CDK5 and cyst: Administration of the broad CDK inhibitor roscovitine (which targets CDK1, CDK2, CDK5 and CDK7, arresting the cell cycle) effectively arrested kidney volume expansion, cyst progression and renal insufficiency in jck/Nek8/Nphp9 and cpk (cystin) mouse models of infantile NPH and PKD, respectively, with long-lasting effects.