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Influence of the N -Terminal Composition on Targeting Properties of Radiometal-Labeled Anti-HER2 Scaffold Protein ADAPT6
KTH, School of Biotechnology (BIO), Protein Technology.
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2016 (English)In: Bioconjugate chemistry, ISSN 1043-1802, E-ISSN 1520-4812, Vol. 27, no 11, p. 2678-2688Article in journal (Refereed) Published
Abstract [en]

Radionuclide-imaging-based stratification of patients to targeted therapies makes cancer treatment more personalized and therefore more efficient. Albumin-binding domain derived affinity proteins (ADAPTs) constitute a novel group of imaging probes based on the scaffold of an albumin binding domain (ABD). To evaluate how different compositions of the N-terminal sequence of ADAPTS influence their biodistribution, a series of human epidermal growth factor receptor type 2 (HER2)-binding ADAPT6 derivatives with different N-terminal sequences were created: GCH(6)DANS (2), GC(HE)(3)DANS (3), GCDEAVDANS (4), and GCVD.ANS(5). These were compared with the parental variant: GCSS(HE)(3)DEAVDANS (1). All variants were site-specifically conjugated with a maleimido-derivative of a DOTA chelator and labeled with In-III. Binding to HER2-expressing cells in vitro, in vivo biodistribution as well as targeting properties of the new variants were compared with properties of the In-III-labeled parental ADAPT variant 1 (In-III-DOTA-1). The composition of the N-terminal sequence had an apparent influence on biodistribution of ADAPT6 in mice. The use of a hexahistidine tag in (InD)-In-III-OTA-2 was associated with elevated hepatic uptake compared to the (HE)(3)-containing counterpart, In-III-DOTA-3. All new variants without a hexahistidine tag demonstrated lower uptake in blood, lung, spleen, and muscle compared to uptake in the parental variant. The best new variants, In-III-DOTA-3 and In-III-DOTA-5, provided tumor uptakes of 14.6 +/- 2.4 and 12.5 +/- 1.3% ID/g at 4 h after injection, respectively. The tumor uptake of In-III-DOTA-3 was significantly higher than the uptake of the parental In-III-DOTA-1 (9.1 +/- 2.0% ID/g). The tumor-to-blood ratios of 395 +/- 75 and 419 +/- 91 at 4 h after injection were obtained for In-III-DOTA-5 and (IIII)n-DOTA-3, respectively. In conclusion, the N-terminal sequence composition affects the biodistribution and targeting properties of ADAPT-based imaging probes, and its optimization may improve imaging contrast.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016. Vol. 27, no 11, p. 2678-2688
National Category
Biochemistry and Molecular Biology
Identifiers
URN: urn:nbn:se:kth:diva-199556DOI: 10.1021/acs.bioconjchem.6b00465ISI: 000388430700011Scopus ID: 2-s2.0-84996523484OAI: oai:DiVA.org:kth-199556DiVA, id: diva2:1065106
Note

QC 20170113

Available from: 2017-01-13 Created: 2017-01-09 Last updated: 2018-03-15Bibliographically approved
In thesis
1. Generation and engineering of ABD-derived affinity proteins for clinical applications
Open this publication in new window or tab >>Generation and engineering of ABD-derived affinity proteins for clinical applications
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Proteins that specifically recognize and bind to other molecules or structures are important tools in industrial and medical applications. Binding proteins engineered from small stable scaffold proteins have been utilized for several purposes due to their favorable biophysical properties, tolerance to mutagenesis, efficient tissue penetration and ease of production. The 46 amino acid long albumin-binding domain (ABD) derived from the bacterial receptor Protein G is a promising scaffold that has been explored in this thesis. The scaffold was subjected to combinatorial protein engineering for generation of ABD-derived binding proteins with novel specificities. Furthermore, the medical potential of engineered ABD- derived affinity proteins (ADAPTs) was evaluated in a series of pre-clinical studies.

In the first studies, ADAPTs suitability as tracers for radionuclide molecular imaging was evaluated. Factors influencing biodistribution and tumor targeting properties were assessed in mice models bearing HER2 positive xenografts. All tested ADAPT constructs demonstrated high and specific targeting of HER2-expressing tumor cells as well as fast clearance from circulation. The results also showed that the size and character of the N- terminus affected the biodistribution profile of ADAPTs. Moreover, the targeting properties of ADAPTs proved to be highly influenced by the residualizing properties of the attached radionuclide label. Taken together, the results provided the first evidence that tumor imaging can be performed using ADAPTs and the favorable pharmacokinetic profiles in the studied mice models suggest that the scaffold is a promising candidate for clinical applications.

In the last study, a platform for generation of stable ABD-derived affinity proteins with novel binding specificities was established using a multi-step approach combining directed evolution and rational protein design. A broad combinatorial protein library with 20 randomized positions in ABD was designed and binders against three distinct targets were selected using phage display. Characterization of the selected binders provided information regarding optimal positions to randomize in a final library. In addition, the isolated binders were subjected to mutagenesis in certain surface exposed positions and mutations that provided increased stability were introduced into the original scaffold. Finally, a more focused combinatorial protein library consisting of 11 randomized positions was designed and constructed. The library was validated by selections against the same set of targets as for the first, broad library. The isolation of highly stable affinity ligands confirms that the library can be used for generation of diverse and stable affinity molecules.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2018. p. 84
Series
TRITA-CBH-FOU ; 2018:7
Keywords
ABD, ADAPT, affinity proteins, protein engineering, radionuclide molecular imaging, HER2
National Category
Pharmaceutical Biotechnology
Research subject
Biotechnology
Identifiers
urn:nbn:se:kth:diva-224256 (URN)978-91-7729-715-4 (ISBN)
Public defence
2018-04-13, FR4 Oskar Kleins Auditorium, Roslagstullsbacken 21, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20180315

Available from: 2018-03-15 Created: 2018-03-15 Last updated: 2018-03-15Bibliographically approved

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Hober, Sophia

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