Genetic polymorphisms of NAT2 and CYP2E1 associated with antituberculosis drug-induced hepatotoxicity in Korean patients with pulmonary tuberculosis

Drug metabolizing enzymes and transporters, and their roles for the development of drug-induced liver injury

INTRODUCTION

Drug-induced liver injury (DILI) poses a significant challenge to drug development and human healthcare. The complex mechanisms underlying DILI make it challenging to accurately predict its occurrence, often leading to substantial financial losses from failed drug development projects and drug withdrawals. Growing evidence suggests that drug-metabolizing enzymes and transporters (DMETs) play a critical role in the development of DILI.

AREAS COVERED

In this review, we explore findings about the contributions of DMETs to DILI, with a focus on the studies examining genetic polymorphisms and their interactions with drugs. Additionally, we highlight the roles of DMETs in the development of predictive models for assessing DILI potential and in uncovering the mechanisms involved in DILI.

EXPERT OPINION

As new approach methods (NAMs) for assessing and predicting drug toxicity gain more prominence, it is imperative to better understand the adverse outcome pathways (AOPs) that underpin these methods. DMETs largely play a pivotal role in the molecular initiating events of DILI-related AOPs. Further research is needed to characterize DILI-related AOP networks and enhance the predictive performance of NAMs for assessing DILI risk.

Pharmacogenomic insights into tuberculosis treatment shows the NAT2 genetic variants linked to hepatotoxicity risk: a systematic review and meta-analysis

BACKGROUND

Tuberculosis (TB) patients undergoing anti-tuberculosis treatment often face serious adverse drug reactions, such as hepatotoxicity. Genetic variants of the N-acetyltransferase 2 (NAT2) gene have been linked to an increased risk of these toxic events.

OBJECTIVE

This study aims to provide a comprehensive evaluation of the evidence linking NAT2 genetic variants to anti-tuberculosis drug-related hepatotoxicity (ATDH).

METHOD

A comprehensive review and meta-analysis was performed by accessing databases such as PubMed, Scopus, and Web of Science. A total of 24 articles were incorporated into the dataset. Meta-analyses were conducted to gather estimates of the association between the slow acetlylators (SA) genotype and ATDH. The studies were stratified by ethnicity, regimen, genotyping methods, criteria for liver toxicity, and dosage. Also, meta-analysis for the specific SA type that was most likely responsible for the ATDH was also conducted.

RESULTS

The included studies showed individuals with a slow NAT2 acetylator had a significantly greater risk of experiencing hepatotoxicity ATDH (odds ratio [OR] 2.52 (95% CI: 1.95-3.27; p value < 0.001) compared to individuals with other types of acetylator (i.e., rapid and immediate). Among individuals with slow acetylator NAT2*5/7, NAT2*5/6, and NAT2*6/6 genotypes, there is a greater likelihood of association compared to other variations.

CONCLUSION

Our meta-analysis confirms a significant association between slow NAT2 acetylator and increased hepatotoxicity risk. The findings from the present underscore the potential of pharmacogenomic testing to improve TB treatment outcomes. By identifying patients with the slow acetylator NAT2 genotype, healthcare providers can predict an increased risk of anti-tuberculosis drug-induced hepatotoxicity. This allows for personalized treatment strategies, such as adjusting drug dosages or selecting alternative therapies, to minimize adverse effects and optimize efficacy.

Impact of CYP2D6*2A, CYP2D6*4 and CYP3A5*3 genetic polymorphisms on Bisoprolol peak concentration and clinical response in acute coronary syndrome patients

AIMS

Acute coronary syndrome (ACS) represents a major cause of death. Bisoprolol is commonly used in the management of ACS. This study aims to investigate the impact of CYP2D6*2A, CYP2D6*4 and CYP3A5*3 genetic polymorphisms on pharmacokinetics and clinical response of bisoprolol in ACS patients.

METHODS

This is an open-label cohort study that included 127 ACS patients and studied the effect of CYP3A5*3, CYP2D6*2A and CYP2D6*4 genotyping using real-time polymerase chain reaction on steady state bisoprolol plasma peak concentration analysed by high performance liquid chromatography-fluorescence detector.

RESULTS

Regarding CYP3A5*3, the mean peak bisoprolol concentration for CC, CT and TT genotypes were 4.25 ± 1.20, 3.93 ± 1.10 and 1.79 ± 0.69 ng/mL, respectively (P < .001). Higher systolic (126 ± 5.47 mmHg), diastolic blood pressure (82 ± 2.73 mmHg) and heart rate (97.80 ± 3.03 beats/min) were also observed in CYP3A5*3 TT carriers (P < .05). In CYP2D6*2A, the peak concentration of bisoprolol was lower in CC carriers (3.54 ± 1 ng/mL) compared to GG (4.38 ± 1.25 ng/mL) and GC carriers (4.07 ± 1.29 ng/mL, P = .019). In CYP2D6*4, the mean bisoprolol peak concentration in CC carriers was 3.98 ± 1.31 ng/mL, which was lower than T allele carriers (4.5 ± 0.8, P = .02). No differences in heart rate, systolic, diastolic blood pressure or bisoprolol dose were observed among CYP2D6*2A or CYP2D6*4 variants. Smokers exhibited lower bisoprolol peak concentration (3.96 ± 1.2 ng/mL) compared to nonsmokers (4.55 ± 1.34 ng/mL, P = .037).

CONCLUSION

There is an association between CYP3A5*3, CYP2D6*4, CYP2D6*2A variants and bisoprolol peak concentration, which may serve as a guide in the future in choosing the optimum dose of bisoprolol in ACS patients.

Isoniazid-historical development, metabolism associated toxicity and a perspective on its pharmacological improvement

Despite the extraordinary anti-tubercular activity of isoniazid (INH), the drug-induced hepatotoxicity and peripheral neuropathy pose a significant challenge to its wider clinical use. The primary cause of INH-induced hepatotoxicity is in vivo metabolism involving biotransformation on its terminal -NH2 group owing to its high nucleophilic nature. The human N-acetyltransferase-2 enzyme (NAT-2) exploits the reactivity of INH's terminal -NH2 functional group and inactivates it by transferring the acetyl group, which subsequently converts to toxic metabolites. This -NH2 group also tends to react with vital endogenous molecules such as pyridoxine, leading to their deficiency, a major cause of peripheral neuropathy. The elevation of liver functional markers is observed in 10%-20% of subjects on INH treatment. INH-induced risk of fatal hepatitis is about 0.05%-1%. The incidence of peripheral neuropathy is 2%-6.5%. In this review, we discuss the genesis and historical development of INH, and different reported mechanisms of action of INH. This is followed by a brief review of various clinical trials in chronological order, highlighting treatment-associated adverse events and their occurrence rates, including details such as geographical location, number of subjects, dosing concentration, and regimen used in these clinical studies. Further, we elaborated on various known metabolic transformations highlighting the involvement of the terminal -NH2 group of INH and corresponding host enzymes, the structure of different metabolites/conjugates, and their association with hepatotoxicity or neuritis. Post this deliberation, we propose a hydrolysable chemical derivatives-based approach as a way forward to restrict this metabolism.

Formation of potentially toxic metabolites of drugs in reactions catalyzed by human drug-metabolizing enzymes

Data are presented on the formation of potentially toxic metabolites of drugs that are substrates of human drug metabolizing enzymes. The tabular data lists the formation of potentially toxic/reactive products. The data were obtained from in vitro experiments and showed that the oxidative reactions predominate (with 96% of the total potential toxication reactions). Reductive reactions (e.g., reduction of nitro to amino group and reductive dehalogenation) participate to the extent of 4%. Of the enzymes, cytochrome P450 (P450, CYP) enzymes catalyzed 72% of the reactions, myeloperoxidase (MPO) 7%, flavin-containing monooxygenase (FMO) 3%, aldehyde oxidase (AOX) 4%, sulfotransferase (SULT) 5%, and a group of minor participating enzymes to the extent of 9%. Within the P450 Superfamily, P450 Subfamily 3A (P450 3A4 and 3A5) participates to the extent of 27% and the Subfamily 2C (P450 2C9 and P450 2C19) to the extent of 16%, together catalyzing 43% of the reactions, followed by P450 Subfamily 1A (P450 1A1 and P450 1A2) with 15%. The P450 2D6 enzyme participated in an extent of 8%, P450 2E1 in 10%, and P450 2B6 in 6% of the reactions. All other enzymes participate to the extent of 14%. The data show that, of the human enzymes analyzed, P450 enzymes were dominant in catalyzing potential toxication reactions of drugs and their metabolites, with the major role assigned to the P450 Subfamily 3A and significant participation of the P450 Subfamilies 2C and 1A, plus the 2D6, 2E1 and 2B6 enzymes contributing. Selected examples of drugs that are activated or proposed to form toxic species are discussed.

