Design and synthesis of peptidomimetic factor VIIa inhibitors.

Selective factor VIIa-tissue factor complex (FVIIa/TF) inhibition is regarded as a promising target for developing new anticoagulant drugs. In previous reports, we described a S3 subsite found in the X-ray crystal structure of compound 2 that bound to FVIIa/soluble tissue factor (sTF). Based on the X-ray crystal structure information and with the aim of improving the inhibition activity for FVIIa/TF and selectivity against other serine proteases, we synthesized derivatives by introducing substituents at position 5 of the indole ring of compound 2. Among them, compound 16 showed high selectivity against other serine proteases. Contrary to our expectations, compound 16 did not occupy the S3-subsite; X-ray structure analysis revealed that compound 16 improved selectivity by forming hydrogen bonds with Gln217, Thr99 and Asn100.

Factor VIIa inhibitors: target hopping in the serine protease family using X-ray structure determination.

Selective factor VIIa-tissue factor complex (FVIIa/TF) inhibition is regarded as a promising target for developing new anticoagulant drugs. Compound 1 was discovered from focused screening of serine protease-directed compounds from our internal collection. Using parallel synthesis supported by structure-based drug design, we identified peptidemimetic FVIIa/TF inhibitors (compounds 4-11) containing L-Gln or L-Met as the P2 moiety. However, these compounds lacked the selectivity of other serine proteases in the coagulation cascade, especially thrombin. Further optimization of these compounds was carried out with a focus on the P4 moiety. Among the optimized compounds, 12b-f showed improved selectivity.

Structure-based design of P3 moieties in the peptide mimetic factor VIIa inhibitor.

Selective factor VIIa-tissue factor complex (FVIIa/TF) inhibition is seen as a promising target for developing new anticoagulant drugs. Structure-based designs of the P3 moiety in the peptide mimetic factor VIIa inhibitor successfully lead to novel inhibitors with selectivity for FVIIa/TF and extrinsic coagulation the same as or even higher than those of previously reported peptide mimetic factor VIIa inhibitors. X-ray crystal structure analysis reveals that one of the novel inhibitors shows improved selectivity by forming interactions between the inhibitor and FVIIa as expected. Another of the novel inhibitors achieves improved selectivity through an unexpected hydrogen bond with Gln217, with a unique bent conformation in FVIIa/TF accompanied by conformational changes of the inhibitor and the protein.

Structure of human factor VIIa/tissue factor in complex with a peptide-mimetic inhibitor: high selectivity against thrombin by introducing two charged groups in P2 and P4.

The crystal structure of human factor VIIa/soluble tissue factor (FVIIa/sTF) in complex with a highly selective peptide-mimetic FVIIa inhibitor which shows 1670-fold selectivity against thrombin inhibition has been solved at 2.6 A resolution. The inhibitor is bound to FVIIa/sTF at the S1, S2 and S3 sites and at the additional S1 subsite. Two charged groups, the amidino group in P2 and the carboxylate group in P4, form ionic interactions with Asp60 and Lys192 of FVIIa, respectively. Structural comparisons between factor VIIa and thrombin show that thrombin has oppositely charged residues, Lys60F and Glu192, in the S2 site and the S1 subsites, respectively. These data suggest that the utilization of the differences of charge distribution in the S2 site and the S1 subsites between FVIIa and thrombin is critical for achieving high selectivity against thrombin inhibition. These results will provide valuable information for the structure-based drug design of specific inhibitors for FVIIa/TF.

Novel interactions of large P3 moiety and small P4 moiety in the binding of the peptide mimetic factor VIIa inhibitor.

Selective factor VIIa-tissue factor complex (FVIIa/TF) inhibition is seen as a promising target for developing new anticoagulant drugs. A novel peptide mimetic factor VIIa inhibitor, ethylsulfonamide-d-biphenylalanine-Gln-p-aminobenzamidine, shows 100-fold selectivity against thrombin in spite of its large P3 moiety, unlike previously reported FVIIa/TF selective inhibitors. X-ray crystal structure analysis reveals that the large P3 moiety, d-biphenylalanine, and the small P4 moiety, ethylsulfonamide, make novel interactions with the 170-loop and Lys192 of FVIIa/TF, respectively, accompanying ligand-induced conformational changes of the 170-loop, Gln217, and Lys192. Structural comparisons of FVIIa with thrombin and amino acid sequence comparisons among coagulation serine proteases suggest that these interactions play an important role in achieving selective inhibition for FVIIa/TF.

Design and efficient synthesis of 2 alpha-(omega-hydroxyalkoxy)-1 alpha,25-dihydroxyvitamin D3 Analogues, including 2-epi-ED-71 and their 20-epimers with HL-60 cell differentiation activity.

