Sensitivity of human cells bearing oncogenic mutant kit isoforms to the novel tyrosine kinase inhibitor INNO-406

The activity of the novel tyrosine kinase inhibitor INNO-406 against human cells with mutated KIT was investigated. Human mast cell (HMC)-1.1 cells with juxtamembrane domain mutation V560G, and HMC-1.2 cells with both V560G and the kinase domain mutation D816V, were treated with INNO-406 (0.02-5.00 μM) or imatinib for 72 h. INNO-406 and imatinib were equipotent against HMC-1 cells regarding cell proliferation (IC₅₀ 51 nM and 75 nM, respectively), inhibition of KIT phosphorylation, and induction of apoptosis. In contrast, neither drug was effective against HMC-1.2 cells at the dose range tested. The present results suggest clinical potential for INNO-406 in KIT V560G-expressing malignancies.