To Evaluate Safety and Tolerability After Multiple Oral Doses of AZD1656 in Type 2 Diabetes Patients on Top of Metformin

Inclusion Criteria: * Male or female (with non child-bearing potential) * Diagnosed diabetes Mellitus patients treated with metformin alone or one other anti-diabetic drugs. Stable blood sugar control indicated by no changed treatment within 3 months prior to study start.t * HbA1c \<11 % at screening (HbA1c value according to international DCCT standard) Exclusion Criteria: * Clinically significant illness or clinically relevant trauma, as judged by the investigator, within two weeks before the first administration of the IP * History of ischemic heart disease, stroke, transitorisk ischemic attack or symptomatic peripheral vascular disease * Clinically significant abnormalities in clinical chemistry, hematology, or urinalysis results.