The U.S. Food and Drug Administration has given its approval to a novel antibody treatment developed by Merck & Co. for preventing respiratory syncytial virus (RSV) infections in infants. The medication, marketed as Enflonsia, represents a significant addition to the limited arsenal of preventive options available for protecting young children against RSV.
Clinical trials demonstrated that Enflonsia reduced RSV disease incidence by 60% and related hospitalizations by 84% over a five-month period when compared to placebo. The drug is specifically indicated for newborns and infants entering their first RSV season, offering a new alternative to existing treatments.
The approval comes at a time when RSV prevention has seen substantial advancement, particularly for older adults who now have access to three different vaccines manufactured by GSK, Pfizer, and Moderna. However, young children remain especially vulnerable to RSV, which continues to be the primary cause of infant hospitalizations in the United States.
Currently, preventive options for infants are limited. While Pfizer’s Abrysvo vaccine is available for pregnant women to provide passive immunity to their newborns, direct vaccination of young children remains unavailable. The FDA recently halted multiple RSV vaccine trials in children following reports of severe RSV cases in a Moderna study.
Enflonsia will compete directly with Beyfortus, a successful antibody treatment jointly developed by Sanofi and AstraZeneca that received FDA approval in 2023. Beyfortus has already achieved blockbuster status, though initial supply constraints forced Sanofi to enhance its manufacturing capacity. In response to Enflonsia’s approval, Sanofi has announced plans to expedite Beyfortus shipments before the upcoming RSV season.
Merck’s new treatment offers several advantages that could help it capture market share. Unlike Beyfortus, Enflonsia can be administered regardless of an infant’s weight and requires only a single injection rather than two. However, some Wall Street analysts remain skeptical about Enflonsia’s commercial prospects, noting that its efficacy data appears comparable to that of Beyfortus.
Dr. Octavio Ramilo, who chairs the Department of Infectious Diseases at St. Jude Children’s Research Hospital and participated in the drug’s clinical studies, emphasized Enflonsia’s combination of convenient dosing and robust clinical results as key benefits for RSV prevention in infants.
The Centers for Disease Control and Prevention’s advisory committee is scheduled to meet later this month to discuss recommendations for Enflonsia’s use. Merck anticipates having the drug available for distribution before the 2025-2026 RSV season begins.
Healthcare providers should note that Enflonsia is contraindicated in infants with a history of severe hypersensitivity reactions, including anaphylaxis, to any of the drug’s components. This safety
consideration aligns with standard precautions for similar biological treatments.
The approval of Enflonsia marks another milestone in addressing RSV, a pathogen that has long challenged public health efforts. While preventive options for young children remain limited compared to those available for adults, this new treatment provides healthcare providers with an additional tool to protect vulnerable infants from serious RSV complications. The upcoming CDC recommendations will further clarify Enflonsia’s role in clinical practice and its potential impact on reducing the burden of RSV disease in the pediatric population.
Be First to Comment