Population Pharmacokinetic Analysis of Isoniazid among Pulmonary Tuberculosis Patients from China

Precision Medicine Strategies to Improve Isoniazid Therapy in Patients with Tuberculosis

Due to interindividual variability in drug metabolism and pharmacokinetics, traditional isoniazid fixed-dose regimens may lead to suboptimal or toxic isoniazid concentrations in the plasma of patients with tuberculosis, contributing to adverse drug reactions, therapeutic failure, or the development of drug resistance. Achieving precision therapy for isoniazid requires a multifaceted approach that could integrate various clinical and genomic factors to tailor the isoniazid dose to individual patient characteristics. This includes leveraging molecular diagnostics to perform the comprehensive profiling of host pharmacogenomics to determine how it affects isoniazid metabolism, such as its metabolism by N-acetyltransferase 2 (NAT2), and studying drug-resistant mutations in the Mycobacterium tuberculosis genome for enabling targeted therapy selection. Several other molecular signatures identified from the host pharmacogenomics as well as other omics-based approaches such as gut microbiome, epigenomic, proteomic, metabolomic, and lipidomic approaches have provided mechanistic explanations for isoniazid pharmacokinetic variability and/or adverse drug reactions and thereby may facilitate precision therapy of isoniazid, though further validations in larger and diverse populations with tuberculosis are required for clinical applications. Therapeutic drug monitoring and population pharmacokinetic approaches allow for the adjustment of isoniazid dosages based on patient-specific pharmacokinetic profiles, optimizing drug exposure while minimizing toxicity and the risk of resistance. Current evidence has shown that with the integration of the host pharmacogenomics-particularly NAT2 and Mycobacterium tuberculosis genomics data along with isoniazid pharmacokinetic concentrations in the blood and patient factors such as anthropometric measurements, comorbidities, and type and timing of food administered-precision therapy approaches in isoniazid therapy can be tailored to the specific characteristics of both the host and the pathogen for improving tuberculosis treatment outcomes.

Diagnosis, prevention and risk-management of drug-induced liver injury due to medications used to treat mycobacterium tuberculosis

INTRODUCTION

Many of the first line medications for the treatment of active and latent M. tuberculosis are hepatoxic and cause a spectrum of anti-tuberculosis drug induced liver injury (ATLI), including acute liver failure (ALF). Despite advances in recognition of and prevention of ATLI, isoniazid remains one of the leading causes of DILI as well as drug-induced ALF.

AREAS COVERED

A literature search of the incidence, risk factors, current societal guidelines, monitoring, and prophylactic medication usage in ATLI was performed using PubMed and institutional websites. Relevant articles from 1972 to 2024 were included in this review.

EXPERT OPINION

Current societal guidelines regarding ATLI monitoring are mixed, but many recommend liver enzyme testing of high-risk populations. We recommend liver test monitoring for all patients on multi-drug therapy as well as those on isoniazid therapy. Precision medicine practices, such as N-acetyltransferase-2 polymorphism genotyping, are thought to be beneficial in reducing the incidence of ATLI in high-risk populations. However, broader implementation is currently cost prohibitive. Hepatoprotective drugs are not currently recommended, although we do recognize their potential. In patients who develop ATLI but require ongoing anti-TB treatment, strategies to restart the same or less hepatotoxic regimens are currently being followed.

Determination of NAT2 Genotypes in a Cohort of Patients with Suspected TB in the State of Rio de Janeiro

The human N-acetyltransferase 2 enzyme, encoded by the NAT2 gene, plays an important role in the metabolism of isoniazid, the main drug used to treat tuberculosis. The interindividual variation in the response of patients to drug treatment for tuberculosis may be responsible for the occurrence of unfavorable outcomes. The presence of polymorphisms in genes associated with the metabolism and transport of drugs, receptors, and therapeutic targets has been identified as a major determinant of this variability. The objective of this study was to identify the genetic profile of NAT2 in the study population. Using the obtained genomic DNA followed by PCR amplification and sequencing, the frequency of nine SNPs as well as alleles associated with slow (47.9%), intermediate (38.7%), and fast acetylation phenotypes (11.3%), in addition to those whose phenotype has not yet been characterized (2.1%), was estimated. The NAT2*5B allele was identified more frequently (31.3%). The description of SNPs in pharmacogenes and the establishment of their relationship with the pharmacokinetics of an individual offer an individualized approach that allows us to reduce the unfavorable outcomes of a therapy, ensure better adherence to treatment, prevent the emergence of MDR strains, reduce the cost of treatment, and improve the quality of patients' lives.

