In a double-blind study , nucleos ( t ) ide-nave patients with high levels of hepatitis B virus ( HBV ) DNA who were positive for HBeAg and had normal levels of alanine aminotransferase were randomly assigned to groups given either oral tenofovir disoproxil fumarate ( TDF , @ mg ) and placebo ( n = @ ) or a combination of TDF ( @ mg ) and emtricitabine ( @ mg , n = @ ) for @ weeks .