Identification and synthesis of a novel selective partial PPARdelta agonist with full efficacy on lipid metabolism in vitro and in vivo.

The aim was to identify a novel selective PPARdelta agonist with full efficacy on free fatty acid (FFA) oxidation in vitro and plasma lipid correction in vivo. Using the triple PPARalpha,gamma,delta agonist 1 as the structural starting point, we wanted to investigate the possibility of obtaining selective PPARdelta agonists by modifying only the acidic part of 1, while holding the lipophilic half of the molecule constant. The structure-activity relationship was guided by in vitro transactivation data using the human PPAR receptors, FFA oxidation efficacy performed in the rat muscle L6 cell line, and in vivo rat pharmacokinetic properties. Compound 7 ([4-[3,3-bis-(4-bromo-phenyl)-allylthio]-2-chloro-phenoxy]-acetic acid) was identified as a selective, partial agonist with good oral pharmacokinetic properties in rat. Chronic treatment of high fat fed ApoB100/CETP-Tgn mice with 7 corrected the plasma lipid parameters and improved insulin sensitivity. These data suggest that selective PPARdelta agonists have the potential to become a novel treatment of dyslipidemia.

Selective PPAR agonists for the treatment of type 2 diabetes.

Type 2 diabetes is a metabolic disease characterized by increased plasma glucose and insulin as well as dyslipidemia. If left untreated, chronic diseases will develop that are associated with neuropathic damage and higher mortality risk. Using a rational drug design, novel compounds have been developed that selectively activate the human PPAR receptors, leading to lessening of hyperglycemia and hyperinsulinemia as well as reduction of lipid levels in conjunction with an increase of the beneficial HDL-cholesterol. These PPAR agonists showed increased potency and efficacy compared to previously marketed insulin sensitizers. Lead compounds with desirable pharmacokinetic properties were chosen for further testing in several animal models. The in vivo activity of some synthetic ligands, capable of activating two or all three members of peroxisome proliferator-activated receptors (PPAR) family of receptors, suggested that they may have improved efficacy in type 2 diabetes therapy. Here, we briefly summarize the development of some novel PPAR agonists identified by our group in recent years.

Large dimeric ligands with favorable pharmacokinetic properties and peroxisome proliferator-activated receptor agonist activity in vitro and in vivo.

Two potent nonselective, but PPARalpha-preferring, PPAR agonists 5 and 6 were designed and synthesized in high yields. The concept of dimeric ligands in transcription factors was investigated by synthesizing and testing the corresponding dimers 7, 8a, and 8b in PPAR transactivation assays. The three dimeric ligands all showed agonist activity on all three PPAR receptor subtypes, but with different profiles compared to the monomers 5 and 6. Despite breaking all the "rule of five" criteria, the dimers had excellent oral bioavailability and pharmacokinetic properties, resulting in good in vivo efficacy in db/db mice. X-ray crystal structure and modeling experiments suggested that the dimers interacted with the AF-2 helix as well as with amino acid residues in the lipophilic pocket close to the receptor surface.

Discovery and SAR of a novel selective and orally bioavailable nonpeptide classical competitive inhibitor class of protein-tyrosine phosphatase 1B.

Reversible phosphorylation and dephosphorylation of key proteins on tyrosine residues are important parts of intracellular signaling triggered by hormones and other agents. Recent knock-out studies in mice have identified PTP1B as a potential target for the treatment of diabetes and obesity. As a consequence, a number of academic and industrial groups are aggressively pursuing the development of selective PTP1B inhibitors. In addition, other protein-tyrosine phosphatases (PTPs) appear to be critically involved in major diseases such as cancer and autoimmunity. Given the diversity of PTPs and their potential as drug targets in different diseases, we have taken a broad approach to develop active site-directed selective inhibitors of specific members of this family of enzymes. Using a high throughput screening, we have previously identified 2-(oxalylamino)benzoic acid 3a as a relatively weak but classical competitive inhibitor of several PTPs.(4) On the basis of our early studies, indicating that 3a might be used as a starting point for the synthesis of selective PTP inhibitors, we now present our efforts in expansion of this concept and provide here a number of new chemical scaffolds for the development of inhibitors of different members of the PTP family. Although the core structure of these inhibitors is charged, good oral bioavailability has been observed in rat for some compounds. Furthermore, we have observed enhancement of 2-deoxy-glucose accumulation in C2C12 cells with prodrug analogues.

Novel tricyclic-alpha-alkyloxyphenylpropionic acids: dual PPARalpha/gamma agonists with hypolipidemic and antidiabetic activity.

Synthesis and structure-activity relationships of tricyclic alpha-ethoxy-phenylpropionic acid derivatives guided by in vitro PPARalpha and PPARgamma transactivation data and computer modeling led to the identification of the novel carbazole analogue, 3q, with dual PPARalpha (EC(50) = 0.36 microM) and PPARgamma (EC(50) = 0.17 microM) activity in vitro. Ten days treatment of db/db mice with 3q improved the insulin sensitivity, as measured by OGTT, better than that seen with both pioglitazone and rosiglitazone treatment, suggesting in vivo PPARgamma activity. Likewise, 3q lowered plasma triglycerides and cholesterol in high cholesterol fed rats after 4 days treatment, indicating in vivo PPARalpha activity. Investigations of the pharmacokinetics of selected compounds suggested that extended drug exposure improved the in vivo activity of in vitro active compounds.

Design of potent PPARalpha agonists.

Computational analysis of the ligand binding pocket of the three PPAR receptor subtypes was utilized in the design of potent PPARalpha agonists. Optimum PPARalpha potency and selectivity were obtained with substituents having van der Waals volume around 260. Compound 6 had a PPARalpha potency of 0.002 microM and a selectivity ratio to PPARgamma and PPARdelta of 410 and 2000, respectively.

Structure-activity relationships of dimeric PPAR agonists.

A series of dimeric PPAR agonists were designed and tested for PPAR activity in vitro. The SAR showed that dimeric ligands with a common group or full dimeric ligands had retained or even increased PPARgamma potency. The dimeric agonist concept can be used to fine tune the subtype selectivity of PPAR agonists. The PPARgamma potency could, at least partly, be explained using molecular modeling.

Prediction of PPAR-alpha ligand-mediated physiological changes using gene expression profiles.

Peroxisome proliferator-activated receptor (PPAR)-alpha controls the transcription of a variety of genes involved in lipid metabolism and is the target receptor for the hypolipidemic drug class of fibrates. In the present study, the molecular and physiological effects of seven different PPAR-activating drugs have been examined in a rodent model of dyslipidemia. The drugs examined were selected to display varying potencies and efficacies toward PPAR-alpha. To help elucidate the link between the gene regulation elicited by PPAR-alpha ligands and the concomitant physiological changes, we have used cDNA microarray analysis to identify smaller gene sets that are predictive of the function of these ligands. A number of genes showed strong correlations to the relative PPAR-alpha efficacy of the drugs. Furthermore, using multivariate analysis, a strong relationship between the drug-induced triglyceride lowering and the transcriptional profiles of the different drugs could be found.

Design and synthesis of novel PPARalpha/gamma/delta triple activators using a known PPARalpha/gamma dual activator as structural template.

Using a known dual PPARalpha/gamma activator (5) as a structural template, SAR evaluations led to the identification of triple PPARalpha/gamma/delta activators (18-20) with equal potency and efficacy on all three receptors. These compounds could become useful tools for studying the combined biological effects of PPARalpha/gamma/delta activation.