SQ109 is an orally active, small molecule antibiotic for treatment of pulmonary T(tuberculosis). In Phase I clinical trials, SQ109 could replace one or more drugs in the current first-line TB drug regimen, simplify therapy, and shorten the TB treatment regimen. SQ109 has excellent in vitro activity against Mycobacterium tuberculosis within a MIC range of 1-0.5 μM (drug susceptible) and drug resistant TB bacteria, including XDR-TB, as well as potent in vivo activity against pulmonary TB alone and with other TB drugs.