In Vitro Skin Sensitization Testing of Medical Devices
GARD® towards integration into ISO 10993-10
As regulatory requirements evolve and the push to reduce animal testing accelerates, New Approach Methodologies (NAMs) are becoming increasingly important in the biological safety evaluation of medical devices. Among all biocompatibility endpoints, skin sensitization is undergoing the most substantial regulatory transition.
This article provides an overview of the evolving regulatory landscape, the role of NAMs in biocompatibility testing, as well as the advancement of GARD® toward formal implementation in ISO 10993-10.
Key takeaways
- Current regulatory momentum driving skin sensitization testing toward NAM-based approaches.
- How GARD®skin Medical Device addresses the unique challenges of testing medical device extracts with both polar and non-polar vehicles.
- Regulatory progress of GARD®skin Medical Device toward integration into ISO 10993-10.
- Typical use scenarios in which GARD® supportss material selection, device development and risk assessment.
- Practical steps manufacturers can take to prepare for the regulatory shift.
Author: Andy Forreryd, PhD, Scientific Liaison Manager at SenzaGen AB, Member of ISO/TC 194/WG 8
Skin sensitization: The biocompatibility endpoint at a regulatory turning point
Biological safety evaluation of medical devices is guided by the ISO 10993 series, which defines requirements for assessing biological risks associated with device materials. Cytotoxicity, irritation, and skin sensitization are three core endpoints and are mandatory to assess for all devices with relevant patient contact.
While in vitro methods for cytotoxicity are fully established and irritation testing has largely transitioned to validated alternatives, skin sensitization remains the last frontier. Until now, regulatory testing has relied primarily on animal-based methods such as the Guinea Pig Maximization Test (GPMT) and the Local Lymph Node Assay (LLNA). However, this is rapidly changing.
Read more about the biocompatibility fundamentals.
Why the transition is happening now
Several converging factors are driving the shift toward NAM-based skin sensitization testing:
Regulatory mandates are intensifying. The European Medical Device Regulation (MDR) explicitly promotes the replacement, reduction, and refinement (3Rs) of animal testing wherever scientifically justified. In parallel, the U.S. FDA Modernization Act 2.0 removes the statutory requirement for animal testing when scientifically valid non-animal alternatives are available. Most recently, the United Kingdom has published a national roadmap outlining a phased transition away from animal testing, further reinforcing the global regulatory momentum toward NAM-based approaches.
Scientific readiness has been achieved. Multiple OECD Test Guideline 442 methods have been validated for skin sensitization assessment and are now listed in Annex C of ISO 10993-10. However, a critical gap remains: these methods were validated using neat chemicals, not medical device extracts, and most are not yet recognized as full replacements for in vivo studies in regulatory submissions.
Industry demand is growing. Medical device manufacturers are increasingly seeking mechanistic-, human-relevant and efficient testing approaches that support faster development cycles, sustainability goals, and ethical commitments, without compromising regulatory acceptance.
ISO 10993-1 explicitly encourages this transition. This standard emphasizes a risk-based approach and recommends the use of scientifically valid alternative methods whenever feasible, supported by robust material characterization and biological justification.
The question is no longer whether NAMs will replace animal testing for skin sensitization, but how quickly and which methods will lead the way.
In this context, GARD®skin Medical Device has reached the most advanced stage toward full implementation in ISO 10993-10, progressing through the structured evaluation framework defined in ISO/TS 11796:2023.
Why applying NAMs to medical device sensitization testing is challenging
While OECD Test Guideline 442 methods represent significant scientific progress, their application to medical device extracts introduces specific technical and regulatory challenges that must be addressed before they can fully replace animal testing.
The extract testing challenge
Medical device extracts differ fundamentally from the neat chemicals used in original NAM validations:
Complex mixtures. Device extracts often contain multiple unknown constituents with diverse physicochemical properties. Potential sensitizers may be present at very low concentrations within complex matrices, requiring assays to demonstrate both sensitivity and specificity across unpredictable mixtures.
Dual extraction vehicle requirement. ISO 10993-12 mandates testing with both polar and non-polar extraction vehicles to capture the full range of extractables. However, many OECD-validated assays are incompatible with non-polar extracts, limiting their applicability to medical device testing.
