Efficacy of Meglumine Antimoniate in a Low Polymerization State Orally Administered in a Murine Model of Visceral Leishmaniasis.

Progress toward the improvement of meglumine antimoniate (MA), commercially known as Glucantime, a highly effective but also toxic antileishmanial drug, has been hindered by the lack of knowledge and control of its chemical composition. Here, MA was manipulated chemically with the aim of achieving an orally effective drug. MA compounds were synthesized from either antimony pentachloride (MA-SbCl5) or potassium hexahydroxyantimonate [MA-KSb(OH)6] and prepared under a low polymerization state. These compounds were compared to Glucantime regarding chemical composition, permeation properties across a cellulose membrane and Caco-2 cell monolayer, and uptake by peritoneal macrophages. MA-SbCl5 and MA-KSb(OH)6 were characterized as less polymerized and more permeative 2:2 Sb-meglumine complexes than Glucantime, which consisted of a mixture of 2:3 and 3:3 Sb-meglumine complexes. The antileishmanial activities and hepatic uptake of all compounds were evaluated after oral administration in BALB/c mice infected with Leishmania infantum chagasi, as a model of visceral leishmaniasis (VL). The synthetic MA compounds given at 300 mg Sb/kg of body weight/12 h for 30 days significantly reduced spleen and liver parasite burdens, in contrast to those for Glucantime at the same dose. The greater activity of synthetic compounds could be attributed to their higher intestinal absorption and accumulation efficiency in the liver. MA-SbCl5 given orally was as efficacious as Glucantime by the parenteral route (80 mg Sb/kg/24 h intraperitoneally). These data taken together suggest that treatment with a less-polymerized form of MA by the oral route may be effective for the treatment of VL.

Glycotriazole-peptides derived from the peptide HSP1: synergistic effect of triazole and saccharide rings on the antifungal activity.

This work proposes a strategy that uses solid-phase peptide synthesis associated with copper(I)-catalyzed azide alkyne cycloaddition reaction to promote the glycosylation of an antimicrobial peptide (HSP1) containing a carboxyamidated C-terminus (HSP1-NH2). Two glycotriazole-peptides, namely [p-Glc-trz-G1]HSP1-NH2 and [p-GlcNAc-trz-G1]HSP1-NH2, were prepared using per-O-acetylated azide derivatives of glucose and N-acetylglucosamine in the presence of copper(II) sulfate pentahydrate (CuSO4·5H2O) and sodium ascorbate as a reducing agent. In order to investigate the synergistic action of the carbohydrate motif linked to the triazole-peptide structure, a triazole derivative [trz-G1]HSP1-NH2 was also prepared. A set of biophysical approaches such as DLS, Zeta Potential, SPR and carboxyfluorescein leakage from phospholipid vesicles confirmed higher membrane disruption and lytic activities as well as stronger peptide-LUVs interactions for the glycotriazole-peptides when compared to HSP1-NH2 and to its triazole derivative, which is in accordance with the performed biological assays: whereas HSP1-NH2 presents relatively low and [trz-G1]HSP1-NH2 just moderate fungicidal activity, the glycotriazole-peptides are significantly more effective antifungal agents. In addition, the glycotriazole-peptides and the triazole derivative present strong inhibition effects on ergosterol biosynthesis in Candida albicans, when compared to HSP1-NH2 alone. In conclusion, the increased fungicidal activity of the glycotriazole-peptides seems to be the result of (A) more pronounced membrane-disruptive properties, which is related to the presence of a saccharide ring, together with (B) the inhibition of ergosterol biosynthesis, which seems to be related to the presence of both the monosaccharide and the triazole rings.

Hepatotoxicity of pentavalent antimonial drug: possible role of residual Sb(III) and protective effect of ascorbic acid.

