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Mesalazine Monotherapy vs Continuing Thiopurines in Older Patients with Ulcerative Colitis in Long-Term Remission

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What is this trial about?

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

This study is being done in older people with Ulcerative Colitis who have been in long-term remission, which means the disease has been quiet for a long time. The purpose of the study is to compare two ways of treating the disease: stopping thiopurines, which are medicines that reduce the immune system’s activity, and continuing treatment, with a switch to mesalazine alone. Mesalazine is an anti-inflammatory medicine used by mouth and may be given as tablets or prolonged-release granules under names such as Salofalk, Pentasa, Asacol, and Claversal.

People in the study are placed into one of the treatment approaches and then followed over time for about 24 months. During this period, regular check-ups are used to watch for signs that Ulcerative Colitis may be becoming active again, and to monitor safety, side effects, hospital stays, surgery to remove the colon, and death. The study also looks at how well the treatment is taken as prescribed.

Ulcerative Colitis is a long-lasting disease that causes swelling and sores in the large bowel, also called the colon. When the disease becomes active again after a quiet period, this is called a relapse or recurrence. Thiopurines are medicines that lower immune system activity to help control the disease, while mesalazine helps reduce swelling in the bowel.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Study start

    At the time of joining the study, you enter a 24-month follow-up period.

    The study compares two treatment paths for ulcerative colitis, a long-lasting bowel condition.

  2. Step 2

    Treatment assignment

    You are assigned to one of two treatment paths.

    One path is mesalazine alone by mouth, and the other path is thiopurines continued during the study.

  3. Step 3

    Mesalazine treatment path

    If you are assigned to the mesalazine path, you take 4 g by mouth.

    The study products listed for this path include salofalk, pentasa, asacol, and claversal.

    The forms listed are prolonged-release granules, gastro-resistant tablets, and prolonged-release tablets.

    The source data do not specify the exact daily frequency or exact duration of each dose beyond the 24-month study follow-up.

  4. Step 4

    Thiopurine treatment path

    If you are assigned to the thiopurine path, you continue taking the same treatment during the study.

    The source data do not provide the name, dose, frequency, or duration of the thiopurine medication.

  5. Step 5

    Follow-up during the study

    During the 24 months of follow-up, your condition is checked for return of disease activity.

    One sign of return is faecal calprotectin above 250 µg/g in two samples in a row; faecal calprotectin is a stool test that shows inflammation in the bowel.

    Another sign is a return of symptoms that requires treatment to be made stronger.

  6. Step 6

    Study outcomes assessed

    The study records whether disease activity returns within 24 months.

    It also records the time until relapse, the number of clinical relapses, the need for colectomy, safety and side effects, death, hospitalisation due to disease activity or side effects, and treatment adherence measured with the Morisky-Green scale, a questionnaire used to check how well treatment is followed.

  7. Step 7

    End of follow-up

    The study ends after 24 months of follow-up for you.

Who can join the trial?

11 criteria

  • Be 60 years of age or older.
  • Have a confirmed diagnosis of ulcerative colitis according to accepted ECCO criteria (medical guidelines used to diagnose this condition).
  • Have taken azathioprine (a medicine that lowers immune activity) at 1 to 2.5 mg per kg per day or mercaptopurine at 0.75 to 1.5 mg per kg per day for at least 5 years in a row.
  • Have been on a stable dose of azathioprine or mercaptopurine for the last 12 months, meaning the dose has stayed at the lowest effective amount without side effects.
  • If also taking oral mesalazine (a medicine taken by mouth to reduce inflammation in the bowel), have been on a stable dose for the last 12 months.
  • Have had clinical remission for at least 3 years, meaning no flare-ups requiring systemic corticosteroids (steroid medicines taken by mouth or through a vein) or biologic medicines (treatments made from living cells that target the immune system).
  • May still use a stable dose of oral mesalazine and/or topical rectal treatments (medicines placed in the rectum, the last part of the bowel), as long as the dose has not changed in the last 12 months.
  • Have objective clinical remission at the study entry visit, shown by a Partial Mayo score of 2 or less, with the rectal bleeding score equal to 0. The Partial Mayo score is a doctor-assessed measure of disease activity.
  • Have had a colonoscopy (a camera test of the large bowel) within the last 12 months showing endoscopic remission, with an endoscopic Mayo score of 0, meaning no visible inflammation.
  • Have subclinical inflammatory remission, meaning no sign of hidden inflammation, shown by a faecal calprotectin level of 150 mg/kg or lower about 1 month before randomisation. Faecal calprotectin is a stool test that helps measure bowel inflammation.
  • Be willing and able to give written informed consent, which means signing a form to show agreement to join the study after understanding it.

