Dose-Response Analysis in GARD™ for Assessment of Skin Sensitizer Potency

Poster presented at ACT 2020

J. Schmidt, A. Forreryd, R. Gradin, H. Johansson.
SenzaGen Inc., Raleigh, NC., SenzaGen AB, Lund, Sweden.

Link to the poster

 

Conclusion

• As an adaptation from the GARDskin assay, GARDskin Dose-Response is suitable for quantitative skin sensitizing potency assessment of chemicals.
• The experimental readout, referred to as cDV₀, corresponds to the lowest dose required to elicit a positive response in GARDskin. As such, experimental protocols are analogous to the LLNA, in which the cDV₀ corresponds to the EC3-value.
• The cDV₀ may be used to directly monitor sensitizing potency, or further used to extrapolate LLNA EC3-values, estimation of Human Potency categories, or CLP 1A/1B classifications.

Abstract

Several non-animal methods for identifying skin sensitizers have been developed with acceptable prediction performance. However, advancement of alternative methods for skin sensitizing potency assessment is still missing although a highly sought-after endpoint. The GARDskin assay is a genomics-based in vitro assay for hazard assessment of skin sensitizers, currently progressing towards regulatory acceptance. Here, we introduce GARDskin Dose-Response (DR), in which test chemicals are evaluated by the GARDskin assay in an extended range of concentrations, in order to investigate the dose-response relationship between GARDskin classifications and test chemical concentration.

For this work, 29 chemicals of various sensitizing potencies were used to evaluate the efficacy of applying the assay in this manner. Each chemical was analyzed at several concentrations using a slightly modified GARDskin protocol. At each concentration, a decision-value was produced and a classification prediction (sensitizing or non-sensitizing) was made by the GARDskin algorithm. Afterwards, the lowest concentration where a test item would provide a positive GARDskin prediction was found using linear interpolation. This concentration (cDV₀) was then hypothesized to reflect the test items skin sensitizing potency. Furthermore, when comparing cDV₀ to LLNA EC3 values, a statistically significant correlation was realized between the values (correlation coefficient =0.74, p-value=4.1*10^-4).

These results suggest that modifying the GARDskin protocol to accommodate dose-response measurements can provide sensitizing potency information analogous to the gold-standard in vivo methods. This presentation will further explain the testing process, expand on results, and demonstrate how this method can be used for decision-making throughout all stages of product development, without having to use animal experimentation.