h-89 and isoquinoline

With the success of protein kinase inhibitors as drugs to target cancer, there is a continued need for new kinase inhibitor scaffolds. We have investigated the synthesis and kinase inhibition of new heteroaryl-substituted diazaspirocyclic compounds that mimic ATP. Versatile syntheses of substituted diazaspirocycles through ring-closing metathesis were demonstrated. Diazaspirocycles directly linked to heteroaromatic hinge binder groups provided ligand efficient inhibitors of multiple kinases, suitable as starting points for further optimization. The binding modes of representative diazaspirocyclic motifs were confirmed by protein crystallography. Selectivity profiles were influenced by the hinge binder group and the interactions of basic nitrogen atoms in the scaffold with acidic side-chains of residues in the ATP pocket. The introduction of more complex substitution to the diazaspirocycles increased potency and varied the selectivity profiles of these initial hits through engagement of the P-loop and changes to the spirocycle conformation, demonstrating the potential of these core scaffolds for future application to kinase inhibitor discovery.

Topics: Adenosine Triphosphate; Aza Compounds; Binding Sites; Crystallography, X-Ray; Cyclic AMP-Dependent Protein Kinases; Isoquinolines; Molecular Dynamics Simulation; Protein Binding; Protein Kinase Inhibitors; Protein Kinases; Protein Structure, Tertiary; Spiro Compounds

Structure-based drug design of novel isoquinoline-5-sulfonamide inhibitors of PKB as potential antitumour agents was investigated. Constrained pyrrolidine analogues that mimicked the bound conformation of linear prototypes were identified and investigated by co-crystal structure determinations with the related protein PKA. Detailed variation in the binding modes between inhibitors with similar overall conformations was observed. Potent PKB inhibitors from this series inhibited GSK3beta phosphorylation in cellular assays, consistent with inhibition of PKB kinase activity in cells.

Topics: Cell Line, Tumor; Cell Proliferation; Crystallography, X-Ray; Cyclic AMP-Dependent Protein Kinases; Drug Design; Humans; Isoquinolines; Ligands; Molecular Structure; Protein Kinase C; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Structure-Activity Relationship; Sulfonamides

The discovery of several hundred different protein kinases involved in highly diverse cellular signaling pathways is in stark contrast to the much smaller number of known modulators of cell signaling. Of these, the H series protein kinase inhibitors (1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7), N-[2-(methylamino)ethyl]-5-isoquinolinesulfonamide (H8) N-[2-(p-Bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide (H89)) are frequently used to block signaling pathways in studies of cellular regulation. To elucidate inhibition mechanisms at atomic resolution and to enable structure-based drug design of potential therapeutic modulators of signaling pathways, we determined the crystal structures of corresponding complexes with the cAPK catalytic subunit. Complexes with H7 and H8 (2.2 A) and with H89 (2.3 A) define the binding mode of the isoquinoline-sulfonamide derivatives in the ATP-binding site while demonstrating effects of ligand-induced structural change. Specific interactions between the enzyme and the inhibitors include the isoquinoline ring nitrogen ligating to backbone amide of Val-123 and an inhibitor side chain amide bonding to the backbone carbonyl of Glu-170. The conservation of the ATP-binding site of protein kinases allows evaluation of factors governing general selectivity of these inhibitors among kinases. These results should assist efforts in the design of protein kinase inhibitors with specific properties.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Animals; Binding Sites; Casein Kinase II; Casein Kinases; Cattle; Crystallography, X-Ray; Cyclic AMP-Dependent Protein Kinases; Cyclic GMP-Dependent Protein Kinases; Enzyme Inhibitors; Glycine; Isoquinolines; Myosin-Light-Chain Kinase; Protein Conformation; Protein Kinase C; Protein Kinase Inhibitors; Protein Serine-Threonine Kinases; Sulfonamides