A new Drug Effectively Treats Thrombocytopenia

A new drug raises platelet blood cell count and decreases bleeding in patients with idiopathic thrombocytopenic purpura (ITP), according to the results of a new study.

Researchers at the Weill-Cornell Medical College (New York, NY, USA) conducted a phase III randomized controlled study of the effects of eltrombopag, a small molecule agonist of the c-mpl (TpoR) receptor, which is the physiological target of the hormone thrombopoietin. The researchers studied 114 patients from 63 sites in 23 countries, all with ITP, and platelet counts of less than 30,000 per µL of blood (normal range 150,000-400,000), and one or more previous ITP treatment. The patients were randomized to receive standard care plus once-daily eltrombopag (76 patients), or placebo (38). After three weeks, the patients who still had platelet counts less than 50,000 per µL could increase study drug to 75 mg. The primary endpoint was the proportion of patients achieving platelet counts of 50,000 per µL or more by day 43.

The study results showed that 59% of eltrombopag patients and 16% of placebo patients achieved the platelet count of 50,000 per µL. A statistical analysis of the results revealed that eltrombopag patients were almost 10 times more likely to reach the target platelet count as placebo patients. Of the 34 eltrombopag patients who increased their dose of eltrombopag, 29% responded. Generally, platelet counts returned to the patients' baseline levels within two weeks after the end of treatment. Eltrombopag patients in the study were half as likely to suffer from bleeding at any time during the study, compared to the placebo patients. Serious adverse events, including those leading to treatment discontinuation, were rare in both groups. The study was published in the February 21, 2009 issue of the Lancet.

"Substantially more patients in the eltrombopag group achieved platelet counts of 50 000 per μL or greater than did those in the placebo group,” said lead author James Bussel, M.D. "In conjunction with the rise in platelet count, a prospective assessment showed a significant reduction in bleeding events both during and at the end of the study.”

ITP appears to be related to antibodies against platelets, and is thus also known as immune or immune-mediated thrombocytopenic purpura. Often ITP is asymptomatic, however a very low platelet count can lead to visible symptoms, such as purpura (bruises), or more seriously, bleeding diathesis. The incidence of ITP is estimated at 50–100 new cases per million per year, with children accounting for half of that amount. More than 70% of childhood cases end up in remission within six months, whether treated or not; moreover, a third of the remaining chronic cases remitted during follow-up observation, and another third ended up with only mild thrombocytopenia.

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Weill-Cornell Medical College