Low Incidence of Adverse Reactions in Clinical Trials

Zero inhibitors observed in clinical trials of previously treated patients

Development of inhibitors to Factor VIII can occur following administration of Factor VIII products.

  • If expected Factor VIII levels are not attained or bleeding is not controlled with appropriate dose, perform a Bethesda inhibitor assay to measure Factor VIII inhibitor concentration

14 of 258 patients reported an adverse reaction

The most common adverse reactions in clinical trials (>0.5%) were dizziness and hypersensitivity.

Adverse reactions







Injection-site pain


Feeling hot





One patient withdrew due to an adverse reaction (hypersensitivity).

Monitor Factor VIII activity using either the chromogenic or one-stage clotting assay

One-stage clotting assay

Use chromogenic assay if available to measure Factor VIII activity

  • Most accurately reflects the clinical hemostatic potential of AFSTYLA
  • Should be used if available

One-stage assay results can be used with a simple calculation

The one-stage clotting assay result underestimates the Factor VIII activity level compared to the chromogenic assay result by approximately one-half.

If the one-stage clotting assay is used, multiply the result by a conversion factor of 2 to determine the patient’s Factor VIII activity level.

One-stage assay results x 2 = Activity level

Study design

Data from three AFSTYLA studies: Safety of AFSTYLA was assessed in patients enrolled in the phase I/III, open-label, multicenter, crossover study, the phase III, open-label study, and the ongoing phase III, open-label, multicenter extension study. Adverse reactions were reported for 14 of 258 (5.4%) patients in all studies. In the clinical studies, there have been a total of 28,418 exposure days, with at least 28,492 injections of AFSTYLA administered.

You are now leaving the current website.

Do you want to continue?

No Yes