Influences of cytochrome b5 expression and its genetic variant on the activity of CYP2C9, CYP2C19 and CYP3A4

Yoo, Sung‐Eun; Yi, Myeongjin; Kim, Woo-Young; Cho, Sun-Ah; Lee, Sang Seop; Lee, Su-Jun; Shin, Jae‐Gook

doi:10.1016/j.dmpk.2019.03.001

Cited by 8 publications

(6 citation statements)

References 35 publications

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“…Other studies also reported variability in cyt b 5 protein and mRNA [49,50]. Correlation between cyt b 5 and CYP3A4 activity was found [48]. Further, single nucleotide polymorphisms in cyt b 5 were associated with very low activity and protein expression [51].…”

Section: Discussionmentioning

confidence: 86%

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Identification of Enzymes Oxidizing the Tyrosine Kinase Inhibitor Cabozantinib: Cabozantinib Is Predominantly Oxidized by CYP3A4 and Its Oxidation Is Stimulated by cyt b5 Activity

et al. 2020

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Herein, the in vitro metabolism of tyrosine kinase inhibitor cabozantinib, the drug used for the treatment of metastatic medullary thyroid cancer and advanced renal cell carcinoma, was studied using hepatic microsomal samples of different human donors, human recombinant cytochromes P450 (CYPs), flavin-containing mono-oxygenases (FMOs) and aldehyde oxidase. After incubation with human microsomes, three metabolites, namely cabozantinib N-oxide, desmethyl cabozantinib and monohydroxy cabozantinib, were detected. Significant correlations were found between CYP3A4 activity and generation of all metabolites. The privileged role of CYP3A4 was further confirmed by examining the effect of CYP inhibitors and by human recombinant enzymes. Only four of all tested human recombinant cytochrome P450 were able to oxidize cabozantinib, and CYP3A4 exhibited the most efficient activity. Importantly, cytochrome b5 (cyt b5) stimulates the CYP3A4-catalyzed formation of cabozantinib metabolites. In addition, cyt b5 also stimulates the activity of CYP3A5, whereas two other enzymes, CYP1A1 and 1B1, were not affected by cyt b5. Since CYP3A4 exhibits high expression in the human liver and was found to be the most efficient enzyme in cabozantinib oxidation, we examined the kinetics of this oxidation. The present study provides substantial insights into the metabolism of cabozantinib and brings novel findings related to cabozantinib pharmacokinetics towards possible utilization in personalized medicine.

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Section: Discussionmentioning

confidence: 86%

“…Protein and mRNA contents show variations with 11-and 6-fold range, respectively. However, the content of cyt b5 mRNA does not strongly correlate with that of cyt b 5 protein [48]. Other studies also reported variability in cyt b 5 protein and mRNA [49,50].…”

Section: Discussionmentioning

confidence: 89%

Identification of Enzymes Oxidizing the Tyrosine Kinase Inhibitor Cabozantinib: Cabozantinib Is Predominantly Oxidized by CYP3A4 and Its Oxidation Is Stimulated by cyt b5 Activity

et al. 2020

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“…Possible MIC formation was measured between ritonavir and insect cell microsomes containing recombinant CYP3A4 supplemented with Cyt b 5 (CYP3A4(+ b 5 )), recombinant CYP3A5 (not supplemented), or human liver microsomes (HLMs), all co-incubated with NADPH to regenerate (added) cytochrome P450 reductase (CPR). It is worth noting that Cyt b 5 is naturally present in the in vivo cellular environment of CYP3A4, and it has been shown that the absence of Cyt b 5 could affect the efficiency of CYP3A4 functioning [ 17 , 18 ]. Based on the absorbance shift, Ernest et al observed apparent MIC formation of up to ~62% of the total CYP3A with CYP3A4(+ b 5 ) at 10 µM ritonavir, which increased with time over 60 min of incubation.…”

