A Pilot Outpatient Assessment of a Fully Closed-Loop Insulin and Pramlintide System

Type 1 diabetes is treated with exogenous insulin using multiple daily injections or insulin pumps. However, both strategies require carbohydrate counting for prandial insulin dosing, which is both burdensome and error prone.

We conducted a pilot, randomized, controlled study to eliminate carbohydrate counting in adults (n = 12, 7 females, age 39.5 [15.1], HbA1c 7.4% [0.6]) using an automated insulin and pramlintide fully closed-loop system. The interventions included five arms during which participants underwent 14 hours of outpatient, free-living, supervised experiments of (1) faster aspart with carbohydrate counting (control), faster aspart and pramlintide without carbohydrate counting at (2) 8 µg/U and (3) 10 µg/U ratios, and aspart and pramlintide without carbohydrate counting at (4) 8 µg/U and (5) 10 µg/U ratios.

The median time in target range (3.9-10.0 mmol/L) with the control arm was 78.6 [65.3-92.9], compared with 76.2 [64.6-86.9] and 78.8 [68.8-86.0] with the fully closed-loop faster aspart and pramlintide systems at 8 and 10 µg/U ratios, respectively, and compared with 65.9 [59.9-83.6] and 77.4 [72.1-82.7] with the fully closed-loop aspart and pramlintide systems at 8 and 10 µg/U ratios, respectively. Times spent below 3.9 and 3.0 mmol/L were numerically higher with the fully closed-loop aspart and pramlintide systems than the control arm. None of the differences were statistically significant.

This study suggests that automated insulin and pramlintide systems have the potential to alleviate carbohydrate counting without degrading time in range. A longer and larger study is underway.