Global estimates and determinants of antituberculosis drug pharmacokinetics in children and adolescents: a systematic review and individual patient data meta-analysis.

BACKGROUND: Suboptimal exposure to antituberculosis (anti-TB) drugs has been associated with unfavourable treatment outcomes. We aimed to investigate estimates and determinants of first-line anti-TB drug pharmacokinetics in children and adolescents at a global level. METHODS: We systematically searched MEDLINE, Embase and Web of Science (1990-2021) for pharmacokinetic studies of first-line anti-TB drugs in children and adolescents. Individual patient data were obtained from authors of eligible studies. Summary estimates of total/extrapolated area under the plasma concentration-time curve from 0 to 24 h post-dose (AUC0-24) and peak plasma concentration (C max) were assessed with random-effects models, normalised with current World Health Organization-recommended paediatric doses. Determinants of AUC0-24 and C max were assessed with linear mixed-effects models. RESULTS: Of 55 eligible studies, individual patient data were available for 39 (71%), including 1628 participants from 12 countries. Geometric means of steady-state AUC0-24 were summarised for isoniazid (18.7 (95% CI 15.5-22.6) h·mg·L-1), rifampicin (34.4 (95% CI 29.4-40.3) h·mg·L-1), pyrazinamide (375.0 (95% CI 339.9-413.7) h·mg·L-1) and ethambutol (8.0 (95% CI 6.4-10.0) h·mg·L-1). Our multivariate models indicated that younger age (especially <2 years) and HIV-positive status were associated with lower AUC0-24 for all first-line anti-TB drugs, while severe malnutrition was associated with lower AUC0-24 for isoniazid and pyrazinamide. N-acetyltransferase 2 rapid acetylators had lower isoniazid AUC0-24 and slow acetylators had higher isoniazid AUC0-24 than intermediate acetylators. Determinants of C max were generally similar to those for AUC0-24. CONCLUSIONS: This study provides the most comprehensive estimates of plasma exposures to first-line anti-TB drugs in children and adolescents. Key determinants of drug exposures were identified. These may be relevant for population-specific dose adjustment or individualised therapeutic drug monitoring.

Pharmacokinetics and Dose Optimization Strategies of Para-Aminosalicylic Acid in Children with Rifampicin-Resistant Tuberculosis.

Treatment options for children with Rifampicin-resistant tuberculosis (RR-TB) remain limited, and para-aminosalicylic acid (PAS) is still a relevant component of treatment regimens. Prevention of resistance to companion drugs by PAS is dose related, and at higher concentrations, PAS may exhibit significant bactericidal activity in addition to its bacteriostatic properties. The optimal dosing of PAS in children is uncertain, specifically for delayed-release granule preparations, which are the most used. A population pharmacokinetic model was developed describing PAS pharmacokinetics in children receiving routine RR-TB treatment. Model-based simulations evaluated current World Health Organization (WHO) weight-band doses against the adult pharmacokinetic target of 50 to 100 mg/liter for peak concentrations. Of 27 children included, the median (range) age and weight were 3.87 (0.58 to 13.7) years and 13.3 (7.15 to 30.5) kg, respectively; 4 (14.8%) were HIV positive. PAS followed one-compartment kinetics with first-order elimination and transit compartment absorption. The typical clearance in a 13-kg child was 9.79 liters/h. Increased PAS clearance was observed in both pharmacokinetic profiles from the only patient receiving efavirenz. No effect of renal function, sex, ethnicity, nutritional status, HIV status, antiretrovirals (lamivudine, abacavir, and lopinavir-ritonavir), or RR-TB drugs was detected. In simulations, target concentrations were achieved only using the higher WHO dose range of 300 mg/kg once daily. A transit compartment adequately describes absorption for the slow-release PAS formulation. Children should be dosed at the higher range of current WHO-recommended PAS doses and in a once-daily dose to optimize treatment.

Tuberculous Meningitis in Children: A Forgotten Public Health Emergency.

