Joint poster with Sonova: Integrating NAMs into early-stage screening of novel materials

Case studies on the use of GARD®skin Medical Device for in vitro skin sensitization assessment


Presented at SOT and Eurotox 2024

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Conclusion

In conclusion, GARDskin Medical Device can detect signals from diluted and complex extracts of solid devices, with a sensitivity superior to animal methods.

This may significantly reduce the need of animal studies, improve the safety of the final product, and avoid potential costly late-stage failures.

Abstract

The recent advancements in New Approach Methodologies enables the use of in vitro method for skin sensitization assessment as part of the biocompatibility testing for medical devices, which is conventionally tested in vivo. GARDskin OECD TG 442E is included in ISO 10993-10:2021 as the only OECD validated in vitro assay that is compatible with both polar and non-polar extraction vehicles, in line with ISO 10993-12:2021.  GARDskin Medical Device is an adaptation of the GARDskin assay, including a pre-sample treatment procedure where solid devices are extracted using both polar and non-polar vehicles.

The aim of this study is to demonstrate the benefits of using GARD for early-stage screening of materials intended for use in medical devices for assessing their skin sensitization potential. Results from two case studies were summarized in which GARDskin Medical Device was used for skin sensitization assessment. The first case study describes the testing of an acrylic-based device with a coating consisting of a UV-cured lacquer, where chemical analysis indicated the potential for skin sensitization. The second case study describes the testing of a polymeric material consisting of Cellulose-Acetate Propionate (CAP) with a plasticizer (Triethylene glycol bis (2-ethylhexanoate), CAS# 94-28-0), with contradictive existing in vivo (negative) and in vitro (positive) data.

In the first case study, the acrylic-based device induced a positive response in both polar and non-polar vehicles in GARDskin Medical Device and was thus classified as a skin sensitizer. It was hypothesized that the positive results may be due to inadequate curing of the lacquer within cavitary structures of the devices, where UV light exposure was insufficient. To confirm the hypothesis, follow-up testing was performed on an identical device, but without cavities, which was classified as non-sensitizer. In vivo data confirmed the outcome of the in vitro assay. Consequently, a modification was made in the manufacturing process to prevent the presence of lacquer in cavitary structures of the device.

In the second case study, the CAP material was positive in the non-polar vehicle and was thus labelled as a skin sensitizer. The plasticizer was identified as a potential culprit, considering a borderline negative result in LLNA (SI=2.97) and reported positive clinical data. To support the hypothesis a follow-up study was conducted using another adaptation of the GARDskin protocol capable of providing continuous potency predictions. The results classified the plasticizer as a weak contact allergen. As a result, a different material was selected for the device.

Keywords: Biocompatiblity, ISO 10993-10, GARDskin Medical Device, Skin Sensitization, ISO 10993-12

Evaluation of the applicability of GARDskin to predict skin sensitizers in extracts from medical device materials

Peer-reviewed article in Frontiers in Toxicology.

The application of GARD®skin to predict potential skin sensitizers in extracts from Medical Device materials has recently been published in a peer-reviewed article in Frontiers in Toxicology.

The study results provide evidence recognizing the GARD®skin Medical Device assay as a scientifically sound and ethical alternative to conventional animal methods, compatible with both polar and non-polar extraction vehicles, in line with the ISO 10993-12:2021 standard.

We are proud to provide the only OECD-validated in vitro assay for sensitization that is fully compatible with testing requirements specified in ISO 10993-12.

Jenvert Rose-Marie, Larne Olivia, Johansson Angelica, Berglin Mattias, Pedersen Emma, Johansson Henrik
Frontiers in Toxicology, Volume 6, 2024,ISSN 2673-3080
DOI=10.3389/ftox.2024.1320367

Keywords

GARD™; In vitro; Skin sensitisation; NAMs; Medical Device, ISO 10993, Biocompatibility

