High-Dose Isoniazid Lacks EARLY Bactericidal Activity Against Isoniazid-resistant Tuberculosis Mediated by katG Mutations: A Randomized, Phase 2 Clinical Trial.

RATIONALE: Observational studies suggest that high-dose isoniazid may be efficacious in treating multidrug-resistant tuberculosis (MDR-TB). However, its activity against Mycobacterium tuberculosis (M.tb) with katG mutations (which typically confer high-level resistance) is not established. OBJECTIVE: To characterize early bactericidal activity (EBA) of high-dose isoniazid in patients with tuberculosis caused by katG-mutated M.tb. METHODS: A5312 was a Phase 2A randomized, open-label trial. Participants with tuberculosis caused by katG-mutated M.tb were randomized to receive 15 or 20 mg/kg isoniazid daily for 7 days. Daily sputum samples were collected for quantitative culture. Intensive PK sampling was performed on day 6. Data were pooled across all A5312 participants for analysis (drug-sensitive, inhA-mutated, and katG-mutated M.tb). EBA was determined using nonlinear mixed-effects modelling. RESULTS: Of 80 treated participants, 21 had katG-mutated M.tb. Isoniazid PK was best described by a two-compartment model with an effect of NAT2 acetylator phenotype on clearance. Model-derived Cmax and AUC in the 15 and 20 mg/kg groups were 15.0 and 22.1 mg/L and 57.6 and 76.8 mg∙h/L, respectively. Isoniazid bacterial kill was described using an effect compartment and a sigmoidal Emax relationship. Isoniazid potency against katG-mutated M.tb was approximately 10-fold lower than against inhA-mutated M.tb. The highest dose (20 mg/kg) did not demonstrate measurable EBA, except in a subset of slow NAT2 acetylators (who experienced the highest concentrations). There were no grade 3 or higher drug-related adverse events. CONCLUSIONS: This study found negligible bactericidal activity of high-dose isoniazid (15-20 mg/kg) in the majority of participants with tuberculosis caused by katG-mutated M.tb. Clinical trial registration available at www. CLINICALTRIALS: gov, ID: NCT01936831.

High rifampicin peak plasma concentrations accelerate the slow phase of bacterial decline in tuberculosis patients: Evidence for heteroresistance.

BACKGROUND: Antibiotic treatments are often associated with a late slowdown in bacterial killing. This separates the killing of bacteria into at least two distinct phases: a quick phase followed by a slower phase, the latter of which is linked to treatment success. Current mechanistic explanations for the in vitro slowdown are either antibiotic persistence or heteroresistance. Persistence is defined as the switching back and forth between susceptible and non-susceptible states, while heteroresistance is defined as the coexistence of bacteria with heterogeneous susceptibilities. Both are also thought to cause a slowdown in the decline of bacterial populations in patients and therefore complicate and prolong antibiotic treatments. Reduced bacterial death rates over time are also observed within tuberculosis patients, yet the mechanistic reasons for this are unknown and therefore the strategies to mitigate them are also unknown. METHODS AND FINDINGS: We analyse a dose ranging trial for rifampicin in tuberculosis patients and show that there is a slowdown in the decline of bacteria. We show that the late phase of bacterial killing depends more on the peak drug concentrations than the total drug exposure. We compare these to pharmacokinetic-pharmacodynamic models of rifampicin heteroresistance and persistence. We find that the observation on the slow phase's dependence on pharmacokinetic measures, specifically peak concentrations are only compatible with models of heteroresistance and incompatible with models of persistence. The quantitative agreement between heteroresistance models and observations is very good ([Formula: see text]). To corroborate the importance of the slowdown, we validate our results by estimating the time to sputum culture conversion and compare the results to a different dose ranging trial. CONCLUSIONS: Our findings indicate that higher doses, specifically higher peak concentrations may be used to optimize rifampicin treatments by accelerating bacterial killing in the slow phase. It adds to the growing body of literature supporting higher rifampicin doses for shortening tuberculosis treatments.

Phase I Single Ascending Dose and Food Effect Study in Healthy Adults and Phase I/IIa Multiple Ascending Dose Study in Patients with Pulmonary Tuberculosis to Assess Pharmacokinetics, Bactericidal Activity, Tolerability, and Safety of OPC-167832.

