ABSTRACT
The work in this paper describes the optimization of the 3-(3-phenyl-3H-imidazo[4,5-b]pyridin-2-yl)pyridin-2-amine chemical series as potent, selective allosteric inhibitors of AKT kinases, leading to the discovery of ARQ 092 (21a). The cocrystal structure of compound 21a bound to full-length AKT1 confirmed the allosteric mode of inhibition of this chemical class and the role of the cyclobutylamine moiety. Compound 21a demonstrated high enzymatic potency against AKT1, AKT2, and AKT3, as well as potent cellular inhibition of AKT activation and the phosphorylation of the downstream target PRAS40. Compound 21a also served as a potent inhibitor of the AKT1-E17K mutant protein and inhibited tumor growth in a human xenograft mouse model of endometrial adenocarcinoma.
Subject(s)
Aminopyridines/pharmacology , Antineoplastic Agents/pharmacology , Carcinoma, Endometrioid/drug therapy , Drug Discovery , Endometrial Neoplasms/drug therapy , Imidazoles/pharmacology , Protein Kinase Inhibitors/pharmacology , Proto-Oncogene Proteins c-akt/antagonists & inhibitors , Administration, Oral , Allosteric Regulation/drug effects , Aminopyridines/administration & dosage , Aminopyridines/chemistry , Animals , Antineoplastic Agents/administration & dosage , Antineoplastic Agents/chemistry , Carcinoma, Endometrioid/pathology , Cell Proliferation/drug effects , Dose-Response Relationship, Drug , Drug Screening Assays, Antitumor , Endometrial Neoplasms/pathology , Female , Humans , Imidazoles/administration & dosage , Imidazoles/chemistry , Mice , Molecular Structure , Neoplasms, Experimental/drug therapy , Neoplasms, Experimental/pathology , Protein Kinase Inhibitors/administration & dosage , Protein Kinase Inhibitors/chemistry , Proto-Oncogene Proteins c-akt/genetics , Proto-Oncogene Proteins c-akt/metabolism , Structure-Activity RelationshipABSTRACT
This paper describes the implementation of a biochemical and biophysical screening strategy to identify and optimize small molecule Akt1 inhibitors that act through a mechanism distinct from that observed for kinase domain ATP-competitive inhibitors. With the aid of an unphosphorylated Akt1 cocrystal structure of 12j solved at 2.25 Å, it was possible to confirm that as a consequence of binding these novel inhibitors, the ATP binding cleft contained a number of hydrophobic residues that occlude ATP binding as expected. These Akt inhibitors potently inhibit intracellular Akt activation and its downstream target (PRAS40) in vitro. In vivo pharmacodynamic and pharmacokinetic studies with two examples, 12e and 12j, showed the series to be similarly effective at inhibiting the activation of Akt and an additional downstream effector (p70S6) following oral dosing in mice.
Subject(s)
Adenosine Triphosphate/physiology , Antineoplastic Agents/chemical synthesis , Imidazoles/chemical synthesis , Proto-Oncogene Proteins c-akt/antagonists & inhibitors , Pyridines/chemical synthesis , Adaptor Proteins, Signal Transducing/antagonists & inhibitors , Administration, Oral , Animals , Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , Biological Availability , Catalytic Domain , Cell Line, Tumor , Cell Proliferation/drug effects , Crystallography, X-Ray , Humans , Imidazoles/chemistry , Imidazoles/pharmacology , Mice , Microsomes, Liver/metabolism , Models, Molecular , Phosphorylation , Protein Binding , Protein Conformation , Pyridines/chemistry , Pyridines/pharmacology , Ribosomal Protein S6 Kinases, 70-kDa/antagonists & inhibitors , Structure-Activity RelationshipABSTRACT
The met proto-oncogene is functionally linked with tumorigenesis and metastatic progression. Validation of the receptor tyrosine kinase c-Met as a selective anticancer target has awaited the emergence of selective c-Met inhibitors. Herein, we report ARQ 197 as the first non-ATP-competitive small molecule that selectively targets the c-Met receptor tyrosine kinase. Exposure to ARQ 197 resulted in the inhibition of proliferation of c-Met-expressing cancer cell lines as well as the induction of caspase-dependent apoptosis in cell lines with constitutive c-Met activity. These cellular responses to ARQ 197 were phenocopied by RNAi-mediated c-Met depletion and further demonstrated by the growth inhibition of human tumors following oral administration of ARQ 197 in multiple mouse xenograft efficacy studies. Cumulatively, these data suggest that ARQ 197, currently in phase II clinical trials, is a promising agent for targeting cancers in which c-Met-driven signaling is important for their survival and proliferation.
