WASHINGTON -- The U.S. Food and Drug Administration said on Tuesday it had approved Roche holding AG's Pegasys drug in combination with another anti-viral compound to treat hepatitis C, a potential blockbuster product for the Swiss-based company, Reuters reported.

Up to 4 million Americans are estimated to be infected with the hepatitis C virus that slowly attacks the liver and sometimes kills.

An FDA advisory panel last month unanimously recommended approval of Pegasys in combination with the antiviral drug ribavirin. The FDA normally follows the recommendations of its advisory panels.