Inclusion Criteria:

• Participants ≥ 18 years (or the minimum country specific age of consent if > 18) at Visit 1 (Screen 1). 
• Participants who are willing and able to comply with all scheduled visits, laboratory tests, and other study procedures.
• Documented BAG3 pathogenic or likely pathogenic mutation interpreted according to the American College of Medical Genetics Guidelines. Testing may be conducted during screening in a CLIA or CAP certified laboratory if a mutation has not yet been documented but there is a high clinician suspicion.
• NHYA Class I-IV at screening (Stage B-D).
• LVEF ≤ 50%, except if LVEF 45-50% and NYHA Class I then NT-proBNP must be ≥ 300 ng/dL. LVEF measurement must be within the last 12 months.
• Capable of giving signed informed consent for the study which includes compliance with the requirements and restrictions listed in the ICD and in this protocol.

Exclusion Criteria:

• Acute decompensated HF within 1 month prior to enrollment.
• Any of the following within 3 months prior to screening: MI, cardiac surgical procedures (other than for pacemaker/ICD/CRT-D implantation), acute coronary syndrome, hospitalization for cardiac arrhythmia, serious systemic infection with evidence of septicemia, or any major surgical procedure requiring general anesthesia.
• History of heart transplantation.
• eGFR <30 mL/min/1.73 m^2 (using the CKD-EPI formula)
• Malignancy that is active or has been diagnosed within 3 years prior to screening, except surgically curatively resected in situ malignancies or surgically cured early breast cancer, prostate cancer, skin cancer (basal cell carcinoma, squamous cell carcinoma), thyroid cancer, or cervical cancer, or, with prior review by the medical monitor, other early stage surgically curatively resected malignancies with greater than a 20% expected 2-year recurrence rate.
• Noncardiac condition that limits lifespan to < 1 year.
• Presence of other form(s) of cardiomyopathy contributing to HF (e.g., inflammatory or infiltrative cardiomyopathy), clinically significant cardiac anatomic abnormality (e.g., LV aneurysm), clinically significant coronary artery disease (e.g., coronary revascularization, exercise induced angina) per Investigator judgment or uncorrected, hemodynamically significant (ie, moderate-severe) primary structural valvular disease not due to HF.
• Any severe concurrent disease or condition (e.g., active systemic infection) that, in the judgment of the investigator, would make the participant inappropriate for study participation.
• Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may increase the risk of study participation or, in the investigator’s judgment, make the participant inappropriate for the study.

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 12/15/23. Questions regarding updates should be directed to the study team contact.