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.