Pentavalent antimonial drugs such as meglumine antimoniate (Glucantime [Glu; Sanofi-Aventis, São Paulo, Brazil]) produce severe side effects, including cardiotoxicity and hepatotoxicity, during the treatment of leishmaniasis. We evaluated the role of residual Sb(III) in the hepatotoxicity of meglumine antimoniate, as well as the protective effect of the antioxidant ascorbic acid (AA) during antimonial chemotherapy in a murine model of visceral leishmaniasis. BALB/c mice infected with Leishmania infantum were treated intraperitoneally at 80 mg of Sb/kg/day with commercial meglumine antimoniate (Glu) or a synthetic meglumine antimoniate with lower Sb(III) level (MA), in association or not with AA (15 mg/kg/day), for a 20-day period. Control groups received saline or saline plus AA. Livers were evaluated for hepatocytes histological alterations, peroxidase activity, and apoptosis. Increased proportions of swollen and apoptotic hepatocytes were observed in animals treated with Glu compared to animals treated with saline or MA. The peroxidase activity was also enhanced in the liver of animals that received Glu. Cotreatment with AA reduced the extent of histological changes, the apoptotic index, and the peroxidase activity to levels corresponding to the control group. Moreover, the association with AA did not affect the hepatic uptake of Sb and the ability of Glu to reduce the liver and spleen parasite loads in infected mice. In conclusion, our data supports the use of pentavalent antimonials with low residue of Sb(III) and the association of pentavalent antimonials with AA, as effective strategies to reduce side effects in antimonial therapy.

Amphiphilic Antimony(V) Complexes for Oral Treatment of Visceral Leishmaniasis.

The need for daily parenteral administration is an important limitation in the clinical use of pentavalent antimonial drugs against leishmaniasis. In this study, amphiphilic antimony(V) complexes were prepared from alkylmethylglucamides (L8 and L10, with carbon chain lengths of 8 and 10, respectively), and their potential for the oral treatment of visceral leishmaniasis (VL) was evaluated. Complexes of Sb and ligand at 1:3 (SbL8 and SbL10) were obtained from the reaction of antimony(V) with L8 and L10, as evidenced by elemental and electrospray ionization-tandem mass spectrometry (ESI-MS) analyses. Fluorescence probing of hydrophobic environment and negative-staining transmission electron microscopy showed that SbL8 forms kinetically stabilized nanoassemblies in water. Pharmacokinetic studies with mice in which the compound was administered by the oral route at 200 mg of Sb/kg of body weight indicated that the SbL8 complex promoted greater and more sustained Sb levels in serum and liver than the levels obtained for the conventional antimonial drug meglumine antimoniate (Glucantime [Glu]). The efficacy of SbL8 and SbL10 administered by the oral route was evaluated in BALB/c mice infected with Leishmania infantum after a daily dose of 200 mg of Sb/kg for 20 days. Both complexes promoted significant reduction in the liver and spleen parasite burdens in relation to those in the saline-treated control group. The extent of parasite suppression (>99.96%) was similar to that achieved after Glu given intraperitoneally at 80 mg of Sb/kg/day. As expected, there was no significant reduction in the parasitic load in the group treated orally with Glu at 200 mg of Sb/(kg day). In conclusion, amphiphilic antimony(V) complexes emerge as an innovative and promising strategy for the oral treatment of VL.

Reduced cardiovascular alterations of tartar emetic administered in long-circulating liposomes in rats.

Trivalent antimonial drugs, including tartar emetic (TA), are known to induce important cardiotoxicity observed by electrocardiographic abnormalities. Liposome encapsulation was found to reduce the overall acute toxicity of TA. The present work investigated the cardiovascular parameters alterations of rats submitted to the treatment with free and encapsulated TA in long-circulating liposomes. Liposomes were made using lipids DSPC, DSPE-PEG and cholesterol. The cardiovascular signals, electrocardiogram (ECG) and arterial blood pressure (AP), were recorded from anaesthetized Wistar rats after intravenous (IV) administration of a single specially high dose (17 mg/kg) of TA in liposomes and in free form. The IV administration of TA solution caused significant increase of QT interval of ECG and significant reduction of AP when compared to the control group. These alterations were not observed when liposomes TA were administered and the profile of ECG and AP data was quite similar to the control groups. In conclusion, a liposomal formulation of TA showed a reduced cardiotoxic profile for TA when compared to the free form.