This is a multicenter, single arm, open label, historical control pilot Study to the antiviral efficacy and safety of Suboptimal Responders to Entecavir Switching to TAF Treatment at week 48 (investigate the rates of complete virological response on switching to TAF in patients with Suboptimal response or ETV intolerance to standard ETV= 0.5 mg monotherapy).

Inclusion Criteria:

1. Must have the ability to understand and sign a written informed consent form, which must be obtained prior to initiation of study procedures;
2. Male and female subjects,18 years of age and older, based on the date of the screening visit;
3. Suboptimal Responders to Entecavir (defined as CHB patients treated with at least 12 months of ETV 0.5mg QD with prior suboptimal response viral load still detectable at week 48).
4. ETV intolerance population (defined as unwilling or poor adherence to administer ETV in fasting food, renal impairment with ETV dosage adjustment required, pts with other unidentified reasons willing to switch, etc);
5. Screening serum ALT level ≤ 10 × ULN;
6. Normal ECG (or if abnormal, determined by the Investigator not to be clinically significant);
7. Must be willing and able to comply with all study requirements.

Exclusion Criteria:

1. Pregnant women, women who are breastfeeding or who believe they may wish to become pregnant during the course of the study;
2. Co-infection with HCV, HIV, or HDV;
3. Any history of, or current evidence of, clinical hepatic decompensation (i.e., moderate-severe ascites, encephalopathy or variceal hemorrhage);
4. Evidence of hepatocellular carcinoma (e.g. as evidenced by recent imaging);
5. Abnormal hematological and biochemical parameters, including: Hemoglobin < 10 g/dl, Absolute neutrophil count < 0.75×109/L, Platelets ≤ 50×109/L, AST or ALT > 10 × ULN, Total bilirubin > 2.5 × ULN, Albumin < 3.0 g/dl, INR > 1.5 × ULN;
6. Received solid organ or bone marrow transplant;
7. Recent history of pancreatitis (within 24 weeks prior to the first dose of study medication);
8. Evidence of other autoimmune or metabolic liver diseases (except non-alcoholic fatty liver disease);
9. Significant renal, cardiovascular, pulmonary, or neurological disease in the opinion of the investigator;
10. Malignancy within the 5 years prior to screening, with the exception of specific cancers that are cured by surgical resection(basal cell skin cancer, etc). Subjects under evaluation for possible malignancy are not eligible;
11. Known hypersensitivity to study drugs, metabolites, or formulation excipients;
12. Current alcohol or substance abuse judged by the investigator to potentially interfere with subject compliance;
13. Any other clinical condition or prior therapy that, in the opinion of the investigator, would make the subject unsuitable for the study or unable to comply with dosing requirements.