PRE-SUBMISSION MEETING PACKAGE
Section 5: Predicate Comparison and Substantial Equivalence Discussion
Solstice Lumina™ CGM System
Pre-Submission (Q-Sub)
Sponsor: Solstice Biomedical Inc. 220 Westbrook Drive, Suite 400 Cambridge, MA 02142
Parent Company: Solstice Biomedical Devices Ltd. Unit 14, Liffey Innovation Park Chapelizod, Dublin D20 FX72, Ireland
Prepared by: Calderwood & Harkness LLP 1401 K Street NW, Suite 900 Washington, D.C. 20005 On behalf of Solstice Biomedical Inc.
Contact Persons:
Dr. Niamh Tierney, VP of Regulatory Affairs Solstice Biomedical Devices Ltd. ntierney@solsticebio.ie
Marcus Hale, VP of U.S. Operations Solstice Biomedical Inc. mhale@solsticebio.com
Miriam Calloway, Responsible Partner Calderwood & Harkness LLP mcalloway@calderwoodharkness.com
Date of Preparation: June 16, 2025 (Target Pre-Submission meeting package submission date)
Intended Recipient: U.S. Food and Drug Administration Center for Devices and Radiological Health (CDRH) Office of Health Technology 2 (OHT2) Division of Chemistry and Toxicology Devices
Target Pre-Submission Meeting Date: August 14, 2025
CONFIDENTIAL — Contains trade secret and commercial confidential information of Solstice Biomedical Inc. and Solstice Biomedical Devices Ltd. Not for public disclosure. Prepared in connection with a Pre-Submission request to the U.S. Food and Drug Administration.
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1. Purpose and Scope
This Section 5 of the Solstice Lumina™ CGM System Pre-Submission (Q-Sub) meeting package presents the predicate device identification, substantial equivalence rationale, and detailed comparative analysis for the Solstice Lumina™ Continuous Glucose Monitoring (CGM) System. The purpose of this section is to provide the U.S. Food and Drug Administration ("FDA" or "Agency") with a comprehensive and transparent discussion of the proposed predicate devices, the regulatory and technical basis for Solstice Biomedical Inc.'s ("Solstice" or "Sponsor") assertion of substantial equivalence, and the supporting analytical framework that will underpin the forthcoming traditional 510(k) submission.
Solstice Biomedical Inc. intends to file a traditional 510(k) premarket notification submission covering both the Lumina C14 implantable sensor and the Lumina R7 wearable reader/transmitter as a single, integrated continuous glucose monitoring system. Both components are designed, manufactured, and intended to function exclusively as an integrated system; accordingly, Solstice proposes to submit a single 510(k) notification encompassing the entire Solstice Lumina™ CGM System rather than separate submissions for each component. This approach is consistent with FDA's treatment of other CGM system submissions under product code QKQ, where the sensor and receiver are evaluated as a unified system.
This predicate comparison and substantial equivalence discussion is submitted to seek FDA feedback on the acceptability of the proposed predicate devices and the substantial equivalence framework prior to the formal 510(k) filing. Solstice's goal in presenting this analysis at the Pre-Submission stage is to identify and resolve any potential concerns regarding the predicate selection, the adequacy of the comparative analysis, or the scope and design of the proposed testing program before committing the substantial resources required for the formal submission. The targeted date for the formal 510(k) submission is April 30, 2026.
The reader is directed to the following additional sections of this Pre-Submission meeting package for further context and supporting information relevant to the substantial equivalence discussion:
• Section 4 — Device Description: Provides a complete technical description of the Solstice Lumina™ CGM System, including detailed specifications, materials, manufacturing, and labeling information.
• Section 6 — Proposed Performance Testing Plan: Sets forth the bench testing, analytical performance testing, and electrical safety and EMC testing protocols that Solstice proposes to include in the 510(k) submission to support substantial equivalence.
• Section 7 — Proposed Clinical Study Protocol Summary: Describes the LUMINA-US clinical study (Protocol SBD-LUM-CL-001), including study design, endpoints, enrollment criteria, and clinical site information.
• Section 8 — Questions for FDA: Presents the specific questions on which Solstice seeks FDA feedback, including questions regarding predicate acceptability, testing sufficiency, iCGM classification pathway eligibility, and IDE exemption status for the proposed clinical study.
2. Regulatory Background
2.1 Applicable Classification and Regulation
The Solstice Lumina™ CGM System is a continuous glucose monitoring system intended for prescription use in adults with diabetes mellitus. Based on its intended use, technological characteristics, and device design, the Lumina CGM System falls within the following regulatory classification:
• Product Code: QKQ — Electrode, Glucose, Subcutaneous
• Regulation Number: 21 C.F.R. § 862.1355 — Glucose test system
• Classification: Class II (Special Controls)
The assignment of product code QKQ and the applicable regulation number 21 C.F.R. § 862.1355 is consistent with FDA's classification of continuous glucose monitoring systems that utilize subcutaneously implanted electrochemical sensors to measure glucose concentrations in interstitial fluid. This classification encompasses CGM systems that include an implantable sensor, a transmitter, and an external reader or display device, which is the configuration of the Solstice Lumina™ CGM System.
