ABSTRACT
Nitric oxide synthase (NOS) enzymes synthesize nitric oxide, a signal for vasodilatation and neurotransmission at low concentrations and a defensive cytotoxin at higher concentrations. The high active site conservation among all three NOS isozymes hinders the design of selective NOS inhibitors to treat inflammation, arthritis, stroke, septic shock and cancer. Our crystal structures and mutagenesis results identified an isozyme-specific induced-fit binding mode linking a cascade of conformational changes to a new specificity pocket. Plasticity of an isozyme-specific triad of distant second- and third-shell residues modulates conformational changes of invariant first-shell residues to determine inhibitor selectivity. To design potent and selective NOS inhibitors, we developed the anchored plasticity approach: anchor an inhibitor core in a conserved binding pocket, then extend rigid bulky substituents toward remote specificity pockets, which become accessible upon conformational changes of flexible residues. This approach exemplifies general principles for the design of selective enzyme inhibitors that overcome strong active site conservation.
Subject(s)
Drug Design , Enzyme Inhibitors , Inflammation/drug therapy , Inflammation/enzymology , Nitric Oxide Synthase/antagonists & inhibitors , Amino Acid Sequence , Aminopyridines/chemistry , Aminopyridines/pharmacology , Animals , Cattle , Crystallography, X-Ray , Disease Models, Animal , Enzyme Inhibitors/chemical synthesis , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacology , Gene Expression , Humans , Isoenzymes/antagonists & inhibitors , Male , Mice , Models, Molecular , Molecular Sequence Data , Molecular Structure , Mutation , Nitric Oxide Synthase/genetics , Nitric Oxide Synthase/metabolism , Quinazolines/chemistry , Quinazolines/pharmacology , RatsABSTRACT
Nitric Oxide (NO) is widely recognized as an important messenger and effector molecule in a variety of biological systems. There is strong evidence from animal models that elevated or lowered NO levels are associated with a variety of pathological states. In nature, NO is synthesised from the amino acid l-arginine by a small family of closely related oxygenase enzymes: the nitric oxide synthases (NOS). A number of studies in animals have associated excessive NO production by one of these enzymes--the inducible NOS isoform (iNOS or NOS-II)--with acute and chronic inflammation in model systems and have also demonstrated that administration of NOS inhibitors can produce beneficial effects. Regrettably, however, the relatively poor potency, selectivity and pharmacokinetic (ADME) profiles of the available inhibitors have so far precluded a convincing demonstration of their efficacy in the clinic. This review will describe the current state of knowledge of the structure and function of NOS and the various approaches that are being followed in the search for truly selective NOS inhibitors as therapeutic agents for inflammatory diseases.
Subject(s)
Anti-Inflammatory Agents/pharmacology , Anti-Inflammatory Agents/therapeutic use , Enzyme Inhibitors/pharmacology , Enzyme Inhibitors/therapeutic use , Inflammation/drug therapy , Nitric Oxide Synthase Type II/antagonists & inhibitors , Animals , Humans , Molecular Structure , Nitric Oxide Synthase Type II/chemistry , Nitric Oxide Synthase Type II/physiology , Structure-Activity RelationshipABSTRACT
This review aims to give an overview of current good practice in the prosecution of Lead Generation. It will assess experiences across the field as judged from the contents of the limited number of peer-review disclosures to date. It will also rely heavily on the experiences of the authors from many campaigns within this organisation. Its focus will be on the assembly of an appropriate compound collection for application in High Throughput Screening (HTS), the prosecution of HTS, the profiling of HTS output and, lastly the Hit-to-Lead optimisation of selected HTS output. Excluded from the scope are detailed aspects of library design [1], parallel synthesis [2], virtual library applications [3], virtual screening [4] and fragment screening [5] approaches, all of which have been the subject of recent reviews.
Subject(s)
Drug Design , Animals , Chemical Phenomena , Chemistry, Physical , Drug Evaluation, Preclinical , Drug-Related Side Effects and Adverse Reactions , HumansABSTRACT
4-Methylaminopyridine (4-MAP) (5) is a potent but nonselective nitric oxide synthase (NOS) inhibitor. While simple N-methylation in this series results in poor activity, more elaborate N-substitution such as with 4-piperidine carbamate or amide results in potent and selective inducible NOS inhibition. Evidently, a flipping of the pyridine ring between these new inhibitors allows the piperidine to interact with different residues and confer excellent selectivity.
Subject(s)
Aminopyridines/chemical synthesis , Nitric Oxide Synthase/antagonists & inhibitors , Aminopyridines/chemistry , Animals , Crystallography, X-Ray , Mice , Models, Molecular , Nitric Oxide Synthase/chemistry , Nitric Oxide Synthase Type IIABSTRACT
The discovery of a novel class of nitric oxide synthase (NOS) inhibitors, 2-substituted 1,2-dihydro-4-quinazolinamines, and the related 4'-aminospiro[piperidine-4,2'(1'H)-quinazolin]-4'-amines is described. Members of both series exhibit nanomolar potency and high selectivity for the inducible isoform of the enzyme (i-NOS) relative to the constitutive isoforms in vitro. Efficacy in acute and chronic animal models of inflammatory disease following oral administration has also been demonstrated using these compounds.
