Large-scale preparation of highly purified human C1-inhibitor for therapeutic use

A two-step chromatographic procedure has been developed to purify human C1-inhibitor from cryoprecipitate-poor plasma after removal of vitamin K-dependent proteins and antithrombin III. The procedure, which is fully compatible with modern plasma fractionation schemes, includes anion-exchange chromatography on DMAE-Fractogel EMD, viral inactivation by solvent-detergent treatment, adsorption on SO3-Fractogel EMD and viral removal by nanofiltration on 35- and 15-nm pore size membranes. Overall yields were about 45% and 58% for antigen and activity, respectively, providing 60-70 mg of highly purified inhibitor per litre of plasma. The purified inhibitor had a specific activity of 6.5 +/- 0.5 units/mg protein, representing a more than 400-fold increase in purity compared with plasma. C1-inhibitor purity with respect to total protein was greater than 80%. The main contaminant was complement component C3 which accounted for 4-10% of the total protein. Minor contaminants included low amounts of IgM, IgG, IgA, fibrinogen and albumin. Complement component C4 was undetectable. The purified inhibitor was stable throughout the purification process and for more than 24 h at room temperature after reconstitution of the freeze-dried material. Animal tests in rats and mice demonstrated that the C1-inhibitor concentrate was well tolerated at relatively high doses.