U.S. drug regulators have shifted language on two monoclonal antibody medicines because of emerging subvariants of the Omicron virus variant. The Food and Drug Administration (FDA) in recent days stipulated that an antibody treatment from GlaxoSmithKline and Vir Biotechnology cannot be used in regions where COVID-19 cases are likely to be caused by a variant “non-susceptible” to the drug. “Sotrovimab is not authorized for treatment of mild to moderate COVID-19 in geographic regions where infection is likely to have been caused by a non-susceptible SARS-CoV-2 variant, based on available information including variant susceptibility to this drug and regional variant frequency,” the FDA said in an updated emergency use authorization letter (pdf) to a GlaxoSmithKline executive. At this time, sotrovimab, the treatment, is still authorized in every U.S. region “until further notice,” the agency says. Several preprint studies published in February indicate that sotrovimab performs worse against BA.2, a subvariant of Omicron. Both …