ReFacto for Hemophilia A

Brand Name: ReFacto
Active Ingredient: recombinant antihemophilic factor VIII
Indication: Control and prevention of bleeding episodes and surgical prophylaxis in patients with hemophilia A
Company Name: American Home Products Corporation
Availability: Approved by FDA on March 6, 2000

Introduction

To date patients with hemophilia A, the most common type, have had to rely on factor VIII products purified from human serum albumin. In March the FDA approved ReFacto (recombinant antihemophilic factor VIII), the first recombinant factor VIII product formulated without human serum albumin, for the control and prevention of bleeding episodes and surgical prophylaxis in patients with hemophilia A. The use of ReFacto, which is expected to be made available in the third quarter, should dramatically reduce the potential of viral contamination for hemophilia A patients, of which there are some 17,000 in the US alone.

Previously, all recombinant factor VIII products added albumin at two production stages: during the cell culture phase when factor VIII cells are grown, and during the product’s final formulation. While albumin is utilized during the cell culture process for ReFacto, it is not added in the product’s final formulation.

ReFacto is administered by the patient via intravenous injection.

How It Works

Hemophilia A is characterized by a deficiency of blood clotting factor VIII. The administration of ReFacto, a purified protein produced by recombinant DNA technology, increases plasma levels of factor VIII activity and can temporarily correct the in vitro coagulation defect in these patients. ReFacto has in vitro functional characteristics comparable to those of endogenous factor VIII.

Activated factor VIII acts as a cofactor for activated factor IX, accelerating the conversion of factor X to activated factor X. Activated factor X converts prothrombin to thrombin, which then converts fibrinogen into fibrin so a blood clot can be formed.

ReFacto: Clinical Study Results

ReFacto was evaluated in clinical studies of ReFacto involving 218 patients (117 previously treated patients and 101 untreated patients), in which more than 84 million IU of ReFacto were administered over a period of up to 54 months. The previously treated patients were given a median of 230 injections over a median of 1,200 days, while the 101 untreated patients received a median of 26 injections over a median of 830 days. The 113 previously treated patients who were evaluated experienced a median of 54 bleeding episodes and the 99 untreated patients who were evaluated experienced a median of 12 bleeding episodes. All were treated successfully on an on-demand basis for the reduction of bleeding episodes. Bleeding episodes included hemarthroses, and bleeding in soft tissue, muscle, and other sites.

Another study compared the efficacy of ReFacto with that of plasma derived factor VIII in 69 previously treated patients with hemophilia A who were treated for 1 to 5.7 years. The mean in vivo half-lives, incremental recoveries at baseline, and response to treatment were similar between ReFacto and the plasma-derived preparation.

ReFacto was also assessed in short-term routine prophylaxis in 64 patients. The mean rate of spontaneous musculoskeletal bleeding episodes was less during periods of ReFacto use. There was an average of 10 bleeding episodes per year during the prophylactic periods compared to an average of 37 episodes per year during the periods when ReFacto was used on demand

Finally, the use of ReFacto for surgical prophylaxis was evaluated in 25 patients undergoing 28 surgical procedures. Circulatory factor VIII levels targeted to restore and maintain hemostasis were achieved. Hemostatic efficacy was rated as excellent or good in all procedures.

What the Patient Should Know

As with the intravenous administration of any protein product, the following reactions may be observed after administration of ReFacto: headache, fever, chills, flushing, nausea, vomiting, lethargy, or manifestations of allergic reactions. Patients should be informed of the early signs of hypersensitivity reactions, including hives, chest tightness, wheezing, hypotension, and anaphylaxis. Patients should be advised to discontinue use of the product should these symptoms occur and contact their physicians.

No related posts.

Jennifer Bowles

Jennifer is a clinical pharmacologist. She helps doctors of all medical specialties choose medications. Jennifer consults about drug dosage, interactions, and side effects.