SANT-1 directly binds to Smoothened (Smo) receptor (Kd: 1.2 nM) and inhibits Smo agonist effects (IC50: 20 nM).

SANT-1 inhibits the transportation of Smo (stimulated by PKA) to the proximal cilia. It equally suppresses both the wild-type and oncogenic forms of Smo. In SmoA1-LIGHT2 cells, SANT-1 impedes pathway activation, displaying similar efficacy to that observed in the Shh-LIGHT2 experiments. Distinct inhibitory activities of SANT-1 are evident in both Shh-LIGHT2 and BODIPY-Cyclopamine studies, where it notably blocks the SAG-modulated pathway activation. Additionally, when used in combination with SAHA, SANT-1 curtails cell proliferation and effectively inhibits colony formation in the pancreatic cancer cell lines Panc-1 and BxPC-3, offering a counteraction to gemcitabine resistance.

CK1 kinase assay: All protein kinase assays (25 μL) are carried out at room temperature (21℃). Assays are performed for 40 min using a Biomek 2000 Laboratory Automation Workstation in a 96-well format. The concentrations of magnesium acetate and [γ-33P]ATP (800 cpm/pmol) in the assays are 10 mM and 0.1 mM, respectively. Assays are initiated with MgATP and stopped by the addition of 5 μL of 0.5 M orthophosphoric acid. Aliquots are then spotted on to P30 ?ltermats, washed four times in 75 mM phosphoric acid to remove ATP, once in methanol, then dried and counted for radioactivity. CK1 δ (5-20 m-units), diluted in 20 mM Hepes, pH 7.5, 0.15 M NaCl, 0.1 mM EGTA, 0.1% (v/v) Triton X-100, 5 mM dithiothreitol, 50% (v/v) glycerol, is assayed against the peptide RRKDLHDDEEDEAMSITA in an incubation containing 20 mM Hepes, pH 7.5, 0.15 M NaCl, 0.1 mM EDTA, 5 mM DTT, 0.1% (v/v) Triton X-100 and 0.5 mM substrate peptide.