Tuberculous meningitis (TBM) remains a major cause of morbidity and mortality in children with tuberculosis (TB), yet there are currently no estimates of the global burden of pediatric TBM. Due to frequent non-specific clinical presentation and limited and inadequate diagnostic tests, children with TBM are often diagnosed late or die undiagnosed. Even when diagnosed and treated, 20% of children with TBM die. Of survivors, the majority have substantial neurological disability with significant negative impact on children and their families. Surveillance data on this devastating form of TB can help to quantify the contribution of TBM to the overall burden, morbidity and mortality of TB in children and the epidemiology of TB more broadly. Pediatric TBM usually occurs shortly after primary infection with Mycobacterium tuberculosis and reflects ongoing TB transmission to children. In this article we explain the public health importance of pediatric TBM, discuss the epidemiology within the context of overall TB control and health system functioning and the limitations of current surveillance strategies. We provide a clear rationale for the benefit of improved surveillance of pediatric TBM using a TB care cascade framework to support monitoring and evaluation of pediatric TB, and TB control more broadly. Considering the public health implications of a diagnosis of TBM in children, we provide recommendations to strengthen pediatric TBM surveillance and outline how improved surveillance can help us identify opportunities for prevention, earlier diagnosis and improved care to minimize the impact of TBM on children globally.

100 years of Mycobacterium bovis bacille Calmette-Guérin.

Mycobacterium bovis bacille Calmette-Guérin (BCG), an experimental vaccine designed to protect cattle from bovine tuberculosis, was administered for the first time to a newborn baby in Paris in 1921. Over the past century, BCG has saved tens of millions of lives and has been given to more humans than any other vaccine. It remains the sole tuberculosis vaccine licensed for use in humans. BCG provides long-lasting strong protection against miliary and meningeal tuberculosis in children, but it is less effective for the prevention of pulmonary tuberculosis, especially in adults. Evidence mainly from the past two decades suggests that BCG has non-specific benefits against non-tuberculous infections in newborn babies and in older adults, and offers immunotherapeutic benefit in certain malignancies such as non-muscle invasive bladder cancer. However, as a live attenuated vaccine, BCG can cause localised or disseminated infections in immunocompromised hosts, which can also occur following intravesical installation of BCG for the treatment of bladder cancer. The legacy of BCG includes fundamental discoveries about tuberculosis-specific and non-specific immunity and the demonstration that tuberculosis is a vaccine-preventable disease, providing a foundation for new vaccines to hasten tuberculosis elimination.

Anton Ghon and His Colleagues and Their Studies of the Primary Focus and Complex of Tuberculosis Infection and Their Relevance for the Twenty-First Century.

Anton Ghon is well known in the field of childhood tuberculosis, and the tuberculosis primary focus and complex are frequently called the Ghon focus and complex; this is largely the result of the wide publication of the English translation of his monograph "Der primäre Lungenherd bei der Tuberkulose der Kinder." Ghon's studies are frequently quoted, but precise details of his monograph are neglected, his results often misquoted, and his later publications virtually unknown. This review highlights aspects of Ghon's anatomical pathology studies in children and adults not necessarily dying of tuberculosis but with signs of tuberculosis infection. Ghon found a single primary tuberculosis focus in approximately 80% of tuberculosis-infected children situated close to the pleura in two-thirds of cases. Cavitation of the focus was common, and lymphatic spread involved lymph nodes in the abdomen and neck in many children. Studies amongst adults and children frequently found the healed primary tuberculosis focus to be completely calcified without histological signs of tuberculosis activity; however, particularly in the presence of pulmonary tuberculosis, histological signs of tuberculosis activity were often found in the lymph nodes of the angulus venosus, despite apparent healing with extensive calcification. Both earlier studies and more recent investigations, with molecular biological tools, unavailable to Ghon and earlier researchers, have confirmed the presence of viable mycobacteria in apparently normal or healed thoracic nodes and also found molecular biological indications of viable mycobacteria in these nodes. As suggested by Ghon, lympho-haematogenous spread of tuberculosis may be more common than is usually appreciated.

Positive Mycobacterium tuberculosis Gastric Lavage Cultures from Asymptomatic Children With Normal Chest Radiography.

Mycobacterium tuberculosis culture from gastric lavage from apparently healthy children following tuberculin skin test conversion, despite normal chest radiography (CR), is well known but is a contentious subject. A consensus statement regarding classification of childhood tuberculosis excluded this condition, stating that more data were needed. To assist in this discussion, we reviewed early publications that reported the occurrence of this phenomenon and early anatomical pathology studies that described changes that occur in children following tuberculosis infection. Pathology studies describe frequent cavitation in primary foci in children from whom positive M. tuberculosis cultures might easily arise. These foci were very small in some children who might have normal CR. Positive cultures might also arise from ulcerated mediastinal lymph nodes that are invisible on CR. Young children with recent infection very likely have active primary pulmonary tuberculosis.

