HIV drug blocks HIV infection

A new study has shown that a once-a-day pill can protect against contracting HIV. The study, published in the New England Journal of Medicine, is being hailed as a breakthrough proving that HIV pre-exposure prophylaxis or “PrEP,” works. PrEP could now become a significant new HIV prevention tool against the HIV pandemic.

The study, called “iPrEx”, enrolled 2500 gay men from six countries. The men were considered at high risk of becoming HIV infected. The study used a drug known as Truvada. Those assigned to take Truvada were 44 percent less likely to contract HIV than those on a placebo. More importantly, blood tests showed that those in the study subgroup that did diligently take Truvada 92 percent of the time were 73 percent less likely to become infected by HIV. Researchers believe that PrEP will also be effective in preventing heterosexual HIV transmission. Studies are ongoing to prove that.

Truvada is not an oral HIV vaccine. It is a one pill combination of two HIV antiviral medications (Emtricitabine, trade name Emtriva, and Tenofovir, trade name Viread). So Truvada only prevents HIV infection when it is in the body. Truvada has been available by prescription for over five years to treat HIV infection but it’s not yet approved as a drug to prevent HIV infection. That may change as a result of the iPrEx results and other forthcoming studies. Doctors are already prescribing Truvada off label to prevent infection by HIV. Meanwhile, the CDC is working on new Truvada pre-exposure prophylaxis guidelines.

Truvada’s cost may be an obstacle to its widespread use. In the U.S. it costs about $800 a month or about $27 per day. At some point health insurance may cover Truvada for PrEP the same way it covers birth control pills. In the meantime, the study results raise the spectre of a Truvada black market. The drug is widely used and available from within the HIV-infected community. A generic, lower cost version of Truvada that is produced in India is also available to the developing world.

Taking Truvada once a day was a problem for many in the study. An alternative “disco dosing” PrEP study is ongoing to determine whether taking Truvada in anticipation of sex is effective. If that works the challenges of frequent dosing, drug costs, and drug side effects may be minimized.

The favorable results of the iPrEx study may also have been enhanced by safe sex practices. This was in contrast to concerns that PrEP will provide a false sense of security resulting in a reduced use of condoms. The opposite occurred in the study. This was possibly because study participants received regular counseling, many for their first time, on safe sex practices. The data also showed that those in that subgroup who did not skip dosing but consistently adhered to taking their Truvada were also more likely to use condoms. This is perhaps the most controversial finding of the study.

Truvada was well suited for the study not just because it could be taken once a day. It is also less vulnerable to developing drug resistance than other HIV drugs. However, resistance was an issue for a few study participants. They were already HIV infected but were enrolled in the study because they had not yet converted from testing HIV negative to HIV positive. So there appears to be a risk of developing resistance when taking PrEP while unknowingly being HIV infected. This could especially be true for high risk behavior individuals.

Side effects for those taking Truvada included nausea, weight loss, some kidney dysfunction, and bone density loss. Had pill adherence for those on Truvada been higher drugs side effects would have been even more pronounced. This raises concerns about the safety of regular long-term use of Truvada as a pre-exposure prophylaxis.

Courtesy of Healthy Living News

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