ABSTRACTOPC-167832, an inhibitor of decaprenylphosphoryl-β-d-ribose 2’-oxidase, demonstrated potent antituberculosis activity and a favorable safety profile in preclinical studies. This report describes the first two clinical studies of OPC-167832: (i) a phase I single ascending dose (SAD) and food effects study in healthy participants; and (ii) a 14-day phase I/IIa multiple ascending dose (MAD; 3/10/30/90 mg QD) and early bactericidal activity (EBA) trial in participants with drug-susceptible pulmonary tuberculosis (TB). OPC-167832 was well tolerated at single ascending doses (10 to 480 mg) in healthy participants and multiple ascending doses (3 to 90 mg) in participants with TB. In both populations, nearly all treatment-related adverse events were mild and self-limiting, with headache and pruritus being the most common events. Abnormal electrocardiograms results were rare and clinically insignificant. In the MAD study, OPC-167832 plasma exposure increased in a less than dose-proportional manner, with mean accumulation ratios ranging from 1.26 to 1.56 forCmaxand 1.55 to 2.01 for area under the concentration-time curve from 0 to 24 h (AUC0–24h). Mean terminal half-lives ranged from 15.1 to 23.6 h. Pharmacokinetics (PK) characteristics were comparable to healthy participants. In the food effects study, PK exposure increased by less than ~2-fold under fed conditions compared to the fasted state; minimal differences were observed between standard and high-fat meals. Once-daily OPC-167832 showed 14-day bactericidal activity from 3 mg (log10CFU mean ± standard deviation change from baseline; −1.69 ± 1.15) to 90 mg (−2.08 ± 0.75), while the EBA of Rifafour e-275 was −2.79 ± 0.96. OPC-167832 demonstrated favorable pharmacokinetic and safety profiles, as well as potent EBA in participants with drug-susceptible pulmonary TB.