Discovery of a novel series of medium-sized cyclic enteropeptidase inhibitors.

Enteropeptidase is located in the duodenum that involved in intestinal protein digestion. We have reported enteropeptidase inhibitors with low systemic exposure. The aim of this study was to discover novel enteropeptidase inhibitors showing more potent in vivo efficacy while retaining low systemic exposure. Inhibitory mechanism-based drug design led us to cyclize ester 2 to medium-sized lactones, showing potent enteropeptidase inhibitory activity and improving the ester stability, thus increasing fecal protein output in vivo. Optimization on the linker between two benzene rings resulted in discovery of ether lactone 6b, exhibiting further enhanced enteropeptidase inhibitory activity and long duration of inhibitory state. Oral administration of 6b in mice significantly elevated fecal protein output compared with the lead 2. In addition, 6b showed low systemic exposure along with low intestinal absorption. Furthermore, we identified the 10-membered lactonization method for scale-up synthesis of 6b, which does not require high-dilution conditions.

Rapid and efficient syntheses of tryptophans using a continuous-flow quaternization-substitution reaction of gramines with a chiral nucleophilic glycine equivalent.

A continuous-flow quaternization reaction of gramines with MeI (<1 min) followed by a substitution reaction with a chiral nucleophilic glycine-derived Ni-complex (S)-2 (<1 min) has successfully been developed to afford the corresponding alkylated Ni-complexes 3 in good yields with excellent diastereoselectivity, based on the results of a one-pot quaternization-substitution reaction of gramines with (S)-2 in a batch process. The continuous-flow process allowed the safe and efficient scale-up synthesis of 3j (84% yield, 99% de, 540 g h-1) to give 7-azatryptophan derivative (S)-4j readily by an acid-catalyzed hydrolysis reaction followed by protection with an Fmoc group. The present method for the rapid and efficient syntheses of enantiopure unnatural tryptophan derivatives from various gramines and (S)-2 will be useful to further promote peptide and protein drug discovery and development research.

Rapid and efficient synthesis of a novel cholinergic muscarinic M1 receptor positive allosteric modulator using flash chemistry.

Continuous flow-flash synthesis of a 2-bromobenzaldehyde derivative 18 as a key intermediate of a novel cholinergic muscarinic M1 positive allosteric modulator 1 bearing an isoindolin-1-one ring system as a pharmacophore has been achieved using flow microreactors through selective I/Li exchange of 1-bromo-2-iodobenzene derivative 17 with BuLi and subsequent formylation at -40 °C of the highly reactive 2-bromophenyllithium intermediate using DMF, which is difficult to achieve by a conventional batch process due to the conversion of the highly reactive 2-bromophenyllithium intermediate into benzyne even at -78 °C. Late-stage cyclization to give the isoindolin-1-one ring system, through reductive amination of 18 followed by palladium-catalyzed carbonylation with carbon monoxide and intramolecular cyclization, efficiently afforded 1 for its further research and development.

Discovery of orally efficacious RORγt inverse agonists, part 1: Identification of novel phenylglycinamides as lead scaffolds.

A series of novel phenylglycinamides as retinoic acid receptor-related orphan receptor-gamma t (RORγt) inverse agonists were discovered through optimization of a high-throughput screen hit 1. (R)-N-(2-((3,5-Difluoro-4-(trimethylsilyl)phenyl) amino)-1-(4-methoxyphenyl)-2-oxoethyl)-3-hydroxy-N-methylisoxazole-5-carboxamide (22) was identified as one of the best of these compounds. It displayed higher subtype selectivity and specificity over other nuclear receptors and demonstrated in vivo potency to suppress the transcriptional activity of RORγt in a mouse PD (pharmacodynamic) model upon oral administration.

Discovery of orally efficacious RORγt inverse agonists. Part 2: Design, synthesis, and biological evaluation of novel tetrahydroisoquinoline derivatives.

