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 (AUC(0–24)). Quantitative susceptibility of the M. tuberculosis isolate was measured by minimum inhibitory concentrations (MICs). Individual drug AUC(0–24)/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 AUC(0–24)/MIC exposures. RESULTS: Among 290 patients, 62 (21%) experienced treatment failure, including 30 deaths. Moxifloxacin AUC(0–24)/MIC target of 58 was associated with favorable treatment outcome (OR, 3.75; 95% confidence interval, 1.21–11.56; P = .022); levofloxacin AUC(0–24)/MIC of 118.3, clofazimine AUC(0–24)/MIC of 50.5, and pyrazinamide AUC(0–24) 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 AUC(0–24)/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.