Genetic Variations and Antibiotic-Related Adverse Events

Antibiotic-related adverse events are common in both adults and children, and knowledge of the factors that favor the development of antibiotic-related adverse events is essential to limit their occurrence and severity. Genetics can condition the development of antibiotic-related adverse events, and the screening of patients with supposed or demonstrated specific genetic mutations may reduce drug-related adverse events. This narrative review discusses which genetic variations may influence the risk of antibiotic-related adverse events and which conclusions can be applied to clinical practice. An analysis of the literature showed that defined associations between genetic variations and specific adverse events are very few and that, at the moment, none of them have led to the implementation of a systematic screening process for patients that must be treated with a given antibiotic in order to select those at risk of specific adverse events. On the other hand, in most of the cases, more than one variation is implicated in the determination of adverse events, and this can be a limitation in planning a systematic screening. Moreover, presently, the methods used to establish whether a patient carries a "dangerous" genetic mutation require too much time and waiting for the result of the test can be deleterious for those patients urgently requiring therapy. Further studies are needed to definitively confirm which genetic variations are responsible for an increased risk of a well-defined adverse event.

Risk adjustment model for tuberculosis compared to non-tuberculosis mycobacterium or latent tuberculosis infection: Center for Personalized Precision Medicine of Tuberculosis (cPMTb) cohort database

BACKGROUND

The Center for Personalized Precision Medicine of Tuberculosis (cPMTb) was constructed to develop personalized pharmacotherapeutic systems for tuberculosis (TB). This study aimed to introduce the cPMTb cohort and compare the distinct characteristics of patients with TB, non-tuberculosis mycobacterium (NTM) infection, or latent TB infection (LTBI). We also determined the prevalence and specific traits of polymorphisms in N-acetyltransferase-2 (NAT2) and solute carrier organic anion transporter family member 1B1 (SLCO1B1) phenotypes using this prospective multinational cohort.

METHODS

Until August 2021, 964, 167, and 95 patients with TB, NTM infection, and LTBI, respectively, were included. Clinical, laboratory, and radiographic data were collected. NAT2 and SLCO1B1 phenotypes were classified by genomic DNA analysis.

RESULTS

Patients with TB were older, had lower body mass index (BMI), higher diabetes rate, and higher male proportion than patients with LTBI. Patients with NTM infection were older, had lower BMI, lower diabetes rate, higher previous TB history, and higher female proportion than patients with TB. Patients with TB had the lowest albumin levels, and the prevalence of the rapid, intermediate, and slow/ultra-slow acetylator phenotypes were 39.2%, 48.1%, and 12.7%, respectively. The prevalence of rapid, intermediate, and slow/ultra-slow acetylator phenotypes were 42.0%, 44.6%, and 13.3% for NTM infection, and 42.5%, 48.3%, and 9.1% for LTBI, respectively, which did not differ significantly from TB. The prevalence of the normal, intermediate, and lower transporter SLCO1B1 phenotypes in TB, NTM, and LTBI did not differ significantly; 74.9%, 22.7%, and 2.4% in TB; 72.0%, 26.1%, and 1.9% in NTM; and 80.7%, 19.3%, and 0% in LTBI, respectively.

CONCLUSIONS

Understanding disease characteristics and identifying pharmacokinetic traits are fundamental steps in optimizing treatment. Further longitudinal data are required for personalized precision medicine.

TRIAL REGISTRATION

This study registered ClinicalTrials.gov NO. NCT05280886.

Association of Cytochrome P450 2E1 and N-Acetyltransferase 2 Genotypes with Serum Isoniazid Level and Anti-Tuberculosis Drug-Induced Hepatotoxicity: A Cross-Sectional Study

Background

Anti-tuberculosis drug-induced hepatotoxicity can result from genetic polymorphism of the isoniazid (INH) metabolizing enzyme. This study aimed to determine the effect of genetic polymorphism of N-acetyltransferase 2 (NAT2) and cytochrome P450 2E1 (CYP2E1) genes on serum isoniazid level and drug-induced hepatotoxicity.

Methods

A cross-sectional study was conducted on 120 patients (with and without hepatotoxicity) with pulmonary tuberculosis from June 2019 to April 2022 in Tehran (Iran). High-performance liquid chromatography was used to measure the serum concentration of INH and acetylisoniazid (AcINH). NAT2 and CYP2E1 genotypes were determined using polymerase chain reaction and restriction fragment length polymorphism methods. Data were analyzed using SPSS software (version 22.0) with independent two-sample t test, Chi square test, or Fisher's exact test. P<0.05 was considered statistically significant.

Results

A total of 40 patients showed hepatotoxicity. The risk of anti-tuberculosis drug-induced hepatotoxicity was significantly higher in patients who are slow acetylator (SA) phenotype than in rapid or intermediate acetylator (P<0.001). NAT2*4/*4 genotypes were not found in patients with hepatotoxicity. The frequency of NAT2*5 and NAT2*6 haplotypes and serum INH concentration was significantly higher in patients with hepatotoxicity than in those without (P=0.003, P<0.001, and P<0.001, respectively). NAT2*4 haplotype was correlated with protection against hepatotoxicity. A combination of SA and CYP2E1 C1/C1 genotype was significantly associated with hepatotoxicity (P<0.001).

Conclusion

Hepatotoxicity in Iranian patients with tuberculosis was confirmed due to the presence of NAT2 SA polymorphism. Determining NAT2 and CYP2E1 genotypes and/or INH concentration can be a valuable tool to identify patients susceptible to hepatotoxicity.

Limited sampling strategies for therapeutic drug monitoring of anti-tuberculosis medications: A systematic review of their feasibility and clinical utility

Therapeutic drug monitoring (TDM) is recommended for medications with high inter-individual variability, narrow therapeutic index drugs, possible drug-drug interactions, drug toxicity, and subtherapeutic concentrations, as well as to assess noncompliance. The area under the plasma concentration-time curve (AUC) is a significant pharmacokinetic parameter since it calculates the drug's total systematic exposure in the body. However, multiple blood samples from the patient are required to calculate the area under the curve, which is inconvenient for both the patient and the healthcare professional. To alleviate the issue, the limited sampling strategy (LSS) was devised, in which sampling is minimized while obtaining complete and precise findings to anticipate the area under the curve. One can reduce costs, labor, and discomfort for patients and healthcare workers by applying this limited sampling strategy. This article examines a systematic evaluation of all the limited sampling done in anti-tuberculosis (anti-TB) medications resulting from the literature search of several research papers. This article also briefly describes the two methodologies: Multiple regression analysis (MRA) and the Bayesian approach used to develop a limited sampling strategy model. Anti-TB medications have been found to have considerable inter-individual variability, and isoniazid has a narrow therapeutic index, both of which are criteria for therapeutic drug monitoring. To avoid multi-drug resistance and therapy failure, it is proposed that limited sampling strategy-based therapeutic drug monitoring of anti-TB medications be undertaken to generate an individualized dose regimen, particularly for individuals at high risk of treatment failure or delayed response.

Polymorphisms in drug metabolism genes as a risk factor for first-line anti-tuberculosis drug-induced liver injury

BACKGROUND

Anti-tuberculosis drug-induced liver injury (AT-DILI) is one of the most common side effects in TB patients during treatment. The prime cause of liver injury during TB treatment is reported to be isoniazid and its metabolites. Different factors influenced the development of AT-DILI, and genetic factors are one of the major factors.

METHODS AND RESULTS

Polymorphisms in drug metabolism genes like NAT2, CYP2E1, PXR, and GST have been reported to be associated with AT-DILI, and they are one of the major areas of focus at present. Attempts are met in this review to analyse the different markers in these drug metabolism genes for their association with AT-DILI.

CONCLUSION

A better understanding of the polymorphisms in these genes and their functional effects will give better insights into the development of AT-DILI, and it could facilitate in designing and developing more effective personalized treatment for TB.

