Frequencies of CYP2D6 genetic polymorphisms in Arab populations

Exploring the Pharmacokinetics of Drugs in Disabled Saudi Patients: A Systematic Review

Background/Objectives: Disability is a term that involves mental, intellectual, or sensory impairment resulting in the loss of one's ability to walk or perform the activities necessary to live in a society. This study aims to collect all the data regarding the absorption, distribution, and disposition of drugs in disabled Saudi patients, i.e., patients suffering from epilepsy, cancer, cardiovascular diseases, etc., and then compare these results with data reported in other ethnicities. Methods: An exhaustive online search used the key terms in Google Scholar, PubMed, Cochrane Library, and Science Direct to extract all articles that met the eligibility criteria. All research studies containing pharmacokinetic (PK) parameters (area under the curve from 0 to infinity (AUC0-∞), maximal plasma concentration (Cmax), clearance (CL), volume of distribution, time to reach maximum plasma concentration, and half-life) were included in this review. Results: In pediatric epileptic patients, carbamazepine showed a notable decrease in Cmax with increasing age, which may be due to ontogenetic changes in its disposition. The AUC0-∞ of busulphan in adult hematopoietic stem cell transplantation patients was recorded as 4392.5 ± 1354.65 μg·h/mL, with high inter-individual variability. Moreover, the CL of vancomycin was reported to be 25% higher among cancer patients in comparison to non-cancer subjects. Conclusions: The complications in disabled patients due to alterations in cytochrome P450 enzymes, pathophysiology, genetics, and ethnicity emphasize the significance of patient-centered drug dosing. These findings may aid healthcare physicians in refining therapeutic care in this population.

Global patterns of hemophilia drug trials, hemophilia care, and health care measures

Background

Drug trials are vital to establish safe and effective treatments for congenital hemophilia, a bleeding disorder that affects about 800,000 males worldwide. The global distribution of hemophilia drug trials (HDTs) and their alignment with hemophilia care is unknown.

Objectives

This study aimed to evaluate the global distribution of HDTs and its association with hemophilia care.

Methods

In this cross-sectional study, HDTs conducted between 2007 and 2022 were selected from the clinicaltrials.gov database. The density of trials per 1000 expected males with hemophilia (eMwH) was assessed according to hemophilia care measures (factor VIII and IX utilization per 1000 eMwH) derived from World Federation of Hemophilia data.

Results

Among 124 trials, 55 countries were represented, with an average of 7.9 countries per trial. Most HDT sites were in high-income (74.4%) or upper middle (20.1%)-income countries. The number of sites in lower-middle-income countries doubled, from 12 in 2007-2011 to 30 in 2017-2022-a nonsignificant increase from 5.8% to 7.0% (P = .53). Factor utilization was substantially reduced in lower-middle (0.4 international units [IUs] per 1000 eMwH) and upper middle (2.8 IUs per 1000 eMwH) compared with high (6.8 IUs per 1000 eMwH) income countries. HDT density was moderately correlated with factor usage (r = 0.436; P ≤ .001).

Conclusion

Most HDT sites were located in high-income countries, although a substantial proportion were in upper middle-income countries. A small but increasing number of trials were conducted in lower-middle-income countries, where factor usage is relatively low. This study provides evidence on the global distribution of HDT and raises questions regarding the generalizability, barriers, opportunities, and ethics of trials for a rare bleeding disorder.

