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Study of zolbetuximab, pembrolizumab and chemotherapy in adults with HER2-negative, Claudin 18.

Fast replyRegistered drugNo placebo
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What is this trial about?

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

This clinical trial studies treatment for gastric cancer and gastroesophageal junction adenocarcinoma that cannot be surgically removed or has spread to other parts of the body. The study tests a combination of medications including zolbetuximab, pembrolizumab, and chemotherapy drugs (capecitabine, oxaliplatin, fluorouracil, and folinic acid). The purpose is to evaluate whether adding zolbetuximab to pembrolizumab and chemotherapy works better than chemotherapy and pembrolizumab alone as a first treatment.

The study involves people whose tumors test negative for a protein called HER2 but positive for two other proteins called CLDN18.2 and PD-L1. During the study, participants will receive either zolbetuximab or a placebo along with pembrolizumab and chemotherapy through intravenous infusions. Some chemotherapy medications will be given as tablets to take by mouth.

Researchers will track how long participants live, whether their cancer grows or spreads, and how their tumors respond to treatment. They will also monitor participants for any side effects from the treatment combination. The study will check blood samples to measure drug levels and test for the body's immune response to the medications.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial treatment phase

    You will receive a combination of medications through different methods:

    - Zolbetuximab (Vyloy) given through an intravenous infusion

    - Pembrolizumab (Keytruda) given through an intravenous infusion

    - One of two chemotherapy combinations:

  2. Step 2

    Chemotherapy option 1 (CAPOX)

    CAPOX combination includes:

    - Oxaliplatin given through an infusion

    - Capecitabine taken as oral medication

  3. Step 3

    Chemotherapy option 2 (mFOLFOX6)

    mFOLFOX6 combination includes:

    - Oxaliplatin given through an infusion

    - Fluorouracil given through intravenous injection or infusion

    - Folinic acid given through an infusion

  4. Step 4

    Monitoring phase

    Regular assessments will include:

    - Evaluation of how the cancer responds to treatment

    - Physical examinations

    - Blood tests

    - Heart monitoring (ECG)

    - Checking for side effects of the treatment

  5. Step 5

    Treatment duration

    The study will continue until:

    - The cancer shows signs of progression

    - Unacceptable side effects occur

    - The planned end date of the study (January 2030)

    Your doctor will regularly evaluate if continuing the treatment is beneficial for you

Who can join the trial?

10 criteria

  • Must be at least 18 years old to sign the consent form
  • Must have a tumor that tests positive for PD-L1 (a protein that helps control immune system responses)
  • Must have confirmed gastric or gastroesophageal adenocarcinoma (cancer of the stomach or where the stomach meets the esophagus)
  • Must have advanced cancer that cannot be surgically removed or has spread to other parts of the body, confirmed by imaging within 28 days before study start
  • Must have cancer that can be measured by imaging scans. If there is only one measurable tumor and previous radiation therapy, the tumor must either be outside the treated area or show growth after radiation
  • Must have good physical function status (ECOG score of 0 or 1), meaning able to perform daily activities with minimal assistance
  • Must have a life expectancy of at least 12 weeks as determined by the doctor
  • Must be able to receive treatment with mFOLFOX6 or CAPOX (types of chemotherapy) and pembrolizumab (an immunotherapy drug)
  • Must have a tumor that is HER2-negative (does not have high levels of a specific protein called HER2)
  • Must have a tumor that is positive for CLDN18.2 (a specific protein found in some stomach cancers)

Who cannot join the trial?

14 criteria

  • Known allergy or sensitivity to any of the study medications or their components
  • Previous treatment with chemotherapy for advanced or metastatic (cancer that has spread to other parts of the body) gastric cancer
  • Active autoimmune disease (condition where your immune system attacks healthy cells) requiring systemic treatment
  • Presence of brain metastases (cancer spread to the brain) that are untreated or unstable
  • History of other cancers within the last 5 years, except for successfully treated non-melanoma skin cancer or cervical cancer in situ
  • Significant heart conditions including heart failure, uncontrolled high blood pressure, or recent heart attack
  • Active hepatitis B or hepatitis C infection
  • Active tuberculosis infection
  • Pregnant or breastfeeding women
  • Unable to swallow oral medications
  • Major surgery within 4 weeks before starting the study treatment
  • Participation in another clinical trial within 4 weeks before starting this study
  • Any condition that, in the opinion of the study doctor, would make participation unsafe
  • Unable to understand or provide informed consent
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Investigated drugs

  • Zolbetuximab

    is an antibody medication that targets a specific protein called Claudin 18.2, which is found on the surface of some stomach and gastroesophageal junction cancer cells. It works by helping the immune system recognize and attack cancer cells.

  • Pembrolizumab

    is an immunotherapy medication that helps the body's immune system detect and fight cancer cells. It works by blocking a protein called PD-L1 that cancer cells use to hide from the immune system.

  • CAPOX

    is a combination chemotherapy treatment that includes two medications: capecitabine and oxaliplatin. These medications work together to kill cancer cells or stop them from growing.

  • mFOLFOX6

    is another combination chemotherapy treatment that includes several medications: fluorouracil, leucovorin, and oxaliplatin. These medications work together in different ways to kill cancer cells or prevent them from multiplying.

What is already known about the treatment

  • Zolbetuximab

    A monoclonal antibody administered intravenously that is currently being investigated in clinical trials for the treatment of gastric and gastroesophageal junction adenocarcinoma. The medication specifically targets Claudin 18.2, a protein found in certain types of stomach cancers, and works by binding to cancer cells and triggering an immune response against them. It is being studied in combination with pembrolizumab and chemotherapy as a first-line treatment for patients with HER2-negative and CLDN 18.2-positive tumors.

  • Pembrolizumab

    An immunotherapy medication administered through intravenous infusion that belongs to the class of PD-1 inhibitors. It works by blocking the PD-1 pathway, helping the immune system recognize and attack cancer cells more effectively. This medication is already approved for various cancer types and is being studied in combination with zolbetuximab and chemotherapy for treating gastric and gastroesophageal junction adenocarcinoma.

Investigated diseases

  • Gastric Adenocarcinoma

    A type of stomach cancer that begins in the glandular cells of the stomach lining. These cells normally produce mucus and other fluids that help with digestion. The disease typically develops slowly over many years, starting with changes in the stomach's inner lining. As the cancer grows, it can spread deeper into the stomach walls and potentially to other parts of the body.

  • Gastric Cancer

    A disease where abnormal cells form in the tissues of the stomach. It usually starts in the mucus-producing cells that line the stomach. The condition can develop in any part of the stomach and can spread throughout the stomach and to other organs. Early stages may have minimal symptoms, while the disease progresses gradually over time.

  • Gastroesophageal Junction Adenocarcinoma

    A cancer that forms in the area where the esophagus joins the stomach. This type of cancer develops in the glandular tissue near the junction of these two organs. The disease begins in the cells that make and release mucus and other fluids. As it progresses, it can affect both the lower esophagus and upper portion of the stomach.

Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-519773-19-00Protocol code8951-CL-0305Estimated enrolment500 patientsSponsorAstellas Pharma Global Development Inc.

sourced from the EU Clinical Trials Register and site verification

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On this site, “treatment” means an investigational medicine being studied in a clinical trial. Its safety and efficacy for the use being studied have not yet been confirmed, some participants may receive a placebo or a comparator medicine, and taking part does not guarantee any health benefit. The decision to take part is made by the doctor at the research site. This site is for information only and does not replace medical advice.

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).