Solstice notes that FDA issued an updated reclassification order for continuous glucose monitoring systems effective March 2024. This reclassification order confirmed the Class II status of CGM systems with special controls, and it provided additional clarity regarding the performance and labeling expectations for devices within this classification. The March 2024 reclassification order has direct relevance to the Solstice submission strategy in several respects. First, it reaffirms the appropriateness of the traditional 510(k) pathway for CGM systems classified under product code QKQ and 21 C.F.R. § 862.1355. Second, the reclassification order's special controls identify specific performance expectations — including accuracy metrics, biocompatibility requirements, and software documentation expectations — that inform the scope of the testing program Solstice has designed to support substantial equivalence. Third, the reclassification order's identification of special controls provides a regulatory framework within which the technological differences between the subject device and the predicate devices can be assessed. Solstice has designed its testing program to satisfy the applicable special controls, as discussed in Section 7 of this document and in greater detail in Section 6 (Proposed Performance Testing Plan) of the Pre-Submission package.
In addition to the traditional Class II classification under product code QKQ, Solstice is aware of the integrated CGM (iCGM) classification framework established by FDA under De Novo classification order DEN170088. The iCGM classification provides a distinct regulatory pathway for CGM systems that meet specified accuracy and reliability criteria, enabling secondary display device compatibility without requiring additional premarket review. Solstice's potential interest in the iCGM classification pathway is addressed separately in Section 8 (Questions for FDA) of this Pre-Submission package, where Solstice poses specific questions to FDA regarding iCGM pathway eligibility for the Lumina CGM System. For purposes of this Section 5, the substantial equivalence analysis is presented under the traditional 510(k) framework using product code QKQ and the predicate devices identified below.
2.2 Solstice Regulatory History with FDA
Solstice Biomedical Inc. is a Delaware corporation (Delaware File Number 7834291) and a wholly owned subsidiary of Solstice Biomedical Devices Ltd., an Irish medical device company. Solstice Biomedical Inc. serves as the intended 510(k) holder for the Solstice Lumina™ CGM System and will be the entity responsible for all U.S. regulatory submissions and post-market obligations.
Solstice Biomedical Inc. has prior experience with the FDA premarket review process. On November 14, 2019, FDA cleared Solstice's GlucoStrip RX-200 Test Strip Reader under 510(k) number K192847. The GlucoStrip RX-200 is classified under product code NBW (Chemistry Analyzer, Auto/Discrete, Stand Alone) as a Class II device. The K192847 clearance is cited here for the limited purpose of demonstrating Solstice Biomedical Inc.'s corporate pedigree and its prior history of regulatory engagement with FDA, including demonstrated compliance with applicable quality system regulations (21 C.F.R. Part 820) and premarket notification requirements.
It is important to note that K192847 (GlucoStrip RX-200 Test Strip Reader) is not cited as a predicate device for purposes of the substantial equivalence determination for the Solstice Lumina™ CGM System. The GlucoStrip RX-200 is a fundamentally different device type — a discrete test strip reader that measures glucose from a capillary blood sample applied to a disposable reagent strip — and it is classified under a different product code (NBW vs. QKQ). The GlucoStrip RX-200 does not perform continuous monitoring, does not include an implantable sensor, and does not use electrochemical sensing of interstitial fluid glucose. Accordingly, it is neither technologically comparable nor suitable as a predicate device for the Lumina CGM System.
Beyond its U.S. regulatory history, Solstice Biomedical Devices Ltd. has successfully navigated the European regulatory pathway for the Solstice Lumina™ CGM System. The Lumina CGM System received an EU Medical Device Regulation (MDR) CE certificate, Certificate Number MCA-2024-07319, issued by Meridian Conformity Assessment GmbH (Notified Body 0483) on September 12, 2024. Commercial launch of the Lumina CGM System in the European Union commenced in September 2024, and the system is currently marketed in Germany, Ireland, France, the Netherlands, and Austria. Clinical performance data generated in the EU post-market setting, as well as the CE technical documentation, are available to support the U.S. 510(k) submission as appropriate.
Solstice Biomedical Devices Ltd. holds ISO 13485:2016 certification for the design, development, manufacturing, and distribution of continuous glucose monitoring systems and in vitro diagnostic devices. The ISO 13485:2016 certificate was issued and is maintained by Meridian Conformity Assessment GmbH. The quality management system encompasses the manufacturing facility located in Chapelizod, Dublin, where the Lumina C14 sensor and Lumina R7 reader are manufactured.
3. Identification of Predicate Devices
Solstice has identified two predicate devices — a primary predicate and a secondary predicate (reference device) — to support the substantial equivalence determination for the Solstice Lumina™ CGM System. In addition, Solstice's previously cleared device (K192847) is referenced solely for corporate pedigree purposes. Each device is described below.
3.1 Primary Predicate Device
Device Description Summary: The NovaSense GlucoTrack NX-500 CGM System is an enzymatic electrochemical continuous glucose monitoring system consisting of a subcutaneously implantable sensor with a ten-day (10-day) wear duration, a platinum electrode, Bluetooth Low Energy (BLE) 5.0 data transmission capability, and a handheld receiver/reader device. The NX-500 is intended for continuous glucose monitoring in adults aged 18 years and older with Type 1 or Type 2 diabetes mellitus. The system is intended for prescription use and provides real-time glucose values, trend information, and alert functionality. The sensor measures glucose concentrations in interstitial fluid via an enzymatic electrochemical reaction at the platinum electrode surface, and data is wirelessly transmitted to the handheld receiver at regular intervals. The handheld receiver displays current glucose values and trend arrows, and provides configurable high and low glucose alerts. The NX-500 system also includes connectivity to a companion mobile application for data logging, display, and sharing. Based on publicly available FDA 510(k) summary information, the NX-500's measurement range encompasses glucose values consistent with established CGM performance standards.
Rationale for Selection as Primary Predicate: The NovaSense GlucoTrack NX-500 CGM System (K211034) is selected as the primary predicate device because it shares all of the fundamental regulatory and technological characteristics with the Solstice Lumina™ CGM System. Specifically:
(a) Same Product Code. Both the NX-500 and the Lumina CGM System are classified under product code QKQ (Electrode, Glucose, Subcutaneous).
