Tag Archive for: Skin Sensitization

Joint publication with IFF and RIFM: GARDskin dose-response assay and its application in conducting Quantitative Risk Assessment (QRA) for fragrance materials using a Next Generation Risk Assessment (NGRA) framework

New joint publication with International Flavors & Fragrances Inc (IFF) and Research Institute for Fragrance Materials (RIFM).

SenzaGen scientists, alongside the scientific teams at International Flavors & Fragrances Inc and Research Institute for Fragrance Materials, have jointly published an article in Regulatory Toxicology and Pharmacology, presenting new peer-reviewed evidence on the performance of the GARD®skin Dose-Response assay for Quantitative Risk Assessment of fragrance materials.

The study results confirm the ability of GARD®skin Dose-Response to predict human NESIL values with good predictive performance, showing good concordance with published reference Human data and demonstrating good reproducibility.

Furthermore, the paper also presents a case study to illustrate how the predicted NESIL value from GARDskin Dose-Response can be used in practice within a NGRA framework to establish a maximum allowable concentration of a sensitizer in different consumer products.

The study represents a major step towards the establishment of the assay to derive NESIL values for conducting QRA evaluations for fragrance materials using an NGRA framework.

Shashikiran Donthamsetty, Andy Forreryd, Paul Sterchele, Xiao Huang, Robin Gradin, Henrik Johansson, Ulrika Mattson, Isabelle Lee, Anne Marie Api, Gregory Ladics,
Regulatory Toxicology and Pharmacology, Volume 149, 2024, 105597, ISSN 0273-2300,
https://doi.org/10.1016/j.yrtph.2024.105597

Keywords

QRA (Quantitative Risk Assesment); Dermal sensitization; Fragrance materials; Next Generation Risk Assesment (NGRA); GARD assay; No Expected Sensitization Induction Level (NESIL); New Approach Methodologies (NAMs); OECD 442E

Highlights

  • Developed a Next Generation Risk Assessment (NGRA) framework for conducting QRA2 for fragrance materials.
  • The GARDskin Dose Response (DR) assay is a reliable and reproducible method for predicting NESIL for fragrance materials.
  • NGRA for QRA2 was validated using isocyclocitral as a case study.


Abstract

Development of New Approach Methodologies (NAMs) capable of providing a No Expected Sensitization Induction Level (NESIL) value remains a high priority for the fragrance industry for conducting a Quantitative Risk Assesment (QRA) to evaluate dermal sensitization. The in vitro GARDskin assay was recently adopted by the OECD (TG 442E) for the hazard identification of skin sensitizers. Continuous potency predictions are derived using a modified protocol that incorporates dose-response measurements. Linear regression models have been developed to predict human NESIL values. The aim of the study was to evaluate the precision and reproducibility of the continuous potency predictions from the GARDskin Dose-Response (DR) assay and its application in conducting QRA for fragrance materials using a Next Generation Risk Assessment (NGRA) framework. Results indicated that the GARDskin Dose-Response model predicted human NESIL values with a good degree of concordance with published NESIL values, which were also reproducible in 3 separate experiments. Using Isocyclocitral as an example, a QRA was conducted to determine its safe use levels in different consumer product types using a NGRA framework. This study represents a major step towards the establishment of the assay to derive NESIL values for conducting QRA evaluations for fragrance materials using a NGRA framework.

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.

 

Joint publication with Corteva Agriscience: GARD™skin and GARD™potency: A proof-of-concept study investigating applicability domain for agrochemical formulations

New joint publication with Corteva Agriscience.

SenzaGen scientists, alongside the toxicology team at Corteva Agriscience, have recently published a joint study in Regulatory Toxicology and Pharmacology, presenting new peer-reviewed evidence on the applicability of GARD® for agrochemical formulations.

The study demonstrates a satisfactory performance of GARD®skin and GARD®potency for skin sensitization hazard and GHS potency categorization of tested agrochemical formulations.

Marco Corvaro, Joseph Henriquez, Raja Settivari, Ulrika Mattson, Andy Forreryd, Robin Gradin, Henrik Johansson, Sean Gehen,
Regulatory Toxicology and Pharmacology, Volume 148, 2024, 105595, ISSN 0273-2300,
https://doi.org/10.1016/j.yrtph.2024.105595.