Who cannot join the trial?

10 criteria

  • You cannot join if you have ulcerative proctitis, which means the inflammation has only affected the last part of the large bowel and the affected area has been shorter than 25 cm during the course of the illness.
  • You cannot join if you have had a total or segmental colectomy, meaning surgery to remove all or part of the large bowel.
  • You cannot join if you have an ileoanal reservoir, which is a surgically created pouch that connects the end of the small bowel to the anus.
  • You cannot join if you have a history of complex perianal disease, meaning serious or difficult disease around the area of the anus.
  • You cannot join if you cannot tolerate oral 5-ASA, a medicine taken by mouth that is used to treat bowel inflammation.
  • You cannot join if you are now using, or have used in the past, any selective immunomodulator or any advanced therapy approved for ulcerative colitis. These are medicines that change how the immune system works or newer special treatments for the disease.
  • You cannot join if you stopped topical treatment such as mesalazine or steroids within the last 3 months. Topical treatment means medicine used locally, usually as a suppository, enema, or rectal foam.
  • You cannot join if you have chronic kidney failure with creatinine of 2 mg/dL or more, or if your kidney filtering rate is 30 mL/min/1.73 m² or less. Creatinine is a blood test that helps show how well the kidneys are working.
  • You cannot join if your liver blood tests are abnormal, meaning AST, ALT, alkaline phosphatase, or GGT are more than 2 times the upper limit of normal. These tests help show how well the liver is working.
  • You cannot join if your blood counts are too low at the time of inclusion: neutrophils below 1500 cells/mm³, lymphocytes below 500 cells/mm³, platelets below 120,000 cells/mm³, or hemoglobin below 12 g/dL for women or 13 g/dL for men. Neutrophils and lymphocytes are types of white blood cells, platelets help blood clot, and hemoglobin carries oxygen in the blood.
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Investigated drugs

Mesalazine is the main study medicine in this trial. It is taken by mouth and comes as tablets or granules that release the medicine slowly or protect it from stomach acid. It is used to help keep ulcerative colitis under control and to lower the chance of the disease becoming active again after thiopurines are stopped. In this study, it is being used as the treatment patients switch to or continue as a single medicine to help maintain remission.

What is already known about the treatment

Mesalazine - Mesalazine is given by mouth as prolonged-release granules or tablets that are designed to pass through the stomach and release the medicine later in the gut. It is a well-known and widely used medicine in medical practice and research, especially for ulcerative colitis, where it helps keep the disease in remission and reduce flare-ups. It belongs to the group of anti-inflammatory bowel medicines, also known as aminosalicylates, and it works mainly by calming inflammation in the bowel lining through blocking several chemical signals that drive swelling and irritation.

Investigated diseases

Ulcerative Colitis - Ulcerative colitis is a long-term disease that causes ongoing inflammation of the large intestine and rectum. It usually develops in episodes, with periods of calm disease followed by flare-ups. Over time, the inflammation can return after a quiet period and may spread more widely within the colon. Symptoms and disease activity can change gradually, with some people remaining stable for long periods and others having repeated relapses.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-524675-23-00Protocol codeIDEAEstimated enrolment304 patients

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