Preclinical Considerations for Long-acting Delivery of Tenofovir Alafenamide from Subdermal Implants for HIV Pre-exposure Prophylaxis

PURPOSE

Long-acting formulations of the potent antiretroviral prodrug tenofovir alafenamide (TAF) hold potential as biomedical HIV prevention modalities. Here, we present a rigorous comparison of three animal models, C57BL/6 J mice, beagle dogs, and merino sheep for evaluating TAF implant pharmacokinetics (PKs).

METHODS

Implants delivering TAF over a wide range of controlled release rates were tested in vitro and in mice and dogs. Our existing PK model, supported by an intravenous (IV) dosing dog study, was adapted to analyze mechanistic aspects underlying implant TAF delivery.

RESULTS

TAF in vitro release in the 0.13 to 9.8 mg d-1 range with zero order kinetics were attained. Implants with equivalent fabrication parameters released TAF in mice and sheep at rates that were not statistically different, but were 3 times higher in dogs. When two implants were placed in the same subcutaneous pocket, a two-week creep to Cmax was observed in dogs for systemic drug and metabolite concentrations, but not in mice. Co-modeling IV and TAF implant PK data in dogs led to an apparent TAF bioavailability of 9.6 in the single implant groups (compared to the IV group), but only 1.5 when two implants were placed in the same subcutaneous pocket.

CONCLUSIONS

Based on the current results, we recommend using mice and sheep, with macaques as a complementary species, for preclinical TAF implant evaluation with the caveat that our observations may be specific to the implant technology used here. Our report provides fundamental, translatable insights into multispecies TAF delivery via long-acting implants.

POS0216 CARDIAC SARCOIDOSIS: AN UNDERDIAGNOSED, LIFE-THREATENING YET TREATABLE DISEASE

Background

Cardiac sarcoidosis (CS) is potentially life-threatening and it typically causes heart failure, ventricular arrhythmia, AV block or sudden death. CS has been reported to account for 25% of sarcoidosis patient deaths, thus highlighting the importance of early diagnosis and treatment. Diagnostic challenges and lack of a unified screening approach make it difficult to estimate its prevalence. Immunosuppression is the mainstay of treatment, but there is paucity of data on optimal dose, duration and efficacy of steroids and synthetic (s) or biologic (b) disease-modifying anti-rheumatic drugs (DMARDs).

Objectives

To describe the demographic and clinical characteristics of our CS patients, and to study their clinical response to steroids, synthetic and biologic DMARDs.

Methods

A retrospective cohort study with a prospective ongoing phase was conducted. ICD-10 codes were used to identify patients over 18 years old with sarcoidosis and CS followed at Montefiore Medical Center from 2017 to 2021. The following variables were recorded: demographics (age, sex, ethnicity), BMI, smoking status, presenting manifestations, histopathology (cardiac and extracardiac), imaging, treatment (corticosteroids and s/bDMARDs), dose and duration of therapy, steroid-sparing effect, response to treatment based on clinical and imaging improvement (echocardiogram, cardiac MRI, PET).

Results

220 patients with sarcoidosis were identified. 154 (70%) female and 124 (56.4%) Black. 42 out of 220 (19.1%) met diagnostic criteria for CS 1,2. Mean age of CS patients was 61.6 years. 23 (54.8%) were male and 24 (57.1%) Black. Heart failure (54.8%), arrhythmias (47.6%) and heart block (28.6%) were the most common presenting manifestations. 28.6% had isolated CS. 5 (11.9%) underwent endomyocardial biopsy and 2 of them (40%) had histopathologic evidence of CS. Mean left ventricular ejection fraction (LVEF) was 40.6 % on echocardiogram, and 29 patients (69%) had PPM/ICD placed for arrhythmia prevention. 35 (83.3%) underwent cardiac MRI, 37 (88.1%) cardiac PET scan and 23 (62.3%) had a follow up PET. 33 (78.6%) CS patients were treated with corticosteroids for a mean duration of 17.3 months. 21 of them were also treated with sDMARDs and 3 were subsequently switched to bDMARDs (Table 1). Mean prednisone dose at 12 months was 4.8mg, and 11 patients (33%) were tapered off corticosteroids.

Table 1.

Treatment of cardiac sarcoidosis

AgentTreated with DMARDs(N=21)*Duration of treatment(months, x̄)Max dose(mg, x̄)Prednisone dose at 12 months(mg, x̄)Response to treatmentMethotrexate (Weekly)16/21(76.1%)16.016.93.6714/16(87.5%)Mycophenolate mofetil (Daily)6/21(28.6%)16.920005.13/6(50%)Hydroxychloroquine (Daily)1/21(4.8%)17.540051/1(100%)Infliximab (q 8 weeks)1/21(4.8%)6.05 (mg/kg)51/1(100%)Adalimumab (q 2 weeks)2/21(9.5%)10.0407.52/2(100%)

*2 patients switched from MTX to MMF and 3 from sDMARDs to bDMARDs

Conclusion

In our sarcoid patient population, the prevalence of CS is 19.1%, which is higher than previously reported in the literature, suggesting CS may be underdiagnosed. There was a greater proportion of male patients in the CS population (54.8%) than the generalized sarcoidosis population (30%). This indicates that males with sarcoidosis may be more likely to have cardiac involvement. Patients treated with s/bDMARDs had a high response rate as reflected by clinical and imaging improvement. Steroid-sparing effect is suggested by the low prednisone dose at 12 months (Table 1). Methotrexate was the most commonly used DMARD (76.2%). Randomized clinical trials are needed to establish robust guidelines for the treatment of CS.

