Worries About Supply of COVID-19 Monoclonal Antibody Treatment After FDA Recommends Doubling the Dose

Agency says evidence points to Evusheld being more effective against omicron variants if doses are doubled.

Some healthcare experts are concerned about the supply of COVID-19 monoclonal antibody Evusheld after the FDA revised its emergency use authorization (EUA) for the medication.

The agency doubled the dose for Evusheld (tixagevimab co-packaged with cilgavimab) because the current dose may be less active against certain omicron subvariants, the agency said in a statement.

Available data indicate that a higher dose of Evusheld may be more likely to prevent infection by the COVID-19 omicron subvariants BA.1 and BA.1.1 than the originally authorized Evusheld dose, the FDA said.

The previous authorized dosage was 150 mg of tixagevimab and 150 mg of cilgavimab administered as two separate consecutive intramuscular injections, with doses every six months while SARS-CoV-2 remains in circulation. FDA increased the initial authorized dose to 300 mg of tixagevimab and 300 mg of cilgavimab.

“Patients who have already received the previously authorized dose (150 mg of tixagevimab and 150 mg of cilgavimab) should receive an additional dose of 150 mg of tixagevimab and 150 mg of cilgavimab as soon as possible to raise their monoclonal antibody levels to those expected for patients receiving the higher dose,” the agency said.

However, there is already inadequate access to Evusheld for immunocompromised individuals, Dorry Segev, M.D., Ph.D., a professor of surgery at Johns Hopkins Medicine, told CNN.

The CDC estimates about 2.7% of the adult population in the U.S. is immunocompromised.

The U.S. government has shipped nearly 600,000 courses of Evusheld, an AstraZenecia product, since December 13, according to the U.S. Department of Health and Human Services, CNN reported. In January, the government announced the purchase of an additional 500,000 doses of Evusheld.

"There already is inadequate access to this product for those who need it, and that will become more challenging now," Segev said. "Of the remaining doses, you have to basically cut them in half in terms of availability to actual people."

Katherine Lontok, director of science and policy communications at the Immune Deficiency Foundation, praised the FDA’s decision, but she told CNN that “doubling the dose will make the treatment even more scarce.”

“We continue to hear that patients with primary immunodeficiency are having trouble accessing the treatment, even with the additional 1 million doses the federal government has purchased and an accelerated distribution schedule to states,” Lontok told CNN.

The duration of protection provided by Evusheld against symptomatic SARS-CoV-2 infection may not be as long as was shown in the clinical trial supporting the initial authorization because the clinical trial data came from a time period before the emergence of the BA.1 and BA.1.1 subvariants, FDA explained.

“However, it is not known whether BA.1 and BA1.1 will still be circulating in the coming months or whether another omicron subvariant, BA.2, for which Evusheld is expected to have greater neutralizing activity, will become dominant,” the FDA said. "Because it is unclear which SARS-CoV-2 variant or omicron subvariant will become dominant in the US over the next few months, the recommended timing for repeat dosing cannot be provided at this time.”

“We will continue to monitor the situation closely and will provide updates with redosing recommendations in the near future when more data are available to determine the appropriate timing of redosing,” the agency added.