Discovery and hit-to-lead optimization of 2,6-diaminopyrimidine inhibitors of interleukin-1 receptor-associated kinase 4

Bioorg Med Chem Lett. 2015 May 1;25(9):1836-41. doi: 10.1016/j.bmcl.2015.03.043. Epub 2015 Mar 28.


Interleukin receptor-associated kinase 4 (IRAK4) is a critical element of the Toll-like/interleukin-1 receptor inflammation signaling pathway. A screening campaign identified a novel diaminopyrimidine hit that exhibits weak IRAK4 inhibitory activity and a ligand efficiency of 0.25. Hit-to-lead activities were conducted through independent SAR studies of each of the four pyrimidine substituents. Optimal activity was observed upon removal of the pyrimidine C-4 chloro substituent. The intact C-6 carboribose is required for IRAK4 inhibition. Numerous heteroaryls were tolerated at the C-5 position, with azabenzothiazoles conferring the best activities. Aminoheteroaryls were preferred at the C-2 position. These studies led to the discovery of inhibitors 35, 36, and 38 that exhibit nanomolar inhibition of IRAK4, improved ligand efficiencies, and modest kinase selectivities.

Keywords: Drug discovery; Inflammation; Interleukin receptor-associated kinases; SAR; Structure based drug design.

MeSH terms

  • Dose-Response Relationship, Drug
  • Drug Discovery*
  • Humans
  • Interleukin-1 Receptor-Associated Kinases / antagonists & inhibitors*
  • Interleukin-1 Receptor-Associated Kinases / metabolism
  • Models, Molecular
  • Molecular Structure
  • Protein Kinase Inhibitors / chemical synthesis
  • Protein Kinase Inhibitors / chemistry
  • Protein Kinase Inhibitors / pharmacology*
  • Pyrimidines / chemical synthesis
  • Pyrimidines / chemistry
  • Pyrimidines / pharmacology*
  • Structure-Activity Relationship


  • 2,6-diaminopyrimidine
  • Protein Kinase Inhibitors
  • Pyrimidines
  • Interleukin-1 Receptor-Associated Kinases