Regeneron reported that a dose of the antibody cocktail it makes reduced the risk of COVID-19 infection by 81.6% for two to eight months after administration of the drug in a final trial.
The results show that antibody therapy, RECEN-COV, has the potential to provide long-term immunity to COVID-19 infection, said Myron Cohen, who is leading efforts for monoclonal antibodies in the COVID-19 Prevention Network for National US Institutes of Health.
The immunity is especially important for immunocompromised people and people who do not respond to vaccines, the company said.
Treatment has previously shown an 81.4% reduction in risk during the first month after administration.
During the eight-month evaluation period, there were no hospitalizations for COVID-19 in the REGEN-COV team, but in the placebo group, six such cases were reported, Regeneron said.
The U.S. health regulator extended REGEN-COV's license in July to allow it to be used as a preventative treatment for people exposed to infected people and those at high risk of exposure in places such as nursing homes or prisons.
The drug was licensed in the United States last November to treat people with mild to moderate COVID-19 disease.