CYP2C19 genotype–phenotype discordance in patients with multiple myeloma leads to an acquired loss of drug-metabolising activity

Phenoconversion of CYP3A4, CYP2C19 and CYP2D6 in Pediatrics, Adolescents and Young Adults With Lymphoma: Rationale and Design of the PEGASUS Study

Phenoconversion is the discrepancy between genotype-predicted phenotype and clinical phenotype, due to nongenetic factors. In oncology patients, the impact of phenoconversion on drug selection, efficacy, toxicity, and treatment outcomes is unknown. This study will assess acceptability and feasibility of investigating phenoconversion using probe medications in a pediatric and adolescent and young adult (AYA) oncology population. This prospective, single-arm, single-blind, nonrandomized feasibility study, will enroll individuals aged 6-25 years with a new diagnosis of Hodgkin Lymphoma or Non-Hodgkin Lymphoma. Genotyping will be performed at baseline using whole genome sequencing or targeted panel testing. Longitudinal phenotyping will be conducted throughout the cancer treatment using exogenous oral enzyme-specific probes, specifically subtherapeutic dextromethorphan (CYP2D6) and omeprazole (CYP2C19, CYP3A4) for enzyme activity assessment. The primary outcome measure will be the proportion of patients who consent to the study and successfully complete baseline and at least two longitudinal time points with valid probe drug metabolic ratio measurements. Secondary outcomes include classification of clinical phenotypes based on probe drug metabolic ratios, probe drug safety, barriers to consent, acceptability of pharmacogenomic and phenoconversion testing, longitudinal genotype/phenotype concordance, inflammatory profiles, and patient and disease factors influencing phenoconversion. The trial has received ethics approval (2023/ETH1954) and is registered at ClinicalTrials.gov (NCT06383338). Findings will be disseminated through peer-reviewed publications and professional conferences, providing critical insights to advance the understanding of phenoconversion in oncology from pediatrics to adults. These results will help shape future research and drive the implementation of more personalized precision medicine strategies for all people with cancer.

Complementary and alternative therapies in the palliative setting

Complementary and alternative medicine (CAM) encompasses a wide range of medication, herbal, dietary and physical therapies that are not usually considered within the realm of conventional therapeutics. Approximately two thirds of the Australian population use CAMs and only around half of this number will discuss their use of these products with their doctor. Clinical use is commonly seen in patients with life-limiting illness, often because they experience a high burden of symptoms. However, it is also the case that many of these therapies do not have demonstrated efficacy, particularly for the often broad list of conditions and symptoms for which they are chosen to be used. Further, depending on whether they are sold as medications, sold as food supplements or imported illegally and distributed via nonstandard therapeutic channels, several products have had reports of toxicity, severe adverse effects, batch irregularities and drug interactions with other therapies. This awareness, together with lack of standardisation of products and lack of interchangeability between brands has made prescribers unwilling to put patients at risk of harm by supporting their use. In this article, we cover general pharmacological principles around use of a small selection of chemicals used in a medical setting to enable some guidance for use.

Influence of Inflammation on Cytochromes P450 Activity in Adults: A Systematic Review of the Literature

Background: Available in-vitro and animal studies indicate that inflammation impacts cytochromes P450 (CYP) activity via multiple and complex transcriptional and post-transcriptional mechanisms, depending on the specific CYP isoforms and the nature of inflammation mediators. It is essential to review the current published data on the impact of inflammation on CYP activities in adults to support drug individualization based on comorbidities and diseases in clinical practice. Methods: This systematic review was conducted in PubMed through 7th January 2021 looking for articles that investigated the consequences of inflammation on CYP activities in adults. Information on the source of inflammation, victim drugs (and CYPs involved), effect of disease-drug interaction, number of subjects, and study design were extracted. Results: The search strategy identified 218 studies and case reports that met our inclusion criteria. These articles were divided into fourteen different sources of inflammation (such as infection, autoimmune diseases, cancer, therapies with immunomodulator…). The impact of inflammation on CYP activities appeared to be isoform-specific and dependent on the nature and severity of the underlying disease causing the inflammation. Some of these drug-disease interactions had a significant influence on drug pharmacokinetic parameters and on clinical management. For example, clozapine levels doubled with signs of toxicity during infections and the concentration ratio between clopidogrel's active metabolite and clopidogrel is 48-fold lower in critically ill patients. Infection and CYP3A were the most cited perpetrator of inflammation and the most studied CYP, respectively. Moreover, some data suggest that resolution of inflammation results in a return to baseline CYP activities. Conclusion: Convincing evidence shows that inflammation is a major factor to be taken into account in drug development and in clinical practice to avoid any efficacy or safety issues because inflammation modulates CYP activities and thus drug pharmacokinetics. The impact is different depending on the CYP isoform and the inflammatory disease considered. Moreover, resolution of inflammation appears to result in a normalization of CYP activity. However, some results are still equivocal and further investigations are thus needed.

