A panel of independent advisers to the Food and Drug Administration unanimously recommended on Thursday that the antibody nirsevimab be approved for use to protect infants from respiratory syncytial virusleading cause of hospitalization in newborns.

If the FDA approves nirsevimab, the antibody would become the first medical intervention available in the U.S. that can protect all infants from RSV. The FDA, which is not bound to follow its advisory panel’s recommendation, is expected to make a final decision on nirsevimab in the third quarter.

Nirsevimab is a monoclonal antibody manufactured by the company AstraZeneca. The drug would be marketed Sanofi.

The advisory panel voted 21-0 to recommend its approval.

In a separate vote, the advisers also recommended the use of nirsevimab in children under 2 years of age who remain vulnerable to the virus in their second RSV season. The vote was 19-2.

RSV kills nearly 100 children in the United States each year, according to researchers.

Infants hospitalized with RSV often require oxygen support, intravenous fluids, and are sometimes placed on a ventilator to support their breathing.

The virus is a major threat to public health. A surge in RSV infections last year overwhelmed children’s hospitals, leading to calls for the Biden administration to declare public health emergency in response.

RSV is circulating at the same time as influenza and Covid-19, putting additional pressure on hospitals.

A second monoclonal antibody called palivizumab is used against RSV. However, this antibody is only intended for premature babies and people with lung and congenital heart disease who are at high risk of serious disease. Palivizumab must also be administered monthly.

Nirsevimab, on the other hand, would also be administered to healthy infants, who make up the majority of hospitalizations. It is also given in a single serving which would make it easier to administer.

Nirsevimab is not considered a vaccine because it is a monoclonal antibody.

It is unclear whether the federal Vaccines for Children program will provide nirsevimab for free to uninsured and underinsured children because the antibody is regulated as a drug.

Nirsevimab is already approved in Canada, Europe and the United Kingdom.

Nimish Patel, an infectious disease drug expert, said nirsevimab worked “extraordinarily well” in both premature and premature babies.

“The single-season dosing is a huge advance, and it’s probably the closest thing to an RSV vaccine that we have, and it really moves the field forward,” said Patel, an FDA committee member and professor of clinical pharmacy at the university. from California, San Diego.


According to FDA evaluations, nirsevimab was up to 75% effective in preventing lower respiratory tract infections that required medical attention and 78% effective in preventing hospitalizations.

A more conservative FDA estimate put the antibody at about 48% effective against lower respiratory tract infections that required medical attention. This estimate assumed that patients with missing data on their health outcomes had lower respiratory tract infections that required medical attention.

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Nirsevimab is given as a single injection, with the dose depending on the child’s weight. Infants weighing less than 5 kilograms would receive a 50 mg injection for their first RSV season, and those weighing 5 kilograms or more would receive a 100 mg injection.

Children younger than 2 years who remain at risk of severe RSV in their second season would receive a single 200 mg injection of nirsevimab.


The FDA found no safety concerns in its review of nirsevimab.

Other monoclonal antibodies have been associated with severe allergic reactions, skin rashes, and other hypersensitivity reactions.

The FDA found no cases of serious allergic reactions in studies with nirsevimab, and cases of skin rash and hypersensitivity reactions were low in infants who received the antibody. But Dr. Melissa Baylor, an FDA official, said cases of these side effects are likely to occur if nirsevimab is approved.

Twelve infants who received nirsevimab in the studies died. None of those deaths were related to the antibody, according to an FDA review.

Four died of heart disease, two died of gastroenteritis, two died of unknown causes but were probably SIDS cases, one died of tumor, one of Covid, one of skull fracture and one of pneumonia.

“Most of the deaths were due to the underlying disease,” Baylor said. “None of the deaths appeared to be related to nirsevimab.”

Much attention has been paid to safety due to historical failures in the development of RSV vaccines. Scientists first tried to develop a vaccine in the 1960s with an inactivated virus, but the injection actually made RSV disease worse in some children when they got their first natural infection, resulting in the deaths of two infants.

Manish Shroff, head of patient safety at AstraZeneca, said the company would closely monitor the safety of nirsevimab through a large global monitoring system: “Safety is of the utmost importance,” he said.

Baylor said there are also unanswered questions about how nirsevimab would interact with vaccines in development that confer protective antibodies on the fetus by injecting the mother.

It is unclear whether giving nirsevimab to children whose mothers received such RSV vaccines would provide additional protection or create potential safety issues, Baylor said.

In May, FDA advisers approved Pfizer’s maternal RSV vaccine to protect infants. The agency is expected to rule on Pfizer’s shot in August.

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