A Food and Drug Administration (FDA) staff review of Merck & Co.'s proposed hepatitis C drug boceprevir has raised safety concerns about anemia and other blood disorders, The Wall Street Journal reported Tuesday.

But the review also said it agreed with Merck's analysis showing adding boceprevir to other drugs currently used to treat hepatitis C was significantly more effective at treating the condition. Broadly, two studies submitted to the FDA in support of boceprevir showed more patients responded to treatment by achieving a so-called sustained virologic response.

However, certain groups such as African-Americans and patients with more advanced hepatitis C did not respond as well.
Boceprevir faces a review by the FDA's Antiviral Drugs Advisory Committee on Wednesday. A similar product, telaprevir, from Vertex Pharmaceuticals Inc., will be reviewed by the panel on Thursday. Both drugs are widely expected to be recommended for approval, as they have shown strong effectiveness in improving the cure rates in patients that use standard therapy for the liver disease. Both drugs are known as protease inhibitors, which are designed to block an enzyme that helps the hepatitis C virus replicate.

Hepatitis C is a liver disease caused by infection with the hepatitis C virus, which is spread when the blood of an infected person enters the body of someone previously not infected. About 3.2 million Americans are infected with hepatitis C.

The FDA advisory panel is being asked to vote on whether it thinks the available data support the approval of boceprevir. The vote will amount to a recommendation about whether the panel thinks the agency should approve the product. The FDA is not required to follow the advice of its advisory panels but usually does.

Merck, in a document also posted on FDA's website, said boceprevir "fulfills a significant unmet medical need" for the treatment of hepatitis C infection. Merck has proposed a brand name of Victrelis for boceprevir.

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