OECD Releases 2025 Test Guideline Programme Updates

In early April 2025, ICAPO representatives attended the 37th annual meeting of the Working Group of the National Coordinators of the Test Guideline Programme. Throughout the year, ICAPO experts work across the Test Guideline Programme to reduce and replace animal use by updating existing guidance and advocating for more effective non-animal methods. Through a process called Mutual Acceptance of Data, these guidelines help to harmonize testing across all 38 OECD Member countries and beyond.  

On June 25, 2025, the OECD released updates on the newly published Test Guidelines. A total of 56 updates were announced. ICAPO-supported Test Guideline updates are listed below: 

• Test No. 467: Defined Approaches for Serious Eye Damage and Eye Irritation was updated to expand the applicability domain of the guidance to include surfactants.
• Test No. 491: Short Time Exposure In Vitro Test Method for Identifying i) Chemicals Inducing Serious Eye Damage and ii) Chemicals Not Requiring Classification for Eye Irritation or Serious Eye Damage was updated to introduce a variation in the STE method, the STE0.5, used in the Test No. 467 Defined Approach for surfactant chemicals.
• Test No. 497: Defined Approaches on Skin Sensitisation was updated to allow in vitro and in chemico methods in TG 442C, TG 442D and TG 442E to be used as alternate sources of information, and to include a new Defined Approach for the determination of point of departure for skin sensitization potential.
• Test No. 444A: In Vitro Immunotoxicity IL-2 Luc and Il-2 Luc LTT Assays was updated with a variant of the IL-2 Luc assay, the IL-2Luc LTT assay, which allows a better predictive capacity immunotoxicant chemicals.
• Test No. 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 was updated for additional guidance on the utility of eye histopathology.
• Test No. 442B: Skin Sensitization: Local Lymph Node Assay: BrdU-ELISA or –FCM was updated to introduce a sub-categorisation criterion for skin senstisers for the ELISA_BrDU method
• Test No. 442C: In Chemico Skin Sensitisation: Assays addressing the Adverse Outcome Pathway key event on covalent binding to proteins was updated to address borderline ranges of the Direct Peptide Reactivity Assay (DRPA).
• Test No. 456: H295R Steroidogenesis Assay was updated to ensure that the results specified for the recommended proficiency chemicals all align with the expected outcomes using the new data interpretation procedure agreed in 2022.
• Test No. 492: Reconstructed human Cornea-like Epithelium (RhCE) test method for identifying chemicals not requiring classification and labelling for eye irritation or serious eye damage was corrected.
• Test No. 431: In vitro skin corrosion and Test No. 439: In Vitro Skin Irritation  were updated to remove the EpiSkin TM model which is no longer commercially available.  

Additionally, while the effectiveness to decrease animal use remains to be seen, seven animal-based Test Guidelines were updated to allow collection of tissue samples for omics analysis, including Test No. 203: Fish, Acute Toxicity Test, Test No. 210: Fish, Early-life Stage Toxicity Test, Test No. 236: Fish Embryo Acute Toxicity (FET) Test, Test No. 407: Repeated Dose 28-day Oral Toxicity Study in Rodents, Test No. 408: Repeated Dose 90-Day Oral Toxicity Study in Rodents, Test No. 421: Reproduction/Developmental Toxicity Screening Test, Test No. 422: Combined Repeated Dose Toxicity Study with the Reproduction/Developmental Toxicity Screening Test.  

ICAPO members continue to work on assisting NAMs through the test guideline program in new and on-going projects. For a list of non-animal test guidelines, please visit www.icapo.org/test-guidelines. A complete list of 2025 Test Guideline Programme updates is available on the OECD website.