A1 Journal article – refereed
Molecular design of radiocopper-labelled Affibody molecules




List of Authors: Tolmachev V, Gronroos TJ, Yim CB, Garousi J, Yue Y, Grimm S, Rajander J, Perols A, Haaparanta-Solin M, Solin O, Ferdani R, Orlova A, Anderson CJ, Karlstrom AE
Publisher: NATURE PUBLISHING GROUP
Publication year: 2018
Journal: Scientific Reports
Journal name in source: SCIENTIFIC REPORTS
Journal acronym: SCI REP-UK
Volume number: 8
Number of pages: 10
ISSN: 2045-2322

Abstract
The use of long-lived positron emitters Cu-64 or Cu-61 for labelling of Affibody molecules may improve breast cancer patients' stratification for HER-targeted therapy. Previous animal studies have shown that the use of triaza chelators for Cu-64 labelling of synthetic Affibody molecules is suboptimal. In this study, we tested a hypothesis that the use of cross-bridged chelator, CB-TE2A, in combination with Gly-Glu-Glu-Glu spacer for labelling of Affibody molecules with radiocopper would improve imaging contrast. CB-TE2A was coupled to the N-terminus of synthetic Affibody molecules extended either with a glycine (designation CB-TE2A-G-ZHER2:342) or Gly-Glu-Glu-Glu spacer (CB-TE2A-GEEE-ZHER2:342). Biodistribution and targeting properties of Cu-64-CB-TE2A-G-ZHER2:342 and Cu-64-CB-TE2A-GEEE-ZHER2:342 were compared in tumor-bearing mice with the properties of Cu-64-NODAGA-ZHER2:S1, which had the best targeting properties in the previous study. Cu-64-CB-TE2A-GEEE-ZHER2:342 provided appreciably lower uptake in normal tissues and higher tumor-to-organ ratios than Cu-64-CB-TE2A-GZHER2:342 and Cu-64-NODAGA-ZHER2:S1. The most pronounced was a several-fold difference in the hepatic uptake. At the optimal time point, 6 h after injection, the tumor uptake of Cu-64-CB-TE2A-GEEE-ZHER2: 342 was 16 +/- 6% ID/g and tumor-to-blood ratio was 181 +/- 52. In conclusion, a combination of the cross-bridged CB-TE2A chelator and Gly-Glu-Glu-Glu spacer is preferable for radiocopper labelling of Affibody molecules and, possibly, other scaffold proteins having high renal re-absorption.

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