Infants in trial were protected by experimental RSV treatment, according to Merck, potentially paving the way for approval.

• The experimental treatment developed by Merck to safeguard infants from respiratory syncytial virus demonstrated positive outcomes in a late-stage trial.
• A new competitor in the market for treatments against RSV, which causes hundreds of infant deaths each year, could emerge from the pharmaceutical giant.
• Regulators worldwide are being consulted by Merck regarding the study data, with the aim of making the treatment accessible to infants during the 2025 to 2026 RSV season.

The company's experimental treatment for protecting infants from respiratory syncytial virus showed positive results in a mid- to late-stage trial, bringing it one step closer to filing for approval of the shot.

If approved, Merck's drug could be a valuable new treatment option for RSV, which causes thousands of deaths among older Americans and hundreds of deaths among infants each year, making it a potential new competitor in the market for treatments against the virus.

According to a release, Merck aims to share study data with global regulators to make the treatment accessible to infants during the 2025 to 2026 RSV season.

The safety and efficacy of a single dose of clesrovimab in healthy preterm and full-term infants during their first RSV season was examined in a trial. Merck presented the findings at the IDWeek medical conference in Los Angeles.

Through five months, infants experienced a more than 84% reduction in RSV-related hospitalizations and a 90% decrease in hospitalizations due to lower respiratory infections when treated with Clesrovimab, compared to a placebo, according to Merck. Additionally, Clesrovimab reduced the number of lower respiratory infections that required medical attention by more than 60% compared to a placebo.

Pneumonia is a common lower respiratory tract infection caused by RSV, and the results of the trial were consistent at both the five-month and six-month time points, according to Merck.

In the trial, the rates of adverse and serious side effects were similar between patients who received Merck's shot and those who took placebos. Additionally, there were no deaths related to treatment or RSV in the study, the company stated.

Dr. Octavio Ramilo, chair of the Department of Infectious Diseases at St. Jude's Children's Research Hospital, stated in Merck's release that the promising results demonstrating decreased incidence of RSV disease, including hospitalizations, highlight the potential for clesrovimab to play an important role in helping to alleviate the continued burden of RSV on infants and their families. Ramilo is also an investigator working on the trials.

Beyfortus, a monoclonal antibody treatment for RSV, was in short supply last season due to unprecedented demand. Merck's clesrovimab could potentially compete against this treatment, as both are monoclonal antibodies that deliver antibodies directly into the bloodstream for immediate protection.

Merck's treatment can be given to infants regardless of their weight, which the company claims may provide convenience in terms of dosing. However, the recommended dosage of Beyfortus is based on an infant's body weight.

Last year, expectant mothers received RSV vaccines that protect their fetuses.