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Fosamprenavir structure.svg
Fosamprenavir ball-and-stick.png
Systematic (IUPAC) name
{[(2R,3S)-1-[N-(2-methylpropyl)(4-aminobenzene)sulfonamido]-3-({[(3S)-oxolan-3-yloxy]carbonyl}amino)-4-phenylbutan-2-yl]oxy}phosphonic acid
Clinical data
Trade names Lexiva
AHFS/ monograph
MedlinePlus a604012
  • C (United States)
Legal status
Routes of
Pharmacokinetic data
Bioavailability Unknown
Protein binding 90%
Metabolism Hydrolysed to amprenavir and phosphate in GI tract epithelium
Biological half-life 7.7 hours
Excretion Fecal (as metabolites of amprenavir)
CAS Registry Number 226700-81-8 N
ATC code J05AE07
PubChem CID: 131536
DrugBank DB01319 YesY
ChemSpider 116245 YesY
NIAID ChemDB 082186
Chemical data
Formula C25H36N3O9PS
Molecular mass 585.608 g/mol
623.700 g/mol (calcium salt)
 N (what is this?)  (verify)

Fosamprenavir (marketed by ViiV Healthcare as the calcium salt), under the trade names Lexiva (U.S.) and Telzir (Europe) is a pro-drug of the protease inhibitor and antiretroviral drug amprenavir. The FDA approved it October 20, 2003, while the EMEA approved it on July 12, 2004. The human body metabolizes fosamprenavir in order to form amprenavir, which is the active ingredient. That metabolization increases the duration that amprenavir is available, making fosamprenavir a slow-release version of amprenavir and thus reducing the number of pills required versus standard amprenavir.

A head-to-head study with lopinavir[1] showed the two drugs to have comparable potency, but patients on fosamprenavir tended to have a higher serum cholesterol. Fosamprenavir's main advantage over lopinavir is that it is cheaper.


  1. ^ Eron J Jr, Yeni P, Gathe J Jr et al. (2006). "The KLEAN study of fosamprenavir-ritonavir versus lopinavir-ritonavir, each in combination with abacavir-lamivudine, for initial treatment of HIV infection over 48 weeks: a randomised non-inferiority trial". Lancet 368 (9534): 476–82. doi:10.1016/S0140-6736(06)69155-1. PMID 16890834.