title: The impact of multiple low-level BCR-ABL1 mutations on response to ponatinib.
abstract: The third-generation tyrosine kinase inhibitor (TKI) ponatinib shows activity against all common BCR-ABL1 single mutants, including the highly resistant BCR-ABL1-T315I mutant, improving outcome for patients with refractory chronic myeloid leukemia (CML). However, responses are variable, and causal baseline factors have not been well-studied. The type and number of low-level BCR-ABL1 mutations present after imatinib resistance has prognostic significance for subsequent treatment with nilotinib or dasatinib as second-line therapy. We therefore investigated the impact of low-level mutations detected by sensitive mass-spectrometry before ponatinib initiation (baseline) on treatment response in 363 TKI-resistant patients enrolled in the PONATINIB for Chronic Myeloid Leukemia Evaluation and Ph(+)Acute Lymphoblastic Leukemia trial, including 231 patients in chronic phase (CP-CML). Low-level mutations were detected in 53 patients (15%, including low-level T315I in 14 patients); most, however, did not undergo clonal expansion during ponatinib treatment and, moreover, no specific individual mutations were associated with inferior outcome. We demonstrate however, that the number of mutations detectable by mass spectrometry after TKI resistance is associated with response to ponatinib treatment and could be used to refine the therapeutic approach. Although CP-CML patients with T315I (63/231, 27%) had superior responses overall, those with multiple mutations detectable by mass spectrometry (20, 32%) had substantially inferior responses compared with those with T315I as the sole mutation detected (43, 68%). In contrast, for CP-CML patients without T315I, the inferior responses previously observed with nilotinib/dasatinib therapy for imatinib-resistant patients with multiple mutations were not seen with ponatinib treatment, suggesting that ponatinib may prove to be particularly advantageous for patients with multiple mutations detectable by mass spectrometry after TKI resistance.
authors.affiliation: Department of Genetics and Molecular Pathology and Australian Cancer Research Foundation Cancer Genomics Facility, Centre for Cancer Biology, SA Pathology, Adelaide, Australia; School of Pharmacy and Medical Science, University of South Australia, Adelaide, Australia;
authors.forename: Wendy T
authors.initials: WT
authors.lastname: Parker
authors.affiliation: Department of Genetics and Molecular Pathology and School of Medicine, University of Adelaide, Adelaide, Australia; Department of Hematology, Centre for Cancer Biology, SA Pathology, Adelaide, Australia; Cancer Theme, South Australian Health and Medical Research Institute, Adelaide, Australia;
authors.forename: David T O
authors.initials: DT
authors.lastname: Yeung
authors.affiliation: Department of Genetics and Molecular Pathology and.
authors.forename: Alexandra L
authors.initials: AL
authors.lastname: Yeoman
authors.affiliation: Department of Genetics and Molecular Pathology and.
authors.forename: Haley K
authors.initials: HK
authors.lastname: Altamura
authors.affiliation: Department of Genetics and Molecular Pathology and.
authors.forename: Bronte A
authors.initials: BA
authors.lastname: Jamison
authors.affiliation: Department of Genetics and Molecular Pathology and.
authors.forename: Chani R
authors.initials: CR
authors.lastname: Field
authors.affiliation: ARIAD Pharmaceuticals, Inc., Cambridge, MA; and.
authors.forename: J Graeme
authors.initials: JG
authors.lastname: Hodgson
authors.affiliation: ARIAD Pharmaceuticals, Inc., Cambridge, MA; and.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Lustgarten
authors.affiliation: ARIAD Pharmaceuticals, Inc., Cambridge, MA; and.
authors.forename: Victor M
authors.initials: VM
authors.lastname: Rivera
authors.affiliation: School of Medicine, University of Adelaide, Adelaide, Australia; Department of Hematology, Centre for Cancer Biology, SA Pathology, Adelaide, Australia; Cancer Theme, South Australian Health and Medical Research Institute, Adelaide, Australia;
authors.forename: Timothy P
authors.initials: TP
authors.lastname: Hughes
authors.affiliation: Department of Genetics and Molecular Pathology and School of Pharmacy and Medical Science, University of South Australia, Adelaide, Australia; School of Medicine, University of Adelaide, Adelaide, Australia; School of Molecular and Biomedical Science, University of Adelaide, Adelaide, Australia.
authors.forename: Susan
authors.initials: S
authors.lastname: Branford
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D004252:DNA Mutational Analysis; D019008:Drug Resistance, Neoplasm; D016044:Fusion Proteins, bcr-abl / Q000235:genetics*; D006801:Humans; D007093:Imidazoles / Q000627:therapeutic use*; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy* / Q000235:genetics*; D013058:Mass Spectrometry; D008875:Middle Aged; D015999:Multivariate Analysis; D009154:Mutation; D011379:Prognosis; D047428:Protein Kinase Inhibitors / Q000627:therapeutic use; D011724:Pyridazines / Q000627:therapeutic use*; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D000970:Antineoplastic Agents; C581634:BCR-ABL1 fusion protein, human; D007093:Imidazoles; D047428:Protein Kinase Inhibitors; D011724:Pyridazines; C545373:ponatinib; D016044:Fusion Proteins, bcr-abl