Impact of Inflammation on Cytochromes P450 Activity in Pediatrics: A Systematic Review

Background and Objective

Cytochromes P450 (CYP) are the major enzymes involved in hepatic metabolism of drugs. Personalization of treatment in pediatrics is a major challenge, as it must not only take into account genetic, environmental, and physiological factors but also ontogeny. Published data in adults show that inflammation had an isoform-specific impact on CYP activities and we aimed to evaluate this impact in the pediatric population.

Methods

Articles listed in PubMed through 7 January, 2021 that studied the impact of inflammation on CYP activities in pediatrics were included in this systematic review. Sources of inflammation, victim drugs (CYP involved), effect of drug–disease interactions, number and age of subjects, and study design were extracted.

Results

Twenty-seven studies and case reports were included. The impact of inflammation on CYP activities appeared to be age dependent and isoform-specific, with some drug–disease interactions having significant pharmacokinetic and clinical impact. For example, midazolam clearance decreases by 70%, while immunosuppressant and theophylline concentrations increase three-fold and two-fold with intensive care unit admission and infection. Cytochrome P450 activity appears to return to baseline level when the disease is resolved.

Conclusions

Studies that have assessed the impact of inflammation on CYP activity are lacking in pediatrics, yet it is a major factor to consider to improve drug efficacy or safety. The scarce current data show that the impact of inflammation is isoform and age dependent. An effort must be made to improve the understanding of the impact of inflammation on CYP activities in children to better individualize treatment.

Cyclophosphamide bioactivation pharmacogenetics in breast cancer patients

PURPOSE

Genetic variation in the activation of the prodrug cyclophosphamide (CP) by cytochrome P450 (CYP) enzymes has been shown to influence outcomes. However, CYP are also subject to phenoconversion due to either the effects of comedications or cancer associated down-regulation of expression. The aim of this study was to assess the relationship between CP bioactivation with CYP2B6 and CYP2C19 genotype, as well as CYP2C19 phenotype, in breast cancer patients.

METHODS

CP and the active metabolite levels were assessed in breast cancer patients (n = 34) at cycle 1 and cycle 3 of treatment. Patients were genotyped for a series of SNP known to affect CYP2B6 and CYP2C19 function. The activity of CYP2C19 was also assessed using a probe drug.

RESULTS

We found a significant linear gene-dose relationship with CYP2B6 coding SNP and formation of 4-hydroxycyclophosphamide. A possible association with CYP2C19 null genotype at cycle 1 was obscured at cycle 3 due to the substantial intra-individual change in CP bioactivation on subsequent dosing.

CONCLUSION

Comedications may be the cause for this inter-occasion variation in bioactivation of cyclophosphamide and the ensuing phenoconversion may account for the conflicting reports in the literature about the relationship between CYP2C19 genotype and CP bioactivation pharmacokinetics. Trial registration ANZCTR363222 (6/11/2012, retrospectively registered).

