European heart journal, 30 5 2025, Pages ehaf660 AAV9-mediated KCNH2 suppression-replacement gene therapy in a transgenic rabbit model of type 1 short QT syndrome. Nimani S, Bains S, Alerni N, Ördög B, Horváth A, Matas L, Louradour J, Giammarino L, Tester DJ, Beslac O, Lopez R, Meier S, Egle M, Christoforou N, Barbieri M, Vashanthakumar V, Perez-Feliz S, Parodi C, Garcia Casalta LG, Kim CSJ, Zhou W, Ye D, Jurgensen J, Barry MA, Bego M, Keyes L, Owens J, Pinkstaff J, Christoph J, Zehender M, Brunner M, Heijman J, Casoni D, Praz F, Haeberlin A, Brooks G, Ackerman MJ, Odening KE
Background and aims
Type 1 short QT syndrome (SQT1) is a genetic channelopathy caused by gain-of-function variants in KCNH2. This shortens cardiac repolarization and QT intervals, predisposing patients to ventricular arrhythmias and sudden cardiac death. This study aimed to investigate the therapeutic efficacy of KCNH2-specific suppression-and-replacement (KCNH2-SupRep) gene therapy in a transgenic rabbit model of SQT1.
Methods
KCNH2-SupRep was developed by combining a KCNH2-shRNA with its corresponding shRNA-immune KCNH2-cDNA into an AAV9 vector, delivered directly into the aortic root (1x1010 vg/kg). Therapeutic efficacy was evaluated in vivo by electrocardiogram, ex vivo by optical mapping, and at cellular levels by patch-clamp, calcium imaging, and qPCR in ventricular cardiomyocytes (VCMs).
Results
In vivo, KCNH2-SupRep normalized the heart rate-corrected QT (QTc) in SQT1 rabbits, without affecting repolarization heterogeneity. Ex vivo, KCNH2-SupRep corrected the action potential duration (APD90) and resolved the increased apicobasal APD90 heterogeneity observed in untreated (UT)-SQT1 hearts, supporting an antiarrhythmic effect, which was further validated by reduced re-entry formation in silico. At cellular levels, KCNH2-SupRep prolonged APD90 in VCMs from SupRep-SQT1 rabbits closer to wildtype levels compared to UT- and sham-SQT1. Additionally, KCNH2-SupRep restored the cellular surrogate of the electro-mechanical window and normalized IKr in nearly 50% of VCMs, in line with a 50-60% suppression of the mutant KCNH2 transcript.
Conclusions
This proof-of-concept study is the first to demonstrate the efficacy of gene therapy for SQT1 in a medium-sized animal model. KCNH2-SupRep gene therapy successfully corrected the pathologic phenotype in vivo, ex vivo and at cellular levels in transgenic SQT1 rabbits.