Probability of mycobactericidal activity of para-aminosalicylic acid with novel dosing regimens.

PURPOSE: Para-aminosalicylic acid (PAS) is currently one of the add-on group C medicines recommended by the World Health Organization for multidrug-resistant tuberculosis treatment. At the recommended doses (8-12 g per day in two to three divided doses) of the widely available slow-release PAS formulation, studies suggest PAS exposures are lower than those reached with older PAS salt formulations and do not generate bactericidal activity. Understanding the PASER dose-exposure-response relationship is crucial for dose optimization. The objective of our study was to establish a representative population pharmacokinetics model for PASER and evaluate the probability of bactericidal and bacteriostatic target attainment with different dosing regimens. METHODS: To this end, we validated and optimized a previously published population pharmacokinetic model on an extended dataset. The probability of target attainment was evaluated for once-daily doses of 12 g, 14 g, 16 g and 20 g PASER. RESULTS: The final optimized model included the addition of variability in bioavailability and allometric scaling with body weight on disposition parameters. Peak PAS concentrations over minimum inhibitory concentration of 100, which is required for bactericidal activity are achieved in 53%, 65%, 72% and 84% of patients administered 12, 14, 16 and 20 g once-daily PASER, respectively, when MIC is 1 mg/L. For the typical individual, the exposure remained above 1 mg/L for ≥ 98% of the dosing interval in all the evaluated PASER regimens. CONCLUSION: The pharmacokinetic/pharmacodynamic parameters linked to bactericidal activity should be determined for 14 g, 16 g and 20 g once-daily doses of PASER.

The pharmacokinetics of para-aminosalicylic acid and its relationship to efficacy and intolerance.

Following its introduction as an antituberculosis agent close to 75 years ago, the use of para-aminosalicylic acid (PAS) has been limited by gastrointestinal intolerance and multiple formulations were produced in attempts to reduce its occurrence. More recently, an enteric-coated, granular, slow-release PAS formulation (PASER) was introduced and is now in wide-spread use for the treatment of drug-resistant tuberculosis. The current PASER dosing regimen is based on recommendations derived from older studies using a variety of different PAS formulations and relegate PAS to a role as an exclusively bacteriostatic agent. However, there is ample evidence that if sufficiently high serum concentrations are reached, PAS can be bactericidal and that intolerance following once daily dosing, that aids the achievement of such concentrations, is no worse than that following intermittent daily dosing. In particular, prevention of resistance to companion drugs appears to be dependent on the size of the single dose, and hence the peak concentrations, and not on maintaining serum levels consistently above minimum inhibitory concentration. We present a narrative review of the development of PAS formulations, dosing practices, and published data regarding pharmacokinetics and pharmacodynamics and the relationship of PAS dosage to intolerance and efficacy. Our conclusions suggests that we are at present not using PAS to its maximum ability to contribute to regimen efficacy and protect companion drugs.

Pharmacokinetics of Para-Aminosalicylic Acid and Its 2 Major Metabolites: A Potential Relationship to the Development of Gastrointestinal Intolerance.

Para-aminosalicylic acid (PAS), often the last drug remaining for treatment of drug-resistant tuberculosis, is notorious for causing gastrointestinal intolerance; however, the cause of PAS intolerance is uncertain. The objective of this study was to assess relationships between peak concentrations of PAS administered as a granular slow-release enteric coated formulation, and its metabolites acetyl-PAS and glycine-PAS, and intolerance. PAS and its metabolites were measured in 29 adult patients with drug-resistant tuberculosis at Brooklyn Hospital, Cape Town, randomized to receive granular slow-release enteric-coated PAS 4 g twice daily or 8 g once daily for 1 week, followed by the alternative regimen. Concentrations of PAS and its metabolites were determined by liquid chromatography and tandem mass spectrometry, and a visual analogue scale evaluated intolerance. Spearman's correlation test assessed the relationship between maximum plasma concentrations (Cmax ) and intolerance scores. A large interindividual variability was observed for the PAS Cmax (40.42-68.55 mg/L) following 4 g twice daily; (62.69-102.41 mg/L) for 8 g once daily and a similar wide Cmax range found for the metabolites acetyl-PAS and glycine-PAS. Twenty-six patients reported at least 1 intolerance episode, but most visual analogue scale scores clustered around 0. Significant inverse associations were found between acetyl-PAS Cmax and bloating (rho = -0.448; P = .025) and diarrhea (rho = -0.407; P = .044) for the twice-daily regimen and a similar inverse association found for glycine-PAS and diarrhea (rho = -0.412; P = .041). Plasma concentrations of the metabolites did not correlate with the occurrence of gastrointestinal symptoms, but higher metabolite concentrations correlated with lower intolerance scores; slow metabolism of PAS and its continued presence in the intestinal tract may be the main cause of intolerance.

