Precise PEGylation Modulates the in Vivo Fate of Peptide Radiopharmaceuticals.

PEGylation has emerged as a promising approach to addressing stability issues and tumor retention challenges in radiopharmaceutical development. Herein, how PEGylation affects the in vivo behavior of peptide radiopharmaceuticals is investigated, focusing on the length and topological structure of the PEG molecules. A peptide ligand that targets CD133 is used and modified with different lengths of PEG (PEG3, PEG10, and PEG20) to study the impact of PEG length. Additionally, a peptide ligand targeting PD-L1 is modified with single-arm PEG, 4-arm PEG, and 8-arm PEG to examine the effects of PEG polyvalency. Through quantitative PET/CT imaging for long-term tracking, the in vivo behavior of the synthesized peptide radioligands is compared. Interestingly, PEG10 is the optimal spacer for achieving maximum tumor retention for the CD133-targeting peptide. However, the PD-L1 peptide derivatives modified with different armed PEG molecules showed complex results, with increased PEG arms leading to a higher tumor therapeutic index but compromising the pharmacokinetic properties. The findings highlight the dual nature of PEGylation in peptide radiopharmaceutical development, emphasizing the importance of considering PEG size, structure, and attachment point in drug design process. This study shed light on the diverse effects of PEGylation and aids in discovering PEGylated radiopharmaceuticals.