The exciting first-ever implantable continuous glucose monitor (CGM) known as Eversense, from Maryland-based Senseonics, just got better. After a long wait, on Feb. 11, 2022, the company announced Food and Drug Administration (FDA) approval of its Eversense E3 version that can stay in the body for a full 6 months — rather than needing to be surgically replaced every 90 days.

"Further extending the duration of the longest lasting CGM system to 6 months represents a massive leap forward for patients and towards our mission of transforming lives in the global diabetes community," Senseonics president and CEO Tim Goodnow said in a press release.

Indeed, while lots of people with diabetes loved the idea of a tiny, twig-sized implantable CGM sensor that beams results to a smartphone app every 5 minutes, they did not love having to visit a doctor for an incision in their upper arm every 3 months to replace the unit. Now, patients in the United States also have access to the longer-wear sensor already available in Europe that is now sold by Ascensia Diabetes Care.

FDA approval for adult patients comes more than a year after Senseonics submitted Eversense E3 to the FDA in September 2020, due in part to COVID-19 delays.

With this approval, Ascensia plans to launch the Eversense E3 by July 2022, and the manufacturer says it will pursue the needed research for pediatric use, as well as making this model compatible with existing insulin pumps and Automated Insulin Delivery (AID) systems.

Traditional CGMs consist of a sensor worn externally on the abdomen or arm that takes glucose readings via a tiny cannula (built-in plastic tube) that pierces the skin. The sensor is typically worn for 7 to 10 days before you need to replace it, using an autoinserter device that comes with the system.

The Eversense implantable diabetes sensor is shown held between two fingers.
Eversense implantable sensor

Eversense is entirely different. It's a first-of-its-kind sensor that is implanted under the skin for a number of months, rather than days. To get readings, you do have to wear a transmitter on top of your skin over the sensor insertion site that stays in place with a silicon-based adhesive backing. But this is something you just slap on like a Band-Aid.

Note that the transmitter is a black square, so not particularly discreet. But the upside is that you can take it off whenever you wish, without wasting anything but a single adhesive backing.

This is the company's third version of the Eversense implantable CGM. The first was the 90-day Eversense sensor, followed by the Eversense XL that lasted 180 days but has only been available outside the United States.

Now, the Eversense E3 offers a new level of convenience:

  • Three extra sensor months. Each tiny sensor lasts 180 days, instead of 90 days. Enabling this longer-wear tech is a proprietary sacrificial boronic acid (SBA) design, reducing oxidation of the glucose-binding indicator chemistry and extending the sensor's longevity. This means a user now only needs two sensor insertion and removal procedures per year, rather than the four needed before.
  • Reduced fingerstick calibrations. Per the FDA, the Eversense E3 requires just two fingerstick calibrations per day for the first 3 weeks of using the sensor. Then after day 21, only one fingerstick is required each day to check the CGM's internal accuracy. The mobile app prompts the user to enter those calibrations.

Aside from that, the basics of the Eversense system remain pretty much the same:

Tiny sensor. The sensor is a miniature transparent rod, thinner than a Tylenol tab, that's implanted several inches under the skin. It's FDA-approved to go in the upper arm, though some users internationally have reported having had it inserted on their abdomen. Once inserted, the sensor has a one-time warmup period of 24 hours where no data is displayed as it gets used to the person's body.

Doctor's office implantation. Insertion takes place in a doctor's office in a roughly 10-minute procedure. All that's needed is lidocaine and a specially designed tool to insert the sensor in a pocket of skin about twice as deep as a regular CGM cannula would go.

Adults only. This is not FDA labeled for anyone under 18 years old, though Senseonics chief medical officer Dr. Fran Kaufman says the company plans to pursue that clinical trial research ASAP now that the product is approved.

Eversense transmitter, worn externally

Black transmitter, needs charging. As noted, the rub for some folks may be the need to wear the transmitter on the skin, attached with an adhesive directly above the inserted sensor. The transmitter is a flat black disc, a little thinner than two stacked quarters. It's smaller than an Omnipod insulin patch pump, but bigger than the Abbott FreeStyle Libre flash glucose sensor. It sends data to the companion smartphone app every 5 minutes.