OPC-167832, an inhibitor of decaprenylphosphoryl-ß-d-ribose 2'-oxidase, demonstrated potent antituberculosis activity and a favorable safety profile in preclinical studies. This report describes the first two clinical studies of OPC-167832: (i) a phase I single ascending dose (SAD) and food effects study in healthy participants; and (ii) a 14-day phase I/IIa multiple ascending dose (MAD; 3/10/30/90 mg QD) and early bactericidal activity (EBA) trial in participants with drug-susceptible pulmonary tuberculosis (TB). OPC-167832 was well tolerated at single ascending doses (10 to 480 mg) in healthy participants and multiple ascending doses (3 to 90 mg) in participants with TB. In both populations, nearly all treatment-related adverse events were mild and self-limiting, with headache and pruritus being the most common events. Abnormal electrocardiograms results were rare and clinically insignificant. In the MAD study, OPC-167832 plasma exposure increased in a less than dose-proportional manner, with mean accumulation ratios ranging from 1.26 to 1.56 for Cmax and 1.55 to 2.01 for area under the concentration-time curve from 0 to 24 h (AUC0-24h). Mean terminal half-lives ranged from 15.1 to 23.6 h. Pharmacokinetics (PK) characteristics were comparable to healthy participants. In the food effects study, PK exposure increased by less than ~2-fold under fed conditions compared to the fasted state; minimal differences were observed between standard and high-fat meals. Once-daily OPC-167832 showed 14-day bactericidal activity from 3 mg (log10 CFU mean ± standard deviation change from baseline; -1.69 ± 1.15) to 90 mg (-2.08 ± 0.75), while the EBA of Rifafour e-275 was -2.79 ± 0.96. OPC-167832 demonstrated favorable pharmacokinetic and safety profiles, as well as potent EBA in participants with drug-susceptible pulmonary TB.

Drug interaction potential of high-dose rifampicin in patients with pulmonary tuberculosis.

Accumulating evidence supports the use of higher doses of rifampicin for tuberculosis (TB) treatment. Rifampicin is a potent inducer of metabolic enzymes and drug transporters, resulting in clinically relevant drug interactions. To assess the drug interaction potential of higher doses of rifampicin, we compared the effect of high-dose rifampicin (40 mg/kg daily, RIF40) and standard-dose rifampicin (10 mg/kg daily, RIF10) on the activities of major cytochrome P450 (CYP) enzymes and P-glycoprotein (P-gp). In this open-label, single-arm, two-period, fixed-order phenotyping cocktail study, adult participants with pulmonary TB received RIF10 (days 1-15), followed by RIF40 (days 16-30). A single dose of selective substrates (probe drugs) was administered orally on days 15 and 30: caffeine (CYP1A2), tolbutamide (CYP2C9), omeprazole (CYP2C19), dextromethorphan (CYP2D6), midazolam (CYP3A), and digoxin (P-gp). Intensive pharmacokinetic blood sampling was performed over 24 hours after probe drug intake. In all, 25 participants completed the study. Geometric mean ratios (90% confidence interval) of the total exposure (area under the concentration versus time curve, RIF40 versus RIF10) for each of the probe drugs were as follows: caffeine, 105% (96%-115%); tolbutamide, 80% (74%-86%); omeprazole, 55% (47%-65%); dextromethorphan, 77% (68%-86%); midazolam, 62% (49%-78%), and 117% (105%-130%) for digoxin. In summary, high-dose rifampicin resulted in no additional effect on CYP1A2, mild additional induction of CYP2C9, CYP2C19, CYP2D6, and CYP3A, and marginal inhibition of P-gp. Existing recommendations on managing drug interactions with rifampicin can remain unchanged for the majority of co-administered drugs when using high-dose rifampicin. Clinical Trials registration number NCT04525235.

Treatment of Highly Drug-Resistant Pulmonary Tuberculosis.

