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ADAPT, a novel scaffold protein-based probe for radionuclide imaging of molecular targets that are expressed in disseminated cancers
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Medical Radiation Science. (Vladimir Tolmachev)
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2015 (English)In: Cancer Research, ISSN 0008-5472, E-ISSN 1538-7445, Vol. 75, no 20, 4364-4371 p.Article in journal (Refereed) Published
Abstract [en]

Small engineered scaffold proteins have attracted attention as probes for radionuclide-based molecular imaging. One class of these imaging probes, termed ABD-Derived Affinity ProTeins (ADAPT), have been created using the albumin-binding domain (ABD) of streptococcal protein G as a stable protein scaffold. In this study, we report the development of a clinical lead probe termed ADAPT6 that binds HER2, an oncoprotein overexpressed in many breast cancers that serves as a theranostic biomarker for several approved targeting therapies. Surface-exposed amino acids of ABD were randomized to create a combinatorial library enabling selection of high affinity binders to various proteins. Further, ABD was engineered to rapidly purify ADAPT6, eradicate its binding to albumin and enable rapid blood clearance. Incorporation of a unique cysteine allowed site-specific conjugation to a maleimido derivative of a DOTA chelator, enabling radionuclide labeling, 111In for SPECT imaging and 68Ga for PET imaging. Pharmacological studies in mice demonstrated that the fully engineered molecule 111In/68Ga-DOTA-(HE)3-ADAPT6 was specifically bound and taken up by HER2-expressing tumors, with a high tumor-to-normal tissue ratio in xenograft models of human cancer. Unbound tracer underwent rapid renal clearance followed by high renal reabsorption. HER2-expressing xenografts were visualized by gamma-camera or PET by one hour post-infusion. PET experiments demonstrated feasibility for discrimination of xenografts with high or low HER2 expression. Our results offer a preclinical proof of concept for the use of ADAPT probes for non-invasive in vivo imaging.

Place, publisher, year, edition, pages
2015. Vol. 75, no 20, 4364-4371 p.
National Category
Medical Genetics
Identifiers
URN: urn:nbn:se:uu:diva-262291DOI: 10.1158/0008-5472.CAN-14-3497ISI: 000365601900013PubMedID: 26297736OAI: oai:DiVA.org:uu-262291DiVA: diva2:853294
Funder
Swedish Cancer Society, 2012/354Swedish Research Council, 521-2012-2228Swedish Research Council, 621-2012-5088
Note

First two authors (Garousi and Lindbo) contributed equally

Last two authors (Tolmachev and Hober) contributed eaually

Available from: 2015-09-12 Created: 2015-09-12 Last updated: 2017-12-04
In thesis
1. Development of ADAPT-based tracers for radionuclide molecular imaging of cancer
Open this publication in new window or tab >>Development of ADAPT-based tracers for radionuclide molecular imaging of cancer
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

ABD-Derived Affinity Proteins (ADAPTs) is a novel class of small engineered scaffold proteins based on albumin-binding domain (ABD) of streptococcal protein G. High affinity ADAPT  binders against various therapeutic targets can be selected.  In this thesis, we report a development of ADAPT-based radionuclide imaging agents providing high sensitivity and specificity of molecular imaging of HER2 expression in disseminated cancers.

We investigated the feasibility of the use of ADAPTs as imaging agents and influence of molecular design and radiolabeling chemistry on in vivo targeting and biodistribution properties of the tracers.

In Paper I we demonstrated the feasibility of the use of anti-HER2 ADAPT6 molecule as a high contrast imaging agent;

In Paper II we evaluated the influence of composition of histidine-containing tag on in vivo biodistribution of ADAPT-based tracers labeled with 99mTc using 99mTc(CO)3 binding to histidine-containing tags and 111In using DOTA chelator at N-terminus;

In Paper III we evaluated the influence of different aspects of N-terminus leading sequence on targeting including effect of sequence size on clearance rate and effect of the composition of the sequence on biodistribution profile;

In Paper IV, we evaluated the influence of residualizing properties and positioning of the label on biodistribution and targeting; and

In Paper V, we compared tumor-targeting properties of the ADAPT6 labeled at C-terminus with 99mTc using N3S chelator and 111In using DOTA chelator.

In conclusion, ADAPTs constitute a very promising class of targeting probes for molecular imaging providing high contrast. Molecular design of the ADAPT proteins and chelators/linkers for labeling has an appreciable effect on their imaging properties.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 99 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1354
Keyword
ADAPT, scaffold protein, albumin-binding domain (ABD), Affinity protein, HER2, radionuclide molecular imaging
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-327419 (URN)978-91-513-0030-6 (ISBN)
Public defence
2017-09-29, Fåhraeus Hall, Rudbecklaboratoriet, Dag Hammarskjölds väg 20, Uppsala, 13:00 (English)
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Available from: 2017-09-06 Created: 2017-08-10 Last updated: 2017-09-08

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Garousi, JavadSandström, MattiasHonarvar, HadisOrlova, AnnaTolmachev, Vladimir

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