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PubMed2026

Evaluation of dried blood spots relative to peripheral blood mononuclear cells for intracellular tenofovir-diphosphate and emtricitabine-triphosphate assessment using liquid chromatography-tandem mass spectrometry.

Tenofovir alafenamide/emtricitabine (TAF/FTC) is widely used for HIV treatment and prevention. Their intracellular metabolites, tenofovir-diphosphate (TFV-DP) and emtricitabine-triphosphate (FTC-TP), provide informative measures of drug exposure. Peripheral blood mononuclear cells (PBMCs) are the primary matrix for these measurements; however, their isolation is labor-intensive, limiting clinical applicability. This study evaluated dried blood spots (DBS) for assessing intracellular TFV-DP and FTC-TP exposure relative to PBMCs. Paired PBMC and DBS samples (n = 124) were analyzed using a validated LC-MS/MS method. Moderate correlations were observed between DBS and PBMC concentrations for TFV-DP (r = 0.44, p < 0.0001) and FTC-TP (r = 0.27, p = 0.0025), with stronger correlations in the central 80% of participants based on the DBS-to-PBMC concentration ratios (r = 0.61 and 0.44, respectively). Log-transformed Bland-Altman analysis, with more than 90% of samples falling within the 95% limits of agreement. Additionally, concentration distributions across different virological statuses were similar between DBS and PBMC. DBS samples (n = 44) were also collected at baseline and on day 29 from people with HIV receiving TAF/FTC in combination with isoniazid plus rifapentine (1HP) to demonstrate the applicability of DBS for investigating potential drug-drug interactions (DDIs). In conclusion, the observed moderate correlations between DBS and PBMC concentrations of TFV-DP and FTC-TP suggest that DBS may serve as a feasible sampling approach for population-level assessment of intracellular TFV-DP and FTC-TP exposure. The simplicity of DBS sample collection and handling may facilitate large-scale clinical studies and highlights its potential utility in future clinical research.

Dried blood spots↗

PubMed2026

Hypertension in a Randomized Trial of Dolutegravir- Versus Efavirenz-Based Antiretroviral Therapy in Pregnant and Postpartum Women with HIV.

INTRODUCTION: We performed an analysis of incident hypertension in a randomized trial comparing dolutegravir (DTG) + emtricitabine (F)/tenofovir alafenamide (TAF) versus DTG + F/tenofovir disoproxil fumarate (TDF) versus efavirenz (EFV)/F/TDF in pregnant and postpartum women with HIV. METHODS: Women were randomized at 14-28 weeks gestational age (GA) to start DTG + F/TAF, DTG + F/TDF, or EFV/F/TDF and followed through 50 weeks postpartum. The composite incident hypertension outcome was defined as initiation of antihypertensive medication or ≥2 elevated blood pressures categorized as elevated (130-139 and/or 80-89 mmHg), mild (140-159 and/or 90-99 mmHg), moderate (≥160-179 and/or ≥100-109 mmHg), and severe (≥180 and/or ≥110 mmHg). Incident gestational hypertension was defined by initiation of antihypertensive medication or ≥2 blood pressures ≥ 140 and/or ≥90 mmHg at ≥20 weeks GA with resolution by 12 weeks postpartum. Cox proportional hazard models were used for by-arm comparisons of the composite outcome and to look for the effect of weight change within arm. RESULTS: Of 626 women without baseline hypertension (median age 26.6 years), the composite incident outcome occurred in 49% (n = 308), predominantly due to the incident elevated category of elevated blood pressure, with no significant differences by arm, although hypertension was numerically more likely in the DTG arms. Each additional 5 kg of weight was associated with an 8%-17% higher hazard of the composite hypertension outcome. Twenty-seven participants (4.3%) had gestational hypertension with no apparent differences between arms. CONCLUSIONS: Our data contribute information regarding the safety of DTG-based ART and TAF in pregnant and postpartum women and highlight the importance of monitoring weight and performing hypertension screening as part of maternal health care for young women with HIV.

Humans↗

PubMed2025

Kinetic Investigation of Resistance to Islatravir Conferred by Mutations in HIV-1 Reverse Transcriptase.

