FDA Approves New Treatment for Chronic Hepatitis B

The Food and Drug Administration (FDA) today announced the approval of Hepsera (adefovir dipivoxil) tablets for the treatment of chronic hepatitis B in adults with evidence of active viral replication and either elevations in serum alanine aminotransferase (ALT) or aspartate aminotransferase (AST), or histologically active disease.

Chronic hepatitis B is a serious disease caused by a virus that attacks the liver. The virus, which is called hepatitis B virus (HBV), can cause lifelong infection, cirrhosis (scarring) of the liver, liver cancer, liver failure, and death. According to the Centers for Disease Control and Prevention, approximately 1.25 million Americans are chronically HBV infected.

Hepsera slows the progression of chronic hepatitis B by interfering with viral replication and causing DNA chain termination after its incorporation into viral DNA.

FDA based its approval of Hepsera on the results of two randomized, double-blind, placebo-controlled studies. At week 48 of the studies, 53% of patients receiving Hepsera in one study and 64% of patients in the other study showed significant improvement in the liver inflammation caused by HBV compared to 25% and 35% of patients receiving placebo. A statistically significant improvement in the degree of liver fibrosis (scarring) was observed in the patients who received Hepsera. Moreover, Hepsera has been shown to be effective in treating patients with clinical evidence of HBV that is resistant to another approved antiviral therapy called lamivudine.

The major adverse events associated with the use of Hepsera include severe, acute exacerbation of hepatitis B after discontinuation of Hepsera and kidney toxicity. Patients who have discontinued other approved products for the treatment of chronic hepatitis B have also experienced severe, acute exacerbation of hepatitis. This adverse event occurred in up to 25% of clinical trial participants after discontinuation of Hepsera. The labeling for Hepsera states that patients who discontinue Hepsera should be monitored at repeated intervals over a period of time for hepatic function.

Kidney toxicity was reported in patients at risk of or having underlying kidney dysfunction. In addition, there is a theoretical concern associated with Hepsera that HIV resistance could emerge in chronic hepatitis B patients with unrecognized or untreated HIV infection.

Today's approval follows an August 6, 2002, recommendation by FDA's Antiviral Drugs Advisory Committee.

Gilead Sciences Inc., of Foster City, Calif., is the sponsor of the approved New Drug Application (NDA) for Hepsera.