Updates to OECD in vitro and in chemico test guidelines

Posted on June 26, 2025

This month, the Organisation for Economic Co-operation and Development (OECD) finalised and adopted new or updated documents. Some are highlighted below:

Eye damage and irritation

  • Revision of TG 467 (defined approaches for serious eye damage and eye irritation) to includea new defined approach (DA) for surfactants, which uses a combination of two test methods, STE0.5, an adapted version of the STE (Short Time Exposure) method (from TG 491), and the EpiOcular™ Eye Irritation Test (EIT) or the SkinEthic™ Human Corneal Epithelium EIT (from TG 492).
  • Revision of TG 437 (bovine corneal opacity and permeability test method for identifying i) chemicals inducing serious eye damage and ii) chemicals not requiring classification for eye irritation or serious eye damage) to include guidance on using histopathology of treated corneas as a supplement to the corneal opacity and permeability endpoint, and an update to the OP-KIT/Duratec prediction model to include identification of serious eye damage. 

Skin sensitisation

  • Revision of TG 497 (defined approaches on skin sensitisation) to include several novel projects as well as minor corrections:
    • Inclusion of the Skin Allergy Risk Assessment-Integrated Chemical Environment (SARA-ICE) model, a DA which uses Bayesian modelling, based on historical and new data to estimate a quantitative point of departure.
    • Inclusion of similar methods for the “2 out of 3” approach and the integrated testing strategy DAs. Several key-event based in vitro test methods from OECD Test Guidelines (i.e., TG 442C, TG 442D, and TG 442E) were added.
    • Correction to a Direct Peptide Reactivity Assay (DPRA) borderline range flowchart in TGs 442C and 497.

Skin corrosion

  • Revision of TG 431 (in vitro skin corrosion: reconstructed human epidermis (RHE) test method) and TG 439 (in vitro skin irritation: reconstructed human epidermis test method) to remove the EpiSkin™ model following its discontinuation.

Immunotoxicity

  • Revision of TG 444A (in vitro immunotoxicity) to combine the IL-2 Luciferase (IL-2 Luc) assay and the IL-2 Luc Leukocyte Toxicity Test in a step-wise approach to increase the overall predictivity of the original IL-2 Luc assay.

Endocrine Disruption

  • Adaptation of TG 456 (H295R steroidogenesis assay) to include changes to the expected results of some proficiency chemicals to align with expected outcomes using a different data interpretation procedure.

For more information, please refer to the webpage on OECD Guidelines for the Testing of Chemicals.