New selective inhibitors of cytochromes P450 2B and their application to antimutagenesis of tamoxifen

Arch Biochem Biophys. 2002 Jul 1;403(1):41-9. doi: 10.1016/S0003-9861(02)00259-X.


2-Isopropenyl-2-methyladamantane (2-PMADA) and 3-isopropenyl-3-methyldiamantane (3-PMDIA) showed potent and selective inhibition of cytochrome P450 (CYP) 2B6-mediated reactions with K(i) values of 5.27 and 2.17 microM, respectively. No effect on activities of other human CYP was found even at concentrations 100-fold higher than those inhibiting CYP2B6. These results indicate that 2-PMADA and 3-PMDIA belong among the most potent CYP2B6-selective inhibitors discovered to date. Both compounds also inhibited reactions catalyzed by CYP2B2 and CYP2B4 with K(i) values ranging between 0.23 and 2 microM. They are competitive inhibitors of all CYP2B. The activation of the anticancer drug tamoxifen by human and rabbit microsomes generating tamoxifen-DNA adducts, which are responsible for carcinogenic side effects of this drug, was strongly inhibited by both compounds. 2-PMADA and 3-PMDIA are very potent for inhibition of formation of these DNA adducts and warrant consideration as candidates for preventing endometrial cancer development by tamoxifen in humans treated with this anticancer drug.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adamantane / analogs & derivatives
  • Adamantane / pharmacology
  • Amantadine / pharmacology
  • Animals
  • Antineoplastic Agents / pharmacology
  • Aryl Hydrocarbon Hydroxylases*
  • Cytochrome P-450 Enzyme Inhibitors*
  • DNA Adducts
  • Endometrial Neoplasms / drug therapy
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology*
  • Female
  • Humans
  • Inhibitory Concentration 50
  • Kinetics
  • Microsomes / drug effects
  • Microsomes / metabolism
  • Models, Chemical
  • Mutagens*
  • Oxygen / metabolism
  • Rabbits
  • Steroid Hydroxylases / antagonists & inhibitors*
  • Tamoxifen / pharmacology


  • 2-isopropenyl-2-methyladamantane
  • 3-isopropenyl-3-methyldiamantane
  • Antineoplastic Agents
  • Cytochrome P-450 Enzyme Inhibitors
  • DNA Adducts
  • Enzyme Inhibitors
  • Mutagens
  • Tamoxifen
  • Amantadine
  • Steroid Hydroxylases
  • Aryl Hydrocarbon Hydroxylases
  • steroid 15-alpha-hydroxylase
  • steroid 16-beta-hydroxylase
  • Adamantane
  • Oxygen