MBX-102/JNJ39659100, a novel peroxisome proliferator-activated receptor-ligand with weak transactivation activity retains antidiabetic properties in the absence of weight gain and edema.

MBX-102/JNJ39659100 (MBX-102) is in clinical development as an oral glucose-lowering agent for the treatment of type 2 diabetes. MBX-102 is a nonthiazolidinedione (TZD) selective partial agonist of peroxisome proliferator-activated receptor (PPAR)-gamma that is differentiated from the TZDs structurally, mechanistically, preclinically and clinically. In diabetic rodent models, MBX-102 has insulin-sensitizing and glucose-lowering properties comparable to TZDs without dose-dependent increases in body weight. In vitro, in contrast with full PPAR-gamma agonist treatment, MBX-102 fails to drive human and murine adipocyte differentiation and selectively modulates the expression of a subset of PPAR-gamma target genes in mature adipocytes. Moreover, MBX-102 does not inhibit osteoblastogenesis of murine mesenchymal cells. Compared with full PPAR-gamma agonists, MBX-102 displays differential interactions with the PPAR-gamma ligand binding domain and possesses reduced ability to recruit coactivators. Interestingly, in primary mouse macrophages, MBX-102 displays enhanced antiinflammatory properties compared with other PPAR-gamma or alpha/gamma agonists, suggesting that MBX-102 has more potent transrepression activity. In summary, MBX-102 is a selective PPAR-gamma modulator with weak transactivation but robust transrepression activity. MBX-102 exhibits full therapeutic activity without the classical PPAR-gamma side effects and may represent the next generation insulin sensitizer.

PPARgamma agonists attenuate proliferation and modulate Wnt/beta-catenin signalling in melanoma cells.

Peroxisome proliferator-activated receptor-gamma (PPARgamma) is a member of the nuclear hormone receptor (NHR) superfamily of ligand-activated transcriptional regulators. Accumulating evidence suggests that PPARgamma agonists such as the thiazolidinediones (TZDs) may prove to be useful anti-cancer agents exhibiting anti-proliferative and/or pro-apoptotic affects in a range of cancer cell types including melanoma, however, the mechanisms underlying this effect remain unclear. We have demonstrated the anti-proliferative effects of full and partial PPARgamma modulators in human melanoma cell lines. Ablation of PPARgamma expression in the MM96L melanoma cell line by siRNA mediated mechanisms attenuates the anti-proliferative effect of these agents suggesting this effect is directly mediated by PPARgamma. The mechanisms underlying the anti-proliferative effects of PPARgamma in melanoma cells involve the regulation of expression of a number of critical cell cycle genes and beta-catenin. Moreover, our data indicate that PPARgamma modulates Wnt/beta-catenin mediated signalling in melanoma cells in an agonist dependent manner.

Halofenate is a selective peroxisome proliferator-activated receptor gamma modulator with antidiabetic activity.

Halofenate has been shown previously to lower triglycerides in dyslipidemic subjects. In addition, significant decreases in fasting plasma glucose were observed but only in type 2 diabetic patients. We hypothesized that halofenate might be an insulin sensitizer, and we present data to suggest that halofenate is a selective peroxisome proliferator-activated receptor (PPAR)-gamma modulator (SPPARgammaM). We demonstrate that the circulating form of halofenate, halofenic acid (HA), binds to and selectively modulates PPAR-gamma. Reporter assays show that HA is a partial PPAR-gamma agonist, which can antagonize the activity of the full agonist rosiglitazone. The data suggest that the partial agonism of HA may be explained in part by effective displacement of corepressors (N-CoR and SMRT) coupled with inefficient recruitment of coactivators (p300, CBP, and TRAP 220). In human preadipocytes, HA displays weak adipogenic activity and antagonizes rosiglitazone-mediated adipogenic differentiation. Moreover, in 3T3-L1 adipocytes, HA selectively modulates the expression of multiple PPAR-gamma-responsive genes. Studies in the diabetic ob/ob mouse demonstrate halofenate's acute antidiabetic properties. Longer-term studies in the obese Zucker (fa/fa) rat demonstrate halofenate's comparable insulin sensitization to rosiglitazone in the absence of body weight increases. Our data establish halofenate as a novel SPPARgammaM with promising therapeutic utility with the potential for less weight gain.

Halofenate and clofibrate inhibition of pyruvate dehydrogenase from Fusarium culmorum.

Pyruvate dehydrogenase (E1, E.C. 1.2.4.1) was obtained from Fusarium culmorum by ammonium sulfate precipitation. An eight-fold purification was obtained with a specific activity of 13 K units/mg protein. Both halofenate and clofibrate inhibited the enzyme complex non-competitively. The inhibitory effect of halofenate was greater than that of clofibrate being 42% higher at 20 mM concentration compared to the inhibition by clofibrate at 40 mM concentration. Both compounds disorganized the normal cytoplasmic lipids including the emptying of cells in the mycelium suggesting membrane disruption.

