Targeting CHI3L1 in Alzheimer’s Disease: Optimization of G721-0282 and Functional Evaluation in Astrocyte Models

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. <b>G721-0282</b> , 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 <b>G721-0282</b> to enable structure-guided optimization, generating a detailed structure-activity map and prioritizing 24 derivatives. Biophysical analyses identified compound <b>G721-0377</b> as the most promising candidate, with optimized substitutions improving CHI3L1 binding affinity. Compound <b>G721-0377</b> also exhibited favorable pharmacokinetic properties, including improved solubility, balanced permeability, reduced microsomal clearance, and an enhanced cardiac safety margin. Functionally, <b>G721-0377</b> 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 <b>G721-0179</b> and <b>G857-1069</b> showed minimal activity. Collectively, these findings establish <b>G721-0377</b> 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.