Islatravir (EFdA) is a novel nucleoside reverse transcriptase translocation inhibitor (NRTTI) that potently blocks HIV-1 replication in vivo. Its unique structural features in contrast to nucleoside reverse transcriptase inhibitors (NRTIs), particularly the 4'-ethynyl and 3'-hydroxy groups, contribute to its high clinical potency. Once intracellularly activated to EFdA 5'-triphosphate (EFdA-TP), it competes with dATP for incorporation by HIV-1 reverse transcriptase (RT) during HIV-1 genomic replication. The 4'-ethynyl group of incorporated EFdA-MP interacts with a hydrophobic pocket of HIV-1 RT, hindering DNA translocation and terminating DNA synthesis. The M184V mutation, commonly associated with resistance to NRTIs such as lamivudine and emtricitabine, and the M184V/A114S mutations, both located within the hydrophobic pocket, were shown to reduce Islatravir susceptibility in cell-based viral resistance selection assays. To elucidate the mechanisms by which these mutations affect Islatravir inhibition, we employed pre-steady-state kinetics to investigate their impact on EFdA-TP incorporation by HIV-1 RT using both DNA and RNA templates. We found that M184V had a modest effect on EFdA-TP incorporation efficiency, increasing it 2-fold with the DNA template and decreasing it 3-fold with the RNA template. In contrast, M184V/A114S significantly inhibited EFdA-TP incorporation, reducing its incorporation efficiency 5.4-fold with the DNA template and 181-fold with the RNA template. These reductions were primarily attributable to corresponding decreases in EFdA-TP incorporation rate constants of 18-fold and 105-fold, respectively. These results suggest that, unlike FDA-approved NRTIs, the clinical efficacy of Islatravir, may not be substantially compromised by the M184V mutation alone but will be significantly reduced by the M184V/A114S mutations.

HIV Reverse Transcriptase↗

PubMed2026

Safety and Tolerability of Oral Islatravir Once Monthly as Pre-exposure Prophylaxis in Cisgender Men and Transgender Women Who Have an Elevated Likelihood of HIV-1 Exposure: Results From the IMPOWER-24 Randomized Phase 3 Study.

BACKGROUND: Islatravir once monthly (qm), a nucleoside reverse transcriptase translocation inhibitor with a long half-life, was evaluated for safety and tolerability in cisgender men and transgender women who have sex with men and are at increased likelihood of HIV-1 (HIV) exposure. METHODS: IMPOWER-24 (NCT04652700) was a double-blind, Phase 3 study. Participants were randomized 2:1 to islatravir 60 mg oral qm or emtricitabine (FTC; 200 mg) coformulated with either tenofovir disoproxil (245 mg) or tenofovir alafenamide (TAF; 25 mg) once daily (qd). After ∼9 months, blinded islatravir was discontinued due to lymphocyte reductions; participants were offered open-label comparator for 20 months. RESULTS: In total, 494 participants were enrolled (328 islatravir; 166 comparator): 91.5% were cisgender men, 41.7% were White, and median age was 27 years. Mean blinded dosing duration was 4.7 months (islatravir) versus 4.3 months (comparator). Overall, 211 participants (64.3%) in the islatravir group and 128 (77.1%) in the comparator group had ≥1 adverse event (AE). Most AEs were mild or moderate, with 1 AE leading to product discontinuation (islatravir; gastroesophageal reflux). Serious AEs occurred in <2%; none were related to study product. Change in total lymphocytes in the islatravir group at Month 3 was -7.4%; a trend toward recovery was observed after islatravir was stopped. Mean total lymphocytes remained within normal range. No HIV infections occurred in either group during the double-blind phase. CONCLUSIONS: Islatravir qm was generally well tolerated; decreases in total lymphocytes were observed with islatravir. Original primary efficacy objectives were not assessed due to early study stoppage.

Humans↗

PubMed1992

Substrate specificity of Escherichia coli thymidine phosphorylase for pyrimidine nucleosides with anti-human immunodeficiency virus activity.

