Romiplostim: a novel thrombopoiesis-stimulating agent.

PURPOSE: The pharmacology, pharmacokinetics, dosage and administration, efficacy, safety, effects on quality of life, and place in therapy of romiplostim are reviewed.
SUMMARY: Romiplostim is a second- generation thrombopoietic agent that stimulates the thrombopoietin receptor and platelet production without inducing production of autoantibodies. Romiplostim, a peptibody, bears no structural resemblance to endogenous thrombopoietin, thus minimizing the risk for development of thrombopoietin autoantibodies. Clinical trials have shown that romiplostim increases platelet counts compared with placebo in both splenectomized and non-splenectomized adult patients with chronic idiopathic thrombocytopenic purpura (ITP). Clinical trials with romiplostim are ongoing for patients with myelodysplastic syndrome and those receiving chemotherapy for treatment of malignancies. Romiplostim may confer an increased risk of bone marrow reticulin formation or fibrosis, malignancy, thrombosis, and thrombocytopenia that is more severe than the level present before initiation of romiplostim. While all patients receiving romiplostim in clinical trials experienced at least one adverse event, most were mild to moderate in severity. The most frequent adverse effects were ecchymosis, headache, and petechiae. Romiplostim is initiated at a dosage of 1 microg/kg subcutaneously once weekly and titrated to achieve platelet counts between 50 and 200 x 10(9) platelets/L, with a maximum dose of 10 microg/kg. Romiplostim is only available through the manufacturer's risk-management program. The current wholesale price of romiplostim is $1,062.50 for a single-use vial of 250 microg or $2,125 for a single-use vial of 500 microg. The extrapolated drug cost for weekly dosing for one year is approximately $55,250.
CONCLUSION: Romiplostim is a novel thrombopoietic-stimulating agent for use in patients with chronic ITP who have not responded to other therapies.