Long-term Study of Romiplostim in Thrombocytopenic Pediatric Patients With Immune Thrombocytopenia (ITP)

- Diagnosis of primary ITP according to The American Society of Hematology (ASH) Guidelines at least 6 months before screening, regardless of splenectomy status - Age ≥ 1 year and < 18 years of age - Refractory to prior ITP therapy, relapsed after at prior ITP therapy, or be ineligible for other therapies. Examples of prior therapy include: corticosteroids, intravenous Immunoglobulin (IVIG), anti-D immunoglobulin, platelet transfusions. - Platelet count ≤ 30 x10^9/L or is experiencing uncontrolled bleeding - Has provided informed consent before any study-specific procedure; - Adequate hematologic, renal, and liver function during screening: -- Hemoglobin > 10.0 g/dL -- Serum creatinine ≤ 1.5 x the upper limit of normal (ULN) -- Total serum bilirubin ≤ 1.5 x the ULN -- Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 3.0 x the ULN - For the EU, Switzerland and Turkey protocol supplement, subject must agree to a scheduled bone marrow biopsy and aspirate at Year 1 or Year 2 following romiplostim treatment and any unscheduled biopsies if clinically indicated - For the EU, Switzerland and Turkey protocol supplement, a reticulin grade of 0, 1, 2, or 3 according to the modified Bauermeister grading scale, as assessed by central laboratory from a bone marrow biopsy performed within 1 year prior to planned first dose of romiplostim or consent to a pre-treatment bone marrow biopsy and aspirate prior to planned first dose of romiplostim

- 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) - Prior bone marrow transplant or peripheral blood progenitor cell transplant - Active or prior malignancy except non-melanoma skin cancers within the last 5 years - History of myelodysplastic syndrome - History of bleeding diathesis - History of congenital thrombocytopenia - History of Hepatitis B, Hepatitis C or human immunodeficiency virus (HIV) - History of systemic lupus erythematosus, Evans syndrome, or autoimmune neutropenia - History of antiphospholipid antibody syndrome or known positive for lupus anticoagulant - History of disseminated intravascular coagulation, hemolytic uremic syndrome, or thrombotic thrombocytopenic purpura - History of venous thromboembolism or thrombotic events - Previous use of romiplostim or previous use of eltrombopag within 4 weeks of enrollment - Previous use of pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF), recombinant human thrombopoietin (rHuTPO) or any other platelet producing agent - Rituximab (for any indication) or 6-mercaptopurine within 8 weeks of enrollment, or anticipated use at any time during the study - Splenectomy within 4 weeks of 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 - Currently enrolled in another investigational device or drug study, or less than 30 days since ending investigational study - Will have investigational procedures while enrolled on study - Female subject of child bearing potential (defined as having first menses) not willing to use, in combination with her partner highly effective methods of birth control during treatment and for 1 month after the end of treatment - Subject is pregnant or breast feeding, or might become pregnant within 1 month after the end of treatment - Subject has known hypersensitivity to any recombinant Escherichia coli derived product (eg, Infergen®, Neupogen®, somatropin, and Actimmune®) - Has previously enrolled into this study - Will not be available for protocol-required study visits or procedures, to the best of the subject’s and investigator’s knowledge - Any kind of disorder that, may compromise the subject to give written informed consent and/or to comply with all required study procedures