A closed-loop insulin delivery system, also referred to as an artificial pancreas, was found to be more effective than sensor-augmented insulin pump therapy in patients with type 1 diabetes (T1D), according to study results published in the New England Journal of Medicine.

At present, Medtronic’s MiniMed 670G is the only commercially available closed-loop system, but limited data on safety and efficacy are available. The International Diabetes Closed Loop (iDCL) study was a 6-month randomized trial aiming to compare the efficacy and safety of a closed-loop system with that of a sensor-augmented pump.

The multicenter trial enrolled 168 patients (50% females; age range, 14-71 years) with T1D who were randomly assigned in a 2:1 ratio to receive treatment with a closed-loop system (112 patients) or with a sensor-augmented pump (56 patients). The groups appeared balanced with regard to baseline characteristics.

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The primary outcome was glucose levels in the target range of 70 to 180 mg/dL, as measured by a continuous glucose monitor.

Users of the closed-loop system had significantly increased time with glucose levels in the target range (61%±17% at baseline to 71%±12% during the 6 months) compared with patients in the control group (59%±14%, which remained unchanged during the study; P <.001). This difference equated to 2.6 more hours per day spent in the target range; this treatment effect was evident in the first month and consistent over the 6-month period.

Users of the closed-loop system also showed improvements in time spent with high (>180 mg/dL) and low (<70 mg/dL or <54 mg/dL) blood glucose and other measurements related to T1D control compared with the control group. At 26 weeks, the mean difference in the glycated hemoglobin level was -0.33% (95% CI, -0.53% to -0.13%; P =.001).

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In the closed-loop group, the median percentage of time that the system was in closed-loop mode was 90%, which was consistent over 6 months. A total of 137 device problems were reported, most commonly secondary to issues with connectivity.

A total of 17 adverse events were reported among 16 patients in the closed-loop group compared with 2 adverse events among 2 patients in the control group (P =.05). There were no severe hypoglycemic events in either group.

The researchers acknowledged several limitations of the study, including more unscheduled contacts in the closed-loop group. In addition, while the suspend insulin feature was not available for the control group, this feature is now available for some pumps and has been found to reduce the frequency of hypoglycemic events.

“Few randomized trials have assessed a closed-loop system for 3 or more months,” wrote the researchers, concluding that “over a 6-month period, the closed-loop system used in our trial led to a greater percentage of time that the glucose levels were in a target range, less hyperglycemia and hypoglycemia, and better glycated hemoglobin levels than a sensor-augmented pump.”

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

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Brown SA, Kovatchev BP, Raghinaru D, et al. Six-month randomized, multicenter trial of closed-loop control in type 1 diabetes. N Engl J Med. 2019;381:1707-1717.