Human Cytochrome P450 1, 2, 3 Families as Pharmacogenes with Emphases on Their Antimalarial and Antituberculosis Drugs and Prevalent African Alleles

Precision medicine gives individuals tailored medical treatment, with the genotype determining the therapeutic strategy, the appropriate dosage, and the likelihood of benefit or toxicity. Cytochrome P450 (CYP) enzyme families 1, 2, and 3 play a pivotal role in eliminating most drugs. Factors that affect CYP function and expression have a major impact on treatment outcomes. Therefore, polymorphisms of these enzymes result in alleles with diverse enzymatic activity and drug metabolism phenotypes. Africa has the highest CYP genetic diversity and also the highest burden of malaria and tuberculosis, and this review presents current general information on CYP enzymes together with variation data concerning antimalarial and antituberculosis drugs, while focusing on the first three CYP families. Afrocentric alleles such as CYP2A6*17, CYP2A6*23, CYP2A6*25, CYP2A6*28, CYP2B6*6, CYP2B6*18, CYP2C8*2, CYP2C9*5, CYP2C9*8, CYP2C9*9, CYP2C19*9, CYP2C19*13, CYP2C19*15, CYP2D6*2, CYP2D6*17, CYP2D6*29, and CYP3A4*15 are implicated in diverse metabolic phenotypes of different antimalarials such as artesunate, mefloquine, quinine, primaquine, and chloroquine. Moreover, CYP3A4, CYP1A1, CYP2C8, CYP2C18, CYP2C19, CYP2J2, and CYP1B1 are implicated in the metabolism of some second-line antituberculosis drugs such as bedaquiline and linezolid. Drug-drug interactions, induction/inhibition, and enzyme polymorphisms that influence the metabolism of antituberculosis, antimalarial, and other drugs, are explored. Moreover, a mapping of Afrocentric missense mutations to CYP structures and a documentation of their known effects provided structural insights, as understanding the mechanism of action of these enzymes and how the different alleles influence enzyme function is invaluable to the advancement of precision medicine.

Pharmacokinetics of isoniazid and rifapentine in young paediatric patients with latent tuberculosis infection

OBJECTIVES

This study investigated the steady-state pharmacokinetic profiles of 3-month weekly rifapentine plus isoniazid (3HP) in children with latent tuberculosis infection (LTBI). Factors including tablet integrity, food, and pharmacogenetics were also assessed.

METHODS

During the 3HP treatment, blood and urine samples were collected on week 4. Isoniazid and rifapentine levels were measured using a high-performance liquid chromatography technique. Genetic variation of arylamine N-acetyltransferase 2 (NAT2) and arylacetamide deacetylase (AADAC) were assessed by the MassARRAY®. Safety and clinical outcomes at week 48 were monitored.

RESULTS

Twelve LTBI children [age 3.8 (range 2.1-4.9 years old)] completed the treatment [isoniazid and rifapentine dose 25.0 (range 21.7-26.8) and 25.7 (range 20.7-32.1) mg/kg, respectively]. No serious adverse events or active tuberculosis occurred. Tablet integrity was associated with decreased area under the concentration-time curve (91 vs 73 mg.hr/L, p = 0.026) and increased apparent oral clearance of isoniazid (0.27 vs 0.32 L/hr/kg, p = 0.019) and decreased rifapentine's renal clearance (CL_R, 0.005 vs 0.003 L/hr, p = 0.014). Food was associated with increased CL_R of isoniazid (3.45 vs 8.95 L/hr, p = 0.006) but not rifapentine. Variability in NAT2 and AADAC did not affect the pharmacokinetics of both drugs.

CONCLUSIONS

There is high variability in the pharmacokinetic profiles of isoniazid and rifapentine in young LTBI children. The variability was partly influenced by tablet integrity and food, but not pharmacogenetics. Further study in a larger cohort is warranted to display the relationship of these factors to treatment outcomes.

NAT2 and CYP2E1 polymorphisms and antituberculosis drug-induced hepatotoxicity in Peruvian patients

BACKGROUND

In Peru, 32,970 people were diagnosed with tuberculosis (TB) in 2019. Although TB treatment is effective, 3.4%-13% is associated with significant adverse drug reactions (ADR), considering drug-induced liver injury (DILI) as the most prevalent. Among the first-line anti-TB drugs, isoniazid (INH) is primarily responsible for the occurrence of DILI. INH is metabolized in the liver by the enzymes N-acetyltransferase-2 (NAT2) and Cytochrome P450 2E1 (CYP2E1). Based on the previous studies, we hypothesized that the interactions between slow CYP2E1 genotype and NAT2 slow acetylators will induce DILI in TB patients.

METHODS

In this cross-sectional study, all 377 participants completed their anti-TB treatment, and we genotyped SNPs: rs1041983, rs1801280, rs1799929, rs1799930, rs1208, and rs1799931 for NAT2 and rs3813867 and rs2031920 for CYP2E1.

RESULTS

We found that rapid, intermediate, and slow NAT2 acetylator were 15%, 38%, and 47%, respectively, in the general population. Intermediate NAT2 acetylator is the least prevalent among patients with adverse reactions (p = 0.024). We did not confirm our hypothesis, however, we found that the combination of intermediate NAT2 acetylators and CYP2E1 c1/c1 genotype significantly protected (OR = 0.16; p = 0.049) against the development of DILI in our population.

CONCLUSION

We propose that the presence of NAT2 intermediate and CYP2E1 c1/c1 genotype could help in therapeutic drug monitoring, and optimize its therapeutic benefits while minimizing its risk for side effects or toxicity.

Relationship between xanthine oxidase gene polymorphisms and anti-tuberculosis drug-induced liver injury in a Chinese population

This study was designed to investigate the association of the xanthine oxidase (XO) polymorphisms and susceptibility to anti-tuberculosis drug-induced liver injury (ATDILI) in Chinese population. A total of 183 tuberculosis patients were enrolled. Patients with ATDILI were classified as cases and those without ATDILI were classified as controls. Genotyping for XO polymorphisms was determined by polymerase chain reaction and direct sequencing. The allele frequencies and genotype distribution was analyzed using the Chi square test to analyze the association between the gene polymorphisms and ATDILI. Binary logistic regression analysis was performed to assess the risk factors of ATDILI. A total of 21 patients were developed liver injury during anti-tuberculosis treatment in this study, with an incidence of 11.48%. In genotype analysis, no significant difference was observed in the alleles and genotypes frequencies of the six SNPs between two groups (P > 0.05). In haplotype analysis, carriers with GGGATA (rs1884725- rs2295475 -rs45523133- rs206812- rs206813- rs7575607) haplotype had a significantly higher risk of ATDILI compared with other haplotypes (OR = 2.445, 95%CI: 1.058-5.652, P < 0.05). This study suggested that the haplotype GGGATA constructed with rs206812 and rs7575607 mutant alleles might contribute to ATDILI susceptibility in a Chinese population.

Development of a population pharmacokinetic model and Bayesian estimators for isoniazid in Tunisian tuberculosis patients

This study aimed to develop a population pharmacokinetic model using full pharmacokinetic (PK) profiles of isoniazid (INH) taking into account demographic and genetic covariates and to develop Bayesian estimators for predicting INH area under the curve (AUC) in Tunisian tuberculosis patients. The INH concentrations in the building data set were fitted using a one- to three-compartment model. The impact of the different covariates was assessed on the PK parameters of the best model. The best limited sampling strategy (LSS) for estimating the INH AUC was selected by comparing the predicted values to an independent data set. INH PK was best described using a three-compartment model with lag-time absorption. The different studied covariates did not have any impact on the PK parameters of the building model. The Bayesian estimation using one-point concentrations gave the lowest values of prediction errors for the C₃ LSS model. This model could be sufficient in routine activity for INH monitoring in this population.

Acetylator Status Among Newly Diagnosed and Recurrent Tuberculosis Patients from Kupang, Eastern Part of Indonesia

Purpose

N-acetyltransferase-2 enzyme in the liver, encoded by NAT2 gene, plays a central role in metabolizing tuberculosis (TB) drug isoniazid (INH). Low compliance of patients toward six-month TB therapy and internal host factors, ie comorbid diseases, immune status, and genetic profiles, are factors leading to treatment failure and recurrence of pulmonary TB infection. This study aimed to explore the NAT2 acetylator status among newly diagnosed and recurrent pulmonary TB patients in eastern part of Indonesia.

Patients and Methods

Archived DNA of TB patients (n=124) and healthy controls (n=124) were sequenced, and NAT2 acetylator status was determined, then categorized as fast, intermediate, or slow acetylators. Pulmonary TB patients who had no previous TB treatment history were designated as newly diagnosed pulmonary TB, whereas patients with a history of TB treatment were designated as recurrent pulmonary TB. The demographic, clinical, and microbiological data between pulmonary TB groups were compared, and acetylator status was described among groups.

