Switching from tenofovir disoproxil fumarate to tenofovir alafenamide fumarate in a cohort of patients with HBV infection: A retrospective study

Background

Tenofovir disoproxil fumarate (TDF) as first-line therapy for chronic HBV infection is related to nephrotoxicity. Tenofovir alafenamide fumarate (TAF) has been approved with a similar virological and serological response, but lower toxicity. TAF is available for older patients, with bone or kidney impairment.

Methods

The primary objective was the evaluation of renal function modification in patients who are switching from TDF to TAF; secondary objective was the use of urinary concentration of tenofovir (TFV) as early marker of renal function improvement or worsening.

Retrospective study including all HBV patients treated with TDF or TAF. Two groups were selected: patients who are switched from TDF to TAF and who continued with TDF. Follow-up was six months.

Results

42 subjects were included; 17 were in TAF group (40 %) and 25 in TDF group (60 %). In TDF group, no estimated glomerular filtration rate (eGFR) improvement was observed, while in TAF group increased by 9 ml/min (p < 0.001). Urinary TFV levels increased by 3 ng/mL in TDF group and decreased by 4.5 ng/mL in TAF group (p < 0.001). The relationship between the eGFR and urinary TFV resulted in reverse proportionality (R² = -0.740, p = 0.001) between the two variables. In multivariate analysis eGFR (β = 0.880, p = 0.043) and pretreatment wit adefovir dipivoxil (ADV) resulted significantly related to TFV urinary excretion.

Conclusions

Switching from TDF to TAF lead to significant improvement in eGFR and lower toxicity (estimated with TFV urinary excretion) at six months of follow-up. ADV pretreatment should be considered as adjunctive risk factor for nephrotoxicity independently from age and eGFR.