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New Drugs on the Horizon

December 2003

New Drugs on the Horizon

In 2003 four new anti-HIV drugs have been FDA approved, including the first drug in a new class called entry inhibitors. To varying degrees, each of these drugs offers something new and important to the toolbox of approved anti-HIV drugs. What follows is a brief overview of each drug, with its pluses and minuses and what we know about their use in women.


The first of the newly approved drugs was enfuvirtide (Fuzeon, T-20). Enfuvirtide is a new kind of drug from the entry inhibitor class. It is the first anti-HIV medicine that attempts to keep HIV from getting inside cells. All of the others attempt to stop HIV that has already entered a cell from reproducing.

The key benefits of enfuvirtide are related to the unique way it works. Because it works outside of cells, it doesn't have many of the same side effects as other anti-HIV drugs. Also, it works well in people who have resistance to other anti-HIV drugs.

However, there are three drawbacks to enfuvirtide. First, it requires two injections a day. This can be inconvenient and possibly intolerable for people who are not comfortable with needles. Next, most people experience some degree of pain, swelling and redness in and around the area of the body where they inject it (called injection site reactions). This problem might be lessened somewhat if there's someone around -- a partner or roommate -- who can give some of the shots, allowing people to inject in more parts of their body. The third problem is the cost. It is by far the most expensive medicine approved to treat HIV. This may keep some people from being able to get the drug paid for.

Enfuvirtide is approved only for use in people with multiple drug resistance. Because it must be injected, it will probably never be used as first-line therapy.

Although enfuvirtide wasn't studied in many women (around 10% of the people in studies were women), scientists observed that it stays in women's bodies longer than men's. It is unknown whether this has any impact on side effects or its effectiveness. In animal studies enfuvirtide did not cause birth defects or other problems with pregnancy. No studies in pregnant women have been done. For a fuller discussion of enfuvirtide, call Project Inform's hotline.

New Drugs on the Horizon


The next drug to be approved this year is the new protease inhibitor (PI), atazanavir (Reyataz). Atazanavir offers two advantages over other PIs. First, it is the only one approved for once-a-day use. This can provide a benefit for people seeking a simplified dosing regimen. The second advantage is that atazanavir hasn't been shown to increase cholesterol and triglycerides (types of fats), which is a problem to various degrees with all the other PIs.

The drawbacks of atazanavir revolve around potency, side effects, drug interactions and cross-resistance. Although the studies have been somewhat unclear on atazanavir's strength, it appears to be stronger than nelfinavir (Viracept) and weaker than Kaletra (lopinavir/ritonavir). In other words it seems like an average-strength PI. Although it doesn't have the blood fat problems seen with other PIs, around a third of people experience a rise in bilirubin levels, which may cause a yellowing of the skin and eyes (jaundice). While increased bilirubin is usually a sign of liver problems, this is not the case with atazanavir.

Atazanavir has a long list of drug interactions. People taking atazanavir should work closely with their doctors and/or pharmacists to identify any possible drug interactions and make any necessary dose adjustments.

We do not currently know the level of cross-resistance that atazanavir has with other PIs. More research is needed before we can be sure how well atazanavir will work in people whose virus has become resistant to other PIs.

Atazanavir can be used in two ways. For people just starting therapy or who have never taken PIs, atazanavir can be taken once a day with food in combination with other anti-HIV drugs. People who have developed resistance to other PIs will need to take atazanavir with a small dose of ritonavir (Norvir), which increases its effectiveness. One drawback to this is that ritonavir, even at this low dose, can increase cholesterol and triglycerides. However, this increase is still less than what's seen when ritonavir is taken with other PIs, including Kaletra.

Thirty-five percent of the people in studies of atazanavir were women. No differences were observed between men and women. In animal studies atazanavir did not cause birth defects or other problems with pregnancy. No studies of pregnant women and atazanavir have been done. For a more thorough discussion of atazanavir, call Project Inform's hotline.


The third medicine to receive FDA approval was emtricitabine (FTC, Emtriva). A close cousin of the older drug lamivudine (3TC, Epivir), emtricitabine perhaps has the least new to offer, at least for now. Because it is so similar to lamivudine, emtricitabine will usually not work for people who have developed resistance to it. It has similar side effects as lamivudine, including headaches, nausea and diarrhea. Emtricitabine is taken once a day. There may be more interest in emtricitabine in early 2005, when its maker Gilead plans to combine it into a single pill with tenofovir (Viread), as an obvious competitor for Combivir.

About 15% of the people in emtricitabine studies were women, and no significant differences were seen between men and women. In animal studies emtricitabine did not cause birth defects or other problems with pregnancy. No studies of emtricitabine have been done with pregnant women. For a more thorough discussion of emtricitabine, call Project Inform.


The fourth drug approved this year is fosamprenavir (Lexiva). It is a new form of the older protease inhibitor, amprenavir (Agenerase). Its main advantage is fewer pills (2 pills a day vs. 16) than the older form, which may improve adherence. The most common side effects are diarrhea, nausea and rash.

No significant differences were seen between men and women in studies of fosamprenavir. Although studies of fosamprenavir and pregnancy have not been concluded, we can look at the data from amprenavir studies. In animal studies amprenavir did not cause birth defects. For a more thorough discussion of fosamprenavir, call Project Inform.

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