A collaborative study to establish the 7th International Standard for Factor VIII Concentrate

Abstract

To cite this article: Raut S., Bevan S., Hubbard A. R., Sands D., Barrowcliffe T. W. A collaborative study to establish the 7th International Standard for Factor VIII Concentrate. J Thromb Haemost 2005; 3: 119-26.Summary. A candidate concentrate, preparation N (99/678), was assayed and calibrated, as a potential replacement, against four established factor (F) VIII concentrate standards: the current WHO 6th International Standard (IS) (97/616), the previous 5th IS (88/640), the Mega 1 standard and Ph. Eur. BRP Batch 2 standard, in a collaborative study involving 38 laboratories. All laboratories were instructed to use the ISTH/ SSC recommendations, including predilution of concentrates in FVIII-deficient plasma. Several laboratories performed more than one assay method and altogether there were 27 sets of assays with the one-stage method, 31 with the chromogenic method, and 18 with both methods. There was good agreement between laboratories using each of the two methods for comparison of preparation N against the four established standards, with overall potencies by one-stage and chromogenic methods differing only by less than 2%. However, there were significant differences in potencies relative to the different standards, ranging from 10.1 IU per ampoule against the Ph. Eur.BRP2 to 11.4 against the WHO 6th IS. Accelerated degradation studies showed that the proposed standard is very stable, with a predicted loss of activity per year of less than 0.001% at the recommended storage temperature of )20°C. Various options for potency of preparation N were considered by the participants and by members of the ISTH/SSC FVIII/ FIX Subcommittee. In November 2003, preparation N (NIBSC 99/678) was proposed to and accepted by the Expert Committee on Biological Standardization of the World Health Organization to be the 7th International Standard for Factor VIII Concentrate with an assigned potency of 11.0 IU per ampoule.

Plasma‐derived clotting factor VIII: Heterogeneity evaluation in the quest for potential inhibitory‐antibody stimulating factors

“…A positive correlation was soon reported for solvent/detergent and heat treatments of the pdFVIII concentrates and inhibitory incidence in PUPs 30, 31. Biochemical investigations evidenced that new epitopes might form at the FVIII light chain C2‐domain level upon solvent/detergent and pasteurization treatment 32, 33. Although inhibitory antibodies developed by PUPs have been shown to target both the A2 domain of the HCh, and the A3 and C2 domains of the light chain, so far only the latter have attracted the main deal of investigative efforts 10, 32, 33.…”

Proteomic characterization of plasma‐derived clotting factor VIII–von Willebrand factor concentrates

“…However, there have been unforeseen accidents after some products were introduced to the market: After the introduction of two F VIII concentrates, unexpected development of inhibitors in previously treated patients occurred [12, 16, 17], resulting in the withdrawal of these products from the market. Some work was done to explain the origin of these unexpected side effects, unfortunately with limited success [12, 31]. It was shown that inhibitory antibodies were directed against the C2 domain in the light chain of the F VIII [32], but the peptide(s) responsible for antibody formation could not be conclusively determined.…”

“…Barrowcliffe et al [33] proposed that the purification process and virus inactivation, specifically heating, may expose new F VIII immunogenic epitopes. This hypothesis was examined further by Raut et al [31], Josic et al [12] and Saenko et al [34] using different chromatographic and electrophoretic methods, combined with surface plasmon resonance (SPR). From the analysis of potentially immunogenic, double virus inactivated F VIII concentrates, they found that some batches showed definitive evidence of elevated F VIII hydrolysis.…”

A collaborative study to establish the 1st International Standard for factor XIII plasma

“…The potency of FXIII activity in pool N ranged from 87% to 111% (with a lower estimate of 69% from only one laboratory); this variation is hence much less than that observed for some other factors involved in hemostasis and thrombosis, such as a 2-fold range for FVIII [15,18]. The degree of variation in levels of FXIII antigen (A 2 B 2 complex) in the normal plasma pools (pool N) was similarly low as compared to that of the activity levels, ranging from 73% to 116%.…”