Merck & Co – known as MSD outside the US and Canada – has announced that its respiratory syncytial virus (RSV) preventive monoclonal antibody has been approved by the US Food and Drug Administration (FDA) for use in infants.
Enflonsia (clesrovimab-cfor), which is given as a single intramuscular injection, has been specifically authorised to prevent RSV lower respiratory tract disease in newborns and infants who are born during or entering their first RSV season.
RSV is a common respiratory virus characterised by several mild, cold-like symptoms. Although most people can recover within a week or two, it can cause severe illnesses such as bronchiolitis and pneumonia in certain groups, including young infants.
Merck’s Enflonsia is designed to provide protection against RSV for five months, a typical RSV season, and is now the first RSV preventive option that can be administered in infants using the same dose regardless of weight.
Among the clinical evidence supporting the FDA’s decision were results from the phase 2b/3 CLEVER trial. A single dose of Enflonsia reduced the incidence of RSV-associated medically attended lower respiratory infections requiring at least one indicator of lower respiratory infection by 60.5% compared to placebo through five months, as well as lowered RSV-associated hospitalisations by 84.3% versus placebo at the time point.
Results from the phase 3 SMART trial comparing Enflonsia against palivizumab, another RSV monoclonal antibody, in infants at increased risk for severe RSV disease also informed the approval.
“Enflonsia combines dosing convenience with strong clinical data showing significant reductions in RSV disease incidence and hospitalisations, making it a promising new intervention to help protect infants from RSV,” said Octavio Ramilo, investigator for the CLEVER and SMART trials.
The US Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices is set to meet later this month to discuss and make recommendations on the use of Enflonsia in infants.
Dean Li, president, Merck Research Laboratories, said: “We are committed to ensuring availability of Enflonsia in the US before the start of the upcoming RSV season to help reduce the significant burden of this widespread seasonal infection on families and healthcare systems.”