Differential inhibition of cytochrome P450 3A4, 3A5 and 3A7 by five human immunodeficiency virus (HIV) protease inhibitors in vitro

Basic Clin Pharmacol Toxicol. 2006 Jan;98(1):79-85. doi: 10.1111/j.1742-7843.2006.pto_249.x.


The effects of five HIV protease inhibitors (amprenavir, indinavir, nelfinavir, ritonavir and saquinavir) on cytochrome P450 (CYP) 3A4, 3A5 and 3A7 activities were studied in vitro using testosterone 6beta-hydroxylation in recombinant CYP3A4, CYP3A5 and CYP3A7 enzymes. The protease inhibitors showed differential inhibitory effects on the three CYP3A forms. Ritonavir and saquinavir were non-selective and preferential inhibitors of CYP3A4 and CYP3A5 (K(i) 0.03 microM and 0.6-0.8 microM for ritonavir and saquinavir, respectively), and weaker inhibitors of CYP3A7 (K(i) 0.6 microM and 1.8 microM, respectively). Nelfinavir was a potent and non-selective inhibitor of all three CYP3A forms (K(i) 0.3-0.4 microM). Amprenavir and indinavir preferentially inhibited CYP3A4 (K(i) 0.1 microM and 0.2 microM, respectively), with weaker inhibitory effects on CYP3A5 (K(i) 0.5 microM and 2.2 microM, respectively) and CYP3A7 (K(i) 2.1 microM and 10.6 microM, respectively). In conclusion, significant differences exist in the inhibitory potency of protease inhibitors for different CYP3A forms. Ritonavir, nelfinavir, saquinavir and amprenavir seem to be prone to drug-drug interactions by inhibiting both CYP3A4 and CYP3A5. Especially nelfinavir and ritonavir also have a potential to inhibit foetal CYP3A7-mediated drug metabolism and some endogenous pathways that may be crucial to normal foetal development, while indinavir has the lowest potential to inhibit CYP3A5 and CYP3A7.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aryl Hydrocarbon Hydroxylases / antagonists & inhibitors*
  • Aryl Hydrocarbon Hydroxylases / genetics
  • Aryl Hydrocarbon Hydroxylases / metabolism
  • Carbamates / pharmacology
  • Cytochrome P-450 CYP3A
  • Cytochrome P-450 Enzyme Inhibitors*
  • Cytochrome P-450 Enzyme System / genetics
  • Cytochrome P-450 Enzyme System / metabolism
  • Dose-Response Relationship, Drug
  • Drug Interactions
  • Furans
  • HIV Protease Inhibitors / pharmacology*
  • Humans
  • Hydroxylation
  • In Vitro Techniques
  • Indinavir / pharmacology
  • Isoenzymes
  • Kinetics
  • Nelfinavir / pharmacology
  • Recombinant Proteins
  • Ritonavir / pharmacology
  • Saquinavir / pharmacology
  • Sulfonamides / pharmacology
  • Testosterone / metabolism


  • Carbamates
  • Cytochrome P-450 Enzyme Inhibitors
  • Furans
  • HIV Protease Inhibitors
  • Isoenzymes
  • Recombinant Proteins
  • Sulfonamides
  • Testosterone
  • amprenavir
  • Indinavir
  • Cytochrome P-450 Enzyme System
  • Aryl Hydrocarbon Hydroxylases
  • CYP3A5 protein, human
  • CYP3A7 protein, human
  • Cytochrome P-450 CYP3A
  • CYP3A4 protein, human
  • Nelfinavir
  • Saquinavir
  • Ritonavir