AZ-3451 is a protease-activated receptor-2 (PAR2) antagonist. PARs are irreversibly activated by proteolytic cleavage of the N-terminus, exposing a tethered peptide ligand that bind to and activates the transmembrane receptor domain (TMD), thereby triggering cellular signaling cascades in response to inflammatory and other stimuli. AZ-3451 binds to a remote allosteric site outside the helical bundle of the PAR2, preventing the conformational rearrangements required for receptor activation and signaling[1].
In vitro, AZ-3451 (10μM; 48h) effectively inhibited PAR2 expression in primary rat chondrocytes and prevented IL-1β (10ng/mL)-induced inflammatory responses, cartilage degradation, and premature senescence[2].
In vivo, AZ-3451 (50μg/mL; 100μL; intra-articular injection; twice weekly for 8 weeks) significantly alleviated osteoarthritis progression in a rat post-traumatic osteoarthritis model, with reduced cartilage damage, increased proteoglycan content, and decreased chondrocyte apoptosis[2]. AZ-3451 (10mg/kg; s.c.; administered 30min prior to treatment) significantly reduced PAR2 agonist-induced paw edema and decreased mast cell and neutrophil activation in rats[3].
References:
[1] Cheng, Robert K Y et al. “Structural insight into allosteric modulation of protease-activated receptor 2.” Nature vol. 545,7652 (2017): 112-115.
[2] Huang X, Ni B, Xi Y, Chu X, Zhang R, You H. Protease-activated receptor 2 (PAR-2) antagonist AZ3451 as a novel therapeutic agent for osteoarthritis. Aging (Albany NY). 2019;11(24):12532-12545.
[3] Kennedy, Amanda J et al. “Protease-activated receptor-2 ligands reveal orthosteric and allosteric mechanisms of receptor inhibition.” Communications biology vol. 3,1 782. 17 Dec. 2020.