Drug Name: Fuzeon (enfuvirtide)
Company: Trimeris, Roche
Approval Status: Approved March 2003
Treatment for: HIV Infection

General Information
Fuzeon (enfuvirtide) is an HIV (human immunodeficiency virus) fusion inhibitor that helps block the viruses ability to infect healthy T- cells. Fuzeon does not lower the chance of passing HIV to other people through unprotected sex, sharing needles or being exposed to blood. This drug does not does not cure HIV infection or AIDS and must be taken as part of a combination antiretroviral regimen.

Fuzeon in combination with other antiretroviral agents is indicated for the treatment of HIV-1 infection in treatment-experienced patients with evidence of HIV-1 replication despite ongoing antiretroviral therapy.

The drug is given under the skin by injection in the upper arm, upper leg or stomach two times a day. The recommended dose of is 90 mg (1 mL) twice daily

Clinical Results
FDA approval of Fuzeon was based on data from two 24-week phase III pivotal studies of approximately 1,000 subjects, TORO 1 (T20-301), conducted in North America and Brazil, and TORO 2 (T20-302), conducted in Europe and Australia. These studies showed that treatment-experienced subjects receiving Fuzeon as a part combination regimen of anti-HIV drugs, experienced greater immunologic improvements and were twice as likely to achieve undetectable plasma levels of HIV compared to subjects receiving a anti-HIV regimen alone. In addition, those subjects with two or more active drugs in their background regimen were more likely to achieve undetectable levels of HIV.

Studies T20-301 and T20-302 are ongoing, randomized, controlled, open label, multicenter trials in HIV-1 infected subjects. Subjects were required to have either (1) viremia despite 3 to 6 months prior therapy with a nucleoside reverse transcriptase inhibitor (NRTI), non-nucleoside reverse transcriptase inhibitor (NNRTI), and protease inhibitor (PI) or (2) viremia and documented resistance or intolerance to at least one member in each of the NRTI, NNRTI, and PI classes.

Side Effects
Adverse events associated with the use of Fuzeon may include (but are not limited to) the following:

Local injection site reaction
Pain and discomfort
Induration
Erythema
Nodules and cysts
Pruritus
Ecchymosis
Diarrhea
Conjunctivitis
Pancreatitis

Mechanism of Action
Fuzeon blocks HIV's ability to infect healthy CD4 cells. When used with other anti- HIV medicines, Fuzeon can reduce the amount of HIV in the blood and increase the number of CD4 cells. This may keep the immune system healthy, so it can help fight infection.

The active ingredient, enfuvirtide, interferes with the entry of HIV-1 into cells by inhibiting fusion of viral and cellular membranes. Enfuvirtide binds to the first heptad-repeat (HR1) in the gp41 subunit of the viral envelope glycoprotein and prevents the conformational changes required for the fusion of viral and cellular membranes.