Dyrk1A/B-IN-1 (compound 3n) is a potent, selective and cell-permeable DYRK1A and DYRK1B inhibitor with Kis of 67.8 nM and 237.9 nM, and IC50s of 1.1 μM and 0.8 μM, respectively. Dyrk1A/B-IN-1 is not toxic to human cells. Dyrk1A/B-IN-1 can be used for researching DYRK1A and DYRK1B cellular functions and their role in pathologies.