The purpose of this study is to determine the safety and efficacy of different doses of CAT-2003 in patients with hyperlipidemia when CAT-2003 is taken for 4 weeks. The study will evaluate effects of CAT-2003 on (1) fasting triglycerides and non-HDL-C in patients with moderate hypertriglyceridemia and (2) fasting LDL-C levels in combination with a statin in patients with hypercholesterolemia who are on a statin.