ABSTRACT
A high throughput screening campaign was designed to identify allosteric inhibitors of Chk1 kinase by testing compounds at high concentration. Activity was then observed at K(m) for ATP and at near-physiological concentrations of ATP. This strategy led to the discovery of a non-ATP competitive thioquinazolinone series which was optimized for potency and stability. An X-ray crystal structure for the complex of our best inhibitor bound to Chk1 was solved, indicating that it binds to an allosteric site approximately 13A from the ATP binding site. Preliminary data is presented for several of these compounds.
Subject(s)
Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/pharmacology , Protein Kinases/drug effects , Quinazolines/chemical synthesis , Quinazolines/pharmacology , Binding Sites , Checkpoint Kinase 1 , Combinatorial Chemistry Techniques , Crystallography, X-Ray , Humans , Molecular Conformation , Molecular Structure , Protein Kinase Inhibitors/chemistry , Protein Kinases/chemistry , Protein Kinases/metabolism , Quinazolines/chemistryABSTRACT
From HTS lead 1, a novel benzoisoquinolinone class of ATP-competitive Chk1 inhibitors was devised and synthesized via a photochemical route. Using X-ray crystallography as a guide, potency was rapidly enhanced through the installation of a tethered basic amine designed to interact with an acidic residue (Glu91) in the enzyme pocket. Further SAR was explored at the solvent front and near to the H1 pocket and resulted in the discovery of low MW, sub-nanomolar inhibitors of Chk1.
Subject(s)
Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/pharmacology , Protein Kinases/drug effects , Quinolones/chemical synthesis , Quinolones/pharmacology , Apoptosis/drug effects , Binding Sites , Cell Line, Tumor , Checkpoint Kinase 1 , Crystallography, X-Ray , Drug Evaluation, Preclinical , Enzyme Inhibitors/chemistry , Humans , Inhibitory Concentration 50 , Models, Molecular , Molecular Structure , Photochemistry , Protein Kinases/chemistry , Quinolones/chemistry , Structure-Activity RelationshipABSTRACT
Through a comparison of X-ray co-crystallographic data for 1 and 2 in the Chek1 active site, it was hypothesized that the affinity of the indolylquinolinone series (2) for Chek1 kinase would be improved via C6 substitution into the hydrophobic region I (HI) pocket. An efficient route to 6-bromo-3-indolyl-quinolinone (9) was developed, and this series was rapidly optimized for potency by modification at C6. A general trend was observed among these low nanomolar Chek1 inhibitors that compounds with multiple basic amines, or elevated polar surface area (PSA) exhibited poor cell potency. Minimization of these parameters (basic amines, PSA) resulted in Chek1 inhibitors with improved cell potency, and preliminary pharmacokinetic data are presented for several of these compounds.
