Using in vitro data for regulatory approval of medical devices according to MDR

Regulatory approval of medical devices according to MDR using in vitro data from GARDskin Medical Device for skin sensitization assessment


Presented at Eurotox 2023

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Conclusion

  • The GARDskin Medical Device assay is a novel method for assessment of skin sensitizing properties in leachables from solid materials, according to ISO 10993 standards.
  • Here, we demonstrate how GARDskin Medical Device data, combined with endpoint data from skin irritation and cytotoxicity testing, were successfully used in a data package for biocompatibility assessment of a novel medical device.
  • Following review by a notified body, an obtained CE-mark for the medical device Tinearity® G1 highlights unique opportunities to comply with the European Medical Device Regulation 2017/745 (MDR) using only in vitro data sources.

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Abstract

Skin sensitizers in medical device extracts are conventionally assessed in vivo, primarily using the Guinea Pig Maximization Test and the Buehler Occluded Patch Test. However, there is a shift in the medical device toxicology field towards an increased use of in vitro methods for the evaluation of the biological safety of medical devices. Recently, in vitro methods for the endpoints skin irritation and skin sensitization have been included in the ISO 10993 standard, what makes it possible to perform this testing in vitro. The GARDskin assay is one of the in vitro methods for assessment of skin sensitization described in ISO 10993-10 and is the first OECD TG 442 method that has been adapted to work with oil, the non-polar extraction vehicle often used in in vivo studies for testing medical devices.

Here we share an example of how in vitro testing results, including results from the GARDskin Medical Device assay, were submitted to obtain CE-marking according to the European Medical Device Regulation 2017/745 (MDR) for Tinearity® G1, an innovative tinnitus treatment medical device. Tinearity® G1 was classified as a non-sensitizer in both polar and non-polar extracts in the GARDskin Medical Device assay. This result was used together with in vitro cytotoxicity and in vitro skin irritation results as weight of evidence together with review of chemical data in the risk assessment and biological evaluation of the medical device.

Joint poster with ExxonMobil: Case study on UVCBs and Formulated Lubricant Products

Assessing the Utility of the Genomic Allergen Rapid Detection (GARDskin) Assay to Detect Dermal Sensitization Potential in UVCBs and Formulated Lubricant Products


Presented at Eurotox 2023

 

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Summary

  • GARD®skin is considered to provide useful information in an overall weight of evidence assessment for difficult to test materials (mixtures, UVCBs) with challenging physical chemical properties.
  • The accuracy for prediction of skin sensitization hazard ranged from 66% for formulated lubricants/greases to 100% for synthetic base oils compared to expected outcomes based on reference data.

Abstract

Advances in new approach methods and their combinations into defined approaches can provide clarity and confidence in concluding on skin sensitization potential. However, challenges remain in utilizing these approaches for difficult to test materials such as those with challenging physical chemical properties (low water solubility, hydrophobic substances) or complex compositions like Unknown or Variable Composition Complex reaction products or Biological Materials (UVCBs) and formulated mixtures. The previously developed available non-animal test methods for skin sensitization based on key-events of the adverse outcome pathway (AOP) have clearly defined requirements for test material properties that impact feasibility or confound reliance on negative results particularly for difficult to test materials and impedes the application of defined approaches to conclude on skin sensitization hazard. A set of difficult to test materials were evaluated in the recently validated GARDskin assay since it offered advantages such as a broader applicability domain, availability of additional validated test solvents for poorly soluble materials and provides mechanistically relevant information on key events from across the skin sensitization AOP. The aim of the study was to evaluate the accuracy of the GARDskin assay for a set of synthetic base oils (UVCBs), lubricant additives (UVCBs/poorly soluble substances) and fully formulated lubricants/greases (mixtures) as well as to provide additional information to assist in a weight of evidence determination given that several of the test materials had borderline or conflicting data from other key events within the skin sensitization AOP. All test items were adequately solubilized in one of the following solvents, Ethanol (0.1% final), DMSO (0.25% or 0.1% final), or Xylenes (0.1% final). SenzaCells were incubated in triplicate under standard conditions with the test items at a max concentration of 500uM for those with a known molecular weight or 100 ppm (w/v) for those without a known molecular weight. Following cell stimulations, RNA was isolated and endpoint measurements were performed using the GARDskin genomic profile signature. Based on the results of this study, the accuracy for prediction of skin sensitization hazard was 100% for synthetic base oils (n=4), 83% for lubricant additives (n=6), and 66% for formulated lubricants/greases (n=6) compared to expected outcomes based on available reference data. In some cases, the available reference data was borderline or considered to have low confidence due to confounding factors such as irritation, and nonmonotonic dose responses impacting the accuracy determination when compared one to one with either animal or human data. However, the GARDskin assay is considered to provide useful insight into the overall weight of evidence for difficult to test materials with conflicting datasets as it provides an additional profile of bioactivity across the skin sensitization adverse outcome pathway. 

