Recently, regulators of G protein signaling (RGS) proteins have emerged as potential therapeutic targets since they provide an alternative method of modulating the activity of G protein-coupled receptors, the target of so many drugs. Inhibitors of RGS proteins must block a protein protein interaction (RGS-G alpha) but also be cell and, depending on the therapeutic target, blood brain barrier permeable. A lead compound (la) was identified as an inhibitor of RGS4 in a screening assay, and this has now been optimized for activity, selectivity, and solubility. The newly developed ligands (11b and 13) display substantial selectivity over the closely related RGS8 protein, lack the off-target calcium mobilization activity of the lead la, and have excellent aqueous solubility. They are currently being evaluated in vivo in rodent models of depression.