High Margin of Pathogen Safety for a Plasma-Derived FXIII Concentrate for the Treatment of Congenital FXIII Deficiency

Abstract 4655

Congenital Factor XIII (FXIII) deficiency is an extremely rare, serious, and life-threatening condition, especially due to intracranial haemorrhage, which can be treated by a plasma-derived FXIII concentrate. The pathogen safety of this plasma-derived protein is achieved by the complementary measures (i) selecting and testing the starting material, human plasma, (ii) releasing the plasma pool for fractionation when non-reactive for viral markers and genomic material of blood-borne viruses, and (iii) ensuring adequate capacity of the production process to reduce a wide range of viruses as well as prions. Virus validation and prion evaluation studies were performed to assess the reduction capacity of the manufacturing process of this FXIII concentrate.

A minimal load of infectious virus, if any, in human plasma, the starting material for the production of a FXIII concentrate, is achieved by selecting donor centers and donors, by testing donations for viral markers and genomic material of HAV, HBV, HCV, HIV-1 and high titers of parvovirus B19 (B19V), and by releasing plasma pools for fractionation when non-reactive for these blood-borne viruses. Two dedicated virus reduction steps and further steps of the manufacturing process of the FXIII concentrate were investigated: heat treatment in aqueous, stabilized solution (“pasteurization”), virus filtration (two filters in series with mean pore sizes of approx. 19 nm (20N/20N)), and partitioning steps. The virus and prion reduction capacity of the manufacturing process of this FXIII concentrate was evaluated in in vitro studies.

Product intermediates from selected steps of the manufacturing process for the FXIII concentrate, derived from different production lots, were spiked with enveloped and non-enveloped viruses of diverse physico-chemical characteristics and processed according to a scaled-down, validated manufacturing process. The virus panel employed in these studies consisted of HIV, BVDV (bovine viral diarrhea virus, a specific model virus for HCV and WNV), WNV, HAV, parvoviruses (B19V and CPV (canine parvovirus)) and PRV (pseudorabies virus, a non-specific enveloped DNA virus). Prion reduction capacity was currently assessed by studying one manufacturing process step with two different spike preparations and based on data for other products from CSL Behring or published data.

Pasteurization (heat treatment) inactivates all blood-borne viruses or their specific model viruses effectively, i.e. HIV, BVDV, WNV, HAV and B19V were inactivated in the order of 4 log₁₀ or more. Virus filtration removed effectively all viruses studied. Further manufacturing steps reliably contribute to the overall virus reduction capacity of the manufacturing process of this FXIII concentrate.

Two different prion preparations prepared from brain homogenate of 263K infected hamsters were used in the prion evaluation study: a membrane-associated preparation of prion material (microsomes) and a PrP^Sc preparation without membranes (purified PrP^Sc). Both spike preparations were removed equally by the manufacturing step Al(OH)₃ adsorption / defibrination. Prion material in the different fractions was quantified using a biochemical/serological method, the Conformation-Dependent Immunoassay (CDI).

The pathogen reduction capacity for this FXIII concentrate is shown in the following table:

Based on the epidemiology in the donor population and donation frequency, the sensitivity of the NAT assay, the amount of plasma needed to produce one vial of FXIII concentrate and the virus reduction factors demonstrated, it can be concluded that the measures taken result in a FXIII concentrate with a very high margin of safety for a wide range of viruses and other pathogens.