Structure optimization of a new class of PPARγ antagonists

Peroxisome proliferator-activated receptor gamma (PPARγ) modulators have found wide application for the treatment of cancers, metabolic disorders and inflammatory diseases. Contrary to PPARγ agonists, PPARγ antagonists have been much less studied and although they have shown immunomodulatory effects, there is still no therapeutically useful PPARγ antagonist on the market. In contrast to non-competitive, irreversible inhibition caused by 2-chloro-5-nitrobenzanilide (GW9662), the recently described (E)-2-(5-((4-methoxy-2-(trifluoromethyl)quinolin-6-yl)methoxy)-2-((4-(trifluoromethyl)benzyl)oxy)-benzylidene)-hexanoic acid (MTTB, T-10017) is a promising prototype for a new class of PPARγ antagonists. It exhibits competitive antagonism against rosiglitazone mediated activation of PPARγ ligand binding domain (PPARγLBD) in a transactivation assay in HEK293T cells with an IC₅₀ of 4.3 µM against 1 µM rosiglitazone. The aim of this study was to investigate the structure-activity relationships (SAR) of the MTTB scaffold focusing on improving its physicochemical properties. Through this optimization, 34 new derivatives were prepared and characterized. Two new potent compounds (T-10075 and T-10106) with much improved drug-like properties and promising pharmacokinetic profile were identified.     

Synthesis of benzopyran derivatives as PPARα and/or PPARγ activators

We describe the synthesis of 26 compounds, small polycerasoidol analogs, that are Lipinski’s rule-of-five compliant. In order to confirm key structural features to activate PPARα and/or PPARγ, we have adopted structural modifications in the following parts: (i) the benzopyran core (hydrophobic nucleus) by benzopyran-4-one, dihydrobenzopyran or benzopyran-4-ol; (ii) the side chain at 2-position by shortening to C3, C4 and C5-carbons versus C-9-carbons of polycerasoidol; (iii) the carboxylic group (polar head) by oxygenated groups (hydroxyl, acetoxy, epoxide, ester, aldehyde) or non-oxygenated motifs (allyl and alkyl). Benzopyran-4-ones 6, 12, 13 and 17 as well as dihydrobenzopyrans 22, 24 and 25 were able to activate hPPARα, whereas benzopyran-4-one (7) with C5-carbons in the side chain exhibited hPPARγ agonism. According to our previous docking studies, SAR confirm that the hydrophobic nucleus (benzopyran-4-one or dihydrobenzopyran) is essential to activate PPARα and/or PPARγ, and the flexible linker (side alkyl chain) should containg at least C5-carbon atoms to activate PPARγ. By contrast, the polar head (“carboxylic group”) tolerated several oxygenated groups but also non-oxygenated motifs. Taking into account these key structural features, small polycerasoidol analogs might provide potential active molecules useful in the treatment of dyslipidemia and/or type 2 diabetes.     

Synthesis and pharmacological evaluation of novel benzoylazole-based PPAR α/γ activators

In our search for new PPARα/γ agonists, we designed and synthesized a series of benzoylazole-based carboxylic acids. Compound 9 showed potent PPARγ partial agonistic activity with modest PPARα agonistic activity. The sodium salt of 9 (9Na) demonstrated potent efficacy in lowering both blood glucose and lipids in an animal model without causing significant body weight gain, a well-known side effect associated with PPARγ full agonists.     

Development of a novel PPARγ ligand screening system using pinpoint fluorescence-probed protein

The activation of peroxisome-proliferator-activated receptor-γ (PPARγ), which plays a central role in adipocyte differentiation, depends on ligand-dependent co-activator recruitment. In this study, we developed a novel method of PPARγ ligand screening by measuring the increase in fluorescent polarization accompanied by the interaction of a fluorescent co-activator and PPARγ. Sterol receptor co-activator-1 (SRC-1), a major PPARγ co-activator, was probed by fluorescent TAMRA by the Amber codon fluorescence probe method. Polarization was increased by adding PPARγ ligands to a solution containing labeled SRC-1 (designated TAMRA-SRC-S) and PPARγ. The disassociation constants (Kd) of the PPARγ synthesized ligands, pioglitazone (221 nM), troglitazone (83.0 nM), and 15-deoxy-Δ12,14-prostaglandin J(2) (15d-ΔPGJ(2)) (156 nM), were determined by this method. Farnesol (2.89 μM) and bixin (21.1 μM), which we have reported to be PPARγ ligands, increased the fluorescent polarization. Their Kd values were in agreement with the ED(50) values obtained in the luciferase assay. The results indicate that the method is valuable for screening natural PPARγ ligands.     

Discovery of new PPARγ agonists based on arylopeptoids

In this study we present the design, synthesis and biological evaluation of a small, first-generation library of small molecule aromatic amides based on the arylopeptoid skeleton. The compounds were efficiently synthesized using a highly convenient submonomer solid-phase methodology which potentially allows for access to great product diversity. The synthesized compounds were tested for their ability to activate peroxisome proliferator-activated receptors (PPARs) and they all acted as PPARγ agonists in the μM range spanning from 2.5- to 14.7-fold activation of the receptor. This is the first discovery of bioactive molecules based on the arylopeptoid architecture.     

