- EC approved clesrovimab (ENFLONSIA) for prevention of RSV lower respiratory tract disease in neonates and infants during their first RSV season across the EU, Iceland, Liechtenstein and Norway
- Single intramuscular 105 mg non-weight-based dose of extended‑half‑life monoclonal antibody designed to provide ~5 months of protection
- CLEVER (N≈3,614; 2,412 ENFLONSIA vs 1,202 placebo) showed 60.4% reduction in RSV-associated medically attended LRI and 84.2% reduction in RSV hospitalizations through 5 months
- SMART interim data in high‑risk infants showed comparable safety and similar RSV incidence versus monthly palivizumab; common adverse reactions included injection-site pain, erythema, swelling and rash
Regulatory approval
The European Commission approved ENFLONSIA (clesrovimab) for prevention of RSV lower respiratory tract disease in neonates and infants during their first RSV season, authorizing marketing across the 27 EU member states plus Iceland, Liechtenstein and Norway; country-level availability depends on national reimbursement.
Indication and dosing
ENFLONSIA is an extended‑half‑life monoclonal antibody given as a single 105 mg intramuscular dose regardless of weight, designed to provide direct protection through approximately five months; for infants born during RSV season administer within the first week of life, for those born outside give shortly before season onset, and an additional 105 mg dose is recommended after cardiopulmonary bypass.
Clinical evidence
The pivotal CLEVER Phase 2b/3 trial (≈3,614 participants; 2,412 ENFLONSIA vs 1,202 placebo) met primary and key secondary endpoints: 60.4% reduction in RSV-associated medically attended lower respiratory infection through 5 months and 84.2% reduction in RSV hospitalizations; exploratory endpoints showed large reductions in severe disease and LRI hospitalizations. Interim SMART data in high‑risk infants showed comparable safety and pharmacokinetic exposure versus monthly palivizumab (ENFLONSIA MALRI 3.6% vs palivizumab 3.0%; hospitalizations 1.3% vs 1.5%).
Safety and co-administration
CLEVER reported most adverse reactions were mild/moderate; common events included injection‑site pain (6.5%), erythema (4.4%), swelling (3.2%) and rash (2.3%); concomitant administration with routine childhood vaccines showed a similar safety profile.
