Efficacy and safety of long-acting cabotegravir compared with daily oral tenofovir disoproxil fumarate plus emtricitabine to prevent HIV infection in cisgender men and transgender women who have sex with men 1 year after study unblinding: a secondary analysis of the phase 2b and 3 HPTN 083 randomised controlled trial

BACKGROUND

Injectable cabotegravir was superior to daily oral tenofovir disoproxil fumarate plus emtricitabine for HIV prevention in two clinical trials. Both trials had the primary aim of establishing the HIV prevention efficacy of long-acting injectable cabotegravir pre-exposure prophylaxis (PrEP) compared with tenofovir disoproxil fumarate plus emtricitabine daily oral PrEP. Long-acting PrEP was associated with diagnostic delays and integrase strand-transfer inhibitor (INSTI) resistance. This report presents findings from the first unblinded year of the HIV Prevention Trials Network (HPTN) 083 study.

METHODS

The HPTN 083 randomised controlled trial enrolled HIV-uninfected cisgender men and transgender women at elevated HIV risk who have sex with men, from 43 clinical research sites in Africa, Asia, Latin America, and the USA. Inclusion criteria included: a negative HIV serological test at the screening and study entry, undetectable HIV RNA levels within 14 days of study entry, age 18 years or older, overall good health as determined by clinical and laboratory evaluations, and a creatinine clearance of 60 mL/min or higher. Participants were randomly allocated to receive long-acting injectable cabotegravir or daily oral tenofovir disoproxil fumarate plus emtricitabine PrEP. After study unblinding, participants remained on their original regimen awaiting an extension study. HIV infections were characterised retrospectively at a central laboratory. Here we report the secondary analysis of efficacy and safety for the first unblinded year. The primary outcome was incident HIV infection. Efficacy analyses were done on the modified intention-to-treat population using a Cox regression model. Adverse events were compared across treatment groups and time periods (blinded vs unblinded). This trial is registered with ClinicalTrials.gov, NCT02720094.

FINDINGS

Of the 4488 participants who contributed person-time to the blinded analysis, 3290 contributed person-time to the first unblinded year analysis between May 15, 2020, and May 14, 2021. Updated HIV incidence in the blinded phase was 0·41 per 100 person-years for long-acting injectable cabotegravir PrEP and 1·29 per 100 person-years for daily oral tenofovir disoproxil fumarate plus emtricitabine PrEP (hazard ratio [HR] 0·31 [95% CI 0·17-0·58], p=0·0003). HIV incidence in the first unblinded year was 0·82 per 100 person-years for long-acting PrEP and 2·27 per 100 person-years for daily oral PrEP (HR 0·35 [0·18-0·69], p=0·002). Adherence to both study products decreased after study unblinding. Additional infections in the long-acting PrEP group included two with on-time injections; three with one or more delayed injections; two detected with long-acting PrEP reinitiation; and 11 more than 6 months after their last injection. Infection within 6 months of cabotegravir exposure was associated with diagnostic delays and INSTI resistance. Adverse events were generally consistent with previous reports; incident hypertension in the long-acting PrEP group requires further investigation.

INTERPRETATION

Long-acting injectable cabotegravir PrEP retained high efficacy for HIV prevention in men and transgender women who have sex with men during the first year of open-label follow-up, with a near-identical HR for HIV risk reduction between long-acting injectable cabotegravir and daily oral tenofovir disoproxil fumarate plus emtricitabine PrEP during the first year after unblinding compared with the blinded period. Extended follow-up further defined the risk period for diagnostic delays and emergence of INSTI resistance.

FUNDING

Division of AIDS at the National Institute of Allergy and Infectious Diseases, ViiV Healthcare, and Gilead Sciences.

Cabotegravir for HIV Prevention in Cisgender Men and Transgender Women

BACKGROUND

Safe and effective long-acting injectable agents for preexposure prophylaxis (PrEP) for human immunodeficiency virus (HIV) infection are needed to increase the options for preventing HIV infection.

METHODS

We conducted a randomized, double-blind, double-dummy, noninferiority trial to compare long-acting injectable cabotegravir (CAB-LA, an integrase strand-transfer inhibitor [INSTI]) at a dose of 600 mg, given intramuscularly every 8 weeks, with daily oral tenofovir disoproxil fumarate-emtricitabine (TDF-FTC) for the prevention of HIV infection in at-risk cisgender men who have sex with men (MSM) and in at-risk transgender women who have sex with men. Participants were randomly assigned (1:1) to receive one of the two regimens and were followed for 153 weeks. HIV testing and safety evaluations were performed. The primary end point was incident HIV infection.

RESULTS

The intention-to-treat population included 4566 participants who underwent randomization; 570 (12.5%) identified as transgender women, and the median age was 26 years (interquartile range, 22 to 32). The trial was stopped early for efficacy on review of the results of the first preplanned interim end-point analysis. Among 1698 participants from the United States, 845 (49.8%) identified as Black. Incident HIV infection occurred in 52 participants: 13 in the cabotegravir group (incidence, 0.41 per 100 person-years) and 39 in the TDF-FTC group (incidence, 1.22 per 100 person-years) (hazard ratio, 0.34; 95% confidence interval, 0.18 to 0.62). The effect was consistent across prespecified subgroups. Injection-site reactions were reported in 81.4% of the participants in the cabotegravir group and in 31.3% of those in the TDF-FTC group. In the participants in whom HIV infection was diagnosed after exposure to CAB-LA, INSTI resistance and delays in the detection of HIV infection were noted. No safety concerns were identified.

CONCLUSIONS

CAB-LA was superior to daily oral TDF-FTC in preventing HIV infection among MSM and transgender women. Strategies are needed to prevent INSTI resistance in cases of CAB-LA PrEP failure. (Funded by the National Institute of Allergy and Infectious Diseases and others; HPTN 083 ClinicalTrials.gov number, NCT02720094.).

