Inclusion Criteria:
- Male or female.
- Age 18 years or above at the time of signing the informed consent.
- Have an established diagnosis of ATTR-CM (wild-type ATTR [ATTRwt] or variant ATTR [ATTRv]), with cardiac amyloid infiltration, increased left ventricular (LV) wall thickness, and HF.
Note: Target ATTRv recruitment is approximately 15 percent of the study population.
Cardiac amyloid infiltration demonstrated by:
- Cardiac biopsy positive for TTR amyloid, OR
- Grade 2 or 3 cardiac uptake at pyrophosphate (PYP)/diphosphono-1,2-propanodicarboxylic acid (DPD)/ hydroxymethylene diphosphonate (HMDP) scintigraphy with single-photon emission computed tomography (SPECT/CT) combined with an extracardiac biopsy positive for TTR amyloid, OR
- Grade 2 or 3 cardiac uptake at PYP/DPD/HMDP scintigraphy with SPECT/CT combined with normal serum free light chain ratio, and negative serum and urine protein electrophoresis with immunofixation (SPIE & UPIE).
Notes:
- Non-invasive diagnostic pathway will be confirmed by a centralised expert review.
- Bone tracer scintigraphy will be conducted using 99m-technetium (Tc)-labelled pyrophosphate (99mTc-PYP), 99mTc-labelled 3,3-diphosphono-1,2-propanodicarboxylic acid (99mTc-DPD), or 99mTc-labeled hydroxymethylene diphosphonate (99mTc-HMDP).
- Increased LV wall thickness, as assessed by centralised review of echocardiography, showing interventricular septal wall thickness greater than or equal to 12 millimeter (mm).
- Chronic HF (New York Heart Association [NYHA] Class I-IV) requiring ongoing treatment with a loop diuretic with:
- At least 1 documented hospitalisation for HF, OR
- History of HF manifested by signs or symptoms of volume overload or elevated intracardiac pressures (e.g., elevated jugular venous pressure, shortness of breath, signs of pulmonary congestion on x-ray or auscultation, or peripheral oedema).
- Expected to be on stable cardiovascular medical therapy (defined as no greater than 50 percent dose adjustment and no categorical changes of medications), with the exception of diuretics, 4 weeks prior to the randomisation visit.
- Completed more than 50 meters on the 6MWT at screening.
Exclusion Criteria:
- Known or suspected hypersensitivity to study intervention(s) or related products.
- Current or previous participation (dosing with active treatment) in a study for an investigational ATTR depleting drug or ATTR gene editing therapy.
- Total bilirubin greater than 3 times the upper limit of normal (ULN) at screening.
- Current diagnosis or history of amyloid light chain, other non-ATTR amyloidosis, known leptomeningeal amyloidosis, or multiple myeloma.
- HF not primarily caused by ATTR-CM (e.g., due to hypertension, valvular heart disease, or ischemic heart disease in the opinion of the investigator).
- Currently hospitalised or hospitalised within 14 days prior to screening.
- Currently treated with positive inotropic medication.
- Uncorrected, severe, haemodynamically significant, left-sided heart valve disease.
Note: Pre-existing echocardiogram up to 2 years old may be used.
- Acute coronary syndrome, unstable angina, stroke, transient ischemic attack, coronary revascularisation, cardiac device implantation, cardiac valve repair, or major surgery within 60 days of screening.
- Prior solid organ transplant or planned solid organ transplant during the study.
- Left ventricular ejection fraction (LVEF) less than 30 percent as assessed by centralised review of echocardiography.
- Presence or history of malignant neoplasm (other than basal or squamous cell skin cancer, in situ carcinomas of the cervix, carcinoma in situ/high-grade prostatic intraepithelial neoplasia [PIN], low-risk prostate cancer, or on stable therapy for prostate cancer) within 3 years before screening.
- End-stage renal disease (estimated glomerular filtration rate [eGFR] less than 15 mL/min/1.73 m^2 at screening, or chronic/intermittent haemodialysis or peritoneal dialysis).
