KIT/PDGFRA-IN-1 (compound 19) is an inhibitor targeting the stem cell growth factor receptor (KIT) and platelet-derived growth factor receptor alpha (PDGFRA). Its IC50 values are 2.3 µM for KIT-wt, 12 µM for KIT-D816H, 492 µM for KIT-T670I, 0.8 µM for PDGFRA-wt, 99.9 µM for PDGFRA-D842V, 42.3 µM for PDGFRA-T674I, and 4.3 µM for PDGFRA-G680R. The GR50 values for GIST-T1, T1-a-D842V, and GIST-48B cell lines (gastrointestinal stromal tumor cell lines with PDGFR and KIT mutations) are 12 nM, 8900 nM, and ≥10,000 nM, respectively.