No abstract

Lipopolysaccharides (LPS), otherwise termed 'endotoxins', are outer-membrane constituents of Gram-negative bacteria. Lipopolysaccharides play a key role in the pathogenesis of 'Septic Shock', a major cause of mortality in the critically ill patient. Therapeutic options aimed at limiting downstream systemic inflammatory processes by targeting lipopolysaccharide do not exist at the present time. We have defined the pharmacophore necessary for small molecules to specifically bind and neutralize LPS and, using animal models of sepsis, have shown that the sequestration of circulatory LPS by small molecules is a therapeutically viable strategy. In this paper, the interactions of a series of acylated homologated spermine compounds with lipopolysaccharide (LPS) have been characterized. The optimal acyl chain length for effective sequestration of LPS was identified to be C 16 for the mono-acyl compounds. The most promising of these compounds, 4e, binds LPS with an ED 50 of 1.37 μM. Nitric oxide production in murine J774A.1 cells, as well as TNF-α in human blood, are inhibited in a dose-dependent manner by 4e at concentrations orders of magnitude lower than toxic doses. Administration of 4e to D-galactosamine-sensitized mice challenged with supralethal doses of LPS provided significant protection against lethality. Potent anti-endotoxic activity, low toxicity, and ease of synthesis render this class of compounds candidate endotoxin-sequestering agents of potential significant therapeutic value.

3,5-bis(4-amidinophenyl)isoxazole (3)-an analogue of 2,5-bis(4-amidinophenyl)furan (furamidine) in which the central furan ring is replaced by isoxazole-and 42 novel analogues were prepared by two general synthetic pathways. The 43 isoxazole derivatives were assayed against Trypanosoma brucei rhodesiense (T. brucei rhodesiense) STIB900, Plasmodium falciparum (P. falciparum) K1, and rat myoblast L6 cells (for cytotoxicity) in vitro. Eleven compounds (3, 13, 16-18, 22, 26, 29, 31, 37, and 41) exhibited antitrypanosomal IC50 values less than 10 nM, five of which displayed cytotoxic indices (ratios of cytotoxic IC50 to antiprotozoal IC50 values) at least 10 times higher than that of furamidine. Eighteen compounds (4-8, 12, 14, 18-22, 25, 26, 28, 29, 32, and 43) were more active against P. falciparum than furamidine, with IC50 values less than 15 nM. Fourteen of these compounds had cytotoxic indices ranging between 10 and 120 times higher than that of furamidine, and five analogues exhibited high selectivity for P. falciparum over T. brucei rhodesiense.

Diamidine 1 (pentamidine) and 65 analogues (2-66) have been tested for in vitro antiprotozoal activities against Trypanosoma brucei rhodesiense, Plasmodium falciparum, and Leishmania donovani, and for cytotoxicity against mammalian cells. Dications 32, 64, and 66 exhibited antitrypanosomal potencies equal or greater than melarsoprol (IC(50) = 4 nM). Nine congeners (2-4, 12, 27, 30, and 64-66) were more active against P. falciparum than artemisinin (IC(50) = 6 nM). Eight compounds (12, 32, 33, 44, 59, 62, 64, and 66) exhibited equal or better antileishmanial activities than 1 (IC(50) = 1.8 microM). Several congeners were more active than 1 in vivo, curing at least 2/4 infected animals in the acute mouse model of trypanosomiasis. The diimidazoline 66 was the most promising compound in the series, showing excellent in vitro activities and high selectivities against T. b. rhodesiense, P. falciparum, and L. donovani combined with high antitrypanosomal efficacy in vivo.