Cyclin-dependent kinase 9 (CDK9) is a transcriptional regulator and a potential therapeutic target in hematologic malignancies. Selective and transient CDK9 inhibition reduces Mcl-1 expression and induces apoptosis in Mcl-1-dependent tumor cells for survival. Here, we describe our efforts to discover a novel series of 2H-benzo[b][1,4]oxazin-3(4H)-one as CDK9 inhibitors. Compound 32k was identified as a selective CDK9 inhibitor with short pharmacokinetic and physicochemical properties suitable for intravenous administration. Short-term treatment with 32k resulted in a rapid dose-dependent decrease in cellular p-Ser2-RNAPII, Mcl-1 and c-Myc, leading to apoptosis in the MV4-11 cell line. Correspondingly, significant in vivo antitumor efficacy was observed in xenograft models derived from multiple hematological tumors with intermittent 32k dosing. These results provide evidence that selective transient CDK9 inhibitors could be used for the treatment of hematologic malignancies.
Antineoplastic Agents , Hematologic Neoplasms , Humans , Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , Apoptosis , Cell Line, Tumor , Cyclin-Dependent Kinase 9/metabolism , Hematologic Neoplasms/drug therapy , Myeloid Cell Leukemia Sequence 1 Protein/metabolism , Protein Kinase Inhibitors/chemistry , Protein Kinase Inhibitors/pharmacology , Protein Kinase Inhibitors/therapeutic use
Hematologic malignancies (HM) start in blood forming tissue or in the cells of the immune system. Cyclin-dependent kinases (CDKs) regulate cell cycle progression, and some of them control cellular transcription. CDK inhibition can trigger apoptosis and could be particularly useful in hematological malignancies. Herein, we describe our efforts toward the discovery of a novel series of quinazoline derivatives as CDK inhibitors. Intensive structural modifications lead to the identification of compound 37d as the most active inhibitors of CDKs 1, 2, 4, 8 and 9 with balancing potency and selectivity against CDKs. Further biological studies revealed that compound 37d can arrest the cell cycle and induce apoptosis via activating PARP and caspase 3. More importantly, compound 37d showed good antitumor efficacy in multiple HM mice xenograft models with no obvious toxicity. These results indicated that CDK 1, 2, 4, 8, and 9 inhibitors could be potentially used to treat certain hematologic malignancies.
Antineoplastic Agents/pharmacology , Protein Kinase Inhibitors/chemistry , Protein Kinase Inhibitors/pharmacology , Administration, Oral , Animals , Antineoplastic Agents/chemistry , Area Under Curve , Catalytic Domain , Cell Line, Tumor , Cyclin-Dependent Kinase 9/chemistry , Cyclin-Dependent Kinase 9/metabolism , Half-Life , Humans , Mice , Molecular Structure , Protein Binding , Protein Kinase Inhibitors/pharmacokinetics , Structure-Activity Relationship , Xenograft Model Antitumor Assays
Specific inhibition of CDK9 is considered a promising strategy for developing effective anticancer therapeutics. However, most of the reported CDK9 inhibitors are still at an early stage of development and lack selectivity against other CDKs. Herein, we discovered coumarin derivative 30i as a potent CDK9 inhibitor with high selectivity (8300-fold over CDK7). Binding mode analysis illustrated that the substituent coumarin moiety is a critical group for CDK9 selectivity by occupying a flexible hinge/αD region, which is sterically hindered in other CDKs. Compound 30i showed excellent cellular antiproliferative activity, moderate pharmacokinetic property and low hERG inhibition. Moreover, 30i significantly induced tumour growth inhibition in a dose-dependent manner without causing an obvious loss of body weight in an MV4-11 xenograft mice model. Altogether, these results suggest that 30i may serve as a potential acute myeloid leukaemia (AML) therapeutics by selectively targeting CDK9.
Antineoplastic Agents/pharmacology , Coumarins/pharmacology , Cyclin-Dependent Kinase 9/antagonists & inhibitors , Drug Discovery , Protein Kinase Inhibitors/pharmacology , Animals , Antineoplastic Agents/chemical synthesis , Antineoplastic Agents/chemistry , Cell Proliferation/drug effects , Coumarins/chemical synthesis , Coumarins/chemistry , Cyclin-Dependent Kinase 9/metabolism , Dose-Response Relationship, Drug , Drug Screening Assays, Antitumor , Female , Humans , Male , Mice , Mice, Inbred BALB C , Mice, Inbred ICR , Mice, Nude , Models, Molecular , Molecular Structure , Neoplasms, Experimental/drug therapy , Neoplasms, Experimental/metabolism , Neoplasms, Experimental/pathology , Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/chemistry , Structure-Activity Relationship
