A HIGH-YIELD FACTOR VIII CONCENTRATE SUITABLE FOR ADVANCED HEAT TREATMENT

The heat treatment of Factor VIII concentrates in the freeze-dried state has been widely adopted to inactivate Human Immunodeficiency Virus (HIV) which may be present. However, the degree of heating that can be applied has been limited by adverse effects on product yield and quality (eg.solubility).The established SNBTS product (1) can be heated for up to 2 hours at 68°C in the absence of stabiliser and for up to 24 hours at 68°C in the presence of 2% sucrose.These conditions are believed to inactivate HIV but are not considered sufficient to destroy the hepatitis viruses.Therefore, a new product has been developed which can be heated more severely (eg.80°C for 72 hours) with the objective of destroying all potential viral contaminants while retaining good product solubility and a yield consistent with the maintenance of national self-sufficiency.The process combines Zn++ precipitation of cryoprecipitate (2) and Ca++ stabilisation of VIII:C (2,3) with developments in extraction, adsorption, formulation, freezing and freeze drying.

Cryoprecipitate is extracted in an equal volume of tris buffer; further purification is achieved by precipitation with cold zinc acetate and adsorption with Al(OH)3.The supernatant solution is stabilised by adding Na3 citrate, CaC12, NaCl and sucrose; then concentrated and diafiltered to a final formulation of 20mM tris, 130mM NaCl, 30mM Na3 citrate, 4mM CaC12 and 3% sucrose.The product is dispensed at 15ml (VIII:C 20iu/ml) for reconstitution in 20ml.A critical part of the process is a special 2-stage freezing procedure where the product is supercooled to -5°C before freezing to -50°C. Sublimation is completed with the product temperature held below -30°C at a pressure of 0.08 - O.10mbar.

This process has been carried out at full-scale (750 litres plasma) giving a readily soluble, improved, intermediate -purity product with an VIII:C yield of 300iu/litre plasma after heat treatment.