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Phase 3 GLSI-100 for HER2/neu Positive Breast Cancer

This study is testing GLSI-100, an immunotherapy, to see if it can help prevent breast cancer from coming back in people with HER2/neu positive breast cancer. You might be able to join if you have HER2/neu positive breast cancer, have finished standard treatments (like trastuzumab-based therapy), and are at high risk for the cancer returning. The study is looking to see how many people remain free of invasive breast cancer over about 4 years. Some participants will receive GLSI-100, and others will receive a placebo (inactive substance). The study is currently unclear on its recruitment status and plans to enroll about 750 people.

Study design
This is a Phase 3, randomized, double-blinded, placebo-controlled study involving about 750 participants. It compares GLSI-100 to a placebo, with an additional arm for those who don't have the HLA-A*02 biomarker.
What's involved
Participants will receive 6 intradermal injections over the first 6 months, followed by 5 booster injections spaced 6 months apart.
Compensation
Not stated in the trial record.
Follow-up
Participants will be followed for a median of 4 years to measure invasive breast cancer-free survival.

AI-generated from the public study record. Only the study team can confirm whether you're eligible — confirm details with them before making decisions.

NCT05232916

Phase 3 Study to Evaluate the Efficacy and Safety of HER2/Neu Peptide GLSI-100 (GP2 + GM-CSF) in HER2/Neu Positive Subjects

Recruiting
PHASE3Ages 18+InterventionalTreatment
Greenwich LifeSciences, Inc.
~2,250 participants
Updated 2026-08-06 on ClinicalTrials.gov
What's tested:PlaceboGLSI-100

At a glance

Recruiting sites
154 of 179 listed sites are recruiting right now
RecruitingSuspended, closed, or not yet open
What they're measuring
Invasive Breast Cancer-free Survival (IBCFS)
Measured over Median 4 years of follow-up (interim analyses planned)

Conditions

Breast Cancer

Explore related trials

Breast CarcinomaERBB2 GeneHLA Class I Histocompatibility Antigen, A-2 Alpha Chain

Where it's being run

179 sites across 33 states
Germany41
Spain40
France20
Italy11
California9
Texas9
Poland9
Romania4

Study leadership

  • Mothaffar F Rimawi, MD · PRINCIPAL_INVESTIGATOR · Baylor College of Medicine

Who to contact

Jaye L Thompson, Ph.D.
[email protected]
(832) 791-2542
Email the study team

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Do you actually qualify for this trial?

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Eligibility criteria

Inclusion

Histologically confirmed diagnosis of HER2/neu positive primary breast cancer for all tumors biopsied at diagnosis (multifocal, multicentric, or synchronous contralateral disease)
Completion of both neoadjuvant and adjuvant trastuzumab-based standard of care breast cancer therapy
Stage I, II, or III at presentation with pathologic evidence of residual invasive carcinoma in the breast or axillary lymph nodes (residual disease) at surgery following completion of neoadjuvant therapy -OR- Stage III at presentation with pathologic complete response (pCR) at surgery following completion of neoadjuvant therapy
The subject can begin study therapy within one year of completion of adjuvant trastuzumab-based therapy and any other standard therapies, but, study therapy can be administered concurrently with endocrine therapy.
No clinical evidence of residual or persistent breast cancer per treating physician assessment
ECOG 0-2
Adequate organ function
Negative pregnancy test or evidence of post-menopausal status
If of childbearing potential, willing to use a form of highly effective contraception
Subject must both reside in and have been treated for their cancer in the country in which the clinical site is located.

Exclusion

Stage IV cancer or metastatic breast cancer at any time
Inflammatory breast cancer
Receiving other investigational agents
Receiving chemotherapy
Requiring long-term systemic treatment with corticosteroids or other immunosuppressive therapy
History of immunodeficiency or active autoimmune disease
A history of serious allergic reactions, including anaphylaxis, to human granulocyte-macrophage colony-stimulating factors such as sargramostim, yeast-derived products, or any component of the investigational product
Other malignancies except adequately treated in situ carcinoma of the cervix or basal cell or squamous cell carcinoma of the skin
Active infection
Known HIV infection with a detectable viral load within 6 months of the anticipated start of treatment. Note: Subjects on effective antiretroviral therapy with an undetectable viral load within 6 months of the anticipated start of treatment are eligible for this trial.

What this trial measures

  • Invasive Breast Cancer-free Survival (IBCFS)Median 4 years of follow-up (interim analyses planned)

    IBCFS is defined as the time from randomization (or the first dose of study medication if in the non-randomized arm) until the date of ipsilateral invasive breast cancer recurrence, ipsilateral local-regional invasive breast cancer recurrence, distant recurrence, contralateral invasive breast cancer, or any cause mortality (STEEP version 2).