Sexually transmitted infections and depot medroxyprogesterone acetate do not impact protection from simian HIV acquisition by long-acting cabotegravir in macaques

Broadly neutralizing antibody-mediated protection against simian-HIV infection among macaques with vaginal sexually transmitted infections

OBJECTIVE

Sexually transmitted infections (STIs) increase mucosal HIV infection risk and have the potential to reduce preexposure prophylaxis efficacy. Clinical trials of a broadly neutralizing antibody (bNAb) provided proof-of-concept that passive immunization against HIV can be efficacious in people. We sought to evaluate preclinically the protective efficacy of passive bNAb immunization against simian-human immunodeficiency virus (SHIV) infection in the context of concurrent vaginal STIs.

DESIGN

Using a macaque model of combined ulcerative and nonulcerative vaginal STIs caused by Treponema pallidum , Chlamydia trachomatis , and Trichomonas vaginalis , we determined the protection that passively administered bNAb 10-1074 conferred against repeated vaginal SHIV challenges and compared correlates of protection to contemporaneous and historical controls without STIs.

METHODS

Plasma viremia was monitored via RT-qPCR assay. Concentrations of 10-1074 were determined longitudinally in plasma samples via TZM-bl pseudovirus neutralization assay.

RESULTS

Among macaques with vaginal STIs, a single subcutaneous injection of 10-1074 durably protected against vaginal SHIV acquisition, as compared with untreated controls. Interestingly, the median plasma concentration of 10-1074 at the time of SHIV breakthrough among macaques with STIs was significantly higher (10-fold) than that previously observed among 10-1074-treated macaques in the absence of STIs.

CONCLUSION

Passive immunization with 10-1074 conferred significant protection against repeated vaginal SHIV challenges among macaques harboring vaginal STIs. However, our findings suggest that higher bNAb concentrations may be required for prophylaxis when STIs are present. Our findings potentially impact dose selection for the clinical development of bNAbs and highlight the importance of additional preclinical efficacy testing in STI models.

Ultra-long-acting in-situ forming implants with cabotegravir protect female macaques against rectal SHIV infection

Ultra-long-acting delivery platforms for HIV pre-exposure prophylaxis (PrEP) may increase adherence and maximize public health benefit. We report on an injectable, biodegradable, and removable in-situ forming implant (ISFI) that is administered subcutaneously and can release the integrase inhibitor cabotegravir (CAB) above protective benchmarks for more than 6 months. CAB ISFIs are well-tolerated in female mice and female macaques showing no signs of toxicity or chronic inflammation. In macaques, median plasma CAB concentrations exceed established PrEP protection benchmarks within 3 weeks and confer complete protection against repeated rectal SHIV challenges. Implant removal via a small incision in 2 macaques at week 12 results in a 7- to 48-fold decrease in plasma CAB levels within 72 hours. Modeling to translate CAB ISFI dosing suggests that a 3 mL injection would exceed protective benchmarks in humans for over 5 months post administration. Our results support the clinical advancement of CAB ISFIs for ultra-long-acting PrEP in humans.

Translational Models to Predict Target Concentrations for Pre-Exposure Prophylaxis in Women

The HIV epidemic remains a significant public health burden. Women represent half of the global HIV epidemic, yet there is an urgent need for a variety of prevention options to meet the needs of more women. Pre-exposure prophylaxis (PrEP) is a valuable prevention tool that uses antiretrovirals before a potential HIV exposure to prevent virus transmission. Development of effective preventive drug regimens for women is dependent on convenient dosing schedules and routes of administration, and on identifying defined target concentrations in mucosal tissues that provide complete protection against HIV transmission. There is a critical need for a translational model that can accurately predict in vivo target concentrations that are completely protective against HIV infection. There is no gold-standard preclinical model to predict PrEP efficacy. In this study, we review the strengths and limitations of three different preclinical models and their utility in predicting target concentrations in the female genital tract: humanized mice, non-human primates, and the ex vivo tissue model.

The predictive value of macaque models of preexposure prophylaxis for HIV prevention

PURPOSE OF REVIEW

We review macaque models for preexposure prophylaxis (PrEP) for HIV prevention and highlight their role in advancing currently approved and novel PrEP agents.

RECENT FINDINGS

The development of the repeat low dose simian HIV (SHIV) challenge models represented a significant advancement in preclinical PrEP modeling that has allowed the investigation of PrEP under conditions that better mimic HIV exposures in humans. These models incorporate relevant drug pharmacology to inform drug correlates of PrEP protection. Models of rectal, vaginal, and penile infection are now available and have been found to predict clinical efficacy of all the currently approved PrEP strategies including daily oral PrEP with the combination of emtricitabine and tenofovir disoproxil fumarate or tenofovir alafenamide, and a long-acting formulation of the integrase inhibitor cabotegravir. These models are being used to test new PrEP modalities including the nucleoside reverse transcriptase-translocation inhibitor islatravir and long-acting capsid inhibitors. The SHIV models have also been supplemented by sexually transmitted infection co-infections with Chlamydia trachomatis, Treponema pallidum or Trichomonas vaginalis to assess the impact of inflammation on PrEP efficacy.

SUMMARY

Clinical efficacy validated current PrEP macaque models supporting their continued use to advance novel PrEP agents to improve global PrEP coverage.