Abstract Congestive heart failure (CHF) caused by a loss of cardiac function typically due to infarction (MI) remains the leading cause of death in the West. Current therapies for CHF including heart transplant are highly costly and invasive and still yield five-year mortality rates of 50%. Stem cell therapy for CHF has yielded disappointing results, likely due to inadequate implant engraftment into the host myocardium. The discovery that fibroblasts can be reprogrammed in situ into induced cardiomyocyte-like cells (iCMs) represents a novel myocardial regenerative strategy, but factors shown to induce robust rodent cell transdifferentiation and post-MI recovery have been ineffective in human cells, likely due to epigenetic repression of reprogramming pathways in higher order species. We have elucidated two prototypical “pro-plasticity” reprogramming strategies that significantly enhance human cell cardio-differentiation into contractile iCMs and improve post-MI cardiac function. These involve: 1) epigenetic activation of reprogramming pathways via blockade of the epigenetic regulator p63, using a novel p63 transactivation inhibitory domain (TID) strategy, and 2) using an endothelial cell differentiation factor (e.g., VEGF) to (pre)-induce fibroblasts into a “trans-cellular” intermediary with enhanced cardio-differentiation potential. We have shown that by combining these strategies with simultaneous overexpression of the cardio- differentiation factors Hand2 and Myocardin (i.e., VEGF/TID/H/M) yields four-fold greater human cell reprogramming than other reprogramming cocktails. We have also shown that transient expression adenoviral (Ad) vectors are at least as potent as persistent expression vectors in inducing reprogramming. Given the established safety record for Ad in providing myocardial transgene delivery in human trials, these data support Ad as an ideal vector for human cell reprogramming. We accordingly seek to: 1) validate an Ad-mediated VEGF/TID/H/M cardio-differentiation strategy in vivo, performing dose-response safety and efficacy studies in a rat coronary ligation MI model, and 2) demonstrate the long-term safety and efficacy of this strategy in our rat model. The benchmark for these Phase I aims is sustained (up to six months) >20% increase in post-MI cardiac function. Successful commercialization of this project is supported by: 1) the large end-stage CHF population with limited treatment options, 2) relevant IP available to XyloCor, 3) XyloCor’s clinical development expertise, including its recent Phase 1/2 trial validating the safety of direct myocardial administration of an Ad vector (encoding VEGF) with a backbone identical to that planned for our clinical reprogramming vectors, 4) access to the manufacturing facility (Reithera) that produced this vector, and 5) robust collaboration between XyloCor, Baylor and the laboratory of our co-PI Todd Rosengart, co-founder of XyloCor. Successful completion of these aims will lead to a Phase II proposal for pre-clinical safety and efficacy studies in a (human-surrogate) porcine MI model. These will be used to an FDA filing for a Phase I end-stage CHF trial. These strategies should advance our goal of innovating a new clinical treatment for post-infarction cardiomyopathy in CHF patients.

Lay Summary Congestive heart failure remains the leading cause of death in the West. Current therapies for CHF including heart transplant are highly costly and invasive and still yield five-year mortality rates of 50%. Cell reprogramming represents a novel myocardial regenerative strategy wherein scar cells are re-differentiated into heart muscle cells. XyloCor in collaboration with Baylor College of Medicine possesses novel reprogramming strategies with associated intellectual property rights, clinical development expertise, and commercial gene therapy product manufacturing capabilities to bring to market a novel cardiac gene therapy product that will if successfully developed offer a new therapy for individuals with end stage congestive heart failure.