A Phase 3b, Randomized, Double-Blind, Double-Dummy Study Evaluating the Antiviral Efficacy, Safety, and Tolerability of Tenofovir Disoproxil Fumarate (DF) Monotherapy Versus Emtricitabine Plus Tenofovir DF Fixed-Dose Combination Therapy in Subjects With Chronic Hepatitis B Who Are Resistant to Lamivudine

The aim of therapy for the treatment of chronic hepatitis B virus (HBV) is to maintain suppression of viral replication to prevent the emergence of complications, which requires long-term therapy. Durable suppression of viral replication is achieved in the treatment of chronic viral diseases by preventing of the emergence of drug-resistant mutations. The clinical guidelines for the management of lamivudine resistant patients are variable. Some recommend switching to another agent without cross-resistance, while others recommend adding on another agent without cross-resistance. Limited clinical data exists to demonstrate whether tenofovir disoproxil fumarate (tenofovir DF; TDF) is an effective monotherapy for lamivudine resistant patients or if it should be used as part of a combination therapy regimen. This study is designed to evaluate the effectiveness, safety, and tolerability of tenofovir DF monotherapy versus emtricitabine (FTC)/tenofovir DF combination therapy in participants with chronic HBV with lamivudine resistance (presence of the rtM204I/V mutation with or without the rtL180M mutation) over a 240-week period. Participants in this study must be receiving lamivudine treatment at the time of enrollment.