Vaccine Info

Nirsevimab RSV Monoclonal Antibody

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Last reviewed
June 24, 2022
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Nirsevimab RSV Monoclonal Antibody Description For 2022

Nirsevimab (MEDI8897) single-dose is being developed in partnership between AstraZeneca and Sanofi. The first investigational extended half-life monoclonal antibody (mAb) was developed as a passive immunization to prevent lower respiratory tract infections (LRTI) caused by RSV. It is designed to protect infants experiencing their first RSV season and infants with congenital heart disease or chronic lung disease entering their first and second RSV season.

Nirsevimab is an immunization designed to provide direct prophylactic 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 protection against disease. The results of MEDLEY, MELODY and the Phase 2b clinical trials demonstrate that nirsevimab protects against RSV in all infants with a single dose.

Nirsevimab is currently under clinical investigation. In addition, Nirsevimab has been granted regulatory designations to facilitate expedited development by several regulatory agencies, including Breakthrough Therapy Designation by The China Center for Drug Evaluation under the National Medical Products Administration; Breakthrough Therapy Designation from the U.S. Food and Drug Administration; access granted to the European Medicines Agency PRIority MEdicines scheme; Promising Innovative Medicine designation by the U.K. 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.

The NEJM published an Original Article, based on a phase 3 study, on March 3, 2022, that concluded a single injection of nirsevimab administered before the RSV season protected healthy late-preterm and term infants from medically attended RSV-associated lower respiratory tract infection.

On May 11, 2022, the companies announced the prespecified pooled analysis from Phase III and Phase IIb trials demonstrated the efficacy of 79.5% against medically attended lower respiratory tract infections, including hospitalizations, caused by RSV.

The U.S. CDC's ACIP meeting on June 23, 2022, reviewed - Nirsevimab For The Prevention of RSV Disease In All Infants.

In March 2017, Sanofi and AstraZeneca announced an agreement to develop and commercialize nirsevimab and share all costs and profits. Sanofi is listed on EURONEXT: SAN and NASDAQ: SNY. AstraZeneca (LSE/STO/Nasdaq: AZN) is a global, science-led biopharmaceutical company.

Nirsevimab Indication

Nirsevimab is designed to be administered from birth to infants born during the RSV season or at the season's start for infants entering their first RSV season. RSV is a common, contagious virus that causes seasonal epidemics of LRTI, leading to bronchiolitis and pneumonia in infants. It is also a leading cause of hospitalizations in all infants.

Nirsevimab Dosage

Nirsevimab is in phase 3 clinical trials to determine the proper dosage. Monoclonal antibodies do not require the activation of the immune system to help offer rapid and direct protection against disease.

Nirsevimab News For 2017 - 2022

May 11, 2022 - AstraZeneca announced results from a prespecified pooled analysis of the pivotal MELODY Phase III and Phase IIb trials showed AstraZeneca and Sanofi's nirsevimab demonstrated an efficacy (relative risk reduction versus placebo) of 79.5% (95% Confidence Interval [CI] 65.9 to 87.7; P<0.0001) against medically attended lower respiratory tract infections (LRTI), such as bronchiolitis or pneumonia, caused by RSV in infants born at term or preterm entering their first RSV season. The pooled analysis studied healthy preterm and term infants who received the optimized dose of nirsevimab compared to placebo through Day 151 and showed an efficacy of 77.3% (95% CI 50.3, 89.7; P<0.001) against RSV LRTI hospitalizations. 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 postdose. 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.

March 3, 2022 - Sanofi announced the New England Journal of Medicine published detailed results from a Phase 3 trial evaluating nirsevimab involving healthy infants born at term or late preterm (35 weeks gestational age or greater) entering their first RSV season and met the primary endpoint, reducing the incidence of medically attended lower respiratory tract infections, such as bronchiolitis or pneumonia, caused by RSV by 74.5% (95% CI 49.6 to 87.1; P<0.001) compared to placebo.

February 17, 2022 - AstraZeneca's Marketing Authorisation Application for nirsevimab has been accepted under an accelerated assessment procedure by the European Medicines Agency to prevent medically attended lower respiratory tract infections in all infants through their first RSV season. 

August 11, 2021 - A peer-reviewed study concluded: Based on the mechanism of action of the new generation of anti-viral mAbs, such as nirsevimab, which is highly specific in targeting viral antigenic sites, it is unlikely that it could interfere with the immune response to other vaccines. Taken together, we anticipate that nirsevimab could be concomitantly administered to infants with routine pediatric vaccines during the same clinic visit.

June 28, 2021 - Sanofi announced Nirsevimab shows positive topline results in RSV Phase 2/3 MEDLEY trial.

July 30, 2020 - Sanofi published detailed results from the Phase 2b trial for nirsevimab showing a significant reduction in medically attended lower respiratory tract infections (LRTI), mainly bronchiolitis and pneumonia, and hospitalizations caused by the respiratory syncytial virus (RSV) in healthy preterm infants.

February 5, 2019 - AstraZeneca and its global biologics research and development arm, MedImmune, announced that the U.S. FDA granted Breakthrough Therapy Designation for MEDI8897.

March 3, 2017 - Sanofi Pasteur announced today an agreement with MedImmune, the global biologics research and development arm of AstraZeneca, to develop and commercialize a monoclonal antibody--called MEDI8897--for the prevention of RSV-associated illness in newborns and infants. 

Nirsevimab Clinical Trials

Nirsevimab has been tested in several clinical trials.

A Phase 3 trial is currently recruiting to evaluate the Safety and Efficacy of Nirsevimab in Healthy Preterm and Term Infants in China. (CHIMES) Eight hundred infants are anticipated to participate in this randomized, double-blind, placebo-controlled, single-dose study to determine if nirsevimab will prevent medically attended RSV-confirmed LRTI in healthy preterm and term infants entering their first RSV season. This study is anticipated to be completed at the end of 2025.