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Comparative evaluation of affibody- and antibody fragments-based CAIX imaging probes in mice bearing renal cell carcinoma xenografts

J. Garousi,F. Huizing,A. Vorobyeva,B. Mitran,K. Andersson,Charles Dahlsson Leitao,F. Frejd,John Löfblom,J. Bussink,A. Orlova,S. Heskamp,V. Tolmachev

Published 2019 in Scientific Reports

ABSTRACT

Carbonic anhydrase IX (CAIX) is a cancer-associated molecular target for several classes of therapeutics. CAIX is overexpressed in a large fraction of renal cell carcinomas (RCC). Radionuclide molecular imaging of CAIX-expression might offer a non-invasive methodology for stratification of patients with disseminated RCC for CAIX-targeting therapeutics. Radiolabeled monoclonal antibodies and their fragments are actively investigated for imaging of CAIX expression. Promising alternatives are small non-immunoglobulin scaffold proteins, such as affibody molecules. A CAIX-targeting affibody ZCAIX:2 was re-designed with the aim to decrease off-target interactions and increase imaging contrast. The new tracer, DOTA-HE3-ZCAIX:2, was labeled with 111In and characterized in vitro. Tumor-targeting properties of [111In]In-DOTA-HE3-ZCAIX:2 were compared head-to-head with properties of the parental variant, [99mTc]Tc(CO)3-HE3-ZCAIX:2, and the most promising antibody fragment-based tracer, [111In]In-DTPA-G250(Fab’)2, in the same batch of nude mice bearing CAIX-expressing RCC xenografts. Compared to the 99mTc-labeled parental variant, [111In]In-DOTA-HE3-ZCAIX:2 provides significantly higher tumor-to-lung, tumor-to-bone and tumor-to-liver ratios, which is essential for imaging of CAIX expression in the major metastatic sites of RCC. [111In]In-DOTA-HE3-ZCAIX:2 offers significantly higher tumor-to-organ ratios compared with [111In]In-G250(Fab’)2. In conclusion, [111In]In-DOTA-HE3-ZCAIX:2 can be considered as a highly promising tracer for imaging of CAIX expression in RCC metastases based on our results and literature data.

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