Novel 7-Substituted-1,2,4-Triazolopyrimidines targeting Nav1.2 channels as low-neurotoxicity antiepileptic agents

In pursuit of novel antiepileptic agents with improved safety profiles, a series of novel 7-substituted-[1,2,4]triazolo[1,5-a]pyrimidine derivatives were synthesized and evaluated for antiepileptic activity using the subcutaneous pentylenetetrazole (Sc-PTZ) and maximal electroshock seizure (MES) models in vivo. Compound 6c showed significant antiepileptic effects in the MES model, with an ED₅₀ value of 13.70 mg/kg. Its TD₅₀ was greater than 261.85 mg/kg, yielding a protective index (PI) >19.11. The antiepileptic efficacy of 6c surpassed that of the reference drugs phenytoin and valproate. Notably, 6c exhibited no neurotoxicity at its maximum soluble concentration, indicating a favorable safety profile. Docking and molecular dynamics (MD) simulations revealed stable binding of 6c within the cavity of the Nav1.2 subunit (PDB: 6J8E). Further electrophysiological evaluation demonstrated state-dependent blockade of Nav1.2 channels: at 10 μM, compound 6c inhibited the inactivated state by 65 ± 18 % (n = 3), with dose-dependent inhibition characterized by an IC₅₀ value of 5.39 ± 0.81 μM (n = 5). These results suggest that compound 6c is a promising lead candidate for the development of novel antiepileptic agents with high efficacy and low neurotoxicity. Preliminary in vitro assessment in rat liver microsomes indicated moderate metabolic stability for 6c, supporting its potential for further development.