Clinical decisions. Preexposure prophylaxis for HIV prevention

PrEP risk perception and adherence among men who have sex with men: a prospective cohort study based on growth mixture model

BACKGROUND

It can be considered that pre-exposure prophylaxis (PrEP) risk perception is the negative experiences or concerns about taking PrEP. The aim of this study is to explore the longitudinal trajectory of PrEP risk perception among men who have sex with men (MSM) and its impact on adherence.

METHODS

Data related to PrEP risk perception and adherence were derived from a prospective cohort study in Western China from 2013 to 2015. Subjects were categorized into the time-driven, event-driven and blank control groups. Tenofovir disoproxil fumarate (TDF) was administered to subjects in the time-driven and event-driven groups, and all subjects were followed up every 12 weeks. The PrEP risk perception scale was constructed, and the growth mixture model (GMM) was used to classify longitudinal PrEP risk perception. The effect of different levels of PrEP risk perception on drug adherence was explored using generalized estimating equations (GEE) with relative risk (RR) and 95% confidence interval (CI).

RESULTS

The PrEP risk perception scale consists of 4 dimensions and 16 items with Cronbach's alpha = 0.828 and a good model fit. According to the GMM analysis, the subjects' PrEP risk perceptions were separated into two groups: a "high-risk perception group" (n = 133) and a "low-risk perception group" (n = 493), where the proportion of high levels of drug adherence were 57.89% and 68.35%, respectively (p = 0.024). High levels of PrEP risk perception in the MSM population hinder drug adherence (RR = 0.71, 95% CI 0.50 to 0.99, p = 0.046). The results of this study were validated in the subsequent PrEP projects conducted in 2019 to 2021.

CONCLUSION

This study demonstrates that high levels of PrEP risk perception in the MSM population are an obstacle to drug adherence, emphasizing the necessity of focusing on PrEP risk perception in this population and the value of its application in the current context.

Healthcare practitioner experiences and willingness to prescribe pre-exposure prophylaxis in the US

Background and objectives

Less than 10 percent of the more than one million people vulnerable to HIV are using pre-exposure prophylaxis (PrEP). Practitioners are critical to ensuring the delivery of PrEP across care settings. In this study, we target a group of prescribers focused on providing HIV care and seeking up-to-date information about HIV. We assessed their experiences prescribing PrEP, whether these experiences differed by clinical specialty, and examined associations between willingness to prescribe PrEP as a “best first step” and different hypothetical prescribing scenarios.

Setting and methods

Between March and May 2015, we circulated a paper survey to 954 participants ((652 of whom met our inclusion criteria of being independent prescribers and 519 of those (80%) responded to the survey)) at continuing medical education advanced-level HIV courses in five locations across the US on practitioner practices and preferences of PrEP. We employed multivariable logistic regression analysis for binary and collapsed ordinal outcomes.

Results

Among this highly motivated group of practitioners, only 54% reported ever prescribing PrEP. Internal medicine practitioners were 1.6 times more likely than infectious disease practitioners to have prescribed PrEP (95% CI: 0.99–2.60, p = .0524) and age, years of training, and sex were significantly associated with prescribing experience. Based on clinical vignettes describing different hypothetical prescribing scenarios, practitioners who viewed PrEP as the first clinical step for persons who inject drugs (PWID) were twice as likely to have also considered PrEP as the first clinical option for safer conception, and vice-a-versa (95% CI: 1.4–3.2, p < .001). Practitioners considering PrEP as the first preventive option for MSM were nearly six times as likely to also consider PrEP as the first clinical step for PWID, and vice-a-versa (95% CI: 2.28–13.56, p = .0002).

Conclusions

Our findings indicate that even among a subset of HIV-focused practitioners, PrEP prescribing is not routine. This group of practitioners could be an optimal group to engage individuals that could most benefit from PrEP.

Weighing the Evidence of Efficacy of Oral PrEP for HIV Prevention in Women in Southern Africa

As oral tenofovir-based regimens for preexposure prophylaxis (PrEP) are adopted as standard of care for HIV prevention, their utilization in clinical trials among women in southern Africa will require an accurate estimate of oral PrEP efficacy in this population. This information is critical for women in choosing this prevention strategy, and in public health policy making. Estimates of the efficacy of oral PrEP regimens containing tenofovir have varied widely across trials that enrolled women, with some studies reporting high efficacy and others reporting no efficacy. Although poor adherence is strongly associated with lack of efficacy, other factors, such as mode of transmission (sexual vs. parenteral), predominant HIV subtype (C vs. non-C), intensity of exposure, and percentage of stable serodiscordant couples, may also contribute to the variation in efficacy estimates. In this article, we evaluate the evidence for PrEP efficacy in women and propose potential explanations for the observed differences in efficacy among studies. Our review emphasizes the need to continue to refine estimates of efficacy and effectiveness of tenofovir-based oral PrEP so as to best develop the next generation of HIV prevention tools, and to inform public policies directed toward HIV prevention.

The impact of patient race on clinical decisions related to prescribing HIV pre-exposure prophylaxis (PrEP): assumptions about sexual risk compensation and implications for access

Antiretroviral pre-exposure prophylaxis (PrEP) has received increasing recognition as a viable prescription-based intervention for people at risk for HIV acquisition. However, little is known about racial biases affecting healthcare providers' willingness to prescribe PrEP. This investigation sought to explore medical students' stereotypes about sexual risk compensation among Black versus White men who have sex with men seeking PrEP, and the impact of such stereotypes on willingness to prescribe PrEP. An online survey presented participants (n = 102) with a clinical vignette of a PrEP-seeking, HIV-negative man with an HIV-positive male partner. Patient race was systematically manipulated. Participants reported predictions about patient sexual risk compensation, willingness to prescribe PrEP, and other clinical judgments. Bootstrapping analyses revealed that the Black patient was rated as more likely than the White patient to engage in increased unprotected sex if prescribed PrEP, which, in turn, was associated with reduced willingness to prescribe PrEP to the patient.

