The duration of the screening period is up to 8 weeks. Eltrombopag will be administered for at least 2-years followed by a 4-week follow-up period. Bone marrow biopsies will be performed at screening, after 1-year and 2-years of eltrombopag treatment, and at early withdrawal of treatment. The screening bone marrow biopsy should be performed within 8 weeks of planned start of study medication and the bone marrow biopsy block must be available for central laboratory processing.