Chronic Inflammatory Status Observed in Patients with Type 2 Diabetes Induces Modulation of Cytochrome P450 Expression and Activity

Diabetes mellitus is a metabolic disease that causes a hyperglycemic status which leads, over time, to serious damage to the heart, blood vessels, eyes, kidneys and nerves. The most frequent form of diabetes is type 2 diabetes mellitus (T2DM) which is often part of a metabolic syndrome (hyperglycaemia, hypertension, hypercholesterolemia, abdominal obesity) that usually requires the use of several medications from different drug classes to bring each of these conditions under control. T2DM is associated with an increase in inflammatory markers such as interleukin-6 (IL-6) and the tumor necrosis factor alpha (TNF-α). Higher levels of IL-6 and TNF-α are associated with a downregulation of several drug metabolizing enzymes, especially the cytochrome P450 (P450) isoforms CYP3As and CYP2C19. A decrease in these P450 isoenzymes may lead to unexpected rise in plasma levels of substrates of these enzymes. It could also give rise to a mismatch between the genotypes determined for these enzymes, the predicted phenotypes based on these genotypes and the phenotypes observed clinically. This phenomenon is described as phenoconversion. Phenoconversion typically results from either a disease (such as T2DM) or concomitant administration of medications inducing or inhibiting (including competitive or non-competitive inhibition) a P450 isoenzyme used by other substrates for their elimination. Phenoconversion could have a significant impact on drug effects and genotypic-focused clinical outcomes. As the aging population is exposed to polypharmacy along with inflammatory comorbidities, consideration of phenoconversion related to drug metabolizing enzymes is of importance when applying pharmacogenomic results and establishing personalized and more precise drug regimens.

Mechanistic insights into the CYP2C19 genetic variants prevalent in the Indian population

PURPOSE

CYP2C19 metabolizes the antiplatelet and antiepileptic drugs. Any alteration in CYP2C19 activity might influence the therapeutic efficacy. The objective of this study was to identify CYP2C19 variants prevalent in Indians and perform their in silico characterization.

METHODS

Infinium global screening array (GSA) was used for CYP2C19 genotyping in 2000 healthy Indians. In addition, we performed in silico characterization of the identified variants.

RESULTS

Out of the 11 variants covered (*2, *3, *4,*5,*6, *7,*8, *9,*10,*11, and *17), five were identified in Indians (*2, *3, *6,*8 and *17). The *2 and *17 were the most prevalent alleles (minor allele frequencies, MAF: 32.0% and 13.95%). The *3, *6 and *8 were rare (MAFs: 0.425%, 0.025% and 0.05%). The *2 variant is shown to affect the splicing at the fifth exon-intron boundary. The *3 variant is a non-sense variant that is predicted to be deleterious. On the otherhand, the *17 variant showed more binding affinity for GATA binding protein 1 (GATA1), myocyte enhancer factor 2 (MEF2) and ectotropic viral integration site 1 (EVI1). The *6 and *8 variants predicted to be deleterious. The *2, *3 and *7 variants showed lesser probability of exon skipping, while *17 showed more probability. The genotype distribution of Indian subjects is comparable with that of South Asians (SAS) (1000 genome project, phase 3).

CONCLUSION

The *2, *3 and *17 variants are the key pharmacogenetic determinants in Indians. The *2 and *3 are loss-of-function variants. The *17 is a gain-of-function variant with increased binding of transcriptional factors.

Influence of serum inflammatory cytokines on cytochrome P450 drug metabolising activity during breast cancer chemotherapy: a patient feasibility study

Individual response to chemotherapy in patients with breast cancer is variable. Obesity and exercise are associated with better and worse outcomes, respectively, and it is known that both impact the systemic cytokine milieu. Cytochrome P450 (CYP) enzymes are responsible for the metabolism of many chemotherapy agents, and CYP enzyme activity has been shown to be modified by inflammatory cytokines in vitro and in vivo. Cytokine-associated changes in CYP metabolism may alter chemotherapy exposure, potentially affecting treatment response and patient survival. Therefore, better understanding of these biological relationships is required. This exploratory single arm open label trial investigated changes in in vivo CYP activity in twelve women treated for stage II or III breast cancer, and demonstrated for the first time the feasibility and safety of utilising the Inje phenotyping cocktail to measure CYP activity in cancer patients receiving chemotherapy. Relative CYP activity varied between participants, particularly for CYP2C9 and CYP2D6, and changes in serum concentrations of the inflammatory cytokine monocyte chemoattractant protein 1 inversely correlated to CYP3A4 activity during chemotherapy. Future use of phenotyping cocktails in a clinical oncology setting may help guide drug dosing and improve chemotherapy outcomes.

