AQP2 and autosomal dominant polycystic kidney disease: This review highlights some of the new insights and recent advances in targeting the vasopressin–AQP2 pathway in some relevant diseases associated with water balance disorders, such as congenital nephrogenic diabetes insipidus (NDI), idiopathic syndrome of inappropriate antidiuretic hormone secretion (SIADH), nephrogenic syndrome of inappropriate antidiuresis (NSIAD), and autosomal dominant polycystic kidney disease (ADPKD).