Eltrombopag effective for treatment of thrombocytopenic purpura

NEW YORK (Reuters Health) - The oral nonpeptide thrombopoietin receptor agonist eltrombopag (Promacta, GlaxoSmithKline) can increase platelet counts and reduce the incidence of bleeding in patients with chronic idiopathic thrombocytopenic purpura (ITP), according to results of an international phase III trial published in the February 21 issue of The Lancet.

Most treatments for ITP - such as immunosuppressants and splenectomy -- inhibit platelet destruction, but many patients fail to respond, and adverse events are common, the researchers note.

Dr. James B. Bussel at Weill-Cornell Medical College in New York City headed the trial, which involved previously treated adult patients at 63 sites in 23 countries. Altogether, 73 patients with platelet counts < 30,000/�L were randomly assigned in a double-blind manner to eltrombopag and 37 were assigned to placebo. Treatment with eltrombopag was initiated at 50 mg/d, which could be increased to 75 mg after 3 weeks if platelet counts were < 50,000/�L.

The primary endpoint -- platelet counts of 50,000/�L or more on day 43 -- was achieved by 59% of patients in the eltrombopag group and 16% in the placebo group (adjusted odds ratio 9.61, p < 0.0001). In addition, 8 patients with low baseline platelet counts considered to be nonresponders nevertheless had clinically meaningful increases, the authors note.

The incidence of bleeding at any point during treatment was significantly lower in the eltrombopag group (61% vs 79%, OR 0.49, p = 0.021).

Dr. Bussel's group notes that eltrombopag was well tolerated, and except for nausea and vomiting, the adverse event profile was similar to that of placebo.

These findings "are remarkable in at least two respects," Drs. Simon Panzer and Ingrid Pabinger, from the Medical University Vienna, Austria, state in a Lancet commentary. "The rate of treatment success was independent of any stratification, such as concomitant drugs and previous response to drugs and splenectomy, and was associated with few and mild adverse effects."

Still, the editorialists maintain, "The role of eltrombopag in long-term treatment, and in deferring splenectomy, will be determined by its price and especially by its safety in long-term observational studies."

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