FDA Updates Warning Label for Hepatitis C Antiviral Drug

The Food and Drug Administration has updated a drug warning label and medication guide for Victrelis (boceprevir) after receiving reports of abnormally low levels of red and white blood cells in patients who received it as a combination drug for treatment of hepatitis C.

Serious cases of pancytopenia, a reduction in the number of red and white blood cells and blood platelets, have been reported postmarketing in patients receiving Victrelis (boceprevir), a pill taken three times a day in combination with peginterferon alfa, an injectable drug, and ribavirin, FDA officials reported. Such triple therapy has been shown to increase sustained virological response in patients with chronic hepatitis C; however, severe side effects such as the potential for anemia are associated with the regimen.

Hepatitis C virus (HCV) is the most common chronic blood borne infection in the United States with approximately 3.2 million people infected, according to CDC estimates. The disease causes inflammation of the liver and can lead to cirrhosis of the liver and liver failure.

In mid-2011, the FDA approved boceprevir to treat certain adults with chronic HCV (genotype 1) in combination with peginterferon alfa and ribavirin. A protease inhibitor that works by binding to the virus and preventing it from multiplying, the drug boceprevir is sold under the trade name Victrelis and is a product of Merck Sharp & Dohme Corp. It was the first direct acting antiviral drug for HCV to be FDA approved.

The safety and effectiveness of Victrelis (boceprevir) was evaluated in two phase 3 clinical trials with 1,500 adult patients. In both trials, two-thirds of patients receiving Victrelis (boceprevir) in combination with pegylated interferon and ribavirin experienced a significantly increased sustained virologic response (ie, the hepatitis C virus was no longer detected in the blood 24 weeks after stopping treatment), compared to pegylated interferon and ribavirin alone, according to an FDA press release issued at the time of approval.

Data from the clinical trials indicated that the most commonly reported side effects in patients receiving boceprevir in combination with pegylated interferon and ribavirin were fatigue, low red blood cell count (anemia), nausea, headache and taste distortion (dysgeusia).

The recent FDA mandate requires that additional information be included in the drug’s label Section 5 Warnings and Precautions section. It states that complete blood counts (with white blood cell differential counts) should be obtained at pretreatment, and at Treatment Weeks 2, 4, 8, and 12, and should be monitored closely at other time points, as clinically appropriate.

The drug label update includes additions of agranulocytosis, pancytopenia, thrombocytopenia, pneumonia and sepsis to Section 6.2, adverse events experienced by patients postmarketing, and corresponding updates to the package insert medication guide for patients.

The FDA has said that the Victrelis (boceprvir) medication guide will also be updated. The updated Victrelis (boceprevir) label can viewed here.