A Study of Olezarsen (Formerly Known as AKCEA-APOCIII-LRx) in Participants With Familial Chylomicronemia Syndrome (FCS)

An Open-Label Extension Study of AKCEA-APOCIII-LRx Administered Subcutaneously to Patients With Familial Chylomicronemia Syndrome (FCS)

The purpose of this study is to evaluate the effect of olezarsen (formerly known as AKCEA-APOCIII-LRx) on the percent change in fasting triglycerides (TG) from baseline.

This is a multi-center, open-label extension (OLE) study of up to 60 participants with FCS rolling-over from Study ISIS 678354-CS3 (NCT04568434). Participants will receive olezarsen during a 157-week treatment period, followed by a 13-week post-treatment follow-up period. The length of participation in this study is approximately 201 weeks, which includes an up to 31-day qualification period, a 157-week treatment period, and a 13-week post-treatment evaluation period.

Treatment has been extended to obtain additional safety assessments and efficacy data and to provide patients with continued access to ISIS 678354 until the drug may be available commercially.

Inclusion Criteria:

• Satisfactory completion of treatment with olezarsen in the index study (ISIS 678354-CS3, last dose as scheduled at Week 49) with an acceptable safety profile, per Investigator judgement.

Exclusion Criteria:

• Have any new condition or worsening of existing condition which in the opinion of the Investigator would make the participant unsuitable for enrollment, or could interfere with the patient participating in or completing the study, including need for treatment with medications disallowed in the index study (ISIS 678354-CS3).