Efficacy and Safety of a 4-Drug Fixed-Dose Combination Regimen Compared With Separate Drugs for Treatment of Pulmonary Tuberculosis The Study C Randomized Controlled Trial

Context Fixed-dose combinations (FDCs) of drugs for treatment of tuberculosis have been advocated to prevent the emergence of drug resistance. Objective To assess the efficacy and safety of a 4-drug FDC for the treatment of tuberculosis. Design, Setting, and Patients The Study C trial, a parallel-group, open-label, noninferiority, randomized controlled trial conducted in 11 sites in Africa, Asia, and Latin America between 2003 and 2008. Patients were 1585 adults with newly diagnosed smear-positive pulmonary tuberculosis. Interventions Patients were randomized to receive daily treatment with 4 drugs (rifampicin, isoniazid, pyrazinamide, ethambutol) given as an FDC (n=798 patients) or separately (n=787) in the 8-week intensive phase of treatment. Main Outcome Measure Favorable treatment outcome, defined as negative culture result at 18 months post randomization and not having already been classified as unfavorable. Noninferiority was dependent on consistent results from a per-protocol and modified intention-to-treat analysis, using 2 different models for the latter, classifying all changes of treatment or refusal to continue treatment (eg, bacteriological failure/relapse, adverse event, default, drug resistance) as unfavorable (model 1) and classifying changes of treatment for reasons other than therapeutic outcomes according to their 18-month bacteriological outcome if available (post hoc model 2). The prespecified noninferiority margin was 4%. Results In the per-protocol analysis, 555 of 591 patients (93.9%) had a favorable outcome in the FDC group vs 548 of 579 (94.6%) in the separate-drugs group (risk difference, -0.7% [90% confidence interval {CI}, -3.0% to 1.5%]). In the model 1 analysis, 570 of 684 patients (83.3%) had a favorable outcome in the FDC group vs 563 of 664 (84.8%) in the separate-drugs group (risk difference, -1.5% [90% CI, -4.7% to 1.8%]). In the post hoc model 2 analysis, 591 of 658 patients (89.8%) in the FDC group and 589 of 647 (91.0%) in the separate-drugs group had a favorable outcome (risk difference, -1.2% [90% CI, -3.9% to 1.5%]). Adverse events related to trial drugs were similarly distributed among treatment groups. Conclusions Compared with a regimen of separately administered drugs, a 4-drug FDC regimen for treatment of tuberculosis satisfied prespecified noninferiority criteria in 2 of 3 analyses. Although the results do not demonstrate full noninferiority of the FDCs compared with single drugs given separately using the strict definition applied in this trial, use of FDCs is preferred because of potential advantages associated with the administration of FDCs compared with separate-drug formulations.