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
Transforming growth factor-beta (TGF-beta) is a proinvasive and immunosuppressive cytokine that plays a major role in the malignant phenotype of gliomas. One novel strategy of disabling TGF-beta activity in gliomas is to disrupt the signaling cascade at the level of the TGF-beta receptor I (TGF-betaRI) kinase, thus abrogating TGF-beta-mediated invasiveness and immune suppression. SX-007, an orally active, small-molecule TGF-betaRI kinase inhibitor, was evaluated for its therapeutic potential in cell culture and in an in vivo glioma model. The syngeneic, orthotopic glioma model SMA-560 was used to evaluate the efficacy of SX-007. Cells were implanted into the striatum of VM/Dk mice. Dosing began three days after implantation and continued until the end of the study. Efficacy was established by assessing survival benefit. SX-007 dosed at 20 mg/kg p.o. once daily (q.d.) modulated TGF-beta signaling in the tumor and improved the median survival. Strikingly, approximately 25% of the treated animals were disease-free at the end of the study. Increasing the dose to 40 mg/kg q.d. or 20 mg/kg twice daily did not further improve efficacy. The data suggest that SX-007 can exert a therapeutic effect by reducing TGF-beta-mediated invasion and reversing immune suppression. SX-007 modulates the TGF-beta signaling pathway and is associated with improved survival in this glioma model. Survival benefit is due to reduced tumor invasion and reversal of TGF-beta-mediated immune suppression, allowing for rejection of the tumor. Together, these results suggest that treatment with a TGF-betaRI inhibitor may be useful in the treatment of glioblastoma.
