A Comparison of Adding Exenatide With Switching to Exenatide in Patients With Type 2 Diabetes Experiencing Inadequate Glycemic Control With Sitagliptin Plus Metformin

Inclusion Criteria: * Present with type 2 diabetes * Patients have been treated with a stable dose of the following for at least 3 months prior to screening: * 100 mg/day sitagliptin and * ≥1500 mg/day metformin, or maximum tolerated dose (extended release or immediate-release). * Have inadequate glycemic control as evidenced by an HbA1c between 7.1% and 9%, inclusive. * Have a body mass index (BMI) ≥20 kg/m2 and \<45 kg/m2 Exclusion Criteria: * Are currently enrolled in, or discontinued within the last 30 days (or longer, if local guidelines require) from, a clinical trial involving an off-label use of an investigational drug or device, or concurrently enrolled in any other type of medical research judged not to be scientifically or medically compatible with this study. * Have previously completed or withdrawn from this study or any other study investigating exenatide. * Have a known allergy or hypersensitivity to exenatide, sitagliptin or excipients contained in exenatide or sitagliptin. * Used drugs for weight loss (for example, orlistat, sibutramine, phenylpropanolamine, or similar over-the-counter medications) within 1 month of screening. * Are currently treated with any of the following excluded medications: * Thiazolidinediones (TZD) within 3 months of screening. * Sulfonylurea (SU) within 3 months of screening. * Dipeptidyl peptidase-4 \[DPP-4\] inhibitors, with the exception of sitagliptin, within 3 months of screening. * Meglitinide derivatives (for example, repaglinide or nateglinide) within 3 months of screening. * Alpha-glucosidase inhibitors (for example, miglitol or acarbose) within 3 months of screening. * Exogenous insulin within the 3 months prior to screening. * Drugs that directly affect gastrointestinal motility, including, but not limited to: metoclopramide, cisapride, and chronic macrolide antibiotics. * Systemic corticosteroids (excluding topical and inhaled preparations) by oral, intravenous (IV), or intramuscular (IM) route used regularly (for longer than 1 month) or used within 1 month immediately prior to screening. * Any other oral antidiabetic (OAD) agent, other than sitagliptin or metformin, within 3 months prior to screening.