Analogs of pentamidine as potential anti-Pneumocystis chemotherapeutics.

A series of 20 pentamidine analogs were prepared using 2 general Schemes that evaluated heteroatoms, sulfobenzene and alkanediamide groups in the aliphatic linker and methoxy substituents attached to the benzene rings for efficacy against the fungal pathogen, Pneumocystis carinii in an ATP bioassay. All but one of the 20 bisamidines reduced the ATP content of the P. carinii over the 72 h of the assay period. The highest activities were associated with the lack of methoxy groups and the presence of the O, N and S heteroatoms. Activity (IC(50)) for compounds 1, 5, 6, 10 ranged from 1.1 to 2.13 μM. The compound 11 with similar activity (1.33 μM), bears a sulfobenzene group at a nitrogen in the aliphatic linker. The alkanediamide-linked bisbenzamidines showed a moderate inhibition of ATP. Generally, the inclusion of a heteroatom in the aliphatic linker and absence of methoxy groups at the benzene rings were associated with higher activities in this assay. Of note, most of the compounds had little to no cytotoxicity in mammalian cell cultures. Although not quite as potent as other pentamidine derivatives, these compounds hold promise for decreased side effects within the mammalian host.