Pharmacokinetics and pharmacogenetics of anti-tubercular drugs: a tool for treatment optimization?

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.

The Role of Efflux Pumps transporter in Multi-drug Resistant Tuberculosis: Mycobacterial memberane protein(MmpL5)

BACKGROUND

The overexpression of efflux pumps (Eps) was reported to contribute to multidrug resistant tuberculosis (MDR-TB). Increases in Eps that expel structurally unrelated drugs contribute to reduced susceptibility by decreasing the intracellular concentration of antibiotics. In the present study, an association of mycobacterial membrane protein (MmpS5-MmpL5) Ep and its gene regulator (Rv0678) was investigated in MDR-tuberculosis isolates.

METHODS

MTB strains were isolated from patients at two different intervals, i.e., once when they had persistent symptoms despite 3-15 ≥ months of treatment and once when they had started new combination therapy ≥2-3 months. Sputum specimens were subjected to Xpert MTB/rifampicin test and then further susceptibility testing using proportional method and multiplex polymerase chain reaction (PCR) were performed on them. The isolates were characterized using both 16S-23S RNA and hsp65 genes spacer (PCR-restriction fragment length polymorphism). Whole-genome sequencing (WGS) was investigated on two isolates from culture-positive specimen per patient. The protein structure was simulated using the SWISS-MODEL. The input format used for this web server was FASTA (amino acid sequence). Protein structure was also analysis using Ramachandran plot.

RESULTS

WGS documented deletion, insertion, and substitution in transmembrane transport protein MmpL5 (Rv0676) of Eps. Majority of the studied isolates (n = 12; 92.3%) showed a unique deletion mutation at three positions: (a) from amino acid number 771 (isoleucine) to 776 (valine), (b) from amino acid number 785 (valine) to 793 (histidine), and (c) from amino acid number 798 (leucine) to 806 (glycine)." One isolate (7.6%) had no deletion mutation. In all isolates (n = 13; 100%), a large insertion mutation consisting of 94 amino acid was observed "from amino acid number 846 (isoleucine) to amino acid number 939 (leucine)". Thirty-eight substitutions in Rv0676 were detected, of which 92.3% were identical in the studied isolates. WGS of mycobacterial membrane proteins (MmpS5; Rv0677) and its gene regulator (Rv0678) documented no deletion, insertion, and substitution. No differences were observed between MmpS5-MmpL5 and its gene regulator in isolates that were collected at different intervals.

CONCLUSIONS

Significant genetic mutation like insertion, deletion, and substitution within transmembrane transport protein MmpL5 (Rv0676) can change the functional balance of Eps and cause a reduction in drug susceptibility. This is the first report documenting a unique amino acid mutation (insertion and deletion ≥4-94) in Rv0676 among drug-resistant MTB. We suggest the changes in Mmpl5 (Rv0676) might occurred due to in-vivo sub-therapeutic drug stress within the host cell. Changes in MmpL5 are stable and detected through subsequent culture-positive specimens.

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.

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.

Designing New Magic Bullets to Penetrate the Mycobacterial Shield: An Arduous Quest for Promising Therapeutic Candidates

Mycobacterium spp. intimidated mankind since time immemorial. The triumph over this organism was anticipated with the introduction of potent antimicrobials in the mid-20th century. However, the emergence of drug resistance in mycobacteria, Mycobacterium tuberculosis, in particular, caused great concern for the treatment. With the enemy growing stronger, there is an immediate need to equip the therapeutic arsenal with novel and potent chemotherapeutic agents. The task seems intricating as our understanding of the dynamic nature of the mycobacteria requires intense experimentation and research. Targeting the mycobacterial cell envelope appears promising, but its versatility allows it to escape the lethal effect of the molecules acting on it. The unique ability of hiding (inactivity during latency) also assists the bacterium to survive in a drug-rich environment. The drug delivery systems also require upgradation to allow better bioavailability and tolerance in patients. Although the resistance to the novel drugs is inevitable, our commitment to the research in this area will ensure the discovery of effective weapons against this formidable opponent.

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.

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.

