Tenofovir intracellular concentration as Tenofovir alafenamide in Bictegravir-including versus Dolutegravir-including antiretroviral regimens

Tenofovir intracellular concentration as Tenofovir alafenamide in Bictegravir-including versus Dolutegravir-including antiretroviral regimens | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 6 April 2026 V1 Latest version Share on Tenofovir intracellular concentration as Tenofovir alafenamide in Bictegravir-including versus Dolutegravir-including antiretroviral regimens Authors : Micol Ferrara 0000-0003-0377-9630 [email protected] , Viviana Maccario , Silvia Fantino , Erica Clemente , Federica Barrera , Alice Palermiti , Sara Soloperto , Amedeo De Nicolò 0000-0002-5973-9948 , Antonio D'Avolio 0000-0002-1321-4126 , Giovanni Di Perri , and Stefano Bonora Authors Info & Affiliations https://doi.org/10.22541/au.177547173.39036280/v1 181 views 83 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract This study investigates intracellular (IC) exposure to tenofovir alafenamide (TAF) and its clinical determinants in experienced people living with HIV. We conducted a monocentric retrospective analysis of 86 adults treated with either Bictegravir (BIC) or dolutegravir (DTG) triple regimen. Plasma and IC trough concentrations (C trough ) of tenofovir diphosphate (TFV-DP) were examined in relation to demographic and renal parameters. A significant correlation emerged between plasma and IC TFV-DP C trough . Higher plasma TFV-DP levels were associated with older age and reduced estimated glomerular filtration rate. Adherence calculated as proportion pf days covered (PDC) did not differ between regimens. These findings provide novel real‑world insights into IC TFV pharmacokinetics and suggest that BIC‑containing regimens may enhance IC drug accumulation and virological outcomes. Prospective studies are needed to clarify the clinical implications of intracellular antiretroviral concentrations. Introduction Tenofovir Alafenamide Fumarate (TAF) is the most recent TFV prodrug, showed to improve several aspects in the long-term safety of the previously developed TFV prodrug, Tenofovir Disoproxil Fumarate (TDF) 1,2 . The latter is associated with higher TFV plasma concentrations due to weak link with disoproxil fumarate salt, and TFV plasma exposure has been recognised as a renal and bone toxicity determinant 3 . A strategic difference of TAF from TDF is its greater plasma stability as alafenamide salt. This property is associated to a much more selective distribution of TFV into cells 2,4 . The latter is driven by cell richness in carboxy-esterase 1 (CES1), as it occurs in case of first-pass metabolism by hepatocytes, and catepsin A (CatA) expressing PBMCs 4 . Tenofovir is subsequently intracellularly activated to tenofovir-diphosphate, that inhibits HIV replication competing with the natural substrate, deoxyadenosine 5’-triphosphate for incorporation within DNA during the HIV transcription phase. The plasma half-life of TAF is 0.51 hours, while TFV free of the alafenamide salt has a T/2 of >32 hours. The intracellular T/2 of the active phosphorylated (TFV-DP) moiety is 69 hours. Thus, the improvement of TAF over TDF took place in two directions, as more drug is made available in target cells and less drug is present in the systemic circulation where its higher concentration may be harmful. Yager et al., in HIV-negative persons, that TAF produced 6.7 to 7.3-fold higher TFV-DP in PBMC vs. TDF across adherence levels, supporting increased potency and pharmacologic forgiveness with F/TAF in the PBMC compartments 5 . In all phase 3 clinical trials and real-life studies, on the other side, TAF-containing regimens showed to be not associated with significant bone and renal toxicity as opposite to TDF-based. However, data of intracellular pharmacokinetics (PK) of TAF in PLWHs are quite scarce, and so far there are no comparative evaluation between different TAF-based regimens. Andreatta et al, for instance, showed higher efficacy of Bictegravir/tenofovir alafenamide/emtricitabine (BIC/F/TAF) regimen as compared to 2 nucleotide retrotranscriptase inhibitors (NRTIs) + Dolutegrvair (DTG) regimen (of whom 46% TAF-containing) in participants with suboptimal compliance from pooled PHASE III study, but no PK data are available 6 . Therefore, aim