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 ClassII/III/ or Class IV defined as:
• Gene positive for a pathogenic, likely pathogenic, or VUS mutation in the LMNA gene asdetermined by an accredited clinical laboratory.
• Evidence of cardiac impairment in LVEF <= 50%
• Patient will have an implantable cardioverter defibrillator/cardiac resynchronizationtherapy defibrillator (ICD/CRT-D). ICD implanted at least 4 weeks prior to initiationof study treatment or CRT-D initiated at least 6 months prior to initiation of studytreatment and defibrillation function activated at least 4 weeks prior to initiationof study treatment.
• Class II/III patients must have objective functional impairment evidenced by areduction 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 HeartAssociation (AHA) / American College of Cardiology (ACC) or European Society ofCardiology (ESC) guidelines at the investigator discretion, without change in heartfailure 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 Criteria:

• Presence of other form(s) of cardiomyopathy contributing to HF (eg, inflammatory orinfiltrative cardiomyopathy), clinically significant cardiac anatomic abnormality (eg,LV aneurysm), clinically significant coronary artery disease (eg, coronaryrevascularization, exercise induced angina) or uncorrected, hemodynamicallysignificant (ie, moderate-severe) primary structural valvular disease not due to HF,per investigator judgment.
• Currently receiving intermittent or continuous IV inotrope infusion, or presence of aventricular assist device, or history of prior heart transplantation. Participantslisted for cardiac transplantation may be enrolled provided transplantation is notlikely to occur in the next 6 months.
• Myocardial infarction, cardiac surgical procedures (other than for pacemaker/ICD/CRT-Dimplantation or replacement), acute coronary syndrome, serious systemic infection withevidence of septicemia, or any major surgical procedure requiring general anesthesiawithin 3 months prior to screening.
• Currently receiving or deemed at high risk of requiring chronic renal replacementtherapy (eg, hemodialysis or peritoneal dialysis) within 6 months.
• Initiation of CRT within 6 months prior to screening.
• Treatment with any investigational agent(s) for HF within 35 days prior to Day 1.
• Malignancy that is active or has been diagnosed within 3 years prior to screening,except surgically curatively resected in situ malignancies or surgically cured earlybreast cancer, prostate cancer, skin cancer (basal cell carcinoma, squamous cellcarcinoma), thyroid cancer, or cervical cancer, or, with prior review by the medicalmonitor, other early stage surgically curatively resected malignancies with less thana 20% expected 2 year recurrence rate.
• Non-cardiac condition that limits lifespan to < 1 year.
• Serum positive for hepatitis B surface antigen, viremic hepatitis C, or humanimmunodeficiency virus (HIV) at screening.