Marmoset cytochrome P450 2J2 mainly expressed in small intestines and livers effectively metabolizes human P450 2J2 probe substrates, astemizole and terfenadine

Polymorphic cytochromes P450 in non-human primates

Cynomolgus macaques (Macaca fascicularis, an Old World monkey) are widely used in drug development because of their genetic and physiological similarities to humans, and this trend has continued with the use of common marmosets (Callithrix jacchus, a New World monkey). Information on the major drug-metabolizing cytochrome P450 (CYP, P450) enzymes of these primate species indicates that multiple forms of their P450 enzymes have generally similar substrate selectivities to those of human P450 enzymes; however, some differences in isoform, activity, and substrate specificity account for limited species differences in drug oxidative metabolism. This review provides information on the P450 enzymes of cynomolgus macaques and marmosets, including cDNA, tissue expression, substrate specificity, and genetic variants, along with age differences and induction. Typical examples of important P450s to be considered in drug metabolism studies include cynomolgus CYP2C19, which is expressed abundantly in liver and metabolizes numerous drugs. Moreover, genetic variants of cynomolgus CYP2C19 affect the individual pharmacokinetic data of drugs such as R-warfarin. These findings provide a foundation for understanding each P450 enzyme and the individual pharmacokinetic and toxicological results in cynomolgus macaques and marmosets as preclinical models. In addition, the effects of induction on some drug clearances mediated by P450 enzymes are also described. In summary, this review describes genetic and acquired individual differences in cynomolgus and marmoset P450 enzymes involved in drug oxidation that may be associated with pharmacological and/or toxicological effects.

Utility of Common Marmoset (Callithrix jacchus) Embryonic Stem Cells in Liver Disease Modeling, Tissue Engineering and Drug Metabolism

The incidence of liver disease is increasing significantly worldwide and, as a result, there is a pressing need to develop new technologies and applications for end-stage liver diseases. For many of them, orthotopic liver transplantation is the only viable therapeutic option. Stem cells that are capable of differentiating into all liver cell types and could closely mimic human liver disease are extremely valuable for disease modeling, tissue regeneration and repair, and for drug metabolism studies to develop novel therapeutic treatments. Despite the extensive research efforts, positive results from rodent models have not translated meaningfully into realistic preclinical models and therapies. The common marmoset Callithrix jacchus has emerged as a viable non-human primate model to study various human diseases because of its distinct features and close physiologic, genetic and metabolic similarities to humans. C. jacchus embryonic stem cells (cjESC) and recently generated cjESC-derived hepatocyte-like cells (cjESC-HLCs) could fill the gaps in disease modeling, liver regeneration and metabolic studies. They are extremely useful for cell therapy to regenerate and repair damaged liver tissues in vivo as they could efficiently engraft into the liver parenchyma. For in vitro studies, they would be advantageous for drug design and metabolism in developing novel drugs and cell-based therapies. Specifically, they express both phase I and II metabolic enzymes that share similar substrate specificities, inhibition and induction characteristics, and drug metabolism as their human counterparts. In addition, cjESCs and cjESC-HLCs are advantageous for investigations on emerging research areas, including blastocyst complementation to generate entire livers, and bioengineering of discarded livers to regenerate whole livers for transplantation.

The marmoset cytochrome P450 superfamily: Sequence/phylogenetic analyses, genomic structure, and catalytic function

The common marmoset (Callithrix jacchus) is a New World monkey that has attracted much attention as a potentially useful primate model for preclinical testing. A total of 36 marmoset cytochrome P450 (P450) isoforms in the P450 1-51 subfamilies have been identified and characterized by the application of genome analysis and molecular functional characterization. In this mini-review, we provide an overview of the genomic structures, sequence identities, and substrate selectivities of marmoset P450s compared with those of human P450s. Based on the sequence identity, phylogeny, and genomic organization of marmoset P450s, orthologous relationships were established between human and marmoset P450s. Twenty-four members of the marmoset P450 1A, 2A, 2B, 2C, 2D, 2E, 3A, 4A, and 4F subfamilies shared high degrees of homology in terms of cDNA (>89%) and amino acid sequences (>85%) with the corresponding human P450s; P450 2C76 was among the exceptions. Phylogenetic analysis using amino acid sequences revealed that marmoset P450s in the P450 1-51 families were located in the same clades as their human and macaque P450 homologs. This finding underlines the evolutionary closeness of marmoset P450s to their human and macaque homologs. Most marmoset P450 1-4 enzymes catalyzed the typical drug-metabolizing reactions of the corresponding human P450 homologs, except for some differences of P450 2A6 and 2B6. Consequently, it appears that the substrate specificities of enzymes in the P450 1-4 families are generally similar in marmosets and humans. The information presented here supports a better understanding of the functional characteristics of marmoset P450s and their similarities and differences with human P450s. It is hoped that this mini-review will facilitate the successful use of marmosets as primate models in drug metabolism and pharmacokinetic studies.

Survey of Drug Oxidation Activities in Hepatic and Intestinal Microsomes of Individual Common Marmosets, a New Nonhuman Primate Animal Model

Background:

Common marmosets (Callithrix jacchus) are potentially useful non-human primate models for preclinical studies. Information for major drug-metabolizing cyto-chrome P450 (P450) enzymes is now available that supports the use of this primate species as an animal model for drug development. Here, we collect and provide an overview of infor-mation on the activities of common marmoset hepatic and intestinal microsomes with respect to 28 typical human P450 probe oxidations.

