Exploration of larger central ring linkers in furamidine analogues: Synthesis and evaluation of their DNA binding, antiparasitic and fluorescence properties

bWe previously reported the synthesis and biological activity of a series of cationic bis-indoles with potent, broad-spectrum antibacterial properties. Here, we describe mechanism of action studies to test the hypothesis that these compounds bind to DNA and that this target plays an important role in their antibacterial outcome. The results reported here indicate that the bis-indoles bind selectively to DNA at A/T-rich sites, which is correlated with the inhibition of DNA and RNA synthesis in representative Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) organisms. Further, exposure of E. coli and S. aureus to representative bis-indoles resulted in induction of the DNA damage-inducible SOS response. In addition, the bis-indoles were found to be potent inhibitors of cell wall biosynthesis; however, they do not induce the cell wall stress stimulon in S. aureus, suggesting that this pathway is inhibited by an indirect mechanism. In light of these findings, the most likely basis for the observed activities of these compounds is their ability to bind to the minor groove of DNA, resulting in the inhibition of DNA and RNA synthesis and other secondary effects.

Section: As It Was Too Weak) These Values Indi-supporting

confidence: 80%

DNA Targeting as a Likely Mechanism Underlying the Antibacterial Activity of Synthetic Bis-Indole Antibiotics

Opperman

Kwasny

et al. 2016

“…These include more than 2,000 derivatives that include dozens of structural classes with various linkers, prodrug moieties, and physiochemical properties. (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31). Many of these compounds have potency in vitro and in vivo against a variety of parasitic protozoa, including Leishmania spp., Plasmodium falciparum, Trypanosoma cruzi, and T. brucei.…”

mentioning

confidence: 99%

Bis-Benzimidazole Hits against Naegleria fowleri Discovered with New High-Throughput Screens

Rice

Colon

Alp

et al. 2015

Self Cite

Naegleria fowleri is a pathogenic free-living amoeba (FLA) that causes an acute fatal disease known as primary amoebic meningoencephalitis (PAM). The major problem for infections with any pathogenic FLA is a lack of effective therapeutics, since PAM has a case mortality rate approaching 99%. Clearly, new drugs that are potent and have rapid onset of action are needed to enhance the treatment regimens for PAM. Diamidines have demonstrated potency against multiple pathogens, including FLA, and are known to cross the blood-brain barrier to cure other protozoan diseases of the central nervous system. Therefore, amidino derivatives serve as an important chemotype for discovery of new drugs. In this study, we validated two new in vitro assays suitable for medium-or high-throughput drug discovery and used these for N. fowleri. We next screened over 150 amidino derivatives of multiple structural classes and identified two hit series with nM potency that are suitable for further lead optimization as new drugs for this neglected disease. These include both mono-and diamidino derivatives, with the most potent compound (DB173) having a 50% inhibitory concentration (IC 50 ) of 177 nM. Similarly, we identified 10 additional analogues with IC 50 s of <1 M, with many of these having reasonable selectivity indices. The most potent hits were >500 times more potent than pentamidine. In summary, the mono-and diamidino derivatives offer potential for lead optimization to develop new drugs to treat central nervous system infections with N. fowleri. The first report of animal pathogenicity by free-living amoebae (FLA) was by Culbertson et al., who identified Acanthamoeba in necrotic lesions of monkeys and mice (1). He later suggested that FLA causes similar disease in humans. Fowler and Carter reported the first cases of an acute fatal disease caused by Naegleria fowleri in four victims in Australia in 1965 (2). Since the identification of primary amoebic meningoencephalitis (PAM), hundreds of cases have been reported worldwide, including 142 cases in the United States (3-5). Most infections with N. fowleri occur during the summer months, victims usually are symptomatic within 5 days, and the disease is almost always fatal. Infection usually occurs after the victim swam in warm, fresh, or brackish water or from exposure to contaminated tap water associated with the use of Neti pots for nasal irrigation (4-7). Amoebic invasion occurs via disruption of the olfactory mucosa, penetration of organisms into the submucosal nervous plexus, and ultimately passage through the cribriform plate to the frontal lobes of the brain (8, 9). Although most cases of PAM occur in warm climates, such as the southern tier states of the United States, pathogenic amoeba found in thermally polluted water sources, hot springs, and poorly chlorinated pools have been linked to infections (10, 11). Interestingly, most of the PAM cases have been diagnosed in developed countries, including the United States, Australia, and Europe. Although sporadic cases have been d...

“…The diamidines (DB2236, DB2259, DB2260, DB2267) were synthesized using a methodology previously reported (17)(18)(19), and the synthesis of the monoamidines (DB2261, DB2262, DB2263, DB2266, DB2268, DB2269) has been described previously (20) (Fig. 1).…”

Section: Methodsmentioning

confidence: 99%

Phenotypic Screening In Vitro of Novel Aromatic Amidines against Trypanosoma cruzi

Simões-Silva

Nefertiti

Araújo

et al. 2016

The current treatment of Chagas disease (CD), based on nifurtimox and benznidazole (Bz), is unsatisfactory. In this context, we performed the phenotypic in vitro screening of novel mono-and diamidines and drug interaction assays with selected compounds. Ten novel amidines were tested for their activities against bloodstream trypomastigote (BT) and amastigote forms of Trypanosoma cruzi (Y and Tulahuen strains) and their toxicities for mammalian host cells (L929 cells and cardiac cells). Seven of 10 molecules were more active than Bz against BT, with the most active compound being the diamidine DB2267 (50% effective concentration [EC 50 ] ‫؍‬ 0.23 M; selectivity index ‫؍‬ 417), which was 28-fold more active and about 3 times more selective than the standard drug. Five of the six monoamidines were also more active than Bz. The combination of DB2267 and DB2236 in fixed-ratio proportions showed an additive effect (sum of fractional inhibitory concentrations < 4) on BT. Interestingly, when intracellular forms were exposed to DB2267, its activity was dependent on the parasite strain, being effective (EC 50 ‫؍‬ 0.87 ؎ 0.05 M) against a discrete typing unit (DTU) II strain (strain Y) but not against a representative DTU VI strain (strain Tulahuen) even when different vehicles (␤-cyclodextrin and dimethyl sulfoxide) were used. The intrinsic fluorescence of several diamidines allowed their uptake to be studied. Testing of the uptake of DB2236 (inactive) and DB2267 (active) by amastigotes of the Y strain showed that the two compounds were localized intracellularly in different compartments: DB2236 in the cytoplasm and DB2267 in the nucleus. Our present data encourage further studies regarding the activities of amidines and provide information which will help with the identification of novel agents for the treatment of CD.