Improved control of non-insulin-dependent diabetes mellitus by combined halofenate and chlorpropamide therapy.

Combined halofenate-chlorpropamide was evaluated for the treatment of NIDDM. Four subjects treated with 500 mg/day chlorpropamide were given 500-1000 mg halofenate daily for 48 wk or longer. Fasting plasma glucose fell from 210 +/- 16 (+/- SEM) (11.67 +/- 0.89 mM) to 107 +/- 10 mg/dl (+/- SEM) (5.94 +/- 0.55 mM), P less than 0.005. Twelve additional subjects were entered into a 16-wk double-blind study testing chlorpropamide plus either placebo or halofenate. In the halofenate group, the mean fasting glucose fell from 227 +/- 27 (+/- SEM) (12.61 +/- 1.50 mM) and reached 107 +/- 19 mg/dl (+/- SEM) (5.94 +/- 1.06 mM) during the fourth month, whereas the placebo groups showed a decrease from 242 +/- 22 (+/- SEM) to 208 +/- 29 mg/dl (+/- SEM) (P less than 0.005). In addition, halofenate reduced the height of postprandial glycemic excursions by lowering fasting plasma glucose. When halofenate was used as the only therapy, reduction in fasting plasma glucose was small [179 +/- 12 reduced to 142 +/- 8 mg/dl (+/- SEM); 9.94 +/- 0.67 mM and 7.89 +/- 0.44 mM], P less than 0.05.

Short-term inhibition of fatty acid biosynthesis in isolated hepatocytes by mono-aromatic compounds.

An overview is presented of a selected number of mono-aromatic derivatives and their short-term effects on hepatic fatty acid biosynthesis. The compounds discussed in this paper are ortho-hydroxybenzoate (salicylate), meta-hydroxybenzoate, para-hydroxybenzoate, benzoate, para-t-butylbenzoate, para-aminosalicylate, clofibrate, halofenate, alpha-cyano-4-hydroxycinnamate and benfluorex. All of these drugs inhibit fatty acid biosynthesis by isolated rat liver cells, albeit with different effectiveness. In contrast, the compounds have differential effects on fatty acid esterification and oxidation by isolated hepatocytes. An attempt is made to describe in molecular terms the underlying mechanisms of the acute inhibitory effects of the mono-aromatic derivatives on hepatic lipogenesis. It is proposed that all of the drugs exert an inhibitory action at the level of acetyl-CoA carboxylase, the enzyme generally considered to catalyse the rate-limiting step in hepatic fatty acid synthesis. This inhibitory effect may be either direct, i.e. by an alteration of the enzyme's structure as a result of interaction between drug and enzyme, or indirect, i.e. through a drug-induced change in the cellular levels of allosteric effectors of acetyl-CoA carboxylase.

The action of halofenate on platelet shape change and prostaglandin synthesis.

HAL, a congener of clofibrate, has previously been shown to inhibit epinephrine- and ADP-induced platelet aggregation and 14C-serotonin release. We further investigated the site of action of HAL by examining platelet shape change, MDA production as a measure of prostaglandin synthesis, and platelet aggregation and MDA production induced by SA. At the usual maximal therapeutic concentration of HAL (0.96 mM), this drug did not affect the velocity of platelet shape change as measured by a spectrophotometric method. However, at a higher concentration (3.12 mM), HAL significantly inhibited shape change (p less than 0.01). When epinephrine was used to initiate aggregation of PRP, HAL (0.96 mM) was found to inhibit MDA production over a wide range of epinephrine concentrations (p less than 0.01). This was not due to a direct inhibition of prostaglandin formation, since HAL had no effect on SA-induced platelet aggregation or MDA production. Aspirin (4 mM), on the other hand, produced a marked inhibition of MDA production and of platelet aggregation after stimulation with SA. We conclude that HAL works to inhibit some step in the platelet reaction prior to the appearance of free arachidonic acid.

Effects of halofenate on glucose tolerance in patients with hyperlipoproteinemia.

Halofenate, a triglyceride- and uric acid-lowering drug, potentiated the effect of oral hypoglycemics. Its effect on serial glucose tolerance was evaluated in ten patients with hypertriglyceridemia without overt diabetes. Six-hour oral glucose tolerance tests were done during a control period and every 24 weeks over two years of halofenate treatment. Abnormal glucose tolerance (chemical diabetes) was observed during the control period in six of ten patients. The number of abnormal tests gradually decreased to none by 48 weeks. Plasma glucose, insulin, and free fatty acid values during the glucose tolerance tests were reduced significantly. Halofenate induced significant serum uric acid reduction. No significant regressions were observed among levels of lipids, hormones, glucose, and uric acid. The mechanisms by which lipid-lowering drugs improve glucose tolerance are as yet unexplained.

