Discovery of DS-6930, a potent selective PPARγ modulator. Part II: Lead optimization.

Attempts were made to reduce the lipophilicity of previously synthesized compound (II) for the avoidance of hepatotoxicity. The replacement of the left-hand side benzene with 2-pyridine resulted in the substantial loss of potency. Because poor membrane permeability was responsible for poor potency in vitro, the adjustment of lipophilicity was examined, which resulted in the discovery of dimethyl pyridine derivative (I, DS-6930). In preclinical studies, DS-6930 demonstrated high PPARγ agonist potency with robust plasma glucose reduction. DS-6930 maintained diminished PPARγ-related adverse effects upon toxicological evaluation in vivo, and demonstrated no hepatotoxicity. Cofactor recruitment assay showed that several cofactors, such as RIP140 and PGC1, were significantly recruited, whereas several canonical factors was not affected. This selective cofactor recruitment was caused due to the distinct binding mode of DS-6930. The calcium salt, DS-6930b, which is expected to be an effective inducer of insulin sensitization without edema, could be evaluated clinically in T2DM patients.

Discovery of DS-6930, a potent selective PPARγ modulator. Part I: Lead identification.

The lead identification of a novel potent selective PPARγ agonist, DS-6930 is reported. To avoid PPARγ-related adverse effects, a partial agonist was designed to prevent the direct interaction with helix 12 of PPARγ-LBD. Because the TZD group is known to interact with helix 12, the TZD in efatutazone (CS-7017) was replaced to discover novel PPARγ intermediate partial agonist 8i. The optimization of 8i yielded 13ac with high potency in vitro. Compound 13ac exhibited robust plasma glucose lowering effects comparable to those of rosiglitazone (3 mg/kg) in Zucker diabetic fatty rats. Upon toxicological evaluation, compound 13ac (300 mg/kg) induced hemodilution to a lower extent than rosiglitazone; however, 13ac elevated liver enzyme activities. X-ray crystallography revealed no direct interaction of 13ac with helix 12, and the additional lipophilic interactions are also suggested to be related to the maximum transcriptional activity of 13ac.

Optimization of 3-aryl-3-ethoxypropanoic acids and discovery of the potent GPR40 agonist DS-1558.

GPR40 agonists stimulate insulin secretion only under the presence of high glucose concentration. Based on this mechanism, GPR40 agonists are believed to be promising novel insulin secretagogues with low risk of hypoglycemia. The optimizations of 3-aryl-3-ethoxypropanoic acids were performed to improve in vitro activity. We discovered compound 29r (DS-1558), (3S)-3-ethoxy-3-(4-{[(1R)-4-(trifluoromethyl)-2,3-dihydro-1H-inden-1-yl]oxy}phenyl)propanoic acid, which was confirmed to have an enhancing effect on glucose-dependent insulin secretion after intravenous glucose injection in SD rats.

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 ß 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.

A novel inhibitor of stearoyl-CoA desaturase-1 attenuates hepatic lipid accumulation, liver injury and inflammation in model of nonalcoholic steatohepatitis.

Stearoyl-CoA desaturase-1 (SCD-1) catalyzes the biosynthesis of monounsaturated fatty acids, and their abnormality is possibly responsible for obesity, insulin resistance, hepatic steatosis and nonalcoholic steatohepatitis (NASH). A novel SCD-1 inhibitor, N-(2-hydroxy-2-phenylethyl)-6-[4-(2-methylbenzoyl)piperidin-1-yl]pyridazine-3-carboxamide, has been obtained. The compound inhibited liver SCD-1 activity and increased liver triglyceride accumulation in mice fed with non-fat, high-sucrose diets. In order to evaluate the effects of the SCD-1 inhibitor on NASH development, rats were fed with lipogenic methionine and choline-deficient (MCD) diets for 8 weeks. The SCD-1 inhibitor was administered once-daily at a dose of 30 or 100 mg/kg/d by oral gavage. Administration of a high dose of the SCD-1 inhibitor decreased triglyceride accumulation in the liver of NASH rats by 80%. Administration of a high dose of the SCD-1 inhibitor attenuated the increase of aspartate aminotransferase (AST) and alanine transaminase (ALT) by 86% and 78%, respectively. Hepatic steatosis, hepatocellular degeneration and inflammatory cell infiltration were histologically observed in the liver of NASH rats, and administration of the SCD-1 inhibitor ameliorated these crucial observations in NASH. In summary, an SCD-1 inhibitor ameliorated hepatic triglyceride accumulation, liver injury, hepatocellular degeneration and inflammation in experimental NASH models. These results suggest that SCD-1 maybe a promising target for the treatment of NASH.

