Switching to once-weekly insulin icodec versus once-daily insulin glargine U100 in individuals with basal-bolus insulin-treated type 2 diabetes (ONWARDS 4): a phase 3a, randomised, open-label, multicentre, treat-to-target, non-inferiority trial. Insulin icodec (icodec) is a basal insulin analogue suitable for once-weekly dosing. ONWARDS 4 aimed to assess the efficacy and safety of once-weekly icodec compared with once-daily insulin glargine U100 (glargine U100) in individuals with long-standing type 2 diabetes on a basal-bolus regimen. In this 26-week, phase 3a, randomised, open-label, multicentre, treat-to-target, non-inferiority trial, adults from 80 sites (outpatient clinics and hospital departments) across nine countries (Belgium, India, Italy, Japan, Mexico, the Netherlands, Romania