Identifying Novel Spiro-Indenoquinoxaline-Pyrrolidine-Based Amyloid Beta Inhibitors in Alzheimer’s Disease from <i>In Silico</i> to <i>In Vitro</i>

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease characterized by memory loss and other cognitive functions. The key hallmarks of AD include extracellular beta-amyloid clumps and intracellular neurofibrillary tau tangles in the neurons. Cholinesterase inhibitors and NMDA-receptor antagonists and their combination are already approved treatments; however, these only give short-term symptom relief. Therefore, new therapeutic techniques and novel drugs are required to combat the century-old AD. This study includes the screening of nine novel small compounds (spiro-indenoquinoxaline-pyrrolidines) via <i>in silico</i> approaches; these compounds have been scrutinized to explore their potential as antiamyloidogenic drugs. Computational tools, including ADMET analysis, molecular docking, and molecular dynamics (MD) simulations, have been used for screening the selected compounds against monomeric peptides of Aβ (Aβ_1-40 and Aβ_1-42) and their oligomeric counterparts, i.e., 6Aβ_9-40 and 6Aβ_1-42. Among the nine molecules screened for this study, ADPR-d reflected the best drug-likeness and negligible toxicity. Further, ADPR-d has the highest binding affinity for all the peptides selected for this study. Additionally, MD simulations of Aβ peptide-ADPR-d complexes confirmed a stable complex formation. <i>In vitro</i> aggregation assay and cell culture studies for Aβ_1-42 also support our <i>in silico</i> findings. The positive findings of the presented study highlight that the ADPR-d molecule may prove to be a potential therapeutic molecule against AD. However, these results would require further <i>in vitro</i> and <i>in vivo</i> analysis before proceeding to clinical settings with these compounds against AD.