Biological Functions

Enfuvirtide is used in combination with other antiretrovirals and works against a variety of HIV-1 variants, but it is not active against HIV-2. Resistance to enfuvirtide can develop when the virus produces changes in a 10-amino-acid domain between residues 36 to 45 in the gp41 HIV surface glycoprotein.

Acquired resistance

Resistance is mediated by amino acid substitutions within the first heptad repeat region of gp41 at amino acids 36–45. Resistance emerges fairly rapidly in patients experiencing virological failure with an enfuvirtide-containing antiretroviral regimen, and is associated with the return of the plasma HIV load toward baseline within a few weeks.

Pharmaceutical Applications

A linear 36-amino acid synthetic peptide with an acetylated N-terminus and a carboxamide C-terminus. It is formulated as a lyophilized powder to be reconstituted for subcutaneous injection.

Biochem/physiol Actions

Enfuvirtide is an HIV fusion inhibitor used to patients with multi-drug resistant HIV. Enfuvirtide binds to gp41 preventing the creation of an entry pore for the HIV-1 virus.

Pharmacokinetics

Subcutaneous absorption c. 84.3% Cmax 90 mg s/c twice daily c. 4.59 mg/L Plasma half-life c. 3.8 h Volume of distribution 5.5 L Plasma protein binding c. 92% Absorption and distribution Absorption of the 90 mg dose is comparable when injected into the subcutaneous tissue of the abdomen, thigh or arm. It does not penetrate the CSF or semen. Distribution into breast milk has not been described. Metabolism and excretion It probably undergoes catabolism to its constituent amino acids, with subsequent recycling of the amino acids in the body pool.

Side effects

It does not seem to have any long-term toxicities (including the HIV lipodystrophy syndrome) associated with other commonly used antiretrovirals. Reaction at the injection site, variously characterized by local pain, erythema, pruritus, induration, ecchymosis, nodules or cysts, is experienced by more than 90% of patients and may lead to treatment fatigue.

Drug interactions

Potentially hazardous interactions with other drugs Orlistat: absorption possibly reduced by orlistat.

Metabolism

As a peptide, enfuvirtide is expected to undergo catabolism to its constituent amino acids, with subsequent recycling of the amino acids in the body pool. In vitro human microsomal studies and in vivo studies indicate that enfuvirtide is not an inhibitor of CYP450 enzymes. In in vitro human microsomal and hepatocyte studies, hydrolysis of the amide group of the C-terminus amino acid, phenylalanine results in a deamidated metabolite. Mass balance studies to determine elimination pathway(s) of enfuvirtide have not been performed in humans.

Definition

ChEBI: A synthetic 36-amino acid peptide consisting of N-acetyltyrosyl, threonyl, seryl, leucyl, isoleucyl, histidyl, seryl, leucyl, isoleucyl, alpha-glutamyl, alpha-glutamyl, seryl, glutaminyl, asparaginyl, glutaminyl, glutamin l, alpha-glutamyl, lysyl, asparaginyl, alpha-glutamyl, alpha-glutamyl, alpha-glutamyl, leucyl, leucyl, alpha-glutamyl, leucyl, alpha-aspartyl, lysyl, tryp ophyl, alanyl, seryl, leucyl, tryptophyl, asparaginyl, tryptophyl, and phenylalaninamide residues joined in sequence. An HIV fusion inhibitor, it was the first of a novel class of antiretroviral drugs used in combination therapy for the treatment of HIV-1 nfection. It interferes with entry of HIV into cells by binding to the gp41 sub-unit of the viral envelope glycoprotein, so inhibiting fusion of viral and cellular membranes.

Brand name

Fuzeon

General Description

Enfuvirtide acetate salt is a linear synthetic peptide made of 36 amino acids. It has an acetylated N-terminus and a carboxamide C-terminus. Enfuvirtide is catabolized with the help of proteolytic enzymes.