Her2-BATS and Pembrolizumab in Metastatic Breast Cancer

Once subjects are determined eligible, white blood cells (lymphocytes) are collected via leukapheresis procedure. Depending on arm/schedule, about 4-5 weeks later, study treatment will begin. For HER2 BATs, the white blood cells, specifically T cells, are then mixed with two proteins - OKT3 and IL-2 -- which activates the cells to multiply. After approximately 14 days in culture, the activated T cells are coated with OKT3 and trastuzumab/Herceptin (HER2Bi), and washed to remove excess Herceptin in order to produce bispecific antibody armed T cells (BATs). Cells are then frozen and stored until scheduled to be infused. Follow-up appointment schedule will include clinic visits 2 weeks, 1 month, 3 months, and 6 months after the last dose of Pembrolizumab.