As a prerequisite to clinical application, we determined the long-term therapeutic effectiveness and safety of adeno-associated viral (AAV) S100A1 gene therapy in a preclinical, large animal model of heart failure. S100A1, a positive inotropic regulator of myocardial contractility, becomes depleted in failing cardiomyocytes in humans and various animal models, and myocardial-targeted S100A1 gene transfer rescues cardiac contractile function by restoring sarcoplasmic reticulum calcium Ca2+ handling in acutely and chronically failing hearts in small animal models. We induced heart failure in domestic pigs by balloon-occlusion of the left circumflex coronary artery, resulting in myocardial infarction. After 2 weeks, when the pigs displayed significant left ventricular contractile dysfunction, we administered through retrograde coronary venous delivery, AAV9-S100A1 to the left ventricular non-infarcted myocardium. AAV9-luciferase and saline treatment served as control. At 14 weeks, both control groups showed significantly decreased myocardial S100A1 protein expression along with progressive deterioration of cardiac performance and left ventricular remodeling. AAV9-S100A1 treatment prevented and reversed this phenotype by restoring cardiac S100A1 protein levels. S100A1 treatment normalized cardiomyocyte Ca2+ cycling, sarcoplasmic reticulum calcium handling and energy homeostasis. Transgene expression was restricted to cardiac tissue and extra-cardiac organ function was uncompromised indicating a favorable safety profile. This translational study shows the pre-clinical feasibility, long-term therapeutic effectiveness and a favorable safety profile of cardiac AAV9-S100A1 gene therapy in a preclinical model of heart failure. Our study presents a strong rational for a clinical trial of S100A1 gene therapy for human heart failure that could potentially complement current strategies to treat end-stage heart failure.

These data--showing sustained amelioration of cardiac function in a post-MI pig HF model--demonstrate the therapeutic potential of βARKct gene therapy for HF.

AAV9-mediated expression of Cre is a promising approach for rapid and efficient conditional cardiac gene knockout in adult mice.

Clinical gene-therapy approaches in cardiology have not fulfilled their promise in randomized, controlled trials, so far, despite striking effects in preclinical models. Lack of clinical success appears not to be related to an unexpected low potency of the therapeutic factors itself in humans, but has rather been attributed to limitations of the vector systems used to transfer the DNA, as well as application modes of the vector itself. Therefore, novel delivery strategies are required with increased efficiency and increased specificity. Recent improvements of vectors using targeting approaches in addition to the development of novel application strategies for cardiac or vascular gene transfer will improve gene delivery in future clinical approaches.