One day before the potential FDA approval of a rival respiratory syncytial virus (RSV) monoclonal antibody from Merck & Co., Sanofi has revealed an aggressive supply effort for its RSV blockbuster Beyfortus, including a plan to begin shipping its AstraZeneca-partnered shot early in the third quarter.
Sanofi said that the current Beyfortus supply for the upcoming RSV season “already matches the total doses distributed last year,” while production remains ongoing. The companies added that they have tripled production capacity and doubled their number of manufacturing sites since the launch Beyfortus in 2023.
“Our third year of providing RSV protection marks a transformative era in infant health,” Thomas Triomphe, Sanofi’s vaccine chief, said in Monday’s release. “Backed by more than 40 real-world studies involving 250,000 immunized infants, Beyfortus has consistently proven itself as an effective RSV immunization.”
While it’s rare to see a company unveil its production plans early in a press release, it is perhaps an indicator of Sanofi and AZ’s concern with the competition it will face if the FDA signs off on Merck’s clesrovimab. The target date for a decision on clesrovimab is tomorrow.
Merck’s monoclonal antibody, also known as MK-1654, has delivered trial results that suggest it can compete with Beyfortus, which has been unchallenged as the premier RSV prophylactic for infants. Last year, Beyfortus generated sales of 1.7 billion euros ($1.8 billion).
Merck made waves eight months ago when it revealed that a single dose of clesrovimab reduced RSV hospitalization by 84% and medically attended lower respiratory infection (MALRI) hospitalization by 91% compared to placebo through five months.
The trial also achieved its primary endpoint, reducing the incidence of RSV-associated MALRI requiring at least one indicator of lower respiratory infection by 60% versus placebo.
Because of the vast differences in their respective trials, it is difficult to draw conclusions between clesrovimab and Beyfortus. While both are monoclonal antibodies, they target different antigenic sites, further complicating any comparisons.
One advantage for clesrovimab is its single dose as opposed to two different doses for Beyfortus depending on the weight of the baby. Merck also has claimed that the virus is less likely to develop resistance to clesrovimab.
Meanwhile, Sanofi has pointed to Beyfortus’ 75% reduction in the incidence of MALRI versus clesrovimab’s figure of 60%. The French company also has emphasized Beyfortus’ duration of protection through six months, which is now reflected on its label in Europe.
Regardless of whether Merck gains approval for clesrovimab, Sanofi still sees Beyfortus continuing its growth in 2025, according to chief financial officer François Roger during the company’s fourth-quarter presentation in January.
Another competitor in the infant RSV market not to be ignored is Pfizer’s Abrysvo, which can be given to women in weeks 32 through 36 of their pregnancies to protect their newborns. The advantage of Abrysvo that could spark more widespread use is its price as a vaccine, as opposed to monoclonal antibodies, which are much more expensive to produce.
As for the 2025 RSV season, all competitors in the market will be anxious for the Centers for Disease Control and Prevention’s ACIP meeting, June 25-27, when recommendations for RSV shots and other immunizations will be formulated.