ST-2657, A DUAL G9A/H3R MODULATOR, AMELIORATES BEHAVIORAL DEFICITS, OXIDATIVE STRESS AND NEUROINFLAMMATION AND RESTORES NEUROPLASTICITY IN BTBR MICE MODEL OF AUTISM

Autism spectrum disorder (ASD) involves complex interactions between epigenetic dysregulation and impaired histaminergic signaling. ST-2657, a novel dual-acting compound was designed combining the G9a inhibitor scaffold with histamine H3 receptor (H3R) antagonist properties. Here, we evaluated its multiple therapeutic potential in the BTBR mouse model of ASD. Molecular docking studies confirmed ST-2657's binding affinity to both G9a and H3R targets. Following systemic treatment of BTBR mice with three doses of ST-2657 (2.5, 5, and 10 mg/kg, i.p.) for 21 days, dose-dependent improvements in ASD-like behaviors were observed, with 10 mg/kg showing optimal efficacy. This dose significantly enhanced sociability and social novelty preference in the three-chamber test, reduced repetitive marble-burying behavior, reduced compulsive nestlet shredding behavior, and decreased anxiety-like behavior in elevated plus maze. Moreover, cognitive function improved significantly in Y-maze spontaneous alternation and novel object recognition tests. Cortical brain samples from the optimal dose group revealed reduced pro-inflammatory cytokines (TNF-α, IL-6, IL-1β) and restored oxidative balance (elevated GSH and SOD levels and reduced MDA). Furthermore, immunofluorescence demonstrated significant attenuation of microglial activation via reduced Iba-1 expression. Also, Western blot analysis confirmed ST-2657's multi-targeted effects. Notably, reduced G9a expression and H3K9me2 levels validated epigenetic inhibition, decreased COX-2, iNOS, and NF-κB expression supported anti-neuroinflammatory effects, and restored BDNF levels indicated improved synaptic plasticity. These findings position ST-2657 as a promising structural template for potential multi-targeted ASD therapeutics addressing epigenetic and neuroimmune pathology, warranting further translational assessments.