Study to Assess dHER2+AS15 Cancer Vaccine Given in Combination With Lapatinib to Patients With Metastatic Breast Cancer

This is a phase I/II study to determine the safety and gain insight into the immune response of the immunologic agent dHER2+AS15 ASCI when administered in combination with lapatinib. This study is for patients with metastatic breast cancer (invasive breast cancer with stage IV disease) that overexpresses HER2 and is resistant to trastuzumab (Herceptin). The dHER2 + AS15 candidate Antigen-Specific Cancer Immunotherapeutic (ASCI) contains a recombinant protein termed dHER2, which is a truncated version of the HER2 protein. HER2 is a protein that is commonly overexpressed in breast cancer. This protein is combined with the immunological adjuvant AS15 Adjuvant System from GSK (GlaxoSmithKline), which is a liposomal formulation containing three immunostimulatory components. Lapatinib is FDA approved for use in combination with capecitabine for the treatment of subjects with advanced or metastatic breast cancer whose tumors overexpress HER2.