Machine Learning Approach in Dosage Individualization of Isoniazid for Tuberculosis

INTRODUCTION

Isoniazid is a first-line antituberculosis agent with high variability, which would profit from individualized dosing. Concentrations of isoniazid at 2 h (C2h), as an indicator of safety and efficacy, are important for optimizing therapy.

OBJECTIVE

The objective of this study was to establish machine learning (ML) models to predict the C2h, that can be used for establishing an individualized dosing regimen in clinical practice.

METHODS

Published population pharmacokinetic (PopPK) models for adults were searched based on PubMed and ultimately four reliable models were selected for simulating individual C2h datasets under different conditions (demographics, genotype, ethnicity, etc.). Machine learning models were trained on simulated C2h obtained from the four PopPK models. Five different algorithms were used for ML model building to predict C2h. Real-world data were used for predictive performance evaluations. Virtual trials were used to compare ML-optimized doses with PopPK model-optimized doses.

RESULTS

Categorical boosting (CatBoost) exhibited the highest prediction ability. Target C2h can be predicted using the ML model combined with the dosing regimen and three covariates (N-acetyltransferase 2 [NAT2] genotypes, weight and race [Asians and Africans]). Real-world data validation results showed that the ML model can achieve an overall prediction accuracy of 93.4%. Using the final ML model, the mean absolute prediction error value decreased by 45.7% relative to the average of PopPK models. Using the ML-optimized dosing regimen, the probability of target attainment increased by 43.7% relative to the PopPK model-optimized dosing regimens.

CONCLUSION

Machine learning models were developed with great predictive performance, which can be used to determine the individualized initial dose of isoniazid in adult patients.

Intracranial tuberculomas diagnosed with Xpert MTB/RIF Ultra assay of formalin-fixed paraffin-embedded brain tissues and treated with an optimized antituberculosis regimen: A case report

Diagnosis of intracranial tuberculoma remains a challenge due to its rarity, non-specific clinical presentation, and radiological findings. Herein, we describe a case of intracranial tuberculomas in a male diabetic patient who presented headache and vomiting on admission. Neuroimaging findings indicated multiple ring contrast-enhanced lesions with extensive perilesional edema. However, a cerebrospinal fluid (CSF) examination was normal. When a biopsy of brain lesions was performed, pathological characteristics of tuberculosis were absent and acid-fast staining was negative. A tuberculosis diagnosis was subsequently obtained from an Xpert MTB/RIF Ultra assay of formalin-fixed paraffin-embedded brain tissue. The patient was treated with an optimized anti-tuberculosis regimen which included high-dose intravenous administration of rifampicin and isoniazid, and oral administration of linezolid. The patient recovered well and exhibited marked clinical improvement. This case report demonstrates that when CSF analysis does not indicate the presence of intracranial tuberculomas, analysis of formalin-fixed paraffin-embedded brain tissue specimens with the Xpert MTB/RIF Ultra assay may be able to confirm a diagnosis. Furthermore, a high dose of rifampicin and isoniazid plus linezolid may improve patient outcome.

Comprehensive Therapeutic Approaches to Tuberculous Meningitis: Pharmacokinetics, Combined Dosing, and Advanced Intrathecal Therapies

