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:

• Histologically confirmed diagnosis of HER2/neu positive primary breast cancer forall tumors biopsied at diagnosis (multifocal, multicentric, or synchronouscontralateral disease)

• Completion of both neoadjuvant and adjuvant trastuzumab-based standard of carebreast cancer therapy

• Stage I, II, or III at presentation with pathologic evidence of residual invasivecarcinoma in the breast or axillary lymph nodes (residual disease) at surgeryfollowing completion of neoadjuvant therapy -OR- Stage III at presentation withpathologic complete response (pCR) at surgery following completion of neoadjuvanttherapy

• The subject can begin study therapy within one year of completion of adjuvanttrastuzumab-based therapy and any other standard therapies, but, study therapy canbe administered concurrently with endocrine therapy.

• No clinical evidence of residual or persistent breast cancer per treating physicianassessment

• 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 effectivecontraception

• Subject must both reside in and have been treated for their cancer in the country inwhich 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 otherimmunosuppressive therapy

• History of immunodeficiency or active autoimmune disease

• A history of serious allergic reactions, including anaphylaxis, to humangranulocyte-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 orbasal cell or squamous cell carcinoma of the skin

• Active infection

• Known HIV infection with a detectable viral load within 6 months of the anticipatedstart of treatment. Note: Subjects on effective antiretroviral therapy with anundetectable viral load within 6 months of the anticipated start of treatment areeligible for this trial.