Identifying genotoxic drug compounds during early preclinical studies allows for further lead refinement and lower drug attrition. Mutagenesis, carcinogenesis, and adverse genetic effects, especially those that affect the germline, are routinely tested. Common assays for mutagenicity, both in vitro and in vivo, identify mutagenic hazards and mitigate risk for regulatory approval. Biochemical assays and cell-based tests used to determine genotoxic events include the Ames test, Comet assay, and micronucleus test. Multiple assays methods are used together to build a complete picture of a drug candidate's genotoxic potential.