Abstract

Biocompatibility testing of medical devices is governed by the ISO 10993 series of standards and includes evaluation of skin sensitization potential of the final product. A majority of all medical devices are tested using in vivo methods, largely due to the lack of in vitro methods validated within the applicability domain of solid materials. The GARDskin method for assessment of chemical skin sensitizers is a validated method included in the OECD Test Guideline 442E, based on evaluation of transcriptional patterns of an endpoint-specific genomic biomarker signature in a dendritic cell-like cell, following test chemical exposure. The current study aimed to evaluate the applicability of GARDskin for the purpose of testing solid materials by incorporation of extraction procedures described in ISO 10993-12:2021, as well as to demonstrate the functionality of the proposed protocols, by testing of custom-made materials spiked with sensitizing agents. It was shown that GARDskin is compatible with both polar and non-polar extraction vehicles frequently used for the purpose of medical device biological testing. Further, exploring three different material types spiked with up to four different sensitizing agents, as well as three unspiked control materials and commercial reference products, it was shown that the method correctly classified all evaluated test materials. Taken together, the data presented suggest that GARDskin may constitute a valid alternative to in vivo experimentation for the purpose of skin sensitization assessment of medical devices.

 

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.

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.

In vitro assays for assessment of the skin sensitization hazard and potency of isobornyl acrylate

Presented at SOT 2023

In vitro assays for assessment of the skin sensitization hazard and potency of isobornyl acrylate

Rose-Marie Jenvert1, Olivia Larne1, Ulrika Mattson1, Robin Gradin1, Kelly P Coleman2 and Andy Forreryd1  1SenzaGen, Lund, Sweden, 2Medtronic, Minneapolis, USA

 

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Conclusion

The GARDskin Medical Device assay can be used

  • with the extraction vehicles saline and oil as described 
    in ISO 10993. 
  • to detect low concentrations of skin sensitizers in a mixture and have the potential to replace in vivo tests 
    for risk assessment of skin sensitizers in medical devices. 
  • as risk assessment tool in combination with the 
    GARDskin Dose-Reponse assay during development of medical devices containing acrylates. 

Abstract

Acrylates have a wide range of applications for medical devices as they can bring several advantages  such as transparency, super-absorbency and hardness in combination with flexibility. The manufacturing of acrylic materials typically involves using at least one monomer of either acrylate or methacrylate which react to form a polymer. Several methodologies can be used for polymerization and the degree of polymerization of the final material can vary, hence some products can contain more residual monomers than others, and human exposure to these well-known skin sensitizers may increase the risk of developing the adverse immunological response, allergic contact dermatitis.

In 2020, the acrylate monomer, isobornyl acrylate (IBOA; CAS 5888-33-5), was named allergen of the year by American Contact Dermatitis Society due to the increased number of patients that were sensitized to IBOA found in glucose sensors and glucose pumps. IBOA is also present in other medical devices as plastic materials, coatings, sealants, glues, adhesives and inks. As a result, it is important to find alternatives to the animal methods used today to assess skin sensitization to properly identify the skin sensitizing potential of IBOA in medical devices and avoid the risk of sensitizing more individuals to this chemical.

The GARDskin (OECD TG 442E) assay, initially developed for hazard identification of a wide range of skin sensitizers, has been adapted for use with polar and non-polar solvents as described in ISO 10993-12:2021 and can be applied to assess the skin sensitization of medical devices. Further development of the GARDskin protocol has also enabled the prediction of skin sensitization potency by using a dose-response measurements. The cDV0 value derived from the assay corresponds to the lowest concentration required to exceed a binary classification threshold in GARDskin, and this concentration correlates significantly with LLNA EC3 and human NOEL values.  Linear regression models have been established to exploit these relationships for potency predictions.

In this study, we explored the ability of GARDskin Medical Device assay to detect the skin sensitizing potential of IBOA in a mixture of chemicals extracted from a silicone material (Nunsil MED-2000) in both saline and oil extract. Additionally, the skin sensitizing potency of IBOA was also investigated using the novel GARDskin Dose-Response assay. The acrylate monomer, IBOA, was correctly classified as a skin sensitizer in extracts of the silicon material spiked with IBOA using the GARDskin Medical Device assay. The correct classification of IBOA as a skin sensitizer provides evidence that the GARDskin Medical Device assay is sensitive enough to detect low concentrations of device-related skin sensitizers in a mixture of extracted chemicals and hence has the potential to replace in vivo tests for risk assessment of medical devices. Furthermore, IBOA was classified as a strong to moderate skin sensitizer (HP 2) with a predicted LLNA EC3 value of 0.848% and human NOEL value of 230 µg/cm2 using the GARDskin Does-Response assay. These predictions agree with existing human data and information from the ECHA registration dossier, illustrating the potential of the GARDskin Dose-Response assay to replace in vivo tests for quantitative potency assessment of potential skin sensitizers.

