At the international HIV conference CROI in Seattle, two studies were presented that show a 861TP3 protective effect of the HIV drug Truvada in HIV-negative gay men. Armin Schafberger, Medical Officer at Deutsche AIDS-Hilfe, analyses the results.
These are two precision landings after numerous crash landings. For the first time, PrEP with Truvada shows a high protective effect in two studies. The PROUD study from the UK and the IPERGAY study from France and Canada attest that PrEP has a protective effect of 86 per cent (reduction in HIV risk compared to no PrEP intake or placebo). This is phenomenal, even if the studies are relatively small.
But didn't we already have such a result? Yes, but only because the results had been glossed over. In previous PrEP studies, adherence to treatment was always the big problem. If at all, only around a third of the test subjects had taken the medication regularly. Those who had enough medication in their blood were then selected and a protective effect of around 90 per cent was estimated on this basis.
Now, however, both studies show a high protective effect without such calculation skills. And that's how it should be. After all, the best prevention method is useless if it is not used. It's no different with condoms. Licensing authorities also want to see hard data - not numbers.
Does the result of the PrEP studies now apply to everyone? No.
In both studies, it was possible to recruit gay men who have a very high risk of HIV infection for the study with great effort - and much success. The men in the PROUD study have condomless anal intercourse with an average of 10 men in three months. Without PrEP, 9 out of 100 men become infected in one year (8.9 %), with PrEP only one (1.3 %). Such a new infection rate of 8.9 % is a world record. This means that after a good decade, almost everyone in the group would be HIV-positive. For this particular and relatively small group, PrEP with one tablet per day seems to be just the right thing - or the only way to remain HIV-negative.
For most gay men, however, taking medication permanently for months or years is out of the question. Some are only at risk intermittently or occasionally. The results of the IPERGAY study are interesting for this group. Here it was tested whether PrEP also has a protective effect if it is taken shortly before or shortly after sex (two tablets a few hours before, one tablet 24 and 48 hours after the first dose).
The result is astonishing: the method works just as well as the permanent intake in PROUD (86 % risk reduction). However, as the men did not have little sex, they took an average of four tablets per week - compared to seven tablets in the PROUD study. The "intermittent" (occasion-related) intake, however, offers the option of not taking tablets if there is no risk. This is closer to everyday life - and more favourable.
However, we do not know whether this high treatment compliance works with men who are not at such high risk. Despite all the enthusiasm about the results, we should bear in mind that the test subjects in the studies were carefully selected. We need to transfer this to prevention - and clarify in the near future who could benefit from PrEP and who could not.
What else is needed for PrEP in prevention? An HIV test must be carried out at least every three months. This is because anyone who becomes infected and continues to take PrEP risks resistance. This risk has been limited in the studies - but will we be able to implement this test frequency outside of studies? Will we succeed in counselling those who take PrEP about adherence to treatment nearly as well as in the trials?
PrEP does not mean the end of prevention through the use of medication. Rather, it can become a further component of successful HIV prevention. Essential components of prevention such as counselling and information are even more important with PrEP than with other prevention methods. Regular HIV testing is also an elementary component.
