Identification of a novel scaffold for a small molecule GPR139 receptor agonist

GPR139 is an orphan G protein-coupled receptor (GPCR) that is primarily expressed in the brain in regions known to regulate motor control and metabolism. Here, we screened a diverse 4,000 compound library in order to identify GPR139 agonists. We identified 11 initial hits in a calcium mobilization screen, including one compound, AC4, which contains a different chemical scaffold to what has previously been described for GPR139 agonists. Our mutagenesis data shows that AC4 interacts with the same hotspots in the binding site of GPR139 as those reported to interact with the reference agonists 1a and 7c. We additionally tested and validated 160 analogs in a calcium mobilization assay and found 5 compounds with improved potency compared to AC4. In total, we identified 36 GPR139 agonists with potencies in the nanomolar range (90-990 nM). The most potent compounds were confirmed as GPR139 agonists using an orthogonal ERK phosphorylation assay where they displayed a similar rank order of potency. Accordingly, we herein introduce multiple novel GPR139 agonists, including one with a novel chemical scaffold, which can be used as tools for future pharmacological and medicinal chemistry exploration of GPR139.