Tuberculous meningitis (TBM) presents a critical neurologic emergency characterized by high mortality and morbidity rates, necessitating immediate therapeutic intervention, often ahead of definitive microbiological and molecular diagnoses. The primary hurdle in effective TBM treatment is the blood-brain barrier (BBB), which significantly restricts the delivery of anti-tuberculous medications to the central nervous system (CNS), leading to subtherapeutic drug levels and poor treatment outcomes. The standard regimen for initial TBM treatment frequently falls short, followed by adverse side effects, vasculitis, and hydrocephalus, driving the condition toward a refractory state. To overcome this obstacle, intrathecal (IT) sustained release of anti-TB medication emerges as a promising approach. This method enables a steady, uninterrupted, and prolonged release of medication directly into the cerebrospinal fluid (CSF), thus preventing systemic side effects by limiting drug exposure to the rest of the body. Our review diligently investigates the existing literature and treatment methodologies, aiming to highlight their shortcomings. As part of our enhanced strategy for sustained IT anti-TB delivery, we particularly seek to explore the utilization of nanoparticle-infused hydrogels containing isoniazid (INH) and rifampicin (RIF), alongside osmotic pump usage, as innovative treatments for TBM. This comprehensive review delineates an optimized framework for the management of TBM, including an integrated approach that combines pharmacokinetic insights, concomitant drug administration strategies, and the latest advancements in IT and intraventricular (IVT) therapy for CNS infections. By proposing a multifaceted treatment strategy, this analysis aims to enhance the clinical outcomes for TBM patients, highlighting the critical role of targeted drug delivery in overcoming the formidable challenges presented by the blood-brain barrier and the complex pathophysiology of TBM.

Model-Informed Precision Dosing of Isoniazid: Parametric Population Pharmacokinetics Model Repository

Introduction

Isoniazid (INH) is a crucial first-line anti tuberculosis (TB) drug used in adults and children. However, various factors can alter its pharmacokinetics (PK). This article aims to establish a population pharmacokinetic (popPK) models repository of INH to facilitate clinical use.

Methods

A literature search was conducted until August 23, 2022, using PubMed, Embase, and Web of Science databases. We excluded published popPK studies that did not provide full model parameters or used a non-parametric method. Monte Carlo simulation works was based on RxODE. The popPK models repository was established using R. Non-compartment analysis was based on IQnca.

Results

Fourteen studies included in the repository, with eleven studies conducted in adults, three studies in children, one in pregnant women. Two-compartment with allometric scaling models were commonly used as structural models. NAT2 acetylator phenotype significantly affecting the apparent clearance (CL). Moreover, postmenstrual age (PMA) influenced the CL in pediatric patients. Monte Carlo simulation results showed that the geometric mean ratio (95% Confidence Interval, CI) of PK parameters in most studies were within the acceptable range (50.00-200.00%), pregnant patients showed a lower exposure. After a standard treatment strategy, there was a notable exposure reduction in the patients with the NAT2 RA or nonSA (IA/RA) phenotype, resulting in a 59.5% decrease in AUC0-24 and 83.2% decrease in Cmax (Infants), and a 49.3% reduction in AUC0-24 and 73.5% reduction in Cmax (Adults).

Discussion

Body weight and NAT2 acetylator phenotype are the most significant factors affecting the exposure of INH. PMA is a crucial factor in the pediatric population. Clinicians should consider these factors when implementing model-informed precision dosing of INH. The popPK model repository for INH will aid in optimizing treatment and enhancing patient outcomes.

The role of Mycobacterium tuberculosis acetyltransferase and protein acetylation modifications in tuberculosis

Tuberculosis (TB) is a widespread infectious disease caused by Mycobacterium tuberculosis (M. tb), which has been a significant burden for a long time. Post-translational modifications (PTMs) are essential for protein function in both eukaryotic and prokaryotic cells. This review focuses on the contribution of protein acetylation to the function of M. tb and its infected macrophages. The acetylation of M. tb proteins plays a critical role in virulence, drug resistance, regulation of metabolism, and host anti-TB immune response. Similarly, the PTMs of host proteins induced by M. tb are crucial for the development, treatment, and prevention of diseases. Host protein acetylation induced by M. tb is significant in regulating host immunity against TB, which substantially affects the disease's development. The review summarizes the functions and mechanisms of M. tb acetyltransferase in virulence and drug resistance. It also discusses the role and mechanism of M. tb in regulating host protein acetylation and immune response regulation. Furthermore, the current scenario of isoniazid usage in M. tb therapy treatment is examined. Overall, this review provides valuable information that can serve as a preliminary basis for studying pathogenic research, developing new drugs, exploring in-depth drug resistance mechanisms, and providing precise treatment for TB.

Parametric population pharmacokinetics of isoniazid: a systematic review

INTRODUCTION

Isoniazid (INH) plays an important role in prevention and treatment of tuberculosis (TB). However, large pharmacokinetic (PK) variations are observed in patients receiving standard INH dosages. Considering the influence of PK variations on INH efficacy or adverse reactions, we reviewed the population PK studies of INH and explored significant covariates that influence INH PK.

