CLK1 and osteosarcoma: Moreover, the compound was found to have a 75-fold, 3-fold, and 2-fold better inhibitory activity against DYRK2, DYRK1B, and CLK1 compared to the reference compound harmine.147 1 μM Thiophene 48 significantly induced cell apoptosis in U2OS osteosarcoma cells by increasing the ratio of caspase 3/7.