title: Influence of the N-Terminal Composition on Targeting Properties of Radiometal-Labeled Anti-HER2 Scaffold Protein ADAPT6.
abstract: Radionuclide-imaging-based stratification of patients to targeted therapies makes cancer treatment more personalized and therefore more efficient. Albumin-binding domain derived affinity proteins (ADAPTs) constitute a novel group of imaging probes based on the scaffold of an albumin-binding domain (ABD). To evaluate how different compositions of the N-terminal sequence of ADAPTs influence their biodistribution, a series of human epidermal growth factor receptor type 2 (HER2)-binding ADAPT6 derivatives with different N-terminal sequences were created: GCH6DANS (2), GC(HE)3DANS (3), GCDEAVDANS (4), and GCVDANS(5). These were compared with the parental variant: GCSS(HE)3DEAVDANS (1). All variants were site-specifically conjugated with a maleimido-derivative of a DOTA chelator and labeled with111In. Binding to HER2-expressing cells in vitro, in vivo biodistribution as well as targeting properties of the new variants were compared with properties of the111In-labeled parental ADAPT variant 1 (111In-DOTA-1). The composition of the N-terminal sequence had an apparent influence on biodistribution of ADAPT6 in mice. The use of a hexahistidine tag in111In-DOTA-2 was associated with elevated hepatic uptake compared to the (HE)3-containing counterpart,111In-DOTA-3. All new variants without a hexahistidine tag demonstrated lower uptake in blood, lung, spleen, and muscle compared to uptake in the parental variant. The best new variants,111In-DOTA-3 and111In-DOTA-5, provided tumor uptakes of 14.6 ± 2.4 and 12.5 ± 1.3% ID/g at 4 h after injection, respectively. The tumor uptake of111In-DOTA-3 was significantly higher than the uptake of the parental111In-DOTA-1 (9.1 ± 2.0% ID/g). The tumor-to-blood ratios of 395 ± 75 and 419 ± 91 at 4 h after injection were obtained for111In-DOTA-5 and111In-DOTA-3, respectively. In conclusion, the N-terminal sequence composition affects the biodistribution and targeting properties of ADAPT-based imaging probes, and its optimization may improve imaging contrast.
authors.affiliation: Department of Immunology, Genetics and Pathology, Uppsala University , SE-75185 Uppsala, Sweden.
authors.forename: Javad
authors.initials: J
authors.lastname: Garousi
authors.affiliation: Department of Protein Technology, KTH - Royal Institute of Technology , SE-10691 Stockholm, Sweden.
authors.forename: Sarah
authors.initials: S
authors.lastname: Lindbo
authors.affiliation: Department of Immunology, Genetics and Pathology, Uppsala University , SE-75185 Uppsala, Sweden.
authors.forename: Hadis
authors.initials: H
authors.lastname: Honarvar
authors.affiliation: Department of Immunology, Genetics and Pathology, Uppsala University , SE-75185 Uppsala, Sweden.
authors.forename: Justin
authors.initials: J
authors.lastname: Velletta
authors.affiliation: Division of Molecular Imaging, Department of Medicinal Chemistry, Uppsala University , SE-75181 Uppsala, Sweden.
authors.forename: Bogdan
authors.initials: B
authors.lastname: Mitran
authors.affiliation: Department of Immunology, Genetics and Pathology, Uppsala University , SE-75185 Uppsala, Sweden.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Altai
authors.affiliation: Division of Molecular Imaging, Department of Medicinal Chemistry, Uppsala University , SE-75181 Uppsala, Sweden.
authors.forename: Anna
authors.initials: A
authors.lastname: Orlova
authors.affiliation: Department of Immunology, Genetics and Pathology, Uppsala University , SE-75185 Uppsala, Sweden.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Tolmachev
authors.affiliation: Department of Protein Technology, KTH - Royal Institute of Technology , SE-10691 Stockholm, Sweden.
authors.forename: Sophia
authors.initials: S
authors.lastname: Hober
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000493:pharmacokinetics; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D005260:Female; D006573:Heterocyclic Compounds, 1-Ring / Q000737:chemistry; D006801:Humans; D007205:Indium Radioisotopes; D007553:Isotope Labeling; D051379:Mice; D057054:Molecular Imaging; D010051:Ovarian Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology; D015202:Protein Engineering; D055550:Protein Stability; D017433:Protein Structure, Secondary; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D013696:Temperature; D014018:Tissue Distribution
chemical_list: D001426:Bacterial Proteins; D006573:Heterocyclic Compounds, 1-Ring; D007205:Indium Radioisotopes; D018719:Erb-b2 Receptor Tyrosine Kinases; C034284:IgG Fc-binding protein, Streptococcus; C071349:1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid; C508053:ERBB2 protein, human