Lumacaftor and fexofenadine prevent donepezil-induced LQTS via PHE656-mediated hERG chaperoning

Donepezil (DPZ), a first-line therapeutic agent for Alzheimer's disease, causes acquired long QT syndrome (LQTS) by inhibiting the hERG potassium channel. However, there are no specific countermeasures to prevent or reverse this side effect. This study aimed to investigate whether fexofenadine (FEX) and lumacaftor (LUM) can prevent DPZ-induced cardiotoxicity and elucidate the underlying molecular mechanisms. We employed molecular docking and molecular dynamics simulations to analyze interactions among FEX, LUM, DPZ, and hERG channel. Site-directed mutagenesis (F656V, Y652A) was utilized to validate the specific binding site of the drugs. Western blot, patch-clamp electrophysiology, co-immunoprecipitation and immunofluorescence were used to record hERG current, assess hERG protein expression level and examine the interaction between hERG and molecular chaperones Hsp70/Hsp90. Finally, the reversal effects of FEX and LUM on DPZ-induced QT interval and action potential duration (APD) prolongation were evaluated in guinea pig hearts and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). The study confirmed that DPZ inhibits hERG channel function by specifically binding to the PHE656 site rather than Y652. FEX and LUM competitively occupied the PHE656 binding site, effectively reversing DPZ-induced hERG current suppression. Mechanistically, both compounds restored the DPZ-disrupted interaction between hERG and the Hsp70/Hsp90 chaperone complex, promoting correct folding and trafficking of hERG protein. FEX and LUM significantly antagonized DPZ-induced prolongation of the QT interval and APD₉₀. Collectively, FEX and LUM effectively prevent DPZ-induced cardiotoxicity by competitively binding to the hERG PHE656 site and repairing the Hsp70/Hsp90 chaperone system, offering a novel therapeutic strategy for clinical management of drug-induced LQTS.