Clinical Trial Registration: Trial was retrospectively registered to the Australia New Zealand Clinical Trial Registry (ANZCTR). ACTRN12620000832976, 21 Aug 2020, https://www.anzctr.org.au/ACTRN12620000832976.aspx.

Phenoconversion of Cytochrome P450 Metabolism: A Systematic Review

Phenoconversion is the mismatch between the individual’s genotype-based prediction of drug metabolism and the true capacity to metabolize drugs due to nongenetic factors. While the concept of phenoconversion has been described in narrative reviews, no systematic review is available. A systematic review was conducted to investigate factors contributing to phenoconversion and the impact on cytochrome P450 metabolism. Twenty-seven studies met the inclusion criteria and were incorporated in this review, of which 14 demonstrate phenoconversion for a specific genotype group. Phenoconversion into a lower metabolizer phenotype was reported for concomitant use of CYP450-inhibiting drugs, increasing age, cancer, and inflammation. Phenoconversion into a higher metabolizer phenotype was reported for concomitant use of CYP450 inducers and smoking. Moreover, alcohol, pregnancy, and vitamin D exposure are factors where study data suggested phenoconversion. The studies reported genotype–phenotype discrepancies, but the impact of phenoconversion on the effectiveness and toxicity in the clinical setting remains unclear. In conclusion, phenoconversion is caused by both extrinsic factors and patient- and disease-related factors. The mechanism(s) behind and the extent to which CYP450 metabolism is affected remain unexplored. If studied more comprehensively, accounting for phenoconversion may help to improve our ability to predict the individual CYP450 metabolism and personalize drug treatment.

Factors involved in phenoconversion of CYP3A using 4β-hydroxycholesterol in stable kidney transplant recipients

BACKGROUND

Phenoconversion is a phenomenon whereby some genotypic extensive metabolizers transiently exhibit drug metabolizing enzyme activity at similar level as that of poor metabolizers. Renal failure is known to decrease CYP3A activity in humans. Indoxyl sulfate, parathyroid hormone (PTH), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) have been reported to cause CYP3A downregulation in renal failure. We measured plasma concentrations of the above compounds in stable kidney transplant recipients, and evaluated their relations with phenoconversion of CYP3A evaluated by plasma concentration of 4β-hydroxycholesterol, a biomarker of CYP3A activity. Phenoconversion was defined as a genotypic extensive/intermediate metabolizer exhibiting CYP3A activity below the cutoff value that discriminates extensive/intermediate from poor metabolizers.

METHODS

Sixty-three Japanese kidney transplant recipients who underwent transplantation more than 180 days prior to the study were included. Morning blood samples were collected, and CYP3A5 polymorphism as well as plasma concentrations of 4β-hydroxycholesterol, indoxyl sulfate, intact-PTH, IL-6 and TNF-α were determined.

RESULTS

Significantly higher plasma 4β-hydroxycholesterol concentration was observed in recipients with CYP3A5*1 allele (n = 23) compared to those without the allele (n = 40), and the cut-off value was 40.0 ng/mL. Ten recipients with CYP3A5*1 allele exhibited CYP3A activity below 40.0 ng/mL (phenoconversion). Only plasma indoxyl sulfate concentration was significantly higher in recipients with CYP3A phenoconversion compared to those without phenoconversion.

CONCLUSIONS

These findings suggest that higher plasma indoxyl sulfate concentration may be involved in CYP3A phenoconversion. Dose adjustment of drugs metabolized by CYP3A may be needed in patients with CYP3A5*1 allele and high blood indoxyl sulfate.

