Skip to main content
Immune functionHIV fusion inhibitor peptide

Enfuvirtide

Also known as: T-20, Fuzeon

By the Peptide Dossier Editorial TeamUpdated How we source

Enfuvirtide is an HIV fusion-inhibitor peptide historically used with other antiretrovirals in treatment-experienced patients. Its entry-blocking mechanism differs from intracellular HIV drugs, while US Fuzeon was discontinued in 2025.

Quick Facts

Class:HIV fusion inhibitor peptide
Product status:Fuzeon received HIV approval in 2003; its manufacturer discontinued the US product in February 2025.
Research context:FDA approved

The T-20 fusion inhibitor

Enfuvirtide is a synthetic 36-amino-acid peptide developed as T-20 and sold as Fuzeon. It was the first HIV fusion/entry inhibitor and received US approval in 2003 for selected treatment-experienced infection.

Preventing HIV membrane fusion

HIV’s gp41 surface protein must fold into a hairpin-like shape to bring viral and CD4-cell membranes together. Enfuvirtide mimics part of gp41 and blocks the region needed for that folding, preventing membrane fusion and viral entry. This extracellular mechanism differs from inhibition of reverse transcriptase, protease or integrase, allowing activity against virus resistant to those classes. In TORO trials, adding it to an optimized background regimen reduced HIV-1 RNA significantly more than background treatment alone.

Supporting references: RNA.

Sources: [1]

Historical indication and discontinuation

FDA approved enfuvirtide in 2003 in combination therapy for treatment-experienced HIV-1 with continuing replication despite antiretrovirals. Twice-daily injections and frequent local reactions generally reserved it for multidrug-resistant settings. The manufacturer discontinued US Fuzeon on February 28, 2025, citing reduced need after newer treatments became available. Historical approval does not establish current product availability.

Supporting references: discontinued.

Sources: [2]

Injection reactions and other risks

Nearly all patients experienced injection-site pain, induration, redness or cysts. Diarrhea, nausea and fatigue were also common. Serious considerations include a higher bacterial-pneumonia rate and hypersensitivity that may recur on restarting the drug.

References and further reading

This reference draws on Superpower’s Peptide Library and the research linked below. Peptide Dossier’s editorial team adapted and integrated the material on .

  1. 10.1056/NEJMoa035026Preventing HIV membrane fusionCited in: Preventing HIV membrane fusion
  2. gene.comHistorical indication and discontinuationCited in: Historical indication and discontinuation

Frequently Asked Questions About Enfuvirtide

Related Peptides

BacitracinBalixafortideBrilacidinCorticotropin (ACTH)

Continue exploring Enfuvirtide

Search all related references →

Our library review is ongoing. Read how we evaluate evidence or report a correction.

Disclaimer: This article is for informational and educational purposes only. It is not intended as medical advice. The information presented is based on published research and should not be used as a substitute for professional medical guidance. Always consult a qualified healthcare provider before starting any peptide protocol. Some peptides discussed may not be approved for human use by the FDA or equivalent regulatory bodies.