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AIDS virusProleukin belongs to a class of anti-HIV drugs called Immune-Based Therapies. For a description of the life-cycle of the AIDS virus, and the targets of each class of drugs, click here.

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Proleukin (aldesleukin, Interleukin-2, or IL-2)


What is the most important information I should know about Proleukin?
  • Proleukin is an immune-based therapy marketed by the Chiron Corporation. Also, Amgen Pharmaceuticals is developing its own formulation of IL-2.
  • The drug is only approved for the treatment of certain types of cancer. It is still considered an experimental drug for HIV-related therapy and it has not yet been evaluated by the U.S. Food and Drug Administration (FDA) for use in people living with the virus.
  • A large clinical trial of IL-2 (SILCAAT) was stopped on October 23, 2002. The study was designed to compare two groups of patients: a group of HIV-positive people taking IL-2 plus standard anti-HIV drugs and a group of HIV-positive people taking standard anti-HIV drugs without IL-2. The main goal of the study was to determine which group of patients would live longer. Because it would take several years to determine this benefit, the Chiron Corporation has made a business decision to stop the study. However, data from the study reviewed so far suggest that the drug is safe and effective in raising T-cells when combined with anti-HIV therapy. If you are a participant in the SILCAAT study, you should contact your study nurse or principle investigator to discuss what this means for you. At this time, it is not clear if another large IL-2 study – the ESPRIT study – will be stopped or continued.

What is Proleukin?
  • Proleukin is a man-made (synthetic) version of a protein produced by T-cells in the body. This protein, or cytokine, is called interleukin-2 (IL-2).
  • Unlike drugs currently used to treat HIV, Proleukin does not attack the virus. Proleukin boosts the production and activity of several important immune system cells. These cells include T-cells (T4 cells and T8 cells), B-cells (which produce antibodies), macrophages, and natural killer cells (NK cells).
  • Researchers believe that Proleukin can be helpful to HIV-positive people in two ways: 1) to help protect the immune system from the damage caused by HIV, and 2) to help the immune system control HIV reproduction.

What is the dose used for HIV?
  • Proleukin is different than many other drugs. Instead of milligrams of milliliters, the drug is administered in "units." Because Proleukin is such a small protein, large amounts of the drug are needed to do the work it needs to do in all parts of the body. This is why Proleukin is administered in doses consisting of several thousand or million units .
  • Proleukin is available in an intravenous (IV) formulation and an injectable formulation. The IV formulation is generally used if high doses are needed; the injectable form will suffice for low or intermediate doses.
  • A "very-high" dose of Proleukin consists of 150 million units every day, given through an IV. This dose is divided up into three daily infusions and is administered for a total of five days. After three weeks off the drug, another five-day cycle of Proleukin is usually administered. This dose has not been studied in people living with HIV, as it causes serious side effects. It must be administered in a hospital, preferably in an intensive-care unit (ICU).
  • A "high" dose of Proleukin has been studied in people living with HIV. The high dose consists of 15 million units ever day for five days, and is broken up into three IV injections, every eight hours. This dose of Proleukin must also be administered in a hospital and will likely cause serious side effects.
  • "Intermediate" and "low" doses of Proleukin are gaining popularity among researchers. These can be administered using an injectable (hypodermic needle) formulation. This allows for patients to take the drug in the privacy of their own home without an immediate risk of dangerous side effects. The intermediate dose of Proleukin is usually 9 million units, divided up into two daily injections, for five days. The low dose of Proleukin is usually no more than 3 million units, also divided up into two daily injections. At least one group of researchers is experimenting with the low-dose Proleukin formulation for every day use. Because the low-dose formulation rarely causes side effects, taking the drug every day might be possible.

What is already known about Proleukin?
  • Proleukin doesn't attack HIV. It helps T-cells and other important immune system cells (e.g., B-cells, macrophages, and natural killer cells) to grow. Many patients who have used Proleukin have seen large increases in their T-cell counts and other important cells.
  • Proleukin – particularly the intermediate and high doses – should be used in combination with anti-HIV drugs. This is because it can also cause viral load to increase in the absence of effective anti-HIV therapy.
  • In the past, Proleukin was found to increase T-cell counts in patients who had relatively high T-cell counts to begin with (i.e., greater than 200 cells/mm3). New research has shown that lower doses of the drug can be used to boost T-cell counts in patients with lower T-cell counts. In other words, Proleukin may have two advantages: 1) to protect the immune system in people who have normal T-cell counts, and 2) to restore the immune system in people who have low T-cell counts.
  • Some researchers believe that Proleukin will help HIV-positive people's immune systems gain better control HIV, even in the absence of anti-HIV drug therapy. This does not mean that Proleukin will be a cure. Researchers are attempting to "prime" the immune system to help keep HIV at low levels so that it won't cause additional damage to the immune system. Studies are now being conducted to examine this possibility.
  • Like other drugs, Proleukin might interact with other medications, including those used to treat HIV. It is important that your personal physician and/or the research nurse or study investigator be aware of all drugs you are taking, including those you buy without a prescription.

What is known about side effects?
  • Side effects often depend on the doses used. Patients treated with the high and very high doses of the drug often have severe flu-like symptoms. If these doses are used, the patient should be given the drug in a hospital. The intermediate dose is better tolerated, but can also cause flu-like symptoms, albeit to a lesser degree. The low doses of Proleukin appear to be well tolerated, but additional research is needed to confirm this.
  • Other side effects may occur as a result of taking Proleukin. These have not yet been fully examined in clinical trials and have not yet been reviewed by the FDA.

Who should not take Proleukin?
  • It is not known whether Proleukin will harm an unborn baby. It is very important to treat HIV/AIDS during pregnancy to reduce the risk of infecting your baby. Talk to your doctor about your treatment options.
  • It is not known whether Proleukin passes into breast milk and what effect it may have on a nursing baby. To prevent transmission of the virus to uninfected babies, it is recommended that HIV-positive mothers not breast-feed.

Where can I learn more about clinical trials of Proleukin?
  • If you are a participant in the SILCAAT study, you should contact your study site's research nurse or principle investigator to learn more about why the study was stopped and how it will affect you. You can also call a 24-hour toll-free number (1-866-874-3153) or visit to learn more about why the study was stopped.
  • To learn more about the ESPRIT study, you can find complete information, including contact numbers, at
  • If you would like to find out if you are eligible for any clinical trials that include Proleukin, visit, a site run by the U.S. National Institutes of Health. The site has information about all HIV-related clinical studies in the United States. For more info, you can call their toll-free number at 1-800-HIV-0440 (1-800-448-0440) or email

Last Revised: October 23, 2002

This content is written by the POZ and AIDSmeds editorial team. For more information, please visit our "About Us" page.

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