Various nucleoside antiviral agents and their metabolites were examined for their ability to be cleaved across the glycosidic bond by Escherichia coli thymidine phosphorylase. The increasing order of susceptibility to cleavage was U greater than T much greater than C derivatives. Nucleosides that were unsaturated in the sugar moiety were more susceptible than saturated ones. 3'-Deoxy-2',3'-didehydrothymidine was a substrate, whereas 3'-azido-, 3'-fluoro-, 3'-oxo- and 3'-thiapyrimidine nucleosides were resistant to this enzyme.

Antiviral Agents↗

PubMed2026

Same-day initiation of tenofovir alafenamide-based pre-exposure prophylaxis with drug-level feedback for transgender women in Uganda.

OBJECTIVE: To evaluate the feasibility and acceptability of same-day initiation of emtricitabine/tenofovir alafenamide (F/TAF) pre-exposure prophylaxis (PrEP) and test the impact of drug-level feedback on PrEP adherence among transgender women (TGW) in Uganda. DESIGN: Randomized controlled trial. METHODS: HIV-negative TGW were randomly assigned 1 : 1 to intervention (drug-level feedback with tailored adherence counseling) or standard-of-care (SOC), and followed quarterly for 12 months (November 2021-July 2023; NCT04491422). Quarterly clinic visits included demographic and socio-behavioral data collection, PrEP refills, STI testing, and quarterly PrEP adherence assessment using tenofovir levels in dried blood spots (DBS; long-term) and urine (short-term). RESULTS: We enrolled 200 TGW (100 per arm), median age 21 years. Same-day F/TAF PrEP initiation was 100%. Tenofovir detection in urine (intervention arm) was 79, 80, 85, and 70% at the 3, 6, 9, and 12-month visits, respectively. Tenofovir detection in DBS was 46, 40, 35, and 31% at 3, 6, 9, and 12 months, respectively. Median tenofovir DBS concentrations were 40.6 and 47.0 fmol/punch in intervention and SOC arms, respectively. There was no intervention effect on PrEP adherence (DBS tenofovir levels) [adjusted incidence rate ratio (aIRR) 1.06; 95% CI: 0.82-1.37]. Never being harassed by police for being transgender (aIRR 1.66; 95% CI: 1.24-2.23), history of taking daily medication for more than 7 days (aIRR 1.51; 95% CI: 1.18-1.93) and higher monthly income (aIRR 1.44; 95% CI: 1.10-2.04) were associated with PrEP adherence. CONCLUSION: Oral F/TAF PrEP adherence among TGW in Uganda was low and not affected by drug-level feedback or tailored adherence counseling. Long-acting injectable PrEP formulations should be considered for this population.

Humans↗

PubMed1992

Selective inhibition of human immunodeficiency viruses by racemates and enantiomers of cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine.

2',3'-Dideoxy-5-fluoro-3'-thiacytidine (FTC) has been shown to be a potent and selective compound against human immunodeficiency virus type 1 in acutely infected primary human lymphocytes. FTC is also active against human immunodeficiency virus type 2, simian immunodeficiency virus, and feline immunodeficiency virus in various cell culture systems, including human monocytes. The antiviral activity can be prevented by 2'-deoxycytidine, but not by other natural nucleosides, suggesting that FTC must be phosphorylated to be active and 2'-deoxycytidine kinase is responsible for the phosphorylation. By using chiral columns or enzymatic techniques, the two enantiomers of FTC were separated. The (-)-beta-enantiomer of FTC was about 20-fold more potent than the (+)-beta-enantiomer against human immunodeficiency virus type 1 in peripheral blood mononuclear cells and was also effective in thymidine kinase-deficient CEM cells. Racemic FTC and its enantiomers were nontoxic to human lymphocytes and other cell lines at concentrations of up to 100 microM. Studies with human bone marrow cells indicated that racemic FTC and its (-)-enantiomer had a median inhibitory concentration of > 30 microM. The (+)-enantiomer was significantly more toxic than the (-)-enantiomer to myeloid progenitor cells. The susceptibilities to FTC of pretherapy isolates in comparison with those of posttherapy 3'-azido-3'-deoxythymidine-resistant viruses in human lymphocytes were not substantially different. Similar results were obtained with well-defined 2',3'-dideoxyinosine- and nevirapine-resistant viruses. (-)-FTC-5'-triphosphate competitively inhibited human immunodeficiency virus type 1 reverse transcriptase, with an inhibition constant of 2.9 microM, when a poly(I)n.oligo(dC)19-24 template primer was used. These results suggest that further development of the (-)-Beta-enantiomer of FTC is warranted as an antiviral agent for infections caused by human immunodeficiency viruses.

