Imdevimab

Patients allocated to the antibody combination were to receive a single dose of casirivimab 4 g and imdevimab 4 g administered together in 250 ml 0·9% saline infused intravenously over 60 min (plus or minus 15 min) as soon as possible after randomisation. The dose of 4 g per antibody was chosen to maximise the probability of a therapeutic effect while ensuring patient safety, based on preliminary data from inpatient (NCT04426695) and outpatient (NCT04425629) studies of the safety, tolerability, and efficacy of casirivimab and imdevimab (unpublished data, Regeneron Pharmaceuticals).
Early safety outcomes were recorded by site staff using an online form 72 h after randomisation (appendix pp 37–41). An online follow-up form was completed by site staff when patients were discharged, had died, or at 28 days after randomisation, whichever occurred first (appendix pp 42–48). Information was recorded on adherence to allocated trial treatment, receipt of other COVID-19 treatments, duration of admission, receipt of respiratory or renal support, and vital status (including cause of death). In addition, routinely collected health-care and registry data were obtained, including information on vital status at day 28 (with date and cause of death), discharge from hospital, and receipt of respiratory support or renal replacement therapy.