Interview: Drug May Be First to Prevent HIV Transmission in Healthy

During our coverage last month of the 30th anniversary of the discovery of HIV, we explored what the earliest, dark days of the epidemic were like -- when a positive diagnosis was as good as a death sentence, and the specter of premature death afflicting San Francisco's gay community affected it in profound ways.

Today, the fear and loathing sowed by the virus has lifted considerably, due to advancements in HIV treatment that have thus far staved off its really deleterious effects for many years.

Now, two new studies, that in the coming days will be presented at the International AIDS Society Conference in Rome, may point to the next advance in AIDS medicine.

The studies found that use of the two-pronged, anti-retroviral drug Truvada acts to prevent HIV transmission from someone who is infected to someone who isn't.

Meaning that the medication acts as the first actual pharmacological prophylactic to contracting HIV.

I interviewed Dr. Paul Volberding, co-director of the Center for AIDS Research at the University of California, San Francisco, about the research. Volberding, whom KQED's Belva Davis describes as "one of the early driving forces in pushing for education as a way to curtail the epidemic," said he's eager to hear more about the studies, which he calls "very big news."

"This is the kind of effect we might expect from a very good vaccine," Dr. Volberding said about his initial review of the results.

Below, you can listen to my interview with Dr. Volberding (who does consulting work for the drug's manufacturer, Gilead Sciences of Foster City) about the studies and their potential implications. An edited transcript follows each audio clip:

Dr. Paul Volberding explains what Truvada is

What is Truvada and what is it currently approved for?

Truvada is a combination of two medicines that we use very commonly in HIV. One is called Tenofovir, the other is called FTC. They're bundled together in a single pill, taken once a day, and they're part of a combination that many of our patients receive. A treatment regimen or somebody with infection would usually use these two drugs or ones like them plus a third drug to form the so called cocktail for HIV treatment that we've heard so much about.

Volberding on what the African studies have shown

What do the new studies show?

There have been several studies that have come at the same question. If a person is at risk of getting infected, does taking a medicine like Truvada prevent infection in somebody who's not infected to start with?

Before these two studies, there were two others, and one showed the medication did seem to work, the other didn't. These two new studies answer an important question; they were done in couples, one of whom was positive at the start of the study, and one who was negative. The HIV-negative person took the medicine; these studies both showed a very striking effect in decreasing the transmission in those HIV-negative people who were taking the medicine.

How definitive would say these studies were?

There's a meeting that I and many of my colleagues are going to in Rome that starts over the weekend that will be focused on these studies. I think we'll come back with a lot more detail.

But of these studies, one had nearly 5,000 couples, the other had about 1200 couples. Both were done in Africa. Both remarkably found almost the same results. In one, Truvada had about a 73% reduction in transmission, the other one had about a 63% reduction in transmission. In big studies like that, those numbers really look very much the same to us. It says that even in a situation where some people will take the drugs exactly as they're supposed to in the study and others won't, even with that the drug was remarkably effective. This is the kind of effect we might expect from a very good vaccine. So this is big news.

What is the regimen for taking the drug in terms of it being a prophylactic?

It's a once a day drug, it's a pill. The recommendation is that if you're negative and in one of these relationship where your partner is positive, then you just take it every day. So it's a very straightforward treatment.

What are the side effects if any that were found?

We haven't seen the detailed results from the study yet. We'll hear a lot more about it in Rome. But we know these drugs very well. We've been using them for a very long time. In people with HIV infection, where Tenofavir, which is one of the parts of Truvada, it's well tolerated but can cause some kidney trouble in a small percent of people and can cause some bone loss in a small percent of people. So we'll be watching the results closely because these are people who are healthy and uninfected, so you don’t' want to subject them to a lot of side effects. But we know these drugs very well, and I don't expect we're going to be surprised by what we hear.

Might there be behavioral considerations in terms of health people following the drug regimen?

We'll find out more in Rome, but what we've found in other studies, especially in people that are uninfected, is that some people decide just to not take the pills. What we've seen is that when people take the pills as prescribed, it works incredibly well. In some studies, it looked close to 100% effective. I think what we'll find in these studies is that a big reason for the "only" 70% effectiveness, is probably a lot of those people weren't taking the drugs or not taking them correctly.

Are there any other medications taken by healthy people as a prophylactic?

Aspirin, perhaps, for people who want to prevent cardiac disease. Or the better example is when I go to Africa, I take a drug called Malerone, which is a malaria prophylaxis. So this isn't a new concept at all.

On behavioral considerations in patients

Potentially I could see some people arguing that some people at high risk for HIV might view a prophylactic pill as a license to engage in riskier behavior. Is that any sort of consideration?

Oh it's absolutely a consideration. In this kind of research one of the things you always try to do is to determine whether or not behavior has changed as a result of being in the study.

What we've seen before is that doesn't usually seem to be the case. So I think the theoretical risk that someone is going to increase their behavior in a risky way doesn't mean that the benefits should be denied to a larger number of people who if they take the medicine will keep from being infected. It's worth asking, and we'll look for the data, but I'm really not concerned about this issue.

On populations that might be helped by use of the drug

Are the implications of this drug greater for Africa than in the U.S.?

Yes. There are certainly people here who find themselves in situations where people can't control their partner's behavior. For example, a woman who's engaged in sex work who can't force her partner to use condoms might want to consider something like this to keep from getting infected. A gay man who for whatever reason is sexually active without the benefit of condoms might choose to use this.

But I think really the most obvious application would be in what are called serodiscordant couples in Africa, where one person is infected and the other person would take this to prevent acquiring infection.

There are some other potential applications that are quite interesting. If a man, for example, is HIV-infected and his wife is uninfected, and they want to have kids, taking a drug like this on the part of the wife might be enough of a reassurance for them to have unprotected sex so she can get pregnant. So there are some interesting smaller populations but really important ones.