Merck's RSV Antibody Faces Tough Competition from Sanofi's 83% Effective Beyfortus

Merck & Co.'s infant respiratory syncytial virus (RSV) antibody clesrovimab is on the brink of approval, while Sanofi has already gained approval for its RSV prevention drug, Beyfortus, in collaboration with AstraZeneca. This development injects new hope into the global healthcare sector, especially in the sphere of RSV vaccines.

Thomas Triomphe, Sanofi's executive vice president for vaccines, expressed optimism about the impending competition in the RSV market during an analyst call on Friday. He emphasized that increased competition fosters innovation and enhances healthcare solutions, benefiting both the industry and patients. Triomphe pointed out that Merck has more data on clesrovimab following their announcement of phase 2b/3 clinical results last week. Despite this, Sanofi remains confident in the data it has released for Beyfortus, particularly noting the sustained protection it offers over six months.

"After six months, we've observed an 83 percent efficacy in preventing hospitalizations," Triomphe stated. He asserted that the duration of Beyfortus's protection is considerably more favorable compared to clesrovimab. This data underlines Beyfortus's significant role in preventing RSV infections.

In Merck's study on infant RSV, clesrovimab demonstrated a notable reduction in RSV-related hospitalizations and lower respiratory tract infection hospitalizations by 84 percent and 91 percent, respectively, over five months compared to a placebo. The primary endpoint of the trial showed that clesrovimab reduced the incidence of RSV-related medical lower respiratory tract infections by 60 percent compared to a placebo, bolstering its effectiveness in RSV prevention.

Sanofi's Chief Financial Officer, Franois-Xavier Roger, highlighted on a Friday conference call that cross-trial comparisons inherently carry uncertainty. However, the existing Beyfortus data suggests a reduction of approximately 75 percent in the incidence of lower respiratory tract infections, compared to 60 percent with clesrovimab. This further strengthens Beyfortus's advantage over clesrovimab in preventing RSV infection.

Whether or not Merck introduces clesrovimab for the 2025-2026 RSV season as planned, Roger stressed that 2025 will be a growth year for Beyfortus. He expressed confidence that Beyfortus's market share and sales will see significant growth.

Since its approval last July, Beyfortus has steadily increased its sales. In the third quarter of 2024, sales of the preventive antibody reached 645 million euros, marking a 382% increase compared to the same period in 2023. Overall, Beyfortus has achieved sales of 845 million euros since the start of the year, nearing the best-seller threshold.

Sanofi noted that Beyfortus experienced a supply crunch shortly after its market release last year due to unexpectedly high demand. To address this, Sanofi and AstraZeneca have taken measures to prevent a repeat of the supply shortage in 2024. They have added a new filling line and shipped antibody doses ahead of the 2024 RSV season.

"There are 20 markets and we don't see any capacity constraints," Triomphe said. "We will increase supply next year and the year after to ensure there are no supply constraints." This statement underscores Sanofi's confidence in Beyfortus's future and its commitment to meeting global market demands.

Sanofi's comments came as the French pharmaceutical giant reported a 15.7 percent increase in third-quarter sales. This growth was largely driven by the strong performance of its immunology product Dupixent, which generated nearly 3.5 billion euros in sales, a 24 percent increase over the third quarter of 2023. Sanofi confirmed its full-year sales target for Dupixent at approximately 13 billion euros.

Additionally, newly launched drugs saw a 67.1 percent increase, reaching 727 million euros, led by hemophilia drug Altuviiio, Pompe disease treatment Nexviazyme, and Rezurock for graft-versus-host disease. The robust performance of these new drugs further solidifies Sanofi's position in the innovative medicine sector.

Sanofi's consumer health division, Opella, also witnessed a 7.9 percent rise in revenue, indicating significant progress in consumer health. Earlier this week, Sanofi confirmed it had entered exclusive negotiations with U.S. private equity firm Clayton, Dubilier & Rice to sell a controlling 50 percent stake in its consumer healthcare business, valued at around 16 billion euros. This move will bolster Sanofi's financial strength and support future expansion plans.