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 , 300 mg ) and placebo ( n = 64 ) or a combination of TDF ( 300 mg ) and emtricitabine ( 200 mg , n = 62 ) for 192 weeks .