Rituximab as a single agent in the management of adult patients with haemophilia A and inhibitors: marked reduction in inhibitor level and clinical improvement in bleeding but failure to eradicate the inhibitor

Summary. Management of patients with severe haemophilia A who develop inhibitors is difficult and expensive. Standard treatment of this complication is immune tolerance induction (ITI) therapy, but is successful in only 60–80% of the patients. Failure of ITI results in a higher risk of morbidity and mortality. We used rituximab, an anti‐CD20 antibody, in three patients with severe haemophilia A and inhibitors. Two patients with high‐titre inhibitors had marked reduction in the inhibitor level; the third patient with low‐titre inhibitor had a disappearance of the inhibitor. All patients improved clinically, with fewer bleeding episodes and a better quality of life. Inhibitor level increased with time in these patients, but the clinical benefit continued in two patients with high‐titre inhibitors initially, after a follow‐up of 48 and 22 months. One of the patients with concomitant human immunodeficiency virus (HIV) infection and a very low CD4 lymphocyte count developed severe truncal herpes zoster after the third weekly dose of rituximab. Caution is required in such patients, and we recommend avoiding rituximab use in HIV‐infected patients with very low CD4 lymphocyte count. In conclusion, rituximab is useful in reducing the inhibitor level with clinical benefit in patients with severe haemophilia A and inhibitors, but it cannot eradicate the inhibitors for long periods with the currently used protocol of up to five doses.