Genetic polymorphism related to ethambutol outcomes and susceptibility to toxicity

The World Health Organization (WHO) stated that ensuring access to effective and optimal treatment is a key component to eradicate tuberculosis (TB) through the End TB Strategy. Personalized medicine that depends on the genetic profile of an individual is one way to optimize treatment. It is necessary because of diverse drug responses related to the variation in human DNA, such as single-nucleotide polymorphisms (SNPs). Ethambutol (EMB) is a drug widely used as the treatment for Mycobacterium Tuberculosis (Mtb) and/non-tuberculous mycobacteria and has become a potential supplementary agent for a treatment regimen of multidrug-resistant (MDR) and extensively drug-resistant (XDR) TB. In human genetic polymorphism studies of anti-tuberculosis, the majority focus on rifampicin or isoniazid, which discuss polymorphisms related to their toxicity. Whereas there are few studies on EMB, the incidence of EMB toxicity is lower than that of other first-line anti-TB drugs. To facilitate personalized medicine practice, this article summarizes the genetic polymorphisms associated with alterations in the pharmacokinetic profile, resistance incidence, and susceptibility to EMB toxicity. This study includes 131 total human studies from 17 articles, but only eight studies that held in the low-middle income country (LMIC), while the rest is research conducted in developed countries with high incomes. Personalized medicine practices are highly recommended to maintain and obtain the optimal therapeutic effect of EMB.

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.

Effect of Genetic Variations in Drug-Metabolizing Enzymes and Drug Transporters on the Pharmacokinetics of Rifamycins: A Systematic Review

Background

Rifamycins are a novel class of antibiotics clinically approved for tuberculosis chemotherapy. They are characterized by high inter-individual variation in pharmacokinetics. This systematic review aims to present the contribution of genetic variations in drug-metabolizing enzymes and transporter proteins to the inter-individual variation of rifamycin pharmacokinetics.

Method

We followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines. The search for relevant studies was done through PubMed, Embase, Web of Science, and Scopus databases. Studies reporting single nucleotide polymorphism in drug transporters and metabolizing enzymes' influence on rifamycin pharmacokinetics were solely included. Two reviewers independently performed data extraction.

Results

The search identified 117 articles of which 15 fulfilled the eligibility criteria and were included in the final data synthesis. The single nucleotides polymorphism in the drug transporters SLCO1B1 rs4149032, rs2306283, rs11045819, and ABCB1 rs1045642 for rifampicin, drug metabolizing enzyme AADAC rs1803155 for rifapentine and CES2 c.-22263A>G (g.738A>G) for rifampicin partly contributes to the variability of pharmacokinetic parameters in tuberculosis patients.

Conclusion

The pharmacokinetics of rifamycins is influenced by genetic variation of drug-metabolizing enzymes and transporters. Controlled clinical studies are, however, required to establish these relationships.

The tale of microencapsulated rifampicin: is it useful for the treatment of periprosthetic joint infection?

Purpose

Microencapsulation techniques have allowed the addition of rifampicin to bone cement, but its in vivo efficacy has not been proven. The aim of our study is to determine the superiority of cement containing gentamicin and rifampicin microcapsules in the treatment of PJI versus cement exclusively containing gentamicin.

Methods

An S. aureus PJI was induced in 15 NZW rabbits. A week after inoculation, the first stage of replacement was carried out, and the animals were divided into two groups: group R received a spacer containing gentamicin and rifampicin microcapsules, and group C received a spacer containing gentamicin. Intra-articular release curve of rifampicin and infection and toxicity markers were monitored for four weeks post-operatively, when microbiological analysis was performed.

Results

The microbiological cultures showed a significantly lower growth of S. aureus in soft tissue (2.3·10⁴ vs 0; p = 0.01) and bone (5.7·10² vs 0; p = 0.03) in the group with rifampicin microcapsules. No differences were found in systemic toxicity markers. Rifampicin release from the cement spacer showed higher concentrations than the staphylococcal MIC throughout the analysis.

Conclusion

The in vivo analyses demonstrated the superiority of cement containing gentamicin and rifampicin microcapsules versus the isolated use of gentamicin in the treatment of PJI in the rabbit model without serious side effects due to the systemic absorption of rifampicin. Given the increasing incidence of staphylococci-related PJI, the development of new strategies for intra-articular administration of rifampicin for its treatment has a high clinical impact.