BACKGROUND: Patients with highly drug-resistant forms of tuberculosis have limited treatment options and historically have had poor outcomes. METHODS: In an open-label, single-group study in which follow-up is ongoing at three South African sites, we investigated treatment with three oral drugs - bedaquiline, pretomanid, and linezolid - that have bactericidal activity against tuberculosis and to which there is little preexisting resistance. We evaluated the safety and efficacy of the drug combination for 26 weeks in patients with extensively drug-resistant tuberculosis and patients with multidrug-resistant tuberculosis that was not responsive to treatment or for which a second-line regimen had been discontinued because of side effects. The primary end point was the incidence of an unfavorable outcome, defined as treatment failure (bacteriologic or clinical) or relapse during follow-up, which continued until 6 months after the end of treatment. Patients were classified as having a favorable outcome at 6 months if they had resolution of clinical disease, a negative culture status, and had not already been classified as having had an unfavorable outcome. Other efficacy end points and safety were also evaluated. RESULTS: A total of 109 patients were enrolled in the study and were included in the evaluation of efficacy and safety end points. At 6 months after the end of treatment in the intention-to-treat analysis, 11 patients (10%) had an unfavorable outcome and 98 patients (90%; 95% confidence interval, 83 to 95) had a favorable outcome. The 11 unfavorable outcomes were 7 deaths (6 during treatment and 1 from an unknown cause during follow-up), 1 withdrawal of consent during treatment, 2 relapses during follow-up, and 1 loss to follow-up. The expected linezolid toxic effects of peripheral neuropathy (occurring in 81% of patients) and myelosuppression (48%), although common, were manageable, often leading to dose reductions or interruptions in treatment with linezolid. CONCLUSIONS: The combination of bedaquiline, pretomanid, and linezolid led to a favorable outcome at 6 months after the end of therapy in a high percentage of patients with highly drug-resistant forms of tuberculosis; some associated toxic effects were observed. (Funded by the TB Alliance and others; ClinicalTrials.gov number, NCT02333799.).

Relative bioavailability of delamanid 50 mg tablets dispersed in water in healthy adult volunteers.

AIM: Delamanid is a novel drug for the treatment of drug-resistant tuberculosis, manufactured as 50-mg solid and 25-mg dispersible tablets. We evaluated the effects of dispersing the 50-mg tablet, focusing on the relative bioavailability. METHODS: Delamanid, 50-mg tablets administered dispersed vs swallowed whole, was investigated in a phase I, four-period, crossover study. Two of three dose strengths of delamanid (25, 50 or 100 mg) were given to healthy adult participants, in both whole and dispersed forms, with a 7-day washout period. Blood samples were collected over 168 h after each dose. Delamanid and its metabolite DM-6705 were analysed with a validated liquid chromatography tandem mass spectrometry assay. The pharmacokinetics of both analytes were analysed using nonlinear mixed-effect modelling. Palatability and acceptability were determined using a standardized questionnaire. RESULTS: Twenty-four participants completed the study. The bioavailability of dispersed tablets was estimated to be 107% of whole tablets, with a 90% confidence interval of 99.7-114%, fulfilling bioequivalence criteria. The two formulations were not significantly different regarding either bioavailability or its variability. Bioavailability increased at lower doses, by 34% (26-42%) at 50 mg and by 74% (64-86%) at 25 mg, relative to 100 mg. The majority of participants (93%) found the dispersed formulation acceptable in palatability across all delamanid doses. CONCLUSIONS: Dispersed 50-mg delamanid tablets have similar bioavailability to tablets swallowed whole in adult volunteers. This can be an option for children and other patients who cannot swallow whole tablets, improving access to treatment.

Early Bactericidal Activity of Meropenem plus Clavulanate (with or without Rifampin) for Tuberculosis: The COMRADE Randomized, Phase 2A Clinical Trial.

Rationale: Carbapenems are recommended for treatment of drug-resistant tuberculosis. Optimal dosing remains uncertain. Objectives: To evaluate the 14-day bactericidal activity of meropenem, at different doses, with or without rifampin. Methods: Individuals with drug-sensitive pulmonary tuberculosis were randomized to one of four intravenous meropenem-based arms: 2 g every 8 hours (TID) (arm C), 2 g TID plus rifampin at 20 mg/kg once daily (arm D), 1 g TID (arm E), or 3 g once daily (arm F). All participants received amoxicillin/clavulanate with each meropenem dose. Serial overnight sputum samples were collected from baseline and throughout treatment. Median daily fall in colony-forming unit (CFU) counts per milliliter of sputum (solid culture) (EBACFU0-14) and increase in time to positive culture (TTP) in liquid media were estimated with mixed-effects modeling. Serial blood samples were collected for pharmacokinetic analysis on Day 13. Measurements and Main Results: Sixty participants enrolled. Median EBACFU0-14 counts (2.5th-97.5th percentiles) were 0.22 (0.12-0.33), 0.12 (0.057-0.21), 0.059 (0.033-0.097), and 0.053 (0.035-0.081); TTP increased by 0.34 (0.21-0.75), 0.11 (0.052-0.37), 0.094 (0.034-0.23), and 0.12 (0.04-0.41) (log10 h), for arms C-F, respectively. Meropenem pharmacokinetics were not affected by rifampin coadministration. Twelve participants withdrew early, many of whom cited gastrointestinal adverse events. Conclusions: Bactericidal activity was greater with the World Health Organization-recommended total daily dose of 6 g daily than with a lower dose of 3 g daily. This difference was only detectable with solid culture. Tolerability of intravenous meropenem, with amoxicillin/clavulanate, though, was poor at all doses, calling into question the utility of this drug in second-line regimens. Clinical trial registered with www.clinicaltrials.gov (NCT03174184).

