Turoctocog alfa (NovoEight®)--from design to clinical proof of concept.
Bottom Line: Viral inactivation is ensured by a detergent inactivation step as well as a 20-nm nano-filtration step.Tyr1680 was also fully sulphated in turoctocog alfa resulting in strong affinity (low nm Kd ) for binding to von Willebrand factor (VWF).The non-clinical data thus confirm the haemostatic effect of turoctocog alfa and, together with the comprehensive clinical evaluation, support the use as FVIII replacement therapy in patients with haemophilia A.
Affiliation: Novo Nordisk A/S, Maaloev, Denmark.Show MeSH
Related in: MedlinePlus
Mentions: The human gene for factor VIII (FVIII) was cloned and expressed in 1984 1–5, making it possible to produce recombinant FVIII (rFVIII) for prevention and treatment of bleeds in patients with haemophilia A. The FVIII gene encodes a single chain of 2332 amino acid residues with the domain structure A1-A2-B-A3-C1-C2 (Fig.1) 1. During cellular processing, the molecule undergoes posttranslational modifications, including sulphation of specific tyrosine residues and glycosylation. Furthermore, the protein is processed into a heterodimer consisting of a heavy chain (HC) with the A1-A2-B domains and a light chain (LC) with the A3-C1-C2 domains. The two chains are held together by metal ions 6. While the B-domain plays a role in restricting the expression of endogenous FVIII, it is apparently not needed for the function of FVIII 7–9. Acidic regions C-terminal to the A1 and the A2 domains and N-terminal to the A3 domain (a1, a2 and a3, respectively) are important for interaction with thrombin and von Willebrand factor (VWF). Sulphation of Tyr1680 is essential for high affinity binding of FVIII to VWF 10,11, which is required for protection of FVIII from degradation and rapid clearance. During haemostasis, FVIII is activated by specific thrombin cleavages, thereby producing the A1, A2 and A3-C1-C2 fragments of activated FVIII (FVIIIa). This results in dissociation of VWF and assembly of the tenase complex (FVIIIa/FIXa) on the surface of activated platelets. FXa is generated, resulting in a thrombin burst, and ultimately leading to the formation of a stable haemostatic plug.