In this domain there are two historical and landmark molecularly well-understood therapies that have been transformative for patients; all trans retinoic acid (ATRA) therapy of acute promyelocytic leukaemia (APL) and BCR:ABL inhibitors in chronic myeloid leukaemia (CML). The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.