Disposition of a silicon-containing amide, an inhibitor of acyl-CoA: cholesterol acyltransferase, in dog and rat

The pharmacokinetics of 3-(decyldimethylsilyl)-N-[2-(4-methylphenyl)-1-phenylethyl]propanamide (DMPP), an inhibitor of acyl-CoA:cholesterol acyltransferase, have been studied in the dog and the rat using 14C and 3H dual-labelled drug. In both species, gastrointestinal absorption of DMPP was slow and incomplete, amounting to approximately 20 per cent of the oral dose given in corn oil. In the rat, use of PEG-400, Tween 80, ethanol, and aqueous CMC as vehicles resulted in similar or lower absorption than corn oil. Absorbed DMPP was rapidly and extensively distributed to body tissues. Data from the rat showed highest concentrations of radioactivity in the liver and spleen, while concentrations in the adrenals and lung also markedly exceeded circulating radioactivity levels. In both dog and rat. DMPP was completely metabolized prior to excretion. The routes of biotransformation involved hydrolysis of the amide bond, oxidation of the phenyl ring, and degradation of the decyldimethylsilyl propanoyl moiety. The metabolites of DMPP were excreted slowly, predominantly in the faeces. The elimination half-life of 14C was 105 h in the dog and 83 h in the rat, while that of 3H was approximately 32 h in both species.     

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 postprandial states. The AUC and C_max 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 C_min 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 C_min 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. Received: 23 April 1996 / Accepted in revised form: 1 August 1996     

Discovery of novel acyl coenzyme a: cholesterol acyltransferase inhibitors: pharmacophore-based virtual screening, synthesis and pharmacology

The present study describes ligand‐based pharmacophore modeling of a series of structurally diverse acyl coenzyme A cholesterol acyltransferase inhibitors. Quantitative pharmacophore models were generated using HypoGen module of Discovery Studio 2.1, whereby the best pharmacophore model possessing two hydrophobic, one ring aromatic, and one hydrogen bond acceptor feature for inhibition of acyl coenzyme A cholesterol acyltransferase showed a very good correlation coefficient (r = 0.942) along with satisfactory cost analysis. Hypo1 was also validated by test set and cross‐validation methods. Developed models were found to be predictive as indicated by low error values for test set molecules. Virtual screening against Maybridge database using Hypo1 was performed. The two most potent compounds ( 47 and 48 ; predicted IC₅₀ = 1 nm ) of the retrieved hits were synthesized and biologically evaluated. These compounds showed 86% and 88% inhibition of acyl coenzyme A cholesterol acyltransferase (at 10 μg/mL) with IC₅₀ value of 3.6 and 2.5 nm , respectively. As evident from the close proximity of biological data to the predicted values, it can be concluded that the generated model (Hypo1) is a reliable and useful tool for lead optimization of novel acyl coenzyme A cholesterol acyltransferase inhibitors.     

Hypolipidemic and antioxidant activity of the novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor KY-455 in rabbits and hamsters

The hypolipidemic and antioxidant effects of N-(4,6-dimethyl-1-pentylindolin-7-yl)-2,2-dimethylpropanamide (CAS 178469-71-1, KY-455), a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, were examined in hyperlipidemic rabbits and normolipidemic hamsters. KY-455 inhibited rabbit intestinal, hepatic, macrophage and adrenal ACAT with IC50 values of 0.4, 0.9, 2.9 and 4.1 micromol/l, respectively. KY-455 also inhibited rabbit plasma and LDL-peroxidation (IC50: 0.4 and 1.7 micromol/l, respectively). In rabbits fed a high-cholesterol diet, treatment with KY-455 (30 mg/kg/day) for 8 days markedly lowered serum esterified, free, low-density lipoprotein (LDL)-cholesterol, and hepatic esterified cholesterol levels. KY-455 tended to inhibit ex vivo hepatic ACAT activity 5 h after the final administration. KY-455 also inhibited ex vivo peroxidation of plasma lipids 1 and 5 h after the final administration in rabbits. In normolipidemic hamsters fed a regular diet, treatment with KY-455 (30 mg/kg, twice a day) for 4 days significantly reduced serum esterified, free and LDL-cholesterol, and hepatic esterified and free cholesterol levels. A single administration of KY-455 (30 mg/kg) significantly inhibited ex vivo hepatic ACAT activity in hamsters. In conclusion, KY-455 showed in vitro inhibitory effects on LDL-peroxidation and macrophage ACAT activity at similar concentrations, and in vivo hypolipidemic and ex vivo antioxidative effects at the same dose. Long-term administration of KY-455 is expected to prevent the progress of atherosclerosis by lowering plasma lipid levels, inhibiting both LDL-oxidation and accumulation of cholesterol in macrophages.     

