Optimising pyrazinamide for the treatment of tuberculosis

Drug Exposure and Susceptibility of Pyrazinamide Correlate with Treatment Response in Pyrazinamide-Susceptible Patients with Multidrug-Resistant Tuberculosis

Exploring the influence of pyrazinamide exposure and susceptibility on treatment response is crucial for optimizing the management of multidrug-resistant tuberculosis (MDR-TB). This study aimed to investigate the association between pyrazinamide exposure, susceptibility, and response to MDR-TB treatment, as well as find clinical thresholds for pyrazinamide. A prospective multi-center cohort study of participants with MDR-TB using pyrazinamide was conducted in three TB-designated hospitals in China. Univariate and multivariate analyses were applied to investigate the associations. Classification and Regression Tree (CART) analysis was used to identify clinical thresholds, which were further evaluated by multivariate analysis and receiver operating characteristic (ROC) curves. The study included 143 patients with MDR-TB. The exposure/susceptibility ratio of pyrazinamide was associated with two-month culture conversion (adjusted risk ratio (aRR), 1.1; 95% confidence interval (CI), 1.07-1.20), six-month culture conversion (aRR, 1.1; 95% CI, 1.06-1.16), treatment success (aRR, 1.07; 95% CI, 1.03-1.10), as well as culture conversion time (adjusted hazard ratio (aHR) 1.18; 95% CI,1.14-1.23). The threshold for optimal improvement in sputum culture results at the sixth month of treatment was determined to be a pyrazinamide AUC0-24h/MIC ratio of 7.8. In conclusion, the exposure/susceptibility ratio of pyrazinamide is associated with the treatment response of MDR-TB, which may change in different Group A drug-based regimens.

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.

Correlations among the plasma concentrations of first-line anti-tuberculosis drugs and the physiological parameters influencing concentrations

Background: The plasma concentrations of the four most commonly used first-line anti-tuberculosis (TB) drugs, isoniazid (INH), rifampicin (RMP), ethambutol (EMB), and pyrazinamide (PZA), are often not within the therapeutic range. Insufficient drug exposure could lead to drug resistance and treatment failure, while excessive drug levels may lead to adverse reactions. The purpose of this study was to identify the physiological parameters influencing anti-TB drug concentrations. Methods: A retrospective cohort study was conducted. The 2-h plasma concentrations of the four drugs were measured by using the high-performance liquid chromatography-tandem mass spectrometry method. Results: A total of 317 patients were included in the study. The proportions of patients with INH, RMP, EMB, and PZA concentrations within the therapeutic range were 24.3%, 31.5%, 27.8%, and 18.6%, respectively. There were positive associations between the concentrations of INH and PZA and RMP and EMB, but negative associations were observed between the concentrations of INH and RMP, INH and EMB, RMP and PZA, and EMB and PZA. In the multivariate analysis, the influencing factors of the INH concentration were the PZA concentration, total bile acid (TBA), serum potassium, dose, direct bilirubin, prealbumin (PA), and albumin; those of the RMP concentration were PZA and EMB concentrations, weight, α-l-fucosidase (AFU), drinking, and dose; those of the EMB concentration were the RMP and PZA concentrations, creatinine, TBA and indirect bilirubin; and those of the PZA concentration were INH, RMP and EMB concentrations, sex, weight, uric acid and drinking. Conclusion: The complex correlations between the concentrations of the four first-line anti-TB drugs lead to a major challenge in dose adjustment to maintain all drugs within the therapeutic window. Levels of TBA, PA, AFU, and serum potassium should also be considered when adjusting the dose of the four drugs.

Is there a need to optimise pyrazinamide doses in patients with tuberculosis? A systematic review

