The compound TB47 is highly bactericidal against Mycobacterium ulcerans in a Buruli ulcer mouse model

Buruli ulcer (BU) is an emerging infectious disease that causes disfiguring skin ulcers. The causative agent, Mycobacterium ulcerans , secretes toxin called mycolactone that triggers inflammation and immunopathology. Existing treatments are lengthy and consist of drugs developed for tuberculosis. Here, we report that a pyrazolo[1,5-a]pyridine-3-carboxamide, TB47, is highly bactericidal against M. ulcerans both in vitro and in vivo. In the validated mouse model of BU, TB47 alone reduces M. ulcerans burden in mouse footpads by more than 2.5 log 10 CFU compared to the standard BU treatment regimen recommended by the WHO. We show that mutations of ubiquinol-cytochrome C reductase cytochrome subunit B confer resistance to TB47 and the dissimilarity of CydABs from different mycobacteria may account for their differences in susceptibility to TB47. TB47 is highly potent against M. ulcerans and possesses desirable pharmacological attributes and low toxicity that warrant further assessment of this agent for treatment of BU. Combination therapy for Buruli ulcer (BU) is suboptimal. Here, Liu et al. show that the candidate drug TB47 has potent bactericidal activity against Mycobacterium ulcerans in vitro and in a mouse model, which underscores its potential for shortening the course of BU and treating other mycobacterial diseases.