The race is on for companies hoping to get vaccines to the market this fall for the start of the respiratory syncytial virus (RSV) season.
Sanofi and AstraZeneca have taken a step toward that goal, revealing data from a real-world trial of their candidate nirsevimab. The companies have submitted the program to the FDA and are awaiting a decision from the agency in the third quarter.
In the phase 3 HARMONIE study of more than 8,000 infants 12 months and younger, those who received a single dose of the antibody were 83% less likely to be hospitalized than those who were not inoculated.
The trial, which was conducted at 250 sites in France, Germany and the U.K., took place in the 2022-23 RSV season. The companies said it confirmed previous results about the safety of nirsevimab.
“This winter saw higher rates of RSV-related infant hospitalizations than during pandemic or pre-pandemic years,” Thomas Triomphe, the vaccines chief at Sanofi, said in a release. "The HARMONIE data demonstrate the real-world impact nirsevimab has on pediatric hospitalizations.”
The companies presented the results of the trial Friday at the 41st European Society for Paediatric Infectious Diseases conference.
Data from HARMONIE also showed that nirsevimab reduced hospitalizations due to severe RSV-related lower respiratory tract disease (LRTD) by 75%. Patients with LRTD have an oxygen level below 90% and require supplementation. Versus those who were not inoculated, nirsevimab also reduced the incidence of all-cause LRTD hospitalization by 58%.
In November, nirsevimab was approved in Europe, where it is known commercially as Beyfortus. The companies developed the antibody to prevent RSV in infants and for children up to 2 years old who remain vulnerable to severe RSV.
Developing a prophylactic for RSV has been an elusive project since the 1960s, when an experimental shot worsened infections in children and caused two deaths. But about a decade ago, researchers zeroed in on the viral fusion protein that RSV uses to enter human cells. Since then, scientists have been more successful in developing vaccines and antibodies to target the virus.
Last week, GSK became the first company to win approval for an RSV vaccine with the FDA’s blessing of Arexvy for adults 60 and older. GSK got to the finish line before Pfizer, which has a shot up for an FDA decision this month, and Moderna, which has completed a phase 3 trial but has yet to apply for approval.
Sanofi and AZ’s antibody might be the lone competitor in the pediatric RSV market, though Pfizer has released promising interim data that show protection for newborns from maternal immunization. GSK’s attempt at maternal immunization stalled in February of 2022 when a trial was halted because of a safety issue.
RSV is the most common cause of LRTD, including bronchiolitis and pneumonia, in infants. It is also a leading cause of hospitalization in all infants. In 2019, there were approximately 33 million cases of acute lower respiratory infections around the world, leading to more than 3 million hospitalizations and an estimated 26,300 deaths of children younger than age 5, Sanofi said.
SVB Securities analyst Geoffrey Porges put the RSV market value at $10.5 billion by 2030. The GSK shot—which the company said last week will cost $60 per dose—could reach $1.8 billion sales in 2028, Evaluate Vantage projected in its annual world preview report published in December.
In March 2017, Sanofi and AZ announced their partnership on nirsevimab. AZ leads development and manufacturing while Sanofi leads commercialization and records revenues.