MK-1654 in Healthy Participants Inoculated With Experimental Respiratory Syncytial Virus

Clinical trial2022-09-14Results posted · ClinicalTrials.gov

Profile

Identifiers & mechanism

Canonical identifiers, marketed brand names and mechanism, resolved across RxNorm, ChEMBL and ATC.

Canonical name
Clesrovimab
Aliases & brands
Enflonsiaclesrovimab (cvx 332)
RxNorm CUI
2716802
UNII
VJO29R4CP9
Regulatory jurisdictions
ema

Regulatory timeline

1 event

The complete regulatory record, grouped by authority — approvals, safety advisories and label changes. Each authority shows its most recent events; expand one to read its full history.

Earliest approval
2026-04-15
Latest approval
2026-04-15
Authorities
EMA
Total events
1
emaEuropean Medicines Agency· 1 event
2026-04-15Approval
Approval: Enflonsia (EMA)
Indication: Enflonsia is indicated for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in neonates and infants during their first RSV season.Enflonsia… Show full indication

Enflonsia is indicated for the prevention of respiratory syncytial virus (RSV) lower respiratory tract disease in neonates and infants during their first RSV season.Enflonsia should be used in accordance with official recommendations.

Evidence ↗

Contains information from the European Medicines Agency (European Medicines Agency), © EMA, reused under CC BY 4.0.

Clinical trials

4 trials

The current development programme across all trial phases — status mix, phase distribution and the late-stage studies shaping the evidence base.

Development programme
CLINICALTRIALS.GOV · LIVE REGISTRY
4
registered trials across all phases
LATEST COMPLETION 2025
2
Late-stage (III+)
4
Completed
PHASE DISTRIBUTIONn = 4
Phase 1 / 21Phase 21Phase 2 / 31Phase 31

Recent completions

Trials that read out recently, adding to the completed evidence base.

A Phase 3, Multicenter, Randomized, Partially Blinded, Palivizumab- Controlled Study to Evaluate the Safety, Efficacy, and Pharmacokinetics of MK-1654 in Infants and Children at Increased Risk for Severe RSV Disease

CompletedPH IIIKey trialMerck Sharp & Dohme LLCn=1,0032025

A Phase 2b/3 Double-Blind, Randomized, Placebo-Controlled Study to Evaluate the Efficacy and Safety of MK-1654 in Healthy Pre-Term and Full-Term Infants

CompletedPH II/IIIKey trialMerck Sharp & Dohme LLCn=3,6322024

A Double-blind, Randomized, Placebo-controlled, Single Ascending Dose Study to Evaluate the Safety, Tolerability, and Pharmacokinetics of MK-1654 in Pre-Term and Full-Term Infants

CompletedPH I/IIMerck Sharp & Dohme LLCn=1832022

A Phase 2a Double-Blind, Randomized, Placebo-Controlled Study to Evaluate the Efficacy and Safety of MK-1654 in Healthy Participants Inoculated With Experimental Respiratory Syncytial Virus

CompletedPH IIMerck Sharp & Dohme LLCn=802020

Research activity

2 papers

Key research shaping understanding of this drug, combining the latest publications with the most influential evidence.

Major research themes7
Antibodies, Monoclonal2Antibodies, Monoclonal, Humanized2Antibodies, Viral2Antiviral Agents2Respiratory Syncytial Virus Infections2Antibodies, Neutralizing1Respiratory Syncytial Virus, Human1
Journals, researchers & institutions
Top journals
  • The Journal of infectious diseases2
Leading researchers
  • Aliprantis AO2
  • Maas BM2
  • Railkar RA2
  • Vora KA2
  • Acevedo A1
  • Arriola CS1
  • Cao X1
  • Cao Y1
Leading institutions
free-text, unnormalised
  • Acevedo Clinical Research Associates1
  • Children's Hospital Colorado1
  • Colorado School of Public Health1
  • Department of Clinical Research Translational Medicine.1
  • Hospital Padre Alberto Hurtado1
  • University of the Witwatersrand1
References & data sources
  • RxNorm (U.S. National Library of Medicine) — drug identity
  • Europe PMC — research literature
  • ClinicalTrials.gov — clinical trials
  • Regulatory event sources are credited in the Regulatory Timeline above.