Abstract Body (Do not enter title and authors here): Introduction
Cardiac reprogramming is a technique to directly convert cardiac fibroblasts into cardiomyocytes to restore heart function under conditions of myocyte loss, such as post-myocardial infarction (MI) heart failure. We have developed a reprogramming gene therapy delivered in a single AAV and previously demonstrated it can improve heart function upon direct open-chest epicardial injection in post-MI mice, rats, or pigs.

Hypothesis
We reasoned that a less invasive delivery of the reprogramming gene therapy via intramyocardial injection catheter would be more clinically relevant and without the risk and burden of surgery, and that placement of the therapy in the peri-infarct zone would be essential for successful treatment.

Methods
We delivered reprogramming gene therapy to pigs 4 weeks after 90-minute coronary occlusion to generate an MI. The therapy was delivered by electrical mapping-enabled intramyocardial injection catheter either around the circumference of the infarct or in a scattered pattern throughout the left ventricle (LV). Cardiac morphology and function were monitored by echocardiography prior to MI, prior to dosing, and every 4 weeks for 16 weeks thereafter.

Results
Animals that received the reprogramming gene therapy delivered to the infarct circumference had improved LV ejection fraction (LVEF) relative to their pre-dose measurement within 8-weeks of treatment. The effect was sustained to the terminal 16-week timepoint. LVEF was improved 10.7% (p<0.01) relative to pre-dose and 17.2% (p=0.01) relative to the saline-treated control group. This group also showed corresponding improvements in LV stroke volume and LV fractional shortening. In contrast, the group dosed in a scattered pattern had LVEF measurements over time that were comparable to saline-injected controls, with none of the animals in this test group showing any improvement in LVEF.

Conclusions
This is the first demonstration that a reprogramming gene therapy can improve heart function when dosed 4 weeks after MI in pigs, which have a human-sized heart, using an intramyocardial injection catheter. Importantly, it also establishes that cardiac reprogramming efficacy is dependent on targeted delivery to the infarct circumference. Our prior studies have shown that this therapy is safe and well tolerated. In sum, these findings support progression of cardiac reprogramming toward the clinic, in combination with an appropriate mapping-enabled intramyocardial injection catheter.