Hemophilia patients may need surgical interventions or invasive procedures for complications either related or not to their coagulopathy. These procedures require the intensified administration of concentrates of the deficient factor (FVIII in the case of hemophilia A and FIX in the case of hemophilia B) to reduce the bleeding risk associated with those procedures. 1,2 In recent years, new strategies have been developed for the prophylactic treatment of patients with hemophilia, such as extended half-life factor concentrates (EHL). These products have shown improved pharmacokinetic properties, achieving parameters of half-life (t 1/2 ) 3-to 5-fold longer in FIX EHL compared with standard FIX concentrates. 3 This enables the extension of the dosing interval and allows for higher trough levels for longer periods of time. 2

The use of chimeric pseudotyped vectors is a common way to modify the adenoviral tropism by replacing the fiber protein. In this chapter the procedure to generate a chimeric adenovirus pre-stock from a plasmid containing the adenoviral genome is described. Also, the chimeric adenovirus replicative cycle to increase the yield in further productions is determined. Finally, two different protocols, in culture plates and in suspension cultures, to produce the virus at large scale are also detailed.