An International Adult Guideline for Making Clozapine Titration Safer by Using Six Ancestry-Based Personalized Dosing Titrations, CRP, and Clozapine Levels

This international guideline proposes improving clozapine package inserts worldwide by using ancestry-based dosing and titration. Adverse drug reaction (ADR) databases suggest that clozapine is the third most toxic drug in the United States (US), and it produces four times higher worldwide pneumonia mortality than that by agranulocytosis or myocarditis. For trough steady-state clozapine serum concentrations, the therapeutic reference range is narrow, from 350 to 600 ng/mL with the potential for toxicity and ADRs as concentrations increase. Clozapine is mainly metabolized by CYP1A2 (female non-smokers, the lowest dose; male smokers, the highest dose). Poor metabolizer status through phenotypic conversion is associated with co-prescription of inhibitors (including oral contraceptives and valproate), obesity, or inflammation with C-reactive protein (CRP) elevations. The Asian population (Pakistan to Japan) or the Americas’ original inhabitants have lower CYP1A2 activity and require lower clozapine doses to reach concentrations of 350 ng/mL. In the US, daily doses of 300–600 mg/day are recommended. Slow personalized titration may prevent early ADRs (including syncope, myocarditis, and pneumonia). This guideline defines six personalized titration schedules for inpatients: 1) ancestry from Asia or the original people from the Americas with lower metabolism (obesity or valproate) needing minimum therapeutic dosages of 75–150 mg/day, 2) ancestry from Asia or the original people from the Americas with average metabolism needing 175–300 mg/day, 3) European/Western Asian ancestry with lower metabolism (obesity or valproate) needing 100–200 mg/day, 4) European/Western Asian ancestry with average metabolism needing 250–400 mg/day, 5) in the US with ancestries other than from Asia or the original people from the Americas with lower clozapine metabolism (obesity or valproate) needing 150–300 mg/day, and 6) in the US with ancestries other than from Asia or the original people from the Americas with average clozapine metabolism needing 300–600 mg/day. Baseline and weekly CRP monitoring for at least four weeks is required to identify any inflammation, including inflammation secondary to clozapine rapid titration.

CYP2C19 Genotyping May Provide a Better Treatment Strategy when Administering Escitalopram in Chinese Population

Depression disorder is one of the most serious mental illnesses in the world. Escitalopram is the essential first-line medication for depression disorder. It is the substrate of hepatic cytochrome P450 (CYP) enzyme CYP2C19 with high polymorphism. The effect of CYP2C19 on pharmacokinetics and pharmacodynamics on Caucasian population has been studied. The Clinical Pharmacogenetics Implementation Consortium Guideline provides dosing recommendations for escitalopram on CYP2C19 genotypes on the basis of the studies on Caucasian population. However, the gene frequency of the alleles of CYP2C19 showed racial differences between Chinese and Caucasian populations. Representatively, the frequency of the *2 and *3 allele, which were considered as poor metabolizer, has been shown to be three times higher in Chinese than in Caucasians. In addition, the environments might also lead to different degrees of impacts on genotypes. Therefore, the guidelines based on the Caucasians may not be applicable to the Chinese, which induced the establishment of a guideline in China. It is necessary to provide the evidence of individual treatment of escitalopram in Chinese by studying the effect of CYP2C19 genotypes on the pharmacokinetics parameters and steady-state concentration on Chinese. In this study, single-center, randomized, open-label, two-period, two-treatment crossover studies were performed. Ninety healthy Chinese subjects finished the trials, and they were included in the statistical analysis. The pharmacokinetics characteristics of different genotypes in Chinese were obtained. The results indicate that the poor metabolizer had higher exposure, and increased half-life than the extensive metabolizer and intermediate metabolite. The prediction of steady-state concentration based on the single dose trial on escitalopram shows that the poor metabolizer might have a higher steady-state concentration than the extensive metabolizer and intermediate metabolite in Chinese. The results indicate that the genetic testing before medication and the adjustment of escitalopram in the poor metabolizer should be considered in the clinical treatments in Chinese. The results provide the evidence of individual treatment of escitalopram in Chinese, which will be beneficial for the safer and more effective application of escitalopram in the Chinese population.Clinical Trial Registration: identifier ChiCTR1900027226.

