title: Characterizing and Overriding the Structural Mechanism of the Quizartinib-Resistant FLT3 "Gatekeeper" F691L Mutation with PLX3397.
abstract: Tyrosine kinase domain mutations are a common cause of acquired clinical resistance to tyrosine kinase inhibitors (TKI) used to treat cancer, including the FLT3 inhibitor quizartinib. Mutation of kinase "gatekeeper" residues, which control access to an allosteric pocket adjacent to the ATP-binding site, has been frequently implicated in TKI resistance. The molecular underpinnings of gatekeeper mutation-mediated resistance are incompletely understood. We report the first cocrystal structure of FLT3 with the TKI quizartinib, which demonstrates that quizartinib binding relies on essential edge-to-face aromatic interactions with the gatekeeper F691 residue, and F830 within the highly conserved Asp-Phe-Gly motif in the activation loop. This reliance makes quizartinib critically vulnerable to gatekeeper and activation loop substitutions while minimizing the impact of mutations elsewhere. Moreover, we identify PLX3397, a novel FLT3 inhibitor that retains activity against the F691L mutant due to a binding mode that depends less vitally on specific interactions with the gatekeeper position.
  
  
  CONCLUSIONS
  We report the first cocrystal structure of FLT3 with a kinase inhibitor, elucidating the structural mechanism of resistance due to the gatekeeper F691L mutation. PLX3397 is a novel FLT3 inhibitor with in vitro activity against this mutation but is vulnerable to kinase domain mutations in the FLT3 activation loop.
authors.affiliation: Division of Hematology/Oncology, University of California, San Francisco, California. Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California.
authors.forename: Catherine C
authors.initials: CC
authors.lastname: Smith
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Chao
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Division of Hematology/Oncology, University of California, San Francisco, California.
authors.forename: Kimberly C
authors.initials: KC
authors.lastname: Lin
authors.affiliation: Division of Hematology/Oncology, University of California, San Francisco, California.
authors.forename: Elisabeth A
authors.initials: EA
authors.lastname: Lasater
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Division of Hematology/Oncology, University of California, San Francisco, California.
authors.forename: Evan
authors.initials: E
authors.lastname: Massi
authors.affiliation: Division of Hematology/Oncology, University of California, San Francisco, California.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Damon
authors.affiliation: Icahn Institute for Genomics and Multiscale Biology, Mount Sinai School of Medicine, New York, New York.
authors.forename: Matthew
authors.initials: M
authors.lastname: Pendleton
authors.affiliation: Icahn Institute for Genomics and Multiscale Biology, Mount Sinai School of Medicine, New York, New York.
authors.forename: Ali
authors.initials: A
authors.lastname: Bashir
authors.affiliation: Icahn Institute for Genomics and Multiscale Biology, Mount Sinai School of Medicine, New York, New York.
authors.forename: Robert
authors.initials: R
authors.lastname: Sebra
authors.affiliation: Abramson Cancer Center of the University of Pennsylvania, Philadelphia, Pennsylvania.
authors.forename: Alexander
authors.initials: A
authors.lastname: Perl
authors.affiliation: Icahn Institute for Genomics and Multiscale Biology, Mount Sinai School of Medicine, New York, New York.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kasarskis
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Rafe
authors.initials: R
authors.lastname: Shellooe
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Garson
authors.initials: G
authors.lastname: Tsang
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Heidi
authors.initials: H
authors.lastname: Carias
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Ben
authors.initials: B
authors.lastname: Powell
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Burton
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Bernice
authors.initials: B
authors.lastname: Matusow
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Jiazhong
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Wayne
authors.initials: W
authors.lastname: Spevak
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Prabha N
authors.initials: PN
authors.lastname: Ibrahim
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Mai H
authors.initials: MH
authors.lastname: Le
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Henry H
authors.initials: HH
authors.lastname: Hsu
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Gaston
authors.initials: G
authors.lastname: Habets
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Brian L
authors.initials: BL
authors.lastname: West
authors.affiliation: Plexxikon Inc., Berkeley, California.
authors.forename: Gideon
authors.initials: G
authors.lastname: Bollag
authors.affiliation: Division of Hematology/Oncology, University of California, San Francisco, California. Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, California. nshah@medicine.ucsf.edu.
