A Study of ARRY-371797 (PF-07265803) in Patients With Symptomatic Dilated Cardiomyopathy Due to a Lamin A/C Gene Mutation

Selected Key Inclusion Criteria: * Patients with symptomatic lamin A/C protein (LMNA)-related cardiomyopathy Class II/III/ or Class IV defined as: * Gene positive for a pathogenic, likely pathogenic, or VUS mutation in the LMNA gene as determined by an accredited clinical laboratory. * Evidence of cardiac impairment in LVEF \<= 50% * Patient will have an implantable cardioverter defibrillator/cardiac resynchronization therapy defibrillator (ICD/CRT-D). ICD implanted at least 4 weeks prior to initiation of study treatment or CRT-D initiated at least 6 months prior to initiation of study treatment and defibrillation function activated at least 4 weeks prior to initiation of study treatment. * Class II/III patients must have objective functional impairment evidenced by a reduction in 6-minute walk test (6MWT); a. Screening: 6MWT distance \>100 m but ≤450 m, AND b. Day -1 visit: 6MWT distance \>100 m but ≤485 m, AND c. Baseline visit (Day 1): 6MWT distance \>100 m but ≤485 * Class II/III patients must be stable for at least 3 months * Stable medical and/or device therapy consistent with regional American Heart Association (AHA) / American College of Cardiology (ACC) or European Society of Cardiology (ESC) guidelines at the investigator discretion, without change in heart failure drug(s) dose in the past 1 month. * Patients must meet acceptable hematology, hepatic and renal laboratory values within 35 days prior to Day 1 as specified in the protocol. Selected Key Exclusion Crite…