Beyfortus

The approval was based on data from the nirsevimab clinical development program, which included a phase 2b trial (ClinicalTrials.gov Identifier: NCT02878330), the phase 3 MELODY trial (ClinicalTrials.gov Identifier: NCT03979313), and the phase 2/3 MEDLEY trial (ClinicalTrials.gov Identifier: NCT03959488).

In the phase 2b trial, infants who were born during or entering their first RSV season were randomly assigned to receive a single dose of Beyfortus (n=969) or placebo (n=484). Findings showed that treatment with Beyfortus significantly reduced the incidence of medically-attended lower respiratory tract disease caused by RSV by 70.1% (95% CI, 52.3-81.2; P <.001) compared with placebo. There were 25 cases reported in the Beyfortus group and 46 cases reported in the placebo group.

The MELODY trial compared a single intramuscular (IM) injection of nirsevimab to placebo in 1490 healthy infants who were born at a gestational age of at least 35 weeks. Patients were randomly assigned 2:1 to receive a single intramuscular injection of nirsevimab 50mg (for infants weighing less than 5kg) or 100mg (for infants weighing at least 5kg), or placebo before the start of an RSV season. The primary endpoint was the incidence of medically-attended RSV-associated lower respiratory tract infection (LRTI) through 150 days after the injection.

Findings from MELODY showed that treatment with nirsevimab was associated with a 74.9% (95% CI, 50.6-87.3; P <.001) reduction in the incidence of medically-attended RSV-associated LRTI compared with placebo (1.2% vs 5.0%, respectively). Additionally, a lower incidence of hospitalization for RSV-associated LRTI was observed in the nirsevimab arm compared with the placebo arm (relative risk reduction: 60.2% [95% CI, -14.6, 86.2]; P =.09).

In the randomized, double-blind MEDLEY trial, the safety and tolerability of nirsevimab was compared with palivizumab in approximately 925 infants with congenital heart disease, chronic lung disease, and/or prematurity before entering their first RSV season. Findings showed that nirsevimab demonstrated a similar safety and tolerability profile compared with palivizumab.