In 2015, tolvaptan, a vasopressin V2 receptor antagonist was approved by the European Medicines Agency for use in ADPKD patients with ‘evidence of rapid disease progression’, following the pivotal Tolvaptan Phase 3 Efficacy and Safety Study in Autosomal Dominant Polycystic Kidney Disease (TEMPO 3:4) trial [5]. The gene discussed is AVPR2; the disease is autosomal dominant polycystic kidney disease.