Purpose of review

Preexposure prophylaxis for HIV prevention is highly effective when taken as prescribed. Adherence to required dosing regimens for protection may pose challenges. Long-acting agents for HIV prevention may have the potential to improve adherence via favorable pharmacokinetics supportive of infrequent dosing. This review focuses on the potential benefits and considerations for the study and use of 2 long-acting injectable agents, cabotegravir (GSK1265744LA, CAB LA) and rilpivirine (TMC278LA, RPV LA), for use as chemoprophylaxis for HIV prevention.

Recent findings

Oral RPV is United States Food and Drug Administration approved for HIV treatment (in combination with other antiretrovirals). Both CAB LA and RPV LA are currently in phase 2a safety/tolerability/pharmacokinetic studies in anticipation and support of future efficacy evaluation. Both agents have favorable pharmacokinetics, and use is complicated by injection site reactions.

Summary

Long-acting injectable formulations, if safe and well tolerated, may improve pharmacokinetic coverage of exposures to HIV infection. Complexities around safety, tolerability, and starting/stopping protocols require careful consideration.

Two multinational clinical trials have shown safety and efficacy of long-acting injectable cabotegravir for HIV pre-exposure prophylaxis (PrEP). These results will alter the landscape of HIV prevention and related research. Nevertheless, designing and conducting this research involved several ethical issues. This Viewpoint describes how we managed ethical issues over the duration of one of these trials (HPTN 083). Specifically, we discuss the rationale for pursuing a long-acting injectable agent in the presence of effective oral PrEP, trial design choices, site selection and local standards of prevention, data monitoring and early stopping, effects of the COVID-19 pandemic, post-trial access, and assessment of long-term safety.

Aims

Cabotegravir delivered as a long-acting intramuscular injection has shown superior efficacy to oral tenofovir-emtricitabine as pre-exposure prophylaxis (PrEP) for HIV. Cabotegravir pharmacokinetics (PK), like those of other long-acting depot preparations, exhibit variability between individuals and between injection occasions. The aim of this study is to describe the population pharmacokinetics of long-acting cabotegravir (CAB-LA).

Methods

Using available PK measurements from 133 participants in the HIV Prevention Trials Network (HPTN) 077 trial, we analysed CAB-LA PK data using nonlinear mixed-effects modelling to develop a population PK model.

Results

A two-compartment model with first order absorption best described the CAB-LA PK. The analysis identified between-occasion variability (BOV, i.e., differences in PK within one individual from one injection to the next) as a significant covariate affecting the absorption rate, with an estimated contribution of BOV to PK variability on the absorption rate (k_a ) of 38.5%. Sex and body weight were identified as significant covariates influencing the absorption rate and apparent clearance of CAB-LA after intramuscular injection at various doses and frequencies. Male participants had 67% higher k_a than female participants. Serially adding to the model body weight on clearance, sex on k_a , and BOV on k_a led to a decrease in the objective function value (OFV) of 24.4, 36 and 321.4, respectively.

Conclusion

The public availability of this model will facilitate and enable a wide variety of future clinically relevant simulations to inform the optimal use of CAB-LA.

Introduction

Tenofovir (TDF)-containing PrEP is effective for HIV prevention, but its effect on health-related quality of life (QOL) is unknown. Using data from HPTN 069/ACTG A5305, a randomized study of potential PrEP regimens comparing maraviroc alone, or together with TDF or emtricitabine (FTC), to TDF + FTC (control), we evaluated the impact of these regimens on QOL in at-risk HIV-uninfected U.S. women and men.

Methods

QOL was measured at baseline (before starting medications) and every 8 weeks through week 48 using the EQ-5D-3L. Responses were converted to a scale from 0.0 (death) to 1.0 (perfect health), using published valuation weights. Mean scores were compared between groups at each time point using nonparametric testing. Multivariable linear regression was used to adjust for potential confounders.

