Successful Phase II Trial for Drug To Control Idiopathic Thrombocytopenic Purpura

A successful phase II study indicated that the drug eltrombopag was effective in increasing platelet counts and decreasing bleeding in patients with chronic idiopathic thrombocytopenic purpura (ITP).

ITP is characterized by increased autoimmune platelet destruction and/or inadequate platelet production. Its cause is currently unknown. Some patients with ITP are asymptomatic or have mild bruising while others develop mucosal bleeding that can become severe. A normal blood platelet count is 150,000/µl to 400,000/µl. A reduction in platelet count (to a level less than 150,000/µl) is the defining characteristic of any type of thrombocytopenia and diagnosis can be confirmed following a routine blood test.

Eltrombopag is a non-peptide thrombopoietin receptor agonist that has been shown in pre-clinical research and clinical trials to stimulate the proliferation and differentiation of megakaryocytes, the bone marrow cells that give rise to blood platelets, and thus may be considered a platelet growth factor. Eltrombopag reduces the risk of bleeding and bruising in patients with ITP by elevating and maintaining platelet levels greater than 50,000/µl. Eltrombopag is administered orally as a once a day tablet. The drug was discovered as a result of research collaboration between GlaxoSmithKline (Greenford, UK) and Ligand Pharmaceuticals (San Diego, CA, USA) and is being developed by GlaxoSmithKline. Eltrombopag is an investigational compound that has not received regulatory approval in any market for any indication at this time.

In the phase II trial, investigators at Weill Cornell Medical College (New York, NY, USA) treated 118 adults with chronic ITP and platelet counts of less than 30,000/µl who had had relapses or whose platelet count was refractory to at least one standard treatment for ITP with eltrombopag at 30, 50, or 75 mg daily or with a placebo. The target was to reach a platelet count of 50,000/µl or more on day 43.

Results published in the November 20, 2007, issue of the New England Journal of Medicine (NEJM) revealed that in the eltrombopag groups receiving 30, 50, and 75 mg per day, the target was achieved in 28%, 70%, and 81% of patients, respectively. In the placebo group, the target was achieved by only 11% of patients. By day 15, more than 80% of patients receiving 50 or 75 mg of eltrombopag daily had an increased platelet count. Bleeding also decreased during treatment in these two groups. The incidence and severity of side effects were similar in the placebo and eltrombopag groups.

"These findings represent an important step in the development of a new treatment option for those living with chronic ITP. The fact that eltrombopag-elevated platelet counts in this study within one week could be very useful to chronic ITP patients in need of short-term treatment,” said first author Dr. James Bussel, professor of medicine at Weill Cornell Medical College.


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GlaxoSmithKline
Ligand Pharmaceuticals
Weill Cornell Medical College