AstraZeneca, Sanofi post RSV data ahead of 2022 approval filings

AstraZeneca and Sanofi’s respiratory syncytial virus (RSV) drug candidate nirsevimab has performed similarly to the incumbent product Synagis in a phase 2/3 assessment of safety and tolerability.

Investigators randomized 925 preterm and high-risk infants entering their first RSV season to receive either the investigational long-acting antibody nirsevimab or Synagis. The population included infants with chronic lung disease and congenital heart disease. AstraZeneca picked occurrence of treatment emergent adverse events (TEAEs) in the 360 days after dosing as the primary endpoint.

The rates of TEAEs, including serious adverse events, were similar between the two arms, according to AstraZeneca. For now, AstraZeneca is yet to share numbers to back up its statement. Publication of the full results is planned for a forthcoming medical meeting.

AstraZeneca’s update comes two months after the release of top-line results from a phase 3 trial of nirsevimab. The study linked the antibody to a statistically significant reduction in the incidence of medically attended lower respiratory tract infections caused by RSV compared to placebo in healthy late preterm and term infants during their first RSV season.

Armed with data from the two studies, AstraZeneca plans to file for approval in the first half of next year. Sanofi is set to handle commercialization of the drug under the terms of a 2017 deal that saw the French pharma company pay AstraZeneca €120 million ($143 million) upfront for an even split of the profits. AstraZeneca is in line to receive up to €495 million in milestones. 

If approved, nirsevimab will end the long pursuit of a successor for Synagis. MedImmune won FDA approval for Synagis in 1998. Having been bought by AstraZeneca for $15.6 billion, MedImmune tried twice to win approval of motavizumab. AstraZeneca dumped the drug in 2010 after the second FDA complete response letter (CRL).

The FDA issued the second CRL after its advisory committee voted against approval amid questions about whether motavizumab worked better than Synagis. The doubts, coupled to tolerability issues, scuttled the effort to bring motavizumab to market.

AstraZeneca is yet to share phase 2/3 data showing how nirsevimab compares to Synagis but the investigational candidate already has one clear advantage over the incumbent. While Synagis is given once a month during the five-month RSV season, a single dose of nirsevimab may provide protection throughout the period. 

Nirsevimab could face competition from alternative ways of providing lasting protection against RSV.  GlaxoSmithKline began a phase 3 clinical trial of a vaccine against RSV late last year. The study is assessing the effect of giving the vaccine to pregnant women to protect their infants from RSV.