Results

We analyzed 186 women (median age 35 years, 65% black, 17% Hispanic) and 405 men (median age 30 years, 28% black, 22% Hispanic), including 9 transgender participants analyzed based on sex-at-birth. Mean baseline QOL was 0.91 for women and 0.95 for men. There were minimal changes in mean QOL over time for any regimen (women: p = 0.29; men: p = 0.14). There were no significant differences between participants who continued the regimen compared to participants who discontinued early (women: p = 0.61; men: p = 0.1). Mean QOL did not differ significantly by regimen at any time point, both unadjusted and after adjustment for age, race/ethnicity, adherence, and use of alcohol, marijuana, opiates, and other substances.

Conclusions

QOL in at-risk individuals starting candidate PrEP regimens in a clinical trial is similar to the general population and maintained over time. This finding did not vary among regimens or when adjusted for demographics, adherence, and substance use. Our findings are the first to show that starting a candidate PrEP regimen in at-risk HIV-uninfected U.S. women and men was not associated with significant changes in QOL.

Trial registration

Clinicaltrials.gov NCT01505114.

Tenofovir (TFV) disoproxil fumarate and emtricitabine (FTC) are used in combination for HIV treatment and pre-exposure prophylaxis (PrEP). TFV disoproxil fumarate is a prodrug that undergoes diester hydrolysis to TFV. FTC and TFV are nucleoside/nucleotide reverse transcriptase inhibitors that upon phosphorylation to nucleotide triphosphate analogs competitively inhibit HIV reverse transcriptase. We previously demonstrated that adenylate kinase 2, pyruvate kinase, muscle and pyruvate kinase, liver and red blood cell phosphorylate TFV in peripheral blood mononuclear cells (PBMC). To identify the kinases that phosphorylate FTC in PBMC, siRNAs targeted toward kinases that phosphorylate compounds structurally similar to FTC were delivered to PBMC, followed by incubation with FTC and the application of a matrix-assisted laser desorption ionization-mass spectrometry method and ultra high performance liquid chromatography-UV to detect the formation of FTC phosphates. Knockdown of deoxycytidine kinase decreased the formation of FTC-monophosphate, while siRNA targeted toward thymidine kinase 1 decreased the abundance of FTC-diphosphate. Knockdown of either cytidine monophosphate kinase 1 or phosphoglycerate kinase 1 decreased the abundance of FTC-triphosphate. Next-generation sequencing of genomic DNA isolated from 498 HIV-uninfected participants in the HIV Prevention Trials Network 069/AIDS Clinical Trials Group A5305 clinical study, revealed 17 previously unreported genetic variants of TFV or FTC phosphorylating kinases. Of note, four individuals were identified as simultaneous carriers of variants of both TFV and FTC activating kinases. These results identify the specific kinases that activate FTC in PBMC, while also providing further insight into the potential for genetic variation to impact TFV and FTC activation.

Background

The HIV Prevention Trials Network (HPTN) 083 trial demonstrated the superiority of long-acting injectable cabotegravir (CAB-LA) compared with oral emtricitabine-tenofovir disoproxil fumarate (F/TDF) for HIV preexposure prophylaxis (PrEP).

Objective

To identify the maximum price premium (that is, greatest possible price differential) that society should be willing to accept for the additional benefits of CAB-LA over tenofovir-based PrEP among men who have sex with men and transgender women (MSM/TGW) in the United States.

Design

Simulation, cost-effectiveness analysis.

Data sources

Trial and published data, including estimated HIV incidence (5.32, 1.33, and 0.26 per 100 person-years for off PrEP, generic F/TDF and branded emtricitabine-tenofovir alafenamide (F/TAF), and CAB-LA, respectively); 28% 6-year PrEP retention. Annual base-case drug costs: $360 and $16 800 for generic F/TDF and branded F/TAF. Fewer side effects with branded F/TAF versus generic F/TDF were assumed.

Target population

476 700 MSM/TGW at very high risk for HIV (VHR).

