Treatment Protocol of Plozasiran in Adults and Adolescents With FCS

Inclusion Criteria: * Fasting triglycerides (TG) ≥ 880mg/dL that is not sufficiently controlled on standard lipid-lowering therapy * Established diagnosis of FCS based on documented history of fasting TG levels in excess of 1000 mg/dL on repeated testing (for at least 3 prior occasions), and at least one of the following: a supportive genetic test, documented history of recurrent episodes of acute pancreatitis not caused by alcohol or cholelithiasis, documented history of recurrent hospitalizations for severe abdominal pain without other explainable cause, documented history of childhood pancreatitis, family history of hypertriglyceridemia-induced pancreatitis * Willing to follow dietary counseling based on local standard of care, consistent with an intake of ≤ 20 g of fat per day * If on medications for management of type 2 diabetes the dosing regimen must be stable. * Participants of childbearing potential must agree to use a highly effective form of contraception in addition to a male condom during the program and for at least 90 days after the last dose of plozasiran Exclusion Criteria: * Diabetes mellitus with any of the following at Day 1: newly diagnosed within the past 24 weeks, HbA1c ≥9.0% within the past 4 weeks, meaningful medical events relating to poor glycemic control, changes in basal insulin regimen of more than =/- 10 units within 12 weeks if insulin-dependent * Clinical evidence of primary hypothyroidism, primary subclinical hypothyroidism, or secondary hypothyroidism * History of bleeding diathesis or coagulopathy * Current diagnosis of nephrotic syndrome * Eligible to receive any commercially available FDA-approved therapeutic for treatment of FCS unless proven to be ineffective or judged inappropriate by the treating physician * History of acute coronary syndrome events (adults with FCS only) * New York Heart Association Class III or IV heart failure or last known ejection fraction of \<30% (adults with FCS only) * History of stroke, transient ischemic attack, or peripheral artery disease within 24 weeks of first dose (adults with FCS only) Note: Additional inclusion/exclusion criteria may apply per protocol