The purpose of this study is to determine the safety and efficacy of multiple doses of CAT-2003 in patients with severe hypertriglyceridemia either naive or refractory to current therapy. The study will evaluate effects of CAT-2003 on fasting and postprandial total triglycerides and chylomicron triglyceride levels in patients with severe hypertriglyceridemia.

This is a single-blind study. All patients will receive placebo for a 14 day treatment period and CAT-2003 for a 28 day treatment period.

Inclusion Criteria:

• Between 18 and 74 years at Screening
• Severe Hypertriglyceridemia (TG ≥ 500 mg/dL). If on lipid lowering therapy including statins, fibrates, and/or omega-3 fatty acids, stable dose for at least 4 weeks prior to Screening
• Body mass index (BMI) ≤ 45 kg/m2

Exclusion Criteria:

• History of any major cardiovascular event within 6 months of Screening
• Type I diabetes mellitus or use of insulin
• History of pancreatitis