Integrated computational and biological assays to identify and validate L. donovani homoserine dehydrogenase inhibitors.

The Neglected Tropical Disease (NTD) Leishmaniasis continues to pose a serious global health burden affecting millions globally. Visceral leishmaniasis, one of three clinical forms, can be fatal, if left untreated. Current treatment regimen relies mostly on re-purposed drugs and is limited by toxicity, high cost and the emergence of drug resistance, highlighting the need for safer, targeted therapies. In this study, we characterized Leishmania donovani homoserine dehydrogenase (LdHSD), a crucial enzyme in the aspartate pathway. As no human homolog exists, it represents a promising target for selective therapeutic intervention. LdHSD was purified to homogeneity, characterized biophysically and its activity biochemically assayed. Docking of the substrate (L-homoserine) and the cofactor (NADP+) to the LdHSD homology model identified adjacent but discrete binding pockets. Structure-based virtual screening of the Maybridge Compound Library was subsequently performed and the top 10 substrate-site bound compounds were taken for experimental validation. Two of the three piperidine/piperazine scaffold compounds inhibited LdHSD activity by ∼90 %. These findings highlight the therapeutic potential of targeting LdHSD for the development of novel, selective anti-leishmanial agents and establish a strong foundation for future optimization of these identified inhibitors.