This clinical trial is focused on studying a condition known as severe hypertriglyceridemia, which is characterized by very high levels of triglycerides in the blood. Triglycerides are a type of fat found in the blood, and having too much can increase the risk of heart disease and other health issues. The study will test a treatment called olezarsen, also known by its code name ISIS 678354. Olezarsen is administered through a subcutaneous injection, which means it is injected under the skin. The study will compare the effects of olezarsen to a placebo, which is an inactive substance used to assess the treatment’s effectiveness.

The purpose of the study is to evaluate how well olezarsen works in reducing the levels of fasting triglycerides from the start of the study. Participants will receive either olezarsen or a placebo and will be monitored over a period of time to see how their triglyceride levels change. The study will also look at other factors, such as changes in certain proteins and cholesterol levels, and the occurrence of any related health events.

Participants in the study will be required to follow a specific diet and lifestyle, and they will continue their current lipid-lowering therapy, which is a treatment to help manage fat levels in the blood. The study will last for about 53 weeks, during which time participants will have regular check-ups to monitor their health and the effects of the treatment. The goal is to determine if olezarsen can effectively lower triglyceride levels and improve overall health outcomes for those with severe hypertriglyceridemia.