Current research toward optimizing dosing of first-line antituberculosis treatment

Genetic and clinical predictors of rifapentine and isoniazid pharmacokinetics in paediatrics with tuberculosis infection

OBJECTIVES

Twelve weekly doses of rifapentine and isoniazid (3HP regimen) are recommended for TB preventive therapy in children with TB infection. However, they present with variability in the pharmacokinetic profiles. The current study aimed to develop a pharmacokinetic model of rifapentine and isoniazid in 12 children with TB infection using NONMEM.

METHODS

Ninety plasma and 41 urine samples were collected at Week 4 of treatment. Drug concentrations were measured using a validated HPLC-UV method. MassARRAY® SNP genotyping was used to investigate genetic factors, including P-glycoprotein (ABCB1), solute carrier organic anion transporter B1 (SLCO1B1), arylacetamide deacetylase (AADAC) and N-acetyl transferase (NAT2). Clinically relevant covariates were also analysed.

RESULTS

A two-compartment model for isoniazid and a one-compartment model for rifapentine with transit compartment absorption and first-order elimination were the best models for describing plasma and urine data. The estimated (relative standard error, RSE) of isoniazid non-renal clearance was 3.52 L·h-1 (23.1%), 2.91 L·h-1 (19.6%), and 2.58 L·h-1 (20.0%) in NAT2 rapid, intermediate and slow acetylators. A significant proportion of the unchanged isoniazid was cleared renally (2.7 L·h-1; 8.0%), while the unchanged rifapentine was cleared primarily through non-renal routes (0.681 L·h-1; 3.6%). Participants with the ABCB1 mutant allele had lower bioavailability of rifapentine, while food prolonged the mean transit time of isoniazid.

CONCLUSIONS

ABCB1 mutant allele carriers may require higher rifapentine doses; however, this must be confirmed in larger trials. Food did not affect overall exposure to isoniazid and only delayed absorption time.

Leading Paediatric Infectious Diseases-Current Trends, Gaps, and Future Prospects in Oral Pharmacotherapeutic Interventions

Paediatric infectious diseases contribute significantly to global health challenges. Conventional therapeutic interventions are not always suitable for children, as they are regularly accompanied with long-standing disadvantages that negatively impact efficacy, thus necessitating the need for effective and child-friendly pharmacotherapeutic interventions. Recent advancements in drug delivery technologies, particularly oral formulations, have shown tremendous progress in enhancing the effectiveness of paediatric medicines. Generally, these delivery methods target, and address challenges associated with palatability, dosing accuracy, stability, bioavailability, patient compliance, and caregiver convenience, which are important factors that can influence successful treatment outcomes in children. Some of the emerging trends include moving away from creating liquid delivery systems to developing oral solid formulations, with the most explored being orodispersible tablets, multiparticulate dosage forms using film-coating technologies, and chewable drug products. Other ongoing innovations include gastro-retentive, 3D-printed, nipple-shield, milk-based, and nanoparticulate (e.g., lipid-, polymeric-based templates) drug delivery systems, possessing the potential to improve therapeutic effectiveness, age appropriateness, pharmacokinetics, and safety profiles as they relate to the paediatric population. This manuscript therefore highlights the evolving landscape of oral pharmacotherapeutic interventions for leading paediatric infectious diseases, crediting the role of innovative drug delivery technologies. By focusing on the current trends, pointing out gaps, and identifying future possibilities, this review aims to contribute towards ongoing efforts directed at improving paediatric health outcomes associated with the management of these infectious ailments through accessible and efficacious drug treatments.

Effect of NAT2, GSTM1 and CYP2E1 genetic polymorphisms on plasma concentration of isoniazid and its metabolites in patients with tuberculosis, and the assessment of exposure-response relationships

