ECVAM Bottom-Up/Top-Down Testing Approach: Testing Strategy to Reduce/Replace the Draize Eye Test and Validation/Regulatory Acceptance of In Vitro Assays: Current Status

Abstract

To reduce and/or replace the Draize test, testing schemes combining strengths of particular in vitro assays were proposed during a 2005 ECVAM expert meeting. The testing scheme proposes, based on expected irritancy of the test substance, a Bottom-Up approach, beginning with test methods that accurately identify non-irritants, or a Top-Down approach, beginning with test methods that accurately identify severe irritants before progression of further in vitro testing. Furthermore as its core activity, ECVAM participated in the retrospective validation of and has peer reviewed scientific validity of four organotypic assays, and undertook retrospective validation of four cell function/cytotoxicity assays. The BCOP and ICE organotypic assays were ICCVAM and ESAC endorsed as scientifically valid for identifying severe irritants, and OECD Test Guidelines are under adoption. NRR, FL and CM cell function/cytotoxicity assays were recommended by an ECVAM Validation Management Group for identification of non-irritants or severe eye irritants in the Bottom-Up/Top-Down approaches. These assays were peer reviewed by ESAC during 2009. Finally, a joint ECVAM-COLIPA prospective validation study was initiated in 2008 to evaluate two Reconstructed human Tissue assays to discriminate non-classified materials from eye irritants, based on the proposed test strategies. The ultimate goal is to combine validated in vitro assays, based on their performances and applicability domains, to define the most suitable testing strategy to classify substances for eye irritation potential and ultimately replace the Draize test. This manuscript presents the proposed testing scheme and provides details on the validation/regulatory status of in vitro assays for use in this scheme.JRC.I.2-Validation of Alternative Method