Ruthenium-Clotrimazole Complexes as Novel Chemotherapeutic agents against Leishmania major

Currently, only one drug is available for the treatment of Leishmaniasis. For this reason, there is an urgent need to improve the chemotherapeutic methods against Leishmaniasis. Azoles derivatives such as clotrimazole (CTZ) have been found to exert their therapeutic effect through a mechanism involving the inhibition of the biosynthesis of sterols essential for the parasite, blocking the proliferation of parasites by inhibiting the cytochrome P-450 dependent C (14)-demethylation of lanosterol to ergosterol. Ruthenium-CTZ complexes have shown promise in the development of pharmaceutical compounds against this parasite, acting as a transport agent across the parasite’s membrane, and subsequently hydrolyzed to be able to liberate CTZ which later goes on to produce its action as sterol biosynthesis inhibitors.

The viability of L. major promastigotes expressing the LUC gene was measured using ONE-GloTM Luciferase Assay System (Promega), while human osteoblasts viability was assayed using Alamar Blue. To mimic the in vivo infection, murine macrophages were infected with the amastigotes from of L. major, followed by treatment with the Ru-CTZ compounds. The percentage of infected cells and the number of amastigotes were determined using high content imaging and data analysis.

The most efficient derivatives were AM160 and AM162 showing the highest parasite toxicity (LD₅₀ 14.6 nM and 400 nM respectively) and low cytotoxicity for mammalian cells. In the proliferation assay AM160 showed best anti-parasitic effect, IC₇₀= 29.25 nM. 

We concluded that Ru-CTZ compounds present low toxicity for murine macrophages as well as in a murine model against L. major.