Successful applications of Abl inhibitor for BCR-Abl-dependent chronic myeloid leukemia, EGFR inhibitors for EGFR mutation dependent non-small cell lung cancer, and ErbB2 inhibitors for ErbB2-dependnet breast cancer are all examples of both the power of targeted therapy and the challenge it faces. The gene discussed is ERBB2; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.