Progressing Preemptive Genotyping of CYP2C19 Allelic Variants for Sickle Cell Disease Patients

AIMS

Interindividual variability in drug response and adverse effects have been described for proton pump inhibitors, anticonvulsants, selective serotonin reuptake inhibitors, tricyclic antidepressants, and anti-infectives, but little is known about the safety and efficacy of these medications in patients with sickle cell disease (SCD). We genotyped the CYP2C19 gene which has been implicated in the metabolism of these drugs in an SCD patient cohort to determine the frequencies of reduced function, increased function, or complete loss-of-function variants.

MATERIALS AND METHODS

DNAs from 165 unrelated SCD patients were genotyped for nine CYP2C19 (*2, *3, *4, *5, *6, *7,*8, *12, and *17) alleles using the iPLEX^® ADME PGx multiplex panel.

RESULTS

Three CYP2C19 alleles (*2, *12, and *17) were detected with the following frequencies: 0.209, 0.006, and 0.236, respectively. The predicted phenotype frequencies were distributed as extensive (31.5%), intermediate (24.8%), poor (5.5%), ultrarapid (30.3%), and unknown metabolizers (7.9%).

DISCUSSION

Prognostic genotyping is potentially useful for identifying SCD patients with allelic variants linked to proven clinical pharmacokinetic consequences for several drugs metabolized by the CYP2C19 gene. However, the main challenge to implementing a genetics-guided prescribing practice is ensuring concordance between CYP2C19 genotypes and metabolic phenotypes in SCD patients.

CYP450 genotype and pharmacogenetic association studies: a critical appraisal

Despite strong pharmacological support, association studies using genotype-predicted phenotype as a variable have yielded conflicting or inconclusive evidence to promote personalized pharmacotherapy. Unless the patient is a genotypic poor metabolizer, imputation of patient's metabolic capacity (or metabolic phenotype), a major factor in drug exposure-related clinical response, is a complex and highly challenging task because of limited number of alleles interrogated, population-specific differences in allele frequencies, allele-specific substrate-selectivity and importantly, phenoconversion mediated by co-medications and inflammatory co-morbidities that modulate the functional activity of drug metabolizing enzymes. Furthermore, metabolic phenotype and clinical outcomes are not binary functions; there is large intragenotypic and intraindividual variability. Therefore, the ability of association studies to identify relationships between genotype and clinical outcomes can be greatly enhanced by determining phenotype measures of study participants and/or by therapeutic drug monitoring to correlate drug concentrations with genotype and actual metabolic phenotype. To facilitate improved analysis and reporting of association studies, we propose acronyms with the prefixes ‘g’ (genotype-predicted phenotype) and ‘m’ (measured metabolic phenotype) to better describe this important variable of the study subjects. Inclusion of actually measured metabolic phenotype, and when appropriate therapeutic drug monitoring, promises to reveal relationships that may not be detected by using genotype alone as the variable.

High CYP2C19 phenotypic variability in gastrointestinal cancer patients

PURPOSE

CYP2C19 contributes to the metabolism of several chemotherapeutic agents. The CYP2C19 homozygous null function genotype strongly predicts activity phenotype in healthy populations. An additional acquired loss of function has been reported in up to one-third of cancer patients. It is not known whether this phenomenon also occurs in patients with earlier stage or in resected disease.

METHODS

This study investigated whether acquired loss of CYP2C19 function was detectable in patients with stage III-IV or resected gastrointestinal cancer. CYP2C19 genotype was determined in 49 patients, and subjects were probed for CYP2C19 activity on three test occasions.

RESULTS

An acquired loss of CYP2C19 activity was observed in 20% of stage III-IV and 17% of resected patients at the first test. Significant (p < 0.01) genotype-phenotype discordance was observed in both groups. There were no direct associations between this discordance and inflammatory markers, tumour burden or chemotherapeutic history. Notably, hepatic CYP2C19 function was not stable over time and phenotype conversion occurred in 23 patients over the period of testing.

CONCLUSION

Reliance on germ-line genotype to infer a poor metaboliser status could substantially underestimate the number of patients with deficient CYP2C19 function. This could compromise the interpretation of genotype-based clinical association studies.

