Discovery of Tyrosine Kinase 2 (TYK2) Inhibitor (PF-06826647) for the Treatment of Autoimmune Diseases

J Med Chem. 2020 Nov 25;63(22):13561-13577. doi: 10.1021/acs.jmedchem.0c00948. Epub 2020 Aug 25.


Tyrosine kinase 2 (TYK2) is a member of the JAK kinase family that regulates signal transduction downstream of receptors for the IL-23/IL-12 pathways and type I interferon family, where it pairs with JAK2 or JAK1, respectively. On the basis of human genetic and emerging clinical data, a selective TYK2 inhibitor provides an opportunity to treat autoimmune diseases delivering a potentially differentiated clinical profile compared to currently approved JAK inhibitors. The discovery of an ATP-competitive pyrazolopyrazinyl series of TYK2 inhibitors was accomplished through computational and structurally enabled design starting from a known kinase hinge binding motif. With understanding of PK/PD relationships, a target profile balancing TYK2 potency and selectivity over off-target JAK2 was established. Lead optimization involved modulating potency, selectivity, and ADME properties which led to the identification of the clinical candidate PF-06826647 (22).

MeSH terms

  • Animals
  • Autoimmune Diseases / drug therapy
  • Autoimmune Diseases / enzymology*
  • Drug Discovery / methods*
  • Humans
  • Mice
  • Mice, Transgenic
  • Microsomes, Liver / drug effects
  • Microsomes, Liver / enzymology
  • Protein Kinase Inhibitors / chemistry*
  • Protein Kinase Inhibitors / pharmacology*
  • Protein Kinase Inhibitors / therapeutic use
  • Protein Structure, Secondary
  • TYK2 Kinase / antagonists & inhibitors*
  • TYK2 Kinase / chemistry
  • TYK2 Kinase / metabolism


  • Protein Kinase Inhibitors
  • TYK2 Kinase