Significance of the minor cytochrome P450 3A isoforms

Major Genetic Drivers of Statin Treatment Response in African Populations and Pharmacogenetics of Dyslipidemia Through a One Health Lens

A One Health lens is increasingly significant to address the intertwined challenges in planetary health concerned with the health of humans, nonhuman animals, plants, and ecosystems. A One Health approach can benefit the public health systems in Africa that are overburdened by noncommunicable, infectious, and environmental diseases. Notably, the COVID-19 pandemic revealed the previously overlooked two-fold importance of pharmacogenetics (PGx), for individually tailored treatment of noncommunicable diseases and environmental pathogens. For example, dyslipidemia, a common cardiometabolic risk factor, has been identified as an independent COVID-19 severity risk factor. Observational data suggest that patients with COVID-19 infection receiving lipid-lowering therapy may have better outcomes. However, among African patients, the response to these drugs varies from patient to patient, pointing to the possible contribution of genetic variation in important pharmacogenes. The PGx of lipid-lowering therapies may underlie differences in treatment responses observed among dyslipidemia patients as well as patients comorbid with COVID-19 and dyslipidemia. Genetic variations in APOE, ABCB1, CETP, CYP2C9, CYP3A4, CYP3A5, HMGCR, LDLR, NPC1L1, and SLCO1B1 genes affect the pharmacogenomics of statins, and they have individually been linked to differential responses to dyslipidemia and COVID-19 treatment. African populations are underrepresented in PGx research. This leads to poor accounting of additional diverse genetic variants that could be important in understanding interindividual and between-population variations in therapeutic responses to dyslipidemia and COVID-19. This expert review examines and synthesizes the salient and priority PGx variations, as seen through a One Health lens in Africa, to improve and inform personalized medicine in both dyslipidemia and COVID-19.

Recurrent high creatine kinase levels under clozapine treatment - a case report assessing a suspected adverse drug reaction

Suspected adverse drug reactions (ADRs) during treatment with clozapine often prompt therapeutic drug monitoring (TDM) in clinical practice. Currently, there is no official recommendation for pharmacogenetic (PGx) testing in the context of clozapine therapy. In this case report, we demonstrate and discuss the challenges of interpreting PGx and TDM results highlighting the possibilities and limitations of both analytical methods. A 36-year-old male patient with catatonic schizophrenia was treated with clozapine. He experienced multiple hospitalizations due to elevated creatine kinase (CK) levels (up to 9000 U/L, reference range: 30-200 U/L). With no other medical explanation found, physicians suspected clozapine-induced ADRs. However, plasma levels of clozapine were consistently low or subtherapeutic upon admission, prompting us to conduct a PGx analysis and retrospectively review the patient's TDM data, progress notes, and discharge reports. We investigated two possible hypotheses to explain the symptoms despite low clozapine plasma levels: Hypothesis i. suggested the formation and accumulation of a reactive intermediate metabolite due to increased activity in cytochrome P450 3A5 and reduced activity in glutathione S-transferases 1, leading to myotoxicity. Hypothesis ii. proposed under-treatment with clozapine, resulting in ineffective clozapine levels, leading to a rebound effect with increased catatonic symptoms and CK levels. After considering both data sources (PGx and TDM), hypothesis ii. appeared more plausible. By comprehensively assessing all available TDM measurements and examining them in temporal correlation with the drug dose and clinical symptoms, we observed that CK levels normalized when clozapine plasma levels were raised to the therapeutic range. This was achieved through hospitalization and closely monitored clozapine intake. Therefore, we concluded that the symptoms were not an ADR due to altered clozapine metabolism but rather the result of under-treatment. Interpreting TDM and PGx results requires caution. Relying solely on isolated PGx or single TDM values can result in misinterpretation of drug reactions. We recommend considering the comprehensive patient history, including treatment, dosages, laboratory values, clinic visits, and medication adherence.

DeepP450: Predicting Human P450 Activities of Small Molecules by Integrating Pretrained Protein Language Model and Molecular Representation

Cytochrome P450 enzymes (CYPs) play a crucial role in Phase I drug metabolism in the human body, and CYP activity toward compounds can significantly affect druggability, making early prediction of CYP activity and substrate identification essential for therapeutic development. Here, we established a deep learning model for assessing potential CYP substrates, DeepP450, by fine-tuning protein and molecule pretrained models through feature integration with cross-attention and self-attention layers. This model exhibited high prediction accuracy (0.92) on the test set, with area under the receiver operating characteristic curve (AUROC) values ranging from 0.89 to 0.98 in substrate/nonsubstrate predictions across the nine major human CYPs, surpassing current benchmarks for CYP activity prediction. Notably, DeepP450 uses only one model to predict substrates/nonsubstrates for any of the nine CYPs and exhibits certain generalizability on novel compounds and different categories of human CYPs, which could greatly facilitate early stage drug design by avoiding CYP-reactive compounds.

Proton-Pump Inhibitors in Eosinophilic Esophagitis: A Review Focused on the Role of Pharmacogenetics

Proton-pump inhibitors (PPIs) are the most administered first-line treatment for eosinophilic esophagitis (EoE). However, only around half of EoE patients respond histologically to a double dosage of PPI. In addition, 70% of responders maintain EoE in remission after tapering the PPI dose. In order to avoid endoscopy with biopsies-the only accurate method of assessing PPI response-efforts have been made to identify PPI responder patients. The clinical or endoscopic features and biomarkers evaluated so far, however, have not proven to be sufficient in predicting PPI response. Although new approaches based on omics technologies have uncovered promising biomarkers, the specialized and complex procedures required are difficult to implement in clinical settings. Alternatively, PPI pharmacogenetics based on identifying variations in CYP2C19 and STAT6 genes have shown promising results in EoE, and could easily be performed in most laboratories. Other genetic variations have also been associated with PPI response and may explain those cases not related to CYP2C19 or STAT6. Here, we provide an overview of PPI treatment in EoE and evidence of how genetic variations in CYP2C19 and other genes could affect PPI effectiveness, and also discuss studies evaluating the role of pharmacogenetics in predicting PPI response in patients with EoE.

Characterization of CYP3A5 Selective Inhibitors for Reaction Phenotyping of Drug Candidates

CYP3A is one of the most important classes of enzymes and is involved in the metabolism of over 70% drugs. While several selective CYP3A4 inhibitors have been identified, the search for a selective CYP3A5 inhibitor has turned out to be rather challenging. Recently, several selective CYP3A5 inhibitors have been identified through high-throughput screening of ~ 11,000 compounds and hit expansion using human recombinant enzymes. We set forth to characterize the three most selective CYP3A5 inhibitors in a more physiologically relevant system of human liver microsomes to understand if these inhibitors can be used for reaction phenotyping studies in drug discovery settings. Gomisin A and T-5 were used as selective substrate reactions for CYP3A4 and CYP3A5 to determine IC50 values of the two enzymes. The results showed that clobetasol propionate and loteprednol etabonate were potent and selective CYP3A5 reversible inhibitors with selectivity of 24-fold against CYP3A4 and 39-fold or more against the other major CYPs. The selectivity of difluprednate in HLM is much weaker than that in the recombinant enzymes due to hydrolysis of the acetate group in HLM. Based on the selectivity data, loteprednol etabonate can be utilized as an orthogonal approach, when experimental fraction metabolized of CYP3A5 is greater than 0.5, to understand CYP3A5 contribution to drug metabolism and its clinical significance. Future endeavors to identify even more selective CYP3A5 inhibitors are warranted to enable accurate determination of CYP3A5 contribution to metabolism versus CYP3A4.

Hydrocodone, Oxycodone, and Morphine Metabolism and Drug-Drug Interactions

Awareness of drug interactions involving opioids is critical for patient treatment as they are common therapeutics used in numerous care settings, including both chronic and disease-related pain. Not only do opioids have narrow therapeutic indexes and are extensively used, but they have the potential to cause severe toxicity. Opioids are the classical pain treatment for patients who suffer from moderate to severe pain. More importantly, opioids are often prescribed in combination with multiple other drugs, especially in patient populations who typically are prescribed a large drug regimen. This review focuses on the current knowledge of common opioid drug-drug interactions (DDIs), focusing specifically on hydrocodone, oxycodone, and morphine DDIs. The DDIs covered in this review include pharmacokinetic DDI arising from enzyme inhibition or induction, primarily due to inhibition of cytochrome p450 enzymes (CYPs). However, opioids such as morphine are metabolized by uridine-5'-diphosphoglucuronosyltransferases (UGTs), principally UGT2B7, and glucuronidation is another important pathway for opioid-drug interactions. This review also covers several pharmacodynamic DDI studies as well as the basics of CYP and UGT metabolism, including detailed opioid metabolism and the potential involvement of metabolizing enzyme gene variation in DDI. Based upon the current literature, further studies are needed to fully investigate and describe the DDI potential with opioids in pain and related disease settings to improve clinical outcomes for patients. SIGNIFICANCE STATEMENT: A review of the literature focusing on drug-drug interactions involving opioids is important because they can be toxic and potentially lethal, occurring through pharmacodynamic interactions as well as pharmacokinetic interactions occurring through inhibition or induction of drug metabolism.

