WASHINGTON — The Food and Drug Administration on Monday took two monoclonal antibody therapies off the list of COVID-19 treatments for now, saying the medications should not be used anywhere in the United States because they are ineffective against the dominant omicron variant.

As a result, the Department of Health and Human Services, which distributes COVID treatments to states, notified state health officials that it has halted distribution of the antibody medications made by Regeneron Pharmaceuticals and Eli Lilly, according to an email sent to the states and obtained by The Washington Post.

Patrizia Cavazzoni, director of the FDA’s Center for Drug Evaluation and Research, said in a statement that data show the two antibody treatments “are highly unlikely to be active against the omicron variant, which is circulating at a very high frequency throughout the United States.” Omicron is responsible for more than 99% of cases in the United States, according to the Centers for Disease Control and Prevention.

The FDA official said it is “highly unlikely that COVID-19 patients seeking care in the U.S. at this time are infected with a variant other than omicron, and these treatments are not authorized to be used at this time.” Cavazzoni added the antibodies could be used again if a future variant emerges that is susceptible to the therapies.

Administration officials hope that ending federal distribution of the two monoclonal antibody treatments to the states will prevent COVID-19 patients from being given drugs that do not work against omicron. Senior officials last week called health officials in several states to urge them to stop using the Regeneron and Lilly drugs and pointed them to alternatives.

Several treatments remain effective against omicron, including sotrovimab – made by GlaxoSmithKline and Vir Biotechnology – and antiviral pills by Pfizer and by Merck and its partner, Ridgeback Biotherapeutics. In addition, the use of the antiviral drug remdesivir as an outpatient therapy recently got the green light from regulators.

However, several doctors and hospitals have complained that some of the COVID treatments, including the Pfizer pill and sotrovimab, are in short supply.

On Monday, Maine Gov. Janet Mills announced that the federal government will nearly double the state’s ration of sotrovimab.

Monoclonal antibodies are manufactured proteins that can enhance or mimic the immune system’s ability to fight viruses and other pathogens. But the highly mutated omicron variant has thwarted the ability of the Regeneron and Lilly therapies to work against the virus, the FDA noted.

The action on the monoclonal antibodies followed a move by Florida Republican Gov. Ron DeSantis to set up new sites in his state that administer the treatments. DeSantis has said he is not convinced the therapies are ineffective against omicron and noted they work on cases caused by delta, the variant that previously was dominant.

DeSantis is a foe of vaccine mandates and has implied erroneously that the shots might hurt fertility.

In an email last week, DeSantis’s spokeswoman, Christina Pushaw, said a small percentage of cases in Florida are still caused by delta. She also said lab tests showing the loss of effectiveness by Regeneron and Lilly against the omicron variant are “not conclusive.”

A Biden administration official Monday who spoke on the condition of anonymity to describe internal discussions expressed frustration that some governors are still promoting ineffective medications.

“Frankly, at this stage, it’s dangerous that they would do that,” the official said. “It’s beyond irresponsible to use these products that aren’t without their own risks when we know they offer basically zero benefit.”

Last week, a treatment-guidelines committee at the National Institutes of Health discouraged use of the Regeneron and Lilly antibody drugs, saying they are “predicted to have markedly reduced activities” against omicron.