New Discovery, Inc.

Both tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF) are potent antiviral agents for hepatitis B virus (HBV) and recommended by the American Association for the Study of Liver Disease (AASLD) as well as the European Association for the Study of Liver (EASL) guidelines for the treatment of nucleos(t)ide therapy induced HBV resistance. However, it is not clear if chronic hepatitis B (CHB) patients with nucleos(t)ide treatment experience without genotypic mutations would be benefit from TAF therapy. Previous studies have observed that suboptimal response (SOR) following antiviral therapy with nucleos(t)ide treatment is associated with an increased risk of subsequent treatment failure and viral resistance. It remains unclear whether switching to TAF is a reasonable approach in patients with SOR to second-line antivirals Lamivudine (LAM)/ Telbivudine (LdT)/ Adefovir Dipivoxil (ADV) and its combinations with other second-line antivirals for 24 weeks, or SOR to the first-line antiviral Entecavir (ETV) or any antiviral combinations containing ETV for 48 weeks. This study is aimed to determine how the aforementioned patients with SOR to nucleos(t)ide treatment respond to TAF monotherapy. The investigator's study will provide evidence base for therapy selection in SOR patients, especially in China where the majority of patients with CHB are treated with nucleos(t)ide therapy.

Immunoprophylaxis failure of hepatitis B (HBV) remains a concern and has been reported in approximately 10-30% of infants born to highly viremic mothers with HBeAg-positive. Maternal HBV DNA >6log10 copies/mL (or 200,000 IU/mL) is the major independent risk for mother-to-child transmission (MTCT). Two recent random controlled trial (RCT) studies have shown that the use of Tenofovir Disoproxil Fumarate (TDF) in highly viremic HBsAg positive mothers may safely reduce the rate of MTCT when compared between groups of TDF treated and untreated patients. Tenofovir Alafenamide (TAF) is the successor to TDF, and both drugs have a similar mechanism of action to reduce HBV DNA levels and normalize serum alanine aminotransferase (ALT) in chronic hepatitis B patients (CHB) with few adverse effects. TAF however, has a better safety profile with less adverse effects to bone mineral density and renal function. The present prospective, double-arm study is to evaluate the non-inferiority in the efficacy and safety of TAF therapy versus TDF therapy in highly viremic mothers and their infants for the prevention of MTCT in the real world setting.

Mother-to-child transmission is the main route of transmission of Hepatitis B Virus (HBV) in China, and about 30% - 50% of chronic HBV carriers are infected by this. Although the current hepatitis B vaccine combined with hepatitis B immunoglobulin scheme has achieved excellent results, about 5% - 10% of infants born to chronic hepatitis B (CHB) mothers are still infected. A pregnant women's blood hepatitis B virus load ≥ 2 × 10^5 IU/mL before delivery is the main risk factor for transmission prevention failure. Two recent random controlled trial (RCT) studies have shown that the use of Tenofovir Disoproxil Fumarate (TDF) in highly viremic HBsAg positive mothers may safely reduce the rate of MTCT in comparisons between groups of TDF treated and untreated patients. Tenofovir Alafenamide (TAF) is the successor to TDF, and both drugs have a similar mechanism of action to reduce HBV DNA levels and normalize serum alanine aminotransferase (ALT) in chronic hepatitis B patients (CHB). TAF however, has a better safety profile with less adverse effects to hip and spine bone mineral density and renal function. Currently, TAF has been approved by the State Food and Drug Administration and marketed in China in December 2018. On the drug label, it has been suggested that TAF may be considered during pregnancy if necessary. However, it has not been reported whether the application of TAF in pregnant women can achieve better effects and safety in prevention of mother-to-child transmission. This prospective, triple arm, multicenter study seeks to evaluate the efficacy and safety of TAF in the prevention of mother-to-child transmission as compared to a retrospective cohort of mothers who were treated with TDF.