Unraveling the plasma dynamics, oxidative metabolism and excretion behavior of M-PEG6-OH by UPLC-MS/MS.

Addressing critical gaps in understanding the in vivo behavior of polyethylene glycol (PEG)-based excipients, this study systematically elucidates the biological fate of methoxy-PEG₆-hydroxyl (M-PEG₆-OH) through comprehensive pharmacokinetic and metabolic investigations in rats. Employing a validated ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) methodology, we reveal distinctive biodistribution characteristics including rapid systemic clearance (Half-life (t1/2) = 1.92 ± 1.16 h) and extensive tissue penetration (Apparent volume of distribution (Vd) = 0.84 ± 0.45 L/kg), suggesting efficient extravascular dissemination. Excretion pathways analysis demonstrated predominant renal elimination, with 59.03 % of the administered dose recovered in urine within 48 h post-IV injection, contrasting with minimal fecal excretion (0.99 %). Quantitative metabolite profiling identified M-PEG₅-CH₂COOH as the oxidative transformation product through terminal hydroxyl modification. The significantly higher relative abundance of metabolites (M-PEG5-CH2COOH) in urine compared to feces within the same time period provides critical insights into the biotransformation processes and metabolic pathways of the PEG polymer. These findings establish the first systematic evidence of metabolic trajectory and elimination mechanisms for M-PEG-OH, offering vital references for optimizing PEGylated drug delivery systems with enhanced biocompatibility and predictable safety profiles.