Transforming Pediatric Health: Sanofi's Nirsevimab in the Fight Against RSV

May 11, 2022
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New nirsevimab data analyses reinforce efficacy against RSV

  • A prespecified pooled analysis of Phase 3 and Phase 2b data demonstrated an efficacy of 79.5% against medically attended lower respiratory tract infections (LRTI), including hospitalizations, caused by respiratory syncytial virus (RSV)1
  • Nirsevimab is the first investigational immunization designed to protect all infants across the RSV season with a single dose
  • Two analyses are being presented at the European Society for Paediatric Infectious Diseases meeting1,2

Paris, May 11, 2022. Results from a prespecified pooled analysis of the pivotal Phase 3 MELODY and Phase 2b nirsevimab trials demonstrated an efficacy (relative risk reduction versus placebo) of 79.5% (95% CI 65.9 to 87.7; P<0.0001) against medically attended LRTI, such as bronchiolitis or pneumonia, caused by RSV in infants born at term or preterm entering their first RSV season.1

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 post-dose. RSV neutralizing antibody levels remained greater than 19-fold higher than placebo recipients with no known RSV infection through Day 361, suggesting protection may extend beyond Day 151.2

The safety profile across the nirsevimab and placebo groups, as reported in previous trials, remains similar.3-6 These findings contribute to the growing body of evidence suggesting that nirsevimab can protect all infants through their first RSV season with a single dose.1-7

Eric Simões, MD
Clinical Professor, Pediatrics-Infectious Diseases, UC Denver School of Medicine
“RSV remains the most common cause of LRTI in infants and results in seasonal epidemics globally each year. These new analyses strengthen nirsevimab’s potential to protect all infants across the RSV season with a single dose, which may lead to a paradigm shift in RSV prevention.”

Jean-François Toussaint
Global Head of Research and Development Vaccines, Sanofi
These new analyses are very consistent with and confirm the strong results observed in all Phase 2 and Phase 3 studies that evaluated nirsevimab in diverse pediatric populations. We take pride in the progress made to develop a potential solution to address this long unmet need for all infants.”

Mene Pangalos
Executive Vice President, BioPharmaceuticals R&D, AstraZeneca
Each year, RSV causes seasonal epidemics of LRTIs in infants. These analyses add to nirsevimab’s compelling body of evidence as the first potential single-dose preventative immunization for all infants against RSV, addressing a clear unmet need in the RSV preventative landscape.”

The data are being presented at the 40th Annual Meeting of the European Society for Paediatric Infectious Diseases (ESPID) from May 9-13 in Athens, Greece.

Nirsevimab is being developed by Sanofi and AstraZeneca.

About nirsevimab

Nirsevimab is an investigational long-acting antibody designed to protect all infants from birth entering their first RSV season with a single dose. Due to its extended half-life technology, nirsevimab is being developed as a single dose for protection of all infants through their first RSV season.5,6,8

Nirsevimab is an immunization designed to provide direct RSV protection to all infants via an antibody to help prevent LRTI caused by RSV. Monoclonal antibodies do not require the activation of the immune system to help offer rapid and direct protection against disease.9

In March 2017, Sanofi and AstraZeneca announced an agreement to develop and commercialize nirsevimab. Under the terms of the agreement, AstraZeneca leads all development and manufacturing activities and Sanofi will lead commercialization activities and record revenues. Under the terms of the global agreement, Sanofi made an upfront payment of €120m, has paid a development milestone of €30m and will pay up to a further €465m upon achievement of certain development and sales-related milestones. The two companies share all costs and profits. Revenue from the agreement is reported as Collaboration Revenue in the Company’s financial statements.

Nirsevimab has been granted regulatory designations to facilitate expedited development by several 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; access granted to the European Medicines Agency (EMA) PRIority MEdicines scheme; Promising Innovative Medicine designation by the UK Medicines and Healthcare products Regulatory Agency; and named “a medicine for prioritized development” under the Project for Drug Selection to Promote New Drug Development in Pediatrics by the Japan Agency for Medical Research and Development (AMED). The safety and efficacy of nirsevimab is currently being evaluated under an accelerated assessment procedure by the EMA. Nirsevimab has not been approved by any regulatory authority.

About the pivotal nirsevimab clinical trials

The Phase 2b trial was a randomized, placebo-controlled trial designed to measure the efficacy of nirsevimab against medically attended LRTI through 150 days post-dose. Healthy preterm infants of 29–35 weeks’ gestation were randomized (2:1) to receive a single 50mg intramuscular injection of nirsevimab or placebo. Between November 2016 and December 2017, 1,453 infants were randomized (nirsevimab, n=969; placebo, n=484) at the RSV season start. Research was conducted in both hemispheres, at 164 sites in 23 countries.6 Data was published in the New England Journal of Medicine (NEJM) in July 2020. The dosing regimen was optimized based on further exploration of this data. The subsquent Phase 3 study MELODY applied the optimized dosing regimen.1,5

The Phase 3 MELODY trial was a randomized, placebo-controlled trial conducted across 21 countries designed to determine efficacy of nirsevimab against medically attended LRTI due to RSV confirmed by reverse transcriptase polymerase chain reaction testing through 150 days after dosing, versus placebo, in healthy late preterm and term infants (35 weeks gestational age or greater) entering their first RSV season.5 Infants were randomized (2:1) to receive a single 50mg (in infants weighing <5kg) or 100mg (in infants weighing ≥5kg) intramuscular injection of nirsevimab or placebo. Between July 2019 and March 2020, 1,490 infants were randomized to either nirsevimab or placebo at the RSV season start.3 Data was published on the primary analysis in NEJM in March 2022.

The prespecified pooled analyses of the Phase 3 and the Phase 2b trials looked at infants receiving the optimized dosing regimen (infants <5 kg at dosing and receiving the 50 mg dose from Phase 2b and the infants from Phase 3), and demonstrated an efficacy of 79.5% (95% CI 65.9 to 87.7, P<0.0001) against medically attended LRTI and 77.3% (95% CI 50.3, 89.7, P<0.001) against RSV LRTI hospitalizations. The analysis was based on 2,350 infants of which 1,564 infants were randomized to receive nirsevimab and 786 infants were randomized to receive placebo.1

The results of MELODY, Phase 2/3 MEDLEY and the Phase 2b trials demonstrate that nirsevimab provides protection against RSV in all infants entering their first RSV season with a single dose.1-5 This all-infant population includes preterm, healthy late preterm and term infants, as well as infants with specific conditions.

These trials form the basis of regulatory submissions that began in 2022.

About RSV

RSV is the most common cause of lower respiratory tract infections (LRTI), including bronchiolitis and pneumonia in infants.10 It is also a leading cause of hospitalization in all infants, with most hospitalizations for RSV occurring in healthy infants born at term.11-14 Globally, in 2015, there were approximately 30 million cases of acute lower respiratory infections leading to more than three million hospitalizations, and it was estimated that there were 60,000 in-hospital deaths of children younger than five years.15,16 In recent months, there has been a resurgence of RSV following the easing of COVID-19 public health measures.17,18 Globally, in 2017, RSV-related direct medical costs—including hospital, outpatient and follow-up care—were estimated at €4.82 billion.19

About Sanofi
We are an innovative global healthcare company, driven by one purpose: we chase the miracles of science to improve people’s lives. Our team, across some 100 countries, is dedicated to transforming the practice of medicine by working to turn the impossible into the possible. We provide potentially life-changing treatment options and life-saving vaccine protection to millions of people globally, while putting sustainability and social responsibility at the center of our ambitions.
Sanofi is listed on EURONEXT: SAN and NASDAQ: SNY

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