Time horizon

10 years.

Perspective

Health care system.

Intervention

CAB-LA versus generic F/TDF or branded F/TAF for HIV PrEP.

Outcome measures

Primary transmissions, quality-adjusted life-years (QALYs), costs (2020 U.S. dollars), incremental cost-effectiveness ratios (ICERs; U.S. dollars per QALY), maximum price premium for CAB-LA versus tenofovir-based PrEP.

Results of base-case analysis

Compared with generic F/TDF (or branded F/TAF), CAB-LA increased life expectancy by 28 000 QALYs (26 000 QALYs) among those at VHR. Branded F/TAF cost more per QALY gained than generic F/TDF compared with no PrEP. At 10 years, CAB-LA could achieve an ICER of at most $100 000 per QALY compared with generic F/TDF at a maximum price premium of $3700 per year over generic F/TDF (CAB-LA price <$4100 per year).

Results of sensitivity analysis

In a PrEP-eligible population at high risk for HIV, rather than at VHR (n = 1 906 800; off PrEP incidence: 1.54 per 100 person-years), CAB-LA could achieve an ICER of at most $100 000 per QALY versus generic F/TDF at a maximum price premium of $1100 per year over generic F/TDF (CAB-LA price <$1500 per year).

Limitation

Uncertain clinical and economic benefits of averting future transmissions.

Conclusion

Effective oral PrEP limits the additional price society should be willing to pay for CAB-LA.

Primary funding source

FHI 360; Eunice Kennedy Shriver National Institute of Child Health and Human Development; National Institute of Allergy and Infectious Diseases; National Heart, Lung, and Blood Institute; National Institute on Drug Abuse; the Reich HIV Scholar Award; and the Steve and Deborah Gorlin MGH Research Scholars Award.

Objectives

To evaluate whether hormonal contraceptive use among cisgender women is associated with differences in pharmacokinetic (PK) parameters of a long-acting injectable formulation of the integrase strand transfer inhibitor, cabotegravir (CAB-LA).

Setting

This is a secondary analysis of 85 cisgender women enrolled in HPTN 077, a phase 2a multicenter study that enrolled HIV-uninfected, low-risk individuals in Malawi, Brazil, South Africa, and the United States.

Methods

Participants received 4-week daily oral cabotegravir lead-in, followed by CAB-LA 800 mg injection every 12 weeks (cohort 1) or 600 mg every 8 weeks (after 4-week initial interval between injections, cohort 2), over 41 weeks. Participants were followed 52-76 weeks subsequent to final injection. Generalized estimating equations and linear regression were used to evaluate differences in CAB-LA PK parameters (peak concentration, trough concentration, area under the curve, apparent terminal half-life, and time to lower limit of quantification) and self-reported hormonal contraceptive stratified by type (oral, injectable, implants, and other), controlling for body mass index and cohort.

Results

Compared to women reporting no hormonal contraception (n = 6), oral contraceptive use (n = 18) was associated with lower CAB-LA peak concentration but was not associated with differences in other PK parameters. No other hormonal contraceptive type (injectable, implants, and other) was associated with significant differences in CAB-LA PK parameters.

Conclusion

Although oral contraceptive use was associated with differences in CAB-LA peak concentration, no differences were observed in other PK parameters, suggesting that this association is not likely to be clinically significant. However, these data highlight the need for further research exploring potential drug-drug interactions between CAB-LA and hormonal contraceptives.

Long-acting injectable PrEP could offer an alternative to daily oral PrEP, improve adherence and protection, if found acceptable, safe and effective. HPTN 077 evaluated injectable cabotegravir safety, tolerability and pharmacokinetics among HIV-uninfected males and females in sequentially-enrolled cohorts of two dosing strategies. We compared acceptability of product attributes, prevention preferences and future interest in injectable PrEP (FIIP) by region, sex-at-birth, arm and cohort and used multivariable analysis to identify FIIP determinants. Baseline injectable PrEP preferences were higher in non-U.S. sites and increased in both regions over time. In multivariable models, FIIP was most strongly associated with acceptability of product attributes, was higher in non-U.S. sites and more altruistic participants. Treatment arm and report of pain were not associated with FIIP. Injectable acceptability was highest in non-U.S. sites. Preferences for injectable versus other PrEP methods were higher among U.S. males than females, but higher among males and females in non-U.S. settings.

