Inter-laboratory ring trial of the GARD™air assay for assessment of respiratory sensitizers

Andy Forreryd1, Joshua Schmidt1, Robin Gradin1, Florence Burleson, Helge Gehrke3, Henrik Johansson1.
1SenzaGen AB, Lund, Sweden. 2Burleson Research Technologies, Morrisville, NC, USA. 3Eurofins BioPharma Product Testing Munich GmbH, Planegg, Germany.

Sensitization of the respiratory tract by sensitizing chemicals may lead to severe bronchoconstriction and asthma-like symptoms with a potentially fatal outcome. However, proactive identification and characterization of respiratory sensitization hazards is currently hampered by the lack of validated or even widely used predictive assays.

The GARD™ platform utilizes exposure-induced gene expression profiles of a dendritic cell-like cell line in combination with machine learning as a basis for predictive in vitro assays for different immunotoxicity endpoints (Johansson et al., 2020). Functional evidence of the ability to accurately identify respiratory sensitizers using the GARD platform has previously been demonstrated (Forreryd et al., 2015). Here, we present GARDair, an adaptation of previous findings on a gene expression analysis platform suited for routine acquisition, based on an optimized predictive biomarker signature. Furthermore, we present the initial results of an inter-laboratory ring-trial, demonstrating the functionality, transferability and reproducibility of the assay.

Conclusion

  • GARDair is a novel in vitro assay for assessment of respiratory sensitizers, based on evaluation of exposure-induced gene expression of genomic biomarkers in a Dendritic Cell-like cell and machine-learning assisted classification.
  • GARDair is the first in its class to be subjected to an inter-laboratory ring trial.
  • The method is highly specific, with high PPV, making it suitable for opt-out applications within product development and candidate prioritization.

Link to poster

Poster abstract accepted at SOT 2020. 

The GARD Skin Assay: A New In Vitro Testing Strategy for Skin Sensitization

E. Schmidt, V. Zuckerstätter, H. Gehrke | Eurofins BioPharma Product Testing Munich GmbH

Introduction 
A skin sensitiser refers to a substance that will lead to an allergic response following skin contact as defined by the United Nations Globally Harmonized System of Classification and Labelling of Chemicals (UN GHS). The potential to induce skin sensitisation is an important consideration included in procedures for the safe handling, packaging and transports of chemicals.

The assessment of skin sensitisation typically involves the use of laboratory animals. Classical methods comprise the Magnusson Kligman Guinea Pig Maximisation Test, the Buehler Test (TG 406) as well as the local lymph node assay, in its radioactive and non-radioactive form (TG 429, TG 442A/B). In order to replace in vivo experiments validation studies on alternative, mechanistically based in chemico and in vitro test methods on skin sensitisation were conducted under the auspices of ECVAM and have been considered scientifically valid for the evaluation of the skin sensitisation hazard of chemicals.

Genomic Allergen Rapid Detection (GARDTM) is an in vitro assay designed to predict the ability of chemical substances to induce skin sensitisation based on the analysis of the relative expression levels of a biomarker signature of 196 genes using a human myeloid leukaemia cell line called SenzaCells. The GARDTM assay is based on chemical stimulation of the SenzaCells, acting as an in vitro model of human Dendritic Cells (DCs). The readout of the assay is a transcriptional quantification of the genomic predictors, collectively termed the GARDTM Prediction Signature (GPS), using Nanostring nCounter technology.

Conclusion
The DPRA, KeratinoSensTM and h-CLAT are well known sensitization assays which address three different key events of the AOP. The GARDTM skin assay is a new procedure that analyses the sensitization potential based on almost 200 human genes. If a substance is a skin sensitiser with the GARDTM skin assay you have the benefit of measuring the potency on top with a different code set to make a 1A or 1B classification.
The GARDTM skin assay is especially for products that have a high log Pow (h-CLAT > 3.5, KeratinoSensTM > 7) because in those cases the classical sensitization tests are inconclusive if negative and there is no option for a replacing test method. Therefore, the GARDTM skin assay is not only an excellent alternative of the sensitization methods for these cases but it can furthermore predict the potency of a skin sensitiser, a unique feature, which makes it a testing method needed in the future.

