Rationale and Design of a Phase 3 Study to Evaluate the Efficacy and Safety of ION-682884 in Patients with Transthyretin-Mediated Amyloid Cardiomyopathy (ATTR-CM)

Background: Transthyretin amyloidosis cardiomyopathy (ATTR-CM) is a life-threatening, irreversible condition, which can lead to heart failure (HF) and, ultimately, heart transplant or death. Despite the recent approval in United States of a TTR stabilizer (VYNDAQEL®-tafamidis meglumine;VYNDAMAX™-tafamidis) for the treatment of ATTR-CM, disease progression still occurs. This study aims to determine if treatment with AKCEA-TTR-LRx (ION-682884), an antisense oligonucleotide (ASO), is safe and superior to placebo in reducing the risk of cardiovascular (CV) death or CV clinical events in patients with hereditary (hATTR-CM) or wild-type ATTR-CM (wtATTR-CM). Study Design and Methods: AKCEA-TTR-LRx (ION-682884) is a follow-on compound that incorporates the Ligand-Conjugated Antisense (LICA) technology; in this case, a triantennary N-acetyl galactosamine (GalNAc) moiety which targets the asialoglycoprotein receptors (ASGPR) expressed abundantly on the hepatocyte cell surface. In comparison to inotersen, its parent compound, ION-682884 requires a lower dose and frequency of administration (27-fold smaller; 45mg SC Q4W) to achieve a similar reduction in ATTR, providing greater patient convenience. ION-682884-CS2 (EudraCT No: 2019-002835-27) is a Phase 3 global, double-blind, randomized, placebo-controlled study assessing the efficacy and safety of AKCEA-TTR-LRx (ION-682884) in hATTR-CM or wtATTR-CM patients receiving available background standard of care (SoC) therapy. Approximately 750 patients with a history of HF due to ATTR-CM will be randomized 1:1 to receive AKCEA-TTR-LRx (ION-682884) or placebo administered by subcutaneous injection once every 4 weeks. The main inclusion criteria include confirmed diagnosis of ATTR-CM by tissue biopsy or positive PYP/DPD scan, end-diastolic interventricular septum thickness of >12mm, NT-proBNP >600 pg/mL, NYHA class I-III and 6-minute walk distance (6MWD) >150 m. The main exclusion criteria include estimated glomerular filtration rate (eGFR) < 30 mL/min/1.73m2, platelet count below the low limit of normality and urine protein/creatinine ratio (UPCR) ≥ 1000 mg/g. Patients are allowed to concomitantly receive tafamidis/tafamidis meglumine as SoC for ATTR-CM, if locally approved and available, per physician's discretion. The study consists of a 120-week Treatment Period and a 20-week Post-Treatment Evaluation Period. During each study visit, subjects will undergo laboratory tests, cardiac assessments (echocardiography), and funct