The strength of target residence time for TTK inhibitor characterization

Kinetic behaviour reflects distinct inhibitor binding modes

  • The protein threonine tyrosine kinase (TTK) is a promising target for the treatment of aggressive cancers, e.g., triple negative breast cancer.
  • TTK inhibitors were studied using SPR as well as activity, thermal shift and cell proliferation assays.

  • The strongest correlations were found between the target residence time, cellular activity and the increase in melting temperature.

  • This demonstrates that TTK inhibitors are an example where target residence time determines the activity in cellular assays.

  • It was shown that different inhibitor types, ATP-pocket binding versus lysine-targeting, can be distinguished by their kinetic behavior.

  • Crystal structure determination of TTK bound to the different inhibitors indicated that a shift of the glycine-rich loop is most likely responsible for the long residence time of the most potent inhibitors.

Overlay of binding curves for TTK inhibitors (adapted from Maia et al., 2015).
Shift of the glycine-rich loop after inhibitor binding. The overlay of five representative X-ray structures is shown.
Comparison of the association (ka) and dissociation (kd) rates of TTK inhibitors. ATP-pocket binding inhibitors are shown as green triangles and lysine-targeting inhibitors as yellow lozenges.