Delafloxacin (developmental code name RX-3341) is a fluoroquinolone antibiotic being developed by Rib-X Pharmaceuticals, Inc. It is more active (lower MIC90) than other quinolones against Gram-positive bacteria such as MRSA. In contrast to most approved fluoroquinolones, which are zwitterionic, delafloxacin has an anionic character, which results in a 10-fold increase in delafloxacin accumulation in both bacteria and cells at acidic pH. This property is believed to confer to delafloxacin an advantage for the eradication of Staphylococcus aureus in acidic environments, including intracellular infections.