Hemophilia Solutions

Issue Six · July 2003

New Assay Standard for ReFacto Approved by the FDA

Wyeth Pharmaceuticals is pleased to announce that ReFacto^® Antihemophilic Factor (Recombinant) calibrated with a new assay standard recently received approval from the U.S. Food and Drug Administration and will be available soon. We are currently working with hemophilia treatment centers and home health care companies to update their inventories of ReFacto.

Why Did Wyeth Make This Change?

Assays are measuring tools that are used in conjunction with hemophilia factor products to measure clotting factor activity. Specifically, they are used in the manufacturing setting to verify the activity level of clotting factor units in a vial. The assay standards used by all pharmaceuticals companies to produce clotting factor products are examined and validated by regulatory authorities before the product receives regulatory approval. In the clinical setting assays are used to measure clotting factor activity in the body.

Assays used to measure clotting factor activity are very complex and results can differ among laboratories conducting the same test, based on the individual laboratories' methods and the chemicals used. As well, there are two different types of assays typically used: The one-stage clotting and the chromogenic substrate assay. The chromogenic substrate assay is used infrequently in the United States; it is more commonly used in Europe.

Since ReFacto became available, Wyeth has learned that the results from chromogenic substrate assays conducted by individual laboratories can vary by approximately 20 percent from the results of assays conducted by Wyeth. To address this variance with the chromogenic substrate assay, Wyeth adjusted its assay standard, with the permission of U.S. and European regulatory authorities, so that the results of assays conducted by laboratories in the community would be in greater agreement with Wyeth's tests.

What Does This Mean for Patients?

In practical terms, the result of this change to the assay standard is that Wyeth is changing how it measures an International Unit (IU) of ReFacto. Each manufacturer (with regulatory approval) determines the amount of protein required to achieve an IU of their product. With the new calibration, the amount of ReFacto protein per IU will increase by approximately 20 percent. The price per IU will remain the same. The new standard should yield greater agreement among test results used to monitor treatment.

Patients can deplete their current supply of ReFacto^® before switching to ReFacto calibrated with the new standard. Patients transitioning to ReFacto calibrated with the new standard should initially use the same dose as previously prescribed. Once transitioned to ReFacto calibrated with the new standard, they should remain on the recalibrated product. As with all factor VIII products, patients' dose should be individually titrated to desired clinical response.

Patients should consult with their health care provider regarding their specific treatment regimen.

How Will ReFacto Calibrated with the New Standard Be Distinguished?

ReFacto^® Antihemophilic Factor (Recombinant) calibrated with the new standard will be available in new and distinctive packaging. Each of the four vial sizes has color-coded packaging:

• Yellow: 250 IU/kg
• Blue: 500 IU/kg
• Green: 1000 IU/kg
• Red: 2000 IU/kg

Commitment to the Hemophilia Community

We will continue to update you on the progress of our activities and programs for the hemophilia community. Today, as always, our goal is to create effective recombinant factor products with enhanced viral safety for the hemophilia community.

Important Product Information

ReFacto^® Antihemophilic Factor (Recombinant) is indicated for the control and prevention of hemorrhagic episodes and for surgical prophylaxis in patients with hemophilia A (congenital factor VIII deficiency or classic hemophilia) and for short-term routine prophylaxis to reduce the frequency of spontaneous bleeding episodes. The effect of regular routine prophylaxis on long-term morbidity and mortality is unknown.

As with the intravenous administration of any protein product, adverse reactions may include headache, fever, chills, flushing, nausea, vomiting, fatigue, or symptoms of allergic reactions. The remote possibility exists for hypersensitivity to non-human mammalian proteins.

For past issues of Hemophilia Solutions, please contact us at (484) 865-3256. If you wish to update your information in our database, please contact us at the same number.

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