Next Generation Risk Assessment (NGRA) using NAMs for skin sensitization: Reproducibility and precision of the GARDskin Dose-Response assay for PoD determination of fragrance chemicals.

Presented at ASCCT 2022

Next Generation Risk Assessment (NGRA) using NAMs for skin sensitization: Reproducibility and precision of the GARDskin Dose-Response assay for PoD determination of fragrance chemicals.

Andy Forreryd1, Shashi Donthamsetty2, Paul Sterchele2, Xiao Huang2, Gregory Ladics2, Mihwa Na3, Isabelle Lee3, Anne Marie Api3, Robin Gradin1, Henrik Johansson1
1SenzaGen, Lund, Sweden , 2International Flavors & Fragrances, Hazlet, NJ, USA, 3Research Institute for Fragrance Materials. Woodcliff lake, NJ, USA

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Conclusion

  • GARD®skin Dose-Response can be used for continous predictions of skin sensitizing potency.
  • 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.
  • 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 assessment of skin sensitizers have been adopted as Test Guidelines (TGs) by OECD. When combined into Integrated Approaches to Testing and Assessment (IATA) or defined approaches (DA), they provide data supporting hazard classifications and GHS potency subcategorization. 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).

GARDskin was recently adopted into OECD TG 442E to support discrimination of skin sensitizers and non-sensitizers. Continous potency predictions are derived using a modified protocol that incorporates dose-response measurements. Linear regression models have further been developed to predict LLNA EC3 and human NOEL values. The aim of the following study, which represents a cross-sector collaboration was to evaluate precision and reproducibility of the potency predictions from GARDskin Dose-Response in blinded studies.

Preliminary results from estimate of precision (n=36 materials) indicated that GARDskin Dose-Response predicted LLNA EC3/ human NOEL values with median fold-misprediction factors < 3.0 and < 2.0, respectively. Interestingly, LLNA predicted human NOEL with a fold-change > 2 in the same dataset. For reproducibility assessment, test materials (n=11) were evaluated in separate experiments (n=3), which generated highly reproducible results, with an average median range of fold-changes between replicates of 2.5.

Results from this study demonstrate that continous potency predictions from GARDskin Dose-Response are reproducible. Together with performance data, this represents a major step towards establishment of the assay as a relevant source of information to derive a PoD for NGRA, avoiding generation of new animal data.

 

 

 

Ability of the GARDskin assay to Predict Skin Sensitization Response in the Guinea Pig Maximization Test

Joint poster with Risk Science Consortium,
Presented at the 2022 SOT

Rose-Marie Jenvert1, Alexandra Zambriczki Lee2, Ronald P Brown2
1SenzaGen, Lund, Sweden, 2Risk Science Consortium, LLC, Arnold, MD USA

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Conclusion

  • The GARD®skin assay is able to predict skin sensitization potential in humans with a level of accuracy that is equal to or exceeds that of GPMT and the LLNA.
  • As a result, the GARDskin assay serves as a promising alternative to assess the skin sensitization potential of medical devices.

Abstract

The preclinical safety assessment of medical devices typically involves an evaluation of the skin sensitization potential of the device. The GARDskin assay is being proposed as an in vitro alternative to the animal-based tests, Local Lymph Node Assay (LLNA) and Guinea Pig Maximization Test (GPMT), that are typically used to assess the skin sensitization potential of medical devices. The ability of the GARDskin assay to replace LLNA for prediction of skin sensitization response has been evaluated (e.g., Johansson et al., 2019) but since GARDskin has also been proposed as an alternative to the GPMT, it is important to compare the concordance of the prediction of the GARDskin assay with the in vivo response obtained in both of the animal-based tests.  Based on the results of the GARDskin assay for 122 compounds, this in vitro assay shows a high concordance with the predicted results of the LLNA (87.5%); however, the concordance for results obtained in the GPMT is much lower (71.2%). The concordance of the GARDskin assay and the GPMT is impacted by the relatively high number of false positive results (15 out of 73) compared to the false positives seen in the comparison between GARDskin and LLNA (2 out of 80).   The high number of false positives found when comparing the results from GARDskin and the GPMT results from the inaccurate characterization of the human skin sensitization potential of these compounds by the GPMT. Therefore, the low concordance between the GARDskin assay and the GPMT is due largely to inaccurate predictions of human skin sensitization potential by the GPMT and not by shortcomings of the GARDskin assay. Notably, the GARDskin assay (88.7% accuracy) outperforms the GPMT (83.0% accuracy) in the ability to predict the human sensitization response of compounds in this dataset. The results of this project show that the GARDskin assay is able to predict skin sensitization potential with a level of accuracy that is equal to or exceeds that of the currently accepted animal-based tests, suggesting that the GARDskin assay can serve as a promising alternative to the GPMT and the LLNA, and provide a more human relevant result for assessment of the skin sensitization potential of medical devices.

