The Food and Drug Administration (FDA) has approved Afstyla (antihemophilic factor [recombinant], single chain; CSL Behring) for the treatment of adults and children with hemophilia A for routine prophylaxis to reduce the frequency of bleeding episodes. Afstyla is a novel, long-lasting recombinant Factor VIII single-chain therapy designed for greater molecular stability and longer duration of action.

The approval was based on results from the AFFINITY clinical development program, which included two pivotal and one extension open-label multicenter studies evaluating the safety and efficacy of Afstyla in adults, adolescents, and children with hemophilia A. Data from the program showed a median annualized spontaneous bleeding rate (AsBR) of 0.00 in both adult and pediatric studies. For patients using Afstyla prophylactically, the median annualized bleeding rate (ABR) was 1.14 in adults and adolescents and 3.69 in children under 12 years old.

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In the pivotal trial, 94% of bleeds in adults and adolescents and 96% of bleeds in pediatric patients were effectively controlled with no more than two infusions of Afstyla weekly. Eighty-one percent of bleeds in adults and adolescents and 86% of bleeds in children were effectively controlled with just one infusion. 

The most common adverse reactions reported during trials were dizziness and hypersensitivity. Afstyla demonstrated a strong safety profile with no inhibitors observed.

Afstyla is expected to be available early this summer. It will be supplied in a kit containing a lyophilized powder in single-use vials containing nominally 250, 500, 1000, 2000, or 3000 International Units (IU).

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