A New Clinical Preparation Of High-Purity Porcine Factor VIII:C Concentrate
Thrombosis and Haemostasis
A polyelectrolyte-fractionated porcine Factor VIII concentrate (Hyate:C, Speywood Laboratories, average specific activity: 10 U Factor VIII:C/mg, platelet aggregating factor (PAF): 0.25 U/ml) has been recently available. Clinical use of this product for the treatment of patients with antibody to Factor VIII (13 haemophilic and 1 non- haemophilic patients for a total of 26 courses of treatment) has shown that: 1/ multiple courses of therapy can be given with both good clinical tolerance and good
... clinical efficacy, 2/ with one exception, no patient developed thrombo- cytopaenia and 3/ with the exception of one case, in which the patient has been treated with human Factor VIII prior to the infusion of porcine Factor VIII. the expected anamnestic response did not occur. These clinical findings prompted us to further purify the porcine Factor VIII concentrate for clinical use.Cryoprecipitate, prepared from frozen porcine plasma, is dissolved in low ionic strength Tris buffer at pH 6.8 and adsorbed with aluminium hydroxide gel. The ionic strength is then adjusted to 0.3 M NaCl before loading on a column of charged and equilibrated polyelectrolyte E-5. After washing the column with 4 bed volumes of buffer, the proteins were eluted with 1 M NaCl at pH 6.5 and precipitated by 20 % polyethylene glycol 4000. The redissolved precipitate is then chromatographed on a preparative column of Sepharose CL-4B. The void volume is sterile-filtered and lyophilised. The new preparation has a specific activity of approximately 100 U Factor VIII:C/mg with a PAF level of 3.3 U/ml. This represents an improvement of 10 fold in specific activity over the existing concentrate.It is expected that the new concentrate will also show low immunogenicity which can only be revealed by clinical results. A clinical trial is envisaged within the next two months.