title: A rationally designed agonist antibody fragment that functionally mimics thrombopoietin.
abstract: By using rational design, antibody fragments (Fabs) that mimic thrombopoietin (TPO) were created. A peptide with cMpl receptor-binding capability was grafted into different complementarity-determining regions of a fully human Fab scaffold. Functional presentation of the peptide was optimized by using phage display and cell-based panning. Select antibodies and fragments containing two grafted peptides were assayed for their ability to stimulate the cMpl receptor in vitro. Several candidates demonstrated agonist activity in an in vitro cMpl receptor signaling reporter assay, including Fab59, which was estimated to be equipotent to TPO. Fab59 additionally was able to effectively stimulate platelet production in normal mice. These rationally designed mimetic Fabs may provide a therapeutic intervention for thrombocytopenia while avoiding the potential generation of neutralizing antibodies to endogenous TPO. Furthermore, this study demonstrates a method by which short-lived linear peptides with binding activity may be converted to more stable and potent agonists capable of activating cell surface receptors.
authors.affiliation: Alexion Antibody Technologies, Inc., 3985-A Sorrento Valley Boulevard, San Diego, CA 92121, USA.
authors.forename: Shana
authors.initials: S
authors.lastname: Frederickson
authors.forename: Mark W
authors.initials: MW
authors.lastname: Renshaw
authors.forename: Bing
authors.initials: B
authors.lastname: Lin
authors.forename: Lynette M
authors.initials: LM
authors.lastname: Smith
authors.forename: Peter
authors.initials: P
authors.lastname: Calveley
authors.forename: Jeremy P
authors.initials: JP
authors.lastname: Springhorn
authors.forename: Krista
authors.initials: K
authors.lastname: Johnson
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.forename: Xiao
authors.initials: X
authors.lastname: Su
authors.forename: Yamin
authors.initials: Y
authors.lastname: Shen
authors.forename: Katherine S
authors.initials: KS
authors.lastname: Bowdish
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D002478:Cells, Cultured; D003432:Cross-Linking Reagents; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000737:chemistry* / Q000276:immunology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D010455:Peptides / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000378:metabolism; D012995:Solubility; D013329:Structure-Activity Relationship; D013926:Thrombopoietin / Q000378:metabolism*
chemical_list: D003432:Cross-Linking Reagents; D007140:Immunoglobulin Fab Fragments; D010455:Peptides; D011956:Receptors, Cell Surface; D013926:Thrombopoietin