A fully automated, fully closed-loop insulin delivery system for use by people with type 2 diabetes has been successfully trialled by UK scientists.

The device – using an algorithm developed at Cambridge University – improved glucose control without increasing hypoglycemia compared with standard insulin therapy, according to results published in Nature Medicine (link here).

Using faster-acting insulin aspart, the device doubled the amount of time patients were in the target range for glucose compared to standard treatment and halved the time adults with type 2 diabetes spent experiencing high glucose levels .

Researchers from the Wellcome-MRC Institute of Metabolic Science in Cambridge combined an off-the-shelf glucose monitor (Dexcom G6 CGM transmitter) and insulin pump (Dana RS) with a smartphone-based insulin prediction app, CamAPS HX.

The app started with participants’ total daily insulin dose and body weight and calculated an insulin infusion rate every 8–12 minutes for the pump in response to the sensor glucose data. Low and high glucose alarms were adjusted according to the participant’s preferences, who were also trained to use the ‘boost’ and ‘ease-off’ functions within the app as required to increase or decrease insulin, respectively, as directed by the algorithm.

The team recruited 26 patients with T2D from the Wolfson Diabetes and Endocrine Clinic at Addenbrooke’s Hospital, Cambridge,. Participants were randomised to two 8-week periods to compare the CamAPS HX fully closed-loop app with standard insulin therapy and a masked glucose sensor (control) in random order, with a 2-week to 4-week washout between periods.

At baseline, participants had average HbA1c levels of  75 ± 15 mmol mol−1 (9.0% ± 1.4%).

The primary outcome was the proportion of time that patients spent with their glucose levels within a target glucose range of between 3.9 and 10.0mmol/L.

On average, patients using the fully closed loop system spent two-thirds (66%) of their time within the target range – double that while on the control (32%).

Overall the proportion of time patients spent in target glucose range was by increased by 35 percentage points, representing an additional 8 hours per day.

A secondary measure was the proportion of time spent with glucose levels above 10.0 mmol/L. Patients taking the control therapy spent two-thirds (67%) of their time with high glucose levels. This was halved to 33% when using the closed loop device.

Average glucose levels fell – from 12.6 mmol/L when taking the control therapy to 9.2 mmol/L while using the artificial pancreas.

The app also reduced levels of HbA1c compared to control (7.3% vs 8.7%)

Time spent at or below 3.9 mmol/ l blood glucose was similar between treatments (a median of 0.44% during the closed-loop therapy period versus a median of 0.08% during the control therapy period; P = 0.43). No severe hypoglycemia events occurred in either period

The researchers said the pilot study had confirmed results seen with a closed loop system in patients with T2D and renal failure requiring dialysis

“Here, we demonstrate that this technology can benefit the wider population with type 2 diabetes requiring insulin and can be safely implemented in the home setting,” they wrote.

“As a considerable proportion of people with type 2 diabetes struggle to achieve the recommended glycaemic targets with currently available therapies, including insulin therapy, fully closed-loop systems offer a new approach to improve glycaemic outcomes to reduce the risk of long-term complications,” they added

The study investigators said one of the barriers to widespread use of insulin therapy has been concern among clinicians and patients over the risk of severe ‘hypos’.

“But we found that no patients on our trial experienced these and patients spent very little time with blood sugar levels lower than the target levels.”

They noted that feedback from participants indicated they were happy to have their glucose levels controlled automatically by the system, and nine out of ten (89%) reported spending less time managing their diabetes overall.

Users highlighted the elimination of the need for injections or fingerprick testing, and increased confidence in managing blood glucose as key benefits. Downsides included increased anxiety about the risk of hypoglycaemia, which the researchers said may reflect increased awareness and monitoring of glucose levels, and practical annoyances with wearing of devices.

The team said they now plan to carry out a much larger multicentre RCT to build on their findings and have submitted the device for regulatory approval with a view to making it commercially available for outpatients with type 2 diabetes.