Findings
The quality of evidence for the analytical validation of sensor-based digital health technologies (sDHTs), which is the evaluation of algorithms converting sensor data into a clinically interpretable measure, is often inconsistent and insufficient. The existing V3+ framework codifies the overall evaluation process, which includes verification, usability validation, analytical validation, and clinical validation. To improve the scientific rigor of analytical validation, a hierarchical framework for selecting reference measures is needed because not all potential reference measures are of equal quality. The framework classifies reference measures based on attributes that contribute to reduced measurement variability, with defining and principal measures being the most rigorous due to objective data acquisition and the ability to retain source data.

Recommendations
The proposed framework sequentially moves the investigator through four steps: (1) Compile preliminary information, including the digital clinical measure, context of use (COU), algorithm requirements, and sensor verification evidence . (2) Select an existing reference measure, develop a novel comparator, or identify a set of anchor measures, prioritizing measures with the highest scientific rigor (defining → principal → manual → reported) . (3) Consider the impact of the data collection environment to determine if the analytical validation study can be conducted in the intended use environment with the highest-order measure, or if in-lab validation is necessary, ensuring the results are generalizable . (4) Describe the rationale for key study design decisions to encourage transparency for evaluators, regulators, and payers . Investigators must justify passing over a higher-ranked reference measure, generally only acceptable if the higher-ranked measure poses unacceptable risk or is not applicable to the context of use.

Regulatory Considerations
The principles of the framework for analytical validation apply regardless of the regulatory status of the sDHT (regulated medical device, low-risk general wellness apps, or research product) or its intended use (clinical care or clinical research). The framework is intended to help investigators support the most rigorous claims regarding sDHT performance, which is important for acceptance by evaluators, peer-reviewers, regulators, and payers. The categorization of the digital clinical measure as a digital biomarker or an electronic clinical outcome assessment also does not change the framework's applicability.

Findings
In a progressive neurodegenerative illness like Alzheimer's disease, slowing the rate of disease progression is considered a clinically meaningful outcome for patients and their caregivers.
The assessment of what constitutes a clinical benefit is highly dependent on the specific stage of AD being studied, the drug's mechanism of action, and the symptoms present in that patient population.
Direct input from patients and caregivers is critical for understanding disease burden and defining treatment benefits that are truly meaningful from their perspective.
The interpretation of score changes on Clinical Outcome Assessments (COAs) requires full context; an absolute point difference must be considered relative to the study's duration, the expected placebo decline, and the specific disease stage.
Evidence from biomarkers that show an effect on underlying disease pathology provides additional support and increases the persuasiveness of the changes observed on clinical endpoints.

Recommendations
Drug developers should implement multiple "fit-for-purpose" COAs that use different reporters (e.g., clinicians, observers) and methods to generate broad and diverse evidence of a drug's clinical benefit.
Sponsors should utilize both qualitative and quantitative methodologies to explore clinical meaningfulness, including assessing "meaningful within-patient change" throughout the development process.
Developers are encouraged to create and validate new COAs and leverage innovative approaches, such as digital health technologies, to better capture concepts that are relevant to patients, especially in the earliest stages of AD.
Throughout the drug development lifecycle, stakeholders should systematically collect and incorporate patient experience data to ensure that the perspectives, needs, and priorities of patients are meaningfully captured.

Regulatory Considerations
For a drug to gain approval, it must meet the regulatory standard of "substantial evidence of effectiveness," which is typically derived from adequate and well-controlled investigations designed to minimize bias.
The FDA defines clinical benefit as a clinically meaningful effect of a drug on how an individual feels, functions, or survives.
An assessment of clinical benefit is not limited to the primary endpoint; the consistency of findings across multiple endpoints (primary and secondary) is a key consideration during regulatory review.
The accelerated approval pathway may be used for serious conditions with unmet needs based on a surrogate endpoint, but traditional approval requires verification of clinical benefit in confirmatory trials.
The FDA's evaluation includes a benefit-risk analysis, which considers the severity of the disease and the availability of alternative therapies, recognizing that patients and physicians may accept greater risks for life-threatening illnesses.

Findings
The traditional process of evaluating biomarkers within the context of a single drug development program is inefficient and creates uncertainty for sponsors. This case-by-case approach leads to redundant efforts, slows down the development of novel therapies, and hinders the broad adoption of promising scientific tools. There is a clear need for a centralized, collaborative pathway to formally validate biomarkers, which can de-risk drug development, encourage innovation, and make the process more predictable and cost-effective for all stakeholders.

