NO-Meal Announcement in Automated Insulin Delivery (Open-source and Commercial) Systems

Automated insulin delivery (AID) systems are the current gold standard for the management of type 1 diabetes (T1D), improving glycemic control, reducing hypoglycemia, and decreasing treatment burden. Although both commercial AID (C-AID) and open-source AID (OS-AID) systems have demonstrated significant clinical benefits, direct randomized comparisons between these systems remain scarce. Moreover, an important limitation of currently available AID systems is their reliance on user-initiated meal announcements and carbohydrate counting, which remain major contributors to postprandial dysglycemia and treatment burden. While emerging evidence suggests that AID systems may partially compensate for missed meal announcements, their comparative performance under these challenging real-world conditions is unknown. The NOMAD study is an international, multicenter, open-label, randomized, non-inferiority crossover trial designed to compare an open-source AID system with commercially available AID systems (including Tandem Control-IQ and Omnipod 5) in adults with type 1 diabetes currently using an open-source AID system. The study specifically evaluates glycemic outcomes following standardized unannounced meal challenges performed under free-living conditions. A total of 33 participants will be enrolled and complete two 4-week intervention periods, each consisting of a 2-week run-in phase followed by a 2-week data collection phase, with crossover between treatment arms. Participants will continue using their own Dexcom G6 or Dexcom G7 continuous glucose monitoring system throughout the study. The primary outcome is the percentage of time spent in the target glucose range (3.9-10.0 mmol/L) during the 4 hours following standardized unannounced meal challenges. Secondary outcomes include additional CGM metrics (time above and below range, glucose variability, mean glucose, and GMI), insulin delivery characteristics, and patient-reported outcomes evaluating treatment satisfaction, usability, and diabetes-related burden.

Inclusion Criteria: * Males and females ≥ 18 years old currently residing in Canada or the United States of America (USA) * Having a clinical diagnosis of T1D for at least one year (based on the investigator's judgment; C peptide level and antibody determinations are not needed.) * Having been on OS-AID therapy for at least 2 weeks and using a Dexcom G6 or G7 CGM. * If using an ultra-rapid acting insulin, be willing to switch to a rapid-acting insulin, as the former are not recommended in the C-AID systems used in the study (due to the risk of cannula or pod blockage). * Accepting that personal pump setting parameters will be collected by the research team. This access will be limited to the study period. Exclusion Criteria: * Using regular insulin (Novolin ge Toronto or Humulin R) or U200 or U500 concentrated insulin (e.g. Humalog U200, Entuzity U500) * Participant-reported clinically significant nephropathy (eGFR \< 25 ml/min/1.73m2, planned or on dialysis), neuropathy (e.g., known uncontrolled gastroparesis) or retinopathy (e.g., proliferative retinopathy with ongoing active treatment such as laser photocoagulation or planned surgery) as judged by the investigator * Recent (\