Synthesis and structure–activity relationships of 2-acylamino-4,6-diphenylpyridine derivatives as novel antagonists of GPR54

GPR54 is a G protein-coupled receptor (GPCR) which was formerly an orphan receptor. Recent functional study of GPR54 revealed that the receptor has an essential role to modulate sex-hormones including GnRH. Though antagonists of GPR54 are expected to be novel drugs for sex-hormone dependent diseases such as prostate cancer or endometriosis, small molecule GPR54 antagonists have not been reported. We have synthesized a series of 2-acylamino-4,6-diphenylpyridines to identify potent GPR54 antagonists. Detailed structure–activity relationship studies led to compound 9l with an IC₅₀ value of 3.7 nM in a GPR54 binding assay, and apparent antagonistic activity in a cellular functional assay.     

Synthetic studies on selective adenosine A2A receptor antagonists: Synthesis and structure–activity relationships of novel benzofuran derivatives

A series of benzofuran derivatives were prepared to study their antagonistic activities to the A_2A receptor. Replacement of the ester group of the lead compound 1 with phenyl ring improved the PK profile, while modifications of the amide moiety showed enhanced antagonistic activity. From these studies, compounds 13c, 13f, and 24a showed good potency in vitro and were identified as novel A_2A receptor antagonists suitable for oral activity evaluation in animal models of catalepsy.     

Novel biphenylcarboxylic acid peroxisome proliferator-activated receptor (PPAR) δ selective antagonists

We designed and synthesized novel PPARδ antagonists based on the crystal structure of the PPARδ full agonist TIPP-204 bound to the PPARδ ligand-binding domain, in combination with our nuclear receptor helix 12 folding modification hypothesis. Representative compound 3a exhibits PPARδ-preferential antagonistic activity.     

Synthesis and SAR of 1,2,3,4-tetrahydroisoquinolin-1-ones as novel G-protein-coupled receptor 40 (GPR40) antagonists

The development of a series of novel 1,2,3,4-tetrahydroisoquinolin-1-ones as antagonists of G protein-coupled receptor 40 (GPR40) is described. The synthesis, in vitro inhibitory values for GPR40, in vitro microsomal clearance and rat in vivo clearance data are discussed. Initial hits displayed high rat in vivo clearances that were higher than liver blood flow. Optimization of rat in vivo clearance was achieved and led to the identification of 15i, whose rat oral pharmacokinetic data is reported.     

Discovery of ORN0829, a potent dual orexin 1/2 receptor antagonist for the treatment of insomnia

Here, we present the design, synthesis, and SAR of dual orexin 1 and 2 receptor antagonists, which were optimized by balancing the antagonistic activity for orexin receptors and lipophilicity. Based on the prototype compound 1, ring construction and the insertion of an additional heteroatom into the resulting ring led to the discovery of orexin 1 and 2 receptor antagonists, which were 3-benzoyl-1,3-oxazinane derivatives. Within these derivatives, (−)-3h enabled a high dual orexin receptor antagonistic activity and a low lipophilicity. Compound (−)-3h exhibited potent sleep-promoting effects at a po dose of 1 mg/kg in a rat polysomnogram study, and optimal PK properties with a rapid T_max and short half-lives in rats and dogs were observed, indicating a predicted human half-life of 0.9–2.0 h. Thus, (−)-3h (ORN0829; investigation code name, TS-142) was selected as a viable candidate and is currently in clinical development for the treatment of insomnia.     

Identification of potent lysophosphatidic acid receptor 5 (LPA5) antagonists as potential analgesic agents

Lysophosphatidic acid (LPA) plays an important role in a variety of cellular functions. In particular, LPA5 receptor is highly expressed in spinal cord and dorsal root ganglion, which are associated with pain. This fact prompted us to hypothesize that LPA5 antagonists show analgesic effects. To search for potent LPA5 antagonists with blood brain barrier (BBB) permeability, we conducted high throughput screening (HTS). In HTS campaign, we found a 2H-isoquinoline-1-one scaffold showing antagonistic activity against LPA5 and synthesized a series of 2H-isoquinoline-1-one derivatives and evaluated their LPA5 activities. Among these compounds, compound 7e showed potent LPA5 activity with an IC₅₀ value of 0.12?μM, and acceptable BBB permeability. Furthermore, it showed effective analgesic effect in a chronic constriction injury rat model. Therefore, 7e may have a potential as novel pain therapeutic approach.     

Discovery of 3-aryl-3-ethoxypropanoic acids as orally active GPR40 agonists

The G protein-coupled receptor 40 (GPR40) mediates enhancement of glucose-stimulated insulin secretion in pancreatic β cells. The GPR40 agonist has been attracting attention as a novel insulin secretagogue with glucose dependency for the treatment of type 2 diabetes. The optimization study of compound 1 led to a potent and bioavailable GPR40 agonist 24, which showed insulin secretion and glucose lowering effects in rat OGTT. Compound 24 is a potential lead compound for a novel insulin secretagogue with a low risk of hypoglycemia.     

