Shares of Regeneron Pharmaceuticals Inc. /zigman2/quotes/203149337/composite REGN -0.65% gained 3.7% in premarket trading on Monday after the company said four subcutaneous injections of its monoclonal antibody treatment protected unvaccinated people from contracting COVID-19 by 81.6% for up to eight months. Four infusions of the treatment are considered one dose. "These results demonstrate that REGEN-COV has the potential to provide long-lasting immunity from SARS-CoV-2 infection, a result particularly important to those who do not respond to COVID-19 vaccines including people who are immunocompromised," Dr. Myron Cohen, a physician in charge of the National Institutes of Health's work on monoclonal antibodies, said in a news release. Regeneron has already shared similar data in a study published in the New England Journal of Medicine but this is a new analysis of that data, which came from a trial assessing giving the treatment to one household member if another was sick to see if it could prevent testing positive for the virus. The results came from 1,684 people who participated in the Phase 3, randomized, placebo-controlled trial. Regeneron's therapy is currently authorized as a treatment for people who are at high risk of severe disease and post-exposure prophylaxis for high-risk people who have been exposed to the virus. Regeneron's stock is up 26.6% so far this year, while the broader S&P 500 /zigman2/quotes/210599714/realtime SPX -1.84% has gained 25.1%.