A non-opioid cannabinoid approach shows broad pain relief in animals

A promising method for managing pain without the negative effects on the central nervous system linked to CB1 receptor activation or opioid analgesics is the selective activation of the cannabinoid CB2 receptor. Nevertheless, the pharmacological profiles of the available CB2 agonists vary and in certain instances they depend on endogenous opioid signalling. We investigated the pharmacology of the selective CB2 receptor agonist LEI-101 in vitro and in vivo in rodent pain models. Radioligand binding, cAMP inhibition and calcium mobilization at cannabinoid receptors in humans and rats were employed to characterize LEI-101. Rat models of osteoarthritis, neuropathic, postoperative and chronic inflammatory pain were used to assess analgesic efficacy. Selective CB1, CB2 and μ-opioid antagonists were used to measure receptor selectivity. To evaluate potential central nervous system side effects, locomotor activity was measured. With significant selectivity over CB1 receptors, LEI-101 had high affinity and functional agonist efficacy at human and rat CB2 receptors. Systemic administration of LEI-101 produced dose-dependent antihyperalgesic and antiallodynic effects across all pain models. These effects were abolished by CB2-selective antagonists but not by CB1 or μ antagonists. LEI-101 did not impair locomotor activity at analgesic doses and showed no evidence of opioid-like tolerance following repeated administration. These findings demonstrate that selective CB2 receptor activation by LEI-101 produces robust analgesia across diverse pain states, with a predominantly CB2-dependent and opioid-independent pharmacological profile. CB2-selective agonists such as LEI-101 represent a promising non-opioid therapeutic strategy for the treatment of chronic pain.