IDWeek: Clesrovimab reduces RSV disease, hospitalization in healthy infants

IDWeek: Clesrovimab RSV vaccine reduces disease, hospitalization in health infants | Image Credit: © surasak - © surasak - stock.adobe.com.

Merck's investigational RSV prophylactic monoclonal antibody, clesrovimab, designed to protect infants from respiratory syncytial virus (RSV) disease during their first RSV season, demonstrated positive phase 2b/3 study data (MK-1654-004; NCT04767373), which was presented at IDWeek 2024, in Los Angeles, California.

According to an announcement from Merck, clesrovimab met all prespecified endpoints in a placebo-controlled, phase 2b/3 pivotal trial evaluating a single dose in healthy preterm and full-term infants aged birth to 1 year. Results were consistent through both the 5-month and 6-month time points.

The study enrolled 3,632 participants who were randomized 2:1 to receive either a single fixed dose of clesrovimab (105 mg intramuscular injection (IM) or placebo on day 1.

According to the announcement, reduction in incidence of RSV-associated medically attended lower respiratory infections (MALRI) that required 1 or more indicator of lower respiratory infection or severity compared to placebo through 5 months post-dose, was 60.4% (95% CI: 44.1, 71.9, [P <0.001]).

A key secondary endpoint was RSV-associated hospitalizations, for which clesrovimab reduced these hospitalizations by 84.2% (95% CI: 66.6, 92.6, [P <0.001]) through 5 months compared to placebo. A third endpoint was RSV-associated lower respiratory infection hospitalizations, which were reduced 90.9% with clesrovimab treatment compared to placebo through 5 months (95% CI: 76.2, 96.5). In addition, clesrovimab reduced the incidence of severe MALRI (tertiary endpoint) by 91.7% (95% CI: 62.9, 98.1), according to the Merck announcement.

“RSV continues to be a widespread seasonal infection that can affect both healthy and at-risk infants and is the leading cause of hospitalization for infants,” said Octavio Ramilo, MD, chair of the Department of Infectious Diseases at St. Jude’s Children’s Research Hospital and investigator for the MK-1654-004 and MK-1654-007 trials.

"The MK-1654-004 study evaluated a broad spectrum of RSV disease ranging from mild outpatient illness to severe disease requiring hospitalization," said Ramilo. These 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.”

“The breadth of data presented at IDWeek highlight the potential for clesrovimab to help lessen the significant impact RSV can have on infants and their families, as well as the strain on healthcare systems due to high infection and hospitalization rates,” said Paula Annunziato, senior vice president, infectious diseases and vaccines, Global Clinical Development, Merck Research Laboratories. “These clinically meaningful findings also reinforce the potential for clesrovimab to be the first and only immunization designed to protect both healthy and at-risk infants using the same dose, regardless of weight. We look forward to continuing to discuss these data with health authorities around the world with the goal of making clesrovimab available for infants as early as the 2025-26 RSV season.”

Reference:

Merck’s Clesrovimab (MK-1654), an Investigational Respiratory Syncytial Virus (RSV) Preventative Monoclonal Antibody, Significantly Reduced Incidence of RSV Disease and Hospitalization in Healthy Preterm and Full-term Infants. Merck. Press release. October 17, 2024. Accessed October 17, 2024.