Enfuvirtide
Also known as: Fuzeon, T-20, DP-178
Enfuvirtide (also called Fuzeon or T-20) is an FDA-approved HIV fusion inhibitor. Enfuvirtide is a thirty-six-amino-acid peptide derived from the HR2 region of the HIV-1 envelope glycoprotein gp41. During viral entry gp41 must fold so that its HR1 and HR2 regions pack into a six-helix bundle, and it is the energy of that collapse that pulls the viral and cell membranes together.
For research use only.
Key Facts
- CAS
- 159519-65-0
- Molecular Weight (MW)
- 4491.4 g/mol
- Half-life
- ~3.8 hours (sc)
- FDA status
- Approved
- Administration Route
- Subcutaneous
- Frequency
- Twice daily
- Last updated
- Aug 30, 2026
- Reviewed
- Aug 30, 2026
- Targets
- HIV-1 gp41
Research summary
FDA-approved HIV-1 fusion inhibitor (Fuzeon) for treatment-experienced patients. 90 mg subcutaneous twice daily with other antiretrovirals.
Peptide Library's Enfuvirtide profile summarises 5 cited studies listed in the Science section, the compound's regulatory status, and research-protocol parameters reported for it. It is a research reference, not medical advice.
Protocol
- Dosage Range
- 90 mg twice daily
- Frequency
- Twice daily
- Cycle
- Long-term use as part of antiretroviral regimen
- Administration Route
- Subcutaneous
- Reconstitution Guide
- Reconstitute 90 mg vial with 1.1 mL sterile water for injection
- Injection Sites
- AbdomenArmThigh
- Concentration Example
- 90 mg vial + 1.1 mL → 90 mg/mL
- Timing Notes
- Inject subcutaneously in upper arm, anterior thigh, or abdomen, rotating injection sites
- Expected Onset
- Viral load reduction typically seen within 2-4 weeks
Not yet checked against primary sources
These figures are compiled from earlier reference material. They have not been verified against FDA labelling, registered trials or published literature, no citation is attached to them, and none of them is a recommended dose. Enfuvirtide is queued for dosage evidence review.
Compare reported doses across the whole librarySequence & molecular data
| Molecular formula | C204H301N51O64 |
|---|---|
| Molecular weight | 4491.4 g/mol |
| CAS number | 159519-65-0 |
| Half-life | ~3.8 hours (sc) |
| Appearance | Lyophilized powder for subcutaneous injection |
| Formulation | Lyophilized Powder |
| PubChem CID | 16130199 |
| FDA UNII | 19OWO1T3ZE |
| ChEMBL | CHEMBL525076 |
Identifiers link to the public PubChem, FDA Substance Registration (UNII), ChEMBL and DrugBank records for the same entity.
Science
Mechanism of Action
Enfuvirtide is a thirty-six-amino-acid peptide derived from the HR2 region of the HIV-1 envelope glycoprotein gp41. During viral entry gp41 must fold so that its HR1 and HR2 regions pack into a six-helix bundle, and it is the energy of that collapse that pulls the viral and cell membranes together. Enfuvirtide binds the exposed HR1 groove in the transient pre-hairpin intermediate and occupies the site HR2 would use, preventing the bundle from forming and arresting fusion before the viral core enters the cell. Because it acts outside the cell on a structural rearrangement rather than on an enzyme, it retains activity against virus resistant to reverse transcriptase and protease inhibitors.
Origin
Synthetic peptide corresponding to gp41 HR2.
Targets
Regulatory & research status
Enfuvirtide is an FDA-approved product for specific labelled indications. Approval does not extend to the research contexts described on this page, and approved products are prescription medicines.
| FDA status | Approved |
|---|---|
| Availability | Prescription-Only |
| WADA (sport) | Permitted |
| Library classification | FDA-Approved |
Benefits
Enfuvirtide side effects
Side Effects
- Injection-site reactions (very common)
- Pneumonia signal
- Hypersensitivity
Storage & stability
Lyophilized (freeze-dried) peptide powder is far more stable than the reconstituted solution. Keep sealed vials cold, dry and away from light; long-term storage is typically frozen, with short-term refrigeration for vials in use.
Once reconstituted in bacteriostatic water, keep the solution refrigerated, avoid repeated freeze–thaw cycles and agitation, and label the vial with the reconstitution date and concentration. Discard any solution that turns cloudy or shows particulates.
Degradation rates differ by sequence: peptides containing methionine, cysteine, asparagine or glutamine are more prone to oxidation and deamidation, so shelf life after reconstitution is compound-specific rather than universal.
Read the full guide: how to store peptides before and after reconstitution →
Source: Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544–575. (PMID 20143256). General guidance for research handling; not product-specific instructions.
Enfuvirtide: frequently asked questions
What is Enfuvirtide?
FDA-approved HIV-1 fusion inhibitor (Fuzeon) for treatment-experienced patients. 90 mg subcutaneous twice daily with other antiretrovirals.
How does Enfuvirtide work?
Enfuvirtide is a thirty-six-amino-acid peptide derived from the HR2 region of the HIV-1 envelope glycoprotein gp41. During viral entry gp41 must fold so that its HR1 and HR2 regions pack into a six-helix bundle, and it is the energy of that collapse that pulls the viral and cell membranes together.
Is Enfuvirtide FDA approved?
Yes. Enfuvirtide is approved by the FDA, and approved products are prescription medicines. Approval is always for specific indications studied in clinical trials, so an approved status does not mean the compound is approved for every use it is discussed for. Research-chemical material sold under the same name is not the approved product.
What is the half-life of Enfuvirtide?
Reported half-life for Enfuvirtide is ~3.8 hours (sc). Half-life describes how long the compound persists in circulation, not how long any effect lasts, and published figures vary with route of administration, formulation and the population studied.
Is Enfuvirtide banned in sport?
Enfuvirtide is recorded here as permitted in sport. Anti-doping status is revised annually, so athletes subject to testing should confirm against the current WADA Prohibited List before use.
What peptides are similar to Enfuvirtide?
Compounds most often compared with Enfuvirtide include Angiotensin II, Cetrorelix, Corticorelin and Cosyntropin. They are grouped by shared mechanism or research area rather than by equivalence, and their regulatory status and evidence base differ.
References
- FDA label — FuzeonExternal reference
- Enfuvirtide, 2012External reference
- Multifaceted action of Fuzeon as virus-cell membrane fusion inhibitor — Biochim Biophys Acta, 2011External reference
- Fuzeon-induced collagenophagic granuloma: a peculiar granulomatous injection site reaction to Fuzeon--a case report and review of literature — Int J Surg Pathol, 2010External reference
- [Spanish recommendations for proper use of enfuvirtide] — Enferm Infecc Microbiol Clin, 2007External reference
- Enfuvirtide, 2006External reference
Related research, comparisons & guides
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Compiled by Peptide Library Editorial · Reviewed Aug 30, 2026 · Updated Aug 30, 2026 · Version 1
This Enfuvirtide profile is compiled from published literature (5 cited studies linked above), public regulatory records and chemical registries. It describes what research reports; it is not medical advice, and nothing here is a dosing recommendation for humans. Peptide Library does not sell peptides. Editorial policy · How profiles are compiled · Report an error
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