In current study, we used an in vitro KIT expressing COS-1 cell-based system to evaluate the inhibitory efficacy of several commercial available TKIs on phosphorylation of KIT with secondary mutation involving exon 17, and validated the findings on their growth inhibition activity on GIST 48 cells harboring exon 11/17 KIT mutant. This evidence concerns the gene KIT and gastrointestinal stromal tumor.