Integration of Physiologically-Based Pharmacokinetic Modeling into Early Clinical Development: An Investigation of the Pharmacokinetic Nonlinearity

BMS-911543, a promising anticancer agent, exhibited time-dependent and dose-dependent nonlinear pharmacokinetics (PKs) in its first-in-human (FIH) study. Initial physiologically based pharmacokinetic (PBPK) modeling efforts using CYP1A2-mediated clearance kinetics were unsuccessful; however, further model analysis revealed that CYP1A2 time-dependent inhibition (TDI) and perhaps other factors could be keys to the nonlinearity. Subsequent experiments in human liver microsomes showed that the compound was a time-dependent inhibitor of CYP1A2 and were used to determine the enzyme inactivation parameter values. In addition, a rat tissue distribution study was conducted and human plasma samples were profiled to support the refinement of the PBPK model. It was concluded that the interplay between four BMS-911543 properties, namely, low solubility, saturation of the metabolizing enzyme CYP1A2, CYP1A2 TDI, and CYP1A2 induction likely resulted in the time-dependent and dose-dependent nonlinear PKs. The methodology of PBPK model-guided unmasking of compound properties can serve as a general practice for mechanistic understanding of a new compound's disposition.

Evaluation of mRNA expression of human drug-metabolizing enzymes and transporters in chimeric mouse with humanized liver

The hepatic mRNA expression of human drug-metabolizing enzymes and transporters in chimeric mise with almost-completely humanized liver (replacement index: 71-89%) was investigated. The mRNAs of 58 human phase I enzymes, 26 human phase II enzymes, 23 human transporters, and five mouse Cyps were measured in the chimeric mice with humanized liver generated using hepatocytes from a Japanese donor. The mRNA expression of 52 human phase I enzymes, which includes 20 human CYPs, 26 human phase II enzymes and 21 human transporters was ascertained in the chimeric mouse liver. Among them, the expression of the target mRNAs vital for liver function such as the metabolism and secretion of endogenous compounds appeared to be maintained. The central value for the expression ratio in all target genes in chimeric mouse liver to the donor liver was 0.46, which was lower than the substitution rate of chimeric mouse liver by donor liver. The ratio of mouse Cyp mRNA expression of chimeric mouse liver to that of control mouse liver was 0.19 or less, except for that of Cyp2b10. There were good correlations between the mRNA expression levels of human hepatic albumin gene, the values of the rate of replacement of mouse liver by human liver, and the human blood albumin concentration in the chimeric mice. The chimeric mice with humanized liver may be a useful tool for the evaluation of drug-drug interactions such as the inhibition and induction of drug-metabolizing enzymes and transporters.

Identification and clearance involved in the formation of glucuronides of RT-3003, a new peripheral blood flow enhancer, and its metabolite in rats

Glucuronides of RT-3003 and its metabolite (9-OH-RT-3003), which was hydroxylated at the 9 position on the benzene ring, were separated by HPLC and identified by liquid chromatography (LC)/MS/MS and NMR. The conjugation sites of these glucuronides were determined by nuclear Overhauser effects (NOE) irradiation; RT-3003 was conjugated at an alcoholic hydroxyl group of the hydroxymethyl moiety, and 9-OH-RT-3003 at a phenolic hydroxyl group on a benzene ring and at an alcoholic hydroxyl group of a hydroxymethyl moiety. On a reversed-phase HPLC of 9-OH-RT-3003, alcoholic glucuronide was eluted later than phenolic glucuronide, indicating the high hydrophobicity of alcoholic glucuronide. Clearance for the glucuronidation (ClG) of RT-3003 was lower than the summation of ClG for two types of glucuronidation of 9-OH-RT-3003. ClG of 9-OH-RT-3003 was high in phenolic glucuronide. The activity of UDP-glucuronyltransferase (UDPGT) for RT-3003 was 9.63 times that for 9-OH-RT-3003, and the activity ratio of the two types of glucuronidation of 9-OH-RT-3003 was similar to the ratio of the corresponding ClG. The difference between ClG and UDPGT activity is discussed in association with clearance for the hydroxylation and interaction of substrates with UDPGT.