of our study was to evaluate intracellular TFV PK in the clinical setting, when TAF was dose in different association with BIC or DTG. Methods In a monocentric, cross-sectional study, experienced adult participants administered with BIC/TAF/FTC as a single tablet regimen (STR) or once daily TAF/FTC + DTG as two-pill regimen were enrolled at our centre, after informed consent given. Main inclusion criteria were to be administered with the TAF-based treatments since at least 6 months, self-reported adherence of not misses doses in last week, proportion of days covered (PDC) by Pharmacy refill more than 90% in last 3 months, regular follow-up and virological and clinical assessment. Plasma sample were collected at the end of dosing interval (24+/-4 hours after las drugs intake), after a median of 9,5 (7,2-11,7) months since start of therapies: 6,5 (4,5-8,4) for B/F/TAF and 18,4 (13,0-24,0) months for F/TAF + DTG respectively. Plasma and IC TFV-DP (as TAF) concentrations as C trough were measured by means of UHPLC-MSMS validated method 7 . Non-compartmental PK parameters were expressed as geometric mean (CI95%). Concomitantly with TFV plasma and IC result we measured BIC, DTG and FTC plasma PK comparing our results with historical data. Pharmacy refills were used to calculate the proportion of days covered (PDC) as follows: total number of ART tablets, for complete ART regimen, dispensed within the respective timeframe divided by the number of timeframe and days multiplied by 100% 8 . Participants’ characteristics were compared by Mann-Whitney and Spearman’s test, as appropriate. Results A total of 86 participants were included in the present study. 71 of them were male (83%) with a mean age of 51 years (48-53) and a mean body mass index (BMI) of 26.3 kg/m2 (22.8-29.8). Sixty-one individuals, (71%) were administered with TAF/FTC/BIC regimen, while the remaining 25 (29%) were treated with TAF/FTC plus DTG. Viral load was observed to be undetectable (<20 cp/mL) in 65 participants (76%), while 14 (16%) were naïve to ART and the remaing 7 had a detectable viral load between 20 and 200 cp/mL in low level viremia, defined as two consecutive detectable viral load. In Table 1 demographic and clinical characteristics of the participants are depicted. Geometric mean TFV plasma C trough dosed with BIC or DTG showed to be 14.9 (13.3-16.6) and 10.7 (7.8-13.6) ng/mL, respectively, with a statistically significant difference (p=0.001). Similarly, TFV IC C trough resulted significantly higher in the BIC-based regimen group compared to the DTG group: 327.5 (283.0-372.0) and 144.6 (76.1-213.1) ng/mL (p<0.001), respectively. TFV IC/plasma ratio resulted also higher in the BIC-treated participants: 23.1 (19.9-26.3) vs. 13.9 (7.4-20.4) (p<0.001). TFV PK data are reported in Figuer 1. BIC, DTG and FTC plasma concentrations were found to be 3238,2 (2760,5-3715,8) ng/mL, 1128,6 (826,1-1431,1) ng and 146,4 (101,0-191,8) ng/mL. In particular FTC was reported to be 150,3 (85,5-215,0) ng dosed in BIC and 138,5 (90,5-186,6) ng/mL in DTG arm respectively (p=0,476) and consistent with previously reported literature values, confirming the expected drug exposure profiles (Tab.2) In the overall evaluated population, TFV plasma C trough showed a positive correlation with age (0.432, p<0.001) and serum creatinine (0.380, p=0.001), while an inverse correlation was found with estimated glomerular filtration rate (eGFR) (-0.453, p<0.001). No correlation was observed between TFV plasma C trough and BMI. Discussion This study is the first one exploring TFV plasmatic and intracellular pharmacokinetics when TAF is combined with BIC or DTG in the real-life clinical setting, TFV plasma exposure resulted to be higher when dosed with BIC as compared with DTG, however the difference of concentrations (geometric means 14.9 vs 10.7 ng/ml) reached statistical significance but a real clinical impact is difficult to foresee due to very low level of exposure in both cases. However, possible bias of adherence could explain this finding or some unknown difference in term of absorption. Observations at the intracellular level are especially noteworthy. TFV-DP accumulation in PBMCs was different in the two groups, resulting 2.26-fold higher with BIC as compared to DTG. Previous data on intracellular TFV-DP with BIC/F/TAF are