Evolution of rifampicin treatment for tuberculosis.

Rifampicin was discovered in 1965 and remains one of the most important drugs in tuberculosis treatment that is valued for its sterilizing activity and ability to shorten treatment. Antimicrobial activity of rifampicin was initially proved in vitro; subsequently numerous in vivo studies showed the bactericidal properties and dose-dependent effect of rifampicin. Rifampicin was first during the late 1960s to treat patients suffering from chronic drug-resistant pulmonary TB. Decades later, rifampicin continues to be studied with particular emphasis on whether higher doses could shorten the duration of treatment without increasing relapse or having adverse effects. Lesion-specific drug penetration and pharmacokinetics of rifampicin are improving our understanding of effective concentration while potentially refining drug regimen designs. Another prospective aspect of high-dose rifampicin is its potential use in treating discrepant mutation thereby eliminating the need for MDR treatment. To date, several clinical trials have shown the safety, efficacy, and tolerability of high-dose rifampicin. Currently, high-dose rifampicin has been used successfully in a routine clinical setting for the treatment of high-risk patients. However, the WHO and other relevant policy makers have not committed to implementing a controlled rollout thereof. This review describes the course that rifampicin has travelled to the present-day exploration of high-dose rifampicin treatment.

Revisiting the mutant prevention concentration to guide dosing in childhood tuberculosis.

The mutant prevention concentration (MPC) is a well-known concept in the chemotherapy of many bacterial infections, but is seldom considered in relation to tuberculosis (TB) treatment, as the required concentrations are generally viewed as unachievable without undue toxicity. Early studies revealed single mutations conferring high MICs of first- and second-line anti-TB agents; however, the growing application of genomics and quantitative drug susceptibility testing in TB suggests a wide range of MICs often determined by specific mutations and strain type. In paediatric TB, pharmacokinetic studies indicate that despite increasing dose recommendations, a proportion of children still do not achieve adult-derived targets. When considering the next stage in anti-TB drug dosing and the introduction of novel therapies for children, we suggest consideration of MPC and its incorporation into pharmacokinetic studies to more accurately determine appropriate concentration targets in children, to restrict the growth of resistant mutants and better manage drug-resistant TB.

Time Trends in Sputum Mycobacterial Load and Two-Day Bactericidal Activity of Isoniazid-Containing Antituberculosis Therapies.

Recent early bactericidal activity (EBA) studies of isoniazid-based antituberculosis therapies have shown a lower EBA over the first two treatment days than in earlier years. To quantify this trend and evaluate factors contributing to it, we extracted individual data from 18 studies with a total of 182 participants using isoniazid-containing therapies between 1992 and 2015 at a single site and laboratory in Cape Town, South Africa. We recalculated EBA as the daily fall in CFU per milliliter sputum up to day 2 of therapy (EBA0-2) for individual patients and treatment groups and used mixed-effects linear models to investigate the correlation between pretreatment CFU, EBA0-2, and year of study. We found that mean pretreatment CFU and year of study accounted for 46% and 47%, respectively, of the variation in mean EBA0-2 Mean pretreatment CFU differed between the periods 1992 to 2001 and 2007 to 2015 by 0.92 log10 CFU (95% confidence interval [CI], 0.57 to 1.28; P < 0.0001). On average, pretreatment CFU dropped by 0.053 log10 CFU (95% CI, 0.029 to 0.076; P = 0.0004) and EBA0-2 by 0.012 log10 CFU (95% CI, 0.006 to 0.018; P = 0.001) per year. The EBA0-2 of isoniazid-based antituberculosis therapy is strongly correlated with baseline mycobacterial load and shows a declining trend over the past 2 decades.