Discovery and Enzyme Kinetic Characterization of Novel CYP2D6 Variants

Cytochrome P450 2D6 (CYP2D6) exhibits rich genetic polymorphism, and functional changes caused by variations are the key reasons for differences in substrate drug systemic exposure. Discovering novel variants and defining their enzymatic kinetic characteristics can contribute to the personalized application of drugs. In this study, a data chain of variant-function-structure was established through population-based sequencing, baculovirus insect cell expression, in vitro enzymatic incubation, and ultrahigh performance liquid chromatography tandem mass spectrometry. Results revealed nine novel missense mutations in the exonic regions. After the corresponding microsomes were obtained, the kinetics of the variants were investigated using dextromethorphan as a probe substrate. It was found that the activities of CYP2D6.2, 10, 17, 35, 65, R28G, T76M, and E215K were significantly reduced, while D301V almost led to loss of enzyme function. Additionally, the relative clearance rate of R25Q was significantly increased. From the molecular structure perspective, the mutation sites are distributed outside the dextromethorphan binding pocket, suggesting that they primarily influence CYP2D6 activity via allosteric modulation. These research findings provide fundamental data for the precise application of CYP2D6 substrate drugs.

The 75-Year Anniversary of the Department of Physiology and Pharmacology at Karolinska Institutet-Examples of Recent Accomplishments and Future Perspectives

Karolinska Institutet is a medical university encompassing 21 departments distributed across three departmental or campus groups. Pharmacological research has a long and successful tradition at the institute with a multitude of seminal findings in the areas of neuronal control of vasodilatation, cardiovascular pharmacology, neuropsychopharmacology, receptor pharmacology, and pharmacogenomics that resulted in, among many other recognitions, two Nobel prizes in Physiology and Medicine, one in 1970 to Ulf von Euler for his discovery of the processes involved in storage, release, and inactivation of neurotransmitters and the other in 1982 to Sune Bergström and Bengt Samuelsson for their work on prostaglandins and the discovery of leukotrienes. Pharmacology at Karolinska Institutet has over the last decade been ranked globally among the top 10 according to the QS World University Ranking. With the Department of Physiology and Pharmacology now celebrating its 75-year anniversary, we wanted to take this as an opportunity to showcase recent research achievements and how they paved the way for current activities at the department. We emphasize examples from preclinical and clinical research where the dpartment's integrative environment and robust infrastructure have successfully facilitated the translation of findings into clinical applications and patient benefits. The close collaboration between preclinical scientists and clinical researchers across various disciplines, along with a strong network of partnerships within the department and beyond, positions us to continue leading world-class pharmacological research at the Department of Physiology and Pharmacology for decades to come. SIGNIFICANCE STATEMENT: Pharmacological research at Karolinska Institutet has a long and successful history. Given the 75-year anniversary of the Department of Physiology and Pharmacology, this perspective provides an overview of recent departmental achievements and future trajectories. For these developments, interdisciplinary and intersectoral collaborations and a clear focus on result translation are key elements to continue its legacy of world-leading pharmacological research.

Genetic analysis: Therapeutic drug monitoring of metformin and glimepiride on diabetic patients' plasma including genetic polymorphism

Diabetes is a widespread disease that needs to be controlled. Therapeutic monitoring of drugs is very helpful in maintaining desirable doses. To study a correlation between the blood level of metformin (to a lesser extent, glimepiride) and genotyping (mainly the SULT1A1 genotype). Determine drug levels using a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) tool. A validated LC-MS/MS method was developed to determine metformin and glimepiride levels in human plasma. DNA extraction was performed using Jena Bioscience's Blood DNA preparation, in which a column kit was used to extract DNA for genetic polymorphism. The investigation was carried out using both medications in type 2 diabetes patients alongside the genetic polymorphism. One hundred and six patients were assessed. The prevalence of homozygosity for SULT1A1 and wild-type CYP2D6 * 4 were 72.6% and 73.6%, respectively. After adjustment for daily intake of metformin, three patients out of five with the highest levels of metformin had no homozygosity (SULT1A1 genotype). Statistically, variables that demonstrated an insignificant correlation with the level of metformin were body mass index (rs (87) = 0.32, P = 0.011) and age (rs (87) =0.26, P = 0.017). The homozygous (SULT1A1 genotype) correlation was moderate (rs (87) =0.21, P = 0.052). According to the findings, patients with the wt/wt CYP2D6 genotype had considerably greater levels of endoxifen than those with the v/v CYP2D6 genotype. The study's results reported a probable correlation between the blood level of metformin (to a lesser extent, glimepiride) and genotyping (mainly the SULT1A1 genotype). Genotype-guided drug therapy may provide a novel contribution to maximize drug efficacy and/or minimize toxicity.

