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
Introduction: 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). Methods: The HER2-targeting NCL-cyclized Affibody molecule Z(HER2:342min) has been designed, synthesized and site-specifically conjugated with a DOTA chelator. DOTA-Z(HER2:342min) was labeled with In-111 and (68) Ga. The binding affinity of DOTA-Z(HER2:342min) was evaluated in vitro. The targeting properties of In-111- and (68) Ga-DOTA-Z(HER2:342min) were evaluated in mice bearing SKOV-3 xenografts and compared with the properties of In-111- and (68) Ga-labeled PEP09239, a DOTA-conjugated 2-helix Affibody analogue cyclized by a homocysteine disulfide bridge. Results: The dissociation constant (K-D) for DOTA-Z(HER2:342min) binding to HER2 was 18 nM according to SPR measurements. DOTA-Z(HER2:342min) was labeled with In-111 and (68) Ga. Both conjugates demonstrated bi-phasic binding kinetics to HER2-expressing cells, with K-D1 in low nanbmolar 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 In-111-DOTA-Z(HER2:342min) and 4.6 +/- 0.7 for (68) Ga-DOTA-Z(HER2:342min). However, the uptake of DOTA-Z(HER2:342min) in lung, liver and spleen was appreciably higher than the uptake of PEP09239-based counterparts. Conclusions: Native chemical ligation enables production of a backbone-cyclized HER2-binding 2-helix Affibody molecule (Z(HER2:342min)) 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:kth:diva-121112DOI: 10.1016/j.nucmedbio.2012.12.009ISI: 000316507400011ScopusID: 2-s2.0-84875265693OAI: oai:DiVA.org:kth-121112DiVA: diva2:617103
FunderVinnovaSwedish Research Council
QC 201304222013-04-222013-04-192013-11-11Bibliographically approved