Early Studies Show Rituximab as an Effective Treatment of Factor VIII Inhibitors

Selective B-cell depletion with rituximab in the treatment of acquired factor VIII and factor XIII inhibitors.

Acquired inhibitors to coagulation factors are rare and usually cause a serious bleeding disorder that is difficult to treat. Acquired factor VIII (FVIII) and acquired factor XIII (FXIII) inhibitors are usually due to an IgG antibody. A novel treatment option for both conditions is rituximab, a chimeric monoclonal antibody targeting the CD20 antigen and blocking proliferation of normal B cells.We describe two cases of acquired FXIII inhibitor and one case of FVIII inhibitor, who had a history of significant bleeding. These patients were treated with rituximab with a usual dose of 375mg/m2/week for a total four doses.The patients with FXIII inhibitor did not show correction of FXIII levels, as measured by the clot solubility tests during and up to 4 weeks after therapy. However, both patients showed transient correction of clot solubility to normal after infusion of high doses of FXIII. The third patient with FVIII inhibitor presented with undetectable FVIII level <1%, and a very high Bethesda assay titre of 840 BU.Immunosuppressive therapy was changed to oral cyclophosphamide and rituximab. After four months of therapy, her FVIII had increased to 20% and her inhibitor titre declined to 10 BU.Preliminary results suggest that FXIII deficiency due to inhibitors can be corrected with high doses of FXIII and rituximab had no measurable effect on the inhibitor level whereas rituximab can be successfully used in the treatment of FVIII inhibitors. The role of rituximab in addition to other immunosuppressive therapy against different coagulation factor inhibitors requires further investigation.If you would like more information on the HOTT congress please contact our office on (08) 9388 0344 or email us at adean@virtualcancercentre.com