Takeru Ehara

Discovery of selective and nonpeptidic cathepsin S inhibitors

Nonpeptidic, selective, and potent cathepsin S inhibitors were derived from an in-house pyrrolopyrimidine cathepsin K inhibitor by modification of the P2 and P3 moieties. The pyrrolopyrimidine-based inhibitors show nanomolar inhibition of cathepsin S with over 100-fold selectivity against other cysteine proteases, including cathepsin K and L. Some of the inhibitors showed cellular activities in mouse splenocytes as well as oral bioavailabilities in rats.

Discovery of Orally Bioavailable Cathepsin S Inhibitors for the Reversal of Neuropathic Pain

Cathepsin S inhibitors are well-known to be an attractive target as immunological therapeutic agents. Recently, our gene expression analysis identified that cathepsin S inhibitors could also be effective for neuropathic pain. Herein, we describe the efficacy of selective cathepsin S inhibitors as antihyperalgesics in a model of neuropathic pain in rats after oral administration.

Overcoming hERG issues for brain-penetrating cathepsin S inhibitors: 2-cyanopyrimidines. Part 2.

We describe here orally active and brain-penetrant cathepsin S selective inhibitors, which are virtually devoid of hERG K(+) channel affinity, yet exhibit nanomolar potency against cathepsin S and over 100-fold selectivity to cathepsin L. The new non-peptidic inhibitors are based on a 2-cyanopyrimidine scaffold bearing a spiro[3.5]non-6-yl-methyl amine at the 4-position. The brain-penetrating cathepsin S inhibitors demonstrate potential clinical utility for the treatment of multiple sclerosis and neuropathic pain.

Effect of Cathepsin K Inhibitors on Bone Resorption

On the basis of the pyrrolopyrimidine core structure that was previously discovered, cathepsin K inhibitors having a spiro amine at the P3 have been explored to enhance the target, bone marrow, tissue distribution. Several spiro structures were identified with improved distribution toward bone marrow. The representative inhibitor 7 of this series revealed in vivo reduction in C-terminal telopeptide of type I collagen in rats and monkeys.

4-Amino-2-cyanopyrimidines: Novel scaffold for nonpeptidic cathepsin S inhibitors

We describe here a novel 4-amino-2-cyanopyrimidine scaffold for nonpeptidomimetic cathepsin S selective inhibitors. Some of the synthesized compounds have sub-nanomolar potency and high selectivity toward cathepsin S along with promising pharmacokinetic and physicochemical properties. The key structural features of the inhibitors consist of a combination of a spiro[2.5]oct-6-ylmethylamine P2 group at the 4-position, a small or polar P3 group at the 5-position and/or a polar group at the 6-position of the pyrimidine.

Structure-based design of substituted piperidines as a new class of highly efficacious oral direct Renin inhibitors.

A cis-configured 3,5-disubstituted piperidine direct renin inhibitor, (syn,rac)-1, was discovered as a high-throughput screening hit from a target-family tailored library. Optimization of both the prime and the nonprime site residues flanking the central piperidine transition-state surrogate resulted in analogues with improved potency and pharmacokinetic (PK) properties, culminating in the identification of the 4-hydroxy-3,5-substituted piperidine 31. This compound showed high in vitro potency toward human renin with excellent off-target selectivity, 60% oral bioavailability in rat, and dose-dependent blood pressure lowering effects in the double-transgenic rat model.

A Novel Selective Soluble Guanylate Cyclase Activator, MGV354, Lowers Intraocular Pressure in Preclinical Models, Following Topical Ocular Dosing

Purpose The nitric oxide/soluble guanylate cyclase/protein kinase G (NO/sGC/PKG) is known to be involved in the regulation of intraocular pressure (IOP) and may be dysregulated in glaucoma. The purpose is to demonstrate that the sGC activator MGV354 lowers IOP in a monkey model of glaucoma and could be considered as a possible new clinical drug candidate. Methods Changes to cGMP were assessed in primary human trabecular meshwork (hNTM) cells and binding studies were conducted using human sGC full-length protein. Ocular safety tolerability, exposure, and efficacy studies were conducted in rabbit and monkey models following topical ocular dosing of MGV354. Results sGC was highly expressed in the human and cynomolgus monkey outflow pathways. MGV354 had a 7-fold greater Bmax to oxidized sGC compared to that of reduced sGC and generated an 8- to 10-fold greater cGMP compared to that of a reduced condition in hTM cells. A single topical ocular dose with MGV354 caused a significant dose-dependent reduction of 20% to 40% (versus vehicle), lasting up to 6 hours in pigmented rabbits and 24 hours postdose in a cynomolgus monkey model of glaucoma. The MGV354-induced IOP lowering was sustained up to 7 days following once-daily dosing in a monkey model of glaucoma and was greater in magnitude compared to Travatan (travoprost)-induced IOP reduction. Mild to moderate ocular hyperemia was the main adverse effect noted. Conclusions MGV354 represents a novel class of sGC activators that can lower IOP in preclinical models of glaucoma. The potential for sGC activators to be used as effective IOP-lowering drugs in glaucoma patients could be further determined in clinical studies.

The Discovery of (S)-1-(6-(3-((4-(1-(Cyclopropanecarbonyl)piperidin-4-yl)-2-methylphenyl)amino)-2,3-dihydro-1H-inden-4-yl)pyridin-2-yl)-5-methyl-1H-pyrazole-4-carboxylic Acid, a Soluble Guanylate Cyclase Activator Specifically Designed for Topical Ocular Delivery as a Therapy for Glaucoma

Soluble guanylate cyclase (sGC), the endogenous receptor for nitric oxide (NO), has been implicated in several diseases associated with oxidative stress. In a pathological oxidative environment, the heme group of sGC can be oxidized becoming unresponsive to NO leading to a loss in the ability to catalyze the production of cGMP. Recently a dysfunctional sGC/NO/cGMP pathway has been implicated in contributing to elevated intraocular pressure associated with glaucoma. Herein we describe the discovery of molecules specifically designed for topical ocular administration, which can activate oxidized sGC restoring the ability to catalyze the production of cGMP. These efforts culminated in the identification of compound (+)-23, which robustly lowers intraocular pressure in a cynomolgus model of elevated intraocular pressure over 24 h after a single topical ocular drop and has been selected for clinical evaluation.