A Study to Investigate the Efficacy and Safety of Lusutrombopag (S-888711) Tablets Administered to Adults With Immune Thrombocytopenia (ITP)

Inclusion Criteria: * A signed and dated written informed consent * Males and females ≥ 18 years of age * All subjects must agree to use barrier contraception * Diagnosis of ITP * Subjects \> 60 years must have had a diagnostic bone marrow aspiration * Relapsed persistent or chronic ITP status, with or without prior splenectomy (exception: in Hungary only splenectomized subjects will be enrolled), after having failed at least 1 prior ITP therapy (excluding TPO agonists) and have a platelet count \< 30,000/μL if not taking medications or \< 50,000/μL despite concomitant steroids or other ITP therapies, such as danazol or immunosuppressive drugs * Subjects receiving steroid therapy must be on a stable dose * Prothrombin time (PT) and activated partial thromboplastin time (aPTT) within 20% of the upper limit of normal (ULN) * Subjects receiving stable dosages of cyclosporine A, mycophenolate mofetil, azathioprine, or danazol are allowed. The dosages of all these medications must be stable for at least 4 weeks prior to Visit 1 (Day 1) Exclusion Criteria: * History of clinically important hemorrhagic clotting disorder * Females who are pregnant, lactating, or taking oral contraceptives * History of alcohol/drug abuse or dependence within 1 year * Use of the following drugs or treatment prior to Visit 1 (Day 1): * Within 12 weeks - alemtuzumab, multi-drug systemic chemotherapy, stem cell therapy; * Within 8 weeks - rituximab * Within 2 weeks - platelet transfusions or plasmapheresis treatment * Within 4 weeks - use of anti-platelet or anti-coagulant drugs * Within 1 week - Rho(D) immune globulin or intravenous immunoglobulin * History of clinically significant cardiovascular or thromboembolic disease within 26 weeks prior to Screening * Splenectomy within 4 weeks prior to Screening * Clinically significant laboratory abnormalities * Hemoglobin \< 10.0 g/dL for men or women, not clearly related to ITP * Absolute neutrophil count \< 1000/mm\^3 * Abnormal peripheral blood smear * Total bilirubin \> 1.5 x upper limit of normal * Alanine aminotransferase (ALT) \> 1.5 x upper limit of normal * Aspartate aminotransferase (AST) \> 1.5 x upper limit of normal * Creatinine \> 1.5 x upper limit of normal * Human immunodeficiency virus (HIV) positive * Hepatitis A immunoglobulin M antibody (IgM HAV) positive, hepatitis B surface antigen (HbsAg) or hepatitis C antibody (HCV) positive * Thyroid stimulating hormone (TSH) \> 1.5 x upper limit of normal * Free thyroxine (T4) \> 1.5 x upper limit of normal * Exposure to previous thrombopoietin (TPO) mimetics/agonists (e.g., eltrombopag,romiplostim, E5501 \[AKR-501\] or LGD-4665) within 4 weeks prior to Screening * Subjects unresponsive to previous TPO mimetics/agonists (e.g., eltrombopag, romiplostim, E5501 \[AKR-501\] or LGD-4665) * Exposure to an investigative medication within the past 30 days