QTc prolongation and treatment of multidrug-resistant tuberculosis

Comparison of QTc interval changes in drug-resistant tuberculosis patients on delamanid-containing regimens versus shorter treatment regimens

BACKGROUND

Delamanid (DLM) is a relatively new drug for drug-resistant tuberculosis (DR-TB) that has been used in Indonesia since 2019 despite its limited safety data. DLM is known to inhibit hERG potassium channel with the potential to cause QT prolongation which eventually leads to Torsades de pointes (TdP).

OBJECTIVE

This study aims to analyse the changes of QTc interval in DR-TB patients on DLM regimen compared to shorter treatment regimens (STR).

METHODS

A retrospective cohort was implemented on secondary data obtained from two participating hospitals. The QTc interval and the changes in QTc interval from baseline (ΔQTc) were assessed every 4 weeks for 24 weeks.

RESULTS

The maximum increased of QTc interval and ΔQTc interval were smaller in the DLM group with mean difference of 18,6 (95%CI 0.3 to 37.5) and 31.6 milliseconds (95%CI 14.1 to 49.1) respectively. The proportion of QTc interval prolongation in DLM group were smaller than STR group (RR=0.62; 95%CI 0.42 to 0.93).

CONCLUSION

This study has shown that DLM regimens are less likely to increase QTc interval compared to STR. However, close monitoring of the risk of QT interval prolongation needs to be carried out upon the use of QT interval prolonging antituberculoid drugs.

Pharmacokinetics and Optimal Dosing of Levofloxacin in Children for Drug-Resistant Tuberculosis: An Individual Patient Data Meta-Analysis

BACKGROUND

Each year 25 000-32 000 children develop rifampicin- or multidrug-resistant tuberculosis (RR/MDR-TB), and many more require preventive treatment. Levofloxacin is a key component of RR/MDR-TB treatment and prevention, but the existing pharmacokinetic data in children have not yet been comprehensively summarized. We aimed to characterize levofloxacin pharmacokinetics through an individual patient data meta-analysis of available studies and to determine optimal dosing in children.

METHODS

Levofloxacin concentration and demographic data were pooled from 5 studies and analyzed using nonlinear mixed effects modeling. Simulations were performed using current World Health Organization (WHO)-recommended and model-informed optimized doses. Optimal levofloxacin doses were identified to target median adult area under the time-concentration curve (AUC)24 of 101 mg·h/L given current standard adult doses.

RESULTS

Data from 242 children (2.8 years [0.2-16.8] was used). Apparent clearance was 3.16 L/h for a 13-kg child. Age affected clearance, reaching 50% maturation at birth and 90% maturation at 8 months. Nondispersible tablets had 29% lower apparent oral bioavailability compared to dispersible tablets. Median exposures at current WHO-recommended doses were below the AUC target for children weighing <24 kg and under <10 years, resulting in approximately half of the exposure in adults. Model-informed doses of 16-33 mg/kg for dispersible tablets or 16-50 mg/kg for nondispersible tablets were required to meet the AUC target without significantly exceeding the median adult Cmax.

CONCLUSIONS

Revised weight-band dosing guidelines with doses of >20 mg/kg are required to ensure adequate exposure. Further studies are needed to determine safety and tolerability of these higher doses.

Serial electrocardiogram recordings revealed a high prevalence of QT interval prolongation in patients with tuberculosis receiving fluoroquinolones

BACKGROUND

Fluoroquinolones, crucial components of treatment regimens for drug-resistant tuberculosis (TB), are associated with QT interval prolongation and risks of fatal cardiac arrhythmias. However, few studies have explored dynamic changes in the QT interval in patients receiving QT-prolonging agents.

METHODS

This prospective cohort study recruited hospitalized patients with TB who received fluoroquinolones. The study investigated the variability of the QT interval by using serial electrocardiograms (ECGs) recorded four times daily. This study analyzed the accuracy of intermittent and single-lead ECG monitoring in detecting QT interval prolongation.

RESULTS

This study included 32 patients. The mean age was 68.6 ± 13.2 years. The results revealed mild-to-moderate and severe QT interval prolongation in 13 (41%) and 5 (16%) patients, respectively. The incremental yields in sensitivity of one to four daily ECG recordings were 61.0%, 26.1%, 5.6%, and 7.3% in detecting mild-to-moderate QT interval prolongation, and 66.7%, 20.0%, 6.7%, and 6.7% in detecting severe QT interval prolongation. The sensitivity levels of lead II and V5 ECGs in detecting mild-to-moderate and severe QT interval prolongation exceeded 80%, and their specificity levels exceeded 95%.

CONCLUSION

This study revealed a high prevalence of QT interval prolongation in older patients with TB who receive fluoroquinolones, particularly those with multiple cardiovascular risk factors. Sparsely intermittent ECG monitoring, the prevailing strategy in active drug safety monitoring programs, is inadequate owing to multifactorial and circadian QT interval variability. Additional studies performing serial ECG monitoring are warranted to enhance the understanding of dynamic QT interval changes in patients receiving QT-prolonging anti-TB agents.