In vitro method for quantitative potency assessment of skin sensitizers during development of novel materials for intended use in medical devices

Joint poster with Sonova,
Presented at the 2022 SOT

Andy Forreryd1, Ulrika T Mattson1, David Waeckerlin2, Karla Lienau2, Robin Gradin1, Rose-Marie Jenvert1
1SenzaGen, Lund, Sweden, 2Sonova AG, Staefa, Switzerland

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Conclusion

The GARD®skin Dose-Response assay can be used as a tool for:

  • quantitative potency information of chemicals that might leach out of materials or medical devices.
  • internal decision-making during development of new materials for use in medical devices.

Abstract

New innovative materials for use in medical devices based on acrylates can bring several advantages such as super-absorbency, transparency, flexibility, toughness and hardness.

The manufacturing of acrylates typically involves using a monomer of either acrylate or methacrylate that is polymerized into the final product. The polymerization or hardening of material makes the monomers inert, however several methodologies can be used for polymerization, and they differ in the degree to which they result in a fully polymerized final product. Some products therefore contain more residual monomers than others and human exposure to these well-known skin sensitizers may increase the risk of skin sensitization and allergic contact dermatitis. To assess the risks resulting from exposure to these chemicals, potentially found in medical device material, it is necessary to accurately identify and characterize their skin sensitizing potential.

The GARDskin (OECD TGP 4.106) assay was initially developed for hazard identification of skin sensitizers. To derive potency information, a modification of the standard GARDskin protocol based on dose-response measurements has been proposed. The readout of the assay is a cDV0 value, which corresponds to the lowest concentration required to exceed a binary classification threshold in GARDskin. This concentration correlates significantly with LLNA EC3 and human NOEL values and linear regression models have been established to exploit these relationships for potency predictions. In this study, we explore the potential to use this novel assay for quantitative potency assessment of two acrylate monomers.

The GARDskin Dose-response assay classified both acrylate monomers as skin sensitizers with predicted LLNA EC3 values and human NOEL values of 0.848% and 22.4%, and 230 µg/cm2and 12200 µg/cm2, resulting in final classifications as a strong to moderate skin sensitizer (HP 2) and a moderate to weak sensitizer (HP 5), respectively. The results agreed with information in the ECHA registration dossiers and gathered human data evidence for the respective monomers, illustrating that GARDskin Dose-Response has the potential to replace the in vivo LLNA method for quantitative potency assessment of potential skin sensitizers during development of novel materials for use in medical devices.

A big step for non-animal methods in skin sensitization testing of medical devices

The new standard for skin sensitization ISO 10993-10 is freshly published and now includes in vitro methods – a big step for non-animal methods in skin sensitization testing of medical devices!

Our GARD assay is included in the standard, can be used with both saline and oil as extraction vehicles and provides human relevant results.

Learn how GARD can be used in your risk assessment

To learn how GARDskin Medical Device can be used in your risk assessment, contact our medical device and ISO expert Rose-Marie Jenvert, PhD on LinkedIn or mail: rose-marie.jenvert@senzagen.com.

Link to the standard: ISO 10993-10:2021: Biological evaluation of medical devices — Part 10: Tests for skin sensitization

Assessment of the skin sensitizing potential of pandemic-associated medical devices using the GARDskin Medical Device assay

Joint poster with Essity Hygiene & Health AB,
Presented at the 2021 Eurotox annual meeting

P. Mohlin, A. Forreryd, O. Larne, R.-M. Jenvert, H. Johansson | Essity Hygiene & Health AB, Product Safety, Clinical & Regulatory Affairs, Mölndal, Sweden; SenzaGen AB, 22381 Lund, Sweden

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Conclusion

  • GARDskin is well adapted to risk assess the skin sensitizing potential of medical devices in accordance with ISO 10993.
  • GARDskin Medical Device classified the tested commercially available face masks as non-sensitizers and the nitrile glove as sensitizers.
  • New in vitro technologies, like GARD, is well suited as a routine tool to increase the speed of decision making in extraordinary situations as a pandemic.

