In the pivotal clinical trials Tolvaptan Efficacy and Safety in Management of Autosomal Dominant Polycystic Kidney Disease and Its Outcomes 3:4 (TEMPO 3:4; NCT00428948) and Replicating Evidence of Preserved Renal Function: an Investigation of Tolvaptan Safety and Efficacy in ADPKD (REPRISE; NCT02160145), the vasopressin V2 receptor antagonist tolvaptan significantly slowed kidney function decline versus placebo in patients with autosomal dominant polycystic kidney disease (ADPKD) who were at elevated risk of rapid disease progression.1 This evidence concerns the gene AVPR2 and autosomal dominant polycystic kidney disease.