Design,Synthesis And Bioactivity Activity Evaluation Of Novel Selective C-KIT/PDGFRα Dual Inhibitor For The Treatment Of Imatinib-resistant Gastrointestinal Stromal Tumors (GISTs)

80%～90%of gastrointestinal stromal tumors(GISTs)harbor a gain-of-function mutation in the genes that encode KIT or platelet-derived growth factor-a(PDGFRa)receptor tyrosine kinases.At present,the discovery of novel dual inhibitors against both wild-type and mutated c-KIT/PDGFRa is an urgent need because of the limited treatment of GISTs with drugs and therapy.In this article,the application of lead optimization strategy based on multi-targeted receptor tyrosine kinase(RTK)inhibitor ABT-869 contributed to the design and synthesis of 46 new compounds(A01-A29,B01-B17)with a novel 3-substituted-1H pyrazolo[3,4-b]pyridine scaffold,discovering the best inhibitor,B09,with single-digit nanomolar potency against c-KIT(IC50=2.4 nM)and PDGFRa(IC50=7.2 nM).Compound B09 bored a high selectivity(S score(1)= 0.01 at 1 μM)among 468 kinases and mutants tested with Discove Rx’s KinomeScan technology.In addition,compound B09 showed better antiproliferative efficacy than imatinib in a range of TEL-c-KIT/PDGFRa-BaF3 isogenic cells,including three imatinib-resistant BaF3 cell lines as well as presenting more potency and better selectivity against two intact GIST cell lines(GIST-T1 and GIST-882).Noteworthily,compound B09 exhibited no effects on the growth of two normal cell lines,almost no hERG inhibitory activity,and a high metabolic stability in liver microsomes,indicating an excellent therapeutic window.More significantly,the in vivo pharmacological results showed that B09 remarkably inhibited GIST-T1 tumor growth(100 mg/kg,TGI=81.5%)and even the c-KIT-T670I tumor progression(TGI = 41.9%,imatinib resistance).Furthermore,immunohistochemistry staining demonstrated that compound B09 could powerfully suppress the cellular proliferation and induce the apoptosis effect in the tumor tissues.Altogether,these data demonstrated that B09 may be an excellent prototype for the treatment of imatinib-resistant GISTs as a c-KIT/PDGFRa dual inhibitor.