Treatment optimisation of multidrug-resistant tuberculosis

A successful treatment outcome is seen in only 60% of persons treated for multidrugresistant tuberculosis (MDR-TB) worldwide, defined as resistance to both rifampicin and isoniazid. To improve these disturbingly low numbers, treatment optimisation is highly needed. Therefore, this thesis will evaluate how to optimise a treatment regimen using both older and repurposed drugs in studies on regimen composition, resistance detection, target attainment for efficacy, and reduction of adverse drug reactions. In the first retrospective observational study (study I), we evaluated the effect of pyrazinamide treatment on end-of-treatment outcomes in a cohort (n=508) of persons affected by MDR-TB in Karakalpakstan, Uzbekistan. We found no evidence (aOR 0.86, 95% CI 0.51-1.44, p=0.6) that pyrazinamide treatment was associated with end-oftreatment outcomes. In study II, pyrazinamide treatment was evaluated using time to sputum culture conversion in a historical Swedish MDR-TB cohort (n=157). We found strong evidence that no pyrazinamide treatment compared to receiving pyrazinamide treatment was associated with a longer time to sputum culture conversion (aHR 0.49, 95% CI 0.29-0.82, p=0.007), when accounting for genotypic drug susceptibility testing (DST). In study III, we assessed the total exposure of moxifloxacin and levofloxacin over the minimum inhibitory concentration of the infecting Mycobacterium tuberculosis strain in persons with MDR-TB in Xiamen (n=32), China. In this prospective observational study, we showed that no participants treated with levofloxacin, and 60-73% receiving moxifloxacin, reached the proposed efficacy targets when dosed according to the Chinese national guidelines. In the last retrospective observational study (study IV), we evaluated risk factors for adverse drug reactions associated with linezolid treatment (n=132) for MDR-TB in Sweden. We found strong evidence that a daily linezolid dose of ≥12 mg/kg was associated with a higher risk of peripheral neuropathy (aHR 2.92, 95% CI 1.09-7.84, p=0.033), anaemia, or leukopenia. Moreover, in an exploratory analysis, a linezolid trough concentration of ≥2 mg/L was associated with a higher risk of anaemia and thrombocytopenia. In conclusion, treatment with pyrazinamide seems to have a role in MDR-TB, at least in terms of improving interim outcomes. The use of genotypic DST is highly promising and may simplify and shorten the time to resistance testing. Adequate dosing of fluoroquinolones is important as underdosing could reduce treatment effects. Linezolid dose adjustment based on weight, or a high trough level might avoid adverse drug reactions. Importantly, dose adjustment needs to consider both efficacy and risk of adverse drug reactions, therefore, therapeutic drug monitoring can be a useful tool in the quest to personalise treatment

Development and validation of a simple LC-MS/MS method for simultaneous determination of moxifloxacin, levofloxacin, prothionamide, pyrazinamide and ethambutol in human plasma

Treatment of multidrug-resistant tuberculosis (MDR-TB) is challenging due to high treatment failure rate and adverse drug events. This study aimed to develop and validate a simple LC-MS/MS method for simultaneous measurement of five TB drugs in human plasma and to facilitate therapeutic drug monitoring (TDM) in MDR-TB treatment to increase efficacy and reduce toxicity. Moxifloxacin, levofloxacin, prothionamide, pyrazinamide and ethambutol were prepared in blank plasma from healthy volunteers and extracted using protein precipitation reagent containing trichloroacetic acid. Separation was achieved on an Atlantis T3 column with gradient of 0.1% formic acid in water and acetonitrile. Drug concentrations were determined by dynamic multiple reaction monitoring in positive ion mode on a LC-MS/MS system. The method was validated according to the United States' Food and Drug Administration (FDA) guideline for bioanalytical method validation. The calibration curves for moxifloxacin, levofloxacin, prothionamide, pyrazinamide and ethambutol were linear, with the correlation coefficient values above 0.993, over a range of 0.1-5, 0.4-40, 0.2-10, 2-100 and 0.2-10 mg/L, respectively. Validation showed the method to be accurate and precise with bias from 6.5% to 18.3% for lower limit of quantification and -5.8% to 14.6% for LOW, medium (MED) and HIGH drug levels, and with coefficient of variations within 11.4% for all levels. Regarding dilution integrity, the bias was within 7.2% and the coefficient of variation was within 14.9%. Matrix effect (95.7%-112.5%) and recovery (91.4%-109.7%) for all drugs could be well compensated by their isotope-labelled internal standards. A benchtop stability test showed that the degradation of prothionamide was over 15% after placement at room temperature for 72 h. Clinical samples (n = 224) from a cohort study were analyzed and all concentrations were within the analytical range. The signal of prothionamide was suppressed in samples with hemolysis which was solved by sample dilution. As the method is robust and sample preparation is simple, it can easily be implemented to facilitate TDM in programmatic MDR-TB treatment

The impact of pyrazinamide resistance on the treatment outcome of patients with multidrug-resistant tuberculosis in Karakalpakstan, Uzbekistan

