A 2-phenylaminopyrimidine derivative CGP53716 was found to inhibit the PDGF receptor and v-ABL in vitro and in vivo and became known as signal transduction inhibitor 571 (SDI571) as studies demonstrated its inhibition of cellular growth in CML [22–26]. The gene discussed is ABL1; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.