Pharmacology and in vitro profiling of a novel peroxisome proliferator-activated receptor γ ligand, Cerco-A.

Peroxisome proliferator-activated receptor γ (PPARγ; NR1C3) is known as a key regulator of adipocytogenesis and the molecular target of thiazolidinediones (TZDs), also known as antidiabetic agents. Despite the clinical benefits of TZDs, their use is often associated with adverse effects including peripheral edema, congestive heart failure, and weight gain. Here we report the identification and characterization of a non-thiazolidinedione PPARγ partial agonist, Cerco-A, which is a derivative of the natural product, (-)-cercosporamide. Cerco-A was found to be a binder of the PPARγ ligand-binding domain in a ligand competitive binding assay and showed a unique cofactor recruitment profile compared to rosiglitazone. A crystal structure analysis revealed that Cerco-A binds to PPARγ without direct hydrogen bonding to helix12. In PPARγ transcriptional activation assay and an adipocyte differentiation assay, Cerco-A was a potent partial agonist of PPARγ. After a 14-day oral administration, once per day of Cerco-A in Zucker diabetic fatty (ZDF) rats, an apparent decrease of plasma glucose and triglyceride was observed, as with pioglitazone. To evaluate drug safety, Cerco-A was administered for 13 days orally in non-diabetic Zucker fatty (ZF) rats. Each of the hemodilution parameters (hematocrit, red blood cells number, and hemoglobin), which are considered as undesirable effects of TZDs, was improved significantly compared to pioglitazone. While Cerco-A showed body weight gain, as with pioglitazone, Cerco-A had significantly lower effects on heart and white adipose tissues weight gain. The results suggest that Cerco-A offers beneficial effects on glycemic control with attenuated undesirable side effects.

Novel benzoylpiperidine-based stearoyl-CoA desaturase-1 inhibitors: Identification of 6-[4-(2-methylbenzoyl)piperidin-1-yl]pyridazine-3-carboxylic acid (2-hydroxy-2-pyridin-3-ylethyl)amide and its plasma triglyceride-lowering effects in Zucker fatty rats.

Starting from a known piperazine-based SCD-1 inhibitor, we obtained more potent benzoylpiperidine analogs. Optimization of the structure of the benzoylpiperidine-based SCD-1 inhibitors resulted in the identification of 6-[4-(2-methylbenzoyl)piperidin-1-yl]pyridazine-3-carboxylic acid (2-hydroxy-2-pyridin-3-yl-ethyl)amide (24) which showed strong inhibitory activity against both human and murine SCD-1. In addition, this compound exhibited good oral bioavailability and demonstrated plasma triglyceride lowering effects in Zucker fatty rats in a dose-dependent manner after a 7-day oral administration (qd).

Novel spiropiperidine-based stearoyl-CoA desaturase-1 inhibitors: Identification of 1'-{6-[5-(pyridin-3-ylmethyl)-1,3,4-oxadiazol-2-yl]pyridazin-3-yl}-5-(trifluoromethyl)-3,4-dihydrospiro[chromene-2,4'-piperidine].

Cyclization of the benzoylpiperidine in lead compound 2 generated a series of novel and highly potent spiropiperidine-based stearoyl-CoA desaturase (SCD)-1 inhibitors. Among them, 1'-{6-[5-(pyridin-3-ylmethyl)-1,3,4-oxadiazol-2-yl]pyridazin-3-yl}-5-(trifluoromethyl)-3,4-dihydrospiro[chromene-2,4'-piperidine] (19) demonstrated the most powerful inhibitory activity against SCD-1, not only in vitro but also in vivo (C57BL/6J mice). With regard to the pharmacological evaluation, 19 showed powerful reduction of the desaturation index in the plasma of C57BL/6J mice on a non-fat diet after a 7-day oral administration (q.d.) without causing notable abnormalities in the eyes or skin up to the highest dose (3mg/kg) in our preliminary analysis.

