Plasma-Derived AT in the U.S. Is in Short Supply
Fractionation bias is the technique used by plasma-protein suppliers to calibrate the quantities of the various proteins they produce. This is a two-step process: separation and purification. The separation process is “biased” to recover more of the high-value proteins—mainly the coagulation factors for hemophiliacs—and less of other proteins. Proteins that are placed in the wrong “bucket” during separation are not recovered during purification and hence are permanently lost.
Talecris Biotherapeutics, which acquired Bayer’s U.S. plasma business in 2005, has an FDA-approved plasma-derived antithrombin called Thrombate. However, due to fractionation bias, Talecris produces very little Thrombate—not nearly enough to satisfy the clinical needs of the antithrombin HD population in the U.S.
To make matters worse, the FDA prohibits the importation of most plasma-derived proteins due to concerns about Mad Cow disease and other pathogens.
Under normal circumstances, individuals with antithrombin HD can get by with an oral anticoagulant such as warfarin. If individuals with antithrombin HD are undergoing surgery or childbirth, however, they have a major dilemma. There are some clumsy ad hoc workarounds with various drug cocktails, but these are unsatisfactory and certainly not a substitute for the antithrombin the patients lack.
The importance of all this? A safe and reliable source of antithrombin for the U.S. is badly needed.
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