The drug, called VIR-7831, is a new treatment for people with mild to moderate illness, and the study has been so successful that it has been stopped early.
GSK and its partner, Vir Biotechnology, plan to immediately seek an emergency use authorisation in the United States and approval in other countries, including potentially in the UK.
Monoclonal antibodies are laboratory-produced molecules that mimic human antibodies.
The global phase 3 clinical trial based its initial analysis on data from 583 patients at risk of hospital admission.
GSK said VIR-7831 works in two ways – by blocking the virus’s entry into healthy cells and also clearing infected cells.
A separate laboratory study has found that VIR-7831 is effective against the main current Covid-19 variants, including the Kent, South African and Brazilian variants, the firm said.
VIR-7831 is designed to be given as a single intravenous (IV) infusion.
Dr Hal Barron, chief scientific officer at GSK, said: “We are pleased that this unique monoclonal antibody was able to bring such a profound benefit to patients.
“We look forward to the possibility of making VIR-7831 available to patients as soon as possible and to further exploring its potential in other settings.”
