Lead Optimization of Influenza Virus RNA Polymerase Inhibitors Targeting PA-PB1 Interaction.

Influenza viruses are responsible for contagious respiratory illnesses in humans and cause seasonal epidemics and occasional pandemics worldwide. Previously, we identified a quinolinone derivative PA-49, which inhibited the influenza virus RNA-dependent RNA polymerase (RdRp) by targeting PA-PB1 interaction. This paper reports the structure optimization of PA-49, which resulted in the identification of 3-((dibenzylamino)methyl)quinolinone derivatives with more potent anti-influenza virus activity. During the optimization, the hit compound 89, which was more active than PA-49, was identified. Further optimization and scaffold hopping of 89 led to the most potent compounds 100 and a 1,8-naphthyridinone derivative 118, respectively. We conclusively determined that compounds 100 and 118 suppressed the replication of influenza virus and exhibited anti-influenza virus activity against both influenza virus types A and B in the range of 50% effective concentration (EC50) = 0.061-0.226 µM with low toxicity (50% cytotoxic concentration (CC50) >10 µM).

Identification of a novel series of potent and selective CCR6 inhibitors as biological probes.

CCR6 has been implicated in both autoimmune diseases and non-autoimmune diseases. Thus, inhibition of CCR6-dependent cell migration is an attractive strategy for their treatment. An orally available small molecule inhibitor of CCR6 could therefore be a useful biological probe for the pathophysiological studies. Initial SAR study of a hit compound provided potent N-benzenesulfonylpiperidine derivatives that suppressed CCL20-induced Gi signals. By subsequent scaffold morphing of the central ring and further optimization, we identified a novel series of 1,4-trans-1-benzenesulfonyl-4-aminocyclohexanes as potent and selective CCR6 inhibitors with good pharmacokinetic properties. Our compounds showed good correlation between Gi signal inhibitory activity and cell migration inhibitory activity in human CCR6-transfected CHO cells. In addition, representative compound 35 potently inhibited CCR6-dependent cell migration and the increase in ERK phosphorylation in human primary cells. Therefore, the compound could be used effectively as a biological probe against human CCR6.

Identification of 3,4-dihydro-2H-thiochromene 1,1-dioxide derivatives with a phenoxyethylamine group as highly potent and selective α1D adrenoceptor antagonists.

A series of phenoxyethylamine derivatives was designed and synthesized to discover potent and selective human α1D adrenoceptor (α1D adrenergic receptor; α1D-AR) antagonists. Compound 7 was taken from our internal compound collection as an attractive starting point and exhibited moderate binding affinity for α1D-AR and high selectivity against α1A- and α1B-ARs. We focused on modifying the 2-methylsulfonylbenzyl group of 7 to discover novel compounds structurally distinct from other reported α1-AR antagonists containing the phenoxyethylamine motif. Study of structure activity relationship guided by a targeted ligand-lipophilicity efficiency score led to the discovery of a novel scaffold of 3,4-dihydro-2H-thiochromene 1,1-dioxide for selective α1D-AR antagonists. Further optimization studies resulted in the identification of (4S)-N4-[2-(2,5-difluorophenoxy)ethyl]-N6-methyl-3,4-dihydro-2H-thiochromene-4,6-diamine 1,1-dioxide, (S)-41, as a novel, highly potent and selective α1D-AR antagonist. Herein, we provide details of the structure activity relationship of the phenoxyethylamine analog for the potency and selectivity.

Design, synthesis, and biological evaluation of a novel series of peripheral-selective noradrenaline reuptake inhibitors-Part 2.

Peripherally selective inhibition of noradrenaline reuptake is a novel mechanism for the treatment of stress urinary incontinence to overcome adverse effects associated with central action. Herein, we describe our medicinal chemistry approach to discover peripheral-selective noradrenaline reuptake inhibitors to avert the risk of P-gp-mediated DDI at the blood-brain barrier. We observed that steric shielding of the hydrogen-bond acceptors and donors (HBA and HBD) of compound 1 reduced the multidrug resistance protein 1 (MDR1) efflux ratio; however, the resulting compound 6, a methoxyacetamide derivative, was mainly metabolized by CYP2D6 and CYP2C19 in the in vitro phenotyping study, implying the risk of PK variability based on the genetic polymorphism of the CYPs. Replacement of the hydrogen atom with a deuterium atom in a strategic, metabolically hot spot led to compound 13, which was mainly metabolized by CYP3A4. To our knowledge, this study represents the first report of the effect of deuterium replacement for a major metabolic enzyme. The compound 13, N-{[(6S,7R)-7-(4-chloro-3-fluorophenyl)-1,4-oxazepan-6-yl]methyl}-2-[(2H(3))methyloxy]acetamide hydrochloride, which exhibited peripheral NET selective inhibition at tested doses in rats, increased urethral resistance in a dose-dependent manner.

