Eltrombopag

Eltrombopag (rINN, codenamed SB-497115-GR) is a medication under development for conditions that lead to thrombocytopenia (abnormally low platelet counts). It is a small molecule agonist of the c-mpl (TpoR) receptor, which is the physiological target of the hormone thrombopoietin. It is under development by GlaxoSmithKline and Ligand Pharmaceuticals, and is likely to be marketed as Promacta.

Development
In preclinical studies, the compound was shown to interact selectively with the thrombopoeitin receptor, leading to activation of the JAK-STAT signaling pathway and increased proliferation and differentiation of megakaryocytes. Animal studies confirmed that administration could increase platelet counts. In 73 healthy volunteers, higher doses of eltrombopag caused larger increases in the number of circulating platelets without tolerability problems.

Clinical trials
Eltrombopag has been studied, and shown to be effective, in two major clinical syndromes: idiopathic thrombocytopenic purpura and cirrhosis due to hepatitis C (in which low platelet counts may be a contraindication for interferon treatment).