Tag Archive for: challenging substances

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

Exploration of the GARDskin applicability domain: Indirectly acting haptens, hydrophobic substances and UVCBs

Joint publication with the Lubrizol Corporation

ALTEX – Alternatives to animal experimentation, published April 21, 2022, accepted manuscript, https://doi.org/10.14573/altex.2201281

Forreryd, A., Gradin, R., Humfrey, C., Sweet, L. and Johansson, H.

Abstract

Hazard assessments of skin sensitizers are increasingly being performed using new approach methodologies (NAMs), with several in chemico, in vitro and most recently also defined approaches (DAs) being accepted for regulatory use. However, keeping track of potential limitations of each method in order to define applicability domains remains a crucial component to ensure adequate predictivity as well as facilitating the appropriate selection of method(s) for each hazard assessment task. The objective of this report is to share test results generated with the GARD™skin assay on chemicals that have traditionally been considered as difficult to test in some of the conventional in vitro and in chemico OECD Test Guidelines for skin sensitization. Such compounds may include, for example, indirectly acting haptens, hydrophobic substances, and substances of unknown variable composition or biological substances (UVCBs). Based on the results of this study, the sensitivity for prediction of skin sensitizing hazard of indirectly acting haptenswas92.4%and 87.5%, when compared with LLNA(n=25)and human data(n=8), respectively. Similarly, the sensitivity for prediction of skin sensitizing hazard of hydrophobic substances was 85.1% and 100%, when compared with LLNA(n=24)and human data(n=9), respectively. Lastly, a case study involving the assessment of a set of hydrophobic UVCBs(n=7) resulted in a sensitivity of 100, as compared to available reference data. Thus, it was concluded that these data provide support for the inclusion of such chemistries in the GARD™skin applicability domain, without an increased risk of false negative classifications.

Key words: GARD, GARDskin, skin sensitization, applicability domain, difficult to test substances, Indirectly acting haptens, hydrophobic substances, UVCBs

 

Full article
Article on line with open access

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.

Applicability of GARD™skin for Accurate Assessment of Challenging Substances in the Context of Skin Sensitization Testing

Poster presented at ACT 2020

J. Schmidt, A. Forreryd, H. Johansson, J. Li, A. Johansson
SenzaGen, Inc., Raleigh, NC, USA, SenzaGen AB, Lund, Sweden

Link to the poster

 

Conclusion

  • GARDskin demonstrated an overall high applicability for the evaluated challenging substances with 80% predictive accuracy compared to existing human data.
  • GARDskin demonstrated excellent applicability for pre/pro-haptens and low water solubility substances, correctly classifying all such compounds in the herein investigated dataset.
  • GARDskin also showed high applicability for assessment of surfactants with 89% predictive accuracy compared to existing human data, correctly classifying 8 out of 9 internally tested surfactants, including well known challenging ones such as Sodium Dodecyl Sulphate (SDS) and Benzalkonium chloride.

Abstract

Current legislations and trends in predictive toxicology advocate a transition from in vivo methods for hazard and risk assessments to non-animal alternatives. However, certain groups of chemicals, including substances with severe membrane-damaging properties, pre- and pro-haptens, and those with high log P ratios, have been shown to be challenging to assess using cell-based assays in the context of skin sensitization testing. The aim of this study was to evaluate the applicability of GARDskin for such challenging substances, using an overlapping subset of chemicals previously tested in an integrated tested strategy (ITS) based on validated, aqueous in vitro assays, as well as in a series of Reconstructed Human Epidermis (RHE)-based assays.

The GARDskin assay (Genomic Allergen Rapid Detection) is a robust in vitro assay for identification of potential chemical skin sensitizers with over 90% prediction accuracy and broad applicability. The assay is included in the OECD Test Guideline Program (OECD TGP 4.106) and has gone through a formal validation study. The assay evaluates the gene expression of endpoint-specific genomic biomarkers in a human dendritic-like cell line following exposure to the test substance. Exposure-induced gene expression patterns are analysed using pattern recognition and machine-learning technology, providing classifications of each test item as a skin sensitizer or a non-sensitizer.

The applicability of GARDskin for a total of twelve challenging substances, including pre- and pro-haptens, low water-soluble substances, two surfactants and three additional substances known to have conflictive results when comparing in vitro and in vivo data were evaluated in this study. All twelve substances were selected from the Mehling et al. 2019 publication which reported results from three OECD validated in vitro methods, the “2 out of 3” Integrated Testing Strategy, three RHE-based models and the murine local lymph node assay (LLNA). Human potency classification was available for ten out of the twelve substances.

The GARDskin prediction results were reported from previously published studies, or from in house validation studies. Predictive accuracies were calculated by comparing skin sensitization classifications from different test methods to the available human data of each substance respectively. (N=10). To further explore and substantiate the GARDskin applicability for surfactants, additional GARDskin data for a total of nine surfactants are presented in order to complement the Mehling dataset with respect to the availability of human data.

The GARDskin assay demonstrated overall high applicability for the evaluated challenging substances, with 80% predictive accuracy compared to existing human data. GARDskin correctly classified all pre-and pro-haptens and low water-soluble substances in the data set. Furthermore, high applicability of GARDskin for severe membrane disruptive substances such as surfactants was demonstrated, with 89% predictive accuracy compared to existing human data.