Evaluate the Long Term Safety and Efficacy of DWP16001 add-on to Metformin in Patients With T2DM Inadequately Controlled on Metformin

Inclusion Criteria: * Participated in the prior phase 3 study (Protocol No: DW\_DWP16001302) for meeting the inclusion criteria and completed the study * Voluntarily decided to participate in the extension study and provided a written consent on the consent form Exclusion Criteria: * Withdrawn from the prior phase 3 study (Protocol No: DW\_DWP16001302) or expected of having safety issue if taking part in the study in the judgment of the investigator * Subjects with the following diseases or signs: * Diabetic ketoacidosis * Moderate to severe renal impairment (estimated glomerular filtration rate \[eGFR\] \< 60 mL/min/1.73 m2 * Females who are pregnant or breast-feeding, or subjects who do not agree to the use of appropriate contraceptive methods throughout the study Subjects must agree to one of the following appropriate contraceptive methods for subjects or their partners: ① Either surgical sterilization (vasectomy, etc.) or insertion of an intrauterine device (copper loop, intrauterine hormone-containing system), or ② A physical barrier method combined with either systemic hormonal contraceptives or spermicide, or ③ Use of male condom combined with either cervical cap or diaphragm Determined to be ineligible for the study by the investigator, besides the above