Eltrombopag olamine is a small molecule thrombopoietin receptor agonist for oral administration. Eltrombopag interacts with the transmembrane domain of the thrombopoietin receptor (also known as cMpl) leading to increased platelet production.
Promacta is specifically indicated for the treatment of thrombocytopenia in patients with chronic immune (idiopathic) thrombocytopenic purpura (ITP) who have had an insufficient response to corticosteroids, immunoglobulins, or splenectomy.
Promacta is supplied as a tablet designed for oral administration. The recommended initial dose of the drug is 50 mg once daily except in patients who are of East Asian ancestry or who have moderate to severe hepatic impairment. In this population, and for patients with moderate or severe hepatic impairment, the recommended initial dose of Promacta is 25 mg once daily. Promacta should be adjusted to achieve and maintain a platelet count >50 x 109/L as necessary to reduce the risk for bleeding. The dosing of Promacta should not exceed 75 mg daily.
Studies 1 and 2
Study 1 randomized 114 subjects to Promacta 50 mg or placebo. Study 2 randomized 117 subjects to placebo or one of three dose regimens of Promacta: 30 mg, 50 mg, or 75 mg, each administered daily. Promacta was administered over a maximum treatment period of 6 weeks, followed by 6 weeks off therapy. Promacta or placebo were discontinued if the platelet count exceeded 200 x 10(9)/L. The primary efficacy endpoint was response rate, defined as a shift from a baseline platelet count of <30 x 10(9)/L to >50 x 10(9)/L at any time during the treatment period. In Study 1, the response rate was met by 59% in the Promacta (50 mg) arm compared to 16% in the placebo group (p <0.001). In Study 2, the response rate was met by 70% in the Promacta (50 mg) arm compared to 11% in the placebo group (p <0.001). Within the placebo and 50 mg dose group, the study drug was discontinued due to an increase in platelet counts to >200 x 10(9)/L in 3% and 27% of the patients, respectively.
This open label, single arm study enrolled any subjects who had completed a prior trial with Promacta. The trial was designed to decrease the dose or eliminate the need for any concomitant ITP medications. Promacta was administered to 109 subjects; 74 completed 3 months of treatment, 53 completed 6 months and three patients completed one year of therapy. The median baseline platelet count was 18 x 10(9)/L prior to administration of Promacta. Median platelet counts at 3, 6, and 9 months on study were 74 x 109/L, 67 x 10(9)/L, and 95 x 10(9)/L, respectively. The median daily dose of Promacta following 6 months of therapy was 50 mg (n = 53); the median daily dose was also 50 mg among patients with no change in the dose regimen of Promacta over 2 months or more of therapy (n = 45).
Adverse events associated with the use of Promacta may include, but are not limited to, the following:
Eltrombopag is an orally bioavailable, small-molecule thrombopoietin receptor agonist that interacts with the transmembrane domain of the human thrombopoietin receptor. It initiates signaling cascades that induce proliferation and differentiation of megakaryocytes from bone marrow progenitor cells.
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Erickson-Miller CL, Delorme E, Tian SS, Hopson CB, Landis AJ, Valoret EI, Sellers TS, Rosen J, Miller SG, Luengo JI, Duffy KJ, Jenkins JM Preclinical Activity of Eltrombopag (SB-497115), an Oral, Non-peptide Thrombopoietin Receptor Agonist. Stem Cells 2008 Nov 26