BACKGROUND AND OBJECTIVES:The For the Assessment of Individualized Risk (FAIR) framework, introduced by NHS Blood and Transplant (NHSBT) in 2021, aims to reduce stigma and improve equity in blood donor selection, particularly for gay, bisexual and other men who have sex with men (GBMSM). While pre-exposure prophylaxis (PrEP) is highly effective at preventing sexual transmission of human immunodeficiency virus, its declared use excludes individuals from blood donation. This study examined PrEP use among male blood donors with current or past syphilis in England to evaluate guideline compliance and implications for blood safety. MATERIALS AND METHODS:Residual plasma samples from syphilis-positive male blood donors collected in 2023 were tested for PrEP. These data were combined with two previous studies of syphilis-positive donors conducted between July 2018 and June 2024, incorporating demographics and reported PrEP use. RESULTS:The rate of syphilis-positive blood donations increased from 4.09 to 10.32 per 100,000 donations between 2018 and 2024 (p = 0.048, Mann-Kendall trend test) with a rising proportion of past syphilis cases attributed to GBMSM (18%-37%; p = 0.004, Fisher's test, p = 0.001 Mann-Kendall test); 7.1% of syphilis-positive blood samples from male blood donors tested positive for PrEP in 2023, indicating frequent non-compliance with donation guidelines. CONCLUSION:Persistent PrEP use among syphilis-positive donors since 2018 suggests gaps in donor education regarding eligibility. Targeted public health interventions, particularly for younger GBMSM, are needed to strengthen sexual health education, PrEP messaging and awareness of donation criteria. Further research into other infections associated with high-risk sexual behaviour is warranted.

BACKGROUND:Countries faced with an impending shortage of antiretrovirals need to conserve supplies and maximize treatment effectiveness while limiting harms. Potential strategies to achieve this could include reduced doses of fixed-dose tenofovir disoproxil-lamivudine-dolutegravir (TLD). METHODS:Nonlinear mixed effects was applied to dolutegravir concentration-time data from three healthy volunteer studies (two including dolutegravir 'washout' over 10 and 15 days post-cessation), adapting a previously published model. The model was used to simulate (n = 1000) pharmacokinetic profiles of standard dolutegravir (one pill TLD daily) and four dose reduction strategies: half a pill TLD daily; one pill TLD every other day; 4 days on, 3 days off (4:3) and 5 days on, 2 days off (5:2) therapy. Proportions above and time below the EC90 (320 ng/mL) were determined and compared. RESULTS:Seventy-three volunteers (60% female, n = 825 concentrations) were included in the model. Marked differences between simulated dose reduction regimens were observed, with alternate day, 4:3 and 5:2 dosing, associated with a lower proportion of dolutegravir trough above the EC90 (41.6%-62.1%, 2.0%-5.2%, 14.1%-20.7%, respectively) across 50, 70 and 90 kg compared with daily dosing at full or half doses (88.7%-99.8%). Of the four dose reduction strategies, 4:3 dosing exhibited the longest predicted time below target before the next due dose (median ∼2 days). CONCLUSIONS:Safety and effectiveness of TLD dose reduction strategies can only be established in clinical studies and cannot be extrapolated from models. However, these models can inform regimen design to limit the window of opportunity for emergence of resistance, i.e. where viral replication occurs in the presence of appreciable drug concentrations.

