Miriam E Tucker

September 27, 2016

MUNICH — A novel implanted continuous glucose sensor (Eversense, Senseonics) is safe and accurately reflected blood glucose levels for an average of about 6 months, study results show.

Data from the pivotal 180-day Prospective, Multicenter Evaluation of the Accuracy of a Novel Continuous Implanted Glucose Sensor Clinical Investigation (PRECISE) were presented September 15, 2016 here at the European Association for the Study of Diabetes (EASD) 2016 Annual Meeting by Jort Kropff, MD, of the University of Amsterdam, the Netherlands.

The first-generation implanted sensor system used in the study comprises a small cylindrical glucose "sticklike" sensor about 15 mm long that is implanted in the upper arm and a transmitter that is placed on the skin over the implanted sensor and that vibrates on-body when patients reach preset high or low glucose levels. The transmitter also wirelessly communicates with a smartphone-based medical app to display glucose results and trigger alarms on the mobile device.

These data from PRECISE gained the first-generation Eversense device a CE Mark approval for 90 days of use in the European Union in May 2016.

In the United States, data from a second pivotal trial of an updated version of the device, PRECISE II, are being submitted to the US Food and Drug Administration as part of a premarketing approval package, according to a company statement.

Why Implant the Sensor? Long-term Stability Is One Advantage

There are several advantages to wearing a glucose sensor under the skin, Dr Kropff told Medscape Medical News. "In the end, the patients are going to have to tell us whether they like it, but I think it brings specific benefits that conventional continuous glucose monitors [CGMs] don't have, such as being able to take off the transmitter without removing the sensor, which normally you wouldn't be able to do."

And, he said, the long-term stability of the implanted sensor is a major advantage over current CGMs that typically only last up to a week. "With sensor life getting longer and longer, benefits for patients become greater," he explained.

Asked to comment, Steven J Russell, MD, of the Diabetes Research Center at Massachusetts General Hospital, Boston, said: "I think it has some really nice advantages. Sensors tend to be a little bit inaccurate the first day, and that's true here as well, but it's just the first day out of 3 to 6 months."

He also noted that implanting the sensor reduces the problem of an external sensor being moved around, which can lead to inaccurate readings. "It heals into its pocket, and you don't have that variability anymore," he told Medscape Medical News.

Dr Russell, who has used the device in four patients but has not received funding from the company, said that in his experience it was accurate and that patients seemed happy with it.

Accuracy Seen to 6 Months

The study enrolled 71 subjects with type 1 or type 2 diabetes using either multiple daily injections or insulin pumps. They had a mean age of 42 years, diabetes duration 22 years, and baseline HbA1c 7.6%. Nearly half (45%) were already using external CGMs.

During the study, subjects wore two implanted sensors, one in each upper arm, calibrated twice daily. Continuous glucose data were available to the patients throughout the study.

Accuracy and safety of the implanted sensors was assessed over 6 months, via comparison with a reference test (Venous Yellow Springs Instrument), and results were expressed as the mean absolute relative difference (MARD) between the two.

The MARDs were 11.6% for the entire range of blood glucose levels (40–400 mg/dL), 21.7% in the hypoglycemic range (< 75 mg/dL), 11.9% in euglycemia (75–180 mg/dL), and 9.2% for hyperglycemia (> 180 mg/dL).

Although it wasn't an official end point, there was a reduction in HbA1c from 7.5% at screening to 7.2% at study end (P < .001) and reduction in time spent in hypoglycemia from 5.3% in the first study month to 4.4% in the last month (P = .003).

Sensor Life Is Around 150 Days

When the device detects variability above a threshold, it indicates to the patient that the sensor life is ending and needs to be replaced in a couple of weeks. In the study, median sensor life was 149 days (as compared with 7 days or fewer for current CGMs).

All of the sensors lasted at least 45 days, 82% reached the 90-day mark, and 40% lasted 180 days. Sensor accuracy was stable until the 151-to-180-day period, when it declined by a small but significant amount, with the MARD rising to just above 12%.

Among a total 292 skin incisions for insertion/removals, there were no device- or procedure-related significant adverse events, Dr Kropff reported.

Of 19 nonsevere adverse events, 14 were related to the device or the insertion/removal procedure, including three skin reactions to the adhesive and two incision-site infections, one requiring antibiotics.

Patient Experience

Transmitter wear compliance was a median of 23.5 hours/day, "so you could actually say they wore it all the time over the full duration. I think that says something about the wearability of this system, in that patients don't mind wearing something on their arm," Dr Kropff observed.

Indeed, in a survey of 50 randomly selected patients at 90 days, participants gave high scores to ease of transmitter use, likability of the implanted sensor, the system's alarms/alerts, and accuracy.

Since they gave lower scores to the look/feel of the transmitter, "I've been informed that updated versions of the transmitter are coming in the next generation," Dr Kropff noted.

On a different survey, patients endorsed, "I don't feel the sensor during wear," "The vibratory alarms from the transmitter provided reassurance (in addition to the audible alarms)," and "The sensor insertion/removal was painless" (lidocaine was used). A majority said they would want to be inserted with a sensor again.

Scoring less well were: "I was able to feel the vibratory alarms on the transmitter at night," and "The CGM system did not give me too many false alarms." The vibratory alarms can be made stronger in future generations, while the high false-alarm rates are a problem for most CGM systems, Dr Kropff pointed out.

The investigators conducted a reanalysis using a new data algorithm, which resulted in an improved MARD of 10.5%. Moreover, in the PRECISE II study, a MARD of 8.8% was reported as a top-line result in August 2016.

"I think the data are pretty impressive," Dr Russell commented,

Dr Kropff is a consultant/advisor on the speaker bureaus for Senseonics and Dexcom. 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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European Association for the Study of Diabetes 2016 Meeting; September 15, 2016; Munich, Germany. Abstract 187.

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