In vivo studies on the antileishmanial activity of buparvaquone and its prodrugs.

OBJECTIVES: The efficacy of different formulations of the naphthoquinone buparvaquone and two phosphate prodrugs in in vivo models of both visceral and cutaneous leishmaniasis is described. METHODS: Several topical formulations of buparvaquone containing acceptable excipients were tested in vivo against Leishmania major cutaneous lesions in BALB/c mice. In vivo studies against Leishmania donovani investigated whether the prodrugs had improved efficacy when compared with buparvaquone. RESULTS: Both a hydrous gel and water-in-oil emulsion of buparvaquone significantly reduced cutaneous parasite burden (P < 0.05, 22 days post-infection) and lesion size, compared with the untreated control (P < 0.0001, 16 days post-infection). The prodrug 3-phosphonooxymethyl-buparvaquone was formulated into an anhydrous gel and this also significantly reduced parasite burden and lesion size (P < 0.0001, 16 days post-infection). Histology confirmed this efficacy. In the visceral model, both prodrugs were significantly more effective at reducing liver parasite burden than the parent drug, buparvaquone. Buparvaquone-3-phosphate was shown to be the most effective antileishmanial (P = 0.0003, 50 mg buparvaquone molar equivalent/kg/day five times), reducing the liver parasite burden by approximately 34% when compared with the untreated control. CONCLUSIONS: The introduction of a topical formulation, such as buparvaquone (or its prodrug), would be a significant advance for the treatment of simple cutaneous lesions. In particular, the avoidance of the parenteral antimonials would greatly increase patient compliance and reduce treatment costs.

Topical buparvaquone formulations for the treatment of cutaneous leishmaniasis.

As the part of a study to develop buparvaquone (BPQ) formulations for the treatment of cutaneous leishmaniasis, the topical delivery of BPQ and one of its prodrugs from a range of formulations was evaluated. In previous studies, BPQ and its prodrugs were shown to be potent antileishmanials in-vitro, with ED50 values in the nanomolar range. 3-Phosphono-oxymethyl-buparvaquone (3-POM-BPQ) was the most potent antileishmanial and was chosen, together with the parent drug, for further investigation. The ability of the parent and prodrug formulations to cross human and murine skin was tested in-vitro using the Franz diffusion cells. Formulations intended for topical application containing either BPQ or 3-POM-BPQ were developed using excipients that were either acceptable for topical use (GRAS or FDA inactive ingredients) or currently going through the regulatory process. BPQ was shown to penetrate both human epidermal membranes and full thickness BALB/c skin from a range of formulations (gels, emulsions). Similarly, 3-POM-BPQ penetrated full-thickness BALB/c skin from several gel formulations. In-vitro binding studies showed that BPQ bound melanin in a dose-dependent manner and preferably bound to delipidized skin over untreated BALB/c skin (on a weight to weight basis). The results confirm that BPQ and its prodrug 3-POM-BPQ can penetrate the skin from several formulations, making them potentially interesting candidates for further investigation of topical formulations using in-vivo models of cutaneous leishmaniasis.

In-vitro and in-vivo studies on a topical formulation of sitamaquine dihydrochloride for cutaneous leishmaniasis.

The efficacy of topical formulations of the 8-aminoquinoline, sitamaquine dihydrochloride, in both in-vitro and in in-vivo models of cutaneous leishmaniasis is reported. In-vitro parasite assays confirmed that sitamaquine dihydrochloride was active against a range of Leishmania species that cause either cutaneous or visceral leishmaniasis, with ED50 values against amastigotes over the range of 2.9 to 19.0 microM. A range of topical sitamaquine dihydrochloride formulations (anhydrous gel, emulsions) were developed for studies on experimental cutaneous leishmaniasis using only topically acceptable excipients or those currently undergoing regulatory approval. An uptake study into murine skin confirmed in-vitro skin penetration and retention. Several formulations were tested in-vivo against Leishmania major cutaneous lesions in BALB/c mice. None of the sitamaquine dihydrochloride formulations tested appeared to either slow lesion progression or reduce parasite burden.

Synthesis and antileishmanial activity of novel buparvaquone oxime derivatives.

Novel oxime derivatives (2, 3 and 5) of buparvaquone (1) and O-methyl-buparvaquone (4) were synthesized and their in vitro activities against Leishmania donovani, the causative agent of visceral leishmaniasis (VL), were determined. Buparvaquone-oxime (2) was also studied as a bioreversible prodrug structure of buparvaquone (1). Buparvaquone-oxime (2) released buparvaquone (1) in vitro when it was incubated with induced rat liver microsomes, which suggests that the oxime-structure is a useful prodrug template for developing novel prodrugs of buparvaquone and other hydroxynaphthoquinones. Moreover, the formation of NO(2)(-) , formed via oxidation of NO, was confirmed during the bioconversion. The release of NO from buparvaquone-oxime (2) may provide an additional therapeutic effect in the treatment of leishmaniasis. Buparvaquone-oxime (2) and buparvaquone-O-methyloxime (3) demonstrated moderate activity against amastigotes of the Leishmania species that causes VL. However, the studied oximes (2, 3) most probably did not release buparvaquone (1) and NO during the present in vitro experiment. Further in vivo studies are needed to verify the biological activity of buparvaquone-oximes in the treatment of leishmaniasis.

Synthesis, in vitro evaluation, and antileishmanial activity of water-soluble prodrugs of buparvaquone.

Water-soluble phosphate prodrugs of buparvaquone (1), containing a hydroxynaphthoquinone structure, were synthesized and evaluated in vitro for improved topical and oral drug delivery against cutaneous and visceral leishmaniasis. The successful prodrug synthesis involved a strong base; e.g., sodium hydride. Buparvaquone-3-phosphate (4a) and 3-phosphonooxymethyl-buparvaquone (4b) prodrugs possessed significantly higher aqueous solubilities (>3.5 mg/mL) than the parent drug (

Topical treatment for cutaneous leishmaniasis.

Parenteral pentavalent antimonials remain the standard therapy for cutaneous leishmaniasis. More effective and patient-compliant topical treatments are an important alternative treatment for the localized self-limiting forms of this disease. Two paromomycin ointments are commercially available but their use is limited by either toxicity or lack of efficacy. Other topical formulations have been in clinical trials, but many results have been equivocal and no major breakthroughs have been achieved. The focus of this review is on recent developments in the field of topical treatment for cutaneous leishmaniasis and rational approaches to enhance topical drug absorption.