Merck’s clesrovimab (MK-1654), an investigational monoclonal antibody aimed at preventing respiratory syncytial virus (RSV) disease in infants, has shown significant efficacy in a Phase 2b/3 clinical trial.
The trial results indicate that a single dose of this investigational monoclonal antibody effectively reduced the incidence of hospitalisations due to RSV. It also significantly lowered the rates of related lower respiratory infections among both healthy preterm and full-term infants, as per Merck, which operates as MSD outside of the US and Canada.
Featuring 3,632 healthy preterm and full-term infants, the MK-1654-004 trial involved a placebo-controlled methodology. Findings revealed a decrease of over 84% in RSV-associated hospitalisations and a reduction of more than 90% in hospitalisations linked to RSV-associated lower respiratory infections over a five-month observation period.
These results were consistent across various endpoints assessed at both the five-month and six-month intervals. The frequency of adverse events in infants receiving clesrovimab was comparable to those in the placebo group, with no deaths attributed to the treatment or RSV reported during the trial.
The primary endpoint of the study focused on the reduction in medically attended lower respiratory infections that required at least one indicator of severity when compared to the placebo group. This endpoint achieved a reduction rate of 60.4%.
Additionally, clesrovimab demonstrated a 91.7% reduction in the incidence of severe medically attended lower respiratory infections. A post hoc analysis further indicated that the rate of medically attended lower respiratory infections requiring two or more indicators of severity was reduced by 88% throughout the five-month follow-up period.
These findings were presented at the IDWeek 2024 conference in Los Angeles, California. Alongside these results, interim data from the ongoing Phase 3 trial, known as MK-1654-007, was also disclosed.
The MK-1654-007 trial is currently evaluating the safety and efficacy of clesrovimab in comparison to palivizumab for infants and children at a heightened risk of severe RSV disease. The primary endpoint of this trial is to assess the safety and tolerability of clesrovimab as infants enter their first RSV season.
The interim analysis suggests that the safety profile of clesrovimab is comparable to that of palivizumab, with no serious adverse events associated with the drug candidate reported to date.
The incidence rates for RSV-associated medically attended lower respiratory infections and hospitalisations were also found to be similar for both clesrovimab and palivizumab, recording rates of 3.6% and 1.3%, respectively, against 3.0% and 1.5% for palivizumab over the same five-month period.
Merck research laboratories global clinical development infectious diseases and vaccines senior vice president Paula Annunziato said: “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 hospitalisation rates.
“These clinically meaningful findings also reinforce the potential for clesrovimab to be the first and only immunisation designed to protect both healthy and at-risk infants using the same dose, regardless of weight.”
