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Study on the Safety and Activity of S095029 and Pembrolizumab for Patients with Advanced Gastric or Gastroesophageal Junction Cancer

Verified siteRegistered 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 is focused on studying advanced forms of gastroesophageal junction cancer and gastric cancer that are characterized by specific genetic features known as MSI-H (microsatellite instability-high) or dMMR (deficient mismatch repair). These types of cancer are often more challenging to treat because they have spread to other parts of the body or cannot be removed through surgery. The study is testing a new treatment combination that includes a medication called S095029, also known as Sym025, which is an anti-NKG2A antibody. This medication is being used alongside another drug called Keytruda, which contains the active substance pembrolizumab. Pembrolizumab is a type of protein that helps the immune system recognize and attack cancer cells.

The purpose of the study is to evaluate the safety and effectiveness of this combination therapy. Participants will receive the treatment through an intravenous infusion, which means the medication is given directly into a vein. The study is divided into two phases. The first phase, known as Phase 1b, will focus on determining the safest dose of S095029 when used in combination with Keytruda. The second phase, Phase 2, will assess how well the treatment works in shrinking tumors and controlling the cancer. Throughout the study, researchers will monitor participants for any side effects and changes in their health to ensure the treatment is safe and effective.

This trial is open-label, meaning both the participants and the researchers know which treatments are being administered. The study is expected to continue for several years, allowing researchers to gather comprehensive data on the treatment's impact on cancer progression and patient well-being. Participants will be closely monitored by healthcare professionals throughout the study to ensure their safety and to collect valuable information on the treatment's effects.

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

    Joining the study

    Upon joining the study, a diagnosis of locally advanced and unresectable or metastatic gastric or gastroesophageal junction adenocarcinoma must be confirmed.

    The tumor must have MSI-H or dMMR status, which can be documented in the medical history or through testing of tumor tissue.

  2. Step 2

    Phase 1b: safety and tolerability evaluation

    The initial phase focuses on evaluating the safety and tolerability of the combination therapy.

    Participants receive S095029 and pembrolizumab intravenously. The dosage and frequency are determined by the study team based on safety assessments.

    Monitoring for any dose-limiting toxicities and adverse events is conducted.

  3. Step 3

    Phase 2: antitumor activity evaluation

    This phase evaluates the antitumor activity of the combination therapy.

    Participants continue to receive S095029 and pembrolizumab intravenously.

    The study assesses the objective response of the tumor to the treatment, as well as the overall safety and tolerability.

  4. Step 4

    Monitoring and assessments

    Throughout the trial, regular monitoring of vital signs and laboratory values is conducted to ensure safety.

    The frequency and severity of any adverse events are recorded.

    The study also measures serum concentrations of S095029 and checks for any antibodies against it.

  5. Step 5

    Completion of the study

    The study is estimated to end by June 2029.

    Final assessments include evaluating the overall survival and progression-free survival of participants.

Who can join the trial?

5 criteria

  • Participants must have a confirmed diagnosis of a type of stomach cancer called **gastric adenocarcinoma** or a cancer at the junction of the stomach and esophagus called **gastroesophageal junction adenocarcinoma**. This diagnosis should be confirmed by examining tissue samples under a microscope.
  • The cancer must be **locally advanced and unresectable** (meaning it has grown too much to be removed by surgery) or **metastatic** (meaning it has spread to other parts of the body).
  • The tumor must have a specific status called **MSI-H** (Microsatellite Instability-High) or **dMMR** (deficient Mismatch Repair). This status can be determined by tests done on tumor tissue, either from past medical records or from a new biopsy if needed.
  • Both men and women can participate in the study.
  • Participants must be adults, which means they should be 18 years or older.

Who cannot join the trial?

10 criteria

  • Patients with other types of cancer that are not **MSI-H/dMMR Gastric cancer** or **MSI-H/dMMR Gastroesophageal-junction Cancer**.
  • Patients who have not recovered from previous cancer treatments.
  • Patients with serious heart problems.
  • Patients with active infections that need treatment.
  • Patients who are pregnant or breastfeeding.
  • Patients with a history of severe allergic reactions to similar medications.
  • Patients with uncontrolled high blood pressure.
  • Patients with severe liver or kidney disease.
  • Patients who have participated in another clinical trial recently.
  • Patients with any other medical condition that the study doctors think would make it unsafe to participate.
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Investigated drugs

S095029 is an experimental medication being studied for its potential to help treat certain types of cancer. It is an anti-NKG2A antibody, which means it is designed to target and block a specific protein that may help cancer cells evade the immune system. By blocking this protein, S095029 may help the body's immune system better recognize and attack cancer cells. This medication is being tested in combination with other therapies to see if it can improve treatment outcomes for patients with advanced gastro-esophageal junction or gastric cancer.

What is already known about the treatment

S095029 – This medication is administered as an intravenous infusion and is currently being studied in clinical trials for its safety, tolerability, and effectiveness in treating certain types of gastric and gastroesophageal-junction cancers. It is specifically being tested for cancers that are MSI-H/dMMR, which are particular genetic profiles of these cancers. S095029 works by targeting the NKG2A receptor, which is involved in immune system regulation, potentially enhancing the body's ability to fight cancer cells. It is classified as an anti-NKG2A antibody, a type of immunotherapy aimed at boosting the immune response against tumors.

Investigated diseases

  • Gastric Cancer

    Gastric cancer, also known as stomach cancer, begins in the cells lining the stomach. It often starts in the mucus-producing cells on the stomach's inner surface. As the disease progresses, it can invade deeper layers of the stomach wall and spread to nearby organs. Symptoms may include indigestion, stomach pain, nausea, and loss of appetite. Over time, the cancer can spread to lymph nodes and other parts of the body. The progression can vary greatly depending on the cancer's type and location within the stomach.

  • Gastroesophageal Junction Cancer

    Gastroesophageal junction cancer occurs where the esophagus meets the stomach. This type of cancer typically starts in the cells lining this area and can affect both the esophagus and the stomach. As it progresses, it may cause difficulty swallowing, chest pain, and weight loss. The cancer can grow into nearby tissues and spread to other parts of the body. It often involves the lymph nodes and can affect the function of the esophagus and stomach. The progression and symptoms can vary based on the cancer's specific location and growth rate.

Trial detailsLast updated 4 Oct 2026
Age18+ yearsPhasePhase ITrial ID2023-507995-33-00Protocol codeCL1-95029-002Estimated enrolment57 patientsSponsorInstitut De Recherches Internationales Servier IRIS

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