 The TBTC performed phase 2 studies to assess the antimicrobial safety and efficacy of daily rifapentine administered with isoniazid, pyrazinamide, and ethambutol for pulmonary TB treatment. In Study 29, adults n 531 who had sputum-smear-positive pulmonary TB were randomized to receive rifapentine 10 mgkgdose or rifampin 10 mgkgdose without food, 5 days per week for 8 weeks, with isoniazid, pyrazinamide, and ethambutol. This study showed no significant difference in antimicrobial activity between regimens, based on the surrogate marker of culture status at completion of the intensive phase culture conversion on solid media: rifampin group, 83; rifapentine group, 86 culture conversion in liquid media: rifampin group, 65; rifapentine group, 68. The rifapentine regimen was well tolerated, and similar proportions of participants between groups discontinued the assigned treatment overall rifampin group, 16; rifapentine group, 15 or because of toxicity rifampin group, 1.2; rifapentine group, 1.5. There were no differences in proportions of participants between treatment groups who had a serious adverse event related to study treatment rifampin group, 0.4; rifapentine group, 1.1 or type or severity of adverse events between groups. The investigators concluded that the rifapentine regimen given on an empty stomach 5 daysweek for 8 weeks was safe and well tolerated but not significantly more active than rifampin-based therapy. 