PO-02-210 AAV9-MEDIATED -SUPPRESSION-REPLACEMENT GENE THERAPY IN TRANSGENIC RABBITS WITH TYPE 1 LONG QT SYNDROME

Type 1 long QT syndrome (LQT1) is characterized by both haploinsufficient and dominant-negative loss-of-function pathogenic variants in the KCNQ1-encoded Kv7.1 K+ channels conducting IKs current, which contributes to cardiac action potential. No current therapies target molecular cause of LQT1. To rescue pathologic phenotype transgenic KCNQ1-Y315S LQT1 rabbit model using our proprietary KCNQ1-specific suppression-replacement (SupRep) gene therapy. Our dual component SupRep therapy was created combining into a single construct custom-designed KCNQ1 shRNA (suppression) cardiac-specific troponin C (cTnC) promoter driven shRNA-immune cDNA (replacement). The KCNQ1-SupRep packaged AAV9 (AAV9-KCNQ1-SupRep), nominally immunogenic cardiotropic viral vector with limited off-target delivery. AAV9-KCNQ1-SupRep injected vivo via targeted intra-aortic root injection (1E12 vg/kg bodyweight) during balloon occlusion Swan Ganz catheter. Two weeks post therapy, 12-lead ECGs were assessed adult wildtype (WT) rabbits ascertain effect on rabbit’s QTc. Patch-clamp calcium transient measurements performed isolated ventricular cardiomyocytes (CMs) evaluate CM’s potential duration (APD90) Ca2+ (Ca2+90) expression verified immunohistochemistry. After 3 so far, no statistically significant changes observed rabbits’ QTc pre/post AAV9-KCNQ1-SupRep. However, CMs from that underwent demonstrated pronounced shortening (ms) APD90 Ca2+90 compared controls, leading levels similar WT controls (APD90, 1Hz, 37°: LQT1: 530±18, WT: 445±18, LQT1-SupRep: 375±25, p<0.0001 vs. LQT1-SupRep, p=ns LQT1-SupRep WT) (Ca2+90: 487±23, 346±16, 393±19, WT). In normalizes cellular AP rabbits. Further experiments will be conducted whether this therapeutic correction at CM level translate normalization rest stress testing.