No abstract

Efforts to identify a suitable follow-on compound to razaxaban (compound 4) focused on modification of the carboxamido linker to eliminate potential in vivo hydrolysis to a primary aniline. Cyclization of the carboxamido linker to the novel bicyclic tetrahydropyrazolopyridinone scaffold retained the potent fXa binding activity. Exceptional potency of the series prompted an investigation of the neutral P1 moieties that resulted in the identification of the p-methoxyphenyl P1, which retained factor Xa binding affinity and good oral bioavailability. Further optimization of the C-3 pyrazole position and replacement of the terminal P4 ring with a neutral heterocycle culminated in the discovery of 1-(4-methoxyphenyl)-7-oxo-6-(4-(2-oxopiperidin-1-yl)phenyl)-4,5,6,7-tetrahydro-1H-pyrazolo[3,4-c]pyridine-3-carboxamide (apixaban, compound 40). Compound 40 exhibits a high degree of fXa potency, selectivity, and efficacy and has an improved pharmacokinetic profile relative to 4.

A high-resolution structure of a ligand-bound, soluble form of human monoglyceride lipase (MGL) is presented. The structure highlights a novel conformation of the regulatory lid-domain present in the lipase family as well as the binding mode of a pharmaceutically relevant reversible inhibitor. Analysis of the structure lacking the inhibitor indicates that the closed conformation can accommodate the native substrate 2-arachidonoyl glycerol. A model is proposed in which MGL undergoes conformational and electrostatic changes during the catalytic cycle ultimately resulting in its dissociation from the membrane upon completion of the cycle. In addition, the study outlines a successful approach to transform membrane associated proteins, which tend to aggregate upon purification, into a monomeric and soluble form.

The three-dimensional structures of proteins contained in the Brookhaven Protein Data Bank were analyzed for bound metal ions. Well over 150 unique protein structures are available which contain seven different types of bound metal ions. Iron, calcium, and zinc are most commonly observed, and the extended coordination polyhedra of biological zinc are the subject of this study. In particular, histidine residues ligating zinc ions are often found to bridge both the zinc ion and the carboxylate side chain of a nearby aspartate (sometimes glutamate) residue. We refer to the carboxylate-histidine-zinc interaction as indirect carboxylate-metal coordination, and we observe this feature in all zinc enzymes of reported three-dimensional structure. Additionally, we also observe a related carbonyl-histidine-zinc interaction in some metalloproteins. We observe some direcr carboxylate-zinc interactions, and their coordination stereochemistry is exclusively syn with respect to the carboxylate. On the basis of available protein structures and known homologues thereof, more than 30 examples of indirect carboxylate-zinc coordination across bridging histidine can be identified. The carboxylate-histidine-zinc triad may be important in the function of many zinc-containing proteins and enzymes, e.g., by strengthening metal complexation or modulating the nucleophilicity of zinc-bound water. The presence of an uncomplexed carboxylate-histidine couple (a grouping more basic than histidine alone) in a native protein can also signal a regulatory metal binding site. Indeed, the Asp----His couple of the serine protease active site may comprise a structural, evolutionary link to the Asp----His of the zinc protease metal coordination polyhedron.Among the first-row transition metals, zinc is second only to iron in terms of abundance and functional importance in biological systems.'From an inorganic perspective, the coordination chemistry of divalent zinc cation (Zn2+, hereafter zinc) might be

A new aspartic protease inhibitory chemotype bearing a 2-amino-3,4-dihydroquinazoline ring was identified by high-throughput screening for the inhibition of BACE-1. X-ray crystallography revealed that the exocyclic amino group participated in a hydrogen bonding array with the two catalytic aspartic acids of BACE-1 (Asp(32), Asp(228)). BACE-1 inhibitory potency was increased (0.9 microM to 11 nM K(i)) by substitution into the unoccupied S(1)' pocket.