title: Structural basis for KIT receptor tyrosine kinase inhibition by antibodies targeting the D4 membrane-proximal region.
abstract: Somatic oncogenic mutations in the receptor tyrosine kinase KIT function as major drivers of gastrointestinal stromal tumors and a subset of acute myeloid leukemia, melanoma, and other cancers. Although treatment of these cancers with tyrosine kinase inhibitors shows dramatic responses and durable disease control, drug resistance followed by clinical progression of disease eventually occurs in virtually all patients. In this report, we describe inhibitory KIT antibodies that bind to the membrane-proximal Ig-like D4 of KIT with significant overlap with an epitope in D4 that mediates homotypic interactions essential for KIT activation. Crystal structures of the anti-KIT antibody in complex with KIT D4 and D5 allowed design of affinity-matured libraries that were used to isolate variants with increased affinity and efficacy. Isolated antibodies showed KIT inhibition together with suppression of cell proliferation driven by ligand-stimulated WT or constitutively activated oncogenic KIT mutant. These antibodies represent a unique therapeutic approach and a step toward the development of "naked" or toxin-conjugated KIT antibodies for the treatment of KIT-driven cancers.
authors.affiliation: Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520.
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Reshetnyak
authors.forename: Bryce
authors.initials: B
authors.lastname: Nelson
authors.forename: Xiarong
authors.initials: X
authors.lastname: Shi
authors.forename: Titus J
authors.initials: TJ
authors.lastname: Boggon
authors.forename: Alevtina
authors.initials: A
authors.lastname: Pavlenco
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Mandel-Bausch
authors.forename: Francisco
authors.initials: F
authors.lastname: Tome
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Sachdev S
authors.initials: SS
authors.lastname: Sidhu
authors.forename: Irit
authors.initials: I
authors.lastname: Lax
authors.forename: Joseph
authors.initials: J
authors.lastname: Schlessinger
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000494:pharmacology; D016367:Baculoviridae; D061505:Cell Surface Display Techniques; D003460:Crystallization; D004797:Enzyme-Linked Immunosorbent Assay; D015151:Immunoblotting; D047468:Immunoprecipitation; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry*; D009154:Mutation / Q000235:genetics; D009369:Neoplasms / Q000188:drug therapy* / Q000276:immunology; D011487:Protein Conformation; D019009:Proto-Oncogene Proteins c-kit / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics; D061987:Sf9 Cells; D018411:Spodoptera
chemical_list: D000911:Antibodies, Monoclonal; D046912:Multiprotein Complexes; D019009:Proto-Oncogene Proteins c-kit
keywords: cancer therapy; cell signaling; phosphorylation; protein kinase; therapeutic antibodies