Journal des techniques de chromatographie et de séparation
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I-Number Assay and Erythropoietin Potency: Retrospective Capillary Zone Electrophoresis Data Analysis of the Biological Reference Preparations of Erythropoietin

Hermentin P*

The capillary zone electrophoresis data of erythropoietin reference preparations batch 1 (BRP1), batch 2 (BRP2) and batch 3 (BRP3) of three collaborative studies published in 2004, 2007 and 2015 have retrospectively been analyzed by the author via the I-number assay, a physicochemical assay that allows potency calculation of erythropoietin samples in a precise and accurate manner. The results are summarized as follows:

The I-number assay revealed an inter-laboratory precision of CV < 1.0% and an accuracy of 100.0 ± < 1.5%. The I-number calculated for an EPO sample and the corresponding EPO reference standard may be regarded analytically “indistinguishable” at I-number differences of < 1.5%, “comparable” at differences of 1.5-3.0% and “different” at differences of >3.0%.

This retrospective analysis by the author of the CZE data of the (candidate) EPO BRPs has revealed that the bioactivity stated for EPO BRP1 (130.0 IU/μg) should have been stated about 5% higher (“BRP1+5%”=136.5 IU/μg) and the bioactivity stated for EPO BRP2 (130.0 IU/μg) should have been stated about 10% higher (“BRP2+10%”=143.0 IU/μg), and the two new potency values are proposed by the author herewith. The potency assigned for EPO BRP3 (141.1 IU/μg) was without any doubt and therefore confirmed.