Pyrazinamide (PZA), is regarded as an important agent in the management of multi-drug resistant tuberculosis (MDR-TB) (defined as resistance to at least rifampicin and isoniazid) and has been shown to reduce treatment duration for drug-sensitive TB (1). Since the inclusion of PZA in a MDR-TB regimen adds significantly to both the pill burden and the side effects, (mainly arthralgia and hepatitis), it is logical to limit usage to patients where PZA has a proven effect. The current World Health Organisation (WHO) recommendation is to include PZA in MDR-TB regimens unless there is demonstrated evidence of resistance (2). However, large-scale data supporting this recommendation are lacking. No evidence was shown of an association between a successful outcome and PZA susceptibility for MDR-TB patients treated with a full intensive phase PZA standard WHO regimen in a high MDR-TB burden setting. Furthermore, there was no evidence of a dose-response association between a successful outcome and different PZA treatment regimens in the intensive phase. The major limitations was the low power for the main analysis and the retrospective and observational nature of the study contributing to an increased risk of bias. A possible explanation for the results might be that PZA treatment mainly has its effect in shortening a regimen (7) instead of improving outcomes or that patients had sufficient likely effective drugs in their regimen. The generalisability would be limited to settings with low HIV prevalence and where there is a high background prevalence of SLD resistance. This study provides provocative but insufficient evidence to warrant changing PZA treatment protocols, although the evidence relating to PZA for the WHO 2016 guideline is weak. Until further evidence emerges supporting these findings, it seems prudent to continue including PZA in standard MDR-TB regimens unless resistance is certain. We recommend research into alternative add-on agents in settings with high PZA resistance

Corrigendum to "Mass spectrometry for therapeutic drug monitoring of anti-tuberculosis drugs" [Clin. Mass Spectrom. 14(Part A) (2019) 34-45]

[This corrects the article DOI: 10.1016/j.clinms.2018.10.002.]

Mass spectrometry for therapeutic drug monitoring of anti-tuberculosis drugs

Therapeutic drug monitoring (TDM) uses drug concentrations, primarily from plasma, to optimize drug dosing. Optimisation of drug dosing may improve treatment outcomes, reduce toxicity and reduce the risk of acquired drug resistance. The aim of this narrative review is to outline and discuss the challenges of developing multi-analyte assays for anti-tuberculosis (TB) drugs using liquid chromatography-tandem mass spectrometry (LC-MS/MS) by reviewing the existing literature in the field. Compared to other analytical methods, LC-MS/MS offers higher sensitivity and selectivity while requiring relatively low sample volumes. Additionally, multi-analyte assays are easier to perform since adequate separation and short run times are possible even when non-selective sample preparation techniques are used. However, challenges still exist, especially when optimizing LC separation techniques for assays that include analytes with differing chemical properties. Here, we have identified seven multi-analyte assays for first-line anti-TB drugs that use various solvents for sample preparation and mobile phase separation. Only two multi-analyte assays for second-line anti-TB drugs were identified (including either nine or 20 analytes), with each using different protein precipitation methods, mobile phases and columns. The 20 analyte assay did not include bedaquiline, delamanid, meropenem or imipenem. For these drugs, other assays with similar methodologies were identified that could be incorporated in the development of a future comprehensive multi-analyte assay. TDM is a powerful methodology for monitoring patient’s individual treatments in TB programmes, but its implementation will require different approaches depending on available resources. Since TB is most-prevalent in low- and middle-income countries where resources are scarce, a patient-centred approach using sampling methods other than large volume blood draws, such as dried blood spots or saliva collection, could facilitate its adoption and use. Regardless of the methodology of collection and analysis, it will be critical that laboratory proficiency programmes are in place to ensure adequate quality control. It is our intent that the information contained in this review will contribute to the process of assembling comprehensive multiplexed assays for the dynamic monitoring of anti-TB drug treatment in affected individuals

Plasma concentrations of second-line antituberculosis drugs in relation to minimum inhibitory concentrations in multidrug-resistant tuberculosis patients in China : a study protocol of a prospective observational cohort study

Individualised treatment through therapeutic drug monitoring (TDM) may improve tuberculosis (TB) treatment outcomes but is not routinely implemented. Prospective clinical studies of drug exposure and minimum inhibitory concentrations (MICs) in multidrug-resistant TB (MDR-TB) are scarce. This translational study aims to characterise the area under the concentration-time curve of individual MDR-TB drugs, divided by the MIC for Mycobacterium tuberculosis isolates, to explore associations with markers of treatment progress and to develop useful strategies for clinical implementation of TDM in MDR-TB. Methods and analysis: Adult patients with pulmonary MDR-TB treated in Xiamen, China, are included. Plasma samples for measure of drug exposure are obtained at 0, 1, 2, 4, 6, 8 and 10 hours after drug intake at week 2 and at 0, 4 and 6 hours during weeks 4 and 8. Sputum samples for evaluating time to culture positivity and MIC determination are collected at days 0, 2 and 7 and at weeks 2, 4, 8 and 12 after treatment initiation. Disease severity are assessed with a clinical scoring tool (TBscore II) and quality of life evaluated using EQ-5D-5L. Drug concentrations of pyrazinamide, ethambutol, levofloxacin, moxifloxacin, cycloserine, prothionamide and para-aminosalicylate are measured by liquid chromatography tandem-mass spectrometry and the levels of amikacin measured by immunoassay. Dried blood spot on filter paper, to facilitate blood sampling for analysis of drug concentrations, is also evaluated. The MICs of the drugs listed above are determined using custom-made broth microdilution plates and MYCOTB plates with Middlebrook 7H9 media. MIC determination of pyrazinamide is performed in BACTEC MGIT 960. Ethics and dissemination: This study has been approved by the ethical review boards of Karolinska Institutet, Sweden and Fudan University, China. Informed written consent is given by participants. The study results will be submitted to a peer-reviewed journal. Trial registration number NCT02816931; Pre-results