Antimicrobial & Antiviral

Enfuvirtide

To infect a cell, HIV, the human immunodeficiency virus, must pull its own envelope and the cell membrane together, and it does that with a viral protein, gp41, that snaps shut like a hinge. Enfuvirtide is a 36-amino-acid peptide copied from a stretch of that same protein, and it jams the mechanism part-closed so the two membranes never meet — a point of attack no other class of HIV drug uses. The US Food and Drug Administration approved it in 2003 on two randomised trials, run in North and South America, Europe and Australia, in people whose virus had already defeated the standard regimens. It has to be injected under the skin twice a day, and salvage treatment is its place: for people who have run out of other options.

Last updated 12 August 2026

Studied forViral load suppression research · Drug-resistant HIV context · Antiretroviral salvage research

Evidence on fileFDA-approved · 2 randomised human trials

Strongest sourceEnfuvirtide, an HIV-1 Fusion Inhibitor, for Drug-Resistant HIV Infection in North and South America (New Engl… (randomised human trial)

Mechanism

Binds the HR1 region of viral gp41, blocking the conformational change required for viral and cell membrane fusion.

Regulatory status

Approved by the FDA. Marketed as FUZEON. Earliest approval 2003-03-13. Application NDA021481.

An approval grades as rung 1 on this site, because 21 CFR 314.126 requires adequate and well-controlled human investigations and one cannot be granted without them. It covers specific indications and doses, though, and does not transfer to other uses of the same molecule.

Reported effects

What sources associate with this compound. Reported categories, not outcomes we have graded — each would need its own citation and rung.

Viral load suppression research
Drug-resistant HIV context
Antiretroviral salvage research

Dosing on file unverified

90 mg (1 mL) SC twice daily (adults); Pediatrics (6-16 yrs): 2 mg/kg SC BID (max 90 mg); 90 mg (1 mL) SC twice daily

Carried from a source that labels it unverified, and reproduced with that label attached. A record of what is reported, not a recommendation. No citation on this page establishes it.

Half-life, storage & sport

Elimination half-life: 1.64 h (rat, SC) — study. European journal of medicinal chemistry 2024; rats.

The half-life on file is 1.6 h, measured subcutaneously in rats. On the schedule this record states — twice daily — each dose has fallen to 0.63% of its own peak by the time the next is given. Nothing accumulates, and there is no loading phase to run.

Dosed twice daily over 2 d, each dose normalised to the first peak.

The measurement is not human. It was made in rat, and small mammals clear peptides faster than people do — so this is the fastest plausible shape rather than the expected one.

The rise is not modelled and the axis is not a blood level. No absorption rate constant and no volume of distribution are on file, so each dose appears at full height the instant it is given, and the axis is percent of this compound's own peak.

Literature on file 3

human RCT
Enfuvirtide, an HIV-1 Fusion Inhibitor, for Drug-Resistant HIV Infection in North and South America (New England Journal of Medicine 2003, cited 741x) graded on: names a randomised controlled trial — the indexed publication type — “Randomized Controlled”
human RCT
Efficacy of Enfuvirtide in Patients Infected with Drug-Resistant HIV-1 in Europe and Australia (New England Journal of Medicine 2003, cited 518x) graded on: names a randomised controlled trial — the indexed publication type — “Randomized Controlled”
human RCT
FDA approval NDA021481 graded on: an FDA approval (NDA021481), which requires adequate and well-controlled human investigations — “NDA021481”

Identity

Space-filling 3D model of Enfuvirtide, carbon grey, nitrogen blue, oxygen red — Built from the SMILES on this record — the atoms and bonds are exact. The shape is **one computed low-energy pose**, not a measured structure: a flexible peptide in solution has no single conformation, and where the SMILES leaves a stereocentre undefined the pose commits to one arbitrarily. The skeletal formula below claims connectivity and nothing more, which is what we actually know.

2D chemical structure of Enfuvirtide — Built from the SMILES on this record — the atoms and bonds are exact. The shape is **one computed low-energy pose**, not a measured structure: a flexible peptide in solution has no single conformation, and where the SMILES leaves a stereocentre undefined the pose commits to one arbitrarily. The skeletal formula below claims connectivity and nothing more, which is what we actually know.