Objectives: Isoniazid is a key drug in the chemotherapy of tuberculosis (TB), however, interindividual variability in pharmacokinetic parameters and drug plasma levels may affect drug responses including drug induced hepatotoxicity. The current study investigated the relationships between isoniazid exposure and isoniazid metabolism-related genetic factors in the context of occurrence of drug induced hepatotoxicity and TB treatment outcomes. Methods: Demographic characteristics and clinical information were collected in a prospective TB cohort study in Latvia (N = 34). Time to sputum culture conversion (tSCC) was used as a treatment response marker. Blood plasma concentrations of isoniazid (INH) and its metabolites acetylisoniazid (AcINH) and isonicotinic acid (INA) were determined at three time points (pre-dose (0 h), 2 h and 6 h after drug intake) using liquid chromatography-tandem mass spectrometry. Genetic variations of three key INH-metabolizing enzymes (NAT2, CYP2E1, and GSTM1) were investigated by application PCR- and Next-generation sequencing-based methods. Depending on variables, group comparisons were performed by Student's t-test, one-way ANOVA, Mann-Whitney-Wilcoxon, and Kruskal-Wallis tests. Pearson correlation coefficient was calculated for the pairs of normally distributed variables; model with rank transformations were used for non-normally distributed variables. Time-to-event analysis was performed to analyze the tSCC data. The cumulative probability of tSCC was obtained using Kaplan-Meier estimators. Cox proportional hazards models were fitted to estimate hazard rate ratios of successful tSCC. Results: High TB treatment success rate (94.1%) was achieved despite the variability in INH exposure. Clinical and demographic factors were not associated with either tSCC, hepatotoxicity, or INH pharmacokinetics parameters. Correlations between plasma concentrations of INH and its metabolites were NAT2 phenotype-dependent, while GSTM1 genetic variants did not showed any effects. CYP2E1*6 (T > A) allelic variant was associated with INH pharmacokinetic parameters. Decreased level of AcINH was associated with hepatotoxicity, while decreased values of INA/INH and AcINH/INH were associated with month two sputum culture positivity. Conclusion: Our findings suggest that CYP2E1, but not GSTM1, significantly affects the INH pharmacokinetics along with NAT2. AcINH plasma level could serve as a biomarker for INH-related hepatotoxicity, and the inclusion of INH metabolite screening in TB therapeutic drug monitoring could be beneficial in clinical studies for determination of optimal dosing strategies.

Estimating the prevalence of poor-quality anti-TB medicines: a neglected risk for global TB control and resistance

OBJECTIVES

Tuberculosis (TB) remains a major global public health problem, especially with the recent emergence of multidrug-resistant TB and extensively drug-resistant TB. There has been little consideration of the extent of substandard and falsified (SF) TB medicines as drivers of resistance. We assessed the evidence on the prevalence of SF anti-TB medicines and discussed their public health impact.

MATERIALS/METHODS

We searched Web of Science, Medline, Pubmed, Google Scholar, WHO, US Pharmacopeia and Medicines Regulatory Agencies websites for publications on anti-TB medicines quality up to 31 October 2021. Publications reporting on the prevalence of SF anti-TB drugs were evaluated for quantitative analysis.

RESULTS

Of the 530 screened publications, 162 (30.6%) were relevant to anti-TB medicines quality; of those, 65 (40.1%) described one or more TB quality surveys in a specific location or region with enough information to yield an estimate of the local prevalence of poor-quality TB medicines. 7682 samples were collected in 22 countries and of those, 1170 (15.2%) failed at least one quality test. 14.1% (879/6255) of samples failed in quality surveys, 12.5% (136/1086) in bioequivalence studies and 36.9% (87/236) in accelerated biostability studies. The most frequently assessed were rifampicin monotherapy (45 studies, 19.5%) and isoniazid monotherapy (33, 14.3%), rifampicin-isoniazid-pyrazinamide-ethambutol fixed dose combinations (28, 12.1%) and rifampicin-isoniazid (20, 8.6%). The median (IQR) number of samples collected per study was 12 (1-478).

CONCLUSIONS

SF, especially substandard, anti-TB medicines are present worldwide. However, TB medicine quality data are few and are therefore not generalisable that 15.2% of global anti-TB medicine supply is SF. The evidence available suggests that the surveillance of the quality of TB medicines needs to be an integral part of treatment programmes. More research is needed on the development and evaluation of rapid, affordable and accurate portable devices to empower pharmacy inspectors to screen for anti-TB medicines.

Effectiveness and pharmacokinetic exposures of first-line drugs used to treat drug-susceptible tuberculosis in children: a systematic review and meta-analysis

BACKGROUND

Optimal doses of first line drugs for drug-susceptible tuberculosis (DS-TB) treatment in children and young adolescents remain uncertain. We aimed to determine if children treated using WHO-recommended or higher doses of first-line drugs achieve successful outcomes and sufficient pharmacokinetic exposures.

