An adamantamine derivative as a drug candidate for the treatment of visceral leishmaniasis.

BACKGROUND: This study aimed to investigate compounds acting on the host cell machinery to impair parasite installation with the possible advantage of limiting drug resistance. The strategy therefore consisted of selecting compounds that are poorly active on the axenic parasite, but very active on the intramacrophage form of Leishmania. OBJECTIVES: To identify a drug candidate from focused screening of adamantamine derivatives that can inhibit the development of Leishmania infantum in macrophages. METHODS: In vitro screening was performed on a library of 142 adamantamine derivatives with axenic and intramacrophage forms of L. infantum, as well as cytotoxicity assays, allowing selection of the most promising compound. Absorption, distribution, metabolism and excretion (ADME) experiments, including pharmacokinetics and microsomal stability, were performed and finally the physicochemical stability of the compound was investigated to assess its suitability for further drug development. RESULTS: VP343 was identified first in vitro, with a CC50 value of 63.7 µM and an IC50 value of 0.32 µM for L. infantum intramacrophage amastigotes and then in vivo, with a 59% reduction of the liver parasite burden after oral administration at 10 mg/kg/day for 5 days. In addition, the ADME data were compatible with moving this compound further through the antileishmanial drug candidate pipeline. CONCLUSIONS: VP343 has the properties of a good drug candidate and merits further investigations.

Inhibitors of retrograde trafficking active against ricin and Shiga toxins also protect cells from several viruses, Leishmania and Chlamydiales.

Medical countermeasures to treat biothreat agent infections require broad-spectrum therapeutics that do not induce agent resistance. A cell-based high-throughput screen (HTS) against ricin toxin combined with hit optimization allowed selection of a family of compounds that meet these requirements. The hit compound Retro-2 and its derivatives have been demonstrated to be safe in vivo in mice even at high doses. Moreover, Retro-2 is an inhibitor of retrograde transport that affects syntaxin-5-dependent toxins and pathogens. As a consequence, it has a broad-spectrum activity that has been demonstrated both in vitro and in vivo against ricin, Shiga toxin-producing O104:H4 entero-hemorrhagic E. coli and Leishmania sp. and in vitro against Ebola, Marburg and poxviruses and Chlamydiales. An effect is anticipated on other toxins or pathogens that use retrograde trafficking and syntaxin-5. Since Retro-2 targets cell components of the host and not directly the pathogen, no selection of resistant pathogens is expected. These lead compounds need now to be developed as drugs for human use.

In vitro and in vivo antileishmanial properties of a 2-n-propylquinoline hydroxypropyl ß-cyclodextrin formulation and pharmacokinetics via intravenous route.

2-n-propylquinoline (2-n-PQ) had shown interesting in vivo antileishmanial activities after administration by oral route on leishmaniasis animal models. However, the lipophilic properties of this compound avoid its use by intravenous route, this route being indicated in cases of severe visceral leishmaniasis with vomiting. Thus, a 2-n-propylquinoline hydroxypropyl beta-cyclodextrin (2-n-PQ-HPC) formulation was set up in this aim. The formulation was active in vitro both on Leishmania donovani axenic and intramacrophage amastigotes with IC50 values at 6.22±0.82µM and 20.01±0.52µM, respectively, without any toxicity on macrophages. 2-n-PQ-HPC exhibited similar activity on WT and drug-resistant parasites. Its in vitro interactions with antimonials, amphotericin B and miltefosine were found as additive both in axenic amastigotes and intramacrophage amastigotes. 2-n-PQ-HPC was not able to generate drug resistance after in vitro drug pressure since the resistance index was less than 4. 2-n-PQ-HPC was also active on the L. donovani/Balb/c mice model with an intravenous treatment regimen at 10mgkg(-1)day(-1) on 10 consecutive days without hepatic, renal and blood toxicity. The pharmacokinetics of 2-n-PQ in rats showed that after an intravenous treatment of the formulation at 10mgkg(-1), the plasma drug concentrations rapidly declined bi-exponentially with a half-life of 58.7min and a total clearance of 18.63lh(-1)kg(-1). The apparent volume of distribution was higher than the blood volume in rats, indicating that 2-n-PQ was well distributed in tissues, allowing parasite elimination. Such a formulation is worth of further antiparasitic and toxicological evaluations.

Selection of the most promising 2-substituted quinoline as antileishmanial candidate for clinical trials.

The antileishmanial evaluation of more than one hundred 2-substituted quinolines led us to identify three compounds for further studies: compound 1 (2-n-propylquinoline), compound 2 (2-(2methoxyethenyl)quinoline) and compound 3 (2-(2-hydroxyprop-2-enyl)quinoline). The final selection of a potential drug candidate was mainly based on chemical stability and acute oral toxicity as discriminating criteria. The most stable compound in various conditions was 2-n-propylquinoline (compound 1). Only reversible toxicity signs were observed for compound 1 at 1000 mg/kg after a treatment by oral route at a single dose and no sign was detected at 100 mg/kg. Interestingly, 2-substituted quinolines were active on a Leishmania donovani line, resistant to sitamaquine, a 8-aminoquinoline, suggesting that 2-substituted quinolines and 8-aminoquinoline probably affect a different target in L. donovani.