TRITON-CM: A Study to Evaluate Nucresiran in Patients With Transthyretin Amyloidosis With Cardiomyopathy

The purpose of this study is to: * Evaluate the efficacy of nucresiran compared to placebo on reducing all-cause mortality and cardiovascular (CV) events * Evaluate the efficacy of nucresiran compared to placebo on additional assessments of CV events and/or death * Evaluate the efficacy of nucresiran compared to placebo on patient-reported health status and health-related quality of life

Inclusion Criteria * Has documented diagnosis of ATTR amyloidosis with cardiomyopathy including those with hereditary ATTR (hATTR) or wild-type ATTR (wATTR) amyloidosis. * Has medical history of heart failure (HF) with at least 1 prior hospitalization for HF or signs and symptoms that require treatment with a diuretic. * Has screening N-terminal prohormone B-type natriuretic peptide (NT-proBNP) \>300 ng/L and \<8500 ng/L; In patients with permanent or persistent atrial fibrillation, screening NT-proBNP \>600 ng/L and \<8500 ng/L. * Patients may be receiving approved TTR stabilizers for ATTR amyloidosis (eg, tafamidis, acoramidis) and may be receiving background therapy for HF at the discretion of the Investigator. Exclusion Criteria * Has New York Heart Association (NYHA) Class IV HF; or NYHA Class III heart failure AND ATTR Amyloidosis Disease Stage 3. * Has a polyneuropathy disability (PND) Score IIIa, IIIb, or IV. * Has an estimated glomerular filtration rate eGFR of \<30 mL/min/1.73m\^2 at screening. * Has received prior or currently receiving TTR-lowering therapy