METHODS

Titles, abstracts, and full-text articles were screened. We searched Pubmed, EMBASE, CENTRAL, and trial registries from 2010 to 2021. We included studies in children <18 years, being treated for DS-TB with rifampicin, pyrazinamide, isoniazid, and ethambutol. Outcomes were treatment success rates and drug exposures. The protocol for the systematic review was preregistered in PROSPERO, CRD42021274222.

RESULTS

Of 304 studies identified, 46 studies were eligible for full-text review and 12 and 18 articles were included for the efficacy and pharmacokinetic analysis, respectively. Of 1,830 children included in the efficacy analysis, 82% had favourable outcomes (range 25%-95%). At WHO-recommended doses, exposures to rifampicin, pyrazinamide, and ethambutol were lower in children as compared to adults. Children ≤6 years have 35% lower AUC than older children (14.4 (9.9-18.8) vs 22.0 (13.8-30.1) μg.h/mL) and children with HIV (CWHIV) had 35% lower rifampicin AUC than HIV negative children (17.3 (11.4-23.2) vs 26.5 (21.3-31.7) μg.h/mL). Heterogeneity and small sample sizes were major limitations.

CONCLUSION

There is large variability in outcomes with an average 82% favourable outcomes. Drug exposures are lower in children than in adults. Younger children and CWHIV are underexposed to rifampicin. Standardization of pharmacokinetic paediatric studies and individual patient data analysis with safety assessment are needed to inform optimal dosing.

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.

Plasma drug concentrations of 4-drug fixed-dose combination regimen and its efficacy for treatment of pulmonary tuberculosis under National Tuberculosis Elimination Programme: A prospective pilot study

BACKGROUND

The thrice weekly dosing regimen of DOTS has shown low rifampicin plasma concentrations as an independent risk factor for unfavourable tuberculosis (TB) outcome. With introduction of daily regimen using fixed dose combinations (FDC) under National Tuberculosis Elimination Programme (NTEP) the existence of suboptimal plasma levels of first-line antitubercular drugs and its clinical significance remain poorly understood.

METHOD

We included a prospective cohort of newly diagnosed pulmonary tuberculosis (PTB) patients receiving 4-FDC daily regimen under NTEP. Plasma concentration at 2 hours (C_2h) of each drug was determined after two weeks of treatment using liquid chromatography (LCMS/MS) developed by us. TB card and laboratory reports were reviewed for baseline characteristics and clinical status at 2, 4 and 6 months after the initiation of treatment. At a 1 year follow-up, therapy failure was defined as death or a relapse of tuberculosis.

RESULTS

Among 40 PTB patients, the C_2h post dose plasma concentrations of H, R and E were suboptimal in 25%, 60% and 10% respectively. The C_2h of H, R, Z and E were respectively 4.2 ± 2.0, 7.3 ± 2.8, 39.2 ± 8.8 and 3.5 ± 1.2 μg/ml; 60% of the patients had suboptimal plasma concentrations and commonly it was observed with H and R. C_2h were lower than expected for at least two drugs i.e. H and R in 25% (10/40) of the patients. Plasma concentration of isoniazid and rifampicin has always been considered important for microbiological response and treatment outcome and low concentrations has been associated with poor treatment response. These patients may require a two year follow up and critical evaluation for prevention of MDR-TB. However, all the TB patients were cured and none of them had recurrence within one year follow up.

CONCLUSIONS

All the pulmonary TB patients administering 4-FDC daily regimen under programmatic settings were cured despite the suboptimal levels of isoniaizd and rifampicin. All the patients achieved pyrazinamide plasma levels and probably this could be the reason behind favourable outcome. Further study is required on large sample size with various subset of population to understand the need of therapeutic drug monitoring.

Pharmacometrics in tuberculosis: progress and opportunities

Tuberculosis remains one of the leading causes of death by a communicable agent, infecting up to one-quarter of the world's population, predominantly in disadvantaged communities. Pharmacometrics employs quantitative mathematical models to describe the relationships between pharmacokinetics and pharmacodynamics, and to predict drug doses, exposures, and responses. Pharmacometric approaches have provided a scientific basis for improved dosing of antituberculosis drugs and concomitantly administered antiretrovirals at the population level. The development of modelling frameworks including physiologically-based pharmacokinetics, quantitative systems pharmacology and machine learning provides an opportunity to extend the role of pharmacometrics to in silico quantification of drug-drug interactions, prediction of doses for special populations, dose optimization and individualization, and understanding the complex exposure-response relationships of multidrug regimens in terms of both efficacy and safety, informing regimen design for future study. In this short clinically-focused review, we explore what has been done, and what opportunities exist for pharmacometrics to impact tuberculosis pharmacotherapy.