Novel and potent inhibitors of stearoyl-CoA desaturase-1. Part II: Identification of 4-ethylamino-3-(2-hydroxyethoxy)-N-[5-(3-trifluoromethylbenzyl)thiazol-2-yl]benzamide and its biological evaluation.

The continuing investigation of SAR studies of 3-(2-hydroxyethoxy)-N-(5-benzylthiazol-2-yl)-benzamides as stearoyl-CoA desaturase-1 (SCD-1) inhibitors is reported. Our prior hit-to-lead effort resulted in the identification of 1a as a potent and orally efficacious SCD-1 inhibitor. Further optimization of the structural motif resulted in the identification of 4-ethylamino-3-(2-hydroxyethoxy)-N-[5-(3-trifluoromethylbenzyl)thiazol-2-yl]benzamide (37c) with sub nano molar IC(50) in both murine and human SCD-1 inhibitory assays. This compound demonstrated a dose-dependent decrease in the plasma desaturation index in C57BL/6J mice on a non-fat diet after 7 days of oral administration.

Novel and potent inhibitors of stearoyl-CoA desaturase-1. Part I: Discovery of 3-(2-hydroxyethoxy)-4-methoxy-N-[5-(3-trifluoromethylbenzyl)thiazol-2-yl]benzamide.

A series of structurally novel stearoyl-CoA desaturase-1 (SCD-1) inhibitors has been identified by optimizing a hit from our corporate library. Preliminary structure-activity relationship (SAR) studies led to the discovery of the highly potent and orally bioavailable thiazole-based SCD-1 inhibitor, 3-(2-hydroxyethoxy)-4-methoxy-N-[5-(3-trifluoromethylbenzyl)thiazol-2-yl]benzamide (23a).

Potent antidiabetic effects of rivoglitazone, a novel peroxisome proliferator-activated receptor-gamma agonist, in obese diabetic rodent models.

The pharmacological effects of rivoglitazone, a novel thiazolidinedione-derivative peroxisome proliferator-activated receptor (PPAR)-gamma agonist, were characterized in vitro and in vivo. Rivoglitazone activated human PPARgamma more potently compared with rosiglitazone and pioglitazone and had little effect on PPARalpha and PPARdelta activity in luciferase reporter assays. In Zucker diabetic fatty (ZDF) rats, 14-day administration of rivoglitazone decreased the plasma glucose and triglyceride (TG) levels in a dose-dependent manner. The glucose-lowering effect of rivoglitazone was much more potent than those of pioglitazone (ED(50): 0.19 vs. 34 mg/kg) and rosiglitazone (ED(50): 0.20 vs. 28 mg/kg). In addition, rivoglitazone showed potent antidiabetic effects in diabetic db/db mice. In Zucker fatty rats, rivoglitazone at a dose of 0.1 mg/kg clearly ameliorated insulin resistance and lowered plasma TG levels by accelerating the clearance of plasma TG. Gene expression analysis in the liver and heart of ZDF rats treated with rivoglitazone for 14 days suggested that rivoglitazone may reduce hepatic glucose production and modulate the balance of the cardiac glucose/fatty acid metabolism in diabetic animals. In summary, we showed that rivoglitazone is a potent and selective PPARgamma agonist and has a potent glucose-lowering effect via improvement of the insulin resistance in diabetic animal models.

Structure-Activity Relationship Studies of 3- or 4-Pyridine Derivatives of DS-6930.

Derivatization efforts were continued to discover backups for a potent selective PPARγ modulator, DS-6930. In this Letter, the replacement of 2-pyridine ring in DS-6930 with 3- or 4-pyridyl group is reported. As the introduction of substituents on the pyridine ring did not provide potent partial agonists, modifications of benzimidazole ring were explored to discover potent intermediate agonists. 4'-Alkoxy substituted benzimidazoles failed to show potent efficacy in vivo, whereas 7'-fluoro benzimidazole 3g (DS19161384) was found to result in robust plasma glucose reductions with excellent DMPK profiles.

Discovery of DS-1558: A Potent and Orally Bioavailable GPR40 Agonist.

