A Sanofi and AstraZeneca respiratory syncytial virus (RSV) drug approved in Europe and currently under review by the FDA now has additional data from a real-world study showing a single shot was able to protect infants younger 12 months old, an age when their undeveloped immune systems make them vulnerable to infection.
A single dose of the drug, nirsevimab, led to an 83.2% reduction in hospitalizations due to lower respiratory tract disease in infants compared to infants who received no RSV therapy. The Phase 3b results were presented Friday during the annual meeting of the European Society for Paediatric Infectious Diseases.
Nirsevimab is an antibody designed to bind to a protein that RSV uses to enter and infect cells. It provides infants with immediate protection while their immune systems are still developing the ability to form their own protective antibodies. Last November, the drug won European Commission approval for preventing lower respiratory illness from RSV infection. It is marketed in Europe under the brand name Beyfortus. The antibody has since received regulatory nods in the U.K. and Canada.
The trial results announced Friday are from study that evaluated how the shot would perform under real-world conditions. The study enrolled more than 8,000 infants at close to 250 sites in France, Germany, and the U.K. The study collected data from the 2022-2023 RSV season. In addition to lowering the rate of hospitalization, the results also showed reduction in hospitalization due to severe RSV-related lower respiratory tract disease, which was defined as patients whose oxygen level falls below 90% and requires supplemental oxygen. On this measure, the incidence of hospitalization was reduced by more than 75%.
The Sanofi and AstraZeneca drug could compete against Abrysvo, a maternal RSV vaccine from Pfizer. This vaccine is administered to the mother, whose immune system produces antibodies against RSV. Those antibodies pass through the placenta to the fetus. Abrysvo is intended to protect an infant from birth through six months of age. It’s currently under FDA review with regulatory decision expected in August. An FDA advisory committee is scheduled to discuss the vaccine on May 18.
While nirsevimab is a drug, Sanofi intends it to be used as a vaccine, Jon Heinrichs, Sanofi associate vice president, research and development, told MedCity News during an interview in February. It’s designed with a long half-life that lasts about five months—long enough to cover the RSV season from November through March, Heinrichs said. He added that the ability to time the administration of the Sanofi shot gives it an advantage over a maternal vaccine.
“That’s important because you can’t control when the infant is born,” Heinrichs said. “The maternal antibodies could be cleared by the time of RSV season. We can time that [administration], even in the case when the RSV season is unpredictable.”
Nirsevimab was initially developed by AstraZeneca. In 2017, Sanofi paid €120 million up front to begin a global partnership on the antibody. According to the agreement, AstraZeneca leads development and manufacturing of the antibody while Sanofi takes the lead on commercialization. To date, Sanofi has paid its partner €55 million in development and regulatory milestones, and could pay out up to €440 million more upon achievement of certain regulatory and sales-related milestones. Costs and profits of the drug will be shared in all regions except the U.S., where Sanofi has rights to all of the profits.
Public domain image by the CDC