(b) Same Regulatory Classification. Both devices are classified as Class II medical devices.
(c) Same Regulation Number. Both devices fall under 21 C.F.R. § 862.1355 (Glucose test system).
(d) Same Intended Use. Both devices are intended for continuous glucose monitoring in adults aged 18 years and older with Type 1 or Type 2 diabetes mellitus, for prescription use.
(e) Same Fundamental Technology Type. Both devices employ enzymatic electrochemical sensing of glucose in interstitial fluid via a subcutaneously implanted sensor, with wireless data transmission to an external reader/receiver device. The fundamental scientific principle underlying both devices is the same: an enzyme (glucose oxidase) catalyzes the oxidation of glucose at the electrode surface, generating an electrical signal proportional to glucose concentration, which is then processed by a proprietary algorithm to generate a clinically meaningful glucose value.
The NX-500 represents the foundational predicate against which the Lumina CGM System's substantial equivalence is assessed. While the Lumina system incorporates certain technological enhancements relative to the NX-500 (discussed in detail in Section 6), these differences do not alter the intended use or the fundamental scientific and technological principles of the device.
3.2 Secondary Predicate Device (Reference Device)
Device Description Summary: The NovaSense GlucoTrack NX-700 CGM System is an enhanced enzymatic electrochemical continuous glucose monitoring system that represents a generational advancement of the NX-500 platform. The NX-700 features a subcutaneously implantable sensor with a fourteen-day (14-day) wear duration — a four-day extension compared to its predecessor — BLE 5.0 data transmission, an updated signal processing algorithm, and a handheld receiver. The NX-700 is intended for continuous glucose monitoring in adults aged 18 years and older with Type 1 or Type 2 diabetes mellitus, for prescription use. The NX-700 sensor employs an updated platinum electrode design and utilizes an enhanced version of NovaSense's proprietary glucose prediction algorithm. The handheld receiver provides enhanced alert functionality compared to the NX-500. Mobile application connectivity is included for data display and sharing.
Rationale for Selection as Secondary Predicate (Reference Device): The NovaSense GlucoTrack NX-700 CGM System (K230489) is identified as a secondary predicate device — more precisely, as a reference device — because it provides critical precedential support for several of the technological differences between the Solstice Lumina™ CGM System and the primary predicate (NX-500). The rationale for this selection is as follows:
(a) Same Product Code, Classification, and Intended Use. The NX-700 shares the same product code (QKQ), classification (Class II), regulation number (21 C.F.R. § 862.1355), and intended use (continuous glucose monitoring in adults aged 18+ with T1D or T2D) as both the primary predicate (NX-500) and the Lumina CGM System.
(b) Identical Sensor Wear Duration. The NX-700 features a 14-day sensor wear duration identical to the Lumina C14 sensor. This is the single most significant technological parameter in which the Lumina system differs from the primary predicate NX-500 (which has a 10-day wear duration). The fact that the NX-700 was cleared by FDA with a 14-day wear duration, using the NX-500 (K211034) as its own predicate device, provides direct precedent for FDA's acceptance of the 10-day to 14-day sensor life extension within the QKQ product code family.
(c) Updated Algorithm. The NX-700 incorporates an updated version of NovaSense's proprietary signal processing algorithm compared to the NX-500. The fact that this algorithmic change was accepted by FDA in the K230489 clearance — without the change being deemed to raise a new question of safety or effectiveness — supports the analogous argument that the Lumina CGM System's use of its own proprietary algorithm (LuminaPredict v2.1) does not, by itself, raise a different question of safety or effectiveness.
(d) Established Clearance Chain. The NX-700 was cleared using the NX-500 (K211034) as its predicate device, thereby establishing a continuous clearance chain from K211034 through K230489. Solstice proposes to extend this clearance chain by citing K211034 as the primary predicate and K230489 as a secondary predicate/reference device for the Lumina CGM System.
3.3 Additional Reference Device (Corporate Pedigree Only)
Note: The GlucoStrip RX-200 Test Strip Reader (K192847) is referenced in this Pre-Submission package solely to demonstrate Solstice Biomedical Inc.'s prior engagement with the FDA premarket review process and its established track record of regulatory compliance. The GlucoStrip RX-200 is not cited as a predicate device for purposes of the substantial equivalence determination for the Solstice Lumina™ CGM System. The GlucoStrip RX-200 is a different device type (a discrete test strip reader that measures glucose from a capillary blood sample using a disposable reagent strip) classified under a different product code (NBW) with fundamentally different technology (no continuous monitoring, no implantable sensor, no interstitial fluid measurement, no wireless data transmission). It would not be appropriate to use the GlucoStrip RX-200 as a predicate for a CGM system, and Solstice does not propose to do so.
4. Subject Device Overview
4.1 Intended Use
The Solstice Lumina™ CGM System is intended for continuous glucose monitoring in persons aged 18 years and older with Type 1 or Type 2 diabetes mellitus. The system is intended for prescription use only.
The Solstice Lumina™ CGM System continuously measures glucose levels in interstitial fluid via a subcutaneously implanted enzymatic electrochemical sensor (the Lumina C14). Glucose data is wirelessly transmitted from the C14 sensor to the Lumina R7 wearable reader/transmitter device, which displays real-time glucose values, trend information, and alerts. The R7 reader/transmitter also communicates with the Solstice Lumina™ companion mobile application (available for iOS and Android platforms) to enable extended data display, logging, sharing, and remote monitoring functionality.
