This Podcast features an interview with Hagit Eldar-Finkelman, author of a Research Article that appears in the 15 November 2016 issue of Science Signaling, about a newly developed inhibitor of glycogen synthase kinase 3 (GSK-3). GSK-3 participates in several signaling networks and has been implicated in various pathologies, including neurodegenerative diseases, cognitive impairments, and cancer. Licht-Murava et al. developed L807mts, a substrate-competitive peptide inhibitor that blocks GSK-3 activity through an unusual mechanism. L807mts not only bound to the substrate recognition domain of GSK-3, it was also phosphorylated by the kinase. This phosphorylated form of L807mts remained associated with GSK-3 and inhibited GSK-3 activity. L807mts treatment reduced cellular, cognitive, and behavioral symptoms in a mouse model of Alzheimer's disease. L807mts is an advance in kinase inhibitor development because it is both highly specific and very potent.