Rituximab and Dexamethasone Followed by Mycophenolate Mofetil or Placebo in Patients With Immune Thrombocytopenia

Inclusion Criteria: * Male or female, greater than 18 years old * Signed written informed consent obtained prior to study entry * Immune Thrombocytopenia according to the American Society of Hematology guidelines, with other potential causes of thrombocytopenia excluded, platelets less than 30 x 109/L at study entry * Have adequate renal and hepatic function (creatinine and bilirubin less than 2 x Upper Limit of Normal (ULN), aspartate aminotransferase and alanine aminotransferase less than 3 x ULN) * No significant cytopenias (hemoglobin greater than10 g/dL without ongoing transfusional support, absolute neutrophil count greater than 1.0 x109/L at study entry). * If on corticosteroids, receiving less than or equal to 20 mg/day prednisone (or equivalent) with no change of dose for at least 2 weeks prior to study entry. No more than two 4-day courses of Dexamethasone prior to study entry. If on danazol, no change of dose for at least 2 weeks prior to study entry. (Thrombopoietin receptor agonist treatment will be allowed until the end of 8th week on study if started prior to study entry) * No treatment with any known non-marketed drug substance or experimental therapy within 5 terminal half-lives or 4 weeks prior to enrollment, whichever is longer, or currently participating in any other interventional clinical study * No prior treatment with anti-B-lymphocyte antigen cluster of differentiation antigen 20 monoclonal antibody at a total dose greater than 375mg/m2 * Screen for …