Primary Objective:

To compare the efficacy of a new formulation of insulin glargine and Lantus in terms of change of HbA1c from baseline to endpoint (scheduled at month 6 [week 26]) in japanese patients with type 1 diabetes mellitus

Secondary Objectives:

To compare a new formulation of insulin glargine and Lantus in terms of change in fasting plasma glucose (FPG), preinjection plasma glucose, 8-point self-measured plasma glucose (SMPG) profile.

To compare a new formulation of insulin glargine and Lantus in terms of occurrence of hypoglycemia

The duration of study will consist of:

• Up to 2-week screening period;
• 6-month open-label comparative efficacy and safety treatment period;
• 6-month open-label comparative safety extension period;
• 4-week post-treatment safety follow-up period

Inclusion criteria:

• Patients with type 1 diabetes mellitus

Exclusion criteria:

• Age < 18 years at screening visit;
• HbA1c < 7.0 % or > 10.0 % (national glycohemoglobin standardization program [NGSP] value) at screening visit;
• Patients less than 1 year before screening visit on any basal plus mealtime insulin;
• Patients not on stable insulin dose (±20% total basal insulin dose) in the last 30 days prior to screening visit;
• Patients using pre-mix insulins, human regular insulin as mealtime insulin and/or any glucose-lowering drugs other than basal insulin and mealtime rapid-insulin analogue in the last 3 months before screening visit;
• Use of an insulin pump in the last 6 months before screening visit and/or plan to switch to insulin pump in next 12 months;
• Severe hypoglycemia resulting in coma/seizures, and/or hospitalization for diabetic ketoacidosis in the last 6 months before screening visit;
• Unstable proliferative diabetic retinopathy or any other rapidly progressive diabetic retinopathy or macular edema likely to require treatment (eq, laser, surgical treatment or injectable drugs) during the study period.

The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.