Group 1: FDA Approval and Product Launch - Merck announced FDA approval for its long-acting monoclonal antibody, clesrovimab, branded as Enflonsia, for the prevention of RSV in newborns and infants [1][7] - The approval was based on data from the pivotal phase IIb/III CLEVER study, which demonstrated a significant reduction in RSV disease and hospitalization in healthy infants [2][7] - Merck plans to launch Enflonsia in the U.S. ahead of the 2025-26 RSV season, with pricing set at $556 per dose and ordering expected to start next month [3][7] Group 2: Market Competition - Enflonsia will face competition from AstraZeneca/Sanofi's RSV antibody Beyfortus, which was also approved in 2023 and achieved blockbuster status in its first full-year sales [6][7] - Sanofi announced plans to increase the supply of Beyfortus, including shipping the antibody early in the third quarter of 2025 [7] - While multiple RSV vaccines are approved for use in the U.S., only Pfizer's Abrysvo is approved for immunizing infants, contrasting with Enflonsia and Beyfortus, which can be administered directly [8] Group 3: Stock Performance - Year to date, Merck's shares have declined by 20%, while the industry has seen a modest decline of 1% [4]