Improvements in Glycemic Control Achieved by Altering the t max Setting in the iLet ® Bionic Pancreas When Using Fast-Acting Insulin Aspart: A Randomized Trial

Diabetes Ther. 2021 Jul;12(7):2019-2033. doi: 10.1007/s13300-021-01087-x. Epub 2021 Jun 19.


Introduction: We investigated the safety of, and glucose control by, the insulin-only configuration of the iLet® bionic pancreas delivering fast-acting insulin aspart (faster aspart), using the same insulin-dosing algorithm but different time to maximal serum drug concentration (tmax) settings, in adults with type 1 diabetes.

Methods: We performed a single-center, single-blinded, crossover (two 7-day treatment periods) escalation trial over three sequential cohorts. Participants from each cohort were randomized to a default tmax setting (t65 [tmax = 65 min]) followed by a non-default tmax setting (t50 [tmax = 50 min; cohort 1], t40 [tmax = 40 min; cohort 2], t30 [tmax = 30 min; cohort 3]), or vice versa, all with faster aspart. Each cohort randomized eight new participants if escalation-stopping criteria were not met in the previous cohort.

Results: Overall, 24 participants were randomized into three cohorts. Two participants discontinued treatment, one due to reported 'low blood glucose' during the first treatment period of cohort 3 (t30). Mean time in low sensor glucose (< 54 mg/dl, primary endpoint) was < 1.0% for all tmax settings. Mean sensor glucose in cohorts 1 and 2 was significantly lower at non-default versus default tmax settings, with comparable insulin dosing. The mean time sensor glucose was in range (70-180 mg/dl) was > 70% for all cohorts, except the default tmax setting in cohort 1. No severe hypoglycemic episodes were reported. Furthermore, there were no clinically significant differences in adverse events between the groups.

Conclusion: There were no safety concerns with faster aspart in the iLet at non-default tmax settings. Improvements were observed in mean sensor glucose without increases in low sensor glucose at non-default tmax settings.

Trial registration:, NCT03816761.

Keywords: Algorithm; Automated delivery; Bionic pancreas; Faster aspart; Glucose control; Insulin; Type 1 diabetes.

Plain language summary

One way to give insulin is to use an insulin delivery system. The iLet® is a new type of insulin delivery system that works together with a continuous sugar monitoring tool (CGM). The CGM shows the blood sugar level in the body throughout the day. Based on this, the iLet automatically gives the insulin that is needed to control the blood sugar. Fast-acting insulin aspart (faster aspart) is a type of insulin that doctors can prescribe for use with insulin pens and insulin pumps. The researchers wanted to test the safety of faster aspart when given to people at different delivery settings in the iLet. Twenty-four men and women with type 1 diabetes from the USA took part. The different insulin delivery settings were the standard setting (tmax65 = 65 min) and new settings (tmax50 = 50 min; tmax40 = 40 min; tmax30 = 30 min). The shorter the tmax setting, the faster the insulin was assumed to be absorbed into the body by the iLet. People had good blood sugar control with faster aspart delivered using the iLet. The time with low blood sugar (i.e., < 54 mg/dl) was low for both the standard setting and the new settings. The average blood sugar was lower with the shorter, non-standard tmax settings. No people had serious side effects. No severe hypoglycemic episodes were reported. In this study, researchers found that it was safe to use faster aspart with the different settings in the iLet.

Associated data