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.

Real-life isoniazid and rifampicin plasma concentrations in children: a tool for therapeutic drug monitoring of tuberculosis

Background

Low plasma levels of first-line antitubercular drugs can be counted among the main causes of poor response to antitubercular therapy, and therapeutic drug monitoring has been proposed as a method to promote tailored treatments for both child and adult patients. The main aim of the study was to evaluate serum concentrations of isoniazid (INH) and rifampicin (RIF) and to investigate reasons for sub-therapeutic plasma concentrations in order to fix dosages.

Methods

Children with TB were prospectively enrolled from January to August 2019. Two venous blood samples were collected (the first at least 15 days after the beginning of antitubercular treatment, and the second between 1 and 8 weeks later). Plasma concentrations were determined by a validated high-performance liquid chromatography method.

Results

In all, 45 children were included. Seventy blood samples for INH plasma concentration were collected between 120 and 240 min after drug intake. Adjusting for dose (mg/kg/day) and time of INH administration, when considering three different age groups (≤ 2 years, 2–12 years, > 12 years), a statistically significant lower INH plasma concentration was observed in younger children compared to the older age groups in the multivariate analysis (p < 0.001 and p < 0.001). A total of 68 blood samples were evaluated for RIF concentrations. Both for INH and RIF a statistically significant lower plasma concentration was also observed in adolescents (p < 0.001). Fifteen children (15/45, 33%) presented drug concentrations under the referral therapeutic range.

Conclusions

Based on our findings, monitoring patients’ drug plasma concentrations in children under 2 years of age and in adolescents can make treatment more patient-tailored.

Allelic and genotypic frequencies of NAT2, CYP2E1, and AADAC genes in a cohort of Peruvian tuberculosis patients

Background

We determined the frequency of genetic polymorphisms in three anti‐TB drug metabolic proteins previously reported: N‐acetyltransferase 2 (NAT2), cytochrome P450 2E1 (CYP2E1), and arylacetamide deacetylase (AADAC) within a Peruvian population in a cohort of TB patients.

Methods

We genotyped SNPs rs1041983, rs1801280, rs1799929, rs1799930, rs1208, and rs1799931 for NAT2; rs3813867 and rs2031920 for CYP2E1; and rs1803155 for AADAC in 395 participants completed their antituberculosis treatment.

Results

Seventy‐four percent of the participants are carriers of slow metabolizer genotypes: NAT2*5, NAT2*6, and NAT2*7, which increase the sensitivity of INH at low doses and increase the risk of drug‐induced liver injuries. Sixty‐four percent are homozygous for the wild‐type CYP2E1*1A allele, which could increase the risk of hepatotoxicity. However, 16% had a NAT2 fast metabolizer phenotype which could increase the risk of acquiring resistance to INH, thereby increasing the risk of multidrug‐resistant (MDR) or treatment failure. The frequency of rs1803155 (AADAC*2 allele) was higher (99.9%) in Peruvians than in European American, African American, Japanese, and Korean populations.

Conclusions

This high prevalence of slow metabolizers for isoniazid in the Peruvian population should be further studied and considered to help individualize drug regimens, especially in countries with a great genetic diversity like Peru. These data will help the Peruvian National Tuberculosis Control Program develop new strategies for therapies.

The Manifesto of Pharmacoenosis: Merging HIV Pharmacology into Pathocoenosis and Syndemics in Developing Countries

Pathocoenosis and syndemics theories have emerged in the last decades meeting the frequent need of better understanding interconnections and reciprocal influences that coexistent communicable and non-communicable diseases play in a specific population. Nevertheless, the attention to pharmacokinetic and pharmacodynamics interactions of co-administered drugs for co-present diseases is to date limitedly paid to alert against detrimental pharmacological combos. Low and middle-income countries are plagued by the highest burden of HIV, tuberculosis, malaria, and helminthiasis, and they are experiencing an alarming rise in non-communicable disorders. In these settings, co-infections and comorbidities are common, but no tailored prescribing nor clinical trials are used to assess and exploit existing opportunities for the simultaneous and potentially synergistic treatment of intertwined diseases. Pharmacoenosis is the set of interactions that take place within a host as well as within a population due to the compresence of two or more diseases and their respective treatments. This framework should pilot integrated health programmes and routine clinical practice to face drug–drug interaction issues, avoiding negative co-administrations but also exploiting potential favourable ones to make the best out of the worst situations; still, to date, guiding data on the latter possibility is limited. Therefore, in this narrative review, we have briefly described both detrimental and favourable physiopathological interactions between HIV and other common co-occurring pathologies (malaria, tuberculosis, helminths, and cardiovascular disorders), and we have presented examples of advantageous potential pharmacological interactions among the drugs prescribed for these diseases from a pharmacokinetics, pharmacodynamics, and pharmacogenetics standpoint.