Disposition, metabolism, and excretion of U-71038, a novel renin inhibitor peptide, in the rat

The in vivo fate of U-71038 (Boc-Pro-Phe-N-MeHis-Leu psi [CHOHCH2] Val-Ile-(aminomethyl)pyridine), a potent renin inhibitor, was investigated in rats by single iv administration of tritium-labeled drug at a dose level of 5 mg/kg. The plasma concentrations of drug-related radioactivity diminished very rapidly during the first hour after dosing, with the initial concentrations measured at 2 min falling by more than 95% during the first 30 min. Estimates of the approximate half-life of this earliest phase of the plasma concentration-time curve gave an average value of 4 min. The residual amount of radioactivity after 30 min was cleared from the plasma more slowly, with trace levels still detected 48 hr after dosing. The radioactivity was recovered chiefly (91% of the dose) in feces, indicating biliary clearance as the primary route of elimination from systemic circulation. Urinary recoveries averaged 4% of the dose. Radio-HPLC profiling of plasma, urine, and bile extracts detected only a single radioactive drug-related component in these samples. Preparative HPLC was used to isolate this component from bile; mass spectral comparison to U-71038 confirmed its identity as the unchanged drug. Therefore, U-71038 does not undergo significant systemic metabolism in this species and is eliminated in bile and urine in intact form. Distribution of drug-related radioactivity was very rapid to most of the organs and tissues that were sampled, with the exception of very limited penetration into the central nervous system. Highest tissue levels of tritium were generally found in organs associated with elimination (liver, intestine, kidney) and in thyroid.     

Effects of NTE-122, a novel acyl-CoA:cholesterol acyltransferase inhibitor, on cholesterol esterification and high-density lipoprotein-induced cholesterol efflux in macrophages

We investigated the effects of a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, NTE-122 (trans-1,4-bis[[1-cyclohexyl-3-(4-dimethylamino phenyl)ureido]methyl]cyclohexane), on ACAT activities in macrophages originating from several species and high-density lipoprotein (HDL)-induced cholesterol efflux in phorbol 12-myristate 13-acetate (PMA)-treated THP-1 cells. NTE-122 inhibited cell-free ACAT activities in human PMA-treated THP-1 cells and mouse J774.1 cells with IC50 values of 0.88 and 360 nM, respectively. NTE-122 competively inhibited the ACAT activity in PMA-treated THP-1 cells. NTE-122 also inhibited cellular ACAT activities in PMA-treated THP-1 cells, rat peritoneal macrophages and J774.1 cells with IC50 values of 3.5, 84 and 6800 nM, respectively. Furthermore, NTE-122 prevented cholesterol accumulation in PMA-treated THP-1 cells incubated with acetylated low density lipoprotein, simultaneously with HDL, while it caused accumulation of a significant amount of free cholesterol in the absence and even in the presence of HDL. NTE-122 also enhanced HDL-induced cholesterol efflux from established foam cells converted from PMA-treated THP-1 cells. These results suggest that NTE-122, capable of inhibiting macrophage ACAT activity in humans more strongly than those in the other species, exhibits anti-atherogenic effects by preventing the foam cell formation and enhancing the foam cell regression in humans.     

