So-called monoclonal antibodies mimic those generated by the body to fight off the virus that causes COVID-19. Administration of antibody therapies bypasses the body’s slower and sometimes less effective process of making its own antibodies. At the time this study began, there were two dual-antibody combination therapies and a single antibody therapy authorized by the FDA for emergency use. The FDA withdrew authorization for the single antibody therapy, bamlanivimab, in April on the grounds that it was not effective against the variants circulating at that time. In May, the FDA authorized the single antibody sotrovimab as a treatment for COVID-19.