Abstract
Recently, it has become necessary to increase the progress of research studies into drug discovery because of the introduction of combinatorial chemistry and robotics. Therefore, genotoxicity screening assays which can be conducted with a small amount of compound, in a short time, and which can predict the results of regulatory genotoxicity tests for pharmaceuticals are required in the early stage of research. The bacterial reverse mutation test (Ames test) is a regulatory genotoxicity test and is conducted in the early stage of non-clinical safety studies. Morita established a high throughput fluctuation Ames test using 384-well plates with Salmonella typhimurium TA100 and TA98 (Environ. Mutagen Res. 2003, 25: 23-31), which is referred to as original FAT in the present study. Here, we report an improved high throughput fluctuation Ames test (improved FAT). The improved FAT indicated a higher positive response than the original FAT in several mutagens. Furthermore, we evaluated the improved FAT with TA100 and TA98 using 40 National Toxicology Program (NTP) chemicals. As a result, there was 80.0% (32/40) concordance between the Ames test and the improved FAT. In conclusion, the improved FAT can predict the results of the Ames test with high concordance (especially its negative specificity). The improved FAT requires a much smaller amount of test chemicals than the Ames test (i.e., 5 mg vs 100 mg when using two tester strains) and is able to be automated. Thus, the improved FAT is considered to be useful as a screening test in the early stage of drug discovery.
