Eligibility Criteria:
Inclusion criteria (comparative period):
* Patients With Type 2 Diabetes diagnosed for at least 1 year,
* Treated with lifestyle interventions and metformin at the maximum tolerated dosage (with a minimum daily dosage of 1g), either alone or in combination with an oral insulin secretagogue (sulfonylurea, glinide or DiPeptidyl Peptidase IV inhibitor), for more than 3 months,
* 7.5% \< HbA1c \<= 12%,
* Body Mass Index (BMI) between 25 and 40 kg/m2 inclusively,
* Ability and willingness to perform PG (Plasma Glucose) self monitoring using the sponsor-provided glucose meter and to complete the patient diary,
* Willingness and ability to comply with the study protocol,
* Signed informed consent obtained prior to any study procedure.
Inclusion criteria (extension period):
* Patients treated with liraglutide (at the maximal tolerated dosage), having a mean FPG ≥ 250 mg/dL at visit 10 (Week 12) or visit 11 (Week 18), or a HbA1c≥ 7% at visit 12 (Week 24)
* Dosage of metformin compliant with the inclusion criteria of visit 1 (i.e. maximum tolerated dosage, with a minimum daily dosage of 1g), and maintained stable during the comparative period.
Exclusion criteria:
* Previous treatment with Glucagon Like Peptide-1 analogues or insulin in the past year (except in case of temporary treatment for gestational diabetes, surgery, hospitalization...),
* Treatment with thiazolidinediones or α-Glucosidases inhibitors within 3 months prior to study entry,
* Diabetes other than Type 2 diabetes (e.g. secondary to pancreatic disorders, drug or chemical agents intake),
* Pregnant women (women of childbearing potential must have a negative pregnancy test at study entry and a medically approved contraceptive method),
* Lactating women,
* Hospitalized patients (except hospitalization for routine diabetes check-up),
* Active proliferative retinopathy, as defined by a photocoagulation or vitrectomy occurrence in the 6 months prior to study entry, or any other unstable (rapidly progressing) retinopathy that may require photocoagulation or surgical treatment during the study, documented by a retina examination within 2 years prior to study entry,
* Impaired renal function (creatinine clearance \< 60 mL/mn),
* Impaired hepatic function (Alanine Aminotransferase, Aspartate Aminotransferase 2.5 times the upper limit of normal range),
* Personal or family history of medullary thyroid carcinoma,
* Multiple endocrine neoplasia syndrome type 2,
* Severe gastro-intestinal disease (including inflammatory bowel disease or diabetic gastroparesis),
* Congestive heart failure,
* History of acute pancreatitis,
* Treatment with corticosteroids with potential systemic action for more than 10 days within 3 months prior to study entry,
* Alcohol or drug abuse in the past 5 years,
* History of sensitivity to the study drugs or to drugs with a similar chemical structure.
* Night shift worker,
* Presence of any condition (medical, psychological, social or geographical), current or anticipated that would compromise the patients safety or limit the patient successful participation in the study,
* Participation in a clinical trial (drug or device) within 3 months prior to study entry,
* Refusal or inability to give informed consent to participate in the study,
* Patient is the Investigator or any sub-Investigator, research assistant, pharmacist, study coordinator, other staff or relative thereof directly involved in the conduct of the protocol.
Additional exclusion criteria for the extension period:
* Treatment with oral antidiabetic drugs other than metformin and patient's usual sulfonylurea if any, or with insulin during the comparative period (except in case of an emergency, for a period of time less than 7 days),
* Treatment with corticosteroids with potential systemic action within the last 3 months of the comparative period.
* History of sensitivity to insulin glargine.