Pharmacokinetic-Pharmacodynamic Modeling of Midazolam in Pediatric Surgery

Midazolam (MDZ) is used for sedation in surgical procedures; its clinical effect is related to its receptor affinity and the dose administered. Therefore, a pharmacokinetic-pharmacodynamic (PK-PD) population model of MDZ in pediatric patients undergoing minor surgery is proposed. A descriptive, observational, prospective, and longitudinal, study that included patients of both sexes, aged 2-17 years, ASA I/II, who received MDZ in IV doses (0.05 mg/kg) before surgery. Three blood samples were randomly taken between 5-120 min; both sedation by the Bispectral Index Scale (BIS) and its adverse effects were recorded. The PK-PD relationship was determined using a nonlinear mixed-effects, bicompartmental first-order elimination model using Monolix Suite™. Concentrations and the BIS were fitted to the sigmoid Emax PK-PD population and sigmoid Emax PK/PD indirect binding models, obtaining drug concentrations at the effect site (biophase). The relationship of concentrations and BIS showed a clockwise hysteresis loop, probably indicating time-dependent protein binding. Of note, at half the dose used in pediatric patients, adequate sedation without adverse effects was demonstrated. Further PK-PD studies are needed to optimize dosing schedules and avoid overdosing or possible adverse effects.

Differences of Atomic-Level Interactions between Midazolam and Two CYP Isoforms 3A4 and 3A5

CYP 3A4 and CYP 3A5 are two important members of the human cytochrome P450 family. Although their overall structures are similar, the local structures of the active site are different, which directly leads to obvious individual differences in drug metabolic efficacy and toxicity. In this work, midazolam (MDZ) was selected as the probe substrate, and its interaction with two proteins, CYP 3A4 and CYP 3A5, was studied by molecular dynamics simulation (MD) along with the calculation of the binding free energy. The results show that two protein-substrate complexes have some similarities in enzyme-substrate binding; that is, in both complexes, Ser119 forms a high occupancy hydrogen bond with MDZ, which plays a key role in the stability of the interaction between MDZ and the enzymes. However, the complex formed by CYP 3A4 and MDZ is more stable, which may be attributed to the sandwich structure formed by the fluorophenyl group of the substrate with Leu216 and Leu482. Our study interprets the binding differences between two isoform-substrate complexes and reveals a structure-function relationship from the atomic perspective, which is expected to provide a theoretical basis for accurately measuring the effectiveness and toxicity of drugs for individuals in the era of precision medicine.

Identification of Drugs Acting as Perpetrators in Common Drug Interactions in a Cohort of Geriatric Patients from Southern Italy and Analysis of the Gene Polymorphisms That Affect Their Interacting Potential

BACKGROUND

Pharmacogenomic factors affect the susceptibility to drug-drug interactions (DDI). We identified drug interaction perpetrators among the drugs prescribed to a cohort of 290 older adults and analysed the prevalence of gene polymorphisms that can increase their interacting potential. We also pinpointed clinical decision support systems (CDSSs) that incorporate pharmacogenomic factors in DDI risk evaluation.

METHODS

Perpetrator drugs were identified using the Drug Interactions Flockhart Table, the DRUGBANK website, and the Mayo Clinic Pharmacogenomics Association Table. Allelic variants affecting their activity were identified with the PharmVar, PharmGKB, dbSNP, ensembl and 1000 genome databases.

RESULTS

Amiodarone, amlodipine, atorvastatin, digoxin, esomperazole, omeprazole, pantoprazole, simvastatin and rosuvastatin were perpetrator drugs prescribed to >5% of our patients. Few allelic variants affecting their perpetrator activity showed a prevalence >2% in the European population: CYP3A4/5*22, *1G, *3, CYP2C9*2 and *3, CYP2C19*17 and *2, CYP2D6*4, *41, *5, *10 and *9 and SLC1B1*15 and *5. Few commercial CDSS include pharmacogenomic factors in DDI-risk evaluation and none of them was designed for use in older adults.

CONCLUSIONS

We provided a list of the allelic variants influencing the activity of drug perpetrators in older adults which should be included in pharmacogenomics-oriented CDSSs to be used in geriatric medicine.

Characterization of Divergent Metabolic Pathways in Elucidating an Unexpected, Slow-Forming, and Long Half-Life Major Metabolite of Iclepertin

PURPOSE

After single oral dosing of the glycine reuptake transporter (GlyT1) inhibitor, iclepertin (BI 425809), a single major circulating metabolite, M530a, was identified. However, upon multiple dosing, a second major metabolite, M232, was observed with exposure levels ~ twofold higher than M530a. Studies were conducted to characterize the metabolic pathways and enzymes responsible for formation of both major human metabolites.

METHODS

In vitro studies were conducted with human and recombinant enzyme sources and enzyme-selective inhibitors. The production of iclepertin metabolites was monitored by LC-MS/MS.

RESULTS

Iclepertin undergoes rapid oxidation to a putative carbinolamide that spontaneously opens to an aldehyde, M528, which then undergoes reduction by carbonyl reductase to the primary alcohol, M530a. However, the carbinolamide can also undergo a much slower oxidation by CYP3A to form an unstable imide metabolite, M526, that is subsequently hydrolyzed by a plasma amidase to form M232. This difference in rate of metabolism of the carbinolamine explains why high levels of the M232 metabolite were not observed in vitro and in single dose studies in humans, but were observed in longer-term multiple dose studies.

CONCLUSIONS

The long half-life iclepertin metabolite M232 is formed from a common carbinolamine intermediate, that is also a precursor of M530a. However, the formation of M232 occurs much more slowly, likely contributing to its extensive exposure in vivo. These results highlight the need to employ adequate clinical study sampling periods and rigorous characterization of unexpected metabolites, especially when such metabolites are categorized as major, thus requiring safety assessment.

Intraindividual Variability in Absolute Bioavailability and Clearance of Midazolam in Healthy Individuals

BACKGROUND AND OBJECTIVE

Midazolam is the preferred clinical probe drug for assessing CYP3A activity. We have previously shown substantial intraindividual variability in midazolam absolute bioavailability and clearance in patients with obesity before and after weight loss induced by gastric bypass or a strict diet. The objective was to describe intraindividual variability in absolute bioavailability and clearance of midazolam in healthy individuals without obesity.

METHODS

This study included 33 healthy volunteers [28 ± 8 years, 21% males, body mass index (BMI) 23 ± 2.5 kg/m2] subjected to four pharmacokinetic investigations over a 2-month period (weeks 0, 2, 4, and 8). Semi-simultaneous oral (0 h) and intravenous (2 h later) midazolam dosing was used to assess absolute bioavailability and clearance of midazolam.

RESULTS

At baseline, mean absolute bioavailability and clearance were 46 ± 18% and 31 ± 10 L/h, respectively. The mean coefficient of variation (CV, %) for absolute bioavailability and clearance of midazolam was 26 ± 15% and 20 ± 10%, respectively. Approximately one-third had a CV > 30% for absolute bioavailability, while 13% had a CV > 30% for clearance.

CONCLUSIONS

On average, intraindividual variability in absolute bioavailability and clearance of midazolam was low to moderate; however, especially absolute bioavailability showed considerable variability in a relatively large proportion of the individuals.

The Influence of Cytochrome P450 Polymorphisms on Pharmacokinetic Profiles and Treatment Outcomes Among Malaria Patients in Sub-Saharan Africa: A Systematic Review

Background

Sub-Saharan Africa (SSA) population is genetically diverse and heterogenous thus variability in drug response among individuals is predicted to be high. Cytochrome P450 (CYP450) polymorphisms is a major source of variability in drug response. This systematic review presents the influence of CYP450 single nucleotide polymorphisms (SNPs), particularly CYP3A4*1B, CYP2B6*6 and CYP3A5*3 on antimalarial drug plasma concentrations, efficacy and safety in SSA populations.

Methods

Searching for relevant studies was done through Google Scholar, Cochrane Central Register of controlled trials (CENTRAL), PubMed, Medline, LILACS, and EMBASE online data bases. The Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines were used. Two independent reviewers extracted data from the studies.

Results

Thirteen studies reporting the influence of CYP450 SNPs on plasma concentrations, efficacy and safety were included in the final data synthesis. CYP3A4*1B, CYP3A5*5, CYP2B6*6 and CYP2C8*2 did not affect antimalarial drug plasma concentration significantly. There was no difference in treatment outcomes between malaria patients with variant alleles and those with wild type alleles.

Conclusion

This review reports lack of influence of CYP3A4*1B, CYP3A5*3, CYP2C8*3 and CYP2B6*6 SNPs on PK profiles, efficacy and safety in SSA among P. falciparum malaria patients.

Drug-drug interactions involving CFTR modulators: a review of the evidence and clinical implications

INTRODUCTION

Cystic fibrosis (CF) is characterized by mucus accumulation impairing the lungs, gastrointestinal tract, and other organs. Cystic fibrosis transmembrane conductance regulator (CFTR) modulators (ivacaftor, tezacaftor, elexacaftor, and lumacaftor) significantly improve lung function and nutritional status; however, they are substrates, inhibitors, and/or inducers of certain CYP enzymes and transporters, raising the risk of drug-drug interactions (DDI) with common CF medications.