Mycobactericidal Effects of Different Regimens Measured by Molecular Bacterial Load Assay among People Treated for Multidrug-Resistant Tuberculosis in Tanzania

Rifampin or multidrug-resistant tuberculosis (RR/MDR-TB) treatment has largely transitioned to regimens free of the injectable aminoglycoside component, despite the drug class’ purported bactericidal activity early in treatment. We tested whether Mycobacterium tuberculosis

Rifampin or multidrug-resistant tuberculosis (RR/MDR-TB) treatment has largely transitioned to regimens free of the injectable aminoglycoside component, despite the drug class’ purported bactericidal activity early in treatment. We tested whether Mycobacterium tuberculosis killing rates measured by tuberculosis molecular bacterial load assay (TB-MBLA) in sputa correlate with composition of the RR/MDR-TB regimen. Serial sputa were collected from patients with RR/MDR- and drug-sensitive TB at days 0, 3, 7, and 14, and then monthly for 4 months of anti-TB treatment. TB-MBLA was used to quantify viable M. tuberculosis 16S rRNA in sputum for estimation of colony forming units per ml (eCFU/ml). M. tuberculosis killing rates were compared among regimens using nonlinear-mixed-effects modeling of repeated measures. Thirty-seven patients produced 296 serial sputa and received treatment as follows: 13 patients received an injectable bedaquiline-free reference regimen, 9 received an injectable bedaquiline-containing regimen, 8 received an all-oral bedaquiline-based regimen, and 7 patients were treated for drug-sensitive TB with conventional rifampin/isoniazid/pyrazinamide/ethambutol (RHZE). Compared to the adjusted M. tuberculosis killing of −0.17 (95% confidence interval [CI] −0.23 to −0.12) for the injectable bedaquiline-free reference regimen, the killing rates were −0.62 (95% CI −1.05 to −0.20) log₁₀ eCFU/ml for the injectable bedaquiline-containing regimen (P = 0.019), −0.35 (95% CI −0.65 to −0.13) log₁₀ eCFU/ml for the all-oral bedaquiline-based regimen (P = 0.054), and −0.29 (95% CI −0.78 to +0.22) log₁₀ eCFU/ml for the RHZE regimen (P = 0.332). Thus, M. tuberculosis killing rates from sputa were higher among patients who received bedaquiline but were further improved with the addition of an injectable aminoglycoside.

Rifampicin and Isoniazid Maximal Concentrations are Below Efficacy-associated Thresholds in the Majority of Patients: Time to Increase the Doses?

BACKGROUND

The treatment of drug-sensitive tuberculosis (TB) is highly effective; however, many patients have suboptimal drug exposure, which possibly explains treatment failures and selection of resistance. This study aimed to describe the prevalence and determinants of suboptimal maximal concentrations (C_max) for anti-TB drugs.

METHODS

An observational study was conducted in patients receiving first-line anti-TB treatment. At two early time points (T1 and T2), blood samples were withdrawn 2 hours post-dose (C_max) and drug concentrations were measured. Data were expressed as medians (interquartile ranges).

RESULTS

The study included 199 participants: 72.9% were male and the median age was 39.8 years (27.5-51.4). The median C_max at T1 and T2 were 7950 ng/mL and 7122 ng/mL (rifampicin), 3260 ng/mL and 3185 ng/mL (isoniazid), 4210 ng/mL and 5742 ng/mL (ethambutol), and 31 008 ng/mL and 30 352 ng/mL (pyrazinamide), respectively. Higher doses/kg and other variables (being born in Italy and female gender for rifampicin, older age and proton pump inhibitor use for isoniazid, female gender and older age for pyrazinamide) were identified by multivariate linear regression analysis. Participants with a higher body mass index received lower doses/kg of all anti-TB drugs. Suboptimal C_max at T1 and T2 were observed in 60% and 66% (rifampicin), 54% and 55% (isoniazid), 33% and 39% (ethambutol), 20% and 11% (pyrazinamide) of patients. Despite 21% of patients at T1 and 24% at T2 showing two or more drugs with suboptimal exposure, no effect on treatment outcome was observed.

