Research Blog—Long-Acting Pre-Exposure Prophylaxis (PrEP) as a Promising HIV Prevention Strategy
PrEP as an HIV Biomedical Prevention Strategy
Gay, bisexual, and other men who have sex with men (MSM) account for 66% of all new HIV infections in the U.S. each year . The number of new HIV infections among MSM increased 12% between 2008 and 2010 in the U.S., with a sharper 22% increase among MSM 13 – 24 years of age . Such disparities in the HIV epidemic show the urgent need to develop new ways to prevent HIV infection among this population. Daily oral pre-exposure prophylaxis (PrEP) is a promising biomedical HIV prevention strategy recommended by the CDC for those at high risk of HIV, including MSM .
PrEP Awareness and Uptake
Among MSM in the U.S., PrEP awareness is increasing, and interest in and willingness to use PrEP are high [3, 4]. Despite high acceptability of PrEP, uptake among MSM is low, often less than 7% in many studies [4-6]. Reasons for low PrEP uptake among MSM include concerns about cost, the burden of daily dosing, and worry about long-term side effects [4, 7, 8].
Adherence to a daily pill has been important for best efficacy in PrEP clinical trials. Across major PrEP trials, greater adherence to daily oral PrEP was associated with greater HIV protection [9 -11]. For example, the iPrEx study showed fewer HIV infections among MSM with higher adherence . In contrast, no HIV protection was found in two trials, VOICE  and FEM-PrEP , in which PrEP adherence was very low.
Long-Acting PrEP as a Strategy to Address Medication Adherence
Alternatives to daily oral pill-taking which could promote PrEP adherence and be easily implemented in clinical and community settings are needed. Current investigations of other delivery options include long-acting injectable antiretroviral (ARV) drugs , and implants with sustained release of ARVs . At the 2016 Conference on Retroviruses and Opportunistic Infections, over a dozen abstracts focused on long-acting and sustained delivery PrEP options. For example, the ÉCLAIR Phase 2a randomized, double-blinded study  evaluated intramuscular injections for PrEP in a sample of 126 men (83% MSM). The study found that the medication was well tolerated over 41 weeks and the majority of participants reported satisfaction with the injections.
At Northwestern University, the Sustained Long-Acting Protection Against HIV (SLAP HIV) program aims to develop and test a PrEP implant to provide HIV protection for up to a year at a time. SLAP HIV is funded by the National Institute of Allergy and Infectious Diseases and led by Drs. Thomas Hope and Patrick Kiser. Collaborating scientists from multiple institutions are developing two additional drug delivery systems, including injectable PrEP. These lines of research indicate that sustained release or long-acting agents are attractive alternatives for use of PrEP. They avoid the need for high adherence to daily oral regimens which limit the effectiveness of PrEP as a prevention strategy [12, 13].
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 Centers for Disease Control and Prevention. (2015, September 29). HIV among gay and bisexual men. Retrieved from http://www.cdc.gov/hiv/group/msm/
 Centers for Disease Control and Prevention. (2014). Preexposure prophylaxis for the prevention of HIV infection in the United States – 2014: A clinical practice guideline. Retrieved from http://www.cdc.gov/hiv/pdf/PrEPguidelines2014.pdf
 Grov, C., Whitfield, T. H., Rendina, H. J., Ventuneac, A., & Parsons, J. T. (2015). Willingness to take PrEP and potential for risk compensation among highly sexually active gay and bisexual men. AIDS and Behavior, 19(12), 2234-2244. doi: 10.1007/s10461-015-1030-1
 Cohen, S. E., Vittinghoff, E., Bacon, O., Doblecki-Lewis, S., Postle, B. S., Feaster, D. J., . . . Liu, A. Y. (2015). High interest in preexposure prophylaxis among men who have sex with men at risk for HIV infection: baseline data from the US PrEP demonstration project. Journal of Acquired Immune Deficiency Syndromes, 68(4), 439-448. doi: 10.1097/QAI.0000000000000479
 Rucinski, K. B., Mensah, N. P., Sepkowitz, K. A., Cutler, B. H., Sweeney, M. M., & Myers, J. E. (2013). Knowledge and use of pre-exposure prophylaxis among an online sample of young men who have sex with men in New York City. AIDS and Behavior, 17(6), 2180-2184. doi: 10.1007/s10461-013-0443-y
 Mayer, K. H., Oldenburg, C., Novak, D. S., Krakower, D., & Mimiaga, M. J. (2014). Differences in PrEP knowledge and use in US MSM users of a popular sexual networking site surveyed in August 2013 and January 2014. AIDS Research and Human Retroviruses, 30(S1), A91-A92. doi:10.1089/aid.2014.5168a.abstract
 Grant, R. M., Anderson, P. L., McMahan, V., Liu, A., Amico, K. R., Mehrotra, M., . . . iPrEx study, T. (2014). Uptake of pre-exposure prophylaxis, sexual practices, and HIV incidence in men and transgender women who have sex with men: A cohort study. Lancet Infectious Diseases, 14(9), 820-829. doi: 10.1016/S1473-3099(14)70847-3
 King, H. L., Keller, S. B., Giancola, M. A., Rodriguez, D. A., Chau, J. J., Young, J. A., . . . Smith, D. M. (2014). Pre-exposure prophylaxis accessibility research and evaluation (PrEPARE Study). AIDS and Behavior, 18(9), 1722-1725. doi: 10.1007/s10461-014-0845-5
 Marazzo, J., Ramjee, G., Nair, G., Palanee, T., Mkhize, B., & Nakabiito, C. (2013). Pre-exposure prophylaxis for HIV in women: daily oral tenofovir, oral tenofovir/emtricitabine or vaginal tenofovir gel in the VOICE study. Paper presented at the Conference on Retroviruses and Opportunistic Infections (CROI). March 3-6. Atlanta, GA.
 Van Damme, L., Corneli, A., Ahmed, K., Agot, K., Lombaard, J., Kapiga, S., . . . Taylor, D. (2012). Preexposure prophylaxis for HIV infection among African women. New England Journal of Medicine, 367(5), 411-422. doi: doi:10.1056/NEJMoa1202614
 Anderson, P. L., Glidden, D. V., Liu, A., Buchbinder, S., Lama, J. R., Guanira, J. V., . . . iPrEx Study, T. (2012). Emtricitabine-tenofovir concentrations and pre-exposure prophylaxis efficacy in men who have sex with men. Science Translational Medicine, 4(151), 151ra125. doi: 10.1126/scitranslmed.3004006
 Spreen, W. R., Margolis, D. A., & Pottage, J. C., Jr. (2013). Long-acting injectable antiretrovirals for HIV treatment and prevention. Current Opinion in HIV and AIDS, 8(6), 565-571. doi: 10.1097/COH.0000000000000002
 Gunawardana, M., Remedios-Chan, M., Miller, C. S., Fanter, R., Yang, F., Marzinke, M. A., . . . Baum, M. M. (2015). Pharmacokinetics of long-acting tenofovir alafenamide (GS-7340) subdermal implant for HIV prophylaxis. Antimicrobial Agents and Chemotherapy, 59(7), 3913-3919. doi: 10.1128/AAC.00656-15
 Markowitz, M., Frank, I., Grant, R., Mayer, K. H., Margolis, D. A., Hudson, K. J., . . . Spreen, W. (2016). ÉCLAIR: Phase 2A Safety and PK Study of Cabotegravir LA in HIV-Uninfected Men. Paper presented at the Conference on Retroviruses and Opportunistic Infections (CROI). February 22-25. Boston, MA.