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Antiviral

Enfuvirtide

The first HIV entry inhibitor — a 36-amino-acid peptide that blocks viral fusion.

L5Practice-changingApproved — narrow indicationApprovedHigh confidenceLast reviewed 2026-08-23
SC injection

Also known as: Fuzeon, T-20

Evidence passport

Last reviewed 2026-08-23

Evidence level
L5Practice-changing
Confidence
High confidence
Human efficacy
82/100
Human safety
78/100
Regulatory status
Approved — narrow indication
Development
Approved
Routes
SC injection
Evidence base
Includes human data
Furthest stage
Approved
Source curation
Sources fully curated
Clinical maturity
Approved antiretroviral, now largely historical in practice

Overview

Human evidence82/100
Preclinical evidence78/100
Human safety evidence78/100

Clinical maturity: Approved antiretroviral, now largely historical in practice

Routes & formulations

Studied / approved routes

SC injection

The approved product is a twice-daily subcutaneous injection as part of combination antiretroviral therapy.

Route availability is not evidence of efficacy, and evidence from one route does not transfer to another. The Registry never provides dosing or sourcing information.

Peptide lifecycle

  1. Discovery

  2. Preclinical

  3. Phase I

  4. Phase II

  5. Phase III

  6. Approved

Approved

What it is

A synthetic peptide mimicking part of the HIV gp41 protein, blocking the conformational change the virus needs to fuse with human cells.

What people claim

  • Reduces viral load in treatment-experienced HIV-1 patients as part of combination therapy

What the evidence actually says

Randomised trials in heavily treatment-experienced patients supported its approval and proved that a peptide could be a viable antiviral class. Newer, easier antiretrovirals have since narrowed its practical role.

Human evidence

  • Pivotal randomised controlled trials in treatment-experienced HIV-1 infection.

Preclinical evidence

  • Viral fusion biology and gp41 peptide-inhibition studies.

Animal and cell findings are Level 1–2 evidence.

Mechanism and pathways

  • Binds gp41 and prevents the six-helix-bundle formation required for viral-cell membrane fusion.

Safety and unknowns

  • Injection-site reactions are near-universal and are the dominant tolerability issue.
  • Labelled considerations include hypersensitivity reactions and a pneumonia signal observed in trials.

Cancer relevance

No concern identified

No established human cancer signal within approved use.

Regulatory status

FDA-approved (Fuzeon) in combination with other antiretrovirals for treatment-experienced patients with HIV-1 with evidence of ongoing viral replication. Approval is specific to that role in combination therapy.

Evidence grade

L5Practice-changingHigh confidence

Replicated large randomised trials, pivotal Phase 3 programmes, or a major regulatory decision.

What would change our rating?

  • Not applicable at this evidence tier.

References and sources

Sources fully curated

Source hierarchy: regulatory documents and trial registries first, peer-reviewed work next, sponsor material flagged as non-independent. We never use supplier or clinic marketing as evidence, and where a verified source has not yet been curated we say so rather than inventing one.

Evidence change history

No recorded changes yet. Baseline position set on 2026-08-23.