YM17E

Pharmacological properties of YM17E, an acyl-CoA:cholesterol acyltransferase inhibitor, and diarrheal effect in beagle dogs

YM17E (1,3-bis[[1-cycloheptyl-3-(p-dimethylaminophenyl)ureido]methyl]ben zene dihydrochloride) was found to be a potent inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT) in rabbit liver and intestine microsomes. Dixon plot analysis revealed that YM17E inhibited microsomal ACAT in a non-competitive manner. YM17E induced a marked decrease in serum cholesterol, especially in non-high-density lipoprotein (HDL) fractions, in cholesterol-fed rats and rats fed normal chow. Measurement of bile secretion after oral administration of YM17E in cholesterol-fed rats showed that the drug markedly accelerated the secretion of bile acids and neutral sterols. Furthermore, absorption of [3H]cholesterol from the gut of cholesterol-fed rats was significantly inhibited by YM17E. From these results, the hypocholesterolemic activity of YM17E in these animals resulted from both a decrease in cholesterol absorption from the gut and the stimulation of excretion of cholesterol from the liver into bile. However, YM17E caused secretory diarrhea in beagle dogs at near lipid lowering doses. When YM17E was administered at the same total dosage but divided into 5 daily administrations, the incidence of diarrhea was significantly reduced while its cholesterol lowering effect became stronger. These results suggest that the inhibition of intestinal and/or liver ACAT increases the risk of diarrhea development which, however, can be avoided by controlled drug administration in beagle dogs.

Pharmacokinetic properties of YM17E, an inhibitor of acyl coenzyme A: cholesterol acyl transferase, and serum cholesterol levels in healthy volunteers

We conducted a single and repeat oral dose study of YM17E, a novel inhibitor of acyl coenzyme A (CoA): cholesterol acyltransferase, in healthy male volunteers to evaluate the pharmacokinetic profile, tolerability and effect of the drug on serum cholesterol. In the single administration study, YM17E was administered after a meal to two groups of subjects (each containing six subjects taking the drug and three taking placebo) receiving 3, 60 and 300 mg or 15, 60 and 450 mg YM17E, respectively. Plasma concentrations of unchanged drug following single oral administration at 3-300 mg after a meal increased with increasing dose. In contrast, plasma concentrations after administration of 450 mg were almost the same as after 300 mg. Unchanged YM17E was not detected in urine after single administration, suggesting that it was excreted via the bile or urine after metabolism. Five active metabolites (M1, M2-a, M2-b, M3 and M4) were observed in plasma at concentrations comparable to those of unchanged YM17E. Their plasma concentrations increased in a slightly greater than dose-dependent manner from 3 to 300 mg. The effect of food was studied in an open crossover design with a 1-week washout period. Twelve subjects received 150 mg YM17E in both the fasted and post-prandial states. The AUC and Cmax after fasting were closely similar to those after a meal, showing that bioavailability was not affected by food intake. In the repeated oral dose study, the subjects received test drug at 150 mg or 300 mg (n = 6 each) or placebo (n = 3) twice a day (after breakfast and after dinner) for 7 days. On days 1 and 7, the subjects received YM17E once a day (after breakfast) for evaluation of pharmacokinetic properties. After repeated oral administration of 150 mg b.d., plasma concentrations reached steady state by day 5 (mean Cmin 48.6 ng.ml-1). After repeated administration of 300 mg b.d., plasma concentrations prior to each daily morning dose increased up to the 5th day (mean Cmin 166.6 ng.ml-1) and then tended to decrease until the 7th day. No significant signs, symptoms or changes in serum cholesterol levels were observed during the single and repeated oral dose studies at 150 mg b.d. Although statistical analysis was not conducted because of the small number of subjects, all subjects receiving repeated oral administration of 300 mg twice daily showed a 25% decrease in serum cholesterol level on day 7, but also the simultaneous occurrence of diarrhoea.

In-vitro metabolism of YM17E, an inhibitor of acyl coenzyme A:cholesterol acyltransferase, by liver microsomes in man