Model-informed drug development is increasingly integrated across the drug development continuum, enabling more efficient, cost-effective, and targeted trials while reducing reliance on animal studies. Achieving pharmacoequity requires not only equitable access to medicines but also to the data and knowledge that inform drug development and regulatory decisions. To address challenges in pharmacokinetic data sharing, PKRxiv (https://pkrxiv.org/) was developed as a discipline-specific repository designed around Findable, Accessible, Interoperable, Reusable (FAIR) principles. This tutorial introduces PKRxiv's rationale, design, data submission and access workflows, and practical use cases. Available datasets at the end of September 2025 include over 5,500 individual drug concentration-time data points from over 900 unique participants across 3 continents. The platform supports structured submission of pharmacokinetic, pharmacogenetic, and safety/efficacy data, with persistent digital object identifiers for discoverability and citation. Contributors can apply one of three data sharing models-unrestricted, noncommercial, or contributor-controlled-with optional embargo periods. Users can explore datasets using the Data Explorer or Data Cards, or submit requests after providing a statement of intended use case. It enables pooling of datasets across multiple studies. Recommendations to help advance the field are proposed as data sharing becomes more widely expected: obtaining consent for unspecified future research use of data, sharing data underlying peer-reviewed publications as standard practice, including discipline-specific repositories in data management plans, and incentivizing post-approval data sharing by industry. Supporting data from all therapeutic areas and population groups, PKRxiv is a critical step toward a more transparent, equitable, and collaborative future in clinical pharmacology research.

Background: AGILE ([NCT04746183][1]) is a Phase Ib/IIa platform, evaluating candidates to treat COVID-19. CST-6 evaluated the safety and optimal dose of a novel intravenous (IV) formulation of favipiravir. Methods: CST-6 was a dose-escalating, open-label, randomised, controlled, Bayesian adaptive Phase Ib trial. Hospitalised adults with PCR-confirmed SARS-CoV-2 infection, within 14 days of symptomatic COVID-19 were randomised 2:1 in groups of 6 (n = 4 favipiravir, n = 2 standard of care (SoC)) to ascending doses of IV favipiravir twice daily (b.i.d.) for 7 days or SoC. Clinical data, safety evaluations, virology and pharmacokinetic (PK) samples were collected. The primary outcome was safety. Secondary outcomes included clinical, PK and virological endpoints. Results: 24 participants enrolled between 10/Sep/2022 and 01/Nov/2023 [10/24 female; median age 74 years (range 52-93)]. Favipiravir was well tolerated despite a high background rate of unrelated adverse events (AEs). No dose limiting toxicities (DLTs) were observed, with a model-predicted DLT risk of 16.8% and probability of unacceptable toxicity of 2.7% at the highest dose level. No SAEs were deemed related to favipiravir but an expected association with asymptomatic, transient hyperuricaemia was observed. PK exposures increased disproportionally to dose with significant accumulation in plasma, but with marked variability between participants within each cohort. Conclusions: A novel formulation of favipiravir was safe at sustained high doses that reached PK targets in a study group with frailty and complex health profiles. Plasma concentrations demonstrated accumulation. Significant variability in PK parameters between individuals was noted. We consider doses up to 2400mg b.i.d. to be safe for further evaluation. https://clinicaltrials.gov/study/[NCT04746183][1]  ### Competing Interest Statement SHK has received research funding from ViiV Healthcare, Gilead Sciences, Pfizer and Merck Sharp & Dohme for the Liverpool HIV Drug Interactions programme and for unrelated clinical studies. GG has received funding from Janssen-Cilag, AstraZeneca, Novartis, Astex, Roche, Heartflow, Celldex, BMS, BioNTech, MSD, IntraOp, Synairgen, Boehringer Ingelheim, Blood Cancer UK, Cancer Research UK, the NIHR, Asthma and Lung UK, UKRI, Wellcome Trust, NHS England, Unitaid, Imugene, and GSK for unrelated academic clinical trials and programme funding, and honoraria/consulting fees from AstraZeneca and Abbvie. AO is a director of Tandem Nano Ltd and co-inventor of drug delivery patents. AO has been co-investigator on funding received by the University of Liverpool or Tandem Nano Ltd from ViiV Healthcare, Bicycle Therapeutics and Gilead Sciences and has received personal fees from Gilead, Shionogi and Assembly Biosciences. ### Clinical Trial NCT04746183 ### Funding Statement The AGILE trial is an academic, non-commercial trial sponsored by the University of Liverpool. This work is supported by the Medical Research Council (grant numbers MR/V028391/1, MR/W005611/1); the Wellcome Trust (grant number 221590/Z/20/Z); the US Food and Drug Administration Medical Countermeasures Initiative contract (75F40120C00085) and the National Institute for Health and Care Research Health Protection Research Unit in Emerging and Zoonotic Infections (award 200907). PM is supported by the NIHR through the NIHR Advanced Fellowship (NIHR300576). PM and TJ are supported by MRC through MRC Core funding (MC\_UU\_00040/03). GG receives funding for SCTU staff from the Southampton NIHR Biomedical Research Centre. The article reflects the views of the authors and does not represent the views or policies of the FDA, the NIHR or the Department of Health and Social Care ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study protocol was reviewed by the UK Medicines and Healthcare products Regulatory Agency (MHRA) (EudraCT 202000186027) and West Midlands Edgbaston Research Ethics Committee (20/WM/0136). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes The AGILE Trial Steering Committee will consider all reasonable requests by health-care providers, investigators, and researchers to provide anonymised data to address specific scientific or clinical objectives. The AGILE investigators are committed to reviewing requests from researchers for access to clinical trial protocols, de-identified patient-level clinical trial data, and study-level clinical trial data. Data will be assigned a DOI through deposition in the University of Liverpool Research Data Catalogue (rdm{at}liverpool.ac.uk) and shared under a Data Transfer agreement (or equivalent e.g. as part of a research collaboration agreement or confidentiality disclosure agreement. [1]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT04746183&atom=%2Fmedrxiv%2Fearly%2F2025%2F06%2F09%2F2025.06.09.25329141.atom