Orally bioavailable,liver-selective stearoyl-CoA desaturase (SCD) inhibitors

We discovered a structurally novel SCD (Δ9 desaturase) inhibitor 4a (CVT-11,563) that has 119 nM potency in a human cell-based (HEPG2) SCD assay and selectivity against Δ5 and Δ6 desaturases. This compound has 90% oral bioavailability (rat) and excellent plasma exposure (dAUC 935 ng h/mL). Additionally, 4a shows moderately selective liver distribution (three times vs plasma and adipose tissue) and relatively low brain penetration. In a five-day study (high sucrose diet, rat) compound 4a significantly reduced SCD activity as determined by GC analysis of fatty acid composition in plasma and liver. We describe the discovery of 4a from HTS hit 1 followed by scaffold replacement and SAR studies focused on DMPK properties.     

Design and optimization of 2,3-dihydrobenzo[b][1,4]dioxine propanoic acids as novel GPR40 agonists with improved pharmacokinetic and safety profiles

GPR40 has become a new potential therapeutic target for the treatment of diabetes due to its role in mediating the enhancement of glucose-stimulated insulin secretion in pancreatic β cells with a low risk of hypoglycemia. As an effort to extend the chemical space and identify structurally distinct GPR40 agonists with improved liver safety, a novel series of fused-ring phenyl propanoic acid analogues were designed. Comprehensive structure-activity relationship studies around novel scaffolds were conducted and led to several analogues exhibited potent GPR40 agonistic activities and high selectivity against other fatty acid receptors. Further evaluation of pharmacokinetic (PK) profiles and in vivo efficacy identified compound 40a with excellent PK properties and significant glucose-lowering efficacy during an oral glucose tolerance test. In addition, compound 40a displayed lower hepatobiliary transporter inhibition and favorable druggability. All results indicate that compound 40a is a promising candidate for further development.     

Discovery of novel selective GPR120 agonists with potent anti-diabetic activity by hybrid design

GPR120 is an attractive target for the treatment of type 2 diabetes. In this study, a series of biphenyl derivatives were designed, synthesized by hybrid design. The selected compound 6a exhibited potent GPR120 agonist activity (EC₅₀?=?93?nM) and high selectivity over GPR40. The results of oral glucose tolerance test (OGTT) demonstrated that 6a exhibited significant glucose-lowering effect in glucose-loaded ICR male mice. Analysis of the structure–activity relationship is also presented. Compound 6a deserves further biological evaluation and structural modifications.     

Structure-activity relationship studies on a series of piperazinebenzylalcohols and their ketone and amine analogs as melanocortin-4 receptor ligands

A series of piperazinebenzylalcohols were prepared and studied to compare with their ketone and amine analogs as MC4R antagonists. Several benzylalcohols such as 14a and 14g displayed low nanomolar binding affinities (K_i < 10 nM), and high selectivities over other melanocortin receptor subtypes.     

Discovery of 1,2,3,4-tetrahydropyrimido[1,2-a]benzimidazoles as novel class of corticotropin releasing factor 1 receptor antagonists

A new class of corticotropin releasing factor 1 (CRF₁) receptor antagonists characterized by a tricyclic core ring was designed and synthesized. Novel tricyclic derivatives 2a–e were designed as CRF₁ receptor antagonists based on conformation analysis of our original 2-anilinobenzimidazole CRF₁ receptor antagonist. The synthesized tricyclic derivatives 2a–e showed CRF₁ receptor binding activity with IC₅₀ values of less than 400?nM, and the 1,2,3,4-tetrahydropyrimido-[1,2-a]benzimidazole derivative 2e was selected as a lead compound with potent in vitro CRF₁ receptor binding activity (IC₅₀?=?7.1?nM). To optimize the pharmacokinetic profiles of lead compound 2e, we explored suitable substituents on the 1-position and 6-position, leading to the identification of compound 42c-R, which exhibited potent CRF₁ receptor binding activity (IC₅₀?=?58?nM) with good oral bioavailability (F?=?68% in rats). Compound 42c-R exhibited dose-dependent inhibition of [¹²⁵I]-CRF binding in the frontal cortex (5 and 10?mg/kg, p.o.) as well as suppression of locomotor activation induced by intracerebroventricular administration of CRF in rats (10?mg/kg, p.o.). These results suggest that compound 42c-R successfully binds CRF₁ receptors in the brain and exhibits the potential to be further examined for clinical studies.     

Synthesis and evaluation of the structural elements in alkylated tetrahydroisoquinolines for binding to CNS receptors

Diseases of the CNS are often complex and involve multiple receptor systems and thus, the treatment options for these diseases must focus on targeting the multiple receptors implicated in the various disorders. Schizophrenia and depression are examples of such diseases and their pharmacotherapy thus depends on agents which target multiple receptors including the dopamine, serotonin and even cholinergic receptors at the same time. In our previous campaign to find multi-receptor ligands, we have identified the benzothiazole 1a as an initial lead molecule. In the current work, we have expanded the structure affinity relationship (SAFIR) of 1a resulting in the identification of a partially restrained butyrophenone 3j as a potent and selective dual 5-HT_1A and 5-HT₇ receptor ligand. It is expected that compound 3j may serve as a new lead for further development in our search for newer and novel ligands with the potential to treat diseases of CNS origin.     