Metabolic pathways and pharmacokinetics of BOF-4272, a sulfoxide-containing drug, in the dog: in vivo and in vitro studies

BOF-4272, (+/-)-8-(3-methoxy-4- phenylsulfinylphenyl)pyrazolo[1,5-a]-1,3,5-triazine-4(1H)-one, is a new drug intended for the treatment of hyperuricemia. This report describes the detailed metabolic pathways of BOF-4272 in the dog. The metabolic pathways were investigated using the metabolites found in plasma, urine, and feces after intravenous or oral administration of BOF-4272, as well as the metabolites found in the liver S9 incubation mixture after the addition of BOF-4272 or BOF-4269. BOF-4269 (the sulfide metabolite of BOF-4272) was the only metabolite detected in plasma and feces after the intravenous or oral administration of BOF-4272. BOF-4269 was detected in dog plasma after a lag time following the oral administration of BOF-4272, and the Cmax and AUC0-t of BOF-4269 were higher in fed dogs than in fasted dogs after the oral administration of BOF-4272. A small amount of BOF-4269 was detected in dog plasma immediately after the intravenous administration of BOF-4272. Only BOF-4276 (the sulfone metabolite of BOF-4272) was detected in the S9 incubation mixture after the addition of BOF-4272. Mainly BOF-4272 was detected and small amounts of BOF-4276 and M-1 (the hydroxy metabolite of BOF-4269) were detected in the S9 incubation mixture after the addition of BOF-4269. These findings suggest that BOF-4272 is mainly metabolized to BOF-4269 by the intestinal flora in dogs, whereas little of this drug is metabolized to BOF-4269 in the dog liver. In conclusion, this work has allowed us to formulate the proposed metabolic pathways of BOF-4272 in the dog.

Key fragments for identification of positional isomer pair in glucuronides from the hydroxylated metabolites of RT-3003 (Vintoperol) by liquid chromatography/electrospray ionization mass spectrometry

The mass spectral properties of glucuronides of the 9- and 10-hydroxylated metabolites of RT-3003 (Vintoperol; (-)-1beta-ethyl-1alpha-hydroxymethyl-1,2,3,4,6,7, 12balpha-octahydroindolo[2,3-a]quinolizine), which were fractionated by high-performance liquid chromatography with fluorescence detection, were investigated using the positive ion electrospray ionization mode. These glucuronides showed predominantly the protonated molecular ion ([M + H](+) ion), and the [M + H](+) ion provided a characteristic product ion spectrum in which abundant ions were obtained at m/z 301, 160 and 142. The first ion, corresponding to the [aglycone + H](+) ion, was produced by neutral loss of the glucuronic acid moiety from the [M + H](+) ion. The product ion spectrum of the [M + H](+) ion of hydroxy-RT-3003 revealed a number of ions common to the glucuronide spectra, suggesting that other two ions observed most likely represent fragmentation of hydroxy-RT-3003. In turn, these glucuronides were positional isomers with respect to the binding site of glucuronic acid. The structures of the isomer pairs were discriminated by the presence of the ion of m/z 318 or 336 in the product ion spectrum. These ions were produced by fission of the C-ring, the same as for the formation of the ions of m/z 160 and 142, as were observed in the product ion spectrum from the [M + H](+) ion of hydroxy-RT-3003. For the formation of these ions, an unusual fragmentation process was proposed, and these ion structures were supported by evidence from the accurate mass measurement data. Additionally, in the sulfates of hydroxylated metabolites, a similar product ion corresponding to the ion of m/z 336 found in the phenolic glucuronides was observed, and was applied for identification of the sulfate metabolites.

Synthesis and hypolipidemic activities of novel 2-[4-[diethoxyphosphoryl)methyl]phenyl]quinazolines and 4(3H)-quinazolinones

The novel compound NO-1886, 4-[(diethoxyphosphoryl)methyl]-N-(4-bromo-2-cyanophenyl)-ben zamide, is a hypolipidemic agent, which appears to increase lipoprotein lipase activity in rats. Various analogs of NO-1886 were synthesized to study the structure-activity relationship of this hypolipidemic drug. A novel series of quinazolines and 4(3H)-quinazolinones were prepared by cyclization of NO-1886 derivatives. Derivatives bearing a 4-[(diethoxyphosphoryl)-methyl]phenyl] group at the 2-position were found to lower triglyceride and total cholesterol levels. In accord with the decrease in log P*, quinazolines and 4(3H)-quinazolinones showed good absorption and hypolipidemic activity. When the quinazolinone ring system is substituted at positions 6 and 7 with methoxy groups, increased hypolipidemic activity was observed. The highest hypolipidemic activity was observed when the 3-position was substituted by a methyl or benzyl group.