Sanofi Ramps Up Beyfortus Production as Merck's RSV Antibody Awaits FDA Approval

Sanofi Unveils Aggressive Supply Strategy for Beyfortus

In a preemptive move ahead of potential competition, Sanofi has announced an ambitious supply plan for its respiratory syncytial virus (RSV) antibody, Beyfortus. The French pharmaceutical giant revealed that its current supply for the upcoming RSV season already matches the total doses distributed last year, with production still ongoing.

Sanofi, in partnership with AstraZeneca, has significantly boosted its manufacturing capabilities, tripling production capacity and doubling the number of manufacturing sites since Beyfortus' launch in 2023. Thomas Triomphe, Sanofi's vaccine chief, emphasized the transformative impact of Beyfortus on infant health, citing over 40 real-world studies involving 250,000 immunized infants that have consistently demonstrated the product's effectiveness.

Merck's Clesrovimab Poses Potential Challenge

As Sanofi bolsters its supply chain, Merck & Co. is poised for a potential FDA approval of its rival RSV monoclonal antibody, clesrovimab (MK-1654). With a target decision date set for tomorrow, Merck's entry into the market could reshape the competitive landscape for infant RSV prophylaxis.

Merck's clesrovimab has shown promising results in clinical trials, with a single dose reducing RSV hospitalization by 84% and medically attended lower respiratory infection (MALRI) hospitalization by 91% compared to placebo through five months. The antibody 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.

While direct comparisons between clesrovimab and Beyfortus are challenging due to differences in trial designs and antigenic targets, Merck's single-dose regimen could offer an advantage over Beyfortus' weight-based dosing. Merck also claims that the virus is less likely to develop resistance to clesrovimab.

Market Dynamics and Future Outlook

Despite the looming competition, Sanofi remains confident in Beyfortus' growth prospects for 2025. The company highlights Beyfortus' 75% reduction in MALRI incidence compared to clesrovimab's 60%, as well as its extended protection duration of up to six months, now reflected on its European label.

The RSV market is further complicated by the presence of Pfizer's Abrysvo, a maternal vaccine administered during pregnancy to protect newborns. Abrysvo's potential for widespread adoption lies in its more cost-effective production as a vaccine compared to monoclonal antibodies.

As the 2025 RSV season approaches, all competitors eagerly await the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices (ACIP) meeting scheduled for June 25-27, where recommendations for RSV immunizations will be formulated, potentially shaping the market landscape for the coming year.