This study is testing a new gene therapy called AB-1002 for people with non-ischemic heart failure, specifically those with NYHA Class III symptoms. Non-ischemic means the heart failure is not caused by blocked arteries, and NYHA Class III means moderate heart failure symptoms. The study lasts 52 weeks, with a long-term follow-up for 4 more years. Participants will receive the therapy through a procedure called intracoronary infusion, where the treatment is delivered directly into the heart's arteries. This is a placebo-controlled study, meaning some participants will receive a placebo (a substance with no active treatment) to compare results.

• The study requires visits over 5 years, with regular check-ins.
• Participants must be stable on heart medications and meet specific health criteria.
• There are certain risks and eligibility requirements, including age and medical history.

Participants will be randomly placed in one of three groups and must use birth control if they're of childbearing potential. This study does not allow people with specific health conditions. If you have questions or want to join, talk to your doctor.