Influence of the length and positioning of the antiestrogenic side chain of endoxifen and 4-hydroxytamoxifen on gene activation and growth of estrogen receptor positive cancer cells

J Med Chem. 2014 Jun 12;57(11):4569-83. doi: 10.1021/jm500569h. Epub 2014 May 22.


Tamoxifen has biologically active metabolites: 4-hydroxytamoxifen (4OHT) and endoxifen. The E-isomers are not stable in solution as Z-isomerization occurs. We have synthesized fixed ring (FR) analogues of 4OHT and endoxifen as well as FR E and Z isomers with methoxy and ethoxy side chains. Pharmacologic properties were documented in the MCF-7 cell line, and prolactin synthesis was assessed in GH3 rat pituitary tumor cells. The FR Z-isomers of 4OHT and endoxifen were equivalent to 4OHT and endoxifen. Other test compounds used possessed partial estrogenic activity. The E-isomers of FR 4OHT and endoxifen had no estrogenic activity at therapeutic serum concentrations. None of the newly synthesized compounds were able to down-regulate ER levels. Molecular modeling demonstrated that some compounds would each create a best fit with a novel agonist conformation of the ER. The results demonstrate modulation by the ER complex of cell replication or gene transcription in cancer.

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

  • Animals
  • Cell Line
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cycloheptanes / chemical synthesis
  • Cycloheptanes / chemistry
  • Cycloheptanes / pharmacology
  • Estrogen Receptor Modulators / chemical synthesis*
  • Estrogen Receptor Modulators / chemistry
  • Estrogen Receptor Modulators / pharmacology
  • Humans
  • Molecular Docking Simulation
  • Rats
  • Receptors, Estrogen / metabolism*
  • Stereoisomerism
  • Structure-Activity Relationship
  • Tamoxifen / analogs & derivatives*
  • Tamoxifen / chemical synthesis
  • Tamoxifen / chemistry
  • Tamoxifen / pharmacology
  • Transcriptional Activation / drug effects


  • Cycloheptanes
  • Estrogen Receptor Modulators
  • Receptors, Estrogen
  • Tamoxifen
  • afimoxifene
  • 4-hydroxy-N-desmethyltamoxifen