Compound 105a (R2 = CH3) had single-digit nanomolar activity against GIST-T1 (GI50 = 7.1 nM) and MOLM-13 (GI50 = 9.4 nM) cell lines and exhibited similar inhibitory activities against c-KIT and FLT3 compared with I. Here, KIT is linked to gastrointestinal stromal tumor.