Antiviral Agents↗

PubMed1992

Pharmacokinetics and metabolism of racemic 2',3'-dideoxy-5-fluoro-3'-thiacytidine in rhesus monkeys.

2',3'-Dideoxy-5-fluoro-3'-thiacytidine (FTC) is a nucleoside analog that selectively inhibits human immunodeficiency and hepatitis B viruses in vitro. In this study, the preclinical pharmacokinetics of racemic FTC in rhesus monkeys following intravenous and oral administration were characterized. The terminal half-life of FTC was independent of the route of administration and averaged 1.34 +/- 0.18 h (mean +/- standard deviation). Total clearance of FTC was moderate to high, averaging 1.49 +/- 0.24 liters/h/kg. Qualitative assessment of urine samples suggests that renal excretion of unchanged FTC was the major route of elimination of the nucleoside. The compound was also eliminated by metabolism and the deaminated biotransformation product 2,3'-dideoxy-5-fluoro-3'-thiauridine (FTU) was detected in serum and urine. This metabolite has no antiviral activity in human lymphocytes and liver cells. FTC and the metabolite FTU were conjugated, to a minor extent yielding the corresponding glucuronides. No 5-fluorouracil was detected in serum or urine. This is consistent with chromatographic studies using a chiral column that indicated that when racemic FTC is treated with cellular cytidine-deoxycytidine deaminase, the D-(+)-enantiomer of FTC is slowly deaminated to D-(+)-FTU, whereas the L-(-)-enantiomer is essentially resistant to this enzyme. The steady-state volume of distribution of FTC in serum averaged 2.23 +/- 0.42 liters/kg, and the nucleoside analog was distributed into the cerebrospinal fluid, which suggests that this drug penetrated the blood-brain barrier. Absorption of FTC after oral administration was rapid, with bioavailability averaging 73 +/- 6%. Taken together, the results indicate that the unusual L-(-)-enantiomer of FTC should be evaluated further in rhesus monkeys prior to determination of whether this compound is useful for treatment of human immunodeficiency and hepatitis B virus infections.

Administration, Oral↗

PubMed1992

The anti-hepatitis B virus activities, cytotoxicities, and anabolic profiles of the (-) and (+) enantiomers of cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine.

The anti-hepatitis B (anti-HBV) activities of the (-) and (+) enantiomers of cis-5-fluoro-1-[2-(hydroxymethyl)-1,3-oxathiolan-5-yl]cytosine (2'-deoxy-3'-thia-5-fluorocytosine [FTC]) were studied by using an HBV-transfected cell line (HepG2 derivative 2.2.15, subclone P5A). The (-) isomer was found to be a potent inhibitor of viral replication, with an apparent 50% inhibitory concentration of 10 nM, while the (+) isomer was found to be considerably less active. Both isomers showed minimal toxicity to HepG2 cells (50% inhibitory concentration, > 200 microM) and showed minimal toxicity in the human bone marrow progenitor cell assay. In accord with the cellular antiviral activity data, the 5'-triphosphate of (-)-FTC inhibited viral DNA synthesis in an endogenous HBV DNA polymerase assay, while the 5'-triphosphate of the (+) isomer was inactive. Unphosphorylated (-)-FTC did not inhibit product formation in the endogenous assay, suggesting that the antiviral activity of the compound is dependent on anabolism to the 5'-triphosphate. Both (-)- and (+)-FTC were anabolized to the corresponding 5'-triphosphates in chronically HBV-infected HepG2 cells. The rate of accumulation and the steady-state concentration of the 5'-triphosphate of (-)-FTC were greater. Also, (-)-FTC was not a substrate for cytidine deaminase and, therefore, is not subject to deamination and conversion to an inactive uridine analog. The (+) isomer is, however, a good substrate for cytidine deaminase.

Animals↗