Link to poster

Poster presented at Eurotox, Helsinki, Sep 9, 2019.

 

In vitro skin sensitization testing of Medical Devices using GARD®

Rose-Marie Jenvert, Angelica Johansson, Olivia Larne, Emelie Danefur, Emil Altonen, Anders Jerre, Robin Gradin, Gunilla Grundström.
SenzaGen, Lund, Sweden.

Introduction
All medical devices need to be evaluated for the end point skin sensitization according to the Biological Evaluation of Medical Devices (ISO 10993-1:2018), today commonly involving in vivo assays. Here, we show that the in vitro assay GARD®skin Medical Devices can classify leachables as either skin sensitizers or non-sensitizers in polar and non-polar extraction of Medical Devices.

Conclusion
GARD®skin Medical Device

  • is an in vitro alternative for assessment of skin sensitization of Medical Devices
  • is compatible with the extraction vehicles salin, olive oil and sesame oil.

Link to poster

Poster presented at Eurotox, Helsinki, Sep 9, 2019.

Extended solvent selection for in vitro sensitization testing using GARD®

Olivia Larne, Ulrika I Torstensdotter Mattson, Rikard Alm, and Gunilla Grundström.
SenzaGen, Lund, Sweden.

Introduction
The GARD®skin assay is an in vitro assay developed for the assessment of skin sensitizers. It is based on SenzaCells™, a human dendritic-like cell line, and a biomarker signature analyzed by a prediction model including pattern recognition and machine learning.

During the development of the GARD®skin platform, two solvents were used: DMSO (0.1%) and water. To increase the applicability domain of GARD®skin and the possibility to dissolve certain test items, for e.g. hard to dissolve substances and UVCBs, where show a broader range of solvents compatible with GARD®skin. Also, use of higher concentrations of the tested solvents were explored for the possibility to increase test item concentrations.

Concluding highlights
GARD®skin compatible solvents:

  • Acetone
  • DMF
  • DMF/Glycerol
  • DMSO
  • Ethanol
  • Glycerol
  • Isopropanol

Increased applicability domain.

Link to poster

Poster presented at Eurotox, Helsinki, Sep 9, 2019.

 

GARDair – A novel assay for assessment of chemical respiratory sensitizers based on a genomic platform

Henrik Johansson, Andy Forreryd, Robin Gradin, Angelica Johansson, Olivia Larne, Emil Aaltonen, Anders Jerre, Carl A.K. Borrebaeck and Malin Lindstedt
SenzaGen AB, Lund, Sweden. Department of Immunotechnology, Lund, Sweden.

Introduction
Exposure to chemicals may induce allergic hypersensitivity reactions in skin or respiratory tract. To minimize exposure, chemicals are routinely screened for their sensitizing potential. Proactive identification has historically been performed using animal models, but the use of animals for safety assessment of cosmetics was recently banned within EU. Today, similar trends are spreading both globally and across industry and market segments. Methods for specific identification of respiratory sensitizers are greatly underdeveloped, with no validated, or even widely used assay readily available. Thus, there is an urgent need for development of non-animal-based methods for hazard classification of respiratory sensitizing chemicals.

GARD– Genomic Allergen Rapid Detection – is a state of the art technology platform for assessment of chemical sensitizers (Figure 1). It is based on a dendritic cell (DC)-like cell line, thus mimicking the cell type involved in the initiation of the response leading to sensitization. Following test chemical exposure, induced transcriptional changes are measured to study the activation state of the cells. These changes are associated with the immunological decision-making role of DCs in vivo and constitutes of e.g. up-regulation of co-stimulatory molecules, induction of cellular and oxidative stress pathways and an altered phenotype associated with recognition of xenobiotic matter. By using state-of-the-art gene expression technologies, high informational content data is generated, that allows the user to get a holistic view of the cellular response induced by the test substance.

