Discovery of IHMT-337 as a potent irreversible EZH2 inhibitor targeting CDK4 transcription for malignancies

Enhancer of zeste homolog 2(EZH2),an enzymatic subunit of PRC2 complex,plays an important role in tumor development and progression through its catalytic and noncatalytic activities.Overexpression or gain-of-function mutations of EZH2 have been significantly associated with tumor cell proliferation of triple-negative breast cancer(TNBC)and diffuse large B-cell lymphoma(DLBCL).As a result,it has gained interest as a potential therapeutic target.The currently available EZH2 inhibitors,such as EPZ6438 and GSK126,are of benefit for clinical using or reached clinical trials.However,certain cancers are resistant to these enzymatic inhibitors due to its noncatalytic or transcriptional activity through modulating nonhistone proteins.Thus,it may be more effective to synergistically degrade EZH2 in addition to enzymatic inhibition.Here,through a rational design and chemical screening,we discovered a new irreversible EZH2 inhibitor,IHMT-337,which covalently bounds to and degrades EZH2 via the E3 ligase CHIP-mediated ubiquitination pathway.Moreover,we revealed that IHMT-337 affects cell cycle progression in TNBC cells through targeting transcriptional regulating of CDK4,a novel PRC2 complex-and enzymatic activity-independent function of EZH2.More significantly,our compound inhibits both DLBCL and TNBC cell proliferation in different preclinical models in vitro and in vivo.Taken together,our findings demonstrate that in addition to enzymatic inhibition,destroying of EZH2 by IHMT-337 could be a promising therapeutic strategy for TNBC and other malignancies that are independent of EZH2 enzymatic activity.

Discovery of IHMT-MST1-39 as a novel MST1 kinase inhibitor and AMPK activator for the treatment of diabetes mellitus

Insulin-producing pancreaticβcell death is the fundamental cause of type 1 diabetes(T1D)and a contributing factor to type 2 diabetes(T2D).Moreover,metabolic disorder is another hallmark of T2D.Mammalian sterile 20-like kinase 1(MST1)contributes to the progression of diabetes mellitus through apoptosis induction and acceleration of pancreaticβcell dysfunction.AMP-activated protein kinase(AMPK)is an energy sensing kinase and its activation has been suggested as a treatment option for metabolic diseases.Thus,pharmacological inhibition of MST1 and activation of AMPK simultaneously represents a promising approach for diabetes therapy.Here,we discovered a novel selective MST1 kinase inhibitor IHMT-MST1-39,which exhibits anti-apoptosis efficacy and improves the survival of pancreaticβcells under diabetogenic conditions,as well as primary pancreatic islets in an ex vivo disease model.Mechanistically,IHMT-MST1-39 activated AMPK signaling pathway in hepatocytes in vitro,combination of IHMT-MST1-39 and metformin synergistically prevented hyperglycemia and significantly ameliorated glucose tolerance and insulin resistance in diabetic mice.Taken together,IHMT-MST1-39 is a promising anti-diabetic candidate as a single agent or in combination therapy for both T1D and T2D.

Discovery of a highly selective VEGFR2 kinase inhibitor CHMFL-VEGFR2-002 as a novel antiangiogenesis agent

Angiogenesis is an essential process in tumor growth,invasion and metastasis.VEGF receptor 2(VEGFR2)inhibitors targeting tumor angiogenic pathway have been widely used in the clinical cancer treatment.However,most of currently used VEGFR2 kinase inhibitors are multi-target inhibitors which might result in target-associated side effects and therefore limited clinical toleration.Highly selective VEGFR inhibitors are still highly demanded from both basic research and clinical application point of view.Here we report the discovery and characterization of a novel VEGFR2 inhibitor(CHMFLVEGFR2-002),which exhibited high selectivity among structurally closed kinases including PDGFRs,FGFRs,CSF1 R,etc.CHMFL-VEGFR2-002 displayed potent inhibitory activity against VEGFR2 kinase in the biochemical assay(IC50=66 nmol/L)and VEGFR2 autophosphorylation in cells(EC50s^100 nmol/L)as well as potent anti-proliferation effect against VEGFR2 transformed BaF3 cells(GI50=150 nmol/L).In addition,CHMFL-VEGFR2-002 also displayed good anti-angiogenesis efficacy in vitro and exhibited good in vivo PK(pharmacokinetics)profile with bioavailability over 49%and antiangiogenesis efficacy in both zebrafish and mouse models without apparent toxicity.These results suggest that CHMFL-VEGFR2-002 might be a useful research tool for dissecting new functions of VEGFR2 kinase as well as a potential anti-angiogenetic agent for the cancer therapy.

Discovery of a highly potent and selective Bruton’s tyrosine kinase inhibitor avoiding impairment of ADCC effects for B-cell non-Hodgkin lymphoma

Dear Editor,Bruton’s tyrosine kinase(BTK)plays a crucial role in the B-cell receptor(BCR)signaling which is essential for B-cell proliferation,differentiation,and cell migration.Aberrant BCR activation has been identified as a major pathogenic factor in several B-cell non-Hodgkin lymphoma(B-NHL)subtypes,including diffuse large Bcell lymphoma(DLBCL),mantle cell lymphoma(MCL),follicular lymphoma(FL),and chronic lymphocytic leukemia(CLL).1 Therefore,BTK has been recognized as a validated therapeutic target for B-cell malignancies.Ibrutinib,the first approved BTK inhibitor that binds irreversibly to cysteine residue 481,has shown potent clinical activity in the majority of CD20 positive B-cell malignancies.2 However,due to the inhibition of off-target kinases such as EGFR,ITK,and TXK,which have a cysteine residue at the identical position of Cys481 of BTK,Ibrutinib also results in some adverse events,such as the antagonizing Rituximab-dependent NK-cell-mediated antibody-dependent cell-mediated cytotoxicity(ADCC)due to its irreversible binding to ITK,which is required for FcR-stimulated NK cell function.3 Although several secondary generation inhibitors have shown improved selectivity,4,5 more pharmacologically diverse novel inhibitors are still highly demanded in the clinic.

Predicting and overcoming resistance to CDK9 inhibitors for cancer therapy

Abnormally activated CDK9 participates in the super-enhancer mediated transcription of short-lived proteins required for cancer cell survival.Targeting CDK9 has shown potent anti-tumor activity in clinical trials among different cancers.However,the study and knowledge on drug resistance to CDK9 inhibitors are very limited.In this study,we established an AML cell line with acquired resistance to a highly selective CDK9 inhibitor BAY1251152.Through genomic sequencing,we identified in the kinase domain of CDK9 a mutation L156F,which is also a coding SNP in the CDK9 gene.By knocking in L156F into cancer cells using CRISPR/Cas9,we found that single CDK9 L156F could drive the resistance to CDK9 inhibitors,not only ATP competitive inhibitor but also PROTAC degrader.Mechanistically,CDK9 L156F disrupts the binding with inhibitors due to steric hindrance,further,the mutation affects the thermal stability and catalytic activity of CDK9 protein.To overcome the drug resistance mediated by the CDK9-L156F mutation,we discovered a compound,IHMT-CDK9-36 which showed potent inhibition activity both for CDK9 WT and L156F mutant.Together,we report a novel resistance mechanism for CDK9 inhibitors and provide a novel chemical scaffold for the future development of CDK9 inhibitors.