Title: The effect of bi-terminal PEGylation of an integrin  α_vβ₆-targeted ¹⁸F peptide on pharmacokinetics and tumor uptake

Abstract

Radiotracers based on the peptide A20FMDV2 selectively target the cell surface receptor integrin α_vβ₆. This integrin has been identified as a prognostic indicator correlating with the severity of disease for several challenging malignancies. In previous studies of A20FMDV2 peptides labeled with 4-¹⁸F-fluorobenzoic acid (¹⁸F-FBA), we have shown that the introduction of poly(ethylene glycol) (PEG) improves pharmacokinetics, including increased uptake in α_vβ₆-expressing tumors. The present study evaluated the effect of site-specific C-terminal or dual (N- and C-terminal) PEGylation, yielding ¹⁸F-FBA-A20FMDV2-PEG₂₈ (4) and ¹⁸F-FBA-PEG₂₈-A20FMDV2-PEG₂₈ (5), on α_vβ₆-targeted tumor uptake and pharmacokinetics. The results are compared with ¹⁸F-FBA–labeled A20FMDV2 radiotracers (1–3) bearing either no PEG or different PEG units at the N terminus. The radiotracers were prepared and radiolabeled on solid phase. Using 3 cell lines, DX3puroβ6 (α_vβ₆+), DX3puro (α_vβ₆–), and BxPC-3 (α_vβ₆+), we evaluated the radiotracers in vitro (serum stability; cell binding and internalization) and in vivo in mouse models bearing paired DX3puroβ6–DX3puro and, for 5, BxPC-3 xenografts. Here, the size and location of the PEG units significantly affected α_vβ₆ targeting and pharmacokinetics. Although the C-terminally PEGylated 4 showed some improvements over the un-PEGylated ¹⁸F-FBA-A20FMDV2 (1), it was the bi-terminally PEGylated 5 that displayed the more favorable combination of high α_vβ₆ affinity,more » selectivity, and pharmacokinetic profile. In vitro, 5 bound to α_vβ₆-expressing DX3puroβ6 and BxPC-3 cells with 60.5% ± 3.3% and 48.8% ± 8.3%, respectively, with a significant fraction of internalization (37.2% ± 4.0% and 37.6% ± 4.1% of total radioactivity, respectively). By comparison, in the DX3puro control 5 showed only 3.0% ± 0.5% binding and 0.9% ± 0.2% internalization. In vivo, 5 maintained high, α_vβ₆-directed binding in the paired DX3puroβ6–DX3puro model (1 h: DX3puroβ6, 2.3 ± 0.2 percentage injected dose per gram [%ID/g]; DX3puroβ6/DX3puro ratio, 6.5:1; 4 h: 10.7:1). In the pancreatic BxPC-3 model, uptake was 4.7 ± 0.9 %ID/g (1 h) despite small tumor sizes (20–80 mg). In conclusion, the bi-PEGylated radiotracer 5 showed a greatly improved pharmacokinetic profile, beyond what was predicted from individual N- or C-terminal PEGylation. It appears that the 2 PEG units acted synergistically to result in an improved metabolic profile including high α_vβ₆+ tumor uptake and retention.« less

Authors:

Hausner, Sven H. ^[1]; Bauer, Nadine ^[2]; Hu, Lina Y. ^[2]; Knight, Leah M. ^[3]; Sutcliffe, Julie L. ^[1]

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+ Show Author Affiliations

1. Univ. of California Davis, Sacramento, CA (United States); Univ. of California, Davis, CA (United States)
2. Univ. of California, Davis, CA (United States)
3. Univ. of California Davis, Sacramento, CA (United States)

Publication Date:

Thu Mar 26 00:00:00 EDT 2015

Research Org.:

Univ. of California, Davis, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1345593

Grant/Contract Number:  

SC0002061

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Nuclear Medicine

Additional Journal Information:

Journal Volume: 56; Journal Issue: 5; Journal ID: ISSN 0161-5505

Publisher:

Society of Nuclear Medicine and Molecular Imaging

Country of Publication:

United States

Language:

English

Subject:

59 BASIC BIOLOGICAL SCIENCES; 60 APPLIED LIFE SCIENCES; integrin αvβ6; positron emission tomography; peptide; PEGylation; metabolism