Recommendations
Drug developers, academic researchers, and other stakeholders should proactively engage with the FDA through the formal Biomarker Qualification Program to validate biomarkers for specific contexts of use. It is recommended to form public-private partnerships and other collaborations to pool resources and data, which strengthens the evidence package for a biomarker's utility. Developers should use the qualification process to establish a biomarker's value early, making it a publicly available and reliable tool that can accelerate the development of multiple drug products.

Regulatory Considerations
The Biomarker Qualification Program provides a distinct regulatory pathway for establishing a biomarker's validity for a specific Context of Use (COU), separate from an individual Investigational New Drug (IND) or New Drug Application (NDA). The process involves a three-stage submission and review cycle: the Letter of Intent, the Qualification Plan, and the Full Qualification Package. Once qualified, a biomarker is publicly listed and can be incorporated into multiple drug development programs without the need for sponsors to re-submit and re-justify the validation data for that specific COU, streamlining subsequent regulatory reviews.

Findings
While verification, analytical validation, and clinical validation have been well-established, usability validation has not been systematically incorporated into digital health technology evaluation.
Variability in device designs, patient populations, and regulatory environments creates barriers to widespread adoption of sensor-based digital health technologies.
Usability problems, such as poor user interfaces and technical errors, can lead to significant data loss in clinical trials and real-world applications.
While some guidance exists for usability in medical devices, there is no unified global standard for assessing usability in digital health products, leading to inconsistencies in implementation.
Stakeholders, including regulators, industry leaders, and researchers, recognize the need for usability validation to ensure the real-world effectiveness of digital health technologies.

Recommendations
Adopt the V3+ framework as a standardized method to ensure that usability is rigorously tested alongside verification, analytical validation, and clinical validation.
Establish clear protocols for usability testing, including use specification development, risk analysis, iterative formative evaluations, and summative evaluations.
Bring together regulators, technology developers, clinicians, and patients to create guidelines that ensure fit-for-purpose digital health solutions.
Work with regulatory agencies such as FDA, EMA, and MHRA to establish harmonized global standards for usability validation.
Encourage the publication of usability study results, including negative findings, to facilitate transparency and continuous improvement in digital health technologies.

Regulatory Considerations
Agencies like FDA and EMA increasingly require usability data for digital health technologies, but standardized methodologies are still evolving.
Usability validation should align with regulatory requirements for medical devices and digital biomarkers, ensuring clinical relevance and data integrity.
Digital health technologies must adhere to HIPAA, GDPR, and other data protection regulations while ensuring seamless usability.
Poor usability can lead to missing or unreliable data, which affects regulatory submissions and real-world evidence generation.
A consistent approach to usability evaluation is needed to support regulatory decision-making and digital health product approvals globally.

Findings
The field lacks a centralized, standardized database of validated digital health technologies, making it difficult for researchers and clinicians to select appropriate tools.
Non-wearable sensors and software applications are the most common types of DHTs, with 83% of ambient technologies categorized as software or applications.
Most DHTs focus on mild cognitive impairment (MCI) and early Alzheimer’s disease, with fewer technologies validated for moderate or severe dementia stages.
Uneven Distribution of Dementia Subtypes – The review identified a gap in DHT validation for frontotemporal dementia (FTD) and Lewy Body dementia, with Alzheimer’s disease being the predominant focus.

Recommendations
Expand and maintain an open-access database of validated DHTs to improve accessibility and standardization.
Increase research on digital measures applicable to moderate and severe stages of dementia, as well as non-Alzheimer’s dementias.
Promote integration of wearable, ambient, and cognitive assessment tools to generate comprehensive digital phenotypes of patients.
Follow clear guidelines for analytical and clinical validation of DHTs to improve regulatory acceptance and research applicability.
Conduct more usability and feasibility assessments, especially for populations with cognitive decline, to ensure DHTs are accessible and effective in real-world settings.

Findings
There is a lack of systematic approaches to guide the processes of collecting, interpreting, analyzing, and translating health data from wearables into digital biomarkers.
Most wearables have fixed measurement capabilities, limiting their translation to digital biomarkers.
Current guidance lacks study design and conduct elements that involve all stakeholders in an iterative approach for implementing digital biomarkers in practice.
Researchers and health professionals often rely on limited guidance for using wearable data in clinical practice and chronic disease management.

Recommendations
Implement the DACIA framework to provide interdisciplinary guidance on using wearable sensor data for digital biomarker development.
Focus on participant needs as a crucial factor for study success, applicable to both short and long-duration studies.
Involve relevant stakeholders in each key step of the DACIA framework in an iterative manner.
Apply the DACIA framework to explore digital biomarkers using various devices or signal measurements.
Reduce participant burden through support and continuous feedback.