Pyrazinamide (PZA) is a first-line antituberculosis drug with potent sterilising activity. Variability in drug exposure may translate into suboptimal treatment responses. This systematic review, conducted according to PRISMA guidelines, aimed to evaluate the concentration-effect relationship. In vitro/in vivo studies had to contain information on the infection model, PZA dose and concentration, and microbiological outcome. Human studies had to present information on PZA dose, measures of drug exposure and maximum concentration, and microbiological response parameter or overall treatment outcome. A total of 34 studies were assessed, including in vitro (n = 2), in vivo (n = 3) and clinical studies (n = 29). Intracellular and extracellular models demonstrated a direct correlation between PZA dose of 15-50 mg/kg/day and reduction in bacterial count between 0.50-27.7 log10 CFU/mL. Consistent with this, higher PZA doses (>150 mg/kg) were associated with a greater reduction in bacterial burden in BALB/c mice models. Human pharmacokinetic studies displayed a linear positive correlation between PZA dose (i.e. 21.4-35.7 mg/kg/day) and drug exposure (AUC range 220.6-514.5 mg·h/L). Additionally, human studies confirmed a dose-effect relationship, with an increased 2-month sputum culture conversion rate at AUC/MIC targets of 8.4-11.3 with higher exposure/susceptibility ratios leading to greater efficacy. A 5-fold variability in AUC was observed at PZA dose of 25 mg/kg. A direct concentration-effect relationship and increased treatment efficacy with higher PZA exposure to susceptibility ratios was observed. Taking into account variability in drug exposure and treatment response, further studies on dose optimisation are justified.

Pharmacodynamics and Bactericidal Activity of Combination Regimens in Pulmonary Tuberculosis: Application to Bedaquiline-Pretomanid-Pyrazinamide

A critical barrier to codevelopment of tuberculosis (TB) regimens is a limited ability to identify optimal drug and dose combinations in early-phase clinical testing. While pharmacokinetic-pharmacodynamic (PKPD) target attainment is the primary tool for exposure-response optimization of TB drugs, the PD target is a static index that does not distinguish individual drug contributions to the efficacy of a multidrug combination. A PKPD model of bedaquiline-pretomanid-pyrazinamide (BPaZ) for the treatment of pulmonary TB was developed as part of a dynamic exposure-response approach to regimen development. The model describes a time course relationship between the drug concentrations in plasma and their individual as well as their combined effect on sputum bacillary load assessed by solid culture CFU counts and liquid culture time to positivity (TTP). The model parameters were estimated using data from the phase 2A studies NC-001-(J-M-Pa-Z) and NC-003-(C-J-Pa-Z). The results included a characterization of BPaZ activity as the most and least sensitive to changes in pyrazinamide and bedaquiline exposures, respectively, with antagonistic activity of BPa compensated by synergistic activity of BZ and PaZ. Simulations of the NC-003 study population with once-daily bedaquiline at 200 mg, pretomanid at 200 mg, and pyrazinamide at 1,500 mg showed BPaZ would require 3 months to attain liquid culture negativity in 90% of participants. These results for BPaZ were intended to be an example application with the general approach aimed at entirely novel drug combinations from a growing pipeline of new and repurposed TB drugs.

Pyrazinamide related prolonged drug-induced liver injury: A case report

RATIONALE

Drug induced liver injury (DILI) is a common side effect causing treatment discontinuation during tuberculosis (TB) treatment, and pyrazinamide (PZA) usually leads to a delayed and prolonged abnormal liver function of the 4 standard anti-tuberculosis regimens. However, a prolonged hepatitis lasting more than 4 months is rarely reported.

PATIENT CONCERNS

A 78-year-old man presented with general weakness and poor appetite on his seventh week of anti-TB treatment for tuberculosis lymphadenitis.

DIAGNOSIS

Drug induced liver injury, PZA-related. NAT2 slow acetylator phenotype was accidentally found during workup of DILI.

INTERVENTION

A liver biopsy was performed and PZA-related DILI was suspected. All anti-TB medications were therefore discontinued.

OUTCOME

After withholding all anti-TB medications for 4 months, the elevations of aminotransferases and hyperbilirubinemia completely resolved. Anti-TB therapy was switched to ethambutol and levofloxacin for 15 months without adverse events. Long-term ultrasound follow-up was performed and cervical lymphadenopathy completely resolved.

CONCLUSION

Our patient presents with PZA related prolonged DILI resolved after drug discontinuation for 4 months. NAT2 slow acetylator phenotype may be related to this condition through unknown mechanisms.

Pharmacokinetic-Pharmacodynamic Determinants of Clinical Outcomes for Rifampin-Resistant Tuberculosis: A Multisite Prospective Cohort Study

BACKGROUND

Rifampin-resistant and/or multidrug-resistant tuberculosis (RR/MDR-TB) treatment requires multiple drugs, and outcomes remain suboptimal. Some drugs are associated with improved outcome. It is unknown whether particular pharmacokinetic-pharmacodynamic relationships predict outcome.