Molecular weight: 4492
Molecular formula: C204H301N51O64
CAS number: 159519-65-0
PubChem CID: 16130199
InChI key: PEASPLKKXBYDKL-FXEVSJAOSA-N
Sequence: YTSLIHSLIEESQNQQEKNEQELLELDKWASLWNWF
SMILES: CC[C@H](C)[C@@H](C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](CO)C(=O)N[C@@H](CCC(=O)N)C(=O)N[C@@H](CC(=O)N)C(=O)N[C@@H](CCC(=O)N)C(=O)N[C@@H](CCC(=O)N)C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CC(=O)N)C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](CCC(=O)N)C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CCC(=O)O)C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CC(=O)O)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CC1=CNC2=CC=CC=C21)C(=O)N[C@@H](C)C(=O)N[C@@H](CO)C(=O)N[C@@H](CC(C)C)C(=O)N[C@@H](CC3=CNC4=CC=CC=C43)C(=O)N[C@@H](CC(=O)N)C(=O)N[C@@H](CC5=CNC6=CC=CC=C65)C(=O)N[C@@H](CC7=CC=CC=C7)C(=O)N)NC(=O)[C@H](CC(C)C)NC(=O)[C@H](CO)NC(=O)[C@H](CC8=CN=CN8)NC(=O)[C@H]([C@@H](C)CC)NC(=O)[C@H](CC(C)C)NC(=O)[C@H](CO)NC(=O)[C@H]([C@@H](C)O)NC(=O)[C@H](CC9=CC=C(C=C9)O)NC(=O)C
InChI: InChI=1S/C204H301N51O64/c1-20-102(15)166(253-195(310)137(75-100(11)12)239-200(315)150(93-258)251-190(305)143(82-112-90-215-95-219-112)248-203(318)167(103(16)21-2)254-196(311)138(76-101(13)14)240-201(316)151(94-259)252-204(319)168(105(18)260)255-197(312)139(221-106(19)261)78-108-45-47-113(262)48-46-108)202(317)233-131(58-68-164(280)281)178(293)228-130(57-67-163(278)279)182(297)250-149(92-257)198(313)232-125(52-62-155(210)266)179(294)245-145(84-157(212)268)191(306)229-124(51-61-154(209)265)175(290)224-122(49-59-152(207)263)173(288)226-126(53-63-159(270)271)176(291)222-120(43-31-33-69-205)172(287)244-144(83-156(211)267)192(307)231-127(54-64-160(272)273)177(292)225-123(50-60-153(208)264)174(289)227-128(55-65-161(274)275)180(295)235-134(72-97(5)6)185(300)237-133(71-96(3)4)184(299)230-129(56-66-162(276)277)181(296)236-135(73-98(7)8)187(302)247-147(86-165(282)283)194(309)223-121(44-32-34-70-206)171(286)241-140(79-109-87-216-117-40-28-25-37-114(109)117)183(298)220-104(17)170(285)249-148(91-256)199(314)238-136(74-99(9)10)186(301)242-142(81-111-89-218-119-42-30-27-39-116(111)119)189(304)246-146(85-158(213)269)193(308)243-141(80-110-88-217-118-41-29-26-38-115(110)118)188(303)234-132(169(214)284)77-107-35-23-22-24-36-107/h22-30,35-42,45-48,87-90,95-105,120-151,166-168,216-218,256-260,262H,20-21,31-34,43-44,49-86,91-94,205-206H2,1-19H3,(H2,207,263)(H2,208,264)(H2,209,265)(H2,210,266)(H2,211,267)(H2,212,268)(H2,213,269)(H2,214,284)(H,215,219)(H,220,298)(H,221,261)(H,222,291)(H,223,309)(H,224,290)(H,225,292)(H,226,288)(H,227,289)(H,228,293)(H,229,306)(H,230,299)(H,231,307)(H,232,313)(H,233,317)(H,234,303)(H,235,295)(H,236,296)(H,237,300)(H,238,314)(H,239,315)(H,240,316)(H,241,286)(H,242,301)(H,243,308)(H,244,287)(H,245,294)(H,246,304)(H,247,302)(H,248,318)(H,249,285)(H,250,297)(H,251,305)(H,252,319)(H,253,310)(H,254,311)(H,255,312)(H,270,271)(H,272,273)(H,274,275)(H,276,277)(H,278,279)(H,280,281)(H,282,283)/t102-,103-,104-,105+,120-,121-,122-,123-,124-,125-,126-,127-,128-,129-,130-,131-,132-,133-,134-,135-,136-,137-,138-,139-,140-,141-,142-,143-,144-,145-,146-,147-,148-,149-,150-,151-,166-,167-,168-/m0/s1

Also called

Fuzeon (Enfuvirtide)

Notes unverified prose

FDA-approved (Fuzeon) 2003; HIV fusion inhibitor; FDA-approved (Fuzeon); see Enfuvirtide; FDA-approved

Not on file 0

All 8 tracked fields hold a value on this record: molecular weight and formula, CAS number, PubChem CID, amino-acid sequence, SMILES, InChI and InChI key.

Counted from the record itself, not from what a source said it was missing. 163 of 188 records still have at least one empty.