Mining local exome and HLA data to characterize pharmacogenetic variants in Saudi Arabia

Pharmacogenomics (PGx) is a promising field of precision medicine where efficacy of drugs is maximized while side effects are minimized for individual patients. Knowledge of the frequency of PGx-relevant variants (pharmacovariants) in the local population is a pre-requisite to informed policy making. Unfortunately, such knowledge is largely lacking from the Middle East. Here, we describe the use of a large clinical exome database (n = 13,473) and HLA haplotypes (n = 64,737) from Saudi Arabia, one of the largest countries in the Middle East, along with previously published data from the local population to ascertain allele frequencies of known pharmacovariants. In addition, we queried another exome database (n = 816) of well-phenotyped research subjects from Saudi Arabia to discover novel candidate variants in known PGx genes (pharmacogenes). Although our results show that only 26% (63/242) of class 1A/1B PharmGKB variants were identified, we estimate that 99.57% of the local population have at least one such variant. This translates to a minimum estimated impact of 9% of medications dispensed by our medical center annually. We also highlight the contribution of rare variants where 71% of the pharmacogenes devoid of common pharmacovariants had at least one potentially deleterious rare variant. Thus, we show that approaches that go beyond the use of commercial PGx kits that have been optimized for other populations should be implemented to ensure universal and equitable access of all members of the local population to personalized prescription practices.

Effects of Genetic Polymorphisms of Drug Metabolizing Enzymes and co-Medications on Tamoxifen Metabolism in Black South African Women with Breast Cancer

Clinical outcomes of tamoxifen (TAM) treatment show wide interindividual variability. Comedications and genetic polymorphisms of enzymes involved in TAM metabolism contributes to this variability. Drug-drug and drug-gene interactions have seldom been studied in African Black populations. We evaluated the effects of commonly co-administered medicines on TAM pharmacokinetics in a cohort of 229 South African Black female patients with hormone-receptor positive breast cancer. We also investigated the pharmacokinetic effects of genetic polymorphism in enzymes involved in TAM metabolism, including the variants CYP2D6*17 and *29, which have been mainly reported in people of African descent. TAM and its major metabolites, N-desmethyltamoxifen (NDM), 4-OH-tamoxifen, and endoxifen (ENDO), were quantified in plasma using the liquid chromatography-mass spectrometry. The GenoPharm open array was used to genotype CYP2D6, CYP3A5, CYP3A4, CYP2B6, CYP2C9, and CYP2C19. Results showed that CYP2D6 diplotype and CYP2D6 phenotype significantly affected endoxifen concentration (P < 0.001 and P < 0.001). CYP2D6*17 and CYP2D6*29 significantly reduced the metabolism of NDM to ENDO. Antiretroviral therapy had a significant effect on NDM levels and the TAM/NDM and NDM/ENDO metabolic ratios but did not result in significant effects on ENDO levels. In conclusion, CYP2D6 polymorphisms affected endoxifen concentration and the variants CYP2D6*17 and CYP2D6*29 significantly contributed to low exposure levels of ENDO. This study also suggests a low risk of drug-drug interaction in patients with breast cancer on TAM.

Personalizing atomoxetine dosing in children with ADHD: what can we learn from current supporting evidence

PURPOSE

There is marked heterogeneity in treatment response of atomoxetine in patients with attention deficit/hyperactivity disorder (ADHD), especially for the pediatric population. This review aims to evaluate current evidence to characterize the dose-exposure relationship, establish clinically relevant metrics for systemic exposure to atomoxetine, define a therapeutic exposure range, and to provide a dose-adaptation strategy before implementing personalized dosing for atomoxetine in children with ADHD.

