Inclusion Criteria:

• Male or female, ≥ 18 years of age (inclusive) at time of screening.
• Diagnosis of one of the following:
  • Congenital NDI;
  • ADPKD by modified Pei criteria: Unified Criteria for  Ultrasonographic Diagnosis of ADPKD and on tolvaptan with stable dosing for > 1 month:
  • For participants with family history of ADPKD, by ultrasound: 18-39 years: ≥ 3 cysts, unilateral or bilateral; 40-59 years: ≥ 2 cysts in each kidney; 60 years: ≥ 4 cysts in each kidney; or
  • For participants with family history of ADPKD, by computerized tomography (CT) or MRI: 18-40 years: ≥ 10 cysts in both kidneys; or
  • For participants without family history of ADPKD, a minimum of 10 cysts per kidney by any radiological method and exclusion of other cystic kidney diseases (multiple simple kidney cysts, renal tubular acidosis, cystic dysplasia of the kidney, multicystic kidney, multilocular cysts of the kidney, medullary cystic kidney, and acquired cystic disease of the kidney); or
  • Genetic diagnosis of ADPKD;
  • Lithium-induced NDI.
• GFR ≥ 30 ml/min/1.73 m^2 at time of screening visit calculated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation from serum creatinine values obtained during screening.
• Morning Uosm <300 mOsm/kg H2O.
• If hypertensive, blood pressure controlled on antihypertensives (<130/80 mm Hg) at least 30 days before day 1.
• Female participants must: not be pregnant, lactating, or breastfeeding. be either postmenopausal (defined as amenorrhea for ≥ 12 months), surgically sterile (defined as having undergone hysterectomy and/or bilateral oophorectomy) or, if of childbearing potential (WOCBP), agree to practice acceptable methods of birth control or remain abstinent (only if this is the usual and preferred lifestyle of the participant) during the full duration of the trial and for 30 days after the last dose of the study drug. Birth control methods that can be used during the study include the following: hormonal contraceptives: combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation (i.e., oral, intravaginal, transdermal); progestogen-only hormonal contraception (i.e., oral, injectable, implantable); intrauterine device (IUD), including progestin-containing intrauterine devices intrauterine hormone-releasing system (IUS); male sexual partner who has been vasectomized for at least 3 months prior to screening and who has obtained a follow-up negative sperm count and is the sole sexual partner; bilateral tubal ligation; Essure procedure (tubal occlusion); male or female condom with spermicide (cream, spray, gel, suppository, or polymer film); diaphragm; cervical cap; or contraceptive sponge with spermicide (with or without male condom).
• Have read, understood, and provided written informed consent after the nature of the study has been fully explained and must be willing to comply with protocol requirements and study-related procedures.
• Negative urinary pregnancy test (if applicable) at Day -1.
• Capable of providing urine samples as dictated by the protocol.

Exclusion Criteria:

• Advanced diabetes (e.g., glycosylated hemoglobin [HgbA1c] > 7.5%, and/or glycosuria by dipstick, significant proteinuria [> 300 mcg albumin/mg creatinine]), other significant kidney disease, kidney cancer, transplanted kidney, single kidney, kidney surgery within the past 6 months (including cyst drainage or fenestration) or acute kidney injury within 6 months prior to screening.
• Clinically significant incontinence, overactive bladder, or urinary retention (e.g., benign prostatic hyperplasia).
• Other significant chronic medical disease (heart failure, diabetes mellitus, liver disease, transient or persistent elevated transaminases).
• History of acute gout attack in the past 30 days.
• History of clinically significant drug or alcohol abuse in the 2 years prior to screening visit.
• Uncontrolled hyperuricemia or active gout.
• History of hepatotoxicity related to tolvaptan; or clinically significant liver disease or impairment; or alanine aminotransferase (ALT), aspartate aminotransferase (AST), or total bilirubin values > 1.2 x ULN during screening.
• Medical history or findings that preclude safe participation in the trial or participants who are likely to be non-compliant with trial procedures in the opinion of the investigator or medical monitor.
• Requirement for ongoing diuretic use.
• Participants who are currently taking, or are expected to be taking, strong or moderate CYP3A4 or CYP2C8 inhibitors or inducers including regular use of grapefruit juice, Seville oranges, or St. John's wort. If applicable, there should be a 14-day washout of these treatments prior to Day 1.
• Prior use of a sodium-glucose cotransporter 2 (SGLT2) inhibitor (e.g., canagliflozin, dapagliflozin, empagliflozin, etc.) within the 2 months prior to screening visit or expected need for initiation of treatment with a SGLT2 inhibitor during the study.
• Prior use of a hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor within the 2 months prior to screening visit or expected need for initiation of treatment with a HIF-PH inhibitor during the study.
• Participants who have taken any investigational drug or used an investigational device within 30 days, or 5 half-lives, whichever is longer, prior to screening visit 1a or plan to participate in an interventional trial during the study.
• Allergy to probenecid.
• History of persistent hyponatremia.
• Positive test results for hepatitis B surface antigen (HBsAg).
• Positive test results for hepatitis C (HCV) antibody (Anti-HCV), with the exception of participants for whom the reflex HCV RNA titer test is negative.

Note: Other protocol defined Inclusion/Exclusion criteria may apply.

Eligibility last updated 9/28/23. Questions regarding updates should be directed to the study team contact.