Evaluation of backbone-cyclized HER2-binding 2-helix Affibody molecule for In Vivo molecular imaging
2013 (English)In: Nuclear Medicine and Biology, ISSN 0969-8051, E-ISSN 1872-9614, Vol. 40, no 3, 378-386 p.Article in journal (Refereed) Published
Affibody molecules, small scaffold proteins, have demonstrated an appreciable potential as imaging probes. Affibody molecules are composed of three alpha-helices. Helices 1 and 2 are involved in molecular recognition, while helix 3 provides stability. The size of Affibody molecules can be reduced by omitting the third alpha-helix and cross-linking the two remaining, providing a smaller molecule with better extravasation and quicker clearance of unbound tracer. The goal of this study was to develop a novel 2-helix Affibody molecule based on backbone cyclization by native chemical ligation (NCL).
The HER2-targeting NCL-cyclized Affibody molecule ZHER2:342min has been designed, synthesized and site-specifically conjugated with a DOTA chelator. DOTA-ZHER2:342min was labeled with 111In and 68 Ga. The binding affinity of DOTA-ZHER2:342min was evaluated in vitro. The targeting properties of 111In- and 68 Ga-DOTA-ZHER2:342min were evaluated in mice bearing SKOV-3 xenografts and compared with the properties of 111In- and 68 Ga-labeled PEP09239, a DOTA-conjugated 2-helix Affibody analogue cyclized by a homocysteine disulfide bridge.
The dissociation constant (KD) for DOTA-ZHER2:342min binding to HER2 was 18 nM according to SPR measurements. DOTA-ZHER2:342min was labeled with 111In and 68 Ga. Both conjugates demonstrated bi-phasic binding kinetics to HER2-expressing cells, with KD1 in low nanomolar range. Both variants demonstrated specific uptake in HER2-expressing xenografts. Tumor-to-blood ratios at 2 h p.i. were 6.1 ± 1.3 for 111In- DOTA-ZHER2:342min and 4.6 ± 0.7 for 68 Ga-DOTA-ZHER2:342min. However, the uptake of DOTA-ZHER2:342min in lung, liver and spleen was appreciably higher than the uptake of PEP09239-based counterparts.
Native chemical ligation enables production of a backbone-cyclized HER2-binding 2-helix Affibody molecule (ZHER2:342min) with low nanomolar target affinity and specific tumor uptake.
Place, publisher, year, edition, pages
2013. Vol. 40, no 3, 378-386 p.
Affibody, HER2, 2-helix protein, SPPS, Native chemical ligation, biodistribution
Radiology, Nuclear Medicine and Medical Imaging
IdentifiersURN: urn:nbn:se:uu:diva-198614DOI: 10.1016/j.nucmedbio.2012.12.009ISI: 000316507400011OAI: oai:DiVA.org:uu-198614DiVA: diva2:617275
NOTICE: this is the author's version of a work that was accepted for publication in Nuclear Medicine and Biology. Changes resulting from the publishing process, such as editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in:Honarvar H, Jokilaasko N, Andersson K, Malmberg J, Rosik D, Orlova A, Eriksson Karlström A, Tolmachev V, Järver P. Evaluation of Backbone-Cyclized HER2-Binding Two-Helix Affibody Molecule for In Vivo Molecular Imaging. Nucl Med Biol, 40,3, 2013 Apr; :378-86