UPDATE 1-Glaxo wins U.S. approval for platelet drug

(Adds details, background)

NEW YORK, Nov 20 (Reuters) - GlaxoSmithKline Plc (GSK.L) said on Thursday its new platelet-boosting drug, Promacta, was granted accelerated approval by the U.S. Food and Drug Administration.

Promacta, also known by the chemical name eltrombopag, is approved for the treatment of patients with chronic immune thrombocytopenic purpura (ITP) who have had an insufficient response to corticosteroids, immunoglobulins or splenectomy.

A green light had been expected after an FDA advisory panel unanimously agreed in May that the drug demonstrated a favorable risk-benefit profile for the short-term treatment of chronic ITP.

ITP is an autoimmune disease which results in low blood platelet counts. Because platelets contribute to blood clotting, patients with low counts bleed more easily than others, heal more slowly and bruise more often.

Glaxo, which views the medicine as a potential blockbuster, expects Promacta to be available in the next week.

The British-based company also plans to submit a marketing application in 2008 for the drug in Europe, where it will be sold as Revolade.

The drug was discovered as a result of a research collaboration between Glaxo and Ligand Pharmaceuticals Inc (LGND.O). (Reporting by Ben Hirschler; Editing by Andre Grenon)