Design and synthesis of 1-(1-benzothiophen-7-yl)-1H-pyrazole,a novel series of G protein-coupled receptor 52 (GPR52) agonists

G-protein-coupled receptor 52 (GPR52) is classified as an orphan Gs-coupled G-protein-coupled receptor. GPR52 cancels dopamine D2 receptor signaling and activates dopamine D1/N-methyl-d-aspartate receptors via intracellular cAMP accumulation. Therefore, GPR52 agonists are expected to alleviate symptoms of psychotic disorders. A novel series of 1-(benzothiophen-7-yl)-1H-pyrazole as GPR52 agonists was designed and synthesized based on compound 1b. Compound 1b has been reported by our group as the first orally active GPR52 agonist, but high lipophilicity and poor aqueous solubility still remained as issues for candidate selection. To resolve these issues, replacement of the benzene ring at the 7-positon of compound 1b with heterocylic rings, such as pyrazole and pyridine, was greatly expected to reduce lipophilicity to levels for which calculated logD values were lower than that of compound 1b. While evaluating the pyrazole derivatives, introduction of a methyl substituent at the 3-position of the pyrazole ring led to increased GPR52 agonistic activity. Moreover, additional methyl substituent at the 5-position of the pyrazole and further introduction of hydroxy group to lower logD led to significant improvement of solubility while maintaining the activity. As a result, we identified 3-methyl-5-hydroxymethyl-1H-pyrazole derivative 17 (GPR52 EC₅₀?=?21?nM, E_max?=?103%, logD?=?2.21, Solubility at pH 6.8?=?21?μg/mL) with potent GPR52 agonistic activity and good solubility compared to compound 1b. Furthermore, this compound 17 dose-dependently suppressed methamphetamine-induced hyperlocomotion in mice.     

Potent P2Y1 urea antagonists bearing various cyclic amine scaffolds

A number of new amine scaffolds with good inhibitory activity in the ADP-induced platelet aggregation assay have been found to be potent antagonists of the P2Y₁ receptor. SAR optimization led to the identification of isoindoline 3c and piperidine 4a which showed good in vitro binding and functional activities, as well as improved aqueous solubility. Among them, the piperidine 4a showed the best overall profile with favorable PK parameters.     

Design,synthesis, and biological evaluation of 3-aryl-3-hydroxy-1-phenylpyrrolidine derivatives as novel androgen receptor antagonists

We designed and synthesized a series of 3-aryl-3-hydroxy-1-phenylpyrrolidine derivatives D and evaluated their potential as novel androgen receptor (AR) antagonists therapeutically effective against castration-resistant prostate cancer (CRPC). Introduction of a methyl group at the 2-position (R²) of the pyrrolidine ring increased the AR binding affinity. The (2S,3R) configuration of the pyrrolidine ring was favorable for the AR antagonistic activity. It was found that introduction of an amide substituent (R¹) and a pyridin-3-yl group (Q) was effective for reducing the AR agonistic activity which appeared during the optimization of lead compound 6. Compound 54 showed potent antitumor effects against a CRPC model of LNCaP-hr cell line in a mouse xenograft, in which bicalutamide exhibited only partial suppression of tumor growth. Thus, the pyrrolidine derivatives such as 54 are novel AR antagonists, and their properties having efficacy against CRPC are distinct from those of a representative first-generation antagonist, bicalutamide.     

Bicyclic and tricyclic heterocycle derivatives as histamine H3 receptor antagonists for the treatment of obesity

A novel series of non-imidazole bicyclic and tricyclic histamine H₃ receptor antagonists has been discovered. Compound 17 was identified as a centrally penetrant molecule with high receptor occupancy which demonstrates robust oral activity in rodent models of obesity. In addition compound 17 possesses clean CYP and hERG profiles and shows no behavioral changes in the Irwin test.     

Synthesis and biological evaluation of 3-aminopyrrolidine derivatives as CC chemokine receptor 2 antagonists

Novel 3-aminopyrrolidine derivatives were synthesized and evaluated for their antagonistic activity against human chemokine receptor 2. Structure–activity studies on 3-aminopyrrolidine incorporating heteroatomic carbocycle moieties led to piperidine compound 19, and piperazine compounds 42, 47 and 49 as highly potent hCCR2 antagonists.     

Identification of novel and orally active spiroindoline NPY Y5 receptor antagonists

A series of spiroindoline-3,4′-piperidine derivatives were synthesized and evaluated for their binding affinities and antagonistic activities at Y5 receptors. Potent Y5 antagonists were tested for their oral bioavailabilities and brain penetration in rats. Some of the antagonists showed good oral bioavailability and/or good brain penetration. In particular, compound 6e was orally bioavailable and brain penetrant, and oral administration of 6e inhibited bPP-induced food intake in rats with a minimum effective dose of 10 mg/kg.