Insulin degludec: Lower day-to-day and within-day variability in pharmacodynamic response compared with insulin glargine 300 U/mL in type 1 diabetes

Aim: To compare day-to-day and within-day variability in glucose-lowering effect between insulin degludec (IDeg) and insulin glargine 300 U/mL (IGlar-U300) in type 1 diabetes. Materials and methods: In this double-blind, crossover study, patients were randomly assigned to 0.4 U/kg of IDeg or IGlar-U300 once daily for two treatment periods lasting 12 days each. Pharmacodynamic variables were assessed at steady-state from the glucose infusion rate profiles of three 24-hour euglycaemic glucose clamps (days 6, 9 and 12) during each treatment period. Results: Overall, 57 patients completed both treatment periods (342 clamps). The potency of IGlar-U300 was 30% lower than IDeg (estimated ratio 0.70, 95% confidence interval [CI] 0.61; 0.80; P <.0001). The distribution of glucose-lowering effect was stable across 6-hour intervals (24%-26%) for IDeg, while IGlar-U300 had greater effects in the first (35%) and last (28%) intervals compared with 6 to 12 hours (20%) and 12 to 18 hours (17%). Within-day variability (relative fluctuation) was 37% lower with IDeg than with IGlar-U300 (estimated ratio IDeg/IGlar-U300: 0.63, 95% CI 0.54; 0.73; P <.0001). The day-to-day variability in glucose-lowering effect with IDeg was approximately 4 times lower than IGlar-U300 (variance ratio IGlar-U300/IDeg: 3.70, 95% CI 2.42; 5.67; P <.0001). The day-to-day variability in glucose-lowering effect assessed in 2-hour intervals was consistently low with IDeg over 24 hours, but steadily increased with IGlar-U300 to a maximum at 10 to 12 hours and 12 to 14 hours after dosing (variance ratios 12.4 and 11.4, respectively). Conclusion: IDeg has lower day-to-day and within-day variability than IGlar-U300 and a more stable glucose-lowering effect, which might facilitate titration and enable tighter glycaemic control with a reduced risk of hypoglycaemia.