Pharmacokinetics of bedaquiline in cerebrospinal fluid (CSF) in patients with pulmonary tuberculosis (TB).

BACKGROUND: With current treatment options most patients with CNS TB develop severe disability or die. Drug-resistant tuberculous meningitis is nearly uniformly fatal. Novel treatment strategies are needed. Bedaquiline, a potent anti-TB drug, has been reported to be absent from CSF in a single report. OBJECTIVES: To explore the pharmacokinetics of bedaquiline and its M2 metabolite in the CSF of patients with pulmonary TB. PATIENTS AND METHODS: Individuals with rifampicin-resistant pulmonary TB established on a 24 week course of treatment with bedaquiline underwent a lumbar puncture along with multiple blood sample collections over 24 h for CSF and plasma pharmacokinetic assessment, respectively. To capture the expected low bedaquiline and M2 concentrations (due to high protein binding in plasma) we optimized CSF collection and storage methods in vitro before concentrations were quantified via liquid chromatography with tandem MS. RESULTS: Seven male participants were enrolled, two with HIV coinfection. Using LoBind® tubes lined with a 5% BSA solution, bedaquiline and M2 could be accurately measured in CSF. Bedaquiline and M2 were present in all patients at all timepoints at concentrations similar to the estimated unbound fractions in plasma. CONCLUSIONS: Bedaquiline and M2 penetrate freely into the CSF of pulmonary TB patients with a presumably intact blood-brain barrier. Clinical studies are urgently needed to determine whether bedaquiline can contribute meaningfully to the treatment of CNS TB.

Sputum lipoarabinomannan (LAM) as a biomarker to determine sputum mycobacterial load: exploratory and model-based analyses of integrated data from four cohorts.

BACKGROUND: Despite the high global disease burden of tuberculosis (TB), the disease caused by Mycobacterium tuberculosis (Mtb) infection, novel treatments remain an urgent medical need. Development efforts continue to be hampered by the reliance on culture-based methods, which often take weeks to obtain due to the slow growth rate of Mtb. The availability of a "real-time" measure of treatment efficacy could accelerate TB drug development. Sputum lipoarabinomannan (LAM; an Mtb cell wall glycolipid) has promise as a pharmacodynamic biomarker of mycobacterial sputum load. METHODS: The present analysis evaluates LAM as a surrogate for Mtb burden in the sputum samples from 4 cohorts of a total of 776 participants. These include those from 2 cohorts of 558 non-TB and TB participants prior to the initiation of treatment (558 sputum samples), 1 cohort of 178 TB patients under a 14-day bactericidal activity trial with various mono- or multi-TB drug therapies, and 1 cohort of 40 TB patients with data from the first 56-day treatment of a standard 4-drug regimen. RESULTS: Regression analysis demonstrated that LAM was a predictor of colony-forming unit (CFU)/mL values obtained from the 14-day treatment cohort, with well-estimated model parameters (relative standard error ≤ 22.2%). Moreover, no changes in the relationship between LAM and CFU/mL were observed across the different treatments, suggesting that sputum LAM can be used to reasonably estimate the CFU/mL in the presence of treatment. The integrated analysis showed that sputum LAM also appears to be as good a predictor of time to Mycobacteria Growth Incubator Tube (MGIT) positivity as CFU/mL. As a binary readout, sputum LAM positivity is a strong predictor of solid media or MGIT culture positivity with an area-under-the-curve value of 0.979 and 0.976, respectively, from receiver-operator curve analysis. CONCLUSIONS: Our results indicate that sputum LAM performs as a pharmacodynamic biomarker for rapid measurement of Mtb burden in sputum, and thereby may enable more efficient early phase clinical trial designs (e.g., adaptive designs) to compare candidate anti-TB regimens and streamline dose selection for use in pivotal trials. Trial registration NexGen EBA study (NCT02371681).

Mycobacteriophages to Treat Tuberculosis: Dream or Delusion?

