Fuzeon – brand name

T-20 – commonly-used name

enfuvirtide – generic name

Fuzeon is the first drug to be approved in a new class of HIV drugs called fusion inhibitors (FIs), also called entry inhibitors.

The older drugs fight HIV once it is inside a cell. But FIs block HIV from entering the cell in the first place. This may slow down HIV disease.

The Food and Drug Administration (FDA) has approved Fuzeon for use in combination with other HIV drugs for the treatment of HIV infection in adults and children over six years old, who have tried other HIV therapies but still have a high viral load and low CD4 cells.

Fuzeon comes in powdered form that must be mixed and injected.

The standard adult dose is 90 milligrams (mg) twice a day.

A new injection device (the Biojector) that does not use needles may be approved for use with Fuzeon in 2006.

Because Fuzeon would be destroyed by stomach acid if taken by mouth, it must be injected under the skin of the upper arm, top of the thigh, or stomach.

Your doctor will teach you how to “reconstitute” (mix) the Fuzeon powder with sterile water and give yourself injections.

• The mixing and injecting of Fuzeon can be difficult and time consuming, but it must be done correctly to ensure that the drug is effective.
• Ask your doctor or nurse for help if you have any problems.

Fuzeon in its powdered form should be stored at room temperature. Once the powder has been mixed with water, it may be kept in the refrigerator for up to 24 hours.

Check with your child’s doctor for children’s dosing.

Fuzeon must be used with other HIV medications to treat HIV.

As with all HIV drugs, it is important to take Fuzeon as prescribed. Missing or skipping doses can cause your blood levels of the drug to fall too low and resistance can develop. When your virus becomes resistant to an HIV medication, that drug may stop working.

Fuzeon has not yet been well studied in HIV+ people who are being treated for the first time, and it is not currently approved for this use.

Because Fuzeon targets a different step in the virus lifecycle, it works against HIV that is resistant to the other classes of HIV drugs.

Fuzeon is approved as “salvage therapy” for people whose previous HIV drugs are no longer working.

Fuzeon works best when combined with at least two other drugs that your HIV is still sensitive to. This may include a protease inhibitor (PI) “boosted” with Norvir (ritonavir).

It is a good idea to use drug resistance testing to determine which other HIV drugs to combine with Fuzeon.

Right now, there are no other fusion inhibitors, so you can’t switch to another drug in the same class if you become resistant.

Resistance to Fuzeon does not cause resistance to drugs from other classes.

Sometimes taking more than one medication can cause drug interactions. Because Fuzeon is such a new drug, doctors don’t yet know whether it interacts with many other medications. But so far, it does not appear to interact with other HIV drugs.

Be sure your doctor knows about all the medications you are taking (including over-the-counter, prescription, street drugs, and herbs), even if you only use them occasionally.

For more information and additional resources to check interactions between the particular drugs you are taking, see our info sheet on drug interactions.

Important additions have been made to the Fuzeon (enfuvirtide) insert label stating that the use of the Biojector 2000 (injection needle) to administer Fuzeon may cause nerve pain lasting up to 6 months. It may also cause bruising and hematoma (which is like a spongy, lumpy, rubbery like bruise). And patients with hemophilia may run a higher risk of post-injection bleeding.

So far, Fuzeon side effects seem to be mild. But the drug is still new; it is possible that unexpected long-term side effects could show up later. Most people who use Fuzeon get some skin irritation from injecting the drug.

If you do experience any side effects from Fuzeon, they are likely to be temporary and go away as your body adjusts to the medication. If you experience any of the side effects listed below, call your doctor for advice.  Do not just stop taking your medication.

• Skin irritation, redness, or rash at injection site
• Headaches
• Insomnia (inability to sleep)
• Pain and numbness in feet or legs
• Depression
• Decreased appetite
• Weakness or loss of strength
• Muscle pain
• Constipation
• Pancreas problems

More serious side effects:

• More severe injection site irritation, rash, swelling, or hard lumps under the skin
• Risk of abscesses (skin infection) at the injection site. Keeping your needles and skin clean can help prevent this
• Peripheral neuropathy (nerve damage): this can cause numbness, pain, or tingling, especially in the feet and hands
• Possible rare hypersensitivity (allergic) reaction
• Possible increased risk of bacterial pneumonia

If you are experiencing persistent, unusual, or serious side effects, call your doctor right away.

Studies of Fuzeon pharmacokinetics (how the drug is processed by the body) showed that clearance (elimination) of the drug is slower in people who weigh less. Clearance is also about 20 percent slower in women, independent of weight. But the drug manufacturer does not recommend any dose adjustments based on weight or gender.

Fuzeon has been studied mostly in people with more advanced HIV disease whose other drugs no longer worked, and trials have included only a small proportion of women. The drug was approved based on two studies, TORO 1 (also known as T20-301) and TORO 2 (also known as T20-302).

TORO 1 included 491 participants and TORO 2 included 504 participants, all of whom either had detectable viral load despite treatment with all three other classes of HIV drugs, or evidence of resistance to drugs in all three classes. Taken together, about 10 percent of the participants in these two studies were women, or about 99 women out of 995 total participants.

In these trials, about one-third of the participants used the best available background regimens (an average of 3-5 drugs). The other two-thirds used the same kind of background regimens plus Fuzeon. After 24 weeks, those taking Fuzeon had lower viral loads and larger CD4 cell increases. People taking Fuzeon were about twice as likely to achieve undetectable HIV viral loads as those taking background regimens without Fuzeon. After one year, people taking Fuzeon still had a better response rate.

In terms of side effects in these studies, women did not seem to experience more or different adverse side effects compared with men.

Studies have shown that pregnant women who use HIV drugs can greatly reduce the risk of passing HIV on to their babies. However, Fuzeon has not been studied in pregnant women. Check with your doctor about the best treatment options for you and your baby if you are thinking of getting pregnant.

Click this link for more information about pregnancy.

People who are starting HIV treatment for the first time may develop Immune Reconstitution Syndrome or IRS (also called Immune Reconstitution Inflammatory Syndrome or IRIS). IRS can happen as a result of the immune system getting stronger and responding to an HIV-related infection such as Mycobacterium avium infection (MAC), cytomegalovirus (CMV), Pneumocystis jirovecii pneumonia (PCP), or tuberculosis (TB). People may have been treated for these infections in the past or not even know they have them. If you notice any unusual symptoms soon after starting HIV drugs for the first time, let your doctor know right away so you can be evaluated and, if necessary, treated.