Background: Poor adherence to ART and pre-exposure prophylaxis (PrEP) can impact patient and public health. Point-of-care testing (POCT) may aid monitoring and adherence interventions. Objectives: We report the pharmacokinetics of tenofovir [dosed as tenofovir disoproxil (TDF) and tenofovir alafenamide (TAF)], emtricitabine (FTC), lamivudine (3TC) and dolutegravir (DTG) in plasma and urine following drug cessation to evaluate adherence targets in urine for POCT. Methods: Subjects were randomized (1:1) to receive DTG/FTC/TAF or DTG/3TC/TDF for 15 days. Plasma and spot urine were collected on Day 15 (0-336 h post final dose). Drug concentrations were quantified using LC-MS, and non-linear mixed-effects models applied to determine drug disposition between matrices and relationship with relevant plasma [dolutegravir protein-adjusted 90% inhibitory concentration (PA-IC90 = 64 ng/mL) and minimum effective concentration (MEC = 324 ng/mL)] and urinary thresholds [tenofovir disoproxil fumarate 1500 ng/mL]. Results: Of 30 individuals enrolled, 29 were included (72% female at birth, 90% Caucasian). Median (range) predicted time to plasma dolutegravir PA-IC90 and MEC were 83.5 (41.0-152) and 49.0 h (23.7-78.9), corresponding to geometric mean (90%) urine concentrations of 5.42 (4.37-6.46) and 27.4 ng/mL (22.1-32.7). Tenofovir in urine reached 1500 ng/mL by 101 h (58.6-205) with an equivalent plasma concentration of 6.20 ng/mL (4.21-8.18). Conclusions: These data support use of a urinary tenofovir threshold of <1500 ng/mL (tenofovir disoproxil fumarate-based regimens) as a marker of three or more missed doses for a POCT platform. However, due to low dolutegravir concentrations in urine, POCT would be limited to a readout of recent dolutegravir intake (one missed dose).

