A Phase 1/2/3 Study to Evaluate the Safety, Tolerability, and Efficacy of VX-880 in Subjects Who Have Type 1 Diabetes Mellitus With Impaired Hypoglycemic Awareness and Severe Hypoglycemia

Key Inclusion Criteria: * Clinical history of T1D with \> 5 years of duration of insulin dependence * At least two episodes of documented severe hypoglycemia in the 12 months prior to enrollment * Stable diabetic treatment * Consistent use of continuous glucose monitor (CGM) for at least 3 months before Screening and willingness to use CGM for the duration of the study Key Exclusion Criteria: -Prior islet cell transplant, organ transplant, or cell therapy Other protocol defined Inclusion/Exclusion criteria may apply