Because YM17E (1,3-bis[[1-cycloheptyl-3-(p-dimethylaminophenyl) ureido]methyl]benzene dihydrochloride) inhibits acyl coenzyme A:cholesterol acyltransferase (ACAT) it has potential application in the treatment of hypercholesterolaemia. In man and animals YM17E is extensively metabolized, via N-demethylation, to five active metabolites (M1, M2-a, M2-b, M3 and M4). The main objectives of this study were to examine inhibition of YM17E metabolism by the products and identify the cytochrome P450 isoforms in liver microsomes which catalyse in-vitro YM17E metabolism in man. In microsomes in man N-demethylation of YM17E to M1 occurred enzymatically; for up to 45 s the rate was linearly proportional to the microsomal protein concentration. This reaction was inhibited by metabolites M2-a, M2-b, M3 and M4. Further, N-demethylation of [14C]-YM17E was also inhibited by its product, M1. These results showed that primary metabolism of YM17E was inhibited by its products, and supported the finding that the non-linear increase in plasma concentration of the parent drug and metabolites observed in an in-vivo study was due to inhibition by these products. Metabolic activity in microsomes from ten individual human livers demonstrated that YM17E N-demethylase activity correlated closely with testosterone 6 beta-hydroxylase activity. When cytochrome P450 isozyme-specific substrates and chemical inhibitors were used to inhibit YM17E N-demethylase activity, CYP3A-specific substrate and inhibitors such as nifedipine, ketoconazole and triacetyloleandomycin strongly inhibited this activity, whereas CYP1A-specific substrate or inhibitor, ethoxyresorufin and alpha-naphthoflavone, inhibited weakly. Other CYP inhibitors, in contrast, had few or no effects. An inhibition study using anti-rat CYP1A1, CYP2B1, CYP2C11, CYP2E1 and CYP3A2 antibodies demonstrated that only anti-rat CYP3A2 antibody inhibited YM17E metabolism, to 40% of control level, with no other antibodies showing an inhibitory effect. Of seven cDNA-expressed P450 isoforms in man (CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2D6, CYP2E1 and CYP3A4), CYP3A4, CYP2D6 and CYP1A2 isozyme exhibited substantial catalytic activity of N-demethylation of YM17E. These results indicate the predominant role of CYP3A4 in liver metabolism of YM17E in man.

Disposition and metabolism of a novel diurea inhibitor of acyl CoA: cholesterol acyltransferase (YM17E) in the rat and dog

1. We have investigated the disposition and metabolism of YM17E after intravenous and oral administration in the rat and dog. 2. Bioavailability of YM17E was 5-9% at oral doses of 3-30 mg/kg in rat, and 9 and 13% at oral doses of 10 and 30 mg/kg in dog. 3. Five N-demethylated metabolites, which have significant pharmacological activity, were found in rat and dog plasma after oral administration. Plasma concentrations of each of these metabolites were comparable with that of unchanged drug. 4. When 14C-YM17E was administered to rat, AUC of unchanged drug was 7% of that of radioactivity. However, AUC of the combined concentration of unchanged drug and five active metabolites was about 50% of that of radioactivity, indicating that the pharmacological activity of the agent was maintained in spite of its biotransformation. 5. After oral administration of 14C-YM17E at a dose of 10 mg/kg to rat, radioactivity was distributed widely to almost all tissues except the brain. The concentration of radioactivity in the liver, one of the target organs, was 65 times higher than that in plasma at 1 h after administration. 6. A significant amount of radioactivity in the liver was located in the microsomal subfraction, which contains much acyl CoA:cholesterol acyl transferase activity. More than 50% of this microsomal radioactivity was derived from unchanged YM17E and five active metabolites. 7. From excretion data in the bile duct-cannulated rat, the absorption ratio of YM17E from the gastrointestinal tract in this species was estimated to be at least 40%, suggesting that the low bioavailability of the drug is due to extensive first-pass metabolism. 8. Some 95% of the administered radioactivity was excreted in the faeces of rat following iv or po doses of 14C-YM17E.

Relationship between bioavailability and hypocholesterolemic activity of YM17E, an inhibitor of ACAT, in cholesterol-fed rats

The relationship between bioavailability and the serum cholesterol-lowering effect of YM17E, an ACAT inhibitor was investigated. Serum cholesterol levels in cholesterol-fed rats decreased after both oral and intravenous administration of YM17E. Marked inhibition of cholesterol absorption was observed after oral administration, but not after intravenous administration. YM17E and its five active metabolites were primarily distributed in the liver after intravenous administration, but in small intestine and liver after oral administration. Hepatic ACAT activity in cholesterol-fed rats was inhibited by intravenous administration. Cholesteryl ester input into plasma by Triton WR-1339 treatment to the rats was inhibited by intravenous administration of YM17E. Plasma clearance of 125I-LDL in cholesterol-fed rats increased after YM17E treatment suggesting a decrease in LDL production. These results indicate that the hypocholesterolemic effect of intravenous YM17E was due to hepatic ACAT inhibition, not an inhibition of intestinal cholesterol absorption. The contribution of ACAT inhibition in small intestine and liver on the pharmacological effect could be explained by plasma inhibitor concentration after oral or intravenous administration of YM17E. From these results, it is concluded that the change in bioavailability of ACAT inhibitors change the mechanism of hypocholesterolemic effects, shifting the relative contributions of small intestinal and hepatic ACAT inhibition.