930089-25-1

Biological Activity: KI-328 is a novel inhibitor targeting KIT kinase that has selective activity against some KIT mutant kinases commonly found in acute myeloid leukemia (AML). KI-328 showed specificity for KIT kinase in in vitro kinase assays and inhibited the growth of wild-type (Wt) and mutant KIT-expressing cells, but had lower activity against D816V-KIT. Comparative analysis of the inhibitory effects of several potent KIT inhibitors on the growth of multiple mutant KIT-expressing cells showed that the multi-kinase inhibitors had comparable activity against D816V-KIT as against other mutant KITs; however, heat shock protein 90 (HSP90) inhibitors showed significant activity against D816V-KIT, inhibiting the growth of D816V-KIT-expressing cells at concentrations that did not affect the growth of other mutant KIT-expressing cells. These results suggest that potent KIT inhibitors have different activities against different types of KIT mutant kinases. Therefore, in clinical development, KIT inhibitors need to validate their activity against multiple types of KIT mutant kinases.