authors.forename: Neil P
authors.initials: NP
authors.lastname: Shah
mesh_terms: D000631:Aminopyridines / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology; D052160:Benzothiazoles / Q000737:chemistry / Q000494:pharmacology*; D045744:Cell Line, Tumor; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D004789:Enzyme Activation / Q000187:drug effects; D064593:Heterografts; D006801:Humans; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000235:genetics / Q000473:pathology; D051379:Mice; D008958:Models, Molecular; D008968:Molecular Conformation; D009154:Mutation; D010671:Phenylurea Compounds / Q000737:chemistry / Q000494:pharmacology*; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000737:chemistry / Q000494:pharmacology; D011758:Pyrroles / Q000737:chemistry / Q000494:pharmacology*; D012008:Recurrence; D013329:Structure-Activity Relationship; D051941:fms-Like Tyrosine Kinase 3 / Q000737:chemistry / Q000235:genetics*
chemical_list: D000631:Aminopyridines; D000970:Antineoplastic Agents; D052160:Benzothiazoles; D010671:Phenylurea Compounds; D047428:Protein Kinase Inhibitors; D011758:Pyrroles; C000600259:pexidartinib; C544967:quizartinib; D051941:fms-Like Tyrosine Kinase 3
references.citation: Cancer Cell. 2002 Aug;2(2):117-25
references.pmid: 12204532
references.citation: Cancer Res. 2002 Aug 1;62(15):4236-43
references.pmid: 12154025
references.citation: N Engl J Med. 2003 Mar 27;348(13):1201-14
references.pmid: 12660384
references.citation: Mol Cell. 2004 Jan 30;13(2):169-78
references.pmid: 14759363
references.citation: Cell. 2004 Mar 19;116(6):855-67
references.pmid: 15035987
references.citation: Gastroenterology. 2004 Jul;127(1):294-9
references.pmid: 15236194
references.citation: Eur J Biochem. 1970 Sep;16(1):1-11
references.pmid: 5456129
references.citation: Science. 2009 Jan 2;323(5910):133-8
references.pmid: 19023044
references.citation: J Med Chem. 2009 Dec 10;52(23):7808-16
references.pmid: 19754199
references.citation: N Engl J Med. 2010 Oct 28;363(18):1734-9
references.pmid: 20979473
references.citation: Chem Biol Drug Des. 2011 Jan;77(1):1-11
references.pmid: 21118377
references.citation: Nature. 2012 May 10;485(7397):260-3
references.pmid: 22504184
references.citation: Blood. 2012 May 31;119(22):5133-43
references.pmid: 22368270
references.citation: N Engl J Med. 2013 May 30;368(22):2059-74
references.pmid: 23634996
references.citation: Nat Methods. 2013 Jun;10(6):563-9
references.pmid: 23644548
references.citation: J Clin Oncol. 2013 Oct 10;31(29):3681-7
references.pmid: 24002496
references.citation: Blood. 2013 Nov 21;122(22):3607-15
references.pmid: 24046014
references.citation: Ann Thorac Surg. 2013 Dec;96(6):2083-9
references.pmid: 23968764
references.citation: Blood. 2014 Jan 2;123(1):94-100
references.pmid: 24227820
references.citation: Proc Natl Acad Sci U S A. 2014 Apr 8;111(14):5319-24
references.pmid: 24623852
references.citation: ACS Chem Biol. 2014 Jun 20;9(6):1230-41
references.pmid: 24730530
references.citation: N Engl J Med. 2015 Jul 30;373(5):428-37
references.pmid: 26222558
references.citation: Proc Natl Acad Sci U S A. 2005 Mar 1;102(9):3395-400
references.pmid: 15705718
references.citation: PLoS Med. 2005 Mar;2(3):e73
references.pmid: 15737014
references.citation: Blood. 2006 Nov 15;108(10):3477-83
references.pmid: 16857987
references.citation: Mol Cell. 2007 Sep 7;27(5):717-30
references.pmid: 17803937
references.citation: J Am Chem Soc. 2002 May 29;124(21):6133-43
references.pmid: 12022848
references.citation: Science. 2000 Sep 15;289(5486):1938-42
references.pmid: 10988075
references.citation: Proc Natl Acad Sci U S A. 2008 Feb 12;105(6):2070-5
references.pmid: 18227510
references.citation: J Biol Chem. 2002 Nov 29;277(48):46265-72
references.pmid: 12196540