Conclusion
GARDair is a novel assay for assessment of respiratory sensitizers. It is an adaptation of the GARD platform, utilizing gene expression analysis of predictive biomarker signatures and state-of-the-art data analysis methodology. GARDair has been proven functional and is currently progressing towards industrial implementation and  regulatory acceptance with financial support from the EU programme Horizon 2020. This progress includes scientific verification of results, assay optimization, assay
transfer and formal validation by a blinded ring trial.

Link to poster

A mechanistic reinterpretation of the AOP for skin sensitisation

David W Roberts, Liverpool John Moores University, Liverpool

Introduction – Non-Animal Prediction: the 21st Century Consensus
Because of the biological complexity of the skin sensitisation process no single in chemico or in vitro assay will be an appropriate replacement for an animal-based assay such as LLNA or GPMT…
…to ensure a mechanistic basis and cover the complexity, multiple methods should be integrated into a testing strategy, in accordance with the adverse outcome pathway that describes all key events in skin sensitisation.

We need an ITS based on the KEs of the AOP…but
Is that what we really need?

Conclusion

A single assay, GARD™, predicts sensitisation potential and absence of sensitisation potential better than any of, or combinations of, the OECD guideline assays DPRA, KeratinosensTM (ARE-Nrf2 ) and h-CLAT.

We do not really need an ITS covering all KE’s of the AOP.

Link to poster

The Validation of GARD®skin

Sandberg P, Johansson A, Agemark M, Gradin R, Larne O, Appelgren H, Forreryd A, Jerre A, Edwards A, Hoepflinger V, Burleson F, Gehrke H, Roggen E, Johansson H
SenzaGen, Lund, Sweden, Burleson Research Technologies, Morrisville, US, Eurofins, Munich, Germany

Introduction
The prevalence of allergic contact dermatitis (ACD) is estimated to >20% in the western world. Not only the individual is affected, but downstream socioeconomic effects are high. To minimize exposure, chemicals must be safety tested. Traditional testing strategies like the murine local lymph node assay (LLNA) comprise animals, but the regulatory authorities, public opinion and economic interests require animal-free models. The Genomic Allergen Rapid Detection skin (GARD®skin) is an in vitro assay addressing this need. Here, we present the results of the GARD®skin ring trial (OECD TGP 4.106) for validity of the assay. In addition, we show data for GARD®potency – a complementary assay developed to categorize identified senitizers as CLP 1A or 1B.

 

Conclusions

Transfer study
Transferability: 100%

Validation study
Reproducibility
WLR: 82 – 89%BLR: 92% (92 – 100%)
Test performance
– Accuracy: 94%
– Sensitivity: 93%
– Specificity: 96%

A blinded ring trial was performed to assess the functionality of the GARDskin assay. The data demonstrates that GARDskin is a powerful tool for assessment of chemical skin sensitizers, with a predictive accuracy of 94% and excellent reproducibility between laboratories.
In addition, we show that GARDpotency accurately assesses potency of identified sensitizers.

Poster download

Predicting skin sensitizers with confidence – Using conformal prediction to determine applicability domain

Objective
GARD – Genomic Allergen Rapid Detection – is a state of the art non-animal based technology platform for classification of skin sensitizing chemicals. The assay has proven to be reliable and highly accurate for identification of skin sensitizing chemicals, and consistently reports predictive performances > 90% across external test sets. The aim of the current project is to complement assessments of average model performance with an estimate of uncertainty involved in each individual prediction, thus allowing for classification of skin sensitizers with confidence.

Results
An Internal validation procedure was initially performed on samples in the GARD training set (n=38) using the strategy described in Fig. 3A. Results from this exercise is summarized in Fig. 4A. Conformal prediction by definition allows the user to determine a reasonable and acceptable significance level to guarantee a maximum error rate in predictions. The significance level was set to 15%, i.e. the model was allowed to make a maximum of 15% errors. Performance of the conformal predictor was measured by validity and efficiency. A model was valid if the number of prediction errors did not exceed the significance level, while efficiency corresponded to the percentage of single class predictions. Internal validation of the training data resulted in a valid and highly effective model (92% single classifications, 1 empty, 2 both), indicating that the ambitious significance level was at a reasonable level for the GARD® assay. Following internal validation, samples in a large external test set (n =70) was classified within the CP framework as described in Fig. 3B, which resulted in generation of a valid and highly efficient model (99% single classifications, 0 empty, 1 both) (Fig.4B). Additional data on model performance is illustrated in Table 1.

