The CORESTA in vitro test battery for combustible tobacco products: update from the 2004 Rationale and Strategy Report
In 2004, the CORESTA In Vitro Toxicity Task Force issued a rationale and strategy report, commonly known as “the CORESTA in vitro test battery guideline”. The goals of this guideline were to: 1) develop the rationale and strategy for conducting in vitro toxicity testing of tobacco smoke and 2) identify key procedures based on internationally recognized guidelines, adapted to accommodate the unique properties of tobacco smoke. The Task Force [now the Sub-Group (IVT SG) since 2015] performed a series of proficiency trials based on the guideline. Considering the time passed, the IVT SG has reviewed the guideline to: 1) re-evaluate the relevance of the initial rationale and strategy of in vitro testing of combustible tobacco products, 2) identify recent and comparable regulatory testing guidelines and examples in publications, and 3) provide a pragmatic summary of key features of each recommended assay. The endeavor revealed the continued usage and reference of the CORESTA in vitro test battery, especially where standardized and validated testing is required (e.g. regulatory submission), upholding that the overall strategy and rationale remain valid and relevant. Sometimes these standardized testing results are supplemented with newer and exploratory in vitro assays (e.g. air-liquid-interface testing with fresh whole smoke). However the CORESTA in vitro test batteries are continuously used in comparative product testing, such as evaluating the biological impact of changes in ingredients or product designs as part of a weight-of-evidence toxicity evaluation. In the updated 2019 guideline, the IVT SG recommends, where standardized in vitro toxicity testing is desired, the following test battery for combustible tobacco products: 1) cytotoxicity (neutral red uptake) assay with mammalian cells; 2) bacterial reverse mutation (Ames) assay in Salmonella thyphimurium; and 3) mammalian cell cytogenetics/mutation assays (the in vitro micronucleus assay, the mouse lymphoma assay, or the chromosome aberration assay). The IVT SG reiterates that the biological significance of the in vitro results needs to be evaluated in conjunction with all available chemical and exposure/dosimetry data, in the context of the overall product risk assessment.