Aloisine A is a cell permeable, potent, selective, reversible, and ATP-competitive inhibitor of Cdc2 (CDK1)/cyclin B (IC50 = 150nM), Cdk2/cyclin A (IC50 = 120nM), Cdk2/cyclin E (IC50 = 400nM), Cdk5/p25 (IC50 = 200nM), Cdk5/p35 (IC50 = 160nM), and GSK-3α (IC50 = 500nM). Aloisine A also inhibits GSK-3β (IC50 = 650nM) and JNK (c-Jun N-terminal kinase) (IC50~3-10μM). Aloisine A is a poor inhibitor of CK1, CK2, Cdk4/cyclin D1, MAPKK, PKA, PKG, PKCs and c-raf (IC50 ≥ 100μM). Aloisine A blocks the cell cycle in both G1 and G2 phase. Aloisine A is an activator of CFTR.