GlaxoSmithKline (NYSE:GSK) wants now wants approval to use its low platelet drug Promacta to treat hepatitis C patients.

GSK has filed regulatory applications in Europe and the United States to add the new indication to the drug. The drug eltrombopag, which is marketed under the brand name Promacta in the United States and Revolade globally, is approved in 88 countires to treat immune thrombocytopenia, a condition in which a patients has low blood counts because the platelets are destroyed by the patient’s own immune system.

The condition puts patients at the risk of bleeding. Promacta was co-discovered by GSK predecessor SmithKline Beecham and partner Ligand Pharmaceuticals.

The British pharmaceutical giant, which has its U.S. headquarters in Research Triangle Park, is now seeking to expand approval of the drug to increase platelet counts in patients who have chronic hepatitis C virus infection. The drug would allow them to start interferon-based therapy and could also be used to optimize interferon-based therapy, according to to GSK’s supplemental new drug application.

GSK last year completed a phase 3 study of Promacta in hepatitis C patients whose low platelet levels make them unable to start interferon therapy to treat the virus. The trial met the primary endpoint of improving the sustained virological response.

Promacta does come with some safety risks. Until late last year, the U.S. Food and Drug Administration required doctors and patients to follow a strict regimen in order to watch for adverse effects including liver damage, blood clots and bleeding risks after discontinuing the drug. But the FDA eased those requirements concluding that it was unlikely the safety data collected could determine whether adverse effects were caused by the drug or by the immune thrombocytopenia.

While mandatory collection of safety data is no longer required, the agency continues to ask that any adverse events be reported.