Efficacy estimates of oral pre-exposure prophylaxis for HIV prevention in cisgender women with partial adherence

HIV diagnosis during acute infection: implications of long-acting preexposure prophylaxis and other evolving challenges

PURPOSE OF REVIEW

Tests for HIV may perform differently in some circumstances such as with preexposure prophylaxis (PrEP) or other HIV prevention agents. Testing algorithms may not account for this, with a risk of false negative or positive HIV results. In this review we have explored the challenges of HIV testing in these special circumstances.

RECENT FINDINGS

Long-acting injectable PrEP using cabotegravir or lenacapavir has been studied in large randomized controlled trials (HPTN083/084 and PURPOSE1/2 respectively). Injectable PrEP was significantly more efficacious than oral PrEP, but infections still occurred risking the emergence of HIV drug-resistance. HIV diagnostic test results were atypical in those receiving injectable PrEP, with low or undetectable HIV viral loads, delayed or diminished antibody, and HIV detection assays reverting from reactive to unreactive; so-called long acting early viral inhibition (LEVI) syndrome. In these cases, missed or delayed HIV diagnoses could be reduced with the use of HIV nucleic acid amplification tests in addition to routine testing, but this remains unfeasible in many settings.

SUMMARY

Finding HIV testing strategies that are affordable and practical in low- and middle-income countries that can accurately diagnose HIV in the context of HIV prevention is of high importance, but more research is needed in this area.

Event-driven PrEP beyond cisgender men who have sex with men

Despite advancements in existing antiretroviral-based prevention strategies, including daily oral, locally acting, and injectable options, there is a pressing need for more inclusive and flexible event-driven pre-exposure prophylaxis (PrEP) strategies for all. Event-driven or intermittent dosing of PrEP in populations beyond cisgender men who have sex with men would offer a promising alternative by fitting prevention into the diverse lifestyles of affected populations and thereby advancing health equity. Evidence from PrEP clinical trials, pharmacokinetic studies, modelling studies, and real-world observational research suggests that event-driven PrEP could be a flexible and inclusive option, yet optimal dosing has not been established across sex and gender spectrums. To advance PrEP equity through inclusivity, studies on event-driven PrEP should include people across the gender spectrum. Real-world demonstration studies and simulation studies of optimal dosing strategies are needed. While awaiting further evidence, clinical providers can offer shared decision making and counselling on available data to include event-driven dosing as an option, especially when daily oral, locally acting, or injectable PrEP are not acceptable or preferred methods. Wider access to diverse PrEP options for all populations fosters a more inclusive and effective global HIV prevention strategy.

Modeling of HIV-1 prophylactic efficacy and toxicity with islatravir shows non-superiority for oral dosing, but promise as a subcutaneous implant

HIV prevention with pre-exposure prophylaxis (PrEP) constitutes a major pillar in fighting the ongoing epidemic. While daily oral PrEP adherence may be challenging, long-acting (LA-)PrEP in oral or implant formulations could overcome frequent dosing with convenient administration. The novel drug islatravir (ISL) may be suitable for LA-PrEP, but dose-dependent reductions inCD 4 + T cell and lymphocyte counts were observed at high doses. We developed a mathematical model to predict ISL pro-drug levels in plasma and active intracellular ISL-triphosphate concentrations after oral vs. subcutaneous implant dosing. Using phase II trial data, we simulated antiviral effects and estimated HIV risk reduction for multiple dosages and dosing frequencies. We then established exposure thresholds where no adverse effects on immune cells were observed. Our findings suggest that implants with 56-62 mg ISL offer effective HIV risk reduction without reducing lymphocyte counts. Oral 0.1 mg daily, 3-5 mg weekly, and 10 mg biweekly ISL provide comparable efficacy, but weekly and biweekly doses may affect lymphocyte counts, while daily dosing regimen offered no advantage over existing oral PrEP. Oral 0.5-1 mg on demand provided> 90 % protection, while not being suitable for post-exposure prophylaxis. These findings suggest ISL could be considered for further development as a promising and safe agent for implantable PrEP.

