Comparative Effectiveness of Switching From First-Generation Basal Insulins to Either Glargine 300 U/mL or Degludec 100 U/mL in Children and Adolescents With Type 1 Diabetes: Results From the ISPED CARD Clinical Registry

Background: To assess the real-world effectiveness of switching from first-generation basal insulins (1BIs) to either glargine U300 (Gla-300) or degludec U100 (Deg-100) in children and adolescents with type 1 diabetes (T1D), using data from the Italian ISPED CARD clinical registry.Materials and Methods: This multicenter retrospective observational study included 1063 pediatric patients with T1D from 22 diabetes centers across Italy who switched from 1BI to either Gla-300 (64.6%) or Deg-100 (35.4%) between 2021 and 2023. Propensity score matching (PSM) was applied to create comparable groups (n = 353 per group). Primary endpoint was the change in HbA1c at 6 months. Secondary endpoints included fasting blood glucose (FBG), standardized body mass index (BMI/SDS), and insulin doses at 6 and 12 months. Longitudinal models for repeated measures were used to assess treatment effectiveness.Results: Both groups showed significant and clinically relevant reductions in HbA1c at 6 months from similar to 8.7% to similar to 7.4% (-1.3 percentage points), maintained at 12 months, with no significant differences between groups. FBG also decreased significantly in both groups, slightly favoring Deg-100, but without statistical significance between groups. BMI/SDS remained stable. Gla-300 was associated with a slight increase in basal insulin dose over 12 months, while Deg-100 showed a temporary reduction at 6 months. A significant reduction in short-acting insulin dose (-0.03 U/kg) was observed in both groups.Conclusion: Switching from 1BI to either Gla-300 or Deg-100 significantly improves glycemic control in pediatric T1D patients without weight gain. Although both insulins showed comparable effectiveness, differences in titration patterns highlight the need for individualized treatment strategies and improved clinician education in insulin optimization. Safety outcomes, particularly hypoglycemia, could not be assessed.