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GSK's New Drug for Low Platelets & HCV Therapy
  GSK's eltrombopag in ITP showcased at ASH
Eltrombopag, GSK's new thrombocytopenia treatment, has performed exceptionally well in a six-week Phase II trial of patients with the autoimmune disease, chronic idiopathic thrombocytopenia purpura, according to lead investigator Dr James Bussell of New York's Presbyterian Hospital's Weill Cornell Medical Center.
Data presented at the American Society of Hematology meeting in Orlando showed the study had already reached its primary endpoint by the time only a third of the planned 270 patients had been treated.
Dr Bussell told an ASH press conference: "The trial was stopped at the interim analysis of the first 90 patients because results were significant at the 0.001 level for both the 50mg and 75mg doses." More than 70% of patients achieved a platelet count greater than 50,000 with a 50mg dose while this rose to 80% with a 75mg dose, he said. "At both these doses there was a dramatic decrease in bleeding in line with platelet increases." The incidence of side effects were similar to those seen with placebo.
Eltrombopag, to be called Promacta in the USA, is the first orally administered, once-daily treatment for thrombocytopenia and is set to be a "major advance in the management of ITP," said Dr Bussell. It is thought to work by stimulating thrombopoietin receptors on megakaryocytes in the bone marrow to increase production of platelets. Previous therapies have focused on inhibiting destruction of platelets by suppressing the immune system or surgically removing the spleen.
Six-month Phase III trial has already begun
GSK announced last week that the product has started a six-month Phase III study and, although ITP is a fairly rare condition affecting around one person in 10,000, thrombocytopenia also occurs in 5%-10% of all patients admitted to hospital as a consequence of chemotherapy and secondary hepatitis C infection.
The company says it expects to submit data in at least one indication to the US and European regulatory authorities in 2007-8.
By Olwen Glynn Owen
GSK drug gets hep C patients onto therapy
GlaxoSmithKline's platelet-boosting drug Promacta can be an effective treatment for patients with hepatitis C whose low blood platelet counts mean that they cannot be treated with interferon, the standard therapy for the infection.
The results of a Phase II study involving 74 patients with chronic hepatitis C revealed that Promacta (eltrombopag) was able to boost platelet levels in more than 95% of patients treated to the extent that therapy with pegylated interferon alpha could be started.
Low platelet counts - or thrombocytopenia - is a common symptoms in patients with chronic liver disease such as HCV. Because treatment with interferon can also reduce platelet levels, patients with thrombocytopenia can be excluded from starting or being continued on treatment.
Paolo Paoletti, senior vice president of oncology drug development at GSK, said: "As we move into Phase III trials for eltrombopag in a variety of conditions where thrombocytopenia is a complicating factor, these data represent a significant milestone for GSK in supportive care." Phase III trials in this indication are due to start next year.
A Phase II trial of the drug in patients with thrombocytopenia caused by chemotherapy failed in its primary endpoint, although this was due to the chemotherapy drug in the study not significantly impacting platelet production in the first place, which was an unexpected result.
Progress in first indication
Eltrombopag is currently in Phase III trials for the haematological disorder idiopathic thrombocytopenic purpura, and GSK is hoping to file for marketing approval of the drug for short-term treatment of ITP in 2007. It had earlier said it wanted to file later this year, but now says it needs discussion with regulatory authorities "to determine whether these data will be sufficient to file for approval next year."
A phase III clinical programme is underway to assess the use of Promacta for the long-term treatment of ITP, with filings for this indication anticipated in 2008.
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