The Mouse Lymphoma Assay (MLA) is a widely used in vitro genotoxicity assay that can detect gene mutations induced by different types of exposures. It uses the L5178Y mouse lymphoma TK+/- cell line, detecting mutagenic events by measuring resistance to the pyridine analogue triflurothymidine (TFT).
The MLA has been shown to be effective as part of the comprehensive toxicological assessment of cigarette smoke and Reduced-Risk Product aerosols and we employ the assay using a methodology underpinned by the Organisation for Economic Co-operation and Development (OECD) guidelines 476.
To date we have used the MLA to test an early prototype version of our Reduced-Risk Product Platform 1 called the Electrically Heated Cigarette Smoking System Series K (EHCSS). The results are shown in the graph below where a significant reduction in mutations can be seen between EHCSS and 2R4F.
Reduction in mutations between EHCSS and 2R4F. S9 fraction describes a range of metabolic enzymes derived from organ tissue. Chemical substances sometimes require metabolic activation in order to become mutagenic. Addition of a S9 tissue fraction provides the enzymes required for such activation. Note: these data alone do not imply or represent a claim of reduced exposure or reduced risk.
 Schramke, H, et al. The mouse lymphoma thymidine kinase assay for the assessment and comparison of the mutagenic activity of cigarette mainstream smoke particulate phase. Toxicology, 2006. 227(3): p. 193-210. Available online at: http://www.sciencedirect.com/science/article/pii/S0300483X06004689
 OECD. OECD guideline for the testing of chemicals: in vitro mammalian cell gene mutation test. 1997.  Werley, MS, et al. Smoke chemistry, in vitro and in vivo toxicology evaluations of the electrically heated cigarette smoking system series K. Regul Toxicol Pharmacol, 2008. 52(2): p. 122-39. Available online at: https://www.sciencedirect.com/science/article/abs/pii/S0273230008001177