Bacterial DNA topoisomerase IV and DNA gyrase inhibitors: history of the quinolones, their clinical usage and potential alternatives for the future

Bacterial topoisomerases are enzymes critical for maintaining genomic DNA integrity and ensuring bacterial cell survival, making them ideal targets for antibacterial agents. Bacterial topoisomerase inhibitors, such as quinolones and fluoroquinolones, target two enzymes, DNA gyrase and topoisomerase IV, and inhibit the control of DNA supercoiling/decatenation, leading to impaired DNA replication and bacterial cell death. Since their initial discovery, many quinolones and fluoroquinolones have been developed with activity against a wide range of bacterial species, contributing significantly to the treatment of various infectious diseases worldwide. Fluoroquinolones such as levofloxacin and ciprofloxacin remain important and effective therapeutic options today due to their broad-spectrum antibacterial activity, chemical stability and high bioavailability. However, side effects of fluoroquinolones have become a concern, leading to warnings being issued in the United States, Europe and the United Kingdom. Furthermore, in many countries, the prevalence of fluoroquinolone-resistant bacteria has been steadily increasing each year, which poses a serious threat to public health. The clinical development of new non-quinolone bacterial topoisomerase inhibitors (for example, zoliflodacin, gepotidacin and fobrepodacin) offers a promising solution to these issues and has the potential to play a crucial role in combating the growing problem of antimicrobial resistance. This review article will discuss the evolution of quinolone and fluoroquinolone antibacterial agents as key topoisomerase inhibitors, examine their current clinical applications and challenges to future development, and explore the potential of new topoisomerase inhibitors.