Nirsevimab Reduced Respiratory Syncytial Virus Infections Requiring Medical Care in Healthy Premature Infants in Phase 2b Trial

READING, England–(BUSINESS WIRE)– Detailed results from the positive Phase 2b trial for nirsevimab showed a significant reduction in medically attended lower respiratory tract infections (LRTI) and hospitalisations caused by respiratory syncytial virus (RSV) in healthy preterm infants. Published in the New England Journal of Medicine, results from this trial demonstrate for the first time that a single dose monoclonal antibody can significantly reduce medically attended RSV LRTI in infants through the average temperate region RSV season (November-March).1

“The data for nirsevimab are exciting, as they highlight the potential for this innovative approach to protect infants from RSV with just one injection for the entire season,” said Dr. Joseph Domachowske, study author, Professor of Pediatrics, Professor of Microbiology and Immunology, and Director of the Global Maternal-Child and Pediatric Health Program at the SUNY Upstate Medical University. “Nirsevimab offers the important potential to reduce hospitalisations and emergency department and in-office visits, which are a significant burden for healthcare systems.”

Nirsevimab is an extended half-life RSV monoclonal antibody (mAb), being developed in partnership with AstraZeneca as a passive immunisation, meaning a protective antibody is administered directly to an infant to help prevent RSV.

Phase 2b trial met primary and secondary endpoints
On the primary endpoint, nirsevimab achieved a statistically significant 70.1% (95% CI: 52.3%-81.2%) reduction of medically attended RSV LRTI compared to placebo through 150 days post-dose. On the secondary endpoint, nirsevimab achieved a 78.4% (95% CI: 51.9%-90.3%) relative reduction in the incidence of hospitalisations due to RSV LRTI compared to placebo through 150 days post-dose. Nirsevimab was found to be tolerable based on types and frequencies of treatment emergent adverse events.1

“It’s encouraging to see from these data that serious complications from RSV can be reduced in healthy preterm infants” said John Shiver, Senior Vice President, Global Research and Development, Sanofi Pasteur. “Most babies who are hospitalised from RSV are otherwise healthy with no prior complications,2 but currently these infants have no approved preventative option to protect them.”

About RSV
RSV is a common, contagious, seasonal virus that infects the respiratory tract.2 RSV infection can cause a range of symptoms, from mild cold-like symptoms through to severe breathing difficulty.2 It is a leading cause of bronchiolitis and pneumonia in infants and young children resulting in approximately 30,000 hospital admissions of children under 5 in the UK every year, of which 6% result in admission to intensive care.2 Most of these admissions are in otherwise healthy babies.2 By the age of 2, almost all infants will have been exposed to RSV.3

Nirsevimab Clinical Trials
The Phase 2b study was conducted by AstraZeneca at 164 sites in 23 countries.1 Healthy preterm infants of 29–35 weeks’ gestation were randomised (2:1) to receive a single intramuscular injection of nirsevimab or placebo. Between November 2016 and December 2017, 1447 infants were dosed (nirsevimab, n=966; placebo, n=481) at the RSV season start.1

In July 2019, Sanofi and AstraZeneca initiated pivotal Phase 3 and Phase 2/3 trials to measure the safety and efficacy of nirsevimab to prevent LRTI caused by RSV in full-term, healthy late preterm and high-risk babies.4,5 The trials will be conducted in more than 350 sites across Northern and Southern Hemispheres.

The full results of the Phase 3 and Phase 2/3 trials are anticipated in 2023.

About Nirsevimab
Nirsevimab is a passive immunisation. Passive immunisations involve delivering an antibody directly as opposed to active immunisations, which induce an antibody response from the immune system. Passive immunisation can offer immediate protection.6 Nirsevimab is not yet licenced.

In March 2017, AstraZeneca and Sanofi Pasteur announced an agreement to develop and commercialise nirsevimab jointly. Under the terms of the agreement, AstraZeneca leads all development activity through initial approvals and retains manufacturing activities and Sanofi Pasteur will lead commercialisation activities. In February 2019, AstraZeneca and Sanofi Pasteur’s nirsevimab received Breakthrough Therapy Designation from the US Food and Drug Administration and was granted access to the PRIority MEdicines (PRIME) scheme by the European Medicines Agency.

About Sanofi
Sanofi is dedicated to supporting people through their health challenges. We are a global biopharmaceutical company focused on human health. We prevent illness with vaccines, provide innovative treatments to fight pain and ease suffering. We stand by the few who suffer from rare diseases and the millions with long-term chronic conditions.

With more than 100,000 people in 100 countries, Sanofi is transforming scientific innovation into healthcare solutions around the globe.

Sanofi, Empowering Life

Sanofi Forward-Looking Statements
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1 Griffin MP, MD et al. (2019). Single Dose Nirsevimab for Prevention of RSV Disease in Preterm Infants. New England Journal of Medicine. Manuscript submitted for publication.

2 Vaccine Knowledge Project. Respiratory Syncytial Virus (RSV). Accessed July 2020

3 NHS. Bronchiolitis. Accessed July 2020

4 A Study to Evaluate the Safety and Efficacy of MEDI8897 for the Prevention of Medically Attended RSV LRTI in Healthy Late Preterm and Term Infants (MELODY). Accessed November 2019.

5 A Study to Evaluate the Safety of MEDI8897 for the Prevention of Medically Attended Respiratory Syncytial Virus (RSV) Lower Respiratory Track Infection (LRTI) in High-risk Children. Accessed July 2020.

6 “Vaccines & Immunizations.” Centers for Disease Control and Prevention. August 18, 2017. Accessed July 2020

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