Repurposing lusutrombopag: unveiling anti-Staphylococcus aureus activity in a novel oral thrombopoietin receptor agonist

Staphylococcus aureus (S. aureus), designated by the World Health Organization (2024) as a high-priority pathogen for hospital-acquired infections, necessitates innovative therapeutics. Drug repurposing has emerged as a pivotal strategy for antimicrobial discovery. To assess the antibacterial efficacy of Lusutrombopag (Lbg) against S. aureus and characterize its mechanism of action. Herein, we discovered Lbg, an FDA-approved thrombopoietin receptor agonist clinically used for thrombocytopenia, as a potent anti-staphylococcal agent. Lbg exhibited activity against methicillin-susceptible and -resistant S. aureus (MSSA/MRSA) clinical isolates, with MIC values of 6.25 ~ 25 µM. Notably, it indicated synergy in combination with erythromycin (FICI = 0.5) and gentamicin (FICI = 0.25) against S. aureus SA113. Proteomic analysis confirmed the downregulation of key virulence factors, such as HrtA, HrtB, and Hly. These findings were further supported by qRT-PCR, which showed corresponding reductions in the transcription levels of these genes. Subsequent in vitro experiments validated the functional impact of these molecular changes: at sub-MIC concentrations, Lbg inhibited biofilm formation and attenuated virulence by suppressing hemolytic activity and staphyloxanthin biosynthesis. Mechanistic studies via Drug Affinity Responsive Target Stability (DARTS) assays indicated ribosomal targeting, with 17 of 44 upregulated proteins being ribosome-related proteins, corresponding to genes such as rplD, rpsR, rpsC and rpsZ. This suggests that Lbg may impair bacterial protein translation, potentially leading to alterations in membrane potential/permeability and a consequent reduction in virulence. Lbg enhanced survival in Galleria mellonella (G. mellonella) infection models and reduced bacterial load in murine pulmonary infection models. Collectively, the dual pharmacological profile of repurposed Lbg, providing both hematological support and direct antimicrobial effects, indicates its potential as a therapeutic approach for MRSA infections.