Gilead Sciences Inc, Foster City, CA, USA.
Gilead Sciences Inc, Foster City, CA, USA.
Anal Biochem. 2020 Mar 15;593:113611. doi: 10.1016/j.ab.2020.113611. Epub 2020 Feb 5.
Tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF) are both tenofovir (TFV) prodrugs, with the same active intracellular metabolite, TFV-diphosphate (TFV-DP). TAF delivers TFV-DP to target cells more efficiently and at lower doses than TDF, thereby substantially reducing systemic exposure to TFV, which results in improved bone and renal safety relative to TDF. As such, the method developed for the determination of TFV following TAF administration involved two key differences from determination of TFV following TDF administration. First, human plasma samples (500 μL) immediately upon collection were treated with 20% formic acid (40 μL) (plasma: formic acid ratio of 100:8) to minimize hydrolysis of TAF to TFV, and thereby avoided overestimation of TFV concentrations. Second, various TFV validation tests were conducted in the presence of TAF to mimic the high TAF:TFV ratios in clinical samples collected within ~2 h after dosing. The method for determination of TFV was developed and validated at a US lab and followed FDA and EMA guidelines. To support global clinical studies of TAF, the method was cross-validated (one-way) between the US lab and a China lab and was successfully used for TFV determination in plasma samples from a clinical study that involved healthy Chinese subjects.
富马酸替诺福韦二吡呋酯（TDF）和替诺福韦艾拉酚胺（TAF）均为替诺福韦（TFV）前药，具有相同的活性细胞内代谢物，替诺福韦二磷酸（TFV-DP）。TAF 比 TDF 更有效地将 TFV-DP 递送至靶细胞，且剂量更低，从而大大降低了全身暴露于 TFV 的水平，与 TDF 相比，改善了骨骼和肾脏安全性。因此，与 TDF 给药后测定 TFV 的方法相比，TAF 给药后测定 TFV 的方法有两个关键区别。首先，收集人血浆样品（500μL）后立即用 20%甲酸（40μL）（血浆：甲酸比为 100:8）处理，以尽量减少 TAF 向 TFV 的水解，从而避免高估 TFV 浓度。其次，在存在 TAF 的情况下进行了各种 TFV 验证测试，以模拟在给药后约 2 小时内采集的临床样品中的高 TAF:TFV 比值。TFV 的测定方法在美国实验室开发和验证，并遵循 FDA 和 EMA 指南。为了支持 TAF 的全球临床研究，该方法在美国实验室和中国实验室之间进行了交叉验证（单向），并成功用于涉及健康中国受试者的临床研究中的血浆样品中 TFV 的测定。