scarce and not methodologically comparable 9 and the same for DTG-based 10,11 . In clinical terms, multiple randomized controlled trial and real word studies have directly compared BIC/F/TAF and DTG plus TAF/FTC, showing no evidence in terms of efficacy 12–15 and in current guidelines BIC- and DTG-based regimen are considered as preferred first line options without superiority of one over the other when combined with TAF. However, in trial or ordinary use of fully active highly potent antiretroviral regimen it not possible find out differences of efficacy due to somewhat lower TFV-DP intracellular exposure. In conditions, instead, where appropriateness of drugs exposure is challenged, e.g. forgiveness of the regimen in patients with suboptimal adherence, higher TFV-DP exposure could play a role. In the above cited analysis of pooled phase III trials by Andreatta et al., BIC/F/TAF showed to be significantly more effective as compared to 2NRTI + DTG, in patients with low adherence (below 85%): in nearly the half of the latter 46% the regimen was TAF/FTC plus DTG, and longer forgiveness of the former is supposed to be a key factor to explain the finding 6 . Our work could have limitations. A bias could be the comparison between a STR, leading to simultaneous intake of drugs, and a 2-pill regimen, potentially allowing non simultaneous intake and/or selective suboptimal adherence. However optimal and balanced bot self-reported adherence and Hospital Pharmacy refill PDC have been registered. Moreover, two considerations appear to considerably counteract the risk of unbalanced adherence. Firstly, DTG, BIC plasma pharmacokinetics are consistent with previous report (Tab. 2), suggesting expected adherence of BIC-based STR on one side, and expected intake of at least DTG pill in the other group. According to this, however, intake of F/TAF could have been not simultaneous with DTG or not regular. On this point, however, IC/plasma ratio resulted higher in the BIC-treated participants by 61% (23.1 vs. 13.9) (Tab. 2). This suggests some unknown biological reason increasing the access or activation of TFV in the cell when dosed with BIC or limiting the effects with DTG. In case of selective suboptimal adherence to TAF/F with DTG, as above speculated as a potential bias, it would not have been expected such dramatic change of IC/plasma ratio. In our pharmacokinetics, cross sectional study, TFV-DP accumulation in PBMCs resulted significantly and markedly higher when TAF is included in BIC-based regimen as compared to DTG-based regimen. This finding could affect TAF activity in terms of regimen forgiveness, or other characteristics that deserve further evaluation. Acknowledgements: M.F. and S.B. conceived the study planned the experiments and contributed to the interpretation of the results. V.M. provided help and support in editing and writing. All authors provided critical feedback and helped shape the research analysis and manuscript. Conflict of interest statement: The authors declare there are no conflicts of interest. Funding information : Funding for this publication was provided by unconditional grant by GILEAD Sciences References 1. Di Perri G. Tenofovir alafenamide clinical pharmacology. Infezioni in Medicina . 2021;29(4). doi:10.53854/liim-2904-4 2. Wassner C, Bradley N, Lee Y. A Review and Clinical Understanding of Tenofovir: Tenofovir Disoproxil Fumarate versus Tenofovir Alafenamide. Journal of the International Association of Providers of AIDS Care (JIAPAC) . 2020;19. doi:10.1177/2325958220919231 3. Podany AT, Bares SH, Havens J, et al. Plasma and intracellular pharmacokinetics of tenofovir in patients switched from tenofovir disoproxil fumarate to tenofovir alafenamide. AIDS . 2018;32(6):761-765. doi:10.1097/QAD.0000000000001744 4. Kearney BP, Flaherty JF, Shah J. Tenofovir Disoproxil Fumarate. Clin Pharmacokinet . 2004;43(9):595-612. doi:10.2165/00003088-200443090-00003 5. Yager J, Brooks KM, Brothers J, et al. Pharmacokinetics of Emtricitabine/Tenofovir Disoproxil Fumarate Among Transgender Adolescents and Young Adults Without HIV Receiving Gender Affirming Hormones. AIDS Res Hum Retroviruses . 2022;38(11):840-846. doi:10.1089/aid.2022.0043 6. Andreatta K, Sax PE, Wohl D, et al. Efficacy of bictegravir/emtricitabine/tenofovir alafenamide versus dolutegravir-based three-drug regimens in people with HIV with varying adherence to antiretroviral therapy. Journal of Antimicrobial Chemotherapy . 