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Study of Dostarlimab for Patients with Untreated Locally Advanced Rectal Cancer

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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 a type of cancer called locally advanced rectal cancer. Specifically, it involves patients with a subtype known as dMMR/MSI-H rectal cancer, which refers to certain genetic characteristics of the cancer cells. The treatment being tested in this study is a medication called Dostarlimab, which is given as an infusion, meaning it is administered directly into the bloodstream through a vein.

The purpose of the study is to evaluate how effective Dostarlimab is in treating patients who have not received any prior treatment for their cancer. Participants in the study will receive this medication and will be monitored over time to see how their cancer responds. The study will track the progress of the disease and assess the overall health and well-being of the participants throughout the treatment period.

During the study, participants will receive regular infusions of Dostarlimab and will have follow-up visits to check on their health and the status of their cancer. The study aims to gather information over several years to understand the long-term effects and benefits of the treatment. Some participants may receive a placebo, which is a substance with no active medication, to compare the effects of Dostarlimab with no treatment. The study is designed to provide valuable insights into the potential of Dostarlimab as a treatment option for this specific type of rectal cancer.

The research process

The trial runs in 4 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, the participant is required to provide a tissue sample for testing. This sample is used to confirm the presence of specific cancer characteristics.

    The participant must have a performance status that indicates they are able to carry out daily activities without significant restriction.

  2. Step 2

    Treatment administration

    The participant receives the medication dostarlimab, which is administered as a solution for infusion. This means the medication is given through a vein, a process known as intravenous use.

    The dosage of the medication is 500 mg. The frequency and duration of administration are determined by the study protocol and the participant's response to the treatment.

  3. Step 3

    Disease assessment

    After the last dose of the study medication, the participant undergoes regular assessments to evaluate the response to the treatment.

    The primary goal is to maintain a complete response for 12 months. This means the cancer does not show signs of returning or progressing during this period.

  4. Step 4

    Extended monitoring

    If the participant maintains a complete response for 12 months, further assessments are conducted to monitor the response for 24 months and 36 months.

    The study also evaluates the participant's survival and freedom from disease progression or recurrence over a period of 3 years from the first dose of the medication.

Who can join the trial?

7 criteria

  • Must be at least 18 years old or the legal age of consent in your area.
  • Must have a confirmed diagnosis of Stage II to III locally advanced rectal adenocarcinoma. This means the cancer is in the rectum and has grown into nearby tissues but has not spread to distant parts of the body.
  • Must have a disease that can be evaluated using imaging tests and a procedure called an endoscopy, which involves looking inside the body with a camera.
  • Must have a stored tissue sample from a previous biopsy or surgery that can be sent for testing.
  • Must have an **ECOG performance status** of 0 or 1. This is a scale used to assess how well you can perform daily activities. A score of 0 means you are fully active, and a score of 1 means you have some symptoms but can still do light work.
  • Must have **adequate organ function**, meaning your organs like the liver and kidneys are working well enough to handle the treatment.
  • Must have a tumor that shows either **dMMR status** or **MSI-H phenotype**. These are specific characteristics of the cancer cells that can affect how the cancer behaves and responds to treatment.

Who cannot join the trial?

5 criteria

  • Patients who have already received treatment for their **rectal cancer** cannot participate. **Rectal cancer** is a type of cancer that affects the last part of the large intestine.
  • Patients with other types of cancer, not specifically **Stage II/III dMMR/MSI-H rectal cancer**, are excluded. **Stage II/III** refers to the extent or severity of the cancer, and **dMMR/MSI-H** are specific characteristics of the cancer cells.
  • Patients who are not within the specified age range for the study cannot participate. The study is open to certain age groups only.
  • Patients who are not able to provide informed consent or understand the study requirements are excluded. **Informed consent** means agreeing to participate in the study after understanding all the details and risks involved.
  • Patients who are part of a vulnerable population, which may include those with certain health conditions or social situations, are excluded to ensure their safety.
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Investigated drugs

Dostarlimab is a medication being studied for its effectiveness in treating certain types of rectal cancer. It is used in patients who have not received any prior treatment for their cancer. The goal of the study is to see how well dostarlimab works in shrinking or controlling the cancer.

What is already known about the treatment

Dostarlimab – Dostarlimab is administered as an intravenous infusion, typically given in a clinical setting under the supervision of healthcare professionals. It is currently being studied in clinical trials for its effectiveness in treating locally advanced rectal cancer, specifically in patients with certain genetic markers known as dMMR/MSI-H. The main therapeutic indication for dostarlimab in this context is to treat untreated Stage II/III rectal cancer. At the molecular level, dostarlimab works by blocking a protein called PD-1 on the surface of immune cells, which helps the immune system recognize and attack cancer cells. It is classified as an immune checkpoint inhibitor, a type of medication that enhances the body's immune response against cancer.

Investigated diseases

Rectal Cancer – Rectal cancer is a type of cancer that begins in the rectum, which is the last several inches of the large intestine before the anus. It often starts as a growth on the inner lining of the rectum, known as a polyp, which can become cancerous over time. As the disease progresses, the cancer can invade deeper layers of the rectal wall and potentially spread to nearby lymph nodes and other organs. Symptoms may include changes in bowel habits, rectal bleeding, and abdominal discomfort. The progression of rectal cancer can vary, with some cases remaining localized while others may spread to distant parts of the body. Early detection and monitoring are crucial for managing the disease effectively.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2023-509583-22-00Protocol code219369Estimated enrolment150 patientsSponsorGlaxosmithkline Research & Development Limited

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