A cell-permeable p-imidobenzamidoquinoline, endo-diastereomer that is shown to inhibit the activity of TNKS1/PARP5a and TNKS2/PARP5b in in vitro auto-PARsylation assays (IC50 = 131 and 56 nM, respectively) and effectively suppress Wnt-stimulated transcription activity in L-Wnt-STF-based reporter assays (IC50 = 180 nM), while exhibiting little activity against PARP1 or PARP2 (IC50 >18.75 μM). Although both IWR-1-endo and XAV939 act as reversible Wnt pathway inhibitors and exhibit similar pharmacological effects both in vitro and in vivo, IWR-1-endo exerts its effect via interaction with Axin, while XAV939 binds TNKS directly.
