UK drug giant GlaxoSmithKline has kicked off two parallel late-stage trials assessing the potential use of its investigational compound Revolade (eltrombopag; US tradename Promacta) to boost blood platelet counts in patients with hepatitis C.

The drug is an oral, non-peptide thrombopoietin receptor agonist that works by stimulating the production of bone marrow cells that give rise to blood platelets, and is therefore considered a platelet growth factor, says GSK.

According to the World Health Organisation, about 180 million people are infected with hepatitis C globally. Thrombocytopenia (low platelet count) is a common symptom, but because treatment with interferon - which is crucial to controlling the disease - can also reduce platelet levels, patients with this complication can be excluded from starting or being continued on treatment, leading to quicker progression of the illness.

The new Phase III trials – ENABLE 1 and 2 – are designed to investigate whether Revolade can raise platelet counts enough to allow patients with hepatitis C-associated thrombocytopenia to start and maintain treatment with antiviral therapy. The drug’s success will be measured by the number of patients who are able to achieve a sustained virological response, ie. an undetectable viral load of hepatitis C for a period of six months after therapy. 

“ENABLE will investigate the effect of eltrombopag over a 12-month treatment period to determine how it may help patients to achieve SVR, which in clinical terms is considered a cure for hepatitis C, as well as better understand any related toxicities or tolerability issues,” explained John McHutchison, MD, Professor of Medicine and Associate Director, Duke Clinical Research Institute, Durham, North Carolina, US.

Nearing approval?
Revolade is yet to receive its first regulatory approval for any market, but it could soon be available in the UK if a European green light is issued. Just a few days ago, the National Institute for Health and Clinical Excellence said it was assessing the cost-effectiveness of the drug for treating the low platelet count disorder refractory chronic idiopathic thrombocytopenic purpura under its accelerated approval process.

Earlier this year, results from a pivotal international Phase III study showed that Revolade at 50mg-75mg once daily resulted in a statistically significant increase in platelet counts and also reduced bleeding in adult patients with chronic idiopathic thrombocytopenia purpura, and analysts are already hailing the drug as a potential blockbuster for GSK.