Evaluation of Avatrombopag for the Treatment of Thrombocytopenia in Japanese Adults With Chronic ITP

Inclusion Criteria: * Subject has a confirmed diagnosis of chronic immune thrombocytopenia (ITP) (≥12 months duration) and has had an insufficient response to a previous ITP treatment, in the opinion of the Investigator. * Subject has an average of 2 platelet counts \<30×10\^9/L (no single count can be \>35×10\^9/L). The 2 samples must be obtained ≥48 hours and ≤2 weeks apart. Exclusion Criteria: * Subjects with known secondary immune thrombocytopenia (e.g., with known Helicobacter pylori-induced ITP, subjects infected with known human immunodeficiency virus (HIV) or hepatitis C virus (HCV) or subjects with known systemic lupus erythematosus). * Subjects with known inherited thrombocytopenia (e.g., Myosin Heavy Chain 9 (MYH-9) disorders) or hereditary thrombophilic disorders (e.g., Factor V Leiden, antithrombin III deficiency). * History of myelodysplastic syndrome (MDS). * History of arterial or venous thrombosis. * Subjects with a history of significant cardiovascular disease (e.g., congestive heart failure (CHF) New York Heart Association Grade III/IV, arrhythmia known to increase the risk of thromboembolic events \[e.g., atrial fibrillation\], angina, coronary artery stent placement, angioplasty, coronary artery bypass grafting). * Subjects with a history of cirrhosis, portal hypertension, or chronic active hepatitis. * Subjects with concurrent malignant disease or receiving cytotoxic chemotherapy for a reason other than ITP treatment. * Use of immunoglobulins (IVIg and anti-D) or corticosteroid rescue therapy within 1 week of Day 1/Baseline. * Splenectomy or use of rituximab within 12 weeks of Day 1/Baseline. * Use of romiplostim or eltrombopag within 1 week of Day 1/Baseline. * Use of chronic corticosteroid treatment or azathioprine within 4 weeks of Day 1/Baseline, unless receiving a stable dose for at least 4 weeks. * Use of mycophenolate mofetil, cyclosporin A, or danazol within 4 weeks of Day 1/Baseline, unless receiving a stable dose for at least 12 weeks. * Use of cyclophosphamide or vinca alkaloid regimens within 4 weeks of Baseline Visit. * Currently receiving moderate or strong dual inhibitors/inducers of CYP2C9 and CYP3A4. * Serum creatinine ≥1.5× the upper limit of normal (ULN). * Serum bilirubin ≥2×ULN. * Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≥3×ULN. * Females who are pregnant (positive beta-human chorionic gonadotropin (β-hCG) test) or breastfeeding. * Received treatment with an investigational drug within 30 days or 5 half-lives (whichever is longer) before Day 1/Baseline.