Elucidation of the GSK3 alpha Structure Informs the Design of Novel, Paralog-Selective Inhibitors

Glycogen synthase kinase 3 (GSK3) remains a therapeutic target of interest for diverse clinical indications. However, one hurdle in the development of small molecule GSK3 inhibitors has been safety concerns related to pan-inhibition of both GSK3 paralogs, leading to activation of the Wnt/,6-catenin pathway and potential for aberrant cell proliferation. Development of GSK3 alpha or GSK3,6 paralog-selective inhibitors that could offer an improved safety profile has been reported but further advancement has been hampered by the lack of structural information for GSK3 alpha. Here we report for the first time the crystal structure for GSK3 alpha, both in apo form and bound to a paralog-selective inhibitor. Taking advantage of this new structural information, we describe the design and in vitro testing of novel compounds with up to similar to 37-fold selectivity for GSK3 alpha over GSK3,6 with favorable drug-like properties. Furthermore, using chemoproteomics, we confirm that acute inhibition of GSK3 alpha can lower tau phosphorylation at disease-relevant sites in vivo, with a high degree of selectivity over GSK3,6 and other kinases. Altogether, our studies advance prior efforts to develop GSK3 inhibitors by describing GSK3 alpha structure and novel GSK3 alpha inhibitors with improved selectivity, potency, and activity in disease-relevant systems.