This is a Phase 1/2, open-label, dose-exploration and dose-expansion, clinical trial evaluating the safety, tolerability, pharmacodynamics, and preliminary efficacy of a single intravenous infusion of AFTX-201 in adults with dilated cardiomyopathy caused by a BAG3 gene mutation

Participants will receive a single intravenous infusion of AFTX-201 and will be followed for safety and clinical assessments. The study includes short-term safety monitoring and long-term follow-up for up to 60 months

Inclusion Criteria:

Male or female, 18 to 55 years of age

Truncating mutation in BAG3

Dilated cardiomyopathy with left ventricular ejection fraction (LVEF) < 45%

NYHA Class II or III heart failure symptoms

NT-proBNP ≥ 300 pg/mL for subjects in sinus rhythm or paced rhythm, or ≥ 600 pg/mL for subjects in atrial fibrillation

Willing and able to sign informed consent and comply with study procedures

Exclusion Criteria:

Prior myocardial infarction, heart transplant, or presence/requirement of a left ventricular assist device (LVAD)

IV therapy with positive inotropes, vasodilators, or diuretics for heart failure within 30 days prior to enrollment

Positive neutralizing antibodies to ATC-0187

Any condition that, in the investigator's opinion, would place the subject at undue risk or interfere with study participation or interpretation of results