METHODS

Adults with pulmonary RR/MDR-TB in Tanzania, Bangladesh, and the Russian Federation receiving local regimens were enrolled from June 2016 to July 2018. Serum was collected after 2, 4, and 8 weeks for each drug's area under the concentration-time curve over 24 hours (AUC0-24). Quantitative susceptibility of the M. tuberculosis isolate was measured by minimum inhibitory concentrations (MICs). Individual drug AUC0-24/MIC targets were assessed by adjusted odds ratios (ORs) for favorable treatment outcome, and hazard ratios (HRs) for time to sputum culture conversion. K-means clustering algorithm separated the cohort of the most common multidrug regimen into 4 clusters by AUC0-24/MIC exposures.

RESULTS

Among 290 patients, 62 (21%) experienced treatment failure, including 30 deaths. Moxifloxacin AUC0-24/MIC target of 58 was associated with favorable treatment outcome (OR, 3.75; 95% confidence interval, 1.21-11.56; P = .022); levofloxacin AUC0-24/MIC of 118.3, clofazimine AUC0-24/MIC of 50.5, and pyrazinamide AUC0-24 of 379 mg × h/L were associated with faster culture conversion (HR >1.0, P < .05). Other individual drug exposures were not predictive. Clustering by AUC0-24/MIC revealed that those with the lowest multidrug exposures had the slowest culture conversion.

CONCLUSIONS

Amidst multidrug regimens for RR/MDR-TB, serum pharmacokinetics and M. tuberculosis MICs were variable, yet defined parameters to certain drugs-fluoroquinolones, pyrazinamide, clofazimine-were predictive and should be optimized to improve clinical outcome.

CLINICAL TRIALS REGISTRATION

NCT03559582.

Population Pharmacokinetic Modelling and Limited Sampling Strategies for Therapeutic Drug Monitoring of Pyrazinamide in Patients with Tuberculosis

Pyrazinamide is one of the first-line antituberculosis drugs. The efficacy of pyrazinamide is associated with the ratio of 24-h area under the concentration-time curve (AUC₂₄) to MIC. The objective of this study was to develop and validate a limited sampling strategy (LSS) based on a population pharmacokinetic (popPK) model to predict AUC₂₄. A popPK model was developed using an iterative two-stage Bayesian procedure and was externally validated. Using data from 20 treatment-naive adult tuberculosis (TB) patients, a one compartment model with transit absorption and first-order elimination best described pyrazinamide pharmacokinetics and fed state was the only significant covariate for absorption rate constant (k_a). External validation, using data from 26 TB patients, showed that the popPK model predicted AUC₂₄ with a slight underestimation of 2.1%. LSS were calculated using Monte Carlo simulation (n = 10,000). External validation showed LSS with time points 0 h, 2 h, and 6 h performed best with RMSE of 9.90% and bias of 0.06%. Food slowed absorption of pyrazinamide, but did not affect bioavailability, which may be advantageous in case of nausea or vomiting in which food can be used to diminish these effects. In this study, we successfully developed and validated a popPK model and LSS, using 0 h, 2 h, and 6 h postdose samples, that could be used to perform therapeutic drug monitoring (TDM) of pyrazinamide in TB patients.

Drug concentration at the site of disease in children with pulmonary tuberculosis

BACKGROUND

Current TB treatment for children is not optimized to provide adequate drug levels in TB lesions. Dose optimization of first-line antituberculosis drugs to increase exposure at the site of disease could facilitate more optimal treatment and future treatment-shortening strategies across the disease spectrum in children with pulmonary TB.

OBJECTIVES

To determine the concentrations of first-line antituberculosis drugs at the site of disease in children with intrathoracic TB.

METHODS

We quantified drug concentrations in tissue samples from 13 children, median age 8.6 months, with complicated forms of pulmonary TB requiring bronchoscopy or transthoracic surgical lymph node decompression in a tertiary hospital in Cape Town, South Africa. Pharmacokinetic models were used to describe drug penetration characteristics and to simulate concentration profiles for bronchoalveolar lavage, homogenized lymph nodes, and cellular and necrotic lymph node lesions.

