The purpose of this study is to determine if implitapide is effective in lowering triglyceride (TG) levels in patients with Fredrickson Type I or V hypertriglyceridemia where the maximum tolerable medication and diet were not sufficient.

Inclusion Criteria:

In order to participate in this study, patients must meet all of the following inclusion criteria:

• be between 8 and 70 years old with diagnosis of Fredrickson Type I or V HTG
• be stable on current maximum tolerated triglyceride lowering therapy
• have a fasting TG level of at least 880 mg/dL (10 mmol/L)
• be male or nonpregnant, nonbreastfeeding female. The women in the study must be surgically sterile, postmenopausal or must practice an effective method of birth control
• must be able to give informed consent or if under the age of 18, parents or legal guardians must give their informed consent
• meet body weight requirements

Exclusion Criteria:

• Recent heart attack, coronary artery intervention, coronary bypass surgery, or stroke.
• Patients with class 3 or 4 heart failure
• Uncontrolled hypothyroidism or other uncontrolled endocrine disease
• Known, clinically significant eye abnormalities, such as cataracts
• History of hepatic disease or AST or ALT levels greater than 1.5 x ULN at Visit 1
• Alkaline phosphatase greater than 2 times ULN
• Serum creatinine greater than 2.0 mg/dL
• Liver cirrhosis and severe liver steatosis
• Clinically significant infection, malignancy, or psychosis
• Use of oral anticoagulants or digoxin unless the dose is stable and is regularly monitored
• Participation in any other investigational study within the last 30 days
• Breastfeeding or pregnant
• Current drug or alcohol abuse
• Serious or unstable medical conditions that would compromise the patient's safety or successful participation in the study
• Unwillingness to comply with study procedures or unwillingness to cooperate fully