Some neoplastic conditions result from excessive activity of a single PTK (Bcr-Abl in chronic myeloid leukaemia (Melo, 1996), c-kit or PDGFRA in gastrointestinal stromal cell tumours (Hirota et al, 1998; Heinrich et al, 2003)), and are effectively treated using the PTK inhibitor Imatinib (STI 571, Gleevec) (Druker et al, 2001; van Oosterom et al, 2001). The gene discussed is PTK2B; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.