Trial of Rituximab Versus Oral Cyclophosphamide to Eradicate or Suppress Autoimmune Anti-Factor VIII Antibodies in Acquired Hemophilia A

Inclusion Criteria: * Diagnosis of acquired hemophilia A in a previously non-coagulopathic individual. * Prior treatment with at least 3 weeks of immunosuppressive therapy * Factor VIII: C levels \<50% within 14 days prior to study entry, which do not correct in coagulation assays in which normal plasma is mixed and incubated with patient plasma. * Measurable anti-factor VIII:C antibody inhibitor activity \> 0.6 Bethesda Units/ml. * Age ³18 years * Written informed consent * Use of an effective means to avoid pregnancy, including abstinence, for women of childbearing potential,. * Serum bilirubin less than or equal to the upper limit of normal (ULN); ALT and AST £2.5´ ULN within 14 days prior to study entry * Serum creatinine £1.5´ the ULN within 14 days prior to study entry * Negative serum pregnancy test, for all women of childbearing potential, within 14 days prior to study entry Exclusion Criteria: * Continued treatment requirement of prednisone ≥30mg/day or equivalent dosing of other corticosteroid preparations to control serious symptoms of an underlying autoimmune disease state. * Treatment with cyclophosphamide, danazol, vinca alkaloids, azathioprine, IVIG, or other immunosuppressive, immunomodulatory, or cytotoxic agents (other than decreasing doses of corticosteroids) within 30 days prior to study entry. * Anticipated need for repeated extracorporeal plasmapheresis in order to reverse refractory bleeding associated with acquired hemophilia. * Treatment with other experimental agents within 30 days prior to study entry * Known sensitivity to murine or chimeric products * Hepatitis BsAg positivity or high risk for reactivation of Hepatitis B. * Active infection requiring antibiotic therapy within 7 days prior to study entry * Current use of any required medications, which in the opinion of the treating physician, could be inducing the formation of auto-FVIII:C inhibitory antibodies * Prior treatment with rituximab or other monoclonal antibody therapy * Known HIV antibody positivity * NCI-CTC Grade ³1 cardiac arrhythmia ( refer to CTC v3) * Any other disease, metabolic dysfunction, physical examination finding, or clinical laboratory finding giving reasonable suspicion of a disease or condition that contraindicates the use of an investigational drug or that may affect the interpretation of the results or render the patient at high risk from treatment complications * Currently pregnant women, lactating women, or women within 12 months of delivery, spontaneous miscarriage, or therapeutic or elective termination of pregnancy. * Known severe leucopenia (absolute neutrophil count \<1000/µL) or thrombocytopenia (\<25,000/µL); * Known pre-existing cystitis or severe urinary outflow obstruction. * Known history of recurrent severe opportunistic infections, eg. generalized herpes zoster; * Inability or unwillingness to comply with study design and requirements and follow-up procedures.