title: Activity of ponatinib against clinically-relevant AC220-resistant kinase domain mutants of FLT3-ITD.
abstract: Secondary point mutations in the Fms-like tyrosine kinase 3 (FLT3) tyrosine kinase domain (KD) are common causes of acquired clinical resistance to the FLT3 inhibitors AC220 (quizartinib) and sorafenib. Ponatinib (AP24534) is a multikinase inhibitor with in vitro and clinical activity in tyrosine kinase inhibitor (TKI)-resistant chronic myeloid leukemia, irrespective of BCR-ABL KD mutation. Ponatinib has demonstrated early clinical efficacy in chemotherapy-resistant acute myeloid leukemia (AML) patients with internal tandem duplication (ITD) mutations in FLT3. We assessed the in vitro activity of ponatinib against clinically relevant FLT3-ITD mutant isoforms that confer resistance to AC220 or sorafenib. Substitution of the FLT3 "gatekeeper" phenylalanine with leucine (F691L) conferred mild resistance to ponatinib, but substitutions at the FLT3 activation loop (AL) residue D835 conferred a high degree of resistance. Saturation mutagenesis of FLT3-ITD exclusively identified FLT3 AL mutations at positions D835, D839, and Y842. The switch control inhibitor DCC-2036 was similarly inactive against FLT3 AL mutations. On the basis of its in vitro activity against FLT3 TKI-resistant F691 substitutions, further clinical evaluation of ponatinib in TKI-naïve and select TKI-resistant FLT3-ITD+ AML patients is warranted. Alternative strategies will be required for patients with TKI-resistant FLT3-ITD D835 mutations.
authors: Division of Hematology/Oncology, University of California, San Francisco, CA, USA.
authors: Catherine C
authors: CC
authors: Smith
authors: Elisabeth A
authors: EA
authors: Lasater
authors: Xiaotian
authors: X
authors: Zhu
authors: Kimberly C
authors: KC
authors: Lin
authors: Whitney K
authors: WK
authors: Stewart
authors: Lauren E
authors: LE
authors: Damon
authors: Sara
authors: S
authors: Salerno
authors: Neil P
authors: NP
authors: Shah
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D052160:Benzothiazoles / Q000494:pharmacology*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm; D020440:Gene Duplication; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy / Q000235:genetics; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000235:genetics; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D009536:Niacinamide / Q000031:analogs & derivatives* / Q000494:pharmacology; D010671:Phenylurea Compounds / Q000494:pharmacology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D017434:Protein Structure, Tertiary; D011724:Pyridazines / Q000494:pharmacology*; D011804:Quinolines / Q000494:pharmacology; D000077157:Sorafenib; D051941:fms-Like Tyrosine Kinase 3 / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics*
chemical_list: D052160:Benzothiazoles; C560099:DCC-2036; D007093:Imidazoles; D010671:Phenylurea Compounds; D047428:Protein Kinase Inhibitors; D011724:Pyridazines; D011804:Quinolines; D009536:Niacinamide; C545373:ponatinib; C544967:quizartinib; D000077157:Sorafenib; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3