Key intended use parameters include:
• Intended Patient Population: Adults aged 18 years and older diagnosed with Type 1 or Type 2 diabetes mellitus
• Use Environment: Prescription use; home and ambulatory settings
• Measurement Range: 40–400 mg/dL
• Sensor Wear Duration: 14 days (336 hours) per sensor
• Monitoring Mode: Continuous (readings at regular intervals throughout the sensor wear period)
The Solstice Lumina™ CGM System is not intended for use in making treatment decisions without confirmation by a standard laboratory glucose measurement. The system is not intended for use in pediatric patients (under age 18), pregnant women, or persons on dialysis. These limitations are consistent with the intended use parameters of the predicate devices.
4.2 Device Components
The Solstice Lumina™ CGM System consists of the following components:
Lumina C14 Implantable Sensor. The Lumina C14 is a fourth-generation enzymatic electrochemical biosensor designed for subcutaneous implantation in the posterior upper arm. The sensor employs a proprietary platinum-iridium (PtIr-4G) electrode coating designed to optimize signal stability and reduce signal drift over the full 14-day wear period. The C14 sensor is inserted using a disposable, single-use applicator device. Once inserted, the sensor measures glucose concentration in interstitial fluid via an enzymatic reaction (glucose oxidase) at the electrode surface, generating an electrical signal proportional to glucose concentration. The C14 sensor communicates wirelessly with the R7 reader/transmitter via Bluetooth Low Energy (BLE) 5.2. The sensor requires a warm-up period of 60 minutes or less following insertion before it begins providing glucose readings. The sensor has a designated functional life of 14 days (336 hours), after which it is removed and disposed of. The C14 sensor is a single-use, disposable device. It is sterilized prior to packaging and distribution.
Lumina R7 Wearable Reader/Transmitter. The Lumina R7 is an arm-worn, integrated reader/transmitter device. The R7 is worn on the upper arm, secured by an adjustable, hypoallergenic adhesive band. The R7 receives glucose data from the C14 sensor via BLE 5.2 and provides the following user-facing functionality:
• Display of real-time glucose values on an integrated OLED screen
• Trend arrow display indicating the rate and direction of glucose change
• Eight-hour (8-hour) trend graphs for visual assessment of glucose patterns
• Configurable hypoglycemia and hyperglycemia alert thresholds with audible, vibration, and visual alert modalities
• Alert latency of five minutes (≤ 5 minutes) or less from sensor reading to user notification
• Communication with the Solstice Lumina™ mobile application (iOS and Android) via BLE for extended data display, logging, sharing, and remote monitoring
The R7 reader/transmitter is a reusable device with a rechargeable battery. It is not implanted; it contacts the skin of the upper arm.
Solstice Lumina™ Mobile Application. The Solstice Lumina™ mobile application is a companion software application compatible with iOS and Android mobile operating systems. The mobile application receives glucose data from the R7 reader/transmitter via BLE and provides the following functionality: real-time glucose value display, trend graphs, historical data review, data export, and optional data sharing with healthcare providers and designated contacts. The mobile application is version 1.0.3 at the time of this Pre-Submission package.
Software Versions. The following software versions are applicable to the Solstice Lumina™ CGM System as of the date of this Pre-Submission package:
A complete technical description of the Solstice Lumina™ CGM System, including materials of construction, manufacturing processes, packaging, labeling, and detailed specifications, is provided in Section 4 (Device Description) of this Pre-Submission package.
4.3 Intended Use Comparison
The intended use of the Solstice Lumina™ CGM System is the same as the intended use of both the primary predicate device (NovaSense GlucoTrack NX-500 CGM System, K211034) and the secondary predicate device (NovaSense GlucoTrack NX-700 CGM System, K230489). All three devices are intended for continuous glucose monitoring in adults aged 18 years and older with Type 1 or Type 2 diabetes mellitus. All three devices are indicated for prescription use only.
All three devices share the following regulatory identifiers:
• Product Code: QKQ (Electrode, Glucose, Subcutaneous)
• Classification: Class II (Special Controls)
• Regulation Number: 21 C.F.R. § 862.1355 (Glucose test system)
There is no difference in the intended use, indications for use, or intended patient population between the subject device and either predicate device. The substantial equivalence analysis therefore proceeds to a comparison of technological characteristics, as set forth in Sections 5 and 6 below.
5. Substantial Equivalence Comparison Table
5.1 Side-by-Side Comparison Matrix
The following comprehensive comparison table presents a detailed side-by-side comparison of the key characteristics and parameters of the subject device (Solstice Lumina™ CGM System), the primary predicate device (NovaSense GlucoTrack NX-500, K211034), and the secondary predicate device (NovaSense GlucoTrack NX-700, K230489). This comparison matrix is organized by parameter category and is intended to facilitate FDA's assessment of substantial equivalence.
Where information regarding the predicate devices is drawn from publicly available FDA 510(k) summary databases, decision summaries, or published labeling, this is noted. Where specific predicate device parameters are not publicly available and are subject to confirmation, this is also noted.
Cells in bold in the "Subject Device" column indicate parameters where a technological difference relative to the primary predicate has been identified. These differences are discussed in detail in Section 6 below.
As reflected in the comparison matrix, the Solstice Lumina™ CGM System and the predicate devices share the same intended use, product code, classification, regulation number, sensor type, fundamental sensing technology (enzymatic electrochemical), implantation site (subcutaneous), measurement range, and general functional architecture (implantable sensor transmitting data wirelessly to an external reader with alert functionality and mobile application connectivity). The five identified areas of technological difference — sensor wear duration, electrode material, BLE version, reader form factor, and glucose prediction algorithm — are discussed in Section 6.