AREAS COVERED

A literature search was conducted for DDIs involving CFTR modulators by reviewing new drug applications, drug package inserts, clinical studies, and validated databases of substrates, inhibitors, and inducers. Clinically, CYP3A inducers and inhibitors significantly decrease and increase systemic concentrations of elexacaftor/tezacaftor/ivacaftor, respectively. Additionally, lumacaftor and ivacaftor alter concentrations of CYP3A and P-gp substrates. Potential DDIs without current clinical evidence include ivacaftor and elexacaftor's effect on CYP2C9 and OATP1B1/3 substrates, respectively, and OATP1B1/3 and P-gp inhibitors' effect on tezacaftor. A literature review was conducted using PubMed.

EXPERT OPINION

Dosing recommendations for CFTR modulators with DDIs are relatively comprehensive; however, recommendations on timing of dosing transition of CFTR modulators when CYP3A inhibitors are initiated or discontinued is incomplete. Certain drug interactions may be managed by choosing an alternative treatment to avoid/minimize DDIs. Next generation CFTR modulator therapies under development are expected to provide increased activity with reduced DDI risk.

The Role of SNPs in the Pathogenesis of Idiopathic Central Precocious Puberty in Girls

The initiation of puberty is a crucial timepoint of development, with its disruptions being associated with multiple physical and psychological complications. Idiopathic Central Precocious Puberty (iCPP) has been correlated with Single-Nucleotide Polymorphisms (SNPs) of certain genes that are implicated in various steps of the process of pubertal onset. The aim of this review was to gather current knowledge on SNPs of genes associated with iCPP. We searched articles published on the PubMed, EMBASE and Google Scholar platforms and gathered current literature. KISS1, KISS1R, PLCB1, PRKCA, ITPR1, MKRN3, HPG axis genes, NPVF/NPFFR1, DLK1, KCNK9Q, LIN28B, PROK2R, IGF-1, IGF2, IGF-1R, IGF-2R, IGFBP-3, insulin, IRS-1, LEP/LEPR, PPARγ2, TAC3, TACR3, Estrogen receptors, CYP3A4 and CYP19A1 were studied for implication in the development of precocious puberty. SNPs discovered in genes KISS1, KISS1R, PLCB1, MKRN3, NPVF, LIN28B, PROK2R, IRS-1 TAC3, and CYP3A4 were significantly correlated with CPP, triggering or protecting from CPP. Haplotype (TTTA)13 in CYP19A1 was a significant contributor to CPP. Further investigation of the mechanisms implicated in the pathogenesis of CPP is required to broaden the understanding of these genes’ roles in CPP and possibly initiate targeted therapies.

Mechanism-based inhibition of CYP3A subfamilies by macrolide antibiotics and piperine

OBJECTIVE

The mechanism-based inhibition of macrolide antibiotics, such as erythromycin and clarithromycin, and piperine on testosterone 6β-hydroxylation activities by cytochrome P450 (CYP) 3A4, polymorphically expressed CYP3A5, and fetal CYP3A7 were compared.

METHODS

6β-Hydroxy testosterone was determined by high-performance liquid chromatography.

RESULTS

Although preincubation with erythromycin and clarithromycin decreased CYP3A4-meditaed testosterone 6β- hydroxylation in a time-dependent manner, and the estimated maximum inactivation rate constant (k inact ) and the inactivation rate constant reaching half of k inact (K i ) for erythromycin were approximately 1/2 and 1/5, respectively, of those for clarithromycin. Obvious preincubation time-dependent inhibition of erythromycin against CYP3A5 and CYP3A7 was not observed. Piperine exhibited preincubation time- dependent inhibition, and the calculated K i and k inact values for CYP3A4 were approximately 1/7 and 1/2, respectively, of those for CYP3A5.

CONCLUSION

It is speculated that the preincubation-dependent inhibition by piperine would be more potent in CYP3A5 non-expressors than CYP3A5-expressors.

Genetic Diversity of CYP3A5 and ABCB1 Variants in East-Central and South European Populations

BACKGROUND

CYP3A5 enzyme encoded by CYP3A5 is important for drug metabolism in gut and liver, whereas P-glycoprotein by ABCB1, is an ATP-dependent drug efflux pump which exports endo- and exogenous substances outside the cell. Aim: The study was to assess the prevalence of CYP3A5 alleles: *1, *2, *3, *4, *6 and *7, and C and T of ABCB1 in Poles, Belarusians and Bosnians and to compare it with the data reported from other European populations. Subjects and methods: Overall, 511 unrelated healthy subjects from Poland (n = 239), Belarus (n = 104) and Bosnia and Herzegovina (n = 168) were included in this study. Allele frequencies and statistical parameters (AMOVA version 2.9.3) were determined. Results: In Poles, Belarusians and Bosnians the *3 allele of CYP3A5 was the most common, and wild-type allele *1, were: 5.8%, 1.6% and 2.1%, respectively. Allele *2 was very rare, and alleles *4, *6 and *7 were not detected. For the populations mentioned above, the ABCB1 allele C was: 48.1%, 51.4%, 52.4%, respectively.

CONCLUSION

In compared populations, the distribution of CYP3A5 variants but not ABCB1, differed significantly. Alleles *4, *6 and *7 of CYP3A5 did not occur or occurred rarely.

Exploration of Potential Ewing Sarcoma Drugs from FDA-Approved Pharmaceuticals through Computational Drug Repositioning, Pharmacogenomics, Molecular Docking, and MD Simulation Studies

Novel drug development is a time-consuming process with relatively high debilitating costs. To overcome this problem, computational drug repositioning approaches are being used to predict the possible therapeutic scaffolds against different diseases. In the current study, computational drug repositioning approaches were employed to fetch the promising drugs from the pool of FDA-approved drugs against Ewing sarcoma. The binding interaction patterns and conformational behaviors of screened drugs within the active region of Ewing sarcoma protein (EWS) were confirmed through molecular docking profiles. Furthermore, pharmacogenomics analysis was employed to check the possible associations of selected drugs with Ewing sarcoma genes. Moreover, the stability behavior of selected docked complexes (drugs-EWS) was checked by molecular dynamics simulations. Taken together, astemizole, sulfinpyrazone, and pranlukast exhibited a result comparable to pazopanib and can be used as a possible therapeutic agent in the treatment of Ewing sarcoma.

Cytochromes P450: Role in Carcinogenesis and Relevance to Cancers

Abstracts:

Cancer is a leading factor of mortality globally. Cytochrome P450 (CYP) enzymes play a pivotal role in the biotransformation of both endogenous and exogenous compounds. Evidence from numerous epidemiological, animal, and clinical studies points to instrumental role of CYPs in cancer initiation, metastasis, and prevention. Substantial research has found that CYPs are involved in activating different carcinogenic chemicals in the environment, such as polycyclic aromatic hydrocarbons and tobacco-related nitrosamines. Electrophilic intermediates produced from these chemicals can covalently bind to DNA, inducing mutation and cellular transformation that collectively result in cancer development. While bioactivation of procarcinogens and promutagens by CYPs has long been established, the role of CYP-derived endobiotics in carcinogenesis has emerged in recent years. Eicosanoids derived from arachidonic acid via CYP oxidative pathways have been implicated in tumorigenesis, cancer progression and metastasis. The purpose of this review is to update on the current state of knowledge about the cancer molecular mechanism involving CYPs with focus on the biochemical and biotransformation mechanisms in the various CYP-mediated carcinogenesis, and the role of CYP-derived reactive metabolites, from both external and endogenous sources, on cancer growth and tumour formation.

Association between gene polymorphism and adverse effects in cancer patients receiving docetaxel treatment: a meta-analysis

PURPOSE

Large interindividual variability in the pharmacokinetic properties of docetaxel has been reported, with the clearance of docetaxel varying nearly six fold, in which pharmacogenetics of docetaxel may play an essential role in addition to physiological factors. The association between the gene polymorphism and risk of adverse clinical effects in docetaxel treated patients has been examined in several studies, but their conclusions are, to some extent, controversial. To clarify the role of gene polymorphism in the clinical outcomes of docetaxel treatment, a meta-analysis was performed in the present study.

METHODS

Pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were employed to evaluate the impact of gene polymorphisms of CYP3A4, CYP3A5 and ABCB1. Four studies with 485 subjects were included in this study. Fixed or random-effects model was chosen according to heterogeneity to conduct the meta-analysis. Publication bias was evaluated by fail-safe numbers.

RESULTS

Significant association was identified between the ABCB1 C3435T (rs1045642) polymorphism and risk of short-term recurrent hematological toxicity (TT vs. CC + TC OR = 2.91, 95% CI 1.30-6.52, P = 0.009; TT vs. CC OR = 4.23, 95% CI 1.69-10.57 P = 0.002). The association of the ABCB1 G2677T/A (rs2032582) polymorphism with risk of fluid retention was statistically significant (T(A)/T(A) vs. GG + GT(A) OR = 2.08, 95% CI 1.16-3.73, P = 0.01). No statistically significant association between the CYP3A5 A6986G (rs776746) polymorphism and adverse effects was observed in this study. Due to the limitations of included literature, we did not conduct meta-analysis on CYP3A4 gene polymorphism and adverse effects.