DISCUSSION

The majority of patients receiving first-line anti-TB drugs had low isoniazid and rifampin C_max. Increased doses or the use of therapeutic drug monitoring in selected patients may be advised.

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.

Optimal Sampling Strategies for Therapeutic Drug Monitoring of First-Line Tuberculosis Drugs in Patients with Tuberculosis

Background

The 24-h area under the concentration–time curve (AUC₂₄)/minimal inhibitory concentration ratio is the best predictive pharmacokinetic/pharmacodynamic (PK/PD) parameter of the efficacy of first-line anti-tuberculosis (TB) drugs. An optimal sampling strategy (OSS) is useful for accurately estimating AUC₂₄; however, OSS has not been developed in the fed state or in the early phase of treatment for first-line anti-TB drugs.

Methods

An OSS for the prediction of AUC₂₄ of isoniazid, rifampicin, ethambutol and pyrazinamide was developed for TB patients starting treatment. A prospective, randomized, crossover trial was performed during the first 3 days of treatment in which first-line anti-TB drugs were administered either intravenously or in fasting or fed conditions. The PK data were used to develop OSS with best subset selection multiple linear regression. The OSS was internally validated using a jackknife analysis and externally validated with other patients from different ethnicities and in a steady state of treatment.

Results

OSS using time points of 2, 4 and 8 h post-dose performed best. Bias was < 5% and imprecision was < 15% for all drugs except ethambutol in the fed condition. External validation showed that OSS_2-4-8 cannot be used for rifampicin in steady state conditions.

Conclusion

OSS at 2, 4 and 8 h post-dose enabled an accurate and precise prediction of AUC₂₄ values of first-line anti-TB drugs in this population.

Trial Registration

ClinicalTrials.gov (NCT02121314).

A population approach of rifampicin pharmacogenetics and pharmacokinetics in Mexican patients with tuberculosis

The aim of this study was to develop a population pharmacokinetic model of rifampicin (RMP) in Mexican patients with tuberculosis (TB) to evaluate the influence of anthropometric and clinical covariates, as well as genotypic variants associated with MDR1 and OATP1B1 transporters. A prospective study approved by Research Ethics Committee was performed at Hospital Central in San Luis Potosí, Mexico. TB patients under DOTS scheme and who signed informed consent were consecutively included. Anthropometric and clinical information was retrieved from medical records. Single nucleotide polymorphisms in MDR1 (C3435T) and SLCO1B1 (A388G and T521C) genes were evaluated. RMP plasma concentrations and time data were assessed with NONMEM software. A total of 71 Mexican TB patients from 18 to 72 years old were included for RMP quantification from 0.3 to 12 h after dose; 329 and 97 plasma concentrations were available for model development and validation, respectively. Sequential process includes a typical lag time of 0.25 h prior to absorption start with a Ka of 1.24 h^-1 and a zero-order absorption of 0.62 h to characterize the gradual increase in RMP plasma concentrations. Final model includes total body weight in volume of distribution (0.7 L/kg, CV = 26.8%) and a total clearance of 5.96 L/h (CV = 38.5%). Bioavailability was modified according to time under treatment and generic formulation administration. In conclusion, a population pharmacokinetic model was developed to describe the variability in RMP plasma concentrations in Mexican TB patients. Genetic variants evaluated did not showed significant influence on pharmacokinetic parameters. Final model will allow therapeutic drug monitoring at early stages.