6. Discussion of Technological Differences and Substantial Equivalence
6.1 Overview of Analytical Framework
The legal standard for substantial equivalence is set forth in Section 513(i) of the Federal Food, Drug, and Cosmetic Act (FD&C Act), 21 U.S.C. § 360c(i), and implemented through the regulations at 21 C.F.R. § 807.100. Under this framework, a new device may be found substantially equivalent to a legally marketed predicate device if the new device:
(a) Has the same intended use as the predicate device; and
(b) Has the same technological characteristics as the predicate device; or
(c) Has different technological characteristics from the predicate device, but the information submitted to FDA demonstrates that the new device is as safe and effective as the predicate device and does not raise different questions of safety and effectiveness than the predicate device.
Where the subject device has different technological characteristics from the predicate, the applicant must demonstrate through appropriate performance data — which may include bench testing, preclinical testing, and/or clinical data — that the differences do not adversely affect safety or effectiveness and do not raise new questions of safety or effectiveness that cannot be resolved through the data submitted. FDA evaluates whether the differences could significantly affect safety or effectiveness and whether the submitted data adequately addresses any such questions.
Application to the Solstice Lumina™ CGM System. As established in Sections 4.3 and 5.1, the Solstice Lumina™ CGM System has the same intended use as both the primary predicate device (NovaSense GlucoTrack NX-500, K211034) and the secondary predicate device (NovaSense GlucoTrack NX-700, K230489). There is no difference in intended use, indications for use, or intended patient population. The analysis therefore turns to technological characteristics.
Solstice acknowledges that the Lumina CGM System has certain technological differences from the primary predicate device (K211034). Specifically, Solstice has identified five areas of technological difference between the Lumina CGM System and the NX-500:
1. Sensor wear duration (14 days vs. 10 days)
2. Electrode material (platinum-iridium PtIr-4G vs. platinum)
3. Wireless communication protocol version (BLE 5.2 vs. BLE 5.0)
4. Reader form factor (arm-worn vs. handheld)
5. Glucose prediction/processing algorithm (LuminaPredict v2.1 vs. NovaSense proprietary algorithm)
Solstice respectfully submits that none of these differences raise new or different questions of safety or effectiveness that cannot be resolved through the proposed performance testing, biocompatibility testing, and clinical data. Each difference is analyzed individually in Sections 6.2 through 6.6 below. For each difference, Solstice demonstrates that the difference either:
(i) Is already represented in the cleared secondary predicate device (NX-700, K230489), providing direct regulatory precedent for FDA acceptance of the difference within the same product code and classification;
(ii) Does not raise new questions of safety or effectiveness because it involves a well-characterized, incremental variation of established technology; or
(iii) Can be fully addressed through the performance testing and/or clinical data that Solstice proposes to include in the 510(k) submission.
In most instances, more than one of the above factors applies to a given difference, strengthening the overall substantial equivalence argument.
6.2 Difference 1: Sensor Wear Duration (14 Days vs. 10 Days)
Description of Difference. The Lumina C14 implantable sensor has a designated sensor wear duration of 14 days (336 hours), compared to the primary predicate NX-500's 10-day sensor wear duration. This represents a four-day (40%) extension of the sensor's functional life.
Mitigating Analysis.
The extension of the sensor wear duration from 10 days to 14 days is directly supported by the clearance history of the secondary predicate device, the NovaSense GlucoTrack NX-700 (K230489), which was cleared by FDA on March 7, 2024, with an identical 14-day sensor wear duration. Critically, the NX-700 was itself cleared using the NX-500 (K211034) as its predicate device. FDA's clearance of K230489 therefore establishes, as a matter of regulatory precedent within the QKQ product code and 21 C.F.R. § 862.1355 classification, that the extension of sensor wear duration from 10 days to 14 days does not, in and of itself, raise a different question of safety or effectiveness that is incompatible with a substantial equivalence finding.
Moreover, the 14-day sensor wear duration is well established in the broader CGM device class. FDA has cleared multiple CGM systems from various manufacturers with 14-day or longer sensor functional lives. The 14-day wear period has become a standard benchmark in the CGM industry, and the safety and effectiveness of sensors designed for this duration have been well characterized through both premarket clinical studies and extensive post-market surveillance data.
Notwithstanding the strong precedential support for the 14-day wear duration, Solstice recognizes that the specific design and materials of the Lumina C14 sensor differ from the NX-700 sensor and that independent performance validation is required. Accordingly, Solstice will provide the following data in the 510(k) submission to support the 14-day wear duration of the Lumina C14 sensor:
(a) Sensor Accuracy Over Full Wear Period. Performance data from the planned LUMINA-US clinical study (Protocol SBD-LUM-CL-001) demonstrating sensor accuracy (MARD ≤ 9.0%) and stability over the full 14-day wear period, including specific analysis of performance during days 11 through 14 to demonstrate that no clinically meaningful degradation in accuracy occurs during the extended wear period relative to the primary predicate's 10-day duration.
(b) Bench Testing of Sensor Functional Life. In vitro sensor functional life testing over 336 hours, including evaluation of signal drift, sensitivity stability, and electrode integrity over the full wear duration, under simulated physiological conditions.
(c) Biocompatibility Testing. Biocompatibility testing designed to assess tissue response over the full 14-day implantation period, including subchronic toxicity testing per ISO 10993-11 and implantation testing per ISO 10993-6. The subchronic toxicity testing protocol is designed with a 14-day exposure duration corresponding to the maximum sensor wear period.
