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New Analyses Reinforce Antibody Treatment Efficacy Against RSV

May 11, 2022 • 11:37 am CDT
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(Precision Vaccinations)

AstraZeneca announced today positive news regarding Nirsevimab, an investigational long-acting antibody for the respiratory syncytial virus (RSV) co-developed with Sanofi.

The clinical results from a prespecified pooled analysis of the pivotal MELODY Phase III and Phase IIb trials showed Nirsevimab demonstrated an efficacy (relative risk reduction versus placebo) of 79.5% (95% Confidence Interval [CI] 65.9 to 87.7; P<0.0001) against medically attended lower respiratory tract infections (LRTI), such as bronchiolitis or pneumonia, caused by RSV in infants born at term or preterm entering their first RSV season.

The pooled analysis studied healthy preterm and term infants who received the optimized dose of nirsevimab compared to placebo through Day 151 and showed an efficacy of 77.3% (95% CI 50.3, 89.7; P<0.001) against RSV LRTI hospitalizations.

In a separate pooled post-hoc 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 postdose.

RSV neutralizing antibody levels remained 19-fold higher than placebo recipients with no known RSV infection through Day 361, suggesting protection may extend beyond Day 151.

And the overall safety profile of nirsevimab in the two trials has previously been reported, and no clinically meaningful differences in safety results were seen between the nirsevimab and placebo groups.

These trial results form the basis of regulatory submissions that began in early 2022.

Mene Pangalos, EVP BioPharmaceuticals R&D, AstraZeneca, said in a press release issued on May 11, 2022, “These analyses add to nirsevimab’s compelling body of evidence as to the first potential single-dose preventative immunization for all infants against RSV, addressing a clear unmet need in the RSV preventative landscape.”

Nirsevimab has not been approved by any regulatory authority, nor has the U.S. FDA approved any RSV vaccine candidate.

The data are presented at the 40th Annual Meeting of the European Society for Paediatric Infectious Diseases in Greece.

RSV-related direct medical costs – including hospital, outpatient, and follow-up care – were estimated at €4.82 billion worldwide in 2017.

Additional RSV development news is posted at

Note: The AZ press release was manually curated and edited for mobile readers.

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