Sanofi-AstraZeneca Say New Nirsevimab Data Reinforce Efficacy Against RSV

Sanofi SA SNY and AstraZeneca plc AZN have announced results from a prespecified pooled analysis of nirsevimab in respiratory syncytial virus (RSV).
Results from the Phase 3 MELODY and Phase 2b nirsevimab trials demonstrated an efficacy (relative risk reduction versus placebo) of 79.5% against medically attended lower respiratory tract infections due to RSV in infants.
In a separate pooled posthoc analysis of the trials, blood samples taken from infants dosed with nirsevimab exhibited RSV neutralizing antibodies that were approximately 50-fold higher than baseline at Day 151 post-dose.
Related: AstraZeneca-Sanofi's Nirsevimab Shows 75% Efficacy Against RSV In Healthy Infants.
RSV neutralizing antibody levels remained greater than 19-fold higher than placebo recipients with no known RSV infection through Day 361, suggesting protection may extend beyond Day 151.
As reported in previous trials, the safety profile across the nirsevimab and placebo groups remains similar.
Nirsevimab is the first investigational immunization designed to protect all infants across the RSV season with a single dose.
Price Action: SNY shares are down 1.36% at $51.46, and AZN stock is down 2.18% at $62.25 during the premarket session on the last check Wednesday.