RESUMO
A series of imidazo[1,2- b]pyridazin-8-amine kinase inhibitors were discovered to allosterically inhibit the endoribonuclease function of the dual kinase-endoribonuclease inositol-requiring enzyme 1α (IRE1α), a key component of the unfolded protein response in mammalian cells and a potential drug target in multiple human diseases. Inhibitor optimization gave compounds with high kinome selectivity that prevented endoplasmic reticulum stress-induced IRE1α oligomerization and phosphorylation, and inhibited endoribonuclease activity in human cells. X-ray crystallography showed the inhibitors to bind to a previously unreported and unusually disordered conformation of the IRE1α kinase domain that would be incompatible with back-to-back dimerization of the IRE1α protein and activation of the endoribonuclease function. These findings increase the repertoire of known IRE1α protein conformations and can guide the discovery of highly selective ligands for the IRE1α kinase site that allosterically inhibit the endoribonuclease.
Assuntos
Endorribonucleases/antagonistas & inibidores , Endorribonucleases/metabolismo , Inibidores de Proteínas Quinases/farmacologia , Proteínas Serina-Treonina Quinases/antagonistas & inibidores , Proteínas Serina-Treonina Quinases/metabolismo , Regulação Alostérica , Biopolímeros/metabolismo , Cristalografia por Raios X , Dimerização , Estresse do Retículo Endoplasmático/efeitos dos fármacos , Endorribonucleases/química , Células HEK293 , Humanos , Fosforilação , Conformação Proteica , Inibidores de Proteínas Quinases/metabolismo , Proteínas Serina-Treonina Quinases/químicaRESUMO
Extracellular regulated kinase 5 (ERK5) signalling has been implicated in driving a number of cellular phenotypes including endothelial cell angiogenesis and tumour cell motility. Novel ERK5 inhibitors were identified using high throughput screening, with a series of pyrrole-2-carboxamides substituted at the 4-position with an aroyl group being found to exhibit IC50 values in the micromolar range, but having no selectivity against p38α MAP kinase. Truncation of the N-substituent marginally enhanced potency (â¼3-fold) against ERK5, but importantly attenuated inhibition of p38α. Systematic variation of the substituents on the aroyl group led to the selective inhibitor 4-(2-bromo-6-fluorobenzoyl)-N-(pyridin-3-yl)-1H-pyrrole-2-carboxamide (IC50 0.82⯵M for ERK5; IC50â¯>â¯120⯵M for p38α). The crystal structure (PDB 5O7I) of this compound in complex with ERK5 has been solved. This compound was orally bioavailable and inhibited bFGF-driven Matrigel plug angiogenesis and tumour xenograft growth. The selective ERK5 inhibitor described herein provides a lead for further development into a tool compound for more extensive studies seeking to examine the role of ERK5 signalling in cancer and other diseases.
Assuntos
Antineoplásicos/farmacologia , Proteína Quinase 14 Ativada por Mitógeno/antagonistas & inibidores , Proteína Quinase 7 Ativada por Mitógeno/antagonistas & inibidores , Proteínas Nucleares/antagonistas & inibidores , Inibidores de Proteínas Quinases/farmacologia , Fatores de Transcrição/antagonistas & inibidores , Administração Oral , Animais , Antineoplásicos/administração & dosagem , Antineoplásicos/química , Disponibilidade Biológica , Proteínas de Ciclo Celular , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ensaios de Seleção de Medicamentos Antitumorais , Feminino , Humanos , Camundongos , Camundongos Nus , Proteína Quinase 14 Ativada por Mitógeno/metabolismo , Proteína Quinase 7 Ativada por Mitógeno/metabolismo , Estrutura Molecular , Neoplasias Experimentais/tratamento farmacológico , Neoplasias Experimentais/metabolismo , Neoplasias Experimentais/patologia , Proteínas Nucleares/metabolismo , Inibidores de Proteínas Quinases/administração & dosagem , Inibidores de Proteínas Quinases/química , Relação Estrutura-Atividade , Fatores de Transcrição/metabolismoRESUMO
The kinesin class of microtubule-associated motor proteins present attractive anticancer targets owing to their roles in key functions in dividing cells. Two interpolar mitotic kinesins Eg5 and HSET have opposing motor functions in mitotic spindle assembly with respect to microtubule movement, but both offer opportunities to develop cancer selective therapeutic agents. Here, we summarize the progress to date in developing inhibitors of Eg5 and HSET, with an emphasis on structural biology insights into the binding modes of allosteric inhibitors, compound selectivity and mechanisms of action of different chemical scaffolds. We discuss translation of preclinical studies to clinical experience with Eg5 inhibitors, recent findings on potential resistance mechanisms and explore the implications for future anticancer drug development against these targets.
Assuntos
Antineoplásicos/farmacologia , Inibidores Enzimáticos/farmacologia , Cinesinas/antagonistas & inibidores , Mitose/efeitos dos fármacos , Neoplasias/tratamento farmacológico , Neoplasias/patologia , Antineoplásicos/química , Inibidores Enzimáticos/química , Humanos , Cinesinas/metabolismo , Modelos Moleculares , Conformação Molecular , Neoplasias/metabolismoRESUMO
The extracellular-related kinase 5 (ERK5) is a promising target for cancer therapy. A high-throughput screen was developed for ERK5, based on the IMAP FP progressive binding system, and used to identify hits from a library of 57â¯617 compounds. Four distinct chemical series were evident within the screening hits. Resynthesis and reassay of the hits demonstrated that one series did not return active compounds, whereas three series returned active hits. Structure-activity studies demonstrated that the 4-benzoylpyrrole-2-carboxamide pharmacophore had excellent potential for further development. The minimum kinase binding pharmacophore was identified, and key examples demonstrated good selectivity for ERK5 over p38α kinase.