METHODS

The PubMed and Embase databases were systematically searched from their inception to 30 January 2023. PPK studies on INH using a parametric nonlinear mixed-effect approach were included in this review. The characteristics and identified significant covariates of the included studies were summarized.

RESULTS

Twenty-one studies conducted in adults, and seven in pediatrics were included. A two-compartment model with first-order absorption and elimination was the frequently used structural model for INH. NAT2 genotype, body size, and age were identified as significant covariates affecting INH PK variation. The median clearance (CL) value in the fast metabolizers was 2.55-fold higher than that in the slow metabolizers. Infants and children had higher CL per weight values than adults with the same metabolic phenotype. In pediatric patients, CL value increased with postnatal age.

CONCLUSIONS

Compared with slow metabolizers, the daily dose of INH should be increased by 200-600 mg in fast metabolizers. To achieve effective treatment, pediatric patients need a higher dose per kilogram than adults. Further PPK studies of anti-tuberculosis drugs are needed to comprehensively understand the covariates that affect their PK characteristics and to achieve accurate dose adjustments.

Influence of NAT2 Genotype and Maturation on Isoniazid Exposure in Low-Birth-Weight and Preterm Infants With or Without Human Immunodeficiency Virus (HIV) Exposure

BACKGROUND

Isoniazid (INH) metabolism depends on the N-acetyl transferase 2 (NAT2) enzyme, whose maturation process remains unknown in low birth weight (LBW) and preterm infants. We aimed to assess INH exposure and safety in infants receiving oral tuberculosis prevention.

METHODS

This population pharmacokinetics (PK) analysis used INH and N-acetyl-isoniazid (ACL) concentrations in infants (BW ≤ 4 kg), including preterm, with follow-up for 6 months. PK parameters were described using nonlinear mixed effects modeling. Simulations were performed to assess INH exposure and optimal dosing regimens, using 2 targets: Cmax at 3-6 mg/L and area under the curve (AUC) ≥ 10.52 mg h/L.

RESULTS

We included 57 infants (79% preterm, 84% LBW) in the PK analysis, with a median (range) gestational age of 34 (28.7-39.4) weeks. At the time of sampling, postnatal age was 2.3 (0.2-7.3) months and weight (WT) was 3.7 (0.9-9.3) kg. NAT2 genotype was available in 43 (75.4%) patients (10 slow, 26 intermediate, and 7 fast metabolizers). Ninety percent of NAT2 maturation was attained by 4.4 post-natal months. WT, postmenstrual age, and NAT2 genotype significantly influenced INH exposure, with a 5-fold difference in AUC between slow and fast metabolizers for the same dose. INH appeared safe across the broad range of exposure for 61 infants included in the safety analysis.

CONCLUSIONS

In LBW/preterm infants, INH dosing needs frequent adjustment to account for growth and maturation. Pharmacogenetics-based dosing regimens is the most powerful approach to deliver safe and equalized exposures for all infants, because NAT2 genotype highly impacts INH pharmacokinetic variability.

Population Pharmacokinetic Modeling of Bedaquiline among Multidrug-Resistant Pulmonary Tuberculosis Patients from China

Bedaquiline has been widely used as a part of combination dosage regimens for the treatment of multidrug-resistant tuberculosis (MDR-TB) patients with limited options. Although the effectiveness and safety of bedaquiline have been demonstrated in clinical trials, limited studies have investigated the significant pharmacokinetics and the impact of genotype on bedaquiline disposition. Here, we developed a population pharmacokinetic model of bedaquiline to describe the concentration-time data from Chinese adult patients diagnosed with MDR-TB. A total of 246 observations were collected from 99 subjects receiving the standard recommended dosage. Bedaquiline disposition was well described by a one-compartment model with first-order absorption. Covariate modeling identified that gamma-glutamyl transferase (GGT) and the single-nucleotide polymorphism (SNP) rs319952 in the AGBL4 gene were significantly associated with the apparent clearance of bedaquiline. The clearance (CL/F) was found to be 1.4 L/h lower for subjects with allele GG in SNP rs319952 than for subjects with alleles AG and AA and to decrease by 30% with a doubling in GGT. The model-based simulations were designed to assess the impact of GGT/SNP rs319952 on bedaquiline exposure and showed that patients with genotype GG in SNP rs319952 and GGT ranging from 10 to 50 U/L achieved the targeted maximum serum concentration at steady state (C_max,ss). However, when GGT was increased to 100 U/L, C_max,ss was 1.68-fold higher than the highest concentration pursued. The model developed provides the consideration of genetic polymorphism and hepatic function for bedaquiline dosage in MDR-TB adult patients.