CONCLUSION

An association between the ABCB1 C3435T (rs1045642), ABCB1 G2677T/A (rs2032582) polymorphism and risk of adverse effects of docetaxel was found by our meta-analysis. Namely, the TT homozygotes of the ABCB1 C3435T polymorphism may be associated with the risk of hematological toxicity. ABCB1 G2677T T(A)/T(A) genotype may be associated with the fluid retention.

TRAIL REGISTRATION

PROSPERO 2020 CRD42020203132.

Evaluation of Pharmacogenomics Testing of Cytochrome P450 Enzymes in the Military Health System From 2015 to 2020

Pharmacogenomics (PGx) plays a fundamental role in personalized medicine, providing an evidence-based treatment approach centered on the relationship between genomic variations and their effect on drug metabolism. Cytochrome P450 (CYP450) enzymes are responsible for the metabolism of most clinically prescribed drugs and a major source of variability in drug pharmacokinetics and pharmacodynamics. To assess the prevalence of PGx testing within the Military Health System (MHS), testing of specific CYP450 enzymes was evaluated. Data were retrospectively obtained from the Military Health System Management Analysis and Reporting Tool (M2) database. Patient demographics were identified for each test, along with TRICARE status, military treatment facility, clinic, and National Provider Identifier. A total of 929 patients received 1,833 PGx tests, predominantly composed of active duty/guard service members (N = 460; 49.5%), with highest testing rates in the army (51.5%). An even distribution in testing was observed among gender, with the highest rates in Caucasians (41.7%). Of the CYP enzymes assessed, CYP2C19 and CYP2D6 accounted for 87.8% of all PGx CYP testing. The majority of patients were tested in psychiatry clinics (N = 496; 53.4%) and primary care clinics (N = 233; 25.1%), accounting for 56.4% and 24.8% of all tests, respectively. Testing was found to be provider driven, suggesting a lack of a standardized approach to PGx and its application in patient care within the MHS. We initially recommend targeted education and revising testing labels to be more uniform and informative. Long-term recommendations include establishing pharmacy-driven protocols and point-of-care PGx testing to optimize patient outcomes.

Vitamin D and Cardiovascular Disease: Current Evidence and Future Perspectives

Vitamin D deficiency is a prevalent condition, occurring in about 30–50% of the population, observed across all ethnicities and among all age groups. Besides the established role of vitamin D in calcium homeostasis, its deficiency is emerging as a new risk factor for cardiovascular disease (CVD). In particular, several epidemiological and clinical studies have reported a close association between low vitamin D levels and major CVDs, such as coronary artery disease, heart failure, and atrial fibrillation. Moreover, in all these clinical settings, vitamin deficiency seems to predispose to increased morbidity, mortality, and recurrent cardiovascular events. Despite this growing evidence, interventional trials with supplementation of vitamin D in patients at risk of or with established CVD are still controversial. In this review, we aimed to summarize the currently available evidence supporting the link between vitamin D deficiency and major CVDs in terms of its prevalence, clinical relevance, prognostic impact, and potential therapeutic implications.

Comparison of the Stimulatory and Inhibitory Effects of Steroid Hormones and α-Naphthoflavone on Steroid Hormone Hydroxylation Catalyzed by Human Cytochrome P450 3A Subfamilies

The inhibitory and stimulatory effects of steroid hormones and related compounds on the hydroxylation activity at the 6β-position of two steroid hormones, progesterone and testosterone, by CYP3A4, polymorphically expressed CYP3A5, and fetal CYP3A7 were compared to clarify the catalytic properties of the predominant forms of the human CYP3A subfamily. Hydroxylation activities of progesterone and testosterone by CYP3A4, CYP3A5, and CYP3A7 were estimated using HPLC. The Michaelis constants (K_m) for progesterone 6β-hydroxylation by CYP3A5 were markedly decreased in the presence of dehydroepiandrosterone (DHEA) and α-naphthoflavone (ANF), whereas progesterone and DHEA competitively inhibited testosterone 6β-hydroxylation mediated by CYP3A4, and progesterone competitively inhibited CYP3A5-mediated activity, which was weaker than that for CYP3A4. ANF noncompetitively inhibited testosterone 6β-hydroxylation mediated by both CYP3A4 and CYP3A5. Progesterone and testosterone 6β-hydroxylation mediated by CYP3A7 was inhibited or unaffected by DHEA, pregnenolone, and ANF. These results suggested that DHEA and ANF stimulated progesterone 6β-hydroxylation by CYP3A5 but not by CYP3A4 and CYP3A7; however, progesterone, DHEA, and ANF inhibited testosterone 6β-hydroxylation mediated by all CYP3A subfamily members. The inhibitory/stimulatory pattern of steroid-steroid interactions is different among CYP3A subfamily members and CYP3A5 is the most sensitive in terms of activation among the CYP3A subfamily members investigated.

Investigating the influence of relevant pharmacogenetic variants on the pharmacokinetics and pharmacodynamics of orally administered docetaxel combined with ritonavir

The anticancer drug docetaxel exhibits large interpatient pharmacokinetic and pharmacodynamic variability. In this study, we aimed to assess the functional significance of 14 polymorphisms in the CYP3A, CYP1B1, ABCB1, ABCC2, and SLCO1B3 genes for the pharmacokinetics and pharmacodynamics of oral docetaxel, co-administered with ritonavir. None of the tested CYP3A, ABCB1, ABCC2, and SLCO1B3 genotypes and diplotypes showed a significant relation with an altered bioavailability or clearance of either docetaxel or ritonavir. Similarly, no clear effect of CYP1B1 genotype on clinical outcomes was observed in a subgroup of non-small cell lung cancer (NSCLC) patients. Our post hoc power analysis indicated that our pharmacogenetic-pharmacokinetic analysis was only powered for relatively high effect sizes, which were to be expected given the high interpatient variability. This makes it unlikely that future studies will explain the high observed interpatient variability in oral docetaxel pharmacokinetics as a result of any of these separate polymorphisms and diplotypes.

Identification of human cytochrome P450 isozymes involved in the oxidative metabolism of carfentanil

Carfentanil is an ultra-potent opioid with an analgesic potency 10,000 times that of morphine but has received little scientific investigation. In the present study, the human cytochrome P450 (CYP) isozymes catalyzing the oxidative metabolism of carfentanil were investigated. Using UHPLC-HRMS, Michaelis-Menten kinetics of formation for three major metabolites norcarfentanil (M1), pharmaceutical active metabolite 4-[(1-oxopropyl)phenylamino]-1-(2-hydroxyl-2-phenylethyl)-4-piperidinecarboxylic acid methyl ester (M11), and 4-[(1-oxopropyl)phenylamino]-1-(2-oxo-2-phenylethyl)-4-piperidinecarboxylic acid methyl ester (M15) were determined. Isozymes catalyzing the formation of the low abundant, highly active metabolite 1-[2-(2-hydroxylphenyl)ethyl]-4-[(1-oxopropyl)phenylamino]-4-piperidinecarboxylic acid methyl ester (M13) were also identified. Selective P450 inhibition studies with pooled human liver microsomes (HLMs) and recombinant CYP isozymes suggested that metabolites M1, M11, and M15 were predominantly formed by isozyme CYP3A5, followed by CYP3A4. Isozymes CYP2C8 and CYP2C9 also made contributions but to a much lesser extent. Highly potent metabolite M13 was predominantly formed by isozyme CYP2C9, followed by CYP2C8. These findings indicate that CYP3A5, CYP3A4, CYP2C8 and CYP2C9 play a major role in the transformation of carfentanil to M1 (norcarfentanil), M11, M13 and M15 through N-dealkylation of piperidine ring, hydroxylation of phenethyl group and ketone formation on phenethyl linker by human liver micrsomes.

The rs776746 variant of CYP3A5 is associated with intravenous midazolam plasma levels and higher clearance in critically ill Mexican paediatric patients

WHAT IS KNOWN AND OBJECTIVE

Midazolam is a drug that is metabolized by cytochrome P450 (CYP450) enzymes, particularly CYP3A4 and CYP3A5. The presence of single-nucleotide polymorphisms (SNPs) in the genes encoding these enzymes, such as CYP3A4*1B which is associated with low enzyme expression and activity and CYP3A5*3, has been associated with decrease in enzymatic activity and reduced drug clearance, with potential effects on drug levels and/or toxicity. The present study was conducted to determine the frequencies of the allelic variants of the CYP3A4 (rs2740574) and CYP3A5 (rs776746) genes and their effects on the plasma levels and clearance of intravenous midazolam in critically ill Mexican paediatric patients.

METHODS

Seventy-two DNA samples were genotyped by real-time PCR with TaqMan probes. Plasma midazolam levels were determined at 3 and 24 h post infusion by high-performance liquid chromatography.

