The most sensitive cell line was the chronic eosinophilic leukemia cell line EoL-1 (IC50 = 59 nmol/L), expressing a fusion gene of Factor Interacting with PAPOLA and CPSF1 (FIP1L1) and platelet-derived growth factor receptor α (PDGFRα) (Figure 2a, Supplementary Table S4) (37). The gene discussed is FIP1L1; the disease is Chronic Eosinophilic Leukemia, Not Otherwise Specified.