EP4 Receptor Antagonist(TCG Lifesciences)

The prostaglandin E2 (PGE2) regulates several biological processes via interaction with 1 of 4 E‐type prostanoid receptors (EP1–EP4). The E‐type prostanoid receptor 4 (EP4) is expressed primarily on myeloid cells, T lymphocytes, and tumor cells, and has emerged as a major contributor to PGE2‐mediated enhancement of tumor survival pathways and as a suppressor of innate and adaptive antitumor immune responses. To date, significant work on the discovery of EP4 receptor antagonists has been carried out, but no compound has been approved for use in humans yet. Toward our aim of discovering potential EP4 antagonists, a pharmacophore‐based scaffold‐hopping approach combined with docking studies has been envisaged. As a result, compound 4 was found to be a non‐toxic, potent EP4 antagonist binding in the orthosteric site. This compound exhibited good aqueous solubility, with acceptable in vitro metabolic stability and permeability. Albeit high protein binding, it displayed sustained exposure and significant oral bioavailability in mice and can thus have the potential for further optimization to yield next‐generation EP4 antagonists.

The inflammatory mediator prostaglandin E₂ (PGE₂) binds to G_s-coupled EP2 and EP4 receptors. These receptors are located in the locus coeruleus (LC), the principal noradrenergic nucleus in the brain, but their functional role remains unknown. In this study, the PGE₂ EP2 and EP4 receptors in LC cells from male rat brain slices were pharmacologically characterized by single-unit extracellular electrophysiology. The EP2 receptor agonists butaprost (0.01-10 μM) and treprostinil (0.03-10 µM) and the EP4 receptor agonists rivenprost (0.01 nM-1 µM) and TCS2510 (0.20 nM-2 µM) increased the firing rate of LC neurons in a concentration-dependent manner. The EP2 receptor antagonist PF-04418948 (10 nM) hindered the excitatory effect of butaprost and treprostinil while the EP4 receptor antagonist L-161,982 (30 and 300 nM) blocked the excitatory effect caused by rivenprost and TCS2510. The effects of butaprost and rivenprost were prevented by extracellular sodium replacement but were not modified by the protein kinase A (PKA) activator 8-Br-cAMP (1 mM) or the inhibitor H-89 (10 μM). However, the G_βγ subunit blocker gallein (20 μM) hindered the stimulatory effect of butaprost while the G_αs subunit inhibitor NF449 (10 µM) prevented that of rivenprost. Finally, rivenprost-induced stimulation (30 nM) was not occluded by butaprost (1 µM). In conclusion, activation of EP2 and EP4 receptors excites LC noradrenergic neurons through sodium-dependent currents via different G protein subunits in male rat brain slices. EP2 and EP4 in the LC may constitute pharmacological targets for the treatment of pain, fever, drug addiction, anxiety and neuroinflammatory diseases.