Pharmacokinetics and metabolism of a selective PDE5 inhibitor (UK-343,664) in rat and dog

1. UK-343,664 is a novel potent and selective PDE5 inhibitor. Plasma clearances in the male and female rat were high (120 and 54 ml min^-1 kg^-1), giving rise to short elimination half-lives (0.2 and 0.3?h respectively). Lower clearance in dog (14 mlmin^-1 kg^-1) was the primary factor resulting in a longer elimination half-life (3.7?h). The higher clearance in rat than dog was in agreement with in vitro metabolism rates in hepatic microsomes. 2. The volume of distribution was lower in rat (1.3-2.1 lkg^-1) compared with dog (4.6?l kg^-1     

Pharmacokinetics and metabolism of a selective PDE5 inhibitor (UK-343,664) in rat and dog

1. UK-343,664 is a novel potent and selective PDE5 inhibitor. Plasma clearances in the male and female rat were high (120 and 54 ml min(-1) kg(-1)), giving rise to short elimination half-lives (0.2 and 0.3h respectively). Lower clearance in dog (14 ml min(-1) kg(-1)) was the primary factor resulting in a longer elimination half-life (3.7 h). The higher clearance in rat than dog was in agreement with in vitro metabolism rates in hepatic microsomes. 2. The volume of distribution was lower in rat (1.3-2.11 kg(-1)) compared with dog (4.61 kg(-1)) probably due to increased plasma protein binding in rat (96 versus 81% in dog). 3. Oral bioavailabilities were 2, 12 and 70% in the male and female rat and dog respectively. Tmax < or = 0.5 h in all animals. 4. In multiple oral dose studies, increased systemic exposure was seen with increasing dose up to doses of 200 mg kg(-1) in rat and 150 mg kg(-1) in dog. A marked super-proportional increase in the male rat indicated a capacity-limited clearance at high doses. 5. At the maximal dose of 200 mg kg(-1) in the female rat, no clinical signs were observed after 14 days of treatment. Only minimal signs were recorded in the male rat and dog at the highest dose levels investigated. 6. After single oral or intravenous doses of [14C]-UK-343,664, the majority of radioactivity was excreted in the faeces of both species. 7. UK-343,664 was extensively metabolized in both rat and dog. The major primary pathways in dog involved piperazine N-deethylation and loss of a two carbon fragment from the piperazine ring (N,N'-de-ethylation). More extensive metabolism in the rat included additional notable metalbolites arising from hydroxylation and lactamization of the piperazine ring, which were only minor metabolites in the dog.     

Effect of SMP-500, a novel acyl-coA:cholesterol acyltransferase inhibitor, on the cholesterol esterification and its hypocholesterolemic properties

We investigated the effects of SMP-500, a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, on ACAT activities in the liver and intestine, and in macrophages. We measured its effects on the serum cholesterol levels and hepatic cholesterol content in mice, rabbits and hamsters. SMP-500 inhibited ACAT activities in rabbit liver and small intestine microsomes with IC(50) values of 72 and 84 nmol/l, respectively, and acted as a competitive inhibitor of rabbit liver ACAT. SMP-500 potently inhibited cholesterol esterification in rat peritoneal macrophages (IC(50) = 15 nmol/l). In high-fat and high-cholesterol diet-fed mice and in high-cholesterol diet-fed rabbits, SMP-500 reduced the serum cholesterol levels and the hepatic cholesterol content. SMP-500 also reduced the serum and hepatic cholesterol in normal chow-fed hamsters in a dose-dependent manner. In all the animal models, SMP-500 reduced the hepatic free cholesterol content as well as the total and esterified cholesterol. Administered orally, SMP-500 had a direct inhibitory effect on hepatic ACAT activity. These results indicate that SMP-500 is a potent and competitive ACAT inhibitor and may have a therapeutic potential for treating hypercholesterolemia and atherosclerosis.     

