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

This is a phase 3b single arm, open label, multicenter study describing the percentage of time pediatric participants with ITP have a platelet response while receiving romiplostim, defined as a platelet count ≥ 50 x 10\^9/L in the absence of ITP rescue medications for the past 4 weeks.


Eligibility Criteria:
Inclusion Criteria:

* 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

Exclusion Criteria:

* 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