Metalloprotease Gp63 targeting novel glycoside exhibits potential antileishmanial activity

Visceral Leishmaniasis (VL) and its aggressive cutaneous exacerbation known as Post Kala-azar Dermal Leishmaniasis (PKDL) cause a huge disease burden in tropics and sub-tropic endemic zones worldwide. Contemporary treatment modalities have been associated with various complications. Encouraged from the recent marked antimalarial effects from plant derived glycosides; here we have chemically synthesized a library of diverse Glycoside derivatives (Gly 1-12) and evaluated their inhibitory efficacy against Ag83 strain of Leishmania donovani. In vitro activity of Glycoside-2 (Gly 2) on promastigote form of Ag83 strain, unravelled its prominent anti-leishmanial property with IC50 value of 1.13μM. In-silico studies also unveiled the efficacy of Gly 2 to bind to the membrane surface of parasite. The toxic effect of Gly 2 causes necrosis like death in promastigote by abrogating its proliferation leading to imbalanced redox homeostasis by disruption of mitochondrial membrane potential. Additionally, Gly 2 treatment demonstrated increased susceptibility of parasites towards complement mediated lysis and displayed strong lethal effect on amastigote-macrophage infection model mimicking pathophysiological condition of body. This lead molecule was quite effective against the clinical on promastigotes form of PKDL strain BS12 with IC50 value of 1.97 μM making it the most suitable drug so far which can target both VL and PKDL simultaneously. Based on the above experimental validations we narrowed our thoughts regarding the potent role of Gly 2 targeting surface protein of L. donovani such as Gp63, a zinc metalloprotease. Further analysis of structure activity relationship (SAR) of these glycoside derivatives, demonstrated exceptional binding affinity of Gly 2 towards Gp63, a zinc metalloprotease of L. donovani ; with strong H-bond interactions of Gly 2 with catalytic domain in the α-helix B region of Gp63. The strong confined interactions between Gly 2 and the target protein Gp63 in a physiologically relevant cellular environment was further assessed by Cellular Thermal Shift Assay (CETSA) which corroborated with our previous results. Taken together, this study reports the serendipitous discovery of glycoside derivative Gly 2 with enhanced leishmanicidal activity and proves to be novel chemotherapeutic prototype against VL and PKDL. Highlights A novel glycoside derivative (Gly 2) targets Gp63 functioning in L. donovani promastigotes, resulting in its abrogated proliferation and severely detabilized redox homeostasis, leading to parasitic death. Structure activity relationship (SAR) analysis revealed exceptional ligandability of Gly 2 towards Gp63 catalytic domain both in silico and in Cellular Thermal Shift Assay (CETSA) based in vitro analysis. Gly 2 treatment exhibited increased parasite susceptibility towards complement mediated lysis and reduced macrophage infection in vitro mimicking the pathophysiological conditions. Gly 2 showed profound antileishmanial activity against the clinical isolates of Post Kala-azar Dermal Leishmaniasis (PKDL).