RESULTS AND DISCUSSION

The allelic variant rs776746 (CYP3A5*3) was associated with high midazolam plasma levels; the median concentration in patients with the normal genotype (CC) <0.01 ng/ml (Q₂₅ 0.01-Q₇₅ 196.09), whereas patients with the allelic variant (TT+TC) had a median midazolam concentration of 320.3 ng/ml (Q₂₅ 37.51-Q₇₅ 529.51), p = 0.001. The median pharmacokinetic clearance rates were 0.10 L/kg/h (Q₂₅ 0.01-Q₇₅ 0.34) in patients with the allelic variant (TT+TC) and 0.03 L/kg/h (Q₂₅ 0.002-Q₇₅ 0.13) in patients with the normal genotype (CC), p = 0.042.

WHAT IS NEW AND CONCLUSION

This is the first study that reports the frequency of the rs776746 polymorphism in critically ill paediatric patients, which is relevant, since carriers of the *1 allele synthesizing a functional enzyme may need higher doses to achieve adequate sedation. Our results show that compared with carriers of the normal allele, patients with the CYP3A5*3 allelic variant (rs776746) had increased plasma midazolam levels at 3 h after infusion discontinuation (320.3 ng/ml) and greater clearance (0.10 L/kg/h) of the drug.

Impact of CYP2C19, CYP3A4, ABCB1, and FMO3 genotypes on plasma voriconazole in Thai patients with invasive fungal infections

Voriconazole is the first-line antifungal choice in the treatment of invasive fungal infections (IFIs). Single nucleotide polymorphisms (SNPs) in drug-metabolizing and transporter genes may affect voriconazole pharmacokinetics. This study aimed to determine the frequency of the CYP2C19 rs4244285, rs4986893, rs72552267, and rs12248560, CYP3A4 rs4646437, ABCB1 rs1045642, and FMO3 rs2266782 alleles and determine the association between these genetic variants and voriconazole concentrations in Thai patients with invasive fungal infections. The study comprised 177 Thai patients with IFIs in whom seven SNPs in CYP2C19, CYP3A4, ABCB1, and FMO3 were genotyped using TaqMan real-time polymerase chain reaction (RT-PCR) 5´ nuclease assays, and voriconazole plasma concentrations were measured by high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS). Of the 177 patients included, 31 were <12 years and 146 were ≥12 years. The CYP2C19 allele frequencies were 0.29 for *2, 0.060 for *3, 0.003 for *6, and 0.008 for *17. The allele frequency of CYP3A4 (rs4646437) was 0.26, ABCB1 (rs1045642) was 0.36, and FMO3 (rs2266782) was 0.16. The median voriconazole dose/weight was significantly lower in patients aged ≥12 years when compared to the patients aged <12 years (P < .001). Patients aged <12 years with CYP2C19*1/*2 exhibited significantly higher median voriconazole plasma concentrations than those with the CYP2C19*1/*1 (P = .038). However, there were no significant differences in median voriconazole plasma concentrations among the CYP2C19 genotypes in the patients aged ≥12 years. There was a lack of association observed among the CYP3A4, ABCB1, and FMO3 genotypes on the plasma voriconazole concentrations in both groups of patients. Our findings indicate that voriconazole plasma concentrations are affected by the CYP2C19*2 allele in patients aged <12 years but not in patients aged ≥12 years.

Effect of the Most Relevant CYP3A4 and CYP3A5 Polymorphisms on the Pharmacokinetic Parameters of 10 CYP3A Substrates

Several cytochrome P450 (CYP) CYP3A polymorphisms were associated with reduced enzyme function. We aimed to evaluate the influence of these alleles on the pharmacokinetic parameters (PK) of several CYP3A substrates. We included 251 healthy volunteers who received a single dose of ambrisentan, atorvastatin, imatinib, aripiprazole, fentanyl, amlodipine, donepezil, olanzapine, fesoterodine, or quetiapine. The volunteers were genotyped for CYP3A4 and CYP3A5 polymorphisms by qPCR. To compare the PK across studies, measurements were corrected by the mean of each parameter for every drug and were logarithmically transformed. Neither CYP3A phenotype nor individual CYP3A4 or CYP3A5 polymorphisms were significantly associated with differences in PK. However, regarding the substrates that are exclusively metabolized by CYP3A, we observed a higher normalized AUC (p = 0.099) and a tendency of lower normalized Cl (p = 0.069) in CYP3A4 mutated allele carriers what was associated with diminished drug metabolism capacity. CYP3A4 polymorphisms did not show a pronounced influence on PK of the analysed drugs. If so, their impact could be detectable in a very small percentage of subjects. Although there are few subjects carrying CYP3A4 double mutations, the effect in those might be relevant, especially due to the majority of subjects lacking the CYP3A5 enzyme. In heterozygous subjects, the consequence might be less noticeable due to the high inducible potential of the CYP3A4 enzyme.

Transcriptional regulation of CYP3A4 by nuclear receptors in human hepatocytes under hypoxia

The human hepatic cytochrome P-450 3A4 (CYP3A4), recognized as a multifunctional enzyme, has a wide range of substrates including commonly used drugs. Previous investigations demonstrated that the expression of CYP3A4 in human hepatocytes could be regulated by some nuclear receptors (NRs) at transcriptional level under diverse situations. The significance of oxygen on CYP3A4-mediated metabolism seems notable while the regulatory mode of CYP3A4 in the particular case still remains elusive. Recently, striking evidence has emerged that both CYP3A4 and its regulator NR could be inhibited by exposure to hypoxia. Therefore, it is of great importance to elucidate whether and how these NRs act in the transcriptional regulation of CYP3A4 in human hepatocytes under hypoxic conditions. In this review, we mainly summarized transcriptional regulation of the pivotal enzyme CYP3A4 by NRs and explored the possible regulatory pathways of CYP3A4 via these major NRs under hypoxia, expecting to provide favorable evidence for further clinical guidance under such pathological situations.

Assessment of biological functions for C3A cells interacting with adverse environments of liver failure plasma

BACKGROUND

For its better differentiated hepatocyte phenotype, C3A cell line has been utilized in bioartificial liver system. However, up to now, there are only a few of studies working at the metabolic alternations of C3A cells under the culture conditions with liver failure plasma, which mainly focus on carbohydrate metabolism, total protein synthesis and ureagenesis. In this study, we investigated the effects of acute liver failure plasma on the growth and biological functions of C3A cells, especially on CYP450 enzymes.

METHODS

C3A cells were treated with fresh DMEM medium containing 10% FBS, fresh DMEM medium containing 10% normal plasma and acute liver failure plasma, respectively. After incubation, the C3A cells were assessed for cell viabilities, lactate dehydrogenase leakage, gene transcription, protein levels, albumin secretion, ammonia metabolism and CYP450 enzyme activities.

RESULTS

Cell viabilities decreased 15%, and lactate dehydrogenase leakage had 1.3-fold elevation in acute liver failure plasma group. Gene transcription exhibited up-regulation, down-regulation or stability for different hepatic genes. In contrast, protein expression levels for several CYP450 enzymes kept constant, while the CYP450 enzyme activities decreased or remained stable. Albumin secretion reduced about 48%, and ammonia accumulation increased approximately 41%.

CONCLUSIONS

C3A cells cultured with acute liver failure plasma showed mild inhibition of cell viabilities, reduction of albumin secretion, and increase of ammonia accumulation. Furthermore, CYP450 enzymes demonstrated various alterations on gene transcription, protein expression and enzyme activities.

Sexual Dimorphism in Drug Metabolism and Pharmacokinetics

Background:

Sex and gender-based differences are observed well beyond the sex organs and affect several physiological and biochemical processes involved in the metabolism of drug molecules. It is essential to understand not only the sex and gender-based differences in the metabolism of the drug but also the molecular mechanisms involved in the regulation of drug metabolism for avoiding sex-related adverse effects of drugs in the human.

Method:

The articles on the sex and gender-based differences in the metabolism of drug molecules were retrieved from the Pub Med database. The articles were classified into the metabolism of the drug molecule, gene expression regulation of drug-metabolizing enzymes, the effect of sex hormones on the metabolism of drug, expression of drugmetabolizing enzymes, etc.

Result:

Several drug molecules are known, which are metabolized differently in males and females. These differences in metabolism may be due to the genomic and non-genomic action of sex hormones. Several other drug molecules still require further evaluation at the molecular level regarding the sex and gender-based differences in their metabolism. Attention is also required at the effect of signaling cascades associated with the metabolism of drug molecules.

Conclusion:

Sex and gender-based differences in the metabolism of drugs exist at various levels and it may be due to the genomic and non-genomic action of sex hormones. Detailed understanding of the effect of sex and related condition on the metabolism of drug molecules will help clinicians to determine the effective therapeutic doses of drugs dependingon the condition of patient and disease.

