Pharmacokinetics of Tenofovir Alafenamide, Tenofovir, and Emtricitabine Following Administration of Coformulated Emtricitabine/Tenofovir Alafenamide in Healthy Japanese Subjects

First-In-Human Study on Pharmacokinetics, Safety, and Tolerability of Single and Multiple Escalating Doses of Hepenofovir, a Novel Hepatic Targeting Prodrug of Tenofovir in Healthy Chinese Subjects

Objective: Hepenofovir, a novel hepatic targeting prodrug of tenofovir, has been developed for the treatment of chronic hepatitis B (CHB). This is a first-in-human study to evaluate the pharmacokinetics (PK) and tolerability of single and multiple escalating doses of hepenofovir in healthy Chinese subjects. Methods: This phase Ia study included two parts: a double-blinded, randomized, placebo-controlled single-ascending-dose (SAD) (25-200 mg) study under fasted conditions comprising a food-effect investigation (200 mg) and a multiple-ascending-dose (MAD) (25 mg) study under fasted conditions. Results: Hepenofovir was well tolerated in healthy Chinese subjects. There was no significant difference in adverse reaction rates between hepenofovir and placebo groups. Hepenofovir was rapidly absorbed and metabolized into tenofovir after dosing. In healthy participants, the median Tmax of hepenofovir and tenofovir was 0.33-0.50 h and 0.62-0.75 h, respectively, and their mean half-life was 2.5-12.3 h and 49.7-53.8 h, respectively. Systemic exposure to tenofovir increased in proportion to the dose. The mean accumulation indexes of hepenofovir and tenofovir were 1.1 vs. 1.8. Moreover, food could reduce the Cmax of both hepenofovir and tenofovir, but did not affect their area under the curve (AUC). Conclusions: Hepenofovir has shown a favorable safety and PK profile, which support the further evaluation of its safety and efficacy in CHB patients. Clinical trial registration number: The trial is registered at Chinese Clinical Trial website (http://www.chinadrugtrials.org.cn/index.html # CTR20191953).

Effect of switching from tenofovir disoproxil fumarate to tenofovir alafenamide on estimated glomerular filtration rate slope in patients with HIV: A retrospective observational study

INTRODUCTION

There is limited data on the effects of switching from tenofovir disoproxil fumarate (TDF) to tenofovir alafenamide (TAF) on estimated glomerular filtration rates (eGFR) slope in patients with human immunodeficiency virus (HIV) infection. This study aimed to compare the eGFR slope when administering TDF and TAF and to investigate the predictors of improvement in eGFR slope after switching from TDF to TAF.

METHODS

We conducted a single-center, retrospective, observational study in Japanese patients with HIV infection who switched the antiretroviral drug from TDF to TAF. eGFR was calculated using serum cystatin C. The eGFR slope was defined as the regression coefficient between eGFR and time. Differences between eGFR slope during TDF and TAF administration were compared using Wilcoxon signed rank test. A stepwise logistic regression model was used to examine the associations between improvement of eGFR slope after switching from TDF to TAF and various parameters.

RESULTS

Overall, 63 patients (656 eGFR) were included in the analysis. The median analyzed durations of TDF and TAF exposures were 1.6 and 1.5 years, respectively. There were no significant differences between eGFR slope during TDF and TAF periods (median: 0.6 vs. 4.0 mL/min/1.73 m²/year, p = 0.165). The eGFR slopes during the TDF period and while switching from TDF to TAF were independent predictors of improvement in eGFR slope after switching from TDF to TAF.

CONCLUSIONS

The results suggest that patients with poor renal function and those with progressive worsening during TDF administration would benefit from switching to TAF.

Can remdesivir and its parent nucleoside GS-441524 be potential oral drugs? An in vitro and in vivo DMPK assessment

Remdesivir (RDV) is the only US Food and Drug Administration (FDA)-approved drug for treating COVID-19. However, RDV can only be given by intravenous route, and there is a pressing medical need for oral antivirals. Significant evidence suggests that the role of the parent nucleoside GS-441524 in the clinical outcomes of RDV could be largely underestimated. We performed an in vitro and in vivo drug metabolism and pharmacokinetics (DMPK) assessment to examine the potential of RDV, and particularly GS-441524, as oral drugs. In our in vitro assessments, RDV exhibited prohibitively low stability in human liver microsomes (HLMs, t_1/2 = ∼1 min), with the primary CYP-mediated metabolism being the mono-oxidation likely on the phosphoramidate moiety. This observation is poorly aligned with any potential oral use of RDV, though in the presence of cobicistat, the microsomal stability was drastically boosted to the level observed without enzyme cofactor NADPH. Conversely, GS-441524 showed excellent metabolic stability in human plasma and HLMs. In further in vivo studies in CD-1 mice, GS-441524 displayed a favorable oral bioavailability of 57%. Importantly, GS-441524 produced adequate drug exposure in the mice plasma and lung, and was effectively converted to the active triphosphate, suggesting that it could be a promising oral antiviral drug for treating COVID-19.