Targeting polyketide synthase 13 for the treatment of tuberculosis

Tuberculosis (TB) is one of the most threatening diseases for humans, however, the drug treatment strategy for TB has been stagnant and inadequate, which could not meet current treatment needs. TB is caused by Mycobacterial tuberculosis, which has a unique cell wall that plays a crucial role in its growth, virulence, and drug resistance. Polyketide synthase 13 (Pks13) is an essential enzyme that catalyzes the biosynthesis of the cell wall and its critical role is only found in Mycobacteria. Therefore, Pks13 is a promising target for developing novel anti-TB drugs. In this review, we first introduced the mechanism of targeting Pks13 for TB treatment. Subsequently, we focused on summarizing the recent advance of Pks13 inhibitors, including the challenges encountered during their discovery and the rational design strategies employed to overcome these obstacles, which could be helpful for the development of novel Pks13 inhibitors in the future.

QT Interval Prolongation with One or More QT-Prolonging Agents Used as Part of a Multidrug Regimen for Rifampicin-Resistant Tuberculosis Treatment: Findings from Two Pediatric Studies

Rifampicin-resistant tuberculosis (RR-TB) involves treatment with many drugs that can prolong the QT interval; this risk may increase when multiple QT-prolonging drugs are used together. We assessed QT interval prolongation in children with RR-TB receiving one or more QT-prolonging drugs. Data were obtained from two prospective observational studies in Cape Town, South Africa. Electrocardiograms were performed before and after drug administration of clofazimine (CFZ), levofloxacin (LFX), moxifloxacin (MFX), bedaquiline (BDQ), and delamanid. The change in Fridericia-corrected QT (QTcF) was modeled. Drug and other covariate effects were quantified. A total of 88 children with a median (2.5th-to-97.5th range) age of 3.9 (0.5 to 15.7) years were included, of whom 55 (62.5%) were under 5 years of age. A QTcF interval of >450 ms was observed in 7 patient-visits: regimens were CFZ+MFX (n = 3), CFZ+BDQ+LFX (n = 2), CFZ alone (n = 1), and MFX alone (n = 1). There were no events with a QTcF interval of >500 ms. In a multivariate analysis, CFZ+MFX was associated with a 13.0-ms increase in change in QTcF (P < 0.001) and in maximum QTcF (P = 0.0166) compared to those when other MFX- or LFX-based regimens were used. In conclusion, we found a low risk of QTcF interval prolongation in children with RR-TB who received at least one QT-prolonging drug. Greater increases in maximum QTcF and ΔQTcF were observed when MFX and CFZ were used together. Future studies characterizing exposure-QTcF responses in children will be helpful to ensure safety with higher doses if required for effective treatment of RR-TB.

Development and Validation of a Nomogram for Prediction of QT Interval Prolongation in Patients Administered Bedaquiline-Containing Regimens in China: a Modeling Study

Corrected QT duration (QTc) interval prolongation is the most frequent adverse event associated with bedaquiline (BDQ) use. It may affect the safety of antituberculosis therapy, which leads to the consequent demands of needing to monitor during therapy. Our objective was to establish and validate a prediction model for estimating the risk of QTc prolongation after initiation of BDQ-containing regimens to multidrug-resistant tuberculosis (MDR-TB) patients. We constructed an individualized nomogram model based on baseline demographic and clinical characteristics of each patient within a Chinese cohort during BDQ treatment. The generalizability of this model was further validated through use of externally acquired data obtained from Beijing Chest Hospital from 2019 to 2020. Overall, 1,215 and 165 patients were included in training and external validation cohorts, respectively, whereby during anti-TB drug treatment, QTc prolongation was observed in 273 (22.5%) and 29 (17.6%) patients within these respective cohorts, for whom QTc values were >500 ms in 86 (31.5%) and 10 (34.7%) patients, respectively. Next, a total of four Cox proportional hazards models were created and assessed; then, nomograms derived from the models were plotted based on independent predictors of clofazimine, baseline QTc interval, creatinine, extensive drug-resistance (XDR), moxifloxacin, levofloxacin, and sex. Nomogram analysis revealed concordance index values of 0.723 (95% confidence interval [CI], 0.695 to 0.750) for the training cohort and 0.710 (95% CI, 0.627 to 0.821) for the external validation cohort, thus indicating relatively fair agreement between predicted and observed probabilities of QTc prolongation occurrence based on data obtained during 8-week, 16-week, and 24-week anti-TB treatment of both cohorts. Taken together, results obtained using these models demonstrated that coadministration of clofazimine and abnormal baseline QTc interval significantly contributed to QTc prolongation development during MDR-TB patient treatment with a BDQ-containing anti-TB treatment regimen.

Moxifloxacin Concentration Correlate with QTc Interval in Rifampicin-Resistant Tuberculosis Patients on Shorter Treatment Regimens

Background

Drug-resistant tuberculosis (DR-TB) continues to be a global threat. Moxifloxacin is one of the components of the shorter treatment regimen which is suspected to increase the risk of QT prolongation, although it is also likely to be the most effective against DR-TB. A study to evaluate the correlation between the concentration of moxifloxacin and QTc interval in RR-TB patients who received shorter regimens is needed.

Methods

This was an observational study in 2 groups of RR-TB patients on shorter treatment regimens (intensive phase and continuation phase), contain moxifloxacin with body weight-adjusted dose. Blood samples were collected at 2 h after taking the 48th-hour dose and 1 h before taking the 72nd-hour dose.

