Peer-Reviewed PublicationDecember 2019

An in vitro depth of injury prediction model for a histopathologic classification of EPA and GHS eye irritants

Toxicology In Vitro, Vol. 61, December 2019 · Lebrun Labs Research Team

Overview

Traditional eye irritation classification under both the EPA and GHS systems relies on histopathological scoring of corneal tissue damage, a measurement that, until now, required animal studies. This paper introduces a novel in vitro depth of injury (DoI) model that replicates that histopathologic classification using a cell-free, macromolecular assay. By measuring how deeply a test substance penetrates and damages a surrogate corneal substrate, the model generates a DoI score that maps directly onto the EPA and GHS classification categories. The result is the first nonanimal method capable of producing the same type of tissue-damage classification data that regulators have historically required from the Draize test.

Abstract

The EPA and GHS eye irritation classification systems use histopathologic scoring of corneal tissue damage, specifically, the depth of injury (DoI) to corneal epithelium, stroma, and endothelium, as a key endpoint for distinguishing Category I/Category 1 corrosives from Category II/Category 2 irritants and non-irritants. Current nonanimal methods do not directly measure DoI, creating a gap in the ability to fully replace the Draize test for regulatory purposes. This study presents a novel in vitro DoI prediction model based on a macromolecular substrate assay that measures the penetration depth of test substances into a surrogate corneal matrix. The model was developed and validated against a reference set of chemicals with known EPA and GHS classifications derived from in vivo histopathology data. The DoI model demonstrated strong concordance with in vivo classifications and correctly distinguished corrosives from irritants and non-irritants across multiple chemical classes. The model provides a mechanistic, tissue-damage-based endpoint that complements existing nonanimal eye irritation tests and supports a weight-of-evidence approach to full Draize test replacement.

Relevance to Lebrun Labs Services

The IVD EIT (In Vitro Depth of Injury Eye Irritation Test) offered by Lebrun Labs as a contract testing service is built on the scientific foundation described in this publication. This is the only nonanimal eye irritation test that generates a depth-of-injury classification, the same type of endpoint that EPA and GHS historically required from the Draize rabbit eye test. For clients seeking to classify chemicals or formulations under EPA Toxicity Category I–IV or GHS Category 1/2/No Category, the IVD EIT provides a fully documented, mechanistically-grounded alternative. This is particularly valuable for pesticide active ingredients, industrial chemicals, and any substance subject to EPA FIFRA or GHS SDS requirements where DoI data has traditionally been required.

Research reported in this publication was supported by the National Institute of Environmental Health Sciences of the National Institutes of Health under Award Number SB1ES038803. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.