Successful Treatment of a Child With Extensively Drug-Resistant Tuberculous Meningitis.

Unlike in pulmonary multidrug-resistant (MDR) tuberculosis, the clinical outcome of MDR tuberculous meningitis (TBM) in children, including extensively drug-resistant tuberculosis, is poor and management is challenging. We report the successful treatment of a case of extensively drug-resistant TBM in a 4-year-old girl, and we discuss implications for tuberculosis diagnosis and chemotherapy.

Para-aminosalicylic acid: the return of an old friend.

Para-aminosalicylic acid (PAS) is one of the last remaining drugs available to treat extensively drug-resistant (XDR) tuberculosis. Good outcomes (81% 5 year survival) were documented when PAS was first used with streptomycin, yet results of PAS with remaining potentially effective drugs for the treatment of XDR tuberculosis are poor (mortality 30-90%). In this Review, we assess published work regarding recommendations for PAS dosing in relation to efficacy and tolerance. PAS 20 g daily acoompanied only by streptomycin is better in prevention of streptomycin resistance than PAS 10 g or 5 g daily. When accompanied by isonazid, a more potent drug than streptomycin, treatment success with PAS 20 g daily is similar to that of PAS 10 g daily. In contemporary, relatively weak XDR tuberculosis regimens, the recommended doseage of PAS 8-12 g in two to three doses daily is probably insufficient. Furthermore, once daily PAS could be considered, because substantial research suggests no worse intolerance than with multiple daily PAS doses. In most countries, PAS is now available in a granular, slow-release formulation that seems well tolerated, but efficacy has never been formally assessed. Once daily dosing with granular PAS might achieve high peak concentrations and a long interval above minimum inhibitory concentration, with the advantage of improved supervision of drug intake.

Simultaneous staining of sputum smears for acid-fast and lipid-containing Myobacterium tuberculosis can enhance the clinical evaluation of antituberculosis treatments.

Dormant, slow-growing, antibiotic-tolerant Mycobacterium tuberculosis undermine the shortening of tuberculosis treatment to less than 6 months and are thought to be characterised by intracellular lipid bodies. Antibiotic effects on such persisting bacilli escape evaluation as they cannot be readily cultured. We identified cells containing lipid bodies in sputum smears from 86 newly diagnosed pulmonary tuberculosis patients and monitored these cells daily in 42 patients over the first 14 days of treatment with rifampicin, the experimental compound SQ-109, or both agents combined. Counts of Nile-Red-positive lipid-body containing cells were correlated with those of Auramine-O-positive cells and colony forming units of viable Mycobacterium tuberculosis on agar plates. Rifampicin but not SQ-109 significantly reduced colony forming units but all treatments distinctively and significantly changed the proportions of lipid body-containing bacilli and viable Mycobacterium tuberculosis. Monitoring lipid-body containing bacilli in sputum during treatment with experimental antituberculosis regimens may identify putative treatment-shortening regimens.

N-acetyltransferase genotypes and the pharmacokinetics and tolerability of para-aminosalicylic acid in patients with drug-resistant pulmonary tuberculosis.

The aim of this study was to examine the relationships between N-acetyltransferase genotypes, pharmacokinetics, and tolerability of granular slow-release para-aminosalicylic acid (GSR-PAS) in tuberculosis patients. The study was a randomized, two-period, open-label, crossover design wherein each patient received 4 g GSR-PAS twice daily or 8 g once daily alternately. The PAS concentration-time profiles were modeled by a one-compartment disposition model with three transit compartments in series to describe its absorption. Patients' NAT1 and NAT2 genotypes were determined by sequencing and restriction enzyme analysis, respectively. The number of daily vomits was modeled by a Poisson probability mass function. Comparisons of other tolerability measures by regimens, gender, and genotypes were evaluated by a linear mixed-effects model. The covariate effects associated with efavirenz, gender, and NAT1*3, NAT1*14, and NAT2*5 alleles corresponded to 25, 37, -17, -48, and -27% changes, respectively, in oral clearance of PAS. The NAT1*10 allele did not influence drug clearance. The time above the MIC of 1 mg/liter was significantly different between the two regimens but not influenced by the NAT1 or NAT2 genotypes. The occurrence and intensity of intolerance differed little between regimens. Four grams of GSR-PAS twice daily but not 8 g once daily ensured concentrations exceeding the MIC (1 mg/liter) throughout the dosing interval; PAS intolerance was not related to maximum PAS concentrations over the doses studied and was not more frequent after once-daily dosing. We confirm that the slow phenotype conferred by the NAT1*14 and NAT1*3 alleles resulted in higher PAS exposure but found no evidence of increased activity of the NAT1*10 allele.