Multiple mechanisms of hypocholesterolemic action of pactimibe, a novel acyl-coenzyme A:cholesterol acyltransferase inhibitor

Novel acyl-coenzyme A:cholesterol acyltransferase inhibitor pactimibe has been evaluated in vivo; it exhibited significant serum cholesterol lowering activities in hamsters and monkeys without affecting non-high density lipoprotein cholesterol levels. The mechanism of the hypocholesterolemic action of pactimibe was examined in normocholesterolemic hamsters in this study. Results with the dual-isotope plasma ratio method indicated that pactimibe inhibits cholesterol absorption from the intestine, reduces cholesteryl ester formation in the liver, and enhances its elimination from the body. The Triton WR-1339 experiment showed that pactimibe inhibited secretion of very low density lipoprotein cholesterol from the liver. These results suggest that pactimibe is likely to have multiple mechanisms of action responsible for its effectiveness in reducing serum cholesterol.     

Disposition and metabolism of codorphone in the rat, dog, and man

The disposition and metabolism of codorphone, 17-cyclopropyl-methyl-4,5 alpha-8 beta-ethyl-3-methoxymorphinan-6-one (I), a new narcotic antagonist, analgesic agent, have been studied in the rat, dog, and man. Rats and dogs were given single 100- and 50-mg/kg po doses, respectively, of I-3H; human volunteers received single 10- to 30-mg doses of unlabeled I po. The compound appeared to be well absorbed in the three species. In rats the highest levels of radioactivity were in liver, adrenals, kidneys, spleen, and lungs. Excretion was primarily fecal in rats and dogs. In man about 50% of the dose appeared in the 24-hr urine. I was about 95% metabolized by each species. The major metabolites in rats resulted from 3- and/or 17-dealkylation. Metabolism in dogs was characterized primarily by 17-dealkylation. The major pathways of I metabolism in man were 17-dealkylation and 6-reduction. In the three species significant glucuronic acid conjugation of metabolites occurred.     

Disposition and metabolism of timiperone in the rat, dog, and monkey

The disposition and metabolism of timiperone (TP), a new butyrophenone antipsychotic, were studied in the rat, dog, and monkey given [14C]TP orally at different dose levels. [14C]TP was absorbed by the three species; the elimination of radioactivity from the blood was most rapid in the rat, and slowest in the dog. In the rat, blood and tissue concentrations of radioactivity were dose-dependent, and persisted after low and high doses. Tissue/blood ratios of radioactivity concentration in most of the rat tissues were much larger than 1.0, indicating that TP has a high affinity for the tissues. Approximately 19, 36, and 54% of the administered dose were excreted into dog, rat, and monkey urine, respectively, within 3 days, and the residue into the feces. [14C]TP was metabolized by N-dealkylation and the reduction of the butyrophenone sidechain to form 4-[4-(2,3-dihydro-2-thioxo-1H-benzimidazol-1-yl)-1-piperidinyl]-1-(4-fluorpheny l)-1-butanol (M-II), 2,3-dihydro-1-(4-piperidinyl)-2-thioxo-1H-benzimidazole (M-V), and N-(4-fluorophenylacetyl)glycine (M-b-l). Urinary major metabolites in all the species were M-V and M-b-l. Metabolite patterns in the rat brain indicated that unchanged TP accounted for the major part of total radioactivity. Similar patterns were obtained in rat and dog plasma, but not in monkey plasma.     

LC determination of YM466, a new factor Xa inhibitor,in rat and dog plasma

A specific method for the determination of YM466, a novel Factor Xa inhibitor, in rat and dog plasma was developed and validated. YM466 was extracted from plasma by solid-phase extraction and analyzed by UV-HPLC at an absorbance wavelength of 240 nm. The intra-day precision and accuracy ranged from 0.8 to 2.4% and 0.1 to 5.0% in rats, and from 1.6 to 2.4% and 0.0 to 4.1% in dogs, respectively. The lower limit of quantification was 10 ng/ml when 1 ml of plasma was used. No endogenous interference was observed in the plasma of rats and dogs.     

