Fuzeon
Evidence Grade A — Regulatory approved. 828 published studies. 54 registered clinical trials.
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Enfuvirtide (sold as Fuzeon) is an injectable antiviral that stops HIV from entering human immune cells — the very first step in the infection process. It was the first "fusion inhibitor" approved for HIV and is reserved for patients whose virus has become resistant to other drug combinations. However, the requirement for twice-daily injections and near-universal injection-site reactions have made it a treatment of last resort.
828 published studies: 719 human, 20 animal, 104 in-vitro, 166 reviews
Enfuvirtide is marketed as Fuzeon (approved March 2003). It requires twice-daily subcutaneous injections, and injection-site reactions occur in nearly all patients (98%). In clinical trials (TORO-1 and TORO-2), enfuvirtide combined with an optimised background regimen achieved significantly greater viral suppression than background regimen alone in treatment-experienced patients.
Enfuvirtide represented a major advance when HIV drug resistance was a more pressing clinical challenge, but its use has declined substantially with the arrival of more convenient oral antiretrovirals. The twice-daily injection burden, injection-site reactions, high cost, and complex manufacturing (it is one of the largest synthetic peptides manufactured at scale) have limited its role to a last-resort option for patients with highly resistant HIV.
When HIV infects a cell, its surface protein gp41 must fold into a specific shape to fuse the viral envelope with the cell membrane. Enfuvirtide is a peptide that mimics part of gp41 and physically blocks this folding step, like jamming a zipper. Without this conformational change, the virus cannot merge with the cell and infection is prevented. This mechanism is effective against HIV strains that have developed resistance to drugs targeting later stages of the viral lifecycle.
Two major clinical trials (TORO-1 and TORO-2) demonstrated that adding enfuvirtide to an optimised drug regimen significantly improved viral suppression in patients with highly resistant HIV. When it was introduced in 2003, it represented an important advance for patients running out of treatment options. In practice, enfuvirtide's role has been drastically reduced by the arrival of oral drugs (particularly integrase inhibitors) that are more potent, better tolerated, and far more convenient. Injection-site reactions occur in 98% of patients, and the twice-daily injection schedule is a heavy burden. The drug is also one of the largest synthetic peptides ever manufactured at commercial scale, contributing to high costs. The manufacturer announced US discontinuation in August 2024, reflecting its minimal remaining clinical use.
Study of a New Anti-HIV Drug, T-20, in HIV-Infected Children
T-20 in HIV Patients With Prior Drug Treatment and/or Resistance to Each of the Three Classes of Anti-HIV Drugs
Adding New Drugs for HIV Infected Patients Failing Current Therapy
EMA Marketing Authorisation
Health Canada Market Authorisation
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