In the two previous articles, we introduced PrEP as a strategy to protect individuals from getting infected with HIV. Pre-exposure prophylaxis refers to taking a combination of HIV medicines prior to a possible exposure (e.g. before sex, injecting recreational drugs) to protect an uninfected person from the virus. When PrEP first came out a few years ago, I thought it could be effective in helping control the HIV epidemic, but I had concerns.
One of my major concerns was whether people would regularly take PrEP. From decades of experience with treating HIV-infected individuals, getting people to reliably take their medicine as prescribed has been a major challenge. I felt that if people infected with HIV often didn’t take their medicines (and these medicines were life-saving for them), why should we expect people who are NOT infected with HIV to take medicines? In all studies, when PrEP fails (a person gets infected while using it), it’s because people aren’t taking it properly.
For people who don’t like taking pills, but want the benefits of PrEP, pharmaceutical scientists and medical researchers may soon come to the rescue.
Very soon, we may have our first long-acting HIV medicines. When I say long acting, I’m not talking about a special cough and cold capsules you take that can last you all day or night. There are combination HIV medicines showing success in clinical studies to treat HIV that are administered once every two months! Imagine that!
One of the drugs in the most
well-studied combination is called Cabotegravir. In addition to effective treatment, it is being studied as a form of injectable PrEP. Cabotegravir belongs to the class of HIV drugs called integrase inhibitors. These drugs prevent the HIV virus from incorporating its genes into our genes and thereby blocks the infection process. They are the most powerful drugs we have so far and are included in many combination tablets, like Triumeq, Genvoya, and Biktavry
Another option being explored as a long-acting product is for ladies only (injectable cabotegravir is for anyone). An HIV medicine called Dapivirine, related to rilpivirine and efavirenz, has been formulated into a vaginal ring. The ring is inserted into the vagina and the medicine is slowly released into vaginal tissues over the period of one month.
The concentration of Dapivirine in the vagina is high enough to protect the woman if she is sexually-exposed to HIV. The ring can be removed and reinserted whenever the woman wants.
However, we aren’t certain how long the ring has to be in place to provide protection. In studies, the ring offers some protection but not surprisingly, it must be used in order to be effective.
Most women feel comfortable using the ring and their partners are often
not aware that the ring is there. Comfort and satisfaction are important for both partners if this intervention is to be successful. It is important that women have control over protecting themselves from HIV because, in some situations and cultures, they cannot insist that their male partners use condoms.
Once injectable Cabotegravir is approved for HIV treatment, it will probably soon be approved for PrEP, hopefully, this year. Not certain how long before the Dapivirine vaginal ring may be ready. But I think we can see the light at the end of the tunnel for folk who just don’t like taking pills every day.
Dr. Crawford received a B.S degree in Biology from Cornell University and a B.S. in Pharmacy from Temple University. He completed a residency in clinical pharmacy at the National Institutes of Health. He earned a doctorate in Pharmacology from the Uniformed Services University of the Health Sciences in Bethesda, Maryland. He completed a post-doctoral fellowship at the National Institutes of Health, studying microbial biochemistry and genetics.
He is currently with the Division of AIDS at the National Institutes of Health. He has over 25 years of experience in HIV treatment and clinical research. This article reflects his personal views and opinions.
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