Fluoroquinolones (FQ) are a first-line antibacterial therapy, used to treat both Gram-negative and Gram-positive bacterial infections. FQ efficacy is achieved by disrupting the bacterial enzymes DNA gyrase and topoisomerase IV. There is extensive SAR analysis of this class of antibiotics – both in terms of microbiological activity1-3 and target-related toxicity. Delafloxacin, a fourth-generation FQ has broad-spectrum activity and reduced FQ-related toxicity. However, it has recently failed a Phase 3 clinical trial for the treatment of N. gonorrhoeae infections due to insufficient efficacy at the dose administered.