Discovery of BR102375, a new class of non-TZD PPARγ full agonist for the treatment of type 2 diabetes

As a potential treatment of type 2 diabetes, a novel PPARγ non-TZD full agonist, compound 18 (BR102375) was identified from the original lead BR101549 by the SAR efforts of the labile metabolite control through bioisosteres approach. In vitro assessments of BR102375 demonstrated its activating potential of PPARγ comparable to Pioglitazone as well as the induction of related gene expressions. Further in vivo evaluation of BR102375 in diabetic rodent models successfully proved its glucose lowering effect as a potential antidiabetic agent, but the anticipated suppression of weight gain was not evident. The X-ray co-crystal analysis of BR102375-PPARγ LBD unexpectedly revealed binding modes totally different from those of BR101549, which was found, instead, closely resembled to those of TZD full agonists.     

Aleglitazar,a new,potent, and balanced dual PPARα/γ agonist for the treatment of type II diabetes

Design, synthesis, and SAR of novel α-alkoxy-β-arylpropionic acids as potent and balanced PPARαγ coagonists are described. One representative thereof, Aleglitazar ((S)-2Aa), was chosen for clinical development. Its X-ray structure in complex with both receptors as well as its high efficacy in animal models of T2D and dyslipidemia are also presented.     

1,3-Diphenyl-1H-pyrazole derivatives as a new series of potent PPARγ partial agonists

A new series of PPARγ partial agonists, 1,3-diphenyl-1H-pyrazole derivatives, were identified using an improved virtual screening scheme combining ligand-centric and receptor-centric methods. An in vitro assay confirmed the nanomolar binding affinity of 1,3-diphenyl-1H-pyrazole derivatives such as SP3415. We also characterized the competitive antagonism of SP3415 against rosiglitazone at micromolar concentrations. They showed a PPARγ partial agonistic activity similar to that of a known PPARγ drug, pioglitazone, in a cell-based transactivation assay. Furthermore, the structure-activity relationships of the pyrazole derivatives were investigated through comparative molecular field analysis and binding mode analysis, which provided new insight concerning their partial agonistic effect on PPARγ.     

Virtual identification of novel PPARα/γ dual agonists by scaffold hopping of saroglitazar

The thiazolidinedione class PPARγ agonists as antidiabetic agents are restricted in clinical use because of the side effects such as edema, weight gain, and heart failure. The single and selective agonism of PPARγ is the main cause of side effects. The multi-target cooperative PPARα/γ dual agonist development is a hot topic in the antidiabetic medicinal chemistry field. Saroglitazar is the first approved PPARα/γ dual agonist, available in India for the treatment of diabetic dyslipidemia. It got rid of these side effects. With the aim of finding more protent PPARα/γ dual agonists, the scaffold hopping was used to replace α-o phenylpropionic acid skeleton of saroglitazar with L-tyrosine skeleton. Then, the structural modification was carried out designing 72 compounds. Considering the importance of chirality, opposite configuration of 72 compounds was also studied. 12 compounds with better -cdocker energy were screened by molecular docking. Subsequently, the pharmacokinetic properties and toxicity evaluated by ADMET prediction, 11 of them showed better properties. Comp#L-17-1 and comp#L-3-1 were regarded as representatives to study the binding stability by molecular dynamics (MD) simulations. The MD simulation results of comp#L-17-1-PPARs (α, γ) and comp#L-3-1-PPARs (α, γ) provided structure reference for the research and development of novel PPARα/γ dual agonists.     

α-1,4-Glucan lyase,a new class of starch/glycogen-degrading enzyme

Antibodies have been raised against an -1,4-glucan lyase purified from the red alga Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Foldvik. Localization of -1,4-glucan lyase in ultra-thin sections of the red alga was performed using immunogold/transmission electron microscopy. The enzyme was found exclusively in the stroma of the chloroplasts of the algal cells, not in the cell wall, cytosol or around the cytosolic starch granules. Partial amino-acid sequences of the algal lyase, with a total length of 100 amino-acid residues, were obtained. No sequence homology was found with proteins and peptides of known sequences.This work was supported by grants from the Swedish Council for Planning and Coordination of Research (FRN), Carl Tryggers Foundation, and Hierta-Retzius Fund. We thank Ms Katrin Österlund and Anette Axén for their expert technical assistance with this work.     

Synthesis and anti-inflammatory activity of new arylidene-thiazolidine-2,4-diones as PPARγ ligands

Eight new 5-arylidene-3-benzyl-thiazolidine-2,4-diones with halide groups on their benzyl rings were synthesized and assayed in vivo to investigate their anti-inflammatory activities. These compounds showed considerable biological efficacy when compared to rosiglitazone, a potent and well-known agonist of PPARγ, which was used as a reference drug. This suggests that the substituted 5-arylidene and 3-benzylidene groups play important roles in the anti-inflammatory properties of this class of compounds. Docking studies with these compounds indicated that they exhibit specific interactions with key residues located in the site of the PPARγ structure, which corroborates the hypothesis that these molecules are potential ligands of PPARγ. In addition, competition binding assays showed that four of these compounds bound directly to the ligand-binding domain of PPARγ, with reduced affinity when compared to rosiglitazone. An important trend was observed between the docking scores and the anti-inflammatory activities of this set of molecules. The analysis of the docking results, which takes into account the hydrophilic and hydrophobic interactions between the ligands and the target, explained why the 3-(2-bromo-benzyl)-5-(4-methanesulfonyl-benzylidene)-thiazolidine-2,4-dione compound had the best activity and the best docking score. Almost all of the stronger hydrophilic interactions occurred between the substituted 5-arylidene group of this compound and the residues of the binding site.     

