In a multicenter, retrospective cohort study, switching from other nucleos(t)ide analogues (NAs) to tenofovir alafenamide (TAF) was found to be effective in improving outcomes among patients with chronic hepatitis B (CHB) and safe for up to 3 years.¹ This study added substantially to the evidence of efficacy and safety of TAF in the real-world setting, supporting its wider adoption in light of the rapidly aging CHB population and increasing the prevalence of aging-related comorbidities.¹

The World Health Organization (WHO) estimated that as many as 296 million people had contracted CHB in 2019.² Apart from increasing the risk of cirrhosis and hepatocellular carcinoma (HCC), CHB is also associated with extrahepatic complications, including kidney diseases such as glomerulonephritis (GN).^2-3 As the CHB population continues to age, renal issues could worsen due to the increasing prevalence of comorbidities, such as hypertension, diabetes mellitus (DM), cardiovascular (CV) diseases, and malignancy, rendering treatment options with renal-preserving benefits ever more important.⁴ TAF, a prodrug of tenofovir, has demonstrated non-inferiority in viral suppression among CHB patients to tenofovir disoproxil fumarate (TDF) with improved renal safety in clinical trials.⁵ A switch to TAF from other NAs has also demonstrated high effectiveness and renal safety for CHB treatment of up to 96 weeks in real-world studies.⁶

This cohort study was conducted to evaluate the long-term effects of switching to TAF from entecavir (ETV), TDF, or a combination of NAs.¹ In the study, 3 groups of patients were considered for the switch, including (i) patients aged >60 years with deteriorating renal functions [estimated glomerular filtration rate (eGFR) <60mL/min/1.73m² or serum phosphate level  <2.5mg/dL] or osteoporosis/osteopenia treated with adefovir (ADF) or TDF; (ii) patients with low-level viremia treated with ETV monotherapy; and (iii) patients who hope to take an NA with food rather than on an empty stomach.¹ CHB patient aged >18 years who had been switched to TAF 25mg monotherapy from at least 2-year course of ETV, TDF, or a combination of NAs were eligible.¹ Follow-up with patients was performed every 12 weeks until at least week 144.¹

Of the 391 patients included in the study, 174 had received prior ETV, 116 had prior TDF and 101 had a prior NA combination.¹ The primary endpoint was the proportion of patients switching to TAF who had hepatitis B virus (HBV) deoxyribonucleic acid (DNA) <10IU/mL at week 144 after the switch, which was achieved by 98.9% (95% CI: 95.6-100), 99.1% (95% CI: 94.8-100) and 99.0% (95% CI: 94.1-99.9) of patients who had been previously treated with ETV, TDF and NA combination therapies, respectively.¹ The antiviral response of TAF was also measured by hepatitis B e antigen (HBeAg) loss, with 23.4% (95% CI: 14.6-35.2) of the HBeAg-positive patients turning negative at week 144.¹ The rates of HBeAg loss were 27.8%, 27.3% and 16.7% in the prior ETV, TDF and NA combination groups, respectively.¹

The biochemical response was analyzed using the alanine aminotransferase (ALT) levels as defined by the American Association for the Study of Liver Diseases (AASLD) criteria.¹ At 144 weeks of the switch, the proportion of patients with a normalized ALT level significantly increased from 78.3% at baseline to about 88.0% (95% CI: 84.4-90.0).¹ Of note, patients who had switched from TDF to TAF (from 72.4% to 85.3%; p=0.016) had a greater positive response than those who switched from ETV to TAF (from 83.3% to 89.1%; p=0.12), respectively).¹

The renal safety profiles differed between NAs (TDF or ADF) and ETV groups after the switchover.¹ The eGFR in the TDF or ADF groups improved in the first year and was significantly different from the ETV group.¹ Moreover, the rate of hypophosphatemia in the TDF or ADF group decreased from 13.4% to 9.7%, while a slight increase was observed in the ETV group (from 2.3% to 5.7%).¹

Among patients with baseline chronic kidney disease (CKD) (mostly stage III CKD), a similarly positive antiviral response and good safety profile of TAF to the overall population were observed after the switch.¹ None of the patients developed stage V CKD during the study period.¹

In conclusion, this study demonstrated the high long-term efficacy and favorable safety profile of TAF among CHB patients who had previously been treated with other NAs, providing clinicians with additional data that facilitate their decision making in clinical practice.¹