272-OR: Effect of 48 Months of Closed-Loop Insulin Delivery on Residual C-Peptide Secretion and Glycemic Control in Newly Diagnosed Youth with Type 1 Diabetes

Background: We evaluated the effect of long-term intensive metabolic control with hybrid closed loop on residual C-peptide secretion and glucose control compared to standard insulin therapy in youth with type 1 diabetes over 48 months. Methods: Following the 24 month primary phase of a multicentre, randomised, parallel trial of 96 newly diagnosed youth aged 10-16.9 years, participants entered an extension phase using either hybrid closed-loop with Cambridge algorithm (CL) or standard insulin therapy (control) until 48 months post diagnosis. Analysis was intention-to-treat. Results: At 24 months after diagnosis, 81 participants (mean±SD age 12±2 years) continued in the extension (47 CL). There was no difference in fasting C-peptide corrected for fasting glucose at 48 months between groups (CL: 0.3±0.5 vs control: 0.3±0.8pmol/L per mg/dL; mean adjusted difference ‑0.1 [95% CI ‑0.4, 0.2; p=0.54]). Central lab HbA1c remained lower in CL group by 10mmol/mol [0.9%] (95% CI 3, 17 [0.2, 1.5%]; p=0.01) at 48 months. Eleven severe hypoglycaemic events (6 CL, 5 control) and seven DKA occurred (3 CL, 4 control). Conclusions: Improved glycaemic control was sustained over 48 months after diagnosis with closed loop insulin delivery compared to standard therapy in youth with type 1 diabetes. This did not appear to confer a protective effect on residual C-peptide secretion.