WASHINGTON — GlaxoSmithKline says its COVID-19 antibody drug appears to be effective against the omicron variant based on initial laboratory testing.

The British drugmaker said it hopes to complete testing by year’s end to confirm whether the drug is effective against all the various mutations seen with the variant.

The announcement on Thursday is one of the first indications that at least some of the current COVID-19 treatments will retain their potency against the emerging strain.

On Tuesday, drugmaker Regeneron cautioned that its antibody cocktail appeared to lose effectiveness against omicron.

Antibody treatments remain one of a handful of therapies that can blunt the worst effects of COVID-19, and they are the only option available to people with mild-to-moderate cases who aren’t yet in the hospital.

The drugs are laboratory-made versions of virus-fighting antibodies that the immune system uses to defend against infections.

The U.S. government has purchased millions of doses of the antibody therapies made by Regeneron, Eli Lilly and GlaxoSmithKline and distributed them to states across the country.

GlaxoSmithKline’s antibody drug is also authorized in the U.K., Canada, Australia and Japan.