Gilead Sciences has received U.S. Food and Drug Administration (FDA) approval on Friday, September 20 for its antiviral agent Hepsera (adefovir dipivoxil) for the treatment of chronic hepatitis B.

Hepsera, administered as an oral 10 mg tablet, is the first nucleotide analogue to receive FDA approval for the treatment of chronic hepatitis B. It works by blocking the replication of the hepatitis B virus (HBV) in the body. In clinical studies, Hepsera treatment was associated with significant improvements in liver histology and fibrosis, reduction in serum HBV DNA levels, increased rates of seroconversion and normalization of alanine aminotransferase (ALT) levels as compared to placebo in treatment-naïve patients and in patients with prior interferon experience.

These pivotal studies included patients with compensated liver function and either "e" antigen-positive (HBeAg-positive) or "e" antigen-negative (HBeAg-negative, or precore mutant) chronic hepatitis B. Hepsera is the first drug for which efficacy has been demonstrated in HBeAg-negative patients in a 48-week double-blind, placebo-controlled study. The drug was studied and proven effective in patients who were treated with and developed resistance to lamivudine, including patients wait-listed for or who had received a liver transplant. Mutations associated with resistance to Hepsera have not been identified through 48 weeks of treatment in pivotal studies (n=467).

This is the second FDA approval for a novel Gilead antiviral in less than one year. Viread (tenofovir disoproxil fumarate), the company''s antiretroviral agent for the treatment of human immunodeficiency virus (HIV) infection, was approved in the United States in October 2001 and in the European Union in February 2002. In March 2002, Gilead submitted a Marketing Authorization Application for adefovir dipivoxil for the treatment of chronic hepatitis B to the European Medicines Evaluation Agency. That application currently is under review.