LEI-101 produces broad-spectrum analgesia in preclinical pain models

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 CB_2-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.