Single Arm, Open-label, Long-term Study of Romiplostim in Thrombocytopenic Pediatric Subjects With ITP.

This is a phase 3b single arm, open label, multicenter study describing the percentage of
time pediatric subjects with ITP have a platelet response while receiving romiplostim,
defined as a platelet count ≥ 50 x 10^9/L and in the absence of ITP rescue medications in the
past 4 weeks. This protocol will provide open label romiplostim to thrombocytopenic pediatric
subjects with ITP diagnosed for at least 6 months and who have received at least 1 prior ITP
therapy (excluding romiplostim) or are ineligible for other ITP therapies.

Inclusion Criteria:

Diagnosis of primary ITP according to The American Society of Hematology (ASH) Guidelines
(Neunert et al, 2011) 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, 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 ULN Total serum bilirubin ≤ 1.5 x the ULN AST and ALT ≤ 3.0 x
the ULN

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 HepB, HepC or 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 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