Results

Forty-five RR-TB patients were included in this study. At 2 h after taking the 48th-hour dose, the mean of QTc interval in intensive phase and continuation phase was 444.38 ms vs. 467.94 ms, p = 0.026, while mean of moxifloxacin concentration in intensive phase and continuation phase was 4.3 µg/mL vs. 4.61 µg/mL, p = 0.686). At 1 h before taking the 72nd-hour dose, both moxifloxacin concentration and QTc interval in intensive phase and continuation showed no significant difference with p-value of 0.610 and 0.325, respectively. At 2 h after taking the 48th-dose, moxifloxacin concentration did not correlate with QTc interval, both in intensive phase (p = 0.576) and in continuation phase (p = 0.691). At 1 h before taking the 72nd-hour dose, moxifloxacin concentration also did not correlate with QTc interval in intensive phase (p = 0.531) and continuation phase (p = 0.209).

Conclusions

Our study found that moxifloxacin concentration did not correlate with QTc interval, which indicates the safe use of moxifloxacin on QTc interval. In addition to close monitoring of QTc interval, the clinicians should also consider other variables which potentially increase risk for QTc prolongation in DR-TB patients who received shorter treatment regimens.

Safety of Treatment Regimens Containing Bedaquiline and Delamanid in the endTB Cohort

BACKGROUND

Safety of treatment for multidrug-resistant tuberculosis (MDR/RR-TB) can be an obstacle to treatment completion. Evaluate safety of longer MDR/RR-TB regimens containing bedaquiline and/or delamanid.

METHODS

Multicentre (16 countries), prospective, observational study reporting incidence and frequency of clinically relevant adverse events of special interest (AESIs) among patients who received MDR/RR-TB treatment containing bedaquiline and/or delamanid. The AESIs were defined a priori as important events caused by bedaquiline, delamanid, linezolid, injectables, and other commonly used drugs. Occurrence of these events was also reported by exposure to the likely causative agent.

RESULTS

Among 2296 patients, the most common clinically relevant AESIs were peripheral neuropathy (26.4%), electrolyte depletion (26.0%), and hearing loss (13.2%) with an incidence per 1000 person months of treatment, 1000 person-months of treatment 21.5 (95% confidence interval [CI]: 19.8-23.2), 20.7 (95% CI: 19.1-22.4), and 9.7 (95% CI: 8.6-10.8), respectively. QT interval was prolonged in 2.7% or 1.8 (95% CI: 1.4-2.3)/1000 person-months of treatment. Patients receiving injectables (N = 925) and linezolid (N = 1826) were most likely to experience events during exposure. Hearing loss, acute renal failure, or electrolyte depletion occurred in 36.8% or 72.8 (95% CI: 66.0-80.0) times/1000 person-months of injectable drug exposure. Peripheral neuropathy, optic neuritis, and/or myelosuppression occurred in 27.8% or 22.8 (95% CI: 20.9-24.8) times/1000 patient-months of linezolid exposure.

CONCLUSIONS

AEs often related to linezolid and injectable drugs were more common than those frequently attributed to bedaquiline and delamanid. MDR-TB treatment monitoring and drug durations should reflect expected safety profiles of drug combinations.

CLINICAL TRIALS REGISTRATION

NCT02754765.

The role of C-Reactive protein as an inflammatory marker to predict prolonged QTc interval in rifampicin-resistant tuberculosis patients: A case-control study

Background

long-term use of anti-tuberculosis drugs (ATD) increases the risk of QTc prolongation, while C-reactive protein (CRP) can be used as an inflammatory marker of Mycobacterium tuberculosis infection.

Objective: correlation of CRP on the QTc interval in Rifampicin-resistant tuberculosis (RR-TB) patients with the short regimen.

Methods

An observational study was conducted in Rifampicin-resistant tuberculosis (RR-TB) patients from 2 groups, patients on intensive phase and patients on continuation phase. CRP levels were measured from blood samples and measured automatically using the immunoturbidimetric assay. QTc interval was calculated using electrocardiography. Levels of CRP levels and QTc interval between the 2 groups were analyzed. The statistical analysis used includes the independent t-test, Mann Whitney test, and Rank Spearman test with p = 0.05.

Results

Forty-five eligible RR-TB patients were included in this study. CRP levels and QTc intervals between 2 groups (intensive and continuation phase) showed significant difference with p < 0.001 but found no significant correlation of CRP levels and QTc interval in both intensive and continuation phase with p = 0.226 and 0.805, respectively. A higher level of CRP strongly indicated the inflammation caused by RR-TB infection at the early phase of the disease, but not correlated with QTc interval in RR-TB patients.

Conclusion

Levels of CRP and QTc interval do not correlate in RR-TB patients and can not be used to be the marker of QTc prolongation in RR-TB Patients.

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CRP levels are markers used for diagnosis and monitoring in RR-TB patients.

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Decrease CRP levels in RR-TB patients are don't a marker of QTc prolongation.

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The significant between intensive and continuation phase of CRP and QTc interval in RR-TB patients.

Correlation of inflammatory cytokines on corrected QT interval in rifampicin-resistant tuberculosis patients

Background

The cases of Rifampicin-Resistant Tuberculosis (RR-TB) in our country have increased every year and RR-TB deaths are thought to be caused by prolongation of the QTc interval due to side effects of anti-tuberculosis drugs. Thus, cytokines are needed to be used as early markers of prolongation of the QTc interval in RR-TB patients.