A selective PPM1A inhibitor activates autophagy to restrict the survival of Mycobacterium tuberculosis

Metal-dependent protein phosphatases (PPMs) have essential roles in a variety of cellular processes, including inflammation, proliferation, differentiation, and stress responses, which are intensively investigated in cancer and metabolic diseases. Targeting PPMs to modulate host immunity in response to pathogens is an ambitious proposition. The feasibility of such a strategy is unproven because development of inhibitors against PPMs is challenging and suffers from poor selectivity. Combining a biomimetic modularization strategy with function-oriented synthesis, we design, synthesize and screen more than 500 pseudo-natural products, resulting in the discovery of a potent, selective, and non-cytotoxic small molecule inhibitor for PPM1A, SMIP-30. Inhibition of PPM1A with SMIP-30 or its genetic ablation (ΔPPM1A) activated autophagy through a mechanism dependent on phosphorylation of p62-SQSTM1, which restricted the intracellular survival of Mycobacterium tuberculosis in macrophages and in the lungs of infected mice. SMIP-30 provides proof of concept that PPMs are druggable and promising targets for the development of host-directed therapies against tuberculosis.

The use of thalidomide to treat children with tuberculosis meningitis: A review

Much of the morbidity and mortality caused by tuberculous meningitis (TBM) is mediated by a dysregulated immune response. Effective host-directed therapy is therefore critical to improve survival and clinical outcomes. Currently only one host-directed therapy (HDT), corticosteroids, is proven to improve mortality. However, there is no evidence that corticosteroids reduce morbidity and the mechanism of action for mortality reduction is uncertain. Further, it has no proven benefit in HIV co-infected individuals. One promising host-directed therapy approach is to restrict the immunopathology arising from tumour necrosis factor (TNF)-α excess is via TNF-α inhibitors. There are accumulating data on the role of thalidomide, anti-TNF-α monoclonal antibodies (infliximab, adalimumab) and the soluble TNF-α receptor (etanercept) in TBM treatment. Thalidomide was developed nearly seventy years ago and has been a highly controversial drug. Birth defects and toxic adverse effects have limited its use but an improved understanding of its immunological mechanism of action suggest that it may have a crucial role in regulating the destructive host response seen in inflammatory conditions such as TBM. Observational studies at our institution found low dosage adjunctive thalidomide safe in treating tuberculous mass lesions and blindness related to optochiasmatic arachnoiditis, with good clinical and radiological response. In this review, we discuss possible mechanisms of action for thalidomide, based on our clinico-radiologic experience and post-mortem histopathological work. We also propose a rationale for its use in the treatment of certain TBM-related complications.

Pharmacokinetics of first-line drugs in children with tuberculosis using WHO-recommended weight band doses and formulations

Background

Dispersible pediatric fixed-dose combination (FDC) tablets delivering higher doses of first-line antituberculosis drugs in World Health Organization–recommended weight bands were introduced in 2015. We report the first pharmacokinetic data for these FDC tablets in Zambian and South African children in the treatment-shortening SHINE trial.

Methods

Children weighing 4.0–7.9, 8.0–11.9, 12.0–15.9, or 16.0–24.9 kg received 1, 2, 3, or 4 tablets daily, respectively (rifampicin/isoniazid/pyrazinamide [75/50/150 mg], with or without 100 mg ethambutol, or rifampicin/isoniazid [75/50 mg]). Children 25.0–36.9 kg received doses recommended for adults <37 kg (300, 150, 800, and 550 mg/d, respectively, for rifampicin, isoniazid, pyrazinamide, and ethambutol). Pharmacokinetics were evaluated after at least 2 weeks of treatment.

Results

In the 77 children evaluated, the median age (interquartile range) was 3.7 (1.4–6.6) years; 40 (52%) were male and 20 (26%) were human immunodeficiency virus positive. The median area under the concentration-time curve from 0 to 24 hours for rifampicin, isoniazid, pyrazinamide, and ethambutol was 32.5 (interquartile range, 20.1–45.1), 16.7 (9.2–25.9), 317 (263–399), and 9.5 (7.5–11.5) mg⋅h/L, respectively, and lower in children than in adults for rifampicin in the 4.0–7.9-, 8–11.9-, and ≥25-kg weight bands, isoniazid in the 4.0–7.9-kg and ≥25-kg weight bands, and ethambutol in all 5 weight bands. Pyrazinamide exposures were similar to those in adults.

