Efficacy and Safety of Lixisenatide in Patients With Type 2 Diabetes Mellitus Insufficiently Controlled by Metformin

Inclusion criteria: \- Type 2 diabetes mellitus, diagnosed for at least 1 year before screening visit, insufficiently controlled with metformin alone or metformin with sulfonylurea at the time of the screening visit Exclusion criteria: * HbA1c \<7% or greater than (\>) 10% at screening * At the time of screening age \< legal age of majority * Pregnant or breastfeeding women or women of childbearing potential with no effective contraceptive method * Type 1 diabetes mellitus * Treatment with metformin not at a stable dose of at least 1.0 gram per day or more than 1.5 gram per day for at least 3 months prior to screening visit * In case of treatment with sulfonylurea, if the sulfonylurea dosage is less than the maximum effective dose (that is, half of the maximum recommended dose according to local labeling), or is not at a stable (unchanged) dose for at least 3 months prior to screening * FPG at screening \>250 milligram per deciliter (mg/dL) (\>13.9 millimole per liter \[mmol/L\]) * History of hypoglycemia unawareness * Body mass index \<=20 kilogram per square meter (kg/m\^2) * Weight change of \>5 kg during the 3 months preceding the screening visit * History of unexplained pancreatitis, chronic pancreatitis, pancreatectomy, stomach/gastric surgery, or inflammatory bowel disease or patients considered by the investigator at high risk for acute pancreatitis (for example, with known history of biliary gallstone\[s\], or with very high triglyceride level \[\>=5.65 mmol/L\]) at the time of screening * Personal or family history of medullary thyroid cancer or genetic conditions that predispose to medullary thyroid cancer (for example, multiple endocrine neoplasia syndromes); * History of metabolic acidosis, including diabetic ketoacidosis within 1 year prior to screening * Hemoglobinopathy or hemolytic anemia, receipt of blood or plasma products within 3 months prior to the time of screening * Within the last 6 months prior to screening: history of myocardial infarction, stroke, or heart failure requiring hospitalization * Known history of drug or alcohol abuse within 6 months prior to the time of screening * Cardiovascular, hepatic, neurological, endocrine disease, active malignant tumor or other major systemic disease or patients with short life expectancy making implementation of the protocol or interpretation of the study results difficult, history or presence of clinically significant diabetic retinopathy, history or presence of macular edema likely to require laser treatment within the study period * Uncontrolled or inadequately controlled hypertension at the time of screening with a resting systolic blood pressure (SBP) or diastolic blood pressure (DBP) \>180 millimeter of mercury (mmHg) or \>95 mmHg, respectively * Laboratory findings at the time of screening: amylase and/or lipase: \>3 times upper limit of normal (ULN); hemoglobin \<11 gram/deciliter and/or neutrophils \<1500 per cubic millimeter (mm\^3) and/or platelets \<100 000/mm\^3; calcitonin \>20 picogram per milliliter (5.9 picomole per liter) ; and positive test for Hepatitis B surface antigen and/or Hepatitis C antibody * Any clinically significant abnormality identified on physical examination, laboratory tests, electrocardiogram, or vital signs at the time of screening that, in the judgment of the investigator or any sub-investigator, precludes safe completion of the study or constrains efficacy assessment * Patients who are considered by the investigator or any sub-investigator as inappropriate for this study for any reason (for example, impossibility to meet specific protocol requirements, such as attending scheduled visits, being able to do self-injections; likelihood of requiring treatment during the screening phase and treatment phase with drugs not permitted by the clinical study protocol; investigator or any sub-investigator, pharmacist, study coordinator, other study staff or relative thereof directly involved in the conduct of the protocol) * Use of oral or injectable antidiabetic or hypoglycemic agents other than metformin and sulfonylurea (for example, alpha-glucosidase inhibitor, thiazolidinedione, glucagon-like peptide -1 \[GLP-1\], receptor agonist, dipeptidyl-peptidase-4 inhibitors, insulin) within 3 months prior to the time of screening * Use of systemic glucocorticoids (excluding topical application or inhaled forms) for 1 week or more within 3 months prior to the time of screening * Use of any investigational drug within 3 months prior to screening; * Participation in a previous study with lixisenatide * Renal impairment defined with creatinine \>1.4 mg/dL in women and creatinine \>1.5 mg/dL in men * Clinically relevant history of gastrointestinal disease associated with prolonged nausea and vomiting, including, but not limited to gastroparesis, unstable (that is, worsening) and not controlled (that is, prolonged nausea and vomiting) gastroesophageal reflux disease requiring medical treatment, within 6 months prior to the time of screening * Allergic reaction to any GLP-1 agonist in the past (for example, exenatide, liraglutide) or to metacresol * Additional exclusion criteria at the end of the run-in phase: informed consent withdrawal; lack of compliance during the single-blind placebo run-in phase (\>2 injections missed); and patient with any adverse event which precludes the inclusion in the study, as assessed by the investigator