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Phase II Study of Intratumoral Hydrogen Peroxide (KRC-01) Combined with Radiotherapy for 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

Locally advanced high‑risk stage III rectal adenocarcinoma (non‑metastatic) is a type of cancer that has grown through the wall of the rectum but has not spread to other parts of the body. The study uses a combination of external beam radiotherapy and injections of KRC-01, an investigational product that contains hydrogen peroxide and is given directly into the tumor (intratumoral injection). The aim is to shrink or eliminate the tumor while trying to keep the rectum intact.

The purpose is to determine how often patients achieve a clinical complete response, meaning that after treatment no tumor can be felt or seen on exams. Participants receive a series of radiation sessions over several weeks together with several KRC-01 injections, followed by visits to check the tumor with imaging and questionnaires about quality of life at about week 6 and week 24. Safety and side effects are recorded, and blood and tissue samples are collected to look for markers that might predict how well the treatment works.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Baseline evaluation

    After joining the trial, you will undergo a baseline evaluation that includes medical history, physical examination, blood tests, and imaging of the rectal tumor.

    Questionnaires about quality of life and symptoms will be completed at this visit.

    The purpose of these assessments is to document the condition of the disease before any treatment begins.

  2. Step 2

    Start of radiotherapy

    You will begin external beam radiotherapy, which is a type of treatment that uses high‑energy rays to target the tumor.

    Treatment is usually given once a day, five days a week, for several weeks according to the study protocol.

  3. Step 3

    Intratumoral krc-01 injections

    During the radiotherapy period you will receive injections of krc-01 directly into the tumor.

    Each injection contains 5 ml of a solution that includes hydrogen peroxide, which is the active substance.

    The injections are administered once a week, on the same day each week, for the duration of the radiotherapy course.

  4. Step 4

    Continuation of combined treatment

    Radiotherapy and weekly krc-01 injections continue together for the planned treatment period, typically about five weeks.

    You will attend the treatment center for each radiotherapy session and for the weekly injection.

  5. Step 5

    Completion of treatment

    After the last radiotherapy session and the final krc-01 injection, the active treatment phase of the trial ends.

    You will be monitored for any immediate side effects before leaving the clinic.

  6. Step 6

    Week 6 follow‑up

    Six weeks after the end of treatment, you will return for a follow‑up visit.

    The visit includes a physical exam, repeat imaging of the tumor area, blood tests, and the same quality‑of‑life questionnaires completed at baseline.

    These assessments help determine early response to the combined therapy.

  7. Step 7

    Week 24 assessment of clinical complete response

    Twenty‑four weeks after treatment completion, a comprehensive evaluation is performed to assess the clinical complete response (ccr).

    Ccr means that no tumor can be detected by clinical examination, imaging, or endoscopy.

    The assessment also includes the quality‑of‑life questionnaires and any additional tests required by the study.

  8. Step 8

    Long‑term follow‑up

    After the week 24 visit, you will continue to be followed at regular intervals as defined by the study protocol.

    Follow‑up visits monitor overall survival, disease progression, and late side effects.

    The schedule may include periodic imaging, blood tests, and questionnaires to track health status over time.

Who can join the trial?

21 criteria

  • Age: You must be 18 years old or older, regardless of gender.
  • ECOG performance status 0 or 1: This measures how well you can carry out daily activities. A score of 0 means you are fully active; a score of 1 means you are limited in physically strenuous activities but can do light work.
  • Confirmed locally advanced rectal adenocarcinoma, stage III (high risk): A tissue sample must show a type of rectal cancer that is advanced but has not spread to other parts of the body.
  • No metastatic disease on CT scan: A CT (computed tomography) scan of your chest and abdomen must show no signs that the cancer has spread to other organs.
  • High‑risk tumor features: Your tumor must have at least one of the following:
    • cT4a or cT4b – the tumor has grown through the outer wall of the rectum.
    • EMVI+ – cancer cells are found in blood vessels outside the rectal wall.
    • cN2 – many nearby lymph nodes contain cancer.
    • MFI+ – the tumor is close to the protective tissue surrounding the rectum.
    • Lat LN+ – side (lateral) lymph nodes are involved.
    • Location within 15 cm of the anal margin: The lower edge of the tumor must be less than 15 centimeters from the opening of the anus.
    • Surgery alone unlikely to achieve clear margins: Doctors expect that removing the tumor with surgery alone would not completely eliminate cancer cells.
    • Measurable by endoscopic visual assessment: The tumor must be visible and measurable using an endoscope, a thin camera inserted through the rectum.
    • Accessible for intratumoral injections: The tumor must be reachable so that the study drug can be injected directly into it.
    • Planned standard treatment: You must intend to receive a treatment plan that includes 5‑fluorouracil‑based chemoradiotherapy together with either CAPOX (six cycles) or FOLFOX (nine cycles), which are standard chemotherapy regimens.
    • Life expectancy greater than 6 months: Doctors must believe you are likely to live at least six more months.
    • Acceptable organ function: Blood and other lab tests must show that your liver, kidneys, bone marrow, and other organs are working well enough for the study.
    • Pregnancy testing for women of childbearing potential: Women who could become pregnant must have a negative blood pregnancy test within the last 7 days or a negative urine test within 12 hours before the first study treatment.
    • Willingness to undergo tumor biopsy: You must agree to have a small tissue sample taken from the tumor, and the tumor must be reachable for this procedure.
    • Signed informed consent: You must read, understand, sign, and date a written consent form before any study procedures begin.
    • Ability to attend study visits: You must be able and willing to come to all scheduled appointments and follow the study procedures.
    • Social security or similar coverage: You must be enrolled in a social security system or a comparable benefit program.

