Updates to OECD in vitro and in chemico test guidelines

Posted on July 6, 2026

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

Liver enzyme induction

  • Test Guideline (TG) 445A: Determination of Cytochrome P450 (CYP) Induction using Differentiated Human Hepatic Cells was adopted. The TG describes the use of human-derived metabolically competent hepatic test systems (e.g., cryopreserved differentiated HepaRGTM cells) to assess whether test chemicals induce three Phase I biotransformation enzymes highly expressed in human liver.

Skin sensitisation

  • TG 442D: In Vitro Skin Sensitisation (Assays Addressing the Adverse Outcome Pathway Key Event on Keratinocyte activation) was revised to include two new methods:
    • EpiDerm-Epidermal Sensitisation Assay (Epi2SensA). Epi2SensA uses a reconstructed human epidermis model, the EpiDerm™ model (EPI-200). As with EpiSensA, this method can be used to quantify marker genes associated with keratinocyte activation.
    • Foetal Bovine Serum-free ARE-Nrf2 Luciferase α-Sens® Test Method. This method measures nuclear factor-erythroid 2-related factor 2 (Nrf2)-mediated activation of antioxidant response element (ARE)-dependent genes using luciferase as a reporter protein.
  • TG 497: Defined Approaches on Skin Sensitisation was revised to include a regression model for the derivation of a quantitative point of departure.

Genotoxicity

  • TG 446A: ToxTracker gene reporter assay for the identification of genotoxic hazard and genotoxic/non‑genotoxic mechanism of action was adopted. The TG describes a high-content stem cell-based reporter assay that identifies the genotoxic properties of chemicals by combining six fluorescent reporter genes that are selectively activated by different cellular signalling responses.

Endocrine Disruption

  • TG 454A:  Human Glucocorticoid Receptor Transactivation Assay (GRTA) was adopted. The TG describes a reporter protein assay for the detection of Glucocorticoidreceptor (GR) agonists and antagonists. It uses a surrogate luciferase gene that is under the control of the GR response element (GRE) to assess GR activity.

Phototoxicity

  • TG 498: In Vitro Phototoxicity – Reconstructed Human Epidermis Phototoxicity Test Method was revised to include the KeraskinTM Phototoxicity assay which was developed and validated as a “me-too” method to the EpiDerm™ Phototoxicity Test. Both assays can be used as stand-alone test methods.

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