Rates of antimicrobial resistance are increasing globally while the pipeline of new antibiotics is drying up, putting patients with disease caused by drug-resistant bacteria at increased risk of complications and death. The growing costs for diagnosis and management of drug resistance threaten tuberculosis control where the disease is endemic and resources limited. Bacteriophages are viruses that attack bacteria. Phage preparations served as anti-infective agents long before antibiotics were discovered. Though small in size, phages are the most abundant and diverse biological entity on earth. Phages have co-evolved with their hosts and possess all the tools needed to infect and kill bacteria, independent of drug resistance. Modern biotechnology has improved our understanding of the biology of phages and their possible uses. Phage preparations are available to treat meat, fruit, vegetables, and dairy products against parasites or to prevent contamination with human pathogens, such as Listeria monocytogenes, Escherichia coli, or Staphylococcus aureus. Such phage-treated products are considered fit for human consumption. A number of recent case reports describe in great detail the successful treatment of highly drug-resistant infections with individualized phage preparations. Formal clinical trials with standardized products are slowly emerging. With its highly conserved genome and relative paucity of natural phage defence mechanisms Mycobacterium tuberculosis appears to be a suitable target for phage treatment. A phage cocktail with diverse and strictly lytic phages that kill all lineages of M. tuberculosis, and can be propagated on Mycobacterium smegmatis, has been assembled and is available for the evaluation of optimal dosage and suitable routes of administration for tuberculosis in humans. Phage treatment can be expected to be safe and active on extracellular organisms, but phage penetration to intracellular and granulomatous environments as well as synergistic effects with antibiotics are important questions to address during further evaluation.

A Semimechanistic Model of the Bactericidal Activity of High-Dose Isoniazid against Multidrug-Resistant Tuberculosis: Results from a Randomized Clinical Trial.

Rationale: There is accumulating evidence that higher-than-standard doses of isoniazid are effective against low-to-intermediate-level isoniazid-resistant strains of Mycobacterium tuberculosis, but the optimal dose remains unknown. Objectives: To characterize the association between isoniazid pharmacokinetics (standard or high dose) and early bactericidal activity against M. tuberculosis (drug sensitive and inhA mutated) and N-acetyltransferase 2 status. Methods: ACTG (AIDS Clinical Trial Group) A5312/INHindsight is a 7-day early bactericidal activity study with isoniazid at a normal dose (5 mg/kg) for patients with drug-sensitive bacteria and 5, 10, and 15 mg/kg doses for patients with inhA mutants. Participants with pulmonary tuberculosis received daily isoniazid monotherapy and collected sputum daily. Colony-forming units (cfu) on solid culture and time to positivity in liquid culture were jointly analyzed using nonlinear mixed-effects modeling. Measurements and Main Results: Fifty-nine adults were included in this analysis. A decline in sputum cfu was described by a one-compartment model, whereas an exponential bacterial growth model was used to interpret time-to-positivity data. The model found that bacterial kill is modulated by isoniazid concentration using an effect compartment and a sigmoidal Emax relationship (a model linking the drug concentration to the observed effect). The model predicted lower potency but similar maximum kill of isoniazid against inhA-mutated compared with drug-sensitive isolates. Based on simulations from the pharmacokinetics-pharmacodynamics model, to achieve a drop in bacterial load comparable to 5 mg/kg against drug-sensitive tuberculosis, 10- and 15-mg/kg doses are necessary against inhA-mutated isolates in slow and intermediate N-acetyltransferase 2 acetylators, respectively. Fast acetylators underperformed even at 15 mg/kg. Conclusions: Dosing of isoniazid based on N-acetyltransferase 2 acetylator status may help patients attain effective exposures against inhA-mutated isolates. Clinical trial registered with www.clinicaltrials.gov (NCT01936831).

Xpert Mycobacterium tuberculosis/Rifampicin-Detected Rifampicin Resistance is a Suboptimal Surrogate for Multidrug-resistant Tuberculosis in Eastern Democratic Republic of the Congo: Diagnostic and Clinical Implications.