BACKGROUND:We investigated the impact of Drug-Drug Interactions (DDIs) on virologic control among HIV-positive pregnant women initiating antiretroviral therapy while identifying drivers for Traditional Medicine (TM) use and exploring the nature and extent of TM-related DDIs. METHODS:Employing a three-pronged approach, we examined DDIs arising from comedication, including TM, in ART. The DolPHIN-2 trial (NCT03249181) randomized 268 HIV-positive pregnant women in Uganda and South Africa to dolutegravir (DTG)-based (135) or efavirenz-based (133) regimens while systematically recording comedications and screening for DDIs. We used Cox regression models to compare time-to-virologic control between participants with and without DDIs. We conducted in-depth interviews and focus group discussions among 37 and 67 women with and without HIV, respectively, to explore reasons for TM use during pregnancy. Additionally, in-vitro and in-vivo studies evaluated the composition and impact of clay-based TM, mumbwa, on DTG plasma exposure. RESULTS:The baseline prevalence of DDIs was 67.2%, with TM use prevalent in 34% of participants, with mumbwa being the most frequent (76%, 69/91). There was no difference in virologic response between participants with and without DDIs. Fetal health and cultural norms were among the reasons cited for TM use. Analysis of mumbwa rods confirmed significant amounts of aluminium (8.4%-13.9%) and iron (4%-6%). In Balb-C mice, coadministration of mumbwa led to a reduction in DTG exposure observed in the AUC0-24 (-21%; P = 0.0271) and C24 (-53%; P = 0.0028). CONCLUSIONS:The widespread use of clay-based TM may compromise HIV treatment, necessitating medication screening and counselling to manage DDIs in pregnant women.

IntroductionTight junctions (TJs) serve as permeability filters between the internal and external cellular environment. A large number of proteins have been identified to be localized at the TJs. Due to limitations in tissue collection, TJs in the male genital tract have been understudied.MethodsWe analysed the transcriptomics of 132 TJ genes in foreskin tissue of men requesting voluntary medical male circumcision (VMMC) and enrolled in the Combined HIV Adolescent Prevention Study (CHAPS) trial conducted in South Africa and Uganda (NCT03986970). The trial evaluated the dose requirements for event-driven HIV pre-exposure prophylaxis (PrEP) with emtricitabine-tenofovir (FTC-TDF) or emtricitabine-tenofovir alafenamide (FTC-TAF) during insertive sex. A total of 144 participants were randomized to either control arm or one of 8 PrEP arms (n=16/arm), receiving oral FTC-TDF or FTC-TAF over one or two days. Following in vivo oral PrEP dosing and VMMC, the expression level of three important TJ proteins (CLDN-1, OCN and ZO-1) was measured ex vivo in foreskin tissue by Western blot. The expression of cytokine genes implicated in TJ regulation was determined. Non-parametric Kruskal-Wallis tests were used to compare TJ gene expression and protein levels by type of PrEP received, and Spearman’s correlation coefficients were calculated to assess whether TJ gene expression levels were related to cytokine gene levels or to PrEP drug concentrations and their active intracellularly phosphorylated metabolites.ResultsA high level of expression in foreskin tissue was found for 118 (of 132) TJ genes analysed; this finding contributed to create a map of TJ components within the male genital tract. Importantly, PrEP regimens tested in the CHAPS trial did not affect the expression of TJ genes and the analysed proteins in the foreskin; thus, further supporting the safety of this prevention strategy against HIV-1 transmission during insertive sex. Additionally, we identified the level of several cytokines’ genes to be correlated to TJ gene expression: among them, IL-18, IL-33 and VEGF.DiscussionTJs can limit viral entry into target cells; to affect this biological function viruses can reduce the expression of TJ proteins. Our study, on the expression and regulation of TJs in the foreskin, contribute important knowledge for PrEP safety and further design of HIV-1 prophylaxis.

