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BackgroundIn the experimental arm of the OFLOTUB trial, gatifloxacin replaced ethambutol in the standard 4-month regimen for drug-susceptible pulmonary tuberculosis. The study included a nested pharmacokinetic (PK) study. We sought to determine if PK variability played a role in patient outcomes.MethodsPatients recruited in the trial were followed for 24 months, and relapse ascertained using spoligotyping. Blood was drawn for drug concentrations on 2 separate days during the first 2 months of therapy, and compartmental PK analyses was performed. Failure to attain sustained sputum culture conversion at the end of treatment, relapse, or death during follow-up defined therapy failure. In addition to standard statistical analyses, we utilized an ensemble of machine-learning methods to identify patterns and predictors of therapy failure from among 27 clinical and laboratory features.ResultsOf 126 patients, 95 (75%) had favorable outcomes and 19 (15%) failed therapy, relapsed, or died. Pyrazinamide and rifampicin peak concentrations and area under the concentration-time curves (AUCs) were ranked higher (more important) than gatifloxacin AUCs. The distribution of individual drug concentrations and their ranking varied significantly between South African and West African trial sites; however, drug concentrations still accounted for 31% and 75% of variance of outcomes, respectively. We identified a 3-way antagonistic interaction of pyrazinamide, gatifloxacin, and rifampicin concentrations. These negative interactions disappeared if rifampicin peak concentration was above 7 mg/L.ConclusionsConcentration-dependent antagonism contributed to death, relapse, and therapy failure but was abrogated by high rifampicin concentrations. Therefore, increasing both rifampin and gatifloxacin doses could improve outcomes.Clinical trials registrationNCT00216385.

Original publication




Journal article


Clinical infectious diseases : an official publication of the Infectious Diseases Society of America

Publication Date





S284 - S292


Center for Infectious Diseases Research and Experimental Therapeutics, Baylor Research Institute, Baylor University Medical Center, Dallas, Texas.


Humans, Tuberculosis, Pulmonary, Pyrazinamide, Rifampin, Antitubercular Agents, Dose-Response Relationship, Drug, Artificial Intelligence, Adolescent, Adult, Middle Aged, Female, Male, Young Adult, Gatifloxacin