Conclusion. The extension of the sensor wear duration from 10 days to 14 days does not raise new or different questions of safety or effectiveness. This conclusion is supported by the direct precedent of K230489 (NX-700, 14-day wear duration cleared using K211034 as predicate), by the broader regulatory landscape of cleared 14-day CGM systems, and by the comprehensive testing program Solstice proposes to validate the C14 sensor's performance and biocompatibility over the full 14-day wear period.
6.3 Difference 2: Electrode Material (Platinum-Iridium vs. Platinum)
Description of Difference. The Lumina C14 sensor employs a proprietary platinum-iridium (PtIr-4G) electrode coating, whereas the primary predicate NX-500 uses a platinum electrode. The PtIr-4G coating is a Solstice-proprietary electrode architecture that incorporates iridium into a platinum-based electrode matrix to enhance electrode stability, improve signal-to-noise ratio, and reduce signal drift over the extended 14-day sensor wear period.
Mitigating Analysis.
Platinum-iridium alloys are well-characterized, biocompatible materials with a long and well-documented history of use in implantable medical devices. Both platinum and iridium are noble metals of the platinum group, and their alloys are widely used in cardiovascular applications (e.g., pacemaker electrodes, defibrillator electrodes), neurostimulation applications (e.g., deep brain stimulation electrodes, spinal cord stimulation electrodes), and other implantable device applications where long-term biocompatibility, corrosion resistance, and electrochemical stability are critical. The biocompatibility profile of platinum-iridium alloys is extensively documented in the scientific literature and in FDA-cleared device submissions across multiple product codes and device classifications.
The PtIr-4G coating does not alter the fundamental enzymatic electrochemical sensing mechanism that underlies the Lumina CGM System. The sensing principle — enzymatic oxidation of glucose at the electrode surface generating an electrical signal proportional to glucose concentration — remains identical to that of the predicate devices. The PtIr-4G coating is a materials optimization at the electrode surface level; it does not change the type of energy used (electrochemical), the biological substrate measured (interstitial fluid glucose), or the physical principle of transduction (amperometric measurement of current generated by enzymatic reaction).
It is worth noting that the secondary predicate NX-700 (K230489) is described in publicly available FDA summary information as featuring an "updated" platinum electrode design. While the specific nature of the NX-700 electrode update is not publicly disclosed, the precedent of FDA accepting electrode material modifications within the QKQ product code further supports the position that incremental electrode material changes do not raise new questions of safety or effectiveness where the fundamental sensing mechanism is unchanged.
To fully validate the safety and biocompatibility of the PtIr-4G electrode coating, Solstice will provide the following data in the 510(k) submission:
(a) Full Biocompatibility Testing Battery. Comprehensive biocompatibility evaluation of the Lumina C14 sensor (including the PtIr-4G electrode coating) per ISO 10993-1:2018, conducted at Whitmore Laboratories Inc. (A2LA Certificate No. 3847.01). The testing battery includes:
• Cytotoxicity testing per ISO 10993-5
• Sensitization testing per ISO 10993-10
• Irritation testing per ISO 10993-23
• Acute systemic toxicity testing per ISO 10993-11
• Subchronic toxicity testing per ISO 10993-11 (14-day exposure)
• Implantation testing per ISO 10993-6 (14-day implantation)
• Hemocompatibility testing per ISO 10993-4
• Genotoxicity testing per ISO 10993-3
(b) Bench Performance Testing. Bench testing comparing the analytical performance of the PtIr-4G electrode to the platinum electrode across the full measurement range of 40–400 mg/dL, including sensitivity, linearity, precision, and interference susceptibility. This testing will demonstrate that the PtIr-4G electrode meets or exceeds the analytical performance of the platinum electrode in the predicate devices.
(c) Signal Stability and Drift Testing. In vitro testing demonstrating the signal stability and drift characteristics of the PtIr-4G electrode over the full 14-day (336-hour) sensor functional life under simulated physiological conditions.
Conclusion. The change in electrode material from platinum to platinum-iridium (PtIr-4G) does not alter the intended use, the fundamental sensing technology, or the type of energy employed. The PtIr-4G coating represents a materials optimization using well-established biocompatible noble metals with an extensive track record in implantable medical devices. This difference will be supported by comprehensive biocompatibility testing and performance data demonstrating equivalent or superior safety and effectiveness compared to the predicate device's platinum electrode.
6.4 Difference 3: Bluetooth Low Energy Version (BLE 5.2 vs. BLE 5.0)
Description of Difference. The Solstice Lumina™ CGM System uses Bluetooth Low Energy (BLE) version 5.2 for wireless communication between the C14 sensor and the R7 reader/transmitter, whereas both the NX-500 (primary predicate) and NX-700 (secondary predicate) use BLE version 5.0.
Mitigating Analysis.
BLE 5.2 is a backward-compatible evolution of the BLE 5.0 standard, as specified by the Bluetooth Special Interest Group (Bluetooth SIG). Both BLE 5.0 and BLE 5.2 operate within the same fundamental communication framework: they utilize the same 2.4 GHz Industrial, Scientific, and Medical (ISM) frequency band; they employ the same basic modulation scheme (Gaussian Frequency-Shift Keying, GFSK); and they share the same overall protocol stack architecture. BLE 5.2 introduces incremental enhancements including improved audio capabilities (LE Audio), enhanced attribute protocol features, and power control improvements. These enhancements are primarily beneficial for medical device applications in that they offer improved power efficiency and more stable connection management, both of which are desirable characteristics for a continuously operating medical device with battery life constraints.
