Synthesis and Antichlamydial Activity of Novel Benzylaminophenazines Against Chlamydia trachomatis.

A series of phenazine derivatives with C-3 or C-4 benzylamino substituents were synthesized via Buchwald-Hartwig amination and evaluated for antichlamydial activity against Chlamydia trachomatis serovars L2 and D. All compounds exhibited micromolar inhibitory activity, with compound 7d showing the most potent effect (IC50 < 1 μM) but significant host cell cytotoxicity. In contrast, compounds 5g and 7c demonstrated favorable selectivity, with potent antichlamydial activity and no cytotoxicity at 16 μM. Mechanistic studies revealed that 5g and 7c inhibit Chlamydia through a dual mechanism: they block the initial stage of infection by targeting host cells, and they also interfere with later stages of intracellular reticulate body (RB) development. This represents the first report of phenazine derivatives acting via host cell targeting rather than direct action on elementary bodies (EBs). Structure-activity relationship analyses indicated that the electronic nature and chain length of substituents significantly influence both activity and cytotoxicity. Collectively, these findings identify 5g and 7c as promising lead compounds for the development of novel antichlamydial agents with a unique mechanism of action.