BACKGROUND: Rifampicin (RIF) resistance is highly correlated with isoniazid (INH) resistance and used as proxy for multidrug-resistant tuberculosis (MDR-TB). Using MTBDRplus as a comparator, we evaluated the predictive value of Xpert MTB/RIF (Xpert)-detected RIF resistance for MDR-TB in eastern Democratic Republic of the Congo (DRC). METHODS: We conducted a cross-sectional study involving data from new or retreatment pulmonary adult TB cases evaluated between July 2013 and December 2016. Separate, paired sputa for smear microscopy and MTBDRplus were collected. Xpert testing was performed subject to the availability of Xpert cartridges on sample remnants after microscopy. RESULTS: Among 353 patients, 193 (54.7%) were previously treated and 224 (63.5%) were MTBDRplus TB positive. Of the 224, 43 (19.2%) were RIF monoresistant, 11 (4.9%) were INH monoresistant, 53 (23.7%) had MDR-TB, and 117 (52.2%) were RIF and INH susceptible. Overall, among the 96 samples detected by MTBDRplus as RIF resistant, 53 (55.2%) had MDR-TB. Xpert testing was performed in 179 (50.7%) specimens; among these, 163 (91.1%) were TB positive and 73 (44.8%) RIF resistant. Only 45/73 (61.6%) Xpert-identified RIF-resistant isolates had concomitant MTBDRplus-detected INH resistance. Xpert had a sensitivity of 100.0% (95% CI, 92.1-100.0) for detecting RIF resistance but a positive-predictive value of only 61.6% (95% CI, 49.5-72.8) for MDR-TB. The most frequent mutations associated with RIF and INH resistance were S531L and S315T1, respectively. CONCLUSIONS: In this high-risk MDR-TB study population, Xpert had low positive-predictive value for the presence of MDR-TB. Comprehensive resistance testing for both INH and RIF should be performed in this setting.

Effect of Clofazimine Concentration on QT Prolongation in Patients Treated for Tuberculosis.

Clofazimine is classified as a WHO group B drug for the treatment of rifampin-resistant tuberculosis. QT prolongation, which is associated with fatal cardiac arrhythmias, is caused by several antitubercular drugs, including clofazimine, but there are no data quantifying the effect of clofazimine concentration on QT prolongation. Our objective was to describe the effect of clofazimine exposure on QT prolongation. Fifteen adults drug-susceptible tuberculosis patients received clofazimine monotherapy as 300 mg daily for 3 days, followed by 100 mg daily in one arm of a 2-week, multiarm early bactericidal activity trial in South Africa. Pretreatment Fridericia-corrected QT (QTcF) (105 patients, 524 electrocardiograms [ECGs]) and QTcFs from the clofazimine monotherapy arm matched with clofazimine plasma concentrations (199 ECGs) were interpreted with a nonlinear mixed-effects model. Clofazimine was associated with significant QT prolongation described by a maximum effect (Emax) function. We predicted clofazimine exposures using 100-mg daily doses and 2 weeks of loading with 200 and 300 mg daily, respectively. The expected proportions of patients with QTcF change from baseline above 30 ms (ΔQTcF > 30) were 2.52%, 11.6%, and 23.0% for 100-, 200-, and 300-mg daily doses, respectively. At steady state, the expected proportion with ΔQTcF of >30 ms was 23.7% and with absolute QTcF of >450 ms was 3.42% for all simulated regimens. The use of loading doses of 200 and 300 mg is not predicted to expose patients to an increased risk of QT prolongation, compared with the current standard treatment, and is, therefore, an alternative option for more quickly achieving therapeutic concentrations.

Increased bactericidal activity but dose-limiting intolerability at 50†mg·kg-1 rifampicin.

BACKGROUND: Accumulating data indicate that higher rifampicin doses are more effective and shorten tuberculosis (TB) treatment duration. This study evaluated the safety, tolerability, pharmacokinetics, and 7- and 14-day early bactericidal activity (EBA) of increasing doses of rifampicin. Here we report the results of the final cohorts of PanACEA HIGHRIF1, a dose escalation study in treatment-naive adult smear-positive patients with TB. METHODS: Patients received, in consecutive cohorts, 40 or 50 mg·kg-1 rifampicin once daily in monotherapy (day 1-7), supplemented with standard dose isoniazid, pyrazinamide and ethambutol between days 8 and 14. RESULTS: In the 40 mg·kg-1 cohort (n=15), 13 patients experienced a total of 36 adverse events during monotherapy, resulting in one treatment discontinuation. In the 50 mg·kg-1 cohort (n=17), all patients experienced adverse events during monotherapy, 93 in total; 11 patients withdrew or stopped study medication. Adverse events were mostly mild/moderate and tolerability rather than safety related, i.e. gastrointestinal disorders, pruritis, hyperbilirubinaemia and jaundice. There was a more than proportional increase in the rifampicin geometric mean area under the plasma concentration-time curve from time 0 to 12 h (AUC0-24 h) for 50 mg·kg-1 compared with 40 mg·kg-1; 571 (range 320-995) versus 387 (range 201-847) mg·L-1·h, while peak exposures saw proportional increases. Protein-unbound exposure after 50 mg·kg-1 (11% (range 8-17%)) was comparable with lower rifampicin doses. Rifampicin exposures and bilirubin concentrations were correlated (Spearman's ρ=0.670 on day 3, p<0.001). EBA increased considerably with dose, with the highest seen after 50 mg·kg-1: 14-day EBA -0.427 (95% CI -0.500- -0.355) log10CFU·mL-1·day-1. CONCLUSION: Although associated with an increased bactericidal effect, the 50 mg·kg-1 dose was not well tolerated. Rifampicin at 40 mg·kg-1 was well tolerated and therefore selected for evaluation in a phase IIc treatment-shortening trial.

