A Study of Olezarsen for the Treatment of Familial Chylomicronemia Syndrome (FCS) in Pediatric Participants

This is a Phase 3 multi-center open-label study to evaluate safety, pharmacokinetics (PK), efficacy, and pharmacodynamics (PD) of olezarsen in pediatric participants (aged 2 to less than (<)18 years) with FCS. This study consists of three to four periods with the following approximate timeframes: 1-month screening period, 1-year treatment period, an optional 1-year long-term extension treatment period, and a 3-month post-treatment follow-up period.

Key Inclusion Criteria:

• Parental or legally authorized representative consent must be obtained, and the participants must provide age-appropriate or cognition-appropriate assent, as determined by the Investigator. The parent or legal guardian must be able to understand and comply with the study visit schedule and all other study procedures.
• Must be able to comply with all study procedures.
• Age 12 to less than 18 years at the time of informed consent/assent (Cohort 1); age 2 to less than 12 years at time of informed consent/assent (Cohort 2).
• Willing to fast for at least 10 hours before visits requiring fasted blood sampling.
• A diagnosis of Familial Chylomicronemia Syndrome (type 1 Hyperlipoproteinemia) by documentation of confirmed homozygote, compound heterozygote or double heterozygote for loss-of-function mutations in type 1-causing genes.
• Fasting TGs ≥880 mg/dL at screening. If fasting TG is < 880 mg/dL, up to two additional tests may be performed during the screening period with any single test used to qualify.

Key Exclusion Criteria:

• Diabetes mellitus with any of the following:

• Newly diagnosed within 12 weeks prior to screening or during the screening period.
• Hemoglobin A1c (HbA1c) ≥9.5% at screening.
• Change in basal insulin regimen >20% within 3 months prior to screening or during the screening period.
• For participants with type 1 diabetes: episode of diabetic ketoacidosis, or ≥3 episodes of severe hypoglycemia within 6 months prior to screening or during the screening period.
• History of bleeding, diathesis, or coagulopathy.
• Major surgery within 3 months of screening.
• Plasma apheresis within 4 weeks prior to screening or planned during the study.
• Treatment with another investigational drug, biological agent, or device within one month of screening, or 5 half-lives of investigational agent, whichever is longer.
• Active pancreatitis within 4 weeks prior to screening or during the screening period.
• Malignancy diagnosed or treated within 5 years prior to screening or during the screening period.

Note: Other protocol-specified inclusion/exclusion criteria may apply.