To assess the safety and efficacy of chronic therapy with KRP-104, a novel DPP-IV inhibitor, in patients with Type 2 Diabetes on stable metformin therapy. In addition, an estimate of how much of the HbA1c response is attributable to nocturnal coverage will be explored.

Inclusion Criteria:

1. Age 18 to 70 years, inclusive;
2. Males and females of non-childbearing potential;
3. Diagnosis of type 2 diabetes mellitus according; and
4. On a stable dose of metformin monotherapy at randomization (can be on other oral therapies or naive at study entry

Exclusion Criteria:

1. History of type 1 diabetes mellitus or history of diabetic ketoacidosis or persistent hypoglycemia;

2. History or presence of alcoholism or drug abuse

3. Typical consumption of ≥10 drinks of alcohol weekly;

4. Presence of any of the following conditions:

   • Significant renal impairment (glomerular filtration rate <60 mL/min [to be calculated by the central laboratory]);
   • Diabetic retinopathy;
   • Diabetic gastroparesis;
   • Active liver disease (other than asymptomatic nonalcoholic fatty liver disease), cirrhosis, or symptomatic gallbladder disease;

5. Uncontrolled high blood pressure;

6. History or evidence of cardiovascular or pulmonary disease

7. Must meet other laboratory and Medical History clinical criteria. Please contact recruitment center for referrals