Using pharmacogenomics and therapeutic drug monitoring to guide drug selection and dosing in outpatient mental health comprehensive medication management

Pharmacogenomic (PGx) testing aided by therapeutic drug monitoring (TDM) has the potential to improve medication-related outcomes in some individuals prescribed psychiatric medications. Many commonly prescribed psychiatric medications are metabolized through polymorphic drug metabolizing enzymes such as cytochrome p450 (CYP) 2D6 (CYP2D6) and CYP2C19. Through PGx testing, clinicians can make biologically informed choices when selecting a new medication, and TDM may help inform dose adjustments or assess exposures to current treatments. Herein, we describe 2 complex case reports of individuals with multiple psychiatric diagnoses and extensive histories of medication failures who underwent PGx testing in addition to TDM as part of a pharmacist-led comprehensive medication therapy management evaluation in a community mental health clinic setting.

Antibiotic-Induced Changes in Microbiome-Related Metabolites and Bile Acids in Rat Plasma

Various environmental factors can alter the gut microbiome’s composition and functionality, and modulate host health. In this study, the effects of oral and parenteral administration of two poorly bioavailable antibiotics (i.e., vancomycin and streptomycin) on male Wistar Crl/Wi(Han) rats for 28 days were compared to distinguish between microbiome-derived or -associated and systemic changes in the plasma metabolome. The resulting changes in the plasma metabolome were compared to the effects of a third reference compound, roxithromycin, which is readily bioavailable. A community analysis revealed that the oral administration of vancomycin and roxithromycin in particular leads to an altered microbial population. Antibiotic-induced changes depending on the administration routes were observed in plasma metabolite levels. Indole-3-acetic acid (IAA) and hippuric acid (HA) were identified as key metabolites of microbiome modulation, with HA being the most sensitive. Even though large variations in the plasma bile acid pool between and within rats were observed, the change in microbiome community was observed to alter the composition of the bile acid pool, especially by an accumulation of taurine-conjugated primary bile acids. In-depth investigation of the relationship between microbiome variability and their functionality, with emphasis on the bile acid pool, will be necessary to better assess the potential adverseness of environmentally induced microbiome changes.

Bile acids, lipid and purine metabolism involved in hepatotoxicity of first-line anti-tuberculosis drugs

OBJECTIVES

Rifampin (RIF), isoniazid (INH) and pyrazinamide (PZA) are essential components of the short-term first-line anti-tuberculosis (anti-TB) chemotherapy regimen and can cause hepatotoxicity. However, the mechanism of anti-TB drug-induced hepatotoxicity (ATDH) is currently unclear. We investigate the relevant contributions to liver injury and the pathway of the above-mentioned drugs administered alone or in combination.

METHODS

UPLC-Q-TOF/MS-based metabolomics, bile acids (BAs) analysis and FXR/SHP detection were used to evaluate the toxicity of these drugs and clarify the underlying metabolism-related pathway.

RESULTS

In C57BL/6 mice administered the corrected clinical doses, RIF, INH and PZA could induced hepatotoxicity; with less toxicity in the combination therapy than RIF. The pathological biochemistry, BAs concentration and metabolically regulated FXR/SHP gene expression analyzes in mice were consistent with the metabolomics results. FXR played a role in the hepatotoxicity of anti-tuberculosis drugs in the obeticholic acid treated and FXR^-/- mice. Additionally, the purine and lipid metabolic pathways were involved in ATDH.

CONCLUSION

ATDH was involved in bile acids and lipid and purine metabolism. The BAs metabolic pathway involvement in mice was validated in TB patients. The noninvasive metabolomics approach is more systemic than routine toxicity evaluation and can be used to assess compound toxicity and the underlying mechanism.

Preclinical Evidence of Nanomedicine Formulation to Target Mycobacterium tuberculosis at Its Bone Marrow Niche

