Study on Bone Marrow Morphology in Adults Receiving Romiplostim for Treatment of Thrombocytopenia Associated With Immune Thrombocytopenia Purpura (ITP)

The purpose of this study is to evaluate changes in bone marrow morphology (structure) after long-term exposure to romiplostim.

Participants diagnosed with ITP according to the American Society of Hematology (ASH) Guidelines were sequentially enrolled into the following groups:

* Bone marrow biopsy at Baseline and Year 1
* Bone marrow biopsy at Baseline and Year 2
* Bone marrow biopsy at Baseline and Year 3.

All participants received romiplostim for 3 years, unless withdrawn from the study early. Participants returned for one visit for End of Study (EOS) procedures 4 weeks after romiplostim discontinuation, or, for participants who were withdrawn from the study due to the presence of collagen fibrosis, or had a change to grade 3 reticulin, at 12 weeks after discontinuation of romiplostim.

Eligibility Criteria:
Inclusion Criteria:

* Diagnosis of ITP according to American Society of Hematology (ASH) guidelines
* Subject must have had a bone marrow biopsy within one year prior to planned first dose of romiplostim (with available bone marrow tissue block or unstained histological slides to send to a central laboratory for interpretation) or must consent to a pre-treatment bone marrow biopsy within 3 weeks prior to planned first dose of romiplostim. Central laboratory interpretation is required prior to first dose of romiplostim
* Subject must agree to a scheduled bone marrow biopsy at Year 1, Year 2, or Year 3 following romiplostim treatment and any unscheduled biopsies if clinically indicated
* Subject ≥18 years of age
* Baseline bone marrow reticulin grade of 0, 1, 2, or 3 according to the modified Bauermeister grading scheme as assessed by central laboratory interpretation
* Platelet count \< 50 x 10\^9/L
* Must have received at least 1 prior ITP therapy (examples of ITP therapy include corticosteroids, intravenous immunoglobulin \[IVIG\], splenectomy)
* Subject (or legally-acceptable representative) is willing and able to provide written informed consent

Exclusion Criteria:

* Baseline bone marrow biopsy positive for collagen fibrosis
* Any known history of or currently active bone marrow stem cell disorder, hematological malignancy, myeloproliferative disorder, myelodysplastic syndrome
* Any current active malignancy
* Any prior exposure to cytostatic chemotherapy or radiotherapy for malignancy
* Subject has undergone pacemaker placement, cardiac ablation of arrhythmia, and/or any current treatment with Vaughan Williams Class IA - IC and Class III agents (Vaughan Williams, 1970)
* Subject has participated in any study evaluating pegylated recombinant human megakaryocyte growth and development factor (PEG-rHuMGDF), recombinant human thrombopoietin (rHuTPO), or thrombopoietin receptor agonists (ie romiplostim or eltrombopag)
* Subject has a known hypersensitivity to any recombinant E coli-derived product
* Subject is currently enrolled in or has not yet completed (at least 4 weeks since ending) other investigational device or drug trial(s) or subject is receiving other investigational agent(s)
* Other investigational procedures are excluded
* Subject of child-bearing potential is evidently pregnant (eg positive pregnancy test) or is breast feeding
* Subject is not using adequate contraceptive precautions
* Subject has any kind of disorder that compromises the ability of the subject to give written informed consent and does not have a legally acceptable representative and/or is unable to comply with study procedures.