In CML patients, in vitro studies indicate BCR-ABL tyrosine kinase inhibitors (TKIs) to have no efficacy over LSCs and leukemic progenitor cells (LPCs) and, while imatinib initial response rates are overwhelmingly positive, disease recurrence is usually the standard for patients after therapy discontinuation due to remaining Philadelphia-positive (Ph+) CD34+ cells (101, 102). Here, ABL1 is linked to chronic myelogenous leukemia, BCR-ABL1 positive.