Overview
On March 5, 2024, the US Food and Drug Administration (FDA) granted clearance to market the first over-the-counter (OTC) continuous glucose monitor (CGM). Dexcom’s Stelo Glucose Biosensor System (Stelo) is an integrated CGM (iCGM) designed for individuals 18 years and older who do not use insulin. Previously, CGMs were only available by prescription and were primarily designed for diabetes management. However, CGMs may offer a new avenue for wellness, proactive health monitoring and accessibility to chronic care management – all without a prescription.
In Depth
UNDERLYING TECHNOLOGY
A Brief History of CGMs
A CGM is a wearable technology that enables users to track their blood sugar levels in real time. Historically, individuals with Type 1 or Type 2 diabetes could monitor their blood sugar levels with fingerstick checks. Individuals would prick their fingertips with a small lancet (i.e., a needle) to produce a blood sample. When a blood sample contacts a glucose meter test strip, the meter promptly displays a blood sugar reading. This information helps determine whether glucose levels are too low or too high, which is particularly useful after meals or when taking medications. However, fingerstick checks have several downsides. For example, they provide static reads, meaning individuals must take frequent samples throughout the day to comprehensively measure their blood sugar levels. Additionally, fingerstick checks can be cumbersome and painful.
CGMs, in contrast, produce reads every five to 15 minutes without any intervention by the user. While CGMs are not new as the FDA first approved them in 1999, Stelo is the first of its kind to be cleared as an OTC device.
The Stelo Glucose Biosensor System
Stelo is an OTC CGM that detects glucose levels from the user’s interstitial fluid, which is the fluid just beneath the skin. It calculates glucose readings and provides this information to the user’s digitally connected device, such as a smartphone or smartwatch. However, it is not intended to be paired with insulin devices, such as insulin pens or automated insulin dosing systems.
Dexcom leveraged the same principles of operation, fundamental design and physical characteristics for Stelo from its most recent G7 CGM system (Predicate Device). The Predicate Device is also an iCGM, but it requires a prescription. Stelo is an OTC advancement that is authorized for marketing via a 510(k) application that was supported, in part, by human factors validation data.
Stelo consists of the following two subsystems:
1. Glucose Sensing Subsystem: Wearable and Applicator
For CGMs, the sensor serves a similar role to the lancet in fingerstick checks. Users insert the small, flexible wire sensor just beneath the skin on the back of the arm using an applicator. An overpatch adhesive secures the sensor in place. The sensor continuously measures glucose levels in the interstitial fluid and converts them into an electric current. The transmitter measures this current and converts it into estimated glucose values, which are then sent to the user’s mobile application.
2. Mobile Applications Subsystem: iOS and Android Mobile Application (App)
The App provides user and onboarding tutorials and updates the user on system status (e.g., warm-up period and signal loss), glucose readings and trend graphs.
Comparison to the Predicate Device
Stelo has the same hardware design as the Predicate Device (e.g., same sensor, patch, applicator and transmitter hardware). Additionally, Stelo’s transmitter firmware has the same primary responsibilities and capabilities as the Predicate Device but deviates notably by supporting extended wear for 15 days compared to 10 days. Users also cannot manually enter their blood glucose levels in 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 (e.g., mobile phones and smartwatches). The App inherited the Predicate Device app’s software development kit, functionality and user interface. However, the Stelo System App deviates from its predecessor in a few ways, notably sending read updates to the App every five minutes, with updated App entries every 15 minutes. Individuals also receive tailored onboarding and “insights,” aka daily reports summarizing glucose levels and sharing related wellness tips.
OTC CGMs and Beyond
The FDA’s clearance of the first OTC CGM paves the way for future devices beyond diabetes management and allows individuals to monitor meaningful health data without a prescription. For example, we may see OTC CGMs trend in the fitness industry. OTC CGMs provide real-time data, allowing individuals to understand how their bodies react to workouts and meal plans. This information can guide nutrition choices, optimize workouts and prevent extreme blood sugar fluctuations. Moreover, OTC CGMs may be used as a preventative tool for those with prediabetes. However, the costs related to replacing sensors every 15 days and the challenge of effectively interpreting the data remains uncertain for the broader population who decide to purchase OTC CGMs.
For more information on CGMs or related developments, contact Jamie Ravitz, Paul Gadiock, Ashley Ogedegbe or any other member of McDermott’s Food, Drug & Medical Device Regulatory Group or Digital Health Group.
