Safety and Outcomes of a Plasmid DNA Vaccine Encoding the ERBB2 Intracellular Domain in Patients With Advanced-Stage ERBB2-Positive Breast Cancer

High levels of ERBB2 (formerly HER2)-specific type 1 T cells in the peripheral blood are associated with favorable clinical outcomes after trastuzumab therapy; however, only a minority of patients develop measurable ERBB2 immunity after treatment. Vaccines designed to increase ERBB2-specific T-helper cells could induce ERBB2 immunity in a majority of patients.