Notes: (R)-ZINC3573 is an agonist of MAS-related G protein-coupled receptor family member X2 (MRGPRX2).{72505} It induces β-arrestin recruitment in a reporter assay using MRGPRX2-expressing HTLA cells and calcium mobilization in LAD 2 mast cells (EC50s = 0.74 and 1 µM, respectively). (R)-ZINC3573 is selective for MRGPRX2 over 21 other G protein-coupled receptors (GPCRs). It induces degranulation of LAD 2 mast cells in a concentration-dependent manner.