BACKGROUND:There are few data on tenofovir-diphosphate (TFV-DP) concentrations in pregnant and postpartum women on Tenofovir Disoproxil Fumarate-Emtricitabine (TDF-FTC) or Tenofovir Alafenamide-Emtricitabine (TAF-FTC). METHODS:Eligible pregnant women were randomized to TDF-FTC or TAF-FTC and followed for 16 weeks (8-weeks pregnant, 8-weeks postpartum) with weekly collection of dried blood spot (DBS) and 4-weekly peripheral blood mononuclear cells (PBMC). PrEP dosing was observed daily via asynchronous videos sent via cell phone. We report geometric means (GM) and their ratios (GMR) with 95% confidence intervals (CIs) for TFV-DP in PBMC and DBS from pregnancy and postpartum. RESULTS:We enrolled N = 39 participants (n = 19 TDF-FTC, n = 20 TAF-FTC): median age was 28 years (IQR:25-34); median gestational age was 24-weeks (IQR:21-28). For TDF-FTC, TFV-DP DBS concentrations at 8-weeks did not differ significantly between pregnancy (GM: 675; 95%CI:537-849) and postpartum (GM: 583; 95%CI:471-722; GMR-TDF = 1.16; 95%CI:0.74-1.80). For TAF-FTC, TFV-DP DBS concentrations at 8-weeks were 44% higher in postpartum (GM: 1199; 95%CI:929-1549) versus pregnancy (GM: 832; 95%CI:751-922; GMR-TAF = 1.44; 95% CI: 1.01-2.06). In PBMC analysis of TDF-FTC, 8-week median TFV-DP (pmol/10^6 cell) was 71 (IQR 44-112) in pregnancy and 73 (IQR 50-102) in postpartum (GMR = 1.04; 95%CI:0.44-2.44). In TAF-FTC, median PBMC at 8-weeks was 580 (IQR:341-985) in pregnancy and 666 (IQR:396-1123) in postpartum (GMR = 1.15; 95%CI:0.30-2.49). CONCLUSION:TFV-DP concentrations were overall lower during pregnancy than postpartum for TAF-FTC. We found high concentrations of TFV-DP in PBMC in pregnancy and postpartum on TAF-FTC, suggesting PrEP efficacy is maintained. Efficacy and safety studies are warranted to evaluate TAF-FTC for PrEP in pregnant and postpartum women.

Favipiravir is a broad-spectrum antiviral that is metabolised intracellularly into the active form, favipiravir ribofuranosyl-5'-triphosphate (F-RTP). Measurement of the intracellular concentration of F-RTP in mononuclear cells is a crucial step to characterising the pharmacokinetics of F-RTP and to enable more appropriate dose selection for the treatment of COVID-19 and emerging infectious diseases. The described method was validated over the range 24 - 2280 pmol/sample. Peripheral blood mononuclear cells (PBMCs) were isolated from whole blood and lysed using methanol-water (70:30, v/v) before cellular components were precipitated with acetonitrile and the supernatant further cleaned by weak anion exchange solid phase extraction. The method was found to be both precise and accurate and was successfully utilised to analyse F-RTP concentrations in patient samples collected as part of the AGILE CST-6 clinical trial.