Regulatory Considerations
Not mentioned

Findings
Misclassification of wakefulness during sleep periods and issues with tracking outside main sleep bouts.
Bias in performance evaluation studies due to limited representation of diverse populations.
Hidden complexities in consumer-grade devices related to data access, fees, privacy, and security.

Recommendations
Carefully interpret study results based on wearable sleep-tracking technology data.
Address biases in study populations by including diverse cohorts.
Ensure proper preprocessing of data from consumer-grade devices.
Avoid inserting personally identifiable information in device settings.
Evaluate issues related to specific populations like minors.

Regulatory Considerations
Complexity of privacy laws across different countries.
Need for strategies to protect personal information in device settings.
Consideration of specific population issues, such as minors, in regulatory frameworks.

Findings
Standard assessments lack sensitivity in early stages of neurodegenerative diseases.
Challenges with the validity and quality of RMT measurements.
Issues related to equity and inclusion in deploying digital tools.
Importance of considering feasibility, acceptance, usability, and ecological validity of digital endpoints.

Recommendations
Develop regulatory strategies early on.
Ensure equity and inclusion in deploying digital tools.
Address challenges related to the validity and usability of digital endpoints.
Promote public-private partnerships to address privacy and security concerns.
Involve patients and stakeholders in the design and implementation of digital tools.

Regulatory Considerations
Acceptance of digital endpoints by regulatory authorities is crucial.
Validation with current gold standards and clinically meaningful legacy endpoints.
Ensure data security and privacy.

Findings
There is a need for a structured framework to leverage prior work in the use of DHTs in clinical trials.
The current body of evidence supporting DHTs is growing, but there is a lack of clarity on how to effectively utilize this evidence.
The V3 framework provides a process for validating DHTs, but its application across different medical product development programs is inconsistent.

Recommendations
Implement a framework to reuse analytical and clinical validation data for existing DHTs.
Encourage early and continuous communication with regulatory health authorities.
Leverage prior work to share best practices and consistent approaches in employing DHTs.
Use the V3 framework to ensure DHTs are fit-for-purpose in clinical trials.
Develop a strategic approach to incorporate DHTs and digitally derived endpoints within clinical development programs.

Regulatory Considerations
Sponsors should ensure their plans to leverage prior work are endorsed by regulatory health authorities.
Alignment with FDA guidance on digital health technologies is crucial.
The regulatory status of the DHT and its intended use should be clearly defined and considered in clinical trial applications.

N/A

Findings
There are gaps in assessing aspects of physical function that matter to patients.
Existing assessment methods have limitations, including their episodic nature and burden to patients.
There are currently no approved drugs in the United States for the treatment of cancer cachexia.

Recommendations
Develop and validate digital measures of health.
Ensure digital measures are meaningful to patients.
Qualify digital measures for use in clinical development and regulatory decision-making.

Regulatory Considerations
Qualification of digital measures as drug development tools is necessary.
Digital measures are gaining traction in regulatory decision-making.
The FDA recommends qualification of digital measures in their PFDD guidelines."

Findings
SV95C provides a reliable and sensitive measure of maximal ambulation, addressing limitations of traditional assessments like the 6MWT.
Real-world data collection via wearable devices enhances accuracy and reflects true ambulatory capabilities.
Longitudinal studies confirmed SV95C's ability to detect disease progression and response to corticosteroid treatments.
Correlations with existing clinical outcome assessments (6MWT, NSAA, and 4SC) validate SV95C’s construct validity.
Patients and caregivers support the use of wearable devices in clinical trials, emphasizing reduced burden and improved trial attractiveness.

Recommendations
Use SV95C as a primary endpoint in DMD clinical trials to monitor maximal stride velocity in real-world conditions.
Incorporate SV95C alongside traditional endpoints to ensure comprehensive assessment of therapeutic efficacy.
Establish training protocols for patients and caregivers to optimize compliance with device usage.
Expand normative data for SV95C in younger and more diverse patient populations.
Conduct further research on meaningful change thresholds (MCTs) to refine clinical relevance.

Regulatory Considerations
Ensure SV95C is included as a primary endpoint with supporting secondary endpoints (e.g., muscle strength assessments) for consistency.
Validate wearable devices used for SV95C measurement to meet regulatory standards for accuracy and reliability.
Address variability and standardize protocols for data collection to ensure regulatory compliance.
Collect additional longitudinal data to strengthen the predictive value of SV95C for regulatory submissions.
Incorporate privacy and data security measures to comply with data protection regulations, including anonymization and encryption.