To evaluate various markers of renal function and bone density after the switch to Tenofovir alafenamide fumarate (TAF) in chronic hepatitis B patients who are currently treated with Tenofovir disoproxil fumarate (TDF) .

The investigators have previously reported the prevalence of abnormal renal tubular reabsorption of phosphate among CHB patients treated with more than 18 months of TDF to be 48%. Renal tubular dysfunction associated with TDF may be reversible when TDF is discontinued 4. Recently, TAF 25 mg daily was shown to have comparable efficacy to TDF 300 mg with respect to viral suppression in both HBeAg positive and HBeAg negative CHB patients (studies 110 and 108) at 48 weeks of therapy. As speculated, the systemic exposure to tenofovir was significantly less in patients exposed to TAF compared to those on TDF with strikingly less effects noted in a variety of renal and bone parameters for individuals receiving TAF. Notably, however, the question remains to what if any improvements may be seen in CHB patients switched from TDF to TAF.

The investigators propose a prospective open label study to evaluate various markers of renal function and bone density in 80 CHB patients who are currently treated with TDF who are switched to TAF.

Inclusion Criteria:

• Patients with chronic hepatitis B (who are either HBeAg reactive or non-reactive)
• Treated with TDF with unquantifiable Hepatitis B Virus (HBV) DNA by a sensitive Polymerase chain reaction (PCR) assay for a minimum of 6 months
• No prior nucleos(t)ide exposure prior to treatment with TDF
• Treatment with TDF for a minimum of 12 months

Exclusion Criteria:

• HIV Infection