Inclusion Criteria

• Adult patients (male and female) with type 1 diabetes mellitus (T1DM)
• Signed written informed consent

Exclusion Criteria

• Age <18 years or >70 years
• Fasting c-peptide ≥0.3 nmol/L as per source document or central lab test at visit 1
• Glycated hemoglobin (HbA1c) <7.0% or >9.0% via central lab test at visit 1
• Experienced none or only 1 episode of documented symptomatic and/or severe hypoglycemia (as per the American Diabetes Association [ADA] classification) during the past month prior to screening
• Experienced >1 episode of severe hypoglycemia resulting in coma/seizures during the last 12 months before screening
• Received less than 1 year treatment with basal plus mealtime insulin
• Used any basal insulins other than Lantus in the past 3 months before screening
• Requires >80 U/day Lantus and/or not on stable Lantus dose (±20% total dose) within 30 days prior to screening
• Using fewer than 2 injections of rapid-acting insulin analog per day within 30 days prior to screening.
• Using human regular insulin as mealtime insulin within 30 days prior to screening
• Using an insulin pump during the last 6 months before screening
• History of unstable proliferative diabetic retinopathy or any other rapidly progressive diabetic retinopathy or macular edema likely to require treatment (eg, laser, surgical treatment, or injectable drugs) during the study period
• Pregnant or breast-feeding women or planning pregnancy during the duration of the study
• Use of any other investigational drug(s) within 1 month or 5 half-lives, whichever is longer prior to screening
• Inappropriate CGM use during screening period evidenced by failure to obtain a minimum of 4 days of usable records by the end of screening
• Noncompliance with self-monitored plasma glucose (SMPG) performance evidenced by failure to demonstrate at least 5 days of 5-point SMPG records by the end of screening
• Other considerations relevant to a patient's potential participation in a clinical trial