Activity of AMN107, a novel aminopyrimidine tyrosine kinase inhibitor, against human FIP1L1-PDGFR-α-expressing cells

Idiopathic hypereosinophilic syndrome (HES) is a myeloproliferative disorder characterized by tissue involvement and organ dysfunction due to abnormal eosinophil proliferation. In a subset of patients, this is caused by the FIP1L1-PDGFR-α fusion tyrosine kinase. Cumulative evidence indicates that the Bcr-Abl tyrosine kinase inhibitor imatinib mesylate (Gleevec) is active for the treatment of patients with HES, particularly those expressing the FIP1L1-PDGFR-α oncoprotein. The novel tyrosine kinase inhibitor AMN107 was initially developed as a potent Bcr-Abl inhibitor based on the molecular structure of imatinib. We tested the in vitro efficacy of imatinib and AMN107 in the EOL-1 cell line and in cells from a patient with HES harboring the FIP1L1-PDGFR-α fusion kinase. AMN107 was as potent as imatinib in inducing apoptosis and inhibiting proliferation of EOL-1 cells, with IC₅₀ values of 0.54 and 0.20 nM, respectively. In addition, both drugs inhibited the phosphorylation of PDGFR-α tyrosine kinase with equivalent efficacy. We conclude that AMN107 and imatinib are active and equipotent against cells expressing the FIP1L1-PDGFR-α fusion gene.