Design, synthesis, and biological evaluation of a novel series of peripheral-selective noradrenaline reuptake inhibitors - Part 3.

Peripheral-selective inhibition of noradrenaline reuptake is a novel mechanism for the treatment of stress urinary incontinence to overcome adverse effects associated with central action. Here, we describe our medicinal chemistry approach to discover a novel series of highly potent, peripheral-selective, and orally available noradrenaline reuptake inhibitors with a low multidrug resistance protein 1 (MDR1) efflux ratio by cyclization of an amide moiety and introduction of an acidic group. We observed that the MDR1 efflux ratio was correlated with the pKa value of the acidic moiety. The resulting compound 9 exhibited favorable PK profiles, probably because of the effect of intramolecular hydrogen bond, which was supported by a its single-crystal structure. The compound 9, 1-{[(6S,7R)-7-(4-chloro-3-fluorophenyl)-1,4-oxazepan-6-yl]methyl}-2-oxo-1,2-dihydropyridine-3-carboxylic acid hydrochloride, which exhibited peripheral NET-selective inhibition at tested doses in rats by oral administration, increased urethral resistance in a dose-dependent manner.

Discovery of 5-Chloro-1-(5-chloro-2-(methylsulfonyl)benzyl)-2-imino-1,2-dihydropyridine-3-carboxamide (TAK-259) as a Novel, Selective, and Orally Active α1D Adrenoceptor Antagonist with Antiurinary Frequency Effects: Reducing Human Ether-a-go-go-Related Gene (hERG) Liabilities.

A novel structural class of iminopyridine derivative 1 was identified as a potent and selective human α1D adrenoceptor (α1D adrenergic receptor; α1D-AR) antagonist against α1A- and α1B-AR through screening of an in-house compound library. From initial structure-activity relationship studies, we found lead compound 9m with hERG K(+) channel liability. To develop analogues with reduced hERG K(+) channel inhibition, a combination of site-directed mutagenesis and docking studies was employed. Further optimization led to the discovery of (R)-9s and 9u, which showed antagonistic activity by a bladder strip test in rats with bladder outlet obstruction, as well as ameliorated cystitis-induced urinary frequency in rats. Ultimately, 9u was selected as a clinical candidate. This is the first study to show the utility of iminopyridine derivatives as selective α1D-AR antagonists and evaluate their effects in vivo.

Design, synthesis and biological evaluation of a novel series of peripheral-selective noradrenaline reuptake inhibitor.

Centrally acting noradrenaline reuptake inhibitor (NRI) is reportedly effective for patients with stress urinary incontinence (SUI) by increasing urethral closure in the clinical Phase IIa study with esreboxetine. Noradrenaline transporters are expressed in both central and peripheral nervous systems and the contribution of each site to efficacy has not been clarified. This report describes the development of a series of peripheral-selective 7-phenyl-1,4-oxazepane NRIs to investigate the contribution of the peripheral site to increasing urethral resistance in rats. (6S,7R)-1,4-Oxazepane derivative 7 exhibited noradrenaline transporter inhibition with high selectivity against inhibitions of serotonin and dopamine transporters. A replacement of hydroxyl with acetamide group contributed to enhancement of peripheral selectivity by increasing molecular polarity. Compound 12, N-{[(6S,7R)-7-(3,4-dichlorophenyl)-1,4-oxazepan-6-yl]methyl}acetamide 0.5 fumarate, which showed effectively no brain penetration in rats, increased urethral resistance in a dose-dependent manner and exhibited a maximal effect on par with esreboxetine. These results demonstrate that the urethral resistance-increasing effects of NRI in rats are mainly caused by the inhibition of noradrenaline transporters in the peripheral sites.