Discovery and SAR of JTE-151: A Novel RORγ Inhibitor for Clinical Development.

A number of RORγ inhibitors have been reported over the past decade. There were also several examples advancing to human clinical trials, however, none of them has reached the market yet, suggesting that there could be common obstacles for their future development. As was expected from the general homology of nuclear receptor ligands, insufficient selectivity as well as poor physicochemical properties were identified as potential risks for a RORγ program. Based on such considerations, we conducted a SAR investigation by prioritizing drug-like properties to mitigate such potential drawbacks. After an intensive SAR exploration with strong emphasis on "drug-likeness" indices, an orally available RORγ inhibitor, JTE-151, was finally generated and was advanced to a human clinical trial. The compound was confirmed to possess highly selective profiles along with good metabolic stability, and most beneficially, no serious adverse events (SAE) and good PK profiles were observed in the human clinical trial.

Selenium and Glutathione-Depleted Rats as a Sensitive Animal Model to Predict Drug-Induced Liver Injury in Humans.

Drug-induced liver injury (DILI) is one of the most serious and frequent drug-related adverse events in humans. Selenium (Se) and glutathione (GSH) have a crucial role for the hepatoprotective effect against reactive metabolites or oxidative damage leading to DILI. The hepatoprotective capacity related to Se and GSH in rodents is considered to be superior compared to the capacity in humans. Therefore, we hypothesize that Se/GSH-depleted rats could be a sensitive animal model to predict DILI in humans. In this study, Se-deficiency is induced by feeding a Se-deficient diet and GSH-deficiency is induced by l-buthionine-S,R-sulfoxinine treatment via drinking water. The usefulness of this animal model is validated using flutamide, which is known to cause DILI in humans but not in intact rats. In the Se/GSH-depleted rats from the present study, decreases in glutathione peroxidase-1 protein expression and GSH levels and an increase in malondialdehyde levels in the liver are observed without any increase in plasma liver function parameters. Five-day repeated dosing of flutamide at 150 mg/kg causes hepatotoxicity in the Se/GSH-depleted rats but not in normal rats. In conclusion, Se/GSH-depleted rats are the most sensitive for detecting flutamide-induced hepatotoxicity in all the reported animal models.

A pharmacologic increase in activity of plasma transaminase derived from small intestine in animals receiving an acyl CoA: diacylglycerol transferase (DGAT) 1 inhibitor.

Acyl CoA: diacylglycerol acyltransferase (DGAT) 1 is an enzyme that catalyzes the re-synthesis of triglycerides (TG) from free fatty acids and diacylglycerol. JTT-553 is a DGAT1 inhibitor and exhibits its pharmacological action (inhibition of re-synthesis of TG) in the enterocytes of the small intestine leading to suppression of a postprandial elevation of plasma lipids. After repeated oral dosing JTT-553 in rats and monkeys, plasma transaminase levels were increased but there were neither changes in other hepatic function parameters nor histopathological findings suggestive of hepatotoxicity. Based on the results of exploratory studies for investigation of the mechanism of the increase in transaminase levels, plasma transaminase levels were increased after dosing JTT-553 only when animals were fed after dosing and a main factor in the diet contributing to the increase in plasma transaminase levels was lipids. After dosing JTT-553, transaminase levels were increased in the small intestine but not in the liver, indicating that the origin of transaminase increased in the plasma was not the liver but the small intestine where JTT-553 exhibits its pharmacological action. The increase in small intestinal transaminase levels was due to increased enzyme protein synthesis and was suppressed by inhibiting fatty acid-transport to the enterocytes. In conclusion, the JTT-553-related increase in plasma transaminase levels is considered not to be due to release of the enzymes from injured cells into the circulation but to be phenomena resulting from enhancement of enzyme protein synthesis in the small intestine due to the pharmacological action of JTT-553 in this organ.

Relationships between plasma and tissue transaminase activities in rats maintained under different feeding conditions.

In order to verify the nutritional aspect of alterations of the plasma and tissue transaminase activities, rats were fed 4 hr per day for 35 days (the spaced-fed (SF) rats) and the time course of the alterations in plasma and tissue transaminase activity was compared with those in the ad libitum fed (ALF) rats. Plasma transaminase activities were stable throughout the experiment period in the ALF rats. In the SF rats there were alterations in the plasma alanine aminotransferase (ALT) activities, the direction of which was different between the early phase and late phase of the experiment period; plasma ALT activities decreased in the early phase and gradually increased in the late phase. Plasma aspartate aminotransferase (AST) activities were stable in the SF rats throughout the experiment period as well as the ALF rats. The decreases in plasma ALT activities in the early phase were considered to be related to decreases in ALT activities in the small intestinal mucosa (SI mucosa). On the other hand, the increases in plasma ALT activities in the late phase were considered to be related to increases in ALT activities in the liver. Multiple regression analyses (MRAs) revealed that plasma ALT activities in the SF rats could be estimated by the ALT activities in the SI mucosa and liver. From these results, the alterations of the plasma ALT activities in the SF rats could be explained by those in the SI mucosa and liver under the conditions in our study.