References

[1]Birnie, David H., et al. HRS expert consensus statement on the diagnosis and management of arrhythmias associated with cardiac sarcoidosis. Heart rhythm 11.7 (2014): 1304-1323.

[2]Terasaki F, Yoshinaga K. New guidelines for diagnosis of cardiac sarcoidosis in Japan. Ann Nuclear Cardiol 2017;3:42–5.

Disclosure of Interests

None declared

Fundamental aspects of long-acting tenofovir alafenamide delivery from subdermal implants for HIV prophylaxis

Global efforts aimed at preventing human immunodeficiency virus type one (HIV-1) infection in vulnerable populations appear to be stalling, limiting our ability to control the epidemic. Long-acting, controlled drug administration from subdermal implants holds significant potential by reducing the compliance burden associated with frequent dosing. We, and others, are exploring the development of complementary subdermal implant technologies delivering the potent prodrug, tenofovir alafenamide (TAF). The current report addresses knowledge gaps in the preclinical pharmacology of long-acting, subdermal TAF delivery using several mouse models. Systemic drug disposition during TAF implant dosing was explained by a multi-compartment pharmacokinetic (PK) model. Imaging mass spectrometry was employed to characterize the spatial distribution of TAF and its principal five metabolites in local tissues surrounding the implant. Humanized mouse studies determined the effective TAF dose for preventing vaginal and rectal HIV-1 acquisition. Our results represent an important step in the development of a safe and effective TAF implant for HIV-1 prevention.

High burnout among the South African orthopaedic community: a cross-sectional study

BACKGROUND: Burnout is epidemic among physicians, with the orthopaedic speciality displaying one of the highest rates of burnout in international studies. The burnout rate of the South African orthopaedic community is unknown. This study aimed to determine the prevalence and causes of burnout, as well as the coping mechanisms and associations with burnout, in South African orthopaedic surgeons and trainees METHODS: We conducted a cross-sectional, secure, online survey of members of the South African Orthopaedic Association. The survey assessed demographic characteristics, workload, professional fulfilment and burnout (utilising the Stanford Professional Fulfilment Index), associated workplace distress conditions, causes of and coping strategies for burnout. A response was not compulsory for any question. Statistical analysis was performed to assess for independent associations with burnout RESULTS: One hundred and fifty-six respondents, with a median age of 46.5 years (interquartile range [IQR] 37-58) participated. Ninety per cent (139 of 155) of respondents were male. Registrars accounted for 17% (27 of 155), while 83% (128 of 155) were qualified specialists. Respondents were in orthopaedic practice for a median of 17 years (IQR 9-28). Sixty per cent (76 of 127) practise in private, 17% (22 of 127) in public and 23% (29 of 127) in both sectors. The overall burnout rate was 72% (113 of 156). Burnout was associated with being the parent of young children and having fewer hours of sleep on call. Registrars were more likely to have burnout than consultants (OR 5.68, 95% CI 1.3-25.2). Gender, practice setting and subspeciality were not associated with burnout. Self-reported causes of burnout that were found to be associated with actual burnout were: 'hours at work', 'lack of free time' and 'work-life imbalance'. No self-reported coping mechanisms were found to be protective in this cohort, but the use of alcohol as a coping mechanism was associated with an increased likelihood of burnout (OR 3.9, 95% CI 1.4-10.7). Respondents felt that the concurrent experience of the COVID pandemic at the time of running the survey reduced their experience of burnout CONCLUSION: The burnout rate in the South African orthopaedic community is 72%. Trainees were found to be particularly vulnerable. There appears to be a need to develop, assess and implement effective system-related initiatives aimed at reducing the burnout rate among orthopaedic surgeons and trainees in South Africa Level of evidence: Level 4

Multispecies Evaluation of a Long-Acting Tenofovir Alafenamide Subdermal Implant for HIV Prophylaxis

New HIV-1 infection rates far outpace the targets set by global health organizations, despite important progress in curbing the progression of the epidemic. Long-acting (LA) formulations delivering antiretroviral (ARV) agents for HIV-1 pre-exposure prophylaxis (PrEP) hold significant promise, potentially facilitating adherence due to reduced dosing frequency compared to oral regimens. We have developed a subdermal implant delivering the potent ARV drug tenofovir alafenamide that could provide protection from HIV-1 infection for 6 months, or longer. Implants from the same lot were investigated in mice and sheep for local safety and pharmacokinetics (PKs). Ours is the first report using these animal models to evaluate subdermal implants for HIV-1 PrEP. The devices appeared safe, and the plasma PKs as well as the drug and metabolite concentrations in dermal tissue adjacent to the implants were studied and contrasted in two models spanning the extremes of the body weight spectrum. Drug and drug metabolite concentrations in dermal tissue are key in assessing local exposure and any toxicity related to the active agent. Based on our analysis, both animal models were shown to hold significant promise in LA product development.

