INDY is a potent and ATP-competitive Dyrk1A and Dyrk1B inhibitor with IC50s of 0.24 μM and 0.23 μM, respectively. INDY binds in the ATP pocket of the enzyme and has a Ki value of 0.18 μM for Dyrk1A. INDY sharply reduces the self-renewal capacity of normal and tumorigenic cells in primary Glioblastoma (GBM) cell lines and neural progenitor cells.