Eltrombopag Okayed to Support Interferon Therapy for HCV


November 19, 2012

The US Food and Drug Administration (FDA) today approved eltrombopag (Promacta, GlaxoSmithKline) to treat thrombocytopenia in patients with chronic hepatitis C virus (HCV) infection and thereby help them qualify for interferon-based therapy, the manufacturer announced this morning.

Roughly 4.2 million Americans have chronic HCV infection, and up to 3.5% have platelet counts lower than 75,000/μL, according to GlaxoSmithKline.

"Commonly prescribed interferon-based therapies can worsen the problem of low blood platelet counts," said Paolo Paoletti, MD, president of GlaxoSmithKline Oncology, in a manufacturer's news release. "Today's FDA approval of Promacta gives doctors a tool to address the low platelet challenge. This means more chronic hepatitis C patients may be able to start and stay on interferon-based therapy."

Eltrombopag is already approved to treat thrombocytopenia in patients with chronic immune (idiopathic) thrombocytopenia who have not responded sufficiently to corticosteroids, immunoglobulins, or splenectomy.

The FDA based its decision to expand the indication for eltrombopag on 2 clinical trials involving some 1500 patients with HCV infection whose platelet counts were lower than 75,000/μL, according to the manufacturer. In one trial, patients also received peginterferon alfa-2a (Pegasys, Genentech) plus ribavirin. Patients in the other trial received peginterferon alfa-2b (Pegintron, Merck Sharp & Dohme) plus ribavirin.

The approval comes with some caveats: Clinicians should not prescribe eltrombopag for patients with both HCV and thrombocytopenia to normalize platelet counts, they should prescribe the drug only for patients whose level of thrombocytopenia prevents the start or maintenance of interferon-based therapy, and they should note that clinical trials have not established the safety and efficacy of eltrombopag in combination with direct-acting antiviral agents approved for chronic HCV genotype 1 infection.

The label for eltrombopag bears a boxed warning about the risk for hepatotoxicity. In addition, in combination with interferon and ribavirin, it may increase the risk for hepatic decompensation. Accordingly, clinicians must regularly monitor serum liver tests.

The label also warns that higher platelet counts with eltrombopag may cause thrombotic and thromboembolic complications.

The most common adverse events reported in the 2 clinical trials included anemia, fever, fatigue, headache, nausea, diarrhea, decreased appetite, and influenza-like illness.