Results:

Marmoset P450 2D6/8-dependent R-metoprolol O-demethylation activities in hepatic microsomes were significantly correlated with those of midazolam 1′- and 4-hydroxylations, testosterone 6β-hydroxylation, and progesterone 6β-hydroxylation, which are probe reactions for marmoset P450 3A4/5/90. In marmosets, the oxidation activities of hepatic microsomes and intestinal microsomes were roughly comparable for midazolam and terfenadine. Overall, multiple forms of marmoset P450 enzymes in livers and intestines had generally similar sub-strate recognition functionalities to those of human and/or cynomolgus monkey P450 enzymes.

Conclusion:

The marmoset could be a model animal for humans with respect to the first-pass extraction of terfenadine and related substrates. These findings provide a foundation for un-derstanding individual pharmacokinetic and toxicological results in nonhuman primates as pre-clinical models and will help to further support understanding of the molecular mechanisms of human P450 function.

Terfenadine t-butyl hydroxylation catalyzed by human and marmoset cytochrome P450 3A and 4F enzymes in livers and small intestines

1. Roles of human cytochrome P450 (P450) 3A4 in oxidation of an antihistaminic drug terfenadine have been previously investigated in association with terfenadine-ketoconazole interaction. Several antihistamine drugs have been recently identified as substrates for multiple P450 enzymes. In this study, overall roles of P450 3A4, 2J2, and 4F12 enzymes in terfenadine t-butyl hydroxylation were investigated in small intestines and livers from humans, marmosets, and/or cynomolgus monkeys. 2. Human liver microsomes and liver and small intestine microsomes from marmosets and cynomolgus monkeys effectively mediated terfenadine t-butyl hydroxylation. Ketoconazole and N-hydroxy-N'-(4-butyl-2-methylphenyl)-formamidine (a P450 4A/F inhibitor) almost completely and moderately inhibited these activities, respectively, in human liver microsomes; however, these chemicals did not show substantially suppression in marmoset liver. Anti-human P450 3A and 4F antibodies showed the roughly supportive inhibitory effects. 3. Recombinant P450 3A4/90 and 4F12 showed high terfenadine t-butyl hydroxylation activities with substrate inhibition constants of 84-144 μM (under 26-76 μM of K_m values), in similar manners to liver and intestine microsomes. 4. These results suggest that human and marmoset P450 3A4/90 and 4F12 in livers or small intestines played important roles in terfenadine t-butyl hydroxylation. Marmosets could be a model for humans during first pass extraction of terfenadine and related substrates.

Unequivocal evidence supporting the segregated flow intestinal model that discriminates intestine versus liver first-pass removal with PBPK modeling

Merits of the segregated flow model (SFM), highlighting the intestine as inert serosa and active enterocyte regions, with a smaller fractional (f_Q < 0.3) intestinal flow (Q_I ) perfusing the enterocyte region, are described. Less drug in the circulation reaches the enterocytes due to the lower flow (f_Q Q_I ) in comparison with drug administered into the gut lumen, fostering the idea of route-dependent intestinal removal. The SFM has been found superior to the traditional model (TM), which views the serosa and enterocytes totally as a well-mixed tissue perfused by 100% of the intestinal flow, Q_I . The SFM model is able to explain the lower extents of intestinal metabolism of enalapril, morphine and midazolam with i.v. vs. p.o. dosing. For morphine, the urine/bile ratio of the metabolite, morphine glucuronide MGurineMGbile for p.o. was 2.6× that of i.v. This was due to the higher proportion of intestinally formed morphine glucuronide, appearing more in urine than in bile due to its low permeability and greater extent of intestinal formation with p.o. administration. By contrast, the TM predicted the same MGurineMGbile for p.o. vs. i.v. The TM predicted that the contributions of the intestine:liver to first-pass removal were 46%:54% for both p.o. and i.v. The SFM predicted same 46%:54% (intestine:liver) for p.o., but 9%:91% for i.v. By contrast, the kinetics of codeine, the precursor of morphine, was described equally well by the SFM- and TM-PBPK models, a trend suggesting that intestinal metabolism of codeine is negligible. Fits to these PBPK models further provide insightful information towards metabolite formation: available fractions and the fractions of hepatic and total clearances that form the metabolite in question. The SFM-PBPK model is useful to identify not only the presence of intestinal metabolism but the contributions of the intestine and liver for metabolite formation. Copyright © 2016 John Wiley & Sons, Ltd.

Marmoset cytochrome P450 4A11, a novel arachidonic acid and lauric acid ω-hydroxylase expressed in liver and kidney tissues

1. A cDNA encoding novel cytochrome P450 (P450) 4A enzyme was cloned from marmoset livers by reverse transcription (RT)-polymerase chain reaction (PCR) based on the marmoset genome sequences. The amino acid sequence deduced from P450 4A11 cDNA contained consensus sequences of six substrate recognition sites and one heme-binding domain. 2. Marmoset P450 4A11, highly identical (85-88%) to cynomolgus monkey and human P450 4A enzymes, was grouped into the same cluster as cynomolgus monkey and human P450 4A enzymes by phylogenetic analysis. 3. The tissue distribution analyses by real-time RT PCR and immunoblotting demonstrated that marmoset P450 4A11 mRNA and proteins were expressed in kidneys and livers. Marmoset P450 4A11 enzyme heterologously expressed in Escherichia coli preferentially catalyzed the ω-hydroxylation of arachidonic acid and lauric acid, similar to cynomolgus monkey and human P450 4A11 enzymes. However, lauric acid ω-hydroxylation activity of marmoset P450 4A11 was low compared with those of marmoset liver microsomes. 4. These results indicated that novel marmoset P450 4A11 was also a fatty acid ω-hydroxylase expressed in kidneys and livers, with the same regioselectivity (at ω-position of fatty acid) as cynomolgus monkey and human P450 4A enzymes.