The use of C-peptide as a surrogate for clinical outcomes in this setting was supported by a recent meta-analysis of four phase 2–3 randomized controlled trials in recent onset T1D, where the degree of preservation of C-peptide following treatment with GAD65 formulated with aluminum hydroxide (GAD-alum) was correlated with HbA1c changes [24]. This evidence concerns the gene GAD2 and type 1 diabetes mellitus.