A bioluminescence-based chemical screen identifies a bactericidal naphthalene scaffold targeting MmpL3 in Mycobacterium abscessus

Mycobacterium abscessus pulmonary disease (Mabs-PD) presents a significant and growing global health threat, particularly in individuals with underlying lung conditions like cystic fibrosis and chronic obstructive pulmonary disease. A key challenge in treating Mabs-PD is the lack of bactericidal antibiotics effective at therapeutically relevant concentrations, underscoring an urgent need for drug discovery. Targeting cell-wall synthesis is a promising approach, as evidenced by the success of broad-spectrum β-lactam antibiotics and the frontline antituberculosis drug isoniazid. However, these agents exhibit limited efficacy against Mabs, often requiring concentrations unachievable in lung tissues. Here, we used a bioluminescence-based whole-cell assay optimized to identify drugs targeting both cell-wall synthesis and the oxidative phosphorylation pathway. Screening a small drug library against Mabs revealed multiple hits, including β-lactam antibiotics, validating the effectiveness of this approach to identify cell wall-targeting agents. Among these, we identified a chemically tractable naphthalene scaffold with potent bactericidal activity. The optimized derivative GM47-1 targets MmpL3, disrupting cell wall integrity, inducing ATP leakage into the extracellular milieu, and uncoupling respiration, predominantly through the cytochrome bcc:aa ₃ branch. Further chemical optimization resulted in a new derivative exhibiting a nanomolar minimum inhibitory concentration, with potent activity against intracellular Mabs and in a zebrafish model of infection. This study offers a promising scaffold for future therapeutic development and highlights the utility of this approach as a rapid assay platform for identifying bactericidal compounds against Mabs.