A series of tetrahydroisoquinoline derivatives were designed, synthesized, and evaluated for their potential as novel orally efficacious retinoic acid receptor-related orphan receptor-gamma t (RORγt) inverse agonists for the treatment of Th17-driven autoimmune diseases. We carried out cyclization of the phenylglycinamide core by structure-based drug design and successfully identified a tetrahydroisoquinoline carboxylic acid derivative 14 with good biochemical binding and cellular reporter activity. Interestingly, the combination of a carboxylic acid tether and a central fused bicyclic ring was crucial for optimizing PK properties, and the compound 14 showed significantly improved PK profile. Successive optimization of the carboxylate tether led to the discovery of compound 15 with increased inverse agonistic activity and an excellent PK profile. Oral treatment of mice with compound 15 robustly and dose-dependently inhibited IL-17A production in an IL23-induced gene expression assay.

Discovery of TAK-925 as a Potent, Selective, and Brain-Penetrant Orexin 2 Receptor Agonist.

TAK-925, a potent, selective, and brain-penetrant orexin 2 receptor (OX2R) agonist, [methyl (2R,3S)-3-((methylsulfonyl)amino)-2-(((cis-4-phenylcyclohexyl)oxy)methyl)piperidine-1-carboxylate, 16], was identified through the optimization of compound 2, which was discovered by a high throughput screening (HTS) campaign. Subcutaneous administration of compound 16 produced wake-promoting effects in mice during the sleep phase. Compound 16 (TAK-925) is being developed for the treatment of narcolepsy and other related disorders.

Design, Synthesis, and Biological Evaluation of Retinoic Acid-Related Orphan Receptor γt (RORγt) Agonist Structure-Based Functionality Switching Approach from In House RORγt Inverse Agonist to RORγt Agonist.

Retinoic acid receptor-related orphan receptor γt (RORγt) agonists are expected to provide a novel class of immune-activating anticancer drugs via activation of Th17 cells and Tc17 cells. Herein, we describe a novel structure-based functionality switching approach from in house well-optimized RORγt inverse agonists to potent RORγt agonists. We succeeded in the identification of potent RORγt agonist 5 without major chemical structure change. The biochemical response was validated by molecular dynamics simulation studies that showed a helix 12 stabilization effect of RORγt agonists. These results indicate that targeting helix 12 is an attractive and novel medicinal chemistry strategy for switching existing RORγt inverse agonists to agonists.

Discovery of imidazo[1,5-c]imidazol-3-ones: weakly basic, orally active factor Xa inhibitors.

The coagulation enzyme factor Xa (FXa) has been recognized as a promising target for the development of new antithrombotic agents. We previously found compound 1 to be an orally bioavailable FXa inhibitor in fasted monkeys; however, 1 showed poor bioavailability in rats and fed monkeys. To work out the pharmacokinetic problems, we focused our synthetic efforts on the chemical conversion of the 4-(imidazo[1,2- a]pyridin-5-yl)piperazine moiety of 1 to imidazolylpiperidine derivatives (fused and nonfused), which resulted in the discovery of the weakly basic imidazo[1,5- c]imidazol-3-one 3q as a potent and selective FXa inhibitor. Compound 3q showed favorable oral bioavailability in rats and monkeys under both fasted and fed conditions and antithrombotic efficacy in a rat model of venous thrombosis after oral administration, without a significant increase in bleeding time (unlike warfarin). On the basis of these promising properties, compound 3q was selected for further evaluation.

Discovery of piperazinylimidazo[1,2-a]pyridines as novel S4 binding elements for orally active factor Xa inhibitors.

We have recently reported the discovery of orally active sulfonylalkylamide Factor Xa (FXa) inhibitors, as typified by compound 1 (FXa IC(50)=0.061 microM). Since the pyridylpiperidine moiety was not investigated in our previous study, we conducted detailed structure-activity relationship studies on this S4 binding element. This investigation led to the discovery of piperazinylimidazo[1,2-a]pyridine 2b as a novel and potent FXa inhibitor (FXa IC(50)=0.021 microM). Further modification resulted in the discovery of 2-hydroxymethylimidazo[1,2-a]pyridine 2e (FXa IC(50)=0.0090 microM), which was found to be a selective and orally bioavailable FXa inhibitor with reduced CYP3A4 inhibition.

