Antitumor agent-171 (Compound 35) is an inhibitor for β-catenin/BCL9 interaction with IC50 of 1.61 μM. Antitumor agent-171 exhibits high affinity to β-catenin with Kd of 0.63 μM. Antitumor agent-171 inhibits the gene expression of axin2 with IC50 of 0.84 μM. Antitumor agent-171 inhibits cell viability of HCT116 with IC50 of 4.39 μM. Antitumor agent-171 activates T cells, promotes antigen presentation, and exhibits antitumor efficacy and good pharmacokinetic characteristics in mouse models.