Tag Archive for: Skin Sensitization
Joint publication with RIFM and IFF: Determining a Point of Departure for Skin Sensitization Potency and Quantitative Risk Assessment of Fragrance Ingredients Using the GARD®skin Dose-Response Assay
Advancing NAMs for Fragrance Safety: Collaborative Research with RIFM and IFF.
As innovators in in vitro skin sensitization testing, addressing key data gaps, we are pleased to share the publication of a new peer-reviewed article in ALTEX, which underscores the performance of GARD®skin Dose-Response in predicting the skin sensitization potency of fragrance ingredients. This study, conducted in collaboration with the expert teams at the Research Institute for Fragrance Materials, Inc. (RIFM) and IFF, contributes valuable insights to the growing body of research supporting more reliable, non-animal testing methods.
The article presents a comprehensive dataset of 100 fragrance ingredients, covering a broad chemical domain with diverse structural reactivity domains and potency levels. The results confirm GARD®skin Dose-Response‘s robust predictivity for skin sensitization potency across this wide chemical spectrum, strengthening its application for deriving No Expected Sensitization Induction Level (NESIL) values in Quantitative Risk Assessment (QRA) within frameworks like Next Generation Risk Assessment (NGRA). These advancements are pivotal in further reducing reliance on animal testing while enhancing risk assessment capabilities.
We would like to extend our gratitude to the exceptional teams who contributed to this collaboration: Isabelle Lee, Andy Forreryd, Mihwa Na, Isabella Schember, Maura Lavelle, Robin Gradin, Ulrika Mattson, Henrik Johansson, Shashi Donthamsetty, Gregory Ladics, and Anne Marie Api.
Isabelle Lee, Andy Forreryd, Mihwa Na, Isabella Schember, Maura Lavelle, Robin Gradin, Ulrika Mattson, Henrik Johansson, Shashi Donthamsetty, Gregory Ladics, and Anne Marie Api. ALTEX - Alternatives to animal experimentation.(2025) https://www.altex.org/index.php/altex/article/view/2810
Keywords
skin sensitization, fragrance materials, point of departure, OECD TG 442E, GARDskin, new approach methodology
Abstract
Potency and quantitative risk assessment are essential for determining safe concentrations for the formulation of potential skin sensitizers into consumer products. Several new approach methodologies (NAMs) for skin sensitization hazard assessment have been developed, validated, and adopted in OECD test guidelines. However, work is ongoing to develop NAMs for predicting skin sensitization potency on a quantitative scale for use as a point of departure (POD) in next-generation risk assessment (NGRA). GARDskin Dose-Response (DR) is an adaptation of the validated GARDskin assay (OECD TG 442E), and the readout of the assay is a quantitative potency prediction similar to the No Expected Sensitization Induction Level (NESIL) value (µg/cm2). The goal of this study was to evaluate the performance of the GARDskin DR assay for potency prediction of fragrance ingredients. One hundred (100) fragrance ingredients from a reference database covering varied structural reactivity domains and potency were tested in GARDskin DR. Materials tested had varied protein-binding reactivity alerts, including Schiff base, Michael addition, SN2, and acylation. Potency categories were predicted with a total accuracy of 37% and an approximate accuracy (exact match or off by 1 category) of 81%. Combining predicted weak and very weak categories increased total accuracy to 53% and approximate accuracy to 98%. The mean prediction error for the NESIL and local lymph node assay (LLNA) EC3 was 3.15- and 3.36-fold, respectively. Based on the results of this study, GARDskin DR is a promising predictor of skin sensitization potency with an applicability domain covering a wide range of fragrance ingredient reaction mechanisms, increasing the confidence in using the assay to conduct NGRA, ultimately reducing the need for animal testing.
Plain language summary
This study focused on testing a new in vitro method, GARDskin Dose-Response (DR), to predict the quantitative potency of fragrance ingredients in causing skin sensitization. This potency is important for setting safe levels of chemicals in consumer products. The GARDskin DR assay, based on an existing skin sensitization test (OECD TG 442E), provides a quantitative measure of potency similar to the No Expected Sensitization Induction Level (NESIL). One hundred (100) fragrance ingredients with different chemical structures and reactivity patterns were tested. The assay accurately distinguished between sensitizers and non-sensitizers for 81% of the materials, and also correctly predicted their approximate potency categories. The results show that GARDskin DR is a promising tool for predicting quantitative potency for skin sensitization risk, helping to reduce animal testing and support safer product development.
Joint publication with L’Oréal: In vitro prediction of skin sensitizing potency using the GARDskin Dose-Response assay: A simple regression approach
New joint publication with L’Oréal.
We are excited to announce the recent publication of a collaborative scientific paper by the expert teams at L’Oréal and SenzaGen, in Toxics MDPI. This peer-reviewed article presents new evidence on the performance of the GARD®skin Dose-Response for quantitative potency assessment of skin sensitizers.
With an extended set of 30 chemicals and a composite potency model for the prediction of sensitizing potency, the study demonstrates the ability of GARD®skin Dose-Response to predict a Point-of-Departure (PoD) for potential skin sensitizers, showing concordance with NESIL values derived from LLNA and Human data.
This research represents a significant advancement in deriving PoD values for chemicals which can be used directly in improving downstream risk assessment strategies.
Gradin R, Tourneix F, Mattson U, Andersson J, Amaral F, Forreryd A, Alépée N, Johansson H. Toxics. 2024; 12(9):626. https://doi.org/10.3390/toxics12090626
Keywords
NAM; GARDskin Dose-Response; Sensitizing potency; Quantitative risk assessment; Point of departure
Abstract
Toxicological assessments of skin sensitizers have progressed towards a higher reliance on non-animal methods. Current technological trends aim to extend the utility of non-animal methods to accurately characterize skin sensitizer potency.
The GARDskin Dose-Response assay was previously described where it was shown that its main readout, the cDV0 concentration, was associated with skin sensitizing potency. The ability to predict potency in the form of NESILs derived from LLNA or human NOEL, from cDV0, was evaluated. The assessment of a dataset of 30 chemicals showed that the cDV0 values still correlated strongly and significantly with both LLNA EC3 and human NOEL values (ρ = 0.645-0.787 [p < 1×10-3]).
A composite potency value that combined LLNA and human potency data was defined, which aided the performance of the proposed model for the prediction of NESIL. The potency model accurately predicted sensitizing potency, with cross-validation errors of 2.75 and 3.22 fold changes compared with NESILs from LLNA and human, respectively.
In conclusion, the results suggest that the GARDskin Dose-Response assay may be used to derive an accurate quantitative continuous potency estimate of skin sensitizers.
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.
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
Full article on line with open access
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