Toshihiko Nishiyama

Design and synthesis of orally bioavailable inhibitors of inducible nitric oxide synthase. synthesis and biological evaluation of dihydropyridin-2(1H)-imines and 1,5,6,7-tetrahydro-2H-azepin-2-imines.

The process of discovery and biological evaluation of alpha,beta-unsaturated cyclic amidines, as selective inhibitors of inducible nitric oxide synthase (iNOS), is reported. Dihydropyridin-2(1H)-imines and 1,5,6,7-tetrahydro-2H-azepin-2-imines were synthesized and biologically evaluated both in vitro and in vivo using a nitric oxide synthase inhibition assay. Compounds 1, 5, 6, 8-12 and 16 exhibited potent inhibition of iNOS. Among these, compounds 6, 7, 10, 11 and 16 showed 5- to 19-fold isoform selectivity. Compounds 1, 6, 10, 11 and 16 also showed potent inhibitory activity in the NOx accumulation assay in mice. Compounds 1 and 6 showed excellent bioavailability (BA) in rats when administered orally. Full details are presented here, including the structure-activity relationship (SAR) studies, the chemistry of these compounds, and the pharmacokinetic data and the computer-aided docking study of 10 with hiNOS.

Spirodiketopiperazine-based CCR5 antagonists: Improvement of their pharmacokinetic profiles.

Spirodiketopiperazine-based CCR5 antagonists, showing improved pharmacokinetic profiles without reduction in antagonist activity, were designed and synthesized. We also demonstrate the anti-HIV activity of a representative compound 12, as measured in a p24 assay.

Discovery of orally available spirodiketopiperazine-based CCR5 antagonists

Using the previously reported novel spirodiketopiperazine scaffold, the design and synthesis of orally available CCR5 antagonists was undertaken. Compounds possessing a carboxylic acid function in the appropriate position showed improved oral exposure (AUC) relative to the initial chemical leads without reduction in the antagonist activity. The optimized compound 40 was found to show potent anti-HIV activity. Full details of structure-activity relationship (SAR) study are presented.

Design and synthesis of orally bioavailable inhibitors of inducible nitric oxide synthase. Identification of 2-azabicyclo[4.1.0]heptan-3-imines.

Further chemical modification of 2-iminopiperidines fused to cyclopropane rings was performed. Optically active isomers 2 and 13 were synthesized and their biological activity was evaluated. Compound 2 exhibited greater potency and more isoform selectivity than enantiomer 13 in the iNOS inhibition assay. One of the gem-chlorines on the fused cyclopropane moiety of 2 was eliminated to produce 3, which showed reduced potency for iNOS inhibition, as well as 4 with an increased potency. The isoform selectivity of 4 was also much higher than that of 3. This was also true for the corresponding methyl derivatives 6-9. The structure-activity relationship (SAR) study and computer aided docking study of the most optimized structure 4 with human iNOS will also be reported.

Design and synthesis of inhibitors of inducible nitric oxide synthase. Discovery of a new chemical lead with potential for oral bioavailability

A series of 2-iminopiperidines fused to small-membered rings (Tables 1 and 2) were synthesised and biologically evaluated using an in vitro human nitric oxide synthase (NOS) inhibition assay. Fused bicyclic compounds 5-9 exhibited nearly the same potency as compound 1 in the hiNOS inhibition assay. Among these, the 1-methyl analogues 8 and 9 showed better isoform selectivity than their corresponding unsubstituted analogues 7 and 6, respectively. Compounds 5 and 6 were also evaluated by an in vivo NO accumulation assay in a mouse model. The discovery process of new chemical leads for an orally bioavailable inhibitor of human inducible NOS (iNOS) is reported. The structure-activity relationship (SAR) study and chemistry of these compounds are also reported.

Design and synthesis of orally bioavailable inhibitors of inducible nitric oxide synthase. Part 1: synthesis and biological evaluation of dihydropyridin-2-imines

Dihydropyridin-2-imines were synthesized and biologically evaluated both in vitro and in vivo using a nitric oxide inhibition assay. Compounds 1, 4, 5 and 7-11 exhibited potent activity in the inducible nitric oxide (iNOS) inhibition assay. Of these 5, 6, 9 and 10 showed 5- to 11-fold increases in isoform selectivity. Compounds 1, 5, 9 and 10 showed potent inhibitory activity in the NOx accumulation assay in mice. Compounds 1 and 5 also showed good bioavailability (BA) when given orally.

Spirodiketopiperazine-based CCR5 antagonist: Discovery of an antiretroviral drug candidate

Following the discovery that hydroxylated derivative 3 (Fig. 1) was one of the oxidative metabolites of the original lead 1, it was found that hydroxylated compound 4 possesses higher in vitro anti-HIV potency than the corresponding non-hydroxylated compound 2. Structural hybridation of 4 with the orally available analog 5 resulted in another orally-available spirodiketopiperazine CCR5 antagonist 6a that possesses more favorable pharmaceutical profile for use as a drug candidate.

Discovery of 4-[4-({(3R)-1-butyl-3-[(R)-cyclohexyl(hydroxy)methyl]-2,5- dioxo-1,4,9-triazaspiro[5.5]undec-9-yl}methyl)phenoxy]benzoic acid hydrochloride: A highly potent orally available CCR5 selective antagonist

Based on the original spirodiketopiperazine design framework, further optimization of an orally available CCR5 antagonist was undertaken. Structural hybridization of the hydroxylated analog 4 derived from one of the oxidative metabolites and the new orally available non-hydroxylated benzoic acid analog 5 resulted in another potent orally available CCR5 antagonist 6a as a clinical candidate. Full details of a structure-activity relationship (SAR) study and ADME properties are presented.

Discovery of new orally active prostaglandin D2 receptor antagonists.

To identify an orally available drug candidate, a series of 3-benzoylaminophenylacetic acids were synthesized and evaluated as prostaglandin D(2) (PGD(2)) receptor antagonists. Some of the compounds tested were found to exhibit excellent inhibitory activity against cAMP accumulation in human platelet rich plasma (hPRP), which is one of the indexes of DP antagonism. The optimization process including improvement of the physicochemical properties such as solubility, which may result in an improved pharmacokinetic (PK) profile, is presented. Optimized compounds were studied for their pharmacokinetics and in vivo potential. A structure-activity relationship study is also presented. Some of the test compounds were found to have in vivo efficacy towards the inhibition of PGD(2)-induced and OVA-induced vascular permeability in guinea pig conjunctiva.