Safety and Efficacy Study of Romiplostim to Treat Immune Thrombocytopenia (ITP) in Pediatric Patients

- Diagnosis of primary ITP according to the American Society of Hematology (ASH) guidelines at least 6 months prior to screening, regardless of splenectomy status -Subject must be refractory to a prior ITP therapy, having relapsed after at least 1 prior ITP therapy, or ineligible for other ITP therapies; prior therapy includes first-line therapies - Age ≥ 1 year and < 18 years at the time of providing informed consent - The mean of 2 platelet counts taken during the screening period must be ≤ 30 x 10^9/L with neither count > 35 x 10^9/L - A serum creatinine concentration ≤ 1.5 times the laboratory normal range (for each age category) during the screening period - Adequate liver function; serum bilirubin ≤ 1.5 times the laboratory normal range during the screening period; aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 3.0 times the laboratory normal range during the screening period - Hemoglobin > 10.0 g/dL during the screening period - Subject and/or subject's legally acceptable representative has provided informed consent prior to any study-specific procedure; subject has provided assent, where required

- Known history of a bone marrow stem cell disorder; any abnormal bone marrow findings other than those typical of ITP must be approved by Amgen before a subject may be enrolled in the study - Known active or prior malignancy except adequately treated basal cell carcinoma - Known history of congenital thrombocytopenia - Known history of hepatitis B, hepatitis C, or human immunodeficiency virus (HIV) - Known history of H. pylori by urea breath test or stool antigen test within 6 months of enrollment or successfully treated with no evidence of infection - Known history of systemic lupus erythematosus, evans syndrome, or autoimmune neutropenia - Known history of antiphospholipid antibody syndrome or positive for lupus anticoagulant - Known history of disseminated intravascular coagulation, hemolytic uremic syndrome, or thrombotic thrombocytopenic purpura - Previous history of venous thromboembolism or thrombotic events - Previous use of romiplostim, pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF), Eltrombopag, recombinant human thrombopoietin (rHuTPO) or any platelet producing agent - Rituximab (for any indication) or 6-mercaptopurine (6-MP) within 14 weeks before the screening visit, or anticipated use during the time of the proposed study - Splenectomy within 4 weeks of the screening visit - All hematopoietic growth factors including interleukin-11 (IL-11) (oprelvekin) within 4 weeks before the screening visit - Alkylating agents within 8 weeks before the screening visit or anticipated use during the time of the proposed study - Vaccinations known to decrease platelet counts within 8 weeks before the screening visit - Known hypersensitivity to any recombinant E coli-derived product (eg, Infergen, Neupogen, Somatropin, and Actimmune) - Other criteria may apply