Vitronectin in clotting factor IX concentrates

Highly purified, plasma-derived factor IX (FIX) concentrates are produced i n large part by a combination of anion exchange and heparin affinity chroma tography. However, the concentrates still contain some accompanying protein s. The main impurity has turned out to be the adhesive glycoprotein, vitron ectin. It occurs in concentrates exclusively in its multimeric form, in con trast to the situation in plasma. The multimeric vitronectin can be removed either by nanofiltration with a crossflow system or by size-exclusion chro matography. When these FIX concentrates are used as therapeutic agents, the fact has to be taken into account that considerable amounts of multimeric vitronectin are given to the patient. The physiological consequences of the dosage of this protein have not yet been investigated. Although no thrombo genicity has been reported in connection with the above-mentioned FIX conce ntrates, we recommend that the impurity should be removed from the preparat ion with the methods described here.