Tolfenpyrad Derivatives Exhibit Potent Francisella-Specific Antibacterial Activity without Toxicity to Mammalian...

Area of Science:

• Microbiology and Infectious Diseases
• Drug Discovery and Development
• Antimicrobial Resistance

Background:

• Tularemia, caused by *Francisella tularensis*, is an emerging infectious disease with increasing incidence globally.
• Current antibiotics are effective, but the threat of antibiotic resistance necessitates the discovery of novel antimicrobial agents targeting new pathways.
• Tolfenpyrad, an environmental pesticide, exhibits anti-Francisella activity but is unsuitable for *in vivo* use due to toxicity.

Purpose of the Study:

• To modify the pesticide tolfenpyrad into safer and more effective antimicrobial compounds against *Francisella* species.
• To identify novel drug candidates with improved therapeutic windows and reduced toxicity for treating tularemia.

Main Methods:

• Employed a structure-activity relationship approach to design and synthesize tolfenpyrad derivatives.
• Screened a library of synthesized compounds for antibacterial activity against *Francisella* species.
• Evaluated the efficacy of lead compounds in blocking intramacrophage growth of *F. novicida* and pathogenesis in an arthropod infection model.

Main Results:

• Identified several tolfenpyrad analogs with significantly improved antibacterial activity and reduced toxicity compared to the parent compound.
• These novel compounds selectively inhibited the growth of *Francisella* species, without affecting other Gram-negative or Gram-positive bacteria.
• The derived compounds demonstrated efficacy in reducing intramacrophage growth and *in vivo* pathogenesis, targeting the same pathway as tolfenpyrad.

Conclusions:

• Tolfenpyrad-derived compounds represent a new class of antimicrobials specifically targeting *Francisella* species.
• These compounds show potential as viable therapeutic agents for tularemia, warranting further investigation and development.
• The study highlights the successful repurposing of pesticide structures for novel antimicrobial drug discovery.