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The Role of ARVs in HIV Prevention: Microbicides and PrEP

December 2010

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General Drawbacks of Using ARVs as a Preventive Technology

Recent data from the PrEP safety trial described above suggest there was no increased risk-behavior in men taking the study pill versus those not yet taking the pills.

Potential for ARV resistant strains of HIV: If ARVs are used as prevention interventions there is a potential for widespread or indiscriminate use of ARVs beyond the currently controlled use in HAART or PMTCT. Even if provided through prescription, potential exists for pill sharing and non-compliance to recommended adherence and dosing. Use of PrEP without strict HIV testing to restrict it to HIV-negative individuals could also result in HIV-positive people receiving mono- or dual-ARV therapy, which could lead to development of resistance.

Behavior Dis-Inhibition: While behavior dis-inhibition in the advent of ARV therapy has been reported among MSM in San Francisco,10 this was before observation studies showed that highly active antiretroviral therapy (HAART) has a preventive effect.4 Further, the more recent data from the PrEP safety trial described above suggest there was no increased risk-behavior in men taking the study pill versus those not yet taking the pills. However, this was in a controlled setting where extensive steps were taken to ensure participants understood they were testing a drug not proven to prevent HIV. If PrEP is proven effective, additional research and interventions will be necessary to prevent the increase of risk behaviors in real world settings. An increase in risk-taking behavior resulting from a false sense of protection could easily outweigh the benefits of any ARV-based prevention method.


Overcoming These Drawbacks and the Way Forward

Overall strengthening of health services: Programming and distribution of these two potential ARV-based prevention methods would inevitably be centered on health care facilities. It should not be assumed that health facilities and systems are optimally functional and have enough personnel, infrastructure, and supplies to provide high quality services that are available to the most vulnerable people.

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Further, as the HIV prevention toolkit expands, the HIV response needs to consider the integrated health systems strengthening approach. It would be prudent to begin conducting cost and systems analysis of this integrated approach compared to the currently accepted vertical approach of specialized HIV projects, such as PMTCT, HAART and male circumcision.

This is an area which requires critical review if ARV-based prevention methods are going to play an increased role in HIV/AIDS programming in developing countries.11

Comprehensive education to PLHA about ARVs and HIV prevention: Now is the time, in anticipation of the expanding list of HIV-prevention methods that rely on ARV, to take the bull by the horns and revise education and counseling messages to PLHAs and the general community about issues regarding the role of ARVs in HIV prevention. Education needs to be accurate and available to properly inform PLHAs that ARVs lower their viral loads and make them less infectious,1 and that taking ARVs before or immediately after exposure to HIV can abort the infection.12

Further, correct and timely information about newly emerging prevention methods, such as ARV-based microbicides and PrEP, needs to be continually updated and available for public consumption. Both prevention methods are still in the clinical development phase, and each new result will bring new information and inevitable new questions.

Setting aside some ARVs for prevention: In order to reduce the risk of developing or transmitting ARV resistant strains, it may be reasonable to propose that certain ARVs be set aside for preventive strategies. The criteria for selecting such ARVs will require much thought.

First, they must be proven effective through clinical trials. Second, they should have the least side effects, as they are going to be taken by persons who have no illness, and thus may easily give them up if they are toxic. Third, they should not be the platform for first or second-line HAART regimens in the developing world since the withdrawal of these agents, due to widespread resistance, could spell disaster if there are no cheap alternatives.


Conclusion

The recent safety and efficacy data surrounding ARV-based microbicides and PrEP has breathed new life and hope into the field of ARV-based HIV prevention interventions. As the clinical science moves forward, there are policy and programmatic implications for expanding the ARV-based HIV prevention toolkit. Now is the time to address policy, programmatic, and ethical drawbacks so we can forge a clear path forward.

Samuel Kalibala, M.D., a physician who started providing AIDS care in his native Uganda in 1988, is a Senior Associate and Country Director (Kenya) at the Population Council. Based in Nairobi, for the past 10 years he has been engaged in operations research to ensure efficient and effective delivery of new interventions against HIV/AIDS, including PMTCT and HAART.

Sarah Littlefield, M.P.H., is a Clinical Trial Specialist in the HIV/AIDS Program at the Population Council. Based at their Center for Biomedical Research in New York City, her current projects seek to improve microbicide clinical trial design, with a focus on recruitment and the reporting of adherence in microbicide trials.


References

  1. Donnell D, Baeten JM, Kiarie J, et al. Heterosexual HIV-1 transmission after initiation of antiretroviral therapy: A prospective cohort analysis. Lancet. 2010; 375: 2092-98.
  2. Cohen MS. HAART and prevention of HIV transmission. Medscape HIV/AIDS. Posted: 07/11/2002.
  3. Cohen MS, Kashuba A. Antiretroviral drugs and the prevention of sexual transmission of HIV. Medscape CME. Posted: 09/24/2003.
  4. Abdool Karim Q, Abdool Karim SS, Frohlich JA, et al. Effectiveness and safety of tenofovir gel, an antiretroviral microbicide, for the prevention of HIV infection in women. Science. 2010 Sep 3; 329(5996): 1168-74.
  5. Skoler-Karpoff S, Ramjee G, Ahmed K, et al. Efficacy of Carraguard for prevention of HIV infection in women in South Africa: A randomised, double-blind, placebo-controlled trial. Lancet. 2008 Dec 6; 372(9654): 1977-87.
  6. McCormack S, Ramjee G, Kamali A, et al. PRO2000 vaginal gel for prevention of HIV-1 infection (Microbicides Development Programme 301): A phase 3, randomised, double-blind, parallel-group trial. Lancet. E-pub: 9/17/2010.
  7. Karim SA, Coletti A, Richardson B, et al. Safety and effectiveness of vaginal microbicides BufferGel and 0.5% PRO 2000/5 gel for the prevention of HIV infection in women: Results of the HPTN 035 trial. 16th Conference on Retroviruses and Opportunistic Infections; Feb 8-11, 2009; Montreal, Canada (abstr 48LB).
  8. Centers for Disease Control. Preliminary results from first safety study of daily tenofovir for HIV prevention among MSM find no significant concerns. Press release posted: July 23, 2010.
  9. Luchters S, Sarna A, Geibel S, et al. Safer sexual behaviors after 12 months of antiretroviral treatment in Mombasa, Kenya: A prospective cohort. AIDS Patient Care and STDs. 2008; 22(7): 587-594.
  10. Baggaley RF, Ferguson NM, Garnett GP. The epidemiological impact of antiretroviral use predicted by mathematical models: A review. Emerg Themes Epidemiol. 2005 Sep 10; 2:9.
  11. Handford CD, Tynan AM, Rackal JM, et al. Setting and organization of care for persons living with HIV/AIDS. Cochrane Database Syst Rev. 2006; 3:CD004348.
  12. Cohen MS, Kashuba A. Antiretroviral drugs and the prevention of sexual transmission of HIV. Medscape CME. Posted: 09/24/2003.
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This article was provided by Gay Men's Health Crisis. It is a part of the publication GMHC Treatment Issues. Visit GMHC's website to find out more about their activities, publications and services.
 
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