Objective

This study aims to analyze the correlation of inflammatory cytokines on QTc interval in RR-TB patients who received shorter regimens.

Methods

This study uses a case-control study with a time series conducted in the period September 2019 to February 2020 in one of the referral hospitals for Tuberculosis in Indonesia. Cytokines levels from blood samples were measured using the ELISA method, while QTc intervals were automatically recorded using an electrocardiography machine. The statistical analysis used was the Chi-square test, Man Whitney test, Independence t-test, and Spearman-rank test with p < 0.05.

Results

There was no significant correlation between inflammatory cytokines and QTc prolongation in intensive phase which TNF-α value (6.8 pg/ml; r = 0.207; p = 0.281), IL-1β (20.13 pg/ml; r = 0.128; p = 0.509), and IL-6 (43.17 pg/ml; r = -0.028; p = 0.886). Meanwhile, in the continuation phase, the values for TNF-α (4.79 pg/ml; r = 0.046; p = 0.865), IL-1β (7.42 pg/ml; r = -0.223; p = 0.406), and IL- 6 (40.61 pg/ml; r = -0.147; p = 0.586).

Conclusion

inflammatory cytokines (TNF-α, IL-1β, and IL-6) cannot be used to identify QTc interval prolongation in RR-TB patients who received shorter regimens.

Prediction of potential drug interactions between repurposed COVID-19 and antitubercular drugs: an integrational approach of drug information software and computational techniques data

Introduction:

Tuberculosis is a major respiratory disease globally with a higher prevalence in Asian and African countries than rest of the world. With a larger population of tuberculosis patients anticipated to be co-infected with COVID-19 infection, an ongoing pandemic, identifying, preventing and managing drug–drug interactions is inevitable for maximizing patient benefits for the current repurposed COVID-19 and antitubercular drugs.

Methods:

We assessed the potential drug–drug interactions between repurposed COVID-19 drugs and antitubercular drugs using the drug interaction checker of IBM Micromedex®. Extensive computational studies were performed at a molecular level to validate and understand the drug–drug interactions found from the Micromedex drug interaction checker database at a molecular level. The integrated knowledge derived from Micromedex and computational data was collated and curated for predicting potential drug–drug interactions between repurposed COVID-19 and antitubercular drugs.

Results:

A total of 91 potential drug–drug interactions along with their severity and level of documentation were identified from Micromedex between repurposed COVID-19 drugs and antitubercular drugs. We identified 47 pharmacodynamic, 42 pharmacokinetic and 2 unknown DDIs. The majority of our molecular modelling results were in line with drug–drug interaction data obtained from the drug information software. QT prolongation was identified as the most common type of pharmacodynamic drug–drug interaction, whereas drug–drug interactions associated with cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp) inhibition and induction were identified as the frequent pharmacokinetic drug–drug interactions. The results suggest antitubercular drugs, particularly rifampin and second-line agents, warrant high alert and monitoring while prescribing with the repurposed COVID-19 drugs.

Conclusion:

Predicting these potential drug–drug interactions, particularly related to CYP3A4, P-gp and the human Ether-à-go-go-Related Gene proteins, could be used in clinical settings for screening and management of drug–drug interactions for delivering safer chemotherapeutic tuberculosis and COVID-19 care. The current study provides an initial propulsion for further well-designed pharmacokinetic-pharmacodynamic-based drug–drug interaction studies.

Plain Language Summary

Design, synthesis, and biological evaluation of benzo[d]imidazole-2-carboxamides as new anti-TB agents

Tuberculosis is the leading cause of death globally among infectious diseases. Due to the development of resistance of Mycobacterium tuberculosis to currently used anti-TB medicines and the TB-HIV synergism the urgent need to develop novel anti-mycobacterial agents has been realized. The drug-to-target path has been the successful strategy for new anti-TB drug development. All the six drug candidates that have shown promise during the clinical trials and some of these being approved for treatment against MDR TB are the results of phenotype screening of small molecule compound libraries. In search of compounds belonging to novel pharmacophoric class that could be subjected to whole cell assay to generate new anti-TB leads the benzo[d]imidazole-2-carboxamide moiety has been designed as a novel anti-TB scaffold. The design was based on the identification of the benzimidazole ring as a prominent substructure of the FDA approved drugs, the structural analysis of reported anti-TB benzimidazoles, and the presence of the C-2 carboxamido functionality in novel bioisoteric anti-TB benzothiazoles. Twenty seven final compounds have been prepared via NH₄Cl-catalyzed amidation of ethyl benzo[d]imidazole-2-carboxylates, as the required intermediates, obtained through a green "all water" one-pot synthetic route following a tandem N-arylation-reduction-cyclocondensation procedure. All of the synthesised target compounds were assessed for anti-TB potential using H₃₇Rv ATCC27294 strain. Thirteen compounds were found with better MIC (0.78-6.25 µg/mL) than the standard drugs and being non-cytotoxic nature (<50% inhibition against RAW 264.7 cell lines at 50 µg/mL). The compound 8e exhibited best anti-TB activity (MIC: 2.15 µM and selectivity index: > 60) and a few others e.g., 8a, 8f, 8k and 8o are the next best anti-TB hits (MIC: 1.56 µg/mL). The determination and analysis of various physiochemical parameters revealed favorable druglike properties of the active compounds. The compounds 8a-l and 8o, with MIC values of ≤ 6.25 μg/mL, have high LipE values (10.66-11.77) that are higher than that of the suggested value of > 6 derived from empirical evidence for quality drug candidates and highlight their therapeutic potential. The highest LipE value of 11.77 of the best active compound 8e with the MIC of 0.78 μg/mL indicates its better absorption and clearance as a probable clinical candidate for anti-TB drug discovery. These findings highlight the discovery of benzimidazole-2-carboxamides for further development as new anti-TB agents.