Comparing rates of mycobacterial clearance in sputum smear-negative and smear-positive adults living with HIV.

BACKGROUND: Pulmonary tuberculosis (TB) in people living with HIV (PLH) frequently presents as sputum smear-negative. However, clinical trials of TB in adults often use smear-positive individuals to ensure measurable bacterial responses following initiation of treatment, thereby excluding HIV-infected patients from trials. METHODS: In this prospective case cohort study, 118 HIV-seropositive TB patients were assessed prior to initiation of standard four-drug TB therapy and at several time points through 35 days. Sputum bacillary load, as a marker of treatment response, was determined serially by: smear microscopy, Xpert MTB/RIF, liquid culture, and colony counts on agar medium. RESULTS: By all four measures, patients who were baseline smear-positive had higher bacterial loads than those presenting as smear-negative, until day 35. However, most smear-negative PLH had significant bacillary load at enrolment and their mycobacteria were cleared more rapidly than smear-positive patients. Smear-negative patients' decline in bacillary load, determined by colony counts, was linear to day 7 suggesting measurable bactericidal activity. Moreover, the decrease in bacterial counts was comparable to smear-positive individuals. Increasing cycle threshold values (Ct) on the Xpert assay in smear-positive patients to day 14 implied decreasing bacterial load. CONCLUSION: Our data suggest that smear-negative PLH can be included in clinical trials of novel treatment regimens as they contain sufficient viable bacteria, but allowances for late exclusions would have to be made in sample size estimations. We also show that increases in Ct in smear-positive patients to day 14 reflect treatment responses and the Xpert MTB/RIF assay could be used as biomarker for early treatment response.

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.

The Utility of Pleural Fluid Lactate Dehydrogenase to Adenosine Deaminase Ratio in Pleural Tuberculosis.

In high-burden settings, the diagnosis of pleural tuberculosis (TB) is frequently inferred in patients who present with lymphocyte predominant exudative effusions and high adenosine deaminase (ADA) levels. Two recent small retrospective studies suggested that the lactate dehydrogenase (LDH)/ADA ratio is significantly lower in TB than in non-TB pleural effusions and that the LDH/ADA ratio may be useful in differentiating pleural TB from other pleural exudates. We compared the pleural LDH/ADA ratios, ADA levels, and lymphocyte predominance of a prospectively collected cohort of patients with proven pleural TB (n = 160) to those with a definitive alternative diagnosis (n = 68). The mean pleural fluid LDH/ADA ratio was lower in patients with pleural TB than alternative diagnoses (6.2 vs. 34.3, p < 0.001). The area under the receiver operating characteristic curve was 0.92 (p < 0.001) for LDH/ADA ratio and 0.88 (p < 0.001) for an ADA ≥40 U/L alone. A ratio of ≤12.5 had the best overall diagnostic efficiency, while a ratio of ≤10 had a specificity of 90% and a positive predictive value of 95%, with a sensitivity of 78%, making it a clinically useful "rule in" value for pleural TB in high incidence settings. When comparing the LDH/ADA ratio to an ADA level ≥40 U/L in the presence of a lymphocyte predominant effusion, the latter performed better. When lymphocyte values are unavailable, our data suggest that the LDH/ADA ratio is valuable in distinguishing TB effusions from other pleural exudates.

Early Bactericidal Activity of Different Isoniazid Doses for Drug-Resistant Tuberculosis (INHindsight): A Randomized, Open-Label Clinical Trial.

