Application of error-corrected sequencing technologies for in vivo regulatory mutagenicity assessment

Error-corrected sequencing (ECS) is a transformative method for in vivo mutagenicity assessment, enabling direct, highly sensitive measurement of mutation frequency and spectrum. ECS addresses key limitations of the transgenic rodent (TGR) assay, including lack of integration into standard toxicity studies, restricted model availability, and limited alignment with the 3R principles. To support regulatory acceptance, an expert workgroup of the International Workshops on Genotoxicity Testing (IWGT) reviewed ECS technologies and developed consensus recommendations for its inclusion into Organisation for Economic Co-operation and Development (OECD) test guidelines. The working group agreed that ECS: produces results that are concordant with validated TGR assays; can be incorporated into standard ≥28-day repeat-dose toxicity studies; and, data interpretation should be based on overall mutation frequency compared with concurrent vehicle controls. The working group emphasized harmonized data reporting aligned with OECD principles and endorsed study designs that enable quantitative risk assessment. Overall, the working group agreed that ECS offers a significant advancement over current mutagenicity assays by enabling the use of diverse models beyond conventional TGR systems described in OECD test guideline 488. The working group fully supports the application of ECS to generate in vivo mutagenicity data for regulatory submissions and recommends its inclusion in future OECD test guidelines.