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Study on the Effectiveness of GP2 and Sargramostim for HER2 Positive Breast Cancer Patients with Residual Disease or High-Risk After Standard Therapy

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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 breast cancer, specifically in patients who have a type of breast cancer known as HER2-positive. The study will evaluate a treatment called GLSI-100, which is a combination of two substances: GP2 and GM-CSF (also known as Sargramostim). These substances are given as an injection under the skin. The trial will also use a placebo, which is a substance with no active medication, to compare the effects of the treatment.

The purpose of the study is to assess how effective and safe GLSI-100 is for patients who have completed standard breast cancer treatments but still have a high risk of the cancer returning. Participants in the study will receive either the GLSI-100 treatment or a placebo. The study will last for a period of time, during which participants will receive regular injections and attend follow-up visits to monitor their health and the effects of the treatment.

Throughout the study, participants will be closely monitored for any changes in their condition, including any side effects or improvements. The study aims to provide valuable information on whether GLSI-100 can help reduce the risk of breast cancer coming back in patients who have already undergone extensive treatment. This research could potentially lead to new treatment options for individuals with high-risk breast cancer.

The research process

The trial runs in 6 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, eligibility is confirmed based on specific criteria such as age, pregnancy status, and medical history related to breast cancer.

    The study is designed for individuals who have completed certain breast cancer therapies and meet specific health conditions.

  2. Step 2

    Randomization and initial assessment

    Participants are randomly assigned to receive either the study medication or a placebo.

    Initial assessments are conducted to establish baseline health status and ensure no residual breast cancer is present.

  3. Step 3

    Medication administration

    The study involves the administration of GLSI-100 or a placebo. GLSI-100 consists of a combination of GP2 and GM-CSF.

    The medication is given as an injection through the skin (intradermal).

  4. Step 4

    Treatment schedule

    The treatment is administered according to a specific schedule, which is determined by the study protocol.

    Participants are monitored regularly to assess the effects of the treatment and any side effects.

  5. Step 5

    Follow-up and monitoring

    Regular follow-up visits are scheduled to monitor health status and the effectiveness of the treatment.

    Assessments include checking for any recurrence of breast cancer and evaluating overall health and quality of life.

  6. Step 6

    Completion of the study

    The study is expected to continue until February 28, 2030, with participants being followed up throughout this period.

    Upon completion, final assessments are conducted to gather comprehensive data on the treatment's efficacy and safety.

Who can join the trial?

11 criteria

  • Must be over 18 years old.
  • If you are a woman, you need a negative pregnancy test or proof that you are post-menopausal, which means you have stopped having periods naturally.
  • If you can have children, you must agree to use a very reliable form of birth control.
  • Must be **HLA-A*02-positive**, which is a specific genetic marker, unless you are joining a special group in the study that does not require this marker.
  • Must have a confirmed diagnosis of **HER2/neu positive primary breast cancer**, which is a type of breast cancer that tests positive for a protein called HER2.
  • Must have completed both **neoadjuvant** (treatment given before surgery) and **adjuvant** (treatment given after surgery) **trastuzumab-based therapy**, which is a standard treatment for breast cancer.
  • Must have been at **Stage I, II, or III** when first diagnosed, with remaining cancer in the breast or lymph nodes after initial treatment, or at **Stage III** with no remaining cancer after initial treatment.
  • Must be able to start the study treatment within one year after finishing adjuvant trastuzumab-based therapy and any other standard treatments. The study treatment can be taken with **endocrine therapy** (hormone therapy), but not with **neratinib**, which is another cancer drug.
  • Must not have any signs of remaining or ongoing breast cancer.
  • Must have an **ECOG** score of 0-2, which is a scale used to assess how well you can perform daily activities. A score of 0 means fully active, and 2 means you are up and about more than half the day.
  • Must have organs that are working well enough to participate in the study.

Who cannot join the trial?

4 criteria

  • Patients who have not completed both neoadjuvant and postoperative adjuvant trastuzumab-based standard of care therapy. This means patients must have finished specific treatments given before and after surgery.
  • Patients who do not have a high risk of disease coming back after treatment. This refers to patients who are not in stage I, II, or III with remaining disease after surgery, or stage III with no disease found after surgery.
  • Patients who are not HLA-A*02 positive. This is a specific genetic marker that must be present.
  • Patients who are not HER2/neu positive. This means the cancer cells must have a certain protein on their surface.
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Investigated drugs

  • GLSI-100 (GP2 + GM-CSF)

    is a combination of a peptide vaccine and an immune system booster. It is designed to help the body recognize and fight cancer cells that express the HER2/neu protein. This therapy is being tested in patients with breast cancer who are at high risk of the disease coming back after surgery and standard treatments. The goal is to see if this combination can reduce the chance of cancer returning.

  • Trastuzumab

    is a medication used in the treatment of breast cancer that targets the HER2/neu protein on cancer cells. It is part of the standard care for patients with HER2-positive breast cancer. In this trial, patients have already received trastuzumab as part of their treatment before participating in the study.

What is already known about the treatment

GLSI-100 – GLSI-100 is administered as an injection and is currently being studied in clinical trials for its effectiveness in treating HER2/neu positive breast cancer. It is in the experimental phase and not yet widely available in medical practice. The main therapeutic indication is for patients with a high risk of disease recurrence after standard trastuzumab-based therapy. At the molecular level, GLSI-100 works by stimulating the immune system to target and attack cancer cells expressing the HER2/neu protein. It is classified as an immunotherapy agent.

Investigated diseases

Breast Cancer – Breast cancer is a disease where cells in the breast grow uncontrollably, forming a tumor that can often be felt as a lump. It typically begins in the ducts or lobules of the breast and can spread to other parts of the body if not managed. The progression of breast cancer can vary, with some tumors growing slowly and others more rapidly. It is often categorized by stages, which indicate the extent of the disease, ranging from early, localized stages to more advanced stages where cancer has spread. Factors such as hormone receptor status and genetic markers like HER2/neu can influence the behavior and progression of the disease. Regular monitoring and medical evaluations are crucial for understanding the progression in individuals diagnosed with breast cancer.
Trial detailsLast updated 4 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-504323-25-01Protocol codeGLSI-21-01Estimated enrolment2 250 patientsSponsorGreenwich LifeSciences Inc.

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