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New Prevention Technologies Updates

CAS is continuing to monitor developments in the field of new prevention technologies through participation in meetings and teleconferences, and updates from networks and publications.

Microbicides

Results from two topical vaginal microbicides candidates, BufferGel and PRO 2000, were released on February 9, 2009 in Montreal, during the CROI meeting. According to the study, which primarily tested gel safety, the PRO 2000 gel is 30% effective in preventing HIV infection. An effectiveness rate of 33% is considered statistically significant. PRO 2000 is manufactured by Indevus Pharmaceuticals and is designed to prevent HIV from attaching to certain white blood cells. Although the findings are not statistically significant, the study is the first to demonstrate a possible beneficial effect from using microbicides.

Following the announcement, CAS participated in a teleconference on Feb 11, hosted by the Global Campaign on Microbicides. Researchers provided details on the results, community involvement and care plans for those infected during the trials. The study results will be submitted to peer-reviewed journals and, if accepted by the scientific community, publication is expected in six to nine months. Researchers urged teleconference participants to continue to stress that condoms are the safest method available to prevent HIV transmission.

In addition, London's Medical Research Council is also currently conducting a study on PRO 2000, which is three times the size of the first study. This study, MDP 301, involves 9,500 women. At the same time, the US National Institute of Allergy and Infectious Diseases (NIAID), the funder of the HPTN 035 trial, is in discussions with Indevus Pharmaceuticals to determine the way forward. NIAID will decide whether to fund additional studies of PRO 2000 after data from MDP 301 are available.

Pre-exposure Prophylaxis PrEP

According to the Kaiser Report of February 10, 2009, two other studies of the Centre for Disease Control presented at CROI found that pre-exposure prophylaxis, or PrEP, with antiretroviral drugs administered by mouth or by vaginal gels to rhesus macaques were highly effective at providing protection from the simian version of HIV, SIV. In the first study, researchers gave the monkeys orally a compound containing tenofovir and emtricitabine, sold under the brand name Truvada. Drugs were administered at different intervals (intermittent PrEP), before and after exposing the monkeys rectally to SIV once weekly for three months. Five out of six of the monkeys receiving the first dose one or three days prior to contact with the virus were protected from SIV. In all five treatment groups, monkeys had significantly lower risk of infection compared with the untreated monkeys. If administered one to seven days prior to exposure, PrEP was most effective in preventing infection, compared with immediately before exposure or only intermittently after exposure. According to the lead author of the study, tenofovir has a long active life in the body; however, it could take longer than two hours for it to enter the immune system and provide protection against the virus.

In the second study, vaginal gels containing either the combination drug or tenofovir alone were tested. The gel was applied to macaques 30 minutes before twice-weekly exposure to SIV. All of the six monkeys that received the two-drug gel and all of the six monkeys that received the tenofovir-only gel were protected from the virus. Ten out of the 11 macaques that received no gels contracted SIV after a median of four exposures to the virus. Findings suggest that single-drug vaginal gel formulations are equally effective as combination-drug formulations in providing complete protection against SIV.

Other on-going new prevention technologies trials include:

• HSV-2 suppression in HIV serodiscordant couples (results are expected mid-year);
• Thai prime-boost vaccine trial: the largest ever efficacy trial of an AIDS vaccine, which is testing a combination vaccine strategy in over 16,000 volunteers with results expected in the third quarter;
• Safety trial on oral PrEP (results are expected by year's end, in addition to the first interim data from PrEP efficacy trials);
• VOICE study, a test of both oral and topical PrEP; and
• HVTN 505, a study pending approval from the US Food and Drug Administration, which is currently being explored by NIH's Vaccine Research Center prime-boost strategy.

Vaccines

CAS participated in a meeting in Ottawa with Seth Berkley, Founder and CEO of the International AIDS Vaccine Initiative. The objectives included a renewed call for AIDS service organisations to focus on advocacy for vaccines because of the strategic role they can play to stop and reverse the epidemic amid the global economic crisis. Participants were informed that, overall, 2% of global funding for HIV goes to vaccine development. IAVI focuses its efforts on the development of the best preventive vaccines worldwide and
supports the Canadian HIV Vaccine Initiative, a project of which CAS is a stakeholder.