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A study of botulinum toxin type A versus placebo to treat bowel movement problems in patients recovering from surgery for rectal cancer

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What is this trial about?

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

This study focuses on individuals who have undergone a surgical procedure called restorative total mesorectal excision (TME) to treat rectal cancer. A common complication following this surgery is Low Anterior Resection Syndrome (LARS), a condition that causes issues with bowel control, such as fragmented defecation, which is when a person cannot fully empty their bowels in one sitting, and urgency, which is a sudden, strong need to have a bowel movement. These symptoms are often caused by damage to the nerves that control the muscles in the colon.

The purpose of the study is to determine if injecting botulinum toxin type a into the wall of the colon can help reduce these symptoms. Botulinum toxin type a is a substance that works by relaxing the smooth muscle, which are the muscles in the body that move automatically to push waste through the digestive tract. During the study, some participants will receive the botulinum toxin type a via injection, while others will receive a placebo.

Participants will be monitored over a period of several months to observe changes in their bowel habits and symptoms. This includes assessing the frequency of bowel movements and the level of urgency experienced. The effects of the treatment will be tracked at different stages following the injections to see how much the symptoms improve compared to the group receiving the placebo.

The research process

The trial runs in 2 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    <b>injection</b> phase

    An injection is administered into the wall of the colon. this involves either botulinum toxin type a (a substance used to reduce muscle contractions) at a dose of 100 units or a placebo, which is an inactive substance, administered via rectal use.

  2. Step 2

    <b>follow-up</b> assessments

    Clinical assessments are performed at 1 month, 3 months, and 6 months after the injection to monitor progress and any side effects.

    At these intervals, different measurements are taken, including patient-reported outcomes, which involve answering questions about symptoms such as fragmented defecation (difficulty passing stool in one continuous movement) and urgency (a sudden, strong need to have a bowel movement).

    The lars score, which is a tool used to measure the severity of bowel symptoms after rectal surgery, is evaluated specifically at the 3-month mark to compare the effectiveness of the botulinum toxin type a against the placebo.

    Additional assessments may include colonic manometry, which is a test used to measure the pressure and muscle contractions within the colon.

Who can join the trial?

4 criteria

  • You must be at least 18 years old.
  • You must provide voluntary written informed consent, which means you or your legal representative must sign a document agreeing to participate after being fully informed about the study.
  • You must be scheduled for an elective restorative total mesorectal excision. This is a planned surgery to remove the rectum and the surrounding fatty tissue to treat rectal cancer.
  • You must use a highly effective method of birth control, such as implants, certain pills, or other reliable ways to prevent pregnancy, to ensure a very low chance of pregnancy during the study.

Who cannot join the trial?

10 criteria

  • You have had a partial mesorectal excision (a surgery where only part of the tissue around the rectum is removed) or a local excision (removal of a small area of tissue).
  • You have undergone a resection beyond TME (a type of surgery that removes more tissue than the standard procedure for rectal cancer).
  • You have a tumor classified as T4 that required a pelvic exenteration (a major surgery to remove organs from the pelvic area).
  • You have Inflammatory Bowel Disease, which is a condition causing long-term swelling and irritation in the digestive tract.
  • You are pregnant, breastfeeding, planning to become pregnant, or are able to become pregnant and are not using highly effective contraception (methods to prevent pregnancy).
  • You are currently participating in another medical study that uses a new investigational medicinal product (an experimental drug) or a new medical device.
  • You have a stoma, which is an opening created surgically that allows waste to leave the body through a bag.
  • You have a known hypersensitivity (an allergic reaction) to botulinum toxin type A or any of its excipients (the inactive substances used to make the medicine).
  • You have an infection at the area where the injection is planned.
  • You have a neuromuscular junction disorder, which is a condition that interferes with how your nerves communicate with your muscles; examples include myasthenia gravis or Lambert-Eaton syndrome.
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Investigated drugs

Botulinum toxin type A is a medication injected into the colon to help relax the muscles in the digestive tract. It works by blocking the signals that cause muscles to contract too strongly or too often, which may help reduce issues with bowel urgency and abnormal movements after surgery.

What is already known about the treatment

  • Botulinum toxin type A

    This medication is administered as an injection into the muscle layer of the colon to treat issues like sudden urges to use the bathroom or fragmented bowel movements. It is a well-established substance used in various medical treatments to relax muscles by blocking a specific chemical signal that tells muscles to contract. In this trial, it acts by stopping the release of a messenger called acetylcholine, which effectively reduces the uncontrolled contractions of the smooth muscles in the digestive tract. This drug is classified as a neurotoxin that functions as a muscle relaxant.

  • Sodium chloride solution

    This is a sterile saltwater solution used as a placebo in this study and is administered via rectal use. It contains no active medicinal ingredients and is used as a control to compare against the effects of the actual test drug. Because it does not have a biological effect on the body's chemistry, it serves as a neutral substance to ensure the trial results are accurate. This substance is classified as a saline solution used for physiological replacement or as a placebo.

Investigated diseases

Rectal Cancer - This is a type of cancer that begins in the tissues of the rectum, which is the last part of the large intestine. It typically develops from abnormal cell growth in the lining of the rectal wall. As the disease progresses, these abnormal cells can form tumors that may grow into deeper layers of the rectal tissue. If left unchecked, the cancer cells can spread to nearby structures or distant parts of the body. This condition is categorized under both digestive system diseases and neoplasms.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-524342-96-00Estimated enrolment20 patientsSponsorUZ Leuven

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