Facile labelling of an anti-epidermal growth factor receptor Nanobody with 68Ga via a novel bifunctional desferal chelate for immuno-PETReport as inadecuate

Facile labelling of an anti-epidermal growth factor receptor Nanobody with 68Ga via a novel bifunctional desferal chelate for immuno-PET - Download this document for free, or read online. Document in PDF available to download.

European Journal of Nuclear Medicine and Molecular Imaging

, Volume 38, Issue 4, pp 753–763

First Online: 06 January 2011Received: 10 August 2010Accepted: 29 November 2010


PurposeThe ∼15 kDa variable domains of camelid heavy-chain-only antibodies called Nanobodies® have the flexibility to be formatted as monovalent, monospecific, multivalent or multispecific single chain proteins with either fast or slow pharmacokinetics. We report the evaluation of the fast kinetic anti-epidermal growth factor receptor EGFR Nanobody 7D12, labelled with Ga via the novel bifunctional chelate BFC p-isothiocyanatobenzyl-desferrioxamine Df-Bz-NCS. Df-Bz-NCS has recently been introduced as the chelate of choice for Zr immuno-positron emission tomography PET.

MethodsNanobody 7D12 was premodified with Df-Bz-NCS at pH 9. Radiolabelling with purified Ga was performed at pH 5.0–6.5 for 5 min at room temperature. For in vitro stability measurements in storage buffer 0.25 M NaOAc with 5 mg ml gentisic acid, pH 5.5 at 4°C or in human serum at 37°C, a mixture of Ga and Ga was used. Biodistribution and immuno-PET studies of Ga-Df-Bz-NCS-7D12 were performed in nude mice bearing A431 xenografts using Zr-Df-Bz-NCS-7D12 as the reference conjugate.

ResultsThe Df-Bz-NCS chelate was conjugated to Nanobody 7D12 with a chelate to Nanobody molar substitution ratio of 0.2:1. The overall Ga radiochemical yield was 55–70% not corrected for decay; specific activity was 100–500 MBq-mg. Radiochemical purity of the conjugate was >96%, while the integrity and immunoreactivity were preserved. Ga-Df-Bz-NCS-7D12 was stable in storage buffer as well as in human serum during a 5-h incubation period <2% radioactivity loss. In biodistribution studies the Ga-labelled Nanobody 7D12 showed high uptake in A431 tumours ranging from 6.1 ± 1.3 to 7.2 ± 1.5%ID-g at 1–3 h after injection and high tumour to blood ratios, which increased from 8.2 to 14.4 and 25.7 at 1, 2 and 3 h after injection, respectively. High uptake was also observed in the kidneys. Biodistribution was similar to that of the reference conjugate Zr-Df-Bz-NCS-7D12. Tumours were clearly visualized in a PET imaging study.

ConclusionVia a rapid procedure under mild conditions a Ga-Nanobody was obtained that exhibited high tumour uptake and tumour to normal tissue ratios in nude mice bearing A431 xenografts. Fast kinetic Ga-Nanobody conjugates can be promising tools for tumour detection and imaging of target expression.

KeywordsGa Radiolabelling Nanobodies Desferal p-Isothiocyanatobenzyl-desferrioxamine EGFR  Download fulltext PDF

Author: Maria J. W. D. Vosjan - Lars R. Perk - Rob C. Roovers - Gerard W. M. Visser - Marijke Stigter-van Walsum - Paul M. P

Source: https://link.springer.com/

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