Staphylococcus aureus is a rapidly
growing health threat in the U.S., with resistance to several commonly
prescribed treatments. A high-throughput screen identified the antihistamine
terfenadine to possess, previously unreported, antimicrobial activity
against S. aureus and other Gram-positive
bacteria. In an effort to repurpose this drug, structure–activity
relationship studies yielded 84 terfenadine-based analogues with several
modifications providing increased activity versus S.
aureus and other bacterial pathogens, including Mycobacterium tuberculosis. Mechanism of action studies
revealed these compounds to exert their antibacterial effects, at
least in part, through inhibition of the bacterial type II topoisomerases.
This scaffold suffers from hERG liabilities which were not remedied
through this round of optimization; however, given the overall improvement
in activity of the set, terfenadine-based analogues provide a novel
structural class of antimicrobial compounds with potential for further
characterization as part of the continuing process to meet the current
need for new antibiotics.