Emtricitabine/tenofovir disoproxil fumarate: a review of its use in HIV-1 pre-exposure prophylaxis

The fixed-dose combination of emtricitabine (FTC) 200 mg and tenofovir disoproxil fumarate (TDF) 300 mg (Truvada(®)), administered orally once daily, is widely used as part of first-line regimens for the treatment of HIV-1 infection. Recently, once-daily administration of FTC/TDF was approved in the USA for pre-exposure prophylaxis in conjunction with safer sex practices to reduce the risk of sexually acquired HIV-1 in high-risk adults who are not infected. To date, results of four large, randomized, double-blind, placebo-controlled, multicentre trials with FTC/TDF as pre-exposure prophylaxis have been published. Three studies showed statistically significant reductions in the number of individuals with emergent HIV-1 infection when FTC/TDF was compared with placebo over the ≈1- to 2-year study periods. Efficacy (i.e. risk reduction relative to placebo) was 44 % in the iPrEx trial in men who have sex with men, 75 % in the Partners PrEP study in heterosexual HIV-1-serodiscordant couples and 62 % in the TDF2 trial in heterosexual men and women. The fourth study (FEM-PrEP) in heterosexual women did not show a statistically significant difference between FTC/TDF and placebo, although low adherence rates reported in this trial may have been a factor. No unexpected adverse events were reported in the trials. However, since pre-exposure prophylaxis involves long-term administration of drugs to healthy individuals, it is important to monitor the long-term safety of FTC/TDF (e.g. renal function, bone mineral density) in this setting. Other notable considerations include adherence, cost and the potential for development of drug resistance. Interim guidelines are available for prescribing FTC/TDF as pre-exposure prophylaxis. If used appropriately in selected high-risk individuals, pre-exposure prophylaxis with FTC/TDF represents an important additional strategy to reduce the spread of HIV-1 infection, which continues to be a significant global concern.

The promise of pre-exposure prophylaxis with antiretroviral drugs to prevent HIV transmission: a review

PURPOSE OF REVIEW

Public health experts are wrestling with how to translate recent scientific findings from pre-exposure prophylaxis (PrEP) effectiveness trials into real-world programmes. This review summarizes clinical trial findings on oral and topical PrEP, discusses how decision-makers can evaluate the place of PrEP within combination prevention and highlights anticipated developments that could be important in future HIV-prevention strategies.

RECENT FINDINGS

PrEP taken daily as oral tablets to create systemic protection has been found to be effective in the Pre-Exposure Prophylaxis Initiative (iPrEx), Partners' PrEP and TDF2 trials, but not in Fem-PrEP or the Vaginal and Oral Interventions to Control the Epidemic (VOICE) tenofovir arm. Tenofovir gel for topical protection was effective in CAPRISA 004 when used peri-coitally but not in VOICE with daily use. These findings underscore the importance of adherence to achieve adequate drug levels and the potential additive role of PrEP within combination prevention. Pivotal phase III trials are underway of the dapivirine ring, whereas phase I trials of injectable formulations show promise.

SUMMARY

Antiretroviral-based HIV-prevention programmes should be tailored to those most likely to be adherent, providing them with state-of-the-art counselling and support to achieve high adherence during the time period of use. Long-acting products, if found well tolerated and effective, could be ideal for overcoming adherence challenges.

New generation humanized mice for virus research: comparative aspects and future prospects

Work with human specific viruses will greatly benefit from the use of an in vivo system that provides human target cells and tissues in a physiological setting. In this regard humanized mice (hu-Mice) have played an important role in our understanding of viral pathogenesis and testing of therapeutic strategies. Limitations with earlier versions of hu-Mice that lacked a functioning human immune system are currently being overcome. The new generation hu-Mouse models are capable of multilineage human hematopoiesis and generate T cells, B cells, macrophages and dendritic cells required for an adaptive human immune response. Now any human specific pathogen that can infect humanized mice can be studied in the context of ongoing infection and immune responses. Two leading humanized mouse models are currently employed: the hu-HSC model is created by transplantation of human hematopoietic stem cells (HSC), whereas the BLT mouse model is prepared by transplantation of human fetal liver, thymus and HSC. A number of human specific viruses such as HIV-1, dengue, EBV and HCV are being studied intensively in these systems. Both models permit infection by mucosal routes with viruses such as HIV-1 thus allowing transmission prevention studies. Cellular and humoral immune responses are seen in both the models. While there is efficient antigen specific IgM production, IgG responses are suboptimal due to inefficient immunoglobulin class switching. With the maturation of T cells occurring in the autologous human thymus, BLT mice permit human HLA restricted T cell responses in contrast to hu-HSC mice. However, the strength of the immune responses needs further improvement in both models to reach the levels seen in humans. The scope of hu-Mice use is further broadened by transplantation of additional tissues like human liver thus permitting immunopathogenesis studies on hepatotropic viruses such as HCV. Numerous studies that encompass antivirals, gene therapy, viral evolution, and the generation of human monoclonal antibodies have been conducted with promising results in these mice. For further improvement of the new hu-Mouse models, ongoing work is focused on generating new strains of immunodeficient mice transgenic for human HLA molecules to strengthen immune responses and human cytokines and growth factors to improve human cell reconstitution and their homeostatic maintenance.