Screening and identification of a novel class of TGF-ß type 1 receptor kinase inhibitor.

Transforming growth factor ß (TGF-ß) type I receptor (activin receptor-like kinase 5, ALK5) has been identified as a promising target for fibrotic diseases. To find a novel inhibitor of ALK5, the authors performed a high-throughput screen of a library of 420,000 compounds using dephosphorylated ALK5. From primary hits of 1521 compounds, 555 compounds were confirmed. In total, 124 compounds were then selected for follow-up based on their unique structures and other properties. Repeated concentration-response testing and final interference assays of the above compounds resulted in the discovery of a structurally novel ALK5 inhibitor (compound 8) (N-(thiophen 2-ylmethyl)-3-(3,4,5 trimethoxyphenyl)imidazo[1,2ß]pyridazin 6-amine) with a low IC(50) value of 0.7 µM. Compound 8 also inhibited the TGF-ß-induced nuclear translocation of SMAD with an EC(50) value of 0.8 µM. Kinetic analysis revealed that compound 8 inhibited ALK5 via mixed-type inhibition, suggesting that it may bind to ALK5 differently than other published adenosine triphosphate site inhibitors.

Conformational analysis and receptor docking of N-[(1S,2S)-3-(4-chlorophenyl)-2-(3-cyanophenyl)-1-methylpropyl]-2-methyl-2-{[5-(trifluoromethyl)pyridin-2-yl]oxy}propanamide (taranabant, MK-0364), a novel, acyclic cannabinoid-1 receptor inverse agonist.

X-ray crystallographic, NMR spectroscopic, and computational studies of taranabant afforded similar low-energy conformers with a significant degree of rigidity along the C11-N13-C14-C16-C17 backbone but with more flexibility around bonds C8-C11 and C8-O7. Mutagenesis and docking studies suggested that taranabant and rimonabant shared the same general binding area of CB1R but with significant differences in detailed interactions. Similar to rimonabant, taranabant interacted with a cluster of aromatic residues (F(3.36)200, W(5.43)279, W(6.48)356, and Y(5.39)275) through the two phenyl rings and with F(2.57)170 and L(7.42)387 through the CF 3-Pyr ring. The notable distinction between taranabant and rimonabant was that taranabant was hydrogen-bonded with S(7.39)383 but not with K(3.28)192, while rimonabant was hydrogen-bonded with K(3.28)192 but not with S(7.39)383. The strong hydrogen bonding between the amide NH of taranabant and hydroxyl of S(7.39)383 was key to the superior affinity of taranabant to CB1R.

Bioisosteric replacement of anilide with benzoxazole: potent and orally bioavailable antagonists of VLA-4.

We have designed and synthesized a series of heterocyclic bioisosteres for an anilide based on molecular modeling. Excellent potency was retained in the benzoxazole and the benzimidazole derivatives, where a hydrogen bond acceptor is appropriately positioned to mimic the amide bond oxygen. The deletion of the hydrogen bond donor (N-H) led to improved lipophilicity and bioavailability. In the process, 9a was identified as a potent, specific, and bioavailable VLA-4 antagonist, while 9c was found to be a potent and bioavailable dual antagonist of VLA-4 and alpha(4)beta(7).

Binding of 2-aryl-4-(piperidin-1-yl)butanamines and 1,3,4-trisubstituted pyrrolidines to human CCR5: a molecular modeling-guided mutagenesis study of the binding pocket.

The results of investigations in these laboratories of 2-aryl-4-(piperidin-1-yl)butanamines and 1,3,4-trisubstituted pyrrolidines as human CCR5 antagonists have recently been disclosed. To facilitate further development of these antagonists, we have developed a pharmacophore model based on the structure-activity relationships (SAR) and a human CCR5 receptor docking model using the crystal structure of rhodopsin as a template [Palczewski, K., et al. (2000) Science 289, 739-745]. Guided by the receptor docking model, we have mapped the compounds' site of interaction with CCR5 using site-directed mutagenesis experiments. Our results are consistent with a binding site for the two series that is located within a cavity near the extracellular surface formed by transmembrane helices 2, 3, 6, and 7. This site is overlapping yet distinct from that reported for another antiviral agent which binds to CCR5 [Dragic, T., et al. (2000) Proc. Natl. Acad. Sci. U.S.A. 97, 5639-5644].