Pharmacogenetic testing for NAT2 genotypes in a Tanzanian population across the lifespan to guide future personalized isoniazid dosing

Despite updated recommendations for weight-based isoniazid dosing in children with drug-susceptible tuberculosis (TB) and higher dose isoniazid in regimens for adults with drug-resistant TB, individual pharmacokinetic variability can lead to sub-target isoniazid exposure. Host pharmacogenetics and isoniazid exposure remain understudied, especially in the East African population. We therefore employed a real-time polymerase chain reaction (qPCR) assay system to test genomic DNA extracted from saliva samples targeting the NAT2 gene responsible for isoniazid metabolism to describe the frequency of human single nucleotide polymorphisms in NAT2 within populations of children and adults in Tanzania, ascribe those polymorphisms to acetylator phenotype, and correlate to serum isoniazid exposures. In adults treated with higher dose isoniazid, genotypes with a predicted allelic phenotype of slow or intermediate acetylation were able to achieve a 0.41 μg/mL higher C_max (p = 0.018) and a 2.9h*μg/mL higher AUC_0-12 (p = 0.003) per mg/kg increase in isoniazid dosage versus adults with rapid acetylation phenotype. A similar relationship was not found in the younger age population as predicted by timing of NAT2 maturation. This saliva based qPCR assay was fieldable to guide personalized isoniazid dosing in adults but not young children that may not have full NAT2 maturation and activity.

Influence of N-acetyltransferase 2 (NAT2) genotype/single nucleotide polymorphisms on clearance of isoniazid in tuberculosis patients: a systematic review of population pharmacokinetic models

Purpose

Significant pharmacokinetic variabilities have been reported for isoniazid across various populations. We aimed to summarize population pharmacokinetic studies of isoniazid in tuberculosis (TB) patients with a specific focus on the influence of N-acetyltransferase 2 (NAT2) genotype/single-nucleotide polymorphism (SNP) on clearance of isoniazid.

Methods

A systematic search was conducted in PubMed and Embase for articles published in the English language from inception till February 2022 to identify population pharmacokinetic (PopPK) studies of isoniazid. Studies were included if patient population had TB and received isoniazid therapy, non-linear mixed effects modelling, and parametric approach was used for building isoniazid PopPK model and NAT2 genotype/SNP was tested as a covariate for model development.

Results

A total of 12 articles were identified from PubMed, Embase, and hand searching of articles. Isoniazid disposition was described using a two-compartment model with first-order absorption and linear elimination in most of the studies. Significant covariates influencing the pharmacokinetics of isoniazid were NAT2 genotype, body weight, lean body weight, body mass index, fat-free mass, efavirenz, formulation, CD4 cell count, and gender. Majority of studies conducted in adult TB population have reported a twofold or threefold increase in isoniazid clearance for NAT2 rapid acetylators compared to slow acetylators.

Conclusion

The variability in disposition of isoniazid can be majorly attributed to NAT2 genotype. This results in a trimodal clearance pattern with a multi-fold increase in clearance of NAT2 rapid acetylators compared to slow acetylators. Further studies exploring the generalizability/adaptability of developed PopPK models in different clinical settings are required.

Population Pharmacokinetics and Pharmacodynamics of Isoniazid and its Metabolite Acetylisoniazid in Chinese Population

Objective: We aimed to establish a population pharmacokinetic (PPK) model for isoniazid (INH) and its major metabolite Acetylisoniazid (AcINH) in healthy Chinese participants and tuberculosis patients and assess the role of the NAT2 genotype on the transformation of INH to AcINH. We also sought to estimate the INH exposure that would achieve a 90% effective concentration (EC₉₀) efficiency for patients with various NAT2 genotypes.