RESULTS

Isoniazid, rifampicin and pyrazinamide showed lower penetration in most lymph node areas compared with plasma, while ethambutol accumulated in tissue. None of the drugs studied was able to reach target concentration in necrotic lesions.

CONCLUSIONS

Despite similar penetration characteristics compared with adults, low plasma exposures in children led to low site of disease exposures for all drugs except for isoniazid.

Safety and pharmacokinetics-pharmacodynamics of a shorter tuberculosis treatment with high-dose pyrazinamide and rifampicin: a study protocol of a phase II clinical trial (HighShort-RP)

INTRODUCTION

Increased dosing of rifampicin and pyrazinamide seems a viable strategy to shorten treatment and prevent relapse of drug-susceptible tuberculosis (TB), but safety and efficacy remains to be confirmed. This clinical trial aims to explore safety and pharmacokinetics-pharmacodynamics of a high-dose pyrazinamide-rifampicin regimen.

METHODS AND ANALYSIS

Adult patients with pulmonary TB admitted to six hospitals in Sweden and subjected to receive first-line treatment are included. Patients are randomised (1:3) to either 6-month standardised TB treatment or a 4-month regimen based on high-dose pyrazinamide (40 mg/kg) and rifampicin (35 mg/kg) along with standard doses of isoniazid and ethambutol. Plasma samples for measurement of drug exposure determined by liquid chromatography tandem-mass spectrometry are obtained at 0, 1, 2, 4, 6, 8, 12 and 24 hours, at day 1 and 14. Maximal drug concentration (C_max) and area under the concentration-time curve (AUC_0-24h) are estimated by non-compartmental analysis. Conditions for early model-informed precision dosing of high-dose pyrazinamide-rifampicin are pharmacometrically explored. Adverse drug effects are monitored throughout the study and graded according to Common Terminology Criteria for Adverse Events V.5.0. Early bactericidal activity is assessed by time to positivity in BACTEC MGIT 960 of induced sputum collected at day 0, 5, 8, 15 and week 8. Minimum inhibitory concentrations of first-line drugs are determined using broth microdilution. Disease severity is assessed with X-ray grading and a validated clinical scoring tool (TBscore II). Clinical outcome is registered according to WHO definitions (2020) in addition to occurrence of relapse after end of treatment. Primary endpoint is pyrazinamide AUC_0-24h and main secondary endpoint is safety.

ETHICS AND DISSEMINATION

The study is approved by the Swedish Ethical Review Authority and the Swedish Medical Products Agency. Informed written consent is collected before study enrolment. The study results will be submitted to a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT04694586.

Performance of Wayne assay for detection of pyrazinamide resistance in Mycobacterium tuberculosis: a meta-analysis study

Conventional culture-based drug susceptibility testing (DST) of Mycobacterium tuberculosis to pyrazinamide (PZA) is time-consuming and difficult to perform. The current systematic review and meta-analysis was aimed to evaluate the diagnostic accuracy of Wayne assay against culture-based DSTs as the reference standard. We searched the MEDLINE/Pubmed, Embase, and Web of Science databases for the relevant records. The QUADAS-2 tool was used to assess the quality of the studies. Diagnostic accuracy measures (i.e., sensitivity and specificity) were pooled with a random-effects model. Statistical analyses were performed with STATA (version 14, Stata Corporation, College Station, TX, USA), RevMan (version 5.3; The Nordic Cochrane Centre, the Cochrane Collaboration, Copenhagen, Denmark), and Meta-DiSc (version 1.4, Cochrane Colloquium, Barcelona, Spain). A total of 31 articles comprising data for 2457 isolates of M. tuberculosis were included in the final analysis. The pooled sensitivity and specificity of the Wayne assay against all reference tests (the combination of BACTEC MGIT 960, BACTEC 460, and proportion method) were 86.6% (95% CI: 84.3-88.7) and 96.0% (95% CI: 94.8-97). The positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and the area under the curve (AUC) estimates were found to be 17.6 (95% CI: 10.5-29.3), 0.11 (95% CI: 0.06-0.20), 164 (95% CI: 83-320) and 97%, respectively. Deek's test result indicated no evidence for publication bias (P > 0.05). Although the current study shows that the Wayne test is sensitive and specific for detecting PZA resistance, it may be used in combination with conventional DSTs to diagnose PZA resistance accurately.