METHODS

A comprehensive search was performed across electronic databases (PubMed and Embase) covering the period of January 1, 1985 to July 10, 2022, to summarize recent advances in the pharmacokinetics, pharmacogenomics/pharmacogenetics (PGx), therapeutic drug monitoring (TDM), physiologically based pharmacokinetics (PBPK), and population pharmacokinetics (PPK) of atomoxetine in children with ADHD.

RESULTS

Some factors affecting the pharmacokinetics of atomoxetine were summarized, including food, CYP2D6 and CYP2C19 phenotypes, and drug‒drug interactions (DDIs). The association between treatment response and genetic polymorphisms of genes encoding pharmacological targets, such as norepinephrine transporter (NET/SLC6A2) and dopamine β hydroxylase (DBH), was also discussed. Based on well-developed and validated assays for monitoring plasma concentrations of atomoxetine, the therapeutic reference range in pediatric patients with ADHD proposed by several studies was summarized. However, supporting evidence on the relationship between systemic atomoxetine exposure levels and clinical response was far from sufficient.

CONCLUSION

Personalizing atomoxetine dosage may be even more complex than anticipated thus far, but elucidating the best way to tailor the non-stimulant to a patient's individual need will be achieved by combining two strategies: detailed research in linking the pharmacokinetics and pharmacodynamics in pediatric patients, and better understanding in nature and causes of ADHD, as well as environmental stressors.

[A precision medication study of atomoxetine in children with attention deficit hyperactivity disorder: CYP2D6 genetic testing and therapeutic drug monitoring]

Atomoxetine is the first non-stimulant drug for the treatment of children and adults with attention deficit hyperactivity disorder (ADHD), and its safety and efficacy show significant differences in the pediatric population. This article reviews the genetic factors influencing the pharmacokinetic differences of atomoxetine from the aspect of the gene polymorphisms of the major metabolizing enzyme CYP2D6 of atomoxetine, and then from the perspective of therapeutic drug monitoring, this article summarizes the reference ranges of the effective concentration of atomoxetine in children with ADHD proposed by several studies. In general, there is an association between the peak plasma concentration of atomoxetine and clinical efficacy, but with a lack of data from the Chinese pediatric population. Therefore, it is necessary to establish related clinical indicators for atomoxetine exposure, define the therapeutic exposure range of children with ADHD in China, and combine CYP2D6 genotyping to provide support for the precision medication of atomoxetine.

Evaluation of the Association between Single Nucleotide Polymorphisms of Metabolizing Enzymes with the Serum Concentration of Paracetamol and Its Metabolites