Challenge to treat pre-extensively drug-resistant tuberculosis in a low-income country: A report of 12 cases

Setting: Democratic Republic of the Congo is a high-burden TB country. Its capital, Kinshasa, reports annually about one-third of all MDR-TB cases in the country; thus, pre-XDRTB management is warranted.

Objectives

To describe the main challenges in treating pre- XDR TB in this low resources setting and possible solutions.

Method

This is a retrospective study of all pre-XDR TB patients diagnosed in Kinshasa in 2018. A personalized regimen was applied according to the clinical profile, drug availability, and the Drug susceptibility testing (DST). Treatment was administered by hospitalization during the intensive phase and in ambulatory care in the continuation phase except in emergencies. Monthly follow up included evaluating clinical and bacteriological features, renal and liver functions, QT interval on ECG, and audiometry for those under aminoglycosides.

Results

Among the 236 MDR-TB patients identified in 2018, 14 had pre-XDR. Two died before treatment initiation. Of the remaining 12. 75% were male, 50% were aged 25-44 years, 66.7% had previous anti-tuberculosis treatment, 75% had a body mass index < 18.5 kg/m², and 1 patient was HIV positive. On radiography, all the patients had cavities. The median time from the diagnosis to treatment initiation was 48.5 days (range: 14-105). A favorable outcome occurred in 10 cases (83.3%), one patient died, and anotherwas lost to follow up. Nine (75%) patients reported adverse reactions, which were mild or moderate in 6 cases and severe in 2 cases. The severe reactions were psychosis (1 case) and ototoxicity (1 case).

Conclusion

Successful pre-XDRTB treatment using the new strategy is possible even in a low-income country. The main challenges are diagnosis access, drug availability and follow-up laboratory facilities. These can be included in a global policy review by the NTP to ensure the sustainability of the strategies implemented.

Update of SEPAR guideline «Diagnosis and Treatment of Drug-Resistant Tuberculosis»

New evidence and knowledge about the clinical management of drug-resistant tuberculosis (TB) in the last 3 years, makes it necessary to update the recent guideline published by SEPAR in 2017, mainly in relation to new diagnostic methods, drug classification, and regimens of treatment recommended to treat patients with isoniazid-resistance TB, rifampicin resistance TB and multidrug-resistant TB. With respect to tuberculosis diagnosis, we recommend the use of rapid molecular assays that also help to detect mutations associated with resistance. In relation to the treatment of multidrug-resistant TB we prioritize effective all-oral shorter treatment regimens including bedaquiline, a fluoroquinolone (levofloxacin or moxifloxacin), bedaquiline and linezolid, instead of the previously recommended short-course treatment with aminoglycosides and other less effective and more toxic drugs. The design of these regimens (initial schedule and changes in the regimen if necessary) should be made in accordance with drug-resistant TB experts; the treatment should be the responsibility of personnel with experience in the treatment of TB and in TB units guaranteeing the follow-up of the treatment and the management of drugs adverse effects.

Early treatment outcome of bedaquiline plus optimised background regimen in drug resistant tuberculosis patients

AIMS

Bedaquiline (BDQ) has been recently approved for drug resistant tuberculosis with active drug safety monitoring under programmatic condition. The present study was conducted to evaluate safety, tolerability and efficacy of bedaquiline plus optimised background regimen.

METHODS

A prospective study was conducted on cohort of pre-extensively drug resistant (XDR) and XDR pulmonary TB patients. Eligible patients were closely monitored for cardiac safety, adverse events (AEs), clinical and microbiological improvement during BDQ (6 months) and post BDQ phase for twelve months.

RESULTS

Of 127 patients enrolled, a significant increase in mean QTc interval was observed on 13th day and 3rd week as compared to baseline (p < 0.0001). Mean maximum increase of QTc was 37.92ms (95% CI, 14.1-61.74ms). Concomitant anti-TB medications, age, gender, low body mass index (BMI) had significant effect on QTc prolongation (p < 0.0001, p < 0.05). However, none of the patient required discontinuation of BDQ. Majority of AEs (86.3%) were non-serious and not preventable 108 (87.1%). The median time for sputum-culture conversion was 40.89 ± 3.5 days (95% CI, 34-48 days) and the treatment outcome was successful in 102 (80.3%) patients with negative sputum culture conversion.

CONCLUSIONS

Bedaquiline containing regimen achieved favourable outcome. Although, bedaquiline along with concomitant anti-TB medications has the potential to prolong QTc interval, the benefit certainly outweighs the risk. This calls for a through pre-treatment cardiovascular and biochemical evaluation as a preventive measure and appropriate selection of patients for safe use of BDQ and successful outcome.

Bedaquiline and Delamanid in Children With XDR Tuberculosis: What is prolonged QTc?

