FDA Panel Supports Dexcom CGM For Insulin Dosing in Diabetes

Miriam E Tucker

Disclosures

July 22, 2016

A US Food and Drug Administration (FDA) advisory panel has voted in favor of allowing the Dexcom G5 Mobile continuous glucose monitoring (CGM) system to be used as a replacement for fingerstick glucose monitoring in patients with diabetes.

At a hearing held July 21, 2016, the FDA's clinical chemistry and clinical toxicology advisory panel voted 8 to 2 in favor of safety, 9 to 1 for efficacy, and 8 to 2 that the benefits of the proposed new indication would outweigh the risks.

Currently, the Dexcom G5 CGM is indicated for adjunctive use along with self-monitoring of blood glucose (SMBG), done using a fingerstick test, to provide trend information and alert the patient of high and low blood glucose values. If the FDA follows the panel's advice, the new indication would allow patients to skip the premeal fingersticks and instead use the CGM's data to determine their insulin doses, as well as make other lifestyle decisions such as whether to exercise.

The new label would provide instructions for patients on how to use the CGM's data to determine their insulin doses, including how to adjust insulin doses up or down based on the trend arrows that the device displays. The label would also advise when SMBG testing is necessary, including twice daily for calibration, when the CGM fails to provide a reading, or when symptoms don't match the reading.

Despite the overall favorable vote, many panelists expressed discomfort with the meal dosing simulation model data presented by the company — validated with clinical data from just 71 patients with type 1 diabetes — to support the indication, rather than results from actual patients in randomized clinical trials. Panel members advised the company to gather additional post-marketing data.

Patients Already Using Devices in This Way

Most panelists also said that Dexcom would need to provide training beyond simply a pamphlet or video to make sure that patients understand how to properly use the CGM data to determine insulin doses. There was debate, however, regarding the extent to which the company could provide usage information vs how much of the responsibility would fall to healthcare providers, who would also need to be up to speed.

The stronger vote on efficacy reflected the fact that the Dexcom technology has advanced considerably in recent years. The current G5 iteration is nearly as accurate as SMBG, with a mean absolute relative difference of about 9%, compared with 4% to 9% for the various cleared SMBG meters.

Also influencing the vote was the fact that many current Dexcom users are already using the devices off-label to dose insulin (69% according to market survey data presented during the public comment session by DiaTribe founder Kelly Close) and at least now the company would be able to advise patients about this use, which it is currently forbidden to do.

Over 30 people, including endocrinologists and patients, spoke during the public comment session — many with travel expenses paid by Dexcom — nearly all in favor of approval for the dosing indication. Representatives from the American Diabetes Association, Endocrine Society, and American Association of Clinical Endocrinologists also spoke in support of the indication.

Overall Vote in Favor, But Panel Wants More Data

Panel member Kathleen Wyne, MD, an endocrinologist/type 1 diabetes specialist at Ohio State University, Columbus, voted yes on all three questions (safety, efficacy, and benefit/risk).

"I think this technology gives us a lot of information about the management of diabetes, but ... it's highlighting that the medical side now has to catch up and learn some things we didn't know about how to calculate and [dose] insulin. I don't think it's the place of the device to help us learn how to do the medical management. I think it's the responsibility of us as physicians to help our patients move forward."

George Grunberger, MD, director of the Grunberger Diabetes Institute, Bloomfield Hills, Michigan, also voted yes on all three counts, despite some remaining concerns about lack of data, he told Medscape Medical News in an interview after the vote. "It's a catch 22. You have to teach people to use it to see what role it plays in diabetes management. But first you need permission to teach people to use it."

And he also added, "This is not the responsibility of the endocrinologist... The burden will be on the company to do the education."

The two panel members who voted against safety both expressed concern — as did other panel members who nonetheless voted for it — that the simulation model data couldn't capture the heterogeneity of the type 1 diabetes population and the wide range of both physiologic and behavioral factors that could affect efficacy and safety of CGM-based dosing.

Pediatric endocrinologist David W Cooke, MD, of Johns Hopkins University, Baltimore, Maryland, voted yes on the efficacy question, but no on safety and benefit/risk.

"Safety is my biggest concern, about the lack of data in a real-world setting. Anecdotal and modeling experience are reassuring, but not reassuring enough without clinical trial data."

As far as accuracy, Dr Cooke said, "The data supporting accuracy are adequate ... but certainly with an expectation of significant postmarketing assessment."

Nonvoting patient representative Anna McCollister-Slipp, cofounder of a data analytics company in Washington, DC, said that despite strong reservations about the lack of clinical data, she would have voted yes on all three questions.

For one thing, she pointed out, dosing insulin based on SMBG measurements is certainly error-prone and the CGM data at least offer additional information as well as the protection offered by the alarms. "This is a lifesaving piece of equipment... There are no ifs, ands, or buts about that."

FDA advisory panel members are vetted for conflicts of interest and waivers are granted for participation if necessary. No waivers were deemed necessary for this meeting.

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