A weak PAR2 partial agonist that can block PAR2 signaling initiated via protease and/or potent peptidomimetics (794.5)

Protease‐activated receptor‐2 (PAR 2 ) is a GPCR activated by proteolytic cleavage of the extracellular NH 2 ‐terminus resulting in a newly exposed peptide sequence or “tethered ligand.” Potent and efficacious peptidomimetic agonists have been developed to PAR 2 , however, similar antagonists have been lacking. We have modified the peptidomimetic agonist, 2‐furoyl‐LIGRLO‐NH 2 , substituting LIG 2‐4 with an azabicycloalkane scaffold and O 6 with a Tyr. At 10 ‐ 50 M, C391 blocks protease and/or peptidomimetic induced, PAR 2 dependent, Ca 2+ and MAPK signaling and, ‐arrestin recruitment. In a PAR 2 ‐dependent behavioral mouse model, C391 dose‐dependently blocked (75 g max effect) mast cell degranulation‐induced thermal hyperalgesia. We transformed C391 into a synthetic tethered ligand (C391‐PEG 3 ‐Hdc) in an effort to increase PAR 2 affinity and efficacy. C391‐PEG 3 ‐Hdc performed as a partial agonist across PAR 2 assays. We conclude that C391 is a weak partial agonist with low M PAR 2 affinity that can act as an antagonist when applied at appropriate concentrations. This represents a pharmacological mechanism of action for PAR 2 that can be fruitful for the development of therapeutics. Grant Funding Source : NIH‐NS073664