Allele frequencies of single nucleotide polymorphisms of clinically important drug-metabolizing enzymes CYP2C9, CYP2C19, and CYP3A4 in a Thai population

Prior knowledge of allele frequencies of cytochrome P450 polymorphisms in a population is crucial for the revision and optimization of existing medication choices and doses. In the current study, the frequency of the CYP2C9*2, CYP2C9*3, CYP2C19*2, CYP2C19*3, CYP2C19*6, CYP2C19*17, and CYP3A4 (rs4646437) alleles in a Thai population across different regions of Thailand was examined. Tests for polymorphisms of CYP2C9 and CYP3A4 were performed using TaqMan SNP genotyping assay and CYP2C19 was performed using two different methods; TaqMan SNP genotyping assay and Luminex x Tag V3. The blood samples were collected from 1205 unrelated healthy individuals across different regions within Thailand. Polymorphisms of CYP2C9 and CYP2C19 were transformed into phenotypes, which included normal metabolizer (NM), intermediate metabolizer (IM), poor metabolizer (PM), and rapid metabolizers (RM). The CYP2C9 allele frequencies among the Thai population were 0.08% and 5.27% for the CYP2C9*2 and CYP2C9*3 alleles, respectively. The CYP2C19 allele frequencies among the Thai population were 25.60%, 2.50%, 0.10%, and 1.80% for the CYP2C19*2, CYP2C19*3, CYP2C19*6, and CYP2C19*17 alleles, respectively. The allele frequency of the CYP3A4 (rs4646437) variant allele was 28.50% in the Thai population. The frequency of the CYP2C9*3 allele was significantly lower among the Northern Thai population (P < 0.001). The frequency of the CYP2C19*17 allele was significantly higher in the Southern Thai population (P < 0.001). Our results may provide an understanding of the ethnic differences in drug responses and support for the utilization of pharmacogenomics testing in clinical practice.

ANALISIS POLIMORFISME CYP2D6*4 DAN CYP2D6*10 SEBAGAI METABOLIZER PRIMAKUIN DI RSUD JAYAPURA PAPUA INDONESIA

Primakuin adalah antimalaria yang digunakan untuk mengeliminasi stadium gametosit Plasmodium falciparum dan stadium hipnozoit dari P. vivax. Efektivitas primakuin dipengaruhi oleh kemampuan individu dalam memetabolisme obat. Metabolisme primakuin utama diperankan melalui jalur enzim sitokrom P 450 2D6. Polimorfisme gen pengkode enzim tersebut, yakni gen CYP2D6 berdampak pada perubahan dalam kemampuan memetabolisme obat. Tujuan penelitian ini adalah untuk mengetahui distribusi genotipe dan frekuensi alotipe dari CYP2D6*4(G/A) dan CYP2D6*10(C/T). Metode yang digunakan untuk menilai polimorfisme pada penelitian ini adalah PCR-RFLP dengan desain penelitian deskriptif observasional. Hasil penelitian menunjukkan bahwa alel CYP2D6*4 yang dapat bermanifestasi sebagai poor metabolizer tidak ditemukan pada sampel penelitian. Frekuensi alel CYP2D6*10 yang dapat bermanifestasi sebagai intermediete metabolizer adalah 10%. Genotipe homozigot mutan CYP2D6*4 dan CYP2D6*10 tidak ditemukan pada penelitian ini. 100% sampel penelitian ini memiliki kemampuan metabolisme yang baik (extensive metabolizer) terhadap primakuin.

Identification of CYP2D6 allelic mutations in a sub-set of Karachi population

CYP2D6 gene polymorphism is considered a main obstacle in the process of drug metabolism under clinical diseases that affect pharmacokinetics of ~25% of antidepressants and other drugs. Inter-individual variation occurs in the amount and functional activity of CYP2D6 enzyme produce undesirable side effects. The primary aim of current research is to evaluate gene and genotypic frequencies of CYP2D6 *1 extensive metabolizer, *4 poor metabolizer and *10 intermediate metabolizer allelic variants among depressed patients and compared with normal subjects and other populations. Human genomic DNA was isolated. Genotyping was performed by Polymerase chain reaction followed by restriction endonucleases digestion for variants analysis. The results indicated gene frequency of CYP2D6*1 was 59% (CI 49.6,68.3%) in normal subjects whereas, CYP2D6*4 was 13% (CI 3.7, 22.3%) and CYP2D6*10 was 54% (44.7, 63.3%) predominantly found in depressed patients. The results demonstrate pronounced association of CYP2D6 *4 and *10 allelic variants with patient’s drug response activity.

