Interaction of human cytochrome P4503A4 with ritonavir analogs

Arch Biochem Biophys. 2012 Apr 15;520(2):108-16. doi: 10.1016/ Epub 2012 Mar 5.


Ritonavir is a HIV protease inhibitor that also potently inactivates cytochrome P450 3A4 (CYP3A4), a major human drug-metabolizing enzyme. To better understand the mechanism of ligand binding and to find strategies for improvement of the inhibitory potency of ritonavir, currently administered to enhance pharmacokinetics of other anti-HIV drugs that are quickly metabolized by CYP3A4, we compared the manner of CYP3A4 interaction with the drug and two analogs lacking either the heme-ligating thiazole nitrogen or the entire thiazole group. Based on the kinetic, mutagenesis and structural data, we conclude that: (i) the active site residue Arg212 assists binding of all investigated compounds and, thus, may play a more prominent role in metabolic transformation of xenobiotics than previously thought, (ii) peripheral binding of ritonavir limits the heme coordination rate and complicates the binding kinetics, (iii) association of ritonavir-like type II ligands is driven by heme coordination whereas hydrophobic forces define the binding mode, and (iv) substitution of one phenyl group in ritonavir with a smaller hydrophobic moiety could prevent steric clashing and, hence, increase the affinity and inhibitory potency of the drug.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Binding Sites
  • Cytochrome P-450 CYP3A / chemistry*
  • Enzyme Activation
  • HIV Protease Inhibitors / chemistry
  • Models, Chemical*
  • Protein Binding
  • Ritonavir / analogs & derivatives*
  • Ritonavir / chemistry*


  • HIV Protease Inhibitors
  • Cytochrome P-450 CYP3A
  • CYP3A4 protein, human
  • Ritonavir