The bis-indole indigoids are a promising protein kinase inhibitor scaffold to be further evaluated against the numerous human diseases that imply abnormal regulation of kinases including neurodegenerative disorders. In an effort to identify new pharmacological inhibitors of disease-relevant protein kinases with increased potency and selectivity, we designed, synthesized new 5,7-disubstituted or 6-substituted bis-indole derivatives. On the basis of our previous synthetic work, 22 selected compounds were tested on CDK1/cyclin B, CDK5/p25, DYRK1A, CK1, and GSK-3alpha/beta kinases, five kinases involved in Alzheimer's disease. Some of them were also evaluated for their cytotoxic and antiproliferative activities. 6-Nitro-3'-N-oxime-indirubin and 5-amino-3'-N-oxime-indirubin derivatives exhibited inhibitory activity in a submicromolar range against CDK1/cyclin B (0.18 and 0.1 microM, respectively), CK1 (0.6 microM and 0.13 microM) and GSK3 (0.04 microM and 0.36 microM).