Efficacy and Safety Assessment of a Treatment Combining Rituximab and Belimumab in Adults With Persistent Immune Thrombocytopenia

Inclusion Criteria: * Age ≥ 18 years, \<75 years * Primary ITP diagnostic defined according to the standard definition criteria (Rodeghiero et al Blood 2008) * Previous transient response to first-line treatments of corticosteroids and/or IgIV characterized by a rise of platelet levels \> 30 G/L with at least a twofold increase from baseline levels followed by a relapse. * Platelet count ≤ 30,000 /µL at inclusion or \<50 G/L if presence of hemorrhagic events or other reason left up to investigator discretion. * A persistent ITP active and existing for more than 3 months but less than 5 years from diagnosis. * Normal Bone marrow smear for patients above 60 years of age * Negative pregnancy test results for women of procreation age * Gammaglobulin level \> 7 g/L * Informed consent Exclusion Criteria: * Splenectomy * Previous treatment by Rituximab or any B-cell targeted therapy * Previous treatment by cyclophosphamide * No medical treatments of a therapeutic protocol nature within the last 30 days * Previous anaphylactic shock * Previous septic shock or severe sepsis * Chronic and ongoing severe infection requiring treatment or hospitalization in the 60 days preceding inclusion. * Severe acute infection within the last 4 weeks * Use of parenteral antibiotics within 60 days current use of suppressive therapy for chronic infection such as tuberculosis, pneumocystis, cytomegalovirus, HSZ, herpes zoster, and atypical mycobacteria * History of primary immunodeficiency, IgG level \< 400 mg/dl and/or IgA level \< 10 mg/dl * Have evidence of serious suicide risk including any history of suicidal behavior in the last 6 months and/or any suicidal ideation in the last 2 months or who in the investigator's judgment, pose a significant suicide risk. * Secondary ITP * History of recurrent infections * Neutrophils count \< 1,000/mm3 at inclusion * Positive HIV test and/or hepatitis virus C infection and/or positive hepatitis B virus surface antigen or core antibody (HbsAg or HBcAb) * Impaired renal function as indicated by a serum creatinine level \> 2 mg/dl * New York Heart Classification III or IV heart disease * Treatment by antiaggregant/antiplatelet or anti-vitamin K drug * Previous history of malignancy in the last 5 years other than cutaneous carcinoma * Previous history of severe psychiatric disorder or previous suicide attempts in the last 6 months or suicidal thoughts in the last 2 months leading up to inclusion * Unable to comply with study and follow-up procedures due to psychiatric disorders or any other reason * Alcohol or drug abuse or dependence, either current or within 1year * Pregnancy or Breast-Feeding * Live, attenuated vaccinations must be administered at least 30 days before inclusion in study * History of significant medical illness or clinically significant laboratory abnormality (or planned surgical procedure) which in the opinion of the investigator would interfere with the study procedures and / or assessments or compromise subject safety