Comparison of steroid hormone hydroxylation mediated by cytochrome P450 3A subfamilies

Hydroxylation activity at the 6β-position of steroid hormones (testosterone, progesterone, and cortisol) by human cytochromes P450 (CYP) 3A4, polymorphic CYP3A5, and fetal CYP3A7 were compared to understand the catalytic properties of the major forms of human CYP3A subfamily. Testosterone, progesterone, and cortisol 6β-hydroxylation activities of recombinant CYP3A4, CYP3A5, and CYP3A7 were determined by liquid chromatography. Michaelis constants (K_m) for CYP3A7-mediated 6β-hydroxylation of testosterone, progesterone, and cortisol were similar to those of CYP3A4 and CYP3A5. The maximal velocity (k_cat) and k_cat/K_m values for CYP3A4 were the highest, followed by CYP3A5 and those for CYP3A7 were the lowest among three CYP3A subfamily members. A decrease in K_m values for progesterone 6β-hydroxylation by CYP3A4, CYP3A5, and CYP3A7 in the presence of testosterone was observed, and the k_cat values for CYP3A5 gradually increased with increasing testosterone. This indicated that testosterone stimulated progesterone 6β-hydroxylation by all three CYP3A subfamily members. However, progesterone inhibited testosterone 6β-hydroxylation mediated by CYP3A4, CYP3A5, and CYP3A7. In conclusion, the k_cat values, rather than K_m values, for 6β-hydroxylation of three steroid hormones mediated by CYP3A7 were different from those for CYP3A4 and CYP3A5. In addition, the inhibitory/stimulatory pattern of steroid-steroid interactions would be different among CYP3A subfamily members.

Effect of Environmental Exposure and Pharmacogenomics on Drug Metabolism

BACKGROUND

Pesticides are major xenobiotic compounds and environmental pollutants, which are able to alter drug-metabolizing enzyme as well as pharmacokinetics of drugs. Subsequent to the release of the human genome project, genetic variations (polymorphism) become an integral part of drug development due to their influence on disease susceptibility/ progression of the disease and their impact on drug absorption, distribution, metabolism of active metabolites and finally excretion of the drug. Genetic polymorphisms crucially regulate pharmacokinetics and pharmacodynamics of drugs under the influence of physiological condition, lifestyle, as well as pathological conditions collectively.

OBJECTIVE

To review all the evidence concerning the effect of environmental exposure on drug metabolism with reference to pharmacogenomics.

METHODS

Scientific data search and review of basic, epidemiological, pharmacogenomics and pharmacokinetics studies were undertaken to evaluate the influence of environmental contaminants on drug metabolism.

RESULTS

Various environmental contaminants like pesticides effectively alter drug metabolism at various levels under the influence of pharmacogenomics, which interferes with pharmacokinetics of drug metabolism. Genetic polymorphism of phase I and phase II xenobiotic-metabolizing enzymes remarkably alters disease susceptibility as well as the progression of disease under the influence of various environmental contaminants at various levels.

CONCLUSION

Individual specific drug response may be attributed to a large variety of factors alone or in combination ranging from genetic variations (SNP, insertion, deletion, duplication etc.) to physiological setting (gender, age, body size, and ethnicity), environmental or lifestyle factors (radiation exposure, smoking, alcohol, nutrition, exposure to toxins, etc.); and pathological conditions (obesity, diabetes, liver and renal function).

Role of vitamin D receptor in the regulation of CYP3A gene expression

Vitamin D₃ (VD₃) is a multifunctional nutrient which can be either synthesized or absorbed from the diet. It plays a pivotal role in systemic calcium and phosphate homeostasis, as well as in various physiological and pathological processes. VD₃ is converted to the active form, 1α,25-dihydroxyvitamin D₃ (1,25-D3), by cytochrome P450 2R1 (CYP2R1)/CYP27A1 and CYP27B1 sequentially, and deactivated by multiple enzymes including CYP3A4. On the other hand, 1,25-D3 is capable of activating the transcription of CYP3A genes in humans, mice and rats. The vitamin D receptor (VDR)-mediated transactivation of human CYP3A4 and CYP3A5 resembles that known for pregnane X receptor (PXR). Activated VDR forms a heterodimer with retinoid X receptor α (RXRα), recruits co-activators, translocates to the cell nucleus, binds to the specific vitamin D responsive elements (VDRE), and activates the gene transcription. In mice, intestinal Cyp3a11 mRNA levels, but not those of hepatic CYP3As, were induced by in vivo administration of VDR and PXR agonists. In rats, intestinal Cyp3a1 and Cyp3a2 mRNAs were induced by 1,25-D3 or lithocholic acid (LCA), whereas hepatic Cyp3a2, but not Cyp3a1 and Cyp3a9, was modulated to 1,25-D3 treatment. In general, the VDR-mediated regulation of CYP3A presents species and organ specificity.

Effect of CYP3A5*3 genetic variant on the metabolism of direct-acting antivirals in vitro: a different effect on asunaprevir versus daclatasvir and beclabuvir

Direct-acting antivirals, asunaprevir (ASV), daclatasvir (DCV), and beclabuvir (BCV) are known to be mainly metabolized by CYP3A enzymes; however, the differences in the detailed metabolic activities of CYP3A4 and CYP3A5 on these drugs are not well clarified. The aim of the present study was to elucidate the relative contributions of CYP3A4 and CYP3A5 to the metabolism of ASV, DCV, and BCV, as well as the effect of CYP3A5*3 genetic variant in vitro. The amount of each drug and their major metabolites were determined using LC-MS/MS. Recombinant CYP3As and CYP3A5*3-genotyped human liver microsomes (CYP3A5 expressers or non-expressers) were used for the determination of their metabolic activities. The contribution of CYP3A5 to ASV metabolism was considerable compared to that of CYP3A4. Consistently, ASV metabolic activity in CYP3A5 expressers was higher than those in CYP3A5 non-expresser. Moreover, CYP3A5 expression level was significantly correlated with ASV metabolism. In contrast, these observations were not found in DCV and BCV metabolism. To our knowledge, this is the first study to directly demonstrate the effect of CYP3A5*3 genetic variants on the metabolism of ASV. The findings of the present study may provide basic information on ASV, DCV, and BCV metabolisms.

Computational insights into the different catalytic activities of CYP3A4 and CYP3A5 toward schisantherin E

The cytochromes CYP3A4 and CYP3A5 share 84% sequence identity, but they exhibit different catalytic activities toward some substrates. Schisantherin E (SE) was recently identified as a selective substrate of CYP3A5, which exhibited catalytic efficiency that was more than 23 times higher than CYP3A4. At present, however, the structural determinants responsible for the different catalytic activities of the two enzymes toward SE have not been fully understood. In this study, a combination of molecular docking, molecular dynamic simulations, and binding free energy calculation was performed on the CYP3A4/CYP3A5-SE systems to investigate the issue. The results demonstrate that Ser119 in CYP3A4 and Glu374 in CYP3A5 formed direct hydrogen bonding with SE, respectively. Additionally, one water molecule located between the B-C loop and the I helix mediated different hydrogen-bonding networks between CYP3A4/3A5 and SE. The residue differences (Phe/Leu108 and Leu/Phe210) triggered the distinct conformational changes of the Phe-cluster residues, especially Phe213 and Phe215, which formed stronger hydrophobic interactions with SE in CYP3A5. The calculated binding free energies were consistent with the experimental results.

Cytochrome P450 3A Enzymes Are Key Contributors for Hepatic Metabolism of Bufotalin, a Natural Constitute in Chinese Medicine Chansu

Bufotalin (BFT), one of the naturally occurring bufodienolides, has multiple pharmacological and toxicological effects including antitumor activity and cardiotoxicity. This study aimed to character the metabolic pathway(s) of BFT and to identify the key drug metabolizing enzyme(s) responsible for hepatic metabolism of BFT in human, as well as to explore the related molecular mechanism of enzymatic selectivity. The major metabolite of BFT in human liver microsomes (HLMs) was fully identified as 5β-hydroxylbufotalin by LC-MS/MS and NMR techniques. Reaction phenotyping and chemical inhibition assays showed that CYP3A4 and CYP3A5 were key enzymes responsible for BFT 5β-hydroxylation. Kinetic analyses demonstrated that BFT 5β-hydroxylation in both HLMs and human CYP3A4 followed the biphasic kinetics, while BFT 5β-hydroxylation in CYP3A5 followed substrate inhibition kinetics. Furthermore, molecular docking simulations showed that BFT could bind on two different ligand-binding sites on both CYP3A4 and CYP3A5, which partially explained the different kinetic behaviors of BFT in CYP3A4 and CYP3A5. These findings are very helpful for elucidating the phase I metabolism of BFT in human and for deeper understanding the key interactions between CYP3A enzymes and bufadienolides, as well as for the development of bufadienolide-type drugs with improved pharmacokinetic and safety profiles.

Is there adaptation in the human genome for taste perception and phase I biotransformation?

Background

During the modern human expansion, new environmental pressures may have driven adaptation, especially in genes related to the perception of ingested substances and their detoxification. Consequently, positive (adaptive) selection may have occurred in genes related to taste, and in those related to the CYP450 system due to its role in biotransformation of potentially toxic compounds. A total of 91 genes (taste receptors and CYP450 superfamily) have been studied using Hierarchical Boosting, a powerful combination of different selection tests, to detect signatures of recent positive selection in three continental human populations: Northern Europeans (CEU), East Asians (CHB) and Africans (YRI). Analyses have been refined with selection analyses of the 26 populations of 1000 Genomes Project Phase 3.