Background: Viperidae snakes are responsible for many of the 94,000 deaths caused by snakebite envenoming each year. The most pathological venom component of this globally diverse family of snakes are the zinc-dependent snake venom metalloproteinase (SVMP) enzymes, which can be inhibited by the metal chelator, unithiol. A short-course oral regimen, readily available and rapidly deployed ahead of hospital admission is needed. Methods: This open-label, phase 1 clinical trial assessed the safety of single ascending oral, multiple ascending oral, and single ascending intravenous doses of unithiol in 64 healthy adult volunteers from Kilifi County, Kenya. The multiple dose stage was informed by an interim safety and pharmacokinetic analysis, and predefined target plasma concentrations. Plasma concentrations of unithiol were measured using high-performance liquid chromatography-mass spectrometry, and safety was described by full adverse event reporting. Findings: 175 individuals were screened, and 64 (median age 30 years, IQR 25-38 years) received the study drug. There were no dose limiting toxicities or serious adverse events. There were 61 solicited adverse events, 17 related unsolicited adverse events, and 53 laboratory adverse events, all of which were of mild or moderate severity. The maximum oral dose of 1,500 mg was well tolerated and demonstrated a Cmax that was equivalent to intravenous administration. Interpretation: The phase 2 recommended dose (1,500 mg loading dose, followed by 900 mg doses at 6-hours and 24-hours) is safe, and has promising pharmacokinetic properties for clinical use. Unithiol is affordable, stable at room temperature, and has the potential to be given orally in remote rural clinics. Its further development for snakebite indication is warranted. Trial Registration: This trial was registered on the Pan African Clinical Trials Registry (PACTR202103718625048)Funding: Wellcome Trust, Bloomsbury Set, and Cures Within Reach.Declaration of Interest: There are no competing interests related to this study.Ethical Approval: The study obtained ethical approval from the Kenya Medical Research Institute Scientific Ethics Review Unit (192/4106) and the Liverpool School of Tropical Medicine Research Ethics Committee (20-032), and regulatory approval from the Pharmacy and Poisons Board of Kenya (136). The trial was conducted in accordance with regulatory requirements, including International Conference on Harmonisation-Good Clinical Practice guidelines.

Favipiravir (FVP) is a broad-spectrum antiviral that selectively inhibits viral RNA-dependent RNA polymerase, first trialled for the treatment of influenza infection. It has been shown to be effective against a number of RNA virus families including arenaviruses, flaviviruses and enteroviruses. Most recently, FVP has been investigated as a potential therapeutic for severe acute respiratory syndrome coronavirus 2 infection. A liquid chromatography tandem mass spectrometry method for the quantification of FVP in human plasma has been developed and validated for use in clinical trials investigating favipiravir as treatment for coronavirus disease-2019. Samples were extracted by protein precipitation using acetonitrile, using 13C, 15N- Favipiravir as internal standard. Elution was performed on a Synergi Polar-RP 150 x 2.1 mm 4 mu m column using a gradient mobile phase programme consisting of 0.2% formic acid in water and 0.2% formic acid in methanol. The assay was validated over the range 500-50,000 ng/mL; this method was found to be precise and accurate and recovery of FVP from the matrix was high. Stability experiments confirmed and expanded on the known stability of FVP, including under heat treatment and for a period of 10 months at - 80 degrees C.

Background The efficacy of on-demand HIV pre-exposure prophylaxis (PrEP) for men in sub-Saharan Africa has not been evaluated, and the on-demand PrEP dosing requirement for insertive sex remains unknown. Methods HIV-negative males 13-24 years, requesting voluntary medical male circumcision (VMMC), were enrolled into an open-label randomised controlled trial (NCT03986970), and randomised 1:1:1:1:1:1:1:1:1 to control arm or one of eight arms receiving emtricitabine-tenofovir disoproxil fumarate (F/TDF) or emtricitabine-tenofovir alafenamide (F/TAF) over one or two days, and circumcised 5 or 21 h thereafter. The primary outcome was foreskin p24 concentrations following ex vivo HIV-1BaL challenge. Secondary outcomes included peripheral blood mononuclear cell (PBMC) p24 concentration, and drug concentrations in foreskin tissue, PBMCs, plasma and foreskin CD4+/CD4-cells. In the control arm, post-exposure prophylaxis (PEP) activity of non-formulated tenofovir-emtricitabine (TFV-FTC) or TAF-FTC was assessed with ex vivo dosing 1, 24, 48 or 72 h post-HIV-1 challenge. Findings 144 participants were analysed. PrEP with F/TDF or F/TAF prevented ex vivo infection of foreskins and PBMCs both 5 and 21 h after PrEP dosing. There was no difference between F/TDF and F/TAF (p24day15 geometric mean ratio 1.06, 95% confidence interval: 0.65-1.74). Additional ex vivo dosing did not further increase inhibition. In the control arm, PEP ex vivo dosing was effective up to 48 post-exposure diminishing thereafter, with TAF-FTC showing prolonged protection compared to TFV-FTC. Participants receiving F/TAF had higher TFV-DP concentrations in foreskin tissue and PBMCs compared with F/TDF, irrespective of dose and sampling interval; but F/TAF did not confer preferential TFV-DP distribution into foreskin HIV target cells. FTC-TP concentrations with both drug regimens were equivalent and & SIM;1 log higher than TFV-DP in foreskin. Interpretation A double dose of either F/TDF or F/TAF given once either 5 or 21 h before ex vivo HIV-challenge provided protection across foreskin tissue. Further clinical evaluation of pre-coital PrEP for insertive sex is warranted.

