Tolvaptan-Octreotide LAR Combination in ADPKD

Inclusion Criteria: 1. Adult (\>18-yr-old) men and women, with a clinical and ultrasonographic diagnosis of ADPKD; 2. Serum creatinine \< 1.0 mg/dl (for man) and \< 1.2 mg/dl (for woman) and changes in serum creatinine (and creatinine clearance when available) \<30% over the last six months; 3. Creatinine clearance \> 80 ml/min/1.73m2 measured one to two weeks apart during the pre-screening period; 4. GFR ≥ 80 ml/min/1.73m2 (by iohexol plasma clearance technique) at screening and baseline evaluations; 5. TKV ranging between 1000 and 2000 ml at screening (by ultrasound imaging) and at baseline (by MRI) evaluations; 6. Female participants must be of non-childbearing potential or must agree to abstinence or use a highly effective form of contraception; 7. Written informed consent. Exclusion Criteria: 1. Patients with concomitant systemic, renal parenchymal or urinary tract disease; 2. Diabetes; 3. Overt proteinuria (urinary protein excretion rate \>1 g/24 hours); 4. Abnormal urinalysis suggestive of concomitant, clinically significant glomerular disease, urinary tract lithiasis, infection or obstruction, biliary tract lithiasis or obstruction; 5. Hemorrhagic or complicated cysts which might acutely affect kidney function and volumes; 6. QT-related ECG abnormalities; 7. Cancer and major systemic diseases that could prevent completion of the planned follow-up or interfere with data collection or interpretation; 8. Hypersensitivity to the IMP active substance or to any of the excipients or to benzazepine or benzazepine derivatives; 9. Concomitant treatment with drugs that may affect glomerular hemodynamics during the three months before the beginning of the study (including ACE inhibitors, angiotensin receptor blockers, aldosterone antagonists and non-steroideal anti-inflammatory medications); 10. Elevated liver enzymes and/or signs or symptoms of liver injury prior to initiation of treatment that meet the requirements for permanent discontinuation of tolvaptan 11. Patients with anuria, volume depletion and hypernatraemia 12. Patients who cannot perceive or respond to thirst 13. Ferro-magnetic prosthesis, aneurysm clips, severe claustrophobia or any other contraindication to MRI evaluation; 14. Psychiatric disorders and any condition that could prevent full comprehension of the purposes and risks of the study; 15. Pregnant or lactating; 16. Participation in another interventional clinical trial within the 4 weeks prior to screening.