Conclusions

Recommended weight band–based FDC doses result in lower drug exposures in children in lower weight bands and in those ≥25 kg (receiving adult doses). Further adjustments to current doses are needed to match current target exposures in adults. The use of ethambutol at the current World Health Organization–recommended doses requires further evaluation.

The within-host evolution of antimicrobial resistance in Mycobacterium tuberculosis

Tuberculosis (TB) has been responsible for the greatest number of human deaths due to an infectious disease in general, and due to antimicrobial resistance (AMR) in particular. The etiological agents of human TB are a closely-related group of human-adapted bacteria that belong to the Mycobacterium tuberculosis complex (MTBC). Understanding how MTBC populations evolve within-host may allow for improved TB treatment and control strategies. In this review, we highlight recent works that have shed light on how AMR evolves in MTBC populations within individual patients. We discuss the role of heteroresistance in AMR evolution, and review the bacterial, patient and environmental factors that likely modulate the magnitude of heteroresistance within-host. We further highlight recent works on the dynamics of MTBC genetic diversity within-host, and discuss how spatial substructures in patients' lungs, spatiotemporal heterogeneity in antimicrobial concentrations and phenotypic drug tolerance likely modulates the dynamics of MTBC genetic diversity in patients during treatment. We note the general characteristics that are shared between how the MTBC and other bacterial pathogens evolve in humans, and highlight the characteristics unique to the MTBC.

Integrating Pharmacokinetics and Pharmacodynamics in Operational Research to End Tuberculosis

Tuberculosis (TB) elimination requires innovative approaches. The new Global Tuberculosis Network (GTN) aims to conduct research on key unmet therapeutic and diagnostic needs in the field of TB elimination using multidisciplinary, multisectorial approaches. The TB Pharmacology section within the new GTN aims to detect and study the current knowledge gaps, test potential solutions using human pharmacokinetics informed through preclinical infection systems, and return those findings to the bedside. Moreover, this approach would allow prospective identification and validation of optimal shorter therapeutic durations with new regimens. Optimized treatment using available and repurposed drugs may have an increased impact when prioritizing a person-centered approach and acknowledge the importance of age, gender, comorbidities, and both social and programmatic environments. In this viewpoint article, we present an in-depth discussion on how TB pharmacology and the related strategies will contribute to TB elimination.

Pharmacokinetics of antiretroviral and tuberculosis drugs in children with HIV/TB co-infection: a systematic review

INTRODUCTION

Management of concomitant use of ART and TB drugs is difficult because of the many drug-drug interactions (DDIs) between the medications. This systematic review provides an overview of the current state of knowledge about the pharmacokinetics (PK) of ART and TB treatment in children with HIV/TB co-infection, and identifies knowledge gaps.

METHODS

We searched Embase and PubMed, and systematically searched abstract books of relevant conferences, following PRISMA guidelines. Studies not reporting PK parameters, investigating medicines that are not available any longer or not including children with HIV/TB co-infection were excluded. All studies were assessed for quality.

RESULTS

In total, 47 studies met the inclusion criteria. No dose adjustments are necessary for efavirenz during concomitant first-line TB treatment use, but intersubject PK variability was high, especially in children <3 years of age. Super-boosted lopinavir/ritonavir (ratio 1:1) resulted in adequate lopinavir trough concentrations during rifampicin co-administration. Double-dosed raltegravir can be given with rifampicin in children >4 weeks old as well as twice-daily dolutegravir (instead of once daily) in children older than 6 years. Exposure to some TB drugs (ethambutol and rifampicin) was reduced in the setting of HIV infection, regardless of ART use. Only limited PK data of second-line TB drugs with ART in children who are HIV infected have been published.

CONCLUSIONS

Whereas integrase inhibitors seem favourable in older children, there are limited options for ART in young children (<3 years) receiving rifampicin-based TB therapy. The PK of TB drugs in HIV-infected children warrants further research.

