This study is seeking participants with BAG3-associated dilated cardiomyopathy (DCM). BAG3-DCM is a rare genetic disorder. Dilated cardiomyopathy is a condition that causes the heart to have a harder time pumping blood to the rest of the body which can lead to heart failure. Current treatment for BAG3-DCM is focused on improving heart function and preventing advanced heart failure with medicines, procedures and devices.

This study involves gene therapy. This will be the first time that a BAG3 gene containing study drug will be tested in human volunteers. The purpose of this research is to learn whether the investigational gene therapy RP-A701 is safe and effective for patients with BAG3-DCM. Gene therapy involves the addition of one or more genes to your cells to replace a missing gene or correct malfunctioning genes. Investigational means it is not currently approved by the Food and Drug Administration (FDA). RP-A701 will be given as a one time infusion into a vein in your arm.

Participation in this study will last about 2 years and include at least 18 visits including an inpatient hospitalization stay of at least 5 days. Study related procedures include review of your medical records, study drug infusion, immunosuppressant and antibiotic medications, echocardiogram (ultrasound test of your heart) exercise testing, electrocardiogram (recording of your heart's electrical activity), heart biopsy (collecting a piece of heart tissue), cardiac MRI, questionnaires, heart rhythm monitoring and ICD interrogations, and collection of blood, saliva, urine and stool collection. Study related risks related to gene therapy and those related to study procedures including risks of the heart catheterization, radiation, and biopsy, exercise testing, blood draw risks, genetic testing risks, the risk of loss of confidentiality and unknown risks.