Regulatory Decision Summary for Afstyla

Afstyla is a new single chain recombinant factor VIII replacement product for treatment of patients with hemophilia A. The prophylactic treatment of hemophilia A is preferred over on demand treatment as there are fewer spontaneous bleeding episodes and less traumatic bleeding which can lead to joint damage and hence increased morbidity. In clinical trials, Afstyla has been shown to be effective in both these treatment options with the annualized spontaneous bleeding rate considerably reduced when treatment is prophylactic. In assessing efficacy, control of bleeding episodes has been rated by treating physicians as excellent or good in over 90% of bleeding episodes and surgeons have most often rated Afstyla as excellent when used in perioperative management. The benefits of the single chain structure of Afstyla are not yet evident.

The risk associated with FVIII replacement is mainly inhibitor formation which can decrease the effectiveness of treatment. No inhibitors have been detected as yet in patients treated with Afstyla but this will be part of the post-marketing surveillance. Other risks such hypersensitivity and rash can occur with FVIII replacement and are not increased with Afstyla.

Monitoring of the clinical hemostatic potential of FVIII products, when necessary, is most often done by the one-stage clotting assay in Canada. It is important to note that this value will need to be multiplied by 2 to give a value close to that of the chromogenic assay which is the more accurate measure of the hemostatic potential of Afstyla. If this is not considered, there could be dosing errors and false suspicion of inhibitors.

Overall the benefit/risk assessment for Afstyla is favourable and a notice of compliance was recommended.

For more information on Health Canadas decision, please view the Summary Basis of Decision.