The evolution from BLE 5.0 to BLE 5.2 does not introduce new types of wireless communication risks. The radio frequency (RF) emission characteristics, the potential for electromagnetic interference (EMI), and the cybersecurity considerations associated with BLE 5.2 are fundamentally the same as those associated with BLE 5.0. BLE 5.2 maintains backward compatibility with BLE 5.0, confirming that the two protocol versions are members of the same protocol family and represent an incremental, well-understood technological progression.
FDA has consistently accepted protocol version upgrades within the Bluetooth standard — and within other wireless communication standards — in cleared medical device submissions without treating such upgrades as raising new questions of safety or effectiveness. The evolution from BLE 5.0 to BLE 5.2 is analogous to firmware or protocol updates within the same protocol family and is well within the range of variations accepted by FDA in the CGM and broader medical device context.
Notwithstanding the incremental nature of this difference, Solstice will provide the following data in the 510(k) submission:
(a) Electromagnetic Compatibility (EMC) Testing. Full EMC testing per IEC 60601-1-2 (Edition 4.1), conducted at Whitmore Laboratories Inc., demonstrating that the Lumina CGM System (including BLE 5.2 wireless communication) complies with applicable EMC emissions and immunity standards and does not create unacceptable electromagnetic interference risks.
(b) Wireless Coexistence Testing. Testing to demonstrate that the BLE 5.2 communication between the C14 sensor and the R7 reader operates reliably in the presence of other wireless devices and signals in the intended use environment.
(c) Cybersecurity Documentation. Comprehensive cybersecurity documentation per the FDA guidance document "Cybersecurity in Medical Devices: Quality System Considerations and Content of Premarket Submissions" (September 2023), addressing the BLE 5.2 communication link. This documentation will include a Software Bill of Materials (SBOM), threat modeling per the STRIDE framework (Spoofing, Tampering, Repudiation, Information Disclosure, Denial of Service, Elevation of Privilege), vulnerability assessment, and a description of security controls implemented in the BLE 5.2 communication protocol (including encryption, authentication, and secure pairing mechanisms).
Conclusion. The incremental upgrade from BLE 5.0 to BLE 5.2 does not raise different questions of safety or effectiveness. BLE 5.2 is a backward-compatible evolution of the same wireless protocol used in both predicate devices. The difference will be fully addressed through EMC testing, wireless coexistence testing, and comprehensive cybersecurity documentation.
6.5 Difference 4: Reader Form Factor (Arm-Worn vs. Handheld)
Description of Difference. The Lumina R7 is an arm-worn, integrated reader/transmitter device designed to be worn continuously on the upper arm, whereas the NX-500 and NX-700 both use a handheld receiver form factor that the user carries separately.
Mitigating Analysis.
The change from a handheld receiver to an arm-worn reader/transmitter is a user-interface and industrial design variation that does not alter the fundamental function or technological purpose of the reader component. Both the R7 arm-worn device and the predicate handheld receivers perform the same core functions:
• Receiving glucose data from the implanted sensor via BLE wireless communication
• Processing and displaying real-time glucose values
• Displaying trend information (trend arrows and trend graphs)
• Generating configurable hypoglycemia and hyperglycemia alerts
• Communicating with a companion mobile application for extended data display and sharing
The arm-worn form factor is an ergonomic and usability-driven design choice. The rationale for the arm-worn design is to improve continuous wearability, reduce the risk of missed alerts (by ensuring the reader is always on the user's body rather than potentially left in a bag, on a table, or in another room), and provide a more seamless, integrated user experience. The arm-worn design places the R7 reader in close and consistent proximity to the C14 sensor (which is also implanted in the upper arm), potentially improving wireless communication reliability.
Because the Lumina R7 is worn on the skin of the upper arm for extended periods, it introduces a skin-contact consideration that is not present (or is present to a lesser degree) with a handheld receiver. To address this, Solstice will conduct biocompatibility testing for the R7 reader consistent with FDA expectations for skin-contacting wearable devices:
(a) R7 Biocompatibility Testing. The external surfaces of the R7 reader that contact the skin will be evaluated per ISO 10993-1:2018 for the following endpoints, consistent with the device's classification as a surface-contacting device with prolonged skin contact:
• Cytotoxicity per ISO 10993-5
• Sensitization per ISO 10993-10
• Irritation per ISO 10993-23
(b) Human Factors and Usability Testing. Solstice will conduct human factors and usability studies per FDA guidance "Applying Human Factors and Usability Engineering to Medical Devices" (February 2016) and related guidance documents. The human factors program will evaluate the safety and effectiveness of the arm-worn R7 design for the intended user population, including assessment of:
• Application, wearing, and removal of the R7 device
• Interpretation of glucose readings, trend arrows, and trend graphs displayed on the R7 screen
• Response to and management of hypoglycemia and hyperglycemia alerts
• Identification and mitigation of potential use errors associated with the arm-worn form factor
• Use environment considerations (e.g., wearing during sleep, exercise, bathing)
(c) Alert Latency Validation. Performance testing will validate that the alert latency requirement (≤ 5 minutes from sensor reading to user notification on the R7 device) is met under representative use conditions, confirming that the arm-worn form factor does not introduce unacceptable delays in alert delivery.
Conclusion. The arm-worn reader form factor does not raise new or different questions of safety or effectiveness. It represents a design variation within the same device functionality — data reception, glucose display, and alert generation — that will be supported by biocompatibility testing, comprehensive human factors data, and alert latency validation. The core technological function of the reader is unchanged.
