Abstract
Alzheimer's disease (AD) involves astrocytic dysfunction characterized by impaired lysosomal activity, defective amyloid clearance, and neuroinflammation, processes strongly regulated by the inflammatory effector CHI3L1. G721-0282 , a reported CHI3L1-binding small molecule with demonstrated modulation of downstream signaling pathways including MAPK and STAT3, provides a validated chemical starting point for targeting CHI3L1-driven astrocytic pathology in AD, but exhibits suboptimal potency and drug-like properties that limit its translational potential. We therefore performed a virtual screening of commercially available analogues of G721-0282 to enable structure-guided optimization, generating a detailed structure-activity map and prioritizing 24 derivatives. Biophysical analyses identified compound G721-0377 as the most promising candidate, with optimized substitutions improving CHI3L1 binding affinity. Compound G721-0377 also exhibited favorable pharmacokinetic properties, including improved solubility, balanced permeability, reduced microsomal clearance, and an enhanced cardiac safety margin. Functionally, G721-0377 uniquely reversed CHI3L1-induced astrocytic dysfunction, restoring amyloid uptake, lysosomal proteolysis and acidification, suppressing CHI3L1 and IL-6 secretion, and inhibiting NF-κB activation to levels comparable to a neutralizing anti-CHI3L1 antibody. In contrast, compounds G721-0179 and G857-1069 showed minimal activity. Collectively, these findings establish G721-0377 as a next-generation CHI3L1 inhibitor with improved affinity, safety, and robust functional efficacy, supporting its further development as a disease-modifying therapeutic for AD.