What NAMs must demonstrate for medical device applications
To be considered suitable for extract-based testing, NAMs must demonstrate:
- Mechanistic relevance to human skin sensitization pathways.
- Broad chemical applicability across diverse material classes.
- Robust performance with complex mixtures and unknowns.
- Sensitivity at low concentrations relevant to device extracts.
- Compatibility with both polar and non-polar extraction vehicles.
- Reproducibility across laboratories and test conditions.
These requirements underscore why device-specific adaptation and validation of NAMs is essential, and why OECD TG 442 methods remain in Annex C rather than in the normative section of ISO 10993-10.
Skin sensitization testing of medical devices with GARD®
Genomic- and machine learning- based technology
GARD® (Genomic Allergen Rapid Detection™) is a genomics- and machine learning-based platform designed for sensitization assessment.
GARD®skin is validated and included in the OECD Test Guideline 442E. It measures expression of 196 biomarkers, covering multiple key events in the skin sensitization Adverse Outcome Pathway (AOP). This broad mechanistic coverage underpins the assay’s high predictive performance.
An adaptation optimized for extract-based testing
For medical device applications, the GARD®skin protocol has been adapted to incorporate extract preparation using saline and oil vehicles in accordance with ISO 10993-12. This enables direct testing of both polar and non-polar extracts, supporting skin sensitization assessment across a wide range of solid materials.
Unique compatibility with both polar and non-polar extraction vehicles
The test system of GARD®skin Medical Device supports both polar (saline) and non-polar (olive or sesame oil) extraction vehicles, as required by ISO 10993-12. Among the ten OECD-validated in vitro assays for skin sensitization testing, only a few have demonstrated compatibility with both extract types in peer-reviewed publications (Jenvert et al., 2024; Okada et al., 2025).
Demonstrated applicability across challenging materials
Published studies and collaborations with industry partners have shown that GARD®skin Medical Device is applicable to a broad range of solid materials and medical device extracts that are often considered challenging to test in other OECD-validated cell-based assays, including:
- Complex mixtures and UVCBs
- Polymers, acrylates, monomers
- Colorants, coatings and pigments
- Plasticizers and additives
- Metals
- Wound dressings
- Disposable hygiene products with absorbent materials
- Textiles
Optional quantitative approach supporting risk assessment
For materials containing potential sensitizers, the standard single-concentration protocol can be combined with the GARD®skin Dose-Response protocol, enabling prediction of quantitative skin sensitization potency. This quantitative approach is a powerful tool for product development, supporting evidence-based decision making in selecting novel materials and quantitative risk assessments:
- Compare sensitizing potency between candidate materials.
- Identify a Point of Departure (PoD) for quantitative risk assessment.
- Determine a safe concentration level for potential sensitizer.
Alignment with 3Rs and sustainability objectives
The traditional GPMT has limited human relevance and relatively low sensitivity, with a risk of false-negative results. It is also associated with long study durations and a high ethical burden.
In contrast, GARD®skin Medical Device offers a human-relevant, high-performance in vitro alternative. The assay supports the principles of 3Rs, aligns with sustainability objectives, and reduces reliance on animal testing in skin sensitization assessment.
Regulatory development of GARD®: Progress towards ISO 10993-10 implementation
ISO/TS 11796:2023 outlines a structured process for evaluating NAMs for medical device testing, including feasibility studies, reference materials, performance assessments, and interlaboratory testing.
Using this framework, GARD®skin Medical Device has successfully completed both feasibility and pre-validation studies. Consequently, the assay is now progressing to the final interlaboratory ring trial, which represents the last step toward potential inclusion in ISO 10993-10.
Figure 1. Overview of the evaluation process in accordance with ISO/TS 11796 (left), alongside a schematic flow of the GARDskin Medical Device feasibility and pre-validation study (right)
Feasibility study
Silicone (MED-2000) and thermoplastic polyurethane (TPU) materials were spiked with four known sensitizers and extracted in both vehicles.
Results:
- All spiked materials correctly classified as sensitizers.