Section: Principal Mechanisms Of Irreversible Inhibition Of Cyp Enzym...mentioning

confidence: 99%

“…The monooxygenase reactions mediated by CYP3A4 and CYP3A5 are dependent on the interactions of the substrates with the heme iron atom. Generally speaking, these CYPs modify their substrates by using electrons received from NADPH through cytochrome P450 oxidoreductase (CPR) and/or cytochrome b5 (Cytb5) to reduce O 2 to H 2 O and simultaneously generate an (often) hydroxylated or otherwise modified substrate [ 16 , 17 , 18 ]. The initial binding of substrates and (most) inhibitors to CYPs displaces a water molecule coordinated to the heme iron and alters the absorption spectrum of the heme group.…”

Section: Introductionmentioning

confidence: 99%

The Mechanism-Based Inactivation of CYP3A4 by Ritonavir: What Mechanism?

Loos

Beijnen

Schinkel

2022

IJMS

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Ritonavir is the most potent cytochrome P450 (CYP) 3A4 inhibitor in clinical use and is often applied as a booster for drugs with low oral bioavailability due to CYP3A4-mediated biotransformation, as in the treatment of HIV (e.g., lopinavir/ritonavir) and more recently COVID-19 (Paxlovid or nirmatrelvir/ritonavir). Despite its clinical importance, the exact mechanism of ritonavir-mediated CYP3A4 inactivation is still not fully understood. Nonetheless, ritonavir is clearly a potent mechanism-based inactivator, which irreversibly blocks CYP3A4. Here, we discuss four fundamentally different mechanisms proposed for this irreversible inactivation/inhibition, namely the (I) formation of a metabolic-intermediate complex (MIC), tightly coordinating to the heme group; (II) strong ligation of unmodified ritonavir to the heme iron; (III) heme destruction; and (IV) covalent attachment of a reactive ritonavir intermediate to the CYP3A4 apoprotein. Ritonavir further appears to inactivate CYP3A4 and CYP3A5 with similar potency, which is important since ritonavir is applied in patients of all ethnicities. Although it is currently not possible to conclude what the primary mechanism of action in vivo is, it is unlikely that any of the proposed mechanisms are fundamentally wrong. We, therefore, propose that ritonavir markedly inactivates CYP3A through a mixed set of mechanisms. This functional redundancy may well contribute to its overall inhibitory efficacy.

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“…It is likely that standardizing in vitro experimental conditions for heterologous expression of CYP2B6.1 and its mutants when determining their kinetic parameters would provide the necessary framework for cross-study comparisons. It may be possible to optimize the CYP2B6 expression system, P450 oxidoreductase (POR):P450 ratio (El-Serafi et al, 2015;Wang et al, 2018;Wang et al, 2020b), and presence/absence/concentration of cytochrome b5 (cyt b5) (Shebley and Hollenberg, 2007;Bumpus and Hollenberg, 2008;Calinski et al, 2015;Yoo et al, 2019) for accessibility, affordability, and most importantly, experimental accuracy and precision for labs in the field to utilize.…”

Section: In Vitro Challenges With Cyp2b6mentioning

confidence: 99%

Multidisciplinary Insights into the Structure–Function Relationship of the CYP2B6 Active Site

Angle

Cox

2022

Drug Metab Dispos

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Influences of cytochrome b5 expression and its genetic variant on the activity of CYP2C9, CYP2C19 and CYP3A4

Cited by 8 publications

References 35 publications

Identification of Enzymes Oxidizing the Tyrosine Kinase Inhibitor Cabozantinib: Cabozantinib Is Predominantly Oxidized by CYP3A4 and Its Oxidation Is Stimulated by cyt b5 Activity

Identification of Enzymes Oxidizing the Tyrosine Kinase Inhibitor Cabozantinib: Cabozantinib Is Predominantly Oxidized by CYP3A4 and Its Oxidation Is Stimulated by cyt b5 Activity

The Mechanism-Based Inactivation of CYP3A4 by Ritonavir: What Mechanism?

Multidisciplinary Insights into the Structure–Function Relationship of the CYP2B6 Active Site

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