New drugs against visceral leishmaniasis with mechanisms of action differing from existing treatments and with adequate cost, stability, and properties are urgently needed. No antitubulin drug is currently in the clinic against Leishmania infantum, the causative agent of visceral leishmaniasis in the Mediterranean area. We have designed and synthesized a focused library of 350 compounds against the Leishmania tubulin based on the structure-activity relationship (SAR) and sequence differences between host and parasite. The compounds synthesized are accessible, stable, and appropriately soluble in water. We assayed the library against Leishmania promastigotes, axenic, and intracellular amastigotes and found 0, 8, and 16 active compounds, respectively, with a high success rate against intracellular amastigotes of over 10%, not including the cytotoxic compounds. Five compounds have a similar or better potency than the clinically used miltefosine. 14 compounds showed a host-dependent mechanism of action that might be advantageous as it may render them less susceptible to the development of drug resistance. The active compounds cluster in five chemical classes that provide structure-activity relationships for further hit improvement and facilitate series development. Molecular docking is consistent with the proposed mechanism of action, supported by the observed structure-activity relationships, and suggests a potential extension to other Leishmania species due to sequence similarities. A new family of diarylsulfonamides designed against the parasite tubulins is active against Leishmania infantum and represents a new class of potential drugs with favorable cost, stability, and aqueous solubility for the treatment of visceral leishmaniasis (VL). These results could be extended to other clinically relevant species of Leishmania spp.
Keywords: Amastigote; Leishmania; Sulfonamides; Tubulin.
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