Results

Genes related to taste perception have not been positively selected in the three continental human populations. This finding suggests that, contrary to results of previous studies, different allele frequencies among populations in genes such as TAS2R38 and TAS2R16 are not due to positive selection but to genetic drift. CYP1 and CYP2 genes, also previously considered to be under positive selection, did not show signatures of selective sweeps. However, three genes belonging to the CYP450 system have been identified by the Hierarchical Boosting as positively selected: CYP3A4 and CYP3A43 in CEU, and CYP27A1 in CHB.

Conclusions

No main adaptive differences are found in known taste receptor genes among the three continental human populations studied. However, there are important genetic adaptations in the cytochrome P450 system related to the Out of Africa expansion of modern humans. We confirmed that CYP3A4 and CYP3A43 are under selection in CEU, and we report for the first time CYP27A1 to be under positive selection in CHB.

Electronic supplementary material

The online version of this article (10.1186/s12862-019-1366-7) contains supplementary material, which is available to authorized users.

Pharmacogenetic impact of docetaxel on neoadjuvant treatment of breast cancer patients

AIM

This study aimed to investigate the effect of CYP3A4 and CYP3A5 genotypes on clinical outcomes of docetaxel treatment.

PATIENTS & METHODS

In the PROMIX trial, 150 breast cancer patients received docetaxel preoperatively. CYP3A4 and CYP3A5 genotype combinations were transformed into total CYP 3A phenotypes.

RESULTS

Seven patients were characterized as poor metabolizer (PM), 22 patients as extensive metabolizer and 121 patients as intermediate metabolizer. The frequency of grade 3/grade 4 adverse events was higher in the PM group (p = 0.002). One PM subject who basically lacked enzyme activity died from typhlitis. Total 45 recurrences were reported after a median of 5-year follow-up; none of these was PM.

CONCLUSION

The allelic variants CYP3A4*22 and CYP3A5*3 contribute to the interpatient variations of docetaxel.

Assessment of Pharmacokinetic Drug-Drug Interactions in Humans: In Vivo Probe Substrates for Drug Metabolism and Drug Transport Revisited

Pharmacokinetic parameters of selective probe substrates are used to quantify the activity of an individual pharmacokinetic process (PKP) and the effect of perpetrator drugs thereon in clinical drug-drug interaction (DDI) studies. For instance, oral caffeine is used to quantify hepatic CYP1A2 activity, and oral dagibatran etexilate for intestinal P-glycoprotein (P-gp) activity. However, no probe substrate depends exclusively on the PKP it is meant to quantify. Lack of selectivity for a given enzyme/transporter and expression of the respective enzyme/transporter at several sites in the human body are the main challenges. Thus, a detailed understanding of the role of individual PKPs for the pharmacokinetics of any probe substrate is essential to allocate the effect of a perpetrator drug to a specific PKP; this is a prerequisite for reliably informed pharmacokinetic models that will allow for the quantitative prediction of perpetrator effects on therapeutic drugs, also in respective patient populations not included in DDI studies.

CYP3A4*22 Impairs the Elimination of Ticagrelor, But Has No Significant Effect on the Bioactivation of Clopidogrel or Prasugrel

CYP3A enzymes participate in the elimination of ticagrelor and the bioactivation of clopidogrel and prasugrel. We studied the effects of functional CYP3A genetic variants (CYP3A4*22; rs35599367 and CYP3A5*3; rs776746) on the pharmacokinetics and pharmacodynamics of ticagrelor, clopidogrel, and prasugrel. Six healthy volunteers with the CYP3A4*1/*22 and CYP3A5*3/*3 genotype (CYP3A4*22 carriers), eight with the CYP3A4*1/*1 and CYP3A5*1/*3 genotype (CYP3A5 expressors), and 11-13 with the CYP3A4*1/*1 and CYP3A5*3/*3 genotypes (controls) ingested single doses of ticagrelor, clopidogrel, and prasugrel on separate occasions. Ticagrelor area under the plasma concentration-time curve (AUC) was 89% (P = 0.004) higher in CYP3A4*22 carriers than in controls. CYP3A4*22 carriers also showed more pronounced platelet inhibition at 24 hours after ticagrelor ingestion than the controls (43% vs. 21%; P = 0.029). The CYP3A5 genotype did not affect ticagrelor pharmacokinetics. Neither CYP3A5 nor CYP3A4 genotypes significantly affected prasugrel or clopidogrel. In conclusion, the CYP3A4*22 allele markedly impairs ticagrelor elimination enhancing its antiplatelet effect.

CYP3A and CYP2C19 activity in urine in relation to CYP3A4, CYP3A5, and CYP2C19 polymorphisms in Russian peptic ulcer patients taking omeprazole

Background

Proton pump inhibitors (PPIs) are metabolized by cytochrome P450. CYP2C19 is the main isoenzyme for the majority of PPI, whereas CYP3A family is a secondary enzyme for PPI biotransformation.

Purpose

The aim of the study was to find if CYP3A4*22, CYP3A5*3, CYP2C19*2, CYP2C19*3, and CYP2C19*17 genotypes are connected with CYP3A and CYP2C19 activities in Russian peptic ulcer patients taking omeprazole.

Patients and methods

Forty-eight gastric or duodenal ulcer patients (15 men, 33 women; mean age 55.0±15.3 years, age range 18-91 years) from Moscow region of Russia were enrolled. Peripheral venous blood was collected for DNA extraction, and real-time polymerase chain reaction was performed for CYP3A5*3 ^A6986G (rs776746), CYP3A4*22 C>T in intron 6 (rs35599367), CYP2C19*2^G681A (rs4244285), CYP2C19*3^G636A (rs4986893), and CYP2C19*17^C-806T (rs12248560) polymorphism analyses. Urine samples of patients were collected in the morning between 6 and 9 am before food or drug intake. Urine cortisol and 6β-hydroxycortisol concentrations (for CYP3A activity) and omeprazole and 5-hydroxyomeprazole concentrations (for CYP2C19 activity) were measured using high-performance liquid chromatography/mass spectroscopy.

Results

We found a connection between CYP2C19 genotypes and CYP3A activity. Median metabolic ratios 6β-hydroxycortisol/cortisol (25%-75% percentiles) were 2.84 (1.99-4.39) for CYP2C19 extensive metabolizers (EMs), 2.51 (1.86-4.73) for CYP2C19 ultra-rapid metabolizers (UMs), and 1.45 (1.12-2.16) for CYP2C19 intermediate metabolizers (IMs) + poor metabolizers (PMs). A statistically significant difference in CYP3A activity (Mann-Whitney test) was found between CYP2C19 EMs vs CYP2C19 IMs+PMs (p=0.006), between CYP2C19 UMs vs CYP2C19 IMs+PMs (p=0.018), and in multiple comparison Kruskal-Wallis test (p=0.014).

Conclusion

In CYP2C19 IMs+PMs, CYP3A activity was significantly lower than in CYP2C19 EMs and UMs.

The prognostic value of differentially expressed CYP3A subfamily members for hepatocellular carcinoma

Objective

The activities of four cytochrome P3A (CYP3A) subfamily members (CYP3A4, CYP3A5, CYP3A7, and CYP3A43) are well documented in drug metabolism. However, the association between CYP3A subfamily members and hepatocellular carcinoma (HCC) remains unclear. This study investigated the prognostic value of CYP3A subfamily mRNA expression levels with HCC prognosis.

Materials and methods

Data from a total of 360 HCC patients were retrieved from The Cancer Genome Atlas database, and data from 231 HCC patients were retrieved from the Gene Expression Omnibus database. Kaplan–Meier analysis and Cox regression models were utilized to determine median survival, overall survival, and recurrence-free survival. Hazard ratios and 95% CI were calculated.

Results

Low expression of CYP3A4, CYP3A5, and CYP3A43 in the tumor tissue was associated with short median survival (crude p=0.004, 0.001, and 0.001; adjusted p=0.022, 0.005, and 0.013, respectively). Joint-effects combination analysis of CYP3A4, CYP3A5/CYP3A4, CYP3A43/CYP3A5, and CYP3A43 revealed that high expression groups of two genes (group C, group c, group 3) were associated with a reduced risk of death, as compared to low expression of two genes (group A, group a, group 1), and the adjusted p values were 0.001, 0.004, and 0.001, respectively. Joint-effects analysis of CYP3A4, CYP3A5, and CYP3A43 showed that groups III and IV had a reduced risk of death, as compared to group I (adjusted p=0.024 and 0.002, respectively).

Conclusion

CYP3A4, CYP3A5, and CYP3A43 mRNA expression levels are potential prognostic markers of HCC.

