@misc{oai:repo.qst.go.jp:00082859,
 author = {Kuan, Hu and Lin, Xie and Zhang, Yiding and Masayuki, Hanyu and Zhang, Ming-Rong and Kuan, Hu and Lin, Xie and Zhang, Yiding and Masayuki, Hanyu and Zhang, Ming-Rong},
 month = {May},
 note = {Objectives: Peptides are a class of important drug molecules for positron emission tomography
(PET) tracers. However, native peptides are prone to enzymatic degradation. Polyethylene glycol
modification (PEGylation) is an FDA approved strategy for improving peptide stability. PEGylation
can prolong the blood circulation and enhance the cellular uptake and tissue retention of peptides,
thus promoting the bioavailability and target accessibility. Despite these benefits, PEGylation is
likely to damage the binding ability of peptides to their targets and cause severe allergic reactions
in the living body, if the PEG is improperly anchored to peptides. Besides, body excretion of
PEGylated peptides is usually slowed compare to unpegylated peptides. However, these issues
thus far are poorly understood. In this light, a systematic investigation of how does the PEGylation
(including PEG size, PEGylation position, and topology of PEG) affect the pharmacological
properties and in vivo fate of peptides is exceptionally significant. In this study, we reported the
PEGylation of a PD-L1 binding peptide with different PEG moieties, and studied the in vivo
behavior of these PEGylated peptides in animal models.
Methods: We synthesized a PD-L1 (immune checkpoint) binding peptide
(NOTA-SGQYASYHCWCWKNPGRSGGSK, NOTA-TPP-1), which has two cysteine residues.
Three kinds of PEG molecules, namely linear PEG (PEG, M.W.=5000), 4 arm PEG (4PEG,
M.W.=5000), and 8 arm PEG (8PEG, M.W.=10000), were used to modify the NOTA-TPP-1. The
PEGylation occurred between the cysteine of TPP-1 and the maleimide of PEG. Specifically, the
NOTA-TPP-1 was firstly incubated with 64Cu for 10 min at 80℃ to generate
[64Cu]NOTA-TPP-1. Then PEG molecules were mixed with [64Cu]NOTA-TPP-1 with
molar ratios of 1.2:1, 1:4.5, 1: 8.5 for PEG, 4PEG, and 8PEG, respectively. The reactions
were monitored by radio HPLC to check the modification efficiency. For PET imaging,
C57/BL6J mice bearing MC38 tumors were injected with different tracers (0.5 mCi per
mouse) intravenously. The mice were imaged at designated time points to monitor the
pharmacokinetics and dynamics of the tracers.
Results: [64Cu]NOTA-TPP-1 was obtained with a radiochemical yield of up to 99%. The
PEGylation with linear PEG achieved an efficiency of 98% after 6 hours of incubation, while that
was 78% for 4PEG and 8PEG accordingly. We also found that more branches of PEG caused an
increase of the retention time in radio HPLC, resulting in the retention times with an order of
[ 64Cu]NOTA-TPP-1-8PEG>[64Cu]NOTA-TPP-1-4PEG
>[64Cu]NOTA-TPP-1-PEG>[64Cu]NOTA-TPP-1. The non-PEGylated [64Cu]NOTA-TPP-1 was
rapidly eliminated by the kidney and bladder, and the tumor uptake of this tracer was weak. For
PEGylated peptides, the tumor uptake and retention were significantly enhanced, and the branch
number correlates well with the tumor uptake of the tracers. In particular, 8PEG modification leads
to the highest tumor uptake and longest retention, followed by 4PEG modification. However, the
PEGylation remarkably influenced the renal clearance of the tracers, and larger PEG delayed
kidney elimination.
Conclusions: Our results indicate that PEGylation modulation of peptides is a viable way to
improve the PET imaging capacity of peptides., eSRS},
 title = {PEGylation modulation of peptides promotes PET detection of cancers},
 year = {2021}
}