2025;80(1):281-291. doi:10.1093/jac/dkae407 7. De Nicolò A, Ianniello A, Ferrara M, et al. Validation of a UHPLC-MS/MS Method to Quantify Twelve Antiretroviral Drugs within Peripheral Blood Mononuclear Cells from People Living with HIV. Pharmaceuticals . 2020;14(1):12. doi:10.3390/ph14010012 8. Loucks J, Zuckerman AD, Berni A, Saulles A, Thomas G, Alonzo A. Proportion of days covered as a measure of medication adherence. American Journal of Health-System Pharmacy . 2022;79(6):492-496. doi:10.1093/ajhp/zxab392 9. Tran TH, Tsuchiya K, Kawashima A, et al. Steady-state pharmacokinetics of plasma tenofovir alafenamide (TAF), tenofovir (TFV) and emtricitabine (FTC), and intracellular TFV-diphosphate and FTC-triphosphate in HIV-1 infected old Japanese patients treated with bictegravir/FTC/TAF. Glob Health Med . 2023;5(4):2023.01060. doi:10.35772/ghm.2023.01060 10. Massih SA, Atta MG, Thio CL, et al. Pharmacokinetics of tenofovir alafenamide, emtricitabine, and dolutegravir in a patient on peritoneal dialysis. AIDS Res Ther . 2024;21(1):34. doi:10.1186/s12981-024-00616-5 11. Fletcher C V., Podany AT, Thorkelson A, et al. The Lymphoid Tissue Pharmacokinetics of Tenofovir Disoproxil Fumarate and Tenofovir Alafenamide in HIV‐Infected Persons. Clin Pharmacol Ther . 2020;108(5):971-975. doi:10.1002/cpt.1883 12. Sax PE, DeJesus E, Crofoot G, et al. Bictegravir versus dolutegravir, each with emtricitabine and tenofovir alafenamide, for initial treatment of HIV-1 infection: a randomised, double-blind, phase 2 trial. Lancet HIV . 2017;4(4):e154-e160. doi:10.1016/S2352-3018(17)30016-4 13. Ciccullo A, Baldin G, Borghi V, et al. Comparing the efficacy and safety of a first-line regimen with emtricitabine/tenofovir alafenamide fumarate plus either bictegravir or dolutegravir: Results from clinical practice. Int J Antimicrob Agents . 2024;63(1):107040. doi:10.1016/j.ijantimicag.2023.107040 14. Sax PE, Rockstroh JK, Luetkemeyer AF, et al. Switching to Bictegravir, Emtricitabine, and Tenofovir Alafenamide in Virologically Suppressed Adults With Human Immunodeficiency Virus. Clinical Infectious Diseases . 2021;73(2):e485-e493. doi:10.1093/cid/ciaa988 15. Orkin C, Antinori A, Rockstroh JK, et al. Switch to bictegravir/emtricitabine/tenofovir alafenamide from dolutegravir-based therapy. AIDS . 2024;38(7):983-991. doi:10.1097/QAD.0000000000003865 Table 1 Demographical and immunovirological characteristics of study population (n=86) Gender M, n (%) 71 (83) BMI (kg/m 2 ), median (IQR) 26,3 (22,8-29,8) Creatinine (mg/dl), median (IQR) 0.97 (0,90-1,03) eGFR (CDK-EPI), median (IQR) 89,4 (83,1-95,6) Time on ARV (yrs), mean (CI95%) 6,8 (5,9-7,7 Time on last ARV pre-switch (yrs), mean (CI95%) 9,5 (7,2-11,7) Reason for switch n (%) ARV simplification Naïve Low level viremia (20-200 cp/mL) 65 (76) 14 (16) 7 (8) CD4+ lymphocytes count (cells/microL) 624 (541-707) CD4+/CD8+ ratio 0,9 (0,8-1,0) HIV-RNA <20 cp/mL, n (%) 65 (76) BMI: body mass index, eGFR: estimated glomerulal filtration rate, ARV: antiretroviral, cp/mL: copies/mL Table 2 Pharmacokinetics (PK) characteristics and adherence data of study population Cumulative adherence %, mean (CI95%) 92,4 (89,2-95,5) 93,0 (89,1-96,8) 0,691 Observational period (d), mean (CI95%) 110,1 (99,1-121,2) 114,0 (96,0-131,9) 0,910 HIV-RNA <20 cp/mL, n (%) 47 (67) 7 (29) 0,001 TFV plasma C trough (ng/mL), mean (CI95%) 14.9 (13.3-16.6) 10.7 (7.8-13.6) 0,001 TFV IC C trough (ng/mL), mean (CI95%) 327.5 (283.0-372.0) 144.6 (76.1-213.1) <0,001 TFV IC/plasma ratio, mean (CI95%) 23,1 (19,9-26,3) 13,9 (7,4-20,4) <0,001 BIC plasma C trough (ng/mL), mean (CI95%) 3238,2 (2760,5-3715,8) - DTG plasma C trough (ng/mL), mean (CI95%) 1128,6 (826,1-1431,1) FTC plasma C trough (ng/mL), mean (CI95%) 150,3 (85,5-215,0) 138,5 (90,5-186,6) 0,476 BIC: bictegravir, DTG: dolutegravir, TFV: tenofovir, FTC: emtricitabile. Data reported as geomean (95%CI) ng/mL. Fig 1. 