The DCLP3 study aimed to assess the efficacy and safety of a closed loop system (t:slim X2 with control-IQ Technology) insulin pump in a large randomized controlled trial. Eligible participants not currently using an insulin pump or Dexcom G4, G5, or G6 continuous glucose monitoring (CGM), initiated a run-in phase of 2 to 8 weeks that was customized based on whether the participant was already a pump or CGM user. Participants who skipped or successfully completed the run-in were randomly assigned 2:1 to the use of closed-loop control (CLC group) using t:stim X2 with Control-IQ Technology versus a sensor-augmented pump (SAP) for 6 months. Out of the 168 participants that underwent randomization, 112 were assigned to the CLC group and 56 were assigned to the SAP group.

Primary objective: Assess the efficacy and safety of the Control-IQ closed loop system over a 6-month period.

Secondary objective: Investigate longer term use of the system compared with switching to sensor-augmented pump therapy.

Primary outcome measure: Time in target range 70-180 mg/dL measured by CGM in CLC group versus SAP group.

Secondary outcome measures (26-week time frame):

• CGM time above or below the target range
• CGM mean glucose
• Standard deviation of CGM
• Low and high blood glucose index by CGM with higher index indicating higher risk of hypoglycemia
• CGM hypoglycemia events
• HbA1c levels
• Total daily insulin
• Basal to bolus insulin ratio
• Weight
• BMI

Inclusion criteria:

• Clinical diagnosis, based on investigator assessment, of type 1 diabetes for at least one year and using insulin for at least 1 year
• Familiarity and use of a carbohydrate ratio for meal boluses
• Age ≥ 14.0 years old
• For females, not currently pregnant and agree to use a form of contraception to prevent pregnancy while a participant in the study
• Willingness to suspend use of any personal CGM for the duration of the clinical trial
• Willingness to use a regular insulin pump during the study with no automatic insulin adjustment based on glucose level when assigned to participate in the SAP group
• Willingness to switch to lispro (Humalog) or aspart (Novolog) if not using already, and to use no other insulin besides lispro (Humalog) or aspart (Novolog) during the study
• Total daily insulin dose (TDD) at least 10 U/day
• Willingness not to start any new non-insulin glucose-lowering agent during the course of the trial

Exclusion criteria:

• Concurrent use of any non-insulin glucose-lowering agent other than metformin (including GLP-1 agonists, Symlin, DPP-4 inhibitors, SGLT-2 inhibitors, sulfonylureas)
• Hemophilia or any other bleeding disorder
• Participation in another pharmaceutical or device trial at the time of enrollment or during the study

At the end of the 6-month trial, the closed-loop group were found to have spent a greater percentage of time in the target glycemic range than the SAP group.

Data generated from this study are available externally outside of the NIDDK Central Repository. Please navigate to the external repository and follow the policies and procedures to access data associated with this study: https://public.jaeb.org/dataset/573