Development of Small Molecules that Specifically Inhibit the D-loop Activity of RAD51

J Med Chem. 2016 May 26;59(10):4511-25. doi: 10.1021/acs.jmedchem.5b01762. Epub 2016 Apr 21.


RAD51 is the central protein in homologous recombination (HR) DNA repair and represents a therapeutic target in oncology. Herein we report a novel class of RAD51 inhibitors that were identified by high throughput screening. In contrast to many previously reported RAD51 inhibitors, our lead compound 1 is capable of blocking RAD51-mediated D-loop formation (IC50 21.3 ± 7.8 μM) at concentrations that do not influence RAD51 binding to ssDNA. In human cells, 1 inhibits HR (IC50 13.1 ± 1.6 μM) without blocking RAD51's ability to assemble into subnuclear foci at sites of DNA damage. We determined that the active constituent of 1 is actually an oxidized derivative (termed RI(dl)-1 or 8) of the original screening compound. Our SAR campaign also yielded RI(dl)-2 (hereafter termed 9h), which effectively blocks RAD51's D-loop activity in biochemical systems (IC50 11.1 ± 1.3 μM) and inhibits HR activity in human cells (IC50 3.0 ± 1.8 μM).

Publication types

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

MeSH terms

  • Cell Line
  • Cell Survival / drug effects
  • Dose-Response Relationship, Drug
  • Humans
  • Molecular Structure
  • Rad51 Recombinase / antagonists & inhibitors*
  • Rad51 Recombinase / metabolism
  • Small Molecule Libraries / chemical synthesis
  • Small Molecule Libraries / chemistry
  • Small Molecule Libraries / pharmacology*
  • Structure-Activity Relationship


  • Small Molecule Libraries
  • RAD51 protein, human
  • Rad51 Recombinase