Merck’s RSV Antibody Clesrovimab Shows Promising Efficacy in Late-Stage Trial

Efficacy:
Merck's experimental RSV antibody, clesrovimab, demonstrated a 60.4% reduction in RSV-associated medically attended lower respiratory infections (MALRI) compared to placebo in a Phase 2b/3 trial involving over 3,600 infants.

Hospitalization Reduction:
The antibody also showed significant reductions in RSV-associated hospitalizations (84.2%) and RSV-associated lower respiratory infection hospitalizations (90.9%) through 5 months post-dose.

Safety:
Clesrovimab was found to be safe and well-tolerated, with no concerning serious toxicity signals or treatment-related deaths reported.

Market Competition:
The results position clesrovimab as a potential challenger to AstraZeneca and Sanofi's Beyfortus, which has set a high efficacy bar with reductions in RSV-related hospitalizations ranging from 70% to 83% in various studies.

Regulatory Plans:
Merck plans to share the data with global health authorities and present detailed findings at an upcoming scientific congress.

Market Impact:
The success of clesrovimab could provide a new option for protecting infants from RSV, a leading cause of hospitalization in children under one year old.

Dosing Advantage:
Clesrovimab is administered as a single fixed dose, which Merck argues is an advantage over Beyfortus, which requires two injections.