3,5-Dimethyl-4-isoxazoyl selenocyanate as promising agent for the treatment of Leishmania infantum-infected mice.

• This is the first in vivo study of a Se compound in visceral leishmaniasis. • Compound 1 showed high metabolic stability in vitro in mice liver microsomes. • The plasma concentration of 1 remained above the ED 50 for more than 24h. • 1 was well-tolerated in mice at the dose of 1mg/Kg daily administered. • 1 reduced the parasite load in liver, spleen and bone marrow. Compounds 1 and 2 (selenocyanate and diselenide derivatives, respectively) were evaluated for their potential use in vivo against visceral leishmaniasis (VL). Both entities showed low cytoxicity in vitro in Vero and Caco-2 cell lines. However, the compounds were not suitable for their oral administration, since they exhibited poor values of intestinal permeability in vitro. Microsomal stability assays did not show any metabolite for compound 1 after 120 min, whereas 2 was highly metabolized by the enzyme CYP450. Thus, the in vivo efficacy of compound 1 was assessed in a murine model of L. infantum VL. The daily i.v. administration of 1 mg/kg of compound 1 during 5 consecutive days reduced parasite load in liver, spleen and bone marrow (99.2%, 91.7% and 61.4%, respectively) compared to non-treated mice. To the best of our knowledge, this is the first time that a selenium compound has been tested in vivo against VL. Thus, this work evidences the possible usefulness of selenocyanate derivatives for the treatment of this disease. Image, graphical abstract [ABSTRACT FROM AUTHOR]