Randomized Trial of Metformin With Anti-Tuberculosis Drugs for Early Sputum Conversion in Adults With Pulmonary Tuberculosis

BACKGROUND: Metformin, by reducing intracellular Mycobacterium tuberculosis growth, can be considered an adjunctive therapy to anti-tuberculosis treatment (ATT). We determined whether metformin with standard ATT reduces time to sputum culture conversion and tissue inflammation in adults with pulmonary tuberculosis (PTB). METHODS: In a randomized, 8-week, clinical trial, newly diagnosed, culture-positive PTB patients were randomized to standard ATT (HREZ = control arm) or standard ATT plus daily 1000 mg metformin (MET-HREZ = Metformin with Rifampicin [METRIF] arm) for 8 weeks during 2018–2020 at 5 sites in India. The primary end point was time to sputum culture conversion by liquid culture during 8 weeks of ATT. Plasma inflammatory markers were estimated in a subset. A Cox proportional hazard model was used to estimate time and predictors of culture conversion. RESULTS: Of the 322 patients randomized, 239 (74%) were male, and 212 (66%) had bilateral disease on chest radiograph with 54 (18%) showing cavitation. The median time to sputum culture conversion by liquid culture was 42 days in the METRIF arm and 41 days in the control arm (hazard ratio, 0.8; 95% confidence interval [CI], .624–1.019). After 8 weeks of ATT, cavitary lesions on X-ray (7, 5.3% vs 18, 12.9%; relative risk, 0.42; 95% CI, .18–.96; P = .041) and inflammatory markers were significantly lower in the METRIF arm. Higher body mass index and lower sputum smear grading were associated with faster sputum culture conversion. CONCLUSIONS: The addition of metformin to standard ATT did not hasten sputum culture conversion but diminished excess inflammation, thus reducing lung tissue damage as seen by faster clearance on X-ray and reduced inflammatory markers. CLINICAL TRIALS REGISTRATION: Clinical Trial Registry of India (CTRI/2018/01/011176)