By now, many of you have heard the preliminary results of a very large study conducted in South America and in the U.S. in which investigators concluded that taking an anti-HIV treatment every day could help prevent infection with the virus.
The study is the iPrEx study. The pill used in this study is Truvada, a well-known anti-HIV medication, currently widely prescribed to treat HIV infection; in fact, it is the most popular medication used today as part of the cocktail of medications to treat patients already infected with the HIV virus.
Truvada is in fact a combination of two anti-HIV medications put together in a single tablet (Emtriva and Viread). This pill is not to be confused with another well-known HIV medication named Atripla. Atripla, is a combination of Truvada and Sustiva (thus three medications in one tablet); but again, Atripla was not the pill used in this study, just the Truvada component.
In medicine, sometimes we use an antibiotic to “prevent” an infection before we get exposed to the organism. For example, if you travel overseas to a place which has malaria, your doctor will prescribe a medication to prevent you from catching it. This medication used to prevent malaria can also be used to treat the disease. The same may happen if you are getting a root canal. Your dentist may give you some preventive penicillin to avoid you from getting an infection in your gums after that dental procedure.
The IPREX study explored this same principle of using a medication to prevent a disease.
In this study (published online in the New England Journal of Medicine), 2,499 HIV-negative volunteers were randomly assigned to get placebo or Truvada. Participants did not know which they were taking. They all got regular HIV testing, risk-reduction counseling, condoms, and treatment for other sexually transmitted infections. The population selected for this study was considered a high risk group with multiple sexual partners.
Despite the measures taken by the investigators to prevent any infections, there were volunteers who became infected because they did not follow all of the precautions.
After following most of the patients for more than a year, there were 100 new cases of HIV among all participants; 36 among those assigned to get Truvada and 64 among the ones assigned to get the placebo pill. Statistically speaking, that is an overall success rate of 44% with Truvada reducing the risk of becoming HIV infected compared to placebo.
Even greater, when investigators looked at the volunteers who took the medication most of the time (90% adherence, or above), the efficacy in this population was about 73%. Additionally, in this study, the drug was well-tolerated with just moderate nausea in the first four weeks of therapy reported by some volunteers.
This is without doubt an exciting step forward in HIV prevention. It is proof that oral pre-exposure prophylaxis, also called PrEP, works to prevent HIV infection (at least in men who have sex with men).
Nonetheless, there are a few things that need consideration: This pill was not 100% effective in HIV prevention. It is probable that some volunteers may have not taken the medication 100% of the time, or that the degree of HIV exposure in some may have been greater (multiple unprotected exposures) than in others.
It is also possible that perhaps the virus to which they were exposed may have been partially resistant to one of the components in the Truvada pill. Therefore, despite the results of this study and the potential use of this tablet to reduce the chances of getting HIV, safer sex practices remain critical in preventing HIV infection among men who have sex with men.
Instead, correct and consistent use of condoms and a reduction in the number of sex partners still remain the most effective ways to protect oneself from HIV infection.
This study does not answer a few other questions: For example, what are the long term consequences of prolonged use of Truvada for HIV prevention?
What other side effects may emerge over time? Will resistance to Truvada emerge in the general community with the wide use of this pill as prevention? And, what is ultimately the cost of this preventive approach?
Currently there are many HIV-negative people who have requested that their provider prescribe this pill for HIV prevention. But again, it is important to note for anyone who is thinking about this that the protection in this study was not 100%, and that this pill is still not indicated for HIV prevention by the FDA (although the company is already looking to add this indication to their label, based on these study results). It is also likely that many insurance carriers will pay for the medication. The current retail price of Truvada in the U.S. is $1,000 for 30 pills!
These results are exciting, but it is not time for anyone to stop using condoms or stop following other proven prevention methods. There are several other studies looking at the use of other dosages of this medication for HIV prevention. In any case, it appears that, ideally, an HIV vaccine should ultimately be the final goal to end this epidemic.
