Pharmacokinetics, excretion, distribution, and metabolism of 60-kDa polyethylene glycol used in BAY 94-9027 in rats and its value for human prediction

Abstract

The covalent binding of proteins with polyethylene glycol (PEG) molecules is a valuable tool to extend the half-life of many biotherapeutics, including factor VIII (FVIII) products to treat patients with haemophilia A. Although PEG has low toxicity, accumulation of large PEG molecules (>20-30 kDa) with long-term exposure is a potential concern. Thus, it is important to determine whether sufficient excretion processes exist for PEG molecules used in biotherapeutics. BAY 94-9027 is an extended-half-life FVIII product modified through addition of a 60-kDa (branched: dual 30-kDa) PEG molecule. BAY 1025662 is the 60-kDa PEG moiety used for PEGylation of BAY 94-9027. This study investigated the pharmacokinetic (PK) properties, distribution, and excretion of BAY 1025662 in rats in order to predict estimated 60-kDa PEG PK properties in patients. Plasma concentrations in male rats after a single 11-mg/kg intravenous dose of BAY 1025662 (approximating the cumulative PEG-60 exposure in patients during 30 years of BAY 94-9027 treatment) decreased with an initial half-life of 119 h (5 days) in the interval of 114-336 h post administration. Single-dose mass balance studies using radiolabeled BAY 1025662 ([prop-¹⁴C]BAY 1025662) showed that 30.4% of radioactivity was excreted within 1 week and 79.1% by Day 168 (primarily in urine). The terminal half-life of radioactivity elimination was approximately 24 days in blood and plasma and was 31-68 days in the majority of other organs up to Day 168. Elimination was nearly complete at the end of the experiment on Day 168; only ~4% of residual radioactivity was present in the animal body. There was no irreversible binding of radioactivity to any tissues and no penetration of the blood-brain barrier. Based on these results, very low steady-state concentrations of 60-kDa PEG were predicted in patients treated with BAY 94-9027, and the validity of these predictions was supported by clinical studies in which almost all 179 patients receiving BAY 94-9027 for prophylaxis had undetectable PEG in plasma for up to >5 years; those with detectable PEG levels demonstrated concentrations within the predicted range. These combined preclinical and clinical observations suggest that excretion processes are in place for high-molecular-weight PEGs such as the PEG-60 moiety used in BAY 94-9027.

Keywords: Distribution; Excretion; Haemophilia A; PEGylation; Pharmacokinetics; Recombinant factor VIII.