Shares of Vir Biotechnology Inc. /zigman2/quotes/214486077/composite VIR -4.95% gained 5.3% in trading on Tuesday after the company said it is expanding the Phase 3 clinical trial for an experimental COVID-19 treatment. The treatment, a monoclonal antibody called VIR-7831, is aimed at patients with COVID-19 who are at high risk of hospitalization. The randomized, placebo-controlled late-stage study will evaluate 1,300 non-hospitalized patients who have tested positive for COVID-19 and whether they need to be hospitalized or die within 29 days. Results are expected in January. GlaxoSmithKline /zigman2/quotes/209463850/composite GSK +1.21% is also involved in the development of the therapy, as part of a coronavirus-focused development agreement announced by Vir and GSK in April. Vir's stock has soared 211.0% so far this year. The S&P 500 /zigman2/quotes/210599714/realtime SPX +0.18% , in comparison, has gained 5.5%.