Method: A total of 45 healthy participants and 157 tuberculosis patients were recruited. For healthy subjects, blood samples were collected 0–14 h after administration of 300 mg or 320 mg of the oral dose of INH; for tuberculosis patients who received at least seven days therapy with INH, blood samples were collected two and/or six hours after administration. The plasma concentration of INH and AcINH was determined by the reverse-phase HPLC method. NAT2 genotypes were determined by allele-specific amplification. The integrated PPK model of INH and AcINH was established through nonlinear mixed-effect modeling (NONMEM). The effect of NAT2 genotype and other covariates on INH and AcINH disposition was evaluated. Monte Carlo simulation was performed for estimating EC90 of INH in patients with various NAT2 genotypes.

Results: The estimated absorption rate constant (K_a), oral clearance (CL/F), and apparent volume of distribution (V₂/F) for INH were 3.94 ± 0.44 h⁻¹, 18.2 ± 2.45 L⋅h⁻¹, and 56.8 ± 5.53 L, respectively. The constant of clearance (K₃₀) and the volume of distribution (V₃/F) of AcINH were 0.33 ± 0.11 h⁻¹ and 25.7 ± 1.30 L, respectively. The fraction of AcINH formation (F_M) was 0.81 ± 0.076. NAT2 genotypes had different effects on the CL/F and F_M. In subjects with only one copy of NAT2 *5, *6, and *7 alleles, the CL/F values were approximately 46.3%, 54.9%, and 74.8% of *4/*4 subjects, respectively. The F_M values were approximately 48.7%, 63.8%, and 86.9% of *4/*4 subjects, respectively. The probability of target attainment of INH EC₉₀ in patients with various NAT2 genotypes was different.

Conclusion: The integrated parent-metabolite PPK model accurately characterized the disposition of INH and AcINH in the Chinese population sampled, which may be useful in the individualized therapy of INH.

Semi-Automated Therapeutic Drug Monitoring as a Pillar toward Personalized Medicine for Tuberculosis Management

Standard tuberculosis (TB) management has failed to control the growing number of drug-resistant TB cases worldwide. Therefore, innovative approaches are required to eradicate TB. Model-informed precision dosing and therapeutic drug monitoring (TDM) have become promising tools for adjusting anti-TB drug doses corresponding with individual pharmacokinetic profiles. These are crucial to improving the treatment outcome of the patients, particularly for those with complex comorbidity and a high risk of treatment failure. Despite the actual benefits of TDM at the bedside, conventional TDM encounters several hurdles related to laborious, time-consuming, and costly processes. Herein, we review the current practice of TDM and discuss the main obstacles that impede it from successful clinical implementation. Moreover, we propose a semi-automated TDM approach to further enhance precision medicine for TB management.

Development of population pharmacokinetics model of isoniazid in Indonesian patients with tuberculosis

OBJECTIVES

No population pharmacokinetics (PK) model of isoniazid (INH) has been reported for the Indonesian population with tuberculosis (TB). Therefore, we aimed to develop a population PK model to optimize pharmacotherapy of INH on the basis of therapeutic drug monitoring (TDM) implementation in Indonesian patients with TB.

MATERIALS AND METHODS

INH concentrations, N-acetyltransferase 2 (NAT2) genotypes, and clinical data were collected from Dr. Soetomo General Academic Hospital, Indonesia. A nonlinear mixed-effect model was used to develop and validate the population PK model.

RESULTS

A total of 107 patients with TB (with 153 samples) were involved in this study. A one-compartment model with allometric scaling for bodyweight effect described well the PK of INH. The NAT2 acetylator phenotype significantly affected INH clearance. The mean clearance rates for the rapid, intermediate, and slow NAT2 acetylator phenotypes were 55.9, 37.8, and 17.7 L/h, respectively. Our model was well-validated through visual predictive checks and bootstrapping.

CONCLUSIONS

We established the population PK model for INH in Indonesian patients with TB using the NAT2 acetylator phenotype as a significant covariate. Our Bayesian forecasting model should enable optimization of TB treatment for INH in Indonesian patients with TB.