The transmitter can be removed and reattached as often as desired, for a shower or sports, but naturally no data will be transmitted while it is off. It also needs to be recharged daily for 10 to 15 minutes using a cable provided. The transmitter has a hard shutoff at 180 days based on an internal clock, so in case you're wondering, there is no possibility to restart an expired sensor.

Light-sensing tech. The device uses novel, proprietary light-based technology to measure glucose levels. The sensor is coated with a fluorescent chemical that, when exposed to blood sugar, produces a small amount of light that is measured by the sensor.

On-body vibration. One very cool feature is that the Eversense transmitter actually vibrates on the body to alert users to highs and lows, varying the amount of vibrations depending on where glucose levels are. This means you can disable all the annoying audio alerts if you so choose.

No receiver, smartphone only. What's also novel is that this system does not include a separate receiver as an option to smartphone connection. That means to use it, you must have a compatible Android or iOS device (iPhone, Android, iTouch, iPod, or tablet). While the straight-to-phone connectivity is an exciting trend, it's also a potential roadblock for some people.

Mobile app. The app displays a colored bar at the top that shows clearly whether your glucose levels stand in Red, Yellow or Green regarding target range. The easy-to-use menu includes an Alert History, where you can see records of every High Alert, Low Alert, Transmitter Disconnected or Calibrate Now alert received, with exact day and time. This is super useful for going back over your day or week to retrace your steps. You can also see a Reports section with a Weekly Modal Summary, a Glucose Pie Chart mapping out your past days and months' of data, as well as a Glucose Stats Report displaying your average, highest and lowest readings, and standard deviation broken down by time of day.

Predictive alerts. Along with the traditional Low, High, and Rate of Change alerts, the Eversense can predict when you're going to go Low or High as much as 10 to 30 minutes in advance, providing those predictive alerts either via the on-body vibration feature or via the mobile app, which can give an audible alert or even flash a light to catch attention.

Data sharing. To email any of these reports to a recipient of your choice, you just click on the Share icon in the upper right of the screen. If you click into the Share My Data area, you can also send email invitations to your doctors or loved ones to be able to view your continuous stream of data, including alerts and events logged.

Per clinical trial data, the Eversense E3 appears to have the most accurate CGM sensor of them all.

The standard measurement of CGM accuracy is known as Mean Absolute Relative Difference (MARD). Note that in the case of MARD, the lower the number, the higher the sensor's accuracy.

According to the PROMISE study published in 2021, the Eversense E3 has an average MARD of 8.5 percent, compared to the Dexcom G6's 9 percent, the Medtronic Guardian 3 sensor at 8.7 percent, and the FreeStyle Libre 2 at 9.3 percent.

You need a doctor's prescription to get an Eversense CGM, and if your physician isn't yet trained to do the insertion, you'll need to work with the company to find an authorized provider to handle that.

Ascensia Diabetes Care — most well known for making the Bayer Contour traditional fingerstick glucose meters — has been selling and marketing the Eversense CGM since 2020, and they're responsible for announcing the costs and launch plans once that time comes. We're told the pricing isn't yet finalized at time of FDA approval, but it will not likely be different from the Eversense 90-day pricing.

The initial Eversense system has been covered by large insurers including Aetna, Cigna, Humana, and Blue Cross Blue Shield plans, and Medicare announced coverage starting in 2020. This will likely be carried over and added for the 180-day sensor, including Medicare.

Also, there is currently no decision on whether the 90-day Eversense CGM will be discontinued. But the companies' goal is to "move users to the 6-month product as quickly as possible." The launch is expected to begin in the second quarter of the year, between early April and late June.

As to future technology, Senseonics has a number of items in the works already.

According to Kaufman, now that the Eversense E3 is FDA-cleared they will plan to pursue FDA's new "iCGM" designation recognizing technology that is ready to integrate with existing and future insulin pumps and AID systems.

They also plan to start clinical trials of their next-generation 365-day sensor, which take some time given that the trial research for that will require a whole year of study compared to the earlier generations only lasting 90 or 180 days.

"This is all a journey, and we're going one step at a time," Kaufman told DiabetesMine.