FIP1L1-PDGFRα D842V, a novel panresistant mutant, emerging after treatment of FIP1L1-PDGFRα T674I eosinophilic leukemia with single agent sorafenib

• Published in: Leukemia Vol. 23; no. 5; pp. 845 - 851
• Main Authors: Lierman, E, Michaux, L, Beullens, E, Pierre, P, Marynen, P, Cools, J, Vandenberghe, P
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2009; Nature Publishing Group
• Subjects: Blast crisis; Blood diseases; Cancer Research; Critical Care Medicine; Eosinophilic leukemia; Fusion protein; Hematology; Imatinib; Intensive; Internal Medicine; Leukemia; Leukocytes (eosinophilic); Medicine; Medicine & Public Health; Mutagenesis; Mutation; N-Nitroso-N-ethylurea; Oncology; original-article; Protein-tyrosine kinase; Resistant mutant; Vascular endothelial growth factor receptors; kinase inhibitor; eosinophilia; oncogene; resistance; tyrosine kinase
• ISSN: 0887-6924; 1476-5551
• DOI: 10.1038/leu.2009.2

Chronic eosinophilic leukemia (CEL) is a rare myeloproliferative neoplasm characterized by the FIP1L1-PDGFRA fusion gene, variant PDGFRA fusions or other genetic lesions. Most FIP1L1–PDGFRA positive patients enjoy durable and complete molecular responses to low-dose imatinib (Glivec/Gleevec). However, resistance mediated by a T674I mutation in the ATP-binding pocket of PDGFRA has been reported in advanced disease, and sorafenib, a potent inhibitor of RAF-1, B-RAF, VEGFR and PDGFR, is active against this mutant in vitro. We describe a case of FIP1L1-PDGFRα T674I CEL in blast crisis that responded to sorafenib (Nexavar). However, this clinical response was short-lived because of the rapid emergence of a FIP1L1-PDGFRα D842V mutant. An N -Nitroso- N -ethylurea-mutagenesis screen indeed identified this mutant as a major sorafenib-resistant mutant. In vitro, the novel FIP1L1-PDGFRα D842V mutant is highly resistant to sorafenib, imatinib, dasatinib (Sprycell) and PKC412 (Midostaurin). Thus, sorafenib is clinically active in imatinib-resistant FIP1L1-PDGFRα T674I CEL, but the rapid emergence of other mutants may limit the response duration. The identification of new PDGFR inhibitors will be required to overcome resistance by this D842V mutant.