– RIOK2-IN-1 (com 4) is a selective RIOK2 inhibitor with a Kd of 150 nM, though it has low cellular activity with an IC50 of 14,600 nM. RIOK2, an atypical kinase, is involved in ribosome maturation and cell cycle progression and is associated with various human cancers. The derivative compound CQ211, an enhanced version of RIOK2-IN-1, shows robust in vivo and in vitro efficacy, effectively inhibiting the proliferation of MKN-1 and HT-29 cancer cell lines and hindering tumor growth in the MKN-1 mouse xenograft model [1].