GPR40 is a G protein-coupled receptor that is predominantly expressed in pancreatic ß-cells. GPR40 agonists stimulate insulin secretion in the presence of high glucose concentration. On the basis of this mechanism, GPR40 agonists are possible novel insulin secretagogues with reduced or no risk of hypoglycemia. The improvement of in vitro activity and metabolic stability of compound 1 led to the discovery of 13, (3S)-3-ethoxy-3-(4-{[(1R)-4-(trifluoromethyl)-2,3-dihydro-1H-inden-1-yl]oxy}phenyl)propanoic acid, as a potent and orally available GPR40 agonist. Compound 13 (DS-1558) was found to have potent glucose lowering effects during an oral glucose tolerance test in ZDF rats.

Discovery of novel SCD1 inhibitors: 5-alkyl-4,5-dihydro-3H-spiro[1,5-benzoxazepine-2,4'-piperidine] analogs.

Expansion of the 6-membered ring and subsequent fine-tuning of the newly obtained 7-membered spiropiperidine structure resulted in the discovery of a series of novel and potent SCD1 inhibitors. Preliminary SAR was explored by modifying an alkyl chain on the azepine nitrogen and resulted in the identification of a highly potent SCD1 inhibitor: 6-[5-(cyclopropylmethyl)-4,5-dihydro-1'H,3H-spiro[1,5-benzoxazepine-2,4'-piperidin]-1'-yl]-N-(2-hydroxy-2-pyridin-3-ylethyl)pyridazine-3-carboxamide (9). Compound 9 exhibited an IC(50) value of 0.01 µM against human SCD1.

Synthesis and evaluation of novel stearoyl-CoA desaturase 1 inhibitors: 1'-{6-[5-(pyridin-3-ylmethyl)-1,3,4-oxadiazol-2-yl]pyridazin-3-yl}-3,4-dihydrospiro[chromene-2,4'-piperidine] analogs.

In continuation of our investigation on novel stearoyl-CoA desaturase (SCD) 1 inhibitors, we have already reported on the structural modification of the benzoylpiperidines that led to a series of novel and highly potent spiropiperidine-based SCD1 inhibitors. In this report, we would like to extend the scope of our previous investigation and disclose details of the synthesis, SAR, ADME, PK, and pharmacological evaluation of the spiropiperidines with high potency for SCD1 inhibition. Our current efforts have culminated in the identification of 5-fluoro-1'-{6-[5-(pyridin-3-ylmethyl)-1,3,4-oxadiazol-2-yl]pyridazin-3-yl}-3,4-dihydrospiro[chromene-2,4'-piperidine] (10e), which demonstrated a very strong potency for liver SCD1 inhibition (ID(50)=0.6 mg/kg). This highly efficacious inhibition is presumed to be the result of a combination of strong enzymatic inhibitory activity (IC(50) (mouse)=2 nM) and good oral bioavailability (F >95%). Pharmacological evaluation of 10e has demonstrated potent, dose-dependent reduction of the plasma desaturation index in C57BL/6J mice on a high carbohydrate diet after a 7-day oral administration (q.d.). In addition, it did not cause any noticeable skin abnormalities up to the highest dose (10 mg/kg).

Identification of molecular target of AMP-activated protein kinase activator by affinity purification and mass spectrometry.

We show an efficient method to identify molecular targets of small molecular compounds by affinity purification and mass spectrometry. Binding proteins were isolated from target cell lysate using affinity columns, which immobilized the active and inactive compounds. All proteins bound to these affinity columns were eluted by digestion using trypsin and then were identified by mass spectrometry. The specific binding proteins to the active compound, a candidate for molecular targets, were determined by subtracting the identified proteins in an inactive compound-immobilized affinity column from that in an active compound-immobilized affinity column. This method was applied to identification of molecular targets of D942, a furancarboxylic acid derivative, which increases glucose uptake in L6 myocytes through AMP-activated protein kinase (AMPK) activation. To elucidate the mechanism of AMPK activation by D942, affinity columns that immobilized D942 and its inactive derivative, D768, were prepared, and the binding proteins were purified from L6 cell lysate. NAD(P)H dehydrogenase [quinone] 1 (complex I), which was shown as one of the specific binding proteins to D942 by subtracting the binding proteins to D768, was partially inhibited by D942, not D768. Because inhibition of complex I activity led to a decrease in the ATP/AMP ratio, and the change in the ATP/AMP ratio triggered AMPK activation, we identified complex I as a potential protein target of AMPK activation by D942. This result shows our approach can provide crucial information about the molecular targets of small molecular compounds, especially target proteins not yet identified.