FUZEON® :: Mechanism of Action

 

 

FUZEON has a unique mechanism of action compared to reverse transcriptase and protease inhibitors in that it works outside of the cell, blocking HIV before it enters the cell. FUZEON interferes with the entry of HIV-1 into cells by inhibiting fusion of viral and cellular membranes.

HIV-1 isolates with reduced susceptibility to FUZEON have been selected in vitro and have been recovered from clinical trial subjects treated with FUZEON in combination with other antiretroviral agents. HIV-1 clinical isolates resistant to NRTIs, NNRTIs and PIs were susceptible to FUZEON in cell culture.



Indication

FUZEON (enfuvirtide) 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.

This indication is based on results from two controlled studies of 48-weeks' duration. Subjects enrolled were treatment-experienced adults; many had advanced disease. There are no studies of FUZEON in antiretroviral-naive patients.

Important Safety Information

FUZEON is contraindicated in patients with known hypersensitivity to FUZEON or any of its components.

Local Injection Site Reactions (ISRs)

The majority of subjects (98%) receiving FUZEON in randomized, controlled, open-label, multicenter clinical trials had at least one local injection site reaction; ISRs occurred throughout treatment with FUZEON. Manifestations may include pain and discomfort, induration, erythema, nodules and cysts, pruritus, and ecchymosis. Reactions are often present at more than one injection site.

Administration with Biojector® 2000

Nerve pain (neuralgia and/or paresthesia) lasting up to 6 months associated with administration at anatomical sites where large nerves course close to the skin, bruising and hematomas have occurred with use of the Biojector 2000 needle-free device for administration of FUZEON. Patients receiving anticoagulants or persons with hemophilia, or other coagulation disorders, may have a higher risk of post-injection bleeding.

Pneumonia

An increased rate of bacterial pneumonia was observed in subjects treated with FUZEON in the Phase III clinical trials compared to the control arm. Three subject deaths in the FUZEON arm were attributed to pneumonia; all three had serious concomitant AIDS-related illnesses that contributed to their deaths. Because it was unclear whether the higher incidence rate of pneumonia was related to FUZEON use, an observational study in 1850 HIV-infected patients was conducted to evaluate the risk of pneumonia in patients treated with FUZEON. Based on this observational study, it is not possible to exclude an increased risk of pneumonia in patients treated with FUZEON compared to non-FUZEON treated patients. It is unclear if the increased incidence of pneumonia is related to FUZEON use. However, because of these findings, patients with HIV infection should be carefully monitored for signs and symptoms of pneumonia, especially if they have underlying conditions that may predispose them to pneumonia. Risk factors for pneumonia included low initial CD4 cell count, high initial viral load, intravenous drug use, smoking and a prior history of lung disease.

Hypersensitivity Reactions

Systemic hypersensitivity reactions have been associated with FUZEON therapy and may recur on re-challenge. Hypersensitivity reactions have occurred in < 1% of patients and have included combinations of rash, fever, nausea and vomiting, chills, rigors, hypotension and elevated serum liver transaminases. Other adverse events that may be immune-mediated and have been reported in subjects receiving FUZEON include primary immune complex reaction, respiratory distress, glomerulonephritis and Guillain-Barre syndrome. Patients developing signs and symptoms suggestive of a systemic hypersensitivity reaction should discontinue FUZEON treatment and should seek medical evaluation immediately. Therapy with FUZEON should not be restarted following systemic signs and symptoms consistent with a hypersensitivity reaction. Risk factors that may predict the occurrence or severity of hypersensitivity to FUZEON have not been identified.

Non-HIV Infected Individuals

There is a theoretical risk that FUZEON use may lead to the production of anti-enfuvirtide antibodies which cross-react with HIV gp41. This could result in a false positive HIV test with an ELISA assay; a confirmatory western blot test would be expected to be negative. FUZEON has not been studied in non-HIV infected individuals.

Immune Reconstitution Syndrome

Immune reconstitution syndrome has been reported in patients treated with combination antiretroviral therapy, including FUZEON. Autoimmune disorders (such as Graves' disease, polymyositis, and Guillain-Barré syndrome) have also been reported to occur in the setting of immune reconstitution, however, the time to onset is more variable and can occur many months after initiation of treatment.

Most Common Adverse Events

Local Injection Site Reactions (ISRs)

In clinical trials, ISRs were the most frequently reported adverse event (98%) and occurred throughout treatment with FUZEON. Four percent of patients discontinued treatment because of ISRs. Signs/symptoms may include pain and discomfort, induration, erythema, nodules and cysts, pruritus, ecchymosis and infection. Eleven percent of patients had local reactions that required analgesics or limited usual activities.

Other Adverse Events

Excluding ISRs, the events most frequently reported in patients receiving FUZEON plus a background regimen were diarrhea (38 per 100 patient-years, or 32%), nausea (27 per 100 patient-years, or 23%) and fatigue (24 per 100 patient-years, or 20%). These events were seen at a lower incidence than in patients receiving a background regimen without FUZEON: diarrhea (73 per 100 patient-years), nausea (50 per 100 patient-years) and fatigue (38 per 100 patient-years).

FUZEON is not a cure for HIV infection and patients may continue to experience illnesses associated with HIV-1 infection, including opportunistic infections. Patients should remain under the care of a physician when using FUZEON.

For more information on FUZEON, please see full Prescribing Information, go to www.FUZEON.com or call 1.877.4.FUZEON (1.877.438.9366).