A pilot study comparing the purity, functionality and isoform composition of alpha-1-proteinase inhibitor (human) products

Objective: Alpha-1-proteinase deficiency predisposes affected individuals to early onset pulmonary emphysema, and is treated with an alpha-1-proteinase inhibitor (A1-PI) from pooled human plasma. The objective of this pilot study was to assess analytical parameters of the three A1-PI products (Aralast*, Prolastin(dagger), Zemaira(double dagger)) that may impact on clinical efficacy, safety, and convenience. These included: purity of the preparation; nature of impurities; functionality; and isoform composition. Methods: Purity was evaluated using reverse phase and size exclusion chromatography high performance liquid chromatography (RP-HPLC and SEC-HPLC), capillary zone electrophoresis (CZE), sodium dodecyl sulfate polyacrylamide gel electrophoresis, sodium dodecyl sulfate capillary gel electrophoresis and Western blot analysis. The identity of protein impurities was determined by immunonephelometry; functionality by calculating the ratio of mg active A1-P1 present (by anti-neutrophil elastase activity assay) to the mg antigenic A1-PI (by immunonephelometry); and normality of the A1-PI isoform pattern by isoelectric focusing (IEF). Three samples of Zemaira and one sample each of Aralast and Prolastin were available for analysis. Results: Zemaira had the highest specific activity. Using RP-HPLC analysis Zemaira averaged 99% purity, Aralast 70% and Prolastin less than 62%. Using SEC-HPLC Zemaira was 95.98% monomeric, Prolastin 79.00% and Aralast 63.55%. Prolastin had lower activity/mg antigenic A1-PI than the other two products. A shift in isoforms in Aralast was suggested by the results of CZE, and was confirmed by IEF Conclusions: Zemaira demonstrated greater purity compared with Aralast and Prolastin. Prolastin had more inactive A1-PI than Zemaira or Aralast. Isoform ratios appeared to be altered in Aralast. The results from this pilot study warrant further investigation.