AP-18

AP-18, a potent and selective TRPA1 inhibitor, blocks activation of TRPA1 by 50 μM Cinnamaldehyde with an IC₅₀ of 3.1 μM and 4.5 μM for human and mouse TRPA1, respectively. AP-18 reverses complete Freund's adjuvant (CFA)-induced mechanical hyperalgesia in mice. AP-18 attenuated 30 μM AITC-induced Yo-Pro uptake in a concentration-dependent manner, with an IC₅₀ of 10.3 μM^[1][2][3]. In Vitro: At concentrations up to 50 μM, AP-18 is unable to appreciably block activation of TRPV1, TRPV2, TRPV3, TRPV4, or TRPM8. AP-18 reversibly blocks mouse TRPA1 responses to iodoacetamide (an irreversible cysteine-alkylating agent) in CHO cells assayed by ratiometric Ca²⁺ imaging. AP-18 also blocks cold- and mustard-oil-induced activation of mouse TRPA1. AP-18 blocks cinnamaldehyde-induced TRPA1 currents in excised patches from Xenopus oocytes^[1]. In Vivo: AP18 (1 mM; injected in hindpaw of mice) significantly blocks cinnamaldehdye-induced but not capsaicin-induced nociceptive events, demonstrating efficacy and specificity^[1].