In this article, Merck announced on Thursday that its experimental vaccine aimed at safeguarding infants from respiratory syncytial virus (RSV) displayed positive outcomes in a mid- to late-stage trial, moving the company closer to seeking approval for the vaccine. This development positions the pharmaceutical giant as a potential new player in the RSV treatment market, where the virus causes numerous fatalities among older individuals and hundreds of deaths in infants annually. RSV complications are a primary reason for newborn hospitalizations, underscoring the significance of Merck’s drug as a promising treatment option pending approval.
Merck intends to engage with regulatory authorities globally to share the study findings, aiming to make the vaccine accessible for infants as early as the 2025 to 2026 RSV season. The trial evaluated the safety and effectiveness of a single dose of the vaccine, clesrovimab, in healthy preterm and full-term infants entering their first RSV season. Merck presented the trial results at the IDWeek medical conference in Los Angeles.
According to Merck, the vaccine reduced RSV-related hospitalizations by over 84% and lowered hospitalizations due to lower respiratory infections by 90% compared to a placebo among infants up to five months old. Clesrovimab also decreased lower respiratory infections requiring medical attention by more than 60% compared to a placebo within the same timeframe. RSV is a common cause of lower respiratory tract infections like pneumonia, with consistent results observed at both the five-month and six-month marks in the trial.
The incidence of adverse and severe side effects was similar between patients receiving Merck’s vaccine and those given placebos during the trial, with no treatment- or RSV-related deaths reported. Dr. Octavio Ramilo, chair of the Department of Infectious Diseases at St. Jude’s Children’s Research Hospital and an investigator in the trials, emphasized the potential impact of clesrovimab in reducing the burden of RSV on infants and families.
Merck’s clesrovimab may compete with a comparable treatment called Beyfortus from Sanofi and AstraZeneca, which faced supply shortages nationwide last RSV season due to high demand. Both are monoclonal antibodies that deliver immediate protection by introducing antibodies directly into the bloodstream. Merck’s advantage lies in its ability to administer the treatment to infants irrespective of their weight, offering dosing convenience compared to Beyfortus, which recommends dosage based on an infant’s body weight.
Sanofi noted that the dosage of Beyfortus was meticulously selected through clinical development, with two different doses based on the infant’s weight. The company managed the implementation of these doses effectively during the previous RSV season. Sanofi anticipates having sufficient Beyfortus supply in the U.S. market for the upcoming RSV season, which typically spans from fall to spring.
Pfizer introduced an RSV vaccine last year administered to expectant mothers to confer protection to their fetuses.
