Merck Seeks Priority Review for RSV Drug in China, Cuts Infection Risk by 60.5%

Merck & Co., Inc. (MRK.US) has submitted an application for its long-acting RSV monoclonal antibody, Clesrovimab (MK-1654), for priority review in China. The drug is intended for the prevention of RSV-related lower respiratory tract infections in newborns and infants who are about to enter or have just entered their first RSV season.

RSV, or respiratory syncytial virus, is a highly contagious virus that causes seasonal infections. Clesrovimab is a prophylactic long-acting monoclonal antibody designed to induce passive immunity against RSV by binding to the virus's fusion glycoprotein. This mechanism aims to provide direct, rapid, and sustained protection for infants. On June 9, Clesrovimab received approval from the U.S. Food and Drug Administration (FDA), becoming the first and only single-dose RSV monoclonal antibody approved for use in infants, regardless of their weight.

The CLEVER study, a randomized, double-blind, placebo-controlled Phase IIb/III clinical trial, evaluated the efficacy of a single dose of Clesrovimab in preterm and full-term infants (from birth to 1 year old). The trial met its primary endpoint and key secondary endpoints. Compared to the placebo group, the incidence of medically attended lower respiratory tract infections (MALRI) related to RSV was reduced by 60.5% in the Clesrovimab group 150 days (5 months) post-administration. Additionally, the RSV-related hospitalization rate was reduced by 84.3%.

The SMART study, a randomized, partially blinded, multicenter Phase III clinical trial, aimed to assess the safety and efficacy of Clesrovimab compared to palivizumab in high-risk infants for severe RSV infection. The results of the SMART trial showed that the incidence of RSV-related MALRI and RSV-related hospitalization rates were comparable between Clesrovimab and palivizumab. The safety profile of Clesrovimab was also similar to that of palivizumab and consistent with the safety data observed in the CLEVER trial.

Currently, in China, only AstraZeneca/Sanofi's nirsevimab has been approved. Merck's Clesrovimab has also submitted an application for market approval. Additionally, two other RSV monoclonal antibodies, TNM001 from Tenebio and RB0026 from Reyon, are in Phase III clinical trials.