BACKGROUND:
Despite significant in vitro data that metronidazole is active against Mycobacterium tuberculosis (MTB) maintained under anaerobic conditions, the utility of this agent has not been evaluated carefully in human disease due to lack of efficacy in murine models of tuberculosis (TB). Unlike disease in rodents, however, human disease is characterized by discrete types of lesions including both aerobic (cavities) and anaerobic (caseous necrotic nodules) areas. Recent experiments in non-human primates have demonstrated that closed caseous necrotic lesions are highly anoxic and are, therefore, likely to contain anaerobic bacilli highly susceptible to metronidazole. Recent studies in TB-infected rabbits have shown that metronidazole therapy is highly effective in an animal model that recapitulates this feature of human disease. Both of these studies support the possibility that metronidazole may have unique activity against an anaerobic sub-population of bacilli in human disease. Such sub-populations may be responsible for the extended duration of chemotherapy typically employed in tuberculosis chemotherapy, as anoxic bacteria are highly resistant to the sterilizing effects of front-line tuberculosis agents. One small clinical trial of metronidazole in an Indian population also suggests that this agent may have a significant unappreciated role in the control of human tuberculosis.
AIMS:
The major aim of this study is to evaluate the ability of metronidazole to kill an anaerobic sub-population of Mycobacterium tuberculosis within multi-drug resistant tuberculosis (MDR-TB) patients. In order to address this sub-population in the context of disease, this study combines traditional measurements of drug efficacy, including the rate of sputum clearance of organisms, with a functional imaging technique, \[(18) F\]-fluoro-2-deoxy-D-glucose -positron emission tomography - high-resolution computed tomography (FDG-PET-HRCT) that has not previously been applied to monitoring tuberculosis chemotherapy. In addition, this clinical trial will evaluate the tolerability and preliminary efficacy of metronidazole (500 mg three times a day (t.i.d.) when given in combination with standard second-line antituberculous treatment.
METHODS:
Type of study to be conducted:
Randomized, double-blinded, placebo controlled phase II study.
Population to be Studied:
The study population will be drawn from subjects at the National Masan Tuberculosis Hospital (NMTH), Changwon, Republic of Korea. Subjects presenting at NMTH who have been previously treated with first-line agents and who are multi-drug resistant (MDR), defined as having TB isolates that are resistant to at least isoniazid and rifampicin, and are therefore eligible for second-line antituberculous drug therapy will be included.
Treatment Regimen and Treatment Period(s):
All patients will receive either: (1) an 8-week course of standard second-line agents plus placebo t.i.d., or (2) an 8-week course of standard second-line agents plus 500 mg t.i.d. metronidazole. In total, sixty subjects will be accrued into two cohorts of 30 patients each. After 8 weeks, all subjects will revert to standard of care (SOC) chemotherapy according to normal procedures at NMTH. According to hospital standard of care, patients are continued on second-line medications for 18-24 months following sputum culture conversion.