Introduction

Tenofovir (TDF)-containing PrEP is effective for HIV prevention, but its effect on health-related quality of life (QOL) is unknown. Using data from HPTN 069/ACTG A5305, a randomized study of potential PrEP regimens comparing maraviroc alone, or together with TDF or emtricitabine (FTC), to TDF + FTC (control), we evaluated the impact of these regimens on QOL in at-risk HIV-uninfected U.S. women and men.

Methods

QOL was measured at baseline (before starting medications) and every 8 weeks through week 48 using the EQ-5D-3L. Responses were converted to a scale from 0.0 (death) to 1.0 (perfect health), using published valuation weights. Mean scores were compared between groups at each time point using nonparametric testing. Multivariable linear regression was used to adjust for potential confounders.

Results

We analyzed 186 women (median age 35 years, 65% black, 17% Hispanic) and 405 men (median age 30 years, 28% black, 22% Hispanic), including 9 transgender participants analyzed based on sex-at-birth. Mean baseline QOL was 0.91 for women and 0.95 for men. There were minimal changes in mean QOL over time for any regimen (women: p = 0.29; men: p = 0.14). There were no significant differences between participants who continued the regimen compared to participants who discontinued early (women: p = 0.61; men: p = 0.1). Mean QOL did not differ significantly by regimen at any time point, both unadjusted and after adjustment for age, race/ethnicity, adherence, and use of alcohol, marijuana, opiates, and other substances.

Conclusions

QOL in at-risk individuals starting candidate PrEP regimens in a clinical trial is similar to the general population and maintained over time. This finding did not vary among regimens or when adjusted for demographics, adherence, and substance use. Our findings are the first to show that starting a candidate PrEP regimen in at-risk HIV-uninfected U.S. women and men was not associated with significant changes in QOL.

Trial registration

Clinicaltrials.gov NCT01505114.

Background

Tenofovir disoproxil fumarate-containing pre-exposure prophylaxis (PrEP) has been associated with decreases in bone mineral density (BMD), but the bone effects of other non-tenofovir disoproxil fumarate candidate PrEP regimens are not well described.

Methods

The HPTN 069/ACTG A5305 study randomized 406 US cisgender men and transgender women, and 188 cisgender women at risk for HIV infection to one of four double-blinded regimens: (i) maraviroc; (ii) maraviroc + emtricitabine; (iii) maraviroc + tenofovir disoproxil fumarate; or (iv) tenofovir disoproxil fumarate + emtricitabine. BMD was measured in a subset of participants at the lumbar spine (LS) and hip by dual-energy X-ray absorptiometry (DXA) at baseline and 48 weeks. Percentage change in LS and hip BMD was compared between the tenofovir disoproxil fumarate- and non-tenofovir disoproxil fumarate-containing arms by Wilcoxon rank-sum tests and multiple linear regression adjusting for sex, race and baseline BMI.

Results

At baseline (n = 307), the median age was 33 years, 56% male and 43% black. At the hip, the median percentage change in BMD at 48 weeks was -1.05% in the tenofovir disoproxil fumarate arms and 0.0% in the non-tenofovir disoproxil fumarate arms (between group P = 0.001). No interaction by sex was observed. The median percentage change in LS BMD was not different between arms.

Conclusions

Tenofovir disoproxil fumarate-containing PrEP was associated with significantly greater bone loss compared with maraviroc ± emtricitabine PrEP at the hip, but not the LS. The BMD changes at the hip were similar in magnitude in men and women.