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

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
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 90 days 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

Exclusion Criteria:

Stage IV cancer or metastatic breast cancer at any time
Inflammatory breast cancer
Receiving other investigational agents
Receiving chemotherapy
Requiring 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.