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Regeneron warns its antibody drug may be less potent versus omicron

Regeneron’s drug is the top-selling COVID-19 treatment in the U.S., one of three antibody drugs currently authorized by the Food and Drug Administration for people who are infected by SARS-CoV-2 and at high risk of severe disease.

The antibody drugs, which include similar medicines from Eli Lilly and Vir Biotechnology, have each proven effective in clinical trials, keeping COVID-19 patients out of the hospital or from dying.

Despite the emergence of virus variants last year and earlier in 2021, Regeneron’s drug has largely held up. It consists of two antibodies that lock onto the coronavirus in two different places, a design meant to reduce the chances of the virus escaping. Laboratory tests showed REGEN-COV retained potency against variants like alpha, beta and, most recently, delta.

(One drug from Lilly, by comparison, was pulled from the market, while that company’s second has been challenged more seriously by the variants.)

Omicron, though, may be a different story because of the high number of mutations the variant has to its spike protein, the target for Regeneron’s drugs as well as Lilly’s. Those evolutionary changes have already alarmed vaccine makers, some of which have readied plans for shots tailored to the variant. Now antibody drug makers, too, are on alert.

Much is unknown about omicron, however. It’s still unclear, for instance, whether omicron’s mutations actually evade vaccines or synthetic antibodies, whether the variant causes more or less severe disease or whether it can spread faster than the delta variant that has become dominant around the world. A previous variant known as beta, which had mutations that made it more immune resistant, didn’t transmit as widely.

As with vaccine makers, Regeneron cautioned that lab tests now underway will “confirm and quantify” how omicron impacts its drug. The company has other antibodies targeting SARS-CoV-2, one of which has begun clinical testing and others that are “nearing clinic readiness,” the company said. Several may retain their potency against omicron, according to Regeneron.

Reduced efficacy against Omicron could leave an opening for other antibody drug developers, too. Adagio Therapeutics, for example, claims its drug can neutralize a variety of variants because it aims at a different viral target. Shares of Adagio nearly doubled on Monday and its treatment is in late-stage testing. AstraZeneca also has an antibody that’s designed to be long-acting and proven effective in clinical testing.

Meanwhile, a Fred Hutchinson Cancer Research Institute study indicated Vir’s drug should remain potent against omicron, according to a report from The Wall Street Journal.

Vir shares have climbed about 26% in the past two days. Regeneron’s, by comparison, fell by 2% at Tuesday’s stock market open.

Antiviral pills developed by Merck & Co. and Pfizer may also come to play a greater role, as their convenience could help them be used more widely than infused antibody drugs like Regeneron’s. A panel of FDA advisers is meeting Tuesday to discuss Merck’s drug.