The Sapphire study validated two molecules implicated in G1 cell cycle arrest as biomarkers for the progression to severe AKI in a heterogenous cohort of 728 ICU patients: Tissue inhibitor of metalloproteinases-2 (TIMP-2) and insulin-like growth factor binding protein 7 (IGFBP7) [11]. Here, IGFBP7 is linked to acute kidney injury.