Bedaquiline and delamanid used to treat extensively drug-resistant tuberculosis are known to cause prolonged QTc. Two children with extensively drug-resistant tuberculosis were put on bedaquiline and delamanid and had prolonged QTc on the Bazett formula but normal QTc by the Fridericia formula. Both had no adverse effects. Correct formula for monitoring QTc should be used thereby preventing unnecessary withholding of medicines.

Adolescent tuberculosis

Adolescence is characterised by a substantial increase in the incidence of tuberculosis, a known fact since the early 20th century. Most of the world's adolescents live in low-income and middle-income countries where tuberculosis remains common, and where they comprise a quarter of the population. Despite this, adolescents have not yet been addressed as a distinct population in tuberculosis policy or within tuberculosis treatment services, and emerging evidence suggests that current models of care do not meet their needs. This Review discusses up-to-date information about tuberculosis in adolescence, with a focus on the management of infection and disease, including HIV co-infection and rifampicin-resistant tuberculosis. We outline the progress in vaccine development and highlight important directions for future research.

Artificial intelligence enabled parabolic response surface platform identifies ultra-rapid near-universal TB drug treatment regimens comprising approved drugs

Background

Shorter, more effective treatments for tuberculosis (TB) are urgently needed. While many TB drugs are available, identification of the best regimens is challenging because of the large number of possible drug-dose combinations. We have found consistently that responses of cells or whole animals to drug-dose stimulations fit a parabolic response surface (PRS), allowing us to identify and optimize the best drug combinations by testing only a small fraction of the total search space. Previously, we used PRS methodology to identify three regimens (PRS Regimens I–III) that in murine models are much more effective than the standard regimen used to treat TB. However, PRS Regimens I and II are unsuitable for treating drug-resistant TB and PRS Regimen III includes an experimental drug. Here, we use PRS methodology to identify from an expanded pool of drugs new highly effective near-universal drug regimens comprising only approved drugs.

Methods and findings

We evaluated combinations of 15 different drugs in a human macrophage TB model and identified the most promising 4-drug combinations. We then tested 14 of these combinations in Mycobacterium tuberculosis-infected BALB/c mice and chose for PRS dose optimization and further study the two most potent regimens, designated PRS Regimens IV and V, consisting of clofazimine (CFZ), bedaquiline (BDQ), pyrazinamide (PZA), and either amoxicillin/clavulanate (AC) or delamanid (DLM), respectively. We then evaluated the efficacy in mice of optimized PRS Regimens IV and V, as well as a 3-drug regimen, PRS Regimen VI (CFZ, BDQ, and PZA), and compared their efficacy to PRS Regimen III (CFZ, BDQ, PZA, and SQ109), previously shown to reduce the time to achieve relapse-free cure in mice by 80% compared with the Standard Regimen (isoniazid, rifampicin, PZA, and ethambutol). Efficacy measurements included early bactericidal activity, time to lung sterilization, and time to relapse-free cure. PRS Regimens III–VI all rapidly sterilized the lungs and achieved relapse-free cure in 3 weeks (PRS Regimens III, V, and VI) or 5 weeks (PRS Regimen IV). In contrast, mice treated with the Standard Regimen still had high numbers of bacteria in their lungs after 6-weeks treatment and none achieved relapse-free cure in this time-period.

Conclusions

We have identified three new regimens that rapidly sterilize the lungs of mice and dramatically shorten the time required to achieve relapse-free cure. All mouse drug doses in these regimens extrapolate to doses that are readily achievable in humans. Because PRS Regimens IV and V contain only one first line drug (PZA) and exclude fluoroquinolones and aminoglycosides, they should be effective against most TB cases that are multidrug resistant (MDR-TB) and many that are extensively drug-resistant (XDR-TB). Hence, these regimens have potential to shorten dramatically the time required for treatment of both drug-sensitive and drug-resistant TB. If clinical trials confirm that these regimens dramatically shorten the time required to achieve relapse-free cure in humans, then this radically shortened treatment has the potential to improve treatment compliance, decrease the emergence of drug resistance, and decrease the healthcare burden of treating both drug-sensitive and drug-resistant TB.

Pyridine and nitro-phenyl linked 1,3,4-thiadiazoles as MDR-TB inhibitors

In the present study, a series of substituted 1,3,4-thiadiazole derivatives 4(a-o), 5(a-m) and 6(a-j) were synthesized and characterized by IR, ¹H NMR, ¹³C NMR and mass spectroscopic technique. The synthesized compounds were evaluated for their in vitro anti-mycobacterial activity against the Mycobacterium tuberculosis H37Rv and resistance MDR-TB strain. Among the compounds tested N-(5-(4-nitrophenyl)-1,3,4-thiadiazol-2-yl)furan-2-carboxamide (4h) showed significant inhibitory activity with MIC of 9.87 μM (H37Rv strain) and 9.87 μM (MDR-TB strain) compared to isoniazide [MIC of 3.64 μM (H37Rv) and >200 μM (MDR-TB strain)] and rifampin [MIC of 0.152 μM (H37Rv) and 128 μM (MDR-TB strain)]. In addition, these compounds have also been assessed for their cyto-toxicity to a mammalian Vero cell line using the MTT assay. The result shows that these compounds exhibit anti-tubercular activity at non-cytototoxic concentrations.

