Fusion and entry inhibitors for HIV


Generic Name Brand Name
enfuvirtide Fuzeon
maraviroc Selzentry

Enfuvirtide is available only as an injection. It is taken 2 times each day: once in the morning and then again 12 hours later.

Maraviroc is also called a chemokine receptor 5 (CCR-5) inhibitor. It is available as a pill taken twice a day.

How It Works

When HIV invades your body, the virus attaches to the outside of a CD4+ cell (a type of white blood cell) where it joins (fuses) with the cell and then multiplies. Fusion and entry inhibitors prevent fusion between the virus and the cell from occurring and prevent the virus from entering the cell. So HIV is unable to infect the cell and multiply.

Why It Is Used

Enfuvirtide and maraviroc are used in combination with other antiretroviral medicines for the treatment of HIV to prevent the virus from spreading in the body and to reduce the amount of virus in your blood (viral load). Enfuvirtide and maraviroc may be effective for people who have taken other anti-HIV drugs without success.

The use of three or more antiretroviral medicines (highly active antiretroviral therapy, or HAART) is the usual treatment for HIV infection.

The combination of medicines used for HAART will depend on your health, other conditions you might have (such as hepatitis), and results of testing. Talk to your doctor about the best treatment plan for you.

Treatment guidelines suggest the following for people with HIV:1, 2

  • When considering treatment, experts currently consider your CD4+ cell count and the presence or absence of symptoms more important than your viral load.
  • If your CD4+ cell count is below 350 cells per microliter (mcL), you should begin treatment to stabilize and increase your CD4+ cell count.
  • If your CD4+ cell count is more than 350 cells per microliter (mcL), treatment may be offered to help keep your immune system healthy and prevent AIDS.
  • If treatment is not started, your condition will be monitored with frequent CD4+ cell counts.
  • If you have symptoms of HIV or AIDS, doctors recommend starting treatment, whatever your CD4+ cell count is.
  • If you are pregnant, you should be treated to prevent your unborn baby (fetus) from becoming infected with HIV.
  • If you also have hepatitis B and are starting treatment for it, you should begin treatment for HIV also.

How Well It Works

Enfuvirtide and maraviroc strengthen the immune system by reducing the amount of virus in the blood and increasing CD4+ counts.3, 4

Side Effects

Enfuvirtide Common side effects of enfuvirtide include skin itchiness, swelling, and pain at the site of the injection. Other side effects may include fatigue, numbness in feet or legs, dizziness, and insomnia.

Maraviroc Common side effects of maraviroc include a cough, fever, dizziness, headache, and nausea. Other side effects reported for maraviroc include an increased risk of some infections and also liver and heart problems.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Maraviroc is effective only against certain strains of HIV. Before maraviroc treatment is considered, you need to be tested to see if maraviroc will work against the virus you are infected with. This is called a tropism test. You should not take maraviroc unless you have had this test and it shows that maraviroc will be effective against the type of virus you have.

Enfuvirtide and maraviroc are used in combination with other anti-HIV drugs.

The U.S. Food and Drug Administration (FDA) approved enfuvirtide and maraviroc for people who have already been taking other anti-HIV medicines. They are not intended for use by people who are just starting drug treatment for HIV infection.

Enfuvirtide and maraviroc should be used to treat a pregnant woman only if the potential benefit is greater than the risk to the unborn baby (fetus).

Enfuvirtide is approved for use in people with HIV who are at least 6 years old.

Enfuvirtide is available only as an injection. It is taken 2 times each day: once in the morning and then again 12 hours later. To prepare each dose, you will need to mix the powdered medicine and sterile water, both of which come with the injector.

HIV can become resistant to enfuvirtide, so your viral load and CD4+ cell counts will be closely monitored while you are taking this medicine.

Maraviroc is approved for use in people with HIV who are at least 16 years old.

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  1. U.S. Department of Health and Human Services (2008). Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. Available online: http://www.aidsinfo.nih.gov/ContentFiles/AdultandAdolescentGL.pdf.
  2. Hammer, Scott M, et al. (2008). Antiretroviral treatment of adult HIV infection: 2008 recommendations of the International AIDS Society USA Panel. JAMA, 300 (5): 555–570.
  3. Lalezari JP, et al. (2003). Enfuvirtide, an HIV-1 fusion inhibitor, for drug-resistant HIV infection in North and South America. New England Journal of Medicine, 348(22): 2175–2185.
  4. Hanson K, Hicks C (2006). New antiretroviral drugs. Current HIV/AIDS Reports, 3(2): 93–101.

Last Updated: April 10, 2009

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