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Baloxavir Exhibits Antibacterial Activity Against Staphylococcus aureus by Inhibiting De Novo Purine Biosynthesis

Xue Li1,2,3, Yan Yang4, Penghe Wang1,2

  • 1Beijing Key Laboratory of Technology and Application for Anti-Infective New Drugs Research and Development, Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100050, China.

International Journal of Molecular Sciences
|May 13, 2026
PubMed

Insights

The influenza antiviral baloxavir shows potent antibacterial activity against Staphylococcus aureus, including MRSA. This repurposed drug effectively treats persistent intracellular infections and improves survival rates in mouse models.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Drug Repurposing

Background:

  • Staphylococcus aureus (S. aureus) is a major global health concern, causing significant morbidity and mortality.
  • Persistent and relapsing S. aureus infections present a substantial challenge.
  • There is a need for novel therapeutic strategies against antibiotic-resistant strains like MRSA.

Purpose of the Study:

  • To investigate the antibacterial activity of baloxavir, an influenza antiviral, against S. aureus.
  • To evaluate baloxavir's efficacy in treating intracellular S. aureus infections.
  • To explore the potential of baloxavir as a repurposed drug for S. aureus infections.

Main Methods:

  • In vitro susceptibility testing (MICs) and time-kill assays against MSSA and MRSA.
  • Intracellular S. aureus killing assays in A549 epithelial cells and RAW264.7 macrophages.
  • In vivo efficacy studies in a mouse model of MRSA infection.
  • Transcriptomic analysis to identify molecular mechanisms of action.

Main Results:

  • Baloxavir demonstrated potent activity against MSSA and MRSA (MICs 2-4 μg/mL).
  • Concentration-dependent killing of S. aureus was observed in time-kill assays.
  • Baloxavir effectively reduced intracellular S. aureus in cell lines and improved survival in a mouse model.
  • Downregulation of purine de novo biosynthesis genes (purF, purK) was identified as a key mechanism.

Conclusions:

  • Baloxavir exhibits significant antibacterial activity against S. aureus, including MRSA.
  • The drug is effective against intracellular S. aureus and shows promise in vivo.
  • Baloxavir represents a potential repurposed therapeutic candidate for persistent S. aureus infections.
  • The mechanism involves the downregulation of purine biosynthesis pathways.
Keywords:
Staphylococcus aureusantibacterialbaloxavirintracellularpurine biosynthesis

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