Prostaglandin E2 (PGE2), a key lipid mediator, drives the inflammation, pain, and cancer progression by activating four G protein-coupled receptors (GPCRs): EP1–EP4. Among these receptors, EP2 and EP4 shape the immunosuppressive tumor microenvironment (TME) by inhibiting immune cells and promoting tumor growth. 

PGE2-EP2/EP4 signaling pathway serves as a key regulatory node connecting active inflammation and immune suppression. Their dual blockade has emerged as a promising strategy for anti-inflammatory and anti-cancer therapies.

In a study published in The EMBO Journal, a team led by Eric H. Xu (XU Huaqiang) from the Shanghai Institute of Materia Medica of the Chinese Academy of Sciences and WU Canrong from Shanghai Jiao Tong University obtained four inactive structures of EP2 and EP4 receptors bound to selective and dual antagonists, and revealed the selectivity and efficacy of EP2 and EP4 antagonists, as well as the “dual-warhead” binding mode of the dual antagonist TG6-129 with both EP2 and EP4.

Using single-particle cryo-electron microscopy, the researchers obtained the structures including EP2 bound to selective antagonist PF-04418948, EP2 bound to dual antagonist TG6-129, EP4 bound with selective antagonist Grapiprant and EP4 bound with TG6-129. These structures showed the key differences in binding pockets and interaction networks. The EP2 structures revealed a unique activation pathway involving transmembrane helices TM1, TM2, TM6, and TM7, providing a structural basis for elucidating the activation mechanism of EP2.

Moreover, the researchers revealed a “dual-warhead” binding mode that dual antagonist TG6-129 adopted. In this mode, one pharmacophore anchored to EP2, while another engaged EP4, which provided a new way for designing balanced EP2/EP4 dual inhibitors.

This study fills a gap in prostaglandin receptor pharmacology. It provides a structural framework for understanding EP2 and EP4 antagonism, and lays a structural foundation for designing improved and more effective selective or dual-targeting next-generation antagonists.