How effective is romiplostim for the treatment of chronic immune thrombocytopenic purpura (ITP) platelet disorder in adults?

Updated: Aug 05, 2017
  • Author: Perumal Thiagarajan, MD; Chief Editor: Srikanth Nagalla, MBBS, MS, FACP  more...
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Answer

Answer

Romiplostim  is another thrombopoietin receptor agonist, consisting of human immunoglobulin Fc region covalently linked to a peptide sequence that binds to and activates the thrombopoietin receptor. The peptide sequence has no homology with human thrombopoietin so that the possibility of a cross-reacting antibody is minimized. The Fc domain extends the half-life of the molecule in the circulation.

Weekly subcutaneous doses of 1-7 μg/kg, romiplostim can increase the platelet count in chronic ITP. The adverse effects include bone marrow reticulin formation.

In 2 parallel trials that assessed the long-term administration of romiplostim in 63 splenectomized and 62 nonsplenectomized patients with ITP, both the splenectomized and nonsplenectomized patients achieved durable platelet counts over a longer period with romiplostim than with placebo; patients receiving romiplostim were also more likely to reduce or discontinue concurrent other ITP therapy compared with patients in the placebo groups. [25]

The responses to thrombopoietin receptor agonists take 10-15 days, and, hence, they are unlikely to replace steroids or intravenous immunoglobulins as initial therapy. Furthermore, relapses are common, necessitating long-term therapy. Thrombopoietin receptor agonists may help postpone or even prevent splenectomies. The advantages of thrombopoietin receptor agonist therapy should be weighed against the risk of marrow fibrosis seen in the limited long-term outcome data. There is also a theoretical possibility that these agents increase the risk of hematologic malignancies, as thrombopoietin receptor is present in hematopoietic stem cells. Currently, these agents are recommended for ITP patients whose conditions are refractory to previous treatments, including splenectomy.


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