Results

Male was more significantly prevalent in the recurrent pulmonary TB group (p=0.025), and anemia was more prevalent in new pulmonary TB (p=0.003). The acetylator status in pulmonary TB patients compared to healthy controls were rapid (33.9% vs 48.1%), intermediate (57.8% vs 33.0%), and slow acetylators (8.3% vs 18.9%), respectively. Interestingly, the rapid and intermediate acetylator were significantly more prevalent in pulmonary TB patients than in healthy controls (p=0.023, OR=2.58 (1.12–5.97). Furthermore, no differences were found in acetylator status between new and recurrent pulmonary (p=0.776).

Conclusion

Rapid and intermediate acetylators status predominated the pulmonary TB patients in Kupang, eastern part of Indonesia, postulating different genetic makeup in this area. As the pulmonary TB patients in Kupang exhibit more rapid acetylator phenotype, the acetylator status might be relevant to be checked before TB therapy for adjusting treatment dose to prevent drug resistances.

Oxidative Stress in Drug-Induced Liver Injury (DILI): From Mechanisms to Biomarkers for Use in Clinical Practice

Idiosyncratic drug-induced liver injury (DILI) is a type of hepatic injury caused by an uncommon drug adverse reaction that can develop to conditions spanning from asymptomatic liver laboratory abnormalities to acute liver failure (ALF) and death. The cellular and molecular mechanisms involved in DILI are poorly understood. Hepatocyte damage can be caused by the metabolic activation of chemically active intermediate metabolites that covalently bind to macromolecules (e.g., proteins, DNA), forming protein adducts-neoantigens-that lead to the generation of oxidative stress, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress, which can eventually lead to cell death. In parallel, damage-associated molecular patterns (DAMPs) stimulate the immune response, whereby inflammasomes play a pivotal role, and neoantigen presentation on specific human leukocyte antigen (HLA) molecules trigger the adaptive immune response. A wide array of antioxidant mechanisms exists to counterbalance the effect of oxidants, including glutathione (GSH), superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPX), which are pivotal in detoxification. These get compromised during DILI, triggering an imbalance between oxidants and antioxidants defense systems, generating oxidative stress. As a result of exacerbated oxidative stress, several danger signals, including mitochondrial damage, cell death, and inflammatory markers, and microRNAs (miRNAs) related to extracellular vesicles (EVs) have already been reported as mechanistic biomarkers. Here, the status quo and the future directions in DILI are thoroughly discussed, with a special focus on the role of oxidative stress and the development of new biomarkers.

Population pharmacokinetic model of isoniazid in patients with tuberculosis in Tunisia

AIMS

To develop a pharmacokinetic model of isoniazid (INH) concentration taking into account demographic factors and genetic variables [N-acetyltransferase 2 (NAT2) genotype], and to propose an initial INH dosage that could maximize the probability of achieving the desired INH concentration.

METHODS

A retrospective analysis was undertaken of INH concentration data collected from patients with tuberculosis in Tunisia.

RESULTS

In total, 118 patients were included in this study. The one-compartment model [volume of distribution (V), elimination rate (Ke)] was found to have good predictive performance. Multi-variate analysis showed that NAT2 affected both V and Ke significantly, but age, gender and weight did not. Internal validation of the final model showed correlation of 0.95 between individual predicted INH concentration 3 h after drug intake (C3) and observed C3. External validation showed that percentage mean absolute prediction error and percentage root mean squared error were 9.11% (range 0.62-35.8%) and 11.6%, respectively. Monte-Carlo simulation showed that doses of at least 225 mg/24 h and at least 450 mg/24 h attained a therapeutic concentration in >80% of patients in the NAT2 slow acetylator group and the NAT2 rapid/intermediate acetylator group, respectively.

CONCLUSION

The pharmacokinetic model allowed optimization of individual dosing regimens of INH in patients with tuberculosis in Tunisia. This tool may facilitate improved efficacy of INH and prevent its toxicity in this population.

Development of a limited sampling strategy for the estimation of isoniazid exposure considering N-acetyltransferase 2 genotypes in Korean patients with tuberculosis

A limited sampling strategy (LSS) to estimate the exposure to isoniazid was developed considering N-acetyltransferase 2 (NAT2) genotypes in Korean patients with tuberculosis. The influence of the genotypes on the pharmacokinetics of isoniazid was also evaluated. A total of 33 participants participated in the study and received isoniazid 300 mg once daily. Evaluable participants consist of ten slow (SA), fourteen intermediate (IA) and six rapid acetylators (RA). As expected, isoniazid exposure was higher (mean AUC, 28.4 versus 7.6 mg*h/L) and systemic clearance lower (mean apparent clearance, 14.8 versus 50.6 L/h) in SAs than RAs. The formulas to estimate isoniazid exposure were constructed using one or more concentration-time points that correlate with the area under the concentration-time curve (AUC). The LSS using a formula of single concentration-time point at 4 h post dose (C₄) is applicable for all acetylators to the therapeutic drug monitoring (TDM) of isoniazid in patients with tuberculosis when evaluated using the Deming regression and Bland-Altman plot (AUC = 1.53 + 10.03*C₄, adjusted r² = 0.95, p < 0.001). Considering that SAs are more prone to adverse effects, pre-dose NAT2 genotyping would be valuable for optimal isoniazid dosing in conjunction with TDM.

Isoniazid Therapeutic Drug Monitoring in Tunisian Patients With Tuberculosis

A regular therapeutic drug monitoring (TDM) of isoniazid could be useful to predict the acetylation profile and to prescribe doses associated with optimal efficacy and safety. We aimed to assess the usefulness of isoniazid TDM in the Tunisian population, to describe the acetylation profile distribution in this population, and to investigate the influence of certain parameters on acetylation phenotype. We performed a retrospective study including Tunisian patients with tuberculosis underwent an isoniazid TDM. Isoniazid concentrations were measured 3 hours after drug intake (C₃ ). Subsequent isoniazid doses were adjusted to maintain the C₃ within the recommended target (1-2 µg/mL). Patients were qualified as slow acetylators (SAs) or rapid acetylators (RAs) according to their acetylation index. Among the 255 patients, 58% were SAs and 42% were RAs. Of all patients, only 30.6% had a C₃ value within the target range. A dose adjustment has been performed for patients with C₃ outside the target range. C₃ was controlled in 77 patients. It became within the target range in 39 patients (50.6%). The median recommended isoniazid weight doses for SAs and RAs were 2.1 ± 0.7 mg/kg and 4.2 ± 1.4 mg/kg, respectively. The multivariate analysis showed that body weight, C_3, and C₃ /isoniazid dose were found to be significantly different between the 2 acetylation groups. In the pediatric group, only 9 had a C₃ value within the target range, and all of them were RAs. The irrevocable interest of isoniazid TDM has been shown in Tunisian patients with tuberculosis, in both adult and pediatric patients, as isoniazid demonstrates an unpredictable pharmacokinetic profile.

The role of NAT2 polymorphism and methylation in anti-tuberculosis drug-induced liver injury in Mongolian tuberculosis patients

WHAT IS KNOWN AND OBJECTIVE

Anti-tuberculosis drug-induced liver injury (ATLI) is one of the most significant adverse reactions for this line of therapy. N-acetyltransferase 2 (NAT2) is an important metabolic enzyme involved in drug metabolism and detoxification. Genetic polymorphism and DNA methylation have been proven to be key factors that affect the expression of NAT2. Therefore, the objective of the study was to investigate the relationship between NAT2 gene polymorphism and DNA methylation in the promoter region with ATLI risk in Mongolian tuberculosis patients.

METHODS

Our study is a case-control design. Chi-square test, Mann-Whitney U non-parametric test and Pearson test were all used to analyse existing relationships. The association between NAT2 gene acetylation phenotype and the total methylation of the NAT2 promoter region was analysed by means of binary logistic regression analysis. The general situation of the patients was evaluated by questionnaire, and the NAT2 genotyping of the three major polymorphism loci of gene coding was carried out by a gene sequencing technique. The methylation status of the NAT2 gene promoter region was detected by bisulphite sequencing and mass spectrometry.

RESULT AND DISCUSSION

Our study found that the detection rate of ATLI in Mongolian tuberculosis patients was 27.6%. There were no significant differences in demographic characteristics and living habits amongst the two groups, while significant differences were observed in the polymorphism of the NAT2 genes 481 (rs1799929) and 590 (rs1799930) and the acetylation phenotype. Moreover, the composition and distribution of the NAT2*4/4 and NAT2*4/5 genotypes were found in the two groups. The risk of ATLI in the slow acetylation type was 3.56 times higher than that of the fast acetylation type. Compared with the control group, the CpG5, CpG10, CpG11.12 and total methylation of the NAT2 promoter region in the ATLI group showed a hypermethylated pattern (P < .05). However, on performing binary logistic regression, neither the slow acetylation, intermediate acetylation nor rapid acetylation were found to be associated with ATLI (P > .05). It was found that the total methylation of NAT2 gene promoter region was an independent influencing factor of ATLI in Mongolian tuberculosis patients. With the increase of the total methylation level of NAT2 gene promoter region, the risk of ATLI increased gradually. (OR = 8.371, 95% CI: 2.391 ~ 29.315). CpG1, CpG4, CpG9, CpG10 and CpG11.12 were positively correlated with a total methylation level in the ATLI group.

