The Erythropoietin (EPO) European Pharmacopoeia (Ph. Eur.) Biological Reference Preparation (BRP) batch 3 was calibrated in 2006 by in vivo bioassay and was used as a reference preparation for these assays as well as for the physicochemical methods in the Ph. Eur. monograph Erythropoietin concentrated solution (1316). In order to avoid the frequent replacement of this standard and thus reduce the use of animals, a new EPO Chemical Reference Substance (CRS) was established to be used solely for the physicochemical methods. Here we report the outcome of a collaborative study aimed at demonstrating the suitability of the candidate CRS (cCRS) as a reference for the physicochemical methods in the Ph. Eur. monograph. Results from the study demonstrated that for the physicochemical methods currently required in the monograph (capillary zone electrophoresis (CZE), polyacrylamide gel electrophoresis (PAGE)/immunoblotting and peptide mapping), the cCRS is essentially identical to the existing BRP. However, data also indicated that, for the physicochemical methods under consideration for inclusion in a revised monograph (test for oxidised forms and glycan mapping), the suitability of the cCRS as a reference needs to be confirmed with additional work. Further to completion of the study, the Ph. Eur. Commission adopted the cCRS as "Erythropoietin for physicochemical tests CRS batch 1" to be used for CZE, PAGE/immunoblotting and peptide mapping.
Keywords: CRS; CZE; Chemical Reference Substance; European Pharmacopoeia; PAGE; biological standardisation; capillary zone electrophoresis; collaborative study; erythropoietin; glycan mapping; immunoblotting; oxidised form; peptide mapping; polyacrylamide gel electrophoresis.