Another “Closed-Loop” Insulin Delivery System

Using a new investigational system, patients with type 1 diabetes had blood glucose levels in a target range 71% of the time.

Closed-loop systems for insulin delivery combine an insulin pump, a sensor for continuous glucose monitoring, and automated algorithmic adjustment of basal insulin infusion rates. In this U.S. trial, 168 patients with type 1 diabetes (71% adults; 29% adolescents [age range, 14–17]) were randomized to an investigational closed-loop system (Control-IQ) or to a control group (using an insulin pump augmented by continuous glucose monitoring). At baseline, mean glycosylated hemoglobin (HbA1c) was 7.4%.

During 6 months of treatment, the percentage of time that blood glucose was in the target range (70–180 mg/dL) was significantly higher in the closed-loop group than in the control group (71% vs. 59%). This outcome reflected less time at both extremes: less time with glucose levels >180 mg/dL or <70 mg/dL. However, the proportion of patients with adverse events was higher in the closed-loop group (14% vs. 4%; P=0.05). “Hyperglycemic events” — 15-minute periods in which blood glucose exceeded 300 mg/dL — comprised most of this difference and resulted from infusion set failures. No patient in either group experienced severe hypoglycemia.


If this closed-loop system gains FDA approval, it will be the second one available in the U.S. (the only currently available system is Medtronic’s MiniMed 670G). These systems offer the promise of improved glycemic control as long as system malfunctions are minimized. Note, however, that current systems still require patients to dose premeal bolus insulin manually.



Brown SA et al. Six-month randomized, multicenter trial of closed-loop control in type 1 diabetes. N Engl J Med 2019 Oct 31; 381:1707. (


Allan S. Brett, MD reviewing