The current study investigates colesevelam as add-on therapy to pioglitazone to improve glycemic control in subjects with type 2 diabetes mellitus not adequately controlled with pioglitazone monotherapy or pioglitazone in combination with either metformin or a sulfonylurea. The study will evaluate if colesevelam add-on to pioglitazone therapy for type 2 diabetes mellitus will be safe, well tolerated, and efficacious.

Inclusion Criteria:

• Diagnosis of Type 2 diabetes mellitus
• Inadequate glycemic control on a stable dose (at least 2 months prior to screening) of pioglitazone at 30 or 45 mg/day, with or without one or two other oral antidiabetic medications [metformin or a sulfonylurea, or dipeptidyl peptidase (DPP-IV) inhibitor]
• Hemoglobin A1c (HbA1c) >= 7.5% and =< 9.5% at screening
• Fasting plasma glucose =<240 mg/dL at randomization (Week 0/Day 1).
• Male or female >= 18 years of age.
• Women of childbearing potential must be using an adequate method of contraception as detailed per-protocol
• Fasting C-peptide level >0.5 ng/mL at screening
• Clinically stable in regards to medical conditions other than type 2 diabetes
• Concomitant medications are at stable doses for at least 30 days prior to enrollment, and are not anticipated to need adjustment during the study period

Exclusion Criteria:

• History of Type 1 diabetes and/or history of ketoacidosis
• History of bowel obstruction
• History of hypertriglyceridemia-induced pancreatitis
• Fasting serum triglyceride concentration >500 mg/dL
• History of dysphagia, swallowing disorders, gastroparesis, other gastrointestinal motility disorders, major gastrointestinal surgery
• History of insulin use >= 2 weeks duration during the previous 3 months or a total of >2 months insulin therapy at any time prior to screening
• Treatment with bile acid sequestrants, including colesevelam within 3 months prior to screening
• Female subject who is pregnant or breastfeeding
• History of unstable angina, myocardial infarction, cerebrovascular accident, transient ischemic attack, or any revascularization within 6 months prior to screening