Intravenous paracetamol is a commonly administered analgesic and antipyretic in inpatient settings. Paracetamol is metabolized by cytochrome P450 (CYP) enzymes followed by conjugating enzymes to mainly glucuronide but to a lesser extent, sulphate metabolites, and oxidative metabolites. Single nucleotide polymorphisms (SNPs) in the CYP enzymes result in modified enzymatic activity. The present study was carried out to evaluate the prevalence of SNPs related to paracetamol metabolism and principal metabolites in critically ill patients, and those with chronic kidney disease. The present study is a cross-sectional study carried out in adults (>21 years) requiring intravenous paracetamol as part of their standard of care. Details regarding their demographics, and renal and liver function tests were collected. Blood was withdrawn for the analysis of paracetamol and their metabolites, and the SNPs of key CYP enzymes. Paracetamol/paracetamol glucuronide (P/PG), paracetamol/paracetamol sulphate (P/PS) and PG/PS were estimated. Acute liver injury (ALI) and renal dysfunction were defined using standard definitions. We observed a significant prevalence of SNPs in CYP1A2*1C, CYP3A4*3, CYP1A2*1K, CYP1A2*6, CYP2D6*10, and CYP2E1*2 amongst the 150 study participants. Those with CYP1A2*6 (CC genotype) were observed with significantly lower PG and PS concentrations, and a higher P/PS ratio; CYP2D6*10 (1/1 genotype) with a significantly lower PG concentration and a higher P/PG ratio; and CYP1A2*1K (CC genotype) was observed with a significantly higher PG/PS ratio. Good predictive accuracies were observed for determining the SNPs with the cut-off concentration of 0.29 μM for PS in determining CYP1A2*1K, 0.39 μM for PG and 0.32 μM for PS in determining CYP1A2*6 genotype, and 0.29 μM for PG in determining the CYP2D6*10 genotype. Patients with renal dysfunction were observed with significantly greater concentrations of paracetamol, PG and P/PS, and PG/PS ratios, with a lower concentration of PS. No significant differences were observed in any of the metabolites or metabolite ratios in patients with ALI. We have elucidated the prevalence of key CYP enzymes involved in acetaminophen metabolism in our population. Alterations in the metabolite concentrations and metabolic ratios were observed with SNPs, and in patients with renal dysfunction. Population toxicokinetic studies elucidating the dose-response relationship are essential to understand the optimized dose in this sub-population.

Categorization of Cytochrome P4502D6 Activity Score by Urinary Amphetamine/Methamphetamine Ratios

Methamphetamine (MA) level in urine has been used for judgment in MA consumption. Metabolism and intoxication of MA are correlated with the activity of cytochrome P450 2D6 (CYP2D6). The activity score (AS) is a potential tool for predicting exposure and personalized dose of drugs metabolized by CYP2D6. Prediction of the CYP2D6 activity score might be described as MA intoxication. The objective of this study was to categorize the CYP2D6 activity score using the urinary amphetamine (AM)/MA ratio. Urine samples (n = 23,258) were collected. The levels of MA and AM were determined by a gas chromatography-nitrogen-phosphorus detector. The log AS was calculated by an AM/MA ratio and classified into four groups following the percentile position: lower than the 2.5th, the 2.5th-the 50th, the 50th-97.5th, and greater than the 97.5th percentile, respectively. The AS value for males presented was less than 0.024, 0.024-0.141, 0.141-0.836, and greater than 0.836. Meanwhile, the AS values were revealed to be lower than 0.023, 0.023-0.148, 0.148-0.850, and higher than 0.850 for females. The AS value of CYP2D6 can be applied to describe the toxicity of MA in forensic crime scenes and relapse behavior.

Variations in the Frequencies of Polymorphisms in the CYP450s Genes in Eight Major Ethnicities of Iran: A Review of the Human Data

Genetic polymorphisms in cytochrome P450 genes can cause variation in metabolism. Thus, single nucleotide variants significantly impact drug pharmacokinetics, toxicity factors, and efficacy and safety of medicines. The distribution of CYP450 alleles varies drastically across ethnicities, with significant implications for personalized medicine and the healthcare system. We combined whole-genome and exome sequencing data to provide a review of CYP450 allele polymorphisms with clinical importance. Data were collected from 800 unrelated Iranians (100 subjects from 8 major ethnicities of Iran), more than 32,000 unrelated Europeans (other than Caucasian), and four Middle Eastern countries. We analyzed the frequencies and similarities of 17 CYP450 frequent alleles related to nine important CYP450 isoenzymes and homozygous and heterozygous genotypes based on these alleles in eight major Iranian ethnics by integrating these data with population-specific linkage information and compared these datasets with mentioned populations.

The frequencies of CYP2D6 alleles and their impact on clinical outcomes of adjuvant tamoxifen therapy in Syrian breast cancer patients

Background

Tamoxifen is one of the fundamental pillars of adjuvant endocrine therapy for hormone receptor-positive breast cancer; however, 30–50% of patients receiving tamoxifen experience tumor relapse. CYP2D6, encoded by an extremely polymorphic CYP2D6 gene, is the rate-limiting enzyme of tamoxifen bioactivation. This study aimed at determining the frequencies of the most clinically relevant CYP2D6 alleles and evaluating their impact on the responsiveness to tamoxifen in a cohort of Syrian breast cancer patients.

