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Study on Hydrochlorothiazide and Tolvaptan for Patients with Autosomal Dominant Polycystic Kidney Disease (ADPKD)

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying Autosomal Dominant Polycystic Kidney Disease (ADPKD), a condition that causes the formation of cysts in the kidneys, leading to a gradual loss of kidney function. The study will explore the effects of adding hydrochlorothiazide, a medication commonly used to treat high blood pressure, to the current treatment with tolvaptan, a drug that helps protect the kidneys in ADPKD patients. Tolvaptan is known to have side effects that increase urine production, which can be uncomfortable for patients. The aim is to see if hydrochlorothiazide can improve the effectiveness of tolvaptan and reduce these side effects.

The purpose of the study is to investigate whether the combination of hydrochlorothiazide and tolvaptan can slow down the decline in kidney function and improve the quality of life for patients with ADPKD. Participants in the study will be randomly assigned to receive either hydrochlorothiazide or a placebo, in addition to their regular tolvaptan treatment. The study will last for a period of time, during which participants will have regular check-ups to monitor their kidney function and overall health.

Throughout the study, researchers will collect data on various health indicators, such as changes in kidney function, urine volume, and blood pressure. They will also assess the participants' quality of life through questionnaires. The results of this study could provide valuable insights into improving treatment options for individuals living with ADPKD.

The research process

The trial runs in 6 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Joining the study

    Upon joining the study, you will be informed about the purpose and procedures of the trial. You will be asked to provide consent to participate.

    You will undergo initial assessments to confirm your eligibility, which includes verifying your diagnosis of autosomal dominant polycystic kidney disease (ADPKD) and ensuring your kidney function is above a certain level.

  2. Step 2

    Baseline assessments

    Before starting the treatment, baseline measurements will be taken. This includes blood tests to measure kidney function and other health indicators.

    You will also complete questionnaires to assess your quality of life and other health-related factors.

  3. Step 3

    Treatment phase

    You will be randomly assigned to receive either hydrochlorothiazide or a placebo, in addition to your current treatment with tolvaptan. The dosage of tolvaptan will be the highest you can tolerate, as determined by your doctor.

    The treatment will be administered orally in the form of tablets. You will take these medications daily for the duration of the study.

  4. Step 4

    Regular follow-ups

    Throughout the study, you will have regular follow-up visits. These visits will include blood tests to monitor your kidney function and other health parameters.

    You will also be asked to complete questionnaires to track any changes in your quality of life and other symptoms.

  5. Step 5

    End of treatment assessments

    At the end of the treatment period, final assessments will be conducted. This includes blood tests and questionnaires similar to those at the beginning of the study.

    The results will help determine the effect of the treatment on your kidney function and overall health.

  6. Step 6

    Study completion

    After completing the study, you will receive information about the overall findings and any potential next steps for your treatment.

    Your participation will contribute to understanding the long-term effects of adding hydrochlorothiazide to tolvaptan treatment in patients with ADPKD.

Who can join the trial?

4 criteria

  • Must have a diagnosis of Autosomal Dominant Polycystic Kidney Disease (ADPKD). This is a condition where cysts form in the kidneys, affecting their function.
  • Must be 18 years old or older.
  • Must have an eGFR (estimated Glomerular Filtration Rate) greater than 25 mL/min/1.73m². In Belgium, this must be greater than 35 mL/min/1.73m². eGFR is a test that measures how well your kidneys are working.
  • Must be on a stable treatment with the highest dose of Vasopressin 2 receptor antagonists (V2RA) that you can tolerate for at least 3 months. V2RA is a type of medication used to treat ADPKD.

Who cannot join the trial?

10 criteria

  • Patients who are not diagnosed with Autosomal Dominant Polycystic Kidney Disease (ADPKD) cannot participate.
  • Patients who are not within the specified age range for the study cannot participate.
  • Patients who are part of a vulnerable population, which means they might need special protection or care, cannot participate.
  • Patients who are not able to follow the study procedures or take the study medications as required cannot participate.
  • Patients who have other medical conditions that might interfere with the study or make it unsafe for them to participate cannot participate.
  • Patients who are currently participating in another clinical trial cannot participate.
  • Patients who have a history of allergic reactions to the study medications cannot participate.
  • Patients who are pregnant or breastfeeding cannot participate.
  • Patients who have severe liver problems cannot participate.
  • Patients who have uncontrolled high blood pressure cannot participate.
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Investigated drugs

  • Hydrochlorothiazide

    is a medication that helps the body get rid of extra salt and water by making you urinate more. It is often used to treat high blood pressure and swelling caused by fluid buildup. In this trial, it is being tested to see if it can help improve the effectiveness of another medication, tolvaptan, in protecting the kidneys of patients with a condition called Autosomal Dominant Polycystic Kidney Disease (ADPKD). The researchers want to find out if adding hydrochlorothiazide can help reduce the side effects of tolvaptan and improve the patients' quality of life.

  • Tolvaptan

    is a medication that works by blocking a specific receptor in the body, which helps to slow down the formation of cysts in the kidneys. This is important for patients with ADPKD, a condition where cysts form in the kidneys and can lead to kidney damage over time. Tolvaptan is currently the only treatment available that can help protect the kidneys in these patients. However, it can cause side effects like increased urination, which can be uncomfortable. This trial is looking at whether using tolvaptan together with hydrochlorothiazide can make the treatment more effective and easier to tolerate for patients.

What is already known about the treatment

Hydrochlorothiazide – Hydrochlorothiazide is taken orally in the form of a tablet. It is currently being studied in combination with tolvaptan for its potential to improve treatment outcomes in patients with Autosomal Dominant Polycystic Kidney Disease (ADPKD). This medication is primarily used to manage high blood pressure and fluid retention. It works by helping the kidneys remove excess salt and water from the body, which can help reduce blood pressure and swelling. Hydrochlorothiazide is classified as a diuretic, commonly known as a "water pill."

Investigated diseases

Autosomal Dominant Polycystic Kidney Disease (ADPKD) – This genetic disorder is characterized by the growth of numerous cysts in the kidneys. These cysts are fluid-filled sacs that can enlarge the kidneys and disrupt their normal function. Over time, the increasing number and size of cysts lead to a gradual decline in kidney function. The disease often progresses with symptoms such as high blood pressure, back or side pain, and blood in the urine. As the condition advances, it can result in complications like kidney stones and urinary tract infections. The progression of ADPKD varies among individuals, with some experiencing more rapid kidney function decline than others.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2022-500210-26-00Protocol code2022-500210-26-00Estimated enrolment445 patientsSponsorUniversitair Medisch Centrum Groningen

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