Clinical and Cardiac Safety of Long-term Levofloxacin in Children Treated for Multidrug-resistant Tuberculosis

Safety concerns persist for long-term pediatric fluoroquinolone use. Seventy children (median age, 2.1 years) treated with levofloxacin 10-20 mg/kg once daily for multidrug-resistant tuberculosis (median observation time, 11.8 months) had few musculoskeletal events, no levofloxacin-attributed serious adverse events, and no Fridericia-corrected QT interval >450 ms. Long-term levofloxacin was safe and well tolerated.

Challenging the Drug-Likeness Dogma for New Drug Discovery in Tuberculosis

The emergence of multi- and extensively drug resistant tuberculosis worldwide poses a great threat to human health and highlight the need to discover and develop new, effective and inexpensive antituberculosis agents. High-throughput screening assays against well-validated drug targets and structure based drug design have been employed to discover new lead compounds. However, the great majority fail to demonstrate any antimycobacterial activity when tested against Mycobacterium tuberculosis in whole-cell screening assays. This is mainly due to some of the intrinsic properties of the bacilli, such as the extremely low permeability of its cell wall, slow growth, drug resistance, drug tolerance, and persistence. In this sense, understanding the pathways involved in M. tuberculosis drug tolerance, persistence, and pathogenesis, may reveal new approaches for drug development. Moreover, the need for compounds presenting a novel mode of action is of utmost importance due to the emergence of resistance not only to the currently used antituberculosis agents, but also to those in the pipeline. Cheminformatics studies have shown that drugs endowed with antituberculosis activity have the peculiarity of being more lipophilic than many other antibacterials, likely because this leads to improved cell penetration through the extremely waxy mycobacterial cell wall. Moreover, the interaction of the lipophilic moiety with the membrane alters its stability and functional integrity due to the disruption of the proton motive force, resulting in cell death. When a ligand-based medicinal chemistry campaign is ongoing, it is always difficult to predict whether a chemical modification or a functional group would be suitable for improving the activity. Nevertheless, in the “instruction manual” of medicinal chemists, certain functional groups or certain physicochemical characteristics (i.e., high lipophilicity) are considered red flags to look out for in order to safeguard drug-likeness and avoid attritions in the drug discovery process. In this review, we describe how antituberculosis compounds challenge established rules such as the Lipinski's “rule of five” and how medicinal chemistry for antituberculosis compounds must be thought beyond such dogmatic schemes.

Benzo[d]thiazole-2-carbanilides as new anti-TB chemotypes: Design, synthesis, biological evaluation, and structure-activity relationship

Tuberculosis is the second leading cause of deaths worldwide. The inadequacy of existing drugs to treat TB due to developed resistance and TB-HIV synergism urges for new anti-TB drugs. Seventy-two benzo[d]thiazole-2-carbanilides have been synthesized through CDI-mediated direct coupling of benzo[d]thiazole-2-carboxylic acids with aromatic amines using a three step methodology which includes a green protocol for synthesis of ethyl benzo[d]thiazole-2-carboxylates, precursor of the desired carboxylic acids. The compounds were evaluated in vitro for anti-tubercular activity against M. tuberculosis H₃₇Rv (ATCC27294 strain). Thirty-two compounds exhibiting MIC values in the range of 0.78-6.25 μg/mL (1.9-23 μM) were subjected to cell viability test against RAW 264.7 cell lines and thirty compounds were found to be non-toxic (<50% inhibition). The most active compounds with MIC of 0.78 μg/mL (e.g., 4i, 4n, 4s, 4w, 6f, 6h, 6u, 7e, 7h, 7p, 7r and 7w) exhibit therapeutic index of 64. The structure activity relationship of the N-arylbenzo[d]thiazole-2-carboxamides has been established for anti-mycobacterial activity. Molecular docking suggests that the compounds 7w, 4i and 4n bind to the catalytic site of the enzyme ATP Phosphoribosyltransferase (HisG) and might be attributed to their anti-TB potential. These can serve as a new starting point for the development of anti-TB agents with therapeutic potential.

Elevated Plasma Moxifloxacin Concentrations and SLCO1B1 g.-11187G>A Polymorphism in Adults with Pulmonary Tuberculosis

Moxifloxacin exhibits concentration-dependent prolongation of human QTc intervals and bactericidal activity against Mycobacterium tuberculosis However, moxifloxacin plasma concentrations are variable between patients. We evaluated whether human gene polymorphisms affect moxifloxacin plasma concentrations in tuberculosis patients from two geographic regions. We enrolled a convenience sample of 49 adults with drug-sensitive pulmonary tuberculosis from Africa and the United States enrolled in two treatment trials of moxifloxacin as part of multidrug therapy. Pharmacokinetic parameters were evaluated by noncompartmental techniques. Human single-nucleotide polymorphisms of transporter genes were evaluated by analysis of covariance (ANCOVA) on moxifloxacin exposure and the peak (maximum) concentration (Cmax). The moxifloxacin area under the concentration-time curve from 0 to 24 h (AUC0-24) and Cmax were significantly increased by the drug milligram-per-kilogram dosage and the genotype of variant g.-11187G>A in the SLCO1B1 gene (rs4149015) but not by geographic region. The median moxifloxacin AUC0-24 was 46% higher and the median Cmax was 30% higher in 4 (8%) participants who had the SLCO1B1 g.-11187 AG genotype than in 45 participants who had the wild-type GG genotype (median AUC0-24 from the model, 34.4 versus 23.6 μg · h/ml [P = 0.005, ANCOVA]; median Cmax from the model, 3.5 versus 2.7 μg/ml [P = 0.009, ANCOVA]). Because moxifloxacin exhibits concentration-dependent prolongation of human QTc intervals and prolonged QTc intervals are associated with cardiac arrhythmia, further study is needed to evaluate the risk associated with the SLCO1B1 g.-11187G>A variant. (This study has been registered at ClinicalTrials.gov under identifier NCT00164463.).

