Inclusion Criteria:

• Subjects eligible for enrolment in the study must meet all of the following criteria:
• Subject has signed and dated a written inform consent.
• Adults (≥18 years) diagnosed with chronic ITP according to the American Society of Hematology/British Committee for Standards in Hematology (ASH/BCSH) guidelines [George, 1996; BCSH, 2003], and a platelet count between ≥20,000/μL and ≤50,000/μL on Day 1 (or within 24 hours prior to dosing on Day 1). In addition, a peripheral blood smear should support the diagnosis of ITP with no evidence of other causes of thrombocytopenia (e.g. pseudothrombocytopenia, myelodysplasia). The physical examination should not suggest any disease which may cause thrombocytopenia other than ITP.
• Subjects who have previously received one or more prior ITP therapies. Previous treatments for ITP include but are not limited to corticosteroids, immunoglobulins, azathioprine, danazol, cyclophosphamide and/or rituximab.
• Subjects must have either initially responded (platelet count >100,000/μL) to a previous ITP therapy or have had a bone marrow biopsy consistent with ITP within 3 years to rule out myelodysplastic syndromes or other causes of thrombocytopenia.

• It is important to clearly differentiate the effect of eltrombopag on platelet count from the treatment effects of prior and concomitant ITP therapies. Therefore:

  1. Previous therapy for ITP with immunoglobulins (IVIg and anti-D) must have been completed at least 1 week prior to randomization and the platelet count must show a clear downward trend after the last treatment with immunoglobulins. Previous treatment for ITP with splenectomy, rituximab and cyclophosphamide must have been completed at least 4 weeks prior to randomization, or clearly be ineffective.
  2. Subjects treated with concomitant ITP medication (e.g. corticosteroids or azathioprine) must be receiving a dose that has been stable for a least 4 weeks prior to randomization. Subjects treated with cyclosporine A, mycophenolate mofetil or danazol must be receiving a dose that has been stable for at least 3 months prior to randomization.
• Prothrombin time (PT/INR) and activated partial thromboplastin time (aPTT) must be within 80 to 120% of normal range with no history of hypercoagulable state.
• A complete blood count (CBC), within the reference range (including differential not indicative of a disorder other than ITP), with the following exceptions:
• Platelet count between ≥20,000/μL and ≤50,000/μL on Day 1 (or within 24 hours of Day 1) is required for inclusion.
• Hemoglobin: Subjects with hemoglobin levels between 10g/dL (100g/L) and the lower limit of normal are eligible for inclusion, if anemia is clearly attributable to ITP (excessive blood loss).
• ANC >1500/mL (1.5 x 10^9/L) is required for inclusion (elevated WBC/ANC above the reference range due to steroid treatment is acceptable).
• The following clinical chemistries MUST NOT exceed the normal reference range by more than 20%: creatinine, ALT, AST, total bilirubin, total albumin and alkaline phosphatase.
• Subject is practicing an acceptable method of contraception (documented in chart). Female subjects (or female partners of male subjects) must either be of non-childbearing potential (hysterectomy, bilateral oophorectomy, bilateral tubal ligation or post-menopausal >1 year), or of childbearing potential and use of one of the following acceptable methods of contraception from two weeks prior to administration of study medication, throughout the study, and 28 days after completion or premature discontinuation from the study:

Complete abstinence from intercourse; Intrauterine device (IUD); Two forms of barrier contraception (diaphragm plus spermicide, and for males condom plus spermicide); Male partner is sterile prior to entry into the study and is the only partner of the female; Systemic contraceptives (combined or progesterone only). Subject is able to understand and comply with protocol requirements and instructions and intends to complete the study as planned.

Exclusion Criteria:

• A subject will NOT be eligible for inclusion in this study if any of the following criteria apply:
• Any clinically relevant abnormality, other than ITP, identified on the screening examination 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).
• Concurrent malignant disease and/or history of cancer treatment with cytotoxic chemotherapy and/or radiotherapy.
• 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, medication for hypertension, cancer, hereditary thrombophilic disorders (e.g., Factor V Leiden, ATIII deficiency, etc), or any other family history of arterial or venous thrombosis.
• Pre-existing cardiovascular disease (congestive heart failure, New York Heart Association [NYHA] Grade III/IV), or arrhythmia known to increase the risk of thromboembolic events (e.g. atrial fibrillation), or subjects with a QTc >450 msec.
• Female subjects who are nursing or pregnant (positive serum or urine b-human chorionic gonadotrophin pregnancy test) at screening or pre-dose on Day 1.
• History of alcohol/drug abuse.
• Treatment with an investigational drug within 30 days or five half-lives (whichever is longer) preceding the first dose of study medication.
• Subject treated with drugs that affect platelet function (including but not limited to aspirin, clopidogrel and/or NSAIDs) or anti-coagulants for > 3 consecutive days within 2 weeks of the study start and until the end of the study.
• History of platelet agglutination abnormality that prevents reliable measurement of platelet counts.
• All subjects with secondary immune thrombocytopenia, including those with laboratory or clinical evidence of HIV infection, anti-phospholipid antibody syndrome, chronic hepatitis B infection, hepatitis C virus infection, or any evidence for active hepatitis at the time of subject screening. If a potential subject has no clinical history that would support HIV infection or hepatitis infection, no further laboratory screening is necessary; however, standard medical practice would suggest further evaluation of patients who have risk factors for these infections.
• Previous participation in a clinical study with eltrombopag.
• Patients planning to have cataract surgery. In France, a subject is neither affiliated with nor a beneficiary of a social security category.

Subjects meeting any of the following criteria must not be enrolled in the study:

• Any clinically relevant abnormality, other than ITP, identified on the screening examination 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).
• Concurrent malignant disease and/or history of cancer treatment with cytotoxic chemotherapy and/or radiotherapy.
• Any prior history of arterial or venous thrombosis AND ≥ two of the following risk factors: hereditary thrombophilic disorders (eg Factor V Leiden, ATIII deficiency, etc), hormone replacement therapy, systemic contraception (containing estrogen), smoking, diabetes, hypercholesterolemia, medication for hypertension or cancer.
• Pre-existing cardiac disease (congestive heart failure New York Heart Association (NYHA) Grade III/IV, or arrhythmias known to involve the risk of thromboembolic events (e.g. atrial fibrillation), or subjects with a QTc >450 msec.
• Female subjects who are nursing or pregnant (positive serum or urine b-human chorionic gonadotrophin pregnancy test) at screening or pre-dose on Day 1.
• History of alcohol/drug abuse.
• Treatment with an investigational drug within 30 days or five half-lives (whichever is longer) preceding the first dose of study medication.
• Subjects treated with drugs that affect platelet function (including but not limited to, aspirin, clopidogrel or NSAIDS) or anti-coagulants for >3 consecutive days within 2 weeks of the start and until the end of the study 'Prohibited Medications and Non-Drug Therapies".
• History of platelet agglutination abnormality that prevents reliable measurement of platelet counts.
• All subjects with secondary immune thrombocytopenia, including those with laboratory or clinical evidence of human immunodeficiency virus (HIV) infection, anti-phospholipid antibody syndrome, chronic hepatitis B infection, hepatitis C virus infection, or any evidence for active hepatitis at the time of subject screening. If a potential subject has no clinical history that would support HIV infection or hepatitis infection, no further laboratory screening is necessary; however, standard medical practice would suggest further evaluation of patients who have risk factors for these infections.
• Previous participation in a clinical study with eltrombopag.
• Patients planning to have cataract surgery.