Leishmaniasis remains one of the neglected tropical diseases. Repurposing existing drugs has proven to be successful for treating neglected tropical diseases while combination therapy is a strategic alternative for the treatment of infectious diseases. Auranofin, lopinavir/ritonavir, and sorafenib are FDA approved drugs used in the treatment of diverse diseases by acting on different essential biological enzymes.
To evaluate the effects of monotherapy and combined therapies with the three drugs against Leishmania infantum.
We compared the leishmanicidal effects of the three drugs on promastigotes in vitro as regards the parasite count, the drug concentration providing a half-maximal response, and the ultrastructural changes of the parasite. We determined the fractional inhibitory concentration index of combined drugs in two ways, as well as the activity of the three drugs together to establish their synergetic effect.
The monotherapy with the three drugs was effective with auranofin showing the best leishmanicidal effect (EC50=1.5 μM), whereas sorafinib reduced parasite growth at EC50=2.5 μM. The scanning electron microscopy of promastigotes from all treated media showed distortion in the shape with loss of flagella and bleb formation. Acidocalcinosis was evident by transmission electron microscopy with all treatments suggesting apoptosis. Treatment with lopinavir/ritonavir showed signs of autophagy. The two-way combination of the drugs led to additive interactions while the combination of the three drugs showed synergistic action.
Each drug when used as monotherapy against Leishmania spp. was effective, but the combination therapy was more effective than the individual drugs due to the additive or synergistic effects.