Abstract

BACKGROUND: Matrix metalloproteinases (MMPs) are implicated as key regulators of tissue destruction in tuberculosis (TB) and may be a target for host-directed therapy. Here, we conducted a Phase 2 randomized, double-blind, placebo-controlled trial investigating doxycycline, a licensed broad spectrum MMP inhibitor, in pulmonary TB patients. METHODS: Thirty pulmonary TB patients were enrolled within 7 days of initiating anti-TB treatment and randomly assigned to receive either doxycycline 100 mg or placebo twice a day for 14 days in addition to standard care. RESULTS: There were significant changes in the host transcriptome, and suppression of systemic and respiratory markers of tissue destruction with the doxycycline intervention. Whole blood RNA-sequencing demonstrated that doxycycline accelerated restoration of dysregulated gene expression patterns in TB towards normality, with more rapid down-regulation of type I and II interferon and innate immune response genes and concurrent up-regulation of B-cell modules relative to placebo. The effects persisted for 6 weeks after doxycycline was discontinued, concurrent with suppression of plasma MMP-1. In respiratory samples, doxycycline reduced MMP-1, -8, -9, -12 and -13 concentrations, suppressed type I collagen and elastin destruction, and reduced pulmonary cavity volume despite unchanged sputum Mycobacterium tuberculosis loads between the study arms. Two weeks of adjunctive doxycycline with standard anti-TB treatment was well-tolerated, with no serious adverse events related to doxycycline. CONCLUSION: These data demonstrate that adjunctive doxycycline with standard anti-TB treatment suppresses pathological MMPs in pulmonary tuberculosis patients, and suggest that larger studies on adjunctive doxycycline to limit immunopathology in TB are merited.