Deciphering the In Vivo Metabolism of Polyethylene Glycol by a Polymeromics Approach

Polyethylene glycols (PEGs), commonly used in pharmaceutical applications, have recently been associated with potential adverse effects, highlighting the necessity for a thorough understanding of their in vivo metabolism. The inherent molecular weight polydispersity of PEGs, as polymers, poses challenges for systematic metabolic investigations. Here, we propose "polymeromics" as an innovative methodology for elucidating PEG metabolism. This approach allows for detailed molecular weight profiling and facilitates the precise identification of metabolites. In this proof-of-concept study, methoxy polyethylene glycol 2000 (mPEG2000) was employed as a model polymer. Using liquid chromatography coupled with high-resolution mass spectrometry and clustering analysis, we achieved, for the first time, a comprehensive molecular-weight-resolved characterization of the in vivo metabolism of mPEG2000. Our findings identified a range of mPEG2000 metabolites and revealed that midchain scission occurs during in vivo metabolism, with the hydroxyl radical being the primary species responsible for this cleavage. Furthermore, we elucidated the plasma kinetics, tissue distribution, and excretion profiles of mPEG2000 and its metabolites. This study introduces an innovative platform for investigating the in vivo metabolism of PEG, providing new insights into its biological fate and informing the development of safer PEGylated pharmaceuticals.