N-glycan charge assay--an alternative for potency assays of therapeutic glycoproteins?

A new in vitro potency assay for erythropoietin has been developed and compared to the exhypoxic polycythemic mouse bioassay for rhuEPO batch release, required according to Ph. Eur. 2001. Evaluation of 14 batches of EPO has shown that the new assay is highly sensitive and able to reveal subtle changes in N-linked carbohydrates. In combination with regular EPO batch release assays (such as sialic acid determination, isoelectric focusing, RP-HPLC, and peptide mapping), this assay may enable to replace the highly variable exhypoxic mouse bioassay for EPO batch release and stability studies and thus reduce the use of laboratory mice.