AAV-Mediated Delivery of Plakophilin-2a Arrests Progression of Arrhythmogenic Right Ventricular Cardiomyopathy in Murine Hearts: Preclinical Evidence Supporting Gene Therapy in Humans

Abstract

BACKGROUND: Pathogenic variants in PKP2 (plakophilin-2) cause arrhythmogenic right ventricular cardiomyopathy, a disease characterized by life-threatening arrhythmias and progressive cardiomyopathy leading to heart failure. No effective medical therapy is available to prevent and arrest the disease. We tested the hypothesis that adeno-associated virus vector–mediated delivery of the human PKP2 gene to an adult mammalian heart deficient in PKP2 can arrest disease progression and significantly prolong survival. METHODS: Experiments were performed using a PKP2-cKO (cardiac-specific, tamoxifen-activated deletion of plakophilin-2). The potential therapeutic, adeno-associated virus vector of serotype rh.74 (AAVrh.74)-PKP2a (PKP2 variant A; RP-A601) is a recombinant AAVrh.74 gene therapy viral vector encoding the human PKP2a. AAVrh.74-PKP2a was delivered to adult mice by a single tail vein injection either before or after tamoxifen-activated PKP2-cKO. PKP2 expression was confirmed by molecular and histopathologic analyses. Cardiac function and disease progression were monitored by survival analyses, echocardiography, and electrocardiography. RESULTS: Consistent with prior findings, loss of PKP2 expression caused 100% mortality within 50 days after tamoxifen injection. In contrast, AAVrh.74-PKP2a–mediated PKP2a expression resulted in 100% survival for >5 months (at study termination). Echocardiographic analysis revealed that AAVrh.74-PKP2a prevented right ventricle dilation, arrested left ventricle functional decline, and mitigated arrhythmia burden. Molecular and histological analyses showed AAVrh.74-PKP2a–mediated transgene mRNA and protein expression and appropriate PKP2 localization at the cardiomyocyte intercalated disc. Importantly, the therapeutic benefit was shown in mice receiving AAVrh.74-PKP2a after disease onset. CONCLUSIONS: These preclinical data demonstrate the potential for AAVrh.74-PKP2a (RP-A601) as a therapeutic for PKP2-related arrhythmogenic right ventricular cardiomyopathy in both early and more advanced stages of the disease.

Crossing the Threshold of Therapeutic Hope for Patients With PKP2 Arrhythmogenic Cardiomyopathy

“…Two recently published studies echo the promising outcomes of van Opbergen et al, 3 reinforcing the groundwork for clinical translation of PKP2 replacement by gene therapy. Bradford et al, 5 utilized a genetically modified mouse with a mutation equivalent to the human splice site variant IVS10-1G>C. They used a cardiotropic rAAV9 vector and an expression cassette with a cTnT promoter expressing wild-type mouse PKP2 gene.…”

“…To date, 3 AAV-mediated gene therapies for PKP2-ACM have US FDA approval for advancing into a phase 1 clinical trials. Among these is RP-A601, the therapeutic used in the study by van Opbergen et al, 3 utilizing rAAVrh.74-hPKP2a as the investigational new drug. The other products are LX2020, the rAAV9-PKP2 used by Bradford et al, 5 and TN-401, a rAAV9-PKP2 variant developed by Tenaya Therapeutics, Inc. 10 This progress to regulatory approval highlights the increasing recognition and validation of AAV-mediated gene therapy as a promising novel treatment for cardiac genetic disorders with an otherwise grim prognosis.…”

Exploring the Therapeutic Potential of Gene Therapy in Arrhythmogenic Right Ventricular Cardiomyopathy

“…The study conducted by van Opbergen et al [ 27 ] further reinforces the importance of careful vector design in AAV-mediated gene therapy for ARVC. To achieve an enhanced targeting of the heart, they utilised an rAAVrh.74 vector, recognised for its preferential binding to striated muscle, in conjunction with the cardiac-specific cTnT promoter to control expression of the human PKP2 transcript variant A ( hPKP2a ).…”

Animal Models and Molecular Pathogenesis of Arrhythmogenic Cardiomyopathy Associated with Pathogenic Variants in Intercalated Disc Genes

“…Accordingly, some of the models described in this review were used to test the efficacy of AAV-mediated therapeutic approaches; this type of therapy could be decisive in patients presenting genetic variants resulting in haploinsufficiency, such as ACM patients manifesting alterations in PKP2 gene. For example, PKP2 restoration carried out via AAV administration of the WT form of either the murine or human gene in knock-in or knockout mouse models previously characterized revealed positive effects, arresting of the disease, or prevention pathogenic manifestations [ 34 , 94 , 95 ]. Furthermore, the gene therapy approach demonstrated a dose-dependent efficacy in preventing the disease development when administrated before evident significant structural changes [ 96 ]; AAV administration after a few weeks of conditional Pkp2 cardiomyocyte deletion, when structural effects have occurred, prevented further decline of heart functionality and reduced mortality [ 96 ].…”