Palivizumab

iStock, graphixchon Merck’s investigational antibody clesrovimab demonstrated more than 60% effectiveness in reducing some types of respiratory syncytial virus-associated infections in infants, while Pfizer’s RSV vaccine Abrysvo showed 90% effectiveness at preventing the most severe RSV cases in adults 60 years and older. At the ongoing IDWeek 2024 Conference in Los Angeles, Merck and Pfizer both presented new data for their respective prophylactic options for respiratory syncytial virus, touting strong protective effectiveness against the infection and related hospitalizations. Their findings come as the U.S. enters a new respiratory syncytial virus (RSV) season, which typically starts in fall and peaks during winter. According to the National Foundation for Infectious Diseases, RSV is the most common reason for hospitalization in children under 1 year , causing up to 80,000 admissions per year. The virus is also a major source of respiratory morbidity in older adults. Merck unveiled Phase IIb/III data for its investigational antibody clesrovimab, a single dose of which was administered to healthy preterm and full-term babies entering their first RSV season. The study’s primary efficacy outcome was the percentage of participants with RSV-associated medically attended lower respiratory infection (MALRI), defined as having at least one indicator of LRI or severity. More than 3,600 infants from birth to 1 year of age were enrolled. Results showed a 60.4% drop in RSV-associated MALRI at 150 days after dosing, compared with placebo. At this time point, clesrovimab also lowered RSV-associated hospitalizations by 84.2% and RSV-associated LRI hospitalizations by 90.9%. Merck backed these data up with additional analysis from a separate Phase III study, which compared the safety and efficacy of clesrovimab versus palivizumab in infants and children who are at heightened risk of severe disease. Findings demonstrated that rates of RSV-associated MALRI and hospitalizations were similar between treatment arms. Clesrovimab was also safe and well-tolerated, with no concerning serious toxicity signals and treatment- or RSV-related deaths, according to Merck. Paula Annunziato, senior vice president of infectious diseases and vaccines clinical research at Merck, in a statement called these findings “clinically meaningful,” which “highlight the potential for clesrovimab to lessen the significant impact RSV can have on infants and their families, as well as the strain on the healthcare system.” At IDWeek 2024, Pfizer unveiled results from a retrospective analysis of adults 60 years and older who presented to emergency care with severe disease. In the study population, immunization with the company’s vaccine Abrysvo showed 90% effectiveness at preventing the most severe RSV cases, according to Endpoints News . The retrospective study was conducted by Kaiser Permanente in California but was funded by Pfizer. These data come after the U.S. Centers for Disease Control and Prevention narrowed its RSV vaccination guidelines for seniors. Per a June 2024 communication, the agency now only recommends RSV shots for all older adults aged 75 and older. In the 60 to 74 age group, vaccination is only recommended for those at risk of severe disease. This change could have significant implications for the industry, with analysts forecasting a nearly 65% drop in RSV revenues. According to a July 2024 report from Airfinity , sales for RSV shots in the U.S. are now only projected to reach $1.7 billion by 2030, down from a previous estimate of $4.7 billion. Despite bleaker sales prospects, Pfizer continues to shore up the evidence base for Abrysvo. In addition to results presented at IDWeek 2024, the pharma in August 2024 announced that the vaccine can elicit a strong neutralizing response against the virus in immunocompromised adults.

Dive Brief:An experimental antibody drug developed by Merck & Co. significantly reduced the incidence of disease due to respiratory syncytial virus infections as well as related hospitalizations in infants, the company said Thursday.Called clesrovimab, the antibody met all the goals of a Phase 2b/3 study testing it in more than 3,600 healthy pre- and full-term infants. A dose of clesrovimab lowered RSV disease incidence by 60%, and RSV-associated hospitalizations by 84%, compared to placebo through five months post-treatment.While three RSV vaccines are approved in the U.S. for older adults, only one antibody drug Sanofi and AstraZenecas Beyfortus is cleared for all infants entering their first RSV season. If approved, clesrovimab would compete with Beyfortus.Dive Insight:RSV is a significant public health concern for vulnerable populations, especially the elderly and newborns. Researchers estimate that nearly every child will be infected by the age of two. While infection typically only causes a mild, cold-like illness, it can be more serious and require hospitalization in some.Like Beyfortus, clesrovimab is designed to work as passive immunization. Merck is testing it as a single-dose shot for healthy preterm infants, full-term and at-risk infants of any weight. Beyfortus, meanwhile, comes in different dose strengths depending on the weight of an infant.In the Phase 2b/3 trial, healthy pre- or full-term infants from birth up to 1 year of age entering their first RSV season received either placebo or clesrovimab. Researchers then evaluated clesrovimabs safety and efficacy through five and six months following treatment.Merck had previously said the study succeeded and on Friday shared the more detailed data. Against endpoints measuring more severe disease, clesrovimab was around 90% effective versus placebo.Rates of adverse events and serious adverse events were comparable between antibody and placebo groups in the Phase 2b/3 study, Merck said. There were no treatment- or RSV-related deaths in that trial.The company also shared interim findings from a Phase 3 trial testing clesrovimab against an older antibody, Synagis, in infants at high risk of severe disease. Otherwise known as palivizumab, Synagis is cleared only for high-risk infants. In the study comparing Synagis and clesrovimab, the safety profile of the two drugs was comparable, according to Merck.The company aims to secure U.S. approval and make clesrovimab available as early as the 2025-2026 RSV season. '