Keywords

GARD™; In vitro; Skin sensitisation; NAMs; Agrochemical formulations

Highlights

  • Tested 42 agrochemical formulations to expand applicability domain of GARD.

  • GARDskin showed good accuracy (76.2%), sensitivity (85.0%) and specificity (68.2%).
  • GARDpotency correctly subcategorized 14/17, correctly predicted sensitisers.
  • GARD satisfactory for Key Event 3 characterisation of agrochemical formulations.


Abstract

Several New Approach Methodologies (NAMs) for hazard assessment of skin sensitisers have been formally validated. However, data regarding their applicability on certain product classes are limited. The purpose of this project was to provide initial evidence on the applicability domain of GARD™skin and GARD™potency for the product class of agrochemical formulations.

For this proof of concept, 30 liquid and 12 solid agrochemical formulations were tested in GARDskin for hazard predictions. Formulations predicted as sensitisers were further evaluated in the GARDpotency assay to determine GHS skin sensitisation category. The selected formulations were of product types, efficacy groups and sensitisation hazard classes representative of the industry’s products.

The performance of GARDskin was estimated by comparing results to existing in vivo animal data. The overall accuracy, sensitivity, and specificity were 76.2% (32/42), 85.0% (17/20), and 68.2% (15/22), respectively, with the predictivity for liquid formulations being slightly higher compared to the solid formulations. GARDpotency correctly subcategorized 14 out of the 17 correctly predicted sensitisers. Lack of concordance was justifiable by compositional or borderline response analysis. In conclusion, GARDskin and GARDpotency showed satisfactory performance in this initial proof-of-concept study, which supports consideration of agrochemical formulations being within the applicability domain of the test methods.

 

New scientific publication by ExxonMobil: Challenges integrating skin sensitization data for assessment of difficult to test substances

New scientific publication by ExxonMobil.

Check out this newly published article by ExxonMobil focusing on the challenges of determining skin sensitization hazard in the case of difficult-to-test substances with conflicting or low-confidence data, where GARDskin data on UVCBs and hydrophobic substances provides valuable input for the integrated hazard assessment.

The article provides new peer-reviewed evidence for the applicability domain of GARDskin on UVCBs, hydrophobic and highly complex substances.

Greminger A, Frasca J, Goyak K, North C. 
Challenges integrating skin sensitization data for assessment of difficult to test substances. 
ALTEX - Alternatives to animal experimentation, published Oct 12, 2023
doi: 10.14573/altex.2201122. Epub ahead of print. PMID: 37843019.

Keywords

LLNA; ToxPi; new approach methodologies; skin sensitization; weight of evidence.


Abstract

Difficult to test substances including poorly soluble, mildly irritating, or Unknown or Variable Composition Complex reaction products or Biological Materials (UVCBs), producing weak or borderline in vivo results, face additional challenges in in vitro assays that often necessitates data integration in a weight of evidence (WOE) approach to inform skin sensitization potential. Here we present several case studies on difficult to test substances and highlight the utility of Toxicological Prioritization Index (ToxPi) as a data visualization tool to compare skin sensitization biological activity. The case study test substances represent two poorly soluble substances, tetrakis (2-ethylbutyl) orthosilicate and decyl palmitate, and two UVCB substances, alkylated anisole and hydrazinecarboximidamide, 2-[(2-hydroxyphenyl)methylene]-, reaction products with 2 undecanone. Data from key events within the skin sensitization adverse outcome pathway were gathered from publicly available sources or specifically generated. Incorporating the data for these case study test substances as well as on chemicals of a known sensitization class (sensitizer, irritating non-sensitizer, and non-sensitizer) into ToxPi produced biological activity profiles which were grouped using unsupervised hierarchical clustering. Three of the case study test substances concluded to lack skin sensitization potential by traditional WOE produced biological activity profiles most consistent with non-sensitizing substances, whereas the prediction was less definitive for a substance considered positive by traditional WOE. Visualizing the data using bioactivity profiles can provide further support for WOE conclusions in certain circumstances but is unlikely to replace WOE as a stand-alone prediction due to limitations of the method including the impact of missing data points.

 

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

Presented at Eurotox 2023

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

​Anna Chérouvrier Hansson1, Lisa Theorin1, Andy Forreryd1, Monica Grekula2 and Anneli Johansson3  1SenzaGen AB, 2Limulus Bio (Veranex), 3Duearity AB

 

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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.

