After genotyping TCF7L2 variants in participants with type 2 diabetes undergoing phase 3 trials with 24 weeks of treatment with linagliptin, a smaller decrease in HbA1c was observed in individuals with the rs7903146 TT genotype (6.2 mmol/mol [0.57%]) compared with other genotypes (9.0 mmol/mol [0.82%] for CC; 8.4 mmol/mol [0.77%] for CT; p = 0.02 for TT vs CC genotypes) [30]. This evidence concerns the gene TCF7L2 and type 2 diabetes mellitus.