A simple and reliable analytical method for simultaneous quantification of first line antitubercular drugs in human plasma by LCMS/MS

The present study describes the optimization of a simple and reliable method for the determination of four first line antitubercular drugs in human plasma. The studied analytes were isoniazid (H), rifampicin (R), pyrazinamide (Z) and ethambutol (E) in fixed dose combination recommended to patients under the Revised National Tuberculosis Control Programme (RNTCP, India). The analytes were extracted from the human plasma (150 μL) using the single step liquid-liquid extraction approach and were analyzed by liquid chromatography (LC) coupled to tandem mass spectrometry (MS/MS). The method was fully validated, according to USFDA guidelines. A linear range of 0.05-10 μg mL^-1, 0.1-20 μg mL^-1, 0.5-100 μg mL^-1 and 0.05-10 μg mL^-1 for H, R, Z and E respectively was established, presenting determination coefficients above 0.99. Concerning imprecision, the CV was lower than 15% for all analytes. All tested analytes were found to be stable in the samples. Although the values obtained for recovery were above 85%, the method proved to be sensitive, since low detection limits of 0.05 μg mL^-1 for H and E, 0.1 μg mL^-1 for R and 0.5 μg mL^-1 for Z were obtained. The intra-day and inter-day accuracy and imprecision were within CV ±15%. The use of the conventional silica column in the extraction of these compounds through a single step protein precipitation method simplifies the analytical process. In addition due to its simplicity and sensitivity, it can be applied to carry out therapeutic drug monitoring and drug level assessment in human plasma samples. The results of analyte levels are comparable to other reported methods. The method had been successfully applied for simultaneous determination of first line anti-tubercular drugs in pulmonary tubercular patients. The method requires 150 μL of patient plasma and offers low volume for injection (10 μL) and blood sample collection (3 mL) which will be an added advantage for pediatric anti-TB drug level assessment and monitoring.

Tuberculosis in children: screening, diagnosis and management

PURPOSE OF REVIEW

The present review focuses on recent advances and current challenges in screening, diagnosis and management of tuberculosis (TB) in children, encompassing TB infection and TB disease, and public health priorities for screening and family engagement.

RECENT FINDINGS

Although awareness has improved in recent years that children in TB endemic areas suffer a huge disease burden, translation into better prevention and care remains challenging. Recent WHO guidelines have incorporated screening of all household contacts of pulmonary TB cases, but implementation in high incidence settings remains limited. Improved tests using noninvasive samples, such as the lateral flow urinary lipoarabinomannan assay and the new Xpert Ultra assay applied to induced sputum or stool in young children, are showing promise and further assessment is eagerly awaited. From a treatment perspective, child-friendly dispersible fixed dose combination tablets are now widely available with excellent acceptability and tolerance reported in young children.

SUMMARY

High-level government commitment to TB control as a public health priority and feasible strategies to achieve this are required to contain the global epidemic, whereas strong engagement of local TB clinics and affected families in TB prevention is essential to limit secondary cases and protect exposed children.

Model-Informed Drug Discovery and Development Strategy for the Rapid Development of Anti-Tuberculosis Drug Combinations

The increasing emergence of drug-resistant tuberculosis requires new effective and safe drug regimens. However, drug discovery and development are challenging, lengthy and costly. The framework of model-informed drug discovery and development (MID3) is proposed to be applied throughout the preclinical to clinical phases to provide an informative prediction of drug exposure and efficacy in humans in order to select novel anti-tuberculosis drug combinations. The MID3 includes pharmacokinetic-pharmacodynamic and quantitative systems pharmacology models, machine learning and artificial intelligence, which integrates all the available knowledge related to disease and the compounds. A translational in vitro-in vivo link throughout modeling and simulation is crucial to optimize the selection of regimens with the highest probability of receiving approval from regulatory authorities. In vitro-in vivo correlation (IVIVC) and physiologically-based pharmacokinetic modeling provide powerful tools to predict pharmacokinetic drug-drug interactions based on preclinical information. Mechanistic or semi-mechanistic pharmacokinetic-pharmacodynamic models have been successfully applied to predict the clinical exposure-response profile for anti-tuberculosis drugs using preclinical data. Potential pharmacodynamic drug-drug interactions can be predicted from in vitro data through IVIVC and pharmacokinetic-pharmacodynamic modeling accounting for translational factors. It is essential for academic and industrial drug developers to collaborate across disciplines to realize the huge potential of MID3.

Tuberculosis in childhood and adolescence: a view from different perspectives

OBJECTIVE

To describe the epidemiological situation of tuberculosis in children under 19 years of age in Brazil and to review the latest publications on disease risk, diagnosis, treatment, and prevention.