Efficiency and safety of the combination of moxifloxacin, pretomanid (PA-824), and pyrazinamide during the first 8 weeks of antituberculosis treatment: a phase 2b, open-label, partly randomised trial in patients with drug-susceptible or drug-resistant pulmonary tuberculosis.

BACKGROUND: New antituberculosis regimens are urgently needed to shorten tuberculosis treatment. Following on from favourable assessment in a 2 week study, we investigated a novel regimen for efficacy and safety in drug-susceptible and multidrug-resistant (MDR) tuberculosis during the first 8 weeks of treatment. METHODS: We did this phase 2b study of bactericidal activity--defined as the decrease in colony forming units (CFUs) of Mycobacterium tuberculosis in the sputum of patients with microscopy smear-positive pulmonary tuberculosis-at eight sites in South Africa and Tanzania. We enrolled treatment-naive patients with drug-susceptible, pulmonary tuberculosis, who were randomly assigned by computer-generated sequences to receive either 8 weeks of moxifloxacin, 100 mg pretomanid (formerly known as PA-824), and pyrazinamide (MPa100Z regimen); moxifloxacin, 200 mg pretomanid, and pyrazinamide (MPa200Z regimen); or the current standard care for drug-susceptible pulmonary tuberculosis, isoniazid, rifampicin, PZA, and ethambutol (HRZE regimen). A group of patients with MDR tuberculosis received MPa200Z (DRMPa200Z group). The primary outcome was bactericidal activity measured by the mean daily rate of reduction in M tuberculosis CFUs per mL overnight sputum collected once a week, with joint Bayesian non-linear mixed-effects regression modelling. We also assessed safety and tolerability by monitoring adverse events. This study is registered with ClinicalTrials.gov, number NCT01498419. FINDINGS: Between March 24, 2012, and July 26, 2013 we enrolled 207 patients and randomly assigned them to treatment groups; we assigned 60 patients to the MPa100Z regimen, 62 to the MPa200Z regimen, and 59 to the HRZE regimen. We non-randomly assigned 26 patients with drug-resistant tuberculosis to the DRMPa200Z regimen. In patients with drug-susceptible tuberculosis, the bactericidal activity of MPa200Z (n=54) on days 0-56 (0·155, 95% Bayesian credibility interval 0·133-0·178) was significantly greater than for HRZE (n=54, 0·112, 0·093-0·131). DRMPa200Z (n=9) had bactericidal activity of 0·117 (0·070-0·174). The bactericidal activity on days 7-14 was strongly associated with bactericidal activity on days 7-56. Frequencies of adverse events were similar to standard treatment in all groups. The most common adverse event was hyperuricaemia in 59 (29%) patients (17 [28%] patients in MPa100Z group, 17 [27%] patients in MPa200Z group, 17 [29%] patients. in HRZE group, and 8 [31%] patients in DRMPa200Z group). Other common adverse events were nausea in (14 [23%] patients in MPa100Z group, 8 [13%] patients in MPa200Z group, 7 [12%] patients in HRZE group, and 8 [31%] patients in DRMPa200Z group) and vomiting (7 [12%] patients in MPa100Z group, 7 [11%] patients in MPa200Z group, 7 [12%] patients in HRZE group, and 4 [15%] patients in DRMPa200Z group). No on-treatment electrocardiogram occurrences of corrected QT interval more than 500 ms (an indicator of potential of ventricular tachyarrhythmia) were reported. No phenotypic resistance developed to any of the drugs in the regimen. INTERPRETATION: The combination of moxifloxacin, pretomanid, and pyrazinamide, was safe, well tolerated, and showed superior bactericidal activity in drug-susceptible tuberculosis during 8 weeks of treatment. Results were consistent between drug-susceptible and MDR tuberculosis. This new regimen is ready to enter phase 3 trials in patients with drug-susceptible tuberculosis and MDR-tuberculosis, with the goal of shortening and simplifying treatment. FUNDING: Global Alliance for TB Drug Development.