One-third of the world’s population is estimated to be latently infected with Mycobacterium tuberculosis (Mtb). Recently, we found that dormant Mtb hides in bone marrow mesenchymal stem cells (BM-MSCs) post-chemotherapy in mice model and in clinical subjects. It is known that residual Mtb post-chemotherapy may be responsible for increased relapse rates. However, strategies for Mtb clearance post-chemotherapy are lacking. In this study, we engineered and formulated novel bone-homing PEGylated liposome nanoparticles (BTL-NPs) which actively targeted the bone microenvironment leading to Mtb clearance. Targeting of BM-resident Mtb was carried out through bone-homing liposomes tagged with alendronate (Ald). BTL characterization using TEM and DLS showed that the size of bone-homing isoniazid (INH) and rifampicin (RIF) BTLs were 100 ± 16.3 nm and 84 ± 18.4 nm, respectively, with the encapsulation efficiency of 69.5% ± 4.2% and 70.6% ± 4.7%. Further characterization of BTLs, displayed by sustained in vitro release patterns, increased in vivo tissue uptake and enhanced internalization of BTLs in RAW cells and CD271+BM-MSCs. The efficacy of isoniazid (INH)- and rifampicin (RIF)-loaded BTLs were shown using a mice model where the relapse rate of the tuberculosis was decreased significantly in targeted versus non-targeted groups. Our findings suggest that BTLs may play an important role in developing a clinical strategy for the clearance of dormant Mtb post-chemotherapy in BM cells.

Challenges of Immune Response Diversity in the Human Population Concerning New Tuberculosis Diagnostics, Therapies, and Vaccines

Universal approaches to the prevention and treatment of human diseases fail to take into account profound immune diversity resulting from genetic variations across populations. Personalized or precision medicine takes into account individual lifestyle, environment, and biology (genetics and immune status) and is being adopted in several disease intervention strategies such as cancer and heart disease. However, its application in infectious diseases, particularly global diseases such as tuberculosis (TB), is far more complex and in a state of infancy. Here, we discuss the impact of human genetic variations on immune responses and how they relate to failures seen in current TB diagnostic, therapy, and vaccine approaches across populations. We offer our perspective on the challenges and potential for more refined approaches going forward.

Management of latent tuberculosis infection in China: Exploring solutions suitable for high-burden countries

China is one of the countries with a high burden of tuberculosis (TB) and latent tuberculosis infection (LTBI). It was recently estimated that China had the highest LTBI burden in the world, with approximately 350 million persons living with the infection. The prevalence of LTBI in China is overestimated by tuberculin skin test (TST) as compared to interferon-gamma release assay (IGRA). A population-based study found that IGRA positivity rates ranged between 13.5% and 19.8%. The annual TB infection rate in the rural population was 1.5% based on persistent positive IGRA results in converters. The development of active TB from LTBI in the general rural population was 0.87 per 100 person-years in the first 2 years among individuals who newly converted to IGRA-positive. TB control in students has been paid more attention by the government, which also improved LTBI management among students in close contact with active TB patients. A 3-month regimen of twice-weekly rifapentine plus isoniazid (3H₂P₂, both with a maximum dose of 600 mg) has been practiced for LTBI treatment in China for years. With respect to LTBI management in populations using immune inhibitors, an expert consensus on TB prevention and management in tumor necrosis factor antagonist application was published in 2013 in China. In order to achieve the global goals of the End TB Strategy, China needs innovative ideas and technologies to reduce the TB incidence by management of LTBI, such as the identification of populations for LTBI testing and treatment, selecting and developing reliable LTBI tests, exploring safe and effective preventive treatment tools, and establishing a set of optimized LTBI management systems.

Pharmacogenetics in the clinical analysis laboratory: clinical practice, research, and drug development pipeline

Introduction: Over the last decade, the spread of next-generation sequencing technology along with the rising cost in health management in national health systems has led to widespread use/abuse of pharmacogenetic tests (PGx) in the practice of many clinical disciplines. However, given their clinical significance, it is important to standardize these tests for having an interaction with the clinical analysis laboratory (CAL), in which a PGx service can meet these requirements. Areas covered: A diagnostic test must meet the criteria of reproducibility and validity for its utility in the clinical routine. This present review mainly describes the utility of introducing PGx tests in the CAL routine to produce correct results useful for setting up personalized drug treatments. Expert opinion: With a PGx service, CALs can provide the right tool to help clinicians to make better choices about different categories of drugs and their dosage and to manage the economic impact both in hospital-based settings and in National Health Services, throughout electronic health records. Advances in PGx also allow a new approach for pharmaceutical companies in order to improve drug development and clinical trials. As a result, CALs can achieve a powerful source of epidemiological, clinical, and research findings from PGx tests.

