In vitro tests of the potential thrombogenicity of factor IX concentrates: inhibition and characterisation studies of NAPTT, TGt50 and PF3 moieties

Characterization of IXINITY® (Trenonacog Alfa), a Recombinant Factor IX with Primary Sequence Corresponding to the Threonine-148 Polymorph

The goal of these studies was to extensively characterize the first recombinant FIX therapeutic corresponding to the threonine-148 (Thr-148) polymorph, IXINITY (trenonacog alfa [coagulation factor IX (recombinant)]). Gel electrophoresis, circular dichroism, and gel filtration were used to determine purity and confirm structure. Chromatographic and mass spectrometry techniques were used to identify and quantify posttranslational modifications. Activity was assessed as the ability to activate factor X (FX) both with and without factor VIIIa (FVIIIa) and in a standard clotting assay. All results were consistent across multiple lots. Trenonacog alfa migrated as a single band on Coomassie-stained gels; activity assays were normal and showed <0.002 IU of activated factor IX (FIXa) per IU of FIX. The molecule has >97%  γ-carboxylation and underwent the appropriate structural change upon binding calcium ions. Trenonacog alfa was activated normally with factor XIa (FXIa); once activated it bound to FVIIIa and FXa. When activated to FIXa, it was inhibited efficiently by antithrombin. Glycosylation patterns were similar to plasma-derived FIX with sialic acid content consistent with the literature reports of good pharmacokinetic performance. These studies have shown that trenonacog alfa is a highly pure product with a primary sequence and posttranslational modifications consistent with the common Thr-148 polymorphism of plasma-derived FIX.

Donor safety and plasma quality in automated plasmapheresis. Comparison of two filter materials

The level of blood cells and differential counts as well as of selected clotting and complement system components and breakdown products were measured in donor plasma of 42 polycarbonate filter (group I) and 7 nylon filter (group II) plasmapheresis procedures. Three different sampling time points were considered: (1) 1 min prior to connecting the donor to the machine (sample A); (2) 1 min after donation by a repeat venipuncture (sample B), and (3) in collected plasma (sample C). The better biocompatibility of the newly introduced nylon filters became evident on the basis of blood cell counts with significant drops of total white blood cell counts, monocytes, lymphocytes and platelets in sample B of group I, but not of group II. Similarly, complement studies revealed significant decrease of CH 50, C4 and C3 in samples B and C of group I, but only in samples C of group II. Coagulation studies showed significant increases of fibrinopeptide A and beta-thromboglobulin in samples B and C of group I; in group II beta-thromboglobulin was significantly increased in sample C compared to sample A. Plasminogen levels were decreased in samples B and C of group I but not of group II. Nonactivated partial thromboplastin time remained normal in group I. Factor VIII:C determinations in group II revealed a recovery of 86% in sample C.