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Current and planned HIV prevention trials: microbicides and PrEP

Current and planned HIV prevention trials: microbicides and PrEP. Presented at: XVIII International AIDS Conference, Vienna, 22 July 2010 Salim S. Abdool Karim Pro Vice-Chancellor (Research): University of KwaZulu-Natal Director: CAPRISA

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Current and planned HIV prevention trials: microbicides and PrEP

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  1. Current and planned HIV prevention trials: microbicides and PrEP Presented at: XVIII International AIDS Conference, Vienna, 22 July 2010 Salim S. Abdool Karim Pro Vice-Chancellor (Research): University of KwaZulu-Natal Director: CAPRISA Professor in Clinical Epidemiology, Columbia University Adjunct Professor of Medicine, Cornell University

  2. Outline • Why the interest in PrEP? • Historical overview of PrEP research • Current PrEP trials • Summary of the CAPRISA 004 findings • Planned PrEP trials • Key challenges in the implementation of PrEP trials • Conclusion

  3. Pre-exposure prophylaxis (PrEP) • Pre-exposure prophylaxis (PrEP) is an experimental HIV prevention strategy that uses antiretroviral agents prior to exposure, to prevent HIV acquisition • PrEP for HIV prevention builds on the concept that medications can be used by healthy people to prevent other infections: • Mefloquine prophylaxis for malaria • INH prophylaxis for tuberculosis • Mathematical modeling impact: 2.7 - 3.2 million new HIV infections could be averted in southern Africa in 10 years by targeting PrEP (if 90% effective) to those at highest behavioral risk Source: Abbas UL, PLoS ONE 2(9): e875. doi:10.1371/journal.pone. 0000875

  4. Why the interest in PrEP…. Biological plausibility – effect of ARVs on viral replication Numerous animal challenge since since 1995 show protection Success of post-exposure prophylaxis for needlestick exposure in observational data pMTCT: Proof of concept via another route of transmission in humans

  5. Initial efforts to test PrEP:Tenofovir PrEP studies halted by activists At what cost? How many infections could have been prevented if these trials went ahead?

  6. TenofovirPrEP trial stopped due to low HIV incidence in study populations in Ghana, Cameroon and Nigeria

  7. Botswana PrEP trial stopped due to low HIV incidence & mobile populations

  8. Current PrEP trials

  9. Available for download from: http://www.sciencemag.org/sciencexpress/recent.dtl

  10. Summary of CAPRISA 004 findings • Safety • No substantive safety concerns • No tenofovir resistance identified • Safe in Hepatitis B virus infected women • No evidence of risk compensation / behavioral disinhibition • Proof of concept that tenofovir gel can prevent HSV-2 infection in women • 51% reduction in HSV-2 • Proof of concept that tenofovir gel can prevent HIV infection in women • 39% protection against HIV overall • 50% reduction in HIV after 1 year of tenofovir gel use • 54% effective in women with high adherence

  11. Comparison of HIV effectiveness: HIVNET 012 and CAPRISA 004 HIVNET 012 - nevirapine Study asap 72 hrs 12 hrs PMTCT - HIVNET 012 41 Tenofovir gel - CAP 004 39 asap 54 Tenofovir gel – high adherence 38 Tenofovir gel – medium adherence 28 Tenofovir gel – low adherence CAPRISA 004 tenofovir gel 0% 10 20 30 40 50 60 70 80 90 100% Efficacy

  12. PrEP trials being planned

  13. Key challenges in future implementation of PrEP: impact on study design • Is it safe to give ARV drugs to healthy people? • Will those who get infected have HIV that is resistant to the PrEP antiretrovirals? Will this affect their subsequent care and choice of ARV treatment? • Will healthy people be willing to take medication everyday or at the time of sex for long periods? • Is this an affordable and practical HIV prevention strategy for scale-up if it is efficacious? • Will there be behavioural disinhibition / risk compensation?

  14. Conclusion • Oral and topical PrEP – promising & results awaited • Current trials: tenofovir gel/pill and truvada pill in: • IDUs, discordant couples, young women, MSM • If effective, implementation programs will require extensive community education to promote PrEP with integrated use of other prevention strategies • The provision of PrEP will require integration into existing HIV prevention and health care services • Need to include long term follow-up and surveillance in sentinel groups to monitor adverse events, adherence, drug resistance, impact of drug resistance on later AIDS treatment and behaviouraldisinhibition

  15. Future questions for PrEP • Which drug? Which formulation (oral or topical)? Which dosing strategy? What impact on adherence, efficacy and safety • Do long-acting formulations such as vaginal rings or slow release bolus dosing impact on adherence and risk of drug resistance? • Are combinations of ARVs better in terms of safety, efficacy and drug resistance? • Should an ARV (or class) be set aside for PrEP?

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