Glaxo's Promacta has little effect-US FDA staffer

WASHINGTON, May 28 (Reuters) - GlaxoSmithKline Plc's (GSK.L) (GSK.N) Promacta, an experimental platelet-boosting drug, did not help control bleeding any better than a placebo, a U.S. Food and Drug Administration reviewer said in documents released on Wednesday.

"The data provided in this NDA (new drug application) do not demonstrate statistically significant, robust ... treatment effect in decreasing bleeding events," the reviewer wrote.

Glaxo is seeking U.S. approval for the drug as a short-term treatment for chronic idiopathic thrombocytopenia purpura (ITP), an autoimmune disease that reduces blood platelets crucial for blood clotting. The documents were released ahead of an FDA advisory panel on Friday to discuss the drug. The agency will make the final approval decision but usually follows panel recommendations. (Reporting by Susan Heavey, editing by Gerald E. McCormick)