Results in three Australian haemophilia B patients with high‐responding inhibitors treated with the Malmö model

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Abstract
Summary: Development of inhibitors to factor IX (F IX) is a serious complication of the treatment of patients with severe haemophilia B. Three Australian haemophilia B patients, a 22‐year‐old man and two 5‐year‐old identical twins, with high‐responding inhibitors and resistant to treatment, were admitted to the centre in Malmö, Sweden, for tolerance induction according to the Malmö treatment model. This tratment consists of a combination of cyclophosphamide, F VIII of F IX, and high‐dose intravenous IgG.Extracorporeal adsorption to protein A in columns, which is included in the protocol when the inhibitor titre is high at the start of treatment, had to be perforemed in the case of the twin brothers. High‐purity F IX concentrates were used. The tolerance inductin was successful in the 22‐year‐old man and in one of the twins; they been toleant for 4 and 2 years, respectively, and are now on a home‐treatment programme taking 30–40 IU F IX/kg twice weekly. These patients have no demonstrable coagulation inhibitory antibodies and in vivo reovery and half‐life of infused F IX are normal. In the other twin it has not been possible to induce tolerance, though after removal of the antibodies by protein A adsorpation it is possible to achieve significant circulalting levels of F IX for 8–10 days.