- have confirmed HER2 gene amplified tumor fluorescence in-situ hybridization (FISH, HER2/cep17 ratio > 2) or HER2 overexpression (IHC 3+) or documented HER2 gene mutation. Documentation of HER2 status using FDA approved test(s) for HER2 testing specific for HER2 breast and gastric cancer is required prior to screening;