Concentrative Nucleoside Transporter 3 Is Located on Microvilli of Vaginal Epithelial Cells

Transporters are specialized integral membrane proteins, which mediate the passage of virtually all molecules through cell membranes. They are expressed in a broad range of human and animal tissues and play important roles in both normal and disease states. For these reasons, they are evaluated when developing and testing drugs. Two major families of drug transporters, the adenosine 5'-triphosphate-binding cassette and solute carrier transporters (SLC), have critical roles in the absorption, distribution, metabolism, and elimination of drugs. The SLC family contains known nucleoside transporters and therefore are important when nucleoside analogs are used as drugs to prevent or treat viral infections. In this study, we wanted to determine if it was possible to locate one member of the SLC family, the human concentrative nucleoside transporter 3 (CNT3) in human vaginal epithelial cells. The CNT3 protein has important roles in drug delivery, subsequent drug tissue distribution, and, hence, efficacy. Vaginal epithelial cells, taken from two human volunteers (one Caucasian and one African American), were labeled for light and electron microscopy, with a commercial antibody to a cytoplasmic domain of CNT3, the protein product of the SLC28A3 gene. Fluorescent secondary antibodies or protein A-gold were used to detect antibody binding. By electron microscopy, gold particle binding was quantified to determine labeling specificity. By light microscopy, positive labeling with anti-CNT3 antibodies was detected on human vaginal epithelial cells, but specificity to any intracellular structure was not easily determined, most likely a result of specimen preparation. Electron microscopy revealed that the CNT3 transporter protein was present predominantly on microvilli located on one side of some human vaginal epithelial cells. Quantification confirmed specific anti-CNT3 labeling over human vaginal epithelial cell microvilli. The CNT3 protein, present in the microvilli of human vaginal epithelial cells, may have a role in redistributing nucleoside homologues delivered to the vaginal tract. Transporter proteins such as CNT3 could shuttle nucleosides and their analogs through the vaginal epithelium to immune cells located in lower cell layers. Outer layers of cells, which are eventually shed from the epithelium, may remove accumulated nucleoside drug analogs from the vaginal tract.

Effects of Amino Acids on Iron-Silicate Chemical Garden Precipitation

Understanding the structure and behavior of chemical gardens is of interest for materials science, for understanding organic-mineral interactions, and for simulating geological mineral structures in hydrothermal systems on Earth and other worlds. Herein, we explored the effects of amino acids on inorganic chemical garden precipitate systems of iron chloride and sodium silicate to determine if/how the addition of organics can affect self-assembling morphologies or crystal growth. Amino acids affect chemical garden growth and morphology at the macro-scale and at the nanoscale. In this reaction system, the concentration of amino acid had a greater impact than the amino acid side chain, and increasing concentrations of organics caused structures to have smoother exteriors as amino acids accumulated on the outside surface. These results provide an example of how organic compounds can become incorporated into and influence the growth of inorganic self-organizing precipitates in far-from-equilibrium systems. Additionally, sample handing methods were developed to successfully image these delicate structures.

The stability of imaging biomarkers in radiomics: a framework for evaluation

This paper studies the sensitivity of a range of image texture parameters used in radiomics to: (i) the number of intensity levels, (ii) the method of quantisation to select the intensity levels and (iii) the use of an intensity threshold. 43 commonly used texture features were studied for the gross target volume outlined on the CT component of PET/CT scans of 50 patients with non-small cell lung carcinoma (NSCLC). All cases were quantised for all values between 4 and 128 intensity levels using four commonly used quantisation methods. All results were analysed with and without a threshold range of  -200 HU to 300 HU. Cases were ranked for each texture feature and for all quantisation methods with the Spearman's rank correlation coefficient determined to evaluate stability. Results showed large fluctuations in ranking, particularly for low numbers of levels, differences between quantisation methods and with the use of a threshold, with values Spearman's Rank Correlation for many parameters below 0.2. Our results demonstrated the sensitivity of radiomics features to the parameters used during analysis and highlight the risk of low reproducibility comparing studies with slightly different parameters. In terms of the lung cancer CT datasets, this study supports the use of 128 intensity levels, the same uniform quantiser applied to all scans and thresholding of the data. It also supports several of the features recommended in the literature for such studies such as skewness and kurtosis. A recommended framework is presented for curation of the data analysis process to ensure stability of results.