Abstract

The current SARS-CoV-2 pandemic have led to an increased use of medical devices such as face masks and nitrile gloves, within occupational groups of medical care as well as within the general population. Consequently, the incidence reports of adverse effects associated with use of such medical devices have increased manyfold, including reports of allergic skin reactions.

The cause of allergic skin reactions, referred to as Allergic Contact Dermatitis (ACD) is the immunological process known as skin sensitization, which is induced by so-called chemical sensitizers. Assessment of skin sensitizing potential of leachables from medical devices is a part of biocompatibility testing of medical devices and is typically performed by use of the Guinea Pig Maximization Test (GPMT), in accordance with the ISO 10993 series of standards. However, recent developments of in vitro assays for assessment of chemical sensitizers motivates the exploration of such methods in the context of rapid pandemic-associated testing.

The GARDskin assay [1] is a next-generation in vitro assay for hazard assessment of skin sensitizers, currently progressing towards regulatory acceptance. The method evaluates the transcriptional patterns of a genomic biomarker signature in a human dendritic-like cell line following exposure, in order to provide hazard assessments of tested substances. The method has been adapted to testing of solid materials from e.g. medical device products, by application of extraction protocols using polar- and non-polar extraction vehicles, in accordance with ISO 10993-12.

Here, we present results from testing of a commonly used face mask and a nitrile glove in the GARDskin Medical Device assay. Results indicate that the face mask does not leach any compounds with skin sensitizing potential (among four different batches tested), while the nitrile glove was classified as a skin sensitizer. These results harmonize with preexisting experience of similar models of nitril gloves, which are known to be associated with adverse skin reactions, potentially induced by skin sensitization. Furthermore, these results may have implications on the continued use of similar medical devices throughout the pandemic and beyond, as the appropriate application and removal of face masks may indeed benefit from the discontinued simultaneous use of nitrile gloves.

Applicability domain of the GARD™skin Medical Device test for in vitro skin sensitization testing of medical devices

Poster presented at SOT 2021

Joshua Schmidt, Ron Brown and Rose-Marie Jenvert
SenzaGen Inc., Raleigh, NC, USA, Risk Science Consortium LLC, Arnold, MD, USA, SenzaGen AB, Lund, Sweden.

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Conclusion

  • The chemical space of compounds tested in GARD closely approximates the chemical space of compounds known to be released from medical device materials.
  • GARDskin is able to predict the skin sensitization potential of compounds released from medical device materials with a high degree of sensitivity and specificity, including: metals, lipophilic compounds and pre/pro haptens.

Abstract

Medical device toxicology is undergoing an exciting evolution; transitioning from a process that largely relied on the results of animal testing to evaluate the biological safety of devices in patients to one which is increasingly focused on the use of in vitro methods for the safety assessment of device materials.

Recently, in vitro methods to assess endpoints such as skin irritation and pyrogenicity have been validated and proposed for medical device testing, but a method to assess the potential for device-related skin sensitization to occur has not been sufficiently qualified. A number of in vitro skin sensitization test methods have been shown to have acceptable predictive ability for known skin sensitizers with structures that span a broad range of chemical classes, but the predictive ability of these methods has not been specifically evaluated using compounds typically found in materials used to manufacture medical devices. As a result, the need exists to qualify in vitro methods to assess the skin sensitization of compounds that may be released from medical devices, taking into account the applicability domain of known or potential skin sensitizers, including metals.

To address this challenge, the predictive ability of the GARD assay has been evaluated using a dataset of compounds known to be released from device materials.  Against these data, the assay correctly predicted 19 out of 21 lipophilic and pre-/pro-hapten compounds (90.5% accuracy), with one false positive (95.2% sensitivity) and one false negative (95.2% specificity) being predicted, thus increasing the confidence in use of this in vitro assay to assess the skin sensitization potential of medical devices.  Furthermore, we have also demonstrated that the GARD assay correctly predicts the skin sensitization response of nickel and cobalt salts (sensitizers) and a zinc salt (non-sensitizer). Overall, our data support the use of the GARDskin Medical Device assay as an in vitro alternative for the in vivo methods (e.g., GPMT, LLNA) that are typically used to assess skin sensitization as part of the biological safety assessment of medical devices.