FDA Grants Priority Review of Eltrombopag (Promacta) for Thrombocytopenia

On March 3, GlaxoSmithKline (GSK) announced that the U.S. Food and Drug Administration (FDA) granted priority review of the company's experimental drug eltrombopag for the treatment of low platelet count, or thrombocytopenia. Platelets enable the blood to clot, and a deficiency can lead to excessive bleeding and easy bruising.

While the FDA is considering eltrombopag for the short-term treatment of patients with chronic idiopathic thrombocytopenic purpura - or bleeding due to thrombocytopenia of an unknown cause - the drug has also been studied as a treatment for low platelet count in patients with chronic hepatitis C.

Patients with advanced fibrosis or cirrhosis often have thrombocytopenia, which can prevent them from using pegylated interferon, which can cause platelet loss as a side effect. Researchers reported in the November 29, 2007 New England Journal of Medicine that eltrombopag increased platelet counts in patients with thrombocytopenia due to HCV-related cirrhosis thereby allowing initiation of antiviral therapy. Further, eltrombopag may enable patients with less advanced liver disease to remain on adequate doses of interferon-based therapy, thus maximizing the likelihood of sustained response.

Below is an edited excerpt from the recent GSK press release announcing the FDA's decision.

FDA grants priority review for
Promacta (eltrombopag)

PHILADELPHIA, PA, and LONDON, UK, March 3, 2008 - GlaxoSmithKline [NYSE: GSK, LSE: GSK] today announced that the United States Food and Drug Administration has granted Priority Review for PROMACTA (eltrombopag) for the short-term treatment of patients with chronic idiopathic thrombocytopenic purpura (ITP). PROMACTA is an investigational, once-daily oral treatment that induces the production of cells in the bone marrow to generate platelets, which are critical in minimizing the incidence of bleeding in chronic ITP.

If approved, PROMACTA would be the first oral thrombopoeitin (TPO) receptor agonist for the short-term treatment of previously treated patients with chronic ITP to increase platelet counts and reduce bleeding.

"Our goal for PROMACTA is to make available a targeted therapy in oral form for patients to help raise their platelet counts without having to suppress the immune system," said Paolo Paoletti, MD, Senior Vice President of the Oncology Medicine Development Center at GSK. "The FDA designation of our submission for priority review is very encouraging and brings us closer to offering physicians and their patients PROMACTA."

The priority review designation means FDA is expected to make a decision on the NDA for the investigational compound within six months of the submission.
In pivotal studies, the most common adverse events observed in patients taking PROMACTA were headache, nausea, nasopharyngitis, diarrhea, and vomiting.
GSK also plans to submit a Marketing Authorization Application (MAA) for eltrombopag in the treatment of chronic ITP in Europe in 2008 where it will be marketed as REVOLADE. The compound is also being studied for long-term treatment of chronic ITP, as well as thrombocytopenia associated with Hepatitis C Virus cirrhosis and chemotherapy induced thrombocytopenia.

About ITP

Chronic ITP is a disorder marked by increased platelet destruction and/or inadequate platelet production in the blood, which causes an increased risk of bruising and bleeding. There are estimated to be approximately 60,000 individuals diagnosed with chronic ITP in the U.S. People with chronic ITP often bleed from small blood vessels causing bruises, nosebleeds or even fatal gastrointestinal or intra cerebral bleeds, although these are rare.

About PROMACTA (eltrombopag)

Eltrombopag is an oral, 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. Eltrombopag was discovered as a result of research collaboration between GlaxoSmithKline and Ligand Pharmaceuticals (NASDAQ: LGND). It 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.

3/07/08