Advancing PEGylated Drug Evaluation: A Novel Approach to Pegfilgrastim Pharmacokinetic Assessment

Addition of polyethylene glycol (PEG), or PEGylation, is a modification that extends the half-life of drug products, thereby reducing the frequency of dosing. However, PEGylation can pose challenges for biosimilar drug development, as replicating the reference product's PEG characteristics to achieve similarity to the reference product's pharmacokinetics (PK) can be difficult. A few biosimilar product submissions have highlighted issues with PK assays, potentially contributing to failures in PK similarity assessment. With many approved PEGylated protein therapeutics soon becoming eligible for biosimilar development, developing alternative methods for PK assessment that can be applied across multiple product categories may help to facilitate a more efficient biosimilar development program. We previously validated an ELISA-based method and observed significant variability even in samples prepared with known drug concentrations. We decided that a cell-based assay (CBA) might offer greater translatability to other PEGylated products. CBAs rely on cells with receptors for the drug product being tested, and the choice of cell line would vary depending on the specific drug product. In this study, we utilized pegfilgrastim, a PEGylated granulocyte-colony stimulating factor (G-CSF) product, for PK determination using the CBA method. This proof-of-concept study demonstrates that while the sensitivity of the CBA is lower than that of the validated ELISA, its ability to capture receptor-accessible drug provides an important advantage for pharmacokinetic assessment. Moreover, it exhibits good reproducibility and can be read using a 96-well platform. This CBA approach may be a viable option for the rapid development of PK assays for other PEGylated drug products.