Effects of CYP3A4*1G and CYP3A5*3 polymorphisms on pharmacokinetics of tylerdipine hydrochloride in healthy Chinese subjects

The aim of this analysis was to explore the influence of CYP3A4*1G and CYP3A5*3 polymorphisms on the pharmacokinetics of tylerdipine in healthy Chinese subjects. A total of 64 and 63 healthy Chinese subjects were included and identified as the genotypes of CYP3A4*1G and CYP3A5*3, respectively. Plasma samples were collected for up to 120 h post-dose to characterize the pharmacokinetic profile following single oral dose of the drug (5, 15, 20, 25 and 30 mg). Plasma levels were measured by a high-performance liquid chromatography-mass spectrometry (LC-MS/MS). The pharmacokinetic parameters were calculated using non-compartmental method. The maximum concentration (C_max) and the area under the curve (AUC_0-24 h) were all corrected by the dose given. In the wild-type group, the mean dose-corrected AUC_0-24 h was 1.35-fold larger than in CYP3A4*1G carriers (p = .018). Among the three CYP3A5 genotypes, there showed significantly difference (p = .008) in the t_1/2, but no significant difference was observed for the AUC_0-24 h and C_max. In subjects with the CYP3A5*3/*3 genotype, the mean t_1/2 was 1.35-fold higher than in CYP3A5*1/*1 group (p = .007). And the t_1/2 in CYP3A5*3 carriers also was 1.32-fold higher than in the wild-type group (p = .004). CYP3A4*1G and CYP3A5*3 polymorphisms may influence tylerdipine pharmacokinetic in healthy Chinese subjects.

Drug metabolism in early infancy: opioids as an illustration

INTRODUCTION

Drug dosing in infants frequently depends on body weight as a crude indicator for maturation. Fentanyl (metabolized by Cytochrome P450 3A4) and morphine (glucuronidated by UDP-glucuronosyltransferase-2B7) served as model drugs to provide insight in maturation patterns of these enzymes and provide understanding of the impact of non-maturational factors to optimize dosing in infants. Areas covered: Systematic searches on metabolism and population pharmacokinetic (Pop-PK) models for fentanyl and morphine were performed. Pre- and post-model selection criteria were applied to assess and evaluate the validity of these models. It was observed that maturational changes have been rather well investigated, be it with variability in the maturational function estimates. The same holds true for Pop-PK models, where non-maturational covariates have also been reported (pharmacogenetics, disease state or external influences), although less incorporated in the PK models and with limited knowledge on mechanisms involved. Expert opinion: PK models for fentanyl and morphine are currently available. Consequently, we suggest that researchers should not continue to develop new models, but should investigate whether collected data fit in already existing models and provide additional value concerning the impact of (non)-maturational factors like drug-drug interactions or pharmacogenetics.

Effectiveness of Measuring Genetic Polymorphisms in Metabolizing Enzymes of Tacrolimus within One Medical Facility

OBJECTIVES

Because genetic polymorphisms cause diverse activity in drug metabolizing enzymes, drug concentrations in the blood may be variable among patients. We analyzed the genotypes of CYP3A5 and MDR1, and investigated their relationship with whole blood drug concentrations.

METHODS

Eight patients were administered an oral dose of tacrolimus for one week or longer prior to enrollment in this study. Whole blood concentrations for tacrolimus were measured 12 hours post oral administration, on the same day as genotyping, within our hospital using a fully automated gene analyzer. The procedures became so rapid that collection of blood samples could be completed within the same day (approximately one hour).

RESULTS

The genotype frequency of CYP3A5 was ^*3/^*3 in five patients, ^*1/^*3 in two patients, and ^*1/^*1 in one patient. All five patients with ^*3/^*3 showed favorable increases in tacrolimus blood concentrations. In the two patients with ^*1/^*3, an increase in tacrolimus blood concentration was not readily achieved in one patient, but increased favorably in the other patient. In the patient with ^*1/^*1, tacrolimus was not detectable in the patient's blood. A favorable treatment effect was obtained by changing tacrolimus to cyclosporine. It is notable that genotypes in patients where tacrolimus was not detected in the blood were wild types: 2677G/G and 3435C/C in MDR1.

CONCLUSIONS

The measurement of genetic polymorphisms in metabolizing enzymes of tacrolimus, within one medical facility, is applicable for the selection of immunosuppressants and individual dosing for the treatment of autoimmune disease.

Genome-wide association study identifies the common variants in CYP3A4 and CYP3A5 responsible for variation in tacrolimus trough concentration in Caucasian kidney transplant recipients

The immunosuppressant tacrolimus (TAC) is metabolized by both cytochrome P450 3A4 (CYP3A4) and CYP3A5 enzymes. It is common for European Americans (EA) to carry two CYP3A5 loss-of-function (LoF) variants that profoundly reduces TAC metabolism. Despite having two LoF alleles, there is still considerable variability in TAC troughs and identifying additional variants in genes outside of the CYP3A5 gene could provide insight into this variability. We analyzed TAC trough concentrations in 1345 adult EA recipients with two CYP3A5 LoF alleles in a genome-wide association study. Only CYP3A4*22 was identified and no additional variants were genome-wide significant. Additional high allele frequency genetic variants with strong genetic effects associated with TAC trough variability are unlikely to be associated with TAC variation in the EA population. These data suggest that low allele frequency variants, identified by DNA sequencing, should be evaluated and may identify additional variants that contribute to TAC pharmacokinetic variability.

Peroxisome Proliferator-Activated Receptor α Activation Suppresses Cytochrome P450 Induction Potential in Mice Treated with Gemfibrozil

Gemfibrozil, a peroxisome proliferator-activated receptor α (PPARα) agonist, is widely used for hypertriglyceridaemia and mixed hyperlipidaemia. Drug-drug interaction of gemfibrozil and other PPARα agonists has been reported. However, the role of PPARα in cytochrome P450 (CYP) induction by fibrates is not well known. In this study, wild-type mice were first fed gemfibrozil-containing diets (0.375%, 0.75% and 1.5%) for 14 days to establish a dose-response relationship for CYP induction. Then, wild-type mice and Pparα-null mice were treated with a 0.75% gemfibrozil-containing diet for 7 days. CYP3a, CYP2b and CYP2c were induced in a dose-dependent manner by gemfibrozil. In Pparα-null mice, their mRNA level, protein level and activity were induced more than those in wild-type mice. So, gemfibrozil induced CYP, and this action was inhibited by activated PPARα. These data suggested that the induction potential of CYPs was suppressed by activated PPARα, showing a potential role of this receptor in drug-drug interactions and metabolic diseases treated with fibrates.

Association between CYP3A5 genotypes with hypertension in Chinese Han population: A case-control study

BACKGROUND

The association of CYP3A5 gene polymorphisms with hypertension in the Chinese population is unknown. We explored the association between the CYP3A5 (rs776746) gene and hypertension in the Chinese Han population.

METHODS

Using a case-control design, 340 cases and 254 controls were enrolled from the Third Affiliated Hospital of South Medical University between July and December of 2015. We used a standardized questionnaire to collect data regarding age, sex, smoking, drinking, family history of hypertension, and physical exercise. Height and weight were measured, and the body mass index (BMI) was calculated by weight/height². Blood pressure was measured three times after 5 min of rest with at least 15 s between measurements, and the mean was considered the final BP. A Clinical examination was conducted.

RESULTS

A total of 594 participants, including 340 cases and 254 controls, were entered into the analyses. The genotype frequencies of the CYP3A5 G>A polymorphism did not deviate from the Hardy-Weinberg equilibrium. The genotype frequencies among the cases were 38.8% (GA, 132 individuals), 42.9% (GG, 146 individuals), and 18.2% (AA, 62 individuals). The differences in genotype between the cases and the controls were statistically significant. The AA genotype was associated with an elevated risk of hypertension after adjusting for potential confounders in Model 2. There was no interaction between smoking and the CYP3A5 genotype, while the interaction between drinking and the CYP3A5 genotype was significant.

CONCLUSION

The CYP3A5 gene may be associated with the risk of hypertension in the Chinese Han population, and this effect may be exacerbated by drinking.

Individual pharmacokinetic variation leads to underdosing of ciprofloxacin in some cystic fibrosis patients

Ciprofloxacin (CIP) is frequently used when treating cystic fibrose (CF) patients with intermittent Pseudomonas aeruginosa (P. aeruginosa) lung colonization. However, approximately 20% of the patients progress to chronic infection despite early intervention. The aim of this study, was to investigate the pharmacokinetics of CIP, to evaluate if CYP3A4-related metabolism is involved and to find the optimal dose needed to eradicate intermittently colonizing bacteria in the lungs of CF patients. Methods An open-label, prospective pharmacokinetic study was performed. Twenty-two adult CF-patients were each given 500 mg CIP orally. One blood sample was taken at t = 0, and the following 12 hr, nine blood samples were collected. The optimal dose and interval was then calculated by Monte Carlo simulation. CYP3A4-activity was mesured using the Erythromycin Breath Test (ERMBT). Results A 14-fold variation in AUC for the 500 mg CIP (median 473.5 µg/ml × min), and a 30-fold variation in Cmax for CIP (median 2 µg/ml) was found. For CYP3A4-activity the variation was 8-fold. No correlation was found between the CYP3A4-activity and CIP-concentrations. The probability of eradicating intermittent P. aeruginosa colonization in the lungs of CF patients was found to be 57% (3 doses/day), when 500 mg CIP was given. It was calculated to be 89% (2 doses/day) and 94% (3 doses/day), respectivly if 750 mg CIP had been given. Conclusion A large pharmacokinetic difference of CIP in CF patiens was found, not explained by CYP3A4 variation. CIP should be given at 750 mg two or three times daily to adult CF patients with intermittently colonization. Pediatr Pulmonol. 2017;52:319-323. © 2016 Wiley Periodicals, Inc.