 This systematic review identifies 75 manuscripts that describe randomized control trials testing T1D disease-modifying therapies and features linked to treatment response. 17 interventions show benefit compared to placebo, but the low quality of precision analyses makes it difficult to draw meaningful conclusions for clinical practice. Future precision studies should incorporate uniform outcome measures, reproducible biomarkers, and pre-specified, fully-powered precision analyses into trial designed to facilitate precision medicine approaches to T1D prevention. This article was authored by Jamie L. Felton, Kurt J. Griffin, Richard A. Orem, and others.