US regulators have expanded the approval of GlaxoSmithKline/Ligand Pharmaceuticals' Promacta to treat thrombocytopaenia (low platelet count) in patients with chronic hepatitis C (HCV). 

According to GSK, Promacta (eltrombopag) is the first supportive treatment for HCV patients who are unable to take or unlikely to benefit from interferon-based therapy due to a low blood platelet count, as this form of therapy can actually magnify the problem.

The US Food and Drug Administration's green light now gives healthcare professionals a means to tackle low platelet in patients with HCV, paving the way for a greater number of to take interferon-based therapy, and thus offering "a better chance to achieve a viral cure", said Paolo Paoletti, president of GlaxoSmithKline Oncology. 

Promacta is a thrombopoietin receptor agonist which has received regulatory clearance in 90 countries (and is also sold as Revolade) as a treatment for thrombocytopenia in patients with chronic immune (idiopathic) thrombocytopenic purpura.

The decision to expand its scope to patients with chronic HCV was based on data from the Phase III ENABLE 1 and 2 trials, which collectively enrolled 1,521 HCV patients with low blood counts and showed that the combination of Promacta and interferon-based therapy induced significant improvements in sustained virological response versus placebo.


However, the use of Promacta is not without safety issues. The drug can cause hepatotoxicity when used in combination with interferon and ribavirin in patients with chronic HCV, and may increase the risk of liver decompensation.

Therefore, patients receiving the drug must be regularly monitored with serum liver tests, and GSK also stressed that Promacta should not be used to attempt to normalise platelet counts.

Investors welcomed the news; shares in Ligand, which developed the drug, were up almost 15% in late-afternoon trading on the Nasdaq.

Around 4.2 million people in the US alone are thought to have chronic HCV, and analysts have estimated sales of more than $3 million for Promacta in 2013.