WHAT IS NEW AND CONCLUSION

The detection rate of ATLI in Mongolian tuberculosis patients was 27.6%, and there were differences in the NAT2 genotypes and acetylated phenotypes. The slow acetylated type was the risk factor for ATLI. Methylation in the promoter region of the NAT2 gene has an effect on the risk of ATLI. After adjusting for the interference of three acetylation types, it was found that the total methylation of the promoter region of NAT2 gene in Mongolian tuberculosis patients is an independent influencing factor of ATLI. Furthermore, there is a moderate to high correlation between some sites and the overall level of methylation.

Comparison of the predictive outcomes for anti-tuberculosis drug-induced hepatotoxicity by different machine learning techniques

BACKGROUND

The study compared the predictive outcomes of artificial neural network, support vector machine and random forest on the occurrence of anti-tuberculosis drug-induced hepatotoxicity.

METHODS

The clinical and genomic data of patients treated with anti-tuberculosis drugs at Taipei Medical University-Wanfang Hospital were used as training sets, and those at Taipei Medical University-Shuang Ho Hospital served as test sets. Features were selected through a univariate risk factor analysis and literature evaluation. The accuracy, sensitivity, specificity, and the area under the receiver operating characteristic curve were calculated to compare the traditional, genomic, and combined models of the three techniques.

RESULTS

Nine models were created with 7 clinical factors and 4 genotypes. Artificial neural network with clinical and genomic factors exhibited the best performance, with an accuracy of 88.67%, a sensitivity of 80%, and a specificity of 90.4% for the test set. The area under the receiver operating characteristic curve of this best model reached 0.894 for training set and 0.898 for test set, which was significantly better than 0.801 for training set and 0.728 for test set by support vector machine and 0.724 for training set and 0.718 for test set by random forest.

CONCLUSIONS

Artificial neural network with clinical and genomic data can become a clinical useful tool in predicting anti-tuberculosis drug-induced hepatotoxicity. The machine learning technique can be an innovation to predict and prevent adverse drug reaction.

An Update on the Immunological, Metabolic and Genetic Mechanisms in Drug Hypersensitivity Reactions

Drug hypersensitivity reactions (DHRs) represent a major burden on the healthcare system since their diagnostic and management are complex. As they can be influenced by individual genetic background, it is conceivable that the identification of variants in genes potentially involved could be used in genetic testing for the prevention of adverse effects during drug administration. Most genetic studies on severe DHRs have documented HLA alleles as risk factors and some mechanistic models support these associations, which try to shed light on the interaction between drugs and the immune system during lymphocyte presentation. In this sense, drugs are small molecules that behave as haptens, and currently three hypotheses try to explain how they interact with the immune system to induce DHRs: the hapten hypothesis, the direct pharmacological interaction of drugs with immune receptors hypothesis (p-i concept), and the altered self-peptide repertoire hypothesis. The interaction will depend on the nature of the drug and its reactivity, the metabolites generated and the specific HLA alleles. However, there is still a need of a better understanding of the different aspects related to the immunological mechanism, the drug determinants that are finally presented as well as the genetic factors for increasing the risk of suffering DHRs. Most available information on the predictive capacity of genetic testing refers to abacavir hypersensitivity and anticonvulsants-induced severe cutaneous reactions. Better understanding of the underlying mechanisms of DHRs will help us to identify the drugs likely to induce DHRs and to manage patients at risk.

Isoniazid acetylation phenotypes in the Sudanese population; findings and implications

Background

Isoniazid (INH) is the mainstay antimicrobial in the treatment of tuberculosis (TB). It is acetlylated in the liver to acetyl-INH. However, there is variation in rate of acetylation of INH among TB patients (i.e. fast, intermediate or slow acetylators) which impacts on the treatment outcomes.

Aim

The isoniazid acetylation phenotypes in the expatriate Sudanese population were determined to provide future guidance since TB is prevalent in Sudan.

Methods

A community-based trial among Sudanese expatriates in Saudi Arabia was undertaken to identify INH-acetylation phenotypes. After overnight fasting, a single dose of 200 mg of INH was given to the volunteers. Three hours later, 5 ml of blood were drawn from each volunteer and prepared for High-Performance Liquid Chromatography (HPLC) analysis. The main outcomes were INH and Acetyl-INH concentrations in plasma and the subsequent Acetyl-INH/INH metabolic ratio (MR).

Results

The findings suggest that slow acetylation is highly prevalent among the study participants (n = 43; 84.31%). Moreover, there was no statistically significant correlation between age and the MR (r = −0.18, P = 0.20). Further, there was no significant association between gender and the MR (P = 0.124). Similarly, no significant association was found between smoking habits and MR (P = 0.24).

Conclusion

Isoniazid phenotyping suggests predominantly slow acetylation among the Sudanese in this sample. The study found no statistically significant associations between the MR and age or gender or smoking.

Association of genetic polymorphisms of CYP2E1, NAT2, GST and SLCO1B1 with the risk of anti-tuberculosis drug-induced liver injury: a systematic review and meta-analysis

OBJECTIVES

The objective of this study was to investigate the association between genetic polymorphisms of N-acetyltransferase 2 (NAT2), cytochrome P450 2E1 (CYP2E1), glutathione S-transferase (GST) and solute carrier organic anion transporter family member 1B1 (SLCO1B1) and the risk of anti-tuberculosis drug-induced liver injury (ATDILI).

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed, Embase, Web of Science and Cochrane Reviews databases were searched through April 2019.

ELIGIBILITY CRITERIA

We included case-control or cohort studies investigating an association between NAT2, CYP2E1, GST or SLCO1B1 polymorphisms and the ATDILI risk in patients with tuberculosis.

DATA EXTRACTION AND SYNTHESIS

Three authors screened articles, extracted data and assessed study quality. The strength of association was evaluated for each gene using the pooled OR with a 95% CI based on the fixed-effects or random-effects model. Sensitivity analysis was performed to confirm the reliability and robustness of the results.

RESULTS

Fifty-four studies were included in this analysis (n=26 for CYP2E1, n=35 for NAT2, n=19 for GST, n=4 for SLCO1B1). The risk of ATDILI was significantly increased with the following genotypes: CYP2E1 RsaI/PstI c1/c1 (OR=1.39, 95% CI 1.06 to 1.83), NAT2 slow acetylator (OR=3.30, 95% CI 2.65 to 4.11) and GSTM1 null (OR=1.30, 95% CI 1.12 to 1.52). No significant association with ATDILI was found for the genetic polymorphisms of CYP2E1 DraI, GSTT1, GSTM1/GSTT1, SLCO1B1 388A>G and SLCO1B1 521T>C (p>0.05).

CONCLUSIONS

ATDILI is more likely to occur in patients with NAT2 slow acetylator genotype, CYP2E1 RsaI/PstI c1/c1 genotype and GSTM1 null genotype. Close monitoring may be warranted for patients with these genotypes.

Genomewide Association Study Confirming the Association of NAT2 with Susceptibility to Antituberculosis Drug-Induced Liver Injury in Thai Patients

Antituberculosis drug-induced liver injury (ATDILI) is a common side effect leading to tuberculosis (TB) treatment disruption. The mechanism of the disease remains poorly understood. We conducted a genomewide association study (GWAS) to investigate all possible genetic factors of ATDILI in Thai patients. This study was carried out in Thai TB patients, including 79 ATDILI cases and 239 tolerant controls from our network hospitals in Thailand. Nearly 1 million single-nucleotide polymorphisms (SNPs) were genotyped across the whole genome using an Illumina OmniExpress Exome BeadChip array. In the discovery stage, we identified strong association signals on chromosome 8 originating from the N-acetyltransferase (NAT2) region. The A allele of rs1495741, the top SNP in the intergenic region of NAT2 and PSD3 (14 kb from NAT2), was significantly associated with ATDILI (recessive model, odds ratio of 6.01 [95% confidence interval, 3.42 to 10.57]; P = 6.86E-11). This particular SNP was reported as a tag SNP for NAT2 inferred phenotypes. The AA, AG, and GG genotypes represented NAT2 slow acetylators, intermediate acetylators, and fast acetylators, respectively. The tag SNP genotypes demonstrated a concordance rate of 94.98% with NAT2 acetylator phenotypes. This GWAS shows that NAT2 is the most important risk factor for ATDILI in the Thai population.