Methods

This case–control study encompassed positive estrogen and/or progesterone receptor, stage 1–3 breast cancer female patients receiving tamoxifen at Al-Bairouni University Hospital, the major National Oncology Center in Syria. Successfully genotyped eligible patients (n = 97) were classified according to their response into; no recurrence group (n = 39) who had completed a five-year recurrence-free adjuvant tamoxifen therapy, and recurrence group (n = 58) who had experienced recurrence. Several star alleles including CYP2D6*4, CYP2D6*10, CYP2D6*41, and CYP2D6*69 were identified via targeted sequencing of specific polymerase chain reaction (PCR) products and phenotypes were assigned according to activity score (AS). The correlation between genotypes and disease-free survival (DFS) was assessed using Kaplan–Meier method and log-rank test. Hazard ratios were estimated using Cox proportional hazards regression models.

Results

The allelic frequencies of CYP2D6*41, CYP2D6*10, CYP2D6*4, and CYP2D6*69 were found to be 9.28%, 7.22%, 7.22%, and 2.58%, respectively. No statistically significant differences were observed in the frequencies of CYP2D6 phenotypes between the two arms (P = 0.24), nor the incidence of tamoxifen-induced hot flashes (P = 0.109). Poor metabolizers (PMs) tended to display shorter DFS than intermediate metabolizers (IMs) and normal metabolizers (NMs) combined (adjusted HR = 2.34, 95% CI = 0.84–6.55, P = 0.104). Notably, patients homozygous for the null CYP2D6*4 allele (1847A/A) had an elevated risk of disease recurrence compared to patients with 1847G/G genotype (adjusted HR = 5.23, 95% CI = 1.22–22.49, P = 0.026).

Conclusions

Our findings show no association between CYP2D6 phenotype and treatment outcomes of tamoxifen in Syrian breast cancer patients. Nevertheless, a worse DFS was revealed in patients with 1847A/A genotype (*4/*4).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-10148-8.

Influence of CYP2D6, CYP2C19 and CYP3A5 polymorphisms on plasma levels of tamoxifen metabolites in Algerian women with ER+ breast cancer

Background

Tamoxifen, a selective estrogen receptor modulator, is indicated for breast cancer developed in response to estrogen.

Findings

In the current study we explored the relationship between the different variants of CYP2D6, CYP2C19, CYP3A5 and plasma Endoxifen levels in Algerian patients with ER + breast cancer. We further conducted the relationship between the candidate genes and the recurrences rate. Endoxifen levels differed significantly (p < .005) between carriers of two functional alleles and patients genotyped as CYP2D6*10, CYP2D6*17, CYP2D6*41 or CYP2D6*5/*5. Patients with elevated Endoxifen concentrations were significantly more likely to not report recurrences than patients with reduced or nul alleles. Such nul/nul, red/red, and red/nul diplotypes have been associated with a higher rate of recurrences than other genotypes during treatment.

Conclusion

Our findings suggest that the CYP2D6 genotype should be considered in tamoxifen-treated women. While quantitatively, CYP2D6 represents only a minor fraction of the total drug metabolizing capacity of the liver, it is polymorphic and, therefore, may alter the balance of metabolism of tamoxifen toward the activation pathways. Breast cancer patients with the CYP2D6 nul/nul or red/nul diplotype may benefit less from Tamoxifen treatment and are more likely to develop recurrences. Comprehensive CYP2D6 genotyping has a good predictive value for CYP2D6 activity. Common variants in CYP2C19 and CYP3A5 did not have a significant impact on the recurrences in this cohort of patients with ER + breast cancer.