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Incorporation of a triglutamyl spacer improves the biodistribution of synthetic affibody molecules radiofluorinated at the N-terminus via oxime formation with (18)F-4-fluorobenzaldehyde.
- Source :
-
Bioconjugate chemistry [Bioconjug Chem] 2014 Jan 15; Vol. 25 (1), pp. 82-92. Date of Electronic Publication: 2013 Dec 27. - Publication Year :
- 2014
-
Abstract
- Affibody molecules are a class of affinity agents for molecular imaging based on a non-immunoglobulin protein scaffold. Previous studies have demonstrated high contrast for in vivo imaging of cancer-associated molecular abnormalities using Affibody molecules. Using the radionuclide (18)F for labeling and PET as the imaging modality, the sensitivity of molecular imaging using Affibody molecules can be further increased. The use of oxime formation between an aminooxy-functionalized peptide and (18)F-fluorobenzaldehyde ((18)F-FBA) is a promising way of radiolabeling of targeting peptides. However, previous studies demonstrated that application of this method to Affibody molecules is associated with high liver uptake. We hypothesized that incorporation of a triglutamyl spacer between the aminooxy moiety and the N-terminus of a synthetic Affibody molecule would decrease the hepatic uptake of the (18)F-N-(4-fluorobenzylidine)oxime) ((18)F-FBO)-labeled tracer. To verify this, we have produced two variants of the HER2-targeting ZHER2:342 Affibody molecule by peptide synthesis: OA-PEP4313, where aminooxyacetic acid was conjugated directly to the N-terminal alanine, and OA-E3-PEP4313, where a triglutamyl spacer was introduced between the aminooxy moiety and the N-terminus. We have found that the use of the spacer is associated with a minor decrease of affinity, from KD = 49 pM to KD = 180 pM. Radiolabeled (18)F-FBO-E3-PEP4313 demonstrated specific binding to HER2-expressing ovarian carcinoma SKOV-3 cells and slow internalization. Biodistribution studies in mice demonstrated that the use of a triglutamyl linker decreased uptake of radioactivity in liver 2.7-fold at 2 h after injection. Interestingly, radioactivity uptake in kidneys was also reduced (2.4-fold). Experiments in BALB/C nu/nu mice bearing SKOV-3 xenografts demonstrated HER2-specific uptake of (18)F-FBO-E3-PEP4313 in tumors. At 2 h pi, the tumor uptake (20 ± 2% ID/g) exceeded uptake in liver 5-fold and uptake in kidneys 3.6-fold. The tumor-to-blood ratio was 21 ± 3. The microPET/CT imaging experiment confirmed the biodistribution data. In conclusion, the use of a triglutamyl spacer is a convenient way to improve the biodistribution profile of Affibody molecules labeled at the N-terminus using (18)F-FBA. It provides a tracer capable of producing high-contrast images of HER2-expressing tumors.
- Subjects :
- Animals
Cell Line, Tumor
Fluorine Radioisotopes chemistry
Fluorine Radioisotopes pharmacokinetics
Humans
Mice
Mice, Inbred BALB C
Mice, Nude
Models, Molecular
Molecular Structure
Positron-Emission Tomography
Tissue Distribution
Tomography, X-Ray Computed
Benzaldehydes chemistry
Benzaldehydes pharmacokinetics
Neoplasms, Experimental diagnosis
Oximes chemistry
Oximes pharmacokinetics
Recombinant Fusion Proteins chemistry
Recombinant Fusion Proteins pharmacokinetics
Subjects
Details
- Language :
- English
- ISSN :
- 1520-4812
- Volume :
- 25
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Bioconjugate chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 24344772
- Full Text :
- https://doi.org/10.1021/bc400343r