Objectives: As topical pre-exposure prophylaxis (PrEP) has been shown to cause immune modulation in rectal or cervical tissue, our aim was to examine the impact of oral PrEP on lymphoid and myeloid changes in the foreskin in response to dosing and timing of drug administration. Design: HIV-negative male individuals ( n = 144) were recruited in South Africa and Uganda into an open-label randomized controlled trial in a 1 : 1 : 1 : 1 : 1 : 1 : 1 : 1 : 1 ratio to control arm (with no PrEP) or one of eight arms receiving emtricitabine–tenofovir disoproxil fumarate (F/TDF) or emtricitabine–tenofovir alafenamide (F/TAF) at one of two different doses, 5 or 21 h before undergoing voluntary medical male circumcision (VMMC). Methods: After dorsal-slit circumcision, foreskin tissue sections were embedded into Optimal Cutting Temperature media and analysed, blinded to trial allocation, to determine numbers of CD4 + CCR5 + , CD1a + cells and claudin-1 expression. Cell densities were correlated with tissue-bound drug metabolites and p24 production after ex-vivo foreskin challenge with HIV-1 bal . Results: There was no significant difference in CD4 + CCR5 + or CD1a + cell numbers in foreskins between treatment arms compared with the control arm. Claudin-1 expression was 34% higher ( P = 0.003) in foreskin tissue from participants receiving PrEP relative to controls, but was no longer statistically significant after controlling for multiple comparisons. There was neither correlation of CD4 + CCR5 + , CD1a + cell numbers, or claudin-1 expression with tissue-bound drug metabolites, nor with p24 production after ex-vivo viral challenge. Conclusion: Oral doses and timing of on-demand PrEP and in-situ drug metabolite levels in tissue have no effect on numbers or anatomical location of lymphoid or myeloid HIV target cells in foreskin tissue.

Background: A rapid and sensitive LC–MS method has been developed and validated for the quantification of nucleoside di/triphosphates using a novel plasma separation card (HemaSep). Materials & methods: Cards were spotted with whole blood and stored at -80°C. Metabolites were extracted using 70:30 MeOH:20% formic acid, followed by weak anion exchange SPE and eluted using a Biobasic-AX column. Quantification was performed using a triple quadrupole mass spectrometer with a calibration range of 1.25–250 pmol/sample. Results: The recovery of metabolites was high (>93%). Precision and accuracy were acceptable and metabolites remained stable on the card after 29 days (stored at ambient temperature). Conclusion: HemaSep dried blood spots are a useful microsampling tool and offer an alternative to liquid plasma as they maintain stability over time.

An individualised blood donor selection policy was implemented in the United Kingdom from summer 2021. We have investigated the impact of this policy by comparing the extent of undeclared use of HIV pre-exposure or post-exposure prophylaxis (PrEP/PEP) before and after this change. The rate of PrEP usage in syphilis-positive male blood donors has not changed since individualised donor assessment was implemented but provides continuing evidence of undisclosed PrEP use which may be associated with current or past higher-risk sexual behaviours.