Repurposing approved drugs targeting Leishmania infantum 5-Methylthioadenosine Phosphorylase as anti-leishmanial candidates

Introduction Drug repurposing is a promising strategy for identifying new treatments against neglected tropical diseases such as leishmaniases, which are endemic in Asia, Africa, the Americas, and Southern Europe, offering the advantages of reduced development time and cost. In this context, computational and biochemical investigation of therapeutic targets plays a key role in guiding the selection of effective drug candidates. Methods In this study, we investigated Leishmania infantum 5′-methylthioadenosine phosphorylase (LiMTAP) as a potential drug target by evaluating criteria defining such targets, including assayability, biochemical properties, and structural features enabling inhibitor selection. Trimeric 3D models of Li MTAP were generated, followed by virtual screening and docking of FDA-approved drugs. A robust miniaturized robotic assay was developed for recombinant Li MTAP to enable biochemical validation. Seven predicted drug candidates were subsequently tested in enzymatic and biological assays. Results Two compounds—Labetalol and Halofuginone—inhibited Li MTAP activity with IC₅₀ values ranging from 200–400 µg/mL. The antileishmanial activity of all seven compounds was evaluated on extracellular promastigotes; four compounds (Dobutamine, Halofuginone, Labetalol, and Pentamidine) showed activity. Pentamidine and Dobutamine did not inhibit Li MTAP despite their anti-promastigote effects. Labetalol exhibited an IC 50 of 29.67 µg/mL against extracellular promastigotes and showed no significant toxicity on THP-1 macrophages at effective doses (CC 50 = 98.29 µg/mL). When tested on intracellular amastigotes, Labetalol demonstrated an IC 50 value of 19.10 µg/mL. Discussion This study confirms the in silico predictions through in vitro validation and highlights repurposed drugs as promising anti- Leishmania candidates .