A novel CD19/CD3 BsAb in a 100 kDa single chain-Fv Fc format (CD19/CD3-scFv-Fc) with a half-life of approximately seven days resulted in apoptosis of primary CLL cells in vitro and near complete elimination of tumor cells in a patient-derived mouse xenograft model [77]. The gene discussed is CD19; the disease is B-cell chronic lymphocytic leukemia.