PrEP Nonadherence, White Coat Dosing, and HIV Risk Among a Cohort of MSM

Among a cohort of men who have sex with men in a pre-exposure prophylaxis (PrEP) adherence trial, syphilis requiring treatment was associated with white coat dosing (increased PrEP adherence immediately preceding study visits) when compared with participants with optimal drug concentrations. The findings highlight the need for identifying and reducing barriers to PrEP adherence.

Effective use of pre-exposure prophylaxis (PrEP) Among stimulant users with multiple condomless sex partners: a longitudinal study of men who have sex with men in Los Angeles

PrEP's potential benefit for men who have sex with men (MSM) who use stimulants may be limited by adherence or prescriber willingness to recommend PrEP due to concerns of non-compliance. Using data from PATH-PrEP, a 48-week study evaluating PrEP for MSM in Los Angeles, we modeled an interaction between stimulant use and condomless sex with multiple partners (CAS-MP) on prevention-effective dried blood spot tenofovir-diphosphate concentrations. At week 4, participants reporting stimulant use and CAS-MP had a decreased odds of prevention-effective adherence compared to non-stimulant use and non-CAS-MP (AOR 0.15, 95% CI 0.04-0.57). From week 4-48, participants reporting stimulant use and CAS-MP had increased odds of prevention-effective adherence (AOR 1.06 per week, 95%CI 1.01-1.12). Participants reporting CAS-MP without stimulant use had no significant change in prevention-effective adherence (AOR 0.99 per week, 95%CI 0.96-1.02). Stimulant use moderated the association of CAS-MP on prevention-effective PrEP adherence over time.

Results from the post-exposure prophylaxis pilot program (P-QUAD) demonstration project in Los Angeles County

Post-exposure prophylaxis (PEP) is a promising but under-utilized strategy for HIV prevention in high-risk populations. Between March 2010 and June 2011, two community-based clinics in Los Angeles County provided PEP in a pilot program to 267 unique individuals. Courses were primarily dispensed to men who have sex with men (84%) and consisted overwhelmingly of a three-drug antiretroviral therapy regimen containing two nucleoside reverse transcriptase inhibitors and either an integrase inhibitor (raltegravir) or a boosted protease inhibitor (lopinavir/ritonavir). Approximately 64% of all PEP courses were followed for at least 12 weeks, and seven individuals seroconverted. Of the seven seroconversions, six had subsequent re-exposure. The low rate of PEP failure calls for expanded funding for PEP in other jurisdictions.

Differentiating Nonoccupational Postexposure Prophylaxis Seroconverters and Non-Seroconverters in a Community-Based Clinic in Los Angeles, California

BACKGROUND

Nonoccupational postexposure prophylaxis (nPEP) is a 28-day regimen of antiretroviral medications taken within 72 hours of human immunodeficiency virus (HIV) exposure to prevent HIV acquisition. Although nPEP has been recommended since 1998, few studies have analyzed the characteristics that distinguish nPEP failures (seroconverters) and successes (non-seroconverters).

METHODS

This retrospective study analyzed all nPEP courses prompted by sexual exposure that were prescribed at the Los Angeles LGBT Center between March 2010 and July 2014. Fisher exact tests and logistic regressions were used to determine characteristics that distinguished nPEP seroconverters from non-seroconverters.

RESULTS

Of the nPEP courses administered, 1744 had a follow-up visit for HIV testing within 24 weeks of exposure and 17 individuals seroconverted. Seven reported a known re-exposure, 8 self-reported only condom-protected sex subsequent to the initial exposure, and 2 reported abstinence since the exposure. In multivariable analyses, seroconverters were more likely than non-seroconverters to report methamphetamine use, incomplete medication adherence, and nPEP initiation later in the 72-hour window.

CONCLUSIONS

Nonoccupational postexposure prophylaxis is an important emergency tool for HIV prevention. Our findings corroborate that timing of the initial nPEP dose is an important predictor of seroconversion. Although the current study did not offer the initial nPEP dose at the beginning of the visit, use of this fast-track dosing schedule will ensure that the first dose is taken as early as possible postexposure and may lower the likelihood for seroconversion. Furthermore, we recommend systematic screening for substance use because these individuals may be well suited for pre-exposure prophylaxis given their sustained risk.

Audio-Enhanced Tablet Computers to Assess Children's Food Frequency From Migrant Farmworker Mothers

This study sought to improve data collection in children's food frequency surveys for non-English speaking immigrant/migrant farmworker mothers using audio-enhanced tablet computers (ATCs). We hypothesized that by using technological adaptations, we would be able to improve data capture and therefore reduce lost surveys. This Food Frequency Questionnaire (FFQ), a paper-based dietary assessment tool, was adapted for ATCs and assessed consumption of 66 food items asking 3 questions for each food item: frequency, quantity of consumption, and serving size. The tablet-based survey was audio enhanced with each question "read" to participants, accompanied by food item images, together with an embedded short instructional video. Results indicated that respondents were able to complete the 198 questions from the 66 food item FFQ on ATCs in approximately 23 minutes. Compared with paper-based FFQs, ATC-based FFQs had less missing data. Despite overall reductions in missing data by use of ATCs, respondents still appeared to have difficulty with question 2 of the FFQ. Ability to score the FFQ was dependent on what sections missing data were located. Unlike the paper-based FFQs, no ATC-based FFQs were unscored due to amount or location of missing data. An ATC-based FFQ was feasible and increased ability to score this survey on children's food patterns from migrant farmworker mothers. This adapted technology may serve as an exemplar for other non-English speaking immigrant populations.