1a Tenofovir diphosphate (TFV-DP) plasma concentration and 1b Tenofovir diphosphate (TFV-DP) intracellular concentration in participants on bictegravir/emtricitabine/tenofovir alafenamide (BIC/F/TAF) vs tenofovir alfenamide/emtricitabine plus dolutegravir (TAF/FTC plus DTG). Data reported as geomean (95%CI) ng/mL. Information & Authors Information Version history V1 Version 1 06 April 2026 Copyright This work is licensed under a Non Exclusive No Reuse License. Authors Affiliations Micol Ferrara 0000-0003-0377-9630 [email protected] Universita degli Studi di Torino Scuola di Medicina View all articles by this author Viviana Maccario Universita degli Studi di Torino Scuola di Medicina View all articles by this author Silvia Fantino Universita degli Studi di Torino Scuola di Medicina View all articles by this author Erica Clemente Universita degli Studi di Torino Scuola di Medicina View all articles by this author Federica Barrera Universita degli Studi di Torino Scuola di Medicina View all articles by this author Alice Palermiti Universita degli Studi di Torino Scuola di Medicina View all articles by this author Sara Soloperto Universita degli Studi di Torino Scuola di Medicina View all articles by this author Amedeo De Nicolò 0000-0002-5973-9948 Universita degli Studi di Torino Scuola di Medicina View all articles by this author Antonio D'Avolio 0000-0002-1321-4126 Universita degli Studi di Torino Scuola di Medicina View all articles by this author Giovanni Di Perri Universita degli Studi di Torino Scuola di Medicina View all articles by this author Stefano Bonora Universita degli Studi di Torino Scuola di Medicina View all articles by this author Metrics & Citations Metrics Article Usage 181 views 83 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Micol Ferrara, Viviana Maccario, Silvia Fantino, et al. Tenofovir intracellular concentration as Tenofovir alafenamide in Bictegravir-including versus Dolutegravir-including antiretroviral regimens. Authorea . 06 April 2026. DOI: https://doi.org/10.22541/au.177547173.39036280/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . Format Please select one from the list RIS (ProCite, Reference Manager) EndNote BibTex Medlars RefWorks Direct import Tips for downloading citations document.getElementById('citMgrHelpLink').addEventListener('click', function() { popupHelp(this.href); return false; }); $(".js__slcInclude").on("change", function(e){ if ($(this).val() == 'refworks') $('#direct').prop("checked", false); $('#direct').prop("disabled", ($(this).val() == 'refworks')); }); View Options View options PDF View PDF Figures Tables Media Share Share Share article link Copy Link Copied! Copying failed. Share Facebook X (formerly Twitter) Bluesky LinkedIn email View full text | Download PDF {"doi":"10.22541/au.177547173.39036280/v1","type":"Article"} Now Reading: Share Figures Tables Close figure viewer Back to article Figure title goes here Change zoom level Go to figure location within the article Download figure Toggle share panel Toggle share panel Share Toggle information panel Toggle information panel Go to previous graphic Go to next graphic Go to previous table Go to next table All figures All tables View all material View all material xrefBack.goTo xrefBack.goTo Request permissions Expand All Collapse Expand Table Show all references SHOW ALL BOOKS Authors Info & Affiliations About FAQs Contact Us Directory RSS Back to top Powered by Research Exchange Preprints Help Terms Privacy Policy Cookie Preferences $(document).ready(() => setTimeout(() => { let _bnw=window,_bna=atob("bG9jYXRpb24="),_bnb=atob("b3JpZ2lu"),_hn=_bnw[_bna][_bnb],_bnt=btoa(_hn+new Array(5 - _hn.length % 4).join(" ")); $.get("/resource/lodash?t="+_bnt); },4000)); (function(){function c(){var b=a.contentDocument||a.contentWindow.document;if(b){var d=b.createElement('script');d.innerHTML="window.__CF$cv$params={r:'9fe1aab0efb958d3',t:'MTc3OTE3ODY2Mg=='};var a=document.createElement('script');a.src='/cdn-cgi/challenge-platform/scripts/jsd/main.js';document.getElementsByTagName('head')[0].appendChild(a);";b.getElementsByTagName('head')[0].appendChild(d)}}if(document.body){var a=document.createElement('iframe');a.height=1;a.width=1;a.style.position='absolute';a.style.top=0;a.style.left=0;a.style.border='none';a.style.visibility='hidden';document.body.appendChild(a);if('loading'!==document.readyState)c();else if(window.addEventListener)document.addEventListener('DOMContentLoaded',c);else{var e=document.onreadystatechange||function(){};document.onreadystatechange=function(b){e(b);'loading'!==document.readyState&&(document.onreadystatechange=e,c())}}}})();