NCT05232916 Phase 3 Study to Evaluate the Efficacy and Safety of HER2/Neu Peptide GLSI-100 (GP2 + GM-CSF) in HER2/Neu Positive Subjects

Eligibility & Interventions

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What to Expect as a Participant

You will actively receive the study intervention — which may be a drug, biologic, device, or procedure.

Phase 3 trials are large pivotal studies comparing the treatment to current standard of care or placebo. Your participation directly contributes to the evidence needed for regulatory approval.

This trial targets 750 participants in total. It began in 2022-08-11 with a primary completion date of 2026-12.

Brief Summary

This is a prospective, randomized, double-blinded, placebo-controlled, multi-center, Phase 3 study of GLSI-100 immunotherapy in HLA-A\*02 positive and HER2/neu positive subjects who are at high risk for disease recurrence and have completed both neoadjuvant and postoperative adjuvant standard of care therapy. Treatment consists of 6 intradermal injections, Primary Immunization Series (PIS), over the first 6 months of treatment and 5 booster intradermal injections spaced 6 months apart. A third open-label arm will explore GLSI-100 immunotherapy in non-HLA-A\*02 positive and HER2/neu positive subjects.

Eligibility Criteria

Inclusion Criteria: * HLA-A\*02-positive, unless being enrolled in the third non-HLA-A\*02 arm * Histologically confirmed diagnosis of HER2/neu positive primary breast cancer for all tumors biopsied (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 Criteria: * 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.

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