Discovery And Machanistic Study Of Inhibitors Against The Major Kinase Targets Of Imatinib

Imatinib,a representative of targeted small molecule drugs,is well known for its clear anti-tumor efficacy and wide application in clinical practice.The indications include cKIT-positive gastrointestinal stromal tumors(GISTs),BCR-ABL-fused chronic myeloid leukemia(CML),and PDGFR kinase-driven chronic eosinophilic leukemia(CEL).However,drug resistance caused by long-term use,as well as off-target toxicity caused by low selectivity has been concerned.Therefore,in view of the above problems in the clinical use of imatinib,we would further explore small molecule kinase inhibitors against various major kinase targets of imatinib and carry out research on relevant mechanisms of action using the drug repurposing approach and structure-based drug design method to provide potential drug candidates for future clinical use.1.Using a functional isogenic BaF3 cell library and high-throughput screening facility,we found that cabozantinib displayed very potent inhibitory activity against cKIT wt kinase.In addition,cabozantinib exhibited more potency than imatinib against primary gain-of-function mutations of cKIT.Moreover,cabozantinib was able to overcome cKIT gatekeeper T670I mutation and the activation loop mutations including N822K,D816E,D820 E/G/Y and A829P which are resistant to imatinib or sunitinib.Also we found that cabozantinib demonstrated good efficacy in vitro and in vivo in the cKIT mutant-driven preclinical models of GISTs while displaying a long-lasting effect after treatment withdrawal.Furthermore,it also exhibited dose-dependent anti-proliferative efficacy in the GIST patient derived primary cells.This report provided the basis for the future clinical applications of cabozantinib as an alternative anti-GISTs therapy in precision medicine.2.Here we reported a novel type ? kinase inhibitor based on structure-based drug design,CHMFL-48,which could potently inhibit BCR-ABL kinase as well as a panel of imatinib resistant mutants including T315I,E255K,M351T,Y253F,F317L etc.CHMFL-48 displayed great inhibitory activity against ABL wt and ABL T315I mutant(over 10000-fold more potent than imatinib)in the biochemical assay and strongly blocked the auto-phosphorylation of BCR-ABL wt as well as BCR-ABL mutants in the cellular context,which further affected downstream signaling pathways.CHMFL-48 also exhibited great anti-leukemic efficacies in vivo in murine models inoculated with K562 cells and p210-T315I transformed BaF3 cells.In addition,in the CML patient derived primary cells,CHMFL-48 was more potent to cells from the patients bearing BCR-ABL kinase than imatinib.This discovery extended the drug structure diversity of BCR-ABL kinase inhibitors and provided more potential options for the CML therapies.3.Here we reported a novel highly potent and selective PDGFR kinase inhibitor based on structure-based drug design,CHMFL-73,which displayed great inhibitory activity against PDGFRa and PDGFR? kinases but not BCR-ABL,cKIT,VEGFR2 etc with structures similar to PDGFR.CHMFL-73 could potently inhibit the proliferation of PDGFR kinase-dependent EOL-1 cells and blocked the auto-phosphorylation of PDGFR in the cellular context.Moreover,CHMFL-73 further affected downstream signaling pathways and led to the cell cycle progression blockage as well as apoptosis induction.CHMFL-73 also exhibited great anti-leukemic efficacies in vivo in the murine xenograft models inoculated with EOL-1 cells.Pharmacokinetic studies indicated that CHMFL-73 exhibits complete oral absorption and moderate metabolic rate.This discovery provided a novel highly potent and selective drug candidate for PDGFR kinase-driven CEL clinical therapy.