GlaxoSmithKline (GSK) has reported that Phase II studies of eltrombopag (SB-497115, or 115), a small-molecule drug that mimics the activity of thrombopoietin, a protein factor that promotes growth and production of blood platelets, were promising.

Data from the dose-ranging trial that showed 115 significantly raised platelet counts in adult patients. The studies are underway in three indications: idiopathic thrombocytopenia purpura, hepatitis C and chemotherapy-induced thrombocytopenia. The results in adult patients with chronic ITP that had failed at least one prior therapy and with platelet counts less than 30,000 showed that 66 percent of patients receiving the 50 mg dose and 87 percent of patients treated with 115's highest dose (75 mg/day) had counts greater than or equal to 50,000 after six weeks and many of those had reached normal platelet levels within the first two to three weeks of treatment.

In comparison, only 13 percent of placebo-treated patients showed platelet increases greater than or equal to 50,000 after six weeks. The frequency of side effects was comparable between patients treated with placebo and those treated with eltrombopag.