Merck’s monoclonal antibody to protect infants from RSV hit its goals in a Phase 2b/3 trial, putting the US drugmaker a step closer to competing against Sanofi and AstraZeneca’s rival product.
The drug, clesrovimab, met the study’s “primary safety and efficacy endpoints,” including preventing medically attended lower respiratory disease caused by the virus, Merck said Tuesday. The company did not say whether it succeeded in a secondary endpoint measuring the rate of RSV-associated hospitalizations.
The company provided no details on how the drug performed numerically, making it impossible to compare against Sanofi and AstraZeneca’s Beyfortus, other than to say it was “encouraged by these findings.”
Merck plans to take the data to regulators at the FDA and around the world for review. If the drug is approved, it could be on the market for the RSV season starting in the fall of 2025, a company spokesperson told Endpoints News.
The trial of clesrovimab included more than 3,600 pre- or full-term infants. The babies were randomized to receive either a single shot of clesrovimab or placebo. Merck shared no details about the safety profile of clesrovimab and what adverse events, if any, arose in the study. It plans to present full results at a future medical conference.
Should a more complete readout validate Merck’s topline claims, then Sanofi and AstraZeneca will have another pharma going up against Beyfortus. Their antibody brought in €547 million ($593.8 million) in 2023 despite only receiving FDA approval in mid-July. Roughly three-quarters of those sales came in the fourth quarter.
The companies have struggled to keep up supply of the drug, which early on in the launch led to limited access compared with demand. At an investor conference in June, Sanofi CFO François-Xavier Roger said inventories now “are less supply-constrained in 2024, but still a bit,” and that the company expects to have no or limited supply issues next year.
There’s likely to be a bit more competition for Beyfortus in the upcoming RSV season this fall. It will be the first full season that Pfizer’s vaccine Abrysvo will be widely available for use during pregnancy, after experts at the Centers for Disease Control that recommend annual vaccines OK’d the shot for that population in September 2023. The RSV season begins in the fall and usually peaks in the winter, according to the CDC.
The federal public health agency recently adjusted its recommendations for adult vaccinations, swapping out advice that all adults 60 and older consult a healthcare provider before getting vaccinated to more concrete guidance. All adults 75 and older are now recommended to get the RSV shot, while adults 60 to 74 should get one if they have a chronic medical condition that puts them at higher risk.