Pharmacokinetics of isoniazid: The good, the bad, and the alternatives

Although isoniazid (INH) has been successful in treating Tuberculosis (TB) since its introduction in 1952, there has been continual reports of drug-associated hepatotoxicity in TB patients. These toxic side effects may reveal more about the recipient of the drug, than the drug itself. A combination of pharmacogenetic and pharmacokinetic studies have identified polymorphisms within enzymes involved in INH metabolism and detoxification. These essential metabolic enzymes include N-acetyltransferase 2, Cytochrome P450 2E1, and glutathione S transferases. Different phenotypes of these enzymes can affect the rate of INH metabolism, resulting in production of hepatotoxic metabolites. This review is intended to elucidate the pharmacokinetics of INH by examining its Administration, Distribution, Metabolism, and Elimination, while suggesting potential alternatives within INH personalized treatment to help reduce hepatotoxicity.

NAT2 variants and toxicity related to anti-tuberculosis agents: a systematic review and meta-analysis

BACKGROUND

Tuberculosis (TB) patients receiving anti-tuberculosis treatment may experience serious adverse drug reactions (ADRs) such as hepatotoxicity. Variants of the N-acetyltransferase 2 (NAT2) gene may increase the risk of experiencing such toxicity events.

OBJECTIVE

To provide a comprehensive evaluation of the evidence base for associations between NAT2 variants and anti-tuberculosis drug-related toxicity.

METHOD

This was a systematic review and meta-analysis. We searched for studies in Medline, PubMed, EMBASE, BIOSIS and Web of Science. We included data from 41 articles (39 distinct cohorts of patients). We pooled effect estimates for each genotype on each outcome using meta-analyses stratified by country.

RESULTS

We assessed the quality of the included studies, which was variable, with many areas of concern. Slow/intermediate NAT2 acetylators were statistically significantly more likely to experience hepatotoxicity than rapid acetylators (OR 1.59, 95%CI 1.26-2.01). Heterogeneity was not detected in the overall pooled analysis (I² = 0%). NAT2 acetylator status was significantly associated with the likelihood of experiencing anti-tuberculosis drug-related hepatotoxicity.

CONCLUSION

We encountered several challenges in performing robust syntheses of data from pharmacogenetic studies, and we outline recommendations for the future reporting of pharmacogenetic studies to enable high-quality systematic reviews and meta-analyses to be performed.

CYP genetic variants and toxicity related to anti-tubercular agents: a systematic review and meta-analysis

BACKGROUND

Treatment with anti-tuberculosis drugs may cause patients to experience serious adverse effects. Genetic factors, such as polymorphisms of CYP genes, may increase the likelihood of a patient experiencing such adverse drug reactions. In this systematic review and meta-analysis, we synthesised evidence for associations between CYP genetic variants and anti-tuberculosis drug-related toxicity outcomes.

METHODS

We searched MEDLINE, PubMed, EMBASE, BIOSIS and Web of Science to identify relevant studies. We performed meta-analyses to obtain an effect estimate for each genetic variant on each outcome, and stratified all analyses by country. We qualitatively assessed the methodological quality of the included studies.

RESULTS

We included data from 28 distinct cohorts of patients in the review. We identified many areas of concern with regard to the quality of included studies. Patients with homozygous mutant-type or heterozygous genotype at the CYP2E1 RsaI polymorphism were significantly less likely to experience hepatotoxicity than patients with homozygous wild-type genotype (odds ratio [OR] = 0.75, 95% confidence interval [CI] 0.56-1.00; p = 0.047, I2 = 58.2%). No significant differences were observed for the CYP2E1 DraI and PstI polymorphisms. For the 96-bp deletion-insertion single-nucleotide polymorphism (SNP) of the CYP2E1 gene, homozygous mutant-type significantly increased hepatotoxicity risk compared with homozygous wild-type (OR = 8.20, 95% CI 1.38-48.68, I2 = 0%); no significant difference was observed for heterozygous genotype compared with homozygous wild-type (OR = 0.77, 95% CI 0.19-3.21, I2 = 0%).

CONCLUSIONS

Generally, we identified that coverage of the association between SNPs of CYP genes and anti-tuberculosis drug-related toxicity outcomes is incomplete. We observed significant associations between the RsaI and 96-bp deletion-insertion SNPs of the CYP2E1 gene and anti-tuberculosis drug-related hepatotoxicity. We were unable to comment on the impact of ethnicity on the investigated associations, as information on participants' ethnicity was sparsely reported in the included studies.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration number: CRD42017068448.

The association between the NAT2 genetic polymorphisms and risk of DILI during anti-TB treatment: a systematic review and meta-analysis

AIMS

The aim of this study is to evaluate the potential association between N-acetyltransferase type 2 (NAT2) polymorphisms and drug-induced liver injury during anti-TB treatment (AT-DILI).

METHODS

We conducted a systematic review and performed a meta-analysis to clarify the role of NAT2 polymorphism in AT-DILI. PubMed, Medline and EMBASE databases were searched for studies published in English to December 31, 2017, on the association between the NAT2 polymorphism and AT-DILI risk. Outcomes were pooled with random-effects meta-analysis. Details were registered in the PROSPERO register (number: CRD42016051722).

RESULTS

Thirty-seven studies involving 1527 cases and 7184 controls were included in this meta-analysis. The overall odds ratio (OR) of AT-DILI associated with NAT2 slow acetylator phenotype was 3.15 (95% CI 2.58-3.84, I²  = 51.3%, P = 0.000). The OR varied between different ethnic populations, ranging from 6.42 (95% CI 2.41-17.10, I²  = 2.3%) for the West Asian population to 2.32 (95% CI 0.58-9.24, I²  = 80.3%) for the European population. Within the slow NAT2 genotype, variation was also observed; NAT2*6/*7 was associated with the highest risk of AT-DILI (OR = 1.68, 95% CI 1.09-2.59) compared to the other slow NAT2 acetylators combined.

CONCLUSIONS

NAT2 slow acetylation was observed to increase the risk of AT-DILI in tuberculosis patients. Our results support the hypothesis that the slow NAT2 genotype is a risk factor for AT-DILI.

Effect of gene-gene and gene-environment interactions associated with antituberculosis drug-induced hepatotoxicity

OBJECTIVES

This study evaluated the association between environmental factors and genetic variations in enzymes that metabolize antituberculosis (anti-TB) drugs [arylamine N-acetyltransferase 2, cytochrome P450 2E1 (CYP2E1), glutathione S-transferase theta 1 (GSTT1), and glutathione S-transferase mu 1] with antituberculosis drug-induced hepatotoxicity (ATDH). We also investigated the potential gene-gene and gene-environment interactions as well as their association with ATDH development in a population of hospitalized TB patients from Buenos Aires.

PATIENTS AND METHODS

We investigated 364 TB patients who received anti-TB drugs. Physicians collected demographic and clinical data to identify environmental risk factors for ATDH development. Polymorphisms were detected using gene sequencing, PCR, and PCR-restriction fragment length polymorphisms. A binary logistic regression analysis was carried out to compare the results of TB patients with and without the development of hepatotoxicity. The multifactor dimensionality reduction method was used to examine genetic and environmental interactions in association with ATDH.

RESULTS

This study suggests that the slow acetylator profile [odds ratio (OR): 3.02; 95% confidence interval (CI): 1.82-5.00; P<0.001], genotypes carrying the c2 variant (OR: 2.16; 95% CI: 1.33-3.51; P=0.002) or the A4 variant of CYP2E1 (OR: 2.13; 95% CI: 1.06-4.29; P=0.050), and female sex (OR: 1.94; 95% CI: 1.20-3.14; P=0.006) were independent predictor variables for ATDH. Patients carrying the slow acetylator profile and the c2 variant showed an increased risk (OR: 7.068; 95% CI: 3.34-14.95; P<0.001). We also identified a synergic interaction (epistasis) between GSTT1 and CYP2E1 associated with an increased risk for ATDH. A meaningful gene-environment interaction was associated with an increased risk of ATDH [testing balance accuracy=0.675 (P=0.001) and cross-validation consistency=10/10].

