Q: What is PrEP?

A: HIV PrEP or pre-exposure prophylaxis has nearly revolutionized the prevention of the viral infection. When administered correctly, PrEP reduces the risk of getting HIV from intercourse by 99% (when used consistently).  Right now, there are at-risk individuals who have taken PrEP for up to five years without experiencing side effects. 

But medical solutions are evolving all the time. Doctors and pharmaceutical companies are seeking opportunities to strengthen HIV prevention even further and that involves discovering stronger formulas and better ways to administer HIV PrEP.

During the 23^rd International AIDS Conference (AIDS 2020: Virtual), some important new findings about the administration of HIV PrEP have been announced.

Q: Does the Form of Administration Matter?

A: It appears that the way in which PrEP is administered indeed happens to be an important factor that correlates to the effectiveness of the medication.

The latest findings suggest that when administered as an injection every eight weeks, PrEP is more effective than preventing the HIV infection than the oral form of the medication. Information presented at the conference was originally published in mid-May 2020 and the results are based on a clinical trial involving 4,600 people.

In the study, participants were given the traditional oral form of PrEP (tenofovir disoproxil fumarate plus emtricitabine (TDF/FTC)) or an injectable form of the medication called cabotegravir.

Participants in the study belonged to multiple high risk groups. Of them, 50 became infected with HIV. Of the infected individuals, 12 were receiving the injectable PrEP and 38 were getting the TDF/FTC combination. These numbers correspond to an annual infection incidence rate of 1.21 per cent for the TDF/FTC group and only 0.38 per cent for those receiving the injectable cabotegravir.

Q: What Makes Injectable PrEP More Effective?

A: Researchers are still speculating as to why injectable HIV PrEP could be delivering such significantly better results. One theory pinpoints a really intriguing reason for the potential failure of oral PrEP, and that’s poor adherence. When blood samples were taken from some of the volunteers, researchers found out that the level of medications in their blood was in no way indicative of taking the recommended at least four pills per week. In other words, people often forget to take their meds.

Even when their life depends on strict adherence to a schedule, there will still be numerous individuals who’ll forget or who’ll be lax in terms of proper administration. For the time being, however, that’s just a theory. Researchers have also tried to find out why 12 people who were administered injectable PrEP became HIV-positive. One of the possible explanations was that they got infected during the lead-in phase. Alternatively, the levels of the active medication were not high enough in this subset. The study has given rise to numerous questions that can be answered through further research.

It’s interesting to note that raltegravir may persist in the body for up to one year after the administration is discontinued. Researchers will need to account for whether drug resistance is likely to develop in long-term use.