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

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

Peter Nählstedt2, Shashi Donthamsetty1 , Andy Forreryd2, Paul Sterchele1, Xiao Huang1, Robin Gradin2, Henrik Johansson2, Ulrika Mattsson2, Isabelle Lee3, Anne Marie Api3, Gregory Ladics1

1 International Flavors & Fragrances USA ,2 SenzaGen AB Sweden, 3Research Institute for Fragrance Materials USA

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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.

 

 

 

 

GARDskin Dose-Response assay for PoD determination of fragrance materials and its application in conducting Quantitative Risk Assessment (QRA)

Presented at SOT 2023

GARDskin Dose-Response assay for PoD determination of fragrance materials and its application in conducting Quantitative Risk Assessment (QRA)

Shashi Donthamsetty1 , Andy Forreryd2, Paul Sterchele1, Xiao Huang1, Robin Gradin2, Henrik Johansson2, Ulrika Mattsson2, Isabelle Lee3, Anne Marie Api3, Gregory Ladics1

1 International Flavors & Fragrances USA ,2 SenzaGen AB Sweden, 3Research Institute for Fragrance Materials USA

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Conclusion

  • The continous readout from the assay is reproductible 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 to be used for conducting the quantitative risk assesment for generating the IFRA standard.

Abstract

The global fragrance industry applies Quantitative risk assessment (QRA) to develop risk management practices (IFRA Standards) for ingredients that are identified as potential dermal sensitizers. An important step in QRA is determination of a ”No Expected Sensitization Induction Level” (NESIL), which has historically been determined using human data with the support of animal data (e.g., murine local lymph node assay (LLNA). The EC3 value determined in the LLNA is used as the guidance for selection of the dose level in HRIPTs (Human Repteated Insult Patch Test) to confirm a NESIL value. The fragrance industry has adopted new approach methodologies (NAM) to address skin sensitization. Although several NAMs for identifying skin sensitizers have been accepted as Test Guidelines by OECD, these methods have thus far been validated only for hazard identification. Since a NESIL value is a key requirement to evaluate sensitizing potency for conducting QRA evaluations, development of a NAM-based strategy capable of providing potency data in the form of NESIL remains a high priority for the fragrance industry. The in vitro GARDskin assay was recently adopted by the OECD (TG 442E) for the hazard identification of skin sensitizers. Continuous 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 NESIL values. The aim of the study was to evaluate the precision and reproducibility of the continuous potency predictions from the GARDskin Dose-Response assay. A total of 17 test materials were evaluated, 11 of which were evaluated in three blinded studies separated in time. Preliminary results indicated that the GARDskin Dose-Response model predicted LLNA EC3 values and human NESIL values with geometric mean fold-misprediction factors of 3.8 and 2.5, respectively. For comparative reasons, the LLNA EC3 predicted the human NESIL values with a fold-misprediction factor of 3.7 in the same dataset. Results from the repeated assessment of the test materials were reproducible, with an estimated geometric mean range of fold-changes between replicates of 2.9. Using isocyclocitral (CAS 1335-66-6) as an example, a QRA was conducted to determine its safe use levels in different consumer product types. The results demonstrate that the LLNA EC3 values and the human NESIL values predicted from the GARDskin Dose-Response assay are reproducible between experiments and show good concordance with the published NESIL and EC3 values. Together with the reported performance data, this represents a major step towards the establishment of the assay as a relevant source of information to derive NESIL values for conducting QRA evaluations for fragrance materials to ensure product safety while avoiding the generation of new animal data.

 

 

 

 

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.

GARD®skin Dose-Response for Photosensitization: ​Assessment of Reference Photoirritants and Photoallergens

Presented at SOT 2023

GARD®skin Dose-Response for Photosensitization: ​Assessment of Reference Photoirritants and Photoallergens

Tim Lindberg1, Gretchen Ritacco2, Anders Jerre1, Robin Gradin1, Andy Forreryd1, Henrik Johansson1, Anne Marie Api 1SenzaGen, Lund, Sweden, 2Research Institute for Fragrance Materials. Woodcliff lake, NJ, USA

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Conclusion

  • Increase in cytotoxicity after UV exposure strongly linked with predominantly photo irritating properties.
  • Decrease in GARDskin Dose-Response cDV0-value after UV exposure indicative of photoallergenic properties​.

