Novel C2-purine Position Analogs of Nitrobenzylmercaptopurine Riboside as Human Equilibrative Nucleoside Transporter 1 Inhibitors

Bioorg Med Chem. 2007 Dec 15;15(24):7726-37. doi: 10.1016/j.bmc.2007.08.058. Epub 2007 Sep 1.


Nucleoside transporter inhibitors have potential therapeutic applications as anticancer, antiviral, cardioprotective, and neuroprotective agents. S(6)-(4-nitrobenzyl)mercaptopurine riboside (NBMPR) is a prototype inhibitor of the human equilibrative nucleoside transporter (hENT1), and is a high affinity ligand with a K(d) of 0.1-1.0 nM. We have synthesized and flow cytometrically evaluated the binding affinity of a series of novel C(2)-purine position substituted analogs of NBMPR at the hENT1. The aim of this research was to understand the substituent requirements at the C(2)-purine position of NBMPR. Structure-activity relationships (SAR) indicate that increasing the steric bulk at the C(2)-purine position of NBMPR led to a decrease in binding affinity of these ligands at the hENT1. New high affinity inhibitors were identified, with the best compound, 2-fluoro-4-nitrobenzyl mercaptopurine riboside (7), exhibiting a K(i) of 2.1 nM. This information, when coupled with the information obtained from other structure-activity relationship studies should prove useful in efforts aimed at modeling the NMBPR and analogs pharmacophore of hENT1 inhibitors.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Cell Line
  • Drug Evaluation, Preclinical
  • Equilibrative Nucleoside Transporter 1 / antagonists & inhibitors*
  • Flow Cytometry
  • Humans
  • Molecular Structure
  • Purines / chemistry*
  • Purines / pharmacology
  • Structure-Activity Relationship
  • Thioinosine / analogs & derivatives*
  • Thioinosine / chemistry
  • Thioinosine / pharmacology


  • 2-fluoro-4-nitrobenzyl mercaptopurine riboside
  • Equilibrative Nucleoside Transporter 1
  • Purines
  • Thioinosine
  • 4-nitrobenzylthioinosine