Employing a drug repurposing strategy to identify B-cell lymphoma-2 (BCL-2) inhibitors with anticancer potential: An in silico and in vitro based study

BCL-2 (B-cell lymphoma-2) is a key protein overexpressed in numerous cancers. Further, its association with cancer cell survival, prognosis, and ability to evade apoptosis makes it an important drug target in cancer chemotherapy. Venetoclax (ABP199) is the only FDA-approved BCL-2 inhibitor for chronic lymphocytic leukemia (CLL). Nevertheless, the BCL-2 active domain mutations, toxicity, and chemoresistance associated with ABP199 further dampen its future efficacy and positive outcome. Considering the gap and quest for rapid drug discovery, we applied the drug repurposing utility on the database of 3584 drugs (HY-L066, from MedChemExpress (MCE)) from sources like USFDA, EMA, NMPA, PMDA, and Pharmacopeia to identify a plausible lead with the potency to inhibit BCL-2. The HTVS, followed by molecular docking, mechanics using prime MMGB-SA free energy calculations, and MD simulation, led us to identify Stevioside A as a structural lead for the BCL-2. Stevioside displayed a profound and robust interaction and the binding pose within the receptor catalytic site via hydrogen bonding with the ASP103 (hydroxyl group), GLN99 (via the oxygen atoms), and TYR202. TYR202 was also associated with the π-π stacking with the aromatic ring of stevioside, further stabilizing its orientation and affinity towards the receptor. Furthermore, in western blotting studies, the maximal impact of Stevioside was observed at 750 nM concentration, whereby it halved the BCL-2 expression in comparison to the untreated control. This response was comparable to the venetoclax. The outcome hence presents a scope to explore Stevioside A and other top hits in the biological arena and establish their impact as BCL-2 antagonists.