Distribution of plasma tenofovir trough concentrations and associated factors in Japanese patients with HIV-1 receiving bictegravir/emtricitabine/tenofovir alafenamide

Abstract Background Previous studies have suggested a possible association between elevated plasma tenofovir (TFV) concentrations and renal dysfunction in patients receiving TFV disoproxil fumarate (TDF). Although TFV alafenamide fumarate (TAF) is considered to have a more favourable renal safety profile than TDF, few studies have investigated plasma TFV concentrations during TAF therapy, particularly among Asian patients with human immunodeficiency virus (HIV). Methods We investigated patient characteristics, the distribution of TFV trough levels, and correlations of plasma TFV concentrations with estimated glomerular filtration rate (eGFR) and plasma bictegravir (BIC). We determined factors associated with high TFV trough levels in Japanese patients with HIV-1 receiving BIC/emtricitabine/TAF combination (BIC/FTC/TAF). Results This study included 71 patients examined at the Infectious Disease Department of NHO Osaka National Hospital until December 2025, who had plasma TFV and BIC concentrations measured 18–27 h after at least 14 days of BIC/FTC/TAF administration. The median age, eGFR, and plasma TFV trough level were 42 years, 69.0 mL/min/1.73 m 2 , and 17.4 ng/mL (interquartile range: 14.3–24.7), respectively. Plasma TFV trough levels were negatively correlated with eGFR and positively correlated with BIC trough levels (both p < 0.01). In the multivariate analysis, eGFR < 60.0 mL/min/1.73 m 2 (odds ratio [OR], 5.76; p = 0.046) and BIC trough levels at or above the median (OR, 3.83; p = 0.029) were independently associated with higher TFV trough levels. Conclusions These findings provide pharmacokinetic evidence that plasma TFV exposure during BIC/FTC/TAF therapy remained relatively low in Japanese patients with HIV-1 who had normal or mildly impaired renal function.