Narayanan Hariharan

Comparative Metabolism of Radiolabeled Muraglitazar in Animals and Humans by Quantitative and Qualitative Metabolite Profiling

Muraglitazar (Pargluva), a dual α/γ peroxisome proliferator-activated receptor (PPAR) activator, has both glucose- and lipid-lowering effects in animal models and in patients with diabetes. This study describes the in vivo and in vitro comparative metabolism of [14C]muraglitazar in rats, dogs, monkeys, and humans by quantitative and qualitative metabolite profiling. Metabolite identification and quantification methods used in these studies included liquid chromatography/mass spectrometry (LC/MS), LC/tandem MS, LC/radiodetection, LC/UV, and a newly described mass defect filtering technique in conjunction with high resolution MS. After oral administration of [14C]muraglitazar, absorption was rapid in all species, reaching a concentration peak for parent and total radioactivity in plasma within 1 h. The most abundant component in plasma at all times in all species was the parent drug, and no metabolite was present in greater than 2.5% of the muraglitazar concentrations at 1 h postdose in rats, dogs, and humans. All metabolites observed in human plasma were also present in rats, dogs, or monkeys. Urinary excretion of radioactivity was low (<5% of the dose) in all intact species, and the primary route of elimination was via biliary excretion in rats, monkeys, and humans. Based on recovered doses in urine and bile, muraglitazar showed a very good absorption in rats, monkeys, and humans. The major drug-related components in bile of rats, monkeys, and humans were glucuronides of muraglitazar and its oxidative metabolites. The parent compound was a minor component in bile, suggesting extensive metabolism of the drug. In contrast, the parent drug and oxidative metabolites were the major components in feces, and no glucuronide conjugates were found, suggesting that glucuronide metabolites were excreted in bile and hydrolyzed in the gastrointestinal tract. The metabolites of muraglitazar resulted from both glucuronidation and oxidation. The metabolites in general had greatly reduced activity as PPARα/γ activators relative to muraglitazar. In conclusion, muraglitazar was rapidly absorbed, extensively metabolized through glucuronidation and oxidation, and mainly eliminated in the feces via biliary excretion of glucuronide metabolites in all species studied. Disposition and metabolic pathways were qualitatively similar in rats, dogs, monkeys, and humans.

The Dual Peroxisome Proliferator-Activated Receptor α/γ Activator Muraglitazar Prevents the Natural Progression of Diabetes in db/db Mice

There are two major defects in type 2 diabetes: 1) insulin resistance and 2) insulin deficiency due to loss of β-cell function. Here we demonstrated that treatment with muraglitazar (a dual peroxisome proliferator-activated receptor α/γ activator), when initiated before or after the onset of diabetes in mice, is effective against both defects. In study 1, prediabetic db/db mice were treated for 12 weeks. The control mice developed diabetes, as evidenced by hyperglycemia, hyperinsulinemia, reduced insulin levels in the pancreas, blunted insulin response to glucose, and impaired glucose tolerance. The muraglitazar-treated mice had normal plasma glucose, and insulin levels, equivalent or higher pancreatic insulin content than normal mice, showed a robust insulin response to glucose and exhibited greater glucose tolerance. In study 2, diabetic db/db mice were treated for 4 weeks. The control mice displayed increased glucose levels, severe loss of islets, and their isolated islets secreted reduced amounts of insulin in response to glucose and exendin-4 compared with baseline. In muraglitazar-treated mice, glucose levels were reduced to normal. These mice showed reduced loss of islets, and their isolated islets secreted insulin at levels comparable to baseline. Thus, muraglitazar treatment decreased both insulin resistance and preserved β-cell function. As a result, muraglitazar treatment, when initiated before the onset of diabetes, prevented development of diabetes and, when initiated after the onset of diabetes, prevented worsening of diabetes in db/db mice.

Genetic and gene expression studies implicate renin and endothelin-1 in edema caused by peroxisome proliferator-activated receptor γ agonists

Objective Peroxisome proliferator-activated receptor &ggr; (PPAR&ggr;) agonists can cause peripheral edema in susceptible individuals. To investigate the mechanistic basis underlying this adverse event, we performed a candidate gene analysis of patients enrolled in clinical trials of muraglitazar, an investigational PPAR&agr;/&ggr; dual agonist, and developed a cell culture-based gene expression assay and nonhuman primate model of edema to study the edemagenic properties of PPAR&ggr; agonists. Methods A total of 213 single nucleotide polymorphisms (SNPs) in 63 genes were genotyped in 730 participants. Chi-square and logistic regression analyses were used to test for association with edema. Transcriptional responses to PPAR&ggr; agonists were evaluated in Calu-6 cells using quantitative real-time PCR. Male Cynomolgus monkeys were treated with PPAR agonists and were evaluated for edema using MRI. Results SNPs in renin (rs2368564) and endothelin-1 (rs5370) were associated with reduced risk of edema (P=0.003 and P=0.028, respectively) and an SNP in &bgr;1 adrenergic receptor (rs1801253) was associated with increased susceptibility to edema (P=0.034). Gene expression studies revealed that renin and endothelin-1 were regulated by PPAR&ggr; in Calu-6 cells. A survey of 10 PPAR&ggr; agonists further revealed that a compounds in vitro potency was correlated with its edemagenic potential leading to the prediction that one of three previously uncharacterized PPAR&ggr; agonists would cause less edema. This prediction was validated in a nonhuman primate model of PPAR&ggr; agonist-induced edema. Conclusion Our results implicate a key role for renin and endothelin-1 in the edema caused by PPAR&ggr; agonists and demonstrate how knowledge gained from pharmacogenetic studies can be applied in drug discovery.

Discovery and evaluation of 1 H -pyrrolo[2,3- b ]pyridine based selective and reversible small molecule BTK inhibitors for the treatment of rheumatoid arthritis

In a pursuit to identify reversible and selective BTK inhibitors, two series based on 7H-pyrrolo[2,3-d]pyrimidine and 1H-pyrrolo[2,3-b]pyridine as the hinge binding core, have been identified. Structure activity relationship (SAR) exploration led to identification of two advanced lead molecules, 11 and 13, which demonstrated desired BTK inhibitory potency in different cellular assays, excellent selectivity in a panel of 50 diverse kinases, favorable in vivo PK properties in mice and anti-arthritic effect in a mouse model of CIA.

Discovery of Potent and Selective A2A Antagonists with Efficacy in Animal Models of Parkinson’s Disease and Depression

Adenosine A2A receptor (A2AAdoR) antagonism is a nondopaminergic approach to Parkinsons disease treatment that is under development. Earlier we had reported the therapeutic potential of 7-methoxy-4-morpholino-benzothiazole derivatives as A2AAdoR antagonists. We herein described a novel series of [1,2,4]triazolo[5,1-f]purin-2-one derivatives that displays functional antagonism of the A2A receptor with a high degree of selectivity over A1, A2B, and A3 receptors. Compounds from this new scaffold resulted in the discovery of highly potent, selective, stable, and moderate brain penetrating compound 33. Compound 33 endowed with satisfactory in vitro and in vivo pharmacokinetics properties. Compound 33 demonstrated robust oral efficacies in two commonly used models of Parkinsons disease (haloperidol-induced catalepsy and 6-OHDA lesioned rat models) and depression (TST and FST mice models).