6.6 Difference 5: Glucose Prediction/Processing Algorithm (LuminaPredict v2.1 vs. NovaSense Algorithm)
Description of Difference. The Solstice Lumina™ CGM System uses Solstice's proprietary glucose prediction and signal processing algorithm, LuminaPredict v2.1, to convert raw electrochemical sensor signals into clinically meaningful glucose values, generate trend data, and trigger hypoglycemia and hyperglycemia alerts. The LuminaPredict v2.1 algorithm is distinct from the NovaSense proprietary algorithms used in the NX-500 (primary predicate) and the NX-700 (secondary predicate).
Mitigating Analysis.
The use of different proprietary signal processing and glucose prediction algorithms by different CGM manufacturers is an inherent and expected feature of the CGM device class. Each CGM manufacturer develops proprietary algorithms optimized for its specific sensor design, electrode characteristics, and signal profile. FDA has consistently cleared CGM devices from multiple manufacturers — each using different proprietary algorithms — where the performance output (glucose accuracy as measured by MARD, consensus error grid performance, alert sensitivity and specificity) meets applicable performance standards. The use of a different algorithm does not, in and of itself, constitute a different question of safety or effectiveness; rather, it is the clinical performance of the algorithm — its accuracy and reliability in converting sensor signals to glucose values — that determines safety and effectiveness.
This principle is directly reinforced by the clearance history of the secondary predicate device. The NX-700 (K230489) incorporates an "updated" version of the NovaSense proprietary algorithm compared to the NX-500 (K211034). The NX-700 was cleared by FDA using the NX-500 as its predicate, indicating that the algorithmic update did not raise a different question of safety or effectiveness. If an algorithmic change within the same manufacturer's product line does not raise such questions, then the use of a different manufacturer's algorithm — which serves the same functional purpose and will be validated to the same or more rigorous performance standards — should similarly not raise different questions of safety or effectiveness.
The LuminaPredict v2.1 algorithm serves the identical functional purpose as the predicate algorithms: it receives raw electrical signals from the electrochemical sensor, applies signal conditioning and noise filtering, calibrates the processed signal against reference glucose values, generates clinically meaningful glucose concentration values, computes trend direction and rate of change, and triggers alerts when configured glucose thresholds are crossed. There is no difference in the functional role or intended output of the algorithm.
Solstice will provide the following comprehensive data in the 510(k) submission to validate the performance of the LuminaPredict v2.1 algorithm:
(a) Software Level of Concern. The Software Level of Concern for the Lumina CGM System is designated as Major, consistent with the FDA software classification framework and consistent with the level of concern assigned to predicate CGM devices. This designation reflects the potential for the software to contribute to a hazardous situation (e.g., display of an inaccurate glucose value that could lead to inappropriate insulin dosing).
(b) IEC 62304 Software Lifecycle Documentation. Full software lifecycle documentation per IEC 62304:2006/A1:2015, including software requirements specifications, software architecture and design documents, software verification test reports, and software validation documentation.
(c) Clinical Validation of Algorithm Performance. Clinical validation of the LuminaPredict v2.1 algorithm will be performed through the LUMINA-US clinical study (Protocol SBD-LUM-CL-001). The primary endpoint is a system-level MARD of ≤ 9.0%, and the secondary endpoint includes ≥ 99% of paired data points in Zones A and B of the Clarke Error Grid (and/or the Consensus Error Grid, as applicable). These endpoints are consistent with or more stringent than applicable FDA performance expectations for CGM systems under product code QKQ.
(d) Algorithm Verification and Validation Testing. Comprehensive verification and validation testing of the LuminaPredict v2.1 algorithm, including edge case analysis (e.g., algorithm performance at the extremes of the measurement range, during rapid glucose excursions, and during known interference conditions), robustness testing, and regression testing.
(e) SBOM and Cybersecurity Documentation. A Software Bill of Materials (SBOM) and cybersecurity threat model per the STRIDE framework will be provided, addressing the algorithm software as well as all other software components of the Lumina CGM System.
Conclusion. The use of a different proprietary glucose prediction and signal processing algorithm does not raise new or different questions of safety or effectiveness. Different algorithms are inherent to the CGM device class, and FDA has consistently cleared CGM devices with proprietary algorithms where performance is validated through appropriate bench and clinical testing. The precedent of K230489 (NX-700 with updated algorithm cleared on predicate K211034) further supports this conclusion. The LuminaPredict v2.1 algorithm will be comprehensively validated through software lifecycle documentation, algorithm verification and validation, and clinical accuracy data from the LUMINA-US study demonstrating performance equivalent to or exceeding that of the predicate devices.
7. Summary of Proposed Testing to Support Substantial Equivalence
The following subsections provide a high-level summary of the testing program that Solstice proposes to conduct in support of the substantial equivalence determination for the Solstice Lumina™ CGM System. Detailed test protocols and study plans are presented in Section 6 (Proposed Performance Testing Plan) and Section 7 (Proposed Clinical Study Protocol Summary) of this Pre-Submission package. The purpose of summarizing the testing program here is to demonstrate to FDA that each identified technological difference between the subject device and the predicate devices will be addressed through appropriate and comprehensive data.
7.1 Performance/Bench Testing
Solstice proposes to conduct the following bench and analytical performance testing to support the 510(k) submission:
• Sensor Accuracy Testing (In Vitro). In vitro analytical accuracy testing of the Lumina C14 sensor across the full measurement range of 40–400 mg/dL, including assessment of linearity, sensitivity, and measurement bias at specified glucose concentrations.
• Sensor Accuracy Testing (In Vivo). In vivo sensor accuracy will be assessed as part of the LUMINA-US clinical study (Protocol SBD-LUM-CL-001; see Section 7.5 below), with the primary endpoint of system-level MARD ≤ 9.0%.
• Sensor Precision Testing. Evaluation of within-sensor and between-sensor precision (repeatability and reproducibility) across the measurement range.