The FDA is joining regulators in Europe, Turkey, Australia and New Zealand by allowing the drug in U.S. Generically known as tenofovir, the drug is taken in the form of a pill once daily. It works by blocking HBV DNA polymerase, the enzyme that is necessary for the virus to replicate in liver cells.
In April, the European Commission approved Viread to treat chronic hepatitis B. The drug has been available in Europe as a part of combination therapy for HIV infection in adults since 2002, DowJones reported.
Gilead manufactures another hepatitis B drug called Hepsera, which made a profit of 90 million in the first half of 2008. Chronic hepatitis B is the leading cause of liver cancer worldwide and affects an estimated 2 million people in the U.S.
Also on Monday, the 9th U.S. Circuit Court of Appeals in San Francisco reinstated a securities class action lawsuit against Gilead that claimed the drug maker misled investors about demand for Viread by allegedly marketing Viread for unapproved or "off-label" uses.
The appeals court reversed a lower court's decision dismissing the suit filed by disgruntled shareholders in November 2003, saying that investors had failed to prove that their 2003 stock losses were related to the off-label sales.
Gilead's shares were at $57, up 1 percent, in after-hours trading.