Who cannot join the trial?

19 criteria

  • Not able to receive radiotherapy because of bowel problems such as fistulas (abnormal connections), severe ulcerative colitis (a type of inflammatory bowel disease, especially if taking sulphasalazine), active Crohn’s disease, or previous scar tissue (adhesions).
  • Having low levels of important minerals (potassium, magnesium, or calcium) or an abnormal heart rhythm measurement called a prolonged QT/QTc interval (greater than 450 ms for men or 470 ms for women).
  • Having any previous radiotherapy to the pelvic area.
  • Having conditions that make an MRI unsafe, such as a pacemaker, severe claustrophobia, or being too heavy for the scanner.
  • Taking part in another clinical study with an experimental drug within the last 3 months.
  • Having had prior rectal surgery.
  • Having received experimental treatment for rectal cancer before.
  • Having a tumor type known as high microsatellite instability (MSI‑H) or mismatch repair deficient (dMMR), which may be better treated with other standard therapies.
  • Having high medical risk from other serious illnesses, such as uncontrolled infections or uncontrolled diabetes.
  • Being on therapeutic blood‑thinning medication (full‑dose anticoagulation). Low‑dose preventive blood thinners may be allowed at the doctor's discretion.
  • Taking the antiviral drug brivudine or having taken it within the past 4 weeks.
  • Having moderate or worse nerve damage (peripheral sensory neuropathy grade 2 or higher) that could affect future chemotherapy with oxaliplatin.
  • Having a deficiency of the enzyme DPD (dihydropyrimidine dehydrogenase) or not having a known DPD test result, which makes certain chemotherapy unsafe.
  • Using other medicines or having health problems that would prevent safe use of the study treatments.
  • Being allergic or otherwise unable to safely receive chemotherapy drugs such as fluoropyrimidines, oxaliplatin, or capecitabine.
  • Having received the yellow fever vaccine or any live‑attenuated vaccine (vaccines made from weakened germs), because they could cause severe infection. (COVID‑19 vaccines are allowed.)
  • Having a known HIV infection or active hepatitis B or hepatitis C infection.
  • Being pregnant, breastfeeding, or planning to become pregnant during the study.
  • Being under legal guardianship, deprived of liberty by a court decision, or otherwise unable to give informed consent.
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Investigated drugs

  • KRC-01

    is a test drug that contains a solution of hydrogen peroxide. In this study it is injected directly into the tumor in the rectum. The purpose of the injection is to help make the cancer cells more sensitive to the radiation treatment, increasing the chance that the tumor will shrink or disappear without needing surgery.

  • Radiotherapy

    is a treatment that uses high‑energy X‑rays aimed at the cancer in the rectum. The radiation damages the DNA of cancer cells, which stops them from growing and can kill them. In this trial radiotherapy is given together with the KRC‑01 injections to try to achieve a complete response, meaning the tumor may disappear completely.

What is already known about the treatment

KRC-01 - KRC-01 is given as an injectable liquid that is directly injected into the tumor (intratumoral injection). It is currently an experimental radiosensitizer being studied in clinical trials and is not yet approved for routine cancer treatment. The drug is used for patients with locally advanced high‑risk stage III rectal adenocarcinoma to improve the effect of radiotherapy. It works by releasing hydrogen peroxide in the tumor, creating reactive oxygen species that increase tumor oxygen levels and make cancer cells more vulnerable to radiation, and it is classified as an oxidative radiosensitizer.

Investigated diseases

Rectal adenocarcinoma, stage III (locally advanced, high‑risk, non‑metastatic) - It is a cancer that begins in the lining of the rectum. At stage III, the tumor has grown through the rectal wall and may involve nearby lymph nodes, but it has not spread to distant organs. The condition often causes changes in bowel habits, bleeding, or a feeling of incomplete emptying. Over time, the tumor can continue to enlarge and involve more surrounding tissues within the pelvis. If the disease progresses without intervention, it may eventually extend beyond the local area.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-524378-40-00Protocol code2025/4237 K-BOOSTEstimated enrolment24 patientsSponsorInstitut Gustave Roussy

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This service is not affiliated with the European Commission, the EMA, or the official CTIS system. Most information comes from publicly available international clinical-trial registries, supplemented by data from academic sites, national regulators and commercial sponsors. On this site, “treatment” and “therapy” mean a medicine being tested in a clinical trial. Its safety and effectiveness in the use being studied are not yet confirmed, some participants may receive a placebo or a comparator, and taking part does not guarantee a health benefit. The doctor at the research site decides who can take part. This site provides information, not medical advice. Certain content and visual elements on this website have been generated or enhanced using artificial intelligence (AI).