Discovery of 5-(3-Chlorophenylamino)benzo[c][2,6]naphthyridine Derivatives as Highly Selective CK2 Inhibitors with Potent Cancer Cell Stemness Inhibition

Multifunctional entities have recently been attractive for the development of anticancer chemotherapeutic drugs. However, such entities with concurrent CK2 along with cancer stem cell (CSC) inhibitory activities are rare in a single small molecule. Herein, a series of 5-(3-chlorophenylamino)benzo[c][2,6]naphthyridine derivatives were synthesized using a known CK2 inhibitor, silmitasertib (CX-4945), as the lead compound. Among the resulting compounds, 1c exhibited stronger CK2 inhibitory activity with higher Clk2/CK2 selectivity than CX-4945. Significantly, 1c could modulate the Akt1(ser129)-GSK-3β(ser9)-Wnt/β-catenin signaling pathway and inhibit the expression of the stemness marker ALDH1A1, CSC surface antigens, and stem genes, showing potent CSC inhibitory activity. Moreover, 1c also displayed superior pharmacokinetics and antitumor activity compared with CX-4945 sodium salt, without obvious toxicity. The favorable antiproliferative and antitumor activity of 1c, its high inhibitory selectivity for CK2, and its potent inhibition of cancer cell stemness make this molecule a candidate for the treatment of cancer.