title: FLT3 D835 mutations confer differential resistance to type II FLT3 inhibitors.
abstract: Activating mutations in FLT3 occur in ~30% of adult acute myeloid leukemia, primarily consisting of internal tandem duplication (ITD) mutations (~25%) and point mutations in the tyrosine kinase domain (~5%), commonly at the activation loop residue D835. Secondary kinase domain mutations in FLT3-ITD, particularly at the D835 residue are frequently associated with acquired clinical resistance to effective FLT3 tyrosine kinase inhibitors (TKIs). Molecular docking studies have suggested that D835 mutations primarily confer resistance by stabilizing an active Asp-Phe-Gly in ('DFG-in') kinase conformation unfavorable to the binding of type II FLT3 TKIs, which target a 'DFG-out' inactive conformation. We profiled the activity of active type II FLT3 TKIs against D835 kinase domain mutants that have been clinically detected to date. We found that type II inhibitors (quizartinib, sorafenib, ponatinib and PLX3397) retain activity against specific D835 substitutions. Modeling studies suggest that bulky hydrophobic substitutions (D835Y/V/I/F) at this residue are particularly resistant, whereas mutations that preserve interactions between D835 and S838 are relatively sensitive (D835E/N). All mutants retain sensitivity to the type I inhibitor crenolanib. These results suggest that patients with relatively sensitive D835 mutations should be included in clinical trials of type II FLT3 TKIs.
authors.affiliation: Division of Hematology/Oncology, University of California, San Francisco, CA, USA.|Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, USA.
authors.forename: C C
authors.initials: CC
authors.lastname: Smith
authors.affiliation: Division of Hematology/Oncology, University of California, San Francisco, CA, USA.
authors.forename: K
authors.initials: K
authors.lastname: Lin
authors.affiliation: Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, USA.
authors.forename: A
authors.initials: A
authors.lastname: Stecula
authors.affiliation: Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA, USA.|California Institute for Quantitative Biosciences, University of California, San Francisco, CA, USA.|Department of Pharmaceutical Chemistry, University of California, San Francisco, CA, USA.
authors.forename: A
authors.initials: A
authors.lastname: Sali
authors.affiliation: Division of Hematology/Oncology, University of California, San Francisco, CA, USA.|Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, CA, USA.
authors.forename: N P
authors.initials: NP
authors.lastname: Shah
mesh_terms: D019008:Drug Resistance, Neoplasm; D006801:Humans; D062105:Molecular Docking Simulation; D009154:Mutation; D011487:Protein Conformation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D051941:fms-Like Tyrosine Kinase 3 / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics*
chemical_list: D047428:Protein Kinase Inhibitors; C497970:FLT3 protein, human; D051941:fms-Like Tyrosine Kinase 3