Poster download

Prediction of chemical respiratory sensitizers using GARD

a novel in vitro assay based on a genomic biomarker signature

Henrik Johansson, Andy Forreryd, Robin Gradin, Angelica Johansson, Olivia Larne, Emil Aaltonen, Anders Jerre, Carl A.K. Borrebaeck and Malin Lindstedt
SenzaGen AB, Lund, Sweden. Department of Immunotechnology, Lund, Sweden.

 

Introduction

Exposure to chemicals may induce allergic hypersensitivity reactions in skin or respiratory tract. To minimize exposure, chemicals are routinely screened for their sensitizing potential. Proactive identification has historically been performed using animal models, but the use of animals for safety assessment of cosmetics was recently banned within EU. Today, similar trends are spreading both globally and across industry and market segments. Methods for specific identification of respiratory sensitizers are greatly underdeveloped, with no validated, or even widely used assay readily available. Thus, there is an urgent need for development of non-animal based methods for hazard classification of respiratory sensitizing chemicals.
GARD – Genomic Allergen Rapid Detection – is a state of the art technology platform for assessment of chemical sensitizers (Figure 1). It is based on a dendritic cell (DC)-like cell line, thus mimicking the cell type involved in the initiation of the response leading to sensitization. Following test chemical exposure, induced transcriptional changes are measured to study the activation state of the cells. These changes are associated with the immunological decision-making role of DCs in vivo and constitutes of e.g. up-regulation of co-stimulatory molecules, induction of cellular and oxidative stress pathways and an altered phenotype associated with recognition of xenobiotic matter. By using state-of-the-art gene expression technologies, high informational content data is generated, that allows the user to get a holistic view of the cellular response induced by the test substance.

Conclusion

GARDair is a novel assay for assessment of respiratory sensitizers. It is an adaptation of the GARD platform, utilizing gene expression analysis of predictive biomarker signatures and state-of-the-art data analysis methodology. GARDair has been proven functional and is currently progressing towards industrial implemetation with financial support from the EU programme Horizon 2020. This progress will include scientific verification of results, assay optimization, transfer and formal validation.

Poster:

Prediction of chemical respiratory sensitizers using GARD_LIVe2018

The Validation of GARDskin

Johansson A, Agemark M, Gradin R, Larne O, Appelgren H, Forreryd A, Jerre A, Edwards A, Hoepflinger V, Burleson F, Gehrke H, Roggen E, Johansson H
SenzaGen, Lund, Sweden, Burleson Research Technologies, Morrisville, US, Eurofins, Munich, Germany

Introduction
The prevalence of allergic contact dermatitis (ACD) is estimated to >20% in the western world. Not only the individual is affected, but downstream socioeconomic effects are high. To minimize exposure, chemicals must be safety tested. Traditional testing strategies like the murine local lymph node assay (LLNA) comprise animals, but the regulatory authorities, public opinion and economic interests require animal-free models. The Genomic Allergen Rapid Detection skin (GARDskin) is an in vitro assay addressing this need. Here, we present the results of the GARDskin ring trial (OECD TGP 4.106) for validity of the assay.

Conclusions
Transfer study
Transferability: 100%

Validation study
Reproducibility:
WLR: 82 – 89%BLR: 92% (92 – 100%)

Test performance
Accuracy: 94%Sensitivity: 93%Specificity: 96%

A blinded ring trial was performed to assess the functionality of the GARDskin assay. The data demonstrates that GARDskin is a powerful tool for assessment of chemical skin sensitizers, with a predictive accuracy of 94% and excellent reproducibility between laboratories.

Poster