Drug exposure and susceptibility of second-line drugs correlate with treatment response in patients with multidrug-resistant tuberculosis: a multicentre prospective cohort study in China.

BACKGROUND: Understanding the impact of drug exposure and susceptibility on treatment response of multidrug-resistant tuberculosis (MDR-TB) will help to optimise treatment. This study aimed to investigate the association between drug exposure, susceptibility and response to MDR-TB treatment. METHODS: Drug exposure and susceptibility for second-line drugs were measured for patients with MDR-TB. Multivariate analysis was applied to investigate the impact of drug exposure and susceptibility on sputum culture conversion and treatment outcome. Probability of target attainment was evaluated. Random Forest and CART (Classification and Regression Tree) analysis was used to identify key predictors and their clinical targets among patients on World Health Organization-recommended regimens. RESULTS: Drug exposure and corresponding susceptibility were available for 197 patients with MDR-TB. The probability of target attainment was highly variable, ranging from 0% for ethambutol to 97% for linezolid, while patients with fluoroquinolones above targets had a higher probability of 2-month culture conversion (56.3% versus 28.6%; adjusted OR 2.91, 95% CI 1.42-5.94) and favourable outcome (88.8% versus 68.8%; adjusted OR 2.89, 95% CI 1.16-7.17). Higher exposure values of fluoroquinolones, linezolid and pyrazinamide were associated with earlier sputum culture conversion. CART analysis selected moxifloxacin area under the drug concentration-time curve/minimum inhibitory concentration (AUC0-24h/MIC) of 231 and linezolid AUC0-24h/MIC of 287 as best predictors for 6-month culture conversion in patients receiving identical Group A-based regimens. These associations were confirmed in multivariate analysis. CONCLUSIONS: Our findings indicate that target attainment of TB drugs is associated with response to treatment. The CART-derived thresholds may serve as targets for early dose adjustment in a future randomised controlled study to improve MDR-TB treatment outcome.

Drug Exposure and Minimum Inhibitory Concentration Predict Pulmonary Tuberculosis Treatment Response.

BACKGROUND: Prospective studies correlating pharmacokinetic/pharmacodynamic (PK/PD) indices to clinical responses are urgently needed. This study aimed to find clinically relevant PK/PD thresholds that can be used for treatment optimization. METHODS: Pharmacokinetic sampling and minimum inhibitory concentration (MIC) measurements were performed for patients with culture-confirmed tuberculosis (TB). Classification and regression tree (CART) analysis was applied to obtain PK and/or PD thresholds for first-line drugs predictive of 2-week/month culture conversion, treatment outcome determined at 6-8 months, acute kidney injury (AKI), and drug-induced liver injury (DILI). Least absolute shrinkage and selection operator (LASSO) logistic regression was used for model development and validation. RESULTS: Finally, 168 and 52 patients with TB were included in development and validation cohorts for analysis, respectively. Area under the concentration-time curve (AUC)/MIC below CART-derived thresholds for pyrazinamide of 8.42, pyrazinamide of 2.79, or rifampicin of 435.45 were the predominant predictors of 2-week culture conversion, 2-month culture conversion, or treatment success, respectively. Isoniazid AUC >21.78 mg · h/L or rifampicin AUC >82.01 mg · h/L were predictive of DILI or AKI during TB treatment. The predictive performance of trained LASSO models in the validation cohort was evaluated by receiver operating characteristic curves and ranged from 0.625 to 0.978. CONCLUSIONS: PK/PD indices and drug exposure of TB drugs were associated with clinical outcome and adverse events. The effect of CART-derived thresholds for individualized dosing on treatment outcome should be studied in a randomized controlled trial.