Phase II Trial of Combination Immunotherapy With NeuVax and Trastuzumab in High-risk HER2+ Breast Cancer Patients

In this study, the investigators intend to assess the ability of the combination of trastuzumab and the HER2 vaccine nelipepimut-S (administered with the immunoadjuvant GM-CSF) given in the adjuvant setting to prevent recurrences in patients with high-risk HER2-positive breast cancer. High-risk is defined as those patients that do not achieve a pCR after neoadjuvant therapy with an approved regimen that includes trastuzumab and at least four cycles (12 weeks) of taxane-containing chemotherapy or those who undergo upfront surgery and are found to have greater than or equal to four positive lymph nodes regardless of hormone receptor status or 1-3 positive lymph nodes and are hormone receptor negative. Following surgery, patients will be screened and HLA-typed (consent #1). Nelipepimut-S is a CD8-eliciting peptide vaccine that is restricted to HLA-2+ or HLA-A3+ or HLA-A24+ or HLA-A26+ patients (approximately 80% of the US population). HLA-A2+/A3+/A24+/orA26+ patients who meet all other eligibility criteria will be randomized to receive trastuzumab + nelipepimut-S/GM-CSF or trastuzumab + GM-CSF alone (consent #2). The trastuzumab will be administered to all patients consistent with current standard of care. Patients randomized to the nelipepimut-S/GM-CSF arm will receive vaccinations of nelipepimut-S (1000 mcg) and GM-CSF (250 mcg) administered intradermally every three weeks for six total vaccinations, 30-120 minutes after completion of trastuzumab infusion. The first vaccination will be given with the third dose of maintenance trastuzumab administered as monotherapy optimally, but may be given with later maintenance doses of trastuzumab, provided there are at least six remaining doses of trastuzumab to overlap with the primary vaccine series. Patients randomized to the GM-CSF alone arm will receive inoculations of GM-CSF (250 mcg) administered in an identical manner to those receiving nelipepimut-S/GM-CSF. Patients will be blinded as to whether they are receiving nelipepimut-S/GM-CSF or GM-CSF alone. Upon completion of the primary vaccination/inoculation series, booster inoculations (same dose and route) will be administered every six months x 4. The first booster inoculation will occur 6 months ± 2 weeks after the completion of the PVS, with subsequent boosters timed every six months + 2 weeks. Boosters will therefore occur at the following time points after completion of the PVS: 6 months ± 2 weeks, 12 months ± 2 weeks, 18 months ± 2 weeks, 24 months ± 2 weeks. Booster inoculations will occur for patients randomized to receive nelipepimut-S/GM-CSF as well as patients randomized to receive GM-CSF alone, and will consist of the same treatment drugs and dosing (i.e., nelipepimut-S/GM-CSF patients will be boosted with nelipepimut-S/GM-CSF while GM-CSF alone patients will be boosted with GM-CSF alone). Patient blinding will be maintained throughout the study. Subjects will be followed for safety issues, immunologic response and clinical recurrence. Patients will be monitored 48-72 hours after each inoculation for reaction to the inoculation as well as documentation of any adverse effects experienced. Immunologic response will be monitored primarily by in vivo delayed type hypersensitivity (DTH) reactions but also may be documented by other immunologic assays. All patients will be followed for a total of 36 months from the time of initiation of trastuzumab maintenance therapy to document disease-free status.