In Vitro: LY2828360 (LY-2828360) is a potent, slowly signaling, G protein-biased CB2 cannabinoid agonist that lacked both toxicity and efficacy in a clinical trial for osteoarthritis. In vitro, LY2828360 was a slowly acting but efficacious G protein-biased CB2 agonist, inhibiting cAMP accumulation and activating extracellular signal-regulated kinase 1/2 signaling while failing to recruit arrestin, activate inositol phosphate signaling, or internalize CB2 receptors.

In Vivo: In WT mice, acute systemic administration of LY2828360 suppresses paclitaxel-induced mechanical and cold allodynia in a dose-dependent manner. LY2828360 produces time-dependent suppressions of paclitaxel-evoked mechanical and cold hypersensitivities and suppression of allodynia is maintained for at least 4.5 h post-injection relative to drug pre-injection levels. At 24 h post-injection, paclitaxel-induced mechanical allodynia has returned to drug pre-injection levels of hypersensitivity. Residual suppression of cold allodynia was absent by 72 h post LY2828360 treatment. Previously chronic administration of LY2828360 blocks the development of tolerance to the antiallodynic effects of morphine in WT but not in CB2KO mice. Chronic LY2828360 treatment suppresses paclitaxel-induced mechanical and cold allodynia in WT mice but not in CB2KO mice previously render tolerant to morphine. In wild-type (WT) mice, LY2828360 (3 mg/kg per day i.p. × 12 days) suppressed chemotherapy-induced neuropathic pain produced by paclitaxel without producing tolerance. Antiallodynic efficacy of LY2828360 was absent in CB2 knockout (KO) mice. Morphine (10 mg/kg per day i.p. × 12 days) tolerance developed in CB2KO mice but not in WT mice with a history of LY2828360 treatment (3 mg/kg per day i.p. × 12 days). LY2828360-induced antiallodynic efficacy was preserved in WT mice previously rendered tolerant to morphine (10 mg/kg per day i.p. × 12 days), but it was absent in morphine-tolerant CB2KO mice. Coadministration of LY2828360 (0.1 mg/kg per day i.p. × 12 days) with morphine (10 mg/kg per day × 12 days) blocked morphine tolerance in WT but not in CB2KO mice. WT mice that received LY2828360 coadministered with morphine exhibited a trend (P = 0.055) toward fewer naloxone-precipitated jumps compared with CB2KO mice. In conclusion, LY2828360 is a slowly signaling, G protein-biased CB2 agonist that attenuates chemotherapy-induced neuropathic pain without producing tolerance and may prolong effective opioid analgesia while reducing opioid dependence. LY2828360 may be useful as a first-line treatment in chemotherapy-induced neuropathic pain and may be highly efficacious in neuropathic pain states that are refractive to opioid analgesics.

References: Mol Pharmacol. 2018 Feb;93(2):49-62.