Merck & Co.’s mAB prevents RSV in infants, teeing up talks with regulators

Moderna recently became the latest biopharma to score an approval to prevent respiratory syncytial virus (RSV), but Merck & Co. hopes to be the next in line with new data showing a monoclonal antibody reduced the incidence of RSV-related infections in infants. 

Clesrovimab, also known as MK-1654, is designed for prophylactic use in infants. A phase 2b/3 trial in healthy pre-term and full-term infants has demonstrated that the antibody hit the primary endpoint of reducing the incidence of RSV-related infections over 150 days when compared to placebo, the company said in a July 23 release.

The trial also hit key safety measures such as the percentage of participants with any injection-related adverse events (AEs), AEs of special interest, solicited systemic AEs, or serious AEs.

But if you want some data on how clesrovimab actually performed in the clinic—you’ll have to wait. The sparse press release only promises that detailed findings of the study will be “presented at an upcoming scientific congress” as well as filed with global regulators.

“We are encouraged by these findings and look forward to working with regulators to provide a new option to help address the impact of RSV on infants and their families,” Paula Annunziato, senior vice president of infectious diseases and vaccines, Global Clinical Development, Merck Research Laboratories, said in the release.

Merck once had an RSV vaccine for adults in early-stage development, but passed it over to long-time partner Moderna in 2020 to focus on what would become clesrovimab. For its part, Moderna has powered ahead in the RSV space, scoring FDA approval for an adult RSV vaccine in May.

For now, the market remains dominated by GSK’s Arexvy shot, which brought in 182 million pounds ($227 million) in the first quarter of the year compared to $145 million for Pfizer’s rival Abrysvo.