Association of CYP2D6*4 gene polymorphism with early papillary thyroid carcinoma

Objectives CYP2D6 is highly polymorphic and a common variant CYP2D6*4 results in the generation of poor metabolizer enzyme. The CYP2D6*4 variant has been associated with altered susceptibility to several cancers. The aim of the present case-control study aims to investigate the association between CYP2D6*4 polymorphism and the risk of papillary thyroid carcinoma (PTC). Materials and methods A study population of 97 cases with PTC and 120 controls were included in the study. Genotyping was done by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to detect the presence of CYP2D6*4. Results The CYP2D6*4 was associated with significantly increased PTC risk when compared with controls (odds ratio [OR]=1.995, 95% confidence interval [CI]=1.060–3.752, p=0.031). Besides, CYP2D6*4 allele frequency was higher in PTC patients with age ≤50 years when compared to those with age >50 (OR=2.380, 95% CI=1.191–4.755, p=0.013). CYP2D6*4 allele frequency was higher in patients who had encapsulated tumors, but it was not statistically significant (p=0.111). No relationship was found between CYP2D6*4 and PTC variants or between early (I/II) and late (III/IV) tumor stages. Conclusions Our findings indicate that the poor metabolizer CYP2D6*4 genotype may be a risk factor, especially in early PTC development. Further research with larger groups is required for the confirmation of our consequences.

Identification of CYP2D6 allelic mutations in a sub-set of Karachi population

CYP2D6 gene polymorphism is considered a main obstacle in the process of drug metabolism under clinical diseases that affect pharmacokinetics of ~25% of antidepressants and other drugs. Inter-individual variation occurs in the amount and functional activity of CYP2D6 enzyme produce undesirable side effects. The primary aim of current research is to evaluate gene and genotypic frequencies of CYP2D6 *1 extensive metabolizer, *4 poor metabolizer and *10 intermediate metabolizer allelic variants among depressed patients and compared with normal subjects and other populations. Human genomic DNA was isolated. Genotyping was performed by Polymerase chain reaction followed by restriction endonucleases digestion for variants analysis. The results indicated gene frequency of CYP2D6*1 was 59% (CI 49.6,68.3%) in normal subjects whereas, CYP2D6*4 was 13% (CI 3.7, 22.3%) and CYP2D6*10 was 54% (44.7, 63.3%) predominantly found in depressed patients. The results demonstrate pronounced association of CYP2D6 *4 and *10 allelic variants with patient’s drug response activity.

Effect of CYP2D6 genetic polymorphism on peak propafenone concentration: no significant effect of CYP2D6*10

Aim: The study aims to investigate the clinical implication of nonfunctional poor metabolizer (PM) alleles and intermediate metabolizer (IM) alleles of CYP2D6, including the CYP2D6*10 allele which shows substrate-dependent decrease in enzymatic activity, in antiarrhythmic therapy using propafenone. Materials & methods: We examined serum propafenone concentrations and metabolic ratio, which was expressed as serum concentrations of propafenone to 5-hydroxypropafenone, in 66 Japanese patients with tachyarrhythmias. Results: The peak propafenone concentration and metabolic ratio in CYP2D6 PM allele carriers were higher than those in extensive metabolizer (EM)/EM, EM/IM and IM/IM genotype groups. Conclusion: Results suggest that CYP2D6 PM alleles affect peak propafenone concentration, but the CYP2D6 IM allele CYP2D6*10 has no clinical implication in propafenone dosing.

Chloroquine Phosphate Metabolism and Gender-based Phenotypic Analysis in Healthy Subjects’ Urine Following Oral Administration

Background: Chloroquine, 4-N-(7-chloroquinolin-4-yl)-1-N,-N-diethylpentane-1,4-diamine has promising activity against corona virus disease 2019 (COVID-19) and as such, it is imperative to thoroughly understand and determine the rate at which individual body systems metabolizes the drug. Chloroquine a known antimalarial drug belongs to the chemical class of 4-aminoquinolines. Objectives: The study aimed to analyze Chloroquine and its metabolite in biological fluids of healthy subjects by simple thin layer chromatography (TLC), which is an efficient, and inexpensive method for quantifying Chloroquine and its metabolites. Methods: A total of 30 healthy volunteers participated in the study by ingesting 500 mg of chloroquine, and the results were compared with side effects experienced by these subjects. Two brands of Chloroquine phosphate were used for the analysis and the urine were collected pre and post-drug administration and the intensities of the spots observed were compared with the reference standard stock solution. The same or greater intensity of sample spot indicates poor metabolizer, less intensity when compared to the stock spot indicates intermediate metabolizer while a much lesser intensity indicates an extensive metabolizer. Results: There was a statistically significant difference between the brands of chloroquine used at P<0.05. 30% of the volunteers were assigned poor metabolizer phenotype, 50% were assigned extensive metabolizer phenotype, and 20% assigned Intermediate metabolizer phenotype based on the intensity of spots observed. The majority of the poor metabolizers were females while the majority of the extensive metabolizers were males. Conclusion: Gender differences plays a vital the role in metabolism, therefore outine implementation of phenotype determination before therapy will therefore greatly improve the goal of therapy and quality of life. implementation of phenotype determination before therapy will, therefore, greatly improve the goal of therapy and quality of life.