Substituted N-Phenyl-5-(2-(phenylamino)thiazol-4-yl)isoxazole-3-carboxamides Are Valuable Antitubercular Candidates that Evade Innate Efflux Machinery

Tuberculosis remains one of the deadliest infectious diseases in the world, and the increased number of multidrug-resistant and extremely drug-resistant strains is a significant reason for concern. This makes the discovery of novel antitubercular agents a cogent priority. We have previously addressed this need by reporting a series of substituted 2-aminothiazoles capable to inhibit the growth of actively replicating, nonreplicating persistent, and resistant Mycobacterium tuberculosis strains. Clues from the structure-activity relationships lining up the antitubercular activity were exploited for the rational design of improved analogues. Two compounds, namely N-phenyl-5-(2-(p-tolylamino)thiazol-4-yl)isoxazole-3-carboxamide 7a and N-(pyridin-2-yl)-5-(2-(p-tolylamino)thiazol-4-yl)isoxazole-3-carboxamide 8a, were found to show high inhibitory activity toward susceptible M. tuberculosis strains, with an MIC₉₀ of 0.125-0.25 μg/mL (0.33-0.66 μM) and 0.06-0.125 μg/mL (0.16-0.32 μM), respectively. Moreover, they maintained good activity also toward resistant strains, and they were selective over other bacterial species and eukaryotic cells, metabolically stable, and apparently not susceptible to the action of efflux pumps.

New and Repurposed Drugs for Pediatric Multidrug-Resistant Tuberculosis. Practice-based Recommendations

It is estimated that 33,000 children develop multidrug-resistant tuberculosis (MDR-TB) each year. In spite of these numbers, children and adolescents have limited access to the new and repurposed MDR-TB drugs. There is also little clinical guidance for the use of these drugs and for the shorter MDR-TB regimen in the pediatric population. This is despite the fact that these drugs and regimens are associated with improved interim outcomes and acceptable safety profiles in adults. This review fills a gap in the pediatric MDR-TB literature by providing practice-based recommendations for the use of the new (delamanid and bedaquiline) and repurposed (linezolid and clofazimine) MDR-TB drugs and the new shorter MDR-TB regimen in children and adolescents.

The importance of clinical pharmacokinetic-pharmacodynamic studies in unraveling the determinants of early and late tuberculosis outcomes

Tuberculosis remains a major infectious cause of morbidity and mortality worldwide. Current antibiotic regimens, constructed prior to the development of modern pharmacokinetic-pharmacodynamic (PK–PD) tools, are based on incomplete understanding of exposure–response relationships in drug susceptible and multidrug resistant tuberculosis. Preclinical and population PK data suggest that clinical PK–PD studies may enable therapeutic drug monitoring for some agents and revised dosing for others. Future clinical PK–PD challenges include: incorporation of PK methods to assay free concentrations for all active metabolites; selection of appropriate early outcome measures which reflect therapeutic response; elucidation of genetic contributors to interindividual PK variability; conduct of targeted studies on special populations (including children); and measurement of PK–PD parameters at the site of disease.

The paradigm shift to end tuberculosis. Are we ready to assume the changes?

INTRODUCTION

Tuberculosis (TB) is the number one infectious disease killer and exemplifies the most neglected of them. Drug-susceptible TB presents with high mortality especially in atypical forms, disproportionally affecting immunosuppressed and vulnerable populations. The drug-resistant TB (DR-TB) epidemic, a world crisis, is sustained and increased through person-to-person transmission in households and the community. TB diagnostics and treatment in recent years are highly evolving fields. New rapid molecular tests are changing the perspectives in diagnosis and resistance screening. Also, new drugs and shorter regimens for DR-TB are appearing. For the first time in recent history, a large number of randomized control trials are incoming. Areas covered: This article reviews most TB advances including new diagnostic tests, drugs, and regimens and outlines upcoming drug trials while disclosing the potential gaps the in development of patient-centered systems and current organizational challenges leading to a delay in the uptake of these innovations. Expert commentary: Innovations are occurring, but not many are implemented on a wide scale in developing countries. TB health systems and staff are not getting updated in parallel. More efforts and funds are needed not only to implement current novelties but also to research for future solutions to eliminate TB.

Management of multidrug-resistant TB: novel treatments and their expansion to low resource settings

Despite overall progress in global TB control, the rising burden of multidrug-resistant TB (MDR-TB) threatens to undermine efforts to end the worldwide epidemic. Of the 27 countries classified as high burden for MDR-TB, 17 are in ‘low’ or ‘low–middle’ income countries. Shorter, all oral and less toxic multidrug combinations are required to improve treatment outcomes in these settings. Suitability for safe co-administration with HIV drugs is also desirable. A range of strategies and several new drugs (including bedaquiline, delamanid and linezolid) are currently undergoing advanced clinical evaluations to define their roles in achieving these aims. However, several clinical questions and logistical challenges need to be overcome before these new MDR-TB treatments fulfil their potential.