Optimization of Orally Bioavailable Enhancer of Zeste Homolog 2 (EZH2) Inhibitors Using Ligand and Property-Based Design Strategies: Identification of Development Candidate (R)-5,8-Dichloro-7-(methoxy(oxetan-3-yl)methyl)-2-((4-methoxy-6-methyl-2-oxo-1,2-dihydropyridin-3-yl)methyl)-3,4-dihydroisoquinolin-1(2H)-one (PF-06821497)

J Med Chem. 2018 Feb 8;61(3):650-665. doi: 10.1021/acs.jmedchem.7b01375. Epub 2017 Dec 27.


A new series of lactam-derived EZH2 inhibitors was designed via ligand-based and physicochemical-property-based strategies to address metabolic stability and thermodynamic solubility issues associated with previous lead compound 1. The new inhibitors incorporated an sp3 hybridized carbon atom at the 7-position of the lactam moiety present in lead compound 1 as a replacement for a dimethylisoxazole group. This transformation enabled optimization of the physicochemical properties and potency compared to compound 1. Analysis of relationships between calculated log D (clogD) values and in vitro metabolic stability and permeability parameters identified a clogD range that afforded an increased probability of achieving favorable ADME data in a single molecule. Compound 23a exhibited the best overlap of potency and pharmaceutical properties as well as robust tumor growth inhibition in vivo and was therefore advanced as a development candidate (PF-06821497). A crystal structure of 23a in complex with the three-protein PRC2 complex enabled understanding of the key structural features required for optimal binding.

MeSH terms

  • Administration, Oral
  • Biological Availability
  • Cell Line, Tumor
  • Drug Design*
  • Enhancer of Zeste Homolog 2 Protein / antagonists & inhibitors*
  • Humans
  • Isoquinolines / administration & dosage
  • Isoquinolines / chemistry
  • Isoquinolines / pharmacokinetics*
  • Isoquinolines / pharmacology*
  • Models, Molecular
  • Molecular Conformation


  • Isoquinolines
  • Enhancer of Zeste Homolog 2 Protein
  • isoquinoline