Type 1 diabetes

Extended-wear insulin infusion set shows promise in Australian pilot trials

A prototype extended-wear insulin infusion set (IIS) has been shown to be tolerable in adults with type 1 diabetes already established on insulin pump therapy.

The investigational CBX IIS aims to reduce the patient burden associated with changing sets every 2–3 days and help minimise waste.

The extended-wear IIS was tested in 20 adults — first in a 7-day run-in phase when the set delivered saline while the patients’ regular insulin delivery was maintained, and then in second and third 7-day periods of insulin delivery.

The feasibility study, published in Diabetes, Obesity and Metabolism, found five (12.2%) IISs were removed before the end of day 7 during insulin delivery periods.

Removal was due to hyperglycaemia which could not be corrected in three cases; a hyperglycaemic episode with elevated ketones in one case; and signs of infection at the insertion site in a fifth case.

Only the latter two cases met the per-protocol definition of infusion set failure.

“No serious adverse events were reported and there were no incidences of a non-resolvable pump occlusion alarm throughout the study.”

The study found 90% of the IISs were worn for 7 days — with a mean of 6.9 days during the run-in phase and 6.6 days during insulin delivery.

It found CGM glucose increased over the 7-day periods and time-in-range (TIR) decreased.

“In conjunction with the fall in TIR, there was a reciprocal increase in time in hyperglycaemia suggesting a deterioration in glucose control when the set is worn beyond 72 h.”

Total daily dose (TDD) of insulin also increased with wear time.

The researchers, including senior investigator Professor David O’Neal said there was a clear clinical need for an improved IIS that could be worn for longer than 3 days.

“Even more important for people with diabetes is the assurance that their IIS will function reliably each time they bolus, independent of day of IIS wear,” they said.

“Changing an IIS every 7 days instead of every 3 days, may halve the number of insertions, reduce the physical (pain, scarring, loss of insertion sites) and the economic (amount and cost of consumables) burden to the user.”

“Moreover, eliminating more than half of consumables associated with insulin pump therapy may have a substantial environmental impact.”


Professor O’Neal, from the University of Melbourne and St Vincent’s Hospital Melbourne, told the limbic that the advantages of the prototype IIS included the coil reinforcement of the cannula, and the side ports in addition to the end port.

“Certainly comparing the performance of the set to historical data from conventional insulin infusion sets or cannulas, it seems to be more durable for three days and it does last for the full 7 days.”

However he said it does need to be refined further because of concerns that insulin delivery starts to drop off after day 3 or 4.

“No one ran into problems with DKA or severe high glucose levels but it is still a significant issue that needs to be addressed before it can become a commercially viable product,” he said.

Professor O’Neal said cannulas were now the weakest link in a potential closed loop system.

“They are the most likely component to fail now; it’s not the sensor. We can’t have the infusion set of a combined product lasting 3 days but the sensor lasting 7 days.”

He said the CBX IIS was not the only effort in this direction.

“Medtronics have developed a 7-day infusion set which is not on the market in Australia. This is one of several efforts being made to extend the durability and reliability of infusion sets because they are really the Achilles heel of closed loop systems.”

Disclosure: Professor O’Neal has received research support from Capillary Biomedical.

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