Matryoshka-type gastro-resistant microparticles for the oral treatment of Mycobacterium tuberculosis

AIM

Production of Matryoshka-type gastroresistant microparticles containing antibiotic-loaded poly lactic-co-glycolic acid (PLGA) nanoparticles (NP) against Mycobacterium tuberculosis.

MATERIALS & METHODS

The emulsification and evaporation methods were followed for the synthesis of PLGA-NPs and methacrylic acid-ethyl acrylate-based coatings to protect rifampicin from degradation under simulated gastric conditions.

RESULTS & CONCLUSION

The inner antibiotic-loaded NPs here reported can be released under simulated intestinal conditions whereas their coating protects them from degradation under simulated gastric conditions. The encapsulation does not hinder the antituberculosis action of the encapsulated antibiotic rifampicin. A sustained antibiotic release could be obtained when using the drug-loaded encapsulated NPs. Compared with the administration of the free drug, a more effective elimination of M. tuberculosis was observed when applying the NPs against infected macrophages. The antibiotic-loaded PLGA-NPs were also able to cross an in vitro model of intestinal barrier.

Short-course regimens of rifapentine plus isoniazid to treat latent tuberculosis infection in older Chinese patients: a randomised controlled study

Latent tuberculosis infection (LTBI) management is now a critical component of the World Health Organization's End TB Strategy.In this randomised controlled trial (Chinese Clinical Trial Registry identifier ChiCTR-IOR-15007202), two short-course regimens with rifapentine plus isoniazid (a 3-month once-weekly regimen and a 2-month twice-weekly regimen) were initially designed to be evaluated for rural residents aged 50-69 years with LTBI in China.Due to the increasingly rapid growth and unexpected high frequency of adverse effects, the treatments were terminated early (after 8 weeks for the once-weekly regimen and after 6 weeks for the twice-weekly regimen). In the modified intention-to-treat analysis on the completed doses, the cumulative rate of active disease during 2 years of follow-up was 1.21% (14 out of 1155) in the untreated controls, 0.78% (10 out of 1284) in the group that received the 8-week once-weekly regimen and 0.46% (six out of 1299) in the group that received the 6-week twice-weekly regimen. The risk of active disease was decreased, with an adjusted hazard ratio of 0.63 (95% CI 0.27-1.43) and 0.41 (95% CI 0.15-1.09) for the treatments, respectively. No significant difference was found in the occurrence of hepatotoxicity (1.02% (13 out of 1279) versus 1.17% (15 out of 1279); p=0.704).The short regimens tested must be used with caution among the elderly because of the high rates of adverse effects. Further work is necessary to test the ultrashort regimens in younger people with LTBI.

A case report of mucocutaneous tuberculosis after orthotopic liver transplantation: a challenging diagnosis

Background

Mycobacterium tuberculosis is responsible for high morbidity and mortality in immune-compromised hosts.

Case presentation

We present a rare case of cutaneous tuberculosis after orthotopic liver transplantation without involvement of any other organs.

Conclusion

TB risk-factors assessment, careful LTBI screening and treatment according to national guidelines, as well as a reduction in missed opportunity for prevention are necessary to avoid MTB related disease in fragile patients.

New drugs and regimens for tuberculosis

Since standardized rifampin-based first-line regimens and fluoroquinolone-based second-line regimens were used to treat tuberculosis (TB), unfortunately without timely modification according to the drug resistance profile, TB and drug-resistant disease are still important public health threats worldwide. Although the last decade has witnessed advances in rapid diagnostic tools and use of repurposed and novel drugs for better managing drug-resistant TB, we need an appropriate TB control strategy and a well-functioning health infrastructure to ensure optimal operational use of rapid tests, judicious use of effective treatment regimens that can be rapidly tailored according to the drug resistance profile and timely management of risk factors and co-morbidities that promote infection and its progression to disease. We searched the published literature to discuss (i) standardized versus individualized therapies, including the choice between a single one-size-fit-all regimen versus different options with different key drugs determined mainly by rapid drug susceptibility testing, (ii) alternative regimens for managing drug-susceptible TB, (iii) evidence for using the World Health Organization (WHO) longer and shorter regimens for multidrug-resistant TB and (iv) evidence for using repurposed and novel drugs. We hope an easily applicable combination of biomarkers that accurately predict individual treatment outcome will soon be available to ultimately guide individualized therapy.