Study of ARO-APOC3 in Adults With Mixed Dyslipidemia

Inclusion Criteria: Based on medical history, evidence of TG ≥ 150 mg/dL but ≤ 499 mg/dL on more than one occasion * Fasting levels at Screening of non-HDL-C ≥ 100 mg/dL OR LDL-C ≥ 70 mg/dL after at least 4 weeks of stable diet and stable optimal statin therapy * Mean fasting TG ≥ 150 mg/dL and ≤ 499 mg/dL during Screening collected at two separate and consecutive visits and at least 7 days apart and not more than 14 days apart * Willing to follow diet counseling as per Investigator judgment based on local standard of care * Participants of childbearing potential (males \& females) must use highly-effective contraception during the study and for at least 24 weeks following the last dose of study medication. Males must not donate sperm and females must ot donate eggs during the study and for at least 24 weeks following the last dose of study medication. * Women of childbearing potential must have a negative pregnancy test at Screening and cannot be breastfeeding * Women of childbearing potential on hormonal contraceptives must be stable on the medication for ≥ 2 menstrual cycles prior to Day 1 * Willing to provide written informed consent and to comply with study requirements Exclusion Criteria: * Current use or use within 365 days from Day 1 of any hepatocyte targeted siRNA or antisense oligonucleotide molecule * Active pancreatitis within 12 weeks prior to Day 1 * Any planned bariatric surgery or similar procedures to induce weight loss from consent through end of study * Acute coronary syndrome event within 24 weeks of Day 1 * Major surgery within 12 weeks of Day 1 * Planned coronary intervention (e.g., stent placement or heart bypass) during the study * New York Heart Association Class II, III or IV heart failure or last known ejection fraction of \<30% * Uncontrolled hypertension * Known history of human immunodeficiency virus (HIV) infection, seropositive for Hepatitis B (HBV), seropositive for Hepatitis C (HCV) * Uncontrolled hypothyroidism or hyperthyroidism * Hemorrhagic stroke within 24 weeks of Day 1 * History of bleeding diathesis or coagulopathy * Current diagnosis of nephrotic syndrome * Systemic use of corticosteroids or anabolic steroids within 4 weeks prior to Day 1 or planned use during the study * Malignancy within the last 2 years prior to date of consent requiring systemic treatment (some exceptions apply) Note: additional inclusion/exclusion criteria may apply per protocol