Intrathecal therapy for tuberculous meningitis: propensity-matched cohort study

OBJECTIVE

The study aimed to determine the safety and efficacy of intrathecally administered isoniazid (INH) and prednisolone in addition to systemic anti-TB therapy and compare it with systemic anti-TB therapy alone in adult patients with tuberculous meningitis (TBM).

METHODS

In this retrospective study, patients were categorized into two groups: Group A patients received systematic anti-TB therapy alone, Group B patients received IT INH (50 mg) and prednisolone (25 mg) twice a week together with the same standard systemic anti-TB therapy as Group A, in addition to the standard systemic anti-TB therapy. Functional outcomes were compared between the two groups in a prosperity-matched cohort using propensity score matching (PSM) method.

RESULTS

A total of 198 patients with TBM were enrolled. After PSM, 30 patients from each group were analyzed, so that there was no significant difference in the characteristics of the two groups. Mortality at follow-up was significantly lower among patients receiving additional IT therapy (4/30, 13.3%) compared with matched patients receiving systemic anti-TB therapy alone (11/30, 36.7%, P value = 0.037).

CONCLUSIONS

In this propensity score-matched cohort, the addition of IT INH and prednisolone to systemic anti-TB therapy could be effective for the better outcome among adult TBM patients. Further large-scale, prospective, and randomized controlled trials are warranted to the best timing and indication of IT therapy.

Decreased mortality seen in rifampicin/multidrug-resistant tuberculous meningitis treated with linezolid in Shenzhen, China

Background

The morbidity of rifampicin/multidrug-resistant tuberculous meningitis (RR/MDR-TBM) has shown an increasing trend globally. Its mortality rate is significantly higher than that of non-rifampicin/multidrug-resistant tuberculous meningitis (NRR/MDR-TBM). This article aimed to explore risk factors related to RR/MDR-TBM, and compare therapeutic effects of linezolid (LZD)- and non-linezolid-containing regimen for RR/MDR-TB patients in Shenzhen city. Furthermore, we aimed to find a better therapy for pathogen-negative TBM with RR/MDR-TBM related risk factors.

Methods

We conducted a retrospective study enrolling 137 hospitalized cases with confirmed TBM from June 2014 to March 2020. All patients were divided into RR/MDR-TBM group (12 cases) and NRR/MDR-TBM group (125 cases) based on GeneXpert MTB/RIF and (or) phenotypic drug susceptibility test results using cerebral spinal fluid (CSF). The risk factors related to RR/MDR-TBM were investigated through comparing clinical and examination features between the two groups. The mortality rate of RR/MDR-TBM patients treated with different regimens was analyzed to compare their respective therapeutic effects. A difference of P < 0.05 was considered statistically significant.

Results

Most patients (111/137, 81%) were from southern or southwestern China, and a large proportion (72/137, 52.55%) belonged to migrant workers. 12 cases were RR/MDR-TBM (12/137, 8.8%) while 125 cases were NRR/MDR-TBM (125/137, 91.2%). The proportion of patients having prior TB treatment history in the RR/MDR-TBM group was significantly higher than that of the NRR/MDR-TBM group (6/12 vs. 12/125, 50% vs. 10.5%, P < 0.01). No significant difference was observed on other clinical and examination features between the two groups. Mortality was significantly lower in RR/MDR-TBM patients on linezolid-containing treatment regimen than those who were not (0/7 versus 3/5, 0% versus 60%, P = 0.045).

Conclusions

The main related risk factor of RR/MDR-TBM is the history of anti-tuberculosis treatment. Linezolid-containing regimen appears to lower mortality rate of RR/MDR-TBM significantly in our study. We think Linezolid should be evaluated prospectively in the treatment of RR/MDR-TBM.

