Determining the Association of TTR Stabilizing Therapy With Circulating TTR Amyloid Aggregates Over Time in Patients With ATTR-CM: Longitudinal Biomarker Study

Inclusion Criteria:

• Men and women ages 30-80 who have symptomatic ATTR-CA as determined by a history ofHF (this will be assessed by study personnel and defined as : 1) history ofhospitalization within the previous 12 months for management of HF; 2) an elevatedB-type natriuretic peptide level ≥100 pg/mL or NT-proBNP ≥360 pg/mL within theprevious 12 months; or 3) a clinical diagnosis of HF from a treating clinician)

• ATTR-CA previously diagnosed histologically by amyloid staining and tissue typingwith immunohistochemistry or mass spectrometry or by bone scintigraphy in withoutabnormal M-protein

• TTR gene sequencing confirming the TTR genotype has resulted or is pending

• Enrollment will be stratified by n/N=30/50 starting on-label TTR-stabilizing therapy (e.g. tafamidis) within 5 days after enrollment or by n/N=20/50 of those currentlytaking TTR-stabilizing therapy

Exclusion Criteria:

• Other known causes of cardiomyopathy

• History of light-chain cardiac amyloidosis

• Cardiac transplantation

• Liver transplantation

• Has taken patisiran in the past 90 days, or inotersen in the past 180 days, has evertaken vutrisiran, or is participating in a clinical trial for ATTR treatments

• Estimated glomerular filtration rate ≤30 mL/min/1.73 m2

• Anticipated gaps in ATTR-CA treatment for 3 months after enrollment