- No false positives for unspiked materials or extraction vehicles.
Figure 2 GARDskin Medical Device classification results of investigated test material extracts. Plotted data corresponds to mean decision values (n=3), with standard deviation represented by error bars.
Pre-validation study
Part 1. Negative control material (MED-2000) was extracted in both vehicles and spiked with sensitizers and non-sensitizers (n = 16, 3 replicates).
- 100% reproducibility (16/16)
- 94% concordance with animal data (15/16)
Part 2: Expanded performance testing with a larger set of chemicals (n = 29, 1 replicate).
- 97% concordance with animal data (28/29)
These results demonstrate that GARD®skin Medical Device is reproducible, reliable, and accurate for assessing sensitization potential of device extracts. It meets the criteria for progressing to an interlaboratory ring trial, final step toward potential inclusion in ISO 10993-10.
Request full data on the prevalidation results of GARDskin Medical Device.
How GARD® supports device development
NAMs are becoming increasingly central to biological safety evaluation, and skin sensitization is among the most important endpoints undergoing modernization. With strong mechanistic foundations, compatibility across extract types, and robust pre-validation results, GARD®skin Medical Device represents one of the most advanced in vitro approaches currently available for medical device sensitization testing.
Typical use scenarios
Product development
- Early screening of new materials
- Comparative testing of material candidates
- Pre-screening to reduce reliance on in vivo studies
Manufacturing optimization
- Evaluating processing parameters (e.g., sterilization, washing, coating)
- Assessing batch-to-batch variation
Regulatory submissions
- Supporting weight-of-evidence approaches
- Strengthening documentation for low-risk material or manufacturing changes
- Integration into structured testing strategies
By integrating NAMs such as GARD®skin Medical Device, manufacturers can improve decision-making, strengthen safety assessments, reduce reliance on animal testing, and accelerate development timelines, ultimately supporting safer and more sustainable medical devices.
Watch our webinar to learn more about real-world GARD user cases , including regulatory submissions for CE-marking, early-stage material screening, and support for hypoallergenicity claims.
Preparing for the regulatory transition in skin sensitization testing
As ISO 10993-10 continues to evolve, medical device manufacturers that start building NAM-based expertise today will be better prepared for future regulatory changes. Early integration of NAMs supports a gradual transition toward a more predictive, human-relevant, and sustainable approach to skin sensitization testing. This aligns with both current scientific best practice and the future regulatory direction of medical device regulation.
Building organizational readiness for NAMs
For medical device manufacturers, this regulatory transition represents both a challenge and a strategic opportunity. Rather than treating NAMs solely as future compliance requirements, forward-looking organizations are already integrating them into product development and biological evaluation workflows.
Early adoption offers practical advantages, such as:
• Building internal datasets linking materials, extracts, and biological responses
• Gaining hands-on experience interpreting NAM-based results
• Strengthening weight-of-evidence justifications in regulatory submissions
• Reducing late-stage regulatory risk as expectations evolve
• Aligning proactively with 3Rs principles and sustainability goals
Manufacturers can implement NAMs alongside existing approaches to support material selection, compare alternatives, and inform risk assessment strategies, preparing for future regulatory expectations.
About the Author
Andy Forreryd, PhD
Scientific Liaison Manager at SenzaGen AB, Member of ISO/TC 194/WG 8
Dr Andy Forreryd has many years of experience working with in vitro assay development, genomics and machine learning, engaging in collaborations with industry leaders to investigate novel applications for NAM-based sensitization testing, with the aim to replace the need for animal studies. Dr Forreryd is a co-developer of the GARDskin assay (OECD TG 442E) for the assessment of chemical sensitizers. He is also an active member of the ISO/TC 194/WG 8 for Irritation and Sensitization.
Adapting to upcoming ISO 10993-10 requirements
As ISO 10993-10 evolves, companies can begin laying the groundwork for NAM-based approaches today, without disrupting current workflows. Early integration of in vitro methods helps build internal expertise and supports smoother regulatory interactions in the future.
Interested in learning more about how NAMs can complement your biocompatibility testing strategy? Explore our resources or connect with our scientific team for an expert discussion.