A concise and efficient synthetic approach to 2 alpha-(omega-hydroxyalkoxy)-1 alpha,25-dihydroxyvitamin D(3) (4a-c), including 2-epi-ED-71, was developed starting from D-glucose as a chiral template for the construction of the 2 alpha-modified A-ring precursors (11a-c). It was found that the best ligand for the bovine thymus vitamin D receptor (VDR) in this series is 4b, which has 1.8 times greater binding affinity for the bovine thymus VDR than that of the natural hormone 1. Interestingly, potency in the induction of HL-60 cell differentiation for 4a-c was almost the same or weaker than that of 1 despite the strong binding affinity for the VDR. Next, we were interested in the "double modification"of 1 based on 4a-c with C20-epimerization, affording 2 alpha-(omega-hydroxyalkoxy)-20-epi-1 alpha,25-dihydroxyvitamin D(3) (20-epi-4a-c). All three 2 alpha-substituted 20-epi analogues of 1 (20-epi-4a-c) exhibited stronger binding affinities for the VDR, and their conformations in the ligand binding domain of VDR were analyzed by molecular modeling. Double-modified analogues of 20-epi-4a-c showed marked HL-60 cell differentiation activity, and 20-epi-4a possesses an activity 58-fold higher than that of the natural hormone 1.

Crystal structure of human factor VIIa/tissue factor in complex with peptide mimetic inhibitor.

The 3D structure of human factor VIIa/soluble tissue factor in complex with a peptide mimetic inhibitor, propylsulfonamide-D-Thr-Met-p-aminobenzamidine, is determined by X-ray crystallography. As compared with the interactions between thrombin and thrombin inhibitors, the interactions at S2 and S3 sites characteristic of factor VIIa and factor VIIa inhibitors are revealed. The S2 site has a small pocket, which is filled by the hydrophobic methionine side chain in P2. The small S3 site fits the small size residue, D-threonine in P3. The structural data and SAR data of the peptide mimetic inhibitor show that these interactions in the S2 and S3 sites play an important role for the improvement of selectivity versus thrombin. The results will provide valuable information for the structure-based drug design of specific inhibitors for FVIIa/TF.

Discovery and structure-activity relationship of coumarin derivatives as TNF-alpha inhibitors.

The discovery and structure-activity relationship of a novel series of coumarin-based TNF-alpha inhibitors is described. Starting from the initial lead 1a, various derivatives were prepared surrounding the coumarin core structure to optimize the in vitro inhibitory activity of TNF-alpha production by human peripheral blood mononuclear cells (hPBMC), stimulated by bacterial lipopolysaccharide (LPS). Selected compounds also demonstrated in vivo inhibition of TNF-alpha production in rats.

Design and synthesis of novel tetra-peptide motilin agonists.

A series of novel tetra-peptide motilin agonists, having the general structure H-Phe-Val-X-Ile-NH(2), were designed, on the basis of structure-activity relationship studies of motilin. Peptides, in which X is a side chain substituted tryptophan residue, have agonistic activity. H-Phe-Val-Trp(2'-CH(2)CH(2)OH)-Ile-NH(2)(7), H-Phe-Val-Trp(2'-SCH(3))-Ile-NH(2)(8), and H-Phe-Val-Trp(2'-SCH(2)CH(2)CH(3))-Ile-NH(2)(9), showed an EC(50) for contractile activity in the rabbit smooth muscle of 14.1+/-3.2, 12.9+/-4.1, and 4.6+/-1.6 microM, respectively. Interaction of the tryptophan aliphatic side chain with motilin receptor appears to influence the signal transduction via motilin receptor.

Design and synthesis of motilin antagonists derived from the [1-4] fragment of porcine motilin.

A series of cyclic peptides having the general structure H-Phe-c[-N(epsilon)-Lys-X-NH-(CH(2))(n)-CO-] were designed on the basis of structure-activity relationship studies of motilin. All were motilin antagonists. The cyclic peptides, in which X is a 3-tert-butyl-substituted tyrosine residue (H-Phe-c[-N(epsilon)-Lys-Tyr(3-tBu)-beta Ala-] (3), H-Phe-c[-N(epsilon)-Lys-Tyr(3-tBu)-Gly-] (6), H-Phe-c[-N(epsilon)-Lys-Tyr(3-tBu)-Abu-] (7), and H-Phe-c[-N(epsilon)-Lys-Tyr(3-tBu)-Ahx-] (8)) showed potent motilin receptor antagonistic activity in the rabbit smooth muscle (pA(2) > 7). The 3-tert-butyl Tyr was found to be the moiety responsible for enhanced binding to the motilin receptor, while the size of the ring had little importance.