Discovery of [ cis-3-({(5 R)-5-[(7-Fluoro-1,1-dimethyl-2,3-dihydro-1 H-inden-5-yl)carbamoyl]-2-methoxy-7,8-dihydro-1,6-naphthyridin-6(5 H)-yl}carbonyl)cyclobutyl]acetic Acid (TAK-828F) as a Potent, Selective, and Orally Available Novel Retinoic Acid Receptor-Related Orphan Receptor γt Inverse Agonist.

A series of tetrahydronaphthyridine derivatives as novel RORγt inverse agonists were designed and synthesized. We reduced the lipophilicity of tetrahydroisoquinoline compound 1 by replacement of the trimethylsilyl group and SBDD-guided scaffold exchange, which successfully afforded compound 7 with a lower log  D value and tolerable in vitro activity. Consideration of LLE values in the subsequent optimization of the carboxylate tether led to the discovery of [ cis-3-({(5 R)-5-[(7-fluoro-1,1-dimethyl-2,3-dihydro-1 H-inden-5-yl)carbamoyl]-2-methoxy-7,8-dihydro-1,6-naphthyridin-6(5 H)-yl}carbonyl)cyclobutyl]acetic acid, TAK-828F (10), which showed potent RORγt inverse agonistic activity, excellent selectivity against other ROR isoforms and nuclear receptors, and a good pharmacokinetic profile. In animal studies, oral administration of compound 10 exhibited robust and dose-dependent inhibition of IL-17A cytokine expression in a mouse IL23-induced gene expression assay. Furthermore, development of clinical symptoms in a mouse experimental autoimmune encephalomyelitis model was significantly reduced. Compound 10 was selected as a clinical compound for the treatment of Th17-driven autoimmune diseases.

Design, Synthesis, and Evaluation of the Highly Selective and Potent G-Protein-Coupled Receptor Kinase 2 (GRK2) Inhibitor for the Potential Treatment of Heart Failure.

A novel class of therapeutic drug candidates for heart failure, highly potent and selective GRK2 inhibitors, exhibit potentiation of ß-adrenergic signaling in vitro studies. Hydrazone derivative 5 and 1,2,4-triazole derivative 24a were identified as hit compounds by HTS. New scaffold generation and SAR studies of all parts resulted in a 4-methyl-1,2,4-triazole derivative with an N-benzylcarboxamide moiety with highly potent activity toward GRK2 and selectivity over other kinases. In terms of subtype selectivity, these compounds showed enough selectivity against GRK1, 5, 6, and 7 with almost equipotent inhibition to GRK3. Our medicinal chemistry efforts led to the discovery of 115h (GRK2 IC50 = 18 nM), which was obtained the cocrystal structure with human GRK2 and an inhibitor of GRK2 that potentiates ß-adrenergic receptor (ßAR)-mediated cAMP accumulation and prevents internalization of ßARs in ß2AR-expressing HEK293 cells treated with isoproterenol. Therefore, 115h appears to be a novel class of therapeutic for heart failure treatment.

Discovery of 3,5-Diphenyl-4-methyl-1,3-oxazolidin-2-ones as Novel, Potent, and Orally Available Δ-5 Desaturase (D5D) Inhibitors.

The discovery and optimization of Δ-5 desaturase (D5D) inhibitors are described. Investigation of the 1,3-oxazolidin-2-one scaffold was inspired by a pharmacophore model constructed from the common features of several hit compounds, resulting in the identification of 3,5-diphenyl-1,3-oxazolidin-2-one 5h as a novel lead showing potent in vitro activity. Subsequent optimization focused on the modification of two metabolic sites, which provided (4S,5S)-5i, a derivative with improved metabolic stability. Moreover, adding a substituent into the upper phenyl moiety further enhanced the intrinsic activity, which led to the discovery of 5-[(4S,5S)-5-(4fluorophenyl)-4-methyl-2-oxo-1,3-oxazolidin-3-yl]benzene-1,3-dicarbonitrile (4S,5S)-5n, endowed with excellent D5D binding affinity, cellular activity, and high oral bioavailability in a mouse. It exhibited robust in vivo hepatic arachidonic acid/dihomo-γ-linolenic acid ratio reduction (a target engagement marker) in an atherosclerosis mouse model. Finally, an asymmetric synthetic procedure for this compound was established.