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New results from AstraZeneca’s MEDLEY trial

AstraZeneca research

The MEDLEY Phase II/III trial evaluated the safety and tolerability of nirsevimab compared to Synagis (palivizumab) when given to infants at high risk of respiratory syncytial virus (RSV) entering their first RSV season.

The trial assessed the safety of nirsevimab in infants with chronic lung disease (CLD), congenital heart disease (CHD) and/or prematurity. Occurrence of treatment emergent adverse events (TEAEs) or treatment emergent serious adverse events (TESAEs) were similar between groups.


Nirsevimab is a long-acting antibody, using AstraZeneca’s YTE technology, being developed by AstraZeneca and Sanofi with the potential to provide immunity directly to all infants and offer immediate protection against RSV through the entire season with a single dose.

“Respiratory syncytial virus is the leading cause of hospitalisations in infants. These results, combined with the recent positive efficacy outcome of our MELODY Phase III trial and our Phase IIb data, contribute to the body of evidence demonstrating nirsevimab’s potential to protect all infants against respiratory syncytial virus with one dose. We look forward to sharing the results with regulators,” says Mene Pangalos, Executive Vice President, BioPharmaceuticals R&D, AstraZeneca.

Full results from the MEDLEY trial will be presented at a forthcoming medical meeting. The trial is ongoing to collect additional safety data.

The MELODY trial

Nirsevimab is also being evaluated in the MELODY Phase III trial, which met its primary endpoint of a statistically significant reduction in the incidence of medically attended LRTI caused by RSV, compared to placebo, in healthy late preterm and term infants during their first RSV season. MEDLEY, MELODY and the Phase IIb trial will form the basis of AstraZeneca’s regulatory submissions planned from the first half of 2022.

Breakthrough designation

Nirsevimab has been granted breakthrough designation by three major regulatory agencies around the world. These include Breakthrough Therapy Designation by The China Center for Drug Evaluation under the National Medical Products Administration; Breakthrough Therapy Designation from the US Food and Drug Administration; and access granted to the European Medicines Agency PRIority MEdicines (PRIME) scheme.

Photo: AstraZeneca R&D