CONCLUSION

ATDH is a severe and prevalent adverse drug reaction and leads to drug discontinuation in 11% of TB patients. Our study created a prediction model that properly classified the 67.5% of TB patients in their risk of developing ATDH. The considerable number of TB patients in our country supports the use of pharmacogenetic testing and a comprehensive clinical history to identify patients with a high risk of suffering hepatotoxicity.

Association and clinical utility of NAT2 in the prediction of isoniazid-induced liver injury in Singaporean patients

BACKGROUND AND AIMS

Isoniazid (INH) is part of the first-line-therapy for tuberculosis (TB) but can cause drug-induced liver injury (DILI). Several candidate single nucleotide polymorphisms (SNPs) have been previously identified but the clinical utility of these SNPs in the prediction of INH-DILI remains uncertain. The aim of this study was to assess the association between selected candidate SNPs and the risk of INH-DILI and to assess the clinical validity of associated variants in a Singaporean population.

METHODS

This was a case-control study where 24 INH-DILI cases and 79 controls were recruited from the TB control unit in a tertiary hospital. Logistic regression was used to test for the association between candidate SNPs and INH-DILI. NAT2 acetylator status was inferred from genotypes and tested for association with INH-DILI. Finally, clinical validity measures were estimated for significant variants.

RESULTS

Two SNPs in NAT2 (rs1041983 and rs1495741) and NAT2 slow acetylators (SA) were significantly associated with INH-DILI (OR (95% CI) = 13.86 (4.30-44.70), 0.10 (0.03-0.33) and 9.98 (3.32-33.80), respectively). Based on an INH-DILI prevalence of 10%, the sensitivity, specificity, positive and negative predictive values of NAT2 SA were 75%, 78%, 28% and 97%, respectively. The population attributable fraction (PAF) and number needed to test (NNT) for NAT2 SA were estimated to be 0.67 and 4.08, respectively. A model with clinical and NAT2 acetylator status provided significantly better prediction for INH-DILI than a clinical model alone (area under receiver operating characteristic curve = 0.863 vs. 0.766, respectively, p = 0.027).

CONCLUSIONS

We show the association between NAT2 SA and INH-DILI in a Singaporean population and demonstrated its clinical utility in the prediction of INH-DILI.

Influence of genetic variants on toxicity to anti-tubercular agents: a systematic review and meta-analysis (protocol)

BACKGROUND

Tuberculosis patients receiving anti-tuberculosis treatment may experience serious adverse drug reactions, such as hepatotoxicity. Genetic risk factors, such as polymorphisms of the NAT2, CYP2E1 and GSTM1 genes, may increase the risk of experiencing such toxicity events. Many pharmacogenetic studies have investigated the association between genetic variants and anti-tuberculosis drug-related toxicity events, and several meta-analyses have synthesised data from these studies, although conclusions from these meta-analyses are conflicting. Many meta-analyses also have serious methodological limitations, such as applying restrictive inclusion criteria, or not assessing the quality of included studies. Most also only consider hepatotoxicity outcomes and specific genetic variants. The purpose of this systematic review and meta-analysis is to give a comprehensive evaluation of the evidence base for associations between any genetic variant and anti-tuberculosis drug-related toxicity.

METHODS

We will search for studies in MEDLINE, EMBASE, BIOSIS and Web of Science. We will also hand search reference lists from relevant studies and contact experts in the field. We will include cohort studies, case-control studies and randomised controlled trials that recruited patients with tuberculosis who were either already established on anti-tuberculosis treatment or were commencing treatment and who were genotyped to investigate the effect of genetic variants on any anti-tuberculosis drug-related toxicity outcome. One author will screen abstracts to identify potentially relevant studies and will then obtain the full text for each potentially relevant study in order to assess eligibility. At each of these stages, a second author will independently screen/assess 10% of studies. Two authors will independently extract data and assess the quality of studies using a pre-piloted data extraction form. If appropriate, we will pool estimates of effect for each genotype on each outcome using meta-analyses stratified by ethnicity.

DISCUSSION

Our review and meta-analysis will update and add to the existing research in this field. By not restricting the scope of the review to a specific drug, genetic variant, or toxicity outcome, we hope to synthesise data for associations between genetic variants and anti-tuberculosis drug-related toxicity outcomes that have previously not been summarised in systematic reviews, and consequently, add to the knowledge base of the pharmacogenetics of anti-tuberculosis drugs.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42017068448.

tagSNP rs1495741 as a useful molecular marker to predict antituberculosis drug-induced hepatotoxicity

INTRODUCTION

It has been widely reported that the slow acetylator phenotype of N-acetyltransferase 2 (NAT2) is associated with the development of antituberculosis drug-induced hepatotoxicity (ATDH). The aim of this report was to evaluate the level of agreement and accuracy of two recently recommended markers, the two-single nucleotide polymorphisms (SNP) (C282T and T341C) and tagSNP of NAT2 (rs1495741) genotypes, to predict the seven-SNP-inferred NAT2 phenotype in Bolivian and Argentinian tuberculosis (TB)-patient populations. In addition, we analyzed the association of these markers with ATDH.

METHODS

We examined 331 TB patients who had been treated with anti-TB drugs. TagSNP of NAT2 genotyping was determined using PCR-restriction fragment length polymorphisms. The seven SNPs of NAT2 were determined using sequencing. Concordance analysis was carried out using Kendall's tau-b coefficient (w) and the degree of agreement with Cohen's κ coefficient (κ). Receiver operating characteristic receiver operating characteristic curves were obtained to measure the specificity and sensitivity of the method. A binary logistic regression was performed to identify variables associated with the development of ATDH.

RESULTS

Both predictors showed a remarkable concordance (>95.0%) and an almost perfect agreement (κ>0.945; P<0.0001) with the predicted acetylator profile. However, the sensitivity of the tagSNP genotypes to predict the NAT2 acetylator phenotype was lower in the Bolivian population (92.3%) compared with the Argentinian population (100.0%).

CONCLUSION

A nearly perfect agreement between both predictors and the predicted acetylation profile was observed with very high levels of sensitivity (>97%) and specificity (>98.0%). Furthermore, and as expected, both the two-SNP (C282T, T341C) and tagSNP were found to be independent variables in predicting ATDH with the same strength as seven-SNP of NAT2.

Clinical Pharmacogenetic Testing and Application: Laboratory Medicine Clinical Practice Guidelines

Pharmacogenetic testing for clinical applications is steadily increasing. Correct and adequate use of pharmacogenetic tests is important to reduce unnecessary medical costs and adverse patient outcomes. This document contains recommended pharmacogenetic testing guidelines for clinical application, interpretation, and result reporting through a literature review and evidence-based expert opinions for the clinical pharmacogenetic testing covered by public medical insurance in Korea. This document aims to improve the utility of pharmacogenetic testing in routine clinical settings.

Genome-Wide Association Studies for Idiosyncratic Drug-Induced Hepatotoxicity: Looking Back-Looking Forward to Next-Generation Innovation

Idiosyncratic drug-induced hepatotoxicity is a formidable challenge for rational drug discovery and development, as well as the science of personalized medicine. There is evidence that hereditary factors, in part, contribute to drug toxicity. This expert analysis and review offer the insights gained, and the challenges ahead, for genome-wide association studies (GWASs) of idiosyncratic drug-induced hepatotoxicity. Published articles on genome-wide and subsequent replication studies were systematically searched in the PubMed electronic database. We found that the genetic risk variants that were identified genome-wide, and replication confirmed, are mainly related to polymorphisms in the human leukocyte antigen (HLA) region that include HLA-DQB1*06:02 for amoxicillin-clavulanate, HLA-B*57:01 for flucloxacillin, HLA-DRB1*15:01 for lumiracoxib, and HLA-DRB1*07:01 for lapatinib and ximelagatran-induced hepatotoxicity. Additionally, polymorphisms in ST6 β-galactosamide α-2, 6-sialyltranferase-1 (ST6GAL1), which plays a role in systemic inflammatory response, and variants in intron of family with sequence similarity-65 member-B (FAM65B) that play roles in liver inflammation displayed association with flucloxacillin and antituberculosis drug-induced hepatotoxicity, respectively. Taken together, these GWAS findings offer molecular leads on the central role that the immune system plays in idiosyncratic drug-induced hepatotoxicity. We conclude the expert review with a brief discussion of the salient challenges ahead. These include, for example, the need for discursive discovery paradigms that incorporate alternating GWASs and candidate gene studies, as well as the study of the environtome, the entire complement of environmental factors, including science and innovation policies that enact on global society and the human host, and by extension, on susceptibility for idiosyncratic drug-induced hepatotoxicity.

