A Trial to Evaluate OPC 67683 in Participants With Pulmonary Sputum Culture-positive, Multidrug-resistant Tuberculosis (TB)

This is a clinical trial to evaluate the safety and efficacy of OPC-67683 in the treatment of multidrug resistant tuberculosis (MDR TB) for 56 days. In addition to an optimized background regimen (OBR), participants will be randomized to receive:

* 100 mg OPC-67683 twice daily (BID) * 200 mg OPC-67683 BID * Placebo BID

After 56 days participants will complete their optimized background regimen (OBR).

This is a multi center, randomized, double-blinded, stratified, placebo-controlled clinical trial in three parallel groups. Participants will be randomized to one of the following three treatment groups:

* OBR plus 100 mg OPC-67683 BID * OBR plus 200 mg OPC-67683 BID * OBR plus placebo BID

The three treatment groups will comprise approximately 140 participants each (male or female). The trial will consist of the following periods:

* Pre-treatment Period (Visits 1 to 3 \[Day -9 to Day -1\]) * Treatment Period (Visits 4 to 59 \[Days 1 to 56\]) * Post-treatment Period (Visits 60 to 64 \[Days 57 to 84\])

Enrolled participants (those accepted into the screening period of the trial who signed an informed consent form) will be stratified at randomization by extent of pulmonary TB; an equal number of participants with and without cavities visible in the lung fields on baseline chest radiograph will be allocated to each treatment group. A total of approximately 430 male or female participants aged 18 to 64 years, inclusive, with pulmonary, sputum culture-positive MDR TB (TB caused by Mycobacterium tuberculosis strains resistant to at least isoniazid and rifampicin) or with sputum smears positive for acid fast bacilli (AFB) and a positive rapid test for rifampicin resistance on direct sputum within 60 days prior to the expected date of enrollment. Participants with positive AFB smears and a positive rapid rifampicin resistance test will be enrolled as presumptively culture positive and withdrawn as ineligible if they are confirmed to not have sputum culture positive MDR TB.