Rationale: High-dose isoniazid is recommended in short-course regimens for multidrug-resistant tuberculosis (TB). The optimal dose of isoniazid and its individual contribution to efficacy against TB strains with inhA or katG mutations are unknown.Objectives: To define the optimal dose of isoniazid for patients with isoniazid-resistant TB mediated by inhA mutations.Methods: AIDS Clinical Trials Group A5312 is a phase 2A, open-label trial in which individuals with smear-positive pulmonary TB with isoniazid resistance mediated by an inhA mutation were randomized to receive isoniazid 5, 10, or 15 mg/kg daily for 7 days (inhA group), and control subjects with drug-sensitive TB received the standard dose (5 mg/kg/d). Overnight sputum cultures were collected daily. The 7-day early bactericidal activity (EBA) of isoniazid was estimated as the average daily change in log10 cfu on solid media (EBAcfu0-7) or as time to positivity (TTP) in liquid media in hours (EBATTP0-7) using nonlinear mixed-effects models.Measurements and Main Results: Fifty-nine participants (88% with cavitary disease, 20% HIV-positive, 16 with isoniazid-sensitive TB, and 43 with isoniazid-monoresistant or multidrug-resistant TB) were enrolled at one site in South Africa. The mean EBAcfu0-7 at doses of 5, 10, and 15 mg/kg in the inhA group was 0.07, 0.17, and 0.22 log10 cfu/ml/d, respectively, and 0.16 log10 cfu/ml/d in control subjects. EBATTP0-7 patterns were similar. There were no drug-related grade ≥3 adverse events.Conclusions: Isoniazid 10-15 mg/kg daily had activity against TB strains with inhA mutations similar to that of 5 mg/kg against drug-sensitive strains. The activity of high-dose isoniazid against strains with katG mutations will be explored next.Clinical trial registered with www.clinicaltrials.gov (NCT01936831).

Drug Effect of Clofazimine on Persisters Explains an Unexpected Increase in Bacterial Load in Patients.

Antituberculosis (anti-TB) drug development is dependent on informative trials to secure the development of new antibiotics and combination regimens. Clofazimine (CLO) and pyrazinamide (PZA) are important components of recommended standard multidrug treatments of TB. Paradoxically, in a phase IIa trial aiming to define the early bactericidal activity (EBA) of CLO and PZA monotherapy over the first 14 days of treatment, no significant drug effect was demonstrated for the two drugs using traditional statistical analysis. Using a model-based analysis, we characterized the statistically significant exposure-response relationships for both drugs that could explain the original findings of an increase in the numbers of CFU with CLO treatment and no effect with PZA. Sensitive analyses are crucial for exploring drug effects in early clinical trials to make the right decisions for advancement to further development. We propose that this quantitative semimechanistic approach provides a rational framework for analyzing phase IIa EBA studies and can accelerate anti-TB drug development.

Fourteen-Day Bactericidal Activity, Safety, and Pharmacokinetics of Linezolid in Adults with Drug-Sensitive Pulmonary Tuberculosis.

Linezolid is increasingly used for the treatment of tuberculosis resistant to first-line agents, but the most effective dosing strategy is yet unknown. From November 2014 to November 2016, we randomized 114 drug-sensitive treatment-naive pulmonary tuberculosis patients from Cape Town, South Africa, to one of six 14-day treatment arms containing linezolid at 300 mg once daily (QD), 300 mg twice daily (BD), 600 mg QD, 600 mg BD, 1,200 mg QD, 1,200 mg three times per week (TIW), or a combination of isoniazid, rifampin, pyrazinamide, and ethambutol. Sixteen-hour sputum samples were collected overnight, and bactericidal activity was characterized by the daily percentage change in time to positivity (TTP) and the daily rate of change in log10(CFU). We also assessed the safety and pharmacokinetics of the study treatments. We found that bactericidal activity increased with increasing doses of linezolid. Based on the daily percentage change in TTP, activity was highest for 1,200 mg QD (4.5%; 95% Bayesian confidence interval [BCI], 3.3 to 5.6), followed by 600 mg BD (4.1%; BCI, 2.5 to 5.7), 600 mg QD (4.1%; BCI, 2.9 to 5.3), 300 mg BD (3.3%; BCI, 1.9 to 4.7), 300 mg QD (2.3%; BCI, 1.1 to 3.5), and 1,200 mg TIW (2.2%; BCI, 1.1 to 3.3). Similar results were seen with bactericidal activity characterized by the daily rate of change in CFU count. Antimycobacterial activity correlated positively with plasma drug exposure and percentage time over MIC. There were no unexpected adverse events. All linezolid doses showed bactericidal activity. For the same total daily dose, once-daily dosing proved to be at least as effective as a divided twice-daily dose. An intermittent dosing regimen, with 1,200 mg given three times weekly, showed the least activity. (This study has been registered at ClinicalTrials.gov under identifier NCT02279875.).