SOURCE OF DATA

Notifiable Diseases Information System (2018), World Health Organization estimates, and PubMed articles selected using the descriptor "Tuberculosis," delimited by type of study, period, age, and language.

SYNTHESIS OF DATA

In 2018, in Brazil, 9.4% of notifications were in children under 19 years. The pulmonary form predominated in 80.1% of the cases. The cure rate was 76.8%, lethality was 0.8%, and abandonment was 10.4%. The prevalence of drug-resistant tuberculosis (2011-2016) was 0.5%. It has been found that the risk of disease can reach up to 56% in children under 5 years, influenced by helminth co-infections, malaria, chronic viral infections, live attenuated virus vaccines, and hypovitaminosis D. Exposure to a bacilliferous patient for periods shorter than 30minutes is sufficient for the development of infection and/or disease. In Brazil, microbiological screening is recommended, but the use of the scoring system, modified in 2019, has been maintained. Studies on infection detection have supported the use of the tuberculin skin test. In the treatment, the great advance was the introduction of dispersible formulations, adjustment of the recommended doses, and shortened regimens for latent infection. Several vaccine studies (stages 1-3) are ongoing, but no BCG-licensed substitute has been implemented yet.

CONCLUSIONS

There has been progress in treatment, but major challenges need to be overcome to improve diagnosis, monitoring, and outcome of cases, aiming to eliminate tuberculosis.

LC-QToF-MS method for quantification of ethambutol, isoniazid, pyrazinamide and rifampicin in human plasma and its application

In this research, we developed and validated a liquid chromatography coupled to mass spectrometry (LC-QToF-MS) method for simultaneous quantification of the anti-tuberculosis drugs ethambutol, isoniazid, pyrazinamide and rifampicin in human plasma. Plasma samples spiked with cimetidine (internal standard) were extracted using protein precipitation with acetonitrile containing 1% formic acid. Separation was performed using a C₁₈ column under flow gradient conditions with water and acetonitrile, both containing 5 mm ammonium formate and 0.1% formic acid. The method was validated according to the ANVISA and US Food and Drug Administration guidelines for bioanalytical method validation. The calibration curve was linear over a concentration range of 0.2-5 μg ml^-1 for ethambutol, 0.2-7.5 μg ml^-1 for isoniazid, 1-40 μg ml^-1 for pyrazinamide and 0.25-2 μg ml^-1 for rifampicin, all with adequate precision and accuracy. The method was reproducible, selective and free of carryover and matrix effects. The validated LC-QToF-MS method was successfully applied to real samples and shown to be applicable to future therapeutic and pharmacokinetic monitoring studies.

Low Antituberculosis Drug Concentrations in HIV-Tuberculosis-Coinfected Adults with Low Body Weight: Is It Time To Update Dosing Guidelines?

Antituberculosis drugs display large pharmacokinetic variability, which may be influenced by several factors, including body size, genetic differences, and drug-drug interactions. We set out to determine these factors, quantify their effect, and determine the dose adjustments necessary for optimal drug concentrations. HIV-infected Ugandan adults with pulmonary tuberculosis treated according to international weight-based dosing guidelines underwent pharmacokinetic sampling (1, 2, and 4 h after drug intake) 2, 8, and 24 weeks after treatment initiation. Between May 2013 and November 2015, we enrolled 268 patients (148 males) with a median weight of 53.5 (interquartile range [IQR], 47.5 to 59.0) kg and a median age of 35 (IQR, 29 to 40) years. Population pharmacokinetic modeling was used to interpret the data and revealed that patients weighing <55 kg achieved lower concentrations than those in higher weight bands for all drugs in the regimen. The models predicted that this imbalance could be solved with a dose increment of one fixed-dose combination (FDC) tablet for the weight bands of 30 to 37 and 38 to 54 kg. Additionally, the concomitant use of efavirenz increased isoniazid clearance by 24.1%, while bioavailability and absorption of rifampin and isoniazid varied up to 30% in patients on different formulations. Current dosing guidelines lead to lower drug exposure in patients in the lower weight bands. Simply adding one FDC tablet to current weight band-based dosing would address these differences in exposure and possibly improve outcomes. Lower isoniazid exposures due to efavirenz deserve further attention, as does the quality of currently used drug formulations of anti-TB drugs. (This study has been registered at ClinicalTrials.gov under identifier NCT01782950.).