 

Joint poster with RIFM and IFF: PoD for NGRA, a case study using isocyclocitral

The GARDskin Dose-Response assay for determination of a point-of-departure (PoD) for Next Generation Risk Assessment (NGRA) of skin sensitizers: A case study using isocyclocitral


Presented at Eurotox 2023

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Conclusion

  • The continous readout from the assay is reproducible and the assay predicts LLNA EC3 and human NESIL values with high correlation to reference benchmark data (geometric mean fold-misprediction factors of 3.8 and 2.5 respectively)
  • The assay provides a nice tool for the fragrance industry to predict the NESIL value which can be used for conducting the quantitative risk assessment for generating the IFRA standard.

Abstract

New Approach Methods (NAMs) for the assessment of skin sensitizers have been adopted as OECD Test Guidelines (TGs), supporting hazard- and GHS potency classifications. However, more granular potency information, preferably on a continuous scale, is needed to derive a point-of-departure (PoD) for Next Generation Risk Assessment (NGRA) of new chemical entities, which still represents a missing element in the application of NAMs for sensitization assessments.

The GARDskin assay (OECD TG 442E) provides a novel and mechanistically different method to monitor the Key Events (KE) in the Adverse Outcome Pathway (AOP) for skin sensitization and is the first harmonized test guideline based on genomics and machine leaning. A modified version of the validated protocol incorporating dose-response measurements has recently been described which uses linear models for the prediction of LLNA EC3/Human No Expected Sensitization Induction Levels (NESIL) values.

The aim of the following study, which represents a cross-sector collaboration involving industry, assay developer, and a non-profit research institute, were to perform a pre-validation exercise to evaluate the precision and reproducibility of the continous potency predictions from the GARDskin dose-response assay, and to demonstrate how the derived continous potency predictions can be implemented into available NGRA-framework to determine safe use levels in consumer products.

Predictive performance was estimated in a blinded study by evaluating a total of 17 fragrance materials, and reproducibility of the continous predictions was assessed by evaluating 11 of the materials in three replicate experiments. Results illustrate that predicted LLNA EC3/human NESIL values from the GARDskin Dose-response assay correlate well with reference data (geometric mean fold-error: 3.8 and 2.5, respectively), and that the continuous potency predictions are reproducible between experiments (geometric mean fold-change: 3.1). A case study using isocyclocitral was used to illustrate how the assay can be implemented into an NGRA-framework, which is an exposure driven risk assessment methodology. The predicted NESIL value from GARDskin Dose-response was used within a weight-of-evidence  approach to derive a PoD for use in QRA. Sensitization assessment factors were applied to the PoD to determine acceptable exposure levels at which no skin sensitization induction would be expected for different product types based on exposure.

In conclusion, the results reported from this study demonstrate that the predicted potency values from the GARDskin Dose-Response assay are reproducible between experiments and show good concordance with the published values. The case study illustrates a proof of concept and establish the assay as a relevant source of information to derive NESIL values for conducting QRA evaluations for fragrance materials without any new animal data.

 

 

 

 

Joint poster with Johnson Matthey: Case study on Metals

Expanding the applicability domain of NAMs for skin sensitization testing: A case study using GARDskin for assessment of metals


Presented at the 12th World Congress on Alternatives and Animal Use in the Life Sciences, 2023

 

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Summary

  • Limited data are currently available to support the inclusion of metals into the applicability domain of the OECD TG 442 series of assays.
  • GARD®skin (OECD TG 442 E) correctly predicted 11/12 metals in this study, including nickel which is a false negative in LLNA.
  • GARD®skin has the potential to reduce the need for animal testing for the endpoint of skin sensitization within the metal production and medical device sectors.

 

Abstract

New Approach Methods (NAMs) for detection of sensitization have been validated and adopted as OECD TGs during the last decade. These assays target different Key Events (KE) in the AOP for skin sensitization and are increasingly being applied to replace animal models within different chemical sectors. However, further characterization of the applicability domain (AD) of these assays is critical to understand limitations and to facilitate regulatory uptake in other industrial sectors. Of particular interest from a scientific and regulatory perspective is the potential to use NAMs for assessment of metals, which have been proposed to act via alternative mechanisms to organic chemicals. The current study describes a joint effort by industry and assay developers to evaluate the AD of the GARDskin assay for metal compounds.  GARDskin is the first harmonised method utilizing a combination of genomics and machine learning for a regulatory endpoint and was recently adopted into OECD TG442E.

A selection of metal salts (n=13) was evaluated and the accuracy, sensitivity, and specificity for prediction of skin sensitizing hazard of metals were estimated to 92% (12/13), 100% (7/7) and 83% (5/6), respectively. Interestingly, transcriptomic analysis revealed almost identical response patterns in dendritic cells for metals and organic compounds, indicating a high similarity in the toxicity pathways driving classifications. In conclusion, the result from this study supports the inclusion of metals into the AD of GARDskin, which is an important step to ensure scientific/regulatory confidence to reduce the need for animal testing within the metal production and medical device sector.