Scaffold-Based Pan-Agonist Design for the PPARα, PPARβ and PPARγ Receptors

As important members of nuclear receptor superfamily, Peroxisome proliferator-activated receptors (PPAR) play essential roles in regulating cellular differentiation, development, metabolism, and tumorigenesis of higher organisms. The PPAR receptors have 3 identified subtypes: PPARα, PPARβ and PPARγ, all of which have been treated as attractive targets for developing drugs to treat type 2 diabetes. Due to the undesirable side-effects, many PPAR agonists including PPARα/γ and PPARβ/γ dual agonists are stopped by US FDA in the clinical trials. An alternative strategy is to design novel pan-agonist that can simultaneously activate PPARα, PPARβ and PPARγ. Under such an idea, in the current study we adopted the core hopping algorithm and glide docking procedure to generate 7 novel compounds based on a typical PPAR pan-agonist {"type":"entrez-nucleotide","attrs":{"text":"LY465608","term_id":"1257853743","term_text":"LY465608"}}LY465608. It was observed by the docking procedures and molecular dynamics simulations that the compounds generated by the core hopping and glide docking not only possessed the similar functions as the original {"type":"entrez-nucleotide","attrs":{"text":"LY465608","term_id":"1257853743","term_text":"LY465608"}}LY465608 compound to activate PPARα, PPARβ and PPARγ receptors, but also had more favorable conformation for binding to the PPAR receptors. The additional absorption, distribution, metabolism and excretion (ADME) predictions showed that the 7 compounds (especially Cpd#1) hold high potential to be novel lead compounds for the PPAR pan-agonist. Our findings can provide a new strategy or useful insights for designing the effective pan-agonists against the type 2 diabetes.     

Synthesis and evaluation of novel α-heteroaryl-phenylpropanoic acid derivatives as PPARα/γ dual agonists

The synthesis of a new series of phenylpropanoic acid derivatives incorporating an heteroaryl group at the α-position and their evaluation for binding and activation of PPARα and PPARγ are presented in this report. Among the new compounds, (S)-3-{4-[3-(5-methyl-2-phenyl-oxazol-4-yl)-propyl]-phenyl}-2-1,2,3-triazol-2-yl-propionic acid (17j), was identified as a potent human PPARα/γ dual agonist (EC₅₀ = 0.013 and 0.061 μM, respectively) with demonstrated oral bioavailability in rat and dog. 17j was shown to decrease insulin levels, plasma glucose, and triglycerides in the ZDF female rat model. In the human apolipoprotein A-1/CETP transgenic mouse model 17j produced increases in hApoA1 and HDL-C and decreases in plasma triglycerides. The increased potency for binding and activation of both PPAR subtypes observed with 17j when compared to previous analogs in this series was explained based on results derived from crystallographic and modeling studies.     

Modulation of PPAR subtype selectivity. Part 2: Transforming PPARα/γ dual agonist into α selective PPAR agonist through bioisosteric modification

A novel series of oxime containing benzyl-1,3-dioxane-r-2-carboxylic acid derivatives (6a-k) were designed as selective PPARα agonists, through bioisosteric modification in the lipophilic tail region of PPARα/γ dual agonist. Some of the test compounds (6a, 6b, 6c and 6f) showed high selectivity towards PPARα over PPARγ in vitro. Further, highly potent and selective PPARα agonist 6c exhibited significant antihyperglycemic and antihyperlipidemic activity in vivo, along with its improved pharmacokinetic profile. Favorable in-silico interaction of 6c with PPARα binding pocket correlate its in vitro selectivity profile toward PPARα over PPARγ. Together, these results confirm discovery of novel series of oxime based selective PPARα agonists for the safe and effective treatment of various metabolic disorders.     

SAR studies of acidic dual γ-secretase/PPARγ modulators

A novel set of dual γ-secretase/PPARγ modulators characterized by a 2-benzyl hexanoic acid scaffold is presented. Synthetic efforts were focused on the variation of the substitution pattern of the central benzene. Finally, we obtained a new class of 2,5-disubstituted 2-benzylidene hexanoic acid derivatives, which act as dual γ-secretase/PPARγ modulators in the low micromolar range. We have explored broad SAR and successfully improved the dual pharmacological activity and the selectivity profile against potential off-targets such as NOTCH and COX. Compound 17 showed an IC(50) Aβ42=2.4 μM and an EC(50) PPARγ=7.2 μM and could be a valuable tool to further evaluate the concept of dual γ-secretase/PPARγ modulators in animal models of Alzheimer's disease.