Isoniazid Population Pharmacokinetics and Dose Recommendation for Korean Patients With Tuberculosis Based on Target Attainment Analysis

The wide variability of isoniazid (INH) pharmacokinetics is mainly attributed to the trimodal N-acetyltransferase 2 (NAT2) acetylator phenotype, that is, rapid, intermediate, and slow. Consequently, a uniform INH dose in current clinical practice may lead to treatment failure and emergence of drug resistance. There is a lack of studies on specific doses of INH for different NAT2 acetylator phenotypes among tuberculosis (TB) patients. Therefore, we aimed to provide insight into the optimal dosing of INH for each NAT2 acetylator phenotype with respect to the probability of achieving a pharmacokinetic (PK)/pharmacodynamic target. PK, the NAT2 genotype, and clinical data were collected in a multicenter prospective cohort study conducted at 13 clinical centers in Korea. Population PK modeling and simulation were carried out. Data from 454 TB patients were divided into a training data set and a test data set at a ratio of 4 to 1. The PK of the training data were best described by a 2-compartment model with allometric scaling for body size effect. Importantly, NAT2 acetylator phenotypes significantly affected the apparent clearance. Our model, which provided better predictive performance compared with previously published models, was evaluated by external validation using the test set. The simulation for assessing target efficacy and toxicity indicated that the best INH dosing regimens for Korean tuberculosis patients were once-daily doses of 400, 300, and 200 mg for rapid, intermediate, and slow acetylators, respectively. In conclusion, our study provides a step forward in precision dosing for antituberculosis management.

Arylamine N-acetyltransferase acetylation polymorphisms: paradigm for pharmacogenomic-guided therapy- a focused review

INTRODUCTION

The N-acetylation polymorphism has been the subject of comprehensive reviews describing the role of arylamine N-acetyltransferase 2 (NAT2) in the metabolism of numerous aromatic amine and hydrazine drugs.

AREAS COVERED

We describe and review data that more clearly defines the effects of NAT2 haplotypes and genotypes on the expression of acetylator phenotype towards selected drugs within human hepatocytes in vitro, within human hepatocyte cultures in situ, and clinical measures such as bioavailability, plasma metabolic ratios of parent to N-acetyl metabolite, elimination rate constants and plasma half-life, and/or clearance determinations in human subjects. We review several drugs (isoniazid, hydralazine, sulfamethazine, amifampridine, procainamide, sulfasalazine, amonafide and metamizole) for which NAT2 phenotype-guided therapy may be important. The value of pharmacogenomics-guided isoniazid therapy for the prevention and treatment of tuberculosis is presented as a paradigm for NAT2 phenotype-dependent dosing strategies.

EXPERT OPINION

Studies in human subjects and cryopreserved human hepatocytes show evidence for rapid, intermediate and slow acetylator phenotypes, with further data suggesting genetic heterogeneity within the slow acetylator phenotype. Incorporation of more robust NAT2 genotype/phenotypes relationships, including genetic heterogeneity within the slow acetylator phenotype, should lead to further advancements in both health outcomes and cost benefit for prevention and treatment of tuberculosis.

A Systematic Review and Meta-analysis of Isoniazid Pharmacokinetics in Healthy Volunteers and Patients with Tuberculosis

PURPOSE

This systematic review and meta-analysis assesses the pharmacokinetic (PK) summary estimates of isoniazid (INH) between healthy volunteers and patients with tuberculosis (TB), evaluates whether the current INH dose regimen is appropriate in patients with TB, and evaluates the impact of N-acetyl-transferase-2 (NAT2) status on the PK properties of INH.

METHODS

A systematic approach was conducted to find studies with relevant INH PK data published in the English language up to February 2018. The PK properties of INH were extracted with their respective INH dosages and were dose normalized to allow a fair comparison between healthy volunteers and patients with TB. Meta-analysis was then performed for the C_max and AUC estimates for all INH dosages.

FINDINGS

Ninety studies were included in this systematic review. TB status significantly affected the INH C_max and AUC estimates. In healthy volunteers, the dose-normalized INH C_max and AUC were statistically higher than those of patients with TB. No significant differences were found in dose-normalized C_max and AUC between adults with TB and adults with TB/HIV; however, the AUC in pediatric patients was significantly different between patients with TB and patients with TB/HIV. In addition, no significance was observed comparing the dose-normalized C_max and AUC of pediatric patients with TB and TB/HIV with their respective adult counterparts. Dose-normalized INH C_max and AUC in patients with fast and intermediate NAT2 were significantly lower than in patients with slow NAT2.

IMPLICATIONS

The current recommended dosages of INH were found to produce less drug exposure in patients with TB when compared with healthy volunteers. NAT2 polymorphism greatly impacts the PK properties of INH; hence, testing for acetylator status is highly recommended, and therapeutic drug monitoring would help reduce INH toxicity.