Subcutaneous administration of glutamic acid decarboxylase (GAD)65 formulated with aluminum hydroxide (GAD-alum) preserved residual insulin secretion in children and adolescents with recent-onset Type 1 diabetes (T1D) (1), but such treatment did not show efficacy in subsequent phase II (2) and phase III (3) trials. This evidence concerns the gene GAD2 and type 1 diabetes mellitus.