FDA Panel Supports Using CGM for Insulin Dosing

After hearing from supporters that included the chief medical officer of the American Diabetes Association (ADA) and a former Miss America, an FDA panel recommended Thursday that Dexcom’s G5 continuous glucose monitoring (CGM) system be approved for dosing insulin—a use that patients say are doing anyway.

Adding a dosing indication to the Dexcom G5 would open the door for widespread patient and clinician training and education to help those with type 1 diabetes (T1D) or their parents, according to company officials and clinicians who spoke during the public hearing, held in Gaithersburg, Maryland.

The meeting of the Clinical Chemistry and Clinical Toxicology Devices Panel, which is a part of the Medical Devices Advisory Committee, voted in favor of all 3 questions put to it after a daylong hearing. Panel members voted 8-2 on the questions of whether the proposed new indication was safe and whether the benefits outweighed the risks. The panel voted 9-1 on the question of whether the CGM system was effective for its proposed new use. Recommendations now go to the full FDA.

CGM uses a sensor and an algorithm fed to a receiver—or a smartphone—to take readings of blood glucose levels every 5 minutes around the clock and guide insulin dosing. Patients can set customized alerts to warn them when their blood glucose levels reach a high or a low level, and a built-in alarm goes off if a patient’s blood glucose reaches 55 mg/dL, a level that puts the person at risk of hypoglycemia and loss of cognitive function.

Unlike self-monitoring of blood glucose (SMBG), Dexcom’s G5 system uses a combination of readings and trending arrows to tell patients if levels are rising or falling. If blood glucose levels are rapidly changing, that may indicate a different response than a SMBG test, a snapshot that shows a reading above or below recommended levels. Dexcom's current approval requires SMBG for every insulin dose.

Until recently, SMBG has been considered more accurate, but Dexcom, patients and several clinicians who spoke yesterday say the CGM technology has evolved to provide accuracy that is on nearly on par with a blood test and in many ways more useful. For these reasons, Dexcom began talks with FDA to discuss what information would be needed for a dosing indication.

While the vast majority of those affected by the panel’s vote have T1D, an increasing number of persons with type 2 diabetes (T2D) could benefit from CGM, as the population ages and more seniors deal with the disease. As patients age, they are less likely to sense symptoms of hypo- or hyperglycemia, making CGM more critical. Because the technology is approved as “adjunctive” and not for dosing, Medicare considers it “precautionary,” and not necessary. Only a handful of patients have been able to appeal for coverage. This has been a point of frustration for T1D patients; increasingly, they gain superior control with CGM and then lose access to the technology when they reach age 65.

Brian Buckingham, MD, of Stanford, who presented information on Dexcom’s clinical utility, said CGM helps patients when they are most vulnerable: at night and when they are distracted. Most hypoglycemic events occur while patients are sleeping, when “finger testing is inadequate,” he said.

Much of the morning centered on 2 simulation studies that Dexcom prepared at FDA’s behest, which examined how CGM would work relative to SMBG. The simulations created 20,000 scenarios in which virtual “patients” made dosing decisions; the use of a simulation allowed Dexcom to incorporate simulated patient errors and aggressive dosing adjustments that might not be safe to do in a clinical trial, but which would happen in real world use.

The use of simulations was just part of the evidence that Dexcom put forward to support its request. Several recent studies—including a group of abstracts presented last month at the ADA Scientific Sessions—show that when patients use CGM and interact with it frequently, they gain improved glycemic control and have fewer incidents of hypoglycemia, even though the number of finger sticks done each day goes down.

More than 30 patients, parents of T1D children, doctors, scientists, and advocates, who spoke in the public hearing said what’s happening now in the real world must be acknowledged—speakers told the panel that CGM users make dosing adjustments based on the real-time information they get from the systems.

“The question of adjunctive vs non-adjunctive use, with all due respect, is silly,” said Robert Ratner, MD, chief scientific and medical officer for the ADA. Patients who have CGM are using it for dosing now. “They look at the data, and they respond to the data,” he said.

Nicole Johnson, DrPH, a public health educator and mother who made history when she was crowned Miss America 1999 while living with T1D, said the Dexcom CGM has dramatically improved both her health and quality of life—and is straightforward to teach to other T1D patients. “My health has never been better,” she said.

William Tamborlane, MD, who is chief of pediatric endocrinology at Yale, noted that FDA has already approved Medtronic’s 530G, which includes a built-in shut off feature on the insulin pump that responds to CGM data. Thus, he said, there is precedent for a dosing “decision” to be based on the technology.

Tamborlane was among the luminaries in the field who came out for the hearing—the lineup of supporters included Boris Kovatchev, PhD, who is working on the artificial pancreas project at the University of Virginia, and Lori Laffel, MD, MPH, chief of pediatrics at Joslin Diabetes Center.

But some of the most gripping testimony came from 2 teenagers and a 10-year-old boy living with T1D, who spoke of the difference Dexcom’s CGM had made in their lives. Owen O’Connell, 16, spoke of how the device helps him stay active in 3 different sports, and all spoke of the quality of life improvements of fewer finger sticks and standing out less at school. O’Connell said before he started using CGM 4 years ago, he suffered 4 hypoglycemic seizures.

Since then, “I haven’t had a single hypoglycemic seizure, and I really believe this is due to Dexcom,” he said.

The reality of being able to reduce the number of finger sticks—a huge quality of life issue for T1D persons—came up repeatedly. Use of CGM promotes better patient engagement in their care, several speakers said. Scientists said the reduction of blood tests in favor of CGM would ultimately save money on supplies and especially on fewer trips to the emergency department.

The panel members discussed at length whether there was sufficient evidence to support a new indication, and whether a full-blown clinical trial was needed before the change. But clinicians on the panel the design of a clinical trial would be inherently difficult and would never take into account all the variables that patients encounter in the real world.

George Grunberger, MD, FACP, FACE, the current president of the American Association of Clinical Endocrinologists who was serving on the panel, said he understood the concerns of a panel member from the National Institutes of Health, Lisa McShane, PhD, who ultimately voted “no” on all 3 questions. But, he said, “As a practicing endocrinologist, the horse has been out of the barn for years.”

Leading advocates were on hand, too, including Kelly Close, founder of diaTribe.org. The update, she said, “is already in practice for a majority of users."

“Not approving this label has risks, too," she said, because “Patients are going to continue dosing off CGM.”

Anna McCollister-Slipp, who served as the non-voting patient representative, echoed many patients when she said she wouldn’t want to manage T1D without her CGM. She also spoke directly to what might be an outcome—changes in payer coverage.

“This meeting comes down to 2 things: CMS refuses to change their decision about access and reimbursement,” because of the current approval, and the fact that FDA doesn’t recognize how patients are actually using the device. (CGM dosing is approved in Europe.)

Kathleen Wyne, MD, of Methodist Hospital Research Institute, said current CGM technology is “at least as good” as the SMBG that patients have been using, and the change will put the onus on clinicians to learn more about how CGM can help patients manage their disease. “The medical side now has to catch up,” she said.