STO-609 is primarily used as a selective inhibitor of the calcium/calmodulin-dependent protein kinase kinase (CaMKK), particularly targeting the alpha and beta isoforms. It is widely applied in biochemical and cellular research to study signaling pathways involving CaMKK and its downstream effectors such as AMP-activated protein kinase (AMPK). Researchers use STO-609 to investigate metabolic regulation, energy homeostasis, and cell proliferation, especially in models related to cancer and metabolic diseases. Due to its ability to modulate AMPK activity indirectly, it serves as a tool compound in studies exploring glucose metabolism, autophagy, and mitochondrial function. Its selectivity makes it valuable for dissecting the roles of CaMKK in complex cellular environments without broadly affecting other kinase pathways.