HALT Progression of Polycystic Kidney Disease Study A

Inclusion Criteria: * Diagnosis of ADPKD. * Age 15-49 (Study A); Age 18-64 (Study B). * GFR \>60 mL/min/1.73 m2 (Study A); GFR 25-60 mL/min/1.73 m2 (Study B). * BP ≥130/80 or receiving treatment for hypertension. * Informed Consent. Exclusion Criteria: * Pregnant/intention to become pregnant in 4-6 yrs. * Documented renal vascular disease. * Spot urine albumin-to-creatinine ratio of \>0.5 (Study A) or ≥1.0 (Study B) and/or findings suggestive of kidney disease other than ADPKD. * Diabetes requiring insulin or oral hypoglycemic agents / fasting serum glucose of \>126 mg/dl / random non-fasting glucose of \>200 mg/dl. * Serum potassium \>5.5 milliequivalent per liter (mEq/L) for participants currently on ACE-I or ARB; \>5.0 mEq/L for participants not currently on ACE-I or ARB. * History of angioneurotic edema or other absolute contraindication for ACE-I or ARB. Intolerable cough associated with ACE-I is defined as a cough developing within six months of initiation of ACE-I in the absence of other causes and resolving upon discontinuation of the ACE-I. * Indication (other than hypertension) for β-blocker or calcium channel blocker therapy (e.g. angina, past myocardial infarction, arrhythmia), unless approved by the site principal investigator. (PI may choose to accept an individual who is on only a small dose of one of these agents and would otherwise be eligible.) * Systemic illness necessitating nonsteroidal antiinflammatory drugs (NSAIDs), immunosuppressant or immunomodulatory medications. * Systemic illness with renal involvement. * Hospitalized for acute illness in past 2 months. * Life expectancy \<2 years. * History of non-compliance. * Unclipped cerebral aneurysm \>7mm diameter. * Creatine supplements within 3 months of screening visit. * Congenital absence of a kidney (also total nephrectomy for Study B). * Known allergy to sorbitol or sodium polystyrene sulfonate. * Exclusions specific to magnetic resonance imaging (Study A).