Prediction of intracellular exposure bridges the gap between target- and cell-based drug discovery

Proc Natl Acad Sci U S A. 2017 Jul 25;114(30):E6231-E6239. doi: 10.1073/pnas.1701848114. Epub 2017 Jul 12.


Inadequate target exposure is a major cause of high attrition in drug discovery. Here, we show that a label-free method for quantifying the intracellular bioavailability (Fic) of drug molecules predicts drug access to intracellular targets and hence, pharmacological effect. We determined Fic in multiple cellular assays and cell types representing different targets from a number of therapeutic areas, including cancer, inflammation, and dementia. Both cytosolic targets and targets localized in subcellular compartments were investigated. Fic gives insights on membrane-permeable compounds in terms of cellular potency and intracellular target engagement, compared with biochemical potency measurements alone. Knowledge of the amount of drug that is locally available to bind intracellular targets provides a powerful tool for compound selection in early drug discovery.

Keywords: MAPK14; drug exposure; intracellular drug bioavailability; published kinase inhibitor set; target engagement.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid Precursor Protein Secretases / antagonists & inhibitors
  • Aspartic Acid Endopeptidases / antagonists & inhibitors
  • Biological Availability
  • Biological Transport
  • Drug Discovery / methods*
  • HEK293 Cells
  • HL-60 Cells
  • Humans
  • Mitogen-Activated Protein Kinase 14 / antagonists & inhibitors
  • Protease Inhibitors / pharmacokinetics
  • Protein Kinase Inhibitors / pharmacokinetics


  • Protease Inhibitors
  • Protein Kinase Inhibitors
  • Mitogen-Activated Protein Kinase 14
  • Amyloid Precursor Protein Secretases
  • Aspartic Acid Endopeptidases
  • BACE1 protein, human