Platelet function in hyperbetalipoproteinemia.

Individuals with familial hyperbetalipoproteinemia are at increased risk of premature atherosclerosis and thrombosis. Although there is controversy whether platelet survival is shortened or normal in this disease, several in vitro tests of platelet function are abnormal including a decreased threshold concentration for stimulation of aggregation by ADP, epinephrine and collagen and increased release of nucleotides to the same agents. These functional changes are accompanied by an increase of cholesterol to phospholipid ratio in the platelet membrane and in low density lipoprotein in individuals with type IIa hyperlipoproteinemia. Clofibrate and halofenate reverse some of the abnormalities in vitro and the former drug, when administered for 6 weeks to patients with type IIa hyperlipoproteinemia decreases platelet sensitivity to ADP and epinephrine. The platelet hypersensitivity to aggregating agents can be reproduced in vitro by increasing the cholesterol to phospholipid rather in normal platelets. These artificially hypersensitive platelets can be returned to normal by halofenate in vitro. Incorporation of cholesterol into platelet membranes increases the basal level of the membrane associated enzyme adenylate cyclase. However, the enzyme no longer responds to stimulation by prostaglandin E1, and this is associated with relative resistance of the platelet to inhibition by this pharmacologic agent. These functional alterations produced by cholesterol enrichment of platelet membranes occur is parallel with an increase in platelet membrane microviscosity suggesting that the more rigid membrane can alter the behavior of membrane associated enzymes and receptors. A correlation appears to exist between the ability of certain drugs to induce phase separation in model membranes and the potency in inhibitory platelet aggregation.

[Effect of halofenate on triglyceride and uric acid levels, coagulation and platelet behaviour in patients with hyperlipoproteinemia type IV and hyperuricemia (author's transl)]. / Wirkung von Halofenat auf Triglycerid- und Harnsäurespiegel sowie auf Gerinnungs- und Thrombozytenverhalten bei Patienten mit Hyperlipoproteinämie Typ IV und Hyperurikämie.

From experimental work, an influence of a drug with hypolipidemic and hypouricemic acition on blood coagulability and platelet function may be expected. Consequently, if these effects were demonstrable in man the drug could be assumed to reduce the tendency to develop thrombosis and atherosclerosis in patients with hyperlipidemia and hyperuricemia. In the study reported, the effect of 2-acetamidoethyl-(p-chlorophenyl)-(m-trifluoro-methylphenoxy)-acetate (halofenate) was investigated in 14 patients suffering from hyperlipoproteinemia type IV and hyperuricemia. Platelet aggregation and adhesiveness, plasma levels of triglycerides, cholesterol, uric acid, and clotting factors were regularly examined during a three-month double blind trial. While uric acid and triglyceride levels decreased, no influence of the drug treatment could be observed on platelet function and blood coagulability by the laboratory methods used.

The effect of halofenate--free acid on aggregation--the release reaction, coagulant activity, and lipid metabolism of human platelets.

Halofenate--free acid (HFA), the major metabolite of the hypolipidemic drug, halofenate, inhibited platelet aggregation induced by collagen and sodium arachidonate and blocked the second phase of aggregation caused by ADP, thrombin and epinephrine in human platelet-rich plasma. The aggregation of washed platelets by thrombin and collagen was also blocked. HFA also inhibited the release by thrombin and collagen of 5-hydroxytryptamine from dense granules of platelets and the release by thrombin of beta-glucuronidase from platelet alpha-granules. These inhibitory effects were concentration and time-dependent. HFA decreased platelet factor 3 activity by 31% and also inhibited the incorporation of 14C-acetate and U-14C-glucose into platelet lipids by 89% and 56% respectively. Thrombin-induced lipid peroxidation and prostaglandin formation was investigated by measuring the by-product malonyldialdehyde, and this was found to be inhibited by HFA. It is suggested that the effect of HFA on aggregation is attributable to inhibition of the release reaction which may in turn be a consequence of the effects of the drug on platelet lipid synthesis.

Potentiation of hypoglycemic effect of chlorpropamide and phenfromin by halofenate.

The potentiation of oral hypoglycemic drugs by the antilipemic agent halofenate is reported. Forty-seven diabetic patients were treated for 48 weeks with halofenate, clofibrate, or placebo. Five patients in the halofenate group were taking phenformin plus either chlorpropamide or tolbutamide. Their average initial fasting plasma glucose was 160 mg./dl. All five patients experienced a slow but but substantial fall in fasting plasma glucose. The mean fasting plasma glucose for the five patients after 80 days of halofenate treatment was 63 mg./dl. As oral treatment for diabetes was reduced, the fasting plasma glucose returned to prehalofenate levels. In this study, we did ont detect an effect of halofenate on the fasting plasma glucose of diabetic patients treated with insulin or on the fasting plasma glucose levels of patients treated with diet alone.