This clinical trial investigates the safety and preliminary effectiveness of YAP101, a gene therapy designed to improve heart function in adults with ischemic heart failure and reduced ejection fraction (HFrEF). Ischemic heart failure, often resulting from a prior heart attack, leads to poor heart function and quality of life. Current treatments are limited, and there is an urgent need for new therapies. YAP101 works by delivering a gene therapy using a specialized vector to heart cells, targeting a pathway involved in heart repair. By temporarily activating heart muscle regeneration, YAP101 aims to restore damaged tissue, reduce scarring, and improve the heart's pumping ability. The study will enroll participants who will receive a one-time dose of YAP101 via a minimally invasive cardiac injection. Researchers will monitor participants over 12 months to assess safety and changes in heart function, exercise tolerance, and quality of life.