U.S. regulators cleared a new Eli Lilly & Co. monoclonal antibody for patients at high risk of mild to moderate COVID-19, after a similar therapy developed by the company turned out to be ineffective against the omicron variant.

The Food and Drug Administration today granted an emergency authorization for use of bebtelovimab in patients 12 and older with confirmed COVID-19 who are at high risk of progressing to severe disease, and for whom other treatment options aren’t accessible or clinically appropriate. The drug is given as an intravenous injection of 175 micrograms over at least 30 seconds.

The therapy will add to the small but growing arsenal of treatments available to doctors as the omicron wave continues to cause elevated infection levels across the country. On Thursday, the U.S. government struck a $720 million deal with Lilly for 600,000 doses of bebtelovimab.

Lilly shares were down 1.4% in New York at 3:21 p.m. on Friday, amid a decline in the wider U.S. stock market.

Daniel Skovronsky, Lilly’s chief scientific and medical officer, said in a statement that the company first started working on developing bebtelovimab to fight highly mutated variants in early 2021. Lilly licensed and developed bebtelovimab after it was discovered by AbCellera Biologics Inc., a Canadian-based antibody-drug discovery company, and scientists at the National Institute of Allergy and Infectious Diseases Vaccine Research Center.

An older Eli Lilly antibody cocktail was pulled from U.S. treatment programs after it proved ineffective against the omicron strain, which accounts for almost all U.S. cases of the disease.

Lilly said the data supporting the authorization was based on subanalyses of clinical trial data that looked at bebtelovimab alone or in combination with Lilly’s antibody cocktail, bamlanivimab and etesevimab. Separate lab tests also demonstrated that bebtelovimab neutralizes omicron and the BA.2 subvariant that is also spreading in some countries.

Possible side effects of bebtelovimab include itching, rash, infusion-related reactions, nausea and vomiting, according to the FDA.

Though the agency cleared the drug for use in all geographic regions, that designation can be pulled in places if a variant crops up that evades its protection, the agency said in a letter to Lilly.

The Department of Health and Human Services said Thursday that it plans to make the drug available to states free of charge, with 300,000 treatment courses available in February, followed by another 300,000 in March. The U.S. has an option to purchase another 500,000 doses through the end of July.