Underlying technology
A brief history of CGM
CGM is a wearable technology that allows users to track their blood sugar levels in real time. Historically, people with type 1 or type 2 diabetes could monitor their blood sugar levels with a fingerstick test. Some people prick their fingertips with a small lancet (In other words, needle) to make a blood sample. When a blood sample contacts the glucose meter’s test strip, the meter instantly displays a blood sugar reading. This information can help you determine if your blood sugar levels are too low or too high, and is especially helpful after meals or when you’re taking medications. However, fingerstick checks have some drawbacks. For example, static readings are provided, so an individual must take frequent samples throughout her day to comprehensively measure blood sugar levels. Additionally, fingerstick checks can be cumbersome and painful.
In contrast, CGMs generate readings every 5 to 15 minutes without user intervention. CGM is not new as it was first approved by the FDA in 1999, but Stelo was the first device of its kind to be approved as an OTC device.
Stelo Glucose Biosensor System
Stelo is an OTC CGM that detects blood sugar levels from the user’s interstitial fluid (the fluid just under the skin). It calculates glucose readings and provides this information to the user’s digitally connected devices such as smartphones and smartwatches. However, it is not intended to be combined with insulin devices such as insulin pens or automated insulin dosing systems.
Dexcom leveraged the same operating principles, basic design, and physical characteristics for Stelo as its latest G7 CGM system (Predicate Device). Predicate Device is also an iCGM, but requires a prescription. Stelo is an OTC advancement permitted for marketing via a 510(k) application supported in part by human factors validation data.
Stelo consists of two subsystems:
1. Glucose Sensing Subsystem: Wearables and Applicators
For CGM, the sensor serves a similar role to a lancet in a fingerstick test. The user uses an applicator to insert a small, flexible wire sensor just under the skin on the back of the arm. Overpatch adhesive secures the sensor in place. The sensor continuously measures the glucose level in the interstitial fluid and converts it into an electrical current. The transmitter measures this current, converts it into an estimated glucose value, and sends it to the user’s mobile app.
2. Mobile application subsystem: iOS and Android mobile applications (apps)
This app provides user and onboarding tutorials and updates users on system status (for examplewarm-up period and signal loss), glucose measurements and trend graphs.
Comparison with predicate devices
Stelo is a Predicate Device (for example, same sensor, patch, applicator, and transmitter hardware). Additionally, the Stelo’s transmitter firmware has the same core roles and functionality as the Predicate Device, but is noticeably different in that it supports extended wear for 15 days compared to 10 days. Users also cannot manually enter blood sugar levels into the app. The Stelo System app is available on both iOS and Android platforms. Users can download the app to compatible Bluetooth Low Energy-enabled smart devices (for example, mobile phones, smart watches). This app inherited the software development kit, functionality, and user interface from the Predicate Device app. However, the Stelo System app deviates from previous apps in several ways, specifically sending read updates to the app every 5 minutes and updating app entries every 15 minutes. Individuals also receive customized onboarding and “insights,” a daily report that summarizes their blood sugar levels and shares relevant health tips.
OTC CGM and beyond
The FDA’s approval of the first OTC CGM paves the way for future devices that go beyond diabetes management and allow individuals to monitor meaningful health data without a prescription. For example, you might see his OTC CGM trend in the fitness industry. OTC CGM provides real-time data, allowing individuals to understand how their bodies are responding to training and eating plans. This information can guide your nutritional choices, optimize your training, and prevent extreme blood sugar fluctuations. Additionally, OTC CGM may be used as a preventive tool in prediabetic patients. However, the costs associated with replacing sensors every 15 days and the challenges of effectively interpreting the data remain uncertain for the wide range of people making OTC CGM purchase decisions.
For more information about CGM or related developments, please contact Jamie Ravitz, Paul Gadiock, Ashley Ogedegbe, or any other member of McDermott’s Food, Drug and Medical Device Regulatory Group or Digital Health Group.