Phenoconversion of CYP2C9 in epilepsy limits the predictive value of CYP2C9 genotype in optimizing valproate therapy

Aim: Since prominent role in valproate metabolism is assigned to CYP2C9 in pediatric patients, the association between children's CYP2C9-status and serum valproate concentrations or dose-requirements was evaluated. Materials & Methods: The contribution of CYP2C9 genotype and CYP2C9 expression in children (n = 50, Caucasian) with epilepsy to valproate pharmacokinetics was analyzed. Results: Valproate concentrations were significantly lower in normal expressers with CYP2C9*1/*1 than in low expressers or in patients carrying polymorphic CYP2C9 alleles. Consistently, the dose-requirement was substantially higher in normal expressers carrying CYP2C9*1/*1 (33.3 mg/kg vs 13.8–17.8 mg/kg, p < 0.0001). Low CYP2C9 expression significantly increased the ratio of poor metabolizers predictable from CYP2C9 genotype (by 46%). Conclusion: Due to the substantial downregulation of CYP2C9 expression in epilepsy, inferring patients’ valproate metabolizing phenotype merely from CYP2C9 genotype results in false prediction.

Inflammation-induced phenoconversion of polymorphic drug metabolizing enzymes: hypothesis with implications for personalized medicine

Phenoconversion transiently converts genotypic extensive metabolizers (EMs) into phenotypic poor metabolizers (PMs) of drugs, potentially with corresponding changes in clinical response. This phenomenon, typically resulting from coadministration of medications that inhibit certain drug metabolizing enzymes (DMEs), is especially well documented for enzymes of the cytochrome P450 family. Nonclinical evidence gathered over the last two decades also strongly implicates elevated levels of some proinflammatory cytokines, released during inflammation, in down-regulation of drug metabolism, especially by certain DMEs of the P450 family, thereby potentially causing transient phenoconversion. Clinically, phenoconversion of NAT2, CYP2C19, and CYP2D6 has been documented in inflammatory conditions associated with elevated cytokines, such as human immunodeficiency virus infection, cancer, and liver disease. The potential of other inflammatory conditions to cause phenoconversion has not been studied but experimental and anecdotal clinical evidence supports infection-induced down-regulation of CYP1A2, CYP3A4, and CYP2C9 as well. Collectively, the evidence supports a hypothesis that certain inflammatory conditions associated with elevated proinflammatory cytokines may cause phenoconversion of certain DMEs. Since inflammatory conditions associated with elevated levels of proinflammatory cytokines are highly prevalent, phenoconversion of genotypic EM patients into transient phenotypic PMs may be more frequent than appreciated. Since drug pharmacokinetics, and therefore the clinical response, is influenced by DME phenotype rather than genotype per se, phenoconversion (whatever its cause) can have a significant impact on the analysis and interpretation of genotype-focused clinical outcome association studies. There is a risk that focusing on genotype alone may miss important associations between clinical outcomes and DME phenotypes, thus compromising future prospects of personalized medicine.

Medication use and multiple myeloma risk in Los Angeles County

BACKGROUND

The role of medication use in multiple myeloma (MM) risk remains unclear.

METHODS

The Los Angeles County Multiple Myeloma Case-Control Study, comprising 278 MM cases and individually matched neighborhood controls, provided data to assess associations between medication use and MM risk. Odds ratios (OR) and 95 % confidence intervals (CI) were estimated using conditional logistic regression.

RESULTS

Erythromycin (ever) use was associated with increased MM risk (OR 1.85, 95 % CI 1.13-3.03). This association was restricted to men (OR 3.77, 95 % CI 1.72-8.29) and was especially apparent among men who took two or more courses of erythromycin (OR 4.68, 95 % CI 1.70-12.87).

CONCLUSIONS

Compared to females, males have lower levels of cytochrome P450 3A4 (CYP3A4), for which erythromycin is both a substrate and inhibitor. Use of CYP3A4-inhibiting drugs such as erythromycin in men may thus result in even lower levels of CYP3A4 and, consequently, higher levels of CYP3A4-metabolized substances. These results could potentially provide clues to explain discrepancies in MM incidence by sex. Consortial efforts to confirm these associations are warranted.