Due to an important role of EP4 in the pathogenesis of many human and animal diseases, multiple specific EP4 antagonists have been developed.[56, 57] Among them, grapiprant is an orally administered EP4 antagonist that has now been proven to have excellent analgesic effects on pets with good safety profile.[58, 59, 60] In the present study, the mice receiving grapiprant treatment prior to or after ISO injection exhibited improved cardiac diastolic function and fibrosis, suggesting grapiprant is likely used for the prevention and treatment of cardiac fibrosis. The gene discussed is PTGER4; the disease is fibrosis.