HIV Pre-Exposure Prophylaxis

Pre-exposure prophylaxis (PrEP) of human immunodeficiency virus (HIV) represents the most significant breakthrough in the HIV prevention field over the past decade. PrEP is an effective strategy in preventing the transmission of HIV across all populations, providing high adherence. The current PrEP options include oral daily and on-demand tenofovir-based regimens, long-acting injections of cabotegravir, and a 1-month dapivirine vaginal ring. As a component of a multifaceted prevention approach, extensive deployment of PrEP holds the promise to significantly reduce the global HIV epidemic. Nonetheless, barriers still exist in terms of uptake, adherence, and persistence, while disparities in PrEP accessibility remain a concern.

How Would You Manage HIV Pre-exposure Prophylaxis in This Patient With Medical Comorbidities? : Grand Rounds Discussion From Beth Israel Deaconess Medical Center

Despite advances in treatment, HIV infection remains an important cause of morbidity and mortality, with more than 30 000 new cases diagnosed in the United States each year. There are several interventions traditionally used to prevent HIV transmission, but these vary in effectiveness and there are challenges to their implementation. In 2014, the Centers for Disease Control and Prevention published initial guidance on the use of antiretroviral pre-exposure prophylaxis (PrEP) to prevent transmission of HIV infection in persons at risk based on multiple studies that showed it to be highly efficacious in various populations. It was updated in 2021 to reflect new drug options. The U.S. Preventive Services Task Force also recently updated its recommendations for PrEP, which strongly support its use in persons at risk. Despite its well-established effectiveness, the implementation of PrEP in clinical practice has been variable, especially among populations underserved by the medical system and marginalized by society. Fewer than one third of persons in the United States who are eligible for PrEP currently receive it. Here, 2 physicians experienced in HIV PrEP debate how best to identify patients who might benefit from PrEP, how to decide what regimen to use, and how to monitor therapy.

HIV Preexposure Prophylaxis With Emtricitabine and Tenofovir Disoproxil Fumarate Among Cisgender Women

Importance

Emtricitabine and tenofovir disoproxil fumarate (F/TDF) for HIV preexposure prophylaxis (PrEP) is highly effective in cisgender men who have sex with men (MSM) when adherence is high (>4 doses/week). Real-world effectiveness and adherence with F/TDF for PrEP in cisgender women is less well characterized.

Objective

To characterize the effectiveness of F/TDF for PrEP and its relationship with adherence in cisgender women.

Design, Setting, and Participants

Data were pooled from 11 F/TDF PrEP postapproval studies conducted in 6 countries that included 6296 cisgender women aged 15 to 69 years conducted from 2012 to 2020. HIV incidence was evaluated according to adherence level measured objectively (tenofovir diphosphate concentration in dried blood spots or tenofovir concentration in plasma; n = 288) and subjectively (electronic pill cap monitoring, pill counts, self-report, and study-reported adherence scale; n = 2954) using group-based trajectory modeling.

Exposures

F/TDF prescribed orally once a day. HIV incidence was analyzed in subgroups based on adherence trajectory.

Main Outcomes and Measures

HIV incidence.

Results

Of the 6296 participants, 46% were from Kenya, 28% were from South Africa, 21% were from India, 2.9% were from Uganda, 1.6% were from Botswana, and 0.8% were from the US. The mean (SD) age at PrEP initiation across all studies was 25 (7) years, with 61% of participants being younger than 25 years. The overall HIV incidence was 0.72 per 100 person-years (95% CI, 0.51-1.01; 32 incident HIV diagnoses among 6296 participants). Four distinct groups of adherence trajectories were identified: consistently daily (7 doses/week), consistently high (4-6 doses/week), high but declining (from a mean of 4-6 doses/week and then declining), and consistently low (less than 2 doses/week). None of the 498 women with consistently daily adherence acquired HIV. Only 1 of the 658 women with consistently high adherence acquired HIV (incidence rate, 0.13/100 person-years [95% CI, 0.02-0.92]). The incidence rate was 0.49 per 100 person-years (95% CI, 0.22-1.08) in the high but declining adherence group (n = 1166) and 1.27 per 100 person-years (95% CI, 0.53-3.04) in the consistently low adherence group (n = 632).

Conclusions and Relevance

In a pooled analysis of 11 postapproval studies of F/TDF for PrEP among cisgender women, overall HIV incidence was 0.72 per 100 person-years; individuals with consistently daily or consistently high adherence (4-6 doses/week) to PrEP experienced very low HIV incidence.