A Study of Olezarsen (ISIS 678354) Administered to Participants With Severe Hypertriglyceridemia

Key Inclusion Criteria: * Fasting TG ≥ 500 mg/dL (5.65 mmol/L) at Screening and Qualification * Patients must be on lipid-lowering therapy that should adhere to standard of care (SOC) per local guidelines. Lipid-lowering medications should be optimized and stabilized for at least 4 weeks prior to Screening to minimize changes in these medications during the study. Key Exclusion Criteria: * Hemoglobin A1c (HbA1c) ≥ 9.5% at Screening * Alanine aminotransferase or aspartate aminotransferase \> 3.0 × upper limit of normal * Total bilirubin \> upper limit of normal unless due to Gilbert's syndrome * Estimated GFR \< 30 mL/min/1.73 m\^2