Pasteurization of antithrombin without generation of the prelatent form of antithrombin

Abstract

Human antithrombin (AT) is the major inhibitor of blood coagulation and has also been shown to exert anti-inflammatory and anti-angiogenic effects. Pasteurization of pharmaceutical AT products is usually performed at 60 °C for 10 h in the presence of sodium citrate as stabilizer, sometimes in combination with sucrose. These stabilizers significantly decrease the aggregation and denaturation of AT, but during the pasteurization, a small amount of latent AT (LAT), a partially denatured form, is usually generated, as is an equal amount of another latent form of AT, the so-called prelatent AT (PLAT). The LAT formed during pasteurization has a rather low affinity to heparin and is easily removed by using a second heparin affinity chromatography step in the production process. This is in contrast to the PLAT, which has a slightly lower affinity to heparin than does native AT, which makes it hard to remove. Hence, four commercial products of pasteurized AT were previously shown to contain about 4% of PLAT. In the present work, an alternative pasteurization method is presented, where 2 M ammonium sulfate and 50% sucrose are used as stabilizers. During this pasteurization, no, or trace amounts (<0.5%), of PLAT may be generated with no formation of aggregates. Moreover, the pasteurized AT has the same specific thrombin-inhibiting activity when compared to incubation in the presence of citrate and sucrose. Heparin affinity high-performance liquid chromatography was used for the determination of PLAT, LAT, and AT.