Comparison of Insulin Glargine 300 U/mL and Insulin Degludec 100 U/mL Around Spontaneous Exercise Sessions in Adults with Type 1 Diabetes: A Randomized Cross-Over Trial (ULTRAFLEXI-1 Study)

Aims: In the ULTRAFLEXI-1 study, we compared basal insulin Glargine 300 U/mL (IGlar U300) and insulin Degludec 100 U/mL (IDeg U100) for time below range <70 mg/dL (TBR^<70; 3.9 mmol/L) in two different doses (100% and 75% of the regular dose) when used around spontaneous exercise sessions in adults with type 1 diabetes. Methods: A randomized, single-center, four-period, cross-over trial was performed and in each of the four 2-weeks-periods, participants attended six spontaneous 60 min moderate-intensity evening cycle ergometer exercise sessions. The basal insulin administered on the exercise days were IGlar U300 100% or 75% of the regular dose or IDeg U100 100% or 75%, respectively (morning injection). The primary outcome was the TBR^<70 during the 24 h postexercise periods of the six spontaneous exercise sessions in the four trial arms and was analyzed in hierarchical order using the repeated measures linear mixed model. Results: Twenty-five people with type 1 diabetes were enrolled (14 males) with a mean age of 41.4 ± 11.9 years and an HbA_1c of 7.5% ± 0.8% (59 ± 9 mmol/mol). The mean ± standard error of mean TBR^<70 during the 24 h periods following the exercise sessions was 2.71% ± 0.51% for IGlar U300 (100%) and 4.37% ± 0.69% for IDeg U100 (100%) (P = 0.023) as well as 2.28% ± 0.53% for IGlar U300 and 2.55% ± 0.58% for IDeg U100 when using a 75% dose on exercise days (P = 0.720). Time in glucose range^70-180 was the highest in the IDeg U100 (100%) group. Conclusions: TBR^<70 within the first 24 h after spontaneous exercise sessions was significantly lower when receiving IGlar U300 compared to IDeg U100 when a regular basal dose was administered.