Longer Acting Factor
The first extended half-life (EHL) recombinant factor VIII concentrate was recently licensed in Europe. The ‘Haemophilia Product Selection Monitoring Advisory Board’ (HPSMAB) recently signed a contract to use some of the new extended half-life (EHL) factor VIII product. This will be used primarily for the treatment of children but will also be available to some adults. The new factor concentrate is fused to the Fc portion of a normal human immunoglobulin. Fusion to the Fc protein allows the factor VIII to be recycled within the cells and therefore last longer in the circulation. The half-life of this factor VIII is approximately 1.5 times greater than the current recombinant factor VIII concentrates. Additional EHL recombinant factor VIII concentrates will be coming on the market very soon. The next EHL recombinant factor VIII to be licensed will almost certainly be a product where the factor VIII is linked to polyethylene glycol (PEG), which slows the degradation and breakdown of factor VIII and also increases the half-life by approximately 1.5 fold. The EHL factor IX concentrates coming on the market will be a product where the factor IX is linked to the Fc portion of immunoglobulin (similar to the current new recombinant factor VIII) and a product where the factor IX is linked to human albumin.
The half-life extension of the recombinant factor IX is even greater where they are able to achieve a three to five-fold increase in the current factor IX half-life. The half-life of the currently available recombinant factor VIII concentrates is typically twelve hours. For the new EHL factor VIII concentrates on the market and coming on the market, the half-life will range from 14 to 19 hours. The half-life of the currently available recombinant factor IX concentrates is typically 18 hours. The new EHL factor IX concentrates coming on the market will have half-lives ranging between 82 and 102 hours. As these products become available over the coming years, they will add to the therapeutic options available for people with haemophilia and will certainly lead to individualisation of treatment. Currently, the majority of people with haemophilia who are on prophylaxis would be treated with a similar number of units per kilogramme, with the same frequency of infusion and little variety in treatment protocols. This will change in the future. With the new EHL factor concentrates available as an option, we expect to see a situation where an individual’s treatment will be individually defined, based on their bleeding history, any target joints they may have, venous access, their activity levels and their lifestyle.