Afstyla for Hemophilia A

What is Afstyla?

Afstyla is a novel single-chain recombinant antihemophilic factor VIII approved by the U.S. Food and Drug Administration (FDA) to treat patients with hemophilia A, an inherited bleeding disorder that prevents the blood from clotting normally due to the lack of a protein called factor VIII.

Afstyla is produced in Chinese hamster ovary cells as a single-chain polypeptide. It has increased stability in circulation and provides long-lasting protection from bleeds with twice-weekly dosing. Once activated, Afstyla is identical to natural factor VIII.


Afstyla is indicated in adults and children with hemophilia A for on-demand treatment and the control of bleeding episodes, routine prophylaxis to reduce the frequency of bleeding episodes and the risk of joint damage due to bleeding, and perioperative management of bleeding.

It is not intended to treat von Willebrand disease.

Dosage forms, strengths and administration

Afstyla is available as a white or slightly yellow dried powder supplied in single-use vials, labeled with the amount of recombinant factor VIII in international units (IU). Each vial contains 250, 500, 1000, 1500, 2000, 2500 or 3000 IU of medication.

After reconstitution, the drug is injected directly into the bloodstream.

Routine prophylaxis:

  • Adults and adolescents (ages 12 or older): the recommended starting regimen is 20 to 50 IU per kg of Afstyla given two to three times weekly.
  • Children (younger than 12): the recommended starting regimen is 30 to 50 IU per kg of Afstyla given two to three times weekly. More frequent or higher doses may be required in children younger than 12 to account for the higher clearance in this age group. The regimen may be adjusted based on patient response.

Warnings and precautions

Afstyla may cause hypersensitive reactions, including anaphylaxis. Afstyla should not be used if the patient experienced a life-threatening allergic reaction to it in the past or is allergic to its ingredients or to hamster proteins. In some cases, neutraliziling antibodies against recombinant factor VIII, also called inhibitors, may develop. Afstyla should be used with caution if the patient is taking other medications, supplements or herbal remedies. Pregnant or breastfeeding women should seek medical advice before starting treatment.

Clinical studies

Afstyla’s approval was based on results from the AFFINITY clinical development program, which included two pivotal (NCT01486927, NCT02093897) trials and one extension (NCT02172950) open-label multicenter clinical trial evaluating the safety and efficacy of Afstyla in children, adolescents and adults with hemophilia A.

The trials demonstrated a strong safety profile with no inhibitors observed. The data showed a median annualized spontaneous bleeding rate (the number of bleeds that occur over a year without an obvious cause) of 0.00 in all studies. For patients undergoing prophylaxis with Afstyla, the median annualized bleeding rate was 1.14 in adult and adolescent patients, and 3.69 in children younger than 12.

Of the 1,195 bleeds treated in the pivotal study (848 in adults and adolescents; 347 in children), 94 percent of bleeds in adult and adolescent patients and 96 percent of bleeding events in children were effectively controlled with no more than two infusions of Afstyla weekly; 81 percent of bleeds in adult and adolescent patients and 86 percent of bleeding events in pediatric patients were effectively controlled by only one infusion.

Of the 16 patients in the study who underwent surgical procedures, hemostatic efficacy of Afstyla was rated as excellent (15 times) or good (once).

Side effects

Common side effects of Afstyla include dizziness and allergic reactions such as rash or hives, itching, tightness of the chest or throat, difficulty breathing, light-headedness, dizziness, nausea or decrease in blood pressure. The body may form neutralizing antibodies or inhibitors, which are part of the body’s defense system, against factor VIII.

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