Romiplostim is a peptide-Fc fusion protein (peptibody) with a molecular weight of approximately 59,000 g/mol that acts as a thrombopoietin (TPO) receptor agonist. It was FDA-approved in August 2008 (Nplate) for the treatment of chronic immune thrombocytopenia (ITP) in adults with an insufficient response to corticosteroids, immunoglobulins, or splenectomy. Romiplostim consists of an IgG1 Fc domain fused to a peptide sequence that binds and activates the TPO receptor (c-Mpl) on megakaryocytes, stimulating platelet production.
Category: Hematology / TPO Agonist. Evidence rating: A (strong human clinical data).
Clinical status: FDA-approved (Nplate for chronic ITP, August 2008)
Romiplostim is a "peptibody" consisting of two identical single-chain subunits, each containing a human IgG1 Fc domain covalently linked to a peptide chain containing two TPO receptor-binding domains. The TPO-mimetic peptide sequences were identified by phage display and have no sequence homology…
Safety considerations: Common (>=5%): headache (26%), fatigue, arthralgia, dizziness, insomnia, myalgia, extremity pain, abdominal pain, diarrhea; Bone marrow reticulin deposition: increased reticulin fibers observed in some patients on long-term treatment; clinical significance uncertain; reversible upon discontinuation in most cases. Peripheral blood smear monitoring recommended; Thromboembolic events: increased platelet counts may increase thrombotic risk; do not target normalization of platelet counts above the level needed to prevent bleeding.
Reviewed by the PeptideAtlas Editorial Team.
| Molecular weight | ~59,000 g/mol |
|---|---|
| CAS number | 267639-76-9 |
| Half-life | ~1-34 days (median 3.5 days) |
| Production method | recombinant |
| Anti-doping status | not-listed |
| US regulatory status | FDA-approved (Nplate, August 2008) for chronic ITP in adults with insufficient response to other treatments. Pediatric ITP indication added 2018. |
Both are TPO receptor agonists for ITP, but romiplostim is a subcutaneous injection (peptibody) while eltrombopag (Promacta) is an oral small molecule. Romiplostim binds to the same site as endogenous TPO on the receptor, while eltrombopag binds to a different (transmembrane) site. Both are effective; choice depends on patient preference and clinical factors.
No. Romiplostim stimulates platelet production to compensate for the increased platelet destruction in ITP, but it does not address the underlying autoimmune mechanism. However, some patients maintain normal platelet counts after discontinuation, suggesting possible long-term remission in a subset.
Reticulin is a connective tissue fiber in bone marrow. Some patients on long-term romiplostim develop increased reticulin fibers, which theoretically could progress to myelofibrosis. Clinical trials show this is generally mild and reversible. Regular monitoring with peripheral blood smears for abnormal cells is recommended.