Inclusion Criteria:  Male or female participants with ADPKD who completed study PA-ADPKD-303 Continued control of hypertension without the use of a diuretic Continued adherence to prohibitions on concomitant medications stated in the study PA-ADPKD-303 protocol  Exclusion Criteria:  Any contraindication to continued treatment with lixivaptan Clinically significant incontinence, overactive bladder, or urinary retention (e.g., benign prostatic hyperplasia) New York Heart Association Functional Class 3 or 4 heart failure or other significant cardiac or electrocardiogram (ECG) findings that could pose a safety risk to the participant Hypovolemia on physical examination at Screening The following laboratory results based on serum drawn at Visit 24 of PA-ADPKD-303:  Serum ALT or aspartate aminotransferase (AST) values >1.5 × upper limit of normal (ULN)  Total bilirubin values >1.5 × ULN  eGFR <20 ml/min/1.73 m2 based on laboratory results from Visit 26 of PA-ADPKD-303 A finding at Screening that precludes safe participation in the study or participants who are likely to be non-compliant with study procedures in the opinion of the Investigator or medical monitor