A Longitudinal 2-year Bone Marrow Study of Eltrombopag in Previously Treated Adults, With Chronic Immune (Idiopathic) Thrombocytopenic Purpura (ITP)

Inclusion Criteria: * Subjects must have signed and dated a written informed consent and be able to understand and comply with protocol requirements and instructions. * Adults (≥18 years) diagnosed with chronic ITP according to the American Society for Hematology/British Committee for Standards in Hematology (ASH/BCSH) guidelines \[George, 1996; BCSH, 2003; Provan, 2009\]. In addition, a peripheral blood smear should support the diagnosis of ITP with no evidence of other disease causative of thrombocytopenia (e.g., pseudo thrombocytopenia, myelofibrosis). The physical examination should not suggest any disease, which may cause thrombocytopenia other than ITP. * Subjects must be physically eligible for serial bone marrow biopsies and must have a bone marrow biopsy performed during screening, and be willing to remain on the study for at least 2 years with annual bone marrow biopsies. * Subjects, who previously received eltrombopag or romiplostim, must have completed treatment with these therapies at least 6 months prior to the screening bone marrow biopsy. * Subjects must have the following clinical chemistry values: * ALT and AST \< 2xULN; * Bilirubin \<1.5xULN (except for Gilbert's Syndrome); * Subjects are practicing an acceptable method of contraception as specified in the protocol. * In France, subjects will be eligible for inclusion in this study, only if either affiliated to or a beneficiary of a social security category. Exclusion Criteria: * Subjects with any clinically relevant abnormality, other than ITP, or any other medical condition or circumstance, which in the opinion of the investigator makes the subject unsuitable for participation in the study or suggests another primary diagnosis (e.g., thrombocytopenia is secondary to another disease). * Subjects with any concurrent malignant disease and/or a recent history of cancer treatment with systemic chemotherapy and/or radiotherapy. Exception: Subjects with a history of completely resected non-melanoma skin cancer or successfully treated in situ carcinoma are eligible. * Subjects with any prior history of arterial or venous thrombosis (stroke, transient ischemic attack, myocardial infarction, deep vein thrombosis or pulmonary embolism), AND ≥ two of the following risk factors: hormone replacement therapy, systemic contraception (containing estrogen), smoking, diabetes, hypercholesterolemia, hypertension, cancer, hereditary thrombophilic disorders (e.g., Factor V Leiden, ATIII deficiency, etc), or any family history of arterial or venous thrombosis. * Subjects with screening bone marrow fibers of either MF Grade 3 using European Consensus scale or Grade 4 using Bauermeister scale. * Subjects with a QTc \>450 msec or \> 480 msec for subjects with Bundle Branch Block. * Female subjects who are nursing or pregnant (positive serum or urine β-human chorionic gonadotrophin (β-hCG) pregnancy test) at screening. * Subjects treated with an investigational drug (other than a thrombopopoetin-receptor (TPO-R) agonist) within 30 days or five half-lives (whichever is longer) preceding the first dose of eltrombopag in the study. (For romiplostim or eltrombopag, see inclusion criterion #4). * Subjects treated with any TPO-R agonist other than romiplostim or eltrombopag. * Subjects with recent history of alcohol/drug abuse as determined by the investigator.