Most BCR-ABL inhibitors, including imatinib, nilotinib, dasatinib, bosutinib, tozasertib, and AT-9283, are FDA-approved for the treatment of hematological malignancies such as leukemia—myelogenous, chronic, BCR-ABL-positive (CML); acute lymphocytic leukemia (ALL); mastocytosis; gastrointestinal stromal tumors; hypereosinophilic syndrome; and other related conditions. This evidence concerns the gene ABL1 and mastocytosis.