title: Binding protein-3-selective insulin-like growth factor I variants: engineering, biodistributions, and clearance.
abstract: Insulin-like growth factor I (IGF-I) is a potent anabolic peptide that mediates most of its pleiotropic effects through association with the IGF type I receptor. Biological availability and plasma half-life of IGF-I are modulated by soluble binding proteins (IGFBPs), which sequester free IGF-I into high affinity complexes. Elevated levels of specific IGFBPs have been observed in several pathological conditions, resulting in inhibition of IGF-I activity. Administration of IGF-I variants that are unable to bind to the up-regulated IGFBP species could potentially counteract this effect. We engineered two IGFBP-selective variants that demonstrated 700- and 80,000-fold apparent reductions in affinity for IGFBP-1 while preserving low nanomolar affinity for IGFBP-3, the major carrier of IGF-I in plasma. Both variants displayed wild-type-like potency in cellular receptor kinase assays, stimulated human cartilage matrix synthesis, and retained their ability to associate with the acid-labile subunit in complex with IGFBP-3. Furthermore, pharmacokinetic parameters and tissue distribution of the IGF-I variants in rats differed from those of wild-type IGF-I as a function of their IGFBP affinities. These IGF-I variants may potentially be useful for treating disease conditions associated with up-regulated IGFBP-1 levels, such as chronic or acute renal and hepatic failure or uncontrolled diabetes. More generally, these results suggest that the complex biology of IGF-I may be clarified through in vivo studies of IGFBP-selective variants.
authors.affiliation: Departments of Protein Engineering Genentech, Inc., South San Francisco, California 94080, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Dubaquié
authors.forename: D L
authors.initials: DL
authors.lastname: Mortensen
authors.forename: A
authors.initials: A
authors.lastname: Intintoli
authors.forename: D A
authors.initials: DA
authors.lastname: Hogue
authors.forename: G
authors.initials: G
authors.lastname: Nakamura
authors.forename: P
authors.initials: P
authors.lastname: Rancatore
authors.forename: P
authors.initials: P
authors.lastname: Lester
authors.forename: M D
authors.initials: MD
authors.lastname: Sadick
authors.forename: E
authors.initials: E
authors.lastname: Filvaroff
authors.forename: P J
authors.initials: PJ
authors.lastname: Fielder
authors.forename: H B
authors.initials: HB
authors.lastname: Lowman
mesh_terms: D000368:Aged; D019943:Amino Acid Substitution; D000818:Animals; D001943:Breast Neoplasms; D002358:Cartilage, Articular / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D014644:Genetic Variation; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000378:metabolism; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism* / Q000493:pharmacokinetics; D007700:Kinetics; D008657:Metabolic Clearance Rate; D016297:Mutagenesis, Site-Directed; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism / Q000493:pharmacokinetics; D013379:Substrate Specificity; D013431:Sulfates / Q000378:metabolism; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured
chemical_list: D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D011994:Recombinant Proteins; D013431:Sulfates; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1