Contractions of mouse trachea in response to the MRGPRX2/MRGPRB2 agonist C48/80 were previously reported.53 In the present study, we demonstrated that PSB-172565 potently blocks tracheal contractions induced by C48/80 via MRGPRB2 inhibition, suggesting that it might be useful for MRGPRX2/B2-induced allergic asthma; however, its value for treating airway inflammation still requires confirmation. Here, MRGPRX2 is linked to allergic asthma.