Disposition and metabolism of ( 3 H)pseudomorphine in the rat

[³H]pseudomorphine (³H-PM) was prepared by the oxidation of [³H]morphine. A method for the estimation of ³H-PM in biological materials was developed with a minimal sensitivity of 2.5 ng/ml of biologic material. Following the subcutaneous injection of ³H-PM (10 mg/kg as free base) in rats, the levels of ³H-PM in brain and spinal cord over a 2-hr period ranged between 4.6 to 17.9 ng/g and 24 to 76.5 ng/g, respectively. No detectable levels of ³H-PM were present at 4 hr in the CNS. Peak plasma levels occurred at 30 min (501 ng/ml) and then fell rapidly with no detectable amounts present at 4 hr. About 78.2 per cent of the administered ³H-PM was accounted for in the urine and feces after 48 hr. Conjugated pseudomorphine was not detected in biological material, and direct chromatography of urine provided evidence for the presence of only free ³H-PM. The existence of a polar metabolite, however, cannot be precluded. Studies on rat brain extracts following the administration of [³H]morphine (10 mg/kg as free base) provided no evidence for the formation of pseudomorphine as an oxidative metabolite of morphine in vivo.     

Effect of SMP-500, a novel acyl-CoA:cholesterol acyltransferase inhibitor,on serum cholesterol level and LDL cholesterol clearance in hamsters with induced hyperlipidemia

The effect of SMP-500, a novel acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, on serum cholesterol levels was investigated in hyperlipidemic hamsters whose condition had been preestablished by diet. SMP-500 reduced the total serum cholesterol level in a dose-dependent manner. SMP-500 also reduced the hepatic free cholesterol content and markedly reduced the esterified cholesterol content compared with the control group. Interestingly, SMP-500 at a dose of 30 mg/kg increased LDL clearance in vivo. As SMP-500 at this dose potently lowered the total serum cholesterol level, the increased LDL clearance was identified as another mechanism for the cholesterol-lowering effect of SMP-500. However, unlike HMG CoA reductase inhibitors, SMP-500 did not affect cholesterol biosynthesis in HepG2 cells. Therefore the etiology of the increased LDL clearance is not yet clear, but the reduced hepatic free cholesterol may play an important role in this process. These results suggest that the cholesterol-lowering effect of SMP-500 is due, not only to the inhibition of ACAT, but also to the increase in cholesterol clearance from the blood. This finding supports the therapeutic potential of SMP-500 for the treatment of human hypercholesterolemia.     

Acaterin, a novel inhibitor of acyl-CoA: cholesterol acyltransferase produced by Pseudomonas sp. A92.

Acaterin, a novel inhibitor of acyl-CoA: cholesterol acyltransferase (ACAT), was isolated from a culture broth of Pseudomonas sp. A92 by Diaion HP-20 column chromatography, solvent extraction and reverse phase HPLC. Spectroscopic analyses of the compound yielded 3-(1-hydroxyoctyl)-5-methyl-2(5H)-furanone as the proposed structure. In the presence of oxidized low density lipoprotein, acaterin inhibited the synthesis of cholesteryl ester in macrophage J774 by 50% at a concentration of 45 microM. Acaterin also inhibited ACAT activity in the rat liver microsomes by 50% at a concentration of 120 microM. Kinetic studies suggested that inhibition of ACAT by acaterin was noncompetitive with respect to oleoyl-CoA.     

Metabolism of the acyl-CoA:cholesterol acyltransferase inhibitor 2,2-dimethyl-N-(2,4,6-trimethoxyphenyl)dodecanamide in rat and monkey. Omega-/beta-oxidation pathway.

2,2-Dimethyl-N-(2,4,6-trimethoxyphenyl)dodecanamide (CI-976) is a newly developed hypocholesterolemic agent. In pharmacokinetic studies, CI-976 was found to have a much shorter elimination half-life in monkey (0.6 hr) compared to rat (8 hr). Radioactivity analysis of biological samples from rats and monkeys administered [14C]CI-976 either iv or orally showed CI-976 to be extensively metabolized to a single major common metabolite. This metabolite was isolated and its structure determined by GC/MS, LC/MS, and NMR spectroscopy as a 6-carbon chain-shortened carboxylic acid derivative, 5,5-dimethyl-6-oxo-6-[(2,4,6-trimethoxyphenyl)amino]-hexanoic acid. A potential pathway leading to this carboxylic acid derivative may involve initial omega-oxidation followed by beta-oxidation. A potential species difference in omega-/beta-oxidative biotransformation capabilities appears to exist.