Abstract

Dermal exposure to certain chemical compounds, so-called sensitizers, can give rise to adverse outcomes induced by an immunological response towards the specific compound. One such class of compounds, photosensitizers, needs to be activated by UV rays to elicit an immune response. Although rare in occurrence, it is a critical human health endpoint in need of investigation to limit potential exposures. Other phototoxic skin reactions include photoirritation, which is manifested as a one-time occurrence at the site of exposure that goes away over time. While testing schemes for photoirritation are clear, testing for photosensitization remains a challenge and no established in vitro model to evaluate this endpoint currently exists. For risk management purposes, distinguishing between phototoxic properties is important, as concentration limits can be set for photoirritants whereas fragrance photoallergens have historically been banned. 

The GARDskin assay is a next-generation in vitro method for hazard classification of conventional skin sensitizers, included in OECD TG 442E. The assay is based on a human dendritic -like cell line and combines genomics and machine learning to achieve a high predictive performance with a large applicability domain. The GARDskin Dose-Response assay is based on the validated GARDskin protocols but instead of giving a binary classification it provides quantitative information about the lowest concentration needed to induce a positive classification in the assay, termed the cDV0 concentration. To investigate phototoxicity, an extra UV-exposure step was added to the original protocol, with photosensitization determined by a drop in cDV0 concentration after UV-exposure, i.e., the cDV0 concentration of the specific compound is lower after UV-exposure than in the non-exposed counterpart.  

The study presented here aimed at investigating the applicability of the GARDskin Photo Dose-Response assay to correctly assess photoallergens and distinguish them from photoirritant effects. Previous studies have indicated that a shift in cytotoxic profile after UV-exposure may indicate a predominantly photoirritant activity rather than photosensitizing and this was also investigated in the present study. Six reference photoirritants and six reference photoallergens were investigated using the GARD®skin Dose-Response assay in combination with a UV irradiation protocol. Cytotoxic profiles and cDV0-values were established for each compound in the presence and absence of UV exposure. 5 out of 6 photoirritants were correctly predicted based on their cytotoxic profile while 3 out of 6 photoallergens where correctly predicted based on the decrease in cDV0-value after UV-exposure. In conclusion, functionality of combining GARDskin Dose-Response protocols with UV irradiation to investigate phototoxicity was shown. Further, photoirritant effects were strongly correlated to a shift in cytotoxic profile after UV-exposure and a decrease in cDV0 values after UV-exposure may indicate on photosensitizing effects. However, further work may be warranted to establish a final prediction model for photosensitization.  

Keywords: Predictive Toxicology, GARDskin, Phototoxicity, Quantitative Risk Assesment

 

 

 

 

The GARDskin assay: Investigation of the applicability domain for metals

Joint publication with Johnson Matthey

ALTEX – Alternatives to animal experimentation, published Nov 03, 2022, accepted manuscript

DOI: https://doi.org/10.14573/altex.2203021

Forreryd, A., Gradin, R., Larne, O., Rajapakse, N., Deag, E. and Johansson, H.


Abstract

New approach methods (NAMs) for hazard identification of skin sensitizing chemicals have been adopted as test guidelines by the OECD during the last decade as alternatives to animal models. These models align to individual key events (KE) in the adverse outcome pathway (AOP) for skin sensitization for which the molecular initiating event (MIE) is covalent binding to proteins. As it currently stands, the AOP does not include mechanistic events of sensitization by metals, and limited information is available on whether NAMs accurately the predict sensitization potential of such molecules, which have been proposed to act via alternative mechanisms to organic chemicals.

Methods for assessing the sensitization potential of metals would comprise valuable tools to support risk management within e.g., occupational settings during production of new metal salts or within the medical device industry to evaluate leachables from metal alloys.

This paper describes a systematic evaluation of the applicability domain of the GARD™skin assay for assessment of metals. Hazard classifications were supplemented with an extended analysis of gene expression profiles induced by metal sensitizers to compare the induction of toxicity pathways between metals and organic sensitizers. Based on the results of this study, the accuracy, sensitivity, and specificity of GARD™skin for prediction of skin sensitizing hazard were 92% (12/13), 100% (7/7) and 83% (5/6), respectively.

Thus, the performance of GARD™skin for assessment of metals was found to be similar to what is observed on conventional organic substances, providing support for inclusion of metals within the applicability domain of the test method.

Keywords

skin sensitization, metals, regulatory testing, medical devices

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