Collaborative study for the establishment of erythropoietin BRP batch 3.

The European Pharmacopoeia (Ph. Eur.) monograph on Erythropoietin concentrated solution (1316) specifies that identification and assay are performed using pharmacopoeial methods requiring the use of a reference preparation. To replace the current erythropoietin Biological Reference Preparation (BRP) of Ph. Eur., in 2006, the European Directorate for the Quality of Medicines undertook a collaborative study designed to establish a replacement batch. In order to guarantee continuity, the formulation of the candidate batch was similar to that of previous batches (1 and 2). The methods chosen to qualify the new standard were those included in the current monograph. The study was defined to allow calibration of the candidate by in vivo bioassay in terms of the current World Health Organization (WHO) International Standard (IS) and to assign a unitage. The suitability of the candidate preparation to serve as a reference standard for the other pharmacopoeial analytical procedures was also investigated. The collaborative study involved 16 laboratories from Europe, Australia, Canada, China, Japan, South Korea and the United States of America. Participants carried out biological and physicochemical assays on the candidate erythropoietin BRP batch 3 (cBRP3), using batch 2 (BRP2) and where necessary the 2nd World Health Organization International Standard (WHO 2nd IS) for recombinant erythropoietin as the reference standards. It was demonstrated that the replacement batch is appropriate for use as erythropoietin BRP in the context of the control of erythropoietin concentrated solutions according to the Ph. Eur. monograph (1316). However as regards the potency of BRP2 and cBRP3 in the mouse bioassay unexpected observations were made. Direct calibration of BRP2 against the WHO 2nd IS yielded, in all laboratories, results that were systematically higher than the potency of 32,500 IU/vial assigned by direct calibration against the WHO 2nd IS in the former study. It was therefore recommended to assign the potency of cBRP3 against BRP2, using the average of all results that were not considered as outlying obtained in the collaborative study, in order to guarantee continuity of unitage between the successive BRP batches. The outcome of the study enabled the Ph. Eur. Commission to establish the proposed standard as 'erythropoeitin BRP batch 3' (BRP3). BRP3 was established in June 2007 for use as a reference preparation for the polycythaemic and normocythaemic mouse bioassay, with an assigned potency of 35,280 IU/vial, the identification by capillary zone electrophoresis, by polyacrylamide gel electrophoresis, immunoblotting and peptide mapping and as a reference for checking the system suitability of size-exclusion chromatographic procedures used in the test for dimers and related substances of higher molecular mass in the Ph. Eur. monograph (1316).