Miriam E Tucker

September 19, 2016

MUNICH — Newly published pivotal trial data for the Medtronic hybrid closed-loop insulin-delivery system, also known as the "artificial pancreas," in patients with type 1 diabetes show use of the system resulted in reductions in both hypoglycemia and hyperglycemia with less glycemic variability compared with baseline data.

The system, known as the Medtronic 670G, is currently under review by the US Food and Drug Administration (FDA). It is viewed as a first-generation "artificial pancreas" since it acts to minimize both high and low blood glucose levels. However, because patients still need a bolus for meals, the company calls it a "hybrid" system.

Data for the pivotal trial, involving 124 patients aged 14 to 75 with type 1 diabetes, were initially presented this past June in a late-breaking poster at the American Diabetes Association's Scientific Sessions.

Last week, they were the subject of a more detailed oral presentation by Richard M Bergenstal, MD, executive director of the International Diabetes Center, Minneapolis, Minnesota, at the European Association for the Study of Diabetes (EASD) 2016 Annual Meeting and were simultaneously published online in the Journal of the American Medical Association.

"After 30-plus years of promising patients that we would have an artificial pancreas, I was never quite certain I'd see it in my career. [Now] I think we're actually going to see it in the near future," Dr Bergenstal told Medscape Medical News.

Asked to comment, Steven J Russell, MD, of the Diabetes Research Center at Massachusetts General Hospital, Boston, said, "I think it's of benefit. It clearly seemed to reduce the glycemic variability."

However, Dr Russell, who is an investigator for a competing product, the dual-chamber "iLet" (Beta Bionics), said he sees the Medtronic 670G as "an incremental improvement" over the devices the company already has — the low-glucose-suspend (Medtronic 530G) insulin pump in the United States and the predictive low-glucose-suspend (640G) pump in Europe and Australia.

"Ultimately people still have to count carbs, give meal boluses, and do corrections. It's a very conservative strategy….It's not going to reduce the burden on patients as much as a more automated system."

In the same abstract session at the EASD meeting, Dr Russell presented some additional data on the iLet — a device also known as the "bionic pancreas" that incorporates both insulin and glucagon — from a home study in adults with type 1 diabetes, for which the principal findings were also presented at meetings earlier this year.

Pivotal Trial Data Under FDA Review

In the Medtronic pivotal trial, 124 patients with a mean age of 37.8 years and diabetes duration 21.7 years wore the hybrid closed-loop system at home and in their usual daily lives for 3 months. No episodes of severe hypoglycemia or ketoacidosis — the primary outcomes — occurred.

Severe hyperglycemia occurred in five patients during the 2-week run-in phase and in six patients during the trial, all attributed to pump infusion-set problems.

The system was in "closed-loop" mode for a median of 87.2% of the study period, during which HbA1c levels dropped from 7.4% at baseline to 6.9% at study end, and the percentage of sensor glucose values within the target range changed from 66.7% at baseline to 72.2%.

Daily insulin doses rose from 47.5 U/d to 50.9 U/d, and patients gained a bit of weight, from a mean of 76.9 kg to 77.6 kg.

Dr Bergenstal and colleagues do acknowledge some limitations of the study, "which include lack of a control group, restriction to relatively healthy and well-controlled patients, the relatively short duration, and an imbalance between the length of the study periods." And differences in HbA1c levels may be attributable to participation in the study, they note.

Still, "to our knowledge, this is the largest outpatient study to date, and it demonstrated that hybrid closed-loop automated insulin delivery was associated with few serious or device-related adverse events in patients with type 1 diabetes," they observe.

To Medscape Medical News, Dr Bergenstal commented: "These findings suggest that the Medtronic hybrid closed-loop system can help effectively and safely manage type 1 diabetes in adolescents and adults in the home setting."

A similar study in children is under way. And longer-term registry data and randomized studies are needed to further characterize the safety and efficacy of the hybrid closed-loop system, Dr Bergenstal and colleagues conclude.

More iLet data

Meanwhile, Dr Russell presented data on 11-day use of the iLet in 39 adults with type 1 diabetes. Over 24 hours, mean blood glucose levels were 141 mg/dL compared to 162 mg/dL for usual care, and time spent with blood glucose levels below 60 mg/dL was 9 minutes with the iLet vs 27 minutes with usual care over the 24 hours.

Overnight, mean blood glucose levels were 134 mg/dL with the bionic pancreas vs 165 mg/dL for usual care, and the percent of time spent at less than 60 mg/dL was 0.3% with the bionic pancreas device vs 1.0% with usual care.

While the Medtronic hybrid closed-loop system could become commercially available as soon as next year, iLet is likely to take longer because of the glucagon component, which would represent a new indication for that drug.

The study was funded by Medtronic. Dr Bergenstal has conducted research, served on a scientific advisory board, or consulted for Medtronic, Dexcom, Roche, Abbott, Johnson & Johnson, Eli Lilly, Novo Nordisk, and Sanofi. He receives no personal income from these activities, as all contracts are with his nonprofit employer HealthPartners Institute. He has inherited stock in Merck. Disclosures for the coauthors are listed in the article. Dr Russell has received honoraria from Tandem and Novo Nordisk, lecture and other fees from Tandem, Sanofi, Dexcom, and Eli Lilly, and nonfinancial support from Dexcom, Tandem Diabetes, SweetSpot Diabetes, International Biomedical, Abbott Diabetes Care, Insulet Corporation, and Medtronic. He owns stocks/shares in Companion Medical, and has patents pending on the bionic pancreas.

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JAMA. Published September 15, 2016. Article

European Association for the Study of Diabetes 2016 Annual Meeting; September 15, 2016; Munich, Germany. Abstract 189.

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