BPR1J373, an oral multiple tyrosine kinase inhibitor, targets c-KIT for the treatment of c-KIT-driven myeloid leukemia

Acute myelogenous leukemia (AML) carrying t(8;21)(q22; q22) or inv(16)/t(16;16)(p13;q22) is classified as core binding factor (CBF)-AML and accounts for approximately 15% of AML. c-KIT mutation can be detected in 17%∼46% of CBF-AML and is associated with poor prognosis. c-KIT mutation is a crucial hit and cooperates with AML1-ETO resulting from t(8;21)(q22; q22) to cause overt AML. Tyrosine kinase inhibitors (TKI) targeting c-KIT, such as imatinib, has been used successfully to treat c-KIT driven gastrointestinal stromal tumors. However, the effect of TKI on c-KIT-driven leukemia, including CBF-AML and systemic mastocytosis (SM), has not been satisfactory. BPR1J373 is a 5-phenylthiazol-2-ylamine-pyriminide derivative targeting multiple tyrosine kinases. It was shown to inhibit cell proliferation and induce apoptosis in AML cells with constitutively activated c-KIT via inhibiting c-KIT phosphorylation and its downstream signals. The compound induced apoptosis by the mitochondrial intrinsic pathway through upregulation of proapoptotic proteins Bax and Bak and caspase 8 and 9 activation in c-KIT mutant Kasumi-1 cells. Furthermore, it induced cell-cycle arrest via targeting aurora kinase B in c-KIT wild-type KG-1 cells. The antitumor response of BPR1J373 was also shown in subcutaneously grafted SCID mice. BPR1J373 was shown to effectively suppress c-KIT phosphorylation of D816V mutation by treating c-KIT-null COS-1 cells transfected with c-KIT D816V mutant plasmid. In conclusion, BPR1J373 inhibits cell proliferation of c-KIT-driven AML cells via induction of apoptosis and cell-cycle arrest. It is also effective for multiple drug-resistant c-KIT D816V mutation. BPR1J373 deserves further development for clinical use in c-KIT-driven myeloid leukemia.