AstraZeneca/Sanofi's single-dose nirsevimab reduces RSV infection in infants by ~80% shows data
Sohel_Parvez_Haque/iStock via Getty Images

AstraZeneca (NASDAQ:AZN) Sanofi's (NASDAQ:SNY) said a pooled analysis from two studies showed 79.5% efficacy of their single dose antibody nirsevimab against lower respiratory tract infections (LRTI), caused by respiratory syncytial virus (RSV), in infants.
The French pharma giant said pooled analysis of a phase 3 trial, dubbed MELODY, and a phase 2b study showed an efficacy (relative risk reduction versus placebo) of 79.5% against medically attended LRTI such as bronchiolitis or pneumonia, including hospitalizations, caused by RSV in infants born at term or preterm entering their first RSV season.
Sanofi added that Nirsevimab is the first investigational immunization aimed to protect all infants across the RSV season with a single dose.
In a separate pooled post-hoc analysis of the trials, blood samples taken from infants dosed with nirsevimab showed RSV neutralizing antibodies that were ~50-fold higher than baseline at Day 151 post-dose, the company said in a May 11 press release.
Sanofi added that RSV neutralizing antibody levels remained greater than 19-fold higher than those receiving placebo, with no known RSV infection through Day 361, suggesting protection may extend beyond Day 151.
The safety profile across the nirsevimab and placebo groups, as reported in previous trials, remained similar.
The company noted that this data add to the evidence suggesting that nirsevimab can protect all infants through their first RSV season with a single dose.
"These analyses add to nirsevimabâs compelling body of evidence as the first potential single-dose preventative immunization for all infants against RSV, addressing a clear unmet need in the RSV preventative landscape," said Mene Pangalos, executive vice president, BioPharmaceuticals R&D, AstraZeneca (AZN).