Primary Objective:

To describe rate of persistence and/or improvement of viral suppression with TAF as with previous anti-HBV (hepatitis B virus) treatment

Secondary Objective(s):

1. Describe persistence of ALT (alanine aminotransferase) normalization and/or improvement of ALT levels with TAF as with previous anti-HBV treatment
2. To describe trends in serum creatinine and calculated creatinine clearance as available by local labs.
3. To describe trends in bone mass from baseline to 24 months after switch.

https://med.stanford.edu/nguyenlab/clinical-trials.html

Inclusion criteria:

1. Male or female, age ≥18 years
2. Chronic hepatitis B diagnosis confirmed by positive HBsAg or HBV DNA or HBeAg or documented history of chronic hepatitis B in physician note
3. Currently maintained on antiviral therapy for at least 48 weeks with any Hepatitis B virus(HBV) DNA value at Screening/Baseline and planned to be switched to TAF by their physician
4. Routinely monitored for serum HBV DNA Polymerase chain reaction(PCR), liver chemistry including Aspartate aminotransferase (AST )/alanine transaminase(ALT)/total bilirubin, renal chemistry including Blood urea nitrogen(BUN)/Creatinine/Carbon dioxide (CO2) by their physicians every 3-6 months and a bone density scan at least every 2 years as per routine clinical care (one at baseline and one 2 years after switch).
5. Estimated creatinine clearance > 15 ml/min (using the Cockcroft-Gault method) at Screening/Baseline Visit. (Note: multiply estimated rate by 0.85 for women).
6. Willing and able to provide informed consent
7. Able to comply with dosing instructions for study drug administration and able to complete the study schedule of assessments

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. Previous recipient of a liver transplant
3. Co-infection with human immunodeficiency virus (HIV) or hepatitis C (HCV) or hepatitis D (HDV)
4. Severe or uncontrolled comorbidities
5. Current or known hepatic decompensation (≤2 years) (e.g ascites, encephalopathy, or variceal hemorrhage) with a Child-Pugh score of B or C
6. Malignancy including liver cancer within 5 years except cancers curable by surgical resection (e.g. basal cell skin cancer and squamous cell cancer)
7. On any of the disallowed concomitant medications listed in the prior and concomitant medications list (pg. 11). Subjects on prohibited medications who are otherwise eligible will need a wash out period of at least 30 days prior to the Screening/Baseline visit.
8. Males and females of reproductive potential who are unwilling to use "effective" protocol-specified method(s) of contraception during the study.
9. Current substance or alcohol abuse judged by the investigator to potentially interfere with subject compliance.
10. Any other clinical conditions that, in the opinion of the Investigator, would make the subject unsuitable or unable to comply with any of the study procedures