SMI-4a is primarily used in biochemical and pharmaceutical research as a selective inhibitor of protein phosphatase 1 (PP1). It plays a key role in studies related to cell cycle regulation, signal transduction, and apoptosis due to its ability to modulate phosphorylation states of key regulatory proteins. Researchers utilize SMI-4a to investigate the function of PP1 in neuronal activity, cancer progression, and viral replication. Its application extends to preclinical studies exploring potential antiviral and anticancer agents, where controlled manipulation of phosphatase activity is required. Due to its cell permeability and specificity, SMI-4a is valuable in cellular assays and in vivo models for probing phosphatase-dependent pathways.