Second generation, B-domain deleted recombinant factor VIII.

A second generation recombinant factor VIII product has been developed and has been undergoing clinical trials since 1993. It is named r-VIII SQ and differs from other recombinant and plasma-derived products in that the B-domain of the molecule, to which no function has yet been ascribed has been deleted. It also has a formulation which does not include albumin. The specific activity is extremely high, 15,000 IU VIII:C/mg protein, and the stability of the reconstituted product is highly satisfactory. The pharmacokinetic properties are similar to those of a monoclonal purified, plasma-derived factor VIII. In clinical trials experience has been acquired from more than 87 previously treated patients on long-term treatment, 20 patients subjected to surgery and 72 previously untreated patients. The record with regard to efficacy and safety is excellent but more experience is needed, especially regarding the risk of inhibitor development. The B-domain-deleted recombinant factor VIII has the potential to improve convenience and cost-benefit in haemophilia care. The safety margin regarding human viruses and other protein contaminants should be better with r-VIII SQ than with earlier products, which all contain far more human protein in their formulations.