Drug metabolism and liver disease: a drug-gene-environment interaction

Despite the central role of the liver in drug metabolism, surprisingly there is lack of certainty in anticipating the extent of modification of the clearance of a given drug in a given patient. The intent of this review is to provide a conceptual framework in considering the impact of liver disease on drug disposition and reciprocally the impact of drug disposition on liver disease. It is proposed that improved understanding of the situation is gained by considering the issue as a special example of a drug-gene-environment interaction. This requires an integration of knowledge of the drug's properties, knowledge of the gene products involved in its metabolism, and knowledge of the pathophysiology of its disposition. This will enhance the level of predictability of drug disposition and toxicity for a drug of interest in an individual patient. It is our contention that advances in pharmacology, pharmacogenomics, and hepatology, together with concerted interests in the academic, regulatory, and pharmaceutical industry communities provide an ideal immediate environment to move from a qualitative reactive approach to quantitative proactive approach in individualizing patient therapy in liver disease.

Effect of Rifampin on Thyroid Function Test in Patients on Levothyroxine Medication

Background

Levothyroxine (LT4) and rifampin (RIF) are sometimes used together; however, no clinical studies have assessed the effects of these drugs on thyroid function or the need to adjust LT4 dose.

Methods

We retrospectively reviewed the records of 71 Korean patients who started RIF during LT4 treatment. Clinically relevant cases that required dose adjustment according to the American Thyroid Association (ATA)/American Association of Clinical Endocrinologists (AACE) guidelines were identified, and risk factors of increased LT4 dose were analyzed.

Results

After administering RIF, median serum thyroid-stimulating hormone (TSH) level (2.58 mIU/L, interquartile range [IQR] 0.21–7.44) was significantly higher than that before RIF (0.25 mIU/L, IQR, 0.03–2.62; P < 0.001). An increased LT4 dose was required for 50% of patients in the TSH suppression group for thyroid cancer and 26% of patients in the replacement group for hypothyroidism. Risk factor analysis showed that remaining thyroid gland (odds ratio [OR] 9.207, P = 0.002), the time interval between starting RIF and TSH measurement (OR 1.043, P = 0.019), and baseline LT4 dose per kg body weight (OR 0.364, P = 0.011) were clinically relevant variables.

Conclusions

In patients receiving LT4, serum thyroid function test should be performed after starting RIF treatment. For patients with no remnant thyroid gland and those receiving a lower LT4 dose, close observation is needed when starting RIF and TB medication.

Tuberculosis of the Liver, Biliary Tract, and Pancreas

Tuberculosis of the liver, biliary tract, and pancreas is discussed. In addition, tuberculosis in the setting of HIV-AIDS and liver transplantation is explored. Drug-induced liver injury secondary to antituberculosis medication and monitoring and prophylactic treatment for such injury is also considered.

The challenges of pharmacokinetic variability of first-line anti-TB drugs

INTRODUCTION

Inter-individual variations in the pharmacokinetics (PK) of anti-TB drugs are known to occur, which could have important therapeutic implications in patient management. Areas covered: We compiled factors responsible for PK variability of anti-TB drugs reported from different settings that would give a better understanding about the challenges of PK variability of anti-TB medications. We searched PubMed data base and Google scholar from 1976 to the present using the key words 'Pharmacokinetics', 'pharmacokinetic variability', 'first-line anti-TB therapy', 'Rifampicin', 'Isoniazid', 'Ethambutol', 'Pyrazinamide', 'food', 'nutritional status', 'HIV', 'diabetes', 'genetic polymorphisms' and 'pharmacokinetic interactions'. We also included abstracts from scientific meetings and review articles. Expert commentary: A variety of host and genetic factors can cause inter-individual variations in the PK of anti-TB drugs. PK studies conducted in various settings have adopted different designs, PK sampling time points, drug estimation methodologies. Hence comparison and interpretation of these results should be done with caution More phamacogenomic studies in different patient populations are needed for further understanding.

Isoniazid metabolism and hepatotoxicity

Isoniazid (INH) is highly effective for the management of tuberculosis. However, it can cause liver injury and even liver failure. INH metabolism has been thought to be associated with INH-induced liver injury. This review summarized the metabolic pathways of INH and discussed their associations with INH-induced liver injury.

Optimizing treatment outcome of first-line anti-tuberculosis drugs: the role of therapeutic drug monitoring

INTRODUCTION

Tuberculosis (TB) remains one of the world's deadliest communicable diseases. Although cure rates of the standard four-drug (rifampicin, isoniazid, pyrazinamide, ethambutol) treatment schedule can be as high as 95-98 % under clinical trial conditions, success rates may be much lower in less well resourced countries. Unsuccessful treatment with these first-line anti-TB drugs may lead to the development of multidrug resistant and extensively drug resistant TB. The intrinsic interindividual variability in the pharmacokinetics (PK) of the first-line anti-TB drugs is further exacerbated by co-morbidities such as HIV infection and diabetes.

METHODS

Therapeutic drug monitoring has been proposed in an attempt to optimize treatment outcome and reduce the development of drug resistance. Several studies have shown that maximum plasma concentrations (C max), especially of rifampicin and isoniazid, are well below the proposed target C max concentrations in a substantial fraction of patients being treated with the standard four-drug treatment schedule, even though treatment's success rate in these studies was typically at least 85 %.

DISCUSSION

The proposed target C max concentrations are based on the concentrations of these agents achieved in healthy volunteers and patients receiving the standard doses. Estimation of C max based on one or two sampling times may not have the necessary accuracy since absorption rate, especially for rifampicin, may be highly variable. In addition, minimum inhibitory concentration (MIC) variability should be taken into account to set clinically meaningful susceptibility breakpoints. Clearly, there is a need to better define the key target PK and pharmacodynamic (PD) parameters for therapeutic drug monitoring (TDM) of the first-line anti-TB drugs to be efficacious, C max (or area under the curve (AUC)) and C max/MIC (or AUC/MIC).

CONCLUSION

Although TDM of first-line anti-TB drugs has been successfully used in a limited number of specialized centers to improve treatment outcome in slow responders, a better characterization of the target PK and/or PK/PD parameters is in our opinion necessary to make it cost-effective.

Risk factors of isoniazid-induced hepatotoxicity in Tunisian tuberculosis patients

Previous studies have shown controversial results on whether acetylator status causes isoniazid-induced hepatotoxicity (IIH). Moreover, the contribution of CYP2E1, a hepatic enzyme implicated in the formation of hepatotoxins, to the risk of developing IIH remains unclear. The objectives of this study were (i) to assess the quantitative relationship between the level of isoniazid serum concentration and the incidence of IIH and (ii) to evaluate the extent of implication of the N-acetyltransferase-2 (NAT2) and CYP2E1 polymorphisms genes to induce this disorder. Seventy-one patients with tuberculosis receiving a conventional antituberculosis regimen were included. NAT2 and CYP2E1 genotypes were determined using polymerase chain reaction. Three restriction enzymes, RsaI, PstI and DraI were used to detect CYP2E1 RFLP and four different restriction enzymes, KpnI, TaqI, BamHI and Ddel were used to determine NAT2 acetylator status. Therapeutic drug monitoring (TDM) of isoniazid (serum concentration performed 3 h after the morning dose: C3) was performed. Cases of isoniazid-induced hepatotoxicity were diagnosed according to Benichou et al. Receiver Operating Characteristics curve analysis was used to evaluate the relationship between risk factors and the incidence of IIH. Eleven (15.4%) patients have developed IIH. Demographic factors, including age, weight and gender were not associated with the incidence of hepatotoxicity. High serum concentration of isoniazid (C3) was found to be a risk factor of IIH (area under the curve: 0.74, P=0.007, 95% confidence interval (95% CI): 0.56-0.93), with a cutoff value at 3.69 mg l^-1 (odds ratio (OR): 13.2, P=0.0007, 95% CI: 2.9-59). Multivariate analysis showed that only a C3 over 3.69 mg l^-1 remains a risk factor of IIH. NAT2 and CYP2E1 variants were not found to increase the risk of IIH when analyzed separately. However, combined analysis of the NAT2/CYP2E1 gene polymorphisms showed that patients with both DraI C/D and slow acetylator have an increased risk of IIH compared with other combined NAT2/CYP2E1 genotype profiles (OR: 8.41, P=0.01, 95% CI: 1.54-45.76). Our results suggest that a serum concentration of isoniazid over 3.69 mg l^-1 and a combined genotype CYP2E1 DraI(C/D)/slow acetylator are major risk factors for IIH. Therefore, TDM of isoniazid and the determination of both NAT2 and CYP2E1 genotypes could be useful for the prediction and prevention of IIH in Tunisian tuberculosis patients.