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Results of the recent iPrEx Pre-Exposure Prophylaxis Trial

In November 2010 the results of the iPrEx trial were released.

The study tested how effective daily doses of the HIV drug Truvada (a combination of Tenofovir and Emtricitabine which prevent the virus replicating in the body) were at preventing HIV infection in HIV negative men who have sex with men. A total of 2,499 men were recruited into the study that was conducted in various countries around the world.

All the participants were provided with condoms and educated about safe-sex. Half the participants were given the study drug and the other half a placebo. Participants were followed up to 2.8 years and monitored on several variables including drug compliance, HIV infections, and risk behaviours.

The main findings are:

  • Overall HIV infections were 44% lower in those in the group that took Truvada. Additionally, if daily doses are taken 50% of the time Truvada is 50% effective and when taken 90% of the time it’s 73% effective at preventing HIV infection.
  • Risk behaviours for HIV decreased during the trial. There was more condom use and less unprotected anal intercourse.
  • Truvada was found to be safe overall, with the main side effects being elevated creatinine levels (which indicates kidney health), nausea and weight loss.
  • There was no drug resistance detected to the Truvada drugs in any of the 100 men (36 in the Truvada group and 64 in the placebo group) who became HIV positive during the trial.

Conclusions from the study include:

  • The results show that, at best, the drug can compliment other prevention strategies such as condom use and safe-sex counselling. However, it also showed that at least in the trial many participants found it difficult to maintain frequent enough dosing to achieve high levels of effectiveness with the drug.
  • A recommended use of the drug might be in high risk groups such as pos-neg couples who find it difficult to maintain consistent condom use.

More trials are being conducted including those investigating different dosing patterns including dosing directly pre and post sex. A longer trial would also help determine the longer term affects of taking Truvada for prevention. With more research needed, the use of HIV medication as a prevention strategy for HIV negative men cannot, as yet, be recommended.

For a more detailed discussion of the trial results and it’s implications in Australia see the Australian federation of AIDS Organisations briefing paper.