Synthesis and SAR of alkanediamide-linked bisbenzamidines with anti-trypanosomal and anti-pneumocystis activity.

A series of alkanediamide-linked bisbenzamidines was synthesized and tested in vitro against a drug-sensitive strain of Trypanosoma brucei brucei, a drug-resistant strain of Trypanosoma brucei rhodesiense and Pneumocystiscarinii. Bisbenzamidines linked with longer alkanediamide chains were potent inhibitors of both strains of T. brucei. However, bisbenzamidines linked with shorter alkanediamide chains were the most potent compounds against P. carinii. N,N'-Bis[4-(aminoiminomethyl)phenyl] hexanediamide, 4 displayed potent inhibition (IC50=2-3 nM) against T. brucei and P. carinii, and was non-cytotoxic in the A549 human lung carcinoma cell line. The inhibitory bioactivity was significantly reduced when the amidine groups in 4 were moved from the para to the meta positions or replaced with amides.

A triclosan-ciprofloxacin cross-resistant mutant strain of Staphylococcus aureus displays an alteration in the expression of several cell membrane structural and functional genes.

Triclosan is an antimicrobial agent found in many consumer products. Triclosan inhibits the bacterial fatty acid biosynthetic enzyme, enoyl-ACP reductase (FabI). Decreased susceptibility to triclosan correlates with ciprofloxacin resistance in several bacteria. In these bacteria, resistance to both drugs maps to genes encoding multi-drug efflux pumps. The focus of this study was to determine whether triclosan resistance contributes to ciprofloxacin resistance in Staphylococcus aureus. In S. aureus, triclosan resistance maps to a fabI homolog and ciprofloxacin resistance maps to genes encoding DNA gyrase, topoisomerase IV and to the multi-drug efflux pump, NorA. Using a norA overexpressing mutant, we demonstrated that upregulation of NorA does not lead to triclosan resistance. To further investigate triclosan/ciprofloxacin resistance in S. aureus, we isolated triclosan/ciprofloxacin-resistant mutants. The mutants were screened for mutations in the genes encoding the targets of triclosan and ciprofloxacin. One mutant, JJ5, was wild-type for all sequences analyzed. We next monitored the efflux of triclosan from JJ5 and determined that triclosan resistance in the mutant was not due to active efflux of the drug. Finally, gene expression profiling demonstrated that an alteration in cell membrane structural and functional gene expression is likely responsible for triclosan and ciprofloxacin resistance in JJ5.

Trypanocidal activity of piperazine-linked bisbenzamidines and bisbenzamidoxime, an orally active prodrug.

A series of 32 piperazine-linked bisbenzamidines (and related analogues) were analysed for their in vitro and in vivo trypanocidal activity against a drug-sensitive strain of Trypanosoma brucei brucei and a drug-resistant strain of Trypanosoma brucei rhodesiense. The compounds showed similar potencies against both strains. The most potent compounds were bisbenzamidines substituted at the amidinium nitrogens with a linear pentyl group (8, inhibitory concentration for 50% (IC(50))=1.7-3.0 nM) or cyclic octyl group (17, IC(50)=2.3-4.6 nM). Replacement of the diamidine groups with diamidoxime groups resulted in a prodrug